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JP2007194789

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DESCRIPTION JP2007194789
PROBLEM TO BE SOLVED: In a conventional piezoelectric speaker, sound pressure
characteristics at 1 kHz to 10 kHz are not good. An object of the present invention is to provide a
piezoelectric speaker in which sound pressure characteristics are improved by providing two
piezoelectric resin composites and enhancing a piezoelectric effect. SOLUTION: A plurality of
piezoelectric element chips, a piezoelectric resin portion made of an organic resin filled on the
side surface side excluding the electrode surface of the piezoelectric element chip, and a
peripheral resin portion of only the organic resin around the piezoelectric resin portion Two
piezoelectric resin composites to be formed are provided, an intermediate electrode film is
provided as an intermediate layer between the electrode surfaces of the two piezoelectric resin
composites, and both surfaces of the two piezoelectric resin composites are in contact with the
intermediate electrode film. The sound pressure characteristic is improved by providing the
conductive electrode film on the A part or all of the surrounding resin portion is a piezoelectric
speaker coupled to the speaker frame. [Selected figure] Figure 1
Piezoelectric speaker
[0001]
The present invention relates to a piezoelectric speaker using a piezoelectric element chip, and
more particularly to a piezoelectric speaker capable of improving sound pressure characteristics.
[0002]
In general, the speaker causes the voice cone to mechanically vibrate due to the interaction
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between the current of the coil and the magnetic field of the permanent magnet by passing a
voice electric signal to the voice coil connected to the voice cone having a role of diaphragm. The
air is vibrated to reproduce the sound.
In the reproduction of speech, it is ideal to reproduce efficiently and without distortion over a
wide range from a few 10 Hz to a few 10 kHz, which is the human audio frequency. However,
since it is difficult to cover a wide frequency range with one speaker, generally, a plurality of
speakers corresponding to each range is used.
[0003]
By the way, in recent years, in audio devices such as stereo devices, televisions, surround sound,
etc., demands for reduction in size, weight and thickness have been extremely increased. In
response to such a demand, an extremely thin and lightweight piezoelectric speaker has been
developed. This piezoelectric speaker is disclosed, for example, in Patent Documents 1, 2, 3 and
the like, and is composed of an epoxy resin and a large number of lead zirconate titanate (PZT)
piezoelectric element chips, a conductive electrode film, etc. By using the piezoelectric element
chip and the organic resin, the piezoelectric effect of the piezoelectric element and the elasticity
of the organic resin are utilized.
[0004]
JP-A-7-327298 JP-A-2000-324598 JP-A-2003-348692
[0005]
However, in the above-described conventional piezoelectric speaker, for example, the sound
pressure characteristics at 1 kHz to 10 kHz are not good.
The present invention has been created in order to effectively solve the above problems. An
object of the present invention is to provide a plurality of piezoelectric element chips and two
piezoelectric resin composites made of organic resin around the piezoelectric element chips, and
an intermediate electrode film as an intermediate layer between the electrode surfaces of the
piezoelectric resin complex, An object of the present invention is to provide a piezoelectric
speaker having improved sound pressure characteristics at 1 kHz to 10 kHz by enhancing the
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piezoelectric effect.
[0006]
The present invention comprises a plurality of piezoelectric element chips, a piezoelectric resin
portion made of an organic resin filled on the side surface excluding the electrode surface of the
piezoelectric element chip, and a peripheral resin portion of only the organic resin around the
piezoelectric resin portion. Two piezoelectric resin composites to be formed are provided, and an
intermediate electrode film is provided as an intermediate layer between the electrode surfaces
of the two piezoelectric resin composites, and the two piezoelectric resin composites in contact
with the intermediate electrode film In the piezoelectric speaker, conductive electrode films are
provided on both sides, and a part or all of the surrounding resin portion is coupled to the
speaker frame.
[0007]
In a conventional known example, there is only one piezoelectric resin composite composed of a
plurality of piezoelectric element chips and an organic resin, and the shape of the piezoelectric
resin composite is convex or concave in the vibration direction of the piezoelectric resin
composite. No film has been formed.
