JP2012015758A - Oscillator, method for manufacturing the same and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a oscillator which realizes both of the increase of an output level of a sound pressure and the miniaturization of a device.SOLUTION: An electro-acoustic transducer 100 comprises a piezoelectric ceramic 111 and an electrode plate 113 joined to a rear face of the piezoelectric ceramic 111. For instance, the piezoelectric ceramic 111 formed of a piezoelectric ceramic can be formed into a predetermined shape while preventing damage by dividing a large piezoelectric ceramic that becomes the piezoelectric ceramic 111 into a predetermined shape after the large electrode plate 113 is joined to the rear face of the piezoelectric ceramic. Such a piezoelectric vibrator 110 is inserted into a recessed part 121 of an elastic diaphragm 120 and joined thereto, thereby the electrode plate 113 of the piezoelectric vibrator 110 can function as a part of the elastic diaphragm 120. Accordingly, both of the increase of the output level of the sound pressure and the miniaturization of the device can be achieved.

Description

  The present invention relates to an oscillation device including a piezoelectric vibrator, and more particularly to an oscillation device in which a piezoelectric vibrator is mounted on a vibration member, a method for manufacturing the oscillation device, and an electronic apparatus having the oscillation device.

  In recent years, demand for portable electronic devices such as mobile phones and notebook computers has been increasing. In such an electronic device, development of a thin portable terminal whose commercial value is an acoustic function such as a videophone, a video playback, and a hands-free phone is being promoted. Under such development, there is an increasing demand for high-quality sound, small size, and thinness for electroacoustic transducers (speaker devices) that are acoustic components.

  Conventionally, electrodynamic electroacoustic transducers have been used as electroacoustic transducers in electronic devices such as mobile phones. This electrodynamic electroacoustic transducer is composed of a permanent magnet, a voice coil, and a diaphragm.

  However, there is a limit to reducing the thickness of electrodynamic electroacoustic transducers due to their operating principles and structures. On the other hand, Patent Documents 1 and 2 describe using a piezoelectric vibrator as an electroacoustic transducer.

  As another example of an oscillation device using a piezoelectric vibrator, in addition to a speaker device, a sound wave sensor that detects a distance to an object using a sound wave oscillated from the piezoelectric vibrator (see Patent Document 3). Various oscillation devices and electronic devices are known (Patent Documents 4 and 5).

No. 2007-026736 Table 2007-083497 JP-A-3-270282 JP 2000-278895 A JP 2004-195432 A

  An oscillating device using a piezoelectric vibrator generates a vibration amplitude by an electrostrictive action by inputting an electric signal by using a piezoelectric effect of a piezoelectric layer. The electrodynamic electroacoustic transducer generates vibration by a piston-type forward / backward movement, whereas the oscillation device using the piezoelectric vibrator has a bending-type vibration state and thus has a small amplitude. For this reason, it is superior in reducing the thickness of the electrodynamic electroacoustic transducer described above.

  Thus, although development of a highly efficient small electroacoustic transducer is necessary, the transducer which satisfy | fills a request | requirement has not been made yet. Therefore, a method for obtaining a highly efficient piezoelectric actuator by increasing the electric field strength by using a thin piezoelectric ceramic has been studied. However, since the piezoelectric ceramic is a brittle material, damage such as cracking or chipping is produced during manufacturing. Occurred and had problems such as a decrease in yield.

  The present invention has been made in view of the above-described problems, and provides an oscillation device that realizes both an increase in sound pressure level of output and a reduction in size of the device, and an electronic device using the oscillation device. Is.

  The oscillation device according to the present invention includes a piezoelectric vibrator in which an electrode layer is formed on the surface of a piezoelectric layer and an electrode plate is bonded to the back surface, and a piezoelectric vibrator is inserted into a recess formed on the surface and bonded. And a vibrating member.

