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DESCRIPTION JP2017028576

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DESCRIPTION JP2017028576
Abstract: The present invention provides a highly reliable acoustic generator capable of
suppressing a drop in sound pressure even when continuously driven with high voltage, and an
acoustic generator and an electronic apparatus provided with the acoustic generator. A sound
generator includes a diaphragm 12, a frame member 13 for supporting an outer peripheral
portion of the diaphragm 12, and a piezoelectric element 11 provided on the diaphragm 12 in
the frame of the frame member 13 as an exciter. , And a part of the outer peripheral portion of
the diaphragm 12 protrudes from the frame member 13 toward the outside of the frame, and the
adhesive 15 is provided from the diaphragm 12 which protrudes to the outer surface of the
frame member 13. [Selected figure] Figure 1
Acoustic generator, acoustic generator provided with the same, electronic device
[0001]
The present invention relates to an acoustic generator, an acoustic generator including the same,
and an electronic device.
[0002]
Conventionally, there is provided a piezoelectric speaker comprising a diaphragm, a frame
member for supporting the outer peripheral portion of the diaphragm, a piezoelectric element
provided on the diaphragm within the frame of the frame member, and a resin layer covering the
piezoelectric element. It is known (see, for example, Patent Document 1).
[0003]
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There is also known a piezoelectric speaker supported so as to sandwich the outer peripheral
portion of the diaphragm with a pair of frame members (see, for example, Patent Document 2).
[0004]
Japanese Utility Model Application Publication No. 57-128299 Japanese Utility Model
Application Publication No. 2-90600
[0005]
In recent years, sound pressure improvement of a piezoelectric speaker is required, and there are
cases where sound pressure is improved by high voltage driving.
However, in the piezoelectric speaker as described above, although the sound pressure can be
initially improved when continuously driven with high voltage, the diaphragm may become loose
with the passage of driving time, and the sound pressure may decrease. .
[0006]
The present invention has been made in view of the above circumstances, and it is an acoustic
generator with excellent reliability capable of suppressing a drop in sound pressure even when
continuously driven with high voltage, an acoustic generator including the same, and an
electronic apparatus. Intended to be provided.
[0007]
The sound generator according to the present invention comprises a diaphragm, a frame member
for supporting the outer peripheral portion of the diaphragm, and an exciter provided on the
diaphragm within the frame of the frame member, and the diaphragm At least a part of the outer
peripheral portion protrudes from the frame member to the outside of the frame, and an
adhesive is provided from the protruding diaphragm to an outer surface of the frame member.
[0008]
A sound generator according to the present invention is characterized by comprising the sound
generator of the above-mentioned configuration and a case for housing the sound generator.
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[0009]
An electronic apparatus according to the present invention is characterized by including the
sound generator of the above configuration, an electronic circuit connected to the sound
generator, and a case for housing the electronic circuit and the sound generator.
[0010]
According to the sound generator of the present embodiment, a decrease in sound pressure can
be suppressed even when continuously driven with a high voltage, and a sound generator
excellent in reliability can be realized.
Further, according to the sound generation device and the electronic device of the present
embodiment, it is possible to realize a sound generation device and an electronic device having
high sound pressure, high sound quality, and excellent sound performance having high
reliability.
[0011]
(A) is a schematic plan view which shows an example of the sound generator of this embodiment,
(b) is a schematic sectional drawing cut | disconnected by the AA shown to (a).
(A) is a schematic plan view which shows the other example of the sound generator of this
embodiment, (b) is the schematic sectional drawing cut | disconnected by the AA shown to (a).
(A) is a schematic plan view which shows the other example of the sound generator of this
embodiment, (b) is the schematic front view seen from the direction of the arrow shown to (a).
It is a schematic sectional drawing which shows the other example of the sound generator of this
embodiment.
It is a schematic sectional drawing which shows the other example of the sound generator of this
embodiment.
