JPS60111600A - Electromechanical transducing element - Google Patents

Abstract

PURPOSE:To improve performance and efficiency of divergence convergence, originating and receiving of oscillation by providing the thin film or the thick film of the material with the first electrode and piezo-electric effects, and the second electrode on the surface of the base plate which is formed in the curved surface condition, and by setting the base plate itself as an oscillation plate. CONSTITUTION:For a base plate 1, a thin plate with 0.1mum-5mm. thickness made of ceramics such as aluminum is used, and formed in the dorm-shape with the radius of curvature: 80mm. and the outer diameter: 30mm.. Metallic aluminum is evaporated at the convex side of the base plate 1 as a lower electrode 2. Next, a piezoelectric film 3 which is smaller than the film of the electrode 2 is formed on the electrode 2. Any one or more materials of zinc oxide, aluminum nitride, lead titanate, barium titanate, lead titanate zirconate, and lead titanate zirconate-based compounds are used for the film 3. Next, the metallic aluminum, which is smaller than the diameter of the film 3, is evaporated on the film 3 as an upper electrode 4. A piezoelectric sound body is formed by bonding a lead 5 to the electrodes 2 and 4. In this way, performance and efficiency of dispersion, ending, originating, and receiving of oscillation can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to an electromechanical transducer having functions such as divergence, convergence, transmission, and reception of sound waves and mechanical vibrations. In particular, the present invention relates to an electromechanical transducer having a curved membrane structure, whose curved surface can be formed into an arbitrary shape, and whose curved surface itself performs electromechanical conversion.

In this specification, the term "electromechanical conversion" refers to the conversion of electrical signals into mechanical signals such as acoustic signals and mechanical vibrations, and the conversion of mechanical signals such as acoustic signals and mechanical vibrations into electrical signals. This shall include both cases.

The present invention relates to an electromechanical transducer, and below, an electroacoustic transducer, which is a typical electromechanical transducer, will be mainly described.

However, the present invention is not limited to electroacoustic transducers.

[Background of the invention]

Conventionally, functional elements have been created by processing functional materials with piezoelectric effects into curved surfaces, but it is difficult to process them into desired curved surfaces, and it is especially difficult to finish them into film-like elements with various curved surfaces. It was difficult and often impossible to manufacture industrially.

On the other hand, due to advances in IC and LSI technology, electronic devices,
Optical equipment is also becoming smaller, thinner, and lighter, and in order to respond technologically to this trend, the industry is trying to make the functional elements used in each equipment smaller, thinner, and lighter. It has been strongly requested by

It is desirable to keep the materials used to achieve the function to the minimum necessary amount in order to keep material costs down, and one way to achieve this is by using a membrane structure, which reduces the amount of human output required to fulfill the function. For this purpose, electrodes and input/output terminals are provided, and by cutting the membrane, drilling holes, microfabrication, laminating, and controlling the composition of the membrane,
Efforts are being made to consolidate the functions of elements and make them multifunctional.

Generally, the membrane itself is thin and therefore has low mechanical strength, and it is often extremely difficult to process just the membrane itself. However, if a functional material is formed as a film on some kind of substrate, it is possible to manufacture it even if it is difficult to create a complex shape, and there are already materials that can fully utilize their performance as a functional material. ing.

It is desirable that the substrate on which the film is formed can be selected depending on the function in relation to the functional thin film to be formed thereon. Examples of the substrate material include EVA, iron, cobalt,
Metals such as nickel, aluminum, silicon, titanium, copper, alloys such as stainless steel and brass, and their oxides, as well as alumina, magnesia, zirconia, silica, calcium oxide, yttrium oxide, beryllium oxide, and oxide. Tungsten, rare earth metal oxides, solid solutions thereof, carbides such as silicon carbide, nitrides such as titanium nitride, aluminum nitride, silicon nitride, single crystals thereof, glasses, or ceramics, or Examples include polymeric substances such as Mylar sheet and polyethylene film.

On the other hand, examples of functional materials include monocomponent oxides such as zinc oxide, tin oxide, iron oxide, and zirconium oxide, materials with compositions composed of these as the main component and other additives, lead titanate, barium titanate, lithium niobate,
Lithium tantalate, lead zirconate titanate compounds,
PL which is lead zirconate titanate doped with lanthanum
Examples include composite oxides such as ZT, nitrides such as aluminum nitride, titanium nitride, and silicon nitride, and carbides such as silicon carbide.

