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DESCRIPTION JP2006121648

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DESCRIPTION JP2006121648
The present invention provides an acoustic element that can realize high sound quality and high
volume for a long time with small power consumption. A piezoelectric acoustic element 10
includes a shim plate 2 and a piezoelectric drive unit 31 formed on one surface of the shim plate
2. In the piezoelectric acoustic element 10, the piezoelectric drive portion 31 is formed by
alternately laminating the electrode layers 18, 19 and the piezoelectric layer 14, and the shim
plate 2 is formed of a ceramic material. Is integrated with firing. [Selected figure] Figure 1
Piezoelectric acoustic element and piezoelectric acoustic generator
[0001]
The present invention relates to a piezoelectric acoustic element in which a shim plate and a
piezoelectric drive unit are integrated by firing, and a piezoelectric acoustic generator which
transmits the vibration generated and amplified by the piezoelectric acoustic element to a panel
and uses the panel as an acoustic source. About.
[0002]
In recent years, in mobile electronic devices such as mobile phones, digital cameras, PDAs
(personal digital assistants) and the like, miniaturization and weight reduction are advancing at
an accelerating pace, and piezoelectric exciters are provided as their exciters (excitation
elements). Panel type speakers are preferably used.
[0003]
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Usually, a piezoelectric drive body provided as an acoustic element in such a panel-type speaker
comprises a piezoelectric element comprising a piezoelectric layer and an electrode layer, and the
piezoelectric element is an adhesive or the like on one side or both sides of a metal shim plate.
Bonded and configured as a piezoelectric driver.
The piezoelectric driving body has a mechanism that emits a sound by being deformed so that
the whole is curved by applying a voltage and expanding and contracting a piezoelectric element
(piezoelectric layer).
For example, according to the description of Patent Document 1, there has been proposed a
piezoelectric drive body characterized in that a piezoelectric element obtained by laminating a
plurality of piezoelectric layers and electrode layers alternately and sintering them
simultaneously is bonded to a shim plate. Further, Patent Document 2 discloses a sound
generating device in which elastic plates are arranged in parallel to a piezoelectric bimorph and
the protection panel is vibrated. In addition, Patent Documents 3 and 4 disclose thin-type
speakers provided with an exciter that excites a vibration on a flat diaphragm although the
vibration generation source is not limited to the piezoelectric element. Patent Document 1: JP-A2002-261341 Patent Document 2: JP-A-2005-26754 Patent Document 2: JP-A-2004-336403
Patent Document 1: International Publication WO 01/54450
[0004]
In the case of using a piezoelectric driver as the acoustic element of the panel type speaker, the
acoustic element used in the panel type speaker for portable electronic devices in particular can
be driven with small power consumption, from electric energy to acoustic energy Conversion
efficiency is required to be high. In addition, excellent sound quality such as a wide reproduction
band and a high dynamic range is also important. Furthermore, durability is also important, such
as no deterioration in sound quality occurs even when used continuously for a long time.
[0005]
However, conventional acoustic elements do not necessarily satisfy these conditions, and more
excellent acoustic elements have been required from the viewpoints of conversion efficiency,
sound quality, and durability described above. The present invention has been made to meet such
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needs, and an object of the present invention is to provide an acoustic element capable of
achieving high sound quality and large volume for a long time with small power consumption. is
there.
[0006]
As a result of repeated studies on a conventional acoustic element (piezoelectric driving body), it
was found that one of the problems is a structure in which the piezoelectric element is bonded to
a shim plate with an adhesive or the like. That is, a part of the vibrational energy generated by
the expansion and contraction of the piezoelectric layer is absorbed by the adhesive layer by the
adhesive or the like, so that a loss of the vibrational energy occurs to reduce the conversion
efficiency to acoustic energy. It has been difficult to achieve high sound quality. In addition, the
drive for a long period of time, in particular, causes the adhesive layer portion to be deteriorated,
resulting in the deterioration of the sound quality, and further the efficiency reduction.
[0007]
As a result of repeated research, in the acoustic element used for a panel type speaker, a means
was conceived to integrate the shim material and the piezoelectric element without an adhesive
layer, and a ceramic material is adopted for the shim plate, and the shim It is found that an
acoustic element having high conversion efficiency, high sound quality, and high durability can
be obtained by adopting a structure in which a plate and a piezoelectric drive portion
(corresponding to a piezoelectric element) having a piezoelectric layer are fired and integrated.
The present invention has been completed.
[0008]
That is, first, according to the present invention, there is provided a piezoelectric acoustic
element comprising a shim plate and a piezoelectric drive portion formed on at least one surface
of the shim plate, the piezoelectric drive portion comprising a plurality of electrode layers And a
piezoelectric layer are alternately laminated, and a piezoelectric acoustic element is provided in
which the shim plate is formed of a ceramic material and the piezoelectric drive portion and the
shim plate are integrated by firing.
[0009]
The piezoelectric acoustic device according to the present invention preferably has a resonance
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frequency in the range of 20 Hz to 20 kHz.
It is further preferable that the frequency is 100 Hz to 1 kHz.
