electroacoustic transducer

Abstract

To realize both of an excellent roll-off frequency characteristic and an excellent sensitivity characteristic.SOLUTION: An electroacoustic transducer (1) includes: an oscillation part (34); a slit (35); and an extension film (4). The oscillation part includes: a fixing end part (341); and a free-end part (342), and is provided so as to allow an oscillation in an aspect that the free-end part is moved along a directional axis (CA) by being extended in cantilever-like along an extension direction orthogonal to the directional axis toward the free-end part from the fixing end part. The slit is formed on both ends of the oscillation part in a width direction orthogonal to the directional axis and the extension direction. The extension film is provided to block the slit to a shaft direction along the directional axis. The slit includes: a wide width part (351) provided onto the free-end part side; and a narrow width part (352) formed narrower than the wide width part. The extension film is provided so as to block the wide width part while not blocking the narrow width part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electro-acoustic transducer. [Background technology]

[0002] The piezoelectric element described in Patent Document 1 includes a piezoelectric element portion, a support portion that supports the peripheral portion of the piezoelectric element portion, and a stretchable film that is more stretchable than the piezoelectric element portion. The stretchable film is provided in a vibration region inside the peripheral portion of the piezoelectric element portion. The vibration region of the piezoelectric element portion is provided with a slit that penetrates the vibration region in the thickness direction. The stretchable film is arranged to cover at least a portion of the opening of the slit in the vibration region and to integrate the vibration regions separated by the slit.

[0003] In this type of piezoelectric element having a cantilever structure with a slit in the piezoelectric film, the bending of the piezoelectric film or electrode film can increase the effective gap between the beams, resulting in a decrease in acoustic resistance. In this regard, according to the configuration described in Patent Document 1, even if a slit is provided in the vibration region, the provision of a stretchable film suppresses bending of the vibration region. Therefore, an increase in the gap between regions facing each other across the slit in the vibration region is suppressed. Furthermore, even if the vibration region is curved, the stretchable film can be arranged to cover at least a portion of the slit, thereby suppressing a decrease in acoustic resistance. Therefore, this configuration can suppress a decrease in the signal-to-noise ratio and sensitivity characteristics. Furthermore, the stretchable film has higher stretchability than the piezoelectric element portion. Therefore, the adverse effect of residual stress in the stretchable film on the resonant frequency can be suppressed. Furthermore, damage to the stretchable film due to vibration of the vibration region in the piezoelectric element portion is also suppressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 024865 Summary of the Invention [Problem to be solved by the invention]

[0005] In this type of configuration, it is known that as the opening area of ​​the slit increases, the roll-off frequency characteristics deteriorate. In this regard, the configuration described in Patent Document 1 attempts to suppress the deterioration of the roll-off frequency characteristics by reducing the opening area of ​​the slit by covering at least a portion of the slit with a stretchable film. On the other hand, increasing the covering area of ​​the slit suppresses deformation of the vibration region, which results in a decrease in sensitivity. The present invention has been made in consideration of the circumstances exemplified above. That is, the present invention provides a configuration that, for example, makes it possible to achieve both good roll-off frequency characteristics and good sensitivity characteristics. [Means for solving the problem]

[0006] The electroacoustic transducer (1) according to claim 1 comprises: a vibration section (34) having a fixed end (34a) and a free end (34b), extending in a cantilevered manner from the fixed end toward the free end along an extension direction perpendicular to a pointing axis (CA) so that the free end can vibrate in a manner that moves along the pointing axis; a slit (35) formed at both ends of the vibrating portion in a width direction perpendicular to the directional axis and perpendicular to the extension direction; Axial direction along the directional axis In plan view A stretchable film (4) provided to close the slit; and The slit has a wide portion (352) provided on the free end side and a narrow portion (351) formed narrower than the wide portion, The stretchable film is provided so as to close the wide portion while leaving the narrow portion unclosed. The electroacoustic transducer (1) according to claim 6 comprises: a vibration section (34) having a fixed end (34a) and a free end (34b), extending in a cantilevered manner from the fixed end toward the free end along an extension direction perpendicular to a pointing axis (CA) so that the free end can vibrate in a manner that moves along the pointing axis; a slit (35) formed at both ends of the vibrating portion in a width direction perpendicular to the directional axis and perpendicular to the extension direction; a through-hole portion (354) formed along an axial direction parallel to the orientation axis and arranged adjacent to the slit in an in-plane direction intersecting the axial direction so as to communicate with the slit on the free end side; The axial direction In plan view a stretchable film (4) that does not close the slit but closes the through-hole portion; It has.

