Sensor and electronic apparatus

Abstract

To provide a sensor capable of uniformizing sensitivity of a plurality of piezoelectric bodies.SOLUTION: A sensor comprises a tabular member including a first principal surface, the tabular member having flexibility, and a piezoelectric element which is provided on the first principal surface. The piezoelectric element includes a plurality of piezoelectric films including at least a first piezoelectric film and a second piezoelectric film. The first piezoelectric film contains at least polylactic acid which is drawn in a first orientation direction. The second piezoelectric film contains at least polylactic acid which is drawn in a second orientation direction. In a view in a normal direction of the first principal surface, the second orientation direction differs from the first orientation direction. In the view in the normal direction, the plurality of piezoelectric films is disposed in a rectangular shape as a whole.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sensor and an electronic device that include a plurality of piezoelectric elements. [Background technology]

[0002] A known example of a conventional invention relating to a sensor including multiple piezoelectric bodies is the displacement sensor described in Patent Document 1. The displacement sensor described in Patent Document 1 includes an elastic body having first and second principal surfaces facing each other, a first flat-membrane piezoelectric element for detecting bending, and a second flat-membrane piezoelectric element for detecting twist. The first flat-membrane piezoelectric element includes a first piezoelectric sheet having third and fourth principal surfaces facing each other, a first electrode formed on the third principal surface, and a second electrode formed on the fourth principal surface. The first piezoelectric sheet includes a first piezoelectric body. The second electrode is attached to the first principal surface by a first adhesive. That is, the first flat-membrane piezoelectric element is attached to the first principal surface of the elastic body by a first adhesive.

[0003] The second flat membrane type piezoelectric element has a second piezoelectric sheet having a fifth main surface and a sixth main surface facing each other, a third electrode formed on the fifth main surface, and a fourth electrode formed on the sixth main surface. The second piezoelectric sheet includes a second piezoelectric body. The third electrode is attached to the second main surface by a second adhesive. That is, the second flat membrane type piezoelectric element is attached to the second main surface of the elastic body by the second adhesive. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5831542 Summary of the Invention [Problem to be solved by the invention]

[0005] Consider detecting deformation of an object to be measured using the displacement sensor described in Patent Document 1. For example, the object to be measured is flat. The object to be measured has seventh and eighth principal surfaces that face each other. The displacement sensor described in Patent Document 1 is attached to the object to be measured by attaching a first electrode to the eighth principal surface of the object to be measured.

[0006] When the seventh principal surface of the object to be measured is pressed, both the first and second piezoelectric sheets deform in accordance with the deformation of the object to be measured. At this time, even though the same pressing force is applied, the amount of deformation of the second piezoelectric sheet is smaller than the amount of deformation of the first piezoelectric sheet due to the viscoelasticity of the first and second adhesives. Therefore, even if the first flat-film type piezoelectric element reacts, the second flat-film type piezoelectric element may not. In other words, the sensitivity of the second piezoelectric element may be lower than the sensitivity of the first piezoelectric element. Therefore, the sensitivity of the first piezoelectric element and the sensitivity of the second piezoelectric element may become uneven.

[0007] Furthermore, for example, if adhesive is provided between the first piezoelectric sheet and the second electrode and between the third electrode and the second piezoelectric sheet, the difference between the sensitivity of the first piezoelectric element and the sensitivity of the second piezoelectric element may become even larger, which may result in greater non-uniformity between the sensitivity of the first piezoelectric element and the sensitivity of the second piezoelectric element.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sensor and electronic equipment capable of equalizing the sensitivity of a plurality of piezoelectric elements. [Means for solving the problem]

[0009] A sensor according to one aspect of the present invention includes: a flexible plate-like member having a first main surface; a piezoelectric element provided on the first main surface; It is equipped with the piezoelectric element includes a plurality of piezoelectric films including at least a first piezoelectric film and a second piezoelectric film; the first piezoelectric film includes polylactic acid stretched in at least a first orientation direction; the second piezoelectric film includes polylactic acid stretched in at least a second orientation direction; When viewed in a normal direction of the first main surface, the second alignment direction is different from the first alignment direction, When viewed in the normal direction, the plurality of piezoelectric films are arranged to have a rectangular outer edge as a whole. [Effects of the Invention]

[0010] According to the present invention, the sensitivity of a plurality of piezoelectric elements can be made uniform. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of the sensor 1. [Figure 2] FIG. 2 is an exploded perspective view of the piezoelectric element 3. As shown in FIG. [Figure 3] FIG. 3 is a plan view of the first piezoelectric film 3a1 and the second piezoelectric film 3b1. [Figure 4] FIG. 4 is a plan view showing an outline of the first simulation. [Figure 5] FIG. 5 is a plan view showing the distribution of strain generated in the first piezoelectric film 3a1 and the second piezoelectric film 3b1 in the first simulation. [Figure 6] FIG. 6 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the first simulation. [Figure 7] FIG. 7 is a graph showing the rate of change in the amount of charge generated by the first piezoelectric film 3a1 in the first simulation. [Figure 8] FIG. 8 is a plan view showing an outline of the second simulation. [Figure 9] FIG. 9 is a plan view showing the distribution of strain generated in the first piezoelectric film 3a1 and the second piezoelectric film 3b1 in the second simulation. [Figure 10] FIG. 10 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the second simulation. [Figure 11] FIG. 11 is a graph showing the rate of change in the amount of charge generated by the first piezoelectric film 3a1 in the second simulation. [Figure 12] FIG. 12 is a plan view showing an outline of the third simulation. [Figure 13] FIG. 13 is a plan view showing the distribution of strain generated in the first piezoelectric film 3a1 and the second piezoelectric film 3b1 in the third simulation. [Figure 14] FIG. 14 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the third simulation. [Figure 15] FIG. 15 is a graph showing the rate of change in the amount of charge generated by the first piezoelectric film 3a1 in the third simulation. [Figure 16] FIG. 16 is a plan view showing an outline of the fourth simulation. [Figure 17] FIG. 17 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the fourth simulation. [Figure 18] FIG. 18 is a plan view showing an outline of the fifth simulation. [Figure 19] FIG. 19 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the fifth simulation. [Figure 20] FIG. 20 is a plan view showing an outline of the sixth simulation. [Figure 21] FIG. 21 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the sixth simulation. [Figure 22] FIG. 22 is a plan view showing an outline of the seventh simulation. [Figure 23] FIG. 23 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the seventh simulation. [Figure 24] FIG. 24 is a plan view of the sensor 1a. [Figure 25] FIG. 25 is a plan view of the sensor 1b. [Figure 26] FIG. 26 is a plan view of the sensor 1c. [Figure 27] FIG. 27 is a plan view of the sensor 1d. [Figure 28] FIG. 28 is a plan view of the sensor 1e. [Figure 29] FIG. 29 is a plan view of the sensor 1f. [Figure 30] FIG. 30 is a plan view of the sensor 1g. [Figure 31] FIG. 31 is a plan view of the sensor 1h. [Figure 32] FIG. 32 is a perspective view of the electronic device 10. As shown in FIG. [Figure 33] FIG. 33 is a plan view of the electronic device 10. As shown in FIG. [Figure 34] FIG. 34 is a plan view showing the direction of distortion when the center of the upper main surface US2a of the FPC 2a is pressed. [Figure 35] FIG. 35 is a plan view showing the direction of distortion when the front left corner of the upper main surface US2a of the FPC 2a is pressed. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First embodiment] A sensor 1 according to a first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view of the sensor 1. Fig. 2 is an exploded perspective view of the piezoelectric element 3. Fig. 3 is a plan view of the first piezoelectric film 3a1 and the second piezoelectric film 3b1.

