JPWO2014034866A1 - SOUND GENERATOR, SOUND GENERATOR, AND ELECTRONIC DEVICE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a difference between a resonance peak and a dip in a frequency characteristic of sound pressure, suppress a frequency variation of sound pressure as much as possible, and improve sound quality, a sound generator and an electronic device. I will provide a. An acoustic generator includes a vibrating body and a piezoelectric vibration element. The vibrating body is a thin plate. The piezoelectric vibration element is provided on the vibrating body. The vibrator has a roughness difference region in which the surface roughness of one surface is larger than the surface roughness of the other surface located on the opposite side of the one surface. [Selection] Figure 3

Description

  Embodiments of the disclosure relate to a sound generator, a sound generation device, and an electronic apparatus.

  Conventionally, it is known that an acoustic generator typified by a piezoelectric speaker can be used as a small and thin speaker. Such a sound generator can be used as a speaker incorporated in an electronic device such as a mobile phone or a thin television.

  As an acoustic generator, for example, there is one including a vibrating body and a piezoelectric vibrating element provided on the vibrating body (see, for example, Patent Document 1). This is a configuration in which a vibrating body is vibrated by a piezoelectric vibration element, and a sound is generated using a resonance phenomenon of the vibrating body.

Japanese Patent Laid-Open No. 2004-23436

  However, in the configuration in which sound pressure is generated by resonance of the vibrating body itself as in the acoustic generator described above, the sound pressure is reduced due to the difference between the resonance peak and the dip (valley between resonance peaks) in the frequency characteristics of the sound pressure. There was a risk of frequency fluctuations. And this may hinder improvement in sound quality.

  One aspect of the embodiment has been made in view of the above, and reduces the difference between the resonance peak and the dip in the frequency characteristic of the sound pressure to suppress the frequency fluctuation of the sound pressure as much as possible, thereby improving the sound quality. An object is to provide a sound generator, a sound generator, and an electronic device that can be improved.

  An acoustic generator according to an aspect of an embodiment includes a thin plate-like vibrating body and a piezoelectric vibrating element provided on the vibrating body. The vibrator has a roughness difference region in which the surface roughness of one surface is larger than the surface roughness of the other surface located on the opposite side of the one surface.

  According to the acoustic generator of one aspect of the embodiment, the presence of the roughness difference regions having different surface roughnesses on both opposing surfaces of the vibrating body reduces the symmetry of the vibrating direction of the vibrating body and reduces the resonance peak. The width can be widened and the height can be lowered, the difference between the resonance peak and the dip can be reduced to suppress the frequency fluctuation of the sound pressure as much as possible, and the sound quality can be improved.

FIG. 1A is a schematic plan view of the sound generator according to the first embodiment. 1B is a cross-sectional view taken along line A-A ′ of FIG. 1A. FIG. 1C is a cross-sectional view taken along the line A-A ′ in the form without the covering layer of the sound generator according to the first embodiment shown in FIG. 1A. FIG. 2 is a schematic plan view illustrating an example of arrangement of roughness different regions in the vibrating body illustrated in FIG. 1. FIG. 3 is a cross-sectional view taken along line B-B ′ of FIG. 2. FIG. 4 is a schematic plan view showing another arrangement example of the roughness difference region according to the first embodiment. FIG. 5 is a block diagram of the sound generator. FIG. 6 is a block diagram of the electronic device. FIG. 7 is a schematic plan view illustrating an arrangement example of roughness different areas according to the second embodiment. FIG. 8 is a schematic plan view showing another arrangement example of the roughness difference area according to the second embodiment. FIG. 9 is a schematic plan view (part 1) showing another arrangement example of the roughness difference region. FIG. 10 is a schematic plan view (No. 2) showing another example of the arrangement of the different roughness areas. FIG. 11 is a schematic plan view (part 3) illustrating another arrangement example of the roughness difference region. FIG. 12 is a schematic plan view (part 4) illustrating another arrangement example of the roughness difference region.

