Stress sensor sheet, stress sensor, and detection device

Abstract

[Problem] To provide: a stress sensor sheet that allows for easy adjustment of the balance between shear force detection sensitivity and pressure detection sensitivity; a stress sensor; and a detection device, the stress sensor and the detection device using the stress sensor sheet. [Solution] The stress sensor sheet comprises a first electrode layer, a second electrode layer, a first elastic layer, and a second elastic layer. The second elastic layer is made of a material different from that of the first elastic layer. The first elastic layer and the second elastic layer are disposed between the first electrode layer and the second electrode layer. The Poisson's ratio of the second elastic layer is greater than the Poisson's ratio of the first elastic layer.

Description

Sheet for Stress Sensor, Stress Sensor, and Detection Device

[0001] The present invention relates to a sheet for a stress sensor, a stress sensor, and a detection device.

[0002] Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2024-092236) discloses a stress sensor capable of detecting shear force and pressure, which includes a first electrode layer, a second electrode layer, an insulating elastic body layer, and a detection circuit. The insulating elastic body layer is located between the first electrode layer and the second electrode layer and electrically insulates the first electrode layer and the second electrode layer.

[0003] When an external force is applied to the stress detection sheet constituting the stress sensor of Patent Document 1, based on the change in capacitance between the first electrode layer and the second electrode layer resulting from the deformation of the insulating elastic body layer, the shear stress and the compressive stress can be detected.

[0004] Japanese Unexamined Patent Application Publication No. 2024-092236

[0005] In a stress sensor as disclosed in Patent Document 1, it is preferable that the balance between the detection sensitivity of shear force and the detection sensitivity of pressure can be adjusted according to its application. The balance between the detection sensitivity of shear force and the detection sensitivity of pressure can be adjusted by changing the elastic modulus and Poisson's ratio of the elastic body layer laminated between the two electrode layers. However, it is not easy to adjust the elastic modulus and Poisson's ratio individually. For example, when the elastic body layer is rubber, the elastic modulus can be adjusted by changing the molecular weight or the degree of crosslinking, but it is difficult to adjust Poisson's ratio by changing the molecular weight or the degree of crosslinking. Also, when the elastic body layer is a foamed elastic body, the elastic modulus and Poisson's ratio can be adjusted by changing the foaming ratio, but it is not easy to control the foaming ratio in the manufacturing process. Even if an elastic body layer with an appropriate balance can be manufactured, developing materials for elastic body layers with different elastic moduli and Poisson's ratios for each application will lead to an increase in manufacturing costs.

[0006] Furthermore, while lowering the modulus of elasticity and Poisson's ratio of the elastic layer can improve both the detection sensitivity of shear force and pressure, lowering these too much increases the amount of deformation, which reduces the durability of the elastic layer. In addition, the electrode layer that follows the elastic layer may also experience a decrease in detection sensitivity due to deterioration caused by deformation.

[0007] For these reasons, there was a need for a stress sensor sheet that allowed for easy adjustment of the balance between shear force detection sensitivity and pressure detection sensitivity.

[0008] The present invention aims to provide a stress sensor sheet that allows for easy adjustment of the balance between shear force detection sensitivity and pressure detection sensitivity, as well as a stress sensor and detection device using the same.

[0009] Several embodiments for solving the problem are described below. These embodiments can be combined as needed.

[0010] A stress sensor sheet according to a first aspect of the present invention comprises a first electrode layer, a second electrode layer, a first elastic layer, and a second elastic layer. The second elastic layer is made of a different material from the first elastic layer. The first and second elastic layers are arranged between the first and second electrode layers. The Poisson's ratio of the second elastic layer is greater than that of the first elastic layer.

[0011] A stress sensor sheet according to a second aspect of the present invention is a stress sensor sheet according to a first aspect, wherein the second elastic layer is positioned closer to the surface to which the load is applied than the first elastic layer.

[0012] A stress sensor sheet according to a third aspect of the present invention is a stress sensor sheet according to the first or second aspect, wherein the second elastic layer connects layers that are in contact with both sides of the second elastic layer.

