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JP2011250343

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DESCRIPTION JP2011250343
The present invention provides a polymer actuator capable of securing a large vibration
amplitude and easily adjusting the frequency of the vibration as desired. A film-like polymer
electrolyte gel 1-b vibrates when an electric field is applied. An electric field is applied to the pair
of electrode layers individually formed on the pair of main surfaces of the polymer electrolyte gel
1-b. The vibrating membrane 1-a which confines the polymer electrolyte gel 1-b, in which the
pair of electrode layers are individually formed on the pair of main surfaces, propagates the
vibration. Therefore, a large vibration amplitude can be secured by the vibrating membrane 1-a,
and the frequency of the vibration can be easily adjusted as desired. [Selected figure] Figure 1
Polymer actuator, electro-acoustic transducer and electronic device
[0001]
The present invention relates to a polymer actuator using vibration of a polymer electrolyte gel,
an electroacoustic transducer provided with the polymer actuator, and an electronic device
provided with the electroacoustic transducer.
[0002]
An electrodynamic electroacoustic transducer is used as an acoustic component of an electronic
device such as a mobile phone.
This electrodynamic electroacoustic transducer is composed of a permanent magnet, a voice coil
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1
and a vibrating membrane. The principle of operation is that a vibrating film such as an organic
film fixed to a voice coil is vibrated by the action of a magnetic circuit of a stator using a magnet
to generate an acoustic wave.
[0003]
At present, there are various proposals as actuators as described above. For example, there is a
proposal for an actuator that autonomously vibrates a polymer electrolyte gel (Patent Document
1).
[0004]
Japanese Patent Application Laid-Open No. 04-053399
[0005]
In recent years, the demand for portable terminals of portable telephones and laptop personal
computers has been increasing, and the demand for downsizing of the electroacoustic transducer
has been increasing.
However, the sound pressure level, which is an important factor in the acoustic performance of
the electroacoustic transducer, is determined by the volume exclusion of the vibrating membrane
against air.
[0006]
Therefore, when the electroacoustic transducer is downsized, the area of the radiation surface of
the vibrating film is reduced, and there is a problem that the sound pressure level is reduced. On
the other hand, as a means for improving the sound pressure level, there is a method of
increasing the generation force of the magnetic circuit to increase the amplitude of the vibrating
film.
[0007]
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However, in this means, an increase in magnetic flux density and an increase in drive current are
required, and there is a problem that the thickness of the magnetic circuit is increased due to the
increase in volume of the permanent magnet and the thickening of the voice coil. Furthermore,
there is also a problem such as an increase in power consumption accompanying an increase in
the amount of current.
[0008]
On the other hand, as a means for realizing a small and thin electroacoustic transducer, there is a
piezoelectric electroacoustic transducer utilizing the piezoelectric effect of piezoelectric ceramics.
In this piezoelectric method, vibration amplitude is generated by an electrostrictive action by an
input of an electric signal by using a piezoelectric effect of a ceramic material.
[0009]
The ceramic itself, in which the upper and lower layers are constrained by the electrode material,
vibrates and functions as a drive source. Therefore, the number of components is smaller than in
a magnetic circuit composed of many members such as magnets and voice coils. is there.
[0010]
However, since a ceramic material having a low internal loss is used as a vibration source, the
mechanical quality factor Q tends to be higher than that of an electrodynamic electroacoustic
transducer that generates an amplitude through an organic film.
[0011]
For example, the electrodynamic type is about 3 to 5 and the piezoelectric type is about 50 or so.
Since the mechanical quality factor Q indicates sharpness at resonance, in summary, in the
piezoelectric electroacoustic transducer, the sound pressure is high near the fundamental
resonance frequency, and the sound pressure is attenuated in the other bands.
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[0012]
That is, peaks and troughs of acoustic characteristics occur in the sound pressure level frequency
characteristics, and a sound of a specific frequency is emphasized or lost, and there is a problem
that sound quality sufficient for music reproduction can not be obtained.
