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JP2007228539

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DESCRIPTION JP2007228539
PROBLEM TO BE SOLVED: To improve electrical connection between a piezoelectric element and
a diaphragm while suppressing an increase in rigidity by improving the structure of the
diaphragm, and to prevent an increase in resonance frequency of the piezoelectric diaphragm
and a reduction in sound pressure. SOLUTION: A diaphragm 10 is provided with a laminate 12
including a plurality of insulator layers 12A and 12B, and a circular inner side provided
substantially in the center of a circular piezoelectric element affixing area 11 of at least one main
surface. The connection electrode 14A, the annular outer connection electrode 17A provided at
least outside of the farthest part of the inner connection electrode from the center, and the inner
connection electrode across the region 11 and the region 11 between the layers of the insulator
layer And an outer extraction electrode 27 connected to the outer connection electrode.
Therefore, since it can be drawn out of the area 11 by the inner lead electrode 24 between the
insulator layers, the terminal electrode of the piezoelectric element and the connection electrode
of the diaphragm can be connected in close contact with each other. It is possible to prevent the
increase in rigidity. [Selected figure] Figure 1
Vibrating plate and piezoelectric vibrating plate
[0001]
The present invention relates to a diaphragm and a piezoelectric diaphragm used for an
electroacoustic transducer such as a speaker and a microphone, and more specifically, the
increase in the rigidity of the diaphragm is prevented to increase the resonant frequency and
sound of the piezoelectric diaphragm. It relates to the prevention of pressure drop.
[0002]
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1
Piezoelectric-type electroacoustic transducers such as piezoelectric-type speakers and
microphones are widely used as simple electroacoustic conversion means, and in recent years,
they are frequently used as speakers etc. in the field of mobile phones and portable information
terminals. .
As an example is shown by FIG.6 and FIG.7 in patent document 1, the lamination type
piezoelectric element 200 in which several piezoelectric ceramic layers 202A and 202B were
laminated | stacked on both sides of the internal electrode 204 is one side of the diaphragm 212.
Is fixed to the main surface of the case, and the edge of the diaphragm 212 is supported by the
step of the inner peripheral surface of the case 218. The lead-out electrodes 204A and 207A of
the piezoelectric element 200 and the terminal 216 of the case 218 are conductive adhesive An
electro-acoustic transducer connected by 214 has been proposed.
[0003]
JP, 2005-260623, A
[0004]
However, in the background art as described above, when the lead-out electrodes 204A and
207A of the piezoelectric element 200 are drawn out through the diaphragm 212, the
conductive adhesive 214 protruding from the upper surface exceeding the thickness dimension
of the piezoelectric element 200 is It will be necessary.
Therefore, there is a problem that the thickness dimension of the entire piezoelectric diaphragm
is increased, the rigidity is increased, the resonance frequency of the piezoelectric diaphragm is
increased, and the sound pressure is decreased.
[0005]
The present invention focuses on the above points, and an object thereof is to achieve an
electrical connection between a piezoelectric element and a diaphragm while suppressing an
increase in rigidity by improving the diaphragm structure. Another object is to prevent the
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increase in resonant frequency of the piezoelectric diaphragm and the reduction in sound
pressure by using the diaphragm.
[0006]
In order to achieve the above object, the diaphragm of the present invention comprises: (1) a
laminate including a plurality of insulator layers, and a substantially central portion within a
circular piezoelectric element attachment region of at least one main surface of the laminate. And
an outer connection electrode provided in the piezoelectric element affixing region and at least
outside the farthest portion of the inner connection electrode from the center of the piezoelectric
element affixing region; The present invention is characterized in that an inner lead electrode is
provided between the outside of the piezoelectric element affixing region and the outside of the
region between the plurality of insulator layers of the laminate and connected to the inner
connection electrode.
[0007]
The main embodiment of the present invention is characterized in that (2) the inner connection
electrode and the outer connection electrode are arranged concentrically.
[0008]
Further, according to the piezoelectric diaphragm of the present invention, (3) in the piezoelectric
element affixing region of the diaphragm of (1) or (2), at least one main surface of the
piezoelectric layer has an inner terminal electrode and an annular outer side. It is characterized
in that a piezoelectric element concentrically provided with the terminal electrode is attached.
[0009]
The above and other objects, features and advantages of the present invention will be apparent
from the following detailed description and the accompanying drawings.
[0010]
The diaphragm according to the present invention comprises: (1) a laminate including a plurality
of insulator layers, and an inner connection electrode provided substantially in the center of a
circular piezoelectric element attachment region on at least one of the main surfaces of the
laminate. An outer connection electrode provided in the piezoelectric element affixing region and
at least the outer side of a portion of the inner connection electrode farthest from a center of the
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piezoelectric element affixing region; and a plurality of insulators of the laminate An inner leadout electrode is provided between the outer side of the piezoelectric element affixing region and
the outer side of the layer between the layers and is connected to the inner connection electrode.