[0013] A stress sensor sheet according to a fourth aspect of the present invention is a stress sensor sheet according to any of the first or third aspects, wherein the first elastic layer has a second elastic layer arranged on both sides.

[0014] A stress sensor sheet according to the fifth aspect of the present invention is a stress sensor sheet according to any of the first or fourth aspects, further comprising a third elastic layer made of a different material from the first elastic layer. The third elastic layer is arranged on both sides between the first elastic layer and the second electrode layer. The Poisson's ratio of the third elastic layer is greater than that of the first elastic layer.

[0015] A stress sensor sheet according to the sixth aspect of the present invention is a stress sensor sheet according to any of the first or fifth aspects, wherein the second elastic layers arranged on both sides of the first elastic layer are made of the same material.

[0016] A stress sensor sheet according to the seventh aspect of the present invention is a stress sensor sheet according to any of the first or sixth aspects, wherein the first elastic layer is an elastic foam.

[0017] A stress sensor sheet according to the eighth aspect of the present invention is a stress sensor sheet according to any of the first or seventh aspects, wherein the second elastic layer is rubber-like.

[0018] A stress sensor sheet according to the ninth aspect of the present invention is a stress sensor sheet according to any of the first or eighth aspects, wherein the third elastic layer is rubber-like.

[0019] A stress sensor sheet according to the tenth aspect of the present invention is a stress sensor sheet according to the fifth aspect, wherein the second elastic layer is an adhesive and the third elastic layer is an elastic sheet.

[0020] A stress sensor according to the eleventh aspect of the present invention comprises a stress sensor sheet according to any of the first or tenth aspects, and a detection circuit connected to a first electrode layer and a second electrode layer of the stress sensor sheet.

[0021] A stress sensor according to the twelfth aspect of the present invention is a stress sensor according to the eleventh aspect, which performs multi-point detection.

[0022] A detection device according to the thirteenth aspect of the present invention comprises a stress sensor and an output device.

[0023] This stress sensor sheet makes it easy to adjust the balance between the detection sensitivity of shear force and the detection sensitivity of pressure.

[0024] This is a schematic diagram of the detection device. This is a cross-sectional view of the stress sensor sheet.

[0025] <Embodiment> (1) The overall configuration diagram 1 of the detection device 1 is a schematic diagram of the detection device 1, including a cross-sectional view of the stress sensor sheet 10 according to an embodiment of the present invention. The detection device 1 comprises a stress sensor 100 and an output device 200.

[0026] (1-1) Stress Sensor 100 The stress sensor 100 is a capacitive type stress sensor. The stress sensor 100 mainly comprises a stress sensor sheet 10 and a detection circuit 20. As will be described in detail later, the stress sensor 100 detects the shear force (stress in the planar direction) and pressure (stress in the thickness direction) acting on the stress sensor sheet 10 at multiple points by a load P applied to the surface of the stress sensor sheet 10 (the surface on the side of the first electrode sheet 11, which will be described later). Multipoint detection means detecting the magnitude and direction of the shear force and the magnitude of the pressure (i.e., their distribution) at multiple locations on the stress sensor sheet 10. Note that the stress sensor 100 does not have to be a multipoint detection. In other words, the stress sensor 100 may be capable of detecting stress at only one location.

[0027] (1-2) Output device 200 The output device 200 outputs information (e.g., position, magnitude, and direction) of the shear force and pressure detected by the stress sensor 100. The output device 200 is a display device such as a display or a mobile terminal, which displays the information of the shear force and pressure detected by the stress sensor 100 as visual information. The output device 200 is not limited to a display device, and may output the information of the shear force and pressure detected by the stress sensor 100 as a signal to another device.

[0028] (2) Detailed configuration of the stress sensor 100 (2-1) Stress sensor sheet 10 The stress sensor sheet 10 includes a first electrode sheet 11, a second electrode sheet 12, a first elastic layer 13, and a second elastic layer 14.