[0013]
In addition, since the ceramic is a brittle material, the impact stability at the time of dropping is
weak, and there is a problem in securing the reliability when it is mounted on a small electronic
device such as a mobile phone.
On the other hand, a polymer film having piezoelectricity, for example, PVDF (polyvinylidene
fluoride) may be used as a vibration source.
[0014]
In this PVDF film, since the material itself has piezoelectricity, by constraining the upper and
lower main surfaces with the electrodes, an expansion and contraction movement is generated by
inputting an electric signal as in the ceramic.
[0015]
For this reason, since it has high flexibility and high internal loss characteristics unique to a
polymer resin, it is expected as a driving source of a high-quality, high-reliability electro-acoustic
transducer.
However, since PVDF is a thermoplastic fluorine polymer of high purity, a compact purification
step is required to obtain piezoelectricity, and it is generally recognized as an expensive material.
In addition, PVDF has a problem that distortion sound is generated at the time of sound
reproduction because the material linearity, that is, the linear characteristic with the amount of
vibration with respect to the input voltage is poor.
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[0016]
For this reason, there has been a demand for a revolutionary technology for a small, largeamplitude actuator that produces high-quality, small-sized electroacoustic transducers that can
replace electrokinetic electroacoustic transducers or piezoelectric electroacoustic transducers. .
[0017]
The actuator described in Patent Document 1 autonomously vibrates the polymer electrolyte gel
as described above.
For this reason, it is difficult to secure a large vibration amplitude, and it is also difficult to adjust
the frequency of the vibration as desired.
[0018]
The present invention has been made in view of the above problems, and is provided with a
polymer actuator capable of securing a large vibration amplitude and easily adjusting the
frequency of the vibration as desired, and the polymer actuator An electro-acoustic transducer,
and an electronic device provided with the electro-acoustic transducer.
[0019]
In the polymer actuator of the present invention, a pair of film-shaped polymer electrolyte gel
that vibrates when an electric field is applied, and a pair of electrodes formed individually on a
pair of main surfaces of the polymer electrolyte gel and to which an electric field is applied It has
a layer and a vibrating membrane which confines the polymer electrolyte gel currently formed in
a pair of main surfaces individually with a pair of electrode layer, and propagates a vibration.
[0020]
The electroacoustic transducer of the present invention comprises the polymer actuator of the
present invention.
[0021]
The electronic device of the present invention comprises the electro-acoustic transducer of the
present invention.
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[0022]
In the polymer actuator of the present invention, the film-like polymer electrolyte gel vibrates
when an electric field is applied.
An electric field is applied to a pair of electrode layers individually formed on a pair of main
surfaces of the polymer electrolyte gel.
A vibrating membrane confining a polymer electrolyte gel in which a pair of electrode layers are
individually formed on a pair of main surfaces propagates vibration.
Therefore, a large vibration amplitude can be secured by the vibrating film, and the frequency of
the vibration can be easily adjusted as desired.
[0023]
FIG. 1 is a schematic vertical front view showing a structure of a polymer actuator according to a
first embodiment of the present invention.
It is a typical longitudinal front view showing the principal part of a polymer actuator. It is a
typical longitudinal front view which shows the structure of the polymer actuator of the 2nd
form of implementation. It is a typical longitudinal elevation front view which shows the
structure of the polymer actuator of the 3rd form of implementation. It is a typical longitudinal
front view showing the principal part of a polymer actuator. It is a typical front view which shows
the external appearance of the mobile telephone terminal which is an electronic device provided
with an electroacoustic transducer. It is a typical front view which shows the external appearance
of the personal computer which is an electronic device provided with an electroacoustic
transducer.
[0024]
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First Embodiment A first embodiment of the present invention will be described below with
reference to FIGS. 1 and 2. FIG. 1 is a schematic longitudinal front view showing a polymer
actuator of the present embodiment. FIG. 2 is a schematic longitudinal front view showing the
main part of the polymer actuator.
[0025]
As shown in FIG. 1, in the polymer actuator of the present embodiment, a vibrating membrane 1a, a polymer electrolyte gel 1-b fixed to one surface of the vibrating membrane 1-a, and a
vibrating membrane fixed and supported And a lead 1-d for connecting electricity.