Therefore, the inner connection electrode on the main surface of the laminate can be drawn out
of the piezoelectric element affixing area by the inner lead electrode inside the laminate, so the
connection electrode of the pair of concentric piezoelectric electrodes of the piezoelectric
element and the diaphragm Can be connected in close contact with each other.
This can prevent the rigidity of the diaphragm from rising.
[0011]
In addition to (1), (2) the inner connection electrode and the outer connection electrode are
arranged concentrically.
For this reason, when affixing a piezoelectric element in which the inner terminal electrode and
the outer terminal electrode are provided at different distances from the center of the
piezoelectric layer on at least one main surface of the piezoelectric layer, the angle of the
piezoelectric element It can be mounted without worrying about the deviation.
[0012]
Further, according to the piezoelectric diaphragm of the present invention, (3) in the piezoelectric
element affixing region of the diaphragm of (1) or (2), at least one main surface of the
piezoelectric layer has an inner terminal electrode and an annular outside. It was assumed that a
piezoelectric element provided concentrically with the terminal electrode was attached.
Therefore, the pair of concentric terminal electrodes of the piezoelectric element and the
connection electrodes of the diaphragm are connected in close contact with each other. This can
prevent the increase in resonance frequency and the decrease in sound pressure.
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[0013]
Next, an embodiment of the diaphragm of the present invention will be described with reference
to FIGS. 1 to 3. FIG. 1 is an external perspective view showing the entire diaphragm 10 of the
first embodiment, and FIG. 2 is a cross-sectional view of the diaphragm 10 taken along the line AA shown in FIG. 2 is an exploded perspective view showing the internal structure of the
diaphragm 10. FIG.
[0014]
As shown in FIGS. 1 to 3, in the diaphragm 10 of the first embodiment, a convex portion 121
extended in the outer peripheral direction to a substantially disc-like laminate 12 in which a
plurality of insulator layers 12A and 12B are laminated. A pair of connection electrodes 14A and
17A are provided in the circular piezoelectric element affixing regions 11 of one main surface
and the other main surface, and the convex portion 121 of the laminated body 12 is provided.
Terminal portions 24A and 27A of lead-out electrodes connected to the connection electrodes
14A and 17A are provided.
[0015]
Specifically, the inner connection electrode provided at a substantially central portion within the
circular piezoelectric element attaching region 11 of one main surface of the laminated body 12
including the plurality of insulator layers 12A and 12B and the main surface of the laminated
body 12 14A and an outer connection electrode 17A provided at least outside (distance L2) from
a portion (distance L1) of the inner connection electrode 14A in the piezoelectric element
affixing region 11 from the center P of the region 11 And.
Further, an inner lead electrode 24 and an outer lead electrode 27 are provided between the
inside of the piezoelectric element affixing region 11 and the outside of the region 11 between
the plurality of insulator layers 12A and 12B of the laminate 12 ing. In the insulator layer 12A, a
through hole 16A1 is provided at a position where the inner connection electrode 14A and the
inner lead electrode 24 face each other, and a through hole conductor 16A is provided in the
through hole 16A1. The inner connection electrode 14A and the inner lead electrode 24 are
conductively connected. In addition, a through hole 19A1 is provided at a position where the
outer connection electrode 17A and the outer lead electrode 27 face each other, and a through
hole conductor 19A is provided in the through hole 19A1 to provide the outer connection
electrode 17A with the outer lead. The electrode 27 is conductively connected. Further, on the
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other main surface of the laminated body 12, an inner connection electrode 14B provided
substantially at the center of the circular piezoelectric element attaching area 11, and in the
piezoelectric element attaching area 11, the area And an outer connection electrode 17B
provided at least outside (distance L2) from a farthest portion (distance L1) of the inner
connection electrode 14B from the center P of 11; similarly to the above, the inner connection
electrode 14B is The outer connection electrode 17 B is connected to the inner extraction
electrode 24 and connected to the outer extraction electrode 27. Then, in the same manner as
described above, in the insulator layer 12B, a through hole 16B1 is provided at a position where
the inner connection electrode 14B and the inner lead electrode 24 face each other, and the
through hole conductor 16B is formed in the through hole 16B1. And the inner connection
electrode 14B and the inner lead electrode 24 are conductively connected. A through hole 19B1
is provided at a position where the outer connection electrode 17B and the outer lead electrode
27 face each other, a through hole conductor 19B is provided in the through hole 19B1, and the
outer connection electrode 17B and the inner lead are provided. The electrode 27 is conductively
connected. Further, in the convex portion 121 of the laminate 12, two rectangular notches are
formed in parallel in the convex portion 121 A of the insulator layer 12 A from the tip end side
of the convex portion 121 A, and the end of the inner lead electrode 24 24A and the end 27A of
the outer extraction electrode 27 are exposed and can be connected to a drive circuit.
