KR20140009651A - Ultrasonic transducer for super-directional speaker and method for manufacturing the same - Google Patents

Abstract

The present invention relates to an ultrasonic transducer that emits a sound in a desired direction using ultrasonic waves and is used in a super directional speaker having high directivity and a method for manufacturing the same, and, more specifically, to an ultrasonic transducer capable of increasing a strain rate and generating a high sound pressure. The ultrasonic transducer comprises: a lamination structure made of a composite layer consisting of a plurality of mutually independent piezoelectric ceramic regions and a dielectric elastomer matrix region that exists as one connected figure; and a lower plate having multiple cavities having a fixed depth on the top surface on which the lamination structure is stacked. The method for manufacturing the ultrasonic transducer includes forming multiple cavities having a fixed depth on the top surface of an lower plate; and stacking a lamination structure made of a composite layer consisting of a plurality of mutually independent piezoelectric ceramic regions and a dielectric elastomer matrix region that exists as one connected figure on the top surface of the lower plate, thereby facilitating mass production and manufacturing of the ultrasonic transducer. According to the present invention, the ultrasonic transducer manufactured by the method has a high strain rate and increased transmission efficiency of ultrasonic waves in the air.

Description

ULTRASONIC TRANSDUCER FOR SUPER-DIRECTIONAL SPEAKER AND METHOD FOR MANUFACTURING THE SAME

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer for a superdirectional speaker used in a speaker having a strong directivity that emits sound in a desired direction using ultrasonic waves, and more particularly, to a plurality of piezoelectric ceramic regions that are independent of each other. For super-directional speakers that can increase the strain and generate a large sound pressure by stacking a laminated structure composed of a composite layer consisting of dielectric elastomer matrix regions that exist as a connecting phase on a lower plate formed with a plurality of cavities at a predetermined depth on the upper surface. An ultrasonic transducer and a method of manufacturing the same.

In general, a speaker generates sound by converting an electrical signal into vibration and transmitting the same in the air, and isotropic when transmitting the vibration in the air. Accordingly, the listener can hear the sound of the speaker generated in all directions with respect to the speaker. At this time, the isotropy of the speaker often causes unnecessary problems. For example, in a space where various works or exhibits, such as an art gallery or a museum, are installed so that descriptions of the works and exhibits can be explained through speakers, the spaces of art galleries and museums may cause Interference occurs between sounds. In addition, if a large number of people simultaneously listen to the descriptions of different works and exhibits from the speaker, a large amount of voice guidance interferes with each other and distorts each other, resulting in large noise. In order to solve this problem, researches on a superdirectional speaker that generates an audible sound using ultrasonic waves have been actively conducted so that sound can be heard only in a specific direction.

The driving principle of the superdirectional speaker using universal ultrasonic waves is as follows. First, a signal of music, voice, etc. to be reproduced is generated, and a signal of an ultrasonic frequency band of a predetermined frequency, which is a reference, is generated and sent to a modulator. The modulator shifts and modulates the original signal by the reference ultrasonic frequency, and amplifies the modulated signal by inputting the original signal to the amplifier together with the reference ultrasonic wave. The ultrasonic waves are then sent to an ultrasonic transducer to generate ultrasonic waves. At this time, the generated ultrasonic wave is transmitted through the air, non-linearity of the air is generated by the difference frequency component of the two ultrasonic waves, the sound wave is present in the audible frequency band is audible sound wave that can be heard by the listener can be audible.

The ultrasonic transducer as described above may be a piezoelectric transducer using a piezoelectric material such as PVDF or piezoelectric ceramic. The piezoelectric transducer converts an electrical signal into an ultrasonic wave by using a resonance phenomenon of the piezoelectric material and converts the ultrasonic wave into an electrical signal, thereby transmitting and receiving the ultrasonic wave.

As an example of the piezoelectric transducer as described above, the 'piezoelectric speaker system' of the Republic of Korea Patent Publication No. 10-2010-0070230 and the 'piezoelectric speaker and its manufacturing method' of the Republic of Korea Patent Publication No. 10-2010-0073075 is presented. . In the prior art, an electrode is formed on upper and lower surfaces of a piezoelectric thin film made of a piezoelectric material such as PVDF or piezoelectric ceramic so as to reproduce sound.

Conventional transducers use piezoelectric properties of polyvinylidene fluoride (PVDF), a polymer material, by connecting electrodes to a piezoelectric thin film in which PVDF is processed into a film, and applying a signal according to sound to generate a sound by vibrating the piezoelectric thin film. However, such a piezoelectric thin film made of PVDF can be used as a transducer only when a high driving voltage is applied, and it is difficult to reduce it to a certain size or less due to a low strain rate.

In addition, in addition to the piezoelectric thin film made of such PVDF, some piezoelectric thin films using piezoelectric ceramics, such as PZT, are used. However, the piezoelectric thin films using the piezoelectric ceramics are difficult to generate sufficient negative pressure due to their small output. In case of thin film of 1mm or less, there is a high risk of breakage during electrode formation, and when it is bonded to a metal plate used as electrode, bubbles are generated or when it is unevenly bonded, negative distortion occurs or piezoelectric properties become poor, There will be a limit on the size.