On the other hand, in the present invention, the shapes of the two piezoelectric resin composites
and the intermediate electrode film may be convex, concave or planar in the vibration direction
of the piezoelectric resin composite. When convex or concave in the vibration direction, the
piezoelectric resin composite of the present invention is a part of a plane, a part of a cylindrical
curved surface, a part of a conical curved surface, a part of a spherical curved surface and a part
of an ellipsoid curved surface. It is also possible to have a form selected from one or more of
them.
[0008]
As the piezoelectric element chip, in addition to lead zirconate titanate (PZT) -based PZT, another
composite material ceramic may be used. Specifically, it is possible to use lead zinc niobate
titanate (PZNT) or magnesium niobate lead titanate (PMNT) whose piezoelectric strain constant is
about three times larger than that of PZT. Importantly, in order to ensure a good piezoelectric
effect, the pair of electrode surfaces of the individual piezoelectric element chips need to be
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substantially parallel. Moreover, in all the piezoelectric element chips used for the piezoelectric
speaker, the distance between the electrode surfaces needs to be the same. The piezoelectric
element chip in the present invention may have any shape except that the electrode surfaces are
parallel and the distance between the electrode surfaces is the same degree. For example, as a
shape of the piezoelectric element chip, a cylindrical body, a rectangular parallelepiped, a
triangular prism, or the like is preferable. Moreover, the shape chosen from 1 or more types in a
cylindrical body, a rectangular parallelepiped, and a triangular cylinder may be sufficient, for
example, a rectangular parallelepiped and a triangular cylinder can be mixed and used.
Industrially, piezoelectric element chips having the same rectangular parallelepiped shape are
recommended.
[0009]
An epoxy resin, a polyurethane resin, etc. can be used as an organic type resin. The speaker
frame may be made of a material capable of fixing and supporting the piezoelectric resin
composite, requires superior strength characteristics as compared to the piezoelectric resin
composite, and the conductive characteristics are not particularly limited. In the speaker frame,
what is important is the coupling state of the speaker frame and the piezoelectric resin
composite. When the piezoelectric resin composite and the speaker frame are formed of the
coupled portion and the non-coupled portion, the flexibility of the piezoelectric resin composite is
increased and the sound pressure characteristic is improved. As the conductive electrode film, a
deposited film of a conductive material such as carbon, aluminum, gold, silver, copper or the like
excellent in conductive characteristics on a piezoelectric element chip, an organic resin film
containing the conductive material, or the deposited film And a composite of the organic resin
film is preferable.
[0010]
As the intermediate electrode film, a conductive material such as carbon, aluminum, gold, silver,
copper or the like excellent in conductive property, an organic resin film containing the
conductive material, or a deposited film of the conductive material on a piezoelectric element
chip And a composite of the organic resin film is preferable. The role of the intermediate
electrode film is to apply the same potential to the piezoelectric element chips present in the two
piezoelectric resin composites in contact with the intermediate electrode film. In the case of a
piezoelectric element chip polarized in the same direction perpendicular to the electrode surface,
one piezoelectric element chip in contact with the intermediate electrode film expands in the
direction perpendicular to the polarization direction by applying the same potential. The other
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piezoelectric element chip in contact with the intermediate electrode film contracts in the
direction perpendicular to the polarization direction. In this case, the shapes of the two
piezoelectric resin composites and the intermediate electrode film may be convex, concave or
planar in the vibration direction of the piezoelectric resin composite.
[0011]
When one piezoelectric element chip in contact with the intermediate electrode film and the
other piezoelectric element chip are polarized in the opposite direction perpendicular to the
electrode surface, one piezoelectric element chip in contact with the intermediate electrode film
by applying the same potential The other piezoelectric element chip expands and contracts in the
same direction perpendicular to the polarization direction. Therefore, in the case of a
piezoelectric element chip polarized in the opposite direction with respect to the intermediate
electrode film, it is not applicable that the two piezoelectric resin composites and the
intermediate electrode film have a planar shape. It is necessary to be convex or concave in the
vibration direction of the resin complex. In addition, it is necessary to connect a lead wire for
energizing the audio electric signal to the intermediate electrode film, and the wire connection of
the lead wire may be provided through the surrounding resin portion. In addition, organic resin
films such as polyurethane resin, polyethylene resin, epoxy resin, etc. are formed on the upper
side of one side or both sides of the conductive electrode film for protection of the conductive
electrode film provided on the upper part of the piezoelectric resin portion and improvement of
speaker output characteristics. May be provided.
