Sensor sheet

Abstract

The aim is to provide a sensor sheet with improved ease of installation on the steering wheel. [Solution] The sensor sheet 18 comprises an insulating sheet 24 made of polyethylene foam having a first surface 27 and a second surface 28; a first electrode sheet 25 made of conductive fabric woven from multiple yarn bundles 41 and facing the first surface 27 of the insulating sheet 24; a first joint 50a that joins the first surface 27 of the insulating sheet 24 and the first electrode sheet 25; a second electrode sheet 26 made of conductive fabric woven from multiple yarn bundles 41 and facing the second surface 28 of the insulating sheet 24; and a second joint 50b that joins the second surface 28 of the insulating sheet 24 and the second electrode sheet 26. The sensor sheet 18 is configured such that, in the stress-strain curve during a tensile test, the maximum stress value at a strain of 0-5% is 1.0 MPa or less.

Description

Technical Field

[0001] The present invention relates to a sensor seat.

Background Art

[0002] Patent Document 1 describes a sensor seat including an insulating sheet and an electrode sheet embedded in one surface of the insulating sheet. The sensor seat is attached to, for example, a steering wheel of a vehicle to detect whether an occupant has contacted the steering wheel.

[0003] Patent Document 2 describes a sensor seat including a sensor electrode, a cancel electrode, a foam disposed between the sensor electrode and the cancel electrode, and a hot melt body disposed between the foam and the sensor electrode and between the foam and the cancel electrode.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a method of assembling a sensor seat to a steering wheel, for example, a method of winding the sensor seat around the steering wheel is known. At this time, depending on the shape of the steering wheel, the sensor seat may be stretched or bent.

[0006] During assembly, stretching or bending of the sensor sheet may cause changes in its electrical resistance. Changes in the sensor sheet's electrical resistance affect its detection accuracy. Therefore, it is desirable to suppress changes in the sensor sheet's electrical resistance.

[0007] This invention has been made in view of the above background, and aims to provide a sensor sheet in which changes in the electrical resistance value of the sensor sheet are suppressed by at least one of stretching and bending of the sensor sheet. [Means for solving the problem]

[0008] One aspect of the present invention is an insulating sheet having a first surface and a second surface and formed of polyethylene foam, A first electrode sheet, facing the first surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, A first joining portion that joins the first surface of the insulating sheet and the first electrode sheet, A second electrode sheet, facing the second surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, The device comprises a second joining portion that joins the second surface of the insulating sheet and the second electrode sheet, The sensor sheet is configured such that, in the stress-strain curve during a tensile test, the maximum stress value at a strain of 0-5% is 1.0 MPa or less.

[0009] Another aspect of the present invention is an insulating sheet having a first surface and a second surface and formed of polyethylene foam, A first electrode sheet, facing the first surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, A first joining portion that joins the first surface of the insulating sheet and the first electrode sheet, A second electrode sheet, facing the second surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, The device comprises a second joining portion that joins the second surface of the insulating sheet and the second electrode sheet, The system is configured such that, based on the DC resistance value of the test specimen before the bending evaluation test is performed, the rate of change in the DC resistance value of the test specimen after 30 bending evaluation tests is 200% or less. The bending evaluation test involves bending the test specimen 180°, applying a load of 5 kgf in the normal direction to the bent specimen, and returning the specimen from the bent state to the unfolded state, all within the sensor sheet. [Effects of the Invention]

[0010] According to one and other embodiments of the present invention, the first electrode sheet and the second electrode sheet are formed from a conductive fabric woven from multiple bundles of threads. Furthermore, a first joint is interposed between the first electrode sheet and the first surface of the insulating sheet, and a second joint is interposed between the second electrode sheet and the second surface of the insulating sheet. When a tensile force is applied to the sensor sheet, the woven first electrode sheet and the second electrode sheet undergo stretch deformation. Since the first electrode sheet and the second electrode sheet are conductive fabrics, they can maintain their conductive paths even when stretched and deformed. Therefore, even when a tensile force is applied to the sensor sheet, changes in electrical resistance can be suppressed.

[0011] Furthermore, in one aspect of the present invention, the sensor sheet is configured such that, in the stress-strain curve during a tensile test, the maximum stress value at a strain of 0-5% is 1.0 MPa or less. In the sensor sheet, the insulating sheet is made of polyethylene foam. This allows the sensor sheet to have the above-mentioned characteristics regarding the stress-strain curve. And, due to the above-mentioned characteristics regarding the stress-strain curve, the assembly of the sensor sheet is improved.

[0012] Furthermore, in another aspect of the present invention, the sensor sheet is configured such that the rate of change in the DC resistance of the test piece after 30 bending evaluation tests is 200% or less, based on the DC resistance of the test piece before the bending evaluation test is performed. Therefore, even if the sensor sheet is bent during assembly, good detection performance can be obtained from the sensor sheet.

Brief Description of the Drawings

[0013] [Figure 1] Front view showing a steering wheel with a sensor sheet attached in Embodiment 1. [Figure 2] Enlarged cross-sectional view taken along line A-A in FIG. 1. [Figure 3] Plan view showing the sensor sheet in Embodiment 1. [Figure 4] View obtained by rotating the enlarged cross-sectional view taken along line B-B in FIG. 3 counterclockwise by 90°. [Figure 5] Partially enlarged plan view showing the first electrode sheet in Embodiment 1. [Figure 6] Enlarged cross-sectional view taken along line C-C in FIG. 5. [Figure 7] Enlarged view showing a part of the surface of the first electrode sheet in a state where no tensile force is applied to the first electrode sheet. [Figure 8] Explanatory diagram of the tensile test. [Figure 9] Graph showing the relationship between strain and stress as a result of the evaluation test for electrode sheet sample 1. [Figure 10] Graph showing the relationship between strain and stress as a result of the evaluation test for insulation sheet samples 2-1, 2-2, and 2-3. [Figure 11] Graph showing the relationship between strain and stress as a result of evaluation test 1 for sensor sheet samples 3-1, 3-2, and 3-3. [Figure 12] Graph showing the relationship between strain and DC resistance value as a result of evaluation test 1 for sensor sheet samples 3-1, 3-2, and 3-3. [Figure 13] Graph showing the relationship between the number of 20% elongation repetitions and the change rate of the DC resistance value as a result of evaluation test 2 for sensor sheet samples 3-1, 3-2, and 3-3. [Figure 14] Explanatory diagram of the bending evaluation test. [Figure 15] Graph showing the relationship between the number of bends and the change rate of the DC resistance value as a result of evaluation test 3 for sensor sheet samples 3-1, 3-2, and 3-3 and comparative sample 4. [Modes for carrying out the invention]

[0014] (Embodiment 1) 1. Overview of the sensor sheet The sensor sheet is electrostatic and functions as a sensor that detects contact or proximity of a conductor with an electrical potential by utilizing, for example, a change in capacitance between an electrode and a conductor. When a conductor comes into contact with or approaches the sensor sheet, the capacitance between the electrode contained in the sensor sheet and the conductor changes. The sensor sheet detects contact or proximity of the conductor by detecting the equivalent value of the changed capacitance. The equivalent value of capacitance is detected as, for example, voltage or current.

