Sensor

Abstract

This sensor comprises: a piezoelectric film sensor having a first main surface and a second main surface opposing the first main surface; a first stretchable base material that has stretchability in a first direction parallel to the first main surface, has a third main surface and a fourth main surface opposing the third main surface, and is in contact with the piezoelectric film sensor; stretchable electrode wiring that has stretchability in the first direction, is disposed on the third main surface, and is in contact with the first main surface; and an adhesive agent disposed on the fourth main surface. The thickness of the piezoelectric film sensor is less than the total value of the thickness of the stretchable electrode wiring, the thickness of the first stretchable base material, and the thickness of the adhesive agent.

Description

Sensor

[0001] The present invention relates to a sensor for detecting deformation of a measurement object.

[0002] Patent Document 1 describes a displacement sensor that includes an elastic body and a piezoelectric element. The elastic body is made of a high-strength polymer. The piezoelectric element 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 element attached to the elastic body deforms as the housing deforms. The piezoelectric element generates a voltage according to the amount of displacement of the piezoelectric element.

[0003] International Publication No. 2012 / 137897

[0004] In the field of the displacement sensor described in Patent Document 1, there is a demand for a sensor that can be easily attached to a soft object to be measured or to the curved surface of an object to be measured having a curved surface. Even if an attempt is made to attach the high-strength displacement sensor described in Patent Document 1 to a soft object to be measured or to a curved surface, there is a possibility that the sensor will peel off due to strong springback.

[0005] An object of the present invention is to provide a sensor that will not peel off even when attached to a soft object to be measured or to the curved surface of an object to be measured having a curved surface.

[0006] A sensor according to one embodiment of the present invention comprises: a piezoelectric film sensor having a first main surface and a second main surface opposite to the first main surface; a first stretchable base material having stretchability in a first direction parallel to the first main surface, having a third main surface and a fourth main surface opposite to the third main surface, and in contact with the piezoelectric film sensor; stretchable electrode wiring having stretchability in the first direction, disposed on the third main surface, and in contact with the first main surface; and an adhesive disposed on the fourth main surface, wherein the thickness of the piezoelectric film sensor is thinner than the sum of the thickness of the stretchable electrode wiring, the thickness of the first stretchable base material, and the thickness of the adhesive.

[0007] According to the sensor of one embodiment of the present invention, the sensor will not come off even when attached to a soft measurement object or to the curved surface of a measurement object having a curved surface.

[0008] FIG. 1 is a top view of sensor 1 according to the first embodiment. FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 3 is a top view of sensor 1a according to modified example 1. FIG. 4 is a cross-sectional view taken along line A-A in FIG. 3. FIG. 5 is a top view of sensor 1b according to modified example 2. FIG. 6 is a cross-sectional view taken along line A-A in FIG. 5. FIG. 7 is a top view of sensor 1c according to modified example 3. FIG. 8 is a cross-sectional view taken along line A-A in FIG. 7. FIG. 9 is an exploded perspective view of sensor 1d according to modified example 4. FIG. 10 is an exploded perspective view of sensor 1e according to modified example 5.

[0009] [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 top view of the sensor 1 according to the first embodiment. Fig. 2 is a cross-sectional view taken along line AA shown in Fig. 1.

[0010] In this embodiment, directions are defined as shown in Figures 1 and 2. The direction in which the piezoelectric film sensor 10 and the first expandable base material 11 are arranged in this order is the negative direction of the Z axis. The direction opposite to the negative direction of the Z axis is the positive direction of the Z axis. Of the directions perpendicular to the Z axis direction, the direction along the long side of the piezoelectric film sensor 10 is the X axis direction. As shown in Figure 2, the direction in which the part of the expandable electrode wiring 12 that is in contact with the piezoelectric film sensor 10 and the part that is not in contact with the piezoelectric film sensor 10 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 direction along the short side of the piezoelectric film sensor 10 is the Y axis direction.

[0011] The sensor 1 detects deformation of a measurement object OB. The measurement object OB is, for example, a soft object or an object with a curved surface. The measurement object OB is, for example, a human arm, a human elbow, a machine arm, or a pipe of a flow meter. As an example, the sensor 1 is attached to a human elbow. In this case, the sensor 1 detects bending and straightening movements of the human elbow. The sensor 1 includes a piezoelectric film sensor 10, a first stretchable substrate 11, stretchable electrode wiring 12, and an adhesive 13.

[0012] As shown in Figures 1 and 2, the piezoelectric film sensor 10 has a plate shape including short sides extending in the Y-axis direction and long sides extending in the X-axis direction. The piezoelectric film sensor 10 has a first main surface SF1 and a second main surface SF2. The second main surface SF2 faces the first main surface SF1. The first main surface SF1 and the second main surface SF2 are aligned in this order in the positive direction of the Z-axis. The first main surface SF1 is parallel to the X-axis direction and the Y-axis direction. As shown in Figure 2, the piezoelectric film sensor 10 includes a first electrode 100, a piezoelectric film 101, and a second electrode 102.

[0013] 1 and 2, the piezoelectric film 101 has a sheet shape with long sides extending in the X-axis direction and short sides extending in the Y-axis direction. The piezoelectric film 101 has a first film principal surface SF11 and a second film principal surface SF12. The first film principal surface SF11 and the second film principal surface SF12 are aligned in this order in the positive direction of the Z-axis.

[0014] The piezoelectric film 101 is polarized according to the amount of deformation of the piezoelectric film 101. The direction of polarization when the piezoelectric film 101 is stretched in the X-axis direction is opposite to the direction of polarization when the piezoelectric film 101 is stretched in the Y-axis direction. For example, the piezoelectric film 101 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 101 has a piezoelectric constant of d14. As shown in FIG. 1 , the piezoelectric film 101 is uniaxially stretched to exhibit piezoelectricity in which the molecules are oriented in an orientation direction OD. The orientation direction OD forms a 45° angle with respect to the X-axis direction and the Y-axis direction. This 45° angle includes, for example, an angle of approximately 45°±10°. As a result, the piezoelectric film 101 is polarized when the piezoelectric film 101 is stretched in the X-axis direction or the Y-axis direction. The potential difference between the first film principal surface SF11 and the second film principal surface SF12 when the piezoelectric film 101 is polarized depends on the time differential value of the deformation amount of the piezoelectric film 101 due to the stretching or compression.