[0013] As an example, the directions are defined as follows. As shown in FIG. 1 , the direction in which the long side of the upper main surface US2 of the FPC2 extends is defined as the left-right direction. The direction in which the short side of the upper main surface US2 of the FPC2 extends is defined as the front-rear direction. The direction in which the upper main surface US2 and the lower main surface DS2 are aligned is defined as the up-down direction. The left-right direction, front-rear direction, and up-down direction are mutually perpendicular. The left-right direction corresponds to the first direction according to the present invention. The front-rear direction corresponds to the second direction according to the present invention. However, the left-right direction, front-rear direction, and up-down direction in this specification are directions defined for the convenience of explanation and may not coincide with the left-right direction, front-rear direction, and up-down direction when the sensor 1 is in use. Furthermore, in each drawing, the left direction and the right direction may be interchanged, the front direction and the rear direction may be interchanged, and the up-down direction may be interchanged.

[0014] In this specification, the term "rectangular" does not necessarily mean a perfect rectangle, but also includes a roughly rectangular shape. An example of a roughly rectangular shape is a shape in which at least one of the four corners of the rectangle is chamfered.

[0015] The sensor 1 is attached to an object to be measured (not shown) and detects at least one of bending and twisting of the object to be measured. As shown in Fig. 1, the sensor 1 includes an FPC 2 and a piezoelectric element 3. The FPC 2 corresponds to the plate-like member according to the present invention.

[0016] The FPC2 is a flexible insulating substrate. Examples of materials for the FPC2 include polyimide, PET (Poly Ethylene Terephthalate), and liquid crystal polymer. The FPC2 is plate-shaped. The FPC2 has an upper principal surface US2 and a lower principal surface DS2 aligned in the vertical direction. The normal direction of the upper principal surface US2 is the upward direction. The upper principal surface US2 and the lower principal surface DS2 each have a rectangular shape with two long sides extending in the left-right direction and two short sides extending in the front-rear direction. The upper principal surface US2 corresponds to the first principal surface according to the present invention. The FPC2 may also be conductive. The upper principal surface US2 and the lower principal surface DS2 do not have to be rectangular.

[0017] The piezoelectric element 3 is flexible. The piezoelectric element 3 is provided on the upper main surface US2 of the FPC 2. As shown in FIG. 2, the piezoelectric element 3 includes a first electrode 31, an adhesive 32, a first piezoelectric film 3a1, a second electrode 3a2, adhesives 3a3 and 3a4, a second piezoelectric film 3b1, a second electrode 3b2, and adhesives 3b3 and 3b4. In this embodiment, the adhesives 32, 3a3, 3a4, 3b3, and 3b4 are each double-sided tape. The adhesives 3a3, 3a4, 3b3, and 3b4 are each conductive. The piezoelectric element 3 may include multiple piezoelectric films, including at least the first piezoelectric film 3a1 and the second piezoelectric film 3b1. The adhesives 32, 3a3, 3a4, 3b3, and 3b4 are not limited to double-sided tape. Furthermore, each of the adhesive materials 3a3, 3a4, 3b3, and 3b4 does not necessarily have to be conductive.

[0018] The first electrode 31 is flexible and conductive. The material of the first electrode 31 is, for example, copper. The first electrode 31 is in the form of a flat film. The first electrode 31 is provided on the upper main surface US2 of the FPC 2 with an adhesive 32. The first electrode 31 is connected to a ground potential, and functions as a reference electrode and a shield conductor. The first electrode 31 corresponds to the reference electrode according to the present invention. The shape of the first electrode 31 is not limited to the shape shown in this embodiment.

[0019] The first piezoelectric film 3a1 is flat and rectangular in shape, with front and rear edges extending in the left-right direction and left and right edges extending in the front-rear direction, when viewed in the up-down direction. The first piezoelectric film 3a1 is attached to the upper main surface of the first electrode 31 by an adhesive 3a3.

[0020] The first piezoelectric film 3a1 has a piezoelectric body. The piezoelectric body is polarized by deformation, generating electric charges on the upper and lower principal surfaces of the first piezoelectric film 3a1. The electric charges generated on the upper and lower principal surfaces of the first piezoelectric film 3a1 correspond to the amount of deformation of the first piezoelectric film 3a1.

[0021] The piezoelectric material is, for example, a chiral polymer. The chiral polymer is, for example, polylactic acid (PLA) such as poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA). The main chain of PLA has a helical structure. PLA has a piezoelectric constant of d14. The piezoelectric material may also be polyvinylidene fluoride.

[0022] The PLA is stretched at least in a first orientation direction OD1. When viewed from below, the first orientation direction OD1 forms a 45-degree counterclockwise angle with respect to the left-right direction. When the first piezoelectric film 3a1 is stretched or compressed in the left-right direction, electric charges are generated on the upper and lower principal surfaces of the first piezoelectric film 3a1. Similarly, when the first piezoelectric film 3a1 is stretched or compressed in the front-rear direction, electric charges are generated on the upper and lower principal surfaces of the first piezoelectric film 3a1. Therefore, in this embodiment, the first piezoelectric film 3a1 is used to detect bending of a measurement object. The magnitude of the electric charges generated on the upper and lower principal surfaces of the first piezoelectric film 3a1 is proportional to the time differential of the deformation of the first piezoelectric film 3a1. Note that the magnitude of the electric charges generated on the upper and lower principal surfaces of the first piezoelectric film 3a1 does not necessarily have to be proportional to the time differential of the deformation of the first piezoelectric film 3a1.

[0023] The second electrode 3a2 is flexible and conductive. The material of the second electrode 3a2 is, for example, copper. The second electrode 3a2 is in the form of a flat film. The second electrode 3a2 is provided on the upper main surface of the first piezoelectric film 3a1 with an adhesive 3a4. In this embodiment, the second electrode 3a2 covers the upper main surface of the first piezoelectric film 3a1. The second electrode 3a2 functions as a signal electrode for outputting charges generated by the first piezoelectric film 3a1. The shape of the second electrode 3a2 is not limited to the shape shown in this embodiment.

[0024] In this embodiment, the second piezoelectric film 3b1, the second electrode 3b2, and the adhesives 3b3 and 3b4 are located to the left of the first piezoelectric film 3a1, the second electrode 3a2, and the adhesives 3a3 and 3a4. Regarding the second piezoelectric film 3b1, the second electrode 3b2, and the adhesives 3b3 and 3b4, only the differences from the first piezoelectric film 3a1, the second electrode 3a2, and the adhesives 3a3 and 3a4 will be described, and the rest will be omitted.

[0025] The second piezoelectric film 3b1 includes PLA stretched at least in a second orientation direction OD2. In this embodiment, the second orientation direction OD2 forms a 0-degree counterclockwise angle with respect to the left-right direction when viewed from below. As a result, the second piezoelectric film 3b1 generates electric charges on the upper and lower principal surfaces of the second piezoelectric film 3b1 when stretched or compressed along a direction that forms a 45-degree or 225-degree counterclockwise angle with respect to the left-right direction when viewed from below. Therefore, in this embodiment, the second piezoelectric film 3b1 is used to detect twist of an object to be measured.