[0015] The sensor sheet is attached, for example, to the steering wheel of a vehicle to detect whether or not the occupant's hand (fingers, palm, back of hand, etc.) is in contact with or close to the steering wheel.

[0016] 2. Steering wheel 10 First, the steering wheel 10 will be described with reference to Figures 1 and 2. As shown in Figure 1, the steering wheel 10 comprises a core portion 11 located in the center, a grip portion 12, and a plurality (three in Embodiment 1) of spoke portions 13 connecting the core portion 11 and the grip portion 12. In the following description, for multiple identical components, reference numerals may be assigned to only some of the components, while the reference numerals for other components may be omitted.

[0017] The grip portion 12 is the part that the driver holds, and is formed in the shape of a circular ring, for example. The grip portion 12 can be formed in any shape, such as a polygonal ring shape or a shape that is separated into left and right sides.

[0018] 3. Grip section 12 The grip portion 12 will be described with reference to Figure 2. The grip portion 12 comprises a core body 16, a resin inner layer material 17, a sensor sheet 18, and a surface material 19. The core body 16 constitutes the central part of the grip portion 12 and is formed in a shape corresponding to the grip portion 12. That is, the core body 16 is formed in a circular ring shape, for example.

[0019] The cross-sectional shape of the core body 16 perpendicular to its axis is, for example, formed in a circular shape. The cross-sectional shape of the core body 16 perpendicular to its axis may be any shape, such as an ellipse, egg shape, U-shape, C-shape, polygon, etc. The core body 16 is made of a metal such as aluminum or magnesium and is electrically conductive. The core body 16 may be made of a material other than metal.

[0020] The resin inner layer material 17 covers the outer circumferential surface of the cross-sectional shape of the core body 16 along its entire ring shape. In the cross-section perpendicular to the axis shown in Figure 2, the shape of the inner circumferential surface of the resin inner layer material 17 corresponds to the outer circumferential surface of the core body 16. The outer circumferential surface of the resin inner layer material 17 is formed, for example, in a circular shape. In the cross-section perpendicular to the axis shown in Figure 2, both the inner and outer circumferential surfaces of the resin inner layer material 17 are formed in a circular shape. If the core body 16 has a U-shaped cross-section perpendicular to the axis, the resin inner layer material 17 fills not only the radially outer side of the cross-section perpendicular to the axis of the core body 16, but also the recess in the U-shape of the core body 16.

[0021] The resin inner layer material 17 is formed by injection molding. The resin inner layer material 17 may or may not be bonded to the outer surface of the core body 16. In a cross-section perpendicular to the axis, the resin inner layer material 17 is not limited to a circular shape, but can be any shape such as an egg shape, ellipse shape, polygon shape, etc. The resin inner layer material 17 is molded from, for example, a foamed resin. For example, foamed polyurethane can be used for the resin inner layer material 17. However, a non-foamed resin can also be used for the resin inner layer material 17.

[0022] The sensor sheet 18 is wrapped around the outer surface of the resin inner layer material 17. When wrapped around the resin inner layer material 17, the sensor sheet 18 has a C-shape in the cross-section perpendicular to the axis shown in Figure 2. However, the ends of the C-shape may be in contact or may have a small gap. The sensor sheet 18 may be arranged along the entire length of the ring shape of the resin inner layer material 17 shown in Figure 1, or it may be arranged in part of the ring shape. The sensor sheet 18 will be described in detail later.

[0023] The outer covering material 19 covers the outer surface of the sensor sheet 18 along the entire length of the ring shape of the grip portion 12. In areas where the sensor sheet 18 is not placed, the outer covering material 19 directly covers the resin inner layer material 17. The outer covering material 19 is molded from leather, cloth, or the like. The outer covering material 19 may be wrapped around the outer surface of the sensor sheet 18 and joined to the outer surface of the sensor sheet 18, or it may not be joined. For joining the outer covering material 19 to the sensor sheet 18, for example, an adhesive or glue may be used. The material of the outer covering material 19 is not particularly limited and can be selected from any material such as leather (genuine leather, synthetic leather, etc.), cloth, rubber, or resin.

[0024] 4. Sensor Sheet 18 The sensor sheet 18 will be described with reference to Figures 3 and 4. First, the planar shape of the sensor sheet 18 will be described with reference to Figure 3. As shown in Figure 3, the sensor sheet 18 is formed in a planar shape (XY plane in Embodiment 1) before being wrapped around the grip portion 12. The planar sensor sheet 18 is formed in a long shape in the longitudinal direction X.

[0025] The sensor sheet 18 comprises a sheet body portion 20 and a sheet extension portion 22. The sheet body portion 20 is formed in a shape approximately rectangular. The sheet body portion 20 comprises a pair of long edges 20a along the longitudinal direction X and a pair of short edges 20b along the direction Y that intersects the longitudinal direction X. In the following description, arrow X indicates the longitudinal direction of the sensor sheet 18, arrow Y indicates the direction (width direction) that intersects the longitudinal direction X in the plane of the sensor sheet 18, and arrow Z indicates the thickness direction of the sensor sheet 18.

[0026] Each of the pair of long edges 20a has a sheet recess 21 formed in the direction Y. However, the sheet recess 21 may be formed on only one of the pair of long edges 20a. Multiple (four in Embodiment 1) sheet recesses 21 are formed at intervals on one long edge 20a. However, one sheet recess 21 may be formed on one long edge 20a. The sheet recesses 21 on both sides are located at the same position in the longitudinal direction X. That is, the sheet recesses 21 on both sides are opposite each other in the direction Y.

[0027] The sheet extension portion 22 is formed on one of the pair of long edges 20a of the sheet body portion 20, at a position near both ends in the longitudinal direction X, extending from the long edge 20a in a direction intersecting the longitudinal direction X.

[0028] Next, the cross-sectional shape of the sensor sheet 18 will be described with reference to Figures 3 and 4. As shown in Figure 4, the sensor sheet 18 comprises an insulating sheet 24, a first electrode sheet 25, a first joint 50a, a second electrode sheet 26, and a second joint 50b.

[0029] The insulating sheet 24 has a first surface 27 and a second surface 28. The insulating sheet 24 is formed of polyethylene foam. Therefore, the insulating sheet 24 is configured to be stretchable in the planar direction and to bendable. Furthermore, the insulating sheet 24 has voids inside. The density of the insulating sheet 24 is preferably 30 to 200 kg / m³. 3 Therefore, it is comfortable at 30-100 kg / m 3 That is the case.