Therefore, in the case of using a piezoelectric thin film made of a piezoelectric material such as PVDF or piezoelectric ceramic as the ultrasonic transducer, each piezoelectric thin film has a low strain and uses a plurality of piezoelectric transducers in order to obtain a sufficient sound pressure. In order to obtain sufficient sound pressure in the above manner, more and more piezoelectric transducers are required to be arranged. Therefore, miniaturization is difficult and manufacturing costs are increased due to the arrangement of a plurality of piezoelectric transducers.

The present invention has been made to solve the above problems, an object of the present invention, when using a piezoelectric transducer made of a piezoelectric material such as PVDF or piezoelectric ceramic used in a conventional super-directional speaker, the ultrasonic wave is low strain The present invention relates to an ultrasonic transducer for a superdirectional speaker and a method of manufacturing the same, which can solve a problem in which it is difficult to generate sufficient sound pressure as a transducer.

Ultrasonic transducer for super-directional speakers according to the present invention for achieving the above object is a lower plate formed with a plurality of cavities at a predetermined depth on the upper surface; And a lower electrode layer disposed on the lower plate and formed of a conductive material, a composite layer consisting of a plurality of mutually independent piezoelectric ceramic regions and a dielectric elastomer matrix region present in one connection phase, and an upper electrode layer formed of a conductive material. It includes a laminated structure formed by being stacked.

In addition, the ultrasonic transducer for a super-directional speaker according to the present invention for achieving the above object is a lower plate formed with a plurality of cavities at a predetermined depth on the upper surface; And a lower electrode layer disposed on the lower plate and formed of a conductive material, and a plurality of stacked on the lower electrode layer, and a plurality of piezoelectric ceramic regions that are independent of each other, and a dielectric elastomer matrix region that is present in one connection phase. A composite layer, an intermediate electrode layer formed between each of the plurality of stacked composite layers, and a stacked structure formed by sequentially stacking the upper electrode layer formed of a conductive material on the stacked plurality of composite layers.

Preferably, the lower plate is formed of a metal or polymer material,

The cavity is formed by a plurality of two-dimensional arrangement at regular intervals, or extend in one direction to have a constant width,

The two-dimensionally arranged cavity is formed in any one shape selected from circles, triangles, squares, pentagons and polygons,

The sound pressure is changed by the width, the depth of the cavity and the gap between the cavities,

A portion of the lower plate on which each of the cavities is formed and a portion of the stack structure corresponding to the portion of the lower plate form a unit ultrasonic transducer,

The unit ultrasonic transducer forms an array,

The contact surface of the lower plate and the laminated structure disposed on the lower plate is bonded by an adhesive member,

The inside of the cavity is formed with a vacuum,

The piezoelectric ceramic is a piezoelectric ceramic having a perovskite structure containing Pb,

The dielectric elastomer matrix is a polydimethyl siloxane (PDMS) matrix,

The piezoelectric ceramic and the dielectric elastomer matrix are mixed at a ratio of 50 to 70:30 to 50 vol%,

The composite layer is characterized in that it has a thickness of less than 100㎛.

In addition, a super-directional speaker according to the present invention for achieving the above object is an audio frequency wave oscillation source for generating a signal of an audible frequency band; A carrier wave oscillation source generating a signal in an ultrasonic frequency band; A modulator for modulating a carrier wave of an ultrasonic frequency band output from the carrier wave oscillation source using a signal of an audio frequency band output from the audio frequency wave oscillation source; A power amplifier amplifying the modulated signal output from the modulator; And the ultrasonic transducer of claim 1 or 2, which is driven by a modulated signal amplified by the power amplifier.

Ultrasonic transducer manufacturing method for a super-directional speaker according to the present invention for achieving the above object is a cavity forming step of forming a plurality of cavities at a constant depth in the lower plate; A laminate in which a lower electrode layer formed of a conductive material, a plurality of mutually independent piezoelectric ceramic regions, a composite layer composed of a dielectric elastomer matrix region present in one connection phase, and an upper electrode layer formed of a conductive material are sequentially stacked to form a laminated structure step; And an attaching step of attaching the laminated structure on the lower plate.

In addition, the ultrasonic transducer manufacturing method for a super-directional speaker according to the present invention for achieving the above object comprises a cavity forming step of forming a plurality of cavities at a constant depth on the lower plate; A lower electrode layer formed of a conductive material, a plurality of composite layers composed of a plurality of mutually independent piezoelectric ceramic regions and a dielectric elastomer matrix region present in one connection phase, an intermediate electrode layer and a conductive material respectively formed between the plurality of composite layers. A stacking step of sequentially stacking the upper electrode layers formed to form a stack structure; And an attaching step of attaching the laminated structure on the lower plate.

