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JP2015109375

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DESCRIPTION JP2015109375
PROBLEM TO BE SOLVED: To provide a piezoelectric actuator in which a gap is formed at a
boundary between a conductive bonding material and a piezoelectric element and generation of a
spark is suppressed, a piezoelectric vibration device provided with the same, a portable terminal,
an acoustic generator and an electronic device. SOLUTION: The piezoelectric actuator 1
according to the present invention is provided on at least one of the main surfaces of a laminate
11 in which an internal electrode and a piezoelectric layer are laminated, and a plurality of
laminates electrically connected to the internal electrode. And a flexible substrate 13 provided
with a wiring conductor 131 which is partially connected to one of the main surfaces via a
conductive bonding material and electrically connected to a plurality of surface electrodes 12, In
the area | region in which the several surface electrode 12 in the one main surface of the body
11 was provided, there exists the protruding part 15 which protruded more than another site |
part. [Selected figure] Figure 1
Piezoelectric actuator and piezoelectric vibration device provided with the same, portable
terminal, sound generator, electronic device
[0001]
The present invention relates to a piezoelectric actuator suitable for a piezoelectric vibration
device, a portable terminal and the like, a piezoelectric vibration device provided with the same, a
portable terminal, an acoustic generator, and an electronic device.
[0002]
As a piezoelectric actuator, one using a bimorph-type piezoelectric element in which a surface
electrode is formed on the surface of a laminate in which a plurality of internal electrodes and
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piezoelectric layers are stacked (see Patent Document 1), piezoelectric element and flexible There
is known one in which a substrate is bonded with a conductive bonding material to electrically
connect a surface electrode of a piezoelectric element and a wiring conductor of a flexible
substrate (see Patent Document 2).
[0003]
JP-A-2002-10393 JP-A-6-14396
[0004]
Here, when stress is repeatedly applied to the conductive bonding material due to external
vibration or bending vibration of the piezoelectric element, a gap may be formed in the boundary
between the conductive bonding material and the piezoelectric element to cause sparks.
As a result, the connection resistance may increase and the displacement may decrease.
A strong bond that is resistant to vibration is required between the surface electrode of the
piezoelectric element and the wiring conductor of the flexible substrate.
[0005]
The present invention has been made in view of the above circumstances, and provides a
piezoelectric actuator in which a gap is formed at the boundary between a conductive bonding
material and a piezoelectric element to suppress generation of a spark, a piezoelectric vibration
device provided with the same, It aims at providing a terminal, a sound generator, and an
electronic device.
[0006]
According to the present invention, there is provided a laminate in which an internal electrode
and a piezoelectric layer are laminated, and a plurality of surface electrodes provided on at least
one principal surface of the laminate and electrically connected to the internal electrode, and
conductive junctions. A flexible substrate including a wiring conductor partially connected to the
one main surface via a material and electrically connected to the plurality of front surface
electrodes; and the flexible substrate on the one main surface of the laminate A piezoelectric
actuator is characterized in that a region where a plurality of surface electrodes are provided has
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a raised portion that is raised more than other portions.
[0007]
The piezoelectric actuator according to the present invention is characterized in that, in the
above-mentioned configuration, there is a recess between the surface electrode and the surface
electrode in proximity to each other.
[0008]
Further, in the piezoelectric actuator of the present invention according to the above-mentioned
configuration, the conductive bonding material is an anisotropic conductive adhesive.
[0009]
In the piezoelectric actuator according to the present invention, in the above-mentioned
configuration, the conductive bonding material protrudes from an overlapping region of the
laminate and the flexible substrate.
[0010]
Further, in the piezoelectric actuator according to the present invention, in the above
configuration, the flexible substrate is deformed along the raised portion.
[0011]
Further, according to the present invention, there is provided a piezoelectric vibration device
comprising: a vibrating plate joined to the other main surface of the laminate.
[0012]
Further, the present invention is characterized by including the above-described piezoelectric
actuator, an electronic circuit, a display, and a housing, and the other main surface of the
laminate is joined to the display or the housing. Is a portable terminal.
[0013]
Further, according to the present invention, the above-described piezoelectric actuator and the
piezoelectric actuator are attached, and provided on at least a part of a diaphragm which vibrates
together with the piezoelectric actuator by vibration of the piezoelectric actuator, and at least a
part of an outer peripheral portion of the diaphragm. And a support for supporting the
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diaphragm.
[0014]
The present invention also includes the above-mentioned sound generator, an electronic circuit
connected to the sound generator, and a case for housing the electronic circuit and the sound
generator, and generating sound from the sound generator. An electronic device characterized by
having a function of
[0015]
According to the present invention, a stress that peels off the flexible substrate due to vibration is
applied by the presence of the raised portions that are raised more than the other portions in the
region provided with the plurality of surface electrodes on one main surface of the laminate.
Even if the ridges deform, their stress is relieved.
Therefore, it is possible to obtain a piezoelectric actuator in which a spark does not occur over a
long period of time and the displacement of the laminate is stable.
[0016]
FIG. 1 (a) is a schematic perspective view showing an example of the embodiment of the
piezoelectric actuator of the present invention, and FIG. 1 (b) is a schematic cross-sectional view
cut along the line A-A shown in FIG. 1 (c) is a schematic cross-sectional view cut along the line BB shown in FIG. 1 (a).
FIG. 2 is a schematic plan view of the internal electrode of the piezoelectric actuator according to
the present invention, in which (a) is a first electrode, (b) is a second electrode disposed on the
one principal surface side of the laminate ( c) has shown the 3rd electrode arrange | positioned at
the other main surface side of a laminated body.