[0007] In addition, in each section of the application documents, each element may be assigned a reference symbol in parentheses. In this case, the reference symbol merely indicates an example of the correspondence between the element and the specific configuration described in the embodiment described below. Therefore, the present invention is not limited in any way by the description of the reference symbol. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side cross-sectional view showing a schematic configuration of an electro-acoustic transducer according to an embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing a schematic configuration of the electro-acoustic transducer shown in FIG. 1 according to the first embodiment. [Figure 3] 1. FIG. 4 is a plan view showing a schematic configuration of a second embodiment of the electro-acoustic transducer shown in FIG. [Figure 4] FIG. 2 is a plan view showing a schematic configuration of a third embodiment of the electro-acoustic transducer shown in FIG. [Figure 5] FIG. 10 is a plan view showing a schematic configuration of a fourth embodiment of the electro-acoustic transducer shown in FIG. [Figure 6]FIG. 10 is a plan view showing a schematic configuration of a fifth embodiment of the electro-acoustic transducer shown in FIG. [Figure 7] FIG. 10 is a plan view showing a schematic configuration of a sixth embodiment of the electro-acoustic transducer shown in FIG. [Figure 8] 1. FIG. 4 is a plan view showing a schematic configuration of a seventh embodiment of the electro-acoustic transducer shown in FIG. [Figure 9] 1. FIG. 4 is a plan view showing a schematic configuration of an eighth embodiment of the electro-acoustic transducer shown in FIG. [Figure 10] 1. FIG. 4 is a side cross-sectional view showing a schematic configuration of a modified example of the stretchable film shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Embodiment) Hereinafter, embodiments of the present invention will be described with reference to the drawings. Incidentally, if various modifications applicable to one embodiment are inserted in the middle of a series of descriptions relating to that embodiment, understanding of that embodiment may be hindered. Therefore, the modifications will not be inserted in the middle of a series of descriptions relating to that embodiment, but will be described together after that. Furthermore, the descriptions of the drawings and the corresponding device configurations, functions, or operations described below are simplified for the purpose of concisely explaining the contents of the present invention and do not in any way limit the contents of the present invention. Therefore, it goes without saying that the exemplary configurations shown in the drawings do not necessarily correspond to the specific configurations actually manufactured and sold. In other words, unless expressly limited by the applicant in the prosecution history of this application, the present invention should not be construed as being limited by the descriptions of the drawings and the corresponding device configurations, functions, or operations described below.

[0010] (First embodiment) An electroacoustic transducer 1 according to a first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 corresponds to a cross-sectional view taken along line II in FIG. 2. For ease of explanation, a right-handed XYZ Cartesian coordinate system is set so that the Z axis is parallel to the directional axis CA, as shown in the figure. The directional axis CA is an imaginary line that serves as a reference for the directivity of the electroacoustic transducer 1 that transmits or receives sound waves or ultrasound waves, and may also be referred to as the "central directional axis." The directional axis CA typically corresponds to an imaginary line that indicates the axial center of a three-dimensional shape, such as a substantially conical or spindle-shaped shape, representing a range of directivity, e.g., a range in which a predetermined gain or a predetermined acoustic level can be obtained. Specifically, for example, the directional axis CA is the central axis of the sound pressure half-angle. Hereinafter, a direction along the directional axis CA, i.e., a direction parallel to the directional axis CA, will be referred to as the "axial direction." Therefore, the axial direction is a direction parallel to the Z axis in the drawings. A direction intersecting the axial direction, typically any direction perpendicular to the axial direction, will be referred to as the "in-plane direction." The "in-plane direction" is a direction parallel to the XY plane in the drawing. The "in-plane direction" may also be referred to as the "radial direction" in some cases. The "radial direction" is a direction perpendicular to the directional axis CA and moving away from the directional axis CA. In other words, the "radial direction" is the direction in which a half-ray extends when a half-ray is drawn in an imaginary plane perpendicular to the directional axis CA, starting from the intersection of the directional axis CA and the imaginary plane perpendicular to the directional axis CA. In other words, the "radial direction" is the radial direction of a circle drawn in an imaginary plane with the intersection of the directional axis CA and the imaginary plane perpendicular to the directional axis CA as its center. The "in-plane direction" may also be referred to as the "circumferential direction" in some cases. The "circumferential direction" is the circumferential direction of a circle drawn in an imaginary plane with the intersection of the directional axis CA and the imaginary plane perpendicular to the directional axis CA as its center. Furthermore, viewing the electro-acoustic transducer 1 and its components from above in FIG. 1 in a direction opposite to the Z axis is referred to as a "planar view." That is, the shape of a certain component in a "planar view" corresponds to the shape of the same component when it is mapped onto the XY plane in the drawing.

[0011] The electroacoustic transducer 1 has a configuration as a so-called piezoelectric MEMS microphone. MEMS is an abbreviation for Micro Electro Mechanical System. Specifically, as shown in FIG. 1 , the electroacoustic transducer 1 includes a support portion 2, a piezoelectric element portion 3, and a stretchable film 4.

