Sensor sheet

Abstract

A sensor sheet (18) comprises: an insulating sheet (24) that has a first surface (27) and a second surface (28); a conductive first electrode sheet (25) that is disposed on the first surface (27) side of the insulating sheet (24) and has first openings (34a) that pass therethrough; a first junction (36) that joins the insulating sheet (24) and the first electrode sheet (25); a conductive second electrode sheet (26) that is disposed on the second surface (28) side of the insulating sheet (24) and has second openings (34b) that pass therethrough; and a second junction (37) that joins the insulating sheet (24) and the second electrode sheet (26). The sensor sheet (18) is configured so as not to have a yield point that indicates a maximum value at a strain of 0.5%–10% on a stress / strain curve from tensile testing. The opening percentage that is the ratio of the opening area of the first openings (34a) to the area of the first electrode sheet is 1%–50%, and the opening percentage of the opening area of the second openings (34b) to the area of the second electrode sheet (26) is 1%–50%.

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a sensor sheet including a dielectric layer and a first electrode sheet disposed on a first surface of the dielectric layer. The sensor sheet is attached to, for example, a steering wheel of a vehicle to detect whether an occupant has contacted the steering wheel.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the sensor sheet described in Patent Document 1, there is a problem in the reliability of the detection accuracy of the sensor. For example, when the sensor sheet is assembled to a steering wheel, since the sensor sheet is wound around the steering wheel while being pulled and stretched, there is a problem that the conductive path of the first electrode sheet changes due to the tensile stress and the electrical resistance value of the first electrode sheet changes.

[0005] The present invention has been made in view of such a background, and aims to provide a sensor sheet in which a change in electrical resistance value is suppressed, and a method for manufacturing the sensor sheet.

Means for Solving the Problems

[0006] An One aspect of the present invention is an insulating sheet having a first surface and a second surface and formed of a foam, and a conductive first electrode sheet disposed on the first surface side of the insulating sheet and having a first opening penetrating therethrough. a first bonding portion that bonds the insulating sheet and the first electrode sheet; a conductive second electrode sheet disposed on the second surface side of the insulating sheet and having a second opening that penetrates therethrough; a second bonding portion that bonds the insulating sheet and the second electrode sheet; and the first electrode sheet and the second electrode sheet are conductive cloths woven with a plurality of filament aggregates, the plurality of filament aggregates include a plurality of filaments and a plating layer formed on at least a part of the surface of the filaments, the first electrode sheet includes the first opening that opens between the plurality of filament aggregates, the second electrode sheet has a second opening that opens between the plurality of filament aggregates, The and is configured not to have a yield point showing a maximum value in the section where the strain is 0.5 to 10% in the stress-strain curve in the tensile test, the aperture ratio, which is the ratio of the opening area of the first opening to the area of the first electrode sheet, is 1% or more and 50% or less, and the aperture ratio, which is the ratio of the opening area of the second opening to the area of the second electrode sheet, is 1% or more and 50% or less. , The filament assembly is further in a sensor sheet having an internal space formed in at least a part between adjacent filaments.

[0007] Another aspect of the present disclosure is a step of forming a filament aggregate by gathering a plurality of filaments; a step of forming a base fabric by weaving a plurality of the filament aggregates; a step of forming a conductive cloth by performing a plating process on the base fabric; and a step of forming a sensor sheet by bonding the conductive cloth to the first surface of an insulating sheet made of an elastomer having a first surface and a second surface. There is also provided a method for manufacturing a sensor sheet. [Effect of the Invention]

[0008] ​According to an aspect of the present invention One When a tensile force is applied to the sensor sheet according to this aspect, the first opening of the first electrode sheet and the second opening of the second electrode sheet are deformed, and the opening areas of the first opening and the second opening are deformed so as to decrease. Then, a new conductive path is formed between the plurality of filament aggregates separated by the first opening. Similarly, a new conductive path is formed between the plurality of filament aggregates separated by the second opening. Thereby, even when a tensile force is applied to the sensor sheet, it is possible to suppress a change in the electrical resistance value.

[0009] Further, according to an aspect of the present invention One The sensor sheet according to this aspect is configured not to have a yield point showing a maximum value in the range of strain of 0.5 to 10% in the stress-strain curve in the tensile test. Thereby, it is possible to suppress the plating layer from breaking in the range of strain of 0.5 to 10%, and thus it is possible to suppress a change in the electrical resistance value of the sensor sheet.

[0010] Further, according to another aspect of the present disclosure, there are those in which the plating layers formed on the surfaces of adjacent filaments are electrically connected by contacting each other, and those in which no plating layer is formed on the surfaces of adjacent filaments and they can move freely with respect to each other. Thereby, when a tensile force is applied to the sensor sheet, the stress is absorbed by the filaments that can move freely with respect to each other, so that an excessively large stress can be prevented from being applied to the sensor sheet. As a result, since the electrical connection of the sensor sheet is maintained by the filaments that are electrically connected to each other, it is possible to suppress a change in the electrical resistance value of the sensor sheet.

[0011] Note that the reference numerals in parentheses described in the claims indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the present invention.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Figure 36

Figure 37

Figure 38

Figure 39

Figure 40

Figure 41

Figure 42

Figure 43

Figure 44

Figure 45

Figure 46

Figure 47

Figure 48

Figure 49

Figure 50

Figure 51

Figure 52

Figure 53

Figure 54

Figure 55

Figure 56

Figure 57

Figure 58

Figure 59

Figure 60

Figure 61

Figure 62

Figure 63

Figure 64

Figure 65

Figure 66

Figure 67

Figure 68

Figure 69

Figure 70

Figure 71

Figure 72

Figure 73

Figure 74

Figure 75

Mode for Carrying Out the Invention

[0013] (Embodiment 1-1) 1.1. Outline of Sensor Sheet and Steering Wheel 1.1.1. Outline of Sensor Sheet The sensor sheet is of the electrostatic type and functions as a sensor that detects the contact or approach of a conductor having a potential, for example, by utilizing the change in capacitance between electrodes. When a conductor having a potential comes into contact with or approaches the sensor sheet, the capacitance between the electrodes changes, and the contact or approach of the conductor is detected by detecting the voltage corresponding to the changed capacitance between the electrodes.

[0014] The sensor sheet is attached to, for example, the steering wheel of a vehicle to detect whether the hand (finger, palm, knuckle, etc.) of the occupant comes into contact with or approaches the steering wheel.

[0015] 1.1.2. Overall Structure of Steering Wheel 10 First, the structure of the steering wheel 10 will be described with reference to FIGS. 1 to 2. As shown in FIG. 1, the steering wheel 10 includes a core portion 11, a ring portion 12, and a plurality (three in this embodiment) of connecting portions 13 that connect the core portion 11 and the ring portion 12.

[0016] The ring portion 12 is formed in a circular ring shape. However, the ring portion 12 is not limited to a circular shape and can be formed in any shape. As shown in FIG. 2, the cross-sectional shape of the ring portion 12 perpendicular to the axis is, for example, formed in a circular shape.

[0017] 1.1.3. Detailed Configuration of Steering Wheel 10 The detailed configuration of the steering wheel 10 will be described with reference to FIGS. 1 to 2. In particular, the detailed configuration of the ring portion 12 will be described.

[0018] The ring portion 12 includes a core body 16, a resin inner layer material 17, a sensor sheet 18, and a skin material 19. The core body 16 constitutes the central portion of the ring portion 12 and is formed in a shape corresponding to the shape of the ring portion 12. That is, the core body 16 is formed in a circular ring shape and has a circular cross-section perpendicular to the axis. Here, the cross-sectional shape of the core body 16 perpendicular to the axis is not limited to a circular shape and can be any shape such as an elliptical shape, an oval shape, a U shape, a C shape, a polygonal shape, etc. The core body 16 of the present embodiment is formed of a metal such as aluminum or magnesium and has conductivity. As the material of the core body 16, materials other than metals can be applied.

[0019] The resin inner layer material 17 covers the outer surface of the core body 16 over the entire circumference of the ring shape of the core body 16 and over the entire circumference of the circular cross-sectional shape of the core body 16. In the present embodiment, the cross-section of the resin inner layer material 17 perpendicular to the axis is 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 is filled not only in the radially outer side of the cross-section perpendicular to the axis of the core body 16 but also in the U-shaped recess of the core body 16. The resin inner layer material 17 is formed on the outer surface side of the core body 16 by injection molding and is directly joined to the outer surface of the core body 16. The cross-sectional shape of the resin inner layer material 17 perpendicular to the axis is not limited to a circular shape and can be any shape such as an oval shape, an elliptical shape, a polygonal shape, etc. The resin inner layer material 17 is formed of, for example, a foamed resin. The resin inner layer material 17 uses, for example, a foamed urethane resin. Note that the resin inner layer material 17 can also use a non-foamed resin.

[0020] The sensor sheet 18 is wound around the outer surface of the resin inner layer material 17. The sensor sheet 18 forms a C shape when wound around the resin inner layer material 17. The sensor sheet 18 will be described in detail later.