[0030] The insulating sheet 24 may be a first structure in which unfoamed resin is simply foamed, or a second structure in which unfoamed resin is foamed and then compressed. The second structure allows for more freedom in setting the foaming ratio compared to the first structure. However, the foaming ratio in the second structure represents the volume per unit mass (1 kg) of the object after compression (unit: mm × m × m). In other words, the foaming ratio is expressed as thickness [mm] × width [m] × length [m] / mass [kg], and density (unit: [g / m³]) 3 It is the reciprocal of ]) / 1000. Therefore, the foaming ratio of the insulating sheet 24 is preferably 5 to 33, and more preferably 10 to 33.

[0031] The first electrode sheet 25 constitutes, for example, a detection electrode. The first electrode sheet 25 is formed from a conductive fabric woven from multiple bundles of threads. Therefore, the first electrode sheet 25 is flexible. That is, the first electrode sheet 25 is configured to be stretchable in the planar direction and to bendable. As shown in Figure 4, the first electrode sheet 25 faces the first surface 27 of the insulating sheet 24. As shown in Figure 3, the first electrode sheet 25 is formed in a similar shape, but slightly smaller than the insulating sheet 24. As a result, the edge of the first surface 27 of the insulating sheet 24 is located outward from the edge of the first electrode sheet 25 along its entire circumference.

[0032] As shown in Figure 3, the first electrode sheet 25 has a recess 30 formed in the direction Y at a position corresponding to the sheet recess 21. The first electrode sheet 25 has extensions 31a and 31b at positions corresponding to the sheet extensions 22, 22 of the sensor sheet 18. The extensions 31a and 31b extend outward from the long edge 35 along the longitudinal direction X of the first electrode sheet 25. The core wire 32a exposed from the end of the electric wire 32 is connected to the extensions 31a and 31b. The core wire 32a and the extensions 31a and 31b are electrically connected by known methods such as soldering, brazing, and ultrasonic welding. In the following description, when the extensions 31a and 31b are not distinguished, they may be referred to as extension 31.

[0033] As shown in Figure 4, the first joint 50a is positioned between the first surface 27 of the insulating sheet 24 and the first electrode sheet 25, joining the first surface 27 of the insulating sheet 24 and the first electrode sheet 25. The contour of the first joint 50a is equal to or smaller than the contour of the insulating sheet 24, and equal to or larger than the contour of the first electrode sheet 25. The first joint 50a ensures that the first electrode sheet 25 and the insulating sheet 24 are completely non-contact.

[0034] The material constituting the first joint 50a is not particularly limited and can be appropriately selected from any material, such as acrylic adhesive, silicone adhesive, urethane adhesive, or rubber adhesive. The Young's modulus of the first joint 50a is smaller than that of the insulating sheet 24.

[0035] The second electrode sheet 26 constitutes an electromagnetic shield or heater, etc. The second electrode sheet 26 is formed from a conductive fabric woven from multiple bundles of threads. Therefore, the second electrode sheet 26 is flexible. In other words, the second electrode sheet 26 is configured to be stretchable in the planar direction and to bendable. As shown in Figure 4, the second electrode sheet 26 faces the second surface 28 of the insulating sheet 24. The second electrode sheet 26 is configured to be substantially the same as the first electrode sheet 25. However, the second electrode sheet 26 and the first electrode sheet 25 may be of different sizes or have different configurations.

[0036] As shown in Figure 4, the second joint 50b is positioned between the second surface 28 of the insulating sheet 24 and the second electrode sheet 26, joining the second surface 28 of the insulating sheet 24 and the second electrode sheet 26. The second joint 50b ensures that the second electrode sheet 26 and the insulating sheet 24 are completely non-contact. The first joint 50a and the second joint 50b have substantially the same configuration.

[0037] 5. First electrode sheet 25 and second electrode sheet 26 The first electrode sheet 25 and the second electrode sheet 26 will be described with reference to Figures 5 and 6. The first electrode sheet 25 and the second electrode sheet 26 are constructed similarly. The first electrode sheet 25 will be described below.

[0038] The first electrode sheet 25 is a conductive fabric with conductivity. The first electrode sheet 25 is flexible while being conductive. The first electrode sheet 25 is stretchable in the longitudinal direction X and direction Y. Furthermore, the first electrode sheet 25 is bendable.

[0039] As shown in Figure 5, the first electrode sheet 25 is a conductive fabric woven with a plurality of yarn bundles 41. The plurality of yarn bundles 41 include a plurality of warp yarn bundles 41a and a plurality of weft yarn bundles 41b. In the first electrode sheet 25, the plurality of warp yarn bundles 41a are arranged side by side, and the plurality of weft yarn bundles 41b are also arranged side by side. In Embodiment 1, the plurality of warp yarn bundles 41a are arranged at approximately equal intervals. On the other hand, the plurality of weft yarn bundles 41b are spaced at different intervals from adjacent weft yarn bundles 41b. However, the plurality of warp yarn bundles 41a and the plurality of weft yarn bundles 41b may be spaced at different intervals or at equal intervals.

[0040] The longitudinal directions XS of the multiple warp bundles 41a intersect with the longitudinal direction X of the first electrode sheet 25. Similarly, the longitudinal directions XT of the multiple weft bundles 41b intersect with the longitudinal direction X of the first electrode sheet 25. Preferably, the acute angle of direction XS with respect to direction X is substantially 45°. Preferably, the acute angle of direction XT with respect to direction X is substantially 45°. In other words, the angle between the multiple warp bundles 41a and the multiple weft bundles 41b is substantially 90°.

[0041] This makes the first electrode sheet 25 and the second electrode sheet 26 more easily deformable. Note that "effectively 45°" includes not only 45° but also angles near 45°. However, directions XS and XT may have acute angles different from 45° with respect to direction X. Figure 3 schematically shows a pattern in which the grid pattern is tilted at a 45° angle in the direction in which the multiple warp bundles 41a and multiple weft bundles 41b of the first electrode sheet 25 extend.

[0042] As shown in Figure 6, the cross-sectional contour of one warp bundle 41a is formed in a flattened shape in the thickness direction of the first electrode sheet 25. The cross-sectional contour shape of one warp bundle 41a is not particularly limited and may be circular, for example. The cross-sectional contour shape of one weft bundle 41b is the same as that of the warp bundle 41a.

[0043] Each yarn bundle 41 comprises a yarn assembly 42 composed of multiple yarns 40 and a plating layer 33. In other words, a warp yarn bundle 41a comprises a yarn assembly 42 composed of multiple warp yarns 40a and a plating layer 33. A weft yarn bundle 41b comprises a yarn assembly 42 composed of multiple weft yarns 40b and a plating layer 33.

[0044] The yarn assembly 42 forms an untwisted bundle of multiple yarns 40. However, the yarn assembly 42 may also form a twisted bundle of multiple yarns 40.