It is a schematic sectional drawing which shows the other example of FIG.1 (b).
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It is a schematic sectional drawing which shows the other example of FIG.1 (b).
It is a schematic sectional drawing which shows the other example of FIG.1 (b).
FIG. 1 is a schematic perspective view schematically showing an embodiment of a piezoelectric
vibration device of the present invention.
It is a schematic perspective view showing typically an embodiment of a portable terminal of the
present invention.
It is the schematic sectional drawing cut | disconnected by the AA shown in FIG.
It is the schematic sectional drawing cut | disconnected by the BB line shown in FIG.
Fig.10 (a) is a typical top view which shows schematic structure of embodiment of the sound
generator of this invention, FIG.10 (b) is an example cut | disconnected by the AA line of Fig.10
(a). FIG. 10 (c) is a schematic cross-sectional view of another example taken along line A-A of FIG.
10 (a).
It is a figure which shows the structure which concerns on embodiment of the electronic device
of this invention.
[0017]
An example of the embodiment of the piezoelectric actuator of the present invention will be
described in detail with reference to the drawings.
[0018]
FIG. 1 (a) is a schematic perspective view showing an example of the embodiment of the
piezoelectric actuator of the present invention, and FIG. 1 (b) is a schematic cross-sectional view
cut along the line A-A shown in FIG. 1 (c) is a schematic cross-sectional view cut along the line BB shown in FIG. 1 (a).
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[0019]
The piezoelectric actuator 1 of the present embodiment shown in FIG. 1 is provided on at least
one of the main surfaces of the laminate 11 in which the internal electrode and the piezoelectric
layer are laminated, and is electrically connected to the internal electrode. A plurality of front
electrodes 12, and a flexible substrate 13 provided with a wiring conductor 131 which is
partially connected to one main surface via a conductive bonding material and electrically
connected to the plurality of front electrodes 12; In the area | region in which the several surface
electrode 12 in the one main surface of the laminated body 11 was provided, there exists the
protruding part 15 which protruded more than another site | part.
[0020]
The laminated body 11 which comprises the piezoelectric actuator 1 of this example is formed by
laminating | stacking an internal electrode and a piezoelectric material layer, and forming it in
plate shape.
It has an active portion in which a plurality of internal electrodes overlap in the stacking
direction, and an inactive portion in which a plurality of other internal electrodes do not overlap
in the stacking direction.
In the case of a piezoelectric actuator attached to a display or a housing of a portable terminal,
the laminate 11 is formed, for example, in a long shape, and the length of the laminate 11 is
preferably 18 mm to 28 mm, for example, and further 22 mm to 25 mm preferable.
The width of the laminate 11 is preferably, for example, 1 mm to 6 mm, and more preferably 3
mm to 4 mm. 0.2 mm-1.0 mm are preferable, for example, and, as for the thickness of the
laminated body 11, 0.4 mm-0.8 mm are still more preferable. In the example shown in the figure,
the laminate 11 is formed in a plate shape having a rectangular plan view, but the present
invention is not limited to this shape, for example, a square, a rectangle, or a circle in a plan view.
It may be a plate-like body.
[0021]
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The internal electrode which comprises the laminated body 11 is formed by simultaneous baking
with the ceramic which forms a piezoelectric material layer, and consists of a 1st electrode and a
2nd electrode. For example, the first electrode is a ground electrode, and the second electrode is
a positive electrode or a negative electrode. The piezoelectric layers are alternately stacked to
sandwich the piezoelectric layer from above and below, and by arranging the first electrode and
the second electrode in the stacking order, the driving voltage is applied to the piezoelectric layer
sandwiched therebetween Is applied. When the laminate 11 is, for example, a plate-like body
having a rectangular shape in plan view, the internal electrode 171 to be the first electrode is
formed in a rectangular shape in plan view as shown in FIG. 2A, for example. Further, in this case,
the internal electrode 172 serving as the second electrode disposed on the one principal surface
side has, for example, as shown in FIG. For example, as shown in FIG. 2 (c), the internal electrode
173 which is formed in the shape of a narrow lead-out portion and which is the second electrode
disposed on the other main surface side faces the opposing portion in a rectangular shape in plan
view. It is formed in the shape which consists of a lead-out part narrower than a part, and it is
made the shape which turned right and left the internal electrode 172 used as the 2nd electrode
just arranged on the one principal surface side. As the forming material, for example, a conductor
containing silver or silver-palladium alloy as a main component having low reactivity with
piezoelectric ceramics, or a conductor containing copper, platinum or the like can be used. You
may make it contain.
[0022]
Although not shown, the end portions of the first electrode and the second electrode are
respectively led out alternately to the pair of opposing side surfaces of the laminate 11. In the
case of a piezoelectric actuator attached to a display or a housing of a portable terminal, the
length of the internal electrode is, for example, preferably 17 mm to 25 mm, and more preferably
21 mm to 24 mm. The width of the internal electrode is, for example, preferably 1 mm to 5 mm,
and more preferably 2 mm to 4 mm. The thickness of the internal electrode is preferably, for
example, 0.1 to 5 μm.