[0026] In this embodiment, the second alignment direction OD2 is offset by 45 degrees from the first alignment direction OD1 when viewed in the vertical direction. The second alignment direction OD2 may be offset by 135 degrees from the first alignment direction OD1 when viewed in the vertical direction. The second alignment direction OD2 only needs to be different from the first alignment direction OD1 when viewed in the vertical direction. This allows the deformation direction detected by the first piezoelectric film 3a1 to be different from the deformation direction detected by the second piezoelectric film 3b1.

[0027] As described above, the first piezoelectric film 3a1 is provided on the upper main surface of the first electrode 31 with the adhesive 3a3. This electrically connects the first electrode 31 to the first piezoelectric film 3a1. The second piezoelectric film 3b1 is provided on the upper main surface of the first electrode 31 with the adhesive 3b3. This electrically connects the first electrode 31 to the second piezoelectric film 3b1.

[0028] As shown in Fig. 3, the plurality of piezoelectric films are arranged to have a rectangular outer edge as a whole when viewed in the vertical direction. In this embodiment, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole. Details of "the plurality of piezoelectric films are arranged to have a rectangular outer edge as a whole when viewed in the vertical direction" will be described below.

[0029] When viewed in the vertical direction, if any of the sides of the first piezoelectric film 3a1 and any of the sides of the second piezoelectric film 3b1 are aligned on the same straight line, the sides may be virtually extended to connect the sides. Furthermore, when any of the sides of the first piezoelectric film 3a1 and any of the vertices of the second piezoelectric film 3b1 are aligned on the same straight line, the sides may be virtually extended to connect the sides and the vertices. Furthermore, when any of the vertices of the first piezoelectric film 3a1 and any of the sides of the second piezoelectric film 3b1 are aligned on the same straight line, the sides may be virtually extended to connect the vertices and the sides. If, after these virtually connected connections, the multiple piezoelectric films have a rectangular outer edge when viewed in the vertical direction, the multiple piezoelectric films can be said to be arranged to have a rectangular outer edge as a whole when viewed in the vertical direction.

[0030] In this embodiment, the front edge of the first piezoelectric film 3a1 and the front edge of the second piezoelectric film 3b1 are located on the same straight line L1 when viewed in the vertical direction. Therefore, the front edge of the first piezoelectric film 3a1 or the front edge of the second piezoelectric film 3b1 is virtually extended to connect the front edge of the first piezoelectric film 3a1 and the front edge of the second piezoelectric film 3b1. Furthermore, the rear edge of the first piezoelectric film 3a1 and the rear edge of the second piezoelectric film 3b1 are located on the same straight line L2 when viewed in the vertical direction. Therefore, the rear edge of the first piezoelectric film 3a1 or the rear edge of the second piezoelectric film 3b1 is virtually extended to connect the rear edge of the first piezoelectric film 3a1 and the rear edge of the second piezoelectric film 3b1. When viewed in the vertical direction, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 have a rectangular outer edge OE (thick line in FIG. 3). Therefore, when viewed in the vertical direction, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole.

[0031] According to the sensor 1, the sensitivity of the piezoelectric element of the first piezoelectric film 3a1 and the sensitivity of the piezoelectric element of the second piezoelectric film 3b1 can be made uniform. More specifically, in the displacement sensor described in Patent Document 1 (Japanese Patent No. 5831542), the sensitivity of the first piezoelectric element and the sensitivity of the second piezoelectric element may become non-uniform in the pressing direction due to the viscoelasticity of the first adhesive and the second adhesive positioned between the first piezoelectric element and the second piezoelectric element. Furthermore, for example, if adhesive is provided between the first piezoelectric sheet and the second electrode and between the third electrode and the second piezoelectric sheet, the sensitivity of the first piezoelectric element and the sensitivity of the second piezoelectric element may become even more non-uniform.

[0032] On the other hand, in the sensor 1, both the first piezoelectric film 3a1 and the second piezoelectric film 3b1 are disposed on the upper main surface US2 of the FPC 2. Therefore, in the upward pressing direction, there is no viscoelastic material between the piezoelectric element of the first piezoelectric film 3a1 and the piezoelectric element of the second piezoelectric film 3b1. Therefore, when the object to be measured is pressed upward, both the first piezoelectric film 3a1 and the second piezoelectric film 3b1 react, preventing only one of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 from reacting. In other words, it is possible to prevent the sensitivity of the piezoelectric element of one piezoelectric film from being lower than the sensitivity of the piezoelectric element of the other piezoelectric film. Therefore, the sensor 1 can equalize the sensitivity of the piezoelectric element of the first piezoelectric film 3a1 and the sensitivity of the piezoelectric element of the second piezoelectric film 3b1.

[0033] In sensor 1, the second orientation direction OD2 is different from the first orientation direction OD1 when viewed in the vertical direction. As a result, the deformation direction detected by first piezoelectric film 3a1 is different from the deformation direction detected by second piezoelectric film 3b1. Therefore, sensor 1 can detect multiple deformation directions with high accuracy by equalizing the sensitivity of the piezoelectric material in first piezoelectric film 3a1 and the sensitivity of the piezoelectric material in second piezoelectric film 3b1. As a result, sensor 1 can detect deformation of the object to be measured with high accuracy.

[0034] Furthermore, sensor 1 can more uniformly balance the sensitivity of the piezoelectric element in first piezoelectric film 3a1 and the sensitivity of the piezoelectric element in second piezoelectric film 3b1. The inventors conducted seven simulations to confirm the effect of the arrangement of first piezoelectric film 3a1 and second piezoelectric film 3b1 on the sensitivity of the piezoelectric element in first piezoelectric film 3a1 and the sensitivity of the piezoelectric element in second piezoelectric film 3b1. Each of the seven simulations (hereinafter referred to as the first to seventh simulations) will be described below.

[0035] FIG. 4 is a plan view showing an overview of the first simulation. FIG. 5 is a plan view showing the distribution of strain generated in the first piezoelectric film 3a1 and the second piezoelectric film 3b1 in the first simulation. FIG. 6 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the first simulation. FIG. 7 is a graph showing the rate of change in the amount of charge generated by the first piezoelectric film 3a1 in the first simulation. The horizontal axes in FIGS. 6 and 7 each represent the amount of displacement [mm]. The vertical axis in FIG. 6 represents the amount of charge [pC]. The vertical axis in FIG. 7 represents the rate of change in the amount of charge [%].

[0036] In the first simulation, the reference state was a state in which the left edge of the first piezoelectric film 3a1 and the right edge of the second piezoelectric film 3b1 overlapped, as shown in FIG. 4 . In the first simulation, the change in the amount of charge generated by the first piezoelectric film 3a1 was observed when the second piezoelectric film 3b1 was moved forward from this reference state. In the reference state, the amount of misalignment along the front-to-rear direction was zero, and the amount of misalignment along the front-to-rear direction was gradually increased. In the reference state, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have an overall rectangular outer edge when viewed in the vertical direction. However, when a misalignment along the front-to-rear direction is provided, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have an overall rectangular outer edge when viewed in the vertical direction. In all of the first through seventh simulations, the pressing point PP is a constant point on the upper principal surface US2 that overlaps with the midpoint of the left edge of the first piezoelectric film 3a1 when viewed in the vertical direction.

