Sensor and electronic apparatus

Abstract

This sensor comprises a holding plate, a piezoelectric film disposed on the holding plate and having four sides and four corner parts, and a reinforcement part for suppressing deformation of the piezoelectric film. The reinforcement part overlaps with a first corner part and a second corner part located on a diagonal line among the four corner parts in a plan view, and does not overlap with a third corner part, which is not the first corner part or the second corner part, among the four corner parts.

Description

Sensors and Electronic Devices

[0001] The present invention relates to a sensor that detects deformation of a member and an electronic device that includes the sensor.

[0002] Patent Document 1 describes a displacement sensor that includes an elastic body and a piezoelectric sheet. The elastic body is made of a high-strength polymer. The piezoelectric sheet is attached to the elastic body. The displacement sensor is provided on a housing. The displacement sensor detects the displacement of the housing. Specifically, the elastic body is attached to the housing. The piezoelectric sheet attached to the elastic body deforms as the housing deforms. The piezoelectric sheet is polarized according to the amount of displacement of the piezoelectric sheet.

[0003] International Publication No. 2012 / 137897

[0004] The direction of polarization of a piezoelectric sheet varies depending on the direction of deformation. Therefore, when a piezoelectric sheet is used in a sensor, polarization of different polarities may occur within the piezoelectric sheet depending on the deformation conditions. In this case, the level of the sensor's output signal may change significantly depending on the position of deformation in the object to be detected, which may reduce the stability of the sensor.

[0005] It is an object of the present invention to provide a sensor that improves the stability of its output signal.

[0006] A sensor according to one embodiment of the present invention comprises a holding plate; a piezoelectric film arranged on the holding plate and having four sides and four corners; and a reinforcing portion that suppresses deformation of the piezoelectric film, wherein the reinforcing portion overlaps, in a planar view, a first corner and a second corner that are arranged diagonally among the four corners, but does not overlap a third corner other than the first corner and the second corner among the four corners.

[0007] A sensor according to one embodiment of the present invention comprises: a holding plate; a piezoelectric film arranged on the holding plate and having four sides and four vertices; and a reinforcing portion that suppresses deformation of the piezoelectric film, wherein the reinforcing portion is arranged near a first vertex and a second vertex that are arranged diagonally among the four vertices in a planar view, and does not overlap with the four vertices.

[0008] According to a sensor according to an embodiment of the present invention, it is possible to provide a sensor that improves the stability of its output signal.

[0009] FIG. 1 is an exploded perspective view of the sensor 1 according to the first embodiment. FIG. 2 is a top view of the sensor 1. FIG. 3 is an enlarged view of the piezoelectric film sensor 11 and the reinforcing portions 13 and 14. FIG. 4 is a side view of the piezoelectric film sensor 11. FIGS. 5A and 5B are views showing deformations of the piezoelectric film sensor 11C1 according to Comparative Example 1. FIG. 6 is a view showing deformations of the piezoelectric film sensor 11. FIGS. 7A, 7B, and 7C are views showing sensors 1a, 1b, and 1c according to Modification Example 1. FIGS. 8A, 8B, 8C, 8D, and 8E are views showing sensors 1d, 1e, 1f, 1g, and 1h according to Modification Example 2. FIG. 9 is a plan view of a sensor 1i according to Modification Example 3. FIG. 10 is a view showing a sensor CP according to Comparative Example 2. FIG. 11 is a view showing a sensor 1k according to Modification Example 4. FIG. 12 is a view showing a sensor 1m according to Modification Example 5. Fig. 13 is an exploded perspective view showing an electronic device EE1 equipped with the sensor 1. Fig. 14 is an exploded perspective view showing an electronic device EE2 which is a modified example of the electronic device EE1.

[0010] [First Embodiment] A sensor 1 according to a first embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is an exploded perspective view of the sensor 1 according to the first embodiment. Fig. 2 is a top view of the sensor 1. Fig. 3 is an enlarged view of the piezoelectric film sensor 11 and reinforcing portions 13 and 14. Fig. 4 is a side view of the piezoelectric film sensor 11.

[0011] In this embodiment, directions are defined as shown in FIGS. 1 and 3 . As shown in FIG. 1 , the direction in which the holding plate 10 and the piezoelectric film sensor 11 are arranged in this order is the positive direction of the Z axis. The direction opposite to the positive direction of the Z axis is the negative direction of the Z axis. As shown in FIG. 3 , the direction in which the first corner D11 and the third corner D13 are arranged in this order is the positive direction of the X axis. The direction opposite to the positive direction of the X axis is the negative direction of the X axis. The X axis direction is perpendicular to the Z axis direction. The direction in which the fourth corner D14 and the first corner D11 are arranged in this order is the positive direction of the Y axis. The direction opposite to the positive direction of the Y axis is the negative direction of the Y axis. The Y axis direction is perpendicular to both the X axis and the Z axis directions. The direction from the first corner D11 to the second corner D12 is the first direction DIR1. The direction from the second corner D12 to the first corner D11 is the second direction DIR2. The direction from the third corner D13 to the fourth corner D14 is the third direction DIR3. The direction from the fourth corner D14 to the third corner D13 is the fourth direction DIR4.