[0021] The skin material 19 covers the entire circumference of the ring shape of the sensor sheet 18 on the outer surface of the sensor sheet 18 (the surface of the sensor sheet 18 opposite to the resin inner layer material 17). That is, as will be described later, when the first electrode sheet 25 is exposed on the first surface 27 side of the insulating sheet 24, the skin material 19 also functions as a covering material for the first electrode sheet 25. The skin material 19 is formed by injection molding, wound around the outer surface side of the sensor sheet 18, and joined to the outer surface of the sensor sheet 18. The skin material 19 is formed of, for example, urethane resin. The outer surface of the skin material 19 constitutes the design surface. The material of the skin material 19 is not particularly limited, and for example, it is preferable to use a non-foamed urethane resin or a slightly foamed urethane resin.

[0022] As another form of the skin material 19, leather or cloth may be used for the skin material 19, and it may be wound around the outer surface side of the sensor sheet 18 and joined to the outer surface of the sensor sheet 18. For the joining of the skin material 19 and the sensor sheet 18, an adhesive material or an adhesive may be used, and further, the skin material 19 may be sewn to cover the periphery of the steering wheel. Also, the outer surface of the skin material 19 constitutes the design surface. The material of the skin material 19 is not particularly limited, and any material such as leather (natural leather, synthetic leather, etc.), cloth, rubber, resin, etc. can be selected, but the skin material 19 is preferably leather (natural leather, synthetic leather, etc.).

[0023] 1.1.4. Overall Structure of Sensor Sheet 18 The overall configuration of the sensor sheet 18 of Embodiment 1-1 will be described with reference to FIGS. 3 to 4. As shown in FIG. 3, the sensor sheet 18 is formed in an elongated shape in the longitudinal direction X as a whole. The sensor sheet 18 includes a sheet main body portion 20 formed in a rectangular shape as a whole. The sheet main body portion 20 includes a pair of long side edges 20a extending along the longitudinal direction X and a pair of short side edges 20b extending in a direction intersecting the longitudinal direction X. In the following description, the arrow X indicates the longitudinal direction of the sensor sheet 18, the arrow Y indicates the intersection direction intersecting the longitudinal direction, and the arrow Z indicates the thickness direction of the sensor sheet 18.

[0024] On a pair of long side edges 20a of the sheet main body portion 20, sheet recesses 21 recessed inward are formed in the intersection direction Y intersecting the longitudinal direction X. The sheet recesses 21 are formed at positions including regions overlapping in the intersection direction Y of the pair of long side edges 20a of the sheet main body portion 20. However, the sheet recesses 21 may be formed only on one of the pair of long side edges 20a.

[0025] A plurality (four in this embodiment) of sheet recesses 21 are formed at intervals on one long side edge 20a. However, one sheet recess 21 may be formed on one long side edge 20a. Also, two to three or five or more sheet recesses 21 may be formed on one long side edge 20a.

[0026] On one of the pair of long side edges 20a of the sheet main body portion 20, a sheet extension portion 22 extending from one long side edge 20a in a direction intersecting the longitudinal direction X is formed at positions near both ends of the sheet main body portion 20 in the longitudinal direction X.

[0027] FIG. 4 shows a cross-sectional view of the sensor sheet 18. The sensor sheet 18 includes an insulating sheet 24, a first electrode sheet 25, and a second electrode sheet 26. The first electrode sheet 25 and the second electrode sheet 26 are conductive and are formed in layers.

[0028] The first electrode sheet 25 is disposed on the first surface 27 side of the insulating sheet 24. Specifically, the first electrode sheet 25 is laminated on the first surface 27 of the insulating sheet 24. The first electrode sheet 25 is formed in a similar shape that is slightly smaller than the insulating sheet 24. As a result, the edge portion of the first surface 27 of the insulating sheet 24 is exposed from the edge portion of the first electrode sheet 25.

[0029] As shown in FIG. 3, in the first electrode sheet 25, at a position corresponding to the sheet recess 21 of the sensor sheet 18, a recess 30 that is recessed inward in the crossing direction Y is formed. In the first electrode sheet 25, at a position corresponding to the sheet extension 22 of the sensor sheet 18, an extension portion 31a that extends in the extension direction E1 crossing the longitudinal direction X from the long side edge along the longitudinal direction X of the first electrode sheet 25, and an extension portion 31b that extends in the extension direction E2 are formed. A core wire 32a exposed from the end of the electric wire 32 is connected to the extension portions 31a and 31b. The core wire 32a and the extension portions 31a and 31b are electrically connected by a known method such as soldering, brazing, or ultrasonic welding. In the following description, when the extension portion 31a and the extension portion 31b are not distinguished and described, they may be described as the extension portion 31.

[0030] As shown in FIG. 4, the second electrode sheet 26 is disposed on the second surface 28 side of the insulating sheet 24. Specifically, the second electrode sheet 26 is laminated on the second surface 28 of the insulating sheet 24. The second electrode sheet 26 is formed in a similar shape that is slightly smaller than the insulating sheet 24. As a result, the edge portion of the second surface 28 of the insulating sheet 24 is exposed from the edge portion of the second electrode sheet 26.

[0031] The first electrode sheet 25 and the second electrode sheet 26 may have the same shape and size, or one may be a similar shape that is slightly larger than the other. In this embodiment, the first electrode sheet 25 and the second electrode sheet 26 have substantially the same configuration.

[0032] Note that since the second electrode sheet 26 has substantially the same configuration as the first electrode sheet 25, duplicate descriptions may be omitted in the following description.

[0033] The insulating sheet 24 has flexibility and is configured to be extensible in the plane direction. The insulating sheet 24 may be formed, for example, by containing a foaming resin as a main component, or may be formed by containing an elastomer as a main component. Therefore, the insulating sheet 24 is flexible.

[0034] When the insulating sheet 24 is formed by containing a foaming resin as a main component, the insulating sheet 24 can be manufactured, for example, from a foam of a resin or an elastomer. Elastomers include crosslinked rubber and thermoplastic elastomers. For example, in addition to urethane foam, polystyrene foam, polyethylene foam, polypropylene foam, polyolefin foam, EVA (ethylene-vinyl acetate copolymer) foam, PET foam, phenol foam, EPDM (ethylene propylene diene rubber) foam, silicone foam, polyvinyl chloride foam, acrylic foam, polyimide foam, polylactic acid-based resin foam, melamine foam, polymethacrylimide foam, fluororesin foam, and the like can be mentioned.

[0035] When the insulating sheet 24 is formed by containing, for example, a thermoplastic material, particularly a thermoplastic elastomer as a main component, the insulating sheet 24 may be formed of the thermoplastic elastomer itself, or may be formed of an elastomer crosslinked by heating a thermoplastic elastomer as a raw material as a main component.

[0036] In addition, the insulating sheet 24 may contain rubber, resin, other materials, etc. other than the thermoplastic elastomer. For example, when the insulating sheet 24 contains rubber such as ethylene-propylene rubber (EPM, EPDM), the flexibility of the insulating sheet 24 is improved. From the viewpoint of improving the flexibility of the insulating sheet 24, a flexibility-imparting component such as a plasticizer may be contained in the insulating sheet 24. Furthermore, the insulating sheet 24 may be configured with a reaction-curable elastomer or a thermosetting elastomer as a main component.

[0037] Furthermore, it is preferable that the insulating sheet 24 is made of a material with good thermal conductivity. Therefore, the insulating sheet 24 may be made of a thermoplastic elastomer with high thermal conductivity, or may contain a filler that can increase the thermal conductivity. Also, the insulating sheet 24 may be configured to have a foamed structure with fine air layers. Furthermore, the insulating sheet 24 may be configured to have perforations (regular physical holes typified by perforations) or slits (cuts, notches).

[0038] The first electrode sheet 25 is disposed on the first surface 27 of the insulating sheet 24, that is, on the upper surface (the upper surface in FIG. 4) side of the insulating sheet 24, and the second electrode sheet 26 is disposed on the second surface 28 of the insulating sheet 24, that is, on the lower surface (the lower surface in FIG. 4) side of the insulating sheet 24. At least the first electrode sheet 25 constitutes a detection electrode. The first electrode sheet 25 and the second electrode sheet 26 have conductivity. Furthermore, the first electrode sheet 25 and the second electrode sheet 26 are flexible. That is, the first electrode sheet 25 and the second electrode sheet 26 have flexibility and are configured to be extensible in the plane direction.

[0039] 1.1.5. Joining structure of the first electrode sheet 25 and the second electrode sheet 26 and the insulating sheet 24 As shown in FIG. 4, the first electrode sheet 25 is joined to the first surface 27 side of the insulating sheet 24 by a first joining portion 36. The material constituting the first joining portion 36 is not particularly limited, and can be appropriately selected from any materials such as acrylic adhesives, silicone adhesives, urethane adhesives, rubber adhesives, etc. Also, as shown in FIG. 4, the second electrode sheet 26 is joined to the second surface 28 side of the insulating sheet 24 by a first joining portion 36. Since the material constituting the second joining portion 37 is the same as that of the first joining portion 36, duplicate explanations are omitted.

