JP2012015759

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DESCRIPTION JP2012015759
An oscillation device capable of wiring a piezoelectric vibrator with a simple structure is
provided. In an electro-acoustic transducer (100), a first wiring layer (131) on the surface of an
elastic diaphragm (120) is electrically connected to a surface electrode layer (112) of a
piezoelectric vibrator (110) by a first conductor (141) made of a conductive polymer material.
The second wiring layer 132 on the surface of the elastic diaphragm 120 is electrically
connected to the back electrode layer 113 of the piezoelectric vibrator 110 by the second
conductor 142 made of a conductive polymer material. Therefore, the piezoelectric vibrator 110
can be wired with a simple structure. [Selected figure] Figure 1
Oscillator and electronic device
[0001]
The present invention relates to an oscillating device provided with 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.
[0002]
In recent years, the demand for portable electronic devices such as mobile phones and notebook
computers has been expanding.
With regard to such electronic devices, development of thin portable terminals in which sound
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functions such as videophone calls, video reproduction, hands-free telephones and the like have
commercial value has been promoted. Among such developments, there is a growing demand for
high-quality, compact, and thin electro-acoustic transducers (speaker devices) that are acoustic
components.
[0003]
BACKGROUND ART 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 vibrating
membrane.
[0004]
However, the electrodynamic electroacoustic transducer is limited in thinning because of its
operation principle and structure. On the other hand, Patent Documents 1 and 2 describe the use
of a piezoelectric vibrator as an electroacoustic transducer.
[0005]
Further, 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 or the like using a sound
wave oscillated from the piezoelectric vibrator (see Patent Document 3) For example, various
oscillation devices and electronic devices are known (Patent Document 4).
[0006]
Japanese Patent Publication No. 2007-026736 Japanese Patent Publication No. 2007-083497
Japanese Patent Application Laid-Open No. 03-270282 Japanese Patent Laid-Open No. 2001298344
[0007]
An oscillation apparatus using a piezoelectric vibrator generates a vibration amplitude by an
electrostrictive action by an input of an electric signal by utilizing a piezoelectric effect of a
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piezoelectric layer.
And while the electrodynamic electroacoustic transducer generates vibration by piston type
forward and backward movement, the oscillation device using the piezoelectric vibrator has a
smaller amplitude because it takes a bending type vibration mode.
Therefore, the present invention is superior to the above-described electrodynamic
electroacoustic transducer in thinning.
[0008]
However, in order to operate the piezoelectric layer as described above, it is necessary to apply
an electric field to the front and back surfaces. For this reason, electrode layers are usually
formed individually on the front and back surfaces of the piezoelectric layer.
[0009]
However, in this case, it is necessary to connect a wire to the front surface and the back surface
of the piezoelectric vibrator by a lead wire or the like, and its manufacture is complicated and the
lead wire inhibits the vibration of the piezoelectric vibrator.
[0010]
The present invention has been made in view of the problems as described above, and provides
an oscillation device capable of wiring a piezoelectric vibrator with a simple structure, and an
electronic device using the oscillation device.
[0011]
The oscillation device of the present invention comprises a piezoelectric vibrator in which a
surface electrode layer is formed on the surface of a piezoelectric layer and a back electrode
layer is formed on the back surface, and a vibrating member on which the piezoelectric vibrator
is mounted. A first wiring layer formed in a predetermined shape on the surface of the vibrating
member, a second wiring layer formed in the predetermined shape on the surface of the
vibrating member, and at least a side surface of the piezoelectric vibrator to the surface of the
vibrating member And a conductive material formed of at least a side surface of the back surface
electrode layer to a surface of the second wiring layer, and a first conductor made of a
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conductive polymer material electrically conducting the surface electrode layer and the first
wiring layer. And a second conductor made of a molecular material and electrically connecting
the back electrode layer and the second wiring layer.
[0012]
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 sound waves in
an audible range.