Namely, zinc oxide with aligned crystal axes, aluminum nitride, quartz whose main component is silicon oxide, barium titanate with Bellowsky 1-type crystal system, lead zirconate titanate, PLZT, lithium niobate. , lithium tantalate, etc. are well known as materials that exhibit piezoelectricity, ceramics such as barium titanate, lead zirconate titanate, lithium tantalate, lithium niobate, triglycine sulfate (TGS), etc.
, triglycine fluoperite (TGFB), strontium barium niobate [(SrBa)Nb
A material with oriented crystal axes, such as 2Oe; SBN], is a pyroelectric material.

In addition, barium titanate to which zinc oxide, tin oxide, manganese, etc. are added also functions as a semiconductor, and zirconium oxide to which calcium or yttrium oxide is added is #1. This is an example of a material that functions as a conductor for elementary ions.

These functional additives can be formed on the above-mentioned substrates by vacuum evaporation, spackling, magnetron sputtering, ion blating, CVD, MOCVD, screen printing, coating, etc., or by heat treatment such as baking or laser annealing. A thin film can be formed by applying .

However, in the conventional concept, a flat substrate was used as a substrate, and circuits and electrodes were formed on it, as seen in silicon single crystal wafers, which are substrates for LSIs, etc., for example.

In addition, in the field of transducers, piezoelectric elements such as PZT ceramics processed into a thin flat plate have been pasted on metal plates and used as transducers, as seen in piezoelectric buzzers and bimorphs, for example. e
According to F-research, a piezoelectric material with a specific crystal orientation is fabricated using a technique such as magnetron sputtering using a piezoelectric functional material such as ZnO or AIN on a flat substrate, and then It has been evaluated that it can be used as an electroacoustic transducer by providing electrodes and as a flat plate speaker.

In order to make full use of the functions of these elements, it is desirable to consider the shape of the functional elements when designing, and as mentioned above, film-like elements are often formed on a substrate. Therefore, when designing functional elements, consider the substrate material,
It is desirable to design the element, taking into account the composition, substrate shape, processing precision, etc. Furthermore, the membrane inner body is not limited to a uniform surface, but may have a complicated shape due to trimming or etching, and two or more types of functional materials may be used in combination on the same surface.

The inventors focused on these points and found that functional elements formed on curved substrates have characteristics that are not seen in functional elements formed on flat substrates, and characteristics that are superior to flat elements. The present invention has been completed based on the fact that it has been demonstrated that the present invention has the following characteristics.

[Purpose of the invention]

The present invention provides a first electrode coating, a thin film of a material having a piezoelectric effect, and a second electrode coating on the surface of a substrate formed in a curved shape, and vibrates this structure itself as a radiator to generate sound waves or The object of the present invention is to provide an electromechanical transducer that can improve the performance and efficiency of divergence, convergence, transmission, and reception of mechanical vibrations, and can provide further unique functions.

[Features of the invention]

The first invention of the present invention is a unimorph invention, which includes a substrate formed in a curved shape, a first electrode formed over most of one surface of the substrate, and a unimorph in contact with the first electrode. A thin film made of a material having a piezoelectric effect is formed on most of the surface of the electrode, and a second electrode is formed on the surface of this thin film. The material having a piezoelectric effect is zinc oxide, aluminum nitride, lead titanate, barium titanate, lead zirconate titanate, and lead zirconate titanate-based compounds, and the thickness of the thin film is 0.1 μm to 5 μm. 000μm,
It is preferably 10 μm to 2.000 μm, and the area is 0. O1 part 2 to 1,000,000 part 2, preferably 0.1 part 2 to 1oo, ooo dragon 2.

In other words, the substrate of the device is composed of a curved surface, and by designing and molding the shape and dimensions of the substrate in advance before manufacturing, the functional device formed in the form of a film on the substrate does not need to be molded again. The feature is that it can be freely manufactured into any desired shape.

Therefore, in terms of the functionality of the device, compared to a functional material molded on a flat substrate, the physical quantity generated by the functional device is
For example, the sound field can be controlled three-dimensionally without using other modulation equipment, and when receiving waves, it is possible to receive physical quantities coming from a wider angle.

