Piezoelectric device

Abstract

To provide a piezoelectric device capable of appropriately deforming a piezoelectric film in response to acoustic pressure.SOLUTION: The piezoelectric device includes: a piezoelectric film having a first main surface, a second main surface opposite the first main surface, and a plurality of slits each extending from the first main surface to the second main surface and forming two or more annular rows; a holding portion holding the outer edge of the piezoelectric film; a first electrode pattern covering the area between the plurality of slits on the first main surface; and a second electrode pattern covering the area between the plurality of slits on the second main surface.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] FIELD Embodiments herein relate to piezoelectric devices. [Background technology]

[0002] In a piezoelectric device, when the piezoelectric film is subjected to acoustic pressure, the film distorts, generating a voltage within the film according to the amount of distortion. In a piezoelectric device, a signal corresponding to the acoustic pressure can be obtained by extracting the voltage change in the piezoelectric film as a signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 024865 Summary of the Invention [Problem to be solved by the invention]

[0004] In a piezoelectric device, in order to improve the acoustic pressure detection characteristics of a piezoelectric film, it is desirable to appropriately distort the piezoelectric film in response to acoustic pressure.

[0005] An object of the present invention is to provide a piezoelectric device that can appropriately distort a piezoelectric film in response to acoustic pressure. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a piezoelectric device according to one aspect of the present invention comprises a piezoelectric film having a first main surface, a second main surface opposite the first main surface, and a plurality of slits, each of which penetrates from the first main surface to the second main surface and forms two or more annular rows; a holding portion that holds the outer edge of the piezoelectric film; a first electrode pattern that covers the area between the plurality of slits on the first main surface; and a second electrode pattern that covers the area between the plurality of slits on the second main surface. [Effects of the Invention]

[0007] According to the present invention, the piezoelectric film can be appropriately distorted in response to acoustic pressure. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view showing a configuration of a piezoelectric device according to an embodiment. [Figure 2] FIG. 1 is a plan view showing a configuration of a piezoelectric device according to an embodiment. [Figure 3] FIG. 1 is a cross-sectional view showing a configuration of a piezoelectric device according to an embodiment. [Figure 4] FIG. 1 is a cross-sectional view showing a configuration of a piezoelectric device according to an embodiment. [Figure 5] 3A and 3B are cross-sectional views in a planar direction showing the configuration of an electrode pattern and a piezoelectric film in the embodiment. [Figure 6] FIG. 10 is a plan view showing the configuration of a piezoelectric device according to a first modified example of the embodiment. [Figure 7] FIG. 10 is a plan view showing the configuration of a piezoelectric device according to a second modified example of the embodiment. [Figure 8] FIG. 10 is a plan view showing the configuration of a piezoelectric device according to a third modified example of the embodiment. [Figure 9] FIG. 10 is a plan view showing the configuration of a piezoelectric device according to a fourth modified example of the embodiment. [Figure 10] FIG. 10 is a plan view showing the configuration of a piezoelectric device according to a fifth modified example of the embodiment. [Figure 11] FIG. 13 is a cross-sectional view in a planar direction showing the configuration of an electrode pattern and a piezoelectric film in a sixth modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the piezoelectric device will be described in detail with reference to the drawings. In the following embodiments, parts with the same reference numerals perform similar operations, and redundant description will be omitted as appropriate.

[0010] (Embodiment) The piezoelectric device according to the embodiment has a piezoelectric film, and when the piezoelectric film is subjected to acoustic pressure, the piezoelectric film distorts, a voltage is generated within the piezoelectric film according to the amount of distortion, and the voltage change in the piezoelectric film is output as a signal, but the device is designed to appropriately distort the piezoelectric film in response to acoustic pressure.

[0011] The piezoelectric device 1 can be configured as shown in FIGS. 1 to 4. FIG. 1 is a perspective view showing the configuration of a piezoelectric device according to an embodiment. FIG. 2 is a plan view showing the configuration of a piezoelectric device according to an embodiment. FIG. 3 is a cross-sectional view showing the configuration of a piezoelectric device according to an embodiment. FIG. 4 is a cross-sectional view showing the configuration of a piezoelectric device according to an embodiment.