[0012] The support portion 2 is formed in a cylindrical or annular shape surrounding the focusing axis CA. In this embodiment, the support portion 2 has a rectangular cylindrical or annular shape with the focusing axis CA as the central axis of symmetry. Specifically, the support portion 2 has a structure in which four flat wall members having a constant thickness and arranged parallel to the focusing axis CA are seamlessly joined together, and has a square shape in plan view. That is, the support portion 2 is configured so that its outer wall surface 21 is square in plan view. Furthermore, the cavity 23, which is a space surrounded by the inner wall surface 22 of the support portion 2, is square in plan view. An upper end surface 24, which is the end surface on one axial side of the support portion 2, i.e., the positive Z-axis side in the figure, is closed by the piezoelectric element portion 3. The support portion 2 may be formed, for example, from a ceramic such as alumina, a silicon-based semiconductor substrate, or the like.

[0013] The piezoelectric element portion 3 is formed in the shape of a thin plate with its thickness in the axial direction. That is, the pair of main surfaces of the piezoelectric element portion 3, the upper surface 30a and the lower surface 30b, are formed in a planar shape perpendicular to the directional axis CA. A "main surface" is a surface of a plate-shaped portion or member that is perpendicular to the plate thickness direction. The piezoelectric element portion 3 is fixedly supported by the support portion 2 by being joined at the peripheral portion of the lower surface 30b, i.e., the outer edge portion in the radial direction, to the upper end surface 24 of the support portion 2. In this embodiment, the piezoelectric element portion 3 is formed in a square shape in a plan view, corresponding to the rectangular cylindrical shape of the support portion 2.

[0014] The piezoelectric element part 3 is composed of a piezoelectric film 31 and an electrode film 32. In this embodiment, the piezoelectric film 31 is formed in the form of a thin film made of a piezoelectric material such as scandium aluminum nitride. The piezoelectric element part 3 has a multilayer structure in which a plurality of piezoelectric films 31 are stacked in the axial direction. Electrode films 32 made of thin metal films such as copper foil are provided on both sides of the piezoelectric film 31.

[0015] The piezoelectric element unit 3 has a fixed portion 33 and a vibrating portion 34. The fixed portion 33 is the peripheral portion of the piezoelectric element unit 3, i.e., the outer edge portion in the radial direction, and is fixed to the support unit 2. The vibrating portion 34 is located radially inward of the fixed portion 33. The vibrating portion 34 is formed in a cantilever shape extending from the fixed portion 33 toward the directional axis CA. That is, the vibrating portion 34 has a fixed end portion 34a and a free end portion 34b. The vibrating portion 34, which is the vibration region of the piezoelectric element unit 3, extends in a cantilever shape from the fixed end portion 34a to the free end portion 34b in an extension direction perpendicular to the directional axis CA, so that the free end portion 34b can vibrate by moving along the directional axis CA. The piezoelectric element unit 3 also has multiple vibrating portions 34. In this embodiment, as shown in FIG. 2, four vibrating portions 34 are arranged at equal intervals in the circumferential direction. 2, the stretchable film 4 is shown by imaginary lines to make it easier to see the shapes of the vibration section 34 and the slits 35 described later in a plan view. The upper vibration section 34 in the figure is formed so that the extension direction is the negative Y-axis direction and the X-axis direction is the width direction. The lower vibration section 34 in the figure is formed so that the extension direction is the positive Y-axis direction and the X-axis direction is the width direction. The right vibration section 34 in the figure is formed so that the extension direction is the negative X-axis direction and the Y-axis direction is the width direction. The left vibration section 34 in the figure is formed so that the extension direction is the positive X-axis direction and the Y-axis direction is the width direction.

[0016] Slits 35 are provided on both ends of the vibration portion 34 in the width direction of the vibration portion 34, which is orthogonal to the directional axis CA and orthogonal to the extension direction of the vibration portion 34. The slits 35 are formed so as to penetrate the piezoelectric element portion 3 in the thickness direction. That is, the vibration portion 34 is provided between a pair of slits 35. In this embodiment, since four vibration portions 34 are provided, four slits 35 are provided in the piezoelectric element portion 3, each extending from a corner of the square shape of the piezoelectric element portion 3 toward the directional axis CA in a plan view.