[0040] 1.1.6. Configuration of the electrode sheet With reference to FIGS. 5(a) to 5(b) and FIGS. 9(a) to 9(b), the configuration of the electrode sheet will be described. FIGS. 5(a) to 5(b) And FIGS. 9(a) to 9(b) The first electrode sheets 25, 25a shownAnd The second electrode sheets 26 and 26a are conductive cloths with conductivity. The first electrode sheets 25 and 25a and the second electrode sheets 26 and 26a have flexibility while having conductivity. The first electrode sheets 25 and 25a and the second electrode sheets 26 and 26a have stretchability in the longitudinal direction X and the intersecting direction Y.

[0041] The first electrode sheet 25 and the second electrode sheet 26 are conductive cloths in which a plurality of filament aggregates 72 are woven. The filament aggregate 72 includes a plurality of filaments 71 and a plating layer 33 formed on at least a part of the surface of the filament 71.

[0042] As shown in FIGS. 5(a) to 5(b) and FIGS. 9(a) to 9(b), the first electrode sheets 25 and 25a and the second electrode sheets 26 and 26a are manufactured by forming a plating layer 33 on a base cloth in which a plurality of untwisted yarn bundles 74 are woven. Each untwisted yarn bundle 74 is formed by bundling a plurality of filaments 71 without twisting.

[0043] Examples of the resin constituting the filament 71 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 resin constituting the filament 71 is not limited to the above, and any resin can be appropriately selected. The second electrode sheet 26 has a similar configuration.

[0044] The method for forming the plating layer 33 is not particularly limited. For example, electrolytic plating, electroless plating, electroless plating may be performed after electrolytic plating, or electrolytic plating may be performed after electroless plating, and any method can be appropriately selected.

[0045] As the metal constituting the plating layer 33 formed on the surface of the base fabric, any metal or alloy such as copper, nickel, tin, solder, etc. can be appropriately selected. The plating layer 33 formed on the surface of the base fabric may be composed of one metal species or may be composed of a plurality of metal species. For example, only copper may be plated on the surface of the base fabric, only nickel may be plated on the surface of the base fabric, a copper plating layer made of copper may be formed on the surface of the base fabric, and a nickel plating layer made of nickel may be formed on the surface of this copper plating layer. The plating layer 33 formed on the surface of the base fabric may be formed by electrolytic plating or may be formed by electroless plating. The second electrode sheet 26 also has a similar configuration.

[0046] As shown in FIGS. 5(a) and 9(a), the first electrode sheets 25, 25a include a first opening 34a that opens between a plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25. The first opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheets 25, 25a to the area of the first electrode sheets 25, 25a, is 1% or more and 40% or less.

[0047] As shown in FIGS. 5(b) and 9(b), the second electrode sheets 26, 26a include a second opening 34b that opens between a plurality of filament aggregates 72. The second opening 34b penetrates the second electrode sheet 26. The second opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheets 26, 26a to the area of the second electrode sheets 26, 26a, is 1% or more and 40% or less.

[0048] 1.1.7. Examples, Comparative Examples, and Samples 1.1.7.1. Example 1-1 and Sample 1-1 (Example 1-1 and Sample 1-1) Referring to FIGS. 5 to 8, Example 1-1 will be described. As shown in FIG. 5(a), the first electrode sheet 25 according to Example 1-1 is a conductive cloth woven with a plurality of filament aggregates 72. The plurality of filament aggregates 72 include an untwisted yarn bundle 74 in which a plurality of filaments 71 are gathered without being twisted, and a plating layer 33 formed on at least a part of the surface of the untwisted yarn bundle 74. The filament aggregate 72 is formed in a flat shape in the thickness direction of the first electrode sheet 25b.

[0049] The first electrode sheet 25 according to this Example 1-1 is formed by weaving a warp in which a plurality of filaments 71 are gathered without being twisted and a weft in which a plurality of filaments 71 are gathered without being twisted to form a base cloth, and forming a plating layer 33 on the surface of this base cloth. However, the manufacturing method of the first electrode sheet 25 is not limited to the above method.

[0050] As shown in FIG. 5(a), the first electrode sheet 25 of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The first electrode sheet 25 includes a first opening 34a that opens between the plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25. The opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25 to the area of the first electrode sheet 25 in Example 1-1, is about 3%. Note that this opening ratio is the ratio of the total opening area of the plurality of first openings 34a formed in the target area of the first electrode sheet 25 to the area of the target area of the first electrode sheet 25. This opening ratio is calculated, for example, by specifying a 10 mm × 10 mm target area in the first electrode sheet 25, summing the areas of the first openings 34a within the target area, and dividing the total area by the area of the target area.

[0051] As shown in Fig. 5(b), the second electrode sheet 26 of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The second electrode sheet 26 of this embodiment includes a second opening 34b that opens between the plurality of filament aggregates 72. The second opening 34b penetrates the second electrode sheet 26. The opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26 in Example 1-1 to the area of the second electrode sheet 26 of this embodiment, is approximately 3%.

[0052] The number of filaments 71 included in the filament aggregate 72 that constitutes the first electrode sheet 25 is not particularly limited. The filament aggregate 72 according to this embodiment includes 75 filaments 71, but any number can be used.

[0053] As shown in Fig. 6, a plating layer 33 is formed on at least a part of the surface of the twisted wire 73 that constitutes the filament aggregate 72. When the plating layer 33 of the warp filament aggregate 72a and the plating layer 33 of the weft filament aggregate 72b come into contact, the warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected.

[0054] As shown in Fig. 5(a), the longitudinal direction S of the plurality of warp filament aggregates 72a and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Specifically, the longitudinal direction S of the plurality of warp filament aggregates 72a is at an acute angle that is substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b is at an acute angle that is substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25a. The fact that the angle is substantially 45° includes the case where it is 45° and also includes cases where it can be recognized as being substantially 45°.

[0055] When the longitudinal direction S of the warp 41 is parallel to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 0°), when the first electrode sheet 25 is stretched parallel to the direction X, the warp 41 itself will be stretched, and a large load is required.

[0056] On the other hand, when the longitudinal direction S of the warp 41 is inclined at 45° with respect to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 45°), when the first electrode sheet 25 is stretched parallel to the longitudinal direction X, the square or rectangular lattice composed of the weft 42 and the warp 41 will be deformed into a rhombus shape, and the warp 41 or the weft 42 itself will not be stretched, so a large load is not required. That is, when the acute angle is substantially 45°, structural flexibility is imparted. Furthermore, the higher the aperture ratio, the easier it is for the square or rectangular lattice to be deformed into a rhombus shape, and the structural flexibility is less likely to be impaired.

[0057] However, the longitudinal direction S of the plurality of warp filament aggregates 72a may be at an angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b may be at an angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25.

[0058] The number of the plurality of filaments 71 constituting the warp filament aggregate 72a and the number of the plurality of filaments 71 constituting the weft filament aggregate 72b may be the same or different. In the present Embodiment 1-1, the number of the plurality of filaments 71 constituting the warp filament aggregate 72a and the number of the plurality of filaments 71 constituting the weft filament aggregate 72b are set to be substantially the same. Substantially the same includes the case where they are the same and also the case where they are not the same but can be recognized as substantially the same. The same applies to the weft filament aggregate 72b, so duplicate explanations are omitted.

[0059] As shown in FIG. 6, the warp filament assembly 72a is composed of a plurality of filaments 71. The warp filament assembly 72a includes an internal space 80 formed at least in part between adjacent filaments 71. The plurality of filaments 71 are arranged in the plane direction of the sheet surface of the first electrode sheet 25 and in the direction normal to the sheet surface, respectively.

[0060] The internal space 80 is formed at least in part between at least some of the filaments 71 adjacent to each other in the plane direction of the sheet surface of the first electrode sheet 25 and between at least some of the filaments 71 adjacent to each other in the direction normal to the sheet surface of the first electrode sheet 25. However, the internal space 80 may be formed only in at least part of the filaments 71 adjacent to each other in the plane direction of the sheet surface of the first electrode sheet 25, or may be formed only in at least part of the filaments 71 adjacent to each other in the direction normal to the sheet surface of the first electrode sheet 25.

[0061] A plating layer 33 is formed on at least part of the surface of the filament 71 that is exposed in the internal space 80. The surface of the filament 71 that is exposed in the internal space 80 and on which the plating layer 33 is not formed is exposed.

[0062] As shown in FIG. 6, a plating layer 33 is formed on at least part of the non-exposed portion 81 where the warp filament assembly 72a and the weft filament assembly 72b face each other and cross. On the other hand, the surface of the filament 71 that is exposed in the non-exposed portion 81 and on which the plating layer 33 is not formed is exposed.

[0063] In the portion where the warp filament assembly 72a and the weft filament assembly 72b cross each other, a plating layer 33 is formed on at least part of the portion where the filament 71 exposed on the outer surface of the warp filament assembly 72a faces the filament exposed on the outer surface of the weft filament assembly 72b, and the outer surface of the filament 71 is exposed in the portion where the plating layer 33 is not formed.

[0064] In a portion where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect, a plating layer 33 is partially formed, and in a portion where the plating layer 33 is not formed, the surface of the filament 71 is exposed. Among the portions where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect, the plating layer 33 is formed in the region closer to the portion exposed to the outside, while in the portion closer to the inside, portions where the plating layer 33 is formed and portions where the plating layer 33 is not formed are mixed.

