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DESCRIPTION JP2004282221

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DESCRIPTION JP2004282221
An object of the present invention is to provide a directional speaker having a conventional
configuration, which can not be mounted on a portable electronic device because the size of the
speaker itself is large. SOLUTION: In a directional speaker which vibrates a vibration generation
source by an external electric signal to oscillate a sound wave from an audible sound to an
ultrasonic wave region, a thin film-like vibrating film for vibrating the sound wave and its
vibration A configuration having a base for holding the film and a vibration source provided in
contact with the vibrating film and separated from other members except the vibrating film is
adopted. [Selected figure] Figure 1
Small and thin directional speaker and electronic device equipped with the same
TECHNICAL FIELD The present invention mounts a small-sized thin directional speaker that
vibrates a vibration source with an external electrical signal to oscillate a sound wave from an
audible sound to an ultrasonic wave region, and the speaker. Small electronic devices. This
electronic device can be configured to generate an audible sound with strong directivity using,
for example, the parametric effect of ultrasonic waves, and when mounted on the electronic
device, it has an effect such that no voice can be heard by anyone other than the user. . [0002]
Ultrasonic directional speakers using parametric effects are known. This directional speaker is an
optimal speaker for explaining exhibits at the exhibition and for guiding broadcasts at the station
home. Here, a directional speaker capable of utilizing the parametric effect in the prior art will be
described (see, for example, Patent Document 1). The cross-sectional structure of the directional
speaker shown in this prior art is shown in FIG. In the directional speaker 30 of the prior art, an
ultrasonic sound source 25 composed of a ceramic piezoelectric element serving as a vibration
generation source of ultrasonic waves is fixed to the base plate 26, and 1 to 2 m ahead of the
ultrasonic sound source 25. A plurality of acoustic filters 27 made of polyethylene film are
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disposed. The directional speaker 30 configured in this manner transmits the audible sound
generated from the ultrasonic wave generated from the ultrasonic sound source 25 to the
outside through the acoustic filter 27 and transmits the ultrasonic sound other than the audible
sound. By the action of attenuating the acoustic filter 27 with this acoustic filter 27, strong
directivity can be obtained. [Patent Document 1] Japanese Examined Patent Publication No. 728462 (Section 2, FIGS. 2 to 5) SUMMARY OF THE INVENTION The directional speaker 30
according to the prior art of the above configuration is Although the speaker has strong
directivity, the ultrasonic sound source 25 is fixed to the base plate 26 as described above, and
the acoustic filter 27 is disposed 1 to 2 m in front of the ultrasonic sound source 25. Because of
this, the size of the directional speaker 30 itself becomes large. Therefore, it has been considered
impossible to mount in a small electronic device with this configuration. An object of the present
invention is to provide a small-sized thin directional speaker that solves the above-mentioned
problems, and an electronic device equipped with the same. In particular, by making the
directional speaker small and thin, at least one directional speaker can be mounted on a portable
electronic device.