[0013]
The second electronic device of the present invention includes the oscillation device of the
present invention, an ultrasonic detection unit that detects an ultrasonic wave emitted 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 of
[0014]
In the oscillation device of the present invention, the first wiring layer on the surface of the
vibrating member is electrically conducted to the surface electrode layer of the piezoelectric
vibrator by the first conductor made of the conductive polymer material, and the first wiring
layer is made of the conductive polymer material The second wiring layer on the surface of the
vibrating member is electrically connected to the back electrode layer of the piezoelectric
vibrator by the two conductors.
Therefore, the piezoelectric vibrator can be wired with a simple structure.
[0015]
It is a typical longitudinal elevation elevation view showing the structure of the electroacoustic
transducer which is an oscillation device of the first form of implementation of the present
invention.
It is a schematic plan view which shows the structure of an electroacoustic transducer.
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[0016]
The first embodiment of the present invention will be described below with reference to FIGS. 1
and 2.
As shown in FIG. 1, the electro-acoustic transducer 100 which is the oscillation device of the
present embodiment has the surface electrode layer 112 formed on the surface of the
piezoelectric ceramic 111 which is a piezoelectric layer and the back electrode layer 113 on the
back surface. The piezoelectric vibrator 110 formed, the elastic diaphragm 120 which is a
vibrating member on which the piezoelectric vibrator 110 is mounted, and the first wiring layer
131 formed in a predetermined shape on the surface of the elastic diaphragm 120 A second
wiring layer 132 formed in a predetermined shape on the surface of the elastic diaphragm 120,
and a conductive polymer material formed from at least the side surface of the piezoelectric
vibrator 110 to the surface of the elastic diaphragm 120 The first conductor 141 electrically
connecting the electrode layer 112 and the first wiring layer 131 and the conductor formed at
least from the side surface of the back electrode layer 113 to the surface of the second wiring
layer 132 A back electrode layer 113 made of sexual polymeric material and the second
conductor 142 are made conductive and the second wiring layer 132, a.
[0017]
More specifically, the first conductor 141 and the second conductor 142 bond the piezoelectric
vibrator 110 to the surface of the elastic diaphragm 120.
In addition, the gap between the first conductor 141 and the back electrode layer 113 is filled
with the insulating adhesive 150 which is an insulating material.
The insulating adhesive 150 bonds the piezoelectric vibrator 110 to the surface of the elastic
diaphragm 120.
[0018]
More specifically, as shown in FIGS. 1 and 2, in the electroacoustic transducer 100 according to
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the present embodiment, a flat rectangular parallelepiped piezoelectric vibration is generated by
the piezoelectric ceramic 111, the front electrode layer 112, and the back electrode layer 113. A
child 110 is formed.
[0019]
The elastic diaphragm 120 is formed in a rectangular planar shape, and the outer peripheral
portion is supported by the frame 121.
The first wiring layer 131 and the second wiring layer 132 are formed on the surface of the
elastic diaphragm 120 by printed wiring or the like.
[0020]
The first and second wiring layers 131 and 132 are connected to, for example, a control unit 160
which is an oscillation drive unit via a lead wire 161. The control unit 160 applies an electric
field that causes the piezoelectric vibrator 110 to oscillate in an audible area or an ultrasonic
wave area.
[0021]
In addition, as the piezoelectric ceramic 111, lead zirconate titanate (PZT) or the like is used, but
it 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.
[0022]
For example, in the case of using a thin film having a thickness of less than 10 μm as a ceramic
material which is a brittle material, chipping and breakage occur due to weak mechanical
strength during handling, which makes handling difficult.
[0023]
In addition, when the piezoelectric ceramic 111 having a thickness of more than 500 μm is
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used, the conversion efficiency for converting electrical energy into mechanical energy is
significantly reduced, and sufficient performance as the electroacoustic transducer 100 can not
be obtained.
[0024]
Generally, in the piezoelectric ceramic 111 which generates an electrostrictive effect by the input
of an electric signal, the conversion efficiency depends on the electric field strength.
Since this electric field strength is expressed by thickness / input voltage with respect to the
polarization direction, an increase in thickness inevitably causes a decrease in conversion
efficiency.