[0029] (2-1-1) First electrode sheet 11 The first electrode sheet 11 is laminated on the first surface S1, which is one of the main surfaces of the first elastic layer 13, via the second elastic layer 14a (described later). The first electrode sheet 11 has a first insulating sheet 11a and a first electrode layer 11b formed on the surface of the first insulating sheet 11a facing the first elastic layer 13.

[0030] The first insulating sheet 11a is a layer that supports the first electrode layer 11b. The material of the first insulating sheet 11a is not particularly limited, but examples include polyethylene terephthalate resin (PET), urethane resin, and silicone resin.

[0031] The first electrode layer 11b includes a first electrode pattern and row wiring (not shown). For example, multiple first electrode patterns are formed in a matrix on the surface of the first insulating sheet 11a facing the first elastic layer 13. Row wiring electrically connects adjacent first electrode patterns in a predetermined first direction. The shape and number of the first electrode pattern and row wiring can be selected as appropriate.

[0032] The material of the first electrode layer 11b is not particularly limited, but examples include metals such as gold, silver, copper, platinum, palladium, aluminum, and rhodium; conductive pastes in which metal particles are dispersed in a resin binder; and organic semiconductors such as polyhexylthiophene, polydioctylfluorene, pentacene, and tetrabenzoporphyrin.

[0033] When a metal is used as the material, the first electrode layer 11b is formed by a method in which a conductive film is formed over the entire surface using a plating method, sputtering method, vacuum deposition method, ion plating method, etc., and then patterned by etching. When a conductive paste or organic semiconductor is used as the material, the first electrode layer 11b is formed by a method in which a pattern is directly formed using a printing method such as screen printing, gravure printing, or offset printing.

[0034] The first electrode layer 11b may consist of only one layer or of two or more layers. The thickness of the first electrode sheet 11 is appropriately selected within the range of 30 μm to 200 μm (preferably within the range of 30 μm to 100 μm).

[0035] (2-1-2) Second electrode sheet The second electrode sheet 12 is laminated on the second surface S2 of the first elastic layer 13, which is the surface opposite to the first surface S1, via the second elastic layer 14b (described later). The second electrode sheet 12 has a second insulating sheet 12a and a second electrode layer 12b formed on the surface of the second insulating sheet 12a facing the first elastic layer 13.

[0036] The second insulating sheet 12a is a layer that supports the second electrode layer 12b. The material of the second insulating sheet 12a is not particularly limited, but examples include polyethylene terephthalate resin (PET), urethane resin, and silicone resin.

[0037] The second electrode layer 12b includes a second electrode pattern and a row of wiring (not shown). For example, multiple second electrode patterns are formed in a matrix on the surface of the second insulating sheet 12a facing the first elastic layer 13, such that each pattern partially overlaps with the first electrode pattern in a plan view of the stress sensor sheet 10. The row of wiring electrically connects adjacent second electrode patterns in a direction intersecting the first direction (typically orthogonal directions). The second electrode layer 12b is an example of a bonded layer. The shape and number of the second electrode pattern and the row of wiring can be selected as appropriate. For example, if the stress sensor 100 does not perform multi-point detection, the first and second electrode patterns may be electrode patterns that detect only one point.

[0038] The material of the second electrode layer 12b is not particularly limited, but examples include metals such as gold, silver, copper, platinum, palladium, aluminum, and rhodium; conductive pastes in which metal particles are dispersed in a resin binder; and organic semiconductors such as polyhexylthiophene, polydioctylfluorene, pentacene, and tetrabenzoporphyrin.

[0039] When a metal is used as the material, the second electrode layer 12b is formed by a method in which a conductive film is formed over the entire surface using a plating method, sputtering method, vacuum deposition method, ion plating method, etc., and then patterned by etching. When a conductive paste or organic semiconductor is used as the material, the second electrode layer 12b is formed by a method in which a pattern is directly formed using a printing method such as screen printing, gravure printing, or offset printing.

[0040] The second electrode layer 12b may consist of only one layer or of two or more layers. The thickness of the second electrode sheet 12 is appropriately selected within the range of 30 μm to 200 μm (preferably within the range of 30 μm to 100 μm).