  The manufacturing method of the present invention is a method of manufacturing an oscillation device of the present invention, in which a large electrode plate is bonded to the back surface of a large piezoelectric ceramic, and the large piezoelectric ceramic bonded to the large electrode plate is shaped into a predetermined shape. The piezoelectric ceramic electrode plate is inserted into and joined to the concave portion of the predetermined shape of the vibration member.

  A first electronic device of the present invention includes the oscillation device of the present invention and an oscillation drive unit that causes the oscillation device to output an audible sound wave.

  A second electronic device according to the present invention includes an oscillation device according to the present invention, an ultrasonic detection unit that detects an ultrasonic wave oscillated from the oscillation device and reflected by the measurement object, and from the detected ultrasonic wave to the measurement object. And a distance measuring unit for calculating the distance.

  In addition, although the manufacturing method of this invention has described several manufacturing processes in order, the order of the description does not limit the order which performs several manufacturing processes. For this reason, when implementing the manufacturing method of this invention, the order of the some manufacturing process can be changed in the range which does not interfere in content.

  Furthermore, the manufacturing method of the present invention is not limited to being executed at a timing when a plurality of manufacturing steps are individually different. For this reason, another manufacturing process may occur during the execution of a certain manufacturing process, or a part or all of the execution timing of a certain manufacturing process and the execution timing of another manufacturing process may overlap.

  The electrode layer in the present invention means a layer film made of metal or the like formed on the surface of an object by thin film technology, and the electrode plate is made of metal formed independently by mechanical technology. It means board material.

  In the oscillation device of the present invention, since the metal plate is bonded to the back surface of the piezoelectric layer, for example, the large metal plate is bonded to the back surface of the large piezoelectric ceramic serving as the piezoelectric layer and then divided into a predetermined shape. The piezoelectric layer made of piezoelectric ceramic can be formed into a predetermined shape while preventing damage. Since such a piezoelectric vibrator is inserted into and joined to the recess of the vibration member, the metal plate of the piezoelectric vibrator can function as a part of the vibration member. For this reason, both an increase in the sound pressure level of the output and a reduction in the size of the device can be realized.

It is a typical longitudinal section front view showing the structure of the electroacoustic transducer which is the oscillation device of the first embodiment of the present invention. It is a typical vertical front view which shows a part of manufacturing method of an electroacoustic transducer. It is a typical top view which shows a part of manufacturing method of an electroacoustic transducer.

  A first embodiment of the present invention will be described below with reference to FIG. 1 and FIG. As shown in FIG. 1, an electroacoustic transducer 100 that is an oscillation device of the present embodiment has an electrode layer 112 formed on the surface of a piezoelectric ceramic 111 that is a piezoelectric layer and an electrode plate 113 bonded to the back surface. And the elastic vibration plate 120 which is a vibration member in which the piezoelectric vibrator 110 is inserted and joined to a recess 121 formed on the surface.

  More specifically, the outer shape of the electrode plate 113 of the piezoelectric vibrator 110 and the inner shape of the recess 121 of the elastic vibration plate 120 are formed in substantially the same shape. The elastic diaphragm 120 is formed with a plate thickness of 180 μm or more and 200 μm or less, and the recess 121 is formed with a depth of 100 μm or more and 120 μm or less.

  Therefore, the electrode plate 113 of the piezoelectric vibrator 110 is formed with a plate thickness of 100 μm or more and 120 μm or less. As will be described in detail later, the piezoelectric vibrator 110 is divided after the large electrode plate 113 is bonded to the back surface of the large piezoelectric ceramic.

  In the electroacoustic transducer 100 according to the present embodiment, a control unit 130 that is an oscillation drive unit is connected to the electrode layer 112 and the electrode plate 113 of the piezoelectric vibrator 110. An electric field that causes the piezoelectric vibrator 110 to oscillate in an audible region or an ultrasonic region is applied from the control unit 130.

  The front electrode layer 112 and the back electrode plate 113 are connected to the control unit 130 by, for example, lead wires 131. In addition, the electrode plate 113 on the back surface can be connected to the control unit 130 by a metal elastic diaphragm 120 and a lead wire 131, for example.