Further, the portable electronic device can reproduce an audible sound only in a specific area by
utilizing a parametric effect, and can be a portable electronic device having a function in which
no one other than the user can hear the sound. SUMMARY OF THE INVENTION In order to
achieve the above object, the structure of the small and thin speaker according to the present
invention adopts the following construction. The small and thin speaker structure according to
the present invention is a thin film for oscillating the sound wave in a directional speaker that
vibrates a vibration generation source by an external electric signal to oscillate a sound wave
from an audible sound to an ultrasonic wave region. A vibrating membrane, a base for holding
the vibrating membrane, and a vibration source provided in contact with the vibrating membrane
and separated from other members except the vibrating membrane. I assume. Further, in the
above-described structure of the small and thin speaker according to the present invention, the
vibration generating source is composed of a plurality of piezoelectric elements disposed so that
the polarization directions are opposite to each other, and one side or both sides of the vibrating
membrane The plurality of piezoelectric elements are bonded to each other. Furthermore, the
electronic device according to the present invention has at least one of the above-mentioned
small-sized thin directional speakers, oscillates an ultrasonic wave from the small-sized thin
directional speakers, and uses the parametric effect as a directional speaker It is characterized by
having it function. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The structure of
the small and thin speaker according to the embodiment of the present invention will be
described below with reference to the drawings. FIG. 1 is a cross-sectional view of a small-sized
thin directional speaker according to a first embodiment of the present invention, and FIG. 2 is a
cross-sectional view of the small-sized thin directional speaker according to the second
embodiment of the present invention. FIG. 3 is a schematic view showing an explanatory diagram
of the parametric effect and an example of the configuration of an electronic device equipped
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with the small thin directional speaker according to the present invention. FIG. 4 is a process
cross-sectional view showing a manufacturing process of the small-sized thin directional speaker
according to the present invention. Hereinafter, the structure and manufacturing method of the
small-sized thin directional speaker of the present invention will be described in detail with
reference to FIGS. 1, 2, 3 and 4. FIG. First Embodiment First, a configuration example of a smallsized thin directional speaker according to a first embodiment of the present invention will be
described with reference to FIG. The structure of the small and thin directional speaker 1
according to the present invention shown in FIG. 1 supports a thin diaphragm 14 on a flat
portion around the recess 17 on a base 11 provided with a recess 17 at the center. The film 13
has a structure in which a piezoelectric element 12 as a vibration source is attached.
It is important that the piezoelectric element 12 disposed here has a structure separated from
other members excluding the vibrating film 13. A wiring pattern 15 for inputting a signal from
an external circuit (not shown) is formed on a flat portion around the base 11, and the wiring
pattern 15 and the piezoelectric element 12 are formed by the lead wire 24. Form connected.
With this configuration, it is possible to generate a sound wave by vibrating the vibration film 13
together with the piezoelectric element 12 which is a vibration generation source by the input of
the electric signal from the external circuit. Further, in the configuration shown in FIG. 1, the
vibrating film 13 is formed to have a larger area than the piezoelectric element 12, and the
piezoelectric element 12 is separated from the other members except the vibrating film 13.
Therefore, the vibration film 13 makes the vibration of the piezoelectric element 12 larger, and a
sound wave larger than the sound wave generated by the vibration of the piezoelectric element
12 alone can be oscillated. Furthermore, a recess 17 is provided in the central portion of the base
11 so that the piezoelectric element 12 and the base 11 do not come into contact with each other
when the diaphragm 13 vibrates with the piezoelectric element 12. The recess 17 is an important
component for providing the piezoelectric element 12 with a large amplitude. As described
above, the small and thin directional speaker 1 according to the present invention has a thin
structure and strong sound pressure even by arranging the vibrating film 13 for increasing the
vibration of the piezoelectric element 12 on the base 11 as a base. Can be output. Next, a method
of manufacturing the small-sized thin directional speaker 1 of the present invention will be
described. FIG. 4 is a process sectional view showing the manufacturing process of the smallsized thin directional directional speaker 1 of the present invention. First, a method of
manufacturing the base plate 4 which constitutes the small-sized thin directional speaker 1 of the
present invention will be described with reference to FIG. 4 (a). In order to obtain the base plate
4, first, an SiO 2 film is formed as the insulating film 16 on the surface of a flat plate-like silicon
substrate having a (100) crystal orientation. On the insulating film 16 is formed a photosensitive
resist having a pattern shape having an opening at the location where the recess 17 of the base
11 will be described later. Furthermore, dry etching is performed in an Ar atmosphere to remove
the insulating film 16 exposed from the opening, and then the photosensitive resist remaining on
the surface is removed by RIE (reactive ion etching) in an oxygen atmosphere. Next, it is
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immersed in 30% KOH heated to about 50 to 70 ° C. for 2 to 6 hours, and the silicon substrate
exposed from the opening is etched using the insulating film 16 as a mask, and the crystal face of
(111) Is etched to form a recess 17 and the base 11 is completed.