[0012] The piezoelectric device 1 includes piezoelectric films 2 and 3, electrode patterns 4, 5, and 6, dummy electrode patterns 7, 8, and 9, and a holder 10.

[0013] In the following description, the direction perpendicular to the main surface 2a of the piezoelectric film 2 is defined as the Z direction, and two directions perpendicular to the Z direction in a plane perpendicular to the Z direction are defined as the X direction and the Y direction.

[0014] In the piezoelectric device 1, a holding portion 10, a piezoelectric film 3, and a piezoelectric film 2 are stacked in this order in the Z direction. The holding portion 10 holds the outer edge of the piezoelectric film 3. The piezoelectric film 2 covers the piezoelectric film 3 on the side opposite the holding portion 10 in the Z direction.

[0015] The holding portion 10 has a rectangular frame shape when viewed in the XY plane. The holding portion 10 has a main surface 10a on the +Z side. The piezoelectric film 3 extends in the XY directions, has a main surface 3a on the +Z side, and has a main surface 3b on the -Z side. The piezoelectric film 2 extends in the XY directions, has a main surface 2a on the +Z side, and has a main surface 2b on the -Z side.

[0016] The main surface 10a of the holding portion 10 contacts the vicinity of the edge of the main surface 3b of the piezoelectric film 3. In this way, the holding portion 10 holds the outer edge of the piezoelectric film 3. The piezoelectric film 2 covers the piezoelectric film 3 up to the vicinity of the outer edge. In this way, the holding portion 10 holds the outer edge of the piezoelectric film 2 via the piezoelectric film 3.

[0017] The piezoelectric films 2 and 3 may each be formed of any piezoelectric material having a piezoelectric effect, including AlN, ScAlN, ZnO, PZT (Pb(Zr,Ti)O3: zinc zirconate titanate), KN (KNbO3: potassium niobate), LN (LiNbO3: lithium niobate), KNN ((K,Na)NbO3), and BaTiO3.

[0018] The main surface 2b of the piezoelectric film 2 covers the main surface 3a of the piezoelectric film 3. As a result, in the piezoelectric device 1, a laminate SST (see FIG. 4) is formed in which multiple piezoelectric films 2 and 3 are stacked in the Z direction. The laminate SST functions as a piezoelectric element. The laminate SST forms a bimorph structure in which the multiple piezoelectric films 2 and 3 are sandwiched between multiple electrode patterns 4, 5, and 6 in the Z direction.

[0019] The piezoelectric films 2 and 3 have a plurality of slits 21 and a plurality of slits 22 .

[0020] As shown in FIGS. 5(a) to 5(c), each slit 21 is formed in common in the piezoelectric film 2 and the piezoelectric film 3. Each slit 22 is formed in common in the piezoelectric film 2 and the piezoelectric film 3. FIG. 5 is a cross-sectional view in a planar direction showing the configuration of the electrode patterns and the piezoelectric film. FIG. 5(a) is an XY cross-sectional view of FIG. 3 taken along line CC, showing the XY cross-sectional configuration of the electrode patterns 4_1 to 4_8 and the piezoelectric film 2. FIG. 5(b) is an XY cross-sectional view of FIG. 3 taken along line DD, showing the XY cross-sectional configuration of the piezoelectric film 2. FIG. 5(c) is an XY cross-sectional view of FIG. 3 taken along line EE, showing the XY cross-sectional configuration of the electrode patterns 5_1 to 5_8 and the piezoelectric film 3.

[0021] The plurality of slits 21 form two or more annular rows. Figures 1 and 2 show an example in which the plurality of slits 21 form three annular rows.

[0022] That is, slits 21_(2,1) to 21_(2,8) are arranged radially outwardly spaced apart from slits 21_(1,1) to 21_(1,8). Slits 21_(3,1) to 21_(3,8) are arranged radially outwardly spaced apart from slits 21_(2,1) to 21_(2,8).