  Further, as the piezoelectric ceramic 111, lead zirconate titanate (PZT) or the like is used, but is not particularly limited. The thickness of the piezoelectric ceramic 111 is not particularly limited, but is preferably 10 μm or more and 500 μm or less.

  For example, when a thin film having a thickness of less than 10 μm is used as a ceramic material that is a brittle material, chipping or breakage occurs due to weak mechanical strength during handling, making handling difficult.

  Further, when the piezoelectric ceramic 111 having a thickness exceeding 500 μm is used, the conversion efficiency for converting electrical energy into mechanical energy is remarkably reduced, and sufficient performance as the electroacoustic transducer 100 cannot be obtained.

  In general, in the piezoelectric ceramic 111 that generates an electrostrictive effect by inputting an electric signal, the conversion efficiency depends on the electric field strength. Since the electric field strength is expressed by the thickness / input voltage with respect to the polarization direction, an increase in thickness inevitably causes a decrease in conversion efficiency.

  In the piezoelectric vibrator 110 of the present embodiment, an electrode layer 112 and an electrode plate 113 are formed on the front surface and the back surface in order to generate an electric field. The electrode layer 112 and the electrode plate 113 are not particularly limited as long as they are electrically conductive materials, but it is preferable to use silver or silver / palladium. Silver is used as a general-purpose electrode layer with low resistance, and has advantages in manufacturing process and cost.

  Further, since silver / palladium is a low-resistance material excellent in oxidation resistance, there is an advantage from the viewpoint of reliability. Further, the thickness of the electrode layer 112 is not particularly limited, but the thickness is preferably 1 μm or more and 50 μm or less.

  For example, when the thickness is less than 1 μm, since the film thickness is thin, it cannot be uniformly formed, and conversion efficiency may be reduced. As a technique for forming the thin-film electrode layer 112, there is a method of applying the paste in a paste form.

  However, since the surface state of the polycrystal such as the piezoelectric ceramic 111 is a textured surface, the wet state at the time of application is poor, and there is a problem that a uniform electrode film cannot be formed without a certain thickness.

  On the other hand, when the film thickness of the electrode layer 112 exceeds 100 μm, there is no particular problem in manufacturing, but there is a problem that the electrode layer 112 becomes a constraining surface with respect to the piezoelectric ceramic 111 and energy conversion efficiency is lowered. .

  As for the piezoelectric vibrator 110 of the electroacoustic transducer 100 of this Embodiment, the one main surface is restrained by the elastic diaphragm 120. The elastic diaphragm 120 propagates the vibration generated from the piezoelectric vibrator 110 to the outside.

  At the same time, the elastic diaphragm 120 has a function of adjusting the fundamental resonance frequency of the piezoelectric vibrator 110. At this time, the electrode plate 113 on the back surface also functions as a part of the elastic diaphragm 120. The fundamental resonance frequency f of the mechanical electroacoustic transducer 100 depends on the load weight and compliance, as shown by the following equation.

[Equation 1]
f = 1 / (2πL√ (mC))
“M” is mass and “C” is compliance.

  In other words, since the compliance is the mechanical rigidity of the electroacoustic transducer 100, this means that the fundamental resonance frequency can be controlled by controlling the rigidity of the piezoelectric vibrator 110.

  For example, the fundamental resonance frequency can be shifted to a low range by selecting a material having a high elastic modulus and reducing the thickness of the electrode plate 113 and the elastic diaphragm 120. On the other hand, the fundamental resonance frequency can be shifted to a high range by selecting a material having a high elastic modulus or increasing the thicknesses of the electrode plate 113 and the elastic diaphragm 120.

  Conventionally, since the basic resonance frequency was controlled by the shape and material of the piezoelectric vibrator 110, there were problems in design restrictions, cost, and reliability. However, as in the present invention, the electrode plate which is a constituent member Since it can be easily adjusted to a desired fundamental resonance frequency by changing 113 and the elastic diaphragm 120, the industrial value is great.