[0010]
In addition, it is preferable that the shape has a strip shape, and the aspect ratio (length / width)
of the shape is 5 to 50.
More preferably, the aspect ratio is 10-20. Usually, the shape refers to the shape of the shim
plate. The length refers to the distance in the longitudinal direction of the plane, and the width
refers to the distance in the short direction of the plane. That is, the shape referred to here is a
shape of a plane, and the aspect ratio corresponds to the aspect ratio of the plane shape.
[0011]
Furthermore, it is preferable that the shim plate be provided with a plurality of exposed portions
in which the piezoelectric drive portion is not formed and the shim plate itself is exposed. In this
case, it is preferable that a plurality of exposed parts, that is, non-formed parts of the
piezoelectric drive parts be provided near the end of the shim plate and / or near the center. The
vicinity of the end of the shim plate refers to the largest (or longest) part from the end to 1/3
when divided into three in a certain direction, and the vicinity of the center refers to the central
part divided into three . A certain direction may be either the longitudinal direction or the
latitudinal direction, but when the shape (of the shim plate) has a strip shape, near the end or
near the center means near the end or near the center in the longitudinal direction. Point to.
[0012]
The piezoelectric acoustic device according to the present invention can be an acoustic source
including a speaker, a sounder, a vibrator and the like alone. Although not limited, when the
piezoelectric acoustic device according to the present invention is used as, for example, a
speaker, a sounder or the like used in an electronic device, the exposed portion (the portion
where the shim plate (ceramic material) is exposed) ) Is preferably fixed to, for example, a
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housing of an electronic device and vibrated via a support member at exposed portions near both
of the end portions.
[0013]
Furthermore, in the piezoelectric drive portion, the thickness in the vicinity of at least one of the
end portions is preferably different from the thickness in the vicinity of the center. And
preferably, the difference in thickness is based on the difference in thickness of the piezoelectric
layer. The vicinity of the end of the piezoelectric drive refers to the largest (or longest) part from
the end to 1/3 when divided into three in a certain direction, and the vicinity of the center refers
to the central part divided into three Point to. The certain direction may be either the
longitudinal direction or the short direction.
[0014]
In the piezoelectric acoustic device according to the present invention, the thickness of each of
the plurality of piezoelectric layers applied to the piezoelectric drive portion is 5 to 100 μm, and
the thickness of each of the plurality of piezoelectric layers is a lamination from the shim plate It
is preferable to differ according to the order. By changing the thickness of the piezoelectric layer,
the piezoelectric acoustic device obtained by firing integration can be effectively operated.
[0015]
Specifically, the thickness of each piezoelectric layer is determined by the method of forming the
piezoelectric drive portion. For example, in the case where a plurality of piezoelectric layers and
an electrode layer are integrally baked together with the shim plate simultaneously, the thickness
of the piezoelectric layer on the side closer to the shim plate (the order of lamination from the
shim plate is earlier) Is preferably relatively smaller than the side farther from the shim plate (the
stacking order from the shim plate is slower). On the other hand, when a plurality of piezoelectric
layers and electrode layers are fired each time each layer is formed and integrated with the shim
plate, the thickness of the piezoelectric layer on the side farther from the shim plate is greater It
is preferable to make the thickness small (thin).
[0016]
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In the piezoelectric acoustic device according to the present invention, the number of layers of
the plurality of piezoelectric layers applied to the piezoelectric drive unit is preferably 2 to 10.
The more preferred number of layers is 2 to 6.
[0017]
In the piezoelectric acoustic device according to the present invention, the thickness of the
plurality of electrode layers applied to the piezoelectric drive portion is not limited, and may be
an appropriate thickness according to the application, but 10 μm or less It is more preferable to
form with a thickness of 5 μm or less.
[0018]
In the piezoelectric acoustic device according to the present invention, the thickness of the shim
plate is not limited, but is preferably 100 μm or less.
More preferably, it is 50 micrometers or less, More preferably, it is 30 micrometers or less. This
is because high-speed response and large bending vibration / amplitude can be obtained.
Moreover, it is preferable that the Young's modulus as a structure of a shim board is 150 GPa or
more and 450 GPa or less. More preferably, it is 200 GPa or more and 400 GPa or less.
Furthermore, 120 MPa or more is preferable and, as for the bending strength as a structure of a
shim board, it is desirable that it is especially 150 MPa or more.
[0019]
In the piezoelectric acoustic device according to the present invention, it is preferable that an
object formed of a material having the same specific gravity or a larger specific gravity as the
ceramic material forming the shim plate is applied to any of the plurality of exposed portions.
And it is more preferable that this object is made of the same ceramic material as the shim plate,
and the object and the shim plate are integrated by firing. This object plays a role like a weight
for increasing an inertial mass applied to vibration, but is referred to as an object in the present
specification because it does not limit the shape, structure and the like.