[0023] Of the three annular rows, slits 21_(1,1) to 21_(1,8) form the first annular row from the inside. In the first annular row from the inside, slits 21_(1,1) to 21_(1,8) are arranged at a substantially uniform pitch in the circumferential direction. Slits 21_(1,1) to 21_(1,8) are spaced apart from one another with substantially uniform clearances in the circumferential direction.

[0024] The length of each of the slits 21_(1,1) to 21_(1,8) corresponds to one of the electrode patterns 4, 5, and 6, for example, a length corresponding to a central angle of 45 degrees. The width of each of the slits 21_(1,1) to 21_(1,8) may be approximately constant in the circumferential direction. A virtual line connecting the midpoints of each of the slits 21_(1,1) to 21_(1,8) in the radial direction is referred to as an axis. The curvature of the axis of each of the slits 21_(1,1) to 21_(1,8) may be approximately constant in the circumferential direction.

[0025] The slits 21_(2,1) to 21_(2,8) form the second annular row from the inside. In the second annular row from the inside, the slits 21_(2,1) to 21_(2,8) are arranged at a substantially uniform pitch in the circumferential direction. The slits 21_(2,1) to 21_(2,8) are spaced apart from one another with a substantially uniform clearance in the circumferential direction.

[0026] The length of each of the slits 21_(2,1) to 21_(2,8) corresponds to one of the electrode patterns 4, 5, and 6, for example, a length corresponding to a central angle of 45 degrees. The width of each of the slits 21_(2,1) to 21_(2,8) may be approximately constant in the circumferential direction. A virtual line connecting the midpoints of each of the slits 21_(2,1) to 21_(2,8) in the radial direction is referred to as an axis. The curvature of the axis of each of the slits 21_(2,1) to 21_(2,8) may be approximately constant in the circumferential direction.

[0027] The slits 21_(3,1) to 21_(3,8) form the third annular row from the inside. In the third annular row from the inside, the slits 21_(3,1) to 21_(3,8) are arranged at a substantially uniform pitch in the circumferential direction. The slits 21_(3,1) to 21_(3,8) are spaced apart from one another with a substantially uniform clearance in the circumferential direction.

[0028] The length of each of the slits 21_(3,1) to 21_(3,8) corresponds to one of the electrode patterns 4, 5, and 6, for example, a length corresponding to a central angle of 45 degrees. The width of each of the slits 21_(3,1) to 21_(3,8) may be approximately constant in the circumferential direction. A virtual line connecting the midpoints of each of the slits 21_(3,1) to 21_(3,8) in the radial direction is referred to as an axis. The curvature of the axis of each of the slits 21_(3,1) to 21_(3,8) may be approximately constant in the circumferential direction.

[0029] The multiple slits 21 are arranged in a staggered pattern in two or more annular rows. The arrangement positions of each of the slits 21_(1,1) to 21_(1,8) in the first annular row from the inside are shifted in the circumferential direction by approximately half the arrangement pitch relative to each of the slits 21_(2,1) to 21_(2,8) in the second annular row from the inside. The arrangement positions of each of the slits 21_(2,1) to 21_(2,8) in the second annular row from the inside are shifted in the circumferential direction by approximately half the arrangement pitch relative to each of the slits 21_(3,1) to 21_(3,8) in the third annular row from the inside.

[0030] The slits 22 are arranged radially along two or more annular rows. The slits 22 electrically separate the electrode pattern 4 in the circumferential direction within the main surface 2a, electrically separate the electrode pattern 5 in the circumferential direction within the main surfaces 2b and 3a, and electrically separate the electrode pattern 6 in the circumferential direction within the main surface 3b.

[0031] 1 and 2 show an example of a configuration in which eight slits 22_1 to 22_8 are radially arranged. The eight slits 22_1 to 22_8 electrically separate the eight electrode patterns 4_1 to 4_8 in the circumferential direction within the main surface 2a (see FIG. 5(a)), electrically separate the eight electrode patterns 5_1 to 5_8 in the circumferential direction within the main surfaces 2b and 3a (see FIG. 5(c)), and electrically separate the eight electrode patterns 6_1 to 6_8 in the circumferential direction within the main surface 3b.