Preferably, in the cavity forming step, the lower plate is formed of a metal or a polymer material,

In the cavity forming step, the plurality of cavities are formed by arranging a plurality of two-dimensionally at regular intervals,

The cavity is formed in any one shape selected from circles, triangles, squares, pentagons and polygons,

In the cavity forming step, the cavity is formed extending in one direction to have a constant width,

In the lamination step, the piezoelectric ceramic is a piezoelectric ceramic having a perovskite structure including Pb,

In the lamination step, the dielectric elastomer matrix is a polydimethyl siloxane (PDMS) matrix,

In the lamination step, the piezoelectric ceramic and the dielectric elastomer matrix are mixed at a ratio of 50 to 70:30 to 50 vol%,

In the attaching step, the bottom contact surface and the laminated structure disposed on the lower plate are bonded by an adhesive member,

A polarization step of polarizing by applying a voltage to the upper electrode layer and the lower electrode layer.

According to the ultrasonic transducer for a superdirectional speaker according to the present invention and a method for manufacturing the same, a multilayer structure including a plurality of piezoelectric ceramic regions that are independent of each other and a dielectric elastomer matrix region that exists as one connection phase is formed at a constant depth on an upper surface thereof. By stacking on the lower plate formed with a plurality of cavities, there is a remarkable effect that it is easy to mass-produce and manufacture, has a high strain rate and improves the transmission efficiency of ultrasonic waves in the air.

In addition, according to the ultrasonic transducer for a super-directional speaker according to the present invention and a method of manufacturing the same, a plurality of composite layers in which piezoelectric ceramic regions are dispersed in the dielectric elastomer matrix region is laminated to form a laminated structure to linearly improve the performance of the piezoelectric body. There is a remarkable effect of improving the properties and thereby generating sufficient sound pressure.

In addition, according to the ultrasonic transducer for a super-directional speaker according to the present invention and a method of manufacturing the same, by attaching a laminated structure to a lower plate on which a plurality of cavities are formed, several unit ultrasonic transducers form an array in one laminated structure. There is a remarkable effect that can generate a sufficient sound pressure in the listening area of the super-directional speaker.

1 is a cross-sectional view showing the structure of an ultrasonic transducer for a superdirectional speaker according to the present invention.
2A and 2B are plan and cross-sectional views illustrating a cavity formed on a lower plate according to an embodiment of the present invention.
3A and 3B are plan and cross-sectional views illustrating a cavity formed on a lower plate according to another exemplary embodiment of the present invention.
4 is a cross-sectional view showing the structure of a laminated structure according to an embodiment of the present invention.
5 is a cross-sectional view showing the structure of the composite layer constituting the laminated structure.
6 is a cross-sectional view showing the structure of a laminated structure according to another embodiment of the present invention.
7A and 7B are sectional views showing the operation of the ultrasonic transducer for a superdirectional speaker according to the present invention.
8 is a block diagram showing the configuration of a superdirectional speaker according to the present invention.
9 is a flowchart of a method of manufacturing an ultrasonic transducer for a superdirectional speaker according to the present invention.

Ultrasonic transducer for a super-directional speaker according to the present invention and a method for manufacturing the same are a plurality of laminated structure consisting of a composite layer consisting of a plurality of mutually independent piezoelectric ceramic region and a dielectric elastomer matrix region present in one connection phase to a predetermined depth on the upper surface. The present invention proposes a technical feature that can increase strain and generate large sound pressure by stacking on lower plates formed with two cavities.

In the following, preferred embodiments, advantages and features of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing the structure of an ultrasonic transducer for a superdirectional speaker according to the present invention. Referring to FIG. 1, the ultrasonic transducer 100 for a superdirectional speaker according to the present invention is attached to a lower plate 70 and a lower plate 70 having a plurality of cavities 60 formed at a predetermined depth on an upper surface thereof. It includes a laminated structure 50 is disposed.

In the lower plate 70 according to the present invention, a plurality of cavities 60 are formed at a predetermined depth on an upper surface thereof. The lower plate 70 may be formed of a metal material to be electrically connected to the lower electrode layer 10 of the stacked structure 50. The lower plate 70 may be formed of a polymer material to form a flat surface and reduce production costs. Can be.

2A and 2B are plan and cross-sectional views illustrating a cavity formed on a lower plate according to an embodiment of the present invention. 2, a plurality of cavities 60 arranged at regular intervals are formed two-dimensionally on an upper surface of the lower plate 70 according to an embodiment of the present invention. In the figure, although a plurality of circular cavities 60 are formed in a rectangular pattern at a predetermined interval, the cavities 60 may be formed in the shape of a circle, a triangle, a rectangle, a pentagon, or various polygons. The plurality of cavities 60 may be variously arranged in an array structure of a regular hexagonal pattern as well as a rectangular pattern.