[0012]
According to the piezoelectric speaker of the present invention, a plurality of piezoelectric
element chips and two piezoelectric resin composites made of organic resin around the
piezoelectric element chips are provided, and an intermediate electrode film is formed as an
intermediate layer between the electrode surfaces of the piezoelectric resin complex. The sound
pressure characteristics at 1 kHz to 10 kHz can be improved by enhancing the piezoelectric
effect. Further, as in the present invention, the two piezoelectric resin composites and the
intermediate electrode film may have any shape of convex, concave or planar in the vibration
direction, which is easy to manufacture and the range of use thereof is also expanded. It can be
said that the effect of the present invention is great.
[0013]
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Hereinafter, an embodiment of a piezoelectric speaker according to the present invention will be
described in detail.
[0014]
FIG. 1 is an enlarged sectional view of an essential part showing a piezoelectric speaker
according to the present invention.
FIG. 2 is a cross-sectional view of the piezoelectric speaker shown in FIG. As illustrated, the
piezoelectric speaker is filled with an organic resin 12 between a plurality of piezoelectric
element chips 11 having the same rectangular parallelepiped shape, and around the piezoelectric
resin portion 13 and the piezoelectric resin portion 13 in which many piezoelectric element chips
11 are coupled. An intermediate electrode film provided as an intermediate layer between the
electrode surfaces of the two piezoelectric resin composites 15A and 15B formed of the organic
resin only surrounding resin portion 14 and the two piezoelectric resin composites 15A and 15B.
15C, conductive electrode films 17A and 17B provided on both surfaces of the two piezoelectric
resin composites 15A and 15B in contact with the intermediate electrode film 15C, and a frame
16 coupled to the surrounding resin portion 14 . The conductive electrode films 17A and 17B
are connected by the lead wire 18A, and the intermediate electrode film 15C is connected by the
lead wire 18B through the surrounding resin portion 14, and the voice electric signal is
transmitted from the audio signal source 18 to the leads 18A and 18B. The sound is obtained by
energizing the As shown in FIGS. 1 and 2, in the present embodiment, two piezoelectric resin
composites 15A and 15B made of an organic resin and provided around a plurality of
piezoelectric element chips 11 and piezoelectric element chips 11 are provided. By providing the
intermediate electrode film 15C as an intermediate layer between the electrode surfaces 15A and
15B and enhancing the piezoelectric effect, it is possible to improve the sound pressure
characteristics at 1 kHz to 10 kHz.
[0015]
Furthermore, the details of the embodiment will be specifically described. Piezoelectric resin
composites 15A and 15B of a piezoelectric speaker were produced by the method disclosed in
Japanese Patent Application Laid-Open No. 2003-348692. The piezoelectric element chip 11
used is a lead zirconate titanate (PZT) -based piezoelectric element and is a rectangular solid of 2
mm in length, 2 mm in width, and 0.2 mm in thickness. In addition, an epoxy resin is used as the
organic resin 12 to be filled in order to bond the plurality of piezoelectric element chips 11. Since
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a flat surface of 2 mm long and 2 mm wide is used as the electrode surface of the piezoelectric
element chip 11, the thickness of the piezoelectric resin composites 15 A and 15 B is about the
same as that of the piezoelectric element chip 11. The manufactured piezoelectric resin
composites 15A and 15B have the same shape, a front view thereof is shown in FIG. 3, and a side
view (illustration of the piezoelectric element chip is omitted) is shown in FIG. In FIG. 3, the
opening angle, the radius of curvature and the width of the piezoelectric resin composite 15A are
denoted by θ, R and D, respectively. Further, in FIG. 4, the length dimension of the piezoelectric
resin composite 15A is L.