[0032] As shown in Figures 1 and 2, the piezoelectric films 2 and 3 have multiple slits 21 and multiple slits 22, which can prevent residual stress from remaining inside them when they are subjected to acoustic pressure from the -Z direction or the +Z direction.

[0033] The piezoelectric films 2, 3 do not have slits inside the two or more annular rows. Accordingly, in a cross-sectional view including the Z axis, the piezoelectric films 2, 3 have a doubly-supported beam-like structure with both ends in the X and Y directions supported by the holders 10, as shown in Figures 3 and 4. In a three-dimensional view, the piezoelectric films 2, 3 have a full-clamp structure with the entire outer edge in the X and Y directions held by the holders 10, as shown in Figure 1. As a result, when the piezoelectric films 2, 3 are subjected to acoustic pressure from the -Z direction or the +Z direction, the piezoelectric films 2, 3 can be appropriately distorted in accordance with the acoustic pressure in a desired frequency range, including low-frequency components, and a voltage corresponding to the stress caused by the distortion can be effectively generated in the piezoelectric films 2, 3, improving the accuracy of the piezoelectric device 1 in detecting acoustic pressure.

[0034] Regarding this, we have investigated the fact that the distortion of the piezoelectric films 2 and 3 when they are subjected to acoustic pressure is not uniform, and the stress caused by the distortion tends to concentrate in the areas between the multiple slits 21. Accordingly, the voltage corresponding to the stress caused by the distortion in the piezoelectric films 2 and 3 also tends to concentrate in the areas between the multiple slits 21.

[0035] Therefore, as shown in Figures 3, 4, and 5(a), the electrode pattern 4 covers the areas between the multiple slits 21 on the main surface 2a of the piezoelectric film 2. The electrode pattern 4 may cover the areas between the multiple slits 21 in the same annular row on the main surface 2a. For example, the electrode pattern 4_1 covers the area between the slit 21_(1,8) and the slit 21_(1,1), the area between the slit 21_(1,1) and the slit 21_(1,2), the area between the slit 21_(2,1) and the slit 21_(2,2), the area between the slit 21_(3,8) and the slit 21_(3,1), and the area between the slit 21_(3,1) and the slit 21_(3,2).

[0036] The electrode pattern 4 may further cover surrounding areas between multiple slits 21 in the same annular row on the main surface 2a. For example, the electrode pattern 4_1 covers the area between the area between slit 21_(1,8) and slit 21_(1,1) and slit 21_(2,1), the area between the area between slit 21_(1,1) and slit 21_(1,2) and slit 21_(2,2), the area between the area between slit 21_(2,1) and slit 21_(2,2) and slit 21_(1,1) and slit 21_(3,1), the area between the area between slit 21_(3,8) and slit 21_(3,1) and slit 21_(2,1), and the area between the area between slit 21_(3,1) and slit 21_(3,2) and slit 21_(2,2).

[0037] 3 and 4, the electrode pattern 5 covers the areas between the slits 21 on the main surface 2b of the piezoelectric film 2. The electrode pattern 5 may cover the areas between the slits 21 in the same annular row on the main surface 2b. The electrode pattern 5 may also cover the areas around the slits 21 in the same annular row on the main surface 2b.

[0038] 3, 4, and 5(c), the electrode pattern 5 covers the areas between the plurality of slits 21 on the main surface 3a of the piezoelectric film 3. The electrode pattern 5 may also cover the areas around the plurality of slits 21 on the main surface 3a.

[0039] 3 and 4, the electrode pattern 6 covers the areas between the slits 21 on the main surface 3b of the piezoelectric film 3. The electrode pattern 6 may cover the areas between the slits 21 in the same annular row on the main surface 3b. The electrode pattern 6 may also cover the areas around the slits 21 in the same annular row on the main surface 3b.