[0012] The X-axis, Y-axis, and Z-axis directions are defined for the purpose of explanation. Therefore, the X-axis, Y-axis, and Z-axis directions during actual use of the sensor 1 do not necessarily have to coincide with the X-axis, Y-axis, and Z-axis directions in each embodiment and each modified example. Similarly, the first direction DIR1, the second direction DIR2, the third direction DIR3, and the fourth direction DIR4 during actual use of the sensor 1 do not necessarily have to coincide with the first direction DIR1, the second direction DIR2, the third direction DIR3, and the fourth direction DIR4 in each embodiment and each modified example.

[0013] The sensor 1 is a module provided in an electronic device such as a smartphone, etc. As shown in Figures 1 and 2, the sensor 1 includes a holding plate 10, a piezoelectric film sensor 11, an adhesive 12, and reinforcing portions 13 and 14.

[0014] As shown in FIGS. 1 and 2 , the retaining plate 10 has a plate shape including a long side extending in the X-axis direction and a short side extending in the Y-axis direction. The retaining plate 10 includes a first main surface DF10 and a second main surface UF10. The first main surface DF10 and the second main surface UF10 are aligned in the positive direction of the Z-axis, in this order. The retaining plate 10 has a rectangular shape with four corners, including a corner D1, in a plan view. As an example, the corner D1 is the end of the retaining plate 10 in the negative direction of the X-axis and the end in the negative direction of the Y-axis (see FIG. 1 ). The retaining plate 10 is an elastic body that undergoes elastic deformation. The retaining plate 10 is made of a material such as metal or resin. For example, the outer edge and its vicinity of the retaining plate 10 are fixed to a frame-shaped housing or the like of an electronic device.

[0015] As shown in Figures 1 to 3, the piezoelectric film sensor 11 has a plate shape including long sides extending in the X-axis direction and short sides extending in the Y-axis direction. The piezoelectric film sensor 11 has a first main surface SF1 and a second main surface SF2. The first main surface SF1 and the second main surface SF2 are aligned in the positive direction of the Z-axis, in this order. The piezoelectric film sensor 11 is disposed on the holding plate 10. In Figures 1 and 2, the piezoelectric film sensor 11 is disposed at a corner D1 of the holding plate 10.

[0016] The piezoelectric film sensor 11 does not necessarily have to be fixed to the corner D1 of the holding plate 10. The piezoelectric film sensor 11 may be fixed to a corner other than the corner D1 among the four corners of the holding plate 10.

[0017] As shown in FIGS. 1 and 4, the piezoelectric film sensor 11 includes a piezoelectric film 110, a first electrode 111, a second electrode 112, and a detection circuit (not shown).

[0018] 1 and 2, the piezoelectric film 110 has a sheet shape with long sides extending in the X-axis direction and short sides extending in the Y-axis direction. As shown in Fig. 4, the piezoelectric film 110 has a first film principal surface DF11 and a second film principal surface UF11. The first film principal surface DF11 and the second film principal surface UF11 are arranged in this order in the positive direction of the Z-axis.

[0019] The piezoelectric film 110 is polarized according to the amount of deformation of the piezoelectric film 110. The direction of polarization when the piezoelectric film 110 is stretched in the first direction DIR1 or the second direction DIR2 is opposite to the direction of polarization when the piezoelectric film 110 is stretched in the third direction DIR3 or the fourth direction DIR4. For example, the piezoelectric film 110 is a film formed from a chiral polymer. An example of a chiral polymer is polylactic acid (PLA), particularly poly-L-lactic acid (PLLA). PLLA, which is a chiral polymer, has a main chain with a helical structure. The piezoelectric film 110 has a piezoelectric constant of d14. As shown in FIGS. 2 and 3 , the piezoelectric film 110 is uniaxially stretched to have piezoelectricity in which the molecules are aligned in an orientation direction OD1. The orientation direction OD1 forms an angle of 0 degrees or 180 degrees with respect to the X-axis direction. For example, this 0 degrees includes angles that include approximately 0 degrees ±10 degrees, and this 180 degrees includes angles that include approximately 180 degrees ±10 degrees. The potential difference between the first film principal surface DF11 and the second film principal surface UF11 when polarized depends on the time differential value of the deformation amount of the piezoelectric film 110 due to expansion or contraction. Note that the orientation direction OD1 does not necessarily have to form an angle of 0 degrees or 180 degrees with respect to the X-axis direction. The orientation direction OD1 may also form an angle of 90 degrees or 270 degrees with respect to the X-axis direction.

[0020] As shown in FIG. 3 , the piezoelectric film 110 has a rectangular shape with four vertices K11, K12, K13, and K14 and four sides H1, H2, H3, and H4 connecting the four vertices K11, K12, K13, and K14. The vertex K11 is located at the end of the piezoelectric film 110 in the negative direction of the X axis and at the end of the piezoelectric film 110 in the positive direction of the Y axis. The vertex K12 is located on the diagonal line of the vertex K11. The vertex K13 is located at the end of the piezoelectric film 110 in the positive direction of the X axis and at the end of the piezoelectric film 110 in the positive direction of the Y axis. The vertex K14 is located on the diagonal line of the vertex K13. The side H1 connects the vertices K11 and K13. The side H2 connects the vertices K12 and K13. The side H3 connects the vertices K12 and K14. The edge H4 connects the vertex K11 and the vertex K14.