[0041] (2-1-3) First Elastic Layer 13 The first elastic layer 13 is an elastic layer that deforms under load P applied to the surface of the stress sensor sheet 10. The second elastic layer 14 is arranged on both sides of the first elastic layer 13. In this embodiment, the first elastic layer 13 is an elastic foam in which bubbles 13a are dispersed inside. The first elastic layer 13 is not limited, but the average diameter of the bubbles 13a is appropriately selected within the range of, for example, 2 to 1000 μm. The Poisson's ratio of the first elastic layer 13 is appropriately selected within the range of 0 or more and 0.4 or less (preferably within the range of 0.2 or more and 0.35 or less).

[0042] The average diameter of bubble 13a can be determined from cross-sectional images obtained through cross-sectional observation using image processing methods. Cross-sectional observation typically involves cutting the sample to create an opening and observing it with an optical microscope or scanning electron microscope. Commercially available image processing software can be used. Alternatively, the bubble diameter can be measured and calculated manually from the cross-sectional photograph. If the cross-section is elliptical, the square root of the product of the major and minor axes can be used as the bubble diameter.

[0043] The material of the first elastic layer 13 is not particularly limited, but examples include polyethylene resin, silicone resin, urethane resin, and various other rubbers such as natural rubber and synthetic rubber. Silicone resin is particularly preferred because it improves the resilience of the first elastic layer 13 after the pressure is released. Silicone resin is also preferred because it is less prone to uneven deformation of the first elastic layer 13 due to temperature changes, and it is possible to maintain a constant sensitivity of the stress sensor 100.

[0044] The first elastic body layer 13, in the case of an elastic foam, is not particularly limited. For example, a thermal decomposition type foaming agent such as azodicarbonamide or bicarbonate, or a thermally expandable microcapsule foaming agent in which a fluorocarbon or hydrocarbon is encapsulated with a thermoplastic resin capsule is dispersed in the above resin, and it is manufactured by a molding method such as bead foaming, batch foaming, press foaming, atmospheric pressure secondary foaming, injection foaming, or extrusion foaming when heat is applied.

[0045] The first elastic body layer 13 is not limited to an elastic foam, and may be an unprocessed elastic sheet or an elastic sheet with cutouts, concavo-convex shapes, etc.

[0046] The thickness of the first elastic body layer 13 is appropriately selected within the range of 10 μm to 1000 μm (preferably within the range of 100 μm to 500 μm).

[0047] (2-1-4) Second elastic body layer 14 The second elastic body layer 14 includes a second elastic body layer 14a and a second elastic body layer 14b. In the present embodiment, the second elastic body layer 14 is an adhesive layer that connects (adheres) the layers in contact with both surfaces. The second elastic body layer 14 may be rubbery. The second elastic body layer 14 also functions as an elastic body layer that deforms with the load P applied to the surface of the stress sensor sheet 10 together with the first elastic body layer 13. The second elastic body layer 14 has a larger Poisson's ratio than the first elastic body layer 13. The second elastic body layer 14 is an example of the second elastic body layer. The Poisson's ratio of the second elastic body layer 14 is appropriately selected within the range of 0 or more to 0.48 or less (preferably within the range of 0.4 or more to 0.48 or less).

[0048] The second elastic body layer 14a connects the first electrode sheet 11 to the first elastic body layer 13. The second elastic body layer 14a is laminated on the first surface S1 of the first elastic body layer 13. The second elastic body layer 14b connects the second electrode sheet 12 to the first elastic body layer 13. The second elastic body layer 14b is laminated on the second surface S2 of the first elastic body layer 13. Thereby, the first elastic body layer 13 and the second elastic body layer 14 are disposed between the first electrode layer 11b and the second electrode layer 12b. The second elastic body layer 14 is disposed closer to the surface of the stress sensor sheet 10 where the load P is applied than the first elastic body layer 13.