[0023]
The piezoelectric layer constituting the laminate 11 is formed of a ceramic having piezoelectric
characteristics, and as such a ceramic, for example, a perovskite oxide or niobium oxide made of
lead zirconate titanate (PbZrO 3 -PbTiO 3) Lithium oxide (LiNbO 3), lithium tantalate (LiTaO 3) or
the like can be used. The thickness of one layer of the piezoelectric layer is preferably set to, for
example, 0.01 to 0.1 mm in order to drive at a low voltage. Further, in order to obtain a large
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flexural vibration, it is preferable to have a piezoelectric constant d31 of 200 pm / V or more.
[0024]
A plurality of surface electrodes 12 electrically connected to the internal electrodes are provided
on at least one of the main surfaces of the laminate 11. The surface electrode 12 shown in the
figure is constituted of, for example, a first surface electrode 121 with a large area, a second
surface electrode 122 with a small area, and a third surface electrode 123. Then, for example, the
first surface electrode 121 is electrically connected to the internal electrode 171 serving as the
first electrode, and the second surface electrode 122 is the internal electrode serving as the
second electrode disposed on the one principal surface side. The third surface electrode 123 is
electrically connected to the internal electrode 173 serving as the second electrode disposed on
the other main surface side.
[0025]
In the case of a piezoelectric actuator attached to a display or a housing of a portable terminal,
the length of the first surface electrode 121 is, for example, preferably 17 mm to 23 mm, and
more preferably 19 mm to 21 mm. The width of the first surface electrode 121 is preferably, for
example, 1 mm to 5 mm, and more preferably 2 mm to 4 mm. The lengths of the second surface
electrode 122 and the third surface electrode 123 are preferably, for example, 1 mm to 3 mm.
The width of the second surface electrode 122 and the third surface electrode 123 is preferably,
for example, 0.5 mm to 1.5 mm. The length of the internal electrode 171 is preferably, for
example, 17 mm to 23 mm, and more preferably 19 mm to 21 mm. The width of the internal
electrode 171 is preferably, for example, 1 mm to 5 mm, and more preferably 2 mm to 4 mm. It
is preferable that the lengths of the lead portions of the internal electrode 172 and the internal
electrode 173 be, for example, 1 mm to 3 mm. The width of the lead portion in the internal
electrode 172 and the internal electrode 173 is preferably, for example, 0.5 mm to 1.5 mm.
[0026]
In the piezoelectric actuator 1 of this example, the flexible substrate 13 provided with the wiring
conductor 131 which is partially connected to one main surface via the conductive bonding
material and electrically connected to the plurality of surface electrodes 12 is used. It contains.
[0027]
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Specifically, the flexible substrate 13 is, for example, a flexible printed wiring substrate in which
a plurality (for example, two) wiring conductors 131 are provided on the main surface of the
base film 132 made of resin on the side facing the laminate 11. The wiring conductor 131 is
electrically connected to the surface electrode 12 through the conductive bonding material.
A cover film 133 may be provided to cover a part of the wiring conductor 131. Here, the cover
film 133 may be provided in the area excluding the connection portion with the front surface
electrode 12 of the wiring conductor 131, but the cover film 133 is not provided in the area
overlapping with the laminated body 11 and the vicinity area thereof. Thus, a reliable electrical
connection can be obtained without being affected by the thickness of the cover film 133. The
flexible substrate 13 is joined to the laminate 11 at one end, for example, and joined to an
external circuit (connector) at the other end.
[0028]
As the conductive bonding material, a conductive adhesive, a solder or the like is used, and
preferably a conductive adhesive is preferable. For example, by using a conductive adhesive in
which conductive particles made of gold, copper, nickel, or resin balls plated with gold are
dispersed in a resin such as acrylic resin, epoxy resin, silicone resin, polyurethane resin, or
synthetic rubber. This is because the stress caused by vibration can be reduced compared to
solder.
[0029]
More preferably, the conductive adhesive is an anisotropic conductive adhesive 14 as shown in
the figure. The anisotropic conductive adhesive 14 consists of conductive particles 141
responsible for electrical bonding and a resin adhesive 142 responsible for adhesion. Specifically,
one conductive particle 141 is in contact with the surface electrode 12 and the wiring conductor
131. The anisotropic conductive adhesive 14 has conductivity in the thickness direction and
insulation in the in-plane direction, so that short-circuited wires do not electrically short between
the surface electrodes of different poles. The connection portion with the flexible substrate 13
can be made compact.
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[0030]
Here, in the area | region in which the several surface electrode 12 in one main surface of the
laminated body 11 was provided, there exists the protruding part 15 which protruded more than
another site | part. Here, the raised portion 15 is a region which is higher by, for example, 0.1 to
100 μm than the other portion (the non-raised peripheral region). The protruding portions 15
are provided in the area of, for example, 2% or more of the area of each of the plurality of surface
electrodes 12 (the first surface electrode 121, the second surface electrode 122, and the third
surface electrode 123). In addition, the ridge 15 may have a shape (convex shape having a
vertex) that gradually rises as it gets farther from other regions (a non-raised peripheral region),
and is the highest. There may be one or more sites (vertices).
[0031]
According to this configuration, even if stress that peels off the flexible substrate 13 is applied by
vibration, the stress can be relaxed by deformation of the raised portion. In addition, the effect of
suppressing the transmission of vibration can also be obtained. As a result, the amount of
displacement of the laminate can be stabilized without generating a spark over a long period of
time.