[0015] The first electrode (sensor electrode) 100 is, for example, a signal electrode. As shown in FIG. 2 , the first electrode 100 is fixed to the first film main surface SF11. The first electrode 100 is, for example, a conductive tape that is conductive and adhesive. In this embodiment, the main surface of the first electrode 100 that is located on the negative side of the Z axis corresponds to the first main surface SF1.

[0016] The second electrode (sensor electrode) 102 is, for example, a reference electrode. The second electrode 102 is connected to a reference potential (for example, ground potential). As shown in FIG. 2 , the second electrode 102 is fixed to the second film main surface SF12. The second electrode 102 is, for example, a conductive tape that is conductive and adhesive. In this embodiment, the main surface of the second electrode 102 that is located on the positive side of the Z axis corresponds to the second main surface SF2.

[0017] As shown in FIGS. 1 and 2 , the first stretchable substrate 11 has a plate shape including a short side extending in the Y-axis direction and a long side extending in the X-axis direction. The first stretchable substrate 11 has a third main surface SF3 and a fourth main surface SF4. The fourth main surface SF4 faces the third main surface SF3. The third main surface SF3 and the fourth main surface SF4 are aligned in this order in the negative direction of the Z-axis. The first stretchable substrate 11 is in contact with the piezoelectric film sensor 10 via the stretchable electrode wiring 12, which will be described later. The first stretchable substrate 11 is in contact with the first electrode 100 via the stretchable electrode wiring 12, which will be described later. The first stretchable substrate 11 is attached to the piezoelectric film sensor 10 via the stretchable electrode wiring 12, which will be described later, by the adhesive first electrode 100. This fixes the first stretchable substrate 11 to the piezoelectric film sensor 10.

[0018] The first stretchable substrate 11 is stretchable at least in the X-axis direction. For example, when a force in the positive direction of the X-axis and the negative direction of the X-axis (hereinafter referred to as the X-axis direction force) is applied to the first stretchable substrate 11, the first stretchable substrate 11 stretches along the X-axis direction. When the force in the X-axis direction is no longer applied to the first stretchable substrate 11, the first stretchable substrate 11 returns to its shape before stretching. The elastic modulus of such a first stretchable substrate 11 is, for example, 1000 MPa or less. The material of the first stretchable substrate 11 is, for example, an elastomeric film. Note that the first stretchable substrate 11 may stretch along the Y-axis direction when a force in the Y-axis direction is applied to the first stretchable substrate 11.

[0019] The stretchable electrode wires 12 are disposed on the third main surface SF3 of the first stretchable base material 11. The stretchable electrode wires 12 are made of a polymer conductive material such as PEDOT (polyethylenedioxythiophene) or a thin-film metal. The stretchable electrode wires 12 are formed directly on the third main surface SF3 by a process such as printing or vapor deposition. Hereinafter, in this embodiment, the electrodes formed directly on the base material will be described as being made of PEDOT or a thin-film metal formed by a process such as printing or vapor deposition. The stretchable electrode wires 12 are in contact with the first main surface SF1. The stretchable electrode wires 12 are fixed to the first main surface SF1 by a first electrode 100, which is an adhesive conductive tape. The stretchable electrode wires 12 are electrically connected to the first electrode 100.

[0020] The expandable electrode wiring 12 has flexibility at least in the X-axis direction. Therefore, similar to the first expandable base material 11, the expandable electrode wiring 12 expands in the X-axis direction when a force in the X-axis direction is applied. When the force in the X-axis direction is no longer applied to the expandable electrode wiring 12, the expandable electrode wiring 12 returns to its shape before expansion. Of course, the expandable electrode wiring 12 may expand along the Y-axis direction when a force in the Y-axis direction is applied.

[0021] The adhesive 13 is disposed on the fourth main surface SF4. The adhesive 13 fixes the first stretchable base material 11, the stretchable electrode wires 12, and the piezoelectric film sensor 10 to the measurement object OB. The adhesive 13 is, for example, a double-sided tape such as OCA (Optical Clear Adhesive).

[0022] In this embodiment, the thickness DS1 of the piezoelectric film sensor 10 is thinner than the sum DS2 of the thickness of the expandable electrode wires 12, the thickness of the first expandable base material 11, and the thickness of the adhesive 13 (see FIG. 2 ). Specifically, the thickness DS1 of the piezoelectric film sensor 10 is the length between the first main surface SF1 and the second main surface SF2. The thickness of the expandable electrode wires 12 is the length between the two main surfaces of the expandable electrode wires 12. The thickness of the first expandable base material 11 is the length between the third main surface SF3 and the fourth main surface SF4. The thickness of the adhesive 13 is the length between the two main surfaces of the adhesive 13.

[0023] (Effects) According to the sensor 1, even if the sensor 1 is attached to a soft object to be measured OB or a curved surface of an object to be measured OB having a curved surface, the sensor 1 will not peel off. Below, a description will be given by comparing the displacement sensor described in Patent Document 1 (hereinafter referred to as Comparative Example 1) with the sensor 1 of this embodiment.

[0024] The elastic modulus of the substrate of Comparative Example 1 is high. Therefore, when Comparative Example 1 is bent, the magnitude of the stress (force due to springback) applied to Comparative Example 1 tends to be large. Therefore, when Comparative Example 1 is attached to a soft, highly deformable test object (hereinafter referred to as the first test object), when the first test object is significantly deformed, strong springback occurs in Comparative Example 1, which may cause Comparative Example 1 to peel off from the first test object. Therefore, even when Comparative Example 1 is attached to the first test object, there is a high possibility that Comparative Example 1 will peel off. Similarly, when Comparative Example 1 is attached to the curved surface of a test object (hereinafter referred to as the second test object) having a curved surface, strong springback occurs in Comparative Example 1, which may cause Comparative Example 1 to peel off from the second test object. Therefore, it is difficult to attach Comparative Example 1 to the first test object or the second test object and use it.