[0021] As shown in FIGS. 2 and 3, the piezoelectric film 110 has four corners: a first corner D11, a second corner D12, a third corner D13, and a fourth corner D14.

[0022] 3, in this embodiment, the first corner D11 is an end portion of the piezoelectric film 110 in the negative X direction and an end portion in the positive Y direction. The first corner D11 includes the vertex K11 and the vicinity of the vertex K11. The first corner D11 includes a position on the piezoelectric film 110 excluding the vertex K11 (the vicinity of the vertex K11). The first corner D11 does not include the midpoint M1 of the side H1 or the midpoint M4 of the side H4.

[0023] In this embodiment, the second corner D12 is located diagonally from the first corner D11. The second corner D12 includes the vertex K12 and the vicinity of the vertex K12. The second corner D12 includes a position on the piezoelectric film 110 excluding the vertex K12 (the vicinity of the vertex K12). The second corner D12 does not include the midpoint M2 of the side H2 or the midpoint M3 of the side H3.

[0024] 3, in this embodiment, the third corner D13 is an end portion of the piezoelectric film 110 in the positive X direction and an end portion in the positive Y direction. The third corner D13 includes the vertex K13 and the vicinity of the vertex K13. The third corner D13 includes a position on the piezoelectric film 110 excluding the vertex K13 (the vicinity of the vertex K13). The third corner D13 does not include the midpoint M1 or the midpoint M2.

[0025] In this embodiment, the fourth corner D14 is located diagonally from the third corner D13. The fourth corner D14 includes the vertex K14 and the vicinity of the vertex K14. The fourth corner D14 includes a position on the piezoelectric film 110 excluding the vertex K14 (the vicinity of the vertex K14). The fourth corner D14 does not include the midpoint M3 or the midpoint M4.

[0026] The first electrode 111 is, for example, a signal electrode. As shown in FIG. 4 , the first electrode 111 is disposed on the first film main surface DF11. The first electrode 111 is fixed to the first film main surface DF11 with an adhesive (not shown) such as OCA (Optical Clear Adhesive). The first electrode 111 covers substantially the entire first film main surface DF11. The first electrode 111 is in contact with the holding plate 10 via an adhesive 12.

[0027] The second electrode 112 is, for example, a reference electrode. The second electrode 112 is connected to a reference potential (for example, ground potential). The second electrode 112 is disposed on the second film main surface UF11. The second electrode 112 is fixed to the second film main surface UF11 with an adhesive (not shown) such as OCA. The second electrode 112 covers substantially the entire surface of the second film main surface UF11. The second electrode 112 connected to the reference potential prevents the signal generated by the piezoelectric film sensor 11 from affecting external devices as noise.

[0028] It is not necessary that the first electrode 111 is the signal electrode and the second electrode 112 is the reference electrode. The first electrode 111 may be the reference electrode and the second electrode 112 may be the signal electrode.

[0029] The detection circuit converts the electric charge generated by the piezoelectric film 110 into a voltage signal, and generates a digital signal by AD converting the voltage signal.

[0030] 1, the adhesive 12 is disposed between the holding plate 10 and the piezoelectric film sensor 11. The adhesive 12 is, for example, a double-sided tape having adhesive properties. Of course, the adhesive 12 does not necessarily have to be a double-sided tape.

[0031] The piezoelectric film sensor 11 is fixed to the second main surface UF10 of the holding plate 10 by the adhesive 12. This causes the piezoelectric film sensor 11 to output a signal corresponding to the deformation of the holding plate 10. Specifically, when a user presses the holding plate 10 in the normal direction, the holding plate 10 bends and deforms. As the holding plate 10 deforms, the piezoelectric film sensor 11 fixed to the holding plate 10 bends and deforms. The piezoelectric film sensor 11 outputs a signal corresponding to the deformation of the piezoelectric film sensor 11.

[0032] As shown in FIGS. 1 to 3 , the reinforcing portion 13 has a rectangular shape with four sides. The reinforcing portion 13 is disposed on the second main surface SF2. The reinforcing portion 13 is disposed at the first corner portion D11. As shown in FIGS. 1 to 3 , the reinforcing portion 13 overlaps the piezoelectric film sensor 11 in a planar view. The reinforcing portion 13 overlaps the first corner portion D11 in a planar view. The reinforcing portion 13 may be formed of a material having a higher elastic modulus than the retaining plate 10, or may be formed of a material having a lower elastic modulus than the retaining plate 10. The reinforcing portion 13 suppresses deformation of the piezoelectric film 110. The reinforcing portion 13 suppresses deformation of the first corner portion D11. Specifically, the presence of the reinforcing portion 13 makes the first corner portion D11 less susceptible to deformation (harder) than portions of the piezoelectric film 110 where the reinforcing portions 13, 14 are not provided. Therefore, even if a normal force is applied to the piezoelectric film sensor 11 (such as when a force is applied by a user pressing the holding plate 10), the first corner portion D11 is less likely to twist in the first direction DIR1 or the second direction DIR2 due to the force.

[0033] 1 to 3, the reinforcing portion 14 is disposed at the second corner portion D12. In plan view, the reinforcing portion 14 overlaps the second corner portion D12. The reinforcing portion 14 suppresses deformation of the second corner portion D12. The other configuration of the reinforcing portion 14 is the same as the configuration of the reinforcing portion 13, and therefore description thereof will be omitted.