[0049] The second elastic layer 14 is made of a different material from the first elastic layer 13. The second elastic layer 14 is not particularly limited, but for example, it can be a thermosetting adhesive, a UV-curing adhesive, or a moisture-curing adhesive. If the first electrode layer 11b, the second electrode layer 12b, the first wiring 21 and the second wiring 22 (described later), etc., have opaque portions, a UV-curing adhesive may result in uneven curing; therefore, it is preferable that the second elastic layer 14 be a thermosetting adhesive.

[0050] Alternatively, a solvent-free liquid rubber may be used as the thermosetting adhesive. By using a solvent-free liquid rubber for the second elastic layer 14, the second elastic layer 14 can be applied to the first electrode sheet 11 and / or the second electrode sheet 12 using screen printing, gravure printing, a die coater, or a comma coater, thereby reducing the manufacturing cost of the stress sensor sheet 10.

[0051] The second elastic layer 14 may be formed by pressurized degassing, in which the layer is brought into contact with the first elastic layer 13 and heat-cured under high pressure. By forming it using pressurized degassing, adhesion can be achieved without air bubbles between layers even when there are irregularities due to the electrode pattern group, thereby suppressing performance degradation caused by air bubbles and improving the yield rate.

[0052] The second elastic layer 14 is not limited to an adhesive, but may be an unprocessed elastic sheet or an elastic sheet with notches, uneven shapes, or the like.

[0053] The second elastic layer 14a and the second elastic layer 14b may be made of the same material. The thickness of the second elastic layer 14 is appropriately selected within the range of 20 μm to 200 μm (preferably within the range of 50 μm to 100 μm).

[0054] (2-2) Detection circuit 20 The detection circuit 20 includes a first wiring 21, a second wiring 22, and a controller 23.

[0055] (2-2-1) First wiring 21 and second wiring 22 The first wiring 21 connects each of the multiple groups of first electrode patterns, which are connected to each other by row wiring, to the controller 23. The second wiring 22 connects each of the multiple groups of second electrode patterns, which are connected to each other by column wiring, to the controller 23.

[0056] (2-2-2) Controller 23 The controller 23 is implemented by a computer. The controller 23 includes a control arithmetic unit and a memory device (neither of which are shown in the diagram). The control arithmetic unit is a processor such as a CPU or GPU. The control arithmetic unit reads a program stored in the memory device and performs shear force and pressure detection processing according to this program. Furthermore, the control arithmetic unit writes the calculation results to the memory device and reads information stored in the memory device according to the program. Depending on its function, the controller 23 may also include an amplification circuit (amplifier circuit) and the like in addition to the control arithmetic unit and memory device.

[0057] In the shear force and pressure detection process, the controller 23 drives each second electrode pattern group at different timings and measures the capacitance between each first electrode pattern group and the second electrode pattern. Based on the measured capacitance, the controller 23 detects the shear force and pressure acting on the stress sensor sheet 10 at multiple points.

[0058] (3) Modified Figure 2 is a cross-sectional view of the modified stress sensor sheet 10a. The difference between the stress sensor sheet 10 and the stress sensor sheet 10a is that the stress sensor sheet 10a further comprises a third elastic layer 15, which is made of a different material from the second elastic layer 14, and a second elastic layer 14c. The second elastic layer 14c is one of the second elastic layers 14. In other words, the second elastic layer 14c is made of the same material (adhesive) as the second elastic layer 14b.

[0059] The third elastic layer 15 has the second elastic layer 14 positioned on both sides between the first elastic layer 13 and the second electrode layer 12b. Specifically, the second elastic layer 14b is positioned on the side facing the first elastic layer 13, and the second elastic layer 14c is positioned on the side facing the second electrode layer 12b. The third elastic layer 15, together with the first elastic layer 13 and the second elastic layer 14, also functions as an elastic layer that deforms under load P applied to the surface of the stress sensor sheet 10. The third elastic layer 15 has a larger Poisson's ratio than the first elastic layer 13. The third elastic layer 15 may be rubbery. The Poisson's ratio of the third elastic layer 15 is appropriately selected within the range of 0 to 0.48 (preferably within the range of 0.4 to 0.48).