[0025]
In the piezoelectric vibrator 110 of the present embodiment, front / back electrode layers 112
and 113 are formed to generate an electric field.
The front / back electrode layers 112 and 113 are not particularly limited as long as they are
materials having electrical conductivity, but it is preferable to use silver or silver / palladium.
Silver is used as a low resistance general purpose electrode layer, and has advantages in
manufacturing process and cost.
[0026]
In addition, silver / palladium is a low resistance material excellent in oxidation resistance, and
thus is advantageous in terms of reliability. The thickness of the front / back electrode layers 112
and 113 is not particularly limited, but the thickness is preferably 1 μm to 50 μm.
[0027]
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For example, if the thickness is less than 1 μm, since the film thickness is small, it can not be
molded uniformly, and the conversion efficiency may be reduced. Incidentally, as a technique for
forming the thin film surface / back electrode layers 112 and 113, there is also a method of
applying it in the form of a paste.
[0028]
However, in a polycrystal such as the piezoelectric ceramic 111, since the surface state is a matte
surface, the wet state at the time of application is bad, and there is a problem that a uniform
electrode film can not be formed without a certain thickness.
[0029]
On the other hand, when the film thickness of the front / back electrode layers 112 and 113
exceeds 100 μm, there is no particular problem in manufacture, but the front / back electrode
layers 112 and 113 become a constraining surface with respect to the piezoelectric ceramic 111
There is a problem of reducing the efficiency.
[0030]
The main surface of the piezoelectric vibrator 110 of the electroacoustic transducer 100 of the
present embodiment is restrained by the elastic diaphragm 120.
The elastic diaphragm 120 propagates the vibration generated from the piezoelectric vibrator
110 to the outside.
[0031]
At the same time, the elastic diaphragm 120 has a function of adjusting the fundamental
resonance frequency of the piezoelectric vibrator 110.
The fundamental resonance frequency f of the mechanical electro-acoustic transducer 100
depends on the load weight and the compliance as shown by the following equation.
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[0032]
[Equation 1] f = 1 / (2πL√ (mC)) where
m
is mass and
C
is compliance.
[0033]
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.
[0034]
For example, by selecting a material with a high elastic modulus or reducing the thickness of the
elastic diaphragm 120, it is possible to shift the fundamental resonance frequency to a low
frequency range.
On the other hand, by selecting a material having a high elastic modulus or increasing the
thickness of the elastic diaphragm 120, the fundamental resonance frequency can be shifted to a
high frequency.
[0035]
Conventionally, since the fundamental 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, elastic vibration which is a component The
industrial value is great because the plate 120 can be easily adjusted to the desired fundamental
resonance frequency by changing the plate 120.
[0036]
The elastic diaphragm 120 is not particularly limited as long as it is a material having a high
elastic modulus to ceramic which is a brittle material such as metal and resin, but from the
viewpoint of processability and cost, general-purpose materials such as phosphor bronze and
stainless steel Is used.
[0037]
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The thickness of the elastic diaphragm 120 is preferably 5 μm or more and 1000 μm or less.
If the thickness is less than 5 μm, mechanical strength is weak, and there is a problem that an
error in mechanical vibration characteristics of the piezoelectric vibrator 110 occurs between
manufacturing lots due to a loss of function as a constraining member or a decrease in
processing accuracy.
[0038]
Further, when the thickness exceeds 1000 μm, there is a problem that the restraint on the
piezoelectric vibrator 110 is strengthened due to the increase in rigidity, and the vibration
displacement amount is attenuated.
Moreover, as for the elastic diaphragm 120 of this embodiment, it is preferable that the
longitudinal elastic modulus which is a parameter ¦ index which shows the rigidity of material is
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 the characteristics and reliability of the mechanical
vibrator are impaired.
[0039]
Here, the manufacturing method of the electroacoustic transducer 100 of this Embodiment is
demonstrated below. First, the piezoelectric vibrator 110 forms a piezoelectric ceramic 111
having a square planar shape with a side of 3 mm and a thickness of 200 μm, and the front
electrode layer 112 and the back electrode layer 113 having a thickness of 8 μm are formed on
both surfaces.