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[0020]
Next, according to the present invention, there is provided any one of the above-described
piezoelectric acoustic elements, and a panel coupled to the exposed portion of the piezoelectric
acoustic elements via a support member, and a piezoelectric drive portion of the piezoelectric
acoustic element. By driving the piezoelectric acoustic element to vibrate, the panel is excited to
generate a sound from the panel. In this piezoelectric acoustic generator, the panel is a
diaphragm that generates sound, and the piezoelectric acoustic element is an excitation element
that vibrates the panel. The panel may be coupled to the exposed portions near both ends of the
piezoelectric acoustic element through the support member, or the piezoelectric acoustic element
may be cantilevered to the exposed portion near one end. It is also possible to couple to the
exposed part near the center.
[0021]
In the piezoelectric acoustics generator concerning the present invention, it is preferred that the
above-mentioned object is given to a piezoelectric acoustic element. This is because the inertial
mass can be increased and the vibrational energy transmitted to the panel through the support
member can be increased. In this case, it is desirable that the object be disposed at a position
farthest from the support member to be coupled to the panel, in other words, at a position where
the amplitude is the largest when the piezoelectric acoustic element vibrates. The reason is that
when a piezoelectric acoustic element is used as an excitation element to vibrate a diaphragm
(panel), the inertia mass of the portion with the largest amplitude is necessary to increase the
vibration energy transmitted to the panel through the support member. It is effective to increase
the
[0022]
Also, by adjusting the inertia mass by changing the mass of the object to be applied, it is possible
to adjust the resonance frequency or Q value of the piezoelectric acoustic element, thereby
making it possible to obtain desired sound such as reproduction range, sound pressure,
frequency characteristics, etc. It is possible to realize the characteristics. In addition, as another
means for obtaining desired acoustic characteristics, vibration characteristics are provided
between the portion of the shim plate to which the support member is fixed and the portion to
which the object is applied, that is, the vibration portion of the piezoelectric acoustic element.
Means of forming a structure for control can be employed. For example, specific means such as
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forming a notch or a hole in a part of the shim plate, or forming the piezoelectric drive portion in
an appropriate pattern to adjust the distribution of the driving force can be used.
[0023]
As a piezoelectric sound generator concerning the present invention, a panel type speaker, a
ceramic speaker, a sounder, a buzzer, a vibrator, etc. are mentioned, for example.
[0024]
The piezoelectric acoustic device according to the present invention is obtained by firing and
integrating a piezoelectric drive portion having a piezoelectric layer and a shim plate formed of a
ceramic material, and using an adhesive or the like between the piezoelectric drive portion and
the shim plate. Since the adhesive layer does not intervene, vibrational energy generated by the
expansion and contraction of the piezoelectric layer is converted to acoustic energy without loss,
and high conversion efficiency is realized.
Further, since there is no adhesive layer, peeling and the like do not occur by driving the
piezoelectric drive unit for a long time, and high durability is realized. Furthermore, the sound
quality is not deteriorated due to the deterioration of the adhesive layer, and high sound quality
can be maintained.
[0025]
Since the piezoelectric acoustic element according to the present invention employs a ceramic
material instead of a metal material for the shim plate, it is difficult to pick up noise as an electric
/ electronic circuit, and higher sound quality can be realized. Moreover, since there is no fear of
causing rust like metal, it is excellent in long-term quality reliability. Furthermore, in the case of a
metal material, when it is formed into a thin plate like a shim plate, it has spreadability, so it is
plastically deformed by vibration for a long time, and it is easy to cause change in sound quality.
Although deterioration of the material itself progresses, such problems do not occur in the
piezoelectric acoustic device according to the present invention, and the durability is higher. In
addition, the weight can be further reduced.
[0026]
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In a preferred embodiment of the piezoelectric acoustic device according to the present
invention, the thickness of each of the plurality of piezoelectric layers applied to the piezoelectric
drive portion is 5 to 100 μm, and the thickness of each of the plurality of piezoelectric layers is
Because they differ according to the stacking order from the shim plates, higher displacement
efficiency can be realized.
[0027]
When a plurality of piezoelectric layers and electrode layers are simultaneously fired together
with a shim plate, the thickness of the piezoelectric layer on the side closer to the shim plate
(early in the stacking order from the shim plate) is If it is relatively smaller than the side far from
the plate (the stacking order from the shim plate is slow), the following effects can be obtained.
When the piezoelectric layer is integrated with the shim plate by firing, some stress is caused, but
the firing stress becomes larger as the piezoelectric layer on the side closer to the shim plate, so
the material property of the piezoelectric layer is far It will be inferior to the material properties
of the layer. In other words, the same electric field induced distortion can not be obtained in the
same electric field, which causes a decrease in displacement efficiency. Therefore, if the thickness
of the piezoelectric layer closer to the shim plate is relatively small (thin), the effective electric
field acting on the piezoelectric layer is increased, and the displacement efficiency as a
piezoelectric acoustic element (piezoelectric drive unit) is improved. is there. Further, since the
thickness of only a part of the piezoelectric layer is changed, the rigidity and the displacement
can be compatible without sacrificing the rigidity of the whole piezoelectric acoustic element.