[0060] Although not particularly limited, in this embodiment, the third elastic layer 15 is a sheet-like member (elastic sheet) formed of a silicone resin-based elastic material such as silicone gel or silicone elastomer. The thickness of the third elastic layer 15 is appropriately selected within the range of 100 μm to 500 μm.

[0061] The second elastic layer 14c is laminated on the side of the third elastic layer 15 facing the second electrode layer 12b, connecting the second electrode sheet 12 to the third elastic layer 15. The thickness of the second elastic layer 14 of the stress sensor sheet 10a is appropriately selected within the range of 10 μm to 100 μm (preferably within the range of 10 μm to 20 μm).

[0062] (4) Features (4-1) The stress sensor sheet 10 comprises a first electrode layer 11b and a second electrode layer 12b, a first elastic layer 13 and a second elastic layer 14. The second elastic layer 14 is made of a different material from the first elastic layer 13. The first elastic layer 13 and the second elastic layer 14 are arranged between the first electrode layer 11b and the second electrode layer 12b. The Poisson's ratio of the second elastic layer 14 is greater than that of the first elastic layer 13.

[0063] In the stress sensor sheet 10, a first elastic layer 13 and a second elastic layer 14, each having a different Poisson's ratio, are laminated between the first electrode layer 11b and the second electrode layer 12b, and these layers function as elastic layers. This makes it possible to adjust the overall elastic modulus and Poisson's ratio of the multiple layers (i.e., the first elastic layer 13 and the second elastic layer 14) that are laminated between the first electrode layer 11b and the second electrode layer 12b and function as elastic layers, by individually changing the thickness and material (elastic modulus and Poisson's ratio) of each of the first elastic layer 13 and the second elastic layer 14. Therefore, with the stress sensor sheet 10, it is easy to adjust the balance between the detection sensitivity of shear force and the detection sensitivity of pressure.

[0064] (4-2) The second elastic layer 14 is positioned closer to the surface to which the load P is applied than the first elastic layer 13.

[0065] Since the second elastic layer 14, which has a larger Poisson's ratio than the first elastic layer 13, is in contact with the first electrode sheet 11, the stress sensor sheet 10 prevents damage (such as wire breakage or cracking) to the first electrode layer 11b when a load P is applied, as the first electrode sheet 11 is locally indented.

[0066] (4-3) The second elastic layer 14 connects the layers that are in contact with both sides of the second elastic layer 14.

[0067] (4-4) The first elastic layer 13 has the second elastic layer 14 arranged on both sides.

[0068] (4-5) The third elastic layer 15 (third elastic layer) is further made of a different material from the first elastic layer 13. The third elastic layer 15 has the second elastic layer 14 arranged on both sides between the first elastic layer 13 and the second electrode layer 12b. The Poisson's ratio of the third elastic layer 15 is greater than that of the first elastic layer 13.

[0069] In the modified stress sensor sheet 10a, a first elastic layer 13, a second elastic layer 14, and a third elastic layer 15, each having a different Poisson's ratio, are laminated between the first electrode layer 11b and the second electrode layer 12b, and these layers function as elastic layers. This makes it possible to adjust the overall elastic modulus and Poisson's ratio of the multiple layers (i.e., the first elastic layer 13, the second elastic layer 14, and the third elastic layer 15) that are laminated between the first electrode layer 11b and the second electrode layer 12b and function as elastic layers, by individually changing the thickness and material (elastic modulus and Poisson's ratio) of each of the first elastic layer 13, the second elastic layer 14, and the third elastic layer 15. Therefore, with the modified stress sensor sheet 10a, it is easy to adjust the balance between the detection sensitivity of shear force and the detection sensitivity of pressure.

[0070] (4-6) Each of the second elastic layers 14, which are arranged on both sides of the first elastic layer 13, is made of the same material.

[0071] (4-7) The first elastic layer 13 is an elastic foam.

[0072] (4-8) The second elastic layer 14 is rubbery.