[0025] On the other hand, in the sensor 1, the first stretchable substrate 11 and the stretchable electrode wires 12 are stretchable in the X-axis direction and therefore very flexible. Furthermore, the thickness DS1 of the piezoelectric film sensor 10 is thinner than the sum DS2 of the thickness of the first stretchable substrate 11, the stretchable electrode wires 12, and the adhesive 13. Therefore, the piezoelectric film sensor 10 is likely to deform in response to the deformation of the first stretchable substrate 11, the stretchable electrode wires 12, and the adhesive 13. The sensor 1 is likely to stretch in response to the extension of the first measurement object. Therefore, the sensor 1 is unlikely to peel off from the first measurement object even when the first measurement object is significantly bent. Furthermore, the sensor 1 can be easily attached to the curved surface of the second measurement object.

[0026] Furthermore, the sensor 1 is likely to expand in accordance with the expansion of the first measurement object, and therefore can appropriately detect the deformation of the first measurement object. Similarly, the sensor 1 can appropriately detect the deformation of the second measurement object.

[0027] The elastic modulus of the first elastic base material 11 is 1000 MPa or less. Therefore, the sensor 1 is very soft compared to the comparative example 1. Therefore, the sensor 1 tends to be comfortable to wear.

[0028] The first stretchable base material 11, the stretchable electrode wiring 12, and the adhesive 13 are stretchable and have cushioning properties. Therefore, the first stretchable base material 11, the stretchable electrode wiring 12, and the adhesive 13 easily absorb minute vibrations of the object to be measured OB. Therefore, minute vibrations generated by the object to be measured OB are not easily transmitted to the sensor 1. As a result, the sensor 1 can prevent malfunction without detecting minute vibrations.

[0029] [Variation 1] A sensor 1a according to Variation 1 of the sensor 1 will be described below with reference to the drawings. FIG. 3 is a top view of the sensor 1a according to Variation 1. FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 3. The second extensible substrate 20 and second electrode 102a shown in FIG. 4 are omitted in FIG. 3. In Variation 1, as shown in FIG. 3, the direction in which the reference electrode 25, the signal electrode 26, and the reference electrode 24 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.

[0030] 3 and 4, the sensor 1a differs from the sensor 1 in that it includes an expandable electrode wiring 12a different from the expandable electrode wiring 12, that it further includes a second expandable substrate 20, a third expandable substrate 21, reference electrodes 22 to 25, and a signal electrode 26, that it further includes an insulator 27, and that it includes a piezoelectric film sensor 10a different from the piezoelectric film sensor 10. The piezoelectric film sensor 10a differs from the piezoelectric film sensor 10 in that it includes a second electrode 102a different from the second electrode 102.

[0031] 3 and 4, the signal electrode 26 has a rectangular shape when viewed in the Z-axis direction. The signal electrode 26 is formed near the center of the third principal surface SF3 in the Y-axis direction and at an end of the third principal surface SF3 in the positive direction of the X-axis. The signal electrode 26 is located on the positive side of the X-axis with respect to the piezoelectric film sensor 10a.

[0032] As shown in Figures 3 and 4, each of the reference electrodes 24, 25 has a rectangular shape when viewed in the Z-axis direction. Each of the reference electrodes 24, 25 is formed at an end of the third principal surface SF3 in the positive direction of the X-axis. Each of the reference electrodes 24, 25 is located on the positive side of the X-axis relative to the piezoelectric film sensor 10a. The reference electrode 24 is located on the positive side of the Y-axis relative to the signal electrode 26. The reference electrode 25 is located on the negative side of the Y-axis relative to the signal electrode 26. Each of the reference electrodes 24, 25 is connected to a reference potential. Each of the reference electrodes 24, 25 is not electrically connected to the signal electrode 26.

[0033] As shown in Figures 3 and 4, the reference electrode 23 has a rectangular shape when viewed in the Z-axis direction. The reference electrode 23 has a shape that extends in the Y-axis direction. The reference electrode 23 is formed at the end of the third principal surface SF3 in the negative direction of the X-axis. The reference electrode 23 is located on the negative side of the X-axis relative to the piezoelectric film sensor 10a. In Figure 4, the reference electrode 23 is not in contact with the second electrode 102a, but when the sensor 1a is actually in use, the reference electrode 23 is in contact with the second electrode 102a. Therefore, the reference electrode 23 is electrically connected to the second electrode 102a. The reference electrode 23 is not electrically connected to the signal electrode 26.

[0034] As shown in FIG. 3, the expandable electrode wiring 12a differs from the expandable electrode wiring 12 in that it includes a signal electrode wiring 120a and reference electrode wirings 121a and 122a.

[0035] The signal electrode wiring 120a is formed near the center of the third main surface SF3 in the Y-axis direction. The signal electrode wiring 120a has a shape that extends in the X-axis direction. As shown in FIG. 4, the signal electrode wiring 120a is fixed to the first electrode 100. The signal electrode wiring 120a is electrically connected to the signal electrode 26 and the first electrode 100. The signal electrode wiring 120a is stretchable in the X-axis direction.

[0036] The reference electrode wiring 121a is formed on the third main surface SF3. The reference electrode wiring 121a is located on the positive side of the Y-axis relative to the piezoelectric film sensor 10a and the signal electrode wiring 120a. The reference electrode wiring 121a has a shape that extends in the X-axis direction. The reference electrode wiring 121a is electrically connected to the reference electrode 23 and the reference electrode 24. As shown in FIG. 3, the reference electrode wiring 121a is not electrically connected to the signal electrode wiring 120a. The reference electrode wiring 121a is stretchable in the X-axis direction.