[0032]
Here, when the conductive bonding material is the anisotropic conductive adhesive 14, the
conductive particles 141 are sandwiched in the vicinity of the apexes of the raised portions 15 in
the regions where the respective surface electrodes 12 are provided, and the surface electrodes
12 and The conductive particles 141 can easily bite into each of the wiring conductors 131, and
a reliable connection can be obtained. In addition, since the conductive particles 141 are crushed
to increase the cross-sectional area, the contact resistance can be reduced. As a result, the
amount of displacement of the stacked body 11 can be stabilized without generating a spark
more.
[0033]
In addition, as shown in FIG. 3, it is preferable that a concave portion 16 be provided between
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the surface electrode 12 and the surface electrode 12 in proximity to each other. Here, the
recessed portion 16 is a region which is recessed by, for example, 0.1 to 100 μm from the other
portion (a non-recessed peripheral region). By providing the concave portion 111, when a
conductive adhesive is used as the conductive bonding material, the thickness of the conductive
adhesive is increased, so that the stress can be relieved more and spark is generated for a longer
period of time. As a result, the displacement of the laminate can be stabilized. In particular, when
the anisotropic conductive adhesive 14 is used, the ratio of the resin of the conductive adhesive
above the recess 16 can be increased, which is more effective.
[0034]
In addition, as shown in FIG. 4, it is preferable that the conductive bonding material (conductive
adhesive, particularly anisotropic conductive adhesive 14) protrudes from the overlapping region
of the laminate 11 and the flexible substrate 13, and the conductive bonding material protrudes.
By bonding the portion to the flexible substrate 13 or the side surface of the laminate 11, the
bonding strength can be increased and stress can be further relieved. In addition, it is effective to
project 0.02 to 2 mm, and in particular, it is preferable to reach the cover film 133 in that the
effect of protecting the wiring conductor 131 is also added.
[0035]
Further, as shown in FIG. 5, it is preferable that the flexible substrate 13 is deformed along the
raised portion 15. The deformation of the flexible substrate 13 along the ridges 15 allows the
stress to be dispersed in different directions. In addition, the raised portion 15 can be further
easily deformed. Therefore, the stress can be further relieved, and peeling of the flexible
substrate 13 can be made difficult to progress.
[0036]
When the other principal surface of the laminate 11 is flat, for example, when the other principal
surface is attached to an object to which vibration is applied (for example, a diaphragm to be
described later), the object to be vibrated As a result, it becomes easy to cause bending vibration,
and the efficiency of bending vibration can be raised as a whole.
[0037]
Further, the piezoelectric actuator 1 of this example is a so-called bimorph piezoelectric actuator,
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which receives an electric signal from the surface electrode 12 and bends and vibrates so that
one main surface and the other main surface become bending surfaces. However, the
piezoelectric actuator of the present invention is not limited to a bimorph type, and may be a
unimorph type, for example, by bonding (pasting) the other main surface of the laminate 11 to a
diaphragm described later Even a unimorph type can be bent and vibrated.
[0038]
Next, a method of manufacturing the piezoelectric actuator 1 of the present embodiment will be
described.
[0039]
First, a ceramic green sheet to be a piezoelectric layer is produced.
Specifically, a ceramic slurry is prepared by mixing a calcined powder of a piezoelectric ceramic,
a binder made of an organic polymer such as acrylic and butyral, and a plasticizer.
Then, a ceramic green sheet is produced using this ceramic slurry by using a tape forming
method such as a doctor blade method or a calender roll method.
Any piezoelectric ceramic may be used as long as it has piezoelectric characteristics, and, for
example, a perovskite oxide made of lead zirconate titanate (PbZrO 3 -PbTiO 3) can be used.
Further, as a plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP) or the like can be used.
[0040]
Next, a conductive paste to be an internal electrode is produced. Specifically, a conductive paste
is prepared by adding and mixing a binder and a plasticizer to a metal powder of a silverpalladium alloy. This conductive paste is applied on the above-mentioned ceramic green sheet in
a pattern of internal electrodes using a screen printing method. Furthermore, a plurality of
ceramic green sheets on which the conductive paste is printed are laminated.
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[0041]
Here, for example, in order to allow the raised portions 15 to be raised more than the other
portions in the region provided with the plurality of surface electrodes 12 on one main surface of
the laminate 11, for example, a region overlapping with the surface electrode 12 The ceramic
green sheet of this part is formed by partially laminating the ceramic green sheet on the surface,
partially applying the ceramic paste, or forming a pattern in which the lead-out portions of the
internal electrode partially overlap. After laminating so as to increase the thickness of the
laminate, a sheet body having high elasticity is disposed on the one main surface side and a plate
body is disposed on the other main surface side opposite to the above, and ceramic green sheet
laminate There is a method of sandwiching and pressure contact. Further, in order to make the
recessed portion 16 recessed from the other portion in the laminate 11, for example, a green
sheet hollowed out in the shape of the recessed portion 16 only at this portion may be laminated,
or the internal electrodes may partially overlap slightly. After forming in a pattern, a sheet-like
body rich in elasticity is disposed on the one principal surface side and a plate-like body is
disposed on the other principal surface side opposite to each other, and the ceramic green sheet
laminate is sandwiched by these, There is a method of putting on clothes. By this method, the
raised portions 15 and the recessed portions 16 can be formed on the one main surface side.
[0042]
Then, after performing binder removal processing at a predetermined temperature, firing was
performed at a temperature of 900 to 1200 ° C., and grinding processing was performed to
obtain a predetermined shape using a surface grinder or the like, thereby alternately laminating
A laminate having an internal electrode and a piezoelectric layer is produced.
[0043]
The laminate is not limited to the one produced by the above-mentioned production method, and
it may be produced by any production method as long as a laminate formed by laminating a
plurality of internal electrodes and piezoelectric layers can be produced. Good.