[0073] (4-9) The third elastic layer 15 is rubbery.

[0074] (4-10) The second elastic layer 14 is an adhesive, and the third elastic layer 15 is an elastic sheet.

[0075] Because the adhesive layer is formed thinly, variations in thickness (in other words, elastic modulus and Poisson's ratio) are likely to occur, which can reduce the detection sensitivity of the stress sensor 100. Also, when a thin adhesive layer is used as an elastic layer, it contributes little to Poisson's ratio. In the modified stress sensor sheet 10a, an elastic sheet that is thicker than the adhesive layer and has a uniform thickness is included between the first electrode layer 11b and the second electrode layer 12b, separate from the first elastic layer 13. As a result, in the modified stress sensor sheet 10a, the influence of variations in the thickness of the second elastic layer 14 (adhesive layer) on the detection sensitivity of shear force and pressure is suppressed.

[0076] (4-11) The stress sensor 100 comprises a stress sensor sheet 10 and a detection circuit 20 connected to the first electrode layer 11b and the second electrode layer 12b of the stress sensor sheet 10.

[0077] The stress sensor 100 can detect the shear force and pressure acting on the stress sensor sheet 10.

[0078] (4-12) The detection circuit 20 performs multi-point detection.

[0079] The shear force and pressure acting on the stress sensor sheet 10 can be detected at multiple points.

[0080] (4-13) The detection device 1 comprises a stress sensor 100 and an output device 200.

[0081] The detection device 1 outputs the shear force and pressure information detected by the stress sensor 100 to the output device 200.

[0082] <Conclusion> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention. In particular, the multiple modifications described herein can be arbitrarily combined as needed.

[0083] 1: Detection device 10: Sheet for stress sensor 11: First electrode sheet 11a: First insulating sheet 11b: First electrode layer 12: Second electrode sheet 12a: Second insulating sheet 12b: Second electrode layer 13: First elastic layer 13a: Bubble 14: Second elastic layer 14a: Second elastic layer 14b: Second elastic layer 15: Third elastic layer 20: Detection circuit 21: First wiring 22: Second wiring 23: Controller 100: Stress sensor 200: Output device S1: First surface S2: Second surface P: Load

Claims

1. A stress sensor sheet comprising a first electrode layer and a second electrode layer, a first elastic layer, and a second elastic layer made of a different material from the first elastic layer, wherein the first and second elastic layers are arranged between the first and second electrode layers, and the Poisson's ratio of the second elastic layer is greater than that of the first elastic layer.

2. The stress sensor sheet according to claim 1, wherein the second elastic layer is positioned closer to the surface to which the load is applied than the first elastic layer.

3. The stress sensor sheet according to claim 1, wherein the second elastic layer connects layers that are in contact with both sides of the second elastic layer.

4. The stress sensor sheet according to claim 1, wherein the first elastic layer is provided with the second elastic layer on both sides.

5. The stress sensor sheet according to claim 4, further comprising a third elastic layer made of a different material from the first elastic layer, wherein the second elastic layer is arranged on both sides of the third elastic layer between the first elastic layer and the second electrode layer, and the Poisson's ratio of the third elastic layer is greater than the Poisson's ratio of the first elastic layer.

6. The stress sensor sheet according to claim 4, wherein each of the second elastic layers is made of the same material.

7. The stress sensor sheet according to claim 1, wherein the first elastic layer is an elastic foam.

8. The stress sensor sheet according to claim 1, wherein the second elastic layer is rubbery.

9. The stress sensor sheet according to claim 5, wherein the third elastic layer is rubbery.

10. The stress sensor sheet according to claim 5, wherein the second elastic layer is an adhesive and the third elastic layer is an elastic sheet.

11. A stress sensor comprising: a stress sensor sheet according to any one of claims 1 to 10; and a detection circuit connected to the first electrode layer and the second electrode layer of the stress sensor sheet.

12. The stress sensor according to claim 11, which performs multi-point detection.

13. A detection device comprising the stress sensor described in claim 11 and an output device.

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