[0034] In this embodiment, the reinforcing portions 13, 14 are not disposed at the third corner portion D13 and the fourth corner portion D14. The reinforcing portions 13, 14 do not overlap the third corner portion D13 and the fourth corner portion D14 in a plan view.

[0035] The reinforcing portions 13 and 14 may be frame-shaped housings provided in electronic devices such as smartphones. For example, the housings fix the side H4 and its vicinity and the side H3 and its vicinity of the piezoelectric film sensor 11 to the holding plate 10. The housings suppress deformation of the first corner D11, the second corner D12, and the fourth corner D14.

[0036] (Effects) The effects of the sensor 1 will be described below in comparison with a sensor according to a comparative example (hereinafter simply referred to as comparative example 1). FIGS. 5A and 5B are diagrams showing deformation of the piezoelectric film sensor 11C1 according to comparative example 1. FIG. 6 is a diagram showing deformation of the piezoelectric film sensor 11. In the experiment according to FIG. 6, the reinforcing portion overlaps the fourth corner D14 in addition to the first corner D11 and the second corner D12. In the experiment according to FIG. 6, the piezoelectric film sensor 11 is disposed at the corner D1 of the holding plate 10, but does not overlap with a frame-shaped housing or the like provided in the electronic device.

[0037] The piezoelectric film sensor 11C1 of Comparative Example 1 differs from the piezoelectric film sensor 11 of the present embodiment in that the reinforcing portions 13, 14 do not overlap the first corner D11 and the second corner D12. Therefore, the reinforcing portions 13, 14 do not suppress deformation of the piezoelectric film 110 of the piezoelectric film sensor 11C1 of Comparative Example 1. FIG. 5A shows the deformation of the piezoelectric film sensor 11C1 when the third corner D13 is pressed in the normal direction. When the third corner D13 is pressed in the normal direction, the piezoelectric film 110 of the piezoelectric film sensor 11C1 expands along the fourth direction DIR4 and contracts along the first direction DIR1 and the second direction DIR2, resulting in a dominant portion being positively polarized with respect to the reference potential. FIG. 5B shows the deformation of the piezoelectric film sensor 11C1 when the second corner D12 is pressed in the normal direction. When the second corner D12 of the piezoelectric film sensor 11C1 is pressed in the normal direction, the piezoelectric film 110 expands along the first direction DIR1 and contracts along the third direction DIR3 and the fourth direction DIR4, so that the portion that is negatively polarized relative to the reference potential becomes dominant.

[0038] The output of the piezoelectric film sensor 11C1 corresponds to the sum of the charges generated in the piezoelectric film 110. Therefore, in the piezoelectric film sensor 11C1 of Comparative Example 1, the polarity of the output of the sensor is reversed when the second corner D12 is pressed in the normal direction and when the fourth corner D14 is pressed in the normal direction.

[0039] In Comparative Example 1, if one of the midpoints of the four sides (midpoints M1 to M4) is pressed, the area of ​​the portion that is positively polarized with respect to the reference potential and the area of ​​the portion that is negatively polarized with respect to the reference potential will be the same. Therefore, in the piezoelectric film sensor 11C1 of Comparative Example 1, if one of the midpoints of the four sides (midpoints M1 to M4) is pressed, the output of the sensor will be extremely small or will be "0".

[0040] In the sensor 1 according to this embodiment, the reinforcing portions 13 and 14 do not overlap the third corner D13. Therefore, when the third corner D13 is pressed in the normal direction, the piezoelectric film 110 expands along the fourth direction DIR4. Meanwhile, the reinforcing portions 13 and 14 suppress deformation of the first corner D11 and the second corner D12. Therefore, the piezoelectric film 110 is less likely to contract or expand along the first direction DIR1 or the second direction DIR2. Therefore, the piezoelectric film 110 has a dominant portion that is positively polarized relative to the reference potential. Therefore, in the sensor 1 according to this embodiment, when the third corner D13 is pressed in the normal direction, the output of the piezoelectric film sensor 11 is similar to the output of the piezoelectric film sensor 11C1 of Comparative Example 1 shown in FIG. 5A .

[0041] FIG. 6 shows the deformation of the piezoelectric film sensor 11 when the second corner D12 is pressed in the normal direction. The first corner D11 and the second corner D12 are suppressed from deformation by the reinforcing portions 13 and 14. Therefore, the piezoelectric film 110 is unlikely to contract or expand along the first direction DIR1 or the second direction DIR2. Meanwhile, the force exerted by pressing the second corner D12 in the normal direction is transmitted to the holding plate 10, causing the piezoelectric film 110 to expand along the fourth direction DIR4. Therefore, the piezoelectric film 110 as a whole has a dominant portion that is positively polarized relative to the reference potential. Therefore, in the piezoelectric film sensor 11 of this embodiment, the polarity of the sensor output is not reversed when the second corner D12 is pressed in the normal direction and when the fourth corner D14 is pressed in the normal direction.

[0042] Furthermore, in the piezoelectric film sensor 11 of this embodiment, even if one of the midpoints of the four sides (midpoints M1 to M4) is pressed, the portion that is positively polarized with respect to the reference potential becomes dominant. Therefore, in the piezoelectric film sensor 11 of this embodiment, when one of the midpoints of the four sides (midpoints M1 to M4) is pressed, the output of the sensor becomes extremely small or does not become "0".