[0037] The reference electrode wiring 122a is formed on the third main surface SF3. The reference electrode wiring 122a is located on the negative side of the Y-axis relative to the piezoelectric film sensor 10a and the signal electrode wiring 120a. The reference electrode wiring 122a has a shape that extends in the X-axis direction. The reference electrode wiring 122a is electrically connected to the reference electrode 23 and the reference electrode 25. As shown in FIG. 3, the reference electrode wiring 122a is not electrically connected to the signal electrode wiring 120a. The reference electrode wiring 122a is stretchable in the X-axis direction.

[0038] 4, the second flexible substrate 20 has a plate shape including a first main surface SF1a and a second main surface SF2a. The first main surface SF1a and the second main surface SF2a are aligned in this order in the positive direction of the Z axis. The entire first main surface SF1a of the second flexible substrate 20 is covered with the second electrode 102a.

[0039] The second stretchable substrate 20 is attached to the second main surface SF2 of the piezoelectric film sensor 10a. Therefore, in this modified example 1, the piezoelectric film sensor 10a is located between the first stretchable substrate 11 and the second stretchable substrate 20. The second stretchable substrate 20 has stretchability in the X-axis direction. The elastic modulus of the second stretchable substrate 20 is 1000 MPa or less. The material of such second stretchable substrate 20 is an elastomer film, similar to the first stretchable substrate 11. The other configurations of the second stretchable substrate 20 are the same as those of the first stretchable substrate 11, so description thereof will be omitted.

[0040] The area of ​​the main surface of the second electrode 102a is larger than the area of ​​the first main surface SF1 or the area of ​​the second main surface SF2 of the piezoelectric film 101. In this modification, the second electrode 102a is attached to the second stretchable substrate 20. The second electrode 102a does not contain a core material such as copper foil, and is made of a conductive adhesive that has conductivity in the Z-axis direction due to conductive filler oriented in the Z-axis direction. This allows the second electrode 102a to have conductivity in the Z-axis direction while also having stretchability in the X-axis direction.

[0041] However, if the orientation of the conductive filler is in the Z-axis direction, the conductivity of the second electrode 102a in the X-axis direction may decrease. Therefore, the second electrode 102a of the sensor 1a is electrically connected to the reference electrode wirings 121a and 122a extending in the X-axis direction, thereby ensuring conductivity in the X-axis direction.

[0042] The reference electrode 22 is disposed on the fourth main surface SF4 of the first stretchable substrate 11. The reference electrode 22 covers substantially the entire fourth main surface SF4. In FIG. 4 , the reference electrode 22 is not in contact with the second electrode 102a. However, during actual use of the sensor 1a, the reference electrode 22 is in contact with the second electrode 102a. Therefore, the reference electrode 22 is electrically connected to the second electrode 102a. Accordingly, the reference electrode 22 is electrically connected to the reference electrode 23, the reference electrode wirings 121a and 122a, and the reference electrodes 24 and 25. This connects the reference electrode 22 to a reference potential. Like the second electrode 102a, the reference electrode 22 is, for example, a conductive adhesive having both electrical conductivity and adhesiveness. This allows the reference electrode 22 to be stretchable in the X-axis direction while being conductive in the Z-axis direction. Although not shown, an electrode is printed or vapor-deposited on the upper surface of the third stretchable substrate 21. Therefore, the reference electrode 22 is also electrically connected to the electrode formed on the upper surface of the third flexible base material 21, thereby ensuring conductivity in the X-axis direction.

[0043] The insulator 27 is disposed on the signal electrode wiring 120a and covers substantially the entire surface of the signal electrode wiring 120a, so that the second electrode 102a is not electrically connected to the signal electrode wiring 120a.

[0044] The third stretchable substrate 21 is disposed on the fourth main surface SF4 side of the first stretchable substrate 11 via the reference electrode 22. When viewed in the Z-axis direction, the size of the third stretchable substrate 21 is approximately the same as the size of the reference electrode 22. The other configurations of the third stretchable substrate 21 are the same as the configurations of the second stretchable substrate 20, and therefore description thereof will be omitted.

[0045] In this modification, the adhesive 13 is not disposed on the first stretchable substrate 11. In this modification, the adhesive 13 is disposed on the third stretchable substrate 21. The other configurations of the adhesive 13 in sensor 1a are the same as the configurations of the adhesive 13 in sensor 1, and therefore, description thereof will be omitted.

[0046] The other configurations of the sensor 1a are the same as those of the sensor 1, and therefore the description thereof will be omitted.

[0047] (Effect) In the sensor 1a, the piezoelectric film sensor 10a is located between the second electrode 102a, which is connected to a reference potential, and the reference electrode 22. This makes it easier for noise generated outside the sensor 1a to be blocked by the second electrode 102a or the reference electrode 22. As a result, the piezoelectric film sensor 10a is less susceptible to the effects of the noise.

[0048] In sensor 1a, stretchable substrates (first stretchable substrate 11, second stretchable substrate 20, third stretchable substrate 21) are disposed on both the positive and negative sides of piezoelectric film sensor 10a along the Z axis. This achieves a balance between the stress (first stress) applied to sensor 1a by second stretchable substrate 20 on the positive side of piezoelectric film sensor 10a along the Z axis and the stress (second stress) applied to sensor 1a by first stretchable substrate 11 and third stretchable substrate 21 on the negative side of piezoelectric film sensor 10a along the Z axis (the first stress and the second stress tend to cancel each other out). This reduces the likelihood of warping in sensor 1a.

[0049] In addition, the sensor 1a has the same effect as the sensor 1.

[0050] [Other Effects of Sensor 1a] The second electrode 102a is attached to the second stretchable substrate 20, which is stretchable in the X-axis direction, and the reference electrode 22 is attached to the third stretchable substrate 21, which is stretchable in the X-axis direction. This improves the adhesion of the second electrode 102a and the reference electrode 22, which function as shields, to the piezoelectric film sensor 10a. As a result, the signal generated by the piezoelectric film sensor 10a does not affect external devices as noise.

