Transducer

Abstract

A transducer (1) comprises: a piezoelectric element (10) provided with a pair of electrodes (11, 12) and a piezoelectric film (13) sandwiched between the pair of electrodes (11, 12); a film support part (17); and a vibration film (16) supported by the film support part (17) so as to be able to vibrate in the thickness direction of the piezoelectric element (10). A plurality of openings (15) that continuously penetrate the vibration film (16) from the piezoelectric element (10) are provided, and the shortest distance between two points facing each other across the center of the opening (15) in each of the plurality of openings (15) is 20 μm or less.

Description

Transducer

[0001] The present disclosure relates to transducers.

[0002] 2. Description of the Related Art Transducers that transmit or receive sound waves or ultrasonic waves are known. Transducers are used, for example, as speakers that transmit sound waves, and are mounted in earphones, wearable devices, and the like.

[0003] For example, Patent Document 1 discloses a sound generating device suitable for earphones. This sound generating device includes a coil that generates a magnetic field and a magnet that interacts with the magnetic field generated by the coil to vibrate a diaphragm.

[0004] Speakers that use a coil and a magnet require a current to flow through the coil to generate a magnetic field, resulting in high power consumption. Therefore, speakers that use a piezoelectric element, which is constructed by sandwiching a piezoelectric film between a pair of electrodes, have been attracting attention (see, for example, Patent Document 2). These types of speakers are manufactured using MEMS (Micro Electro Mechanical Systems), a semiconductor manufacturing technology that enables microfabrication.

[0005] JP 2018-170592 A JP 2012-105170 A

[0006] Piezoelectric MEMS transducers are micromechanisms that convert electric field and motion by using a laminated structure of a piezoelectric film that deforms when an electric field is applied and a base made of silicon or other material. The laminated film warps depending on whether the film is deformed or not. However, when an electric field is applied to move the laminated film, the film that tries to contract laterally and the film that does not contract pull against each other, resulting in stress within and between the layers. When this stress is repeated or during resonance, the stress from the vibration can cause cracks between crystals, between grain boundaries, and in crystal defects, potentially damaging the vibrating film.

[0007] The present disclosure has been proposed in view of the above-described circumstances, and an object of the present disclosure is to provide a transducer that can reduce stress on a vibrating membrane and prevent damage to the vibrating membrane.

[0008] A transducer according to one embodiment of the present disclosure comprises a first electrode that deforms in response to an external force, a membrane support portion, and a vibration membrane supported by the membrane support portion so as to be vibrable in the thickness direction of the first electrode, the vibration membrane being stacked in contact with the first electrode, and a plurality of openings continuously penetrating the first electrode and the vibration membrane from the surface of the first electrode opposite the vibration membrane side to the surface of the vibration membrane opposite the surface in contact with the first electrode, and the shortest distance between two points facing each other across the center of each of the plurality of openings is 20 μm or less.

[0009] Another aspect of the transducer of the present disclosure includes a first electrode that deforms due to an external force, a membrane support portion, and a vibration membrane supported by the membrane support portion so as to be vibrable in the thickness direction of the first electrode, the vibration membrane being stacked in contact with the first electrode, and a plurality of openings that penetrate the first electrode and have bottom surfaces inside the vibration membrane.

[0010] According to the present disclosure, it is possible to provide a transducer that can reduce the stress applied to the vibrating membrane and prevent damage to the vibrating membrane.

[0011] FIG. 1 is a top view showing the structure of a transducer according to the first embodiment. FIG. 2 is a cross-sectional view taken along the arrow direction of FIG. 1 . FIG. 3 is a top view showing the structure of a transducer according to a first modified example of the first embodiment. FIG. 4 is a cross-sectional view taken along the arrow direction of FIG. 3 . FIG. 5 is a top view showing the structure of a transducer according to a second modified example of the first embodiment. FIG. 6 is a cross-sectional view taken along the arrow direction of FIG. 7 . FIG. 7 is a top view showing the structure of a transducer according to a fourth modified example of the first embodiment. FIG. 8 is a cross-sectional view taken along the arrow direction of FIG. 7 . FIG. 9 is a top view showing the structure of a transducer according to a fifth modified example of the first embodiment. FIG. 10 is a top view showing the structure of a transducer according to a sixth modified example of the first embodiment. FIG. 11 is a top view showing the structure of a transducer according to a seventh modified example of the first embodiment. FIG. 12 is a top view showing the structure of a transducer according to an eighth modified example of the first embodiment. FIG. 13 is a top view showing the structure of a transducer according to a ninth modified example of the first embodiment. Fig. 14 is a top view showing the structure of a transducer according to a tenth modification of the first embodiment. Fig. 15 is a top view showing the structure of a transducer according to an eleventh modification of the first embodiment. Fig. 16 is a top view showing the structure of a transducer according to a twelfth modification of the first embodiment. Fig. 17 is a diagram illustrating the structure of a transducer and the displacement amount of a vibrating membrane in a higher vibration mode according to another embodiment. Fig. 18 is a diagram illustrating another structure of the transducer and the displacement amount of a vibrating membrane in the higher vibration mode of Fig. 17.

