JP2012015757A - Oscillation device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillation device where it is possible to install a piezoelectric oscillator without fear of a short circuit using a simple structure.SOLUTION: In an electroacoustic transducer 100, a front face electrode layer 112 is continuously formed on a front face, a side face, and a part of a rear face of a piezoelectric ceramic 111 and a rear face electrode layer 113 is formed on the rear face of the piezoelectric ceramic 111 in an area where the rear face electrode layer 113 does not interfere with the front face electrode layer 112. A first wiring layer 121 formed on a front face of an elastic diaphragm 130 conducts with the front face electrode layer 112 without conducting with the rear face electrode layer 113, a second wiring layer 122 formed on the front face of the elastic diaphragm 130 conducts with the rear face electrode layer 113 without conducting with the front face electrode layer 112, and an insulation material 140 fills a gap between the first wiring layer 121 and the second wiring layer 122 and a gap between the front face electrode layer 112 and the rear face electrode layer 113.

Description

  The present invention relates to an oscillating device including a piezoelectric vibrator, and more particularly to an oscillating device in which a piezoelectric vibrator is mounted on a vibrating member, and an electronic apparatus having the oscillating 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 oscillators and electronic devices are known (Patent Document 4).

No. 2007-026736 Table 2007-083497 Japanese Patent Laid-Open No. 03-270282 JP 2001-298344 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.

  However, in order for the piezoelectric layer to act as described above, it is necessary to apply an electric field to the front and back surfaces. For this reason, usually, electrode layers are individually formed on the front and back surfaces of the piezoelectric layer.

  However, in this case, it is necessary to connect wiring to the front and back surfaces of the piezoelectric vibrator with lead wires or the like, which is complicated to manufacture and the lead wires inhibit vibration of the piezoelectric vibrator.

  The present invention has been made in view of the above-described problems, and provides an oscillation device in which a piezoelectric vibrator can be wired with a simple structure, and an electronic apparatus using the oscillation device.

  The oscillation device of the present invention has a piezoelectric layer that oscillates in a polarization direction by a piezoelectric action, a surface electrode layer that is continuously formed on the surface, side surfaces, and part of the back surface of the piezoelectric layer, and does not interfere with the surface electrode layer. Without being electrically connected to the back electrode layer, the back electrode layer formed on the back surface of the piezoelectric layer, the vibrating member on which the piezoelectric vibrator composed of the piezoelectric layer, the front electrode layer, and the back electrode layer is mounted on the surface A first wiring layer formed on the surface of the vibrating member in a shape that conducts to the front electrode layer, and a second formed on the surface of the vibrating member in a shape that conducts to the back electrode layer without conducting to the front electrode layer A wiring layer; and an insulating material filling the gap between the first wiring layer and the second wiring layer and the gap between the front electrode layer and the back electrode layer.

  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 the oscillation device of the present invention, the first wiring layer formed on the surface of the vibration member is electrically connected to the surface electrode layer without being connected to the back electrode layer, and the second wiring formed on the surface of the vibration member The layer is connected to the back electrode layer without being connected to the front electrode layer, and the insulating material fills the gap between the first wiring layer and the second wiring layer and the gap between the front electrode layer and the back electrode layer. . For this reason, it is possible to wire the piezoelectric vibrator with a simple structure without worrying about a short circuit.

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. The structure of a piezoelectric vibrator is shown, (a) is a schematic longitudinal front view, (b) is a schematic bottom view.

  A first embodiment of the present invention will be described below with reference to FIG. 1 and FIG. As shown in FIG. 1, the electroacoustic transducer 100 according to the present embodiment includes a piezoelectric ceramic 111 that is a piezoelectric layer that oscillates in a polarization direction by piezoelectric action, and a front surface, a side surface, and a back surface of the piezoelectric ceramic 111. The surface electrode layer 112 continuously formed in a part, the back electrode layer 113 formed on the back surface of the piezoelectric ceramic 111 within a range not interfering with the surface electrode layer 112, the piezoelectric ceramic 111 and the surface electrode layer 112 And an elastic diaphragm 130 that is a vibration member on which a piezoelectric vibrator 110 composed of a back electrode layer 113 is mounted on the surface, and an elastic diaphragm 130 in a shape that conducts to the front electrode layer 112 without conducting to the back electrode layer 113. The first wiring layer 121 formed on the surface of the elastic electrode plate 130 and the elastic diaphragm 130 in a shape that is electrically connected to the back electrode layer 113 without being electrically connected to the surface electrode layer 112. A second wiring layer 122 formed on the surface; an insulating material 140 filling a gap between the first wiring layer 121 and the second wiring layer 122 and a gap between the front electrode layer 112 and the back electrode layer 113; Have

  More specifically, in the electroacoustic transducer 100 of the present embodiment, as shown in FIG. 2, the piezoelectric ceramic 111, the front electrode layer 112, and the back electrode layer 113 include a flat rectangular parallelepiped piezoelectric vibrator 110. Is formed.