[0017] The slit 35 has a narrow portion 351 provided on the fixed end 34a side, i.e., on the outer side, and a wide portion 352 provided on the free end 34b side, i.e., on the inner side. The narrow portion 351 is narrower than the wide portion 352. In this embodiment, the narrow portion 351 and the wide portion 352 are formed to have a constant width. That is, an outer edge 353, which is the edge of the wide portion 352 on the narrow portion 351 side, i.e., the outer edge in the radial direction, is formed in a straight line perpendicular to the extension direction of the narrow portion 351 in a plan view. In other words, the narrow portion 351 and the wide portion 352 are connected to each other at a step provided at the outer edge 353. The through-hole portion 354, which penetrates the piezoelectric element unit 3 along the directional axis CA, is provided as a square region in a plan view where two rectangular virtual regions, each connecting a pair of wide portions 352 facing each other across the directional axis CA, overlap each other. That is, the through-hole portion 354 is disposed adjacent to the slit 35 in the in-plane direction so as to communicate with the slit 35 on the free end portion 34b side (i.e., the side in the extension direction from the fixed end portion 34a of the vibrating portion 34). The through-hole portion 354 is provided in the center portion in the in-plane direction of the piezoelectric element portion 3. The wide width portion 352 extends from the through-hole portion 354 toward the narrow width portion 351.

[0018] The stretchable film 4 is attached to the piezoelectric element unit 3 so as to close the slit 35 in the axial direction. The stretchable film 4 has higher stretchability than the piezoelectric element unit 3. Specifically, the stretchable film 4 is formed of a synthetic resin such as polyimide resin or polybenzoxazole resin. In this embodiment, the stretchable film 4 is provided so as to close only a portion of the slit 35 in the extension direction, rather than the entire slit 35. That is, as shown in FIG. 2 , the stretchable film 4 is provided so as not to close the narrow width portion 351 but to close the wide width portion 352. Specifically, the stretchable film 4 is provided so as not to close the end of the wide width portion 352 on the narrow width portion 351 side, i.e., the outer edge 353 and its vicinity. More specifically, a gap G is formed between the outer edge 353 and the stretchable film 4. The gap G is preferably formed to be equal to or smaller than the width of the narrow width portion 351. The stretchable film 4 is provided from the upper surface 30a side of the piezoelectric element portion 3 so as to close the through-hole portion 354 and the portion of the wide portion 352 that is inside the outer edge 353 in the radial direction.

[0019] In this embodiment, the stretchable film 4 fills the inside of the slit 35 until it reaches the lower surface 30b of the piezoelectric element portion 3. Also, notches 401 are formed in the stretchable film 4. The notches 401 are provided on both sides of the wide portion 352. That is, the stretchable film 4 is formed in a substantially X-shape in plan view, corresponding to the substantially X-shaped hole shape in plan view formed by the four wide portions 352 and the through-hole portions 354.

[0020] (effect) The operation of the configuration of this embodiment will be outlined below, along with the effects achieved by the configuration, with reference to the accompanying drawings. The electroacoustic transducer 1 according to this embodiment has a function of converting strain caused by bending when the free end 34b of the vibrating portion 34 moves along the directional axis CA into a voltage between a pair of electrode films 32 provided on both sides of the piezoelectric film 31. That is, for example, bending vibration of the vibrating portion 34 due to reception of sound waves or ultrasonic waves is extracted as an inter-electrode voltage. Alternatively, for example, application of an inter-electrode voltage from an external device causes the vibrating portion 34 to bend and vibrate, thereby transmitting sound waves or ultrasonic waves.

[0021] In the configuration of this embodiment, even if the fixed portion 33, which is the peripheral portion of the piezoelectric element portion 3, is fixed to the support portion 2, the provision of the slits 35 makes it possible to suppress changes in the resonant frequency, a decrease in the S / N ratio, and a decrease in sensitivity characteristics due to residual stress in the vibrating portion 34. Furthermore, by using the stretchable film 4 to cover the opening of the slits 35, the vibrating portion 34 separated by the slits 35 is integrated. This makes it possible to suppress a decrease in acoustic resistance due to an increase in the effective gap between the vibrating portions 34 caused by bending of the piezoelectric film 31 or the electrode film 32 resulting from the cantilever structure of the vibrating portion 34. Furthermore, since the opening area of ​​the slits 35 is reduced, deterioration of the roll-off frequency characteristics is suppressed. Therefore, this configuration makes it possible to suppress a decrease in the S / N ratio and sensitivity characteristics.