[0043] Therefore, the sensor 1 can prevent the output of a signal having an unintended polarity, either positive or negative, and can prevent the value of the output signal from decreasing significantly. Therefore, the sensor 1 can improve the stability of the output signal of the piezoelectric film sensor 11.

[0044] Furthermore, an arithmetic circuit (not shown) connected to the sensor 1 determines that a user has performed a pressing operation when the value of the output signal from the piezoelectric film sensor 11 exceeds a predetermined threshold. The arithmetic circuit (not shown) determines that the user has released the pressing operation when the value of the output signal from the piezoelectric film sensor 11 falls below a predetermined threshold (a predetermined negative value). The sensor 1 of this embodiment does not reverse the polarity of the output signal or significantly decrease the value of the output signal, preventing erroneous determination by the arithmetic circuit.

[0045] In addition, even if the orientation direction OD1 of the piezoelectric film 110 in the sensor 1 forms an angle of 0 degrees or 180 degrees with respect to the X-axis direction, the polarity of the output of the sensor 1 is not reversed when the second corner D12 is pressed in the normal direction and when the fourth corner D14 is pressed in the normal direction. Therefore, the output of the piezoelectric film sensor 11 as a sensor is extremely small or does not become "0".

[0046] [Modification 1] Hereinafter, sensors 1a, 1b, and 1c according to Modification 1 of sensor 1 will be described with reference to the drawings. Figures 7(A), 7(B), and 7(C) are diagrams showing sensors 1a, 1b, and 1c according to Modification 1, respectively.

[0047] 7A, sensor 1a differs from sensor 1 in that it includes reinforcing portions 13a and 14a that are different from reinforcing portions 13 and 14. Specifically, reinforcing portions 13a and 14a each have an L-shape in plan view. The other configuration of sensor 1a is the same as that of sensor 1, and therefore a description thereof will be omitted.

[0048] 7B, sensor 1b differs from sensor 1 in that it includes reinforcing portions 13b and 14b that are different from reinforcing portions 13 and 14. Specifically, reinforcing portions 13b and 14b each have a triangular shape in plan view. The other configuration of sensor 1b is the same as that of sensor 1, and therefore a description thereof will be omitted.

[0049] 7C, sensor 1c differs from sensor 1 in that it includes one reinforcing portion 13c. Reinforcing portion 13c has a rectangular shape extending from a first corner D11 to a second corner D12. The other configuration of sensor 1c is the same as that of sensor 1, and therefore a description thereof will be omitted.

[0050] Each of the sensors 1a, 1b, and 1c has the same effect as the sensor 1.

[0051] [Modification 2] Hereinafter, sensors 1d, 1e, 1f, 1g, and 1h according to Modification 2 of sensor 1 will be described with reference to the drawings. Figures 8(A), 8(B), 8(C), 8(D), and 8(E) are diagrams showing sensors 1d, 1e, 1f, 1g, and 1h according to Modification 2, respectively.

[0052] Each of the sensors 1d, 1e, 1f, 1g, and 1h differs from the sensor 1 in that the reinforcing portion overlaps the fourth corner portion D14 in plan view.

[0053] As shown in Fig. 8A, the sensor 1d further includes a reinforcing portion 15. The reinforcing portion 15 is disposed at the fourth corner D14. In plan view, the reinforcing portion 15 overlaps with the fourth corner D14. The other configurations of the reinforcing portion 15 are the same as those of the reinforcing portion 13, and therefore will not be described.

[0054] As shown in FIG. 8B , the sensor 1e includes one reinforcing portion 13e that overlaps the first corner D11, the second corner D12, and the fourth corner D14 in a plan view. The reinforcing portion 13e has an L-shape in a plan view. A portion of the reinforcing portion 13e extends from the first corner D11 toward the fourth corner D14. Therefore, the reinforcing portion 13e is disposed in a portion connecting the fourth corner D14 to the first corner D11. The remaining portion of the reinforcing portion 13e extends from the fourth corner D14 toward the second corner D12. Therefore, the reinforcing portion 13e is disposed in a portion connecting the fourth corner D14 to the second corner D12. The rest of the configuration of the reinforcing portion 13e is the same as that of the reinforcing portion 13, and therefore a description thereof will be omitted.

[0055] 8C, the sensor 1f includes a reinforcing portion 13f that is different from the reinforcing portion 13e. A portion of the reinforcing portion 13f extends from the first corner D11 toward the second corner D12. The rest of the configuration of the reinforcing portion 13f is the same as the configuration of the reinforcing portion 13e, and therefore a description thereof will be omitted.

[0056] As shown in Figure 8(D), the sensor 1g includes one reinforcing portion 13g. The reinforcing portion 13g is triangular in plan view. The three vertices of the reinforcing portion 13g are located at a first corner D11, a second corner D12, and a fourth corner D14. The rest of the configuration of the reinforcing portion 13g is the same as that of the reinforcing portion 13, so a description thereof will be omitted.

[0057] As shown in Fig. 8(E), the sensor 1h has one reinforcing portion 13h. The reinforcing portion 13h does not cover the vertex K13 or the area surrounding the vertex K13. The reinforcing portion 13h covers all parts of the piezoelectric film sensor 11 except for the vertex K13 and the area surrounding the vertex K13. The other configuration of the reinforcing portion 13h is the same as that of the reinforcing portion 13, so a description thereof will be omitted.