3A and 3B are plan and cross-sectional views illustrating a cavity formed on a lower plate according to another exemplary embodiment of the present invention. Referring to FIG. 3, a plurality of cavities 60 extending in one direction are formed on the upper surface of the lower plate 70 according to another embodiment of the present invention. The process of acting as the ultrasonic transducer 100 for the superdirectional speaker by placing the stacked structure 50 on the lower plate 70 of FIGS. 2 and 3 will be described later with reference to the corresponding drawings.

4 is a cross-sectional view showing the structure of a laminated structure according to an embodiment of the present invention, Figure 5 is a cross-sectional view showing the structure of a composite layer constituting the laminated structure. 6 is a cross-sectional view showing the structure of a laminated structure according to another embodiment of the present invention. 4 and 5, the multilayer structure 50 according to the exemplary embodiment of the present invention includes a lower electrode layer 10 formed of a conductive material and a plurality of piezoelectric ceramics disposed on the lower electrode layer 10 and mutually independent. (22) a composite layer 20 consisting of a region of dielectric elastomer matrix 24 present in one connection phase with a region, and an upper electrode layer 30 formed of a conductive material on the composite layer 20 are sequentially stacked Is formed.

The lower electrode layer 10 is formed of a conductive material such as a conductive metal or a conductive polymer. In general, the lower electrode layer 10 may be formed of a conductive polymer such as polyaniline, polythiophene, PEDOT (poly (3,4-ethylene-dioxythiophene)), polypyrrole, or PPV (polyphenylenevinylene) using a paste containing Ag or carbon powder. Derivatives thereof, organic conductors and the like can be used.

The composite layer 20 is disposed on the lower electrode layer 10 and includes a plurality of piezoelectric ceramic 22 regions that are independent of each other, and a dielectric elastomer matrix 24 region that is present in one connection phase.

In general, when the piezoelectric element is manufactured using only the piezoelectric ceramic 22, it can be driven even at a relatively low voltage (2 kV / mm). However, due to the characteristics of the ceramic material, it is difficult to manufacture a thin piezoelectric element. Due to this, the piezoelectric element was very likely to break. In addition, it is difficult to form a piezoelectric element more than a certain size, it is not easy to configure it in a stacked form, there is a limit that is vulnerable to bass characteristics.

In addition, when the piezoelectric element is manufactured using only the dielectric elastomer, the dielectric elastomer requires a very high driving voltage (≥10 kV / mm), but has a high strain rate of 100% or more when the driving voltage is applied.

Therefore, when forming the composite layer 20 composed of a plurality of piezoelectric ceramic 22 regions which are independent of each other and a dielectric elastomer matrix 24 region present in one connection phase as shown, the piezoelectric properties of the piezoelectric ceramics 22 are formed. It is possible to effectively transmit and to form a piezoelectric material having a relatively high strain under an appropriate driving voltage.

Preferably, the piezoelectric ceramic 22 is a piezoelectric ceramic having a perovskite structure including Pb, and is basically a compound including lead, zirconium, titanium, and oxygen, and a number of changes are made depending on the ratio of zirconium and titanium. All piezoelectric ceramics having a high piezoelectric constant can be used as a representative of PZT (Pb (Ti, Zr) O3) which can be used.

In addition, the dielectric elastomer matrix 24 may use a polydimethyl siloxane (PDMS) matrix. PDMS is a transparent inert polymer compound with very low surface energy, easy change of form, and hydrophobic material. It has the following advantages as an elastomer.

Firstly, PDMS stably adheres to a relatively wide adhesive surface, which applies equally to uneven surfaces. Secondly, PDMS has low interfacial free energy, so that adhesion does not occur well when molding with other polymers. Third, PDMS is homogeneous isotropic and optically transparent up to 300 nm thick. Fourthly, PDMS is extremely durable and does not cause degradation of properties even after a long time.

Therefore, when the dielectric elastomer matrix 24 is used as the PDMS matrix to form a composite layer with the piezoelectric ceramics 22, the ultra-durable transparent thin film form that can effectively transmit the vibration of the piezoelectric ceramics 22 is formed. Ultrasonic transducers for directional speakers can be manufactured, which can be used to produce loudspeakers that improve volume and sound quality and enhance bass.

In addition, in the case where the piezoelectric ceramics 22 are distributed in the dielectric elastomer matrix 24 to form a composite layer, the piezoelectric properties are improved as the amount of the dielectric elastomer matrix 24 is lowered, but the piezoelectric ceramics 22 and the dielectric elastomers are improved. In order to form a uniform composite layer 20 without bubbles between the matrices 24, the piezoelectric ceramics 22 and the dielectric elastomer matrix 24 are preferably mixed at a ratio of 50 to 70: 30 to 50 vol%. Do.

More preferably, the composite layer 20 is formed in the form of a film to have a thickness of 100 μm or less, capable of driving to have a relatively large strain even under a low driving voltage, and for a super-directional speaker capable of generating a sufficient sound pressure. Ultrasonic transducers can be obtained.