[0022] Here, if the coverage area of ​​the slit 35 is increased, deformation of the vibrating portion 34 is suppressed, which causes a decrease in sensitivity. In this regard, by forming the portion of the slit 35 that is blocked by the stretchable film 4 as the wide portion 352, which is wider than the narrow portion 351 that is the portion that is not blocked by the stretchable film 4, it is possible to effectively suppress a decrease in sensitivity characteristics. For example, when the electroacoustic transducer 1 according to this embodiment is used as a MEMS microphone for voice recognition, it is preferable to set the width of the narrow portion 351 so that the roll-off frequency is 100 Hz or less. Furthermore, let L be the length of the beam in the cantilever structure of the vibrating portion 34, H be the thickness of the vibrating portion 34, g be the width of the narrow portion 351, and R be the slit resistance. slit In this case, it is preferable that the width g of the narrow portion 351 be set so as to satisfy the following formula.

number

[0023] In the configuration of this embodiment, unlike the configuration described in Patent Document 1, a portion of the wide portion 352 of the slit 35 is not blocked by the stretchable film 4 and is open in the axial direction. That is, the stretchable film 4 is provided so as not to block the end of the wide portion 352 on the narrow portion 351 side. Furthermore, a gap G equal to or smaller than the width of the narrow portion 351 is formed between the outer edge 353 of the wide portion 352 and the stretchable film 4. This makes it possible to achieve both good roll-off frequency characteristics and good sensitivity characteristics.

[0024] In this embodiment, the stretchable film 4 is made of synthetic resin. By forming the stretchable film 4 from a synthetic resin that is more stretchable than the material constituting the vibrating section 34, i.e., a material with a low Young's modulus, it is possible to effectively suppress a decrease in sensitivity. In particular, by forming the stretchable film 4 from a polyimide resin or polybenzoxazole resin, which has excellent heat resistance and chemical resistance, process adaptability and reliability are improved. Furthermore, by forming the vibrating section 34 from scandium aluminum nitride, piezoelectricity is improved, thereby improving sensitivity characteristics.

[0025] Second Embodiment The second embodiment will be described below with reference to FIG. 3. In the following description of the second embodiment, differences from the first embodiment will be mainly described. In addition, identical or equivalent parts in the first and second embodiments are denoted by the same reference numerals. Therefore, in the following description of the second embodiment, the description of the first embodiment can be appropriately applied to components having the same reference numerals as those in the first embodiment, unless there is a technical contradiction or a special additional explanation. The same applies to the other embodiments described below.

[0026] In the first embodiment described above, the stretch film 4 is provided with a notch 401 in order to optimize the sensitivity characteristics. However, the present invention is not limited to this aspect. That is, the notch 401 in the stretch film 4 shown in FIG. 2 may be omitted. Therefore, in this embodiment, as shown in FIG. 3, the stretch film 4 is formed in a rectangular shape, specifically a square shape, in a plan view. Even with this configuration, the same effects as in the first embodiment described above can be achieved. Similarly, the stretch film 4 may be formed in a polygonal shape in a plan view.

[0027] (Third embodiment) A third embodiment will be described below with reference to FIG. 4. In this embodiment, the stretch film 4 is formed in an elliptical shape, specifically a circular shape, in a plan view. This configuration can also achieve the same effects as the first embodiment. Note that in this embodiment, the cutouts 401 in the stretch film 4 shown in FIG. 2 are omitted. However, in the configuration shown in FIG. 4, cutouts 401 as shown in FIG. 2 may be provided in the stretch film 4 at the 0 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions in the figure.

[0028] (Fourth embodiment) A fourth embodiment will be described below with reference to FIG. 5. In this embodiment, the narrow width portion 351 is formed so that its width varies. Specifically, the narrow width portion 351 is formed in a tapered shape such that its width increases continuously, i.e., linearly, toward the directional axis CA. On the other hand, the wide width portion 352 is formed to have a constant width. This configuration can also achieve the same effects as the first embodiment. Note that, contrary to the configuration shown in FIG. 5, the narrow width portion 351 may be formed to have a constant width while the width of the wide width portion 352 varies.

[0029] Fifth Embodiment A fifth embodiment will be described below with reference to FIG. 6 . In this embodiment, the wide portion 352 and the through-hole portion 354 are integrated. That is, the wide portion 352 is formed by the through-hole portion 354 that is rectangular, i.e., square, in plan view. In this case, a recess 402 that opens toward the narrow portion 351 is provided in the stretch film 4 at a position corresponding to the connection between the narrow portion 351 and the wide portion 352. By providing this recess 402, the end of the narrow portion 351 that connects to the wide portion 352 and the portion of the wide portion 352 near the connection with the narrow portion 351 are not blocked by the stretch film 4 and are open in the axial direction. This makes it possible to achieve both good roll-off frequency characteristics and good sensitivity characteristics.

[0030] (Sixth embodiment) A sixth embodiment will be described below with reference to FIG. 7 . In this embodiment, the shape of the through-hole 354 constituting the wide portion 352 in the fifth embodiment in plan view is changed to an elliptical shape, specifically a circular shape. Even with this configuration, the same effects as those of the fifth embodiment can be achieved. Note that FIG. 7 can be considered to disclose a configuration in which the narrow portion 351 is formed to have a constant width, while the width of the wide portion 352 varies. Furthermore, the shape of the through-hole 354 constituting the wide portion 352 in plan view is not limited to a rectangular or elliptical shape as in the above examples, and may be, for example, a polygonal shape.