[0065] As shown in FIG. 8, the cross-sectional area A1 of each of the warp filament aggregates 72a is larger than the opening area A2 of the first opening 34a in a state where no strain is generated in the first electrode sheet 25 shown in FIG. 7. The cross-sectional area A1 of the warp filament aggregate 72a refers to the cross-sectional area formed by the outer contour line of the warp filament aggregate 72a. The same applies to the weft filament aggregate 72b hereinafter. Although not shown in detail, the cross-sectional area A1 of each of the weft filament aggregates 72b is larger than the opening area A2 of the first opening 34a in a state where no strain is generated in the first electrode sheet 25. Although not shown in detail, in the second electrode sheet 26, the cross-sectional area A1 of each of the warp filament aggregates 72a and the cross-sectional area A1 of each of the weft filament aggregates 72b are larger than the opening area A2 of the second opening 34b in a state where no strain is generated in the second electrode sheet 26.

[0066] As seen from the thickness direction of the first electrode sheet 25 shown in FIG. 7, the intersection area A3, which is the area of the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other, is larger than the opening area A2 of the first opening 34a shown in FIG. 7. Although not shown in detail, as seen from the thickness direction of the second electrode sheet 26, the intersection area A3, which is the area of the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other, is larger than the opening area A2 of the second opening 34b.

[0067] Also in the weft filament aggregate 72b, since it is the same as above, duplicate explanations are omitted.

[0068] In the present Embodiment 1-1, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is about 10 μm. The metal constituting the plating layer 33 is formed in a three-layer structure, with the outermost layer being Ni, the intermediate layer being Cu, and the innermost layer (on the filament 71 side) being Ni. The diameter of the warp filament aggregate 72a is about 185 μm, and the diameter of the weft filament aggregate 72b is about 185 μm.

[0069] As shown in FIG. 4, the above-described first electrode sheet 25 is joined to the first surface 27 of the insulating sheet 24 via the first joint portion 36. Also, a second electrode sheet 26 having the same configuration as the first electrode sheet 25 is joined to the second surface 28 of the insulating sheet 24 via the second joint portion 37. The insulating sheet 24 is an ether-based polyurethane foam. The first joint portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first joint portion 36 is 50 μm. Since the first joint portion 36 and the second joint portion 37 are the same, duplicate explanations are omitted. In this way, Sample 1 of the sensor sheet 1 according to the first electrode sheet 25 and the second electrode sheet 26b of Example 1-1 is produced.

[0070] 1.1.7.2. Example 1-2 and Sample 1-2 (Example 1-2 and Sample 1-2) Next, with reference to FIGS. 9(a) to 9(b), the configurations of the first electrode sheet 25a and the second electrode sheet 26a according to Example 1-2 will be described. In the first electrode sheet 25a according to this Example 1-2, the number of filaments 71 constituting the warp filament aggregate 72a is different from the number of filaments 71 constituting the weft filament aggregate 72b. In this Example 1-2, the number of filaments 71 constituting the warp filament aggregate 72a is larger than the number of filaments 71 constituting the weft filament aggregate 72b. However, the configuration may be such that the number of filaments 71 constituting the warp filament aggregate 72a is smaller than the number of filaments 71 constituting the weft filament aggregate 72b.

[0071] In this Example 1-2, the number of filaments 71 constituting the warp filament aggregate 72a is set to be about twice the number of filaments 71 constituting the weft filament aggregate 72b. However, the difference in the number of filaments 71 constituting the warp filament aggregate 72a and the number of filaments 71 constituting the weft filament aggregate 72b is not limited to the above.

[0072] Since the second electrode sheet 26a has the same configuration as the first electrode sheet 25a, duplicate explanations will be omitted.

[0073] In this Example 1-2, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is about 10 μm. The metal constituting the plating layer 33 is a Ni single layer. The diameter of the warp filament aggregate 72a is about 180 μm, and the diameter of the weft filament aggregate 72b is about 90 μm.

[0074] Since the configurations other than the above are the same as those in Example 1-1, duplicate explanations will be omitted.

[0075] In addition, in this Sample 1-2, the insulating sheet 24 is an ether-based polyurethane foam. The first joint portion 36 is an acrylic-based adhesive. The thickness of the first joint portion 36 is approximately 50 μm. Since the first joint portion 36 and the second joint portion 37 are the same, duplicate explanations are omitted. Except for the above, in the same manner as in Sample 1-1, a sample 1-2 of the sensor sheet 18 related to the first electrode sheet 25a and the second electrode sheet 26a of Example 1-2 is produced. Duplicate explanations with Sample 1-1 are omitted.

[0076] 1.1.7.3. Comparative Example 1-1 and Sample 1-3 (Comparative Example 1-1 and Sample 1-3) Next, referring to FIGS. 10(a) to 10(b), Comparative Example 1-1 will be described. The warp filament aggregate 72a and the weft filament aggregate 72b according to Comparative Example 1-1 include six filaments 71.

[0077] As shown in FIG. 10(a), the first electrode sheet 25b of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The first electrode sheet 25b includes a first opening 34a that opens between the plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25b. In this Comparative Example 1-1, the opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25b to the area of the first electrode sheet 25b, is 20%.

[0078] As shown in FIG. 10(b), the second electrode sheet 26b of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The second electrode sheet 26b of this embodiment includes a second opening 34b that opens between the plurality of filament aggregates 72. The second opening 34b penetrates the second electrode sheet 26b. In this Comparative Example 1-1, the opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26b to the area of the second electrode sheet 26 of this embodiment, is 20%.

[0079] In Comparative Example 1-1, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is 10 to 20 μm. The metal constituting the plating layer 33 is formed in a three-layer structure, with the outermost layer being Ni, the intermediate layer being Cu, and the innermost layer (on the filament 71 side) being Ni. The diameter of the warp filament aggregate 72a is about 70 μm, and the diameter of the weft filament aggregate 72b is about 70 μm.

[0080] Since the configurations other than the above are the same as those in Embodiment 1-1, duplicate explanations are omitted.

[0081] Also, in Comparative Example 1-1, the insulating sheet 24 is an ether-based polyurethane foam. The first joint portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first joint portion 36 is 50 μm. Since the first joint portion 36 and the second joint portion 37 are the same, duplicate explanations are omitted. In the same manner as in Sample 1-1, a sample 1-3 of the sensor sheet 18 related to the first electrode sheet 25b and the second electrode sheet 26b is produced. Duplicate explanations with Sample 1-1 are omitted.

[0082] 1.1.7.4. Tensile Test of the First Electrode Sheet Next, with reference to FIG. 11, the tensile test performed on the first electrode sheet will be described. The first electrode sheets according to Examples 1-1 to 1-2 and Comparative Example 1-1 were cut into strips of 150 mm × 20 mm to prepare test pieces. The thickness of the first electrode sheet is different in Examples 1-1 to 1-2 and Comparative Example 1-1, but is about 0.1 mm. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a is set to 45°.

[0083] The test piece is gripped by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is carried out on the test piece 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 piece. The tensile testing machine is AGS-X 1 kN manufactured by Shimadzu Corporation. The tensile test is carried out in the range where the strain is 0 to 20%. Fig. 11 shows a graph showing the change of stress with respect to strain.

[0084] In Example 1-1 and Example 1-2, in the region where the strain is 0 to 20%, the stress increased gently and monotonically. Example 1-1 and Example 1-2 do not have a yield point showing a maximum value in the section where the strain is 0.5 to 10% in the stress-strain curve in the tensile test.

[0085] Example 1-1 shows a stress of about 1.4 MPa when the strain is 5%, and shows a stress of about 7.5 MPa when the strain is 20%. Example 1-2 shows a stress of about 0.9 MPa when the strain is 5%, and shows a stress of about 5.9 MPa when the strain is 20%. In the sample example and the first electrode sheets 25, 25a according to the sample example, the maximum value of the stress when the strain is 0 to 5% is 3 MPa or less, and the maximum value of the stress when the strain is 0 to 20% is 15 MPa or less.

[0086] Comparative Example 1-1 has a yield point showing a maximum value in the section where the strain is 0.5 to 10% in the stress-strain curve in the tensile test. In the region where the strain is 0 to about 1%, the stress increased linearly and monotonically. When the strain is about 1%, the stress shows a maximum value of about 17 MPa and decreased rapidly to about 12 MPa. Thus, in Comparative Example 1-1, before and after the strain is about 1%, the stress changed from an increasing trend to a decreasing trend. Thereafter, in the region where the strain is about 1 to about 13%, the stress decreased monotonically from about 12 to about 10 MPa. Thereafter, in the region where the strain is about 13 to 20%, the stress increased monotonically from about 10 to about 12 MPa. Thus, Comparative Example 1-1 has a maximum value of the stress when the strain is 0 to 5% greater than 3 MPa and a maximum value of the stress when the strain is 0 to 20% greater than 15 MPa in the stress-strain curve.

[0087] 1.1.7.5. Tensile Test of Sensor Sheet Next, the tensile test performed on the sensor sheet will be described. Test pieces are prepared by cutting out the sensor sheets related to Samples 1-1 to 1-2 and Sample 1-3 into strips of 90 mm × 20 mm. The thickness of the sensor sheet is about 1 mm although it is different for Samples 1-1 to 1-2 and Sample 1-3. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a constituting the first electrode sheet and the second electrode sheet is set to 45°.