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It is a block diagram showing an example of a sound generation device of this embodiment.
It is a block diagram which shows an example of the electronic device of this embodiment. (A) is
a graph which shows an example of the frequency-sound pressure characteristic of the sound
generator of this embodiment, (b) is a graph which shows the frequency-sound pressure
characteristic of the conventional sound generator used as a comparative example.
[0012]
Hereinafter, an example of the sound generator of the present embodiment will be described in
detail with reference to the attached drawings. Note that the present invention is not limited by
the embodiments described below.
[0013]
Fig.1 (a) is a schematic plan view which shows an example of the sound generator of this
embodiment, FIG.1 (b) is the schematic sectional drawing cut | disconnected by the AA shown to
Fig.1 (a). The sound generator 1 shown in FIG. 1 includes a diaphragm 12, a frame member 13
for supporting the outer peripheral portion of the diaphragm 12, and a piezoelectric element as
an exciter provided on the diaphragm 12 in the frame of the frame member 13. 11, and at least a
part of the outer peripheral portion of the diaphragm 12 protrudes from the frame member 13
toward the outside of the frame, and the adhesive 15 is provided from the diaphragm 12 which
protrudes to the outer surface of the frame member 13.
[0014]
The structure of the piezoelectric element 11 constituting the sound generator 1 is not shown,
but, for example, it comprises a laminate formed by laminating a piezoelectric layer and an
internal electrode layer into a plate shape, and this laminate The form provided with the external
electrode provided in the side from which the internal electrode layer was derived | led-out and
the surface electrode connected to this external electrode and provided in the main surface of the
laminated body is employable. The piezoelectric element 11 is provided by being attached to the
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main surface of the diaphragm 12 positioned in the frame of the frame member 13 or the like,
and vibrates the diaphragm 12 by receiving voltage application and vibrating.
[0015]
The piezoelectric layer constituting the piezoelectric element 11 is formed of a ceramic having
piezoelectric characteristics, and as such ceramics, lead zirconate titanate, lithium niobate,
lithium tantalate, Bi layered compound Conventional piezoelectric ceramics such as lead-free
piezoelectric materials such as tungsten bronze structure compounds can be used. The thickness
of the piezoelectric layer is set to, for example, 0.04 to 1.0 mm. Further, in order to obtain a large
flexural vibration, it is preferable to have a piezoelectric constant d31 of 200 pm / V or more.
[0016]
Further, the internal electrode layer constituting the piezoelectric element 11 is formed by cofiring with the ceramic forming the piezoelectric layer, and comprises a first internal electrode
layer and a second internal electrode layer, and the piezoelectric layer They are alternately
stacked to sandwich the piezoelectric layer from above and below. Various metal materials can
be used as a material for forming the internal electrode layer. For example, a conductor
containing silver or silver-palladium as a main component which can be fired at a low
temperature, or a conductor containing copper, platinum or the like can be used, but these may
contain a ceramic component or a glass component. When the internal electrode layer is made of
a material containing a metal component of silver and palladium and a ceramic component of the
piezoelectric layer, the stress due to the thermal expansion difference between the piezoelectric
layer and the internal electrode layer is reduced. As a result, it is possible to obtain a piezoelectric
element 11 free from stacking faults.
[0017]
Further, as a material of the external electrode and the surface electrode constituting the
piezoelectric element 11, a silver compound containing silver or the like, a glass whose main
component is silica, or the like, nickel, or the like can be used.
[0018]
The piezoelectric element 11 is preferably formed of a plate-like body whose main surfaces on
the upper surface side and the lower surface side have a polygonal shape such as a rectangular
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shape or a square shape, or a circular shape or an elliptical shape, for example. By using the
piezoelectric element 11 and the diaphragm 12 and the frame member 13 described later, the
acoustic generator can be made thin.
[0019]
The piezoelectric element 11 may have, for example, a monomorph structure (a single-layer
piezoelectric body) in which the piezoelectric layer is a single layer, but it is preferable that the
piezoelectric layer has a bimorph structure with two or more layers.