Subsequently, aluminum (Al), copper (Cu), gold (Au) or the like is formed on the base 11 by vapor
deposition or sputtering, and the wiring pattern 15 is formed on the insulating film 16 by
photolithography. Thus, the base plate 4 shown in FIG. 4A can be obtained. Next, a method of
manufacturing the vibration generating unit 5 for generating a sound wave will be described
with reference to FIG. 4 (b). First, as shown in FIG. 4B, the vibration generating portion 5 is
formed by bonding the piezoelectric element 12 serving as a vibration generation source to the
thin film-like vibrating film 13. As a material of the piezoelectric element 12, ceramics having a
piezoelectric effect such as barium titanate or lead zirconate titanate can be used. In addition, a
thin plate such as aluminum or plastic can be used for the vibrating film 13. Here, the forming
means of the small thin directional speaker 1 formed by combining the base plate 4 of FIG. 4A
described above and the vibration generating unit 5 of FIG. 4B will be described. . As shown in
FIG. 4C, a vibrating film in which the piezoelectric element 12 produced in FIG. 4B is attached to
the base plate 4 on which the recess 17 produced in FIG. 4A and the wiring pattern 15 are
formed. A vibration generating unit 5 having 13 is disposed. At this time, the piezoelectric
element 12 is disposed so as to straddle the recess 17 formed in the base 11, and the peripheral
portion of the vibrating film 13 is fixed with an adhesive 14 or the like. Further, as shown in FIG.
4 (c), the wiring pattern 15 and the piezoelectric element 12 can be connected by lead wires 24
such as gold or copper wire, and a signal from an external circuit can be transmitted to the
piezoelectric element Can be obtained. In the above embodiment, a configuration example using
a silicon substrate for the base 11 has been described, but a base or a metal plate manufactured
by melting a resin such as plastic and pouring it into a mold is cut and processed. You may use
the formed base. Further, the arrangement may be such that the arrangement positions of the
vibrating film 13 and the piezoelectric element 12 shown in FIG. 1 are reversed, that is, the
piezoelectric element 12 is higher than the vibrating film 13 in the drawing. Second Embodiment
Next, another configuration example according to the second embodiment will be described with
reference to FIG. As shown in FIGS. 2A and 2B, in the structure of the small and thin directional
speaker according to the present embodiment, two piezoelectric elements 12 serving as a
vibration source are attached to both sides or one side of the diaphragm 13. It is a structure.
When adopting the small thin directional speakers 2 and 3 using two piezoelectric elements 12
shown in FIGS. 2 (a) and 2 (b), the two piezoelectric elements are arranged so that the
polarization directions are reversed. It is necessary to bond the element 12 to the vibrating film
13. In this manner, the polarization directions of the two piezoelectric elements 12 are reversed
and attached to the vibrating film 13 as compared with the amplitude of the vibrating film 13 in
the first embodiment formed of one piezoelectric element. The amplitude of the vibrating
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membrane 13 can be increased, and a stronger sound wave can be generated. In the above
description, the embodiment in which the two piezoelectric elements 12 are bonded to the
vibrating film 13 has been described, but the polarization directions of the three or more
piezoelectric elements 12 are reversed in order to generate larger sound waves. Of course, it
does not matter as a form bonded to the vibrating film 13 so that it may become. In addition to
the configuration of the first embodiment, the small and thin directional speakers 2 and 3
according to the second embodiment of the present invention shown in FIG. 2 further includes
one or more piezoelectric elements 12. The only difference is in the provision, and the other
manufacturing steps are the same. Third Embodiment Next, as a third embodiment, the
parametric effect of ultrasonic waves, which is the principle of directivity in the present
invention, will be described with reference to FIG. As shown in FIG. 3 (a), a primary sound wave
for generating a target audible sound is output from the small thin directional speaker 1 of the
present invention functioning as an ultrasonic speaker. Here, the case where two types of
ultrasonic waves “f1” and “f2” of different frequencies are output as primary sound waves
will be described below. When the two ultrasonic waves f 1 and f 2 are outputted from the small
thin directional speaker 1, the respective ultrasonic waves interfere with each other, and
modulated waves of two wavelength frequencies (hereinafter referred to as “secondary sound
waves 19”) Will be generated. The secondary sound wave 19 is composed of a sum component
and a difference component of the wavelengths of the two primary sound waves f1 and f2. Since
the two primary sound waves are sound waves in the ultrasonic region, the sum component also
becomes ultrasonic waves. Therefore, although this sum component is not audible to the user, it
becomes an audible sound when the difference component is a sound wave of an audio
frequency, so that only the user can hear this audible sound. In addition, when the distance from
the small and thin directional speaker 1 increases, the primary sound wave and the secondary
sound wave are attenuated by the resistance of the air when the sound wave is propagated, so
the small and thin directional speaker 1 The farther you go, the less audible you can hear.