[0088] Connect an electric wire to one end of the first electrode sheet in the longitudinal direction and connect it to a DC power supply. Connect an electric wire to the other end of the first electrode sheet in the longitudinal direction and connect it to a voltage measuring instrument.

[0089] Grip the test piece with a pair of chucks. The distance between the pair of chucks is 50 mm. Perform a tensile test on the test piece at a tensile speed of 1 mm / sec, and calculate the stress by dividing the load by the cross-sectional area of the test piece. Also, during the tensile test, calculate the DC resistance value (an example of the electrical resistance value) of the sensor sheet from the voltage of the DC power supply and the voltage drop of the sensor sheet.

[0090] Fig. 12 shows the stress-strain curve in the tensile test performed on the sensor sheet. Fig. 12 shows the graph in the region where the strain is 0 to 20%. The stress of Samples 1-1 to 1-2 increased monotonically in the region where the strain was 0 to 20%. Samples 1-1 and 1-2 do not have a yield point showing a maximum value in the section where the strain is 0.5 to 10% in the stress-strain curve in the tensile test.

[0091] Sample 1-1 shows a stress of approximately 0.5 MPa when the strain is 5%, and shows a maximum stress of approximately 2.6 MPa when the strain is 20%. Sample 1-2 shows a stress of approximately 0.3 MPa when the strain is 5%, and shows a maximum stress of approximately 1.5 MPa when the strain is 20%. For Sample 1-1 and Sample 1-2, in the stress-strain curve, the maximum stress in the strain range of 0 to 5% is 0.5 MPa or less, and the maximum stress in the strain range of 0 to 20% is 3 MPa or less.

[0092] For Sample 1-1 and Sample 1-2, in the stress-strain curve, the stress in the strain range of 0 to 5% is 0.5 MPa or less, and the maximum stress in the strain range of 0 to 20% is 3 MPa or less.

[0093] Sample 1-3 has a yield point with a maximum value in the strain range of 0.5 to 10% in the stress-strain curve of the tensile test. In the region where the strain is from 0 to approximately 3%, the stress increased linearly and monotonically. When the strain was approximately 3%, the stress showed a maximum value of approximately 0.7 MPa and then decreased rapidly to approximately 0.6 MPa. Thus, in Sample 1-3, before and after the strain of approximately 3%, the stress changed from an increasing trend to a decreasing trend. Thereafter, in the region where the strain was from approximately 1 to approximately 13%, the stress decreased slightly. Thereafter, in the region where the strain was from approximately 13 to 20%, the stress increased monotonically from approximately 0.6 to approximately 0.8 MPa. Thus, for Sample 1-3, in the stress-strain curve, the maximum stress in the strain range of 0 to 5% is greater than 0.5 MPa, and the maximum stress in the strain range of 0 to 20% is greater than 0.7 MPa.

[0094] When a tensile force is applied to Sample 1-1 and Sample 1-2, the first opening 34a of the first electrode sheet extends in the tensile direction and contracts in the direction intersecting the tensile direction. Fig. 13 shows the state in which the first opening 34a is deformed, taking Sample 1-2 as an example. As shown in Fig. 13(a), in the state with an elongation rate of 0%, the first opening 34a is open, but as the elongation rate increases to 10% (see Fig. 13(b)), 20% (see Fig. 13(c)), and 30% (see Fig. 13(d)), the gap between the fibers of the conductive cloth decreases, and in the state with an elongation rate of 30%, the first opening 34a almost disappears. Due to such a change in the fiber shape, it can be easily stretched, so it is considered that the stress generated during stretching is small. That is, it is considered that the presence of the first opening 34a contributes to the expression of the structural stretchability and flexibility of this fiber. Since the above configuration is the same for the second electrode sheet, the description is omitted. Note that the same applies to Sample 1-1, so the description is omitted.

[0095] Note that since the opening ratio of Sample 1-2 is larger than that of Sample 1-1, due to the decrease in the opening area accompanying the change in the spatial arrangement of the entire filament 71 during stretching, the structural stretchability and flexibility are exhibited, so the stress generated is smaller than that of Sample 1-1.

[0096] It is considered that the smaller the generated stress, the smaller the tensile strain applied to the filament 71 itself. Therefore, Sample 1-2 can suppress damage to the plating layer 33 formed on the surface of the filament 71 more than Sample 1-1, and it is expected that even when a tensile force is applied to the sensor sheet 18, the change in the electrical resistance value can be suppressed.

[0097] In Samples 1-1 and 1-2, when a tensile force is applied to the sensor sheet, it is considered that the first opening 34a gradually deforms, thereby absorbing the tensile force. As a result, at the portion where the warp filament assembly 72a and the weft filament assembly 72b intersect, since the relative positions of the warp filament assembly 72a and the weft filament assembly 72b do not change significantly, it is considered that the electrical connection state between the warp filament assembly 72a and the weft filament assembly 72b is maintained. Thus, in Samples 1-1 and 1-2, it is considered that the DC resistance value hardly changes even when a tensile force is applied to the sensor sheet.

[0098] Also, Samples 1-1 and 1-2 do not have a yield point showing a maximum value in the strain range of 0.5 to 5%. This is presumably because in Samples 1-1 and 1-2, in the strain range of 0.5 to 5%, there is no significant change in the structure of the plating layer 33 formed on the first electrode sheet and the second electrode sheet. As a result, the change in the electrical resistance value of the sensor sheet 18 is suppressed.

[0099] On the other hand, Sample 1-3 has a yield point showing a maximum value in the strain range of 0.5 to 5%. In Sample 1-3, in the section from a strain of 0% to the yield point, it is considered that elastic deformation occurs because the plating layer 33 formed at the portion where the warp filament assembly 72a and the weft filament assembly 72b intersect is maintained. Thereafter, at the yield point, it is considered that the plating layer 33 formed at the portion where the warp filament assembly 72a and the weft filament assembly 72b intersect is broken.

[0100] Thereafter, in the section where the stress hardly changes (the strain range of about 5 to about 15%), similar to Samples 1-1 and 1-2, it is considered that the tensile force is absorbed by the deformation of the first opening 34a and the second opening 34b.

[0101] After that, when the strain becomes greater than about 15%, since the first and second opening ratios of Samples 1-3 are 20%, the first opening 34a and the second opening 34b are completely blocked, and it is considered that the tensile force acting on the first and second electrode sheets cannot be absorbed. As a result, it is considered that the stress increases.

[0102] 1.1.7.6. Change Rate of DC Resistance Value of Sensor Sheet Next, the change rate of the DC resistance value was measured for the sensor sheet. The sensor sheet was cut into a strip shape of 90 mm × 20 mm to prepare a test piece. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a is set to 45°.

[0103] The test piece is gripped by a pair of chucks. The distance between the pair of chucks is 50 mm. A tensile test is performed on the test piece at a tensile speed of 1 mm / sec. Wires are connected to both ends of the first electrode sheet, and the DC resistance value between the two wires is measured. For the DC resistance value at this time, the change rate of the DC resistance value is calculated based on the following formula (1). The measurement of the DC resistance value uses a digital multimeter 2000 series manufactured by KEITHLEY. The above test is performed on Samples 1-1 to 1-2 and Sample 1-3.

[0104]

Equation

[0105] Figure 14 is a graph showing the change of the DC resistance value change rate with respect to strain. The change rate of the DC resistance value of Sample 1-1 increased in the range where the strain was 0 to about 2%, and when the strain was about 2%, the change rate of the DC resistivity was about 5%. After that, it decreased in the range of about 2 to about 5%, and the change rate of the DC resistivity became about 0%. After that, when the strain was about 25% or more, the change rate of the DC resistance value increased gently, and the change rate of the DC resistance value was about 7% when the strain was 30%. Thus, the change rate of the DC resistance value of Sample 1-1 was 10% or less in the range where the strain was 0 to 30%.

[0106] The change rate of the DC resistance value of Sample 1-2 increased in the range where the strain was 0 to approximately 3%. When the strain was approximately 3%, the change rate of the DC resistivity became approximately 10%. Thereafter, it decreased in the range of approximately 3 to approximately 5%, and the change rate of the DC resistivity became approximately 0%. Thereafter, even when the strain was 30%, the change rate of the DC resistance value was approximately 0%. Thus, the change rate of the DC resistance value of Sample 1-2 was 10% or less in the range where the strain was 0 to 30%.

[0107] The change rate of the DC resistance value of Sample 1-3 was approximately 2% in the range where the strain was 0 to approximately 3%. Thereafter, in the range where the strain was approximately 3 to 30%, the change rate of the DC resistance value increased monotonically. When the strain was 30%, it became approximately 130%. Thus, the change rate of the DC resistance value of Sample 1-3 was greater than 10% in the range where the strain was 0 to 30%. Compared with Sample 1-1 and Sample 1-2, the resistance change during extension was extremely large.

[0108] 1. 1. 7.7.10% Change rate of the DC resistance value of the sensor sheet at 10% elongation Next, the change rate of the DC resistance value at 10% elongation was measured for the sensor sheet. When measuring the change rate of the DC resistance value of the above-mentioned sensor sheet, the sensor sheet was elongated by 10% with respect to the reference length (50 mm) in the state before applying a tensile force to the sensor sheet, then returned to the reference length, and the test of elongating by 10% again was repeated a predetermined number of times. The number of repetitions in this test was 1, 5, and 10 times. Regarding the DC resistance value at this time, the change rate of the DC resistance value was calculated based on the above formula (1). The above test was carried out for Samples 1-1 to 1-2 and Sample 1-3.