[0040] This allows the piezoelectric device 1 to effectively detect voltages corresponding to stresses caused by strains on each of the principal surfaces 2a, 2b, 3a, and 3b, thereby improving the detection sensitivity of the piezoelectric device 1 to acoustic pressures in a desired frequency range. The desired frequency range can be set to a range slightly lower than the resonant frequency of the piezoelectric films 2 and 3.

[0041] 3 and 4, the dummy electrode pattern 7 covers the inner region of two or more annular rows of the slits 21 on the main surface 2a of the piezoelectric film 2. The dummy electrode pattern 7 is arranged radially inward and spaced apart from the electrode patterns 4_1 to 4_8.

[0042] 3 and 4, the dummy electrode pattern 8 covers the inner region of two or more annular rows of the slits 21 on the main surface 2b of the piezoelectric film 2. The dummy electrode pattern 8 is arranged radially inward and spaced apart from the electrode patterns 5_1 to 5_8.

[0043] 3, 4, and 5(c), the dummy electrode pattern 8 covers the inner region of two or more annular rows of the slits 21 on the main surface 3a of the piezoelectric film 3. The dummy electrode pattern 8 is arranged radially inward and spaced apart from the electrode patterns 5_1 to 5_8.

[0044] 3 and 4, the dummy electrode pattern 9 covers the inner region of two or more annular rows of the slits 21 on the main surface 3b of the piezoelectric film 3. The dummy electrode pattern 9 is arranged radially inward and spaced apart from the electrode patterns 6_1 to 6_8.

[0045] This allows the strength of the piezoelectric films 2 and 3 to be reinforced on the respective main surfaces 2a, 2b, 3a, and 3b.

[0046] As described above, in the embodiment, in the piezoelectric device 1, the piezoelectric films 2 and 3, whose outer edges are held by the holding portion 10, have a plurality of slits 21 arranged along two or more annular rows, and the areas between the plurality of slits 21 on each of the main surfaces 2a, 2b, 3a, and 3b are covered with the electrode patterns 4, 5, and 6. As a result, when the piezoelectric films 2 and 3 are subjected to acoustic pressure from the -Z direction or the +Z direction, the piezoelectric films 2 and 3 can be appropriately distorted, and the voltage corresponding to the stress caused by the distortion can be effectively detected by the piezoelectric device 1, thereby improving the accuracy and sensitivity of the piezoelectric device 1 in detecting acoustic pressure.

[0047] The number of divisions of the electrode patterns 4, 5, and 6 is not limited to eight, but may be, for example, four or sixteen.

[0048] The holding portion 10 may hold a portion of the entire circumference of the outer edges of the piezoelectric films 2 and 3. For example, the holding portion 10 may selectively hold the outer edges of the piezoelectric films 2 and 3 near corners, or may selectively hold the outer edges of the piezoelectric films 2 and 3 at multiple points spaced apart at a predetermined pitch.

[0049] The width of each slit 21 may vary depending on the circumferential position. For example, the slit 21 may have a first width at a first circumferential position and a second width at a second circumferential position. The slit 21 may further have a third width at a third circumferential position.

[0050] The curvature of each slit 21 may vary depending on the circumferential position. For example, the slit 21 may have a first curvature at a first circumferential position and a second curvature at a second circumferential position. The slit 21 may further have a third curvature at a third circumferential position. Each slit 21 may extend in the shape of a polygonal arc, may extend in a wavy, or may extend in a zigzag, serpentine, or broken line shape.

[0051] The number of annular rows formed by the slits 21, the row spacing, and the length of each slit within the row can be determined depending on the performance required of the piezoelectric device 1. That is, the arrangement of the multiple slits 21 can be changed depending on the required performance, thereby changing the rigidity of the piezoelectric device 1 and changing the resonant frequency, thereby adjusting the frequency range of acoustic pressure to be detected by the piezoelectric device 1.

[0052] For example, in the piezoelectric device 101, the arrangement of the plurality of slits 121 may be changed as shown in Fig. 6. Fig. 6 is a plan view showing the configuration of a piezoelectric device 101 according to a first modified example of the embodiment.