[0012] Next, embodiments will be described with reference to the drawings. In the drawings described below, identical or similar parts are designated by identical or similar reference numerals. The drawings are schematic. Furthermore, the embodiments shown below are intended to exemplify devices or methods for embodying technical ideas, and do not specify the materials, shapes, structures, arrangements, dimensions, dimensional ratios, etc. of parts. Various modifications can be made to the embodiments.

[0013] First Embodiment The structure of a transducer according to this embodiment will be described with reference to the drawings.

[0014] Fig. 1 is a top view showing the structure of a transducer 1 according to this embodiment, and Fig. 2 is a cross-sectional view taken along the arrow in Fig. 1 .

[0015] The transducer 1 according to this embodiment is a piezoelectric transducer, and is mainly composed of a piezoelectric element 10, a membrane support portion 17, and a vibration membrane 16. In the following description, the up and down directions are defined based on the state of the transducer 1 shown in Figure 2, but this does not limit the direction in which the transducer 1 is used.

[0016] The piezoelectric element 10 is composed of a pair of electrodes 11, 12 and a piezoelectric film 13 sandwiched between the pair of electrodes 11, 12. The pair of electrodes 11, 12 and the piezoelectric film 13 have shapes corresponding to the shape of a vibration film 16, which will be described later, and are rectangular in the example shown in Figures 1 and 2.

[0017] Each of the pair of electrodes 11, 12 is formed using a thin film of a conductive metal such as platinum, molybdenum, iridium, or titanium. One electrode 11 is located above the piezoelectric film 13 and connected to an electrode pad 11a, which is a circuit pattern for applying a drive voltage to the electrode 11. The other electrode 12 is located below the piezoelectric film 13 and connected to an electrode pad 12a, which is a circuit pattern for applying a drive voltage to the electrode 12.

[0018] The piezoelectric film 13 is made of, for example, a lead zirconate titanate (PZT) film. The piezoelectric film 13 may be made of aluminum nitride (AlN), zinc oxide (ZnO), or lead titanate (PbTiO ３ ) etc. can be used.

[0019] The vibration membrane 16 is made of a thin film and is laminated in contact with the electrode 12. The vibration membrane 16 is supported by the membrane support portion 17 so as to be vibrable in the thickness direction of the piezoelectric element 10, i.e., in the normal direction to the vibration membrane 16 (the direction perpendicular to the front and back of the paper in FIG. 1: Z direction, and the direction up and down on the paper in FIG. 2: Z direction).

[0020] The membrane support portion 17 has a rectangular cylindrical inner peripheral surface that forms a cavity (hollow portion). The vibration membrane 16 is inscribed on one side of the inner peripheral surface of the membrane support portion 17 at the connecting portion 21, whereby the vibration membrane 16 is supported by the membrane support portion 17. The vibration membrane 16 is connected to the upper end side of the membrane support portion 17.

[0021] The vibration membrane 16 and the membrane support portion 17 are made of, for example, silicon (Si). For example, the vibration membrane 16 and the membrane support portion 17 are integrally formed by etching the back side of a silicon substrate. The vibration membrane 16 has a cantilever shape that protrudes from the membrane support portion 17. The tip of the vibration membrane 16 is configured as a free end. However, the vibration membrane 16 may also have a cantilever shape in which both ends are fixed by the membrane support portion 17.

[0022] The transducer 1 also includes a slit 2. The slit 2 is a cut that penetrates the vibration membrane 16 in the thickness direction.