[0028]
In the case where a plurality of piezoelectric layers and electrode layers are fired each time each
layer is formed and integrated with the shim plate, the thickness of the piezoelectric layer on the
side farther from the shim plate is reduced (thinned) as follows: The effect of In this case, if it is
the layer to be fired, the base (already fired) is rigid like the shim plate, and if the number of fired
layers is large, the thickness of the base is that much Since the thickness is increased, the rigidity
is increased and the stress at the time of newly firing is also increased. Therefore, by reducing
the thickness of the piezoelectric layer on the side farther from the shim plate, the effective
electric field can be increased to increase the displacement efficiency.
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[0029]
Although a metal material is used as a shim plate in the conventional piezoelectric drive body
shown in Patent Document 1, the piezoelectric acoustic generator according to the present
invention is a shim as an excitation element for vibrating a panel to generate sound. A
piezoelectric acoustic element (according to the present invention) using a ceramic material for
the plate is adopted. In a preferred embodiment, an object formed of a material having a specific
gravity greater than that of the ceramic material forming the shim plate is applied near the end
(which is the exposed portion) or near the center of the shim plate. Therefore, for example, a
panel which is a diaphragm is coupled to one end (which is an exposed portion) of the shim plate
via a support member, and an object is adjacent to the other (which is exposed portion) of the
shim plate. By adopting the embodiment to be applied, the piezoelectric sound generator
according to the present invention can obtain higher excitation efficiency than the conventional
one. This is because, in general, the specific gravity of ceramic materials is lighter than that of
metal materials, so if they have the same weight, the shim plates of ceramic materials will have
the largest amplitude when vibrating, as compared to the case of metal material shims. This is
because it is possible to increase the distribution of mass to a portion that is to be increased (also
referred to as an excitation portion of the piezoelectric acoustic element) and to further increase
the inertial force. Further, in the piezoelectric acoustic generator according to the present
invention, since the piezoelectric drive portion and the shim plate are integrated by firing, the
mass other than the object to be applied can be further reduced by the amount not using the
adhesive. It can.
[0030]
In the piezoelectric acoustic generator according to the present invention, the piezoelectric drive
unit and the shim plate are integrated by firing, and when the same (ie, with the same specific
gravity) ceramic material as the shim plate is used as the material of the object, the shim plate,
piezoelectric The drive unit and the whole of the object can be integrated by firing. Therefore,
peeling and the like can not occur by long time use, and high durability is realized. Furthermore,
the sound quality deterioration due to the deterioration of the adhesive layer does not occur, and
high sound quality can be maintained.
[0031]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe
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embodiments of the present invention as needed, referring to the drawings, but the present
invention should not be construed as being limited thereto. Various changes, modifications,
improvements, and substitutions can be made based on the knowledge of those skilled in the art
without departing from the scope of the present invention. For example, although the drawings
show preferred embodiments of the present invention, the present invention is not limited by the
embodiments shown in the drawings and the information shown in the drawings. In carrying out
or verifying the present invention, means similar or equivalent to those described herein may be
applied, with the preferred means being the means described hereinafter.
[0032]
The piezoelectric acoustic device according to the present invention, which is expressed as
piezoelectric, is an element capable of generating sound by using distortion induced by an
electric field, and distortion substantially proportional to an applied electric field in a narrow
sense. Not limited to acoustic elements that use the piezoelectric effect that generates a quantity,
the electrostrictive effect that generates an amount of strain approximately proportional to the
square of the applied electric field, polarization inversion seen in all ferroelectric materials,
antiferroelectric materials Also included are acoustic elements that utilize phenomena such as
the phase transition between antiferroelectric phase and ferroelectric phase that can be
observed. Whether or not the polarization process is performed is also appropriately determined
based on the property of the material of the piezoelectric layer which is the main component of
the piezoelectric acoustic device. The term "piezoelectric layer" refers to a layered piezoelectric
material (not similarly narrow sense).
[0033]
First, a piezoelectric acoustic device according to the present invention will be described. FIG. 1 is
a cross-sectional view showing an embodiment of a piezoelectric acoustic device according to the
present invention. The piezoelectric acoustic element 10 clearly shown in FIG. 1 includes a shim
plate 2 and a piezoelectric drive portion 31 formed on the upper surface (in the figure) of the
shim plate 2. The piezoelectric drive unit 31 is formed by alternately laminating three electrode
layers 18 and 19 and two piezoelectric layers 14. The material of the shim plate 2 is ceramic, and
the piezoelectric drive portion 31 and the shim plate 2 are integrated by firing.
[0034]
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The shape of the piezoelectric acoustic element 10 does not show a plan view, but exhibits a strip
shape (rectangle) in plan view, and the aspect ratio (length / width) of the shape is 30 mm / 3
mm = 10. Further, as shown in the drawing, on the upper surface of the shim plate 2 on which
the piezoelectric drive portion 31 is formed, the piezoelectric drive portion 31 is not formed in
the vicinity of both ends, and the shim plate 2 is exposed on the upper surface An exposed
portion 7 is provided. When the piezoelectric acoustic element 10 is used as an acoustic source,
for example, as a ceramic speaker itself, it can be supported by this exposed portion 7 and
vibrated.