[0045] The warp threads 40a and weft threads 40b are composed of, for example, resin fibers. Examples of resins include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and polyamides such as nylon 6 and nylon 6,6. However, the resins constituting the warp threads 40a and weft threads 40b are not limited to those mentioned above, and any resin can be appropriately selected.

[0046] In Embodiment 1, the number of warp threads 40a constituting one warp bundle 41a is equal to the number of weft threads 40b constituting one weft bundle 41b. Furthermore, the number of warp threads 40a constituting each warp bundle 41a is equal. Furthermore, the number of weft threads 40b constituting each weft bundle 41b is equal. However, the number of warp threads 40a constituting a warp bundle 41a is not particularly limited, and the number of weft threads 40b constituting a weft bundle 41b is not particularly limited.

[0047] Each warp thread 40a has a non-circular cross-sectional shape. In Embodiment 1, the cross-sectional shape of each warp thread 40a in the direction perpendicular to the axis is polygonal. For example, the cross-sectional shape of each warp thread 40a can be any polygon, such as a triangle, quadrilateral, pentagon, or hexagon. As an example of a non-circular cross-sectional shape, each warp thread 40a may have any shape formed by a curve that does not have a single curvature. For example, the cross-sectional shape of each warp thread 40a can be an oval, ellipse, egg, oval, or oval track. Note that each warp thread 40a may also have a circular cross-sectional shape. Furthermore, the cross-sectional shape of each weft thread 40b is the same as that of the warp thread 40a.

[0048] As shown in Figure 6, the plating layer 33 is formed on at least the outer surface of the yarn assembly 42. Here, the first electrode sheet 25 has an overlapping region 44 in which the warp bundle 41a and the weft bundle 41b overlap in the thickness direction (Z direction). The overlapping region 44 corresponds to the opposing surfaces 43 in which the warp bundle 41a and the weft bundle 41b face each other.

[0049] In Embodiment 1, the plating layer 33 is formed on all parts of the outer circumferential surface of the yarn assembly 42 (the surface that forms the contour of the yarn assembly 42), excluding the opposing surface 43. On the other hand, the plating layer 33 is formed only on a part of the opposing surface 43 of the outer circumferential surface of the yarn assembly 42, and is not formed on the remaining parts of the opposing surface 43. In the parts of the opposing surface 43 where the plating layer 33 is not formed, the warp threads 40a and weft threads 40b are either in direct contact or facing each other with a gap in between.

[0050] The thickness of the plating layer 33 formed on the opposing surface 43 is thinner than the thickness of the plating layer 33 formed on the outer circumferential surface of the yarn assembly 42, excluding the opposing surface 43. However, the thickness of the plating layer 33 formed on the outer circumferential surface of the yarn assembly 42 may be the same around its entire circumference.

[0051] Furthermore, the plating layer 33 is also formed inside the yarn assembly 42. In Embodiment 1, the plating layer 33 does not fill the entire interior of the yarn assembly 42, but has internal spaces 80 formed in at least a portion of the space between adjacent yarns 40. The internal spaces 80 act to allow movement of the yarns 40 that make up the yarn assembly 42. In other words, the internal spaces 80 allow deformation of the cross-sectional contour of the yarn bundle 41. As a result, the first electrode sheet 25 and the second electrode sheet 26 become more easily deformed.

[0052] In particular, the yarn assembly 42 forms an untwisted yarn bundle with multiple yarns 40 and has an internal space 80, which increases the allowable range of movement of the yarns 40. The first electrode sheet 25 and the second electrode sheet 26 become more easily deformable.

[0053] The plating layer 33 is formed on a portion of the surface of the yarn 40 that faces the internal space 80, but not on the remaining portion. Having a portion where the plating layer 33 is not formed increases the allowable range of movement of the yarn 40. However, the plating layer 33 may be formed over the entire surface of the yarn 40 that faces the internal space 80. In addition, the plating layer 33 may be formed to fill the entire interior of the yarn assembly 42 without having an internal space 80.

[0054] The metal of the plating layer 33 can be any metal or alloy, such as copper, nickel, tin, or solder, as appropriate. The plating layer 33 may be composed of one type of metal or multiple types of metal. For example, the plating layer 33 may be composed only of a copper plating layer, or only of a nickel plating layer, or it may have a multi-layer structure having a copper plating layer and a nickel plating layer. The plating layer 33 may be formed by electrolytic plating or by electroless plating.

[0055] In Embodiment 1, the metal species constituting the plating layer 33 of the warp bundle 41a and the metal species constituting the plating layer 33 of the weft bundle 41b are the same. However, the metal species constituting the plating layer 33 of the warp bundle 41a and the metal species constituting the plating layer 33 of the weft bundle 41b may be different. By using different metal species, the properties of the warp bundle 41a and the properties of the weft bundle 41b can be made different. Examples of electrical properties include electrical resistance. Examples of chemical properties include ionization tendency and affinity. Examples of mechanical properties include friction coefficient, strength, and elongation.

[0056] Furthermore, the types of metals constituting the plating layer 33 of the warp bundles 41a may differ in the direction in which the warp bundles 41a are arranged. The same applies to the weft bundles 41b.

[0057] In each yarn bundle 41, the plating layer 33 formed on the outer surface of one yarn 40 and the plating layer 33 formed on the outer surface of another yarn 40 adjacent to this yarn 40 come into contact, thereby electrically connecting the two plating layers 33. The plating layers of adjacent yarns 40 may be formed integrally to create a state of contact, or they may be formed separately but still in contact with each other.

[0058] Furthermore, on the opposing surface 43, the plating layer 33 of the warp bundle 41a and the plating layer 33 of the weft bundle 41b are in contact. This electrically connects the warp bundle 41a and the weft bundle 41b.

[0059] The method for manufacturing the first electrode sheet 25 is not particularly limited. For example, a resin cloth may be formed by weaving warp threads 40a and weft threads 40b, and then a plating layer 33 may be formed by coating the cloth with a conductive material. Alternatively, a plating layer 33 may be formed on the outer surface of each warp thread 40a and each weft thread 40b, and then the warp threads 40a and weft threads 40b with the plating layer 33 formed on them may be woven. The first electrode sheet 25 according to Embodiment 1 is manufactured by the former method.

[0060] 6. Opening 34 of the first electrode sheet 25 As shown in Figure 5, the first electrode sheet 25 has an opening 34 that opens between the multiple yarn bundles 41. The opening 34 acts as a region that allows movement of the yarn bundles 41. The presence of the opening 34 in both the first electrode sheet 25 and the second electrode sheet 26 makes them more deformable.