[0023] In the transducer 1 configured as described above, the piezoelectric element 10 is provided on the vibration membrane 16. That is, a lower electrode 12, a piezoelectric membrane 13, and an upper electrode 11 are layered in this order on the vibration membrane 16. When a drive voltage is applied to each of the pair of electrodes 11 and 12, an electric field is generated between the pair of electrodes 11 and 12. This electric field causes the piezoelectric membrane 13 to deform, specifically, contract, due to the piezoelectric effect. This contraction displaces the vibration membrane 16 to which the piezoelectric element 10 is attached. Specifically, the tip end of the vibration membrane 16 is displaced so as to bend.

[0024] By repeatedly applying a drive voltage to the pair of electrodes 11 and 12, the vibrating membrane 16 alternately repeats an upward displacement and a restoration displacement to the horizontal state shown in Fig. 2. The vibration of the vibrating membrane 16 vibrates the air around the vibrating membrane 16, and the vibration of the air is output as a sound wave.

[0025] As shown in Fig. 1, the transducer 1 has a plurality of openings 15 formed therein. The plurality of openings 15 continuously penetrate the piezoelectric element 10 and the vibrating membrane 16 from the upper surface of the electrode 11 to the surface of the vibrating membrane 16 opposite the surface in contact with the electrode 11, as shown in Fig. 1. When a drive voltage is applied to the pair of electrodes 11, 12, the piezoelectric membrane 13 contracts. By forming the plurality of openings 15 from the piezoelectric element 10 to the vibrating membrane 16, it is possible to reduce the apparent rigidity at the openings 15, even if the vibrating membrane 16 is formed to a thickness that allows the desired strength to be obtained. As a result, the vibrating membrane 16 can be displaced more significantly while preventing damage.

[0026] If the shortest distance between two opposing points in the opening 15 (hereinafter also referred to as the "shortest opposing distance") is too long, the rigidity of the diaphragm 16 decreases, making it more susceptible to vibration (displacement). This means that while the air can be vibrated significantly, excessive air flow results in air leakage. As a result, even though the vibration (displacement) of the diaphragm 16 is large, the air pressure difference between the front and back sides of the diaphragm 16 (the upper and lower sides in FIG. 2 ) that would otherwise be generated by the vibration (displacement) is alleviated, resulting in a decrease in the sound pressure level. On the other hand, if the shortest opposing distance of the opening 15 is too short, air leakage from the opening 15 can be suppressed, allowing the air to be vibrated efficiently, but the rigidity of the diaphragm 16 is high, making it difficult to vibrate (displace). Therefore, it is important to specify the shortest opposing distance of the opening 15.

[0027] In this embodiment, when the shortest facing distance L of the opening 15 is 20 μm or less, the movement of air due to the deformation of the vibrating membrane 16 through the opening 15 can be controlled. Specifically, the air can be controlled to be less likely to pass through the opening 15. This suppresses air leakage, efficiently vibrates the air, and increases the vibration (displacement) of the vibrating membrane 16. Furthermore, the shortest facing distance L of the opening 15 may be 18 μm or less or 15 μm or less. The lower limit of the shortest facing distance L of the opening 15 is not particularly limited, but may be, for example, 8 μm or more, 10 μm or more, or 12 μm or more. This partially reduces the rigidity of the vibrating membrane 16, as described above, making it easier to vibrate (displace) the vibrating membrane 16. When the shape of the opening 15 is circular, the shortest facing distance is the diameter. When the shape of the opening 15 is oval, the shortest facing distance is the minor axis. In addition, when the shape of the opening 15 is elliptical, the shortest facing distance is the minor axis, and when the shape of the opening 15 is rectangular, the shortest facing distance is the minor side. In this embodiment, the shape of the opening 15 is circular with a diameter of 20 μm or less, but is not limited to this.

[0028] The specific numerical value of the minimum opposing distance L of the opening 15 described above is based on the assumption that the inner surface of the opening 15 is smooth. Here, assuming that the opening 15 is a pipe (tube), when a fluid (in this case, air) flows, the velocity of the fluid in contact with the pipe surface is zero due to friction with the pipe surface, and the velocity increases as the fluid moves away from the pipe surface, resulting in a laminar flow (Hagen-Poiseuille flow). Therefore, as the diameter of the pipe becomes smaller, the distance to the center of the pipe becomes shorter, resulting in a slower maximum flow velocity. Furthermore, the flow velocity is determined by taking into account the length of the pipe. If the inner surface of the pipe is smooth, the flow will be relatively regular, but if the inner surface of the pipe is rough, the flow will become turbulent and the flow velocity will be slower. Therefore, as described above, the specific numerical value of the minimum opposing distance L of the opening 15 is based on the assumption that the inner surface of the opening 15 is smooth.