[0035]
In the piezoelectric acoustic device 10, the thickness in the vicinity of both ends (portions near
the end 17) of the piezoelectric drive portion 31 is the thickness in the vicinity of the center (the
central vicinity 16) based on the difference in thickness Is different. The piezoelectric acoustic
element 10 is a combination of the shim plate 2 and the piezoelectric drive portion 31 (two
piezoelectric layers 14 and three electrode layers 18 and 19) simultaneously and integrally
sintered, and the thickness of the piezoelectric layer 14 is The length is 40 μm closer to the
shim plate 2 and 50 μm farther.
[0036]
FIG. 2 is a cross-sectional view showing another embodiment of the piezoelectric acoustic device
according to the present invention. The piezoelectric acoustic element 20 clearly shown in FIG. 2
includes a shim plate 2 and two piezoelectric drive portions 31 formed on both sides (upper and
lower surfaces in the figure) of the shim plate 2. Each of the two piezoelectric drive units 31 is
formed by alternately stacking three electrode layers 18 and 19 and two piezoelectric layers 14.
Similar to the piezoelectric acoustic element 10, the material of the shim plate 2 is a ceramic, and
the piezoelectric drive portion 31 and the shim plate 2 are integrated by firing.
[0037]
The shape of the piezoelectric acoustic element 20 does not show a plan view, but has a
rectangular shape (rectangular shape) in plan view, and the aspect ratio (length / width) of the
shape is 32 mm / 4 mm = 8. Further, as illustrated, on both surfaces of the shim plate 2 on which
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the piezoelectric drive portion 31 is formed, the piezoelectric drive portion 31 is not formed in
the vicinity of both end portions of the shim plate 2. An exposed portion 7 in which 2 is exposed
on both sides is provided. As in the case of the piezoelectric acoustic element 10, when the
ceramic speaker itself is used as an acoustic source, it can be supported by this exposed portion
7 and vibrated.
[0038]
The piezoelectric acoustic element 20 has a thickness in the vicinity of both ends (near end 17)
of the two piezoelectric drive units 31 based on the difference in thickness of the piezoelectric
layer 14 as in the piezoelectric acoustic element 10. The thickness is different from the thickness
in the vicinity of the center (in the vicinity of the center 16). Further, unlike the piezoelectric
acoustic element 10, the piezoelectric acoustic element 20 has the electrode layer 19, the
piezoelectric layer 14, the electrode layer 18, the piezoelectric layer 14, and the electrode layer
19 laminated on the shim plate 2 on both sides, In each case, it is integrated by firing, and the
thickness of the piezoelectric layer 14 is 60 μm closer to the shim plate and 50 μm farther.
[0039]
Next, a piezoelectric sound generator according to the present invention will be described. FIG. 4
is a side view schematically showing an embodiment of a piezoelectric acoustic generator
according to the present invention including the piezoelectric acoustic element according to the
present invention, and FIG. 3 is a piezoelectric according to the present invention constituting the
same. It is a figure which shows an acoustic element, (a) is a top view, (b) is a side view. The
piezoelectric drive is omitted in FIG. 4 (hereinafter the same in FIGS. 6 and 8), and the
piezoelectric drive in FIG. 3 does not clearly show the piezoelectric layer and the electrode layer
(hereinafter the same in FIGS. 5 and 7) ). The piezoelectric acoustic generator 40 shown in FIG. 4
has the piezoelectric acoustic element 30 shown in FIG. 3 as a main component, and further, one
exposed portion provided in the vicinity of the end of the shim plate 2 of the piezoelectric
acoustic element 30. 33a includes a panel 41 coupled via a support member 42, and the
piezoelectric drive unit 31 of the piezoelectric acoustic element 30 is driven to vibrate (the shim
plate 2) to excite the panel 41, and the panel 41 is excited. It is a device that generates sound 8.
[0040]
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In the piezoelectric acoustic element 30, in the shim plate 2, in addition to the exposed portion
33a fixed to the support member 42, an exposed portion 33b similarly provided in the vicinity of
the end portion of the shim plate 2 is present. An object 32 formed of, for example, a metal
material having a specific gravity greater than that of the ceramic material forming the plate 2 is
applied by adhesion. The object 32 is disposed farthest from the support member 42 and at a
position (excitation portion of the piezoelectric acoustic element 30) at which the amplitude
becomes largest when the piezoelectric acoustic element 30 (the shim plate 2) vibrates. The
vibrational energy generated by the element 30 is increased.
[0041]
In the piezoelectric acoustic element 30, although the object 32 is applied to both surfaces of the
shim plate 2, it may be a single surface, or may be made of materials having different sizes or
different specific gravities. The inertial mass can be adjusted, and in the piezoelectric acoustic
element 30, the exposed portions 33a and 33b are portions where the piezoelectric drive portion
31 is not formed and the shim plate 2 itself is exposed (see FIG. Hereinafter, the same applies to
the piezoelectric acoustic element and the piezoelectric acoustic generator of other aspects
described later).