[0026]
The polymer electrolyte gel 1-b functions as a drive source for generating vibration, and as
shown in FIG. 2, the upper and lower main surfaces are constrained by the electrode layers 2-a
and 2-c.
The polyelectrolyte gel 2-b is a material having stimulus response characteristics to external
stimuli such as an electric field.
[0027]
That is, it is a material having a function of repeatedly contracting and expanding by application
of an electric field and converting electric energy into vibration energy, and oscillates vibration
by the following mechanism.
[0028]
The polymer electrolyte gel 2-b is a substance in a state in which the solvent is contained in the
three-dimensional polymer network structure.
Its feature is that it has stimulus responsiveness to external stimuli such as salt concentration,
temperature, electric field, magnetic field, light and the like.
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[0029]
That is, since the gel is composed of a three-dimensional network having molecules as a basic
unit, structural changes between molecules, polymer chains, and microdomains can be converted
into various scale forms, and these changes can be accumulated. Means that it can be converted
to mechanical energy.
[0030]
By the way, as an example showing the electrical responsiveness of a polymer electrolyte gel,
there are electrical contraction and electroosmosis.
By bringing the electrode into contact with a polymer electrolyte gel containing water and
applying a voltage, the gel shrinks anisotropically while discharging the water taken into the
polymer chain while stopping the application of the voltage. Then, the gel has a function to
expand the water by absorption and recover its original size again.
[0031]
The contraction due to the electrical stimulation is a phenomenon that occurs in all the
electrolyte gels, and the electric contraction of the ionic network in this electric field is the
influence of the electroosmosis of water molecules in the gel. For example, in the case of an
anionic polymer electrolyte gel, application of a voltage causes the polymer ion to move to the
anode and the counter ion to the cathode, but since the polymer ion is fixed, most can not move.
However, electrophoresis occurs, which is a phenomenon in which small molecule counter ions
move to the cathode.
[0032]
That is, the counter ion that has reached the electrode is counteracted by the electrochemical
reaction, the water that has been hydrated is discharged on the cathode side, and the gel shrinks.
Along with this mechanism, contraction and expansion are repeated to convert electric energy
into vibrational energy.
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[0033]
In the polymer actuator according to the present embodiment, the polymer electrolyte gel 2-b is
not particularly limited as long as it is a polymer material having stimulus responsiveness to an
electric field, but as an example, img class = "EMIRef" id = "205001383-00003" /> Poly (Nisopropylacrylamide) (hereinafter, abbreviated as PNIPA) or the like can be used.
[0034]
PNIPA having a hydrophobic group (isopropyl group) and a hydrophilic group (amide group) in
the molecule is a general-purpose material widely recognized as a material having high stimulus
responsiveness, and thus is superior in terms of cost and reliability.
[0035]
Further, in the polymer actuator of the present embodiment, the thickness of the polymer
electrolyte gel 2-b is not particularly limited, but the thickness is preferably 50 μm.
When the thickness is less than 50 μm, there is a problem that dispersion due to the thickness
or an extremely unstable three-dimensional network is formed in constructing the molecular
structure, and sufficient contraction can not be obtained.
[0036]
Further, in order to generate an electric field in the polymer electrolyte gel 2-b of the present
invention, electrode layers 2-a and 2-c are formed on the upper and lower main surfaces.
The electrode material is not particularly limited as long as it is a material having electrical
conductivity, but it is preferable to use gold, silver or silver / palladium.
[0037]
The thickness of the electrode material is not particularly limited, but preferably 1 to 50 μ. For
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example, if the thickness is less than 1 μm, there is a problem that the film can not be uniformly
formed on the electrode because the film thickness is small.
[0038]
On the other hand, when the film thickness exceeds 100 μm, molding becomes easy, but the
electrode layers 2-a and 2-c become a constraining surface, which causes a problem of reducing
the conversion efficiency to vibration energy. In addition, sputtering method etc. are mentioned
as an electrode formation method.