[0029] According to this embodiment, by defining the shortest opposing distance L of the openings 15, the air is vibrated efficiently (without leakage), while the rigidity of the diaphragm 16 is reduced by the openings 15, making it more susceptible to vibration (warping). This makes it possible to provide a transducer 1 that can increase sound pressure while maintaining the desired strength (thickness) of the diaphragm 16 and preventing damage. In particular, it is possible to provide a transducer 1 that is suitable for ultrasonic applications in which the diaphragm 16 and the piezoelectric element 10 are driven at a resonant frequency.

[0030] In addition, in this embodiment, as shown in FIG. 1, an opening 15 is provided that continuously penetrates the piezoelectric element 10 and the vibration membrane 16 from the upper surface of the electrode 11 to the surface of the vibration membrane 16 opposite to the surface that is in contact with the electrode 11. However, this is not limited to this, and various modified examples such as those shown below may also be used.

[0031] <Modification 1> A description will be given of the configuration of a transducer 1A according to Modification 1. The above description will be used to refer to the points common to Modification 1 and the transducer 1 shown in Figures 1 and 2, and only the points of difference will be described below.

[0032] Fig. 3 is a top view showing the structure of a transducer 1A according to Modification 1. Fig. 4 is a cross-sectional view taken along the arrow direction of Fig. 3. The transducer 1A according to Modification 1 differs from the above-described transducer 1 in that, instead of the opening 15, an opening 15a is provided that penetrates the piezoelectric element 10 and has a bottom surface inside the vibration membrane 16.

[0033] In transducer 1A, opening 15a has its bottom surface inside vibrating membrane 16, so air does not move through opening 15a. Therefore, unlike transducer 1 described above, there is no need to specify the shortest facing distance L of opening 15a. However, from the viewpoint of reducing the rigidity and facilitating vibration (warping) while maintaining the thickness of vibrating membrane 16, the shortest facing distance L of opening 15a may also be 20 μm or less, 18 μm or less, or 15 μm or less. Furthermore, the shortest facing distance L of opening 15a may be 8 μm or more, 10 μm or more, or 12 μm or more. In variant 1, opening 15a has a circular shape with a diameter of 20 μm or less, but is not limited to this.

[0034] In variant example 1, as described above, the opening 15a can be used to provide a transducer 1A that can increase the sound pressure while maintaining the desired strength (thickness) of the vibration membrane 16 and prevent damage to the vibration membrane 16.

[0035] <Modification 2> A description will be given of the configuration of a transducer 1B according to Modification 2. The above description will be used to refer to the points common to Modification 2 and the transducer 1 shown in Figures 1 and 2, and only the points of difference will be described below.

[0036] 5 is a top view showing the structure of a transducer 1B according to Modification 2. The transducer 1B according to Modification 2 differs from the above-described transducer 1 in that an oval opening 15b is provided instead of the opening 15.

[0037] The minor axis of opening 15b is 20 μm or less, and may be 18 μm or less, or 15 μm or less. The lower limit of the minor axis of opening 15b may be, for example, 8 μm or more, 10 μm or more, or 12 μm or more. Opening 15b having a minor axis within the above range can control the movement of air caused by deformation of diaphragm 16 through opening 15b, specifically, can control the flow of air through opening 15b so that it is difficult for air to pass through. This suppresses air leakage, efficiently vibrates the air, and also facilitates vibration (displacement) of diaphragm 16. Furthermore, the thickness of diaphragm 16 can be maintained, preventing damage to diaphragm 16.

[0038] The shape of opening 15b may be an ellipse with a minor axis of 20 μm or less or a rectangle with a minor side of 20 μm or less, an ellipse with a minor axis of 18 μm or less or a rectangle with a minor side of 18 μm or less, or an ellipse with a minor axis of 15 μm or less or a rectangle with a minor side of 15 μm or less. The lower limit of the minor axis of the ellipse and the lower limit of the short side of the rectangle may be, for example, 8 μm or more, 10 μm or more, or 12 μm or more.