[0042]
FIG. 6 is a side view schematically showing another embodiment of the piezoelectric acoustic
generator according to the present invention including the piezoelectric acoustic device
according to the present invention, and FIG. 5 is a piezoelectric according to the present
invention constituting the same. It is a figure which shows an acoustic element, (a) is a top view,
(b) is a side view.
The piezoelectric acoustic generator 60 shown in FIG. 6 has the piezoelectric acoustic element 50
shown in FIG. 5 as a main component, and further, both exposed portions provided in the vicinity
of the end of the shim plate 2 of the piezoelectric acoustic element 50 53a is provided with a
panel 41 coupled respectively via a support member 42, and by driving the piezoelectric drive
portion 51 of the piezoelectric acoustic element 50 (the shim plate 2 vibrates), the panel 41 is
excited, and from the panel 41 It is a device that generates sound 8. In the same manner as the
piezoelectric drive unit 31, the piezoelectric drive unit 51 is formed by alternately laminating
three electrode layers and two piezoelectric layers.
[0043]
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In the piezoelectric acoustic element 50, in the shim plate 2, in addition to the exposed portion
53a fixed to the support member 42, an exposed portion 53b provided in the vicinity of the
center of the shim plate 2 is present. An object 52 formed of the same ceramic material (and
hence the same specific gravity) as that of the ceramic material that forms the above is applied
and integrated with the shim plate 2 by firing. The object 52 is disposed at a position (excitation
portion of the piezoelectric acoustic device 50) where the amplitude is the largest when the
piezoelectric acoustic device 50 (the shim plate 2) vibrates the farthest from the two support
members 42, The vibrational energy generated by the piezoelectric acoustic element 50 is
increased.
[0044]
FIG. 8 is a side view schematically showing still another embodiment of the piezoelectric acoustic
generator according to the present invention including the piezoelectric acoustic device
according to the present invention, and FIG. 7 according to the present invention constituting the
same. It is a figure which shows a piezoelectric acoustic element, (a) is a top view, (b) is a side
view. The piezoelectric acoustic generator 80 shown in FIG. 8 has the piezoelectric acoustic
element 70 shown in FIG. 7 as a main component, and is supported by an exposed portion 73b
provided near the center of the shim plate 2 of the piezoelectric acoustic element 70. A panel 41
coupled via a member 42 is provided, and by driving the piezoelectric drive unit 51 of the
piezoelectric acoustic element 70 (the shim plate 2 vibrates), the panel 41 is excited to generate
the sound 8 from the panel 41 Device.
[0045]
In the piezoelectric acoustic element 70, in the shim plate 2, in addition to the exposed portions
73b fixed to the support member 42, there are two exposed portions 73a provided in the vicinity
of both end portions of the shim plate 2, Further, an object 32 formed of, for example, a metal
material having a specific gravity greater than that of the ceramic material forming the shim
plate 2 is applied by adhesion. The object 32 is disposed farthest from the support member 42
and at a position (excitation portion of the piezoelectric acoustic element 70) at which the
amplitude is largest when the piezoelectric acoustic element 70 (the shim plate 2) vibrates. The
vibrational energy generated by the element 70 is increased.
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[0046]
Next, a method of manufacturing a piezoelectric acoustic device according to the present
invention will be described. First, a method of manufacturing a shim plate will be described. The
shim plate can be produced by a powder pressing method or the like without limiting the
production method. However, it is preferable to produce by the green sheet method with higher
productivity, and the following description will be made based on this method.
[0047]
First, a slurry is prepared by adding a binder, a solvent, a dispersant, a plasticizer and the like to
ceramic powder such as zirconium oxide to prepare a slurry, which is defoamed by a reverse roll
coater method, a doctor blade method, etc. A ceramic green sheet having a predetermined
thickness is produced.
[0048]
Then, the ceramic green sheet is processed into a predetermined shape by a method such as
punching using a mold or laser processing to obtain a shim plate precursor.
Here, a shim plate precursor refers to what becomes a functional member which comprises a
shim plate by baking, and means a green molded object. In the case of a thicker shim plate, a
single green sheet having a desired thickness may be used, or a plurality of thin green sheets
may be stacked to correspond. Thereafter, the shim plate precursor processed into a
predetermined shape is degreased and then fired to obtain a predetermined shim plate.
[0049]
Next, a method of manufacturing the piezoelectric drive unit will be described. In order to form
the piezoelectric drive portion by providing the electrode layer and the piezoelectric layer on the
previously obtained shim plate, various known film forming methods are appropriately adopted.
For example, a thick film forming method such as screen printing, spraying, dipping, coating,
electrophoresis, etc., and a thin film forming method such as ion beam, sputtering, vacuum
deposition, ion plating, CVD, plating, etc. are appropriately selected.
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[0050]
In particular, in order to form the piezoelectric layer, a thick film formation method by screen
printing, spraying, dipping, coating or the like is preferably employed. When these thick film
forming methods are used, particles of piezoelectric material having an average particle diameter
of 0.01 to 5 μm, preferably 0.05 to 3 μm, paste or slurry containing powder as a main
component, or suspension, emulsion, sol, aerosol It is possible to form a film by using, etc., and
by firing it, good piezoelectric properties can be obtained.