[0016]
Therefore, the inner connection electrode 14A on one main surface of the laminate 12 and the
inner connection electrode 14B on the other main surface of the laminate 12 are placed inside
the interlayers of the plurality of insulator layers 12A and 12B of the laminate 12. Since it can be
drawn out of the piezoelectric element affixing region 11 by the drawing electrode 24, the pair of
concentric terminal electrodes 34, 37 of the piezoelectric element 30 and the connection
electrodes 14A, 14B, 17A, 17B of the diaphragm 10 are closely attached. Can be connected in
the Thereby, the increase in the rigidity of the diaphragm 10 can be prevented.
[0017]
As the insulator layers 12A and 12B, flexible insulating films such as PET (PolyEthylene
Terephtalate), acrylic resin, polystyrene resin, polycarbonate resin, etc. are preferable, but the
present invention is not limited to this, and various other insulating properties A resin sheet can
be used. In the diaphragm 10 of the first embodiment, both the inner extraction electrode 24 and
the outer extraction electrode 27 are provided between the plurality of insulator layers 12A and
12B of the laminate 12, but the present invention is limited thereto. It is sufficient that at least
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the inner lead electrode 24 be provided between the layers, and the outer lead electrode 27 is
either one of the outer connection electrodes 17A and 17B on one or the other main surface of
the laminate 12 Can be extended to form an extraction electrode. Further, the number of the
insulator layers may be three or more, and the inner lead electrode 24 and the outer lead
electrode 27 may be provided between different layers of the plurality of insulator layers, and
the inner lead electrode and the outer lead The electrodes may be respectively provided in a
plurality of layers, and the connection electrode on one main surface of the laminate 12 and the
connection electrode on the other main surface may be connected to lead electrodes in different
layers.
[0018]
As the connection electrodes 14A, 14B, 17A, 17B and the lead-out electrodes 24, 27, a
conductive resin paste containing Ag powder or the like is applied to one main surface of the
flexible insulating sheet by screen printing or the like. After drying at ° C, it is formed, for
example, by heat curing at 150 ° C. In addition, since the adhesive strength with respect to a
PET film etc. is weak since the conductive resin paste contains a large amount of conductive
powder such as Ag powder as a filler, adhesion with the conductive resin paste such as an epoxy
resin layer etc. in advance on the surface of PET film etc. It is preferable to coat an underlayer
having a good strength or to roughen the surface of a PET film or the like in advance by
sandblasting. In addition, as a method of forming each of the electrodes, the application and
curing of the conductive resin paste is an example, and a metal or other thin film conductor layer
may be provided by a sputtering method or the like.
[0019]
As the circular piezoelectric element attaching area 11, an area surrounded by a circle may be
formed flat so that at least one entire main surface of the disk-like piezoelectric element can be
overlapped. The inner connection electrode and the outer connection electrode in the
piezoelectric element affixing region 11 need not necessarily be arranged concentrically, but the
inner connection electrode and the outer connection electrode may be arranged concentrically. Is
preferred. According to this, when the piezoelectric element in which the inner terminal electrode
and the outer terminal electrode are provided at positions at different distances from the center
of the piezoelectric layer is attached to at least one main surface of the piezoelectric layer, the
vibration is generated. It is possible to mount without worrying about the angular deviation
between the plate and the piezoelectric element, and it is possible to improve the reliability of
connection and to prevent the vibration from being unbalanced.
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[0020]
The inner connection electrodes 14A and 14B on the main surface of the laminate 12 and the
inner lead electrodes 24 between the plurality of insulator layers 12A and 12B of the laminate
12 are connected by through hole conductors 16A and 16B. preferable.
[0021]
In the first embodiment, the outer lead electrode 27 is a straight line extending from the same
annular area as the outer connection electrodes 17A and 17B on the insulator layer 12B to the
convex portion 121B of the insulator layer 12B. Extended in a shape, and the end 27A of the tip
is exposed by the notch formed in the convex portion 121A of one insulator layer 12A of the
laminated body 12, and a part of the annular region is a circle Although it is cut open so as to
connect the inside and the outside of the ring, through which the inner lead electrode 24 linearly
extends over the convex portion 121B of the insulator layer 12B of the diaphragm 10, but The
invention is not limited to this, and the inside of the piezoelectric element affixing region 11 is
formed between the plurality of insulator layers 12A and 12B of the laminate 12 or on one of the
main surfaces of the laminate 12 and / or the other. Region 1 The connection electrode 17A
provided along the the outside, may be connected to 17B.
[0022]
The connection between the outer connection electrodes 17A and 17B on the main surface of the
laminate 12 and the outer extraction electrode 27 between the plurality of insulator layers 12A
and 12B of the laminate 12 is connected by through hole conductors 19A and 19B. However, the
present invention is not limited to this, and the outer connection electrodes 17A and 17B of the
main surface of the laminate 12 and the outer extraction electrode 27 between the plurality of
insulator layers 12A and 12B of the laminate 12 are preferable. Are respectively extended from
the inside of the circular piezoelectric element affixing region 11 to the outer peripheral side
surface of the laminated body 12, and a connection conductor is formed on the outer peripheral
side surface of the laminated body 12 to form the outer connection electrode and the outer lead
electrode. And may be connected.