[0037] As shown in FIG. 5, in the reference state where the amount of displacement in the front-rear direction is zero, the first piezoelectric film 3a1 is distorted symmetrically around the pressure point PP. As the amount of displacement in the front-rear direction increases, the first piezoelectric film 3a1 tends to distort toward the second piezoelectric film 3b1, even though the position of the pressure point PP remains unchanged. As a result, as shown in FIG. 6, the amount of charge generated by the first piezoelectric film 3a1 decreases as the amount of displacement in the front-rear direction increases. Therefore, as shown in FIG. 7, the rate of change in the amount of charge generated by the first piezoelectric film 3a1 increases as the amount of displacement in the front-rear direction increases.

[0038] The first simulation confirmed that the greater the amount of displacement in the front-to-rear direction, the smaller the amount of charge generated by the first piezoelectric film 3a1 becomes, and the greater the rate of change in the amount of charge generated by the first piezoelectric film 3a1 becomes.

[0039] FIG. 8 is a plan view showing an overview of the second simulation. FIG. 9 is a plan view showing the distribution of strain generated in the first piezoelectric film 3a1 and the second piezoelectric film 3b1 in the second simulation. FIG. 10 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the second simulation. FIG. 11 is a graph showing the rate of change in the amount of charge generated by the first piezoelectric film 3a1 in the second simulation. The horizontal axes in FIGS. 10 and 11 each represent the distance [mm]. The vertical axis in FIG. 10 represents the amount of charge [pC]. The vertical axis in FIG. 11 represents the rate of change in the amount of charge [%].

[0040] In the second simulation, as in the first simulation, the reference state was a state in which the left edge of the first piezoelectric film 3a1 and the right edge of the second piezoelectric film 3b1 overlapped, as shown in FIG. 8. In the second simulation, the change in the amount of charge generated by the first piezoelectric film 3a1 was confirmed when the second piezoelectric film 3b1 was moved to the left from this reference state. In the reference state, the amount of separation in the left-right direction was 0, and the amount of separation in the left-right direction was gradually increased. In all states in the second simulation, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 were arranged so that they had a rectangular outer edge as a whole when viewed in the vertical direction.

[0041] As shown in FIG. 9, in the reference state where the separation distance in the left-right direction is zero, the first piezoelectric film 3a1 is distorted symmetrically around the pressure point PP. It was confirmed that even if the separation distance in the left-right direction increases, the tendency of the first piezoelectric film 3a1 to be distorted symmetrically around the pressure point PP remains unchanged. As a result, as shown in FIG. 10, even if the separation distance in the left-right direction increases, the amount of charge generated by the first piezoelectric film 3a1 does not change substantially. Therefore, as shown in FIG. 10, even if the separation distance in the left-right direction increases, the rate of change in the amount of charge generated by the first piezoelectric film 3a1 can be kept below 10%.

[0042] FIG. 12 is a plan view showing an overview of the third simulation. FIG. 13 is a plan view showing the distribution of strain generated in the first piezoelectric film 3a1 and the second piezoelectric film 3b1 in the third simulation. FIG. 14 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the third simulation. FIG. 15 is a graph showing the rate of change in the amount of charge generated by the first piezoelectric film 3a1 in the third simulation. The horizontal axes in FIGS. 14 and 15 each represent the distance [mm]. The vertical axis in FIG. 14 represents the amount of charge [pC]. The vertical axis in FIG. 15 represents the rate of change in the amount of charge [%].

[0043] In the third simulation, as shown in Figure 12, the left edge of the first piezoelectric film 3a1 and the right edge of the second piezoelectric film 3b1 overlapped, and the offset between the first piezoelectric film 3a1 and the second piezoelectric film 3b1 in the front-to-back direction was 1 mm. In the third simulation, the change in the amount of charge generated by the first piezoelectric film 3a1 was confirmed when the second piezoelectric film 3b1 was moved to the left from this reference state. In the reference state, the offset in the front-to-back direction was 1 mm and the offset in the left-to-right direction was 0 mm, and the offset in the left-to-right direction was gradually increased.

[0044] It was confirmed that the first piezoelectric film 3a1 distorts in the same manner as in the reference state even when the separation distance in the left-right direction increases, as shown in Fig. 13. Therefore, the amount of charge generated by the first piezoelectric film 3a1 remains substantially unchanged even when the separation distance in the left-right direction increases, as shown in Figs.

[0045] The second and third simulations confirmed that the distance in the left-right direction has almost no effect on the amount of charge generated by the first piezoelectric film 3a1.

[0046] Fig. 16 is a plan view showing an overview of the fourth simulation. Fig. 17 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the fourth simulation. The horizontal axis in Fig. 17 represents the distance [mm]. The vertical axis in Fig. 17 represents the amount of charge [pC].

[0047] In the fourth simulation, as in the second simulation, the change in the amount of charge generated by the first piezoelectric film 3a1 when the second piezoelectric film 3b1 was moved to the left was confirmed, as shown in Fig. 16. Therefore, in all states of the fourth simulation, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 were arranged so as to have a rectangular outer edge as a whole when viewed in the vertical direction. However, in the fourth simulation, the first alignment direction OD1 forms a 45-degree angle with each of the left-right and front-back directions, and the change in the amount of charge generated by the first piezoelectric film 3a1 when the second piezoelectric film 3b1 is moved to the left was confirmed in four cases: (1) when the second alignment direction OD2 forms a 0-degree counterclockwise angle with the left-right direction when viewed downward, (2) when the second alignment direction OD2 forms a 45-degree counterclockwise angle with the left-right direction when viewed downward, (3) when the second alignment direction OD2 forms a 90-degree counterclockwise angle with the left-right direction when viewed downward, and (4) when the second alignment direction OD2 forms a 135-degree counterclockwise angle with the left-right direction when viewed downward. That is, in the fourth simulation, the effect of the orientation of the second alignment direction OD2 on the change in the amount of charge generated by the first piezoelectric film 3a1 was confirmed.

[0048] As shown in FIG. 17, the amount of charge generated by the first piezoelectric film 3a1 is the same in all of the cases (1) to (4).

[0049] The second and fourth simulations confirmed that the orientation of the second alignment direction OD2 does not affect the amount of charge generated by the first piezoelectric film 3a1.

[0050] Fig. 18 is a plan view showing an overview of the fifth simulation. Fig. 19 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the fifth simulation. The horizontal axis in Fig. 19 represents the distance [mm]. The vertical axis in Fig. 19 represents the amount of charge [pC].

[0051] In the fifth simulation, as shown in FIG. 18 , similar to the second simulation, the change in the amount of charge generated by the first piezoelectric film 3a1 when the second piezoelectric film 3b1 was moved to the left was confirmed. Therefore, in all states of the fifth simulation, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 were arranged to have a rectangular outer edge as a whole when viewed from the top-bottom direction. However, in the fifth simulation, the change in the amount of charge generated by the first piezoelectric film 3a1 when the second piezoelectric film 3b1 was moved to the left was confirmed in two cases: (5) when the lengths of the front and rear edges of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 were 20 mm, and (6) when the lengths of the front and rear edges of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 were 10 mm. That is, in the fifth simulation, the effect of the lengths of the front and rear edges of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 on the change in the amount of charge generated by the first piezoelectric film 3a1 was confirmed.

[0052] As shown in Figure 19, in both cases (5) and (6), even if the separation in the left-right direction increases, the amount of charge generated by the first piezoelectric film 3a1 remains almost unchanged, and the rate of change in the amount of charge generated by the first piezoelectric film 3a1 can be kept below 10%.