[0061] In detail, the first electrode sheet 25 has openings 34 between two adjacent warp bundles 41a and two adjacent weft bundles 41b. The opening ratio, which is the ratio of the opening area of ​​the openings 34 formed in the first electrode sheet 25 to the area of ​​the first electrode sheet 25, is preferably 1% to 50%, more preferably 1% to 30%, and even more preferably 1% to 20%. In Embodiment 1, the opening ratio is 2 to 7%. The same applies to the opening ratio of the openings 34 in the second electrode sheet 26.

[0062] Figure 7 shows a portion of the first electrode sheet 25 in a state where no tensile force is applied to the first electrode sheet 25, that is, in a state where no tensile strain is occurring in the first electrode sheet 25. As shown in Figure 7, in a state where no strain is occurring in the first electrode sheet 25, the intersection area A1, which is the area where the warp bundles 41a and weft bundles 41b intersect each other when viewed from the thickness direction of the first electrode sheet 25, is larger than the opening area A2 of the opening 34. This allows for good electrical connection between the warp bundles 41a and weft bundles 41b while allowing for stretching deformation of the first electrode sheet 25. The same applies to the second electrode sheet 26.

[0063] 7. Evaluation Test Next, evaluation tests were conducted on the first electrode sheet 25, the insulating sheet 24, and the sensor sheet 18. The details of each evaluation test and its results are described below.

[0064] 7-1. Evaluation test of electrode sheet sample 1 This section describes the evaluation test of a sample (electrode sheet sample 1) for the first electrode sheet 25. The first electrode sheet 25 and the second electrode sheet 26 have the same configuration.

[0065] Electrode sheet sample 1 is the first electrode sheet 25 shown in Figure 6. More specifically, electrode sheet sample 1 is as shown in Table 1.

[0066] [Table 1]

[0067] Electrode sheet sample 1 is formed by weaving warp bundles 41a and weft bundles 41b. The warp bundles 41a and weft bundles 41b have the same structure. The warp bundles 41a and weft bundles 41b have an untwisted bundle structure made up of multiple threads 40, and multiple threads 40 are laminated. The total thickness of electrode sheet sample 1 is 135.9 μm. The opening ratio of the openings 34 in electrode sheet sample 1 is 3%. The surface resistance of electrode sheet sample 1 is 4.3E-2Ω / □.

[0068] The number of threads 40 constituting the warp bundle 41a and the weft bundle 41b is 75. The width of the warp bundle 41a and the weft bundle 41b is 185 μm.

[0069] The resin forming the thread 40 is PET (polyethylene terephthalate), and the diameter of the thread 40 is 10 μm. The plating layer 33 has a three-layer structure, with the outermost layer being Ni, the middle layer being Cu, and the innermost layer (on the thread 40 side) being Ni. The thickness of the outermost Ni layer is 0.058 μm, the thickness of the middle Cu layer is 0.49 μm, and the thickness of the innermost Ni layer is 0.028 μm.

[0070] This section describes the evaluation test performed on electrode sheet sample 1. Electrode sheet sample 1 was cut into strips measuring 90 mm x 20 mm to prepare test specimens TP of electrode sheet sample 1. The angle between the longitudinal direction of test specimen TP of electrode sheet sample 1 and the longitudinal direction of the warp bundle 41a was set to 45°.

[0071] In the evaluation test, a tensile test was performed on the test specimen as shown in Figure 8. The test specimen TP of electrode sheet sample 1 was gripped by a pair of chucks C1 and C2. The distance between the pair of chucks C1 and C2 was 50 mm. A tensile test was performed on this test specimen TP at a tensile speed of 1 mm / sec, and the stress was calculated by dividing the load by the cross-sectional area of ​​the test specimen TP. The tensile testing machine was a Shimadzu AGS-X 1kN. The tensile test was performed in the strain range of 0 to 30%. The results of the evaluation test are shown in Table 2 and Figure 9.

[0072] [Table 2]

[0073] Electrode sheet sample 1 shows a very slight increase in stress when the strain is less than 1%, and a more gradual, monotonically increasing stress in the strain range of 1% to 30% than the increase rate below 1%. Note that the stress at strains below 1% is extremely small (approximately 1 MPa) and therefore contains a large margin of error. Consequently, the strain range below 1% can be practically ignored.

[0074] As shown in Table 2 and Figure 9, in the stress-strain curve, electrode sheet sample 1 has a maximum stress of 5 MPa or less when the strain is between 0 and 5%, and is particularly 3 MPa or less. In the stress-strain curve, electrode sheet sample 1 has a maximum stress of 7 MPa or less when the strain is between 0 and 10%, and is particularly 5 MPa or less. In the stress-strain curve, electrode sheet sample 1 has a maximum stress of 15 MPa or less when the strain is between 0 and 20%, and is particularly 10 MPa or less. In the stress-strain curve, electrode sheet sample 1 has a maximum stress of 25 MPa or less when the strain is between 0 and 30%, and is particularly 20 MPa or less.

[0075] Here, the first electrode sheet 25 and the second electrode sheet 26 are required to exhibit a monotonically increasing stress with increasing strain within the strain usage range (e.g., strain 1% to 30%). Within the strain usage range, it is preferable that the stress be as small as possible. Furthermore, within the strain usage range, it is preferable that the rate of increase in stress (the ratio of the increase in stress to the increase in strain) does not show a locally large value. In particular, within the strain usage range, it is preferable that the rate of increase in stress does not show an extremely large value relative to the average rate of increase in stress.

[0076] In electrode sheet sample 1, the rate of stress increase is smaller as the strain decreases and larger as the strain increases, at strains of 1% to 30%. The rate of stress increase at around 30% strain is larger than at other strains, but it does not increase abruptly. Therefore, electrode sheet sample 1 can be said to have good performance.

[0077] 7-2. Evaluation Test of Insulation Sheet Samples 2-1, 2-2, and 2-3 This section describes the evaluation tests of the insulating sheet 24 samples (insulating sheet samples 2-1, 2-2, and 2-3). Insulating sheet samples 2-1, 2-2, and 2-3 are shown in Table 3. Note that the cross-sectional images of insulating sheet samples 2-2 and 2-3 show a similar structure to insulating sheet sample 2-1, but with more empty space.

[0078] [Table 3]

[0079] Insulating sheet samples 2-1, 2-2, and 2-3 were all manufactured by extruding polyethylene and a foaming agent into sheets, crosslinking, and then foaming. For insulating sheet samples 2-1, 2-2, and 2-3, the target thickness after foaming was set to 1 mm, and the sheet thickness during extrusion molding was determined accordingly.

[0080] This section describes the evaluation tests conducted on insulating sheet samples 2-1, 2-2, and 2-3. Insulating sheet samples 2-1, 2-2, and 2-3 were cut into 90mm x 20mm strips to prepare test specimens TP for insulating sheet samples 2-1, 2-2, and 2-3.