[0051]
In order to make the piezoelectric layer into a predetermined shape, in addition to forming a
pattern in a predetermined shape by using a screen printing method, a photolithography method
or the like, a mechanical processing method such as a laser processing method, slicing or
ultrasonic processing is used. Unnecessary portions may be removed and patterned.
[0052]
The electrode layer and the piezoelectric layer formed by the above method on the shim plate
may be subjected to firing (heat treatment) each time the respective layers are formed to be
integrated with the shim plate, or all layers may be integrated. After formation, they may be
simultaneously fired to simultaneously integrate the layers into the shim plate.
In addition, when forming an electrode layer by the said film formation method, in order to unify
with a shim board, baking (heat processing) may not necessarily be required.
[0053]
Generally, a temperature of about 900 ° C. to about 1,400 ° C. is employed as a firing (heat
treatment) temperature for integrating the electrode layer and the piezoelectric layer, which are
formed in this manner, and the shim plate, preferably 1000 ° C. to about 1400 ° C.
Temperatures in the range of ° C. are advantageously chosen. When firing the piezoelectric
layer, it is preferable to perform firing while controlling the atmosphere together with the
evaporation source of the piezoelectric material forming the piezoelectric layer so that the
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composition of the piezoelectric layer does not become unstable at high temperature. When the
same ceramic material as that of the shim plate is used as the material of the object for inertia
mass adjustment, and the object and the shim plate are integrated by firing, the object is placed
on the shim plate before firing. It needs to be formed. For example, using the same ceramic green
sheet as the shim plate, press the object onto the shim plate simultaneously with the formation of
the shim plate, or separately prepare an object before and after the process of forming the
piezoelectric drive portion on the shim plate. The paste of the ceramic material may be
temporarily fixed on the shim plate.
[0054]
Next, a method of manufacturing a piezoelectric sound generator according to the present
invention will be described. The piezoelectric acoustic generator according to the present
invention can be obtained by obtaining a piezoelectric acoustic element by the means described
above and bonding the support to a panel. The adhesive used for adhesion may be any of
thermoplastic, thermosetting and synthetic rubber, and can be selected based on the use
atmosphere and the like. For example, it is preferable to employ a thermosetting resin such as an
epoxy resin.
[0055]
The panel is not limited to the manufacturing method, and for example, it is processed into a
predetermined shape by molding, punching, cutting a glass plate of a desired thickness
commercially available, or a thin plate made of a resin material such as acrylic. It can be made.
The supporting member can also be manufactured by processing a thick plate or the like made of
a commercially available resin-based material, for example, into a predetermined shape by
molding, punching, or cutting, without limiting the manufacturing method.
[0056]
In the piezoelectric acoustic generator, the electrode layer of the piezoelectric driving body of the
piezoelectric acoustic element constitutes a positive electrode or a negative electrode for each
layer, but a wire for applying a voltage between the positive electrode and the negative electrode
is fixed along the support member. Preferably, a wiring pattern is formed on the support member
itself. This is to prevent the wiring from becoming a factor that inhibits the vibration.
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[0057]
The piezoelectric acoustic device according to the present invention and the method of
manufacturing the same, and the piezoelectric acoustic generator and the method of
manufacturing the same have been described above. Subsequently, the piezoelectric acoustic
device and the piezoelectric acoustic generation device according to the present invention are
described below. The materials used for First, the ceramic material forming the shim plate will be
described. The ceramic material of the shim plate may be oxide or non-oxide as long as it has
high mechanical strength and can be integrated by firing with the above-described piezoelectric
drive unit. Among them, it is preferable to use a ceramic material containing at least one of
aluminum oxide, magnesium oxide, zirconium oxide, aluminum nitride and silicon nitride as a
main component. In particular, a shim plate containing zirconium oxide as a main component is
advantageously used because excellent vibration characteristics can be obtained even if the plate
thickness is small, and the reactivity at the time of firing (heat treatment) with the piezoelectric
drive portion is low. .
[0058]
The amount of silicon oxide (SiO, SiO2) contained in the ceramic material of the shim plate is
preferably 5% by mass or less, and more preferably 1% by mass or less. Such regulation of the
silicon oxide content is important in order to avoid reaction with the piezoelectric material
forming the piezoelectric layer described later at the time of firing and to obtain good device
characteristics.
[0059]
Next, materials of the electrode layer and the piezoelectric layer constituting the piezoelectric
drive unit will be described. First, as a piezoelectric material for forming a piezoelectric layer, a
material having a high piezoelectric constant and a high electromechanical coupling coefficient is
preferable. Specifically, lead zirconate, lead manganese tungstate, sodium bismuth titanate,
bismuth ferrate, Potassium niobate, strontium bismuth tantalate, lead magnesium niobate, lead
nickel niobate, lead zinc niobate, lead manganese niobate, lead magnesium tantalate, lead nickel
tantalate, lead antimony stannate, lead titanate, titanium Examples include barium oxide, copper
barium tungstate, magnesium lead tungstate, lead cobalt niobate, or a composite oxide composed
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of two or more of these.