[0109] Fig. 15 shows a graph showing the relationship between the number of repetitions of the extension test and the change rate of the DC resistance value. For Sample 1-1, the change rate of the DC resistance value at the first measurement was approximately 0%. Thereafter, as the number of repetitions increased, the change rate of the DC resistance value increased to approximately 36% for 1 repetition, approximately 48% for 5 repetitions, and approximately 57% for 10 repetitions. When repeated 10 times, the change rate of the DC resistivity of Sample 1-1 was 60% or less.

[0110] For Sample 1-2, the change rate of the DC resistivity at the first measurement was approximately 14%, which was larger than that of Sample 1-1. However, at the first repetition, it was approximately 9%, and at the fifth repetition, it was approximately 15%. As the number of repetitions increased, the change rate of the DC resistance value did not increase significantly. At the tenth repetition, it was approximately 30%. At the tenth repetition, the change rate of the DC resistance value of Sample 1-2 was 50% or less.

[0111] For Sample 1-3, the change rate of the DC resistance value at the first measurement was equivalent to that of Sample 1-1, approximately 0%. However, at the first repetition, it was approximately 61%, at the fifth repetition, it was approximately 89%, and at the tenth repetition, it was approximately 115%. As the number of repetitions increased, the change rate of the DC resistance value increased more than that of Sample 1-1 and Sample 1-2.

[0112] As described above, it was found that the sensor sheets related to Samples 1-1 and 2 had a smaller change in the DC resistance value compared to Sample 1-3 even when the 10% elongation test was repeated.

[0113] 1.1.7.8. Change Rate of DC Resistance Value of Sensor Sheet at 20% Elongation Subsequently, for Samples 1-1 to 1-2 and Sample 1-3, the change rate of the DC resistance value when the sensor sheet was elongated by 20% was measured.

[0114] Fig. 16 shows a graph regarding the relationship between the number of repetitions of the stretching test and the change rate of the DC resistance value. For Sample 1-1, the change rate of the DC resistance value at the first measurement was approximately 0%. Subsequently, at the first repetition, it was approximately 35%, and at the fifth repetition, it was approximately 91%. As the number of repetitions increased, the change rate of the DC resistance value increased. At the tenth repetition, the change rate of the DC resistance value was approximately 137%.

[0115] For Sample 1-2, the rate of change of the DC resistivity during the first measurement was approximately 10%, which was greater than that of Sample 1-1. However, during the first repetition, it was approximately 27%, and during the fifth repetition, it was approximately 32%. The rate of change of the DC resistance value did not increase significantly even as the number of repetitions increased. At the tenth repetition, the rate of change of the DC resistance value of Sample 1-2 was approximately 55%.

[0116] For Sample 1-3, the rate of change of the DC resistance value during the first measurement was approximately 0%, which was equivalent to that of Sample 1-1. However, it showed approximately 114% during the first repetition and exceeded 200% during the fifth repetition.

[0117] As described above, it was found that the sensor sheets related to Samples 1-1 and 2 had a smaller change in the DC resistance value compared to Sample 1-3 even when the 20% elongation test was repeated.

[0118] 1.1.7.9 Variant 1 of Embodiment 1-1 As shown in FIG. 17, the cross-sectional shape of the filament 71 according to Variant 1 of Embodiment 1-1 is formed in a hexagonal shape. However, the cross-sectional shape of the filament 71 may be a triangle, a quadrilateral, a pentagon, or a polygon with seven or more sides. Also, the cross-sectional shape of the filament 71 does not have to be a regular polygon. Further, the cross-sectional shapes of the plurality of filaments 71 do not have to be of one type. For example, a configuration in which a part is formed in a quadrilateral shape and another part is formed in a pentagon shape is also acceptable.

[0119] 1.1.7.10 Variant 2 of Embodiment 1-1 As shown in FIG. 18, the cross-sectional shape of the filament 71 according to Variant 2 of Embodiment 1-1 may be a non-circular shape. For example, it may be an oval shape. Also, the cross-sectional shape of the filament 71 can be selected as any shape such as a track shape or a strange shape with different maximum diameters of the inscribed circles. Further, the cross-sectional shapes of the plurality of filaments 71 do not have to be of one type. For example, a configuration in which a part is formed in a polygonal shape and another part is formed in an oval shape is also acceptable.

[0120] Furthermore, the cross-sectional shapes of the plurality of filaments 71 do not have to be of one type. For example, a configuration in which a part is formed in a polygonal shape and another part is formed in an oval shape is also acceptable.

[0121] 1.1.8. Operational effects of this embodiment Subsequently, the operational effects of this embodiment will be described. The sensor sheet 18 according to this embodiment includes an insulating sheet 24, a first electrode sheet 25, a first joint portion 36, a second electrode sheet 26, and a second joint portion 37. The insulating sheet 24 has a first surface 27 and a second surface 28 and is formed of a foam. The first electrode sheet 25 is conductive and is disposed on the first surface 27 side of the insulating sheet 24 and has a first opening 34a that penetrates therethrough. The first joint portion 36 joins the insulating sheet 24 and the first electrode sheet 25. The second electrode sheet 26 is conductive and is disposed on the second surface 28 side of the insulating sheet 24 and has a second opening 34b that penetrates therethrough. The second joint portion 37 joins the insulating sheet 24 and the second electrode sheet 26. The first electrode sheet 25 and the second electrode sheet 26 are conductive fabrics in which a plurality of filament aggregates 72 are woven. The plurality of filament aggregates 72 include a plurality of filaments 71 and a plating layer 33 formed on at least a part of the surface of the filaments 71. The first electrode sheet 25 includes a first opening 34a that opens between the plurality of filament aggregates 72. The second electrode sheet 26 includes a second opening 34b that opens between the plurality of filament aggregates 72. The sensor sheet 18 is configured not to have a yield point that exhibits a maximum value in the range of strain from 0.5% to 10% in the stress-strain curve in a tensile test. The opening ratio, which is the ratio of the opening area of the first opening 34a to the area of the first electrode sheet 25, is 1% or more and 50% or less. The opening ratio, which is the ratio of the opening area of the second opening 34b to the area of the second electrode sheet 26, is 1% or more and 50% or less.

[0122] According to this embodiment, when a tensile force is applied to the sensor sheet, the first opening 34a of the first electrode sheet 25 deforms so that the opening area of the first opening 34a decreases. Then, new conductive paths 72 are formed between the plurality of filament aggregates that were separated by the first opening. Thereby, even when a tensile force is applied to the sensor sheet 18, it is possible to suppress a change in the electrical resistance value. The same applies to the second opening 34b of the second electrode sheet 26.

[0123] The aperture ratio of the first opening 34a is preferably 1% or more and 50% or less. When the aperture ratio is 50% or less, when the aperture area of the first opening 34a is deformed in a direction of decreasing, it becomes easier for the plurality of filament aggregates 72 to come into contact with each other. Thus, since it becomes easier for the plurality of filament aggregates 72 to come into contact with each other, the aperture ratio of the first opening 34a is preferably 1% or more and 50% or less, more preferably 1% or more and 40% or less, and still more preferably 1% or more and 30% or less. The same applies to the aperture ratio of the second opening 34b as that of the first opening 34a.

[0124] In addition, the sensor sheet according to the present embodiment is configured not to have a yield point showing a maximum value in the stress-strain curve in the tensile test in the section where the strain is 0.5 to 10%. Thereby, it is possible to suppress the plating layer from breaking in the section where the strain is 0.5 to 10%, so that it is possible to suppress a change in the electrical resistance value of the sensor sheet. Further, in a region where the strain is relatively small, such as 0.5 to 10%, a large stress is not generated and a rapid change in the stress is suppressed. As a result, the efficiency of the work of assembling the sensor sheet 18 to the steering wheel 10 can be improved. Furthermore, by not having a yield point showing a maximum value in the section where the strain is 0.5 to 5%, when the sensor sheet 18 is slightly pulled, a large stress is not generated and the stress does not change, so that the workability is further improved, which is more preferable.

[0125] When a tensile force is applied to the sensor sheet 18, the first opening 34a of the first electrode sheet 25 is deformed so that the aperture area of the first opening 34a decreases. That is, without the tensile strain concentrating on the filament 71 itself, the spatial arrangement of the entire filament 71 changes, so that it is stretchable. That is, due to the decrease in the aperture area accompanying the change in the spatial arrangement of the entire filament 71, structural expansion and contraction flexibility is exhibited, so that the tensile strain applied to the filament 71 itself is small, and damage to the plating layer 33 formed on the filament 71 can be suppressed. Therefore, even when a tensile force is applied to the sensor sheet 18, a change in the electrical resistance value can be suppressed.