[0053] The fifth simulation confirmed that regardless of the lengths of the front and rear edges of the first piezoelectric film 3a1 and the second piezoelectric film 3b1, even if the separation in the left-right direction increases, the amount of charge generated by the first piezoelectric film 3a1 remains almost unchanged, and the rate of change in the amount of charge generated by the first piezoelectric film 3a1 can be kept below 10%.

[0054] Fig. 20 is a plan view showing an overview of the sixth simulation. Fig. 21 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the sixth simulation. The horizontal axis in Fig. 21 represents the amount of displacement [mm]. The vertical axis in Fig. 21 represents the amount of charge [pC].

[0055] In the sixth simulation, as shown in Figure 20, the aspect ratio of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 was changed, and the change in the amount of charge generated by the first piezoelectric film 3a1 was confirmed when the second piezoelectric film 3b1 was moved forward, as in the first simulation.

[0056] As shown in FIG. 21, even if the aspect ratio of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 is changed, the amount of charge generated by the first piezoelectric film 3a1 decreases as the amount of misalignment in the front-rear direction increases.

[0057] The first and sixth simulations confirmed that, regardless of the aspect ratio of the first piezoelectric film 3a1 and the second piezoelectric film 3b1, the greater the amount of misalignment along the front-to-back direction, the smaller the amount of charge generated by the first piezoelectric film 3a1 becomes, and the greater the rate of change in the amount of charge generated by the first piezoelectric film 3a1 becomes.

[0058] Fig. 22 is a plan view showing an overview of the seventh simulation. Fig. 23 is a graph showing the amount of charge generated by the first piezoelectric film 3a1 in the seventh simulation. The horizontal axis in Fig. 23 represents the separation distance [mm]. The vertical axis in Fig. 23 represents the amount of charge [pC].

[0059] In the seventh simulation, as shown in Figure 22, the aspect ratio of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 was changed, and the change in the amount of charge generated by the first piezoelectric film 3a1 was confirmed when the second piezoelectric film 3b1 was moved to the left, as in the second simulation.

[0060] As shown in Figure 23, even if the aspect ratio of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 is changed or the separation in the left-right direction is increased, the amount of charge generated by the first piezoelectric film 3a1 remains almost unchanged, and the rate of change in the amount of charge generated by the first piezoelectric film 3a1 can be kept below 10%.

[0061] The second and seventh simulations confirmed that, regardless of the aspect ratio of the first piezoelectric film 3a1 and the second piezoelectric film 3b1, even if the separation in the left-right direction increases, the amount of charge generated by the first piezoelectric film 3a1 remains almost unchanged, and the rate of change in the amount of charge generated by the first piezoelectric film 3a1 can be kept below 10%.

[0062] The first through seventh simulations confirmed that the greater the misalignment in the front-to-rear direction, the smaller the amount of charge generated by the first piezoelectric film 3a1 and the greater the rate of change in the amount of charge generated by the first piezoelectric film 3a1. That is, the greater the misalignment in the front-to-rear direction, the greater the non-uniformity between the sensitivity of the piezoelectric element in the first piezoelectric film 3a1 and the sensitivity of the piezoelectric element in the second piezoelectric film 3b1. On the other hand, it was confirmed that the amount of charge generated by the first piezoelectric film 3a1 remains almost unchanged even with an increase in the separation in the left-to-right direction. Therefore, even with an increase in the separation in the left-to-right direction, the sensitivity of the piezoelectric element in the first piezoelectric film 3a1 and the sensitivity of the piezoelectric element in the second piezoelectric film 3b1 do not become non-uniform but become uniform. Therefore, by arranging the first piezoelectric film 3a1 and the second piezoelectric film 3b1 so that they have a rectangular outer edge as a whole when viewed in the up-down direction, the sensitivity of the piezoelectric element in the first piezoelectric film 3a1 and the sensitivity of the piezoelectric element in the second piezoelectric film 3b1 can be made more uniform.

[0063] In the sensor 1, the second alignment direction OD2 is shifted by 45 degrees or 135 degrees from the first alignment direction OD1 when viewed in the vertical direction. This allows the sensor 1 to use the first piezoelectric film 3a1 and the second piezoelectric film 3b1 to detect bending and twisting of the object to be measured.

[0064] In the sensor 1, a single first electrode 31 is electrically connected to the first piezoelectric film 3a1 and the second piezoelectric film 3b1. In other words, the single first electrode 31 serves as a common reference electrode for the first piezoelectric film 3a1 and the second piezoelectric film 3b1. Therefore, the sensor 1 requires only one wire to connect the reference electrode of the first piezoelectric film 3a1 and the reference electrode of the second piezoelectric film 3b1 to the ground potential, thereby shortening the wire length.

[0065] The first electrode 31 and the second electrodes 3a2 and 3b2 may be interchanged.

[0066] In addition, the first electrode 31 may be divided into an electrode that is electrically connected to the first piezoelectric film 3a1 and not electrically connected to the second piezoelectric film 3b1, and an electrode that is not electrically connected to the first piezoelectric film 3a1 and is electrically connected to the second piezoelectric film 3b1.

[0067] [First Modification] A sensor 1a according to a first modified example of the present invention will be described below with reference to the drawings. Fig. 24 is a plan view of the sensor 1a. Only the parts of the sensor 1a that are different from the sensor 1 will be described, and the rest will be omitted.

[0068] 24, in this modification, the first piezoelectric film 3a1 has a rectangular shape with one of its four corners chamfered when viewed in the vertical direction. The second piezoelectric film 3b1 also has a rectangular shape with one of its four corners chamfered when viewed in the vertical direction. The first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole.

[0069] The sensor 1a also has the same effect as the sensor 1.

[0070] [Second Modification] A sensor 1b according to a second modified example of the present invention will be described below with reference to the drawings. Fig. 25 is a plan view of sensor 1b. Only the parts of sensor 1b that are different from sensor 1 will be described, and the rest will be omitted.

[0071] 25, in this modification, the first piezoelectric film 3a1 has a rectangular shape with one of its four corners chamfered when viewed in the vertical direction. The second piezoelectric film 3b1 also has a rectangular shape with one of its four corners chamfered when viewed in the vertical direction. The first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole.

[0072] The sensor 1b also has the same effect as the sensor 1.

[0073] [Third Modification] A sensor 1c according to a third modified example of the present invention will be described below with reference to the drawings. Fig. 26 is a plan view of sensor 1c. Only the parts of sensor 1c that are different from sensor 1 will be described, and the rest will be omitted.

[0074] 26, in this modification, the first piezoelectric film 3a1 is not rectangular when viewed in the vertical direction. The second piezoelectric film 3b1 is also not rectangular when viewed in the vertical direction. The first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole.

[0075] The sensor 1c also has the same effect as the sensor 1.

[0076] [Fourth Variation] A sensor 1d according to a fourth modified example of the present invention will be described below with reference to the drawings. Fig. 27 is a plan view of the sensor 1d. Only the parts of the sensor 1d that are different from the sensor 1 will be described, and the rest will be omitted.

[0077] 27, in this modification, the first piezoelectric film 3a1 has an L-shape when viewed in the vertical direction. The first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole.

[0078] The sensor 1d also has the same effect as the sensor 1.

[0079] [Fifth Variation] A sensor 1e according to a fifth modified example of the present invention will be described below with reference to the drawings. Fig. 28 is a plan view of sensor 1e. Only the parts of sensor 1e that are different from sensor 1 will be described, and the rest will be omitted.