[0039] As described above, in the second modification, it is also possible to provide a transducer 1B in which the opening 15b makes it easier for the vibrating membrane 16 to vibrate (displace), while preventing damage to the vibrating membrane 16. Furthermore, because the opening 15b of the transducer 1B is oval, the area fraction of the opening is larger than that of the transducer 1. This makes it possible to increase the original thickness of the vibrating membrane 16 and to increase the vibration (displacement).

[0040] <Modification 3> A description will be given of the configuration of a transducer 1C according to Modification 3. The above description will be used for the points common to Modification 3 and the transducer 1 shown in Figures 1 and 2, and the following will describe the points that are different.

[0041] 6 is a cross-sectional view showing the structure of a transducer 1C according to Modification 3. The transducer 1C according to Modification 3 differs from the above-described transducer 1 in that the vibrating membrane has a doubly supported beam shape, with both ends fixed by membrane support parts.

[0042] The membrane support portion 17 surrounds the periphery of the vibrating membrane 16a and is connected to two sides of the vibrating membrane 16a. Slits are formed between the remaining two sides of the vibrating membrane 16a and the membrane support portion 17, and the vibrating membrane 16a alternately repeats upward displacement and horizontal restoration displacement.

[0043] In the third modification, as described above, it is also possible to provide a transducer 1C that can prevent damage to the vibrating membrane 16a while making it easier for the vibrating membrane 16a to vibrate (displace) by the opening 15.

[0044] <Modification 4> A description will be given of the configuration of a transducer 1D according to Modification 4. The above description will be used to refer to the points common to Modification 4 and the transducer 1 shown in Figures 1 and 2, and only the points that are different will be described below.

[0045] Fig. 7 is a top view showing the structure of a transducer 1D according to Modification 4. Fig. 8 is a cross-sectional view taken along the arrow in Fig. 7. The transducer 1D according to Modification 4 differs from the above-described transducer 1 in that a plurality of openings 15c are provided concentrically with respect to the center of the vibration membrane 16a.

[0046] Since the transducer 1D can have multiple openings 15c extending from the center of the vibration membrane 16a toward the outer periphery, it is possible to provide a transducer 1D that can reduce rigidity and make the vibration (warp) easier while maintaining thickness from the center to the outer periphery of the vibration membrane 16a.

[0047] <Modification 5> A description will be given of the configuration of a transducer 1E according to Modification 5. The above description will be used for the points common to Modification 5 and the transducer 1 shown in Figures 1 and 2, and only the points that are different will be described below.

[0048] 9 is a top view showing the structure of a transducer 1E according to Modification 5. The transducer 1E according to Modification 5 differs from the above-described transducer 1 in that no openings 15 are formed in the vibration membrane 6 and the piezoelectric element 10 within a predetermined range from the membrane support portion 17 (connecting portion 21). Another difference from Modification 5 is that the openings 15 are arranged more densely as they approach from the free end side of the cantilevered vibration membrane 6 to the predetermined range of the membrane support portion 17 (connecting portion 21) on the base end side.

[0049] In the transducer 1E, no openings 15 are formed within a predetermined range from the membrane support portion 17 (connecting portion 21), making that portion less likely to bend and increasing the radius of curvature, thereby alleviating the concentration of bending stress in that portion and preventing breakage. On the other hand, in the transducer 1E, the openings 15 are arranged more densely as they approach from the free end side of the vibrating membrane 6 to the predetermined range of the membrane support portion 17 (connecting portion 21) on the base end side, making it possible to provide a transducer 1E that can be largely displaced (warped) from a portion (root) relatively close to the base end beyond the predetermined range.

[0050] <Modification 6> A description will be given of the configuration of a transducer 1F according to Modification 6. The above description will be used to refer to the points common to Modification 6 with the transducer 1B shown in Fig. 5 and the transducer 1E shown in Fig. 9, and the following will describe the points that are different.

[0051] 10 is a top view showing the structure of a transducer 1F according to Modification 6. The transducer 1F according to Modification 6 differs from the above-described transducer 1B in that, like the transducer 1E, no openings 15b are formed in the vibration membrane 6 and the piezoelectric element 10 within a predetermined range from the membrane support portion 17 (connecting portion 21). Another difference from Modification 6 is that the openings 15b are arranged more densely from the free end side of the cantilevered vibration membrane 6 to the predetermined range of the membrane support portion 17 (connecting portion 21) on the base end side.