[0044]
Thereafter, a silver glass-containing conductive paste prepared by adding a binder, a plasticizer
and a solvent to a mixture of conductive particles containing silver as a main component and
glass, is applied to the main and side surfaces of the laminate in the pattern of the surface
electrode. After printing and drying by screen printing or the like, baking is performed at a
temperature of 650 to 750.degree. C. to form a surface electrode.
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[0045]
When the surface electrode and the internal electrode are electrically connected, a via
penetrating the piezoelectric layer may be formed and connected, or a side electrode may be
formed on the side surface of the laminate, and any manufacturing method It may be produced
by a method.
[0046]
Next, the flexible substrate is connected and fixed (joined) to the laminate using, for example, a
conductive adhesive as the conductive bonding material.
[0047]
First, a conductive adhesive paste is applied to a predetermined position of the laminate by
screen printing or the like.
Then, the flexible substrate is connected and fixed to the piezoelectric element by curing the
conductive adhesive paste in a state in which the flexible substrate is in contact.
The conductive adhesive paste may be applied and formed on the flexible substrate 6 side.
[0048]
When the resin constituting the conductive adhesive is a thermoplastic resin, the conductive
adhesive is applied and formed on a predetermined position of the laminate or the flexible
substrate, and then the laminate and the flexible substrate are interposed via the conductive
adhesive. The thermoplastic resin softens and flows by heating and pressurizing in a state where
it abuts, and then the thermoplastic resin hardens again by returning to normal temperature, and
the flexible substrate is connected and fixed to the laminate.
[0049]
In particular, when an anisotropic conductive adhesive is used as the conductive bonding
material, it is necessary to control the amount of pressure so that adjacent conductive particles
do not contact.
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[0050]
In the above, the conductive adhesive is applied and formed on the laminate or the flexible
substrate, but in a state in which the sheet of the laminate formed in a sheet form is sandwiched
between the laminate and the flexible substrate. It may heat and press and may join.
[0051]
As shown in FIG. 6, the piezoelectric vibration device of the present embodiment includes the
piezoelectric actuator 1 and a diaphragm 81 joined to the other main surface of the laminate 11
constituting the piezoelectric actuator 1.
In addition, the flexible substrate joined to one main surface of the laminated body 11 is
abbreviate | omitted in FIG.
[0052]
The diaphragm 81 is, for example, a rectangular thin plate.
The diaphragm 81 can be formed by suitably using a material having high rigidity and elasticity
such as acrylic resin or glass.
The thickness of the diaphragm 81 is set to, for example, 0.4 mm to 1.5 mm.
[0053]
The diaphragm 81 is joined to the other main surface of the laminate 11 via a joining member
82.
The entire surface of the other main surface may be bonded to the diaphragm 81 via the bonding
member 82, or substantially the entire surface may be bonded.
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[0054]
The bonding member 82 has a film-like shape.
The bonding member 82 is formed of a material that is softer and easier to deform than the
diaphragm 81, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity,
and bulk modulus than the diaphragm 81.
That is, the bonding member 82 is deformable when the diaphragm 81 is vibrated by driving the
piezoelectric actuator 1 (laminated body 11), and is deformed larger than the diaphragm 81
when the same force is applied. is there. The other main surface (main surface on the −z
direction side in the drawing) of the laminate 11 is entirely fixed to one main surface (the main
surface on the + z direction side in the drawing) of the bonding member 82. A part of one main
surface (main surface on the + z direction side in the drawing) of the diaphragm 81 is fixed to the
other main surface (the main surface on the −z direction side in the drawing).
[0055]
When vibration is transmitted from the piezoelectric actuator 1 (laminate 11) by joining the
laminate 11 and the diaphragm 81 with the deformable joint member 82, the deformable joint
member 82 is larger than the diaphragm 81. Deform.
[0056]
At this time, since the vibration in the opposite phase reflected from the diaphragm 81 can be
mitigated by the deformable bonding member 82, the piezoelectric actuator 1 (laminated body
11) is not affected by the surrounding vibration and the diaphragm 81 is not affected. Can be
transmitted to a strong vibration.
[0057]
Above all, at least a part of the bonding member 82 is formed of a visco-elastic body, so that the
strong vibration from the piezoelectric actuator 1 (laminated body 11) is transmitted to the
diaphragm 81 while the weak vibration reflected from the diaphragm 81 Is preferable in that the
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bonding member 82 can absorb.
For example, a double-sided tape in which an adhesive is attached to both sides of a substrate
made of non-woven fabric or a bonding member having a configuration including an adhesive
having elasticity can be used, and the thickness thereof is, for example, 10 μm to 2000 μm. It
can be used.
[0058]
The bonding member 82 may be a single member or a composite of several members.
As such a joining member 82, for example, a double-sided tape in which an adhesive is attached
to both sides of a base material made of non-woven fabric or the like, various elastic adhesives
which are adhesives having elasticity, etc. can be suitably used. Further, the thickness of the
bonding member 82 is desirably larger than the amplitude of the flexural vibration of the
piezoelectric actuator 1 (laminated body 11), but since the vibration is attenuated if it is too
thick, for example, 0.1 mm to 0.6 mm. It is set. However, in the piezoelectric vibration device of
the present invention, the material of the bonding member 82 is not limited, and the bonding
member 82 may be formed harder than the diaphragm 81 and less likely to be deformed.