[0126] The aperture ratio of the first opening 34a is preferably 1% or more and 50% or less. When the aperture ratio is 50% or less, when the aperture area of the first opening 34a is deformed in a direction of decreasing, it becomes easier for the plurality of filament aggregates 72 to come into contact with each other. Thus, since it becomes easier for the plurality of filament aggregates 72 to come into contact with each other, the aperture ratio of the first opening 34a is preferably 1% or more and 50% or less, more preferably 1% or more and 40% or less, and still more preferably 1% or more and 30% or less. The same applies to the second opening 34b as to the first opening 34a.

[0127] The sensor sheet 18 according to this embodiment is configured such that, in the stress-strain curve, the maximum value of the stress when the strain is 0 to 5% is 0.5 MPa or less. Further, the sensor sheet 18 is configured such that, in the stress-strain curve, the maximum value of the stress when the strain is 0 to 20% is 3 MPa or less. Thereby, when a tensile force is applied to the sensor sheet 18, it is possible to suppress an excessive stress from being applied to the first electrode sheets 25, 25a. As a result, it is possible to suppress the structure of the first electrode sheets 25, 25a from being destroyed, and thus it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0128] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or from the viewpoint of reducing the stress applied to the second electrode sheets 26, 26a, in the stress-strain curve, the maximum value of the stress of the sensor sheet 18 when the strain is 0 to 5% is preferably 0.5 MPa or less, more preferably 0.4 MPa or less, and still more preferably 0.3 MPa or less.

[0129] Similarly, from the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or from the viewpoint of reducing the stress applied to the second electrode sheets 26, 26a, in the stress-strain curve, the maximum value of the stress of the sensor sheet 18 when the strain is 0 to 20% is preferably 3 MPa or less, more preferably 2 MPa or less, and still more preferably 1.5 MPa or less.

[0130] Further, the first electrode sheets 25 and 25a according to this embodiment are configured such that, in the stress-strain curve, the maximum value of the stress of the first electrode sheets 25 and 25a when the strain is 0 to 5% is 3 MPa or less. Also, the first electrode sheets 25 and 25a are configured such that, in the stress-strain curve, the maximum value of the stress when the strain is 0 to 20% is 15 MPa or less. Note that the same applies to the second electrode sheets 26 and 26a.

[0131] From the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, or from the viewpoint of reducing the stress applied to the second electrode sheets 26 and 26a, in the stress-strain curve, the maximum value of the stress of the first electrode sheets 25 and 25a, or the second electrode sheets 26 and 26a when the strain is 0 to 5% is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1 MPa or less.

[0132] Similarly, from the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, or from the viewpoint of reducing the stress applied to the second electrode sheets 26 and 26a, the maximum value of the stress of the first electrode sheets 25 and 25a, or the second electrode sheets 26 and 26a when the strain is 0 to 20% is preferably 15 MPa or less, more preferably 10 MPa or less, and even more preferably 7 MPa or less.

[0133] The stress-strain curve of the sensor sheet 18 according to this embodiment is a stress-strain curve obtained when a tensile test is performed at a tensile speed of 1 mm / s while gripping a 20 mm × 90 mm test piece.

[0134] Further, the cross-sectional shape of the filament 71 may be non-circular or polygonal. As a result, an irregular space is formed between the plurality of filaments 71. When the filament 71 moves within this space, the tensile force applied to the sensor sheet 18 is absorbed, so that an excessive stress is prevented from being applied to the sensor sheet 18. As a result, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0135] In addition, in the filament assembly 72 according to the present embodiment, a portion where the plating layers 33 formed on the surfaces of adjacent filaments 71 are electrically connected by contacting each other is also present on the outer surfaces of a plurality of filaments 71 located inside the untwisted yarn bundle 74 formed in a bundle shape. Therefore, when a tensile force is applied to the sensor sheet 18, even if the plating layer 33 formed on the outer surface of the filament 71 located on the surface of the untwisted yarn bundle 74 is broken, there is still a plating layer 33 formed on the outer surfaces of a plurality of filaments 71 located inside the untwisted yarn bundle 74. As a result, when the plating layers 33 formed on the outer surfaces of a plurality of filaments 71 located inside the untwisted yarn bundle 74 contact each other, even when a tensile force is applied to the sensor sheet 18, a change in the electrical resistance value can be suppressed.

[0136] In addition, the filament assembly 72 according to the present embodiment includes an internal space 80 formed in at least a part between adjacent filaments 71. Since the filaments 71 can move freely within the internal space 80, when a tensile force is applied to the sensor sheet 18, the filaments 71 can move within the internal space 80 to absorb stress. Thereby, it is possible to suppress an excessive stress from being applied to the sensor sheet 18, and thus it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0137] In addition, in the filament assembly 72 according to the present embodiment, a plurality of filaments 71 are arranged in each of the surface direction of the sheet surface of the first electrode sheet 25 and the normal direction of the sheet surface. The internal space 80 is formed in at least a part between adjacent filaments 71 in the surface direction and at least a part between adjacent filaments 71 in the normal direction. Thereby, since the filaments 71 can move in the surface direction and the normal direction, the stress applied to the sensor sheet 18 by the filaments 71 can be efficiently absorbed. As a result, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0138] Further, a plating layer 33 is formed on at least a part of the surface of the filament 71 that is exposed to the internal space 80. A part of the surface of the filament 71 that is exposed to the internal space 80 and on which the plating layer 33 is not formed has the surface of the filament exposed. As a result, the filament 71 exposed to the internal space 80 can move freely without being restricted by the plating layer 33. Thus, since the filament 71 can move within the internal space 80, the stress applied to the sensor sheet 18 by the filament 71 can be efficiently absorbed. As a result, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0139] Further, a plating layer 33 is formed on at least a part of the non-exposed portion 81 where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and cross. As a result, the warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected, so that a conduction path of the sensor sheet 18 can be formed.

[0140] Further, a plating layer 33 is formed on at least a part of the surface of the filament 71 that is exposed on the outer surface of the filament aggregate 72. A part of the surface of the filament 71 that is exposed on the outer surface of the filament aggregate 72 and on which the plating layer 33 is not formed has the surface of the filament exposed. Since a plating layer 33 is formed on at least a part of the surface of the filament 71 that is exposed on the outer surface of the filament aggregate 72, the plating layer 33 formed on the surface of one filament 71 and the plating layer 33 formed on the surface of another filament 71 come into contact with each other, whereby the filaments 71 are electrically connected. Also, since the part of the surface of the filament 71 on which the plating layer is not formed allows the filament 71 to move relatively freely, the tensile force applied to the sensor sheet 18 can be absorbed. As a result, excessive stress being applied to the sensor sheet 18 can be suppressed, so that a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0141] The plurality of filament aggregates 72 according to this embodiment includes a warp filament aggregate 72a and a weft filament aggregate 72b. At a portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other, a plating layer 33 is formed on at least a part of a portion where the filaments 71 exposed on the outer surface of the warp filament aggregate 72a and the filaments 71 exposed on the outer surface of the weft filament aggregate 72b face each other. Where the plating layer 33 is not formed, the outer surface of the filament 71 is exposed.

[0142] The plating layer 33 according to this embodiment is a single layer made of nickel or a plurality of layers including a layer made of copper and a layer made of nickel.

[0143] Further, the manufacturing method of the sensor sheet 18 according to this embodiment is as follows. A step of forming a filament aggregate 72 by gathering a plurality of filaments 71. A step of forming a base fabric by weaving a plurality of filament aggregates 72. A step of forming a conductive fabric by performing a plating process on the base fabric. A step of forming the sensor sheet 18 by joining the conductive fabric to the first surface 27 of an insulating sheet 24 made of an elastomer having a first surface 27 and a second surface 28.

[0144] According to the manufacturing method of the sensor sheet 18 described above, there are those in which the plating layers 33 formed on the surfaces of adjacent filaments 71 are electrically connected by contacting each other, and those in which the plating layer 33 is not formed on the surfaces of adjacent filaments 71 and can move freely relative to each other. Thus, when a tensile force is applied to the sensor sheet 18, the filaments 71 that can move freely relative to each other absorb stress, thereby suppressing the application of an excessively large stress to the sensor sheet 18. As a result, since the electrical connection of the sensor sheet 18 is maintained by the filaments 71 that are electrically connected to each other, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0145] ( Reference Form 2-1) Next, Reference Form 2-1 will be described. Reference Since Form 2-1 has the same configuration as that described in 1.1.1 to 1.1.5 of Embodiment 1-1, the descriptions in 1.1.1 to 1.1.5 are read as 2.1.1 to 2.1.5, and duplicate explanations are omitted.

[0146] 2.1.6. Configuration of the electrode sheet With reference to FIGS. 19 and 21, the first electrode sheets 25, 25a and the second electrode sheets 26, 26a will be described. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a are conductive conductive fabrics. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a have conductivity and flexibility. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a have stretchability in the longitudinal direction X and the crossing direction Y.

[0147] As shown in FIG. 19, the first electrode sheet 25 and the second electrode sheet 26 are manufactured by forming a plating layer 33 on a base fabric woven with a plurality of filaments 71. Also, as shown in FIG. 21, the first electrode sheet 25a and the second electrode sheet 26a are manufactured by forming a plating layer 33 on a base fabric woven with a plurality of twisted yarns 73. Each twisted yarn 73 is formed by twisting a plurality of filaments 71.