[0080] 28, in this modification, the first piezoelectric film 3a1 has a triangular shape when viewed in the vertical direction. The second piezoelectric film 3b1 also has a triangular shape when viewed in the vertical direction. The first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole.

[0081] The sensor 1e also has the same effect as the sensor 1.

[0082] [Sixth Modification] A sensor 1f according to a sixth modified example of the present invention will be described below with reference to the drawings. Fig. 29 is a plan view of the sensor 1f. Note that with regard to the sensor 1f, only the parts that are different from the sensor 1 will be described, and the rest will be omitted.

[0083] 28, in this modification, the first piezoelectric film 3a1 has a ring shape surrounding the second piezoelectric film 3b1 when viewed in the vertical direction. The first piezoelectric film 3a1 has a rectangular outer edge. The first piezoelectric film 3a1 and the second piezoelectric film 3b1 are arranged to have a rectangular outer edge OE as a whole.

[0084] The sensor 1f also has the same effect as the sensor 1.

[0085] [Seventh Variation] A sensor 1g according to a seventh modified example of the present invention will be described below with reference to the drawings. Fig. 30 is a plan view of the sensor 1g. Only the parts of the sensor 1g that are different from the sensor 1 will be described, and the rest will be omitted.

[0086] 30, the sensor 1g further includes a third piezoelectric film 3c1, a second electrode 3c2, and adhesives 3c3 and 3c4. Note that the third piezoelectric film 3c1, the second electrode 3c2, and the adhesives 3c3 and 3c4 have the same structures as the first piezoelectric film 3a1, the second electrode 3a2, and the adhesives 3a3 and 3a4, and therefore their description will be omitted. Note that the orientation direction of the third piezoelectric film 3c1 is arbitrary.

[0087] The first piezoelectric film 3a1, the second piezoelectric film 3b1, and the third piezoelectric film 3c1 are arranged in this order toward the left, and are arranged so as to have a rectangular outer edge OE as a whole.

[0088] The sensor 1g also has the same effect as the sensor 1.

[0089] [Eighth Modification] A sensor 1h according to an eighth modified example of the present invention will be described below with reference to the drawings. Fig. 31 is a plan view of the sensor 1h. Only the parts of the sensor 1h that are different from the sensor 1g will be described, and the rest will be omitted.

[0090] 31, the first piezoelectric film 3a1, the second piezoelectric film 3b1, and the third piezoelectric film 3c1 are arranged in this order toward the rear. The first piezoelectric film 3a1, the second piezoelectric film 3b1, and the third piezoelectric film 3c1 are arranged so as to have a rectangular outer edge OE as a whole.

[0091] The sensor 1h also has the same effect as the sensor 1g.

[0092] [Second embodiment] An electronic device 10 according to a second embodiment of the present invention will be described below with reference to the drawings. Fig. 32 is a perspective view of the electronic device 10. Fig. 33 is a plan view of the electronic device 10.

[0093] As shown in FIG. 32, the electronic device 10 includes a sensor 1i, a housing 4, and an adhesive 5. In this embodiment, the adhesive 5 is double-sided tape. The sensor 1i includes an FPC 2a, a first piezoelectric element 36, a second piezoelectric element 37, a third piezoelectric element 38, and a fourth piezoelectric element 39. The adhesive 5 is not limited to double-sided tape. The sensor 1i is not limited to four piezoelectric elements, and may include four or more piezoelectric elements. Regarding the FPC 2a, only the differences from the FPC 2 will be described, and the rest will be omitted.

[0094] The FPC 2a has an upper principal surface US2a and a lower principal surface DS2a aligned in the up-down direction. The normal direction of the lower principal surface DS2a is downward. The upper principal surface US2a and the lower principal surface DS2a are each rectangular with two long sides extending in the left-right direction and two short sides extending in the front-rear direction. In other words, the lower principal surface DS2a has a pair of first opposite sides, i.e., a front side and a rear side, extending in the left-right direction, a pair of second opposite sides, i.e., a left side and a right side, extending in the front-rear direction, and four corners, i.e., a left front corner CLF, a right front corner CRF, a left rear corner CLB, and a right rear corner CRB. The lower principal surface DS2a corresponds to the second principal surface according to the present invention.

[0095] The housing 4 has a rectangular parallelepiped shape. However, the top surface of the housing 4 is open. Thus, the housing 4 includes a bottom part BP and a support part SP.

[0096] The bottom part BP has a rectangular parallelepiped shape. In this embodiment, the bottom part BP is plate-shaped. The support part SP is located on the upper surface of the bottom part BP. The support part SP is supported by the bottom part BP. The support part SP has a frame shape. In this embodiment, when viewed in the vertical direction, the inner edge and outer edge of the support part SP are each rectangular. Note that the shape and arrangement of the housing according to the present invention are not limited to the shape and arrangement shown in this embodiment.

[0097] The outer edge of the lower main surface DS2a of the FPC 2a is supported by the adhesive 5 on the upper surface of the support portion SP of the housing 4. In other words, the support portion SP supports the lower main surface DS2a at the outer edge of the lower main surface DS2a.

[0098] The first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39 are provided on the lower main surface DS2a of the FPC 2a. More specifically, one of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39 is disposed at each of the four corners: the left front corner CLF, the right front corner CRF, the left rear corner CLB, and the right rear corner CRB. In this embodiment, the first piezoelectric element 36 is disposed at the left front corner CLF. The second piezoelectric element 37 is disposed at the right front corner CRF. The third piezoelectric element 38 is disposed at the left rear corner CLB. The fourth piezoelectric element 39 is disposed at the right rear corner CRB. Each of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39 includes a plurality of piezoelectric films, including at least a first piezoelectric film 3a1 and a second piezoelectric film 3b1.

[0099] As shown in FIG. 33 , the first piezoelectric film 3a1 of the first piezoelectric element 36 has a rectangular shape when viewed in the vertical direction. In this embodiment, the first piezoelectric film 3a1 of the first piezoelectric element 36 has a rectangular shape with sides parallel to the left-right direction or the front-rear direction when viewed in the vertical direction. The second piezoelectric film 3b1 of the first piezoelectric element 36 has a rectangular shape when viewed in the vertical direction. In this embodiment, the second piezoelectric film 3b1 of the first piezoelectric element 36 has a rectangular shape when viewed in the vertical direction. The first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36 are arranged to have a rectangular outer edge OE36 as a whole, with sides parallel to the left-right direction or the front-rear direction when viewed in the vertical direction. In this embodiment, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36 are arranged to have a rectangular outer edge OE36 as a whole, with sides parallel to the left-right direction or the front-rear direction when viewed in the vertical direction.

[0100] The left front corner CLF is defined as the first corner C1, and the two sides that form the first corner C1 are defined as the first side S1 and the front side S2. When viewed in the up-down direction, the first side S1, the first piezoelectric film 3a1, and the second piezoelectric film 3b1 are aligned in this order toward the right.

[0101] When viewed in the up-down direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the first piezoelectric element 36 forms an angle of 45 degrees with respect to each of the left-right direction and the front-rear direction. When viewed in the up-down direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the first piezoelectric element 36 is parallel to the direction from the left side (first side S1) to the front side (second side S2). In this embodiment, when viewed in the up-down direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the first piezoelectric element 36 is the direction from the left side (first side S1) to the front side (second side S2). When viewed in the up-down direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the first piezoelectric element 36 may be the direction from the front side (second side S2) to the left side (first side S1).