[0016]
The piezoelectric element chips 11 are arranged in a grid shape along a curved surface, with
intervals between the piezoelectric element chips being equal intervals of 0.4 mm on average.
That is, along the R curved surface of FIG. 3, in the direction of the angle θ, the distance between
the position of the long side of the piezoelectric element chip 11 and the arc-shaped end of the
piezoelectric resin composites 15A and 15B is approximately the same. Fourteen piezoelectric
element chips 11 are arranged at an equal interval of 0.4 mm on average. The arrangement in
which the above 14 arrangements in the θ direction are parallel shifted at an equal interval of
2.4 mm on average in the L direction in FIG. 4 is repeated along the R curved surface, and a total
of 196 in each of the piezoelectric resin composites 15A and 15B. The piezoelectric element chip
11 is disposed. The dimensions of the obtained piezoelectric resin composites 15A and 15B are
substantially the same, and the width D = 37.0 mm, the length L = 37.5 mm, and the average
curvature radius R = 45 mm. The dimensions of the piezoelectric resin portion 13 excluding the
surrounding resin portion 14 from the piezoelectric resin composites 15A and 15B were
substantially the same, 33.1 mm in width, 33.6 mm in length, and 45 mm in average radius of
curvature. An enlarged plan view of an essential part of a part of the piezoelectric resin
composite 15A according to the first embodiment is shown in FIG. As shown in FIG. 5, a total of
196 piezoelectric element chips 11 are arranged in a grid at an equal interval of 0.4 mm, 14 in
the X direction (see FIG. 5) and 14 in the Y direction (see FIG. 5). Ru.
[0017]
Next, an intermediate electrode film 15C having an average thickness of 0.1 mm is provided
between the piezoelectric resin composite 15A and the piezoelectric resin composite 15B, and
the piezoelectric resin composite 15A, the intermediate electrode film 15C, and the piezoelectric
resin composite 15B are provided. A piezoelectric resin composite 15 was produced. As the
intermediate electrode film 15C, an epoxy resin containing silver which is a conductive metal was
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used. The dimensions of the obtained piezoelectric resin composite 15 were 37 mm in width, 38
mm in length, and 45 mm in average radius of curvature. A frame 16 to be bonded to the
piezoelectric resin composite 15 is prepared with an acrylic resin having a thickness of 5 mm.
The outside dimension of the frame 16 is a rectangular solid of 60 mm long, 60 mm wide, and 5
mm thick, and a gap of 37.2 mm long and 38.2 mm wide is provided at the center. The
piezoelectric resin composite 15 (width 37 mm, length 38 mm) is inserted into the gap (length
37.2 mm, width 38.2 mm) of the frame 16, and the two linear ends (length) of the piezoelectric
resin composite 15 The 38 mm portion was aligned with the two upper sides (38.2 mm in
length) of the frame void portion, and the meeting portions were bonded with epoxy resins 19A,
19a, 19B and 19b. FIG. 6 shows a perspective view (illustration of the piezoelectric element chip
is omitted) of a part of the bonded state of the piezoelectric resin composite 15 and the frame 16.
As shown in FIG. 6, in the present embodiment, the linear end of the piezoelectric resin
composite 15 and the frame 16 are bonded by the epoxy resin 19A, but two arced ends of the
piezoelectric resin composite 15 and It is not coupled to the frame 16. That is, in the bonding of
the piezoelectric resin composite 15 and the frame 16, a bonding portion and a non-bonding
portion are formed.