Thus, the diaphragm 12 can be vibrated efficiently with a small amount of energy, as well as
contributing to thinning.
In addition, in a bimorph structure in which the direction of displacement due to an electric field
applied at a certain moment is reversed such that the direction of displacement in one side and
the other side in the thickness direction is reversed, the piezoelectric element 11 itself is bent
and vibrated to form a diaphragm Since the mechanical loss in the joint surface with 12 can be
reduced, it can contribute to the improvement of sound pressure.
[0020]
The electrical connection between the surface electrode and the internal electrode layer may be
by a through conductor penetrating the piezoelectric layer instead of the external electrode as
described above.
[0021]
The diaphragm 12 constituting the sound generator 1 can be formed using various materials
such as resin and metal.
For example, it is possible to use the diaphragm 12 having a thickness of 10 to 200 μm with a
metal plate such as stainless steel, or a resin film such as polyethylene, polyimide, acrylic,
polycarbonate, polybutylene terephthalate or the like.
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[0022]
A piezoelectric element 11 as an exciter is attached to the diaphragm 12. Specifically, the main
surface of the piezoelectric element 11 is bonded to the main surface of the diaphragm 12 with
an adhesive such as epoxy resin.
[0023]
The vibrating plate 12 vibrates due to the vibration of the piezoelectric element 11. For example,
a wiring member (not shown) is connected to the surface electrode of the piezoelectric element
11, and an electrical signal is input to the piezoelectric element 11 through the wiring member.
Here, when the piezoelectric element 11 extends in the in-plane direction (the direction parallel
to the main surface of the diaphragm 12), the diaphragm 12 is bent to be convex toward the
piezoelectric element 11. Next, when the positive and negative electrodes of the electric signal
are reversed in this state, the piezoelectric element 11 contracts and the diaphragm 12 bends so
as to be concave toward the piezoelectric element 11 side. That is, by applying an alternating
current signal to the piezoelectric element 11, the piezoelectric element 11 can be expanded and
contracted to give bending vibration to the diaphragm 12.
[0024]
In addition, a frame member 13 is provided to support the outer peripheral portion of the main
surface of the diaphragm 12. Here, in the frame member 13, the main surface (the lower surface
in FIG. 1) of the frame member 13 and the outer peripheral portion of the main surface (the
upper surface in FIG. 1) of the diaphragm 12 are made of, for example, thermosetting resin or UV
thermosetting resin. The outer peripheral portion of the main surface of the diaphragm 12 is
supported by being bonded through an adhesive.
[0025]
As the frame member 13, for example, a frame member whose inner and outer peripheral shapes
are rectangular can be used. In the example shown in FIG. 1, the frame member 13 is provided
only on the one main surface side of the diaphragm 12, but as shown in FIG. 5 described later, it
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is also provided on the other main surface side of the diaphragm 12. The outer peripheral
portion of the diaphragm 12 may be held and supported by the first frame member 131 on the
one main surface side and the second frame member 132 on the other main surface side.
[0026]
As thickness (height) of frame member 13 (the 1st frame member 131, the 2nd frame member
132), a 100 micrometers-5.0 mm thing is employable, for example.
[0027]
Moreover, as a material of the frame member 13, various materials, such as glass, a metal, and
resin, can be used, for example.
When the frame member 13 is made of glass or metal, the rigidity is high, so the deformation is
small and the sound quality is stable. On the other hand, when the frame member 13 is made of
resin, the rigidity is smaller than that of glass or metal, and deformation due to the vibration of
the diaphragm 12 is likely to occur, so spurious vibration is easily induced to the resonance of
the diaphragm 12. Therefore, in the sound pressure characteristic, the resonance peak is
dispersed, the peak and dip can be reduced, and the frequency characteristic can be flattened.
Therefore, the sound quality can be improved by flattening the sound pressure.