[0031] Seventh Embodiment The seventh embodiment will be described below with reference to FIG. 8 . The configuration of this embodiment is the same as that of the first embodiment, except for the configuration of the stretchable film 4. In this embodiment, the stretchable film 4 has a cutout 403. The cutout 403 is provided so as to penetrate the stretchable film 4 along the axial direction. Specifically, the cutout 403 is configured as a groove or slit formed in the stretchable film 4 along the axial direction. The cutout 403 is also provided so as to open toward the narrow width portion 351. That is, the cutout 403 is disposed so as to be continuous with the narrow width portion 351 in a plan view. This configuration makes it possible to effectively suppress a decrease in sensitivity due to the stretchable film 4 suppressing deformation of the vibrating unit 34. Note that, in order to suppress deterioration of the roll-off frequency characteristics, it is preferable that the cutout 403 have a width approximately equal to or smaller than that of the narrow width portion 351.

[0032] Eighth Embodiment An eighth embodiment will be described below with reference to FIG. 9 . In this embodiment, the slit 35 has only a narrow portion 351. The narrow portion 351 may be formed to have a constant width as shown in FIG. 9 , or may be formed in a tapered shape as shown in FIG. 5 . Meanwhile, the through-hole portion 354 is disposed adjacent to the slit 35 in the in-plane direction so as to communicate with the slit 35 on the free end portion 34b side, i.e., on the extension direction side of the vibration portion 34. Furthermore, in the exemplary configuration shown in FIG. 9 , the through-hole portion 354 is formed to include a recess R that opens toward the extension direction (i.e., toward the directional axis CA) at the free end portion 34b. In other words, the through-hole portion 354 is formed in a generally cross shape in the figure so as not to overlap with the slit 35 (i.e., the narrow portion 351), which is formed in a generally X-shape in the figure. The recess R may be rectangular as shown in FIG. 9 , semicircular, or polygonal. The stretchable film 4 is provided so as to close the through-hole 354 while not closing the slit 35 in the axial direction parallel to the directional axis CA. The stretchable film 4 may be provided so as to cover almost the entire through-hole 354 in the width direction of the vibrating section 34. Alternatively, the stretchable film 4 may expose both ends of the through-hole 354 in the width direction of the vibrating section 34 without covering them. With such a configuration, the same effects as those of the above embodiments can be achieved.

[0033] 2, the wide portion 352 of the slit 35 can also be understood as part of the through-hole portion 354. Therefore, in the first embodiment shown in FIG. 2, the through-hole portion 354 including the wide portion 352 can also be interpreted as being disposed adjacent to the slit 35 (i.e., the narrow portion 351) in the in-plane direction. The stretchable film 4 can also be interpreted as being provided so as to close the through-hole portion 354 including the wide portion 352 while not closing the slit 35 (i.e., the narrow portion 351) in the axial direction parallel to the directional axis CA. The same applies to the second embodiment shown in FIG. 3 to the seventh embodiment shown in FIG. 8. In this case, the fifth embodiment shown in FIG. 6 corresponds to the case where the recess R shown in FIG. 9 is triangular.

[0034] (Variation) The present invention is not limited to the above-described embodiment. Therefore, the above-described embodiment can be modified as appropriate. Representative modifications will be described below. In the following description of the modifications, differences from the above-described embodiment will be mainly described. Furthermore, the same reference numerals are used for parts that are identical or equivalent to each other in the above-described embodiment and the modifications. Therefore, in the following description of the modifications, the description of the above-described embodiment can be used as appropriate for components that have the same reference numerals as the above-described embodiment, unless there is a technical contradiction or special additional explanation.

[0035] The present invention is not limited to the specific device configurations described in the above embodiments. That is, as mentioned above, the description of the above embodiments has been simplified to concisely explain the contents of the present invention. For this reason, illustrations and descriptions of components that are normally provided in products that are actually manufactured and sold, such as casings, bonding materials, terminals, and wiring, are appropriately omitted in the above embodiments and corresponding drawings.

[0036] The support portion 2 may have a shape such as a cylindrical shape, an elliptical shape, a triangular shape, a pentagonal shape, a hexagonal shape, or an octagonal shape surrounding the pointing axis CA. Alternatively, the support portion 2 may have a shape such as a circular ring shape, an elliptical ring shape, a triangular ring shape, a pentagonal ring shape, a hexagonal ring shape, or an octagonal ring shape surrounding the pointing axis CA. Similarly, the piezoelectric element portion 3 may have a shape such as a circular shape, an elliptical shape, a triangular shape, a pentagonal shape, a hexagonal shape, or an octagonal shape in a plan view.