From this phenomenon, it is possible to generate an audible sound only in a specific area, to form
a highly directional audible sound field 20, and to have a parametric effect in which the sound
can be heard only in a specific place. . A configuration example for achieving the principle is
shown in FIG. 3 (b). According to this configuration, for example, the small-sized thin directional
speaker 1 of the present invention can be mounted on a mobile phone, which is the electronic
device 6, to provide a portable electronic device in which an audible sound can be heard only by
the user. In addition, two small thin directional speakers 1 according to the present invention are
mounted on the electronic device 6 so as to generate secondary sound waves in the audible
range from the two primary sound waves. It does not matter as a form having a strong speaker.
As described above, when the small thin directional speaker 1 of the present invention having the
above configuration is mounted on an electronic device such as a mobile phone, a portable
information terminal, a portable TV, a personal computer, an audible sound can be heard only by
the user. It can be an electronic device in which the surrounding person can not hear the sound.
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As is apparent from the above description, the directional speaker according to the present
invention vibrates the vibration source with the external electric signal to oscillate the sound
wave from the audible sound to the ultrasonic wave region. In a directional speaker, a thin filmlike vibrating membrane for oscillating the sound wave, a base for holding the vibrating
membrane, and members other than the vibrating membrane which are in contact with the
vibrating membrane are separated. And the vibration generating source provided so as to make it
possible to reduce the size of the speaker so that it can be mounted on a small electronic device,
and to output a sound wave with strong sound pressure even with a thin structure. Become. In
addition, by mounting a small thin directional speaker of such a configuration in a portable
electronic device, it is possible for the user to emit sound without taking care of the
surroundings, for example, a television using a mobile phone. When making a call or the like,
electronic devices can be used in which the person in the vicinity can not hear the conversation.
Furthermore, the small-sized thin directional speaker according to the present invention can also
be mounted on an electronic device capable of reproducing moving pictures with voice or
listening to music or the like. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional
view for explaining the structure of a small thin directional speaker according to a first
embodiment of the present invention. FIG. 2 is a cross-sectional view for explaining a structure of
a small-sized thin directional speaker according to a second embodiment of the present
invention.
FIGS. 3A and 3B are a principle view for explaining a parametric effect in the case where a small
thin directional speaker according to a third embodiment of the present invention is mounted on
a portable electronic device, and an explanatory view showing an example of the electronic
device. . FIG. 4 is a process cross-sectional view for explaining a manufacturing process of the
small thin flat directional speaker of the present invention. FIG. 5 is a cross-sectional view for
explaining the structure of a directional speaker in the prior art. <Explanation of mark> 1-3 small
thin directional directional speaker 4 base board 5 vibration generating section 6 portable
electronic equipment 11 base 12 piezoelectric element 13 vibrating membrane 14 adhesive 15
wiring pattern 16 insulating film 17 concave section 19 secondary sound wave 20 acceptable
Listening field 24 lead
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