[0148] Examples of the resin constituting the filament 71 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 41 and the weft 42 are not limited to the above, and any resin can be appropriately selected. The second electrode sheet 26 has the same configuration.

[0149] The method for forming the plating layer 33 is not particularly limited. For example, electrolytic plating, electroless plating, electroless plating may be performed followed by electrolytic plating, or electrolytic plating may be performed followed by electroless plating. Any method can be appropriately selected.

[0150] As the metal constituting the plating layer 33 formed on the surface of the base fabric, any metal or alloy such as copper, nickel, tin, solder, etc. can be appropriately selected. The plating layer 33 formed on the surface of the base fabric may be composed of one metal species or a plurality of metal species. For example, only copper may be plated on the surface of the base fabric, or only nickel may be plated on the surface of the base fabric. A copper plating layer made of copper may be formed on the surface of the base fabric, and a nickel plating layer made of nickel may be formed on the surface of this copper plating layer. The plating layer 33 formed on the surface of the base fabric may be formed by electrolytic plating or electroless plating. The second electrode sheet 26 has a similar configuration.

[0151] 2.1.7. Reference Examples, Comparative Examples, and Samples 2.1.7.1. Reference Example 2-1 and Sample 2-1 ( Reference (Example 2-1 and Sample 2-1) Referring to FIGS. 19 to 20, Reference Example 2-1 will be described. As shown in FIG. 19(a), the first electrode sheet 25 of this Reference Example 2-1 includes a plurality of warp threads 41 and a plurality of weft threads 42. The first electrode sheet 25 is formed by weaving the warp threads 41 and the plurality of weft threads 42. The warp thread 41 is composed of one filament 71 and a plating layer 33 formed on the surface of the filament 71, and the weft thread 42 is composed of one filament 71 and a plating layer 33 formed on the surface of the filament 71. Since the first electrode sheet 25 and the second electrode sheet 26 have substantially the same configuration, in the following description, overlapping explanations will be omitted except when specifically mentioned.

[0152] The first electrode sheet 25 includes a first opening 34a that opens between two adjacent ones of the plurality of warp threads 41 and two adjacent ones of the plurality of weft threads 42. The first opening 34a penetrates the first electrode sheet 25. This Reference In Example 2-1, the opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25 to the area of the first electrode sheet 25, is approximately 63%. Note that this opening ratio is the ratio of the total opening area of the plurality of first openings 34a formed in the target area of the first electrode sheet 25 to the area of the target area of the first electrode sheet 25. This opening ratio is calculated, for example, by specifying a target area of 10 mm × 10 mm in the first electrode sheet 25, summing the areas of the first openings 34a within the target area, and dividing the total area by the area of the target area.

[0153] As shown in FIG. 19(b), this Reference The second electrode sheet 26 of Example 2-1 includes a plurality of warp threads 41 and a plurality of weft threads 42. The second electrode sheet 26 is formed by weaving the warp threads 41 and the plurality of weft threads 42. The warp thread 41 is composed of one filament 71, and the weft thread 42 is composed of one filament 71.

[0154] The second electrode sheet 26 includes a second opening 34b that opens between two adjacent ones of the plurality of warp threads 41 and two adjacent ones of the plurality of weft threads 42. This Reference In Example 2-1, the opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26 to the area of the second electrode sheet 26, is approximately 63%.

[0155] As shown in Fig. 19(a), the longitudinal direction S of a plurality of warp threads 41 and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Also, the longitudinal direction T of a plurality of weft threads 42 and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Specifically, the longitudinal direction S of the plurality of warp threads 41 is at an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft threads 42 is at an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25. The fact that the angle is substantially 45° includes the case where it is 45° and also includes cases where it can be recognized as being substantially 45°.

[0156] When the longitudinal direction S of the warp thread 41 is parallel to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 0°), when the first electrode sheet 25 is stretched parallel to the direction X, the warp thread 41 itself will be stretched, and a large load is required.

[0157] On the other hand, when the longitudinal direction S of the warp thread 41 is inclined at an angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 45°), when the first electrode sheet 25 is stretched parallel to the longitudinal direction X, the square or rectangular lattice formed by the weft thread 42 and the warp thread 41 will be deformed into a rhombus shape, and the warp thread 41 or the weft thread 42 itself will not be stretched, so a large load is not required. That is, when the acute angle is substantially 45°, structural flexibility is imparted. Furthermore, the higher the aperture ratio, the easier it is for the square or rectangular lattice to be deformed into a rhombus shape, and the structural flexibility is less likely to be impaired.

[0158] However, the longitudinal direction S of the plurality of warp threads 41 may be at an acute angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft threads 42 may be at an acute angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25. Regarding the second electrode sheet 26, since it is the same as the first electrode sheet 25, duplicate explanations are omitted.

[0159] As shown in Fig. 19(a), the intervals between the plurality of warp threads 41 according to this embodiment are arranged at substantially equal intervals. However, "substantially equal intervals" includes the case of equal intervals, and also includes the case where, even if the intervals are not equal, they can be recognized as substantially equal intervals. Note that the intervals between the plurality of warp threads 41 may be different from each other.

[0160] Also, the intervals between the plurality of weft threads 42 according to this embodiment are arranged at substantially equal intervals. However, "substantially equal intervals" includes the case of equal intervals, and also includes the case where, even if the intervals are not equal, they can be recognized as substantially equal intervals. Note that the intervals between the plurality of weft threads 42 may be different from each other.

[0161] As shown in Fig. 19(b), the configuration of the second electrode sheet 26 is the same as that of the first electrode sheet 25, so overlapping explanations are omitted.

[0162] As shown in Fig. 20, a plating layer 33 is formed on at least a part of the warp thread 41. The plating layer 33 may be formed on the entire surface of the warp thread 41, or the plating layer 33 may be formed on a part of the surface of the warp thread 41.

[0163] Also, a plating layer 33 is formed on at least a part of the weft thread 42. The plating layer 33 may be formed on the entire surface of the weft thread 42, or the plating layer 33 may be formed on a part of the surface of the weft thread 42.

[0164] This Reference In the example, the plating layer 33 formed on the surface of the warp thread 41 and the plating layer 33 formed on the surface of the weft thread 42 come into contact with each other, whereby the warp thread 41 and the weft thread 42 are electrically connected.

[0165] This ReferenceIn Example 2-1, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is 60 to 65 μm. The metal constituting the plating layer 33 is formed in a three-layer structure, with the outermost layer being Ni, the intermediate layer being Cu, and the innermost layer (on the filament 71 side) being Ni.

[0166] As shown in FIG. 4, the above-described first electrode sheet 25 is joined to the first surface 27 of the insulating sheet 24 formed by containing a foamed resin as a main component via a first joint portion 36. The insulating sheet 24 is an ether-based polyurethane foam. The thickness of the insulating sheet is about 1.0 mm. The first joint portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first joint portion 36 is 50 μm. Further, a second electrode sheet 26 having the same configuration as the first electrode sheet 25 is joined to the second surface 28 of the insulating sheet 24 via a second joint portion 37. Since the first joint portion 36 and the second joint portion 37 are the same, duplicate explanations are omitted. In this way, Reference A sample 2-1 of the sensor sheet 18 related to the first electrode sheet 25 and the second electrode sheet 26 of Example 2-1 is produced.

[0167] 2.1.7.2. Reference Example 2-2 and Sample 2-2 ( Reference Example 2-2 and Sample 2-2) Subsequently, referring to FIGS. 21(a) to 21(b), ReferenceThe configuration of the first electrode sheet 25a and the second electrode sheet 26a according to Example 2-2 will be described. The first electrode sheet 25a according to this embodiment is a conductive cloth in which a plurality of filament aggregates 72 are woven. The plurality of filament aggregates 72 include a twisted yarn 73 formed by twisting a plurality of filaments 71, and a plating layer 33 formed on at least a part of the surface of the twisted yarn 73. Further, the plurality of filament aggregates 72 include a warp filament aggregate 72a and a weft filament aggregate 72b. In the following description, when the warp filament aggregate 72a and the weft filament aggregate 72b are not distinguished and described, they may be described as the filament aggregate 72. Among the reference numerals used hereinafter, those the same as those used in the previously described embodiments represent the same components as those in the previously described embodiments unless otherwise specified.

[0168] The first electrode sheet 25a according to this embodiment is formed by weaving a twisted yarn 73 that constitutes a warp formed by twisting a plurality of filaments 71 and a twisted yarn 73 that constitutes a weft formed by twisting a plurality of filaments 71 to form a base cloth, and forming a plating layer 33 on the surface of this base cloth. However, the manufacturing method of the first electrode sheet 25a is not limited to the above method. Since the first electrode sheet 25a and the second electrode sheet 26a have substantially the same configuration, in the following description, overlapping descriptions will be omitted except when specifically mentioned.

[0169] As shown in FIG. 21(a), the first electrode sheet 25a of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The first electrode sheet 25a includes a first opening 34a that opens between the plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25a. This Reference In Example 2-2, the opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25a to the area of the first electrode sheet 25a, is 63%.

[0170] As shown in FIG. 21(b), the second electrode sheet 26a of this embodiment is substantially the same as the first electrode sheet 25a except that it has a second opening 34b that opens between a plurality of filament aggregates 72, and thus duplicate explanations are omitted. This