[0039]
The polymer electrolyte gel 2-b of the present invention is constrained by the vibrating
membrane 1-a. For example, the vibrating membrane 1-a has a function of transmitting a sound
wave, and a sound wave is generated by propagation of vibration due to contraction and
expansion from the polymer electrolyte, and the polymer actuator itself has a function as an
electroacoustic transducer .
[0040]
The vibrating membrane 1-a also has a function of enhancing shock stability when dropped and
a function of adjusting the fundamental resonance frequency of the polymer actuator or the
electroacoustic transducer. That is, since the vibrating membrane 1-a is made of an elastic
material, it is possible to absorb impact energy at the time of drop by the vibrating membrane 1a, and the shock stability of the electroacoustic transducer is improved.
[0041]
Further, the fundamental resonance frequency of the mechanical oscillator depends on the load
weight and the compliance, as expressed by the following Equation 1, f = 1 / 2π L ((m · C) ...
Equation 1
[0042]
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In other words, since the compliance is the mechanical rigidity of the vibrator, this means that
the fundamental resonance frequency can be controlled by controlling the rigidity of the
vibrating membrane 1-a.
For example, the fundamental resonance frequency can be shifted to a lower range by selecting a
material having a high elastic modulus or reducing the thickness of the material.
[0043]
On the other hand, the fundamental resonance frequency can be shifted to a high frequency by
selecting a material having a high elastic modulus or increasing the thickness of the elastic
material. It is superior to design constraints and costs without changing the basic structure.
[0044]
As in the present embodiment, by changing the elastic material which is a component, it can be
easily adjusted to a desired fundamental resonance frequency, and therefore, the industrial value
is large. The vibrating membrane 1-a is not particularly limited as long as it is a material having a
high elastic modulus such as an organic polymer material, but general-purpose materials such as
polyethylene terephthalate, polyethylene, and polyethylene are used from the viewpoint of
processability and cost. .
[0045]
The thickness of the vibrating membrane 1-a is preferably 5 to 1000 μm. If the thickness is less
than 5 μ, mechanical strength is weak, and there is a problem that the mechanical vibration
characteristic of the vibrator varies among manufacturing lots due to the loss of the function as a
constraining member and the decrease due to the processing accuracy.
[0046]
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In addition, when the thickness exceeds 1000 μm, there is a problem that the restraint on the
polymer electrolyte gel 2-b is strengthened due to the increase in rigidity, and the vibration
displacement amount is attenuated. Moreover, as for the elastic material of this Embodiment, it is
preferable that the longitudinal elastic modulus which is a parameter | index which shows the
rigidity of material is 1-500 GPa. As described above, when the rigidity of the elastic material is
excessively low or excessively high, there is a problem of impairing the characteristics and
reliability as a mechanical vibrator.
[0047]
In the present embodiment, the vibrating membrane 1-a is bonded to the support 1-c. The
support 1-c serves as a case of the polymer actuator. The material of the support 1-c may be any
material such as metal, resin, or a composite material of metal and resin, but in order to
efficiently transmit vibration energy from the vibrating film 1-a, It is preferable that the material
has a certain degree of rigidity with respect to the amount of transmission vibration.
[0048]
The operation principle of the polymer actuator of the present embodiment will be described
below. The polymer actuator of the present embodiment repeats contraction and expansion by
repeatedly applying and stopping an electric signal to the polymer electrolyte gel 2-b.
[0049]
As described above, by applying electrical stimulation to the polyelectrolyte gel 2-b, a reversible
continuous bending movement is generated by contraction and expansion. It is the operation
principle of the polymer actuator or the electroacoustic transducer of the present embodiment
that propagates this bending motion to the vibrating membrane 1-a and generates vibration
amplitude and sound waves.
[0050]
As described above, in the polymer actuator according to the present embodiment, since the
driving source is composed of the vibrating membrane 1-a and the polymer electrolyte gel 2-b,
an electrodynamic type electric circuit composed of a conventionally used magnetic circuit is
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used. It is superior to the acoustic transducer in miniaturization.