[0051] For example, when mounting the piezoelectric film sensor 10a on a printed circuit board or the like, resin potting may be used, which may result in cracks occurring at the mounting boundary. Here, in the sensor 1a, the piezoelectric film sensor 10a is covered with a soft second stretchable substrate 20 and a first stretchable substrate 11. Therefore, even when mounting using potting, contraction of the second stretchable substrate 20 and the first stretchable substrate 11 makes it difficult for a large force to be generated at the mounting boundary. This makes it difficult for cracks to occur at the mounting boundary. As a result, the reliability of the sensor 1a is likely to be improved.

[0052] Of the second and third stretchable substrates 20 and 21, a certain portion (first portion) overlaps the entire piezoelectric film sensor 10a in a planar view, while a certain portion (second portion) other than the first portion does not overlap the piezoelectric film sensor 10a. This tends to reduce the difference in hardness between the hard portion of the sensor 1a (e.g., the portion where the piezoelectric film sensor 10a is provided) and the soft portion of the sensor 1a (e.g., the portion where the piezoelectric film sensor 10a is not provided). This reduces stress concentration at the boundary between the hard portion and the soft portion, making the sensor 1a less susceptible to damage. As a result, the reliability of the sensor 1a is improved.

[0053] 3, in the sensor 1a, the reference electrode wirings 121a, 122a and the reference electrode 23 surround the periphery of the signal electrode wiring 120a, thereby preventing the signal generated by the piezoelectric film sensor 10a from affecting external devices as noise.

[0054] [Modification 2] A sensor 1b according to Modification 2 of the sensor 1 will now be described with reference to the drawings. Fig. 5 is a top view of the sensor 1b according to Modification 2. Fig. 6 is a cross-sectional view taken along the line A-A shown in Fig. 5. In Fig. 5, the second stretchable substrate 20, the stretchable substrate electrode 30, the second electrode 102a, and the second electrode 102b shown in Fig. 6 are omitted.

[0055] 5 and 6, the sensor 1b differs from the sensor 1a in that it includes a piezoelectric film sensor 10b different from the piezoelectric film sensor 10a, in that it further includes a stretchable substrate electrode 30, and in that it includes stretchable electrode wiring 12b different from the stretchable electrode wiring 12a. The piezoelectric film sensor 10b differs from the piezoelectric film sensor 10a in that it further includes a first electrode 100b and a second electrode 102b.

[0056] 6, the first electrode 100b is located between the piezoelectric film 101 and the first electrode 100. In this second modification, the first electrode 100b (sensor electrode) is formed directly on the first film main surface SF11. The first electrode 100b is formed on the first film main surface SF11 by a process such as printing or vapor deposition. The first electrode 100b is formed over the entire surface of the first film main surface SF11.

[0057] 6, the second electrode 102b is located between the piezoelectric film 101 and the second electrode 102a. In this second modification, the second electrode 102b (sensor electrode) is formed directly on the second film main surface SF12 in the same manner as the first electrode 100b. The other configuration of the second electrode 102b is the same as the configuration of the first electrode 100b, so a description thereof will be omitted.

[0058] 6, the stretchable substrate electrode 30 is located between the second electrode 102a and the second stretchable substrate 20. The stretchable substrate electrode 30 is formed directly on the second stretchable substrate 20. The stretchable substrate electrode 30 is formed on the first main surface SF1a, and thereby fixed to the first main surface SF1a. The stretchable substrate electrode 30 is formed over substantially the entire first main surface SF1a. The stretchable substrate electrode 30 has stretchability in the X-axis direction.

[0059] The expandable electrode wiring 12b differs from the expandable electrode wiring 12a in that it is formed directly on the third main surface SF3, and therefore the signal electrode wiring 120b, the reference electrode wiring 121b, and the reference electrode wiring 122b included in the expandable electrode wiring 12b are each formed directly on the third main surface SF3.

[0060] (Effect) In sensor 1b, first electrode 100b is formed directly on the first film main surface SF11. As a result, the distance (inter-electrode distance) between first electrode 100b and second electrode 102b, which sandwich piezoelectric film 101, is shorter than in the configuration of Modification 1. As a result, the stray capacitance generated between first electrode 100b and second electrode 102b is smaller than in the configuration of Modification 1. Therefore, sensor 1b is less susceptible to the influence of this stray capacitance. As a result, the sensitivity of sensor 1b is improved compared to the configuration of Modification 1. Similarly, since second electrode 102b is formed directly on the second film main surface SF12, the sensitivity of sensor 1b is improved compared to the configuration of Modification 1.

[0061] In addition, the sensor 1b has the same effects as the sensors 1 and 1a.

[0062] [Other Effects of Sensor 1b] For example, even in a sensor (hereinafter referred to as Comparative Example 2) in which a conductive tape containing a core material such as copper foil is attached to the second stretchable substrate instead of forming the stretchable substrate electrode directly on the second stretchable substrate, the second stretchable substrate can be attached to the piezoelectric film sensor without reducing the conductivity of Comparative Example 2. However, sensors containing a core material such as copper foil have a higher elastic modulus than the conductive adhesive described above. Therefore, Comparative Example 2 is more likely to experience strong springback, which may cause Comparative Example 2 to peel off from the object being measured.

[0063] On the other hand, in sensor 1b, the stretchable substrate electrode 30 is formed directly on the second stretchable substrate 20, and the second stretchable substrate 20 is attached to the piezoelectric film sensor 10b by the second electrode 102a, which is a stretchable conductive adhesive that does not contain a core material. This allows the second stretchable substrate 20 to be attached to the piezoelectric film sensor 10b without reducing the conductivity of sensor 1b, and the elastic modulus of sensor 1b is smaller than that of comparative example 2. Therefore, sensor 1b is less likely to peel off from the measurement object OB without reducing the conductivity of sensor 1b.