[0102] When viewed in the up-down direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the first piezoelectric element 36 is parallel to the left-right direction. In this embodiment, when viewed in the up-down direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the first piezoelectric element 36 is rightward. However, when viewed in the up-down direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the first piezoelectric element 36 may be leftward.

[0103] In this embodiment, the second piezoelectric element 37 is bilaterally symmetrical to the first piezoelectric element 36. When viewed in the vertical direction, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the second piezoelectric element 37 are arranged to have a rectangular outer edge OE37 with sides parallel to the left-right direction or the front-rear direction. However, in this embodiment, when viewed in the vertical direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the second piezoelectric element 37 forms a 45-degree angle with each of the left-right direction and the front-rear direction and is a direction from the right edge toward the front edge. Also, when viewed in the vertical direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the second piezoelectric element 37 is a right direction. However, when viewed in the vertical direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the second piezoelectric element 37 may also form a 45-degree angle with each of the left-right direction and the front-rear direction and be a direction from the front edge toward the right edge. Furthermore, when viewed from the top-bottom direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the second piezoelectric element 37 may be oriented leftward.

[0104] In this embodiment, the third piezoelectric element 38 is symmetrical to the first piezoelectric element 36 in the front-to-back direction. When viewed in the up-down direction, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the third piezoelectric element 38 are arranged to have a rectangular outer edge OE38 with sides parallel to the left-right direction or the front-to-back direction. However, in this embodiment, when viewed in the up-down direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the third piezoelectric element 38 forms a 45-degree angle with each of the left-right direction and the front-to-back direction and extends from the rear edge to the left edge. When viewed in the up-down direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the third piezoelectric element 38 extends to the right. However, when viewed in the up-down direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the third piezoelectric element 38 may also form a 45-degree angle with each of the left-right direction and the front-to-back direction and extend from the left edge to the rear edge. Furthermore, when viewed from the top-bottom direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the third piezoelectric element 38 may be oriented leftward.

[0105] In this embodiment, the fourth piezoelectric element 39 is point-symmetric with the first piezoelectric element 36 when viewed in the vertical direction. When viewed in the vertical direction, the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the fourth piezoelectric element 39 are arranged to have a rectangular outer edge OE39 with sides parallel to the left-right direction or the front-rear direction as a whole. However, in this embodiment, when viewed in the vertical direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the fourth piezoelectric element 39 forms a 45-degree angle with each of the left-right direction and the front-rear direction and is a direction from the rear edge to the right edge. Furthermore, when viewed in the vertical direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the fourth piezoelectric element 39 is a right direction. However, when viewed in the vertical direction, the first orientation direction OD1 of the first piezoelectric film 3a1 of the fourth piezoelectric element 39 may also form a 45-degree angle with each of the left-right direction and the front-rear direction and be a direction from the right edge to the rear edge. Furthermore, when viewed from the top-bottom direction, the second orientation direction OD2 of the second piezoelectric film 3b1 of the fourth piezoelectric element 39 may be oriented leftward.

[0106] In a vertical view, the distance between the support portion SP and the outer edge OE2a of the lower principal surface DS2a is shorter than the distance between the outer edge OE2a of the lower principal surface DS2a and each of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39. In other words, in a vertical view, the support portion SP supports the lower principal surface DS2a in an area outside the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39. In addition, in a vertical view, the support portion SP does not overlap with the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39.

[0107] Sensor 1i has the same effect as sensor 1. Furthermore, sensor 1i can detect pressure regardless of where on the upper main surface US2a of FPC 2a that pressure is applied. The following description will be given with reference to the drawings. Fig. 34 is a plan view showing the direction of strain when the center of the upper main surface US2a of FPC 2a is pressed. Fig. 35 is a plan view showing the direction of strain when the front left corner of the upper main surface US2a of FPC 2a is pressed.

[0108] 34 , when the pressure point PP is located at the center of the upper main surface US2a of the FPC 2a in a vertical view, strain occurs in the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39 in the direction from the left front corner CLF, the right front corner CRF, the left rear corner CLB, and the right rear corner CRB toward the pressure point PP. Because the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39 are located at the left front corner CLF, the right front corner CRF, the left rear corner CLB, and the right rear corner CRB, respectively, the direction of this strain is a torsional direction for each of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39. Therefore, when viewed from the vertical direction, if the pressure point PP is located in the center of the upper main surface US2a of the FPC 2a, the second piezoelectric film 3b1 of each of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38 and the fourth piezoelectric element 39 will react and the pressure can be detected.

[0109] 35, when the pressure point PP is located at the left front corner of the upper main surface US2a of the FPC 2a in a vertical view, the first piezoelectric element 36 and the second piezoelectric element 37 are strained in a direction generally parallel to the left-right direction, the third piezoelectric element 38 is strained in a direction generally parallel to the front-rear direction, and the fourth piezoelectric element 39 is strained in a direction from the right rear corner CRB toward the pressure point PP. However, because the distance between the pressure point PP and the fourth piezoelectric element 39 is long, the amount of strain generated in the fourth piezoelectric element 39 is relatively small. Therefore, when the pressure point PP is located at the left front corner of the upper main surface US2a of the FPC 2a in a vertical view, the first piezoelectric films 3a1 of the first piezoelectric element 36, the second piezoelectric element 37, and the third piezoelectric element 38 react and can detect the pressure.

[0110] Furthermore, when viewed in the vertical direction, if the pressure point PP is located at the right front corner of the upper main surface US2a of the FPC 2a, the first piezoelectric films 3a1 of the first piezoelectric element 36, the second piezoelectric element 37, and the fourth piezoelectric element 39 will react, allowing the pressure to be detected. When the pressure point PP is located at the left rear corner of the upper main surface US2a of the FPC 2a, the first piezoelectric films 3a1 of the first piezoelectric element 36, the third piezoelectric element 38, and the fourth piezoelectric element 39 will react, allowing the pressure to be detected. When the pressure point PP is located at the right rear corner of the upper main surface US2a of the FPC 2a, the first piezoelectric films 3a1 of the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39 will react, allowing the pressure to be detected.

[0111] Therefore, the sensor 1i can detect the pressure no matter where on the upper main surface US2a of the FPC 2a the pressure is applied.

[0112] As described above, in the electronic device 10, the distance between the support portion SP and the outer edge OE2a of the lower principal surface DS2a is shorter than the distance between the outer edge OE2a of the lower principal surface DS2a and the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39, respectively. Furthermore, when viewed in the vertical direction, the support portion SP does not overlap the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39. Therefore, the support portion SP does not hinder the deformation of the first piezoelectric film 3a1 and the second piezoelectric film 3b1 of the first piezoelectric element 36, the second piezoelectric element 37, the third piezoelectric element 38, and the fourth piezoelectric element 39. As a result, the electronic device 10 can detect a pressure applied to any portion of the upper principal surface US2a of the FPC 2a with a small pressure. In other words, the electronic device 10 can detect pressure with high sensitivity.

[0113] [Other embodiments] The sensor according to the present invention is not limited to the sensors 1, 1a to 1i, and can be modified within the scope of the gist thereof. Furthermore, the structures of the sensors 1, 1a to 1i may be combined arbitrarily.

[0114] The electronic device according to the present invention is not limited to the electronic device 10, and can be modified within the scope of the gist thereof.

[0115] The sensor and electronic device according to the present invention are not limited to detecting deformation or pressure, but may also detect load, vibration, or the like.

