JP2012100048A - Electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability of a piezoelectric film in an electronic apparatus having a function to oscillate acoustic waves by means of the piezoelectric film.SOLUTION: An electronic apparatus 300 comprises: a housing 310; a piezoelectric film 22; a first electrode 24; and a second electrode 26. The piezoelectric film 22 is attached to an inner face of the housing 310. The first electrode 24 is attached to a first surface of the piezoelectric film 22, and the second electrode 26 is attached to a second surface of the piezoelectric film 22. The second electrode 26 overlaps with the first electrode 24 in plan view. The electronic apparatus 300 is a mobile terminal such as a mobile communication terminal. An oscillation member 20 of the electronic apparatus 300 is made up of the piezoelectric film 22, the first electrode 24, and the second electrode 26. The oscillation member 20 functions as a parametric speaker, and modulation signals in the parametric speaker is input from a control unit.

Description

  The present invention relates to an electronic device having a sound wave output function.

  In recent years, the demand for mobile terminals such as mobile phones and laptop computers has been increasing. In particular, the development of thin mobile terminals with commercial functions such as videophones, video playback, and hands-free phone functions is underway. In these developments, there is an increasing demand for electroacoustic transducers that are small in size and large in output. Conventionally, an electrodynamic electroacoustic transducer is used as an electroacoustic transducer in an electronic device such as a mobile phone. This electrodynamic electroacoustic transducer is composed of a permanent magnet, a voice coil, and a diaphragm. However, the electrodynamic electroacoustic transducer is limited in thickness because of its operation principle and structure. Therefore, it is expected to use the piezoelectric vibrator as a parametric speaker.

  Patent Document 1 discloses a speaker using a piezoelectric film as a piezoelectric vibrator. In Patent Document 1, the speaker is incorporated in a recess provided on the surface side of the housing.

JP 2006-339834 A

  In the technique described in Patent Document 1, the piezoelectric vibrator is provided on the surface side of the housing. For this reason, the durability of the piezoelectric vibrator may be lowered.

  An object of the present invention is to improve the durability of a piezoelectric film in an electronic device having a function of oscillating sound waves using the piezoelectric film.

According to the present invention, a housing;
A piezoelectric film attached to the inner surface of the housing;
A first electrode attached to the first surface of the piezoelectric film;
A second electrode attached to the second surface of the piezoelectric film and overlapping the first electrode in plan view;
An electronic device is provided.

  ADVANTAGE OF THE INVENTION According to this invention, durability of a piezoelectric film can be improved in the electronic device which has a function which oscillates a sound wave using a piezoelectric film.

It is sectional drawing which shows the structure of the principal part of the electronic device which concerns on 1st Embodiment. It is a top view of an electronic device. It is a top view of an oscillation member. It is sectional drawing which shows the structure of the principal part of the electronic device which concerns on 2nd Embodiment. It is a top view which shows the positional relationship of an oscillation member and a flame | frame. It is sectional drawing which shows the structure of the principal part of the electronic device which concerns on 3rd Embodiment. It is sectional drawing which shows the modification of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

(First embodiment)
FIG. 1 is a cross-sectional view illustrating a configuration of a main part of an electronic device 300 according to the first embodiment, and FIG. 2 is a plan view of the electronic device 300. The electronic device 300 includes a housing 310, the piezoelectric film 22, the first electrode 24, and the second electrode 26. The piezoelectric film 22 is attached to the inner surface of the housing 310. The first electrode 24 is attached to the first surface of the piezoelectric film 22, and the second electrode 26 is attached to the second surface of the piezoelectric film 22. The second electrode 26 overlaps the first electrode 24 in plan view. Details will be described below.

  In the present embodiment, the electronic device 300 is a mobile terminal such as a mobile communication terminal, and has a display screen 200. The piezoelectric film 22, the first electrode 24, the second electrode 26, and the housing 310 constitute a speaker of the electronic device 300. This speaker functions as a parametric speaker, and a modulation signal in the parametric speaker is input from a control unit (not shown). The transport wave of the modulation signal is an ultrasonic wave having a frequency of 20 kHz or higher, for example, an ultrasonic wave having a frequency of 100 kHz.