[0028]
Further, the frame member 13 may be assembled by arranging a plurality of members in the
circumferential direction, and these may be joined to each other.
[0029]
Further, FIG. 1 shows an example in which the outer peripheral shape of the frame member 13 is
a rectangular shape and the inner peripheral shape is also a rectangular shape. It contributes to
the dispersion of resonance and can contribute to the reduction of peaks and dips.
However, it may be a polygon such as a square, a parallelogram, a trapezoid and a regular n-gon,
or may be a circle or an ellipse.
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[0030]
Further, as shown in FIG. 1, if necessary, a resin layer 14 may be provided in the frame of the
frame member 13 so as to cover the piezoelectric element 11.
[0031]
Although the case where the number of piezoelectric elements 11 is one is illustrated in FIG. 1,
the number of piezoelectric elements 11 is not limited.
Further, although FIG. 1 shows an example in which the piezoelectric element 11 is provided on
one main surface of the diaphragm 12, the piezoelectric element 11 may be provided on both
main surfaces of the diaphragm 12, respectively.
[0032]
And, in the sound generator of the present embodiment, at least a part of the diaphragm 12
protrudes from the frame member 13 toward the outside of the frame, and in the sound
generator 1 shown in FIG. Both ends along the side project from the frame member 13 toward
the outside of the frame. The term "outside of the frame" as used herein means the outer side of
the outer periphery of the frame member 13 when viewed from the direction perpendicular to
the main surface of the diaphragm 12, and projecting out of the frame means from the outer
periphery of the frame member 13. Also means that there is a part of the diaphragm 12 on the
outside.
[0033]
Further, an adhesive 15 is provided from the projecting diaphragm 12 to the outer surface of the
frame member 13. In other words, the adhesive 15 is raised on the main surface of the
diaphragm 12 projecting out of the frame of the frame member 13, the adhesive 15 adheres to
the outer surface of the frame member 13, and the main surface of the diaphragm 12 The upper
portion and the outer surface of the frame member 13 are joined.
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[0034]
Here, as the adhesive 15, for example, an adhesive such as a thermosetting resin or a UV
thermosetting resin can be adopted, and the main surface (the lower surface in FIG. 1) of the
frame member 13 and one main surface (the lower surface in FIG. In FIG. 1, the same adhesive as
that interposed between the outer peripheral portion of the upper surface) and the adhesive may
be used, or different ones may be used.
[0035]
With such a configuration, the adhesive strength between the diaphragm 12 and the frame
member 13 is increased, and the diaphragm 12 is not loosened even if the driving voltage is
increased and the continuous driving is performed, so that the reduction of the sound pressure
level can be suppressed. The sound generator 1 can be improved in reliability.
[0036]
The maximum projection amount (maximum projection distance) of the diaphragm 12 projecting
from the frame member 13 to the outside of the frame in plan view is set to, for example, 50 μm
to 2.0 mm.
The maximum distance from the outer periphery of the frame member 13 to the tip of the
adhesive 15 (maximum projection distance of the adhesive 15) in plan view is set to, for example,
50 μm to 1.0 mm, as viewed from the horizontal direction The maximum distance (maximum
height of the adhesive 15) from the main surface of the diaphragm 12 to the tip of the adhesive
15 is set to, for example, 80 μm to 1.0 mm.
[0037]
Here, as shown in FIG. 2, the diaphragm 12 protrudes from the frame member 13 over the entire
circumference toward the outside of the frame, and the adhesive 15 is provided from the
diaphragm 12 that protrudes to the outer surface of the frame member 13. More preferable.
With such a configuration, the adhesive strength with the frame member 13 is further increased,
and the diaphragm 12 is not further loosened even if the drive voltage is increased and the
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continuous drive is performed, so that the reduction of the sound pressure level can be further
suppressed.