  Hereinafter, embodiments of a sound generator, a sound generator, and an electronic device disclosed in the present application will be described in detail with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

(First embodiment)
FIG. 1A is a schematic plan view of the sound generator 1 according to the first embodiment viewed from a direction perpendicular to the main surface of the vibrating body 10, and FIG. 1B is a cross-sectional view taken along the line AA ′ in FIG. 1A. is there. In FIG. 1B, for easy understanding, the sound generator 1 is expanded and deformed in the vertical direction.

  As shown in FIGS. 1A and 1B, the sound generator 1 according to the first embodiment includes a vibrating body 10, a piezoelectric vibrating element 20, and a frame body 30. Such an acoustic generator 1 is called a so-called piezoelectric speaker, and generates a sound pressure using a resonance phenomenon of the vibrating body 10 itself.

  The vibrating body 10 can be formed using various materials such as resin, metal, and paper. For example, the thin plate-like vibrating body 10 can be formed of a resin film such as polyethylene, polyimide, or polypropylene having a thickness of 10 to 200 μm. Since the resin film is a material having a lower elastic modulus and mechanical Q value than a metal plate or the like, the vibrating body 10 is made of a resin film to bend and vibrate the vibrating body 10 with a large amplitude so that the sound pressure is reduced. It is possible to reduce the difference between the resonance peak and the dip by widening the width of the resonance peak and reducing the height in the frequency characteristics.

  The vibrating body 10 has a surface roughness of one surface 10a (hereinafter referred to as an upper surface 10a) on which the piezoelectric vibration element 20 is provided and the other surface 10b located on the opposite side of the upper surface 10a (hereinafter referred to as a lower surface 10b). The surface roughness difference area 11 is different from the surface roughness.

  In this way, since the roughness difference region 11 having different surface roughness between the upper surface 10a and the lower surface 10b opposed to each other exists in the vibrating body 10, the symmetry of the vibrating direction of the vibrating body 10 is reduced, and the amplitude of the vibrating body 10 is reduced. Becomes uneven on both surfaces of the vibrating body 10. Therefore, the width of the resonance peak can be widened and the height can be lowered, and the sound quality can be improved by reducing the difference between the resonance peak and the dip. The roughness difference area 11 will be described in detail later.

  The piezoelectric vibration element 20 includes a laminated body 21, surface electrode layers 22 and 23 formed on the upper and lower surfaces of the laminated body 21, and an external surface formed on a side surface from which an end face of the internal electrode layer 24 of the laminated body 21 is derived. Electrodes 25 and 26 are provided. Then, lead terminals 27 a and 27 b are connected to the external electrodes 25 and 26.

  The laminate 21 is formed by alternately laminating four piezoelectric layers 28a, 28b, 28c, 28d made of ceramics and three internal electrode layers 24. The piezoelectric vibration element 20 has a rectangular main surface on the upper surface side and the lower surface side, and the piezoelectric layers 28a and 28b and the piezoelectric layers 28c and 28d are alternately polarized in the thickness direction.

  Therefore, when a voltage is applied to the piezoelectric vibration element 20 via the lead terminals 27a and 27b, for example, the lower surface side of the piezoelectric vibration element 20, in other words, the piezoelectric layers 28c and 28d on the vibration body 10 side contract, while the upper surface The piezoelectric layers 28a and 28b on the side are deformed so as to extend. As described above, the piezoelectric layers 28a and 28b on the upper surface side of the piezoelectric vibration element 20 and the piezoelectric layers 28c and 28d on the lower surface side exhibit opposite expansion and contraction behavior, and as a result, the piezoelectric vibration element 20 is bent bimorph-shaped. By vibrating, a certain vibration can be given to the vibrating body 10 to generate a sound.

  Here, as materials constituting the piezoelectric layers 28a, 28b, 28c, 28d, conventionally used are lead-free piezoelectric materials such as lead zirconate titanate, Bi layered compounds, tungsten bronze structure compounds, and the like. Piezoelectric ceramics can be used.