The upper electrode layer 30 is formed of a conductive material such as a conductive metal or a conductive polymer on the composite layer 20. In general, like the lower electrode layer 10 described above, the upper electrode layer 30 uses a paste containing Ag or carbon powder, or polyaniline, polythiophene, PEDOT (poly (3,4-ethylene-dioxythiophene)), polypyrrole, PPV. conductive polymers such as (polyphenylenevinylene), derivatives thereof, and organic conductors may be used.

Referring to FIG. 6, a stack structure 50 according to another embodiment of the present invention is formed by stacking a plurality of lower electrode layers 10 formed of a conductive material on the lower electrode layer 10 and a plurality of independent layers. A composite layer 20 formed of a dielectric elastomer matrix 24 region existing as a piezoelectric ceramic 22 region of the piezoelectric ceramic 22 region, and an intermediate electrode layer 40 formed between the plurality of stacked composite layers 20, respectively. And an upper electrode layer 30 formed of a conductive material on the plurality of stacked composite layers 20 sequentially stacked.

The composite layer 20 may be arranged in a plurality of stacked as shown. Accordingly, the intermediate electrode layers 40 are sequentially formed between the plurality of composite layers 20, and the upper electrode layers 30 and the lower electrode layers 10 are disposed on upper and lower portions of the plurality of composite layers 20. Each of them may be formed to form a composite layer 20 of various stacked forms.

When the plurality of composite layers 20 are stacked as described above, the piezoelectric properties of the entire laminate structure 50 are improved when the same voltage is applied as compared to the case where the composite layer 20 is formed as a single layer. Sound pressure can be obtained.

The lower electrode layer 10, the composite layer 20, and the upper electrode layer 30 of the stacked structure 50 according to another embodiment of the present invention are described above with reference to FIGS. 4 and 5. The lower electrode layer 10, the composite layer 20, and the upper electrode layer 30 of the stack structure 50 according to the exemplary embodiment are the same as the detailed description thereof will be omitted.

7A is a cross-sectional view showing a state in which no voltage is applied to the ultrasonic transducer for a superdirectional speaker according to the present invention, and FIG. 7B is a cross-sectional view illustrating operation when voltage is applied to the ultrasonic transducer for a superdirectional speaker according to the present invention. to be. 7A and 7B, the operation of the ultrasonic transducer 100 for a superdirectional speaker according to the present invention will be described.

The frequency of the ultrasonic waves used in the superdirectional speaker is in the range of about 30 to 100 kHz, and the wavelength is about 3.4 to 10 mm in length. Therefore, the ultrasonic waves used in the superdirectional speaker have a small wavelength, and it is difficult to generate sufficient sound pressure with one ultrasonic transducer.

The greatest influence on the sound pressure of the ultrasonic waves emitted from the ultrasonic transducer is the strain of the laminated structure 50 disposed on the lower plate 70. The ultrasonic transducer 100 for a superdirectional speaker according to the present invention has a composite layer 20 composed of a plurality of piezoelectric ceramic 22 regions, which are independent of each other, and a dielectric elastomer matrix 24 region that is present in one connection phase. By forming the laminated structure 50 by using a), it is possible to increase the sound pressure by greatly improving the strain compared with piezoelectric elements such as conventional piezoelectric ceramics or PVDF.

In addition, since the ultrasonic waves used in the superdirectional speaker are difficult to generate a sufficient sound pressure with one ultrasonic transducer, it is necessary to arrange the ultrasonic transducers to generate constructive interference of the ultrasonic waves to generate a large sound pressure.

Two or more waves are intermingled with each other, causing interference, which is large when they meet waves of the same phase, and smaller when they meet waves of opposite phases. The case where it becomes large is called constructive interference, and the case where it becomes small is called cancellation interference. The ultrasonic transducer 100 for the superdirectional speaker according to the present invention forms an array of several unit ultrasonic transducers in one stacked structure 50, so that constructive interference occurs only in the listening area of the superdirectional speaker, and in other places. The destructive interference is caused.

In more detail, the ultrasonic transducer 100 for a superdirectional speaker according to the present invention includes a part of a lower plate 70 in which each cavity 60 is formed and a laminated structure disposed on the lower plate 70. 50) forms each unit ultrasonic transducer. In addition, each of the unit ultrasonic transducers form an array, so that constructive interference of ultrasonic waves emitted from each unit ultrasonic transducer is generated to generate a large sound pressure.

At this time, the generated sound pressure is variously determined by the shape of the cavity 60, such as the diameter, depth, and spacing of the cavity 60 formed in plural lower plates 70. In addition, the generated sound pressure is the frequency and wavelength of the ultrasonic wave used, the type and mixing ratio of the piezoelectric ceramic 22 and the dielectric elastomer medium formed in the composite layer 20 formed on the laminated structure 50 and the composite layer. Since the value varies according to various conditions such as the thickness of 20, the diameter, depth, and spacing between the cavities 60 are determined experimentally according to each condition.