[0040]
A lead zirconate titanate ceramic is used for the piezoelectric ceramic 111, and a silver /
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palladium alloy (70% by weight: 30%) is used for the front / back electrode layers 112 and 113.
The piezoelectric ceramic 111 is produced by a green sheet method, and is fired at 1100 ° C.
for 2 hours in the atmosphere, and then the piezoelectric ceramic 111 is subjected to
polarization treatment.
[0041]
On the other hand, the first wiring layer 131 and the second wiring layer 132 are formed on the
surface of the elastic diaphragm 120 by printed wiring or the like. Then, the piezoelectric
vibrator 110 is bonded to the surface of the elastic diaphragm 120 by the first conductor 141
and the second conductor 142 and wired. The gap between the back electrode layer 113 of the
piezoelectric vibrator 110 and the first conductor 141 is filled with the insulating adhesive 150.
[0042]
In the electroacoustic transducer 100 of the present embodiment, ultrasonic waves are oscillated
in order to realize acoustic reproduction capable of privacy protection. Here, the principle of a
parametric speaker that demodulates modulated ultrasonic waves into audible sound is used. The
piezoelectric vibrator 110 oscillates an ultrasonic wave having a frequency of 20 kHz or more.
[0043]
Here, ultrasonic waves with AM (Amplitude Modulation) modulation, DSB (Double Sideband)
modulation, SSB (Single-Sideband modulation) modulation, and FM (Frequency Modulation)
modulation are emitted into the air, and the ultrasonic waves enter the air. Sound reproduction is
performed on the principle that an audible sound appears due to the non-linear characteristic at
the time of propagation.
[0044]
As the non-linearity, there is a phenomenon that the transition from laminar flow to turbulent
flow occurs when the Reynolds number indicated by the ratio of the flow inertia action to the
viscosity action increases.
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That is, since the sound waves are minutely and disturbed in the fluid, the sound waves are nonlinearly propagating.
[0045]
However, while the amplitude of the sound wave in the low frequency band is non-linear, the
amplitude difference is very small and is usually treated as a phenomenon of linear theory. On
the other hand, in the case of ultrasonic waves, non-linearity can be easily observed, and when it
is emitted into the air, harmonics associated with the non-linearity are significantly generated.
[0046]
In summary, sound waves are in a dense / dense state in which molecular groups are mixed in
the air, and when time is required for air molecules to recover more than compression, air that
can not be recovered after compression continuously propagates. It is a principle that collides
with a molecule and a shock wave is generated to generate an audible sound.
[0047]
Subsequently, the operation principle of the piezoelectric vibrator 110 will be described.
The piezoelectric ceramic 111 is formed 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 of the main surfaces of the piezoelectric ceramic 111.
[0048]
The polarization direction of the piezoelectric ceramic 111 is not particularly limited, but in the
electro-acoustic transducer of this embodiment, it is upward in the vertical direction (the
thickness direction of the piezoelectric vibrator 110). In the piezoelectric vibrator 110 configured
in this manner, when an alternating voltage is applied from the control unit 160 to the surface
electrode layer 112 and the back electrode layer 113 and an alternating electric field is applied,
both principal surfaces are simultaneously expanded or Performs a radial expansion and
contraction movement that reduces.
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[0049]
In other words, the piezoelectric vibrator 110 performs a motion that repeats a first deformation
mode in which the main surface is expanded and a second deformation mode in which the main
surface is reduced. By repeating such a motion, the elastic diaphragm 120 generates an up and
down vibration by an inertial action and a restoring action using an elastic effect to generate a
sound wave.
[0050]
Further, in the configuration of the present invention, the piezoelectric vibrator 110 oscillates an
ultrasonic wave having a frequency of 20 kHz or more. Sound is reproduced based on the
principle of a so-called parametric speaker which oscillates an ultrasonic wave modulated by FM
or AM and demodulates a modulated wave and reproduces an audible sound by utilizing a nonlinear state (density state) of air. This is to propagate the sound wave using the high directivity
characteristic of the ultrasonic wave, and it becomes possible to realize a privacy sound source
that can only be heard by the user.