[0023]
Next, a manufacturing process of the diaphragm 10 according to the embodiment of the present
invention will be described with reference to FIG.
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First, using a PET film as the insulator layer, annealing is performed by heating at 150 ° C. for
30 minutes to prepare two insulator layers 12A and 12B.
Next, through holes 16A1 and 19A1 are formed at predetermined positions of the insulator layer
12A by a known punching method such as a punching press and, similarly, through holes 16B1
and 19B1 are formed at predetermined positions of the insulator layer 12B. Pierce.
Next, a conductive resin paste is prepared by mixing conductive powder such as Ag, carbon and
the like, insulating resin such as epoxy resin and solvent, and one main of the insulator layer 12A
is formed by the screen printing method. A circular inner connection electrode 14A and an
annular outer connection electrode 17A are printed on the surface, and conductive resin paste is
filled in the through holes 16A1 and 19A1 to form through hole conductors 16A and 19A.
Similarly, the inner lead electrode 24 and the outer lead electrode 27 are printed on one main
surface of the insulator layer 12B, and the conductive resin paste is filled in the through holes
16B1 and 19B1 to form the through hole conductors 16B and 19B. Form Furthermore, a circular
inner connection electrode 14B and an annular outer connection electrode 17B are printed on
the other main surface of the insulator layer 12B in the same manner as the insulator layer 12A.
After drying the obtained insulator layers 12A and 12B at 100 ° C., a thermosetting resin or a
thermoplastic resin is removed on the other main surface of the insulator layer 12A except for
the locations where the through hole conductors 16A and 19A are formed. An insulating
adhesive as the main component is applied, and the insulator layer 12A and the insulator layer
12B are laminated and heated / cured or heated at 150 ° C., then cooled / cured and attached,
or The diaphragm 10 is obtained by laminating the insulator layer 12A and the insulator layer
12B and bonding the insulator layers 12A and 12B together by ultrasonic welding or the like.
[0024]
Next, an embodiment of the piezoelectric diaphragm of the present invention will be described
with reference to FIG. 4 and FIG. FIG. 4 is a perspective view showing the piezoelectric diaphragm
20 of the second embodiment, FIG. 4 (A) is an external perspective view showing the whole of the
piezoelectric diaphragm 20, and FIG. 4 (B) is a piezoelectric diaphragm 20. FIG. 5 is an exploded
perspective view showing an example of the internal structure of the piezoelectric element 30
used for the piezoelectric diaphragm of the second embodiment.
[0025]
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As shown in FIG. 4, the piezoelectric vibration plate 20 of the second embodiment includes at
least one of the piezoelectric layers in the piezoelectric element affixing region 11 on one and the
other main surfaces of the vibration plate 10 of the first embodiment. A piezoelectric element 30
in which an inner terminal electrode and an annular outer terminal electrode are concentrically
provided on the main surface is attached using an adhesive or the like. Therefore, the inner
terminal electrode 34 of the piezoelectric element 30 and the inner connection electrode 14 of
the diaphragm 10 are connected in close contact with each other without intervening a resist
layer for preventing connection between the electrodes. Similarly, the outer terminal electrode
37 of the piezoelectric element 30 and the outer connection electrode 17 of the diaphragm 10
are connected in close contact with each other without intervening a resist layer for preventing
connection between the electrodes. An increase in diaphragm stiffness due to the presence of the
resist layer can be avoided, and an increase in resonant frequency and a decrease in sound
pressure can be prevented.
[0026]
Next, the piezoelectric element 30 attached to the piezoelectric vibrating plate 20 will be
described with reference to FIG. The piezoelectric element 30 includes two piezoelectric layers
32A and 32B in the stacking direction of the multilayer piezoelectric body 32, one main surface
of the piezoelectric layer 32A, the other main surface of the piezoelectric layer 32B, and A pair of
circular and annular electrodes is provided between the piezoelectric layer 32A and the
piezoelectric layer 32B.
[0027]
Specifically, a circular first electrode 34A and an annular second electrode 37A with an annular
gap 31 on the surface of the laminated piezoelectric body 32 and on one main surface of the
piezoelectric layer 32A Are provided concentrically as a pair of terminal electrodes, and a
circular third electrode 37B facing the first electrode 34A and the second electrode on the
second main surface of the piezoelectric layer 32A. And 37 A and an annular fourth electrode 34
B facing each other. And, the connection conductor 35A and the connection conductor 35A on
the surface different from the first main surface and the second main surface of the laminated
piezoelectric body 32 are the first electrode 34A and the fourth electrode 34B. Are connected via
a through-hole conductor 36A connecting the first electrode 34A and the first electrode 34A, and
a through-hole conductor 36B connecting the connection conductor 35A and the fourth
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electrode 34B, and the second electrode A connection conductor 38A on a surface of the
laminated piezoelectric body 32 different from the first main surface and the second main
surface 37A of the third electrode 37B and the connection conductor 38A and the second
electrode 37A And the through-hole conductor 39B connecting the connecting conductor 38A
and the third electrode 37B.