  The material of the internal electrode layer 24 preferably contains a metal component made of silver and palladium and a material component constituting the piezoelectric layers 28a, 28b, 28c, 28d. When the internal electrode layer 24 contains the ceramic component constituting the piezoelectric layers 28a, 28b, 28c, 28d, the difference in thermal expansion between the piezoelectric layers 28a, 28b, 28c, 28d and the internal electrode layers 24, 24, 24. Thus, it is possible to obtain the piezoelectric vibration element 20 in which the stress due to the above is reduced.

  Further, as the wiring connected to the lead terminals 27a and 27b, in order to reduce the height of the piezoelectric vibration element 20, it is preferable to use a flexible wiring in which a metal foil such as copper or aluminum is sandwiched between resin films.

  The piezoelectric vibration element 20 configured as described above is bonded to the upper surface 10 a of the vibrating body 10 via an adhesive 40. The thickness of the adhesive 40 between the piezoelectric vibration element 20 and the vibrating body 10 is relatively thin, for example, 20 μm or less. Thus, when the thickness of the adhesive 40 is 20 μm or less, the vibration of the laminated body 21 can be easily transmitted to the vibrating body 10.

  As the adhesive 40, for example, a known material such as an epoxy resin, a silicon resin, or a polyester resin can be used, but the adhesive is not limited thereto. In addition, as a method for curing the resin used for the adhesive 40, any method such as thermosetting, photocuring, and anaerobic curing may be used.

  The frame body 30 plays a role of holding the vibrating body 10 and forming a fixed end of vibration. For example, as shown in FIG. 1B, a frame body 30 is configured by joining a rectangular upper frame member 30a and a lower frame member 30b in the vertical direction. And the outer peripheral part of the vibrating body 10 is pinched | interposed between the upper frame member 30a and the lower frame member 30b, and it fixes in the state which provided predetermined tension. Therefore, the acoustic generator 1 including the vibrating body 10 with less deformation such as deflection even when used for a long time is obtained.

  The thickness and material of the upper frame member 30a and the lower frame member 30b constituting the frame body 30 are not particularly limited. However, in the present embodiment, for example, the thickness is increased because of excellent mechanical strength and corrosion resistance. A stainless steel material having a thickness of 100 to 5000 μm is used.

  In the acoustic generator 1, as shown in FIG. 1B, the piezoelectric vibration element 20 and the upper surface 10a of the vibrating body 10 are covered with a coating layer 50 made of resin. Specifically, the coating layer 50 is configured to cover the piezoelectric vibration element 20 and the like by pouring resin into the frame of the upper frame member 30a of the frame body 30. In FIG. 1A, the covering layer 50 is not shown for easy understanding.

  The resin forming the coating layer 50 is, for example, an epoxy resin, an acrylic resin, a silicon resin, or rubber, but these are examples and are not limited. Thus, by covering the piezoelectric vibration element 20 with the coating layer 50, an appropriate damping effect can be induced, and the difference between the resonance peak and the dip can be suppressed as well as the resonance phenomenon can be suppressed. preferable. Furthermore, the piezoelectric vibration element 20 can be protected from the external environment.

  In the acoustic generator 1 according to the present embodiment, the entire upper surface 10a of the vibrating body 10 is covered with the coating layer 50, but it is not necessary to cover the entire surface. That is, the acoustic generator 1 only needs to cover the piezoelectric vibrating element 20 and at least a part of the upper surface 10a of the vibrating body 10 on which the piezoelectric vibrating element 20 is provided with the coating layer 50.

  On the other hand, as shown in FIG. 1C, the acoustic generator may be configured such that the covering layer 50 is removed from the acoustic generator 1 according to the first embodiment shown in FIG. 1A. Although the moderate damping effect by the coating layer 50 cannot be obtained, there is no problem in that the effect by the roughness difference region 11 described later is expressed.

  Here, the roughness difference region 11 arranged in the above-described vibrating body 10 will be described. FIG. 2 is a schematic plan view illustrating an arrangement example of the roughness different regions 11 in the vibrating body 10, and FIG. 3 is a cross-sectional view taken along the line B-B 'of FIG.

  In FIG. 2, the region where the roughness difference region 11 is arranged is indicated by hatching, and the outer shape of the piezoelectric vibration element 20 is illustrated in order to clarify the positional relationship between the roughness difference region 11 and the piezoelectric vibration element 20. It is indicated by a broken line. In FIG. 3, the surface roughness is exaggerated and deformed to clarify the difference in surface roughness between the upper surface 10a and the lower surface 10b.