For example, if functional materials are applied to the outer surfaces of curved surfaces such as spherical, parabolic, and ellipsoidal surfaces, that is, the convex surfaces,
The physical quantity generated from the element is emitted into space at a wider angle than the physical quantity from the planar element. Furthermore, if a functional material is formed in the form of a film on the inside of the curved surface, the physical amount generated from this element can be concentrated at the focal point of the curved surface of the substrate. Conversely, when such an element is used to receive physical quantities from the outside world, it is possible to receive physical quantities from a wide angle.

In addition, due to the thinness of the substrate and its integration with piezoelectric materials, it is possible to reduce the size and size even for speakers, for example.
It can be made lighter, and it can meet the demands for smaller, lighter, and thinner functional elements.Thinner substrates have higher heat dissipation effects, and for translucent substrates, the thinner the substrate, the better the light transmission. Furthermore, by selecting the material used for the substrate, the performance of the functional element itself can be improved.

The second invention of the present invention is an invention of a bimorph, which includes a substrate formed into a curved shape, a first electrode formed over a large part of one surface of the substrate, and a first electrode in contact with the first electrode. A material with a piezoelectric effect formed in most of the electrode'
a thin film made of a material having a piezoelectric effect, a second electrode formed on the surface of this thin film, a thin film made of a material having a piezoelectric effect formed on the majority of the electrode in contact with this second electrode, and a thin film formed on the surface of this thin film. and a third electrode, and the substrate itself is a diaphragm.

[Explanation based on examples]

Next, as an example of the electromechanical transducer of the present invention, an electroacoustic transducer will be described in detail based on the drawings.

FIG. 1 is a front view of an electroacoustic transducer according to a first embodiment of the present invention;
FIG. 2 is a sectional view of the electroacoustic transducer according to the first embodiment of the present invention;
FIG. 3 is a front view of an electroacoustic transducer according to a second embodiment of the present invention;
FIG. 4 is a sectional view of an electroacoustic transducer according to a second embodiment of the present invention;
Fig. 5 is a manufacturing process flowchart of an electroacoustic transducer according to an embodiment of the present invention, Fig. 6 is an impedance measurement circuit diagram of an electroacoustic transducer according to an embodiment of the present invention, and Fig. 7 is an impedance measurement of an electroacoustic transducer according to an embodiment of the present invention. Figure showing the results, No. 8
The figure is a sound pressure measurement circuit diagram of an electroacoustic transducer according to an embodiment of the present invention.
The ninth circle is a diagram showing the sound pressure measurement results of the electroacoustic transducer according to the embodiment of the present invention, FIG. 10 is a front view of the electroacoustic transducer according to the third embodiment of the present invention, and FIG. 12 and 13 are explanatory diagrams of the drive circuit of the electroacoustic transducer according to the third embodiment of the present invention, and Fig. 14 is the sound pressure measurement results of the electroacoustic transducer according to the third embodiment of the present invention. FIG. 15 is a front view of an electroacoustic transducer according to a fourth embodiment of the present invention, FIG. 16 is a cross-sectional view of an electroacoustic transducer (smell element) according to a fourth embodiment of the present invention, and FIG. 17 is a cross-sectional view of an electroacoustic transducer according to a fourth embodiment of the present invention. FIG. 18 is a front view of the electroacoustic transducer according to the embodiment, and a sectional view of the electroacoustic transducer according to the fifth embodiment of the present invention. I will explain.

A dome-shaped alumina thin plate is used as a substrate for a speaker cone, metal aluminum is vacuum-deposited as an electrode on the concave surface, and zinc oxide is formed to a thickness of 20 μm by magnetron sputtering. Oriented perpendicular to the plane of the substrate. If aluminum is vapor-deposited on top of this to form a counter electrode, the zinc oxide functions as a piezoelectric element, making it possible to create a speaker that directly drives an alumina cone. At this time, the film thickness of zinc oxide can be freely controlled by sputtering time or sputtering speed, etc., and can be manufactured to a thickness of 2 to 3 μm or more, but the best results are obtained with a thickness of 10 μm to 200 μm, which can be easily manufactured. can be obtained.