[0028]
Therefore, when signal voltages of different polarities are applied to the first electrode 34A and
the second electrode 37A on one main surface of the piezoelectric layer 32A, the through-hole
conductor 36A, the connection conductor 35A, and The same signal voltage as that of the first
electrode 34A is applied to the fourth electrode 34B that faces the second electrode 37A with the
piezoelectric layer 32A interposed therebetween through the through-hole conductor 36B. The
third electrode 37B facing the first electrode 34A across the piezoelectric layer 32A via the
through-hole conductor 39A, the connection conductor 38A, and the through-hole conductor
39B is also used for the second electrode 37A. The same signal voltage as is applied. As a result,
the piezoelectric layer 32A sandwiched between the electrodes is displaced in the thickness
direction / surface direction.
[0029]
The piezoelectric element may be any one having the laminated piezoelectric body 32 including
at least one piezoelectric layer 32A, but in the piezoelectric element 30 of an example used for
the piezoelectric vibration plate of the second embodiment, another piezoelectric element is used.
Similarly to the piezoelectric layer 32A described above, an electrode, a connection conductor,
and a through hole conductor are formed and connected to the piezoelectric layer 32B. That is,
the piezoelectric element 30 has the laminated piezoelectric body 32 including at least one
piezoelectric layer 32B, and an electrode corresponding to the first electrode on the surface
corresponding to the first main surface of the piezoelectric layer 32B. An electrode 37B
corresponding to the electrode 34B and the second electrode is provided with a gap in between,
and an electrode 34B corresponding to the first electrode is provided on the surface
corresponding to the second main surface of the piezoelectric layer 32B. An electrode 37C
corresponding to a third opposing electrode and an electrode 34C corresponding to a fourth
electrode opposite to the second electrode 37B are similarly provided with a gap in between. The
electrode 34B corresponding to the first electrode and the electrode 34C corresponding to the
fourth electrode correspond to the surface corresponding to the first main surface of the
piezoelectric layer 32B and the second main surface. Connecting conductor 35B on a surface
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different from any of the surfaces, through-hole conductors 36B connecting the connecting
conductor 35B and the electrode 34B corresponding to the first electrode, and corresponding to
the connecting conductor 35B and the fourth electrode And the electrode 37B corresponding to
the second electrode and the electrode 37C corresponding to the third electrode are connected to
each other through the through-hole conductor 36C connecting the electrode 34C. A connection
conductor 38B on a surface different from any of the surface corresponding to the first main
surface and the surface corresponding to the second main surface, and the connection conductor
38B and the electrode 37B corresponding to the second electrode are connected. Through ho Le
conductor 39B, and is connected via a through-hole conductor 39C which connects the electrode
37C corresponding to the third electrodes and the connecting conductor 38B.
[0030]
Therefore, when signal voltages of different polarities are applied to the electrode 34B
corresponding to the first electrode of the surface corresponding to one main surface of the
piezoelectric layer 32B and the electrode 37B corresponding to the second electrode. An
electrode corresponding to a fourth electrode opposed to the electrode 37B corresponding to the
second electrode with the piezoelectric layer 32B interposed therebetween via the through-hole
conductor 36B, the connection conductor 35B, and the through-hole conductor 36C The same
signal voltage as that applied to the electrode 34B corresponding to the first electrode is applied
to the electrode 34C, and the piezoelectric layer 32B is similarly passed through the through-hole
conductor 39B, the connection conductor 38B, and the through-hole conductor 39C. The same
signal voltage as that applied to the electrode 37B corresponding to the second electrode is also
applied to an electrode 37C corresponding to a third electrode facing the electrode 34B
corresponding to the first electrode therebetween. As a result, the piezoelectric layer 32B
sandwiched between the electrodes is displaced in the thickness direction / surface direction.
[0031]
For this reason, when signal voltages of different polarities are applied to the electrodes 34A and
37A on the surface of the laminated piezoelectric body 32, the piezoelectric element 30 of the
first embodiment, the connection conductors 35A and 35B, and the through-hole conductors
36A, The same voltage as the electrode 34A is applied to the electrodes 34B and 34C via 36B
and 36C, and the electrodes 37B and 37C are connected via the connection conductors 38A and
38B and the through-hole conductors 39A, 39B and 39C. The same voltage as that of the
electrode 37A is applied. As a result, in the piezoelectric element 30, the piezoelectric layers 32A
and 32B of the laminated piezoelectric body 32 are displaced in the thickness direction / surface
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direction.