[0018]
The piezoelectric resin composite 15 bonded to the frame 16 was subjected to a curing treatment
at 60 ° C. for 1 hour. After the curing process, the piezoelectric resin composite 15 bonded to
the frame 16 is washed, and the conductive aluminum electrode film 17A by vacuum evaporation
is formed on both sides of the piezoelectric resin portion 13 where the electrode surface of the
piezoelectric element chip 11 is present. 17B was provided. The thickness of the aluminum
electrode films 17A and 17B was almost the same and 0.4 μm on average. The conductive
aluminum electrode films 17A and 17B are connected by the lead wire 18A, and the intermediate
electrode film 15C is connected by the lead wire 18B through the surrounding resin portion 14,
and the voice electric signal is transmitted from the audio signal source 18 to the lead wire 18A
and 18B was energized, and the sound pressure characteristics with respect to the frequency of
the piezoelectric speaker were evaluated. The evaluation results of the sound pressure
characteristics are shown in Table 1. As shown in Table 1, it can be seen that the sound pressure
characteristic of Example 1 shows 40 to 68 relative sound pressure dB in the frequency range of
1 kHz to 10 kHz.
[0019]
[0020]
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As a comparative example, a piezoelectric resin composite 25 without an intermediate electrode
film was produced by the method disclosed in Japanese Patent Laid-Open No. 2003-348692.
The present comparative example is also a piezoelectric speaker disclosed and filed by the
present inventors in Japanese Patent Application No. 2005-371403. The piezoelectric resin
composite 25 is substantially the same as the piezoelectric resin composite 15A manufactured in
Example 1. The piezoelectric element chip 21 used is the same as that of the first embodiment,
and the organic resin 22 for bonding the piezoelectric element chip is also the same as that of
the first embodiment. A total of 196 piezoelectric element chips 21 are arranged in a lattice at an
equal interval of 0.4 mm, 14 in the X direction (see FIG. 5) and 14 in the Y direction (see FIG. 5).
The dimensions of the obtained piezoelectric resin composite 25 are width D = 37.0 mm, length L
= 37.5 mm, and average curvature radius R = 45 mm. The dimensions of the piezoelectric resin
portion 23 obtained by removing the surrounding resin portion 24 from the piezoelectric resin
composite 25 were 33.0 mm in width, 33.5 mm in length, and 45 mm in average radius of
curvature.
[0021]
Next, a frame 26 to be bonded to the piezoelectric resin composite 25 is prepared of acrylic resin
having a thickness of 5 mm. The outside dimension of the frame 26 is a rectangular solid of 60
mm long, 60 mm wide, and 5 mm thick, and a gap of 37.2 mm long and 37.7 mm wide is
provided at the center. The piezoelectric resin composite 25 (width 37.0 mm, length 37.5 mm) is
inserted into the gap (length 37.2 mm, width 37.7 mm) of the frame 26, and the two linear ends
of the piezoelectric resin composite 25 The parts (length 37.5 mm) were aligned with the two
upper sides (length 37.7 mm) of the frame void, and the meeting parts were bonded with epoxy
resins 29A, 29a, 29B and 29b. FIG. 7 shows a perspective view (illustration of the piezoelectric
element chip is omitted) of a part of the bonded state of the piezoelectric resin composite 25 and
the frame 26. As shown in FIG. 7, in this comparative example, the linear end of the piezoelectric
resin composite 25 and the frame 26 are bonded by the epoxy resin 29A, but two arced ends of
the piezoelectric resin composite 25 and It is not coupled with the frame 26. That is, in the
bonding of the piezoelectric resin composite 25 and the frame 26, a bonding portion and a nonbonding portion are formed.
[0022]
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The piezoelectric resin composite 25 bonded to the frame 26 was subjected to a curing treatment
at 60 ° C. for 1 hour. After the curing process, the piezoelectric resin composite 25 bonded to
the frame 26 is washed, and the conductive aluminum electrode film 27A by vacuum evaporation
is formed on both surfaces of the piezoelectric resin portion 23 where the electrode surface of
the piezoelectric element chip 21 exists. 27B was provided. The thicknesses of the aluminum
electrode films 27A and 27B were almost the same and 0.4 μm on average. After connecting the
two lead wires 28A and 28B to the electrode films 27A and 27B, the voice electric signal is
supplied from the voice signal source 18 to the lead wires, and the evaluation of the sound
pressure characteristics against the frequency of the piezoelectric speaker is performed as in the
first embodiment. went. The evaluation results of the sound pressure characteristics are shown in
Table 1. As shown in Table 1, in the frequency range of 1 kHz to 10 kHz, the comparative
example shows 35 to 61 relative sound pressure dB, and it can be seen that the sound pressure
characteristic of the comparative example is inferior to that of the first embodiment.