[0064] [Modification 3] A sensor 1c according to Modification 3 of the sensor 1 will now be described with reference to the drawings. Fig. 7 is a top view of the sensor 1c according to Modification 3. Fig. 8 is a cross-sectional view taken along the line A-A shown in Fig. 7. In Fig. 7, the second stretchable substrate 20 and the second electrode 102a shown in Fig. 8 are omitted.

[0065] As shown in FIGS. 7 and 8 , sensor 1c differs from sensor 1a in that it further includes a mounting component 40 and a mounting component electrode 400, which is a signal electrode electrically connected to the mounting component 40. The mounting component 40 and the mounting component electrode 400 are each disposed on the third main surface SF3 of the first stretchable substrate 11. The mounting component 40 is disposed on the mounting component electrode 400. The mounting component 40 is a thermistor, an acceleration sensor, or the like. By including the mounting component 40, sensor 1c becomes a flexible sensor capable of detecting, for example, strain, temperature, or acceleration. In this case, in addition to the piezoelectric film sensor 10, the mounting component 40 can also be attached to a soft measurement object OB or a curved surface of the measurement object OB. This improves the ease of use of sensor 1c as a flexible sensor. The other configurations of sensor 1c are the same as those of sensor 1a, and therefore will not be described here. Although not shown, substantially the entire surface of the mounting component electrode 400 is covered with an insulator similar to insulator 27.

[0066] [Modification 4] A sensor 1d according to Modification 4 of the sensor 1 will now be described with reference to the drawings. Fig. 9 is an exploded perspective view of the sensor 1d according to Modification 4.

[0067] As shown in FIG. 9 , sensor 1d differs from sensor 1 in that it includes a piezoelectric film sensor 10d different from piezoelectric film sensor 10, a stretchable electrode wiring 12d different from stretchable electrode wiring 12, an adhesive 13d different from adhesive 13, and a second stretchable substrate 20 and an insulator 27. Piezoelectric film sensor 10d differs from piezoelectric film sensor 10 in that it includes a second electrode 102d different from the second electrode 102. The stretchable electrode wiring 12d differs from the stretchable electrode wiring 12 in that it includes a signal electrode wiring 120d and a reference electrode wiring 121d. The second electrode 102d, the stretchable electrode wiring 12d, and the adhesive 13d will be described, focusing on the differences from the second electrode 102, the stretchable electrode wiring 12, and the adhesive 13, respectively. The second stretchable substrate 20 and the insulator 27 will be described, focusing on the differences from the second stretchable substrate 20 and the insulator 27 of sensor 1a, respectively.

[0068] The entire first film main surface SF11 is covered with the first electrode 100. The entire second film main surface SF12 is covered with the second electrode 102d.

[0069] When viewed in the Z-axis direction, the second electrode 102d has a shape of two rectangles (hereinafter referred to as a first rectangle R1 and a second rectangle R2) aligned in the X-axis direction. The second electrode 102d is, for example, a conductive mesh fabric and a conductive adhesive having conductivity in the Z-axis direction by including an adhesive film provided in the openings of the conductive mesh fabric. This allows the second electrode 102a to have high flexibility while still being conductive in the Z-axis direction. When viewed in the Z-axis direction, the second electrode 102d has an area OA1 that overlaps with the second film main surface SF12.

[0070] The second elastic base material 20 has a shape of two rectangles aligned in the X-axis direction when viewed in the Z-axis direction. As in the sensor 1a, in the sensor 1d, the entire first main surface SF1a of the second elastic base material 20 is covered with the second electrode 102d.

[0071] The first stretchable substrate 11 has a shape in which two rectangles (hereinafter referred to as a third rectangle R3 and a fourth rectangle R4) are arranged side by side in the X-axis direction when viewed in the Z-axis direction. The length L4 of the fourth rectangle R4 in the Y-axis direction is shorter than the length L2 of the second rectangle R2 in the Y-axis direction. Furthermore, the third rectangle R3 has, at its end in the positive direction of the X-axis, a region NOA that does not overlap with the piezoelectric film 101 or the first electrode 100 when viewed in the Z-axis direction. The length L4 of the fourth rectangle R4 in the Y-axis direction does not have to be shorter than the length L2 of the second rectangle R2 in the Y-axis direction. Furthermore, the third rectangle R3 does not have to have, at its end in the positive direction of the X-axis, a region NOA that does not overlap with the piezoelectric film 101 or the first electrode 100 when viewed in the Z-axis direction.

[0072] The signal electrode wiring 120d is formed on the third main surface SF3 of the first stretchable base material 11. When viewed in the Z-axis direction, the signal electrode wiring 120d has a third portion P3 located in an area OA2 overlapping with the first electrode 100, and a fourth portion P4 extending from the third portion P3 in the positive direction of the X-axis. The third portion P3 covers substantially the entire main surface of the first electrode 100 located on the negative side of the Z-axis. This allows the signal electrode wiring 120d to be electrically connected to the first electrode 100. The signal electrode wiring 120d is stretchable in the X-axis direction.

[0073] The reference electrode wiring 121d is formed on the third main surface SF3 of the first stretchable substrate 11. More specifically, the reference electrode wiring 121d is formed at the end of the third main surface SF3 of the first stretchable substrate 11 in the positive direction of the X axis. The reference electrode wiring 121d and the fourth portion P4 are arranged in this order in the negative direction of the Y axis at the end of the third main surface SF3 of the first stretchable substrate 11 in the positive direction of the X axis. The reference electrode wiring 121d does not overlap with the piezoelectric film 101 or the first electrode 100 when viewed in the Z axis direction. On the other hand, the reference electrode wiring 121d overlaps with the second electrode 102d when viewed in the Z axis direction. Therefore, the reference electrode wiring 121d is electrically connected to the second electrode 102d. When the reference electrode wiring 121d is connected to a reference potential, the second electrode 102d is connected to the reference potential.