[0053] 6 illustrates a configuration in which a plurality of slits 121 form two annular rows. Of the two annular rows, slits 121_(1,1) to 121_(1,8) form the first annular row from the inside. Slits 121_(2,1) to 121_(2,8) form the second annular row from the inside.

[0054] The electrode pattern 104 may cover the areas between the slits 121 in the same annular row on the main surface 2a. For example, the electrode pattern 104_1 covers the area between the slits 121_(1,1) and slits 121_(1,2), the area between the slits 121_(2,8) and slits 121_(2,1), and the area between the slits 121_(2,1) and slits 121_(2,2). The electrode pattern 105 (not shown) may cover the areas between the slits 121 in the same annular row on the main surface 2b. The electrode pattern 106 (not shown) may cover the areas between the slits 121 in the same annular row on the main surface 3b.

[0055] The configuration of Fig. 6 has a smaller number of annular rows than the configuration of Fig. 2. This can result in a higher resonance frequency and lower sensitivity in the configuration of Fig. 6 than in the configuration of Fig. 2.

[0056] With this configuration, the sensitivity of the acoustic pressure to be detected by the piezoelectric device 101 can be adjusted to be lower than that of the piezoelectric device 1.

[0057] Alternatively, in the piezoelectric device 201, the arrangement of the plurality of slits 221 may be changed as shown in Fig. 7. Fig. 7 is a plan view showing the configuration of a piezoelectric device 201 according to a second modified example of the embodiment.

[0058] FIG. 7 illustrates a configuration in which the plurality of slits 221 form three annular rows. Of the three annular rows, slits 221_(1,1) to 221_(1,4) form the first annular row from the inside. The lengths of the slits 221_(1,1) to 221_(1,4) correspond to the lengths of the two electrode patterns 204, 205, and 206, for example, the lengths corresponding to a central angle of 90 degrees. The slits 221_(2,1) to 221_(2,4) form the second annular row from the inside. The lengths of the slits 221_(2,1) to 221_(2,4) correspond to the lengths of the two electrode patterns 204, 205, and 206, for example, the lengths corresponding to a central angle of 90 degrees. The slits 221_(3,1) to 221_(3,4) form the second annular row from the inside. Each of the slits 221_(3,1) to 221_(3,4) has a length corresponding to the two electrode patterns 204, 205, and 206, for example, a length corresponding to a central angle of 90 degrees.

[0059] The electrode pattern 204 may cover the areas between the slits 221 in the same annular row on the main surface 2a. For example, the electrode pattern 204_1 covers the area between the slits 221_(1,4) and slits 221_(1,1), the area between the slits 221_(2,1) and slits 221_(2,2), and the area between the slits 221_(3,4) and slits 221_(3,1). The electrode pattern 205 (not shown) may cover the areas between the slits 221 in the same annular row on the main surface 2b. The electrode pattern 206 (not shown) may cover the areas between the slits 221 in the same annular row on the main surface 3b.

[0060] The configuration of Figure 7 has a longer length for each slit in the row than the configuration of Figure 2. This can result in a lower resonant frequency and higher sensitivity in the configuration of Figure 7 than the configuration of Figure 2.

[0061] With this configuration, the sensitivity of the acoustic pressure to be detected by the piezoelectric device 101 can be adjusted to be higher than that of the piezoelectric device 1.

[0062] Alternatively, in the piezoelectric device 301, the arrangement of the plurality of slits 321 may be changed as shown in Fig. 8. Fig. 8 is a plan view showing the configuration of a piezoelectric device 301 according to a third modified example of the embodiment.

[0063] 8 illustrates a configuration in which a plurality of slits 321 form four annular rows. Of the four annular rows, slits 321_(1,1) to 321_(1,4) form the first annular row from the inside. Slits 321_(2,1) to 321_(2,4) form the second annular row from the inside. Slits 321_(3,1) to 321_(3,4) form the third annular row from the inside. Slits 321_(4,1) to 321_(4,4) form the fourth annular row from the inside.