[0032]
The piezoelectric layers 32A and 32B of the piezoelectric element 30 preferably include a
ceramic piezoelectric body, an organic piezoelectric body, or a mixture thereof. The electrodes
34A to 34C, 37A to 37C, the connection conductors 35A, 35B, 38A, 38B of the piezoelectric
element 30, and the through-hole conductors 36A to 36C, 39A to 39C are electrode materials
such as Ag, Ag-Pd, Pd, or Preferably, the electrode material is mixed with a small amount of the
piezoelectric material as a co-material. The multilayer piezoelectric body 32 of the piezoelectric
element is provided with at least one piezoelectric layer, and one having a plurality of
piezoelectric layers is preferable because a larger displacement can be obtained. Of course, the
laminate may be a laminate of the at least one piezoelectric layer and another insulator layer.
[0033]
Next, a case where a sheet lamination method is used as an example of a manufacturing process
will be described for a laminated piezoelectric element 30 using a ceramic piezoelectric material
as a piezoelectric material layer. First, a PZT-based piezoelectric ceramic material powder is
prepared, mixed with a binder and a solvent to prepare a ceramic slurry, and using the obtained
slurry, a doctor blade method is performed on a carrier film made of PET (polyethylene
terephthalate) or the like. , After applying a known method such as gravure printing and drying
to form a ceramic green sheet mainly composed of a long piezoelectric material having a
thickness of 10 to 100 μm, cut into a predetermined size, and a plurality of sheets Create a
ceramic green sheet of Next, through holes are punched at predetermined positions of the
obtained ceramic green sheet by a punching press or the like. Next, a conductive powder such as
Ag, Ag-Pd, Pd, etc. is prepared, mixed with a binder and a solvent to form an electrode material
paste, and the obtained electrode material paste is used to obtain predetermined on the ceramic
green sheet. The electrodes and connection conductors are printed in a pattern, and the through
holes are filled with the through hole conductors. A ceramic laminate is prepared by laminating
and pressing the ceramic green sheets obtained above in a predetermined order such that the
electrodes and the connection conductors and the through conductors are in contact with each
other, and removing the binder at 400 to 800 ° C. Then, it is fired at 850 ° C. to 1100 ° C. for
1 to 3 hours to obtain a piezoelectric element formed of a laminate. The above is the outline of
the manufacturing process using the sheet lamination method, but the manufacturing process for
obtaining the piezoelectric element of the present invention is not limited to the above sheet
lamination method, and in addition to the known slurry build method, organic piezoelectric It can
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also be formed using a body material and a process similar to a printed wiring board.
[0034]
Next, with respect to an example of the piezoelectric element 30 used for the piezoelectric
vibration plate 20 of the above embodiment, a manufacturing process will be described by taking
a sheet laminating method as an example. First, a powder of a known PZT-based ceramic
piezoelectric material is prepared, mixed with a binder and a solvent to form a ceramic slurry,
and the obtained slurry is used to form a 30 μm thick film on a PET film by the doctor blade
method. Create a ceramic green sheet of measure. The obtained ceramic green sheets are cut into
predetermined dimensions to form a plurality of ceramic green sheets 32A1, 32A2, 32B1, and
32B2. For convenience of explanation, one piezoelectric element is illustrated (the same applies
to the following). Next, through holes 36A1 and 39A1 are provided at predetermined positions of
ceramic green sheet 32A1 obtained above, through holes 36B1 and 39B1 are provided at
predetermined positions of ceramic green sheet 32A2, and at predetermined positions of ceramic
green sheet 32B1. The holes 36B2 and 39B2 are respectively punched through the through
holes 36C1 and 39C1 at predetermined positions of the ceramic green sheet 32B2 by a punching
press. Next, an electrode material paste prepared by mixing Pd electrode material powder, a
binder and a solvent is prepared, and printing of electrodes and connection conductors is
performed at predetermined positions of each green sheet by screen printing, and filling of
through-hole conductors is performed. I do. First, a pair of connection conductors 35A and 38A
are printed on one main surface of the ceramic green sheet 32A2 and the through holes are filled
in the through holes 36B1 and 39B1. Similarly, a pair of connection conductors 35B and 38B are
printed on one main surface of the ceramic green sheet 32B2 and the through holes 36C1 and
39C1 are filled with the through holes. Further, a pair of electrodes 34A and 37A are printed on
one main surface of the ceramic green sheet 32A1 and the through holes 36A1 and 39A1 are
filled with a through hole conductor. Similarly, a pair of electrodes 34B and 37B are printed on
one main surface of the ceramic green sheet 32B1 and the through holes 36B2 and 39B2 are
filled with a through hole conductor. In addition, a pair of electrodes 34C and 37C are printed on
the other main surface of the ceramic green sheet 32B2. The ceramic green sheets 32A1, 32A2,
32B1, and 32B2 obtained above are sequentially laminated and crimped so that the electrodes
and the through-hole conductors, and the connection conductors and the through-hole
conductors respectively contact, and the binder is removed at a predetermined temperature After
the treatment, the laminate is fired at a predetermined temperature for 3 hours to obtain a
laminated piezoelectric body 32.