[0052] The transducer 1F can also achieve the same effects as the transducer 1E. That is, it is possible to provide a transducer 1F that can reduce the concentration of bending stress in a predetermined range from the membrane support portion 17 (connecting portion 21), prevent breakage, and allow for large displacement (warping) from a portion (root) relatively close to the base end that exceeds the predetermined range. Furthermore, because the opening 15b of the transducer 1F is oval, the area fraction of the opening is larger than that of the transducer 1E. This allows the original thickness of the vibrating membrane 16 to be increased and the vibration (displacement) to be increased.

[0053] <Modification 7> A description will be given of the configuration of a transducer 1G according to Modification 7. The above description will be used to refer to the points common to the transducer 1 shown in Figures 1 and 2 and the transducer 1E shown in Figure 9 in Modification 7, and the following will describe the points that are different.

[0054] 11 is a top view showing the structure of a transducer 1G according to Modification 7. The transducer 1G according to Modification 7 differs from the above-described transducer 1 in that, like the transducer 1E, no openings 15 are formed in the vibration membrane 6 and the piezoelectric element 10 within a predetermined range from the membrane support portion 17 (connecting portion 21). Another difference from Modification 7 is that the openings 15 are arranged more densely as they move away from the predetermined range of the membrane support portion 17 (connecting portion 21), which is the base end side of the vibration membrane 6 having a cantilever structure, toward the free end side.

[0055] In the transducer 1G, as in the transducer 1E, it is possible to provide a transducer 1G that can reduce the concentration of bending stress in a predetermined range from the membrane support part 17 (connecting part 21) and prevent breakage. On the other hand, once the predetermined range is exceeded, the openings 15 are densely arranged toward the free end, so it is possible to provide a transducer 1G that can gradually reduce rigidity and increase displacement (warping).

[0056] <Modification 8> A description will be given of the configuration of a transducer 1H according to Modification 8. The above description will be used to refer to the points common to the transducer 1B shown in Fig. 5, the transducer 1F shown in Fig. 10, and the transducer 1G shown in Fig. 11 in Modification 8, and the following will describe the points of difference.

[0057] 12 is a top view showing the structure of a transducer 1H according to Modification 8. The transducer 1H according to Modification 8 differs from the above-described transducer 1G in that the opening 15b has an oval shape, and therefore the area fraction of the opening is larger than that of the transducer 1G. This allows the original thickness of the vibrating membrane 16 to be increased, and the vibration (displacement) to be increased.

[0058] <Modification 9> A description will be given of the configuration of a transducer 1I according to Modification 9. The above description will be used to refer to the points common to Modification 9 and the transducer 1D shown in Figures 7 and 8, and only the points of difference will be described below.

[0059] 13 is a top view showing the structure of a transducer 1I according to Modification 9. The transducer 1I according to Modification 9 differs from the above-described transducer 1D in that the openings 15c are arranged more densely as they approach the membrane support portion 17.

[0060] Since the openings 15c of the transducer 1I are arranged more densely as they approach the membrane support portion 17, it is possible to provide a transducer 1I that can be largely displaced (bent) from the portion (base) near the connection portion where the vibration membrane 16a and the membrane support portion 17 are connected.

[0061] <Modification 10> A description will be given of the configuration of a transducer 1J according to Modification 10. The above description will be used to refer to the points common to Modification 10 and the transducer 1D shown in Figures 7 and 8, and only the points of difference will be described below.

[0062] 14 is a top view showing the structure of a transducer 1J according to Modification 10. The transducer 1J according to Modification 10 differs from the above-described transducer 1D in that the area fraction of the openings 15c is arranged to increase as it approaches the membrane support portion 17.

[0063] The transducer 1J is arranged so that the area fraction of the opening 15c increases as it approaches the membrane support portion 17, making it possible to provide a transducer 1J that can be largely displaced (bent) from the portion (base) near the connection portion where the vibration membrane 16a and the membrane support portion 17 are connected.

[0064] <Modification 11> A description will be given of the configuration of a transducer 1K according to Modification 11. The above description will be used to refer to the points common to Modification 11 and the transducer 1D shown in Figures 7 and 8, and only the points of difference will be described below.

[0065] 15 is a top view showing the structure of a transducer 1K according to Modification 11. The transducer 1K according to Modification 11 differs from the above-described transducer 1D in that the openings 15c are arranged more densely as they move away from the membrane support portion 17.