[0051]
As described above, the electro-acoustic transducer 100 of the present embodiment is compact
and can reproduce a large volume. In addition, since ultrasonic waves are used, the directivity is
narrow, and the industrial value is great in terms of user privacy protection and the like.
[0052]
That is, the electro-acoustic transducer 100 of the present embodiment has high sound wave
straightness compared with the conventional electro-acoustic transducer, and can selectively
propagate the acoustic wave to a position to be transmitted to the user. Summarizing the above,
the electro-acoustic transducer 100 of the present embodiment can also be used as a sound
source of an electronic device (for example, a mobile phone, a notebook personal computer, a
small game machine, etc.). Moreover, since the electro-acoustic transducer 100 can be prevented
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from being enlarged and the acoustic characteristics are improved, the electro-acoustic
transducer 100 can be suitably used for portable electronic devices.
[0053]
Moreover, in the electroacoustic transducer 100 according to the present embodiment, the first
wiring layer 131 on the surface of the elastic diaphragm 120 is the surface of the piezoelectric
vibrator 110 by the first conductor 141 made of the conductive polymer material as described
above. The second wiring layer 132 on the surface of the elastic diaphragm 120 is electrically
connected to the back electrode layer 113 of the piezoelectric vibrator 110 by the second
conductor 142 made of a conductive polymer material.
[0054]
Therefore, the piezoelectric vibrator 110 can be wired with a simple structure.
Furthermore, since the first and second conductors 141 and 142 for wiring the piezoelectric
vibrator 110 bond the piezoelectric vibrator 110 to the elastic diaphragm 120 as described
above, the productivity is also good with a simple structure.
[0055]
In addition, the gap between the first conductor 141 and the back electrode layer 113 is filled
with the insulating adhesive 150. Therefore, the first conductor 141 and the back electrode layer
113 do not short circuit. Moreover, the insulating adhesive 150 also bonds the piezoelectric
vibrator 110 to the surface of the elastic diaphragm 120.
[0056]
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 use of the piezoelectric ceramic 111 such as lead zirconate titanate (PZT) as the
piezoelectric element of the piezoelectric vibrator 110 is exemplified.
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[0057]
However, as to the piezoelectric element, both inorganic materials and organic materials are not
particularly limited as long as they have a piezoelectric effect, and materials having high
electromechanical conversion efficiency, for example, materials such as barium titanate (BaTiO 3)
can be used.
[0058]
Moreover, in the said form, it illustrated that the piezoelectric vibrator 110 consisted of the
piezoelectric ceramic 111 of one layer, and the electrode layers 112 and 113 of both surfaces.
However, such a piezoelectric vibrator may have a laminated structure in which a plurality of
piezoelectric ceramics and a plurality of electrode layers are alternately formed (not shown).
[0059]
Further, in the above-described embodiment, a mobile phone or the like that outputs sound by
the electroacoustic transducer 100 or the like is assumed as the electric device. However, as an
electronic device, an electroacoustic transducer 100 or the like which is an oscillating device, an
ultrasonic detection unit for detecting an ultrasonic wave oscillated from the electroacoustic
transducer 100 or the like and reflected by an object to be measured, A sonar (not shown) having
a distance measuring unit for calculating the distance from the sound wave to the measurement
object can also be implemented.
[0060]
As a matter of course, the plurality of embodiments and the plurality of modifications described
above can be combined as long as the contents do not conflict with each other. Further, in the
above-described embodiment, the structure and the like of each part are specifically described,
but the structure and the like can be variously changed as long as the present invention is
satisfied.
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[0061]
100 electro-acoustic transducer 110 piezoelectric vibrator 111 piezoelectric ceramic 112 front
surface electrode layer 113 back surface electrode layer 120 elastic diaphragm 121 frame 131
first wiring layer 132 second wiring layer 141 first conductor 142 second conductor 150
insulating adhesive Agent 160 control unit 161 lead wire
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