[0064] The electrode pattern 304 may cover the areas between multiple slits 321 in the same annular row on the main surface 2a. For example, the electrode pattern 304_1 covers the area between the slits 321_(1,1) and slits 321_(1,2), the area between the slits 321_(2,4) and slits 321_(2,1), the area between the slits 321_(3,1) and slits 321_(3,2), and the area between the slits 321_(4,4) and slits 321_(4,1). The electrode pattern 305 (not shown) may cover the areas between multiple slits 321 in the same annular row on the main surface 2b. The electrode pattern 306 (not shown) may cover the areas between multiple slits 321 in the same annular row on the main surface 3b.

[0065] The configuration of Fig. 8 has a larger number of annular rows than the configuration of Fig. 2. This allows the configuration of Fig. 8 to have a lower resonance frequency and higher sensitivity than the configuration of Fig. 2.

[0066] With this configuration, the sensitivity of the acoustic pressure to be detected by the piezoelectric device 301 can be adjusted to be higher than that of the piezoelectric device 1.

[0067] Alternatively, in the piezoelectric device 401, the arrangement of the plurality of slits 421 may be changed as shown in Fig. 9. Fig. 9 is a plan view showing the configuration of a piezoelectric device 401 according to a fourth modified example of the embodiment.

[0068] 9 illustrates a configuration in which a plurality of slits 421 form two annular rows. Of the two annular rows, slits 421_(1,1) to 421_(1,4) form the first annular row from the inside. The lengths of the slits 421_(1,1) to 421_(1,4) correspond to the lengths of the two electrode patterns 404, 405, and 406, for example, the lengths corresponding to a central angle of 90 degrees. The slits 421_(2,1) to 421_(2,4) form the second annular row from the inside. The lengths of the slits 421_(2,1) to 421_(2,4) correspond to the lengths of the two electrode patterns 204, 205, and 206, for example, the lengths corresponding to a central angle of 90 degrees.

[0069] The electrode pattern 404 may cover the areas between the slits 421 in the same annular row on the main surface 2a. For example, the electrode pattern 404_1 covers the area between the slits 421_(1,1) and slits 421_(1,2) and the area between the slits 421_(2,4) and slits 421_(2,1). The electrode pattern 405 (not shown) may cover the areas between the slits 421 in the same annular row on the main surface 2b. The electrode pattern 406 (not shown) may cover the areas between the slits 421 in the same annular row on the main surface 3b.

[0070] The configuration of Figure 9 has a longer length for each slit in the row than the configuration of Figure 6. This can result in a lower resonant frequency and higher sensitivity in the configuration of Figure 9 than in the configuration of Figure 6.

[0071] With this configuration, the sensitivity of the acoustic pressure to be detected by the piezoelectric device 401 can be adjusted to be higher than that of the piezoelectric device 101 .

[0072] Alternatively, in the piezoelectric device 501, the arrangement of the plurality of slits 521 may be changed as shown in Fig. 10. Fig. 10 is a plan view showing the configuration of a piezoelectric device 501 according to a fifth modified example of the embodiment.

[0073] 10 illustrates a configuration in which a plurality of slits 521 form two annular rows. Of the two annular rows, slits 521_(1,1) to 521_(1,4) form the first annular row from the inside. Slits 421_(2,1) to 421_(2,4) form the second annular row from the inside.

[0074] The electrode pattern 504 may cover the areas between the multiple slits 521 in the same annular row on the main surface 2a. For example, the electrode pattern 504_1 covers the area between the slits 521_(1,1) and slits 521_(1,2) and the area between the slits 521_(2,4) and slits 521_(2,1). The electrode pattern 505 (not shown) may cover the areas between the multiple slits 521 in the same annular row on the main surface 2b. The electrode pattern 506 (not shown) may cover the areas between the multiple slits 521 in the same annular row on the main surface 3b.

[0075] The configuration of Figure 10 has a wider column spacing than the configuration of Figure 6. This may result in the configuration of Figure 10 being stronger and less sensitive than the configuration of Figure 6.