  The elastic diaphragm 120 is not particularly limited as long as it is a material having a high elastic modulus with respect to a ceramic that is a brittle material such as a metal or resin, but a general-purpose material such as phosphor bronze or stainless steel from the viewpoint of workability and cost. Is used.

  The thickness of the elastic diaphragm 120 is preferably 5 μm or more and 1000 μm or less. When the thickness is less than 5 μm, there is a problem that mechanical strength is weak, the function as a restraining member is impaired, and the mechanical vibration characteristics of the piezoelectric vibrator 110 are varied between production lots due to a decrease in processing accuracy.

  Further, when the thickness exceeds 1000 μm, there is a problem that the restraint on the piezoelectric vibrator 110 due to the increase in rigidity is strengthened and the vibration displacement amount is attenuated. The elastic diaphragm 120 of the present embodiment preferably has a longitudinal elastic modulus, which is an index indicating the rigidity of the material, of 1 GPa or more and 500 GPa or less.

  As described above, when the rigidity of the elastic diaphragm 120 is excessively low or excessively high, there is a problem that characteristics and reliability are impaired as a mechanical vibrator. Therefore, in the present embodiment, as described above, the elastic diaphragm 120 is formed with a plate thickness of 180 μm or more and 200 μm or less, and the recess 121 is formed with a depth of 100 μm or more and 120 μm or less.

  Here, the manufacturing method of the electroacoustic transducer 100 of this Embodiment is demonstrated below. First, as shown in FIG. 2, the piezoelectric vibrator 110 forms a large piezoelectric ceramic 111 having a thickness of 200 μm.

  The piezoelectric ceramic 111 is made of a lead zirconate titanate ceramic, and the electrode layer 112 and the electrode plate 113 are made of a silver / palladium alloy (weight ratio 70%: 30%). The piezoelectric ceramic 111 is manufactured by the green sheet method, fired in the atmosphere at 1100 ° C. for 2 hours, and then the piezoelectric ceramic 111 is subjected to polarization treatment.

  Next, a large electrode plate 113 having a thickness of 100 μm or more and 120 μm or less is adhered to the back surface of the completed large piezoelectric ceramic 111 with a conductive adhesive. As shown in FIG. 2 and FIG. 3, such a large piezoelectric ceramic 111 and electrode plate 113 are joined to each other by dicing using a dicer (not shown). Divide into

  At this time, since the electrode plate 113 having low brittleness is integrally joined to the entire back surface of the piezoelectric ceramic 111 having high brittleness, damage to the piezoelectric ceramic 111 to be divided is prevented.

  The electrode layer 112 is formed on the surface of the piezoelectric ceramic 111 as described above by a thin film technique such as sputtering or paste. Note that the electrode layer 112 may be formed before being divided. Further, a recess 121 having a predetermined shape is formed in the elastic diaphragm 120, and the piezoelectric vibrator 110 is joined to the recess 121 with an epoxy adhesive.

  Further, in this configuration, ultrasonic waves are oscillated in order to realize sound reproduction that can protect privacy. Here, the principle of a parametric speaker that demodulates modulated ultrasonic waves into audible sounds is used. The piezoelectric vibrator 110 oscillates an ultrasonic wave having a frequency of 20 kHz or more.

  Here, AM (Amplitude Modulation) modulation, DSB (Double Sideband) modulation, SSB (Single-Sideband modulation) modulation, FM (Frequency Modulation) modulated ultrasonic waves are emitted into the air, and the ultrasonic waves enter the air. Sound reproduction is performed on the principle that audible sound appears due to nonlinear characteristics when propagating.

  Non-linearity includes a phenomenon in which the flow changes from laminar flow to turbulent flow when the Reynolds number indicated by the ratio between the inertial action and viscous action of the flow increases. That is, since the sound wave is slightly disturbed in the fluid, the sound wave propagates in a non-linear manner.