Furthermore, by using alumina as the cone, the Young's modulus of alumina is 50 x 1010 Pa, which is about 7 times larger than that of conventional metal aluminum, making it possible to manufacture a speaker with excellent high-frequency reproduction limit characteristics. If a flat plate transducer is used in the driving part, it is not possible to obtain directivity characteristics suitable for an S speaker, so the transducer having a curved substrate according to the present invention has a great advantage. Furthermore, by directly driving the alumina cone, the device can be made smaller than conventional devices. Specific examples will be described below.

In the embodiment of the present invention, as shown in FIGS. 1 to 4, a lower electrode 2 is laminated on the upper surface of a curved substrate 1, and a piezoelectric coating 3 is placed on top of the lower electrode 2.
is formed, its upper surface is covered with an upper electrode 4, and lead wires 5 are fixed on the upper electrode 4 and the lower electrode 2, respectively.

The first embodiment of the present invention shown in FIGS. 1 and 2 is a speaker cone using a convex piezoelectric element, and the second embodiment of the present invention shown in FIGS. 3 and 4 is a speaker cone using a concave piezoelectric element. It's a speaker cone. The laminated structures of the first and second embodiments are exactly the same, but the lead wire 5 is located at the outer periphery of the lower electrode 2 and the upper electrode 4 in the first embodiment, and the upper electrode 4 is located in the second embodiment. The lead wire 5 from is located in the center.

The piezoelectric element according to the embodiment of the present invention constructed in this way is a piezoelectric sound element according to the first embodiment, which is a curved substrate having a radius of curvature of 80 mm, an outer diameter of 30 Wlffi, and a thickness of 30 μm, using a dome-shaped thin plate made of alumina. The manufacturing method will be explained based on FIG. 5. First, the curved substrate 1 is cleaned. Thoroughly remove dirt such as oil and fat from the surface and dry. Metallic aluminum is deposited as a lower electrode 2 on the convex side of the curved substrate 1.

Next, a piezoelectric coating 3 of a functional material is formed. Here, piezoelectric materials such as zinc oxide (ZnO) and aluminum nitride (A
A thin film such as IN) was formed on the curved substrate 1 by sputtering. The device uses a planar magnetron type high-speed RF sputtering device. For example, for sputtering an AIN thin film, a high-purity aluminum plate is used as the target, and a high-purity nitrogen/argon mixed gas (1:1) is used as the sputtering gas. Using. The composition of the sputtering gas can be varied by varying the ratio of nitrogen to argon; for example, the ratio of nitrogen to argon can be varied from 1:1 (100) until the ratio is all nitrogen gas. However, in order to obtain an aluminum nitride (AIN) thin film with more desirable characteristics, it is preferable to use a composition of 1:10, consisting entirely of nitrogen gas.The sputtering conditions are: input RF power of 150 to 200 W, spack gas Pressure 2~10X
The temperature was 10-3 Torr. Note that at this time, it is desirable to form the piezoelectric film 3 smaller than the lower electrode 2 using a mask or the like.

Sputtering time is 40-60 minutes, film thickness is 15.3
It was set to 0 μm, etc. After forming the piezoelectric film 3 having a convex surface in this manner, aluminum was deposited on this film to provide an upper electrode 4. At this time, a mask or the like is used to protect the aluminum from being deposited on the side surfaces, and an upper electrode 4 having a smaller diameter than the piezoelectric coating 3 is deposited to prevent a short circuit between the electrodes, and the lower electrode 2 formed in this way is A piezoelectric sounding element (
speakers).

Next, the electrical characteristics of the piezoelectric sounding body manufactured in this manner will be explained. FIG. 6 is a configuration diagram of the measuring circuit. Using a variable frequency type low frequency constant voltage generating power source 11, the sample to be measured 13 is monitored while its output is monitored by a frequency measuring device 12.
A voltage is applied through a precise constant resistance Ro. At this time, the voltage appearing across the constant resistance Ro is measured with a voltmeter 14. Since the voltage of the power supply 11 is automatically controlled to a constant value, the voltage across the resistor Ro is proportional to the current value passing through the resistor Ro, that is, inversely proportional to the absolute value of the impedance of the sample 13 to be measured.

As shown in FIG. 7, the impedance measured in this manner shows a high impedance of 10 6 Ω or more even at a low frequency of 100 Hz. There is a linear relationship between the impedance frequency characteristics 20011z and 100kHz.