[0058] Each of the sensors 1a to 1h has the same effect as the sensor 1.

[0059] [Modification 3] A sensor 1i according to Modification 3 of the sensor 1 will now be described with reference to the drawings. Fig. 9 is a plan view of the sensor 1i according to Modification 3.

[0060] As shown in Figure 9, sensor 1i differs from sensor 1 in that it includes reinforcing portions 13i, 14i, 15i, and 16i that are different from reinforcing portions 13 and 14. Reinforcing portions 13i, 14i, 15i, and 16i are not disposed at vertices K11 to K14 in piezoelectric film sensor 11. In other words, reinforcing portions 13i, 14i, 15i, and 16i do not overlap with vertices K11 to K14 in plan view. Vertex K11 corresponds to the first vertex in this application. Vertex K12 corresponds to the second vertex in this application. Vertex K13 corresponds to the third vertex in this application. Vertex K14 corresponds to the fourth vertex in this application.

[0061] The reinforcing portion 13i is disposed near the vertex K11 in plan view. The reinforcing portion 13i is located between the vertex K11 and the midpoint M1. The reinforcing portion 13i does not overlap with the vertex K11 or the midpoint M1 in plan view. The reinforcing portion 14i is disposed near the vertex K11 in plan view. The reinforcing portion 14i is located between the vertex K11 and the midpoint M4. The reinforcing portion 14i does not overlap with the vertex K11 or the midpoint M4 in plan view. The reinforcing portions 13i and 14i suppress deformation of the first corner portion D11.

[0062] The reinforcing portion 15i is disposed near the vertex K12 in plan view. The reinforcing portion 15i is located between the vertex K12 and the midpoint M2. The reinforcing portion 15i does not overlap with the vertex K12 or the midpoint M2 in plan view. The reinforcing portion 16i is disposed near the vertex K12 in plan view. The reinforcing portion 16i is located between the vertex K12 and the midpoint M3. The reinforcing portion 16i does not overlap with the vertex K12 or the midpoint M3 in plan view. The reinforcing portions 15i, 16i suppress deformation of the second corner portion D12.

[0063] Each of the reinforcing portions 13i to 16i does not suppress deformation of the third corner portion D13 and the fourth corner portion D14.

[0064] (Effects) Sensor 1i has the same effects as sensor 1. These effects will be described below with reference to the drawings. FIG. 10 is a diagram showing sensor CP according to comparative example 2. As shown in FIG. 10, sensor CP has four reinforcing portions CP13, CP14, CP15, and CP16. Reinforcing portions CP13, CP14, CP15, and CP16 are not disposed at the corners of the piezoelectric film of piezoelectric film sensor CP11 in sensor CP. Reinforcing portions CP13, CP14, CP15, and CP16 overlap midpoints CPM1, CPM4, CPM2, and CPM3, respectively, in a plan view.

[0065] In sensor CP, the reinforcement portions CP13, CP14, CP15, and CP16 do not overlap the four corners of the piezoelectric film. Therefore, when the third corner portion DP13 or the fourth corner portion DP14 is pressed in the normal direction, the piezoelectric film in sensor CP expands along the third direction DIR3 and the fourth direction DIR4 and contracts along the first direction DIR1 and the second direction DIR2, resulting in a predominant portion of the film being positively polarized with respect to the reference potential. On the other hand, when the first corner portion DP11 or the second corner portion DP12 is pressed in the normal direction, the piezoelectric film in sensor CP expands along the first direction DIR1 and the second direction DIR2 and contracts along the third direction DIR3 and the fourth direction DIR4, resulting in a predominant portion of the film being negatively polarized with respect to the reference potential.

[0066] The output of the sensor CP as a piezoelectric film sensor corresponds to the sum of the charges generated in the piezoelectric film. Therefore, in the piezoelectric film sensor of Comparative Example 2, for example, the polarity of the output as a sensor is reversed when the second corner D12 is pressed in the normal direction and when the fourth corner D14 is pressed in the normal direction.

[0067] On the other hand, in sensor 1i, reinforcing portions 13i and 14i are located near vertex K11, and reinforcing portions 15i and 16i are located near vertex K12. This makes it difficult for the piezoelectric film 110 to stretch along the first direction DIR1 and the second direction DIR2 compared to sensor CP. Therefore, for the same reason as sensor 1, the polarity of the sensor output is indeterminable when the second corner D12 is pressed in the normal direction and when the fourth corner D14 is pressed in the normal direction. Furthermore, when the piezoelectric film sensor 11 of sensor 1i is pressed at any of the midpoints of the four sides (midpoints M1 to M4), the sensor output becomes extremely small or never becomes "0." Therefore, like sensor 1, sensor 1i can prevent signals from being output that have an unintended polarity, either positive or negative. Furthermore, sensor 1i can prevent a significant decrease in the value of the output signal. Therefore, the sensor 1i can improve the stability of the output signal of the piezoelectric film sensor 11.

[0068] [Modification 4] A sensor 1k according to Modification 4 of the sensor 1 will now be described with reference to the drawings. Fig. 11 is a diagram showing the sensor 1k according to Modification 4.