  A surface electrode layer 112 is formed on the surface of the piezoelectric ceramic 111 with the left edge in the drawing blank. As shown in FIG. 2B, the surface electrode layer 112 is formed up to a part on the right side of the back surface of the piezoelectric ceramic 111 via the right side surface of the figure. The back electrode layer 113 is formed on the back surface of the piezoelectric ceramic 111 with the right edge in the figure blank.

  The insulating material 140 is made of an insulating adhesive, and bonds the piezoelectric vibrator 110 to the surface of the elastic diaphragm 130. On the other hand, the front electrode layer 112 and the first wiring layer 121 are bonded by a conductive adhesive (not shown), and the back electrode layer 113 and the second wiring layer 122 are also bonded by a conductive adhesive. Yes. Such an adhesive is made of, for example, a conductive resin in which conductive particles are dispersed in an insulating resin.

  The elastic diaphragm 130 includes a resin layer 131 located on the front surface and a metal layer 132 located on the back surface. For this reason, the elastic diaphragm 130 has necessary elasticity on the surface by the resin layer 131 while having the necessary elasticity by the metal layer 132.

  The elastic diaphragm 130 is formed in a circular or rectangular planar shape, and an outer peripheral portion is supported by a frame 133. A first wiring layer 121 and a second wiring layer 122 are formed on the surface of the elastic diaphragm 130 with printed wiring or the like.

  The first / second wiring layers 121 and 122 are connected to the control unit 150 which is an oscillation driving unit by, for example, a lead wire 151. 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 150.

  The piezoelectric ceramic 111 is not particularly limited, although lead zirconate titanate (PZT) or the like is used. 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, front / back electrode layers 112 and 113 are formed in order to generate an electric field. The front / back electrode layers 112 and 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 thicknesses of the front / back electrode layers 112 and 113 are 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. In addition, as a technique for forming the thin film-like front / back electrode layers 112 and 113, there is a method of applying 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 front / rear electrode layers 112 and 113 exceeds 100 μm, there is no particular problem in manufacturing, but the front / rear electrode layers 112 and 113 serve as constraining surfaces with respect to the piezoelectric ceramic 111 and energy conversion is performed. There is a problem that reduces efficiency.

  The front electrode layer 112 is not formed on the left surface edge of the piezoelectric ceramic 111 in order to prevent conduction with the back electrode layer 113 by melting due to migration.

  As for the piezoelectric vibrator 110 of the electroacoustic transducer 100 of this Embodiment, the one main surface is restrained by the elastic diaphragm 130. The elastic diaphragm 130 propagates the vibration generated from the piezoelectric vibrator 110 to the outside.

  At the same time, the elastic diaphragm 130 has a function of adjusting the basic resonance frequency of the piezoelectric vibrator 110. 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 elastic diaphragm 130. 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 thickness of the elastic diaphragm 130.

  Conventionally, since the basic resonance frequency was controlled by the shape and material of the piezoelectric vibrator 110, there were problems in design constraints, cost, and reliability. Since the plate 130 can be easily adjusted to a desired fundamental resonance frequency, the industrial value is great.

  The elastic diaphragm 130 is not particularly limited as long as it is a material having a high modulus of elasticity with respect to a ceramic that is a brittle material such as 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 130 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 130 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 130 is excessively low or excessively high, there is a problem that characteristics and reliability are impaired as a mechanical vibrator.

  Here, the manufacturing method of the electroacoustic transducer 100 of this Embodiment is demonstrated below. First, in the piezoelectric vibrator 110, a piezoelectric ceramic 111 having an outer diameter = φ3 mm and a thickness = 200 μm is formed, and a surface electrode layer 112 and a back electrode layer 113 having a thickness of 8 μm are formed on both surfaces thereof.

  The piezoelectric ceramic 111 is made of lead zirconate titanate ceramic, and the front / back electrode layers 112 and 113 are made of silver / palladium alloy (weight ratio 70%: 30%). The piezoelectric ceramic 111 was manufactured by a green sheet method, fired at 1100 ° C. for 2 hours in the atmosphere, and then the piezoelectric ceramic 111 was subjected to polarization treatment. An epoxy adhesive is used for bonding the piezoelectric vibrator 110 and the elastic diaphragm 130.

  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 the front electrode layer 112 and the back electrode layer 113 are formed on each main surface 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). In the piezoelectric vibrator 110 configured as described above, when an alternating voltage is applied from the control unit 150 to the front electrode layer 112 and the back electrode layer 113 and an alternating electric field is applied, both main surfaces are simultaneously expanded or A radial expansion and contraction movement (diameter expansion movement) is performed.