  As shown in FIG. 2, the roughness difference region 11 is disposed in a part of the vibrating body 10, and more specifically, in the vibrating body 10, for example, near the center portion in plan view, and the piezoelectric vibrating element 20. Is disposed over the entire surface of the region in which is provided. In the vibrating body 10, the surface roughness of the upper surface 10 a and the surface roughness of the lower surface 10 b are uniform in the regions other than the above-described roughness different region 11.

  As shown in FIG. 3, the roughness difference region 11 arranged in the vibrating body 10 has a surface roughness of the upper surface 10a (a surface roughness of a region indicated by reference numeral 11a in FIG. 3) as a surface roughness (a surface roughness of the lower surface 10b). The surface roughness of the region indicated by reference numeral 11b in FIG.

  Specifically, in the roughness difference region 11, the upper surface 10a has, for example, a maximum height Rmax1 of 0.5 to 10 μm, and the lower surface 10b has, for example, a maximum height Rmax2 of 0.05 to 4 μm (provided that Rmax1> Rmax2). In addition, the specific numerical value of the surface roughness Rmax1 and Rmax2 mentioned above is an illustration, and is not limited.

  Such a roughness difference region 11 can be formed using, for example, laser irradiation, plasma irradiation, or the like.

  As a method for measuring the difference between the surface roughness of the upper surface 10a and the surface roughness of the lower surface 10b, for example, a method of measuring by analyzing the coordinate data after acquiring data using a three-dimensional measuring instrument, And a method of measuring with a scanning microscope such as an atomic force microscope (AFM).

  Here, the surface roughness may be measured in advance at the location where the coating layer 50 and the piezoelectric vibration element 20 are joined.

  When the covering layer 50 and the piezoelectric vibration element 20 are already bonded, if the covering layer 50 and the piezoelectric vibration element 20 are peeled off using a solvent, the surface roughness of the upper surface 10a and the surface roughness of the lower surface 10b are different. It can be measured. Alternatively, the sample may be measured after the sample of the acoustic generator 1 is put into liquid nitrogen to peel off the coating layer 50 and the piezoelectric vibration element 20 from the vibrating body 10. Moreover, since the sample of the sound generator 1 that has been freeze-cured after being put into liquid nitrogen can be easily broken, it can also be measured by observing the fractured surface by SEM after breaking.

  As for the measurement method, in addition, Rutherford backscattering analysis method, a method of measuring without scattering the coating layer 50 and the piezoelectric vibration element 20 by irradiating with X-rays or proton rays and measuring from scattered light, By measuring the binding energy while etching from the surface by scanning X-ray photoelectron spectroscopy, the surface state can be measured from the difference in binding energy, and there is no particular limitation.

  As described above, in the sound generator 1 according to the present embodiment, there are the roughness different regions 11 having different surface roughnesses on the opposing surfaces 10a and 10b of the vibrating body 10. Due to the roughness difference region 11, the symmetry of the vibration direction of the vibrating body 10 (vertical direction in FIG. 1B) is reduced, and the amplitude of the vibrating body 10 is uneven between the upper surface 10a side and the lower surface 10b side of the vibrating body 10. Become. Therefore, the width of the resonance peak can be widened and the height can be lowered, and the sound quality can be improved by reducing the difference between the resonance peak and the dip.

  Furthermore, in the acoustic generator 1, since the piezoelectric vibration element 20 is provided on the upper surface 10a having a large surface roughness and large unevenness, the so-called anchor effect that the adhesive 40 enters into the uneven portion of the upper surface 10a causes the vibration body 10 and The bonding strength with the piezoelectric vibration element 20 can also be improved.