[0037] In the above embodiment, the piezoelectric element portion 3 is fixed to the upper end surface 24 of the support portion 2, but the present invention is not limited to this. That is, for example, the outer edge of the piezoelectric element portion 3 in the in-plane direction or the radial direction may be fixed by a groove, an adhesive layer, or the like provided on the inner wall surface 22 of the support portion 2.

[0038] There is no particular limitation on the number of vibration parts 34 provided in the piezoelectric element part 3. That is, for example, the piezoelectric element part 3 may have a pair of vibration parts 34 facing each other, similar to the configuration described in International Publication No. 2007 / 060768. Alternatively, for example, the piezoelectric element part 3 may have three or five or more vibration parts 34.

[0039] The stretchable film 4 may be formed as a flat film having a constant thickness bonded onto the upper surface 30a of the piezoelectric element part 3. That is, the stretchable film 4 does not need to penetrate into the slit 35 in the axial direction, i.e., the thickness direction of the piezoelectric element part 3, and may be provided so as to cover the slit 35 from the outside. Furthermore, the stretchable film 4 is not limited to being provided on the upper surface 30a of the piezoelectric element part 3. That is, for example, the stretchable film 4 may be provided on the lower surface 30b of the piezoelectric element part 3.

[0040] 2 and the like, outer edge 353 of wide portion 352 may be formed in a curved shape in plan view, or may be formed in a straight line inclined with respect to the extension direction of narrow portion 351. Further, wide portion 352 may be formed in a tapered shape whose width increases as it approaches directional axis CA. There are no other particular limitations on the planar shape of slit 35.

[0041] As shown in FIG. 10, the stretchable membrane 4 may have a membrane through-hole 404 penetrating in the axial direction. The number of membrane through-holes 404 may be one or more. The shape of the membrane through-hole 404 in plan view may also be circular, elliptical, or polygonal. When multiple membrane through-holes 404 are provided, there are no particular limitations on their arrangement in the in-plane direction. Note that the area of ​​the membrane through-hole 404 (for example, the total area when multiple membrane through-holes 404 are provided) is preferably equal to or less than the area of ​​the narrow width portion 351 in order to maintain good roll-off frequency characteristics.

[0042] In the above description, multiple components that are formed seamlessly together may be formed by bonding separate members together. Similarly, multiple components that are formed by bonding separate members together may be formed seamlessly together.

[0043] In the above description, multiple components that are made of the same material may be made of different materials, and similarly, multiple components that are made of different materials may be made of the same material.

[0044] It goes without saying that the elements constituting the above-described embodiments are not necessarily essential unless they are particularly clearly stated as essential or are considered to be clearly essential in principle. Furthermore, when numerical values ​​such as the number, value, amount, range, etc. of components are mentioned, the present invention is not limited to those specific numbers unless they are particularly clearly stated as essential or are clearly limited to specific numbers in principle. Similarly, when the shape, direction, positional relationship, etc. of components are mentioned, the present invention is not limited to those shapes, directions, positional relationship, etc. unless they are particularly clearly stated as essential or are clearly limited to specific shapes, directions, positional relationship, etc. in principle.

[0045] The modified examples are not limited to the above examples. That is, for example, multiple embodiments may be applied in combination. In other words, a part of one embodiment may be combined with a part of another embodiment. There are no particular limitations on the number or manner in which multiple embodiments are combined. Furthermore, any one of the multiple embodiments and any one of the multiple modified examples may be combined with each other as long as there is no technical contradiction. Similarly, one of the multiple modified examples may be combined with another one of the multiple modified examples as long as there is no technical contradiction.