[0074] The signal electrode wiring 120d and the reference electrode wiring 121d are made of, for example, carbon. By using carbon instead of metal as the material for the signal electrode wiring 120d and the reference electrode wiring 121d, it is possible to suppress the occurrence of ion migration.

[0075] The insulator 27 is disposed on the fourth portion P4 of the signal electrode wiring 120d. The insulator 27 covers the entire surface of the fourth portion P4. As a result, the signal electrode wiring 120d is not electrically connected to the second electrode 102d.

[0076] When viewed in the Z-axis direction, the adhesive 13d has a shape of two rectangles lined up in the X-axis direction. The adhesive 13d is disposed on the fourth main surface SF4 of the first stretchable substrate 11. The adhesive 13d covers the entire fourth main surface SF4. The adhesive 13d fixes the second stretchable substrate 20, the piezoelectric film sensor 10d, the stretchable electrode wiring 12d, and the first stretchable substrate 11 to the measurement object OB. The adhesive 13d is, for example, a conductive double-sided tape. Such an adhesive 13d is, for example, a conductive adhesive having conductivity in the Z-axis direction by including a conductive mesh fabric and an adhesive film provided in the openings of the conductive mesh fabric. This allows the adhesive 13d to have high elasticity while maintaining conductivity in the Z-axis direction. The adhesive 13d is connected to a reference potential. For example, the conductive mesh fabric is connected to the reference potential.

[0077] As described above, the second electrode 102d and the adhesive 13d each include a conductive mesh fabric and an adhesive film provided at the openings of the conductive mesh fabric, so that the second electrode 102d and the adhesive 13d each have high stretchability, thereby improving the stretchability of the sensor 1d.

[0078] Similar to the sensor 1a, the sensor 1d has a piezoelectric film sensor 10d located between a second electrode 102d connected to a reference potential and an adhesive 13d. This makes it easier for noise generated outside the sensor 1d to be blocked by the second electrode 102d or the adhesive 13d. As a result, the piezoelectric film sensor 10d is less susceptible to the effects of the noise.

[0079] The sensor 1d may further include an adhesive 13 disposed on a principal surface of the adhesive 13d located on the negative side of the Z axis. The adhesive 13 fixes the second stretchable substrate 20, the piezoelectric film sensor 10d, the stretchable electrode wiring 12d, the first stretchable substrate 11, and the adhesive 13d to the measurement object OB. The adhesive 13 is, for example, a double-sided tape such as OCA (Optical Clear Adhesive). In this case, the adhesive 13d may be, for example, a single-sided tape having electrical conductivity.

[0080] [Modification 5] A sensor 1e according to Modification 5 of the sensor 1 will now be described with reference to the drawings. Fig. 10 is an exploded perspective view of the sensor 1e according to Modification 5.

[0081] The sensor 1e differs from the sensor 1d in that the first electrode 100, the piezoelectric film 101, and the first extensible substrate 11 move in the positive direction of the X-axis.

[0082] Because the first electrode 100, piezoelectric film 101, and first stretchable base material 11 move in the positive direction of the X axis, the second electrode 102d has an area OA3 at its end in the negative direction of the X axis where it overlaps with the adhesive 13d without overlapping with the first electrode 100, piezoelectric film 101, and first stretchable base material 11. Similarly, the adhesive 13d has an area OA4 at its end in the negative direction of the X axis where it overlaps with the second electrode 102d without overlapping with the first electrode 100, piezoelectric film 101, and first stretchable base material 11. Therefore, the second electrode 102d and the adhesive 13d are in direct contact at their end in the negative direction of the X axis. This results in a direct electrical connection between the second electrode 102d and the adhesive 13d.

[0083] As described above, the second electrode 102a and the adhesive 13d are conductive in the Z-axis direction, respectively, by including a conductive mesh fabric and an adhesive film provided in the openings of the conductive mesh fabric. Contact between such conductive adhesives ensures electrical connection between the second electrode 102a and the adhesive 13d, thereby achieving both electrical connection between the second electrode 102a and the adhesive 13d and high stretchability in the X-axis direction.

[0084] Because the first electrode 100, the piezoelectric film 101, and the first stretchable substrate 11 are moved in the positive direction of the X-axis, the second electrode 102d has an area OA5 that overlaps with the first stretchable substrate 11 without overlapping with the first electrode 100 and the piezoelectric film 101. Similarly, the first stretchable substrate 11 has an area OA6 that overlaps with the second electrode 102d without overlapping with the first electrode 100 and the piezoelectric film 101. Therefore, the second electrode 102d and the first stretchable substrate 11 are in direct contact.

[0085] Because the second electrode 102d and the first flexible base material 11 are in direct contact with each other, the second electrode 102d covers the periphery of the signal electrode wiring 120d. This allows the signal electrode wiring 120d to be shielded from noise from a direction perpendicular to the Z-axis direction. Furthermore, because the second electrode 102d and the first flexible base material 11 can be cut out to the same dimensions, the second electrode 102d and the first flexible base material 11 can be cut out simultaneously when cutting out the sensor 1e during the manufacturing process of the sensor 1e, thereby improving the processability of the sensor 1e.

[0086] [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.

[0087] The sensors according to the present invention are not limited to the sensors 1, 1a to 1e, but may be modified within the scope of the gist thereof. The configurations of the sensors 1, 1a to 1e may be combined in any desired manner.

[0088] 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 when the sensors 1, 1a to 1e are actually used do not necessarily have to match the X-axis, Y-axis, and Z-axis directions in each embodiment and each modified example.

[0089] In the sensor 1b, it is sufficient that the first electrode 100b is formed directly on the first film main surface SF11 or the second electrode 102b is formed directly on the second film main surface SF12.

[0090] Similarly to the first electrode 100b and the like, the reference electrodes 23, 24, and 25 and the signal electrode 26 of the sensor 1b may be formed directly on the third main surface SF3.