[0023]
The piezoelectric resin composite 35 of the piezoelectric speaker was manufactured by the
method disclosed in Japanese Patent Application Laid-Open No. 2003-348692. The piezoelectric
element chip 31 used is the same as that of the first embodiment, and the organic resin 32 for
bonding the piezoelectric element chip 31 is also the same as that of the first embodiment. In
Example 2, unlike the example 1, the piezoelectric resin composites 35A and 35B were produced
in a planar shape having no curvature. The piezoelectric resin composites 35A and 35B have
substantially the same shape, and an enlarged plan view of a part of the piezoelectric resin
composites 35A and 35B is shown in FIG. As shown in FIG. 8, a total of 196 piezoelectric element
chips 31 are arranged in a grid at an equal interval of 0.4 mm, 14 in the X direction (see FIG. 8)
and 14 in the Y direction (see FIG. 8). ing. Since a flat surface of 2 mm long and 2 mm wide is
used as the electrode surface of the piezoelectric element chip 31, the thickness of the
piezoelectric resin composites 35 A and 35 B is about the same as that of the piezoelectric
element chip 31. The dimensions of the obtained piezoelectric resin composites 35A and 35B are
approximately the same, 38 mm wide and 38 mm long. The dimensions of the piezoelectric resin
portion 33 excluding the surrounding resin portion 34 from the piezoelectric resin composites
35A and 35B were substantially the same, and were 34 mm wide and 34 mm long.
[0024]
Next, an intermediate electrode film 35C having an average thickness of 0.1 mm is provided
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between the piezoelectric resin composite 35A and the piezoelectric resin composite 35B, and
the piezoelectric resin composite 35A, the intermediate electrode film 35C, and the piezoelectric
resin composite 35B are provided. A piezoelectric resin composite 35 was produced. As the
intermediate electrode film 35C, as in Example 1, an epoxy resin containing silver which is a
conductive metal was used. The dimensions of the obtained piezoelectric resin composite 35
were 38 mm wide and 38 mm long. A frame 36 to be bonded to the piezoelectric resin composite
35 is prepared of acrylic resin having a thickness of 5 mm. The outside dimension of the frame
body 36 is a rectangular solid of 60 mm long, 60 mm wide, and 5 mm thick, and a gap of 38.2
mm long and 38.2 mm wide is provided at the central portion thereof. The piezoelectric resin
composite 35 (width 38 mm, length 38 mm) is inserted into the gap (length 38.2 mm, width 38.2
mm) of the frame 36, and four linear ends (length) of the piezoelectric resin composite 35 The
38 mm portion was aligned with the four upper side portions (38.2 mm length portion) of the
frame void portion, and the meeting portions were bonded with epoxy resins 39A and 39B. FIG. 9
shows a perspective view (illustration of the piezoelectric element chip is omitted) of the coupled
state of the piezoelectric resin composite 35 and the frame 36. As shown in FIG. 9, in the second
embodiment, all the four linear ends of the piezoelectric resin composite 35 are joined by the
frame 36 and the epoxy resins 39A and 39B, and no non-joined part is formed. A cross-sectional
view of the piezoelectric resin composite 35 combined with the frame 36 is shown in FIG. As
shown in FIG. 10, in Example 2, it can be seen that the piezoelectric resin composite 35
composed of the piezoelectric resin composite 35A, the intermediate electrode film 35C and the
piezoelectric resin composite 35B has a planar shape having no curvature.