[0081] The test specimens TP of insulating sheet samples 2-1, 2-2, and 2-3 are gripped by a pair of chucks C1 and C2. The distance between the pair of chucks C1 and C2 is 50 mm. A tensile test is performed on these test specimens TP at a tensile speed of 1 mm / sec, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test specimen TP. The tensile testing machine is a Shimadzu AGS-X 1kN. The tensile test is performed within a strain range of 0 to 30%. The results of the evaluation test are shown in Table 4 and Figure 10.

[0082] [Table 4]

[0083] As shown in Table 4 and Figure 10, for insulating sheet samples 2-1, 2-2, and 2-3, the maximum stress value at 0-5% strain in the stress-strain curve is 1.0 MPa or less. For insulating sheet samples 2-2 and 2-3, the maximum stress value at 0-5% strain in the stress-strain curve is 0.5 MPa or less. For insulating sheet samples 2-1, 2-2, and 2-3, the maximum stress value at 0-10% strain in the stress-strain curve is 2.0 MPa or less. For insulating sheet samples 2-2 and 2-3, the maximum stress value at 0-10% strain in the stress-strain curve is 1.0 MPa or less.

[0084] Insulation sheet samples 2-1, 2-2, and 2-3 all show a maximum stress of 2.0 MPa or less in the stress-strain curve when the strain is between 0 and 20%. Insulation sheet samples 2-2 and 2-3 all show a maximum stress of 1.0 MPa or less in the stress-strain curve when the strain is between 0 and 20%. Insulation sheet samples 2-1, 2-2, and 2-3 all show a maximum stress of 2.0 MPa or less in the stress-strain curve when the strain is between 0 and 30%. Insulation sheet samples 2-2 and 2-3 all show a maximum stress of 1.0 MPa or less in the stress-strain curve when the strain is between 0 and 30%.

[0085] Here, the insulating sheet 24 is required to exhibit a monotonically increasing stress as the strain increases within the strain range (e.g., strain 1% to 30%). Within the strain range, it is preferable that the stress be as small as possible. Furthermore, within the strain range, it is preferable that the rate of increase in stress (the ratio of the increase in stress to the increase in strain) does not show a locally large value. In particular, within the strain range, it is preferable that the rate of increase in stress does not show an extremely large value relative to the average rate of increase in stress.

[0086] Insulating sheet samples 2-1, 2-2, and 2-3 exhibit a tendency for the rate of stress increase to be greater as the strain decreases from 1% to 30%. However, while the rate of stress increase at strains below 10% is greater than at other strains, it does not increase abruptly. Therefore, insulating sheet samples 2-1, 2-2, and 2-3 can be said to have good performance.

[0087] 7-3. Evaluation Test 1 for Sensor Sheet Samples 3-1, 3-2, and 3-3 This section describes evaluation test 1 for the sensor sheet 18 samples (sensor sheet samples 3-1, 3-2, and 3-3). Each of the sensor sheet samples 3-1, 3-2, and 3-3 consists of electrode sheet sample 1 and insulation sheet samples 2-1, 2-2, and 2-3, respectively.

[0088] Sensor sheet sample 3-1 is prepared by attaching electrode sheet sample 1 to the first surface 27 of insulating sheet sample 2-1 via the first joint 50a, and by attaching electrode sheet sample 1 to the second surface 28 of insulating sheet sample 2-1 via the second joint 50b. The first joint 50a and the second joint 50b use an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd., and have a thickness of 50 μm. Sensor sheet samples 3-2 and 3-3 are constructed in the same way as sensor sheet sample 3-1, except that the insulating sheet sample is different.

[0089] Evaluation test 1, conducted on sensor sheet samples 3-1, 3-2, and 3-3, is described below. Sensor sheet samples 3-1, 3-2, and 3-3 were cut into strips measuring 90 mm x 20 mm to prepare test specimens TP. The angle between the longitudinal direction of the test specimen TP and the longitudinal direction of the warp bundle 41a of electrode sheet sample 1 was set to 45°.

[0090] The test specimen TP is gripped by a pair of chucks C1 and C2. The distance between the pair of chucks C1 and C2 is 50 mm. A tensile test is performed on the test specimen TP at a tensile speed of 1 mm / sec, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test specimen TP. The tensile testing machine is a Shimadzu AGS-X 1kN. The tensile test is performed in the strain range of 0 to 30%. The relationship between strain and stress as a result of the evaluation test is shown in Table 5 and Figure 11.

[0091] Furthermore, during the tensile test, the DC resistance between the two ends of the test specimen TP in the tensile direction is calculated. Specifically, during the tensile test, the DC resistance (an example of electrical resistance) of sensor sheet samples 3-1, 3-2, and 3-3 is calculated from the voltage of the DC power supply and the voltage drop across sensor sheet samples 3-1, 3-2, and 3-3. The DC resistance is measured using a KEITHLEY 2000 series digital multimeter. As a result of evaluation test 1, the relationship between strain and DC resistance is shown in Figure 12.

[0092] [Table 5]

[0093] As shown in Table 5 and Figure 11, sensor sheet samples 3-1, 3-2, and 3-3 all have a maximum stress of 1.0 MPa or less in the stress-strain curve when the strain is between 0 and 5%. Sensor sheet samples 3-2 and 3-3 have a maximum stress of 0.6 MPa or less in the stress-strain curve when the strain is between 0 and 5%. Sensor sheet samples 3-1, 3-2, and 3-3 all have a maximum stress of 2.0 MPa or less in the stress-strain curve when the strain is between 0 and 10%. Sensor sheet samples 3-2 and 3-3 have a maximum stress of 1.5 MPa or less in the stress-strain curve when the strain is between 0 and 10%.

[0094] Sensor sheet samples 3-1, 3-2, and 3-3 all show that the maximum stress value in the stress-strain curve at 0-20% strain is 3.0 MPa or less. Sensor sheet samples 3-2 and 3-3 show that the maximum stress value in the stress-strain curve at 0-20% strain is 2.5 MPa or less. Sensor sheet samples 3-1, 3-2, and 3-3 all show that the maximum stress value in the stress-strain curve at 0-30% strain is 5.0 MPa or less. Sensor sheet samples 3-2 and 3-3 show that the maximum stress value in the stress-strain curve at 0-30% strain is 4.5 MPa or less.

[0095] Here, the sensor sheet 18 is required to exhibit a monotonically increasing stress with increasing strain within its strain usage range (e.g., strain 1% to 30%). Within the strain usage range, it is preferable that the stress be as small as possible. Furthermore, within the strain usage range, it is preferable that the stress increase rate (the ratio of the increase in stress to the increase in strain) does not show locally large values. In particular, within the strain usage range, it is preferable that the stress increase rate does not show an extremely large value relative to the average stress increase rate.

[0096] Sensor sheet samples 3-1, 3-2, and 3-3 do not exhibit a rapid change in stress increase rate when strains range from 1% to 30%. Therefore, sensor sheet samples 3-1, 3-2, and 3-3 can be said to possess good performance.