  The piezoelectric film 22 is made of a resin material having a piezoelectric effect as described above, and is polarized in the thickness direction. The resin material is not particularly limited as long as it has a piezoelectric effect, but a material having high mechanical conversion efficiency, such as polyvinylidene fluoride or polyvinyl chloride, can be used. The thickness of the piezoelectric film 22 is not particularly limited, but is preferably 5 μm to 1 mm. When the thickness of the piezoelectric film 22 is less than 5 μm, variations in thickness are likely to occur due to the manufacturing process. Moreover, when the thickness of the piezoelectric film 22 exceeds 1 mm, the thickness of the oscillation device increases.

Although the material which comprises the 1st electrode 24 and the 2nd electrode 26 is not specifically limited, For example, silver and silver / palladium can be used. Since silver is used as a general-purpose electrode material with low resistance, it has advantages in manufacturing process and cost. Since silver / palladium is a low-resistance material excellent in oxidation resistance, there is an advantage from the viewpoint of reliability. The thickness h ₂ of the first electrode 24 and the second electrode 26 is not particularly limited, but the thickness h ₂ is preferably 1 μm or more and 50 μm or less. The thickness h ₂ is less than 1 [mu] m, it becomes difficult to uniformly mold the first electrode 24 and the second electrode 26, as a result, the electromechanical conversion efficiency may be lowered. Moreover, when the film thickness of the 1st electrode 24 and the 2nd electrode 26 exceeds 100 micrometers, the 1st electrode 24 and the 2nd electrode 26 become a constraining surface with respect to the piezoelectric film 22, and may reduce energy conversion efficiency. Sex comes out.

  In the present embodiment, a plurality of first electrodes 24 are provided on the first surface of the piezoelectric film 22 so as to be separated from each other. A plurality of second electrodes 26 are provided on the second surface of the piezoelectric film 22 so as to be separated from each other. The plurality of second electrodes 26 are opposed to different first electrodes 24. In the present embodiment, the first electrode 24 and the second electrode 26 have the same planar shape.

  That is, in this embodiment, a plurality of first electrodes 24 and a second electrode 26 are provided on one piezoelectric film 22, so that a plurality of piezoelectric vibrators are formed in an array from one piezoelectric film 22. The above-described control unit controls the directivity of the parametric speaker by controlling the plurality of piezoelectric vibrators using the phased array method. Specifically, the control unit controls the space where the parametric speaker is demodulated by adjusting the modulation signal input to each of the plurality of piezoelectric vibrators.

  In the present embodiment, the piezoelectric film 22 is attached to the housing 310 by attaching the first electrode 24 to the housing 310.

  FIG. 3 is a plan view of the oscillation member 20. A plurality of first electrodes 24 and second electrodes 26 are arranged in an array in the piezoelectric film 22 so as to be separated from each other. The layout of the plurality of first electrodes 24 can be easily changed at the patterning stage of the metal film to be the first electrode 24.

  Next, the operation and effect of this embodiment will be described. According to this embodiment, the piezoelectric film 22 forms a plurality of piezoelectric vibrators. The vibrations of these piezoelectric vibrators are radiated to the outside through the housing 310 of the electronic device 300. Since the oscillation frequency of each piezoelectric vibrator is high, it is possible to suppress the vibrations of adjacent piezoelectric vibrators from interfering with each other during transmission through the housing 310.

  The piezoelectric film 22, the first electrode 24, and the second electrode 26 are located inside the housing 310. For this reason, since the piezoelectric film 22, the 1st electrode 24, and the 2nd electrode 26 are protected by the housing | casing 310, these durability improves.

  Moreover, when the housing | casing 310 is formed with resin, it can suppress that the thermal expansion coefficient of the housing | casing 310 and the piezoelectric film 22 differs greatly. In this case, it can suppress that a thermal stress arises between the housing | casing 310 and the piezoelectric film 22. FIG.