[0051]
In the polymer actuator of the present embodiment, as described above, the film-like polymer
electrolyte gel 1-b is vibrated by applying the electric field, and the pair of electrode layers are
individually formed on the pair of main surfaces. The vibrating membrane 1-a constraining the
polymer electrolyte gel 1-b that is propagating propagates the vibration.
[0052]
Therefore, a large vibration amplitude can be secured by the vibrating membrane 1-a.
Therefore, compared to the actuator of Patent Document 1 described above, it is possible to
generate a sound wave of a large volume at power saving.
Moreover, it is easy to adjust the frequency of vibration as desired. Therefore, unlike the patent
document 1 mentioned above, the sound wave of a desired scale can be generated.
[0053]
In addition, since the component members of the drive source are made of a resin material
having a large internal loss compared to metal and ceramics, the mechanical quality factor Q is
lower and the flat amplitude frequency characteristic is lower than that of a piezoelectric
electroacoustic transducer. Become an advantage in achieving
[0054]
In addition, when this polymer actuator is used as a drive source of an electroacoustic
transducer, machining at the time of manufacture is easy because the component member is a
resin material with high flexibility, and the manufacturing cost is also conventional. It is superior
to electroacoustic transducers.
[0055]
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Furthermore, since it is made of a resin material, it also has an advantage in impact stability
when dropped.
As described above, the polymer actuator or the electroacoustic transducer according to the
present embodiment is small in size and can realize high sound quality, and can be easily
mounted on a mobile phone, so the industrial value is large.
[0056]
The electronic component using the polymer actuator according to the present embodiment, for
example, an electroacoustic transducer, is an electronic device (for example, a portable telephone,
a laptop personal computer, a small game, as shown in FIGS. 6 and 7). It can also be used as a
sound source of equipment etc.).
As described above, because of the small size and high sound quality and high reliability, it can
be suitably used for a portable electronic device.
[0057]
Second Embodiment of the Embodiment A second embodiment of the present invention will be
described below with reference to FIG. The present embodiment is characterized in that an elastic
member 5-e is newly disposed to the first embodiment. The support 5-c and the lead wire 5-d are
the same as in the first embodiment.
[0058]
That is, by interposing the elastic member 5-e between the vibrating membrane 5-a and the
polymer electrolyte gel 5-b, adjustment to a fundamental resonance frequency suitable as a
polymer actuator is easily possible. .
[0059]
For example, in consideration of an electroacoustic transducer, a frequency band of 100 to 20
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kHz is conventionally used for reproduction such as music reproduction.
For this reason, in order to prevent the sound pressure level difference between bands, the
fundamental resonance number of the electroacoustic transducer is adjusted to about 1 kHz.
[0060]
Usually, since the fundamental resonance frequency of the mechanical oscillator depends on the
rigidity and the non-weight as in the above-mentioned "Equation 1", the electro-acoustic
transducer of the present invention, which is made of a resin material having a small Young's
modulus, is inevitable. There is a problem of shifting to a very low frequency.
[0061]
Therefore, by interposing an elastic member between the vibrating membrane and the polymer
electrolyte gel, the rigidity is enhanced, and adjustment to a desired fundamental resonance
frequency becomes possible.
The elastic material is not particularly limited as long as it is a material having a high Young to
polymer electrolyte gel, such as metal and resin-metal composite material, but from the
viewpoint of processability and cost, general-purpose materials such as phosphor bronze and
stainless steel Is used.
[0062]
The thickness of the elastic material is preferably 5 to 1000 μm. If the thickness is less than 5
μ, mechanical strength is weak, and there is a problem that the mechanical vibration
characteristic of the vibrator varies among manufacturing lots due to the loss of the function as a
constraining member and the decrease due to the processing accuracy.
[0063]
In addition, when the thickness exceeds 1000 μm, there is a problem that the restraint to the
piezoelectric element is strengthened due to the increase in rigidity, the attenuation of the
vibration displacement amount is caused, and the fundamental resonance frequency is increased.
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[0064]
Moreover, as for the elastic material of this Embodiment, it is preferable that the longitudinal
elastic modulus which is a parameter | index which shows the rigidity of material is 1-500 GPa.