When a voltage is applied to the ultrasonic transducer 100 for a superdirectional speaker according to the present invention, the laminated structure 50 disposed on the lower plate 70 becomes thin and expands due to piezoelectric properties. At this time, the portion in contact with the lower plate 70 is in a fixed state, the laminated structure 50 of the upper portion of the cavity 60 formed in the lower plate 70 is expanded.

Preferably, the surface in contact with the lower plate 70 and the laminated structure 50 disposed on the lower plate 70 in order to fix the laminated structure 50 of the portion in contact with the lower plate 70 Silver may be bonded by an adhesive member such as epoxy. In addition, although not shown, the contact surface of the laminated structure 50 and the lower plate 70 may be fixed by a pressing member that applies pressure to the contact surface on the upper portion of the laminated structure 50.

As described above, the ultrasonic transducer 100 for the superdirectional speaker expands the stack structure 50 on the cavity 60 when voltage is applied, and radiates ultrasonic waves into the air by the up / down movement of the diaphragm. do. In this case, the plurality of unit ultrasonic transducers are arranged in an array, and the ultrasonic waves radiated from each unit ultrasonic transducer may generate sufficient sound pressure in the listening area of the superdirectional speaker by constructive interference.

Preferably, the inside of the cavity 60 of the lower plate 70 sealed by the laminated structure 50 may be formed in a vacuum. When the inside of the cavity 60 is formed in a vacuum, offsetting by unnecessary rear waves during the operation of the ultrasonic transducer 100 may be suppressed. Since the wave can move only with the medium, the ultrasonic transducer 100 for the superdirectional speaker according to the present invention forms the inside of the cavity 60 of the lower plate 70 sealed by the laminated structure 50 by vibration, It is possible to suppress the generation of unnecessary back waves opposite to the radiation direction of the ultrasonic waves and to effectively radiate ultrasonic waves having sufficient sound pressure into the listening area.

8 is a block diagram showing the configuration of a superdirectional speaker according to the present invention. Referring to FIG. 8, the superdirectional speaker according to the present invention includes an audio frequency wave oscillation source 140 generating a signal in an audible frequency band, a carrier wave oscillation source 120 generating a signal in an ultrasonic frequency band, and the audio frequency. A modulator 150 for modulating a carrier wave of an ultrasonic frequency band output from the carrier wave oscillation source 120 using a signal of an audio frequency band output from the wave oscillator 140, and outputted from the modulator 150 A power amplifier 160 for amplifying a modulated signal and the ultrasonic transducer 100 for a superdirectional speaker according to the present invention, which is driven by the modulated signal amplified by the power amplifier 160.

The ultrasonic transducer 100 is driven by a modulated signal amplified by the power amplifier 160 to convert the modulated signal into a sound wave having a finite amplitude level. These sound waves are radiated into the medium (i.e. air) and reproduced as the sound of the original audio frequency band due to the nonlinear effect of the medium. The reproduction signal of the audio frequency band reproduced as described above proceeds in the form of a beam output along the radial axis of the ultrasonic transducer 100.

Hereinafter, a method of manufacturing an ultrasonic transducer for a superdirectional speaker according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

9 is a flowchart of a method of manufacturing an ultrasonic transducer for a superdirectional speaker according to the present invention. Referring to FIG. 9, in the method of manufacturing an ultrasound transducer for a superdirectional speaker according to an embodiment of the present invention, a cavity forming step (S1) of forming a plurality of cavities 60 at a predetermined depth in a lower plate 70 is conducted. A lower electrode layer 10 formed of a material, a composite layer 20 consisting of a plurality of mutually independent piezoelectric ceramic 22 regions and a dielectric elastomer matrix 24 region present in one connection phase, and an upper electrode layer formed of a conductive material. Laminating step (S2) to form a laminated structure 50 by sequentially stacking the 30 (30) and the attaching step (S3) for attaching the laminated structure 50 on the lower plate 70.

Cavity forming step (S1) is formed by processing a plurality of cavities 60 to a predetermined depth in the lower plate (70). In the cavity forming step (S2), a plurality of cavities 60 are two-dimensionally arranged at regular intervals, and each of the cavities 60 is a circle or a triangle, a rectangle, a pentagon or more polygons, and the like. It may be formed in a shape. In addition, in the cavity forming step S2, a plurality of cavities 60 may extend in one direction to have a predetermined width, and thus a plurality of cavities 60 may be formed.

The stacking step S2 may include a lower electrode layer 10 formed of a conductive material, a plurality of piezoelectric ceramic 22 regions that are independent of each other, and a composite layer 20 including regions of a dielectric elastomer matrix 24 that exist in one connection phase. And sequentially stacking the upper electrode layer 30 formed of a conductive material.

More specifically, in the laminating step, first, the piezoelectric ceramics 22 are uniformly distributed in the dielectric elastomer matrix 24 so as not to be connected to each other, thereby preparing the piezoelectric ceramics 22 to form a composite, and the dielectric elastomer matrix ( 24) are prepared and mixed to form a slurry in the form of a slurry.