  Further, by changing the pattern of the first electrode 24 and the second electrode 26 on the first surface and the second surface of the piezoelectric film 22, the size and layout of the plurality of piezoelectric vibrators can be changed. Accordingly, the oscillation member 20 can be easily manufactured.

  Further, since it is not necessary to provide a sound hole in the housing 310, the waterproofness of the housing 310 can be improved.

(Second Embodiment)
FIG. 4 is a cross-sectional view illustrating a configuration of a main part of an electronic device 300 according to the second embodiment, and corresponds to FIG. 1 in the first embodiment. FIG. 5 is a plan view showing the positional relationship between the oscillation member 20 and the frame 312. The electronic device 300 according to the present embodiment is the same as the electronic device 300 according to the first embodiment except that the electronic device 300 includes a frame 312.

  The frame 312 is located between the plurality of first electrodes 24 in plan view and is made of a material heavier than the housing 310. For example, when the housing 310 is made of resin, the frame 312 is made of metal such as stainless steel. In the present embodiment, the frame 312 forms a lattice with a planar shape. The first electrode 24 and the second electrode 26 are located inside each lattice formed by the frame 312. That is, in plan view, a plurality of piezoelectric vibrators constituted by one piezoelectric film 22 are separated from each other by the frame 312.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained. The housing 310 is separated by a plurality of piezoelectric vibrators by a frame 312. Therefore, it is possible to further suppress the vibrations of adjacent piezoelectric vibrators from interfering with each other during transmission through the housing 310.

(Third embodiment)
FIG. 6 is a cross-sectional view illustrating a configuration of a main part of an electronic device 300 according to the third embodiment, and corresponds to FIG. 1 in the first embodiment. The electronic device 300 according to the present embodiment has the same configuration as the electronic device 300 according to the first embodiment, except that the housing 310 has a plurality of particles 314.

  The particles 314 are made of a material heavier than the material constituting the housing 310. For example, when the housing 310 is made of resin, the particles 314 are made of metal, for example.

  Also according to this embodiment, the same effect as that of the first embodiment can be obtained. Further, by providing the particles 314, the rigidity of the housing 310 can be increased. Further, by changing the amount of the particles 314, it is possible to adjust the mass of the portion of the housing 310 that faces the oscillation member 20. For this reason, the fundamental resonance peripheral number and the mechanical quality factor Q of the speaker including the oscillation member 20 and the housing 310 can be adjusted.

  In addition, as shown in FIG. 7, you may provide the flame | frame 312 shown in 2nd Embodiment in this embodiment.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable. For example, one of the first electrode 24 and the second electrode 26 may be provided as one electrode on the entire surface of the piezoelectric film 22. In this case, a ground potential is applied to one of the first electrode 24 and the second electrode 26 that is formed as one electrode.

20 Oscillating member 22 Piezoelectric film 24 First electrode 26 Second electrode 200 Display screen 300 Electronic device 310 Housing 312 Frame 314 Particles

Claims (6)

A housing,
A piezoelectric film attached to the inner surface of the housing;
A first electrode attached to the first surface of the piezoelectric film;
A second electrode attached to the second surface of the piezoelectric film and overlapping the first electrode in plan view;
Electronic equipment comprising. The electronic device according to claim 1,
An electronic apparatus in which a plurality of the first electrodes are attached to the first surface of the piezoelectric film so as to be separated from each other. The electronic device according to claim 2,
The second surface of the piezoelectric film is provided with a plurality of the second electrodes spaced apart from each other,
The plurality of second electrodes are electronic devices facing the different first electrodes. The electronic device according to claim 2 or 3,
The electronic device includes a frame made of a material heavier than the housing, which is located between the plurality of first electrodes in a plan view. The electronic device according to claim 4,
The housing is made of resin,
The frame is an electronic device made of metal. In the electronic device as described in any one of Claims 1-5,
The electronic device in which the housing contains a plurality of particles made of a material heavier than the housing.

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