[0091] The expandable electrode wires 12 may be made of a conductor such as copper foil and may be fixed to the third main surface SF3 with double-sided tape.

[0092] When the adhesive 13 is a double-sided tape, it is preferable that the adhesive 13 does not contain a core material such as a film. When the adhesive 13 contains a core material such as a film, the elastic modulus of the adhesive 13 becomes higher than when the adhesive 13 does not contain a core material. This makes it easier for strong springback to occur in the sensor 1, increasing the possibility that the sensor 1 will peel off from the measurement object OB.

[0093] The present invention has the following structure:

[0094] (1) A sensor comprising: a piezoelectric film sensor having a first main surface and a second main surface opposite to the first main surface; a first stretchable base material having stretchability in a first direction parallel to the first main surface, a third main surface and a fourth main surface opposite to the third main surface, and in contact with the piezoelectric film sensor; stretchable electrode wiring having stretchability in the first direction, disposed on the third main surface, and in contact with the first main surface; and an adhesive disposed on the fourth main surface; wherein the thickness of the piezoelectric film sensor is thinner than the sum of the thickness of the stretchable electrode wiring, the thickness of the first stretchable base material, and the thickness of the adhesive.

[0095] (2) The sensor according to (1), wherein the first elastic base material has an elastic modulus of 1000 MPa or less.

[0096] (3) The sensor according to (2), wherein the material of the first elastic substrate is an elastomer film.

[0097] (4) The sensor according to any one of (1) to (3), further comprising a second stretchable base material that is stretchable in the first direction and is attached to the second main surface.

[0098] (5) The sensor according to (4), further comprising a stretchable substrate electrode formed directly on the second stretchable substrate and stretchable in the first direction.

[0099] (6) The sensor according to (4) or (5), wherein the second elastic base material has an elastic modulus of 1000 MPa or less.

[0100] (7) The sensor according to any one of (1) to (6), wherein the expandable electrode wiring is formed directly on the third main surface.

[0101] (8) The sensor according to (7), wherein the expandable electrode wiring includes a signal electrode wiring and a reference electrode wiring.

[0102] (9) The sensor described in any one of (1) to (8), wherein the piezoelectric film sensor includes: a piezoelectric film having a first film main surface and a second film main surface; and a sensor electrode formed directly on at least one of the first film main surface and the second film main surface.

[0103] (10) The sensor according to any one of (1) to (9), further comprising a mounting component disposed on the third main surface.

[0104] 1, 1a to 1e: Sensors 10, 10a, 10b, 10d: Piezoelectric film sensors 11: First stretchable substrate 12, 12a, 12b, 12d: Stretchable electrode wiring 13, 13d: Adhesive 20: Second stretchable substrate 21: Third stretchable substrate 22, 23, 24, 25: Reference electrode 26: Signal electrode 27: Insulator 30: Stretchable substrate electrode 40: Mounted component 100, 100b: First electrode 101: Piezoelectric film 102, 102a, 102b, 102d: Second electrode 120a, 120b, 120d: Signal electrode wiring 121a, 121b, 121d, 122a, 122b: Reference electrode wiring 400: Mounted component electrode DS1: Thickness DS2: Total value NOA, OA1 to OA6: Area OB: Measurement object OD: Orientation direction P3: Third part P4: Fourth part R1: First rectangle R2: Second rectangle R3: Third rectangle R4: Fourth rectangle SF1, SF1a: First main surface SF2, SF2a: Second main surface SF3: Third main surface SF4: Fourth main surface SF11: First film main surface SF12: Second film main surface

Claims

1. a piezoelectric film sensor having a first main surface and a second main surface opposite to the first main surface; a first stretchable substrate having stretchability in a first direction parallel to the first main surface, having a third main surface and a fourth main surface opposite the third main surface, and in contact with the piezoelectric film sensor; stretchable electrode wiring that is stretchable in the first direction, that is disposed on the third principal surface, and that is in contact with the first principal surface; an adhesive disposed on the fourth main surface; It is equipped with a thickness of the piezoelectric film sensor is smaller than a total value of a thickness of the expandable electrode wiring, a thickness of the first expandable base material, and a thickness of the adhesive; Sensor.

2. The elastic modulus of the first elastic base material is 1000 MPa or less. The sensor of claim 1 .

3. The material of the first elastic substrate is an elastomeric film. The sensor of claim 2 .

4. Further provided is a second stretchable substrate that is stretchable in the first direction and is attached to the second main surface. The sensor according to any one of claims 1 to 3.

5. The flexible substrate further includes a flexible substrate electrode formed directly on the second flexible substrate and having flexibility in the first direction. The sensor of claim 4.

6. The elastic modulus of the second elastic base material is 1000 MPa or less. The sensor of claim 4.

7. the expandable electrode wiring is formed directly on the third main surface, The sensor according to any one of claims 1 to 3.

8. The expandable electrode wiring includes a signal electrode wiring and a reference electrode wiring. The sensor of claim 7.

9. The piezoelectric film sensor includes: a piezoelectric film having a first film principal surface and a second film principal surface; a sensor electrode formed directly on at least one of the first film principal surface and the second film principal surface; Contains, The sensor according to any one of claims 1 to 3.

10. Further comprising a mounting component disposed on the third main surface. The sensor according to any one of claims 1 to 3.

11. the material of the signal electrode wiring and the material of the reference electrode wiring are carbon; The sensor of claim 8.

12. The piezoelectric film sensor includes: a piezoelectric film having a first film principal surface and a second film principal surface; a sensor electrode fixed to the second film main surface and having a main surface corresponding to the second main surface; It contains The sensor electrode and the adhesive each include: A conductive mesh fabric; an adhesive film provided at an opening of the conductive mesh fabric; Contains, The sensor according to any one of claims 1 to 3.

13. the sensor electrode and the first elastic substrate are in direct contact with each other; The sensor of claim 12.

14. the sensor electrode and the adhesive are in direct contact with each other; The sensor of claim 12.