  In addition, the acoustic generator 1 has a coating layer 50 that covers the piezoelectric vibration element 20 and at least a part of the upper surface 10a. Since the upper surface 10a has a large surface roughness, the vibrating body 10 and the coating layer 50 are provided. Voids are likely to occur between Thus, when a void exists in the coating layer 50, the stress generated by the vibration of the member including the vibrating body 10 and the coating layer 50 integrated with the piezoelectric vibration element 20 is concentrated in the vicinity of the void, and the local in the vicinity of the void. Strain increases. As a result, energy generated by vibration can be effectively lost, so that the difference between the resonance peak and the dip can be further reduced.

  As described above, in the first embodiment, in the sound generator 1, the vibrating body 10 is configured to have the roughness difference region 11 where the surface roughness of the upper surface 10a and the surface roughness of the lower surface 10b are different. Therefore, the difference between the resonance peak and the dip in the frequency characteristic of the sound pressure can be reduced to suppress the frequency fluctuation as much as possible, and the sound quality can be improved.

  In the above description, the example in which the roughness different region 11 is arranged over the entire surface of the region where the piezoelectric vibration element 20 is provided has been described. However, the roughness difference region is partially included in the region where the piezoelectric vibration element 20 is provided. 11 may be formed. For example, as shown in FIG. 4, the roughness difference region 11 may be locally arranged at the end of the region where the piezoelectric vibration element 20 is provided in the vibrating body 10. Also with this configuration, the symmetry of the vibration direction of the vibrating body 10 can be reduced, and the sound quality can be improved.

  Further, as shown in FIG. 5, the sound generator 2 can be configured by housing the sound generator 1 having the above-described configuration in a resonance box 200. The resonance box 200 is a housing that houses the sound generator 1, and resonates the sound emitted from the sound generator 1 and radiates it as sound waves from the housing surface. Such a sound generator 2 can be used alone as a speaker, and can be suitably incorporated into various electronic devices 3, for example.

  As described above, since the difference between the resonance peak and the dip in the frequency characteristic of sound pressure, which is disadvantageous in the piezoelectric speaker, can be reduced, the sound generator 1 according to the present embodiment can be used for a mobile phone or a thin television. Alternatively, it can be suitably incorporated into the electronic device 3 such as a tablet terminal.

  The electronic device 3 to which the sound generator 1 can be incorporated is not limited to the above-described mobile phone, flat-screen TV, tablet terminal, and the like, and for example, a refrigerator, a microwave oven, a vacuum cleaner, a washing machine, and the like. Conventionally, home appliances that have not been focused on sound quality are also included.

  Here, the electronic device 3 including the above-described sound generator 1 will be briefly described with reference to FIG. FIG. 6 is a block diagram of the electronic device 3. The electronic device 3 includes the acoustic generator 1 described above, an electronic circuit connected to the acoustic generator 1, and a housing 300 that houses the acoustic generator 1 and the electronic circuit.

  Specifically, as illustrated in FIG. 6, the electronic device 3 accommodates an electronic circuit including a control circuit 301, a signal processing circuit 302, a wireless circuit 303 as an input device, an antenna 304, and these. And a housing 300. Although the wireless input device is shown in FIG. 6, it can be provided as a signal input by normal electric wiring.

  In addition, description was abbreviate | omitted here about the other electronic members (for example, devices and circuits, such as a display, a microphone, a speaker) with which the electronic device 3 is provided. Moreover, in FIG. 6, although one acoustic generator 1 was illustrated, two or more acoustic generators 1 and other transmitters can be provided.

  The control circuit 301 controls the entire electronic device 3 including the wireless circuit 303 via the signal processing circuit 302. An output signal to the sound generator 1 is input from the signal processing circuit 302. Then, the control circuit 301 generates a sound signal S by controlling the signal processing circuit 302 from the signal input to the radio circuit 303 and outputs the sound signal S to the sound generator 1.

  In this way, the electronic device 3 shown in FIG. 6 incorporates the small and thin sound generator 1 and reduces the difference between the resonance peak and the dip to suppress the frequency fluctuation as much as possible. It is possible to improve the sound quality as a whole even in a high sound region including a low sound region having a low sound level.

  6 exemplifies the electronic apparatus 3 in which the sound generator 1 is directly mounted as the sound output device. However, as the sound output device, for example, the sound generator 2 in which the sound generator 1 is housed in the housing is mounted. It may be the configuration.