[0076] With this configuration, the sensitivity of the acoustic pressure to be detected by the piezoelectric device 501 can be adjusted to be lower than that of the piezoelectric device 401 .

[0077] Alternatively, in a piezoelectric device 601, as shown in FIG. 11, electrode patterns 604, 605, and 606 may selectively cover areas between multiple slits 21 in the same annular row. FIG. 11 is a planar cross-sectional view showing the configuration of the electrode patterns and piezoelectric film in a sixth modified example of the embodiment. Electrode patterns 604_1a and 604_1b shown in FIG. 11(a) selectively cover the area between slit 21_(1,8) and slit 21_(1,1), and the area between slit 21_(3,8) and slit 21_(3,1), respectively. Electrode pattern 604_2 selectively covers the area between slit 21_(2,1) and slit 21_(2,2).

[0078] 11(c) selectively cover the area between slit 21_(1,8) and slit 21_(1,1) and the area between slit 21_(3,8) and slit 21_(3,1), respectively. Electrode pattern 605_2 selectively covers the area between slit 21_(2,1) and slit 21_(2,2).

[0079] Note that FIG. 11(b) is the same as FIG. 5(b).

[0080] With this configuration, it is possible to more selectively cover areas in the piezoelectric films 2 and 3 where stress due to distortion is concentrated, allowing the piezoelectric device 1 to more effectively detect voltage corresponding to stress due to distortion, and further improving the sensitivity of the piezoelectric device 1 to detecting acoustic pressure in the desired frequency range.

[0081] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. The novel embodiments described above can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0082] 1, 101, 201, 301, 401, 501, 601 Piezoelectric devices 2,3 Piezoelectric film 4~6, 104~106, 204~206, 304~306, 404~406, 504~506, 604~606 Electrode Pattern 10 Holding part

Claims

1. a piezoelectric film having a first main surface, a second main surface opposite to the first main surface, and a plurality of slits each penetrating from the first main surface to the second main surface and forming two or more annular rows; a holding portion that holds an outer edge of the piezoelectric film; a first electrode pattern covering an area between the plurality of slits on the first main surface; a second electrode pattern covering an area between the plurality of slits on the second main surface; A piezoelectric device comprising:

2. The plurality of slits are arranged in a staggered pattern. The piezoelectric device according to claim 1 .

3. the first electrode pattern covers an area between a plurality of slits in the same annular row on the first main surface; The second electrode pattern covers an area between a plurality of slits in the same annular row on the second main surface. The piezoelectric device according to claim 1 .

4. the first electrode pattern further covers a peripheral area between the plurality of slits in the same annular row on the first main surface; The second electrode pattern further covers a peripheral area between the plurality of slits in the same annular row on the second main surface. The piezoelectric device according to claim 3 .

5. The number of annular rows, the row spacing, and the length of each slit within the row are determined according to the required performance. The piezoelectric device according to claim 1 .

6. The holding portion holds the outer edge of the piezoelectric film around the entire periphery. The piezoelectric device according to claim 1 .

7. The holding portion holds the outer edge of the piezoelectric film at a portion of the entire circumference. The piezoelectric device according to claim 1 .

8. The width of the slit is substantially constant in the circumferential direction. The piezoelectric device according to claim 1 .

9. The slit has a first width at a first circumferential position and a second width at a second circumferential position. The piezoelectric device according to claim 1 .

10. The curvature of the slit is substantially constant in the circumferential direction. The piezoelectric device according to claim 1 .

11. The slit has a first curvature at a first circumferential position and a second curvature at a second circumferential position. The piezoelectric device according to claim 1 .

12. The piezoelectric film does not have a slit inside the two or more annular rows. The piezoelectric device according to claim 1 .

13. a first dummy electrode pattern covering an area inside the two or more annular rows on the first main surface; a second dummy electrode pattern covering an area inside the two or more annular rows on the second main surface; Further equipped The piezoelectric device according to claim 1 .

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