[0038]
Further, as shown in FIG. 3, it is more preferable that the adhesive 15 has unevenness in the
height direction of the adhesive surface of the outer surface of the frame member 13. With such
a configuration, the stress against peeling of the adhesive 15 from the outer surface of the frame
member 13 is dispersed, so that it is possible to further suppress the decrease in the bonding
strength between the diaphragm 12 and the frame member 13 and the sound pressure level. Can
be further suppressed.
[0039]
Here, the difference in height between the top of the adjacent mountain and the bottom of the
valley on the outer surface of the frame member 13 is set to, for example, 10 to 30 μm, and the
maximum height (the height of the highest peak) and the minimum height The difference with
(the height of the bottom of the lowest valley) is set to, for example, 10 to 20 μm.
[0040]
Although not shown, the outer peripheral shape of the bonding surface of the main surface of the
diaphragm 12 in plan view may be a shape having unevenness.
[0041]
Further, as shown in FIG. 4, the adhesive 15 may be adhered to the outer surface of the
diaphragm 12 and the frame member 13 in a meniscus shape.
With such a configuration, the reflected wave of the vibration propagated to the frame member
13 is dispersed, so that distortion caused by the reflected wave can be reduced, and the sound
quality can be improved.
In addition to the meniscus shape, the surface may be a curved surface, or the surface may be
inclined with respect to the vertical direction.
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[0042]
Here, as shown in FIG. 5, the frame member 13 is composed of the first frame member 131 and
the second frame member 132, and the outer surface of the first frame member 131 is seen from
one main surface of the projecting diaphragm 12. And the second adhesive 152 is provided from
the other main surface of the projecting diaphragm 12 to the outer surface of the second frame
member 132, and the first adhesive 151 is provided. More preferably, the height of the adhesive
surface of the agent 151 on the outer surface of the first frame member 131 is different from the
height of the adhesive surface on the outer surface of the second frame member 132 of the
second adhesive 152.
[0043]
With such a configuration, it is possible to superimpose spurious vibrations different in
resonance frequency on the vibration caused by the reflected wave of the vibration propagated
to the frame member 13, the vibration of the reflected wave is divided, and the peak / dip in the
frequency characteristic The sound quality can be improved because the
[0044]
In the case where the height of the adhesive surface of the first adhesive 151 on the outer
surface of the first frame member 131 is 50 to 100 μm, for example, the adhesive surface of the
second adhesive 152 on the outer surface of the second frame member 132 The difference from
the height is set to, for example, 50 to 100 μm.
[0045]
Next, a method of manufacturing the sound generator of the present embodiment will be
described.
[0046]
First, a ceramic green sheet to be a piezoelectric layer constituting a piezoelectric element is
manufactured.
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.
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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.
[0047]
In addition, you may produce a ceramic molded object using other manufacturing methods, such
as press molding and extrusion molding.
[0048]
Moreover, when producing the laminated body which consists of a piezoelectric material layer
and an internal electrode layer, the conductive paste used as an internal electrode layer is
produced.
Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to
silver-palladium metal powder. This conductive paste is applied on the above-mentioned ceramic
green sheet by screen printing using a desired pattern of internal electrode layers, and a plurality
of ceramic green sheets on which this conductive paste is printed are laminated to form a
ceramic green sheet. It may be a laminate.
[0049]
Then, the ceramic green sheet or the ceramic green sheet laminate obtained above is subjected to
a binder removal treatment at a predetermined temperature, and then fired at a temperature of
900 ° C. to 1200 ° C., and then predetermined using a surface grinder or the like. A grinding
process is performed to form a laminate having a single-layer piezoelectric body or alternately
stacked internal electrode layers and a piezoelectric layer.
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[0050]
Note that any manufacturing method may be used as long as a single-layer piezoelectric body or
a stacked body formed by stacking a plurality of internal electrode layers and a plurality of
piezoelectric layers can be manufactured.