  However, the amplitude of the sound wave in the low frequency band is nonlinear, but the amplitude difference is very small, and is usually handled as a phenomenon of linear theory. On the other hand, nonlinearity can be easily observed with ultrasonic waves, and when radiated into the air, harmonics accompanying the nonlinearity are remarkably generated.

  In summary, sound waves are a dense state where molecular groups are mixed in the air, and if it takes time for the air molecules to recover rather than compress, the air that cannot be recovered after compression is continuously propagated air. This is the principle that an audible sound is generated by colliding with a molecule and generating a shock wave.

  Next, the operation principle of the piezoelectric vibrator 110 will be described. The piezoelectric ceramic 111 is composed of a piezoelectric plate having two main surfaces as described above, and an electrode layer 112 and an electrode plate 113 are formed on each of the main surfaces of the piezoelectric ceramic 111.

  Although the polarization direction of the piezoelectric ceramic 111 is not particularly limited, in the electroacoustic transducer of the present embodiment, it is upward in the vertical direction (thickness direction of the piezoelectric vibrator 110). The piezoelectric vibrator 110 configured as described above has such a radius that both main surfaces simultaneously expand or contract when an alternating voltage is applied to the electrode layer 112 and the electrode plate 113 and an alternating electric field is applied. Performs direction expansion and contraction (diameter expansion).

  In other words, the piezoelectric vibrator 110 performs a motion that repeats a first deformation mode in which the main surface expands and a second deformation mode in which the main surface contracts. By repeating such a motion, the elastic diaphragm 120 uses the elastic effect to generate vertical vibration due to inertial action and restoring action, thereby generating sound waves.

  However, although the concave portion 121 is formed in the elastic diaphragm 120, the electrode plate 113 is located in the concave portion 121. For this reason, the electrode plate 113 of the piezoelectric vibrator 110 functions as a part of the elastic vibration plate 120.

  In the configuration of the present invention, the piezoelectric vibrator 110 oscillates an ultrasonic wave having a frequency of 20 kHz or more. Sound reproduction is performed based on the principle of a so-called parametric speaker that oscillates FM or AM-modulated ultrasonic waves and demodulates the modulated wave to reproduce audible sound using the nonlinear state (dense / dense state) of air. This propagates sound waves using the high directivity that is characteristic of ultrasonic waves, and it is possible to realize a privacy sound source that can only be heard by the user.

  As described above, in the electroacoustic transducer 100 according to the present embodiment, since the electrode plate 113 is joined to the back surface of the piezoelectric ceramic 111, the large electrode plate 113 is mounted on the back surface of the large piezoelectric ceramic that becomes the piezoelectric ceramic 111. The piezoelectric ceramic 111 made of a piezoelectric ceramic can be formed in a predetermined shape while preventing damage and by dividing into a predetermined shape after bonding.

  Since such a piezoelectric vibrator 110 is inserted into and joined to the recess 121 of the elastic diaphragm 120, the electrode plate 113 of the piezoelectric vibrator 110 can function as a part of the elastic diaphragm 120. In addition, since the position of the piezoelectric vibrator 110 is regulated by the recess 121, the piezoelectric vibrator 110 can be easily and accurately disposed at a desired position of the elastic diaphragm 120.

  For this reason, both an increase in the sound pressure level of the output and a reduction in the size of the device can be realized. Further, since ultrasonic waves are used, directivity is narrow, and industrial value is great in terms of protecting user privacy.

  That is, the electroacoustic transducer 100 according to the present embodiment has higher rectilinearity of the sound wave than the conventional electroacoustic transducer, and can selectively propagate the sound wave to a position to be transmitted to the user. In summary, the electroacoustic transducer 100 according to the present embodiment can be used as a sound source of an electronic device (for example, a mobile phone, a notebook personal computer, a small game device, etc.). In addition, since the electroacoustic transducer 100 can be prevented from being enlarged and the acoustic characteristics are improved, the electroacoustic transducer 100 can be suitably used for portable electronic devices.