(Second Embodiment)
FIG. 7 is a schematic plan view illustrating an arrangement example of the roughness different regions 11 in the vibrating body 10 of the sound generator 1 according to the second embodiment. As shown in FIG. 7, in the sound generator 1 according to the second embodiment, the roughness difference region 11 is continuous over the entire vibration surface of the vibrating body 10 in the frame of the frame body 30. Placed in. That is, the roughness difference region 11 is arranged not only in the portion where the piezoelectric vibration element 20 is provided, but also in the portion where the piezoelectric vibration element 20 is not provided in the vibration surface of the vibrating body 10.

  In the second embodiment, since the roughness difference region 11 is arranged over the entire vibration surface of the vibrating body 10, the symmetry of the vibration direction of the vibrating body 10 extends over the entire vibration surface of the vibrating body 10. descend. Therefore, the symmetry of the vibration direction of the vibrating body 10 is further reduced, the amplitude of the vibrating body 10 can be made more uneven on the upper surface 10a side and the lower surface 10b side of the vibrating body 10, and sound quality can be improved. it can. Further, by disposing the roughness difference region 11 over the entire vibration surface of the vibrating body 10, vibration transmitted from the piezoelectric vibrating element 20 to the vibrating body 10 can be further relaxed, and the damping effect can be generated most. The sound can have very few peaks and dips. The remaining configuration and effects are the same as those in the first embodiment, and a description thereof will be omitted.

  In the example shown in FIG. 7, the roughness different region 11 is continuously arranged over the entire vibration surface of the vibrating body 10, but intermittently over the entire vibration surface of the vibrating body 10 as shown in FIG. 8. It can also be arranged. Also by this, the symmetry of the vibration direction of the vibration body 10 can be reduced over the entire vibration surface of the vibration body 10.

  In the above-described embodiment, the example in which the roughness different region 11 is disposed over the region where the piezoelectric vibration element 20 is provided or the entire vibration surface of the vibrating body 10 has been described. 11 may be arranged as shown in FIGS.

  In the example illustrated in FIG. 9, the roughness difference region 11 is locally disposed in the vibrating body 10 other than the region where the piezoelectric vibration element 20 is provided. Specifically, a plurality of (for example, two) roughness different regions 11 are arranged at positions symmetrical with respect to the center of the piezoelectric vibration element 20, for example. As described above, even when the roughness different region 11 is arranged in the region where the piezoelectric vibration element 20 is provided, the symmetry of the vibration direction of the vibrating body 10 can be reduced, thereby widening the width of the resonance peak, Therefore, the difference between the resonance peak and the dip can be further reduced.

  In the example shown in FIG. 10, the roughness difference region 11 is a region in which the roughness difference region 11 is locally disposed in a region other than the region where the piezoelectric vibration element 20 is provided and the piezoelectric vibration element 20 is provided. Also, the roughness difference region 11 is arranged. With such a configuration, by reducing the symmetry of the vibration direction of the vibrating body 10, the difference between the resonance peak and the dip can be further reduced.

  In the example shown in FIG. 11 and FIG. 12, the roughness difference region 11 is arranged in a position other than the region where the piezoelectric vibration element 20 is provided in the vibrating body 10 and at a position deviated from the vibration surface center of the vibrating body 10. Is done. When the roughness difference region 11 is arranged in this manner, the symmetry of the vibration direction of the vibrating body 10 can be reduced, and the symmetry of the vibration surface of the vibrating body 10 can also be reduced. Can be made wide and low in height. In the example shown in FIGS. 11 and 12, since the roughness difference region 11 is located at a position deviated from the center of the vibration surface of the vibrating body 10, the difference between the resonance peak and the dip can be further reduced.

  In the above-described embodiment, the position where the roughness different region 11 is arranged in the vibrating body 10 has been specifically described. However, these are examples and are not necessarily limited. In the sound generator 1, it is only necessary that the roughness difference region 11 is arranged in the vibrating body 10 so as to reduce the difference between the resonance peak and the dip.