[0051]
Next, similarly, 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 used as a main surface of a piezoelectric body or a laminate and After
printing and drying on the side surface by a screen printing method or the like in a
predetermined pattern, baking is performed at a temperature of 600 ° C. to 800 ° C. to form a
surface electrode and an external electrode.
[0052]
Thereafter, the piezoelectric body or the laminate is subjected to polarization treatment to impart
piezoelectric activity.
For polarization processing, using a DC power supply device, for example, the first surface
electrode provided on the surface of the piezoelectric element is connected to the negative
electrode, and the second surface electrode is connected to the positive electrode, for example 2
kV / mm to 3 kV / mm The potential difference may be applied at an ambient temperature of 15
° C. to 35 ° C. for several seconds as an application time.
The voltage, the ambient temperature, and the application time are suitably selected depending
on the properties of the piezoelectric material.
[0053]
Although the desired piezoelectric element 11 can be obtained as described above, when a wiring
member is required, it may be connected to the piezoelectric element 11 by the following
method.
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For example, when connecting and fixing (joining) the flexible wiring substrate to the
piezoelectric element 11 using a conductive adhesive, a conductive adhesive paste is applied and
formed on a predetermined position of the piezoelectric element 11 using a method such as
screen printing. Do. Then, the flexible wiring board is connected and fixed to the piezoelectric
element 11 by curing the conductive adhesive paste in a state where the flexible wiring board is
in contact. The conductive adhesive paste may be applied and formed on the flexible wiring
substrate side.
[0054]
In addition, a lead wire which carried out insulation covering may be used as a wiring member,
solder may be used as a joining member, and a member which has the same function can be
chosen suitably.
[0055]
Next, the diaphragm 12 is manufactured.
For example, in the case of producing the diaphragm 12 with a metal such as stainless steel, it is
produced by press punching and etching in a desired shape. When the diaphragm 12 is made of
a resin such as an acrylic resin, a polycarbonate resin, or a polybutylene terephthalate resin, it is
manufactured by injection molding using a mold manufactured to have a desired shape.
Moreover, when producing the diaphragm 12 with resin films, such as polyethylene and a
polyimide, it produces with a desired shape by the press punching process or a laser cut.
[0056]
Next, the piezoelectric element 11 is bonded and fixed to one main surface of the diaphragm 12
using a bonding material. When, for example, an anaerobic resin adhesive is used as the bonding
material, the anaerobic adhesive paste is applied and formed on a predetermined position on the
one main surface side of the diaphragm 12 using a method such as screen printing.
[0057]
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Thereafter, pressure is applied in a state in which the piezoelectric element 11 is in contact, and
the paste for anaerobic adhesive is cured to bond and fix the piezoelectric element 11 to the
diaphragm 12. The anaerobic adhesive paste may be applied and formed on the piezoelectric
element 11 side.
[0058]
Next, the frame member 13 is manufactured. For example, in the case of producing the frame
member 13 with a metal such as stainless steel, the frame member 13 is produced by a press
punching process or an etching process. Moreover, when producing the frame member 13 with
resin materials, such as an acrylic resin, polycarbonate resin, polybutylene terephthalate resin, it
produces by injection molding using a metal mold | die.
[0059]
Next, the diaphragm 12 is bonded and fixed to the main surface of the frame member 13
processed by the above method using the adhesive 15. When, for example, an anaerobic resin
adhesive is used as the adhesive 15, the anaerobic adhesive paste is applied and formed at a
predetermined position on the main surface side of the diaphragm 12 using a method such as
screen printing, and then a frame is formed. The frame member 13 is joined and fixed to the
diaphragm 12 by applying pressure in a state where the member 13 is in contact and curing the
anaerobic adhesive paste. The anaerobic adhesive paste may be applied and formed on the frame
member 13 side. As the other adhesive 15, for example, an adhesive such as a heat-curable
epoxy-based adhesive can be used.