[0097] As shown in Figure 12, the DC resistance values ​​of sensor sheet samples 3-1, 3-2, and 3-3 hardly change at strains of 1% to 30%. Therefore, even when strain occurs, the DC resistance values ​​of sensor sheet samples 3-1, 3-2, and 3-3 are suppressed, indicating that their electrical characteristics are stable.

[0098] 7-4. Evaluation Test 2 for Sensor Sheet Samples 3-1, 3-2, and 3-3 This section describes evaluation test 2 for the sample sensor sheet 18 (sensor sheet samples 3-1, 3-2, and 3-3).

[0099] Evaluation Test 2 for sensor sheet samples 3-1, 3-2, and 3-3 involved repeatedly stretching the same test piece TP as in Evaluation Test 1 by 20%, and measuring the rate of change in DC resistance for each repetition. DC resistance was measured initially, after 1 stretch, and after 5 and 10 stretching repetitions.

[0100] The initial DC resistance value of the test specimen TP was used as the baseline, and the rate of increase relative to the baseline was defined as the rate of change in DC resistance. The 20% stretched state refers to the state in which the distance between chucks C1 and C2 (50 mm) on the test specimen TP of sensor sheet samples 3-1, 3-2, and 3-3 is stretched by 20% relative to the baseline length. As a result of evaluation test 2, the relationship between the number of stretches and the rate of change in DC resistance is shown in Table 6 and Figure 13.

[0101] [Table 6]

[0102] For up to 10 repetitions of 20% extension, sensor sheet samples 3-1, 3-2, and 3-3 all showed a DC resistance change rate of 200% or less. More specifically, after 1 repetition, sensor sheet samples 3-1, 3-2, and 3-3 all showed a DC resistance change rate of 50% or less. After 5 repetitions, sensor sheet samples 3-1, 3-2, and 3-3 all showed a DC resistance change rate of 85% or less. After 10 repetitions, sensor sheet samples 3-1, 3-2, and 3-3 all showed a DC resistance change rate of 120% or less.

[0103] Therefore, sensor sheet samples 3-1, 3-2, and 3-3 can all suppress changes in electrical resistance even when stretched during assembly, thus enabling good sensor performance.

[0104] 7-5. Evaluation Test 3 for Sensor Sheet Samples 3-1, 3-2, and 3-3 This section describes evaluation test 3 for sensor sheet 18 samples (sensor sheet samples 3-1, 3-2, 3-3). Comparative sample 4 of sensor sheet 18 uses an insulating sheet made of non-foamed elastomer instead of insulating sheet samples 2-1, 2-2, 2-3. The other components are the same. The non-foamed elastomer in comparative sample 4 mainly consists of olefin resin (ethylene octene) and SEBS (styrene-ethylene-butadiene-styrene block copolymer). Non-foamed elastomer has a lower modulus of elasticity in the compression direction than non-foamed polyethylene.

[0105] Evaluation test 3, conducted on sensor sheet samples 3-1, 3-2, 3-3 and comparison sample 4, is described below. Test specimens TP were prepared by cutting sensor sheet samples 3-1, 3-2, 3-3 and comparison sample 4 into strips measuring 90 mm x 20 mm. The angle between the longitudinal direction of the test specimen TP and the longitudinal direction of the warp bundle 41a of electrode sheet sample 1 was set to 45°.

[0106] In evaluation test 3, a bending evaluation test was performed on the test specimen TP, as shown in Figure 14. In evaluation test 3, the bending evaluation test was performed on the test specimen TP 5, 10, 15, and 30 times, and the DC resistance value between the two ends of the test specimen TP in the longitudinal direction was measured for each test.

[0107] A single bending evaluation test is performed as follows: First, the test specimen TP is folded 180° along its longitudinal center. That is, since the test specimen TP is 90mm x 20mm before folding, the test specimen TP after folding will be 45mm x 20mm. The folded test specimen TP is placed on the upper surface of plate D1.

[0108] Next, the load-applying member D2 is lowered to apply a load of 5 kgf in the normal direction to the bent specimen TP. The load is applied to at least the surface of the bent specimen TP that includes the bent portion. Here, the axis of the load-applying member D2 is positioned at the tip of the bent portion of the bent specimen TP. The load is applied to a range of 5 mm inward from the tip of the bent portion of the bent specimen TP (an area of ​​5 mm x 20 mm). In other words, the area ratio of the region to which the load is applied within the bent specimen TP is 1 / 9.

[0109] Immediately after a 5kgf load is applied to the test specimen TP, the load-applying member D2 is raised. Finally, the test specimen TP is returned from the bent state to the unfolded state. If multiple bending evaluation tests are to be performed, the above procedure is repeated.

[0110] The DC resistance value of the test specimen TP before the bending evaluation test was used as the baseline, and the rate of increase relative to the baseline was defined as the rate of change in the DC resistance value of the test specimen TP. As a result of Evaluation Test 3, the relationship between the number of bending evaluation tests and the rate of change in the DC resistance value is shown in Table 7 and Figure 15.

[0111] [Table 7]

[0112] Sensor sheet samples 3-1, 3-2, and 3-3 showed a rate of change of 50% or less in the DC resistance value of test specimen TP after 5 bending evaluation tests. Comparison sample 4 also showed a rate of change of 50% or less in the DC resistance value of test specimen TP after 5 bending evaluation tests. Sensor sheet samples 3-1, 3-2, and 3-3 showed a rate of change of 80% or less in the DC resistance value of test specimen TP after 10 bending evaluation tests. Comparison sample 4 also showed a rate of change of 80% or less in the DC resistance value of test specimen TP after 10 bending evaluation tests.

[0113] Sensor sheet samples 3-1, 3-2, and 3-3 showed a change in the DC resistance value of test specimen TP of 15 tests of 100% or less. On the other hand, comparative sample 4 showed a change in the DC resistance value of test specimen TP of 15 tests of 100% or more.

[0114] Sensor sheet samples 3-1, 3-2, and 3-3 showed a rate of change of 200% or less in the DC resistance value of test specimen TP after 30 bending evaluation tests. In particular, sensor sheet samples 3-2 and 3-3 showed a rate of change of 150% or less in the DC resistance value of test specimen TP after 30 bending evaluation tests. On the other hand, comparative sample 4 showed a rate of change of 200% or more in the DC resistance value of test specimen TP after 30 bending evaluation tests.

[0115] Therefore, sensor sheet samples 3-1, 3-2, and 3-3 can all suppress changes in electrical resistance even when bent during assembly, thus improving sensor performance. In particular, sensor sheet samples 3-2 and 3-3 can further suppress changes in electrical resistance even when the number of folds during assembly increases, thus improving sensor performance.

[0116] The insulating sheet 24 is formed from polyethylene foam. Therefore, when the sensor sheet 18 is bent, the air bubbles contained in the insulating sheet 24 are thought to function as regions that allow deformation. As a result, the load on the first electrode sheet 25 and the second electrode sheet 26 can be reduced, and changes in electrical resistance can be suppressed.