Next, the acoustic performance of this piezoelectric sounding body was measured using a sound pressure measurement circuit shown in FIG. A low frequency constant voltage generator 21 is used as a driving power source, and constant voltages Vo of different frequencies are applied between both electrodes of the measurement sample 23. The frequency at this time is monitored by the frequency measuring device 22. The sound generated from the measurement sample 23 was received by an electric i-lett condenser microphone 24, the signal was amplified by an amplifier 25, and the voltage was measured by a voltmeter 26. The measurement was performed with the distance β between the measurement sample 23 and the electret condenser microphone 24 set to 2 cm.

The measurement results are shown in FIG. Here, the noise level is expressed as OdB, and the output specific voltage of the microphone 24 is expressed in dB. In this measurement, 1 at a frequency of 1 kllz
At 5 dB, the sound can be heard even from a distance of 1 meter. Therefore, with this prototype device, it is sufficient to listen to sounds of 2 kllz or more.

Furthermore, by using a curved substrate, it is possible to change the directivity of the sound, and while the sound coming from the convex side propagates over a wide angle, the sound coming from the concave side can have a convergence point. .

The curvature of the curved surface is related to the focus of convergence and divergence of the sound field. For example, on the concave side, the distance to the point of convergence of sound is the distance to the focus, which theoretically ranges from 0 to infinity. However, if the distance is too long, it becomes meaningless to have a curved surface, so a certain finite value is selected. The distance cannot be specified because it depends on the size of the element itself. In addition, it is known that for a vibrating body that is curved like a spherical surface, the frequency at which the first resonant vibration occurs will be higher if a diaphragm with a large degree of curvature is used. , can reproduce sounds up to higher frequencies. Furthermore, by using a curved substrate, the element can be made more resistant to external mechanical forces.

Next, a case will be described in which a piezoelectric element made of lead zirconate titanate ceramic is formed on a thin alumina substrate with a curved surface. The alumina substrate has a radius of curvature of 80 mm, an outer diameter of 401 mm, and a thickness of 50 μm, forming part of a spherical surface. A paste mainly composed of platinum metal powder is applied to the concave surface of the sphere,
The lower electrode was formed by baking. On the other hand, a paste is made by adding binder, plasticizer, solvent, etc. to lead zirconate titanate powder raw material that has been calcined and finely ground.
Print and coat onto the already formed lower electrode so that it has a uniform thickness. At this time, the paste of the calcined powder is applied in such a manner that it does not cover a portion of the lower electrode. For example, in the case of the concave piezoelectric speaker shown in FIGS. 3 and 4 showing the second embodiment, the piezoelectric coating 3 is formed within a smaller concentric circle than the lower electrode 2. After drying this base coating, main firing is performed to form a titanic acid film that is integrated with the curved substrate 1 and has a thickness of 5 μm to 3,500 μm, preferably 15 μm to 300 μm, for example, 30 to 100 μm. Zino-C lead conate ceramics are produced. When forming the upper electrode 4 on the lead zirconate titanate ceramic, metal aluminum is vapor-deposited in smaller concentric circles on the lead zirconate titanate coating.

The element formed in this way is immersed in insulating oil at about 100°C, and about 2.5 mm is placed between the upper electrode 2 and the lower electrode 4.
A direct current electric field of 5 kV/mm was applied for 30 minutes to perform polarization treatment to obtain a piezoelectric element. This polarization condition is not necessarily 2
．． 5 is not limited to ν/dragon, but is preferably set depending on the material. After cleaning the element and removing the oil, lead wires 5 were attached to the upper and lower electrodes 2 and 4, and a sounding body was manufactured in which a dome-shaped alumina cone could be directly driven by a piezoelectric element.

In the above example, a spherical alumina thin plate was used as the substrate, but materials can also be made of not only ceramics such as alumina, zirconia, and beryllia, but also metals such as aluminum, stainless steel, and copper, as well as high-grade materials such as Mylar film. A thin, curved substrate, including molecular materials, can be used. In some cases, a metal substrate can be used in common even without providing a lower electrode. The shape of the curved surface is not a spherical scale, for example, a parabola, a hyperbola, a sinus curve, a curved surface created by rotation of a part of an ellipse, a surface shaped like a gutter cut vertically, a corrugated curved surface, etc. Various shapes of substrates can be considered as long as they can be processed, and can be selected depending on the intended use.