Further, depending on the case, a configuration without the bonding member 82 may be
employed.
[0059]
The piezoelectric vibration device of this example provided with such a configuration functions
as a piezoelectric vibration device that causes the piezoelectric actuator 1 (laminated body 11) to
bend and vibrate by applying an electric signal, thereby vibrating the diaphragm 81. The other
end in the lengthwise direction of the diaphragm 81 (the end in the −y direction in the figure,
the peripheral edge of the diaphragm 81, etc.) may be supported by a support member (not
shown).
[0060]
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Further, in the piezoelectric vibration device of this example, the diaphragm 81 is joined to the
flat other main surface of the laminate 11. Thereby, it is possible to obtain a piezoelectric
vibration device in which the laminate 11 and the vibration plate 81 are firmly joined.
[0061]
The piezoelectric vibration device of this example is configured using the piezoelectric actuator 1
in which no spark is generated for a long time and the displacement amount of the laminated
body is stable, and therefore, the piezoelectric is excellent in durability and stably driven for a
long time It can be a vibrating device.
[0062]
The portable terminal according to the present embodiment includes the piezoelectric actuator 1,
an electronic circuit (not shown), a display 91, and a housing 92, as shown in FIGS. The other
main surface is joined to the housing 92.
7 is a schematic perspective view schematically showing the portable terminal of the present
invention, FIG. 8 is a schematic sectional view cut along the line AA shown in FIG. 7, and FIG. 9 is
a line BB shown in FIG. It is a schematic sectional view cut at. The flexible substrate joined to one
main surface of the laminate 11 is omitted in FIGS. 8 and 9.
[0063]
Here, it is preferable that the laminate 11 and the housing 92 be joined using a deformable
joining member. That is, in FIG. 8 and FIG. 9, the joining member 82 is a deformable joining
member.
[0064]
When vibration is transmitted from the piezoelectric actuator 1 (laminate 11) by joining the
laminate 11 and the casing 92 with the deformable joining member 82, the deformable joining
member 82 is larger than the casing 92. Deform.
[0065]
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At this time, since the vibration in the opposite phase reflected from the housing 92 can be
mitigated by the deformable bonding member 82, the housing 92 is not affected by the vibration
of the piezoelectric actuator 1 (laminated body 11). Can be transmitted to a strong vibration.
[0066]
Above all, at least a part of the bonding member 82 is formed of a visco-elastic body, so that the
strong vibration from the piezoelectric actuator 1 (laminated body 11) is transmitted to the
housing 92 while the weak vibration reflected from the housing 92 Is preferable in that the
bonding member 82 can absorb.
For example, a double-sided tape in which an adhesive is attached to both sides of a substrate
made of non-woven fabric or a bonding member having a configuration including an adhesive
having elasticity can be used, and the thickness thereof is, for example, 10 μm to 2000 μm. It
can be used.
[0067]
Further, in this example, the laminate 11 is attached to a part of a housing 92 which is a cover of
the display 91, and a part of the housing 92 functions as a diaphragm 922.
[0068]
In addition, although the thing in which the laminated body 11 was joined to the housing | casing
92 was shown in this example, the laminated body 11 may be joined to the display 91. FIG.
[0069]
The housing 92 has a box-shaped housing body 921 with one surface open, and a diaphragm
922 for closing the opening of the housing body 921.
The housing 92 (the housing body 921 and the diaphragm 922) can be formed preferably using
a material such as a synthetic resin having high rigidity and elastic modulus.
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[0070]
The peripheral portion of the diaphragm 922 is vibratably attached to the housing body 921 via
a bonding material 93.
The bonding material 93 is formed of a material that is softer and easier to deform than the
diaphragm 922, and has a smaller elastic modulus and rigidity such as Young's modulus, rigidity,
and bulk modulus than the diaphragm 922.
That is, the bonding material 93 is deformable, and deforms more than the diaphragm 922 when
the same force is applied.
[0071]
The bonding material 93 may be a single material or a composite of several members. As such a
bonding material 93, for example, a double-sided tape or the like in which an adhesive is
attached to both sides of a base material made of non-woven fabric or the like can be suitably
used. The thickness of the bonding material 93 is set so as not to be too thick and the vibration is
attenuated, and is set to, for example, 0.1 mm to 0.6 mm. However, in the portable terminal of
the present invention, the material of the bonding material 93 is not limited, and the bonding
material 93 may be formed harder than the diaphragm 922 and less likely to be deformed. In
addition, depending on the case, the bonding material 93 may not be provided.
[0072]
As the electronic circuit (not shown), for example, a circuit that processes image information to
be displayed on the display 91 or audio information transmitted by the mobile terminal, a
communication circuit, and the like can be exemplified. At least one of these circuits may be
included, or all of the circuits may be included. Alternatively, a circuit having another function
may be used. Furthermore, a plurality of electronic circuits may be included. The electronic
circuit and the piezoelectric actuator 1 are connected by a connection wiring (not shown).
[0073]
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The display 91 is a display device having a function of displaying image information. For
example, known displays such as a liquid crystal display, a plasma display, and an organic EL
display can be suitably used. The display 91 may have an input device such as a touch panel. In
addition, the cover (diaphragm 922) of the display 91 may have an input device such as a touch
panel. Furthermore, the entire display 91 or a part of the display 91 may function as a
diaphragm.