  Further, in the above-described embodiment, the surface roughness of the upper surface 10a is larger than the surface roughness of the lower surface 10b in the roughness different region 11, but the surface roughness of the upper surface 10a is smaller than the surface roughness of the lower surface 10b. May be. Also in this case, the symmetry of the vibration direction of the vibrating body 10 can be reduced, and the difference between the resonance peak and the dip can be suppressed.

  Further, the vibration difference of the vibration body 10 includes a roughness different region where the surface roughness of the upper surface 10a is larger than the surface roughness of the lower surface 10b, and a roughness difference region where the surface roughness of the upper surface 10a is smaller than the surface roughness of the lower surface 10b. It may be arranged on the surface. Also with such a configuration, the symmetry of the vibration direction of the vibrating body 10 can be reduced, and the difference between the resonance peak and the dip can be suppressed.

  In the above-described embodiment, the piezoelectric vibration element 20 and the vibrating body 10 are covered with the covering layer 50. However, the present invention is not limited to this, and a configuration without the covering layer 50 may be used.

  Further, in the above-described embodiment, an example in which one piezoelectric vibration element 20 is disposed on the vibrating body 10 is illustrated, but two or more piezoelectric vibration elements 20 may be disposed. When there are two or more piezoelectric vibration elements 20, even if the piezoelectric vibration elements 20 are disposed on the same surface of the upper surface 10a (or the lower surface 10b) of the vibrating body 10, they are disposed on both the upper surface 10a and the lower surface 10b. May be. Further, although the piezoelectric vibration element 20 is rectangular in plan view, it may be square. Further, although the example in which the piezoelectric vibration element 20 is disposed at the approximate center of the vibration surface of the vibration body 10 is illustrated, the piezoelectric vibration element 20 may be disposed at a position deviated from the vibration surface center of the vibration body 10.

  Further, as the piezoelectric vibration element 20, a so-called bimorph type laminated type is illustrated, but a unimorph type piezoelectric vibration element can also be used.

  Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

DESCRIPTION OF SYMBOLS 1 Sound generator 2 Sound generator 3 Electronic device 10 Vibration body 11 Roughness difference area | region 20 Piezoelectric vibration element 30 Frame body 40 Adhesive 50 Covering layer 200 Resonance box (housing | casing)
300 Housing 301 Control circuit 302 Signal processing circuit 303 Radio circuit 304 Antenna

An acoustic generator according to an aspect of an embodiment includes a thin plate-like vibrating body and a piezoelectric vibrating element provided on one surface of the vibrating body. The acoustic generator includes a coating layer that covers the piezoelectric vibration element and at least a part of a surface of the vibrating body on the side where the piezoelectric vibration element is provided. The vibrating body has a roughness difference region where the surface roughness of one surface is larger than the surface roughness of the other surface located on the opposite side of the one surface in a region where the piezoelectric vibration element is not provided. There is a void between the coating layer and the roughness difference region .

Claims (8)

A thin plate-like vibrator,
A piezoelectric vibration element provided on the vibrating body,
The vibration generator has a roughness difference region in which the surface roughness of one surface is larger than the surface roughness of the other surface located on the opposite side of the one surface.   The acoustic generator according to claim 1, wherein the roughness difference region is arranged in a part of the vibrating body.   3. The acoustic generator according to claim 1, wherein the roughness different region includes at least a part of a region of the vibrating body in which the piezoelectric vibration element is provided.   The sound generator according to claim 1, wherein the roughness difference region is arranged over the entire vibration surface of the vibrating body.   The acoustic generator according to claim 1, wherein the piezoelectric vibration element is provided on the one surface of the roughness difference region.   6. The method according to claim 1, further comprising a covering layer that covers the piezoelectric vibration element and at least a part of a surface of the vibrating body on the side where the piezoelectric vibration element is provided. The described sound generator. The sound generator according to any one of claims 1 to 6,
A sound generation device comprising at least a housing for housing the sound generator. The sound generator according to any one of claims 1 to 6,
An electronic circuit connected to the acoustic generator;
A housing for housing the electronic circuit and the acoustic generator,
An electronic apparatus having a function of generating sound from the sound generator.

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