As the piezoelectric material, in addition to the above-mentioned AIN and lead zirconate titanate, many other piezoelectric materials having a perovskite structure or a tungsten bronze structure can be used, including zinc oxide (ZnO). Furthermore, although the piezoelectric material in the above element has a unimorph structure, it can also form a bimorph structure.

For example, an electrode formed as an upper electrode on a unimorph is used as an intermediate electrode, and a piezoelectric material cover and an electrode are stacked on top of that, or a unimorph is formed on both the convex and concave surfaces of a curved substrate. obtained by In order to obtain larger sound output, it is effective to use a bimorph structure.

Next, an electroacoustic transducer according to a third embodiment of the present invention shown in FIGS. 10 to 14 will be described. This third embodiment is similar to the first
As shown in FIG. 0 and FIG.
An upper electrode 36 is formed on the lower surface, and a lower electrode 33 and an upper electrode 36 are formed on the lower surface.
It has a double-sided bimorph structure in which a piezoelectric coating 35 and a lower electrode 37 are formed. That is, on both sides of the curved substrate 31,
It is characterized by the provision of electrodes and a film-like piezoelectric element.

The curved substrate 31 is a dome-shaped alumina substrate with an outer diameter of 30 mm.
The curved substrate 31 has a radius of curvature of 80 mm and a thickness of 30 μm. After cleaning and drying this curved substrate 31, metal aluminum is independently vapor-deposited on its convex and concave surfaces to form an upper electrode 32 and a lower electrode 33, and these are formed on this convex surface. A piezoelectric coating 34 is formed on the upper electrode 32 .

In this example, aluminum nitride (AIN) is formed by sputtering and has a thickness of 5 μm. An upper electrode 36 is formed on the upper surface of this piezoelectric coating 34 .

As with convex surfaces, aluminum nitride (A
IN ) was sputtered to form a piezoelectric film 3 with a thickness of 5 μm.
5 has a lower opening 13 electrode 37 formed on its lower surface.

The piezoelectric coatings 34 and 35 have a smaller diameter than the upper electrode 3Z and the lower electrode 33, and are structured to avoid wrapping around each other. The sputtering conditions are the same as in the second embodiment.

Using the sound pressure measurement circuit shown in FIG. 8, we measured the sound pressure by driving only the convex element as a unimorph in FIG. It is shown in FIG. The solid line A shows the sound pressure when driving as a bimorph, and the dotted line B shows the sound pressure when driving as a unimorph.

As described above, bimorph drive provides a greater sound pressure than unimorph drive, with an improvement of 5 to 8 dB.

The piezoelectric film can be made from not only aluminum nitride (8IN), but also zinc oxide (ZnO), PZT ceramics, etc., and similar effects can be expected, and the two piezoelectric films can be driven independently. .

FIGS. 15 and 16 show a fourth embodiment of a single-sided bimorph structure. This example has a dome-shaped alumina fin with an outer diameter of 30, a radius of curvature of 80, and a thickness of 30 μm.
A curved substrate 41 is cleaned and dried, an electrode 42 is formed on the convex surface by vapor depositing metal aluminum, and aluminum nitride is sputtered on the upper surface to a thickness of 10 mm.
A piezoelectric film 43 with a thickness of 10 μm is coated, and an electrode 44 is formed by vapor-depositing aluminum thereon, and then a piezoelectric film 45 with a thickness of 10 μm is formed by sputtering aluminum nitride, and an electrode 46 is formed on the upper surface thereof. This is what I did.

The sound pressure was measured using the sound pressure measurement circuit shown in FIG. 8, and it was possible to obtain a sound pressure 3 to 7 dB higher when driving as a bimorph than when driving as a unimorph.

In this example, the bimorph structure is formed on the convex surface, but it can also be formed on the concave surface.

Next, a fifth embodiment shown in FIGS. 17 and 18 will be described. As a curved substrate, a shape that forms part of a cylinder (
A platinum electrode 52 is formed on the concave surface of an alumina curved substrate 51 (semi-cylindrical), and titanate zirconate paste is applied to the concave surface of the electrode 52 to a uniform thickness, dried and fired to reduce the thickness. A 100-μm piezoelectric film 53 is coated, and aluminum is deposited on the concave surface of the piezoelectric film 53 to form a counter electrode 54.
was formed.