  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 130 uses the elastic effect to generate vertical vibrations due to inertial action and restoring action, thereby generating sound waves.

  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, the electroacoustic transducer 100 according to the present embodiment is small and can reproduce a large volume. 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.

  In the electroacoustic transducer 100 according to the present embodiment, the first wiring layer 121 formed on the surface of the elastic diaphragm 130 is electrically connected to the surface electrode layer 112 without being electrically connected to the back electrode layer 113. The second wiring layer 122 formed on the surface of the elastic diaphragm 130 is electrically connected to the back electrode layer 113 without being electrically connected to the surface electrode layer 112.

  For this reason, the first wiring layer 121 and the second wiring layer 122 formed on the surface by the printed wiring of the elastic diaphragm 130 can be connected to the front electrode layer 112 and the back electrode layer 113 of the piezoelectric vibrator 110. Therefore, the structure is simple and the productivity is good.

  Nevertheless, the insulating material 140 fills the gap between the first wiring layer 121 and the second wiring layer 122 and the gap between the front electrode layer 112 and the back electrode layer 113. For this reason, the piezoelectric vibrator 110 can be wired with a simple structure without worrying about a short circuit.

  In addition, the insulating material 140 bonds the piezoelectric vibrator 110 to the surface of the elastic diaphragm 130. Therefore, the piezoelectric vibrator 110 can be bonded to the elastic diaphragm 130 at the same time while preventing a short circuit between the first wiring layer 121 and the second wiring layer 122 and a short circuit between the front electrode layer 112 and the back electrode layer 113. it can.

  The front electrode layer 112 and the first wiring layer 121 are bonded with a conductive adhesive, and the back electrode layer 113 and the second wiring layer 122 are bonded with a conductive adhesive. For this reason, the piezoelectric vibrator 110 can be bonded to the elastic diaphragm 130 at the same time while the front electrode layer 112 and the first wiring layer 121 are conducted and the back electrode layer 113 and the second wiring layer 122 are conducted. .

  Furthermore, the elastic diaphragm 130 includes a resin layer 131 located on the front surface and a metal layer 132 located on the back surface. For this reason, while the required elasticity is ensured by the metal layer 132, the resin layer 131 also ensures the necessary insulation on the surface.

  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, it illustrated that the 2nd wiring layer 122 was formed to center vicinity of the piezoelectric vibrator 110 in the figure. However, since this only needs to be conducted to the back electrode layer 113 of the piezoelectric vibrator 110, it may be formed only up to the vicinity of the left end of the piezoelectric vibrator 110, or may be formed over the entire lower surface of the back electrode layer 113. (Both not shown).

  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 Front Electrode Layer 113 Back Electrode Layer 121 First Wiring Layer 122 Second Wiring Layer 130 Elastic Vibration Plate 131 Resin Layer 132 Metal Layer 133 Frame 140 Insulating Material 150 Control Unit 151 Lead line

Claims (9)

A piezoelectric layer that oscillates in the polarization direction due to piezoelectric action;
A surface electrode layer formed continuously on the surface, side surface and part of the back surface of the piezoelectric layer;
A back electrode layer formed on the back surface of the piezoelectric layer within a range not interfering with the front electrode layer;
A vibrating member having a piezoelectric vibrator comprising the piezoelectric layer, the front electrode layer, and the back electrode layer mounted on the surface;
A first wiring layer formed on the surface of the vibrating member in a shape that is electrically connected to the front electrode layer without being electrically connected to the back electrode layer;
A second wiring layer formed on the surface of the vibrating member in a shape conducting with the back electrode layer without conducting with the front electrode layer;
An insulating material filling a gap between the first wiring layer and the second wiring layer and a gap between the front electrode layer and the back electrode layer;
An oscillation device having   The oscillation device according to claim 1, wherein the insulating material adheres the piezoelectric vibrator to a surface of the vibrating member. The surface electrode layer and the first wiring layer are bonded with a conductive adhesive,
The oscillation device according to claim 1, wherein the back electrode layer and the second wiring layer are bonded with a conductive adhesive.   The oscillation device according to any one of claims 1 to 3, wherein the vibration member includes a resin layer located on a front surface and a metal layer located on a back surface.   The oscillation device according to claim 1, wherein the piezoelectric layer is made of a piezoelectric ceramic.   The oscillation device according to any one of claims 1 to 5, 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 6, wherein the piezoelectric vibrator oscillates an ultrasonically modulated ultrasonic wave. The oscillation device according to any one of claims 1 to 7,
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 7,
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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