[0116] The present invention has the following configuration.

[0117] (1) a flexible plate-like member having a first main surface; a piezoelectric element provided on the first main surface; It is equipped with the piezoelectric element includes a plurality of piezoelectric films including at least a first piezoelectric film and a second piezoelectric film; the first piezoelectric film includes polylactic acid stretched in at least a first orientation direction; the second piezoelectric film includes polylactic acid stretched in at least a second orientation direction; When viewed in a normal direction of the first main surface, the second alignment direction is different from the first alignment direction, When viewed in the normal direction, the plurality of piezoelectric films are arranged to have a rectangular outer edge as a whole. Sensor.

[0118] (2) When viewed in the normal direction, the second alignment direction is shifted by 45 degrees or 135 degrees with respect to the first alignment direction. The sensor according to (1).

[0119] (3) When viewed in the normal direction, each of the plurality of piezoelectric films has a rectangular shape. The sensor according to (1) or (2).

[0120] (4) the piezoelectric element includes a single reference electrode; the reference electrode is electrically connected to the first piezoelectric film and the second piezoelectric film; A sensor according to any one of (1) to (3).

[0121] (5) a flexible plate-like member having a rectangular second main surface; four or more piezoelectric elements; It is equipped with The second main surface is a pair of first opposite sides extending in a first direction; a pair of second opposite sides extending in a second direction perpendicular to the first direction; Four corners and It has Any of the four or more piezoelectric elements is disposed at each of the four corners, each of the four or more piezoelectric elements includes a plurality of piezoelectric films including at least a first piezoelectric film and a second piezoelectric film; the first piezoelectric film includes polylactic acid stretched in at least a first orientation direction; the second piezoelectric film includes polylactic acid stretched in at least a second orientation direction; When viewed in a normal direction of the second principal surface, the plurality of piezoelectric films arranged at the same corner portion are arranged so as to have an outer edge that is rectangular as a whole, When a corner where the first piezoelectric film and the second piezoelectric film are arranged is defined as a first corner, and two sides forming the first corner are defined as a first side and a second side, When viewed in the normal direction, the first side, the first piezoelectric film, and the second piezoelectric film are arranged in this order, When viewed in the normal direction, the first alignment direction forms an angle of 45 degrees with each of the first direction and the second direction, and is parallel to a direction from the first side toward the second side, the second alignment direction is parallel to the direction in which the second side extends; Sensor.

[0122] (6) When viewed in the normal direction, the first piezoelectric film has a rectangular shape having sides parallel to the first direction or the second direction, When viewed in the normal direction, the second piezoelectric film has a rectangular shape having sides parallel to the first direction or the second direction. (5) The sensor according to (5).

[0123] (7) the piezoelectric element includes a single reference electrode; the reference electrode is electrically connected to the first piezoelectric film and the second piezoelectric film; The sensor according to (5) or (6).

[0124] (8) A sensor according to any one of (5) to (7), The housing and It is equipped with the housing includes a support portion that supports the second main surface at an outer edge of the second main surface, a distance between the support portion and an outer edge of the second main surface is shorter than a distance between each of the plurality of piezoelectric films arranged at the four corner portions and the outer edge of the second main surface, as viewed in the normal direction; When viewed in the normal direction, the support portion does not overlap with the plurality of piezoelectric films. electronic equipment. [Explanation of symbols]

[0125] 1, 1a to 1i: Sensor 2,2a:FPC 3: Piezoelectric element 3a1: first piezoelectric film 3a2, 3b2, 3c2: 2nd electrode 3a3,3a4,3b3,3b4,3c3,3c4,5,32:Adhesive material 3b1: second piezoelectric film 3c1: third piezoelectric film 4: Housing 10:Electronic equipment 31: 1st electrode 36: First piezoelectric element 37: Second piezoelectric element 38: Third piezoelectric element 39: Fourth piezoelectric element BP:Bottom C1: 1st corner CLB: Left posterior corner CLF: Left front corner CRB: Right rear corner CRF: Right anterior corner DS2, DS2a: Lower main surface OD1: First orientation direction OD2: Second orientation direction OE, OE2a, OE36, OE37, OE38, OE39: outer edge PP: Press point S1: First side S2: Second side SP: Support Department US2, US2a: Upper Main Face

Claims

1. a flexible plate-like member having a first main surface; a piezoelectric element provided on the first main surface; It is equipped with the piezoelectric element includes a plurality of piezoelectric films including at least a first piezoelectric film and a second piezoelectric film; the first piezoelectric film includes polylactic acid stretched in at least a first orientation direction; the second piezoelectric film includes polylactic acid stretched in at least a second orientation direction; When viewed in a normal direction of the first main surface, the second alignment direction is different from the first alignment direction, When viewed in the normal direction, the plurality of piezoelectric films are arranged to have a rectangular outer edge as a whole. Sensor.

2. When viewed in the normal direction, the second alignment direction is shifted by 45 degrees or 135 degrees with respect to the first alignment direction. The sensor of claim 1 .

3. When viewed in the normal direction, each of the plurality of piezoelectric films has a rectangular shape. The sensor according to claim 1 or 2.

4. the piezoelectric element includes a single reference electrode; the reference electrode is electrically connected to the first piezoelectric film and the second piezoelectric film; The sensor according to claim 1 or 2.

5. a flexible plate-like member having a rectangular second main surface; four or more piezoelectric elements; It is equipped with The second main surface is a pair of first opposite sides extending in a first direction; a pair of second opposite sides extending in a second direction perpendicular to the first direction; Four corners; It has any one of the four or more piezoelectric elements is disposed at each of the four corners, each of the four or more piezoelectric elements includes a plurality of piezoelectric films including at least a first piezoelectric film and a second piezoelectric film; the first piezoelectric film includes polylactic acid stretched in at least a first orientation direction; the second piezoelectric film includes polylactic acid stretched in at least a second orientation direction; When viewed in a normal direction of the second principal surface, the plurality of piezoelectric films arranged at the same corner portion are arranged so as to have an outer edge that is rectangular as a whole, When a corner where the first piezoelectric film and the second piezoelectric film are arranged is defined as a first corner, and two sides forming the first corner are defined as a first side and a second side, When viewed in the normal direction, the first side, the first piezoelectric film, and the second piezoelectric film are arranged in this order, When viewed in the normal direction, the first alignment direction forms an angle of 45 degrees with each of the first direction and the second direction, and is parallel to a direction from the first side toward the second side, the second alignment direction is parallel to the direction in which the second side extends; Sensor.

6. When viewed in the normal direction, the first piezoelectric film has a rectangular shape having sides parallel to the first direction or the second direction, When viewed in the normal direction, the second piezoelectric film has a rectangular shape having sides parallel to the first direction or the second direction. The sensor of claim 5.

7. the piezoelectric element includes a single reference electrode; the reference electrode is electrically connected to the first piezoelectric film and the second piezoelectric film; The sensor according to claim 5 or claim 6.

8. The sensor according to claim 5 or 6; The housing and It is equipped with the housing includes a support portion that supports the second main surface at an outer edge of the second main surface, a distance between the support portion and an outer edge of the second main surface is shorter than a distance between each of the plurality of piezoelectric films arranged at the four corner portions and the outer edge of the second main surface, as viewed in the normal direction; When viewed in the normal direction, the support portion does not overlap with the plurality of piezoelectric films. electronic equipment.

Images