As described above, in the case where the Young's modulus is excessively low or excessively
high, there is a problem of impairing the characteristics and reliability as a mechanical oscillator.
[0065]
As described above, according to the present embodiment, by interposing the elastic material
between the polymer electrolyte gel and the vibrating membrane, it is possible to easily adjust to
the fundamental resonance frequency suitable for the acoustic transducer, and the voice of high
sound quality Can be played back.
[0066]
In the polymer actuator configured as described above, since the drive source is composed of a
polymer electrolyte gel material that performs bending movement according to the state of the
electric field, an electrodynamic electroacoustic transducer composed of a magnetic circuit As
compared with the above, a small converter can be realized.
[0067]
That is, since the drive source itself is made of a polymer electrolyte gel material with high
internal loss, the mechanical quality factor Q of the actuator itself is low, the amplitude peak near
the resonance frequency is small, and the flat of the frequency amplitude characteristic width is
flat. Frequency characteristics can be realized.
[0068]
In addition, since a polymer electrolyte gel having a covalently cross-linked basic structure is
chemically stable, a polymer actuator using it as a driving source has high reliability.
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Furthermore, since a polymer electrolyte gel is a colloid of a solid dispersion medium in a broad
sense, it has high flexibility and high viscosity, so it is also strong in impact stability when
dropped.
[0069]
Moreover, since it is a viscous solid represented by agar, shape processing is also easy.
Therefore, a highly reliable, low-cost polymer actuator can be realized.
Furthermore, by using this polymer actuator as a drive source of an electronic component and an
electroacoustic transducer, a compact, high-quality electroacoustic transducer can be realized.
[0070]
As described above, as shown in FIGS. 6 and 7, the polymer actuator and the electroacoustic
transducer according to the present embodiment are used as a sound source of an electronic
device (for example, a mobile phone, a laptop personal computer, a small game machine, etc.). Is
also available. Since the overall shape of the electroacoustic transducer is not significantly
increased and the acoustic characteristics are improved, it can be suitably used for portable
electronic devices.
[0071]
Third Embodiment of the Present Invention A third embodiment of the present invention will be
described below with reference to FIG. In the polymer actuator of the present embodiment, two
polymer electrolyte gels 6-b1 and 6-b2 restrain the upper and lower main surfaces of the
vibrating membrane 6-a. The support 6-c and the lead 6-d are the same as in the first
embodiment.
[0072]
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That is, the amount of vibration of the vibrating membrane 6-a is amplified by utilizing the
bending motions of the two polymer electrolyte gels 6-b1 and 6-b2. In the polymer actuator of
the present embodiment, by driving the polymer electrolyte gels 6-b1 and 6-b2 to be in phase, as
shown in FIG. 5, two polymer electrolyte gels 7-b1 and 7- can be obtained. The vibration
generated from b2 interferes and the amount of vibration of the vibrating film 7-a is amplified.
[0073]
Therefore, the present embodiment is advantageous in that the amount of vibration can be
increased without significantly increasing the shape of the vibrator. As described above, as
shown in FIGS. 6 and 7, the polymer actuator and the electroacoustic transducer according to the
present embodiment are used as a sound source of an electronic device (for example, a mobile
phone, a laptop personal computer, a small game machine, etc.). Is also available. Since the
overall shape of the electroacoustic transducer is not increased and the acoustic characteristics
are improved, it can be suitably used for portable electronic devices.
[0074]
[Example 1 of the Invention] In order to demonstrate the effect of the polymer actuator of the
present invention, the electroacoustic transducers of the following examples are manufactured,
and their characteristics are evaluated as follows: evaluation items of evaluation 1 to evaluation 3
I went there.
[0075]
(Evaluation 1) Measurement of sound pressure level frequency characteristics: The sound
pressure level when an AC voltage of 1 V was input was measured by a microphone placed at a
predetermined distance from the element.
The predetermined distance is 10 cm unless otherwise specified, and the frequency measurement
range is 10 Hz to 10 kHz.