[0069] As shown in FIG. 11 , sensor 1k differs from sensor 1 in that the reinforcing portions 13, 14 do not overlap with the piezoelectric film sensor 11 in a plan view. The reinforcing portions 13, 14 are arranged, for example, on the holding plate 10. The reinforcing portion 13 is arranged near the first corner D11. In sensor 1k, the reinforcing portion 13 is arranged next to the first corner D11. The reinforcing portion 13 is located on the positive side of the Y axis relative to the piezoelectric film sensor 11. The reinforcing portion 13 is not in contact with the piezoelectric film sensor 11. The reinforcing portion 14 is arranged near the second corner D12. The reinforcing portion 14 is arranged next to the second corner D12. The reinforcing portion 14 is located on the positive side of the X axis relative to the piezoelectric film sensor 11.

[0070] Because the reinforcing portion 13 is located near the first corner D11, the first corner D11 is fixed to the holding plate 10. Because the reinforcing portion 14 is located near the second corner D12, the second corner D12 is fixed to the holding plate 10. Therefore, in the piezoelectric film sensor 11 of sensor 1k, similar to sensor 1, the polarity of the sensor output does not reverse when the second corner D12 is pressed in the normal direction and when the fourth corner D14 is pressed in the normal direction. Furthermore, when any of the midpoints of the four sides (midpoints M1 to M4) of the piezoelectric film sensor 11 of sensor 1k is pressed, the sensor output does not become extremely small or become "0." Therefore, for the same reasons as sensor 1, sensor 1k can improve the stability of the output signal of the piezoelectric film sensor 11.

[0071] [Modification 5] A sensor 1m according to Modification 5 of the sensor 1 will now be described with reference to the drawings. Fig. 12 is a diagram showing a sensor 1m according to Modification 5.

[0072] As shown in FIG. 12 , sensor 1m differs from sensor 1 in that multiple pairs of a piezoelectric film sensor and a reinforcing portion are arranged on the holding plate 10. In FIG. 12 , two pairs of a piezoelectric film sensor and a reinforcing portion are arranged on the holding plate 10. Specifically, sensor 1m differs from sensor 1 in that sensor 1m further includes a piezoelectric film sensor 20 and reinforcing portions 23 and 24. The piezoelectric film sensor 20 is arranged at corner D2 of the holding plate 10. Corner D2 is located diagonally from corner D1 of the holding plate 10. The reinforcing portion 23 is arranged at a first corner of the piezoelectric film sensor 20. The reinforcing portion 24 is arranged at a second corner of the piezoelectric film sensor 20. The other configurations of the piezoelectric film sensor 20 are the same as those of piezoelectric film sensor 11, and therefore description thereof will be omitted.

[0073] The piezoelectric film sensor 20 may be disposed at a corner of the holding plate 10 other than the corners D1 and D2.

[0074] The sensor 1m may include three or more pairs of a piezoelectric film sensor and a reinforcing portion.

[0075] [Electronic Device EE1] The electronic device EE1 including the sensor 1 will be described below with reference to the drawings. Fig. 13 is an exploded perspective view showing the electronic device EE1 including the sensor 1.

[0076] 13 , the electronic device EE1 includes a sensor 1 and a touch panel 30. As an example, the touch panel 30 is located between a holding plate 10 and a piezoelectric film sensor 11. The size of the touch panel 30 is approximately the same as the size of the holding plate 10. In the electronic device EE1, the piezoelectric film sensor 11 is disposed at a corner of the touch panel 30. The touch panel 30 is a resistive or capacitive touch panel. Such an electronic device EE1 is a smartphone or the like.

[0077] [Modification of Electronic Device EE1] An electronic device EE2 that is a modification of the electronic device EE1 will now be described with reference to the drawings. Fig. 14 is an exploded perspective view showing the electronic device EE2 that is a modification of the electronic device EE1.

[0078] 14 , the electronic device EE2 differs from the electronic device EE1 in that it further includes a display panel 40. As an example, the display panel 40 is located between the touch panel 30 and the piezoelectric film sensor 11. The size of the display panel 40 is approximately the same as the size of the holding plate 10. In the electronic device EE2, the piezoelectric film sensor 11 is disposed at a corner of the display panel 40. The display panel 40 is an organic EL display, a liquid crystal display, or the like. Such an electronic device EE2 is a smartphone or the like.

[0079] The display panel 40 does not necessarily have to be located between the touch panel 30 and the piezoelectric film sensor 11. The display panel 40 may be located between the touch panel 30 and the holding plate 10, for example.

[0080] [Other Embodiments] The description of the present embodiment should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above-described embodiments. Furthermore, the scope of the present invention includes the scope equivalent to the claims.

[0081] The sensors according to the present invention are not limited to the sensors 1, 1a to 1m, and can be modified within the scope of the present invention. The configurations of the sensors 1, 1a to 1m may be combined arbitrarily.

[0082] The first corner and the second corner in the present invention may be arranged diagonally. Therefore, the combination of the first corner and the second corner does not necessarily have to be the combination of two corners shown in Figures 1 to 14. For example, in the sensor 1, the second corner D12 may correspond to the first corner in the present invention, and the fourth corner D14 may correspond to the second corner in the present invention.