[0060]
Here, in order to make at least a part of the outer peripheral portion of the diaphragm 12 project
from the frame member 13 toward the outside of the frame, the diaphragm 12 may be cut larger
than the frame member 13 by a laser. Further, in order to provide the adhesive 15 from the
projecting diaphragm 12 to the outer surface of the frame member 13, the application amount
and application position of the adhesive may be adjusted and applied.
[0061]
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The same applies to the configuration in which the outer peripheral portion of the diaphragm 12
protrudes from the frame member 13 to the outside of the frame over the entire periphery and
an adhesive is provided from the diaphragm 12 projecting to the outer surface of the frame
member 13. Obtained by the method of
[0062]
Further, in order to make the configuration in the height direction of the adhesive surface of the
outer surface of the frame member 13 have a configuration, the application amount may be
appropriately adjusted by a dispenser or printing, and the adhesive 15 has a meniscus shape
with the diaphragm 12 and the frame member. The application direction and the application
amount may be appropriately adjusted even in the configuration of being adhered to the outer
surface of 13.
[0063]
Further, the frame member 13 is composed of the first frame member 131 and the second frame
member 132, and the first adhesive 151 extends from one main surface of the projecting
diaphragm 12 to the outer surface of the first frame member 131. A second adhesive 152 is
provided from the other main surface of the projecting diaphragm 12 to the outer surface of the
second frame member 132 while being provided, and the first frame member 131 of the first
adhesive 151 is provided. The coating amount and the application time may be appropriately
adjusted in order to make the height of the adhesive surface on the outer surface of the second
adhesive 152 different from the height of the adhesive surface on the outer surface of the second
frame member 132 of the second adhesive 152. .
[0064]
In the above description, the diaphragm 12 processed into a desired shape is prepared, the
piezoelectric element 11 is adhered, and then the diaphragm 11 and the frame member 13 are
adhered. In the case of using it, after bonding the plurality of piezoelectric elements 11 and the
plurality of frame members 13 to a large area resin film, the resin film may be laser cut so as to
have a desired shape.
[0065]
The acoustic generator of this embodiment is obtained by the above manufacturing method.
[0066]
Next, an example of the sound generator of the present embodiment will be described.
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[0067]
The sound generation device is a so-called speaker-like sound generation device, and as shown in
FIG. 6, the sound generation device 20 of this example includes a sound generator 1 and a
housing 30 that houses the sound generator 1.
In addition, a part of case 30 may be diaphragm 12 which constitutes sound generator 1, and
case 30 accommodating sound generator 1 is a part of sound generator 1 (piezoelectric element
11 ) Is meant to be included.
[0068]
The housing 30 resonates the sound emitted by the sound generator 1 internally, and radiates
the sound to the outside from an opening (not shown) formed in the housing 30.
By including such a housing 30, sound pressure in, for example, a low frequency band can be
increased.
[0069]
The sound generation device 20 can be used alone as a speaker, and can be suitably incorporated
into a portable terminal, a flat-screen television, a tablet terminal, or the like as described later.
In addition, it can be incorporated into home appliances such as refrigerators, microwave ovens,
vacuum cleaners, washing machines, etc., for which sound quality has not been emphasized
conventionally.
[0070]
The sound generation device 20 according to the present embodiment described above can
suppress a decrease in sound pressure even when continuously driven with a high voltage, and is
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configured using a sound generator with improved reliability, so high sound pressure and high
sound quality can be obtained. Sound performance with high reliability.
[0071]
Next, an example of the electronic device of the present embodiment will be described.
[0072]
As shown in FIG. 7, the electronic device 50 of the present example includes an acoustic
generator 1, an electronic circuit 60 connected to the acoustic generator 1, and a case 40 that
accommodates the electronic circuit 60 and the acoustic generator 1. It has a function to
generate sound from the sound generator 1.
[0073]
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 1 and has a function of outputting
an audio signal to the sound generator 1.
The sound generator 1 generates a sound based on the sound signal input from the electronic
circuit 60.