[0076]
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(Evaluation 2) Flatness Measurement of Sound Pressure Level Frequency Characteristic: The
sound pressure level when an AC voltage of 1 V was input was measured by a microphone
disposed at a predetermined distance from the element. The measurement range of the
frequency was 10 Hz to 10 kHz, and in the measurement range of 2 kHz to 10 kHz, the flatness
of the sound pressure level frequency characteristics was measured by the sound pressure level
difference between the maximum sound pressure level Pmax and the minimum sound pressure
level Pmin.
[0077]
As a result, the sound pressure level difference (referring to the difference between the maximum
sound pressure level Pmax and the minimum sound pressure level Pmin) is 20 dB or less as 、,
and 20 dB or more as x. This predetermined distance is 10 cm unless otherwise stated.
[0078]
(Evaluation 3) Drop Impact Test: A drop impact stability test was conducted by causing a mobile
phone equipped with an electroacoustic transducer to drop spontaneously five times from 50 cm
immediately above. Specifically, breakage such as cracks after the drop impact test was visually
confirmed, and the sound pressure characteristics after the test were measured. As a result, the
sound pressure level difference (referring to the difference between the sound pressure level
before the test and the sound pressure level after the test) was 3 dB or less within 3 dB, and 3 dB
or more was x.
[0079]
Example 1 The characteristics of the electroacoustic transducer consisting of the polymer
actuator described in the first embodiment of the present invention were evaluated. The
evaluation results are as follows. [Results] Sound pressure level (1 kHz): 80 dB Sound pressure
level (3 kHz): 81 dB Sound pressure level (5 kHz): 82 dB Sound pressure level (10 kHz): 83 dB
Flatness of sound pressure level frequency characteristics: ○ Drop shock stability: ○
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[0080]
As is clear from the above results, according to the electroacoustic transducer of this example, it
has been proved that the sound pressure level frequency characteristics are flat, high volume
reproduction is possible, and high reliability is obtained. .
[0081]
Comparative Example 1 As a comparative example 1, a conventional electrodynamic
electroacoustic transducer was produced.
[Results] Sound pressure level (1 kHz): 77 dB Sound pressure level (3 kHz): 75 dB Sound
pressure level (5 kHz): 76 dB Sound pressure level (10 kHz): 97 dB Flatness of sound pressure
level frequency characteristics: × Drop shock stability: ×
[0082]
[Example 2 of the Invention] As Example 2, an electroacoustic transducer composed of the
polymer actuator of the second embodiment of the present invention was produced. [Results]
Sound pressure level (1 kHz): 85 dB Sound pressure level (3 kHz): 87 dB Sound pressure level (5
kHz): 84 dB Sound pressure level (10 kHz): 86 dB Flatness of sound pressure level frequency
characteristics: ○ Drop shock stability: ○ As apparent from the above results, according to the
electro-acoustic transducer of the present embodiment, it has the same characteristics as the first
embodiment, and the sound pressure level frequency characteristic is flat and has high reliability.
[0083]
[Example 3 of the Invention] As Example 3, an electroacoustic transducer composed of the
polymer actuator of the third embodiment was produced. [Results] Sound pressure level (1 kHz):
87 dB Sound pressure level (3 kHz): 91 dB Sound pressure level (5 kHz): 88 dB Sound pressure
level (10 kHz): 86 dB Flatness of sound pressure level frequency characteristics: ○ Drop shock
stability: ○ As apparent from the above results, according to the electro-acoustic transducer of
the present embodiment, it has the same characteristics as the first embodiment, and the sound
pressure level frequency characteristic is flat and has high reliability.
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[0084]
Fourth Embodiment of the Invention As a fourth embodiment, a mobile phone as shown in FIG. 6
is prepared, and the electro-acoustic transducer of the first embodiment is mounted in this
housing. Specifically, an electroacoustic transducer is attached to the inner surface of the casing
of the mobile phone.