The thickness of the piezoelectric coating 53 is controlled by the thickness of the applied lead zirconate titanate paste, and is 2.5 k.
It was harvested at V/ms and used as a piezoelectric element.

As a result of sound pressure measurements, the sound pressure was highest near the focal point of the cylinder, and unlike elements on a spherical surface, we created an element that is characterized by forming a linear focal region in the length direction of the semi-cylindrical cylinder. can do.

An outline of an embodiment other than the above will be explained below.

As a sixth example, metal aluminum was vapor-deposited on the convex surface of a thin substrate of a hemispherical 0.1 mm Mylar film, and aluminum nitride (AIN>) was formed on the convex surface to a thickness of 15 μm using a magnetron sputter deposition device. As a result, the C-axis of aluminum nitride (ΔIN) was oriented perpendicular to the substrate, and metal aluminum was evaporated onto this to form opposing electrodes to form a piezoelectric element. Approximately 10 V was applied between these two electrodes. When an alternating current electric field of 500 to 10,00011 z was applied, it produced an audible sound that could be heard over a wide angle.

In addition, as a seventh embodiment, a hemispherical substrate with a thickness of 40 mm is used.
Using an alumina substrate with a radius of curvature of 30+amR,
After providing a platinum electrode on the concave side of the spherical surface, a slurry of calcined powder of PZT, which is a ferroelectric material and exhibits piezoelectricity, was applied to a thin film of uniform thickness to form a film, and heated at 1200°C. A heat treatment was performed for 2 hours to integrate the alumina substrate and sinter it. After forming electrodes by vapor-depositing aluminum on the film, an electric field of approximately 2.5 kV/mu was applied between the two electrodes to polarize the film, resulting in a direct-drive speaker element. The speaker manufactured using this element has a vibration cone and a driving element integrated, and has a simple structure, small size, and light weight, and the Young's modulus of alumina is 50 × 1.
Since the pressure was as large as 0.10 Pa, it was possible to obtain an excellent high-frequency reproduction limit characteristic.

Furthermore, as an eighth embodiment, a hemispherical substrate with a thickness of 0.
Using a zirconia substrate with a radius of curvature of 30 mm and a diameter of 40 mm at the cut portion of the R1 spherical surface, metal aluminum to be one electrode was first vapor-deposited on the convex surface, and then zinc oxide ZnO was magnetron-spun on top of it. After forming it to a thickness of 30 μm, metal aluminum was vapor-deposited on it to form the other electrode, and between the two electrodes, IOV, 1
,000 = 10,000 tlz of alternating current was applied, and an audible sound was generated. On the concave side, an increase in sound pressure was observed near the focal point of the curved surface, indicating that the sound field was converging.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to easily mold a functional element having a thin film of a material having a piezoelectric effect sandwiched between electrode coatings on a curved substrate. It is now possible to vibrate itself as a radiator, improving the performance and efficiency of dispersing, focusing, transmitting, and receiving sound waves or mechanical vibrations, and providing unique functions. Since layering can be achieved and materials can be selected from a wide range, materials suitable for purposes can be selected and the performance of the conversion element itself can be improved, which is an excellent effect.

[Brief explanation of drawings]