[0060]
Moreover, these piezoelectric materials include lanthanum, calcium, strontium, molybdenum,
tungsten, barium, niobium, zinc, nickel, manganese, cerium, cadmium, chromium, cobalt,
antimony, iron, yttrium, tantalum, lithium, bismuth, tin And oxides such as copper may be solidsolved.
[0061]
In addition, lithium bismuthate or lead germanate is added to a material obtained by adding
lithium bismuthate, lead germanate or the like to the above-mentioned materials, such as lead
zirconate, lead titanate, and lead oxide of magnesium niobate. Materials can be adopted.
These materials can exhibit high material properties while realizing low-temperature firing of the
piezoelectric layer.
[0062]
Among the above-mentioned piezoelectric materials, a material mainly composed of components
comprising lead magnesium niobate, lead zirconate and lead titanate, a component mainly
composed of lead nickel niobate, lead zirconate and lead titanate Preferably, the material is a
material mainly composed of lead nickel niobate, lead magnesium niobate, lead zirconate and
lead titanate and, among them, lead magnesium niobate, lead zirconate and lead titanate.
Particularly preferred is a material having as a main component a component consisting of and is
recommended as a material in the case of forming a piezoelectric film by a thick film forming
method such as screen printing, spraying, dipping or coating. The reason is that there is little
reaction with the ceramic material forming the shim plate during firing (heat treatment), and as a
result, segregation of components does not easily occur, and treatment for maintaining the
composition can be suitably performed. Moreover, it is because the target composition and
crystal structure can be easily obtained, and furthermore, they have a high piezoelectric constant,
an electromechanical coupling coefficient, and a low mechanical quality factor.
[0063]
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Next, the material forming the electrode layer is preferably made of a metal which is solid at
room temperature and has excellent conductivity, and, for example, aluminum, titanium,
chromium, iron, cobalt, nickel, copper, zinc, Metals such as niobium, molybdenum, ruthenium,
palladium, rhodium, silver, tin, tantalum, tungsten, iridium, platinum, gold, lead and the like, or
alloys thereof are used. Moreover, you may use the cermet material which disperse | distributed
the same material as a piezoelectric layer or a shim board to these, and it is preferable to
disperse | distribute in the ratio of about 5-30 volume% in this case.
[0064]
Next, the material forming the panel, the support member, and the object for inertial mass
adjustment will be described. The material of the panel is not limited as long as it can generate
sound. For example, resin materials such as acryl, ABS, and polycarbonate, glass materials such
as phosphoric acid-silica glass, carbon fiber materials, metal materials such as aluminum and
stainless steel, and the like are used. The material of the support member is not limited and can
be adopted according to the material of the panel. As for the object, among the material of the
panel and the ceramic material of the shim plate, one having the same specific gravity as or
larger than the ceramic material of the shim plate can be selected and adopted.
[0065]
The piezoelectric acoustic device and the piezoelectric acoustic generator using the same
according to the present invention are incorporated in portable electronic devices selectively
provided with functions such as a laptop computer, a telephone, a camera, a GPS, a radio, a
television, etc. Used in place of a speaker. For example, the liquid crystal protective panel of the
portable electronic device is adopted as a panel in the piezoelectric acoustic generator according
to the present invention, and the piezoelectric acoustic generator according to the present
invention is incorporated into the portable electronic device. Sound can be generated. Moreover,
the piezoelectric acoustic element of the present invention and the piezoelectric acoustic
generator using the same are suitably used as a buzzer, a sounder, a vibrator and the like.
[0066]
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1 is a cross-sectional view showing an embodiment of a piezoelectric acoustic device according to
the present invention. FIG. 7 is a cross-sectional view showing another embodiment of a
piezoelectric acoustic device according to the present invention. It is a figure which shows the
piezoelectric acoustic element which concerns on this invention which comprises the
piezoelectric sound generator shown by FIG. 4, (a) is a top view, (b) is a side view. It is a side view
showing typically one embodiment of a piezo-electric sound generator concerning the present
invention. It is a figure which shows the piezoelectric acoustic element which concerns on this
invention which comprises the piezoelectric acoustic generator shown by FIG. 6, (a) is a top view,
(b) is a side view. It is a side view which shows typically another embodiment of the piezoelectric
sound generator concerning the present invention. It is a figure which shows the piezoelectric
acoustic element which concerns on this invention which comprises the piezoelectric acoustic
generator shown by FIG. 8, (a) is a top view, (b) is a side view. It is a side view which shows
typically other embodiment of the piezoelectric sound generator concerning this invention.
Explanation of sign
[0067]
Reference Signs List 2 shim plate 8 acoustic 10, 20 30, 30, 50, 70 piezoelectric acoustic element
14 piezoelectric layer 16 near central portion 17 near end portion 18, 19 electrode layer 31, 51
... Piezoelectric drive part 32, 52 ... Object, 7, 33a, 33b, 53a, 53b, 73a, 73b ... Exposed part 40,
60, 80 ... Piezoelectric acoustic generator, 41 ... Panel, 42 ... Support member
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