[0085]
(Evaluation): A sound pressure level and frequency characteristics were measured by a
microphone placed at a position 10 cm away from the element. In addition, a drop impact test
was also conducted. [Results] Sound pressure level (1 kHz): 81 dB Sound pressure level (3 kHz):
82 dB Sound pressure level (5 kHz): 84 dB Sound pressure level (10 kHz): 80 dB Flatness of
sound pressure level frequency characteristics: ○ Drop impact test: 5 Even after the drop, no
breakage of the piezoelectric element was observed, and the sound pressure level (1 kHz) was
measured after the test and was 84 dB.
[0086]
Fifth Embodiment of the Invention A mobile phone as shown in FIG. 6 is prepared as a fifth
embodiment, and the electro-acoustic transducer of the second embodiment is mounted in the
housing. Specifically, an electroacoustic transducer is attached to the inner surface of the casing
of the mobile phone.
[0087]
(Evaluation): A sound pressure level and frequency characteristics were measured by a
microphone placed at a position 10 cm away from the element. In addition, a drop impact test
was also conducted. [Results] Sound pressure level (1 kHz): 81 dB Sound pressure level (3 kHz):
84 dB Sound pressure level (5 kHz): 87 dB Sound pressure level (10 kHz): 83 dB Flatness of
sound pressure level frequency characteristics: ○ Drop impact test: 5 Even after the drop, no
breakage of the piezoelectric element was observed, and after the test, the sound pressure level
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(1 kHz) was measured to be 78 dB.
[0088]
Sixth Embodiment of the Invention As a sixth embodiment, a mobile phone as shown in FIG. 6 is
prepared, and the electro-acoustic transducer of the third embodiment is mounted in the
housing. Specifically, an electroacoustic transducer is attached to the inner surface of the casing
of the mobile phone.
[0089]
(Evaluation): A sound pressure level and frequency characteristics were measured by a
microphone placed at a position 10 cm away from the element. In addition, a drop impact test
was also conducted. [Results] Sound pressure level (1 kHz): 81 dB Sound pressure level (3 kHz):
82 dB Sound pressure level (5 kHz): 85 dB Sound pressure level (10 kHz): 80 dB Flatness of
sound pressure level frequency characteristics: ○ Drop impact test: 5 Even after the drop, no
breakage of the piezoelectric element was observed, and after the test, the sound pressure level
(1 kHz) was measured to be 78 dB.
[0090]
Seventh Embodiment of the Invention As a seventh embodiment, a laptop PC (Personal
Computer) as shown in FIG. 7 is prepared, and the electro-acoustic transducer of the first
embodiment is mounted in this case. Specifically, an electroacoustic transducer is attached to the
inner surface of the casing of the mobile phone.
[0091]
(Evaluation): A sound pressure level and frequency characteristics were measured by a
microphone placed at a position 10 cm away from the element. In addition, a drop impact test
was also conducted. [Results] Sound pressure level (1 kHz): 79 dB Sound pressure level (3 kHz):
81 dB Sound pressure level (5 kHz): 84 dB Sound pressure level (10 kHz): 80 dB Flatness of
sound pressure level frequency characteristics: ○ Drop impact test: 5 Even after the drop, no
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22
breakage of the piezoelectric element was observed, and after the test, the sound pressure level
(1 kHz) was measured to be 78 dB.
[0092]
The present invention is not limited to the present embodiment, and various modifications are
allowed without departing from the scope of the present invention. In addition, as a matter of
course, the above-described embodiment and a plurality of examples can be combined within the
scope where the contents do not contradict each other. Further, in the embodiment and the
modification described above, 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.
[0093]
1-a vibrating membrane 1-b polymer electrolyte gel 1-c support 1-d lead wire 2-a upper
electrode layer 2-b polymer electrolyte gel 2-c lower electrode layer 5-a vibrating membrane 5-b
high Molecular electrolyte gel 5-c support 5-d Lead wire 5-e elastic member 6-a vibrating
membrane 6-b1 polymer electrolyte gel 6-b2 polymer electrolyte gel 6-c support 6-d lead wire 7a Vibrating membrane 7-b1 polymer electrolyte gel 7-b2 polymer electrolyte gel
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