FIG. 1 is a front view of an electroacoustic transducer according to a first embodiment of the present invention. FIG. 2 is a sectional view of the electroacoustic transducer element according to the first embodiment of the present invention. FIG. 3 is a front view of an electroacoustic transducer according to a second embodiment of the present invention. FIG. 4 is a sectional view of an electroacoustic transducer element according to a second embodiment of the present invention. FIG. 5 is a flowchart of the manufacturing process of an electroacoustic transducer according to an embodiment of the present invention. FIG. 6 is an impedance measurement circuit diagram of an electroacoustic transducer according to an embodiment of the present invention. FIG. 7 is a diagram showing the impedance measurement results of the electroacoustic transducer according to the embodiment of the present invention. FIG. 8 is a sound pressure measurement circuit diagram of an electroacoustic transducer according to an embodiment of the present invention. FIG. 9 is a diagram showing the sound pressure measurement results of the electroacoustic transducer according to the embodiment of the present invention. FIG. 10 is a front view of an electroacoustic transducer according to a third embodiment of the present invention. FIG. 11 is a sectional view of an electroacoustic transducer element according to a third embodiment of the present invention. FIGS. 12 and 13 are explanatory diagrams of a drive circuit for an electroacoustic transducer according to a third embodiment of the present invention. FIG. 14 is a diagram showing the sound pressure measurement results of the electroacoustic transducer according to the third embodiment of the present invention. FIG. 15 is a front view of an electroacoustic transducer element according to a fourth embodiment of the present invention. FIG. 16 is a sectional view of an electroacoustic transducer element according to a fourth embodiment of the present invention. FIG. 17 is a front view of an electroacoustic transducer according to a fifth embodiment of the present invention. FIG. 18 is a sectional view of an electroacoustic transducer according to a fifth embodiment of the present invention. 1.31.41.5I...Curved substrate, 2.33.37
... lower electrode, 3.34.35.43.45.53.
...Piezoelectric coating, 4.32.36...Top electrode, 5...
・Lead wire, 11.21...Low frequency constant voltage generation power supply,
12.22... Frequency measuring device, 13.23... Measurement sample, 14, Ah... Voltmeter, 24... Electret condenser microphone, 25... Amplifier, 42
．． 44.46.52.54--electrode, Ro,, R1
- Fixed resistance, V. ...Applied voltage, l...Distance between sample and microphone. C 5 (21 No. 6 M (Frequency plate: Hz) Brother 7 Ro M 8 figure (, drive frequency: Hz) Kabuto 9 Zutsuki 12 figure J/Yan 13 figure (Release frequency reform/H2) JP 140 Ha 18 Figure Procedure Amendment 1, Case Indication 1982 Patent Application No. 220189 2, Title of Invention Electromechanical Transducer - Address 5-1 Marunouchi-chome, Chiyoda-ku, Tokyo Name
Mitsubishi Mining Cement Co., Ltd. Representative Hisaaki Kobayashi 4, Agent 5 Date of amendment order (voluntary amendment) 6 Number of inventions increased by amendment None 8 Contents of amendment (1) Page 23, line 3 of the specification Correct eyes "bronze" to [bronze]. μ) "The diameter is small" on page 24, line 16 of the specification is corrected to "the diameter is small." (3) “Zirconate titanate” on page 26, line 13 of the specification is corrected to “lead zirconate titanate J.” (4) “Do” on page 28, line 2 of the specification is changed to “do”. to correct.

Claims (7)

[Claims] (1) A substrate formed in a curved shape, a first electrode formed over most of the convex and concave surfaces of this substrate, and a first electrode that extends over most of the convex and concave surfaces in contact with the first electrode. A thin film or a thick film made of a material having a piezoelectric effect is formed, and a second electrode is formed on the surface of the film-like material made of the thin film and/or the thick film, and the substrate itself is used as a diaphragm. Characteristic electromechanical transducer. (2) The electromechanical transducer according to claim 11, wherein the curved surface is spherical. (3) Claim No. (1) in which the curved surface shape is semi-cylindrical
The electromechanical transducer described in . (4) The electromechanical transducer according to claim 11, wherein the material of the curved substrate is made of ceramic and has a thickness of 0.1 μm to 5 μm. (5) Claim No. 11 in which the material having a piezoelectric effect is any one or more of zinc oxide, aluminum nitride, lead titanate, barium titanate, lead zirconate titanate, and lead zirconate titanate-based compounds. The electromechanical transducer described in . (6) Thin film thickness is 0.1 μm to 2,000 μm
and its area is 0.111I112 to 100,
The electromechanical transducer according to claim 11, which is 000KIN2. (7) A substrate formed in a curved shape, a first electrode formed over most of one surface of this substrate, and a piezoelectric effect formed on most of the electrode in contact with this first electrode. A thin film made of a material, a second electrode formed on the surface of this thin film, a thin film made of a material having a piezoelectric effect formed on the majority of the electrode in contact with the second electrode, and a thin film made of a material having a piezoelectric effect formed on the surface of this thin film. an electromechanical transducer, characterized in that the substrate itself is a diaphragm, and the substrate itself is a diaphragm.