As the piezoelectric ceramic 22, a piezoelectric ceramic having a perovskite structure including Pb may be used as described above, and a PDMS matrix may be used as the dielectric elastomer matrix 24. In addition, in order to form a uniform composite without bubbles between the piezoelectric ceramics 22 and the dielectric elastomer matrix 24, the piezoelectric ceramics 22 and the dielectric elastomer matrix 24 are 50 to 70: 30 to 50 vol%. Preference is given to mixing in proportions.

Thereafter, the composite is molded into a film to form a composite layer 20. In order to form the composite layer 20, the slurry-type composite may be repeatedly molded and printed several times to have a desired thickness, or may be formed in a desired thickness and shape through various methods such as a doctor blade.

In addition, the stacking step (S2) is a composite formed by mixing the piezoelectric ceramic 22 and the dielectric elastomer matrix 24 in the form of a film according to another embodiment of the present invention to form a plurality of composite layers 20 The intermediate electrode layer 40 may be formed between the plurality of composite layers 20 and laminated.

As described above, when the plurality of composite layers 20 are formed by laminating, the piezoelectric properties of the entire laminate structure 50 are improved when the same voltage is applied, compared to the case where the composite layer 20 is formed as a single layer. This results in a sound pressure that is large enough.

After the composite layer 20 is formed as above, the upper electrode layer 30 and the lower electrode layer 10 are formed on the upper and lower portions of the composite layer 20 with a conductive material such as a conductive metal or a conductive polymer. The upper electrode layer 30 and the lower electrode layer 10 generally use a paste containing Ag or carbon powder, or polyaniline, polythiophene, PEDOT (poly (3,4-ethylene-dioxythiophene)), polypyrrole, PPV (polyphenylenevinylene) It forms by printing or vapor deposition using conductive polymers, derivatives thereof, organic conductors, and the like.

Thereafter, the upper electrode layer 30 and the lower electrode layer 10 are polarized by applying a voltage. In this case, when a plurality of the composite layers 20 are formed by stacking according to another embodiment of the present invention, the polarization directions coincide with each other. It is preferable to polarize the composite layer 20.

In the attaching step S3, the stacking structure 50 formed in the stacking step S2 is attached to the lower plate 70 on which the plurality of cavities 60 are formed at a predetermined depth on the upper surface. In the attaching step S3, a surface where the lower plate 70 and the laminated structure 50 disposed on the lower plate 70 contact each other may be bonded by an adhesive member such as epoxy, thereby allowing each cavity to be bonded. A portion of the lower plate 70 in which 60 is formed and the stacked structure 50 disposed on the lower plate 70 form respective unit ultrasonic waves, and each unit ultrasonic transducer forms an array. It is possible to generate sufficient sound pressure by causing constructive interference of the emitted ultrasonic waves.

While the preferred embodiments of the present invention have been described and illustrated above using specific terms, such terms are used only for the purpose of clarifying the invention, and it is to be understood that the embodiment It will be obvious that various changes and modifications can be made without departing from the spirit and scope of the invention. Such modified embodiments should not be understood individually from the spirit and scope of the present invention, but should be regarded as being within the scope of the claims of the present invention.

10: lower electrode layer 20: composite layer
22: piezoelectric ceramic 24: dielectric elastomer matrix
30: upper electrode layer 40: intermediate electrode layer
50: laminated structure 60: cavity
70: lower plate 100: ultrasonic transducer
120: carrier wave oscillator 140: audio frequency wave oscillator
150: modulator 160: power amplifier

Claims (26)