[0066] In the transducer 1K, the openings 15c are arranged more densely as they move away from the membrane support portion 17, so that it is possible to provide a transducer 1K that can cause a large displacement (warp) near the center of the vibration membrane 16a.

[0067] <Modification 12> A description will be given of the configuration of a transducer 1L according to Modification 12. The above description will be used for the points common to Modification 12 and the transducer 1D shown in Figures 7 and 8, and the following will describe the points that are different.

[0068] 16 shows a top view illustrating the structure of a transducer 1L according to Modification 12. The transducer 1L according to Modification 12 differs from the above-described transducer 1D in that the area fraction of the openings 15c increases with increasing distance from the membrane support portion 17.

[0069] The transducer 1L is arranged so that the area fraction of the opening 15c increases as it moves away from the membrane support portion 17, thereby providing a transducer 1L that can be largely displaced (warped) near the center of the vibration membrane 16a.

[0070] (Other Embodiments) As described above, several embodiments have been described, but the descriptions and drawings that form part of the disclosure are illustrative and should not be understood as limiting. Various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art from this disclosure. Thus, the embodiments include various embodiments not described herein.

[0071] For example, in a high-order vibration mode such as a frequency of 175 Hz, a transducer may be used in which, as shown in Fig. 17, a portion A where the displacement amount in the vibration direction of the vibrating membrane 16 is greatest has a plurality of openings 15 arranged more densely than other portions of the vibrating membrane 16. With this configuration, the rigidity of the vibrating membrane 16 at portion A of the vibration antinode of the vibrating membrane 16, which is the inflection point, can be reduced, thereby increasing the displacement amount of the vibrating membrane 16.

[0072] 18 , the portion A where the displacement of the vibrating membrane 16 in the vibration direction is maximum may be a transducer in which the plurality of openings are arranged more sparsely (including cases where no openings are provided) than in other portions of the vibrating membrane 16. Since the portion A where the displacement of the vibrating membrane 16 in the vibration direction is maximum varies depending on the vibration mode, the arrangement of the plurality of openings 15 in the vibrating membrane 16 needs to be adjusted appropriately. For example, the arrangement of the plurality of openings 15 can be adjusted by predicting the portion A where the displacement is maximum, which is obtained by analyzing device characteristics such as the natural frequency and damping characteristics. In the case of an ultrasonic transducer in which the vibrating membrane 16 and the piezoelectric element 10 are driven at a resonant frequency, the portion A can be set according to the resonant frequency.

[0073] Although the present specification has described a structure in which the vibrating membrane 16 is driven by the piezoelectric effect, a driving method using electrostatic force (Coulomb force) generated between the two electrodes 11, 12 may also be used. Furthermore, even in examples in which the openings 15 are described as through-holes, such as the transducer 1B shown in Fig. 5 and the transducer 1C shown in Fig. 6, the openings 15a may be non-through (have a bottom). Furthermore, any of the openings 15, 15a may be sparsely packed (including cases in which no openings are provided).

[0074] <Examples of Embodiments> Examples of embodiments are given below: The embodiments are not limited to the following examples.

[0075] (Supplementary Note 1) The transducer 1 has a piezoelectric element 10 including a pair of electrodes 11, 12 and a piezoelectric film 13 sandwiched between the pair of electrodes 11, 12, a film support portion 17, and a vibration film 16 supported by the film support portion 17 so as to be vibrable in the thickness direction of the piezoelectric element 10. A plurality of openings 15 are provided continuously penetrating the vibration film 16 from the piezoelectric element 10, and the shortest distance between two points facing each other across the center of the opening 15 in each of the plurality of openings 15 is 20 μm or less.

[0076] (Supplementary Note 2) The transducer 1A has a piezoelectric element 10 including a pair of electrodes 11, 12 and a piezoelectric film 13 sandwiched between the pair of electrodes 11, 12, a film support portion 17, and a vibration film 16 supported by the film support portion 17 so as to be vibrable in the thickness direction of the piezoelectric element 10. A plurality of openings 15a are provided which penetrate the piezoelectric element 10 and have bottom surfaces inside the vibration film 16.

[0077] (Supplementary Note 3) In the transducer 1 described in Supplementary Note 1, the opening 15 is any one selected from the group consisting of a circle with a diameter of 20 μm or less, an oval with a minor axis of 20 μm or less, an ellipse with a minor axis of 20 μm or less, and a rectangle with a minor side of 20 μm or less.