[0035]
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Next, when polarization voltages of different polarities are applied to the electrodes 34A and 37A
on the surface of the laminated piezoelectric body 32, the electrodes via the connection
conductors 35A and 35B and the through hole conductors 36A, 36B and 36C. The same voltage
as that of the electrode 34A is applied to 34B, 34C, and the same voltage as that of the electrode
37A is applied to the electrodes 37B, 37C via the connection conductors 38A, 38B and throughhole conductors 39A, 39B, 39C. Ru. As a result, in the piezoelectric element 30, the piezoelectric
layers 32A and 32B of the multilayer piezoelectric body 32 are polarized in the thickness
direction.
[0036]
The piezoelectric element 30 described above has a laminated piezoelectric body 32 provided
with at least one piezoelectric body layer 32A, and on the first main surface of the piezoelectric
body layer 32A, a first electrode 34A and a second electrode 37A. Are provided across the gap
31, and a third electrode 37B facing the first electrode 34A and a second electrode 37A facing
the first electrode 34A are provided on the second main surface of the piezoelectric layer 32A.
The four electrodes 34B are similarly provided across the gap. Then, the first electrode 34A and
the fourth electrode 34B are connected via the connection conductor 35A on the surface
different from any of the first main surface and the second main surface of the laminated
piezoelectric body 32. And the second electrode 37A and the third electrode 37B pass through
the connection conductor 38A on the surface different from either the first main surface or the
second main surface of the laminated piezoelectric body 32. Is connected. For this reason, the
first electrode 34A and the second electrode 37A of the first main surface of the piezoelectric
layer, and the third electrode 37B and the fourth electrode 34B of the second main surface are
disposed between the electrodes, respectively. Since the conductive connection can be made
without providing an extension part which protrudes beyond the gap 31, the opposing areas of
the electrodes 34 A and 37 B and the electrodes 37 A and 34 B facing each other across the
piezoelectric layer 32 A are not reduced. For this reason, the area size of the piezoelectric
element 30 required to obtain the same sound pressure can be reduced to realize miniaturization.
[0037]
Further, the piezoelectric element 30 used for the piezoelectric vibration plate 20 of Embodiment
2 described above includes the first electrode 34A and the fourth electrode 34B, and the second
electrode 37A and the third electrode 37B. At least one side is connected via the connection
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conductors 35A, 38A on the third surface inside the laminated piezoelectric body 32 and the
through hole conductors 36A, 36B, 39A, 39B provided in the piezoelectric layer 32A. Because it
is not necessary to provide a through hole connection within the limited area of the electrode gap
on the first and second main surfaces of the piezoelectric layer 32A, the through hole formation
position is arbitrarily selected. As a result, concentration of stress in the through holes can be
prevented, and even if a slight positional deviation occurs in the surface direction between layers,
short circuits between electrodes, connection defects in connection portions, and the like are less
likely to occur. Although the action and effect have been described focusing on at least one
piezoelectric layer of the piezoelectric element 30 used in the piezoelectric vibration plate 20 of
the second embodiment, the same action and effect can be obtained for the other piezoelectric
layer 32B. Play.
[0038]
Next, an example of a manufacturing process of the piezoelectric diaphragm 20 of the second
embodiment will be described with reference to FIG. After thinly applying an epoxy-based
insulating adhesive on the connection electrodes 14A and 17A on one main surface of the
diaphragm 10 of the first embodiment, connection of the terminal electrode 34C of the
piezoelectric element 30 and the diaphragm 10 is performed. The piezoelectric element 30 is
overlapped so that the electrode 14A, the terminal electrode 37C of the piezoelectric element 30
and the connection electrode 17A of the diaphragm 10 are in contact with each other, and
pressure bonding is performed with a pressure that does not break the laminated piezoelectric
body 32. Heat cure. As a result, the fine irregularities on the surfaces of the terminal electrodes
34C and 37C of the piezoelectric element 30 and the fine irregularities on the surfaces of the
connection electrodes 14A and 17A of the diaphragm 10 are in contact with each other, and one
connection of the diaphragm 10 is made. The electrode 14A and the connection electrode 34C
on the main surface of the piezoelectric element 30 are conductively connected, and the other
terminal electrode 17A of the diaphragm 10 and the electrode layer 37C on the main surface of
the piezoelectric element 30 are conductively connected. . Similarly, after thinly applying an
epoxy-based insulating adhesive on the connection electrodes 14B and 17B on the other main
surface of the diaphragm 10, piezoelectric having the same internal structure as that of the
piezoelectric element 30 but having only the polarization direction is reversed. The piezoelectric
element is arranged such that the terminal electrode 34A 'of the element 30' and the connection
electrode 14B of the diaphragm 10 are in contact with each other, and the terminal electrode
37A 'of the piezoelectric element 30' and the connection electrode 17B of the diaphragm 10 are
in contact with each other. The element 30 'is stacked, and the laminated piezoelectric body 32'
is pressure-bonded and heat-hardened at a pressure that does not cause cracking. As a result, the
fine irregularities of the surface of the terminal electrodes 34A 'and 37A' of the piezoelectric
element 30 'and the fine irregularities of the surfaces of the connection electrodes 14B and 17B
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16
of the diaphragm 10 are in contact with each other. The connection electrode 14B on one side
and the connection electrode 34A 'on the main surface of the piezoelectric element 30' are
conductively connected, and the other terminal electrode 17B of the diaphragm 10 and the
electrode layer 37A on the main surface of the piezoelectric element 30 ' Thus, the piezoelectric
diaphragm 20 is obtained.