[0117] 8. Effects The first electrode sheet 25 and the second electrode sheet 26 are formed from a conductive fabric woven from multiple yarn bundles 41. Furthermore, a first joint 50a is interposed between the first electrode sheet 25 and the first surface 27 of the insulating sheet 24, and a second joint 50b is interposed between the second electrode sheet 26 and the second surface 28 of the insulating sheet 24. When a tensile force is applied to the sensor sheet 18, the woven first electrode sheet 25 and the second electrode sheet 26 undergo stretch deformation. Since the first electrode sheet 25 and the second electrode sheet 26 are conductive fabrics, they can maintain their conductive paths even when stretched and deformed. Therefore, even when a tensile force is applied to the sensor sheet 18, changes in electrical resistance can be suppressed.

[0118] Furthermore, the sensor sheet 18 is configured such that, in the stress-strain curve during a tensile test, the maximum stress value at a strain of 0-5% is 1.0 MPa or less. In the sensor sheet 18, the insulating sheet 24 is made of polyethylene foam. This allows the sensor sheet 18 to have the above-mentioned characteristics regarding the stress-strain curve. And, as a result of these characteristics regarding the stress-strain curve, the assembly of the sensor sheet 18 is improved.

[0119] Furthermore, the sensor sheet 18 is configured such that the rate of change in the DC resistance of the test specimen TP after 30 bending evaluation tests is 200% or less, based on the DC resistance value of the test specimen TP before the bending evaluation test is performed. Therefore, even if the sensor sheet 18 is bent during assembly, good detection performance can be obtained from the sensor sheet 18.

[0120] The first electrode sheet 25 and the second electrode sheet 26 are configured such that, in the stress-strain curve during a tensile test, the maximum stress value at a strain of 0-5% is 5 MPa or less. This makes it possible to achieve the characteristics of the sensor sheet 18 described above.

[0121] Furthermore, the insulating sheet 24 is configured such that, in the stress-strain curve during a tensile test, the maximum stress value at a strain of 0-5% is 1.0 MPa or less. This makes it possible to achieve the characteristics of the sensor sheet 18 described above. [Explanation of Symbols]

[0122] 18 Sensor Sheet 24 Insulating Sheet 25 First electrode sheet 26 Second electrode sheet 27 Front page 28 Second side 40 threads 41 Thread bundle 50a First joint 50b Second joint 80 Interior space TP test specimen

Claims

1. An insulating sheet having a first surface and a second surface, formed from polyethylene foam, A first electrode sheet, facing the first surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, A first joining portion that joins the first surface of the insulating sheet and the first electrode sheet, A second electrode sheet, facing the second surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, The device comprises a second joining portion that joins the second surface of the insulating sheet and the second electrode sheet, A sensor sheet configured such that, in a stress-strain curve during a tensile test, the maximum stress value at a strain of 0-5% is 1.0 MPa or less.

2. The sensor sheet according to claim 1, wherein the sensor sheet is configured such that, in the stress-strain curve during a tensile test, the maximum value of the stress at a strain of 0 to 5% is 0.6 MPa or less.

3. The sensor sheet according to claim 1, wherein the sensor sheet is configured such that, in the stress-strain curve during a tensile test, the maximum value of the stress at a strain of 0 to 20% is 3.0 MPa or less.

4. The sensor sheet according to claim 2, wherein the sensor sheet is configured such that, in the stress-strain curve during a tensile test, the maximum value of the stress at a strain of 0 to 20% is 2.5 MPa or less.

5. The sensor sheet according to any one of claims 1 to 4, wherein the stress-strain curve in a tensile test is the relationship between stress and strain when a tensile test is performed on a 90 mm x 20 mm specimen held at a tensile speed of 1 mm / s.

6. The sensor sheet is configured such that, based on the DC resistance value of the test specimen before the bending evaluation test is performed, the rate of change in the DC resistance value of the test specimen after 30 bending evaluation tests is 200% or less. The sensor sheet according to claim 1, wherein one bending evaluation test involves bending the test piece 180°, applying a load of 5 kgf in the normal direction to the bent test piece, and returning the test piece from the bent state to the unfolded state.

7. The sensor sheet according to claim 6, wherein the sensor sheet is configured such that the rate of change in the DC resistance of the test piece after 30 bending evaluation tests is 150% or less, based on the DC resistance of the test piece before the bending evaluation test is performed.

8. The density of the insulating sheet is 30 to 200 kg / m³. ３ The sensor sheet according to any one of claims 1 to 4 or 6.

9. The density of the insulating sheet is 30 to 100 kg / m³. ３ The sensor sheet according to claim 2, 4, or 7.

10. The sensor sheet according to any one of claims 1 to 4, 6 to 7, wherein the first electrode sheet and the second electrode sheet are configured such that, in the stress-strain curve during a tensile test, the maximum value of the stress at a strain of 0 to 5% is 5 MPa or less.

11. The sensor sheet according to any one of claims 1 to 4, 6 to 7, wherein the first electrode sheet and the second electrode sheet are configured such that, in the stress-strain curve during a tensile test, the maximum value of the stress at a strain of 0 to 20% is 10 MPa or less.

12. The sensor sheet according to any one of claims 1 to 4, 6, wherein the insulating sheet is configured such that, in the stress-strain curve during a tensile test, the maximum value of the stress at a strain of 0 to 5% is 1.0 MPa or less.

13. The sensor sheet according to claim 2, 4, or 7, wherein the insulating sheet is configured such that, in the stress-strain curve during a tensile test, the maximum value of the stress at a strain of 0 to 5% is 0.5 MPa or less.

14. The sensor sheet according to any one of claims 1 to 4, 6 to 7, wherein the cross-sectional shape of each thread forming the thread bundle is polygonal.

15. The sensor sheet according to any one of claims 1 to 4, 6 to 7, wherein the yarn bundle has an internal space formed in at least a portion of the space between adjacent yarns forming the yarn bundle.

16. An insulating sheet having a first surface and a second surface, formed from polyethylene foam, A first electrode sheet, facing the first surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, A first joining portion that joins the first surface of the insulating sheet and the first electrode sheet, A second electrode sheet, facing the second surface of the insulating sheet, is formed from a conductive fabric woven from multiple bundles of threads, The device comprises a second joining portion that joins the second surface of the insulating sheet and the second electrode sheet, The system is configured such that, based on the DC resistance value of the test specimen before the bending evaluation test is performed, the rate of change in the DC resistance value of the test specimen after 30 bending evaluation tests is 200% or less. The aforementioned bending evaluation test involves bending the test specimen 180°, applying a load of 5 kgf in the normal direction to the bent specimen, and returning the specimen from the bent state to the unfolded state, using a sensor sheet.

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