[0078] (Supplementary Note 4) In the transducer 1 described in Supplementary Note 1 or Supplementary Note 3, the opening 15 is any one selected from the group consisting of a circle with a diameter of 8 μm or more, an oval with a minor axis of 8 μm or more, an ellipse with a minor axis of 8 μm or more, and a rectangle with a minor side of 8 μm or more.

[0079] According to Supplementary Notes 1 to 4, the rigidity of the diaphragm 16 is reduced by the opening 15, making it more susceptible to vibration (warping). This makes it possible to obtain the transducers 1 and 1A that can increase the sound pressure while maintaining the diaphragm 16 at a desired strength (thickness) and preventing damage.

[0080] (Supplementary Note 5) In the transducers 1, 1A, 1B, 1C, 1E, 1F, 1G, and 1H described in any one of Supplementary Notes 1 to 4, the opening 15 is not formed within a predetermined range from the membrane support portion 17.

[0081] According to Appendix 5, since no openings 15 are formed within a predetermined range from the membrane support portion 17, the portion in question is less likely to bend, the radius of curvature is increased, the concentration of bending stress on the portion in question is alleviated, and breakage can be prevented, thereby obtaining transducers 1, 1A, 1B, 1C, 1E, 1F, 1G, and 1H.

[0082] (Supplementary Note 6) In the transducers 1E and 1F described in Supplementary Note 5, the vibration membrane 6 has a cantilever structure, and a plurality of openings 15, 15a are arranged densely from the free end side toward the membrane support part 17 on the base end side.

[0083] According to Supplementary Note 6, it is possible to obtain transducers 1E and 1F that can largely displace (bend) the vibrating membrane 6 from a portion (root) that is relatively close to the base end and exceeds the predetermined range.

[0084] (Appendix 7) In the transducer described in any one of Appendices 1 to 5, the plurality of openings 15, 15a are arranged more densely in part A where the displacement amount in the vibration direction of the vibrating membrane 16 is maximum in a predetermined vibration mode than in other parts of the vibrating membrane 16.

[0085] According to Supplementary Note 7, it is possible to obtain a transducer that can increase the displacement of the vibrating membrane 16 by reducing the rigidity of the vibrating membrane 16 at the antinode A of the vibration of the vibrating membrane 16, which is the inflection point.

[0086] 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L Transducer 2 Slit 10 Piezoelectric element 11, 12 Electrode 11a, 12a Electrode pad 13 Piezoelectric film 15, 15a, 15b, 15c Opening 16, 16a Vibration film 17 Film support portion

Claims

1. A transducer comprising: a piezoelectric element having a pair of electrodes and a piezoelectric membrane sandwiched between the pair of electrodes; a membrane support section; and a vibration membrane supported by the membrane support section so as to be capable of vibrating in the thickness direction of the piezoelectric element, wherein a plurality of openings are provided continuously penetrating the vibration membrane from the piezoelectric element, and the shortest distance between two points opposing each other across the center of each of the plurality of openings is 20 μm or less.

2. A transducer comprising: a piezoelectric element having a pair of electrodes and a piezoelectric membrane sandwiched between the pair of electrodes; a membrane support portion; and a vibration membrane supported by the membrane support portion so as to be capable of vibrating in the thickness direction of the piezoelectric element, the transducer having a plurality of openings penetrating the piezoelectric element and having a bottom surface inside the vibration membrane.

3. The transducer according to claim 1, wherein the opening is any one selected from the group consisting of a circle with a diameter of 20 μm or less, an oval with a minor axis of 20 μm or less, an ellipse with a minor axis of 20 μm or less, and a rectangle with a minor side of 20 μm or less.

4. The transducer according to claim 3, wherein the opening is any one selected from the group consisting of a circle with a diameter of 8 μm or more, an oval with a minor axis of 8 μm or more, an ellipse with a minor axis of 8 μm or more, and a rectangle with a minor side of 8 μm or more.

5. A transducer as claimed in claim 1 or 2, wherein the opening is not formed within a specified range from the membrane support portion.

6. A transducer as described in claim 5, wherein said vibration membrane has a cantilever structure, and said plurality of openings are arranged more densely from the free end side toward said membrane support part which is the base end side.

7. A transducer as claimed in claim 1 or 2, wherein the plurality of openings are arranged more densely in a portion where the amount of displacement in the vibration direction of the diaphragm is maximum in a predetermined vibration mode than in other portions of the diaphragm.

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