[0074]
In addition, the portable terminal of the present embodiment is characterized in that the display
91 or the housing 92 generates a vibration that transmits sound information through the
cartilage or air conduction of the ear. The portable terminal of this example can transmit sound
information by transmitting vibration to the cartilage of the ear by bringing the diaphragm (the
display 91 or the housing 92) into contact with the ear directly or through another object. That
is, sound information can be transmitted by transmitting vibration to the cartilage of the ear by
bringing the diaphragm (the display 91 or the housing 92) into contact with the ear directly or
indirectly. As a result, for example, even when the surrounding area is noisy, sound information
can be clearly transmitted, and a portable terminal capable of recognizing speech even by a
person who is deaf can be obtained. An object interposed between the diaphragm (the display 91
or the housing 92) and the ear may be, for example, a cover of a portable terminal, a headphone
or an earphone, and it may be one that can transmit vibration. Anything will do. In addition, the
portable terminal may be one that transmits sound information by propagating the sound
generated from the diaphragm (the display 91 or the housing 92) into the air. Furthermore, it
may be a portable terminal that transmits sound information via a plurality of routes.
[0075]
The portable terminal of this example is configured using the piezoelectric actuator 1 in which no
spark is generated for a long time and the displacement amount of the laminate is stabilized, so
the durability is excellent, and the quality is stable for a long time. Sound information can be
transmitted.
[0076]
Further, as shown in FIG. 10, in the sound generator 10 of the present embodiment, the abovedescribed piezoelectric actuator 1 and the piezoelectric actuator 1 are attached, and the
diaphragm 2 vibrates together with the piezoelectric actuator 1 by the vibration of the
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piezoelectric actuator 1. And the frame 3 provided on the outer peripheral portion of the
diaphragm 2.
[0077]
The piezoelectric actuator 1 is an exciter that excites the diaphragm 2 by vibrating upon
receiving an applied voltage.
The main surface of the piezoelectric actuator 1 and the main surface of the diaphragm 2 are
joined by an adhesive such as epoxy resin, and the piezoelectric actuator 1 bends and vibrates,
whereby the piezoelectric actuator 1 gives a constant vibration to the diaphragm 2. Sound can be
generated.
[0078]
The diaphragm 2 has its peripheral edge fixed to the frame 3 in a tensioned state, and vibrates
together with the piezoelectric actuator 1 by the vibration of the piezoelectric actuator 1.
The diaphragm 2 can be formed using various materials such as resin and metal. For example,
the diaphragm 2 can be made of a resin film such as polyethylene, polyimide, or polypropylene
having a thickness of 10 to 200 μm. Since the resin film is a material having a lower elastic
modulus and mechanical Q value than a metal plate or the like, by forming the diaphragm 2 with
a resin film, the diaphragm 2 is bent and vibrated with a large amplitude to obtain sound
pressure The width and height of the resonance peak in the frequency characteristic can be
increased to reduce the difference between the resonance peak and the dip.
[0079]
The frame 3 functions as a support for supporting the diaphragm 2 at the peripheral portion of
the diaphragm 2 and can be formed using various materials such as metals such as stainless steel
and resin. The frame 3 may be formed by one frame member (upper frame member 31) as
shown in FIG. 10 (b), and as shown in FIG. 10 (c), two frame members (upper frame member 31
and The lower frame member 32) may be used. In this case, the tension of the diaphragm 2 can
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be stabilized by sandwiching the diaphragm 2 with two frame members. Each of the upper frame
member 31 and the lower frame member 32 has a thickness of, for example, 100 to 5000 μm.
[0080]
In the sound generator 10 of the present example, as shown in FIGS. 10B and 10C, it is provided
so as to cover at least the peripheral portion of the surface of the diaphragm 2 from the
piezoelectric actuator 1. It is preferable to further include the resin layer 4. For example, an
acrylic resin can be used as the resin layer 4. Since the appropriate damper effect can be induced
by embedding the piezoelectric actuator 1 (laminated body 11) in the resin layer 4, the
resonance phenomenon is suppressed to suppress the peak and dip in the frequency
characteristic of the sound pressure to a small value. Can. As shown in FIGS. 10B and 10C, the
resin layer 4 may be formed to have the same height as that of the upper frame member 31.
[0081]
Such a sound generator 10 is excellent in durability and stable for a long time since it is
configured using the piezoelectric actuator 1 in which no spark is generated for a long time as
described above and the displacement amount of the laminate is stable. Can be driven.
[0082]
Next, an electronic device equipped with a sound generator will be described with reference to
FIG.
FIG. 11 is a view showing the configuration of the electronic device 50 according to the
embodiment. In both figures, only the components necessary for the description are shown, and
the description of general components is omitted.
[0083]
As shown in FIG. 11, the electronic device 50 of the present example includes an acoustic
generator 10, an electronic circuit 60 connected to the acoustic generator 10, and a case 40 that
accommodates the electronic circuit 60 and the acoustic generator 10. And has a function of
generating sound from the sound generator 10.
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[0084]
The electronic device 50 includes an electronic circuit 60.
The electronic circuit 60 includes, for example, a controller 50a, a transmitting / receiving unit
50b, a key input unit 50c, and a microphone input unit 50d. The electronic circuit 60 is
connected to the sound generator 10 and has a function of outputting an audio signal to the
sound generator 10. The sound generator 10 generates a sound based on an audio signal input
from the electronic circuit 60.
[0085]
The electronic device 50 further includes a display unit 50 e, an antenna 50 f, and the sound
generator 10. In addition, the electronic device 50 includes a housing 40 that accommodates
each of these devices. Although FIG. 11 shows a state in which all the devices including the
controller 50a are housed in one housing 40, the housing form of the devices is not limited. In
the present embodiment, at least the electronic circuit 60 and the sound generator 10 may be
accommodated in one housing 40.