[0083] The present invention has the following structure:

[0084] (1) A sensor comprising: a holding plate; a piezoelectric film disposed on the holding plate and having four sides and four corners; and a reinforcing portion for suppressing deformation of the piezoelectric film, wherein the reinforcing portion overlaps, in a plan view, a first corner and a second corner of the four corners that are disposed diagonally, but does not overlap a third corner of the four corners other than the first corner and the second corner.

[0085] (2) A sensor comprising: a holding plate; a piezoelectric film disposed on the holding plate and having four sides and four vertices; and a reinforcing portion for suppressing deformation of the piezoelectric film, wherein the reinforcing portion is disposed near a first vertex and a second vertex that are disposed diagonally among the four vertices in a plan view, and does not overlap with the four vertices.

[0086] (3) The sensor according to (1), wherein the reinforcing portion overlaps a fourth corner portion located diagonally opposite the third corner portion.

[0087] (4) The sensor according to (3), wherein the reinforcing portion is arranged at a position overlapping a portion of the piezoelectric film connecting the fourth corner portion to the first corner portion and a portion of the piezoelectric film connecting the fourth corner portion to the second corner portion.

[0088] (5) The sensor according to (2), wherein the reinforcing portion is arranged at a position that does not overlap with a vicinity of a third vertex other than the first vertex and the second vertex among the four vertices, but overlaps with a vicinity of a fourth vertex that is located on a diagonal line of the third vertex.

[0089] (6) The sensor according to (2) or (5), wherein the reinforcing portion does not overlap the piezoelectric film in a plan view.

[0090] (7) The sensor according to any one of (1) to (6), wherein the piezoelectric film is disposed at a corner of the holding plate.

[0091] (8) The sensor according to any one of (1) to (7), wherein a plurality of pairs of the piezoelectric film and the reinforcing portion are arranged on the holding plate.

[0092] (9) The sensor described in any one of (1) to (8), further comprising a piezoelectric film sensor including the piezoelectric film, a first electrode, and a second electrode, wherein the piezoelectric film has a first film main surface and a second film main surface, the first electrode is disposed on the first film main surface and is in contact with the holding plate, and the second electrode is disposed on the second film main surface and is connected to a reference potential.

[0093] (10) An electronic device comprising: the sensor according to any one of (1) to (9); and a touch panel.

[0094] (11) The electronic device according to (10), further comprising a display panel.

[0095] 1, 1a to 1m, CP: sensor 10: holding plate 11, 11C1, CP11, 20: piezoelectric film sensor 110: piezoelectric film 111: first electrode 112: second electrode 12: adhesive 13, 13a to 13i, 14, 14a, 14b, 14i, 15, 15i, 16i, 23, 24, CP13 to CP16: reinforcing portion 30: touch panel 40: display panel D1, D2: corner D11, DP11: first corner D12, DP12: second corner D13, DP13: third corner D14, DP14: fourth corner H1 to H4: sides M1 to M4, CPM1 to CPM4: midpoints K11 to K14: vertices EE1, EE2: Electronic device DF10, SF1: First main surface UF10, SF2: Second main surface DF11: First film main surface UF11: Second film main surface DIR1: First direction DIR2: Second direction DIR3: Third direction DIR4: Fourth direction OD1: Orientation direction

Claims

1. A sensor comprising: a retaining plate; a piezoelectric film arranged on the retaining plate and having four sides and four corners; and a reinforcing portion for suppressing deformation of the piezoelectric film, wherein, in a planar view, the reinforcing portion overlaps with a first corner and a second corner arranged diagonally among the four corners, but does not overlap with a third corner other than the first corner and the second corner.

2. A sensor comprising: a retaining plate; a piezoelectric film arranged on the retaining plate and having four sides and four vertices; and a reinforcing portion that suppresses deformation of the piezoelectric film, wherein the reinforcing portion is arranged near a first vertex and a second vertex that are arranged diagonally among the four vertices in a planar view, and does not overlap with the four vertices.

3. The sensor according to claim 1, wherein the reinforcing portion overlaps a fourth corner portion located diagonally opposite the third corner portion.

4. The sensor described in claim 3, wherein the reinforcing portion is arranged at a position overlapping a portion of the piezoelectric film connecting the fourth corner to the first corner, and a portion connecting the fourth corner to the second corner.

5. The sensor described in claim 2, wherein the reinforcing portion is arranged at a position that does not overlap with the vicinity of a third vertex other than the first vertex and the second vertex among the four vertices, but overlaps with the vicinity of a fourth vertex located diagonally from the third vertex.

6. The sensor according to claim 2 or claim 5, wherein the reinforcing portion does not overlap the piezoelectric film in a plan view.

7. The sensor according to any one of claims 1 to 6, wherein the piezoelectric film is disposed at a corner of the holding plate.

8. The sensor according to any one of claims 1 to 7, wherein a plurality of pairs of the piezoelectric film and the reinforcing portion are arranged on the holding plate.

9. A sensor as described in any one of claims 1 to 8, further comprising a piezoelectric film sensor including the piezoelectric film, a first electrode and a second electrode, the piezoelectric film having a first film principal surface and a second film principal surface, the first electrode being disposed on the first film principal surface and in contact with the retaining plate, and the second electrode being disposed on the second film principal surface and connected to a reference potential.

10. An electronic device comprising: a sensor according to any one of claims 1 to 9; and a touch panel.

11. The electronic device according to claim 10, further comprising a display panel.

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