  The present invention is not limited to the present embodiment, and various modifications are allowed without departing from the scope of the present invention. For example, in the present embodiment, the piezoelectric ceramic 111 such as lead zirconate titanate (PZT) is used as the piezoelectric element of the piezoelectric vibrator 110.

  However, the piezoelectric element is not particularly limited as long as it has a piezoelectric effect, and a material having high electromechanical conversion efficiency, for example, a material such as barium titanate (BaTiO 3) can be used.

  Moreover, in the said form, the mobile telephone etc. which output an audio | voice with the electroacoustic transducer 100 grade | etc., Were assumed as an electric equipment. However, as an electronic device, an electroacoustic transducer 100 that is an oscillation device, an ultrasonic detection unit that detects an ultrasonic wave oscillated from the electroacoustic transducer 100 and reflected by a measurement object, and a detected ultrasonic wave A sonar (not shown) having a distance measuring unit that calculates the distance from the sound wave to the measurement object can also be implemented.

  Needless to say, the above-described plurality of embodiments and the plurality of modifications can be combined within a range in which the contents do not conflict with each other. In the above-described embodiment, the structure of each part has been specifically described. However, the structure and the like can be variously changed within a range that satisfies the present invention.

100 Electroacoustic Transducer 110 Piezoelectric Vibrator 111 Piezoelectric Ceramic 112 Electrode Layer 113 Electrode Plate 120 Elastic Vibrating Plate 121 Recess 130 Control Unit 131 Lead Wire

Claims (12)

A piezoelectric vibrator having an electrode layer formed on the surface of the piezoelectric layer and an electrode plate bonded to the back surface;
A vibration member in which the piezoelectric vibrator is inserted and joined to a recess formed on the surface;
An oscillation device having   The oscillation device according to claim 1, wherein an outer shape of the electrode plate of the piezoelectric vibrator and an inner shape of the concave portion of the vibration member are formed in substantially the same shape.   3. The oscillation device according to claim 1, wherein the vibration member is formed with a plate thickness of 180 μm or more and 200 μm or less, and the recess is formed with a depth of 100 μm or more and 120 μm or less.   The oscillation device according to claim 3, wherein the electrode plate of the piezoelectric vibrator is formed with a plate thickness of 100 μm or more and 120 μm or less.   The oscillation device according to claim 1, wherein the piezoelectric layer is made of a piezoelectric ceramic. The piezoelectric vibrator is divided after the separate large electrode plate is joined to the back surface of the large piezoelectric ceramic,
The oscillation device according to claim 5, wherein the electrode layer is formed on a surface of the piezoelectric ceramic by a thin film technique.   The oscillation device according to any one of claims 1 to 6, wherein a frequency of an ultrasonic wave oscillated by the piezoelectric vibrator exceeds 20 kHz.   The oscillation device according to any one of claims 1 to 7, wherein the piezoelectric vibrator oscillates an ultrasonically modulated ultrasonic wave. A method for manufacturing an oscillation device according to any one of claims 1 to 14,
Bonding the large electrode plate to the back of the large piezoelectric ceramic,
Dividing the large piezoelectric ceramic to which the large electrode plate is bonded into a predetermined shape
A manufacturing method in which the electrode plate of the piezoelectric ceramic is inserted into and joined to the concave portion of the vibration member having a predetermined shape. Forming the vibration member having the concave portion of a predetermined shape formed on the surface;
The manufacturing method according to claim 9, wherein the electrode plate of the piezoelectric ceramic is inserted and joined into the concave portion of the vibration member. The oscillation device according to any one of claims 1 to 9,
An oscillation drive unit for outputting an audible sound wave to the oscillation device;
Electronic equipment having The oscillation device according to any one of claims 1 to 9,
An ultrasonic detector for detecting the ultrasonic wave oscillated from the oscillation device and reflected by the measurement object;
A distance measuring unit for calculating a distance from the detected ultrasonic wave to the measurement object;
Electronic equipment having

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