[0086]
The controller 50 a is a control unit of the electronic device 50. The transmitting and receiving
unit 50b transmits and receives data via the antenna 50f based on the control of the controller
50a. The key input unit 50c is an input device of the electronic device 50, and receives a key
input operation by the operator. The microphone input unit 50d is also an input device of the
electronic device 50, and receives a voice input operation and the like by the operator. The
display unit 50 e is a display output device of the electronic device 50, and outputs display
information based on the control of the controller 50 a.
[0087]
The sound generator 10 then operates as a sound output device in the electronic device 50. The
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sound generator 10 is connected to the controller 50a of the electronic circuit 60, and emits a
sound in response to the application of a voltage controlled by the controller 50a.
[0088]
Although the electronic device 50 has been described as a portable terminal device in FIG. 11, it
does not ask the type of the electronic device 50, and may be applied to various consumer
devices having a function of emitting sound. . For example, flat-screen TVs and car audio devices
may be used for various products such as vacuum cleaners, washing machines, refrigerators,
microwave ovens, etc. .
[0089]
Such an electronic device 50 is configured to include the acoustic generator 10 using the
piezoelectric actuator 1 in which the spark does not occur for a long period of time and the
displacement amount of the laminate is stable as described above. Can be driven stably for a long
time.
[0090]
A specific example of the piezoelectric actuator of the present invention will be described.
Specifically, the piezoelectric actuator shown in FIG. 1 was produced as follows.
[0091]
The piezoelectric element was a rectangular solid having a length of 23.5 mm, a width of 3.3 mm,
and a thickness of 0.5 mm. The piezoelectric element had a structure in which 30 μm thick
piezoelectric layers and internal electrodes were alternately stacked, and the total number of
piezoelectric layers was 16. The piezoelectric layer was formed of lead zirconate titanate. An
internal electrode was made of an alloy of silver and palladium.
[0092]
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A ceramic green sheet on which a conductive paste composed of silver palladium was printed
was laminated. Here, after increasing the thickness of the ceramic green sheet laminate at the
portion where the raised portions of the surface electrode are to be provided, the sheet surface
on one main surface side is rich in elasticity, and the plate surface on the other main surface side
opposite The ridges were provided by holding them in place and bringing them into pressure
contact. Then, after degreasing at a predetermined temperature, firing was performed at 1000 °
C. to obtain a laminated sintered body.
[0093]
A voltage of 2 kV / mm electric field strength was applied between the internal electrodes
(between the first electrode and the second electrode) via the surface electrode to polarize the
piezoelectric layer.
[0094]
Thereafter, on the surface of the laminate to be bonded to the flexible substrate, a conductive
adhesive containing 10 vol% of resin balls plated with gold as conductive particles was applied
and formed.
[0095]
After that, the flexible substrate was fixed by heating and pressing in a state where the flexible
substrate was in contact, and a piezoelectric actuator (sample No. 1) of the example of the
present invention was manufactured.
As the above-mentioned conductive adhesive, an anisotropic conductive adhesive which is
conductive in the thickness direction and not conductive in the in-plane direction was used.
[0096]
In addition, as a comparative example, the ceramic green sheet laminate was sandwiched
between flat plates and was heat-pressed to obtain a surface electrode having a flat surface. A
piezoelectric actuator (sample No. 2) outside the scope of the present invention having the same
configuration as No. 1 was produced.
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[0097]
Then, for each piezoelectric actuator, a sine wave signal with an effective value of ± 10 Vrms
was applied to the piezoelectric element at a frequency of 1 kHz through the flexible substrate,
and a drive test was performed. Bending vibration having displacement of 100 μm was obtained
for both 1 and 2.
[0098]
Thereafter, a drive test was performed by continuously adding a sine wave signal of effective
value ± 10 Vrms for 100,000 cycles.
Sample No. 1 which is outside the scope of the present invention. In the case of No. 2, the
displacement amount decreased, and the flexible substrate peeled off from the laminate at
90,000 cycles.
[0099]
On the other hand, sample No. 1 of the example of the present invention. The piezoelectric
actuator 1 was continuously driven without a decrease in displacement even after 100,000
cycles.
Further, no cracks or cracks were observed in the conductive adhesive for connecting and fixing
the flexible substrate, and no peeling of the flexible substrate was observed.
[0100]
By using the piezoelectric actuator of the present invention, no spark is generated, the
displacement amount is stabilized, and the flexible substrate does not peel off from the laminate
even when driven for a long period of time, and excellent durability is obtained. Was confirmed.
[0101]
1: Piezoelectric actuator 11: laminate 12: surface electrode 121: first surface electrode 122:
second surface electrode 123: third surface electrode 13: flexible substrate 131: wiring
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conductor 132: base film 133: cover film 14 Anisotropic conductive adhesive 141: conductive
particles 142: resin 15: raised portion 16: recessed portion 171, 172, 173: internal electrode 81:
diaphragm 82: bonding member 91: display 92: housing 921, housing main body 922 A:
diaphragm 93: bonding material 10: sound generator 2: diaphragm 3: frame 31: upper frame
member 32: lower frame member 4: resin layer 50: electronic device 60: electronic circuit 40:
housing 50a: controller 50b : Transmission / reception unit 50c: Key input unit 50d: Microphone
input unit 50e: Display unit 50f: Antenna
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