[0025]
The piezoelectric resin composite 35 bonded to the frame 36 was subjected to curing treatment
at 60 ° C. for 1 hour. After the curing process, the piezoelectric resin complex 35 bonded to the
frame 36 is washed, and on both surfaces of the piezoelectric resin portion 33 where the
electrode surface of the piezoelectric element chip 31 exists, the conductive aluminum electrode
film 37A by vacuum evaporation and 37 B was provided. The thicknesses of the aluminum
electrode films 37A and 37B were almost the same and 0.4 μm on average. The conductive
aluminum electrode films 37A and 37B are connected by the lead wire 38A, and the intermediate
electrode film 35C is connected by the lead wire 38B through the surrounding resin portion 34,
and the audio electric signal is transmitted from the audio signal source 18 Power was applied to
38 B, and the sound pressure characteristics with respect to the frequency of the piezoelectric
speaker were evaluated in the same manner as in Example 1. The evaluation results of the sound
pressure characteristics are shown in Table 1. As shown in Table 1, Example 2 exhibits 38 to 65
relative sound pressure dB in the frequency range of 1 kHz to 10 kHz, and it can be seen that the
sound pressure characteristics of Example 2 are superior to those of the Comparative Example.
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[0026]
Table 2 shows the shape, approximate dimensions, the state of connection with the frame, the
number of piezoelectric element chips, and the sound pressure characteristics of the piezoelectric
resin composite in Example 1 and Comparative Examples and Example 2. It can be seen from
Table 2 that the sound pressure characteristics of Example 1 and Example 2 according to the
present invention are superior to those of the comparative example. That is, two piezoelectric
resin composites composed of a plurality of piezoelectric element chips and an organic resin
around the piezoelectric element chips are provided, and an intermediate electrode film is formed
as an intermediate layer between the electrode surfaces of the two piezoelectric resin composites.
It is thought that the sound pressure characteristics at 1 kHz to 10 kHz have been improved by
enhancing the piezoelectric effect. In addition, when the bonded portion and the non-bonded
portion are formed in the bonding of the piezoelectric resin composite and the frame, it is
considered that the flexibility of the piezoelectric resin composite is enhanced and the sound
pressure characteristics are further improved.
[0027]
In addition, although the example of a part of cylindrical body curved surface was shown in
Example 1 as a shape of a piezoelectric resin composite, and the example of a part of plane was
shown in Example 2, a part of other cone curved surface, an ellipsoid An approximate curved
surface such as part of a curved surface is also applicable. That is, as the shape of the
piezoelectric resin composite, at least one of a part of a plane, a part of a cylindrical curved
surface, a part of a conical curved surface, a part of a spherical curved surface and a part of an
ellipsoid curved surface Even in the chosen form, the effect of the invention is not lost.
[0028]
It is a principal part expanded sectional view showing a piezoelectric speaker of the present
invention. It is AA arrow sectional drawing of the piezoelectric speaker shown in FIG. 5 is a front
view of a piezoelectric resin composite 15A in Example 1. FIG. 5 is a side view of a piezoelectric
resin composite 15A in Example 1. FIG. FIG. 7 is an enlarged plan view of an essential part
showing a part of the piezoelectric resin composite 15A in Example 1; FIG. 7 is a perspective
view showing a coupled state of the piezoelectric resin composite 15 and the frame in Example 1;
It is a perspective view which shows the combined state of the piezoelectric resin complex and
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frame in a comparative example. FIG. 16 is an enlarged plan view of an essential part showing a
part of a piezoelectric resin composite 35A in Example 2; FIG. 18 is a perspective view showing a
state of bonding of the piezoelectric resin composite 35 and the frame in Example 2. FIG. 10 is a
cross-sectional view of a piezoelectric resin composite 35 combined with a frame in Example 2;
Explanation of sign
[0029]
11 piezoelectric element chip 12 organic resin 13 piezoelectric resin portion 14 peripheral resin
portion 15 piezoelectric resin composite 15A piezoelectric resin composite 15B piezoelectric
resin composite 15C intermediate electrode film 16 frame body 17A conductive electrode film
17B conductive electrode film 18A lead wire 18B lead wire 19A epoxy resin 19a epoxy resin 19B
epoxy resin 19b epoxy resin 19b
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