[0046] (Disclosure details) As is clear from the above description of the embodiments and modifications, this specification discloses at least the following matters. [Claim 1] An electroacoustic transducer (1), a vibration section (34) having a fixed end (34a) and a free end (34b), extending in a cantilevered manner from the fixed end toward the free end along an extension direction perpendicular to a pointing axis (CA) so that the free end can vibrate in a manner that moves along the pointing axis; a slit (35) formed at both ends of the vibrating portion in a width direction perpendicular to the directional axis and perpendicular to the extension direction; a stretchable film (4) provided to close the slit in an axial direction along the orientation axis; and The slit has a wide portion (352) provided on the free end side and a narrow portion (351) formed narrower than the wide portion, The stretchable film is provided so as to close the wide portion while not closing the narrow portion. Electroacoustic transducer. [Claim 2] The wide portion and / or the narrow portion are formed to have a constant width. 2. The electroacoustic transducer according to claim 1. [Claim 3] The stretchable film is provided so as not to close the end of the wide portion on the narrow portion side. 3. The electroacoustic transducer according to claim 1 or 2. [Claim 4] A gap (G) equal to or smaller than the width of the narrow width portion is formed between the outer edge (353) of the wide width portion, which is the edge of the narrow width portion on the narrow width portion side, and the stretchable film. 4. The electroacoustic transducer according to claim 3. [Claim 5] The stretchable film has a defect (402) penetrating the stretchable film along the axial direction, The cutout portion is provided so as to open toward the narrow width portion. 5. The electroacoustic transducer according to claim 1. [Claim 6] An electroacoustic transducer (1), a vibration section (34) having a fixed end (34a) and a free end (34b), extending in a cantilevered manner from the fixed end toward the free end along an extension direction perpendicular to a pointing axis (CA) so that the free end can vibrate in a manner that moves along the pointing axis; a slit (35) formed at both ends of the vibrating portion in a width direction perpendicular to the directional axis and perpendicular to the extension direction; a through-hole portion (354) formed along an axial direction parallel to the orientation axis and arranged adjacent to the slit in an in-plane direction intersecting the axial direction so as to communicate with the slit on the free end side; a stretchable film (4) that does not close the slit in the axial direction but closes the through-hole portion; having Electroacoustic transducer. [Claim 7] The through-hole portion includes a recess (R) provided at the free end portion so as to open toward the extension direction. 7. The electroacoustic transducer according to claim 6. [Claim 8] The stretchable membrane has a membrane through-hole (404) penetrating in the axial direction. 8. The electroacoustic transducer according to claim 1. [Claim 9] The stretchable film is formed from a synthetic resin. 9. The electroacoustic transducer according to claim 1. [Claim 10] The stretchable film is formed from a polyimide resin or a polybenzoxazole resin. 10. The electroacoustic transducer according to claim 9. [Claim 11] The vibration part is formed of scandium aluminum nitride, 11. The electroacoustic transducer according to claim 1. [Explanation of symbols]

[0047] 1. Electroacoustic transducer 3 Piezoelectric element part 34 Vibration unit 34a Fixed end 34b Free end 35 Slit 351 Narrow section 352 Wide section 4 Stretch membrane CA orientation axis

Claims

1. An electroacoustic transducer (1), a vibration section (34) having a fixed end (34a) and a free end (34b), and extending in a cantilevered manner from the fixed end toward the free end along an extension direction perpendicular to a pointing axis (CA), so that the free end can vibrate in a manner that moves along the pointing axis; A slit (35) formed at both ends of the vibration part in a width direction perpendicular to the directional axis and perpendicular to the extension direction; a stretchable film (4) provided to close the slit in a plan view seen in an axial direction along the directional axis; and The slit has a wide portion (352) provided on the free end side and a narrow portion (351) formed narrower than the wide portion, The stretchable film is provided so as to close the wide portion while not closing the narrow portion. Electroacoustic transducer.

2. The wide portion and / or the narrow portion are formed to have a constant width.

2. The electroacoustic transducer according to claim 1.

3. The stretchable film is provided so as not to close the end of the wide portion on the narrow portion side.

2. The electroacoustic transducer according to claim 1.

4. A gap (G) equal to or smaller than the width of the narrow width portion is formed between the outer edge (353) of the wide width portion, which is the edge on the narrow width portion side of the wide width portion, and the stretchable film.

4. The electroacoustic transducer according to claim 3.

5. The stretchable film has a defect (403) penetrating the stretchable film along the axial direction, The cutout portion is provided so as to open toward the narrow width portion.

2. The electroacoustic transducer according to claim 1.

6. An electroacoustic transducer (1), a vibration section (34) having a fixed end (34a) and a free end (34b), and extending in a cantilevered manner from the fixed end toward the free end along an extension direction perpendicular to a pointing axis (CA), so that the free end can vibrate in a manner that moves along the pointing axis; A slit (35) formed at both ends of the vibration part in a width direction perpendicular to the directional axis and perpendicular to the extension direction; a through-hole portion (354) formed along an axial direction parallel to the orientation axis and arranged adjacent to the slit in an in-plane direction intersecting the axial direction so as to communicate with the slit on the free end side; a stretchable film (4) that does not close the slit in a plan view in the axial direction but closes the through-hole portion; having Electroacoustic transducer.

7. The through-hole portion includes a recess (R) provided at the free end portion so as to open toward the extension direction.

7. The electroacoustic transducer according to claim 6.

8. The stretchable membrane has a membrane through-hole (404) penetrating in the axial direction.

7. The electroacoustic transducer according to claim 1 or 6.

9. The stretchable film is formed from a synthetic resin.

7. The electroacoustic transducer according to claim 1 or 6.

10. The stretchable film is formed from a polyimide resin or a polybenzoxazole resin.

10. The electro-acoustic transducer according to claim 9.

11. The vibration part is formed of scandium aluminum nitride, 7. The electroacoustic transducer according to claim 1 or 6.

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