[0074]
In addition, the electronic device 50 includes the display unit 50e, the antenna 50f, and the
sound generator 1, and includes the housing 40 that accommodates these devices.
Although FIG. 7 shows a state in which all the devices including the controller 50a are housed in
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one housing 40, the housing form of each device is not limited.
In the present embodiment, at least the electronic circuit 60 and the sound generator 1 may be
accommodated in one housing 40.
[0075]
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.
[0076]
The sound generator 1 then operates as a sound output device in the electronic device 50. The
sound generator 1 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.
[0077]
Although FIG. 7 describes the electronic device 50 as a portable terminal device, 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
and the like, as a matter of course, products having a function of emitting sound, for example.
[0078]
The electronic device according to the present invention described above is configured using a
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highly reliable sound generator that can suppress a drop in sound pressure even when
continuously driven with high voltage, and thus has high sound pressure, high sound quality, and
high reliability. It has excellent sound performance with elasticity.
[0079]
Next, a specific example of the sound generator of the present embodiment will be described.
[0080]
A piezoelectric element of a bimorph structure in which eight piezoelectric layers made of lead
zirconate titanate and seven internal electrode layers made of silver are stacked has a length of
65 mm, a width of 35 mm, and a thickness of 2 mm. It was plate-shaped.
Further, the diaphragm was made of a resin film having a thickness of 25 μm, and the
diaphragm was manufactured so as to protrude from the frame member to the outside of the
frame, and the acoustic generator of the example was prepared.
[0081]
The frame member is formed of a pair of upper and lower frame members made of stainless
steel, and the outer peripheral portion of the diaphragm is held by the pair of frame members.
Each frame member has dimensions of 30 mm in length, 60 mm in width, and 35 mm in width,
65 mm in width, and has a width of 2.5 mm in plan view and a thickness (height) of 1.0 mm. It
was.
[0082]
Further, the diaphragm was protruded from the frame member to the outside of the frame over
the entire circumference, and the protrusion distance was 1 mm.
[0083]
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Furthermore, the adhesive is made of an epoxy adhesive, and the adhesive between the frame
member and the diaphragm protrudes over the entire circumference of the frame member
outside the frame member, and there is unevenness in the height direction of the adhesive
surface on the outer surface of the frame member. It was set as the form (form of FIG. 3).
Here, the maximum protrusion distance of the adhesive from the outer periphery of the frame
member in plan view was 100 μm, and the maximum height of the adhesive was 100 μm when
viewed from the direction perpendicular to the outer surface of the frame member.
[0084]
The characteristics of the sound pressure level, which is the acoustic characteristics of the
example produced as described above, were measured. The results are shown in FIG. 8 (a).
[0085]
On the other hand, as a comparative example, a diaphragm was not made to stick out of a frame
from a frame member, and the sound generator made into the same composition as the sound
generator of an example except composition which is not provided with adhesives outside a
frame was produced. . The characteristics of the sound pressure level, which is the acoustic
characteristics, were also measured for this acoustic generator as in the above-described
example. The results are shown in FIG. 8 (b).
[0086]
A comparison of FIG. 8 (a) with FIG. 8 (b) shows that the sound pressure level characteristics of
the sound generator of the example are clearly improved compared to the sound generator of the
comparative example.
[0087]
From the above, at least a part of the outer peripheral portion of the diaphragm protrudes from
the frame member to the outside of the frame, and the sound pressure is provided by providing
the adhesive from the projecting diaphragm to the outer surface of the frame member. It has
been confirmed that the level characteristics can be improved.
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[0088]
DESCRIPTION OF SYMBOLS 1 sound generator 11 piezoelectric element 12 diaphragm 13 frame
member 131 1st frame member 132 2nd frame member 14 resin layer 15 adhesive agent 151
1st adhesive agent 152 2nd adhesive agent 20 acoustic generator 30, 40 Case 50 electronic
device 60 electronic circuit
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