A lower plate having a plurality of cavities formed at a predetermined depth on an upper surface thereof; And
A lower electrode layer disposed on the lower plate, a lower electrode layer formed of a conductive material, a plurality of mutually independent piezoelectric ceramic regions, and a composite layer composed of a dielectric elastomer matrix region present in one connection phase, and an upper electrode layer formed of a conductive material are sequentially Ultrasonic transducer for super-directional speakers comprising a laminated structure formed by being stacked.
A lower plate having a plurality of cavities formed at a predetermined depth on an upper surface thereof; And
A lower electrode layer disposed on the lower plate, a lower electrode layer formed of a conductive material, and a plurality of stacked on the lower electrode layer and formed of a plurality of mutually independent piezoelectric ceramic regions and a dielectric elastomer matrix region present in one connection phase Ultrasonic for a super-directional speaker comprising a layered structure formed by sequentially stacking a layer, an intermediate electrode layer formed between each of the plurality of laminated composite layers and a conductive material on the plurality of stacked composite layers Transducer.
3. The method according to claim 1 or 2,
The lower plate is an ultrasonic transducer for a super-directional speaker, characterized in that formed of a metal or polymer material.
3. The method according to claim 1 or 2,
The cavity is an ultrasonic transducer for a super-directional speaker, characterized in that formed in a plurality of two-dimensional arrangement at a predetermined interval or extending in one direction to have a predetermined width.
5. The method of claim 4,
The two-dimensionally arranged cavity is an ultrasonic transducer for a super-directional speaker, characterized in that formed in any one shape selected from a circle, triangle, rectangle, pentagon and polygon.
5. The method of claim 4,
Ultrasonic transducer for super-directional speakers characterized in that the sound pressure is changed by the width, depth of the cavity and the interval between the cavity.
5. The method of claim 4,
And a portion of the lower plate on which each of the cavities is formed and a portion of the laminated structure corresponding to the portion of the lower plate form a unit ultrasonic transducer.
The method of claim 7, wherein
The unit ultrasonic transducer is an ultrasonic transducer for a super-directional speaker, characterized in that to form an array.
3. The method according to claim 1 or 2,
Ultrasonic transducer for super-directional speakers, characterized in that the contact surface of the lower plate and the laminated structure disposed on the lower plate is bonded by an adhesive member.
The method of claim 9,
Ultrasonic transducer for super-directional speaker, characterized in that the inside of the cavity is formed by a vacuum.
3. The method according to claim 1 or 2,
The piezoelectric ceramic is an ultrasonic transducer for a super-directional speaker, characterized in that the piezoelectric ceramic having a perovskite structure containing Pb.
3. The method according to claim 1 or 2,
The dielectric elastomer matrix is an ultrasonic transducer for a superdirectional speaker, characterized in that the PDMS (polydimethyl siloxane) matrix.
3. The method according to claim 1 or 2,
The piezoelectric ceramic and the dielectric elastomer matrix is an ultrasonic transducer for a speaker, characterized in that the mixture of 50 to 70: 30 to 50 vol% ratio.
3. The method according to claim 1 or 2,
The composite layer is an ultrasonic transducer for a super-directional speaker, characterized in that having a thickness of less than 100㎛.
An audio frequency wave oscillator for generating a signal in an audible frequency band;
A carrier wave oscillation source generating a signal in an ultrasonic frequency band;
A modulator for modulating a carrier wave of an ultrasonic frequency band output from the carrier wave oscillation source using a signal of an audio frequency band output from the audio frequency wave oscillation source;
A power amplifier amplifying the modulated signal output from the modulator; And
A superdirectional speaker comprising the ultrasonic transducer of claim 1 or claim 2 driven by a modulated signal amplified by the power amplifier.
Cavity forming step of forming a plurality of cavities at a constant depth in the lower plate;
A laminate in which a lower electrode layer formed of a conductive material, a plurality of mutually independent piezoelectric ceramic regions, a composite layer composed of a dielectric elastomer matrix region present in one connection phase, and an upper electrode layer formed of a conductive material are sequentially stacked to form a laminated structure step; And
And attaching the laminate structure on the bottom plate.
Cavity forming step of forming a plurality of cavities at a constant depth in the lower plate;
A lower electrode layer formed of a conductive material, a plurality of composite layers composed of a plurality of mutually independent piezoelectric ceramic regions and a dielectric elastomer matrix region present in one connection phase, an intermediate electrode layer and a conductive material respectively formed between the plurality of composite layers. A stacking step of sequentially stacking the upper electrode layers formed to form a stack structure; And
And attaching the laminate structure on the bottom plate.
18. The method according to claim 16 or 17,
In the cavity forming step, the lower plate is an ultrasonic transducer manufacturing method for a super-directional speaker, characterized in that formed of a metal or polymer material.
18. The method according to claim 16 or 17,
In the cavity forming step, the plurality of cavities are ultrasonic transducers manufacturing method for a super-directional speaker, characterized in that formed in a plurality of two-dimensional arrangement at a predetermined interval.
The method of claim 19,
The cavity is a method of manufacturing an ultrasonic transducer for a super-directional speaker, characterized in that formed in any one shape selected from a circle, triangle, square, pentagon and polygon.
18. The method according to claim 16 or 17,
In the cavity forming step, the cavity is an ultrasonic transducer manufacturing method for a super-directional speaker, characterized in that is formed extending in one direction to have a predetermined width.
18. The method according to claim 16 or 17,
The piezoelectric ceramic in the laminating step is a piezoelectric ceramic piezoelectric perovskite (perovskite) structure, characterized in that the transducer for producing a super-directional speaker for the speaker.
18. The method according to claim 16 or 17,
The dielectric elastomer matrix in the laminating step is a polydimethyl siloxane (PDMS) matrix manufacturing method of the ultrasonic transducer for a super-directional speaker.
18. The method according to claim 16 or 17,
In the lamination step, the piezoelectric ceramic and the dielectric elastomer matrix is 50 ~ 70: 30 ~ 50 vol% Ultrasonic transducer manufacturing method for a super-directional speaker, characterized in that the mixture.
18. The method according to claim 16 or 17,
In the attaching step, the lower plate and the surface in which the laminated structure disposed on the lower plate is in contact with the ultrasonic transducer manufacturing method for a super-directional speaker, characterized in that bonded by an adhesive member.
18. The method according to claim 16 or 17,
And a polarization step of polarizing by applying a voltage to the upper electrode layer and the lower electrode layer.

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