[0039]
The terminal portions 24A and 27A of the diaphragm 10 are connected to a power supply (not
shown). For example, signal voltages of different polarities are alternately applied to the one
terminal portion 24A in the plus direction and the other terminal portion 27A in the minus
direction. Be done.
[0040]
In the piezoelectric diaphragm 20 of Embodiment 2 using the diaphragm 10 of Embodiment 1 of
the present invention, since the piezoelectric element 30 is fixed to the diaphragm 10 including
the pair of connection electrodes 14A and 17A, the terminal electrode 34 is used. 37 can all be
performed from the diaphragm 10, and the thickness of the piezoelectric diaphragm 20 can be
reduced.
Further, the opposing areas of the electrodes 34A, 34B, 37A, 37B are not reduced to connect the
terminal electrodes 34A, 37A of the first main surface and the electrodes 34B, 37B of the second
main surface, respectively. Thus, a large displacement can be obtained, and the sound pressure of
the piezoelectric diaphragm 20 can be improved.
[0041]
In the piezoelectric diaphragm 20 of the second embodiment, the connection electrodes 14A,
17A, 14B, and 17B are formed on both main surfaces of the diaphragm 10, and the piezoelectric
element 30 is fixed to each main surface independently to form a bimorph structure. However,
the present invention is not limited to this, and the terminal electrodes 14A and 17A may be
formed only on one main surface of the diaphragm 10 to form a unimorph structure in which
one piezoelectric element 30 is fixed. . In the first embodiment, the overall shapes of the
piezoelectric element and the diaphragm are circular and substantially circular. However, the
present invention is not limited to this, and the diaphragm may be rectangular or other different
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shape. Alternatively, a plurality of piezoelectric elements may be bonded to one main surface of
the diaphragm separately from each other. Moreover, in the said embodiment, although the
insulating adhesive was used for bonding of the diaphragm 10 and the piezoelectric element 30,
this invention is not limited to this, The connection electrode of the diaphragm 10 and the
piezoelectric element 30 A conductive adhesive may be applied to and bonded to a region of the
main surface facing the terminal electrode.
[0042]
Preferred applications of the diaphragm and the piezoelectric diaphragm of the present invention
include speakers of various electronic devices such as mobile phones, personal digital assistants
(PDAs), voice recorders, PCs (personal computers), etc. It does not prevent applying to various
electronic devices.
[0043]
According to the present invention, the present invention is suitable for the use of a piezoelectric
diaphragm for a sounding body which is required to be thin and an electronic device using the
same.
[0044]
It is a perspective view which shows the external appearance of Embodiment 1 of the diaphragm
of this invention.
It is sectional drawing cut | disconnected along the AA of the said FIG. 1 of the said Embodiment
1. FIG.
FIG. 2 is an exploded perspective view showing the internal structure of the diaphragm of the
first embodiment. FIG. 4 (A) is an external perspective view showing the entire piezoelectric
diaphragm, and FIG. 4 (B) is the piezoelectric vibration of the piezoelectric diaphragm of
Embodiment 2 using the diaphragm of Embodiment 1. It is a disassembled perspective view for
demonstrating the internal structure of a board. It is a disassembled perspective view which
shows the internal structure of the piezoelectric element used for the piezoelectric diaphragm of
Embodiment 2 of this invention. It is a perspective view showing an example of background art.
It is sectional drawing which shows the said background art.
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Explanation of sign
[0045]
10: Diaphragm 11: Piezoelectric element affixing area 12: Laminate 121: convex part 12A, 12B:
insulator layer 121A, 121B: convex part 14A, 14B: connection electrode 16A, 16B: through hole
conductor 17A, 17B: connection Electrode 19A, 19B: Through-hole conductor 20: Piezoelectric
diaphragm 24: Extraction electrode 24A: End 27: Extraction electrode 27A: End 30: Piezoelectric
element 30 ': Piezoelectric element 31: Gap 32: Multilayer piezoelectric body 32': Layering
Piezoelectric body 32A, 32B: Piezoelectric layer 34A, 34B, 34C: Electrode 34A ': Electrode 35A,
35B: Connection conductor 36A, 36B, 36C: Through-hole conductor 37A, 37B, 37C: Electrode
37A': Electrode 38A, 38B: Connecting conductor 39A, 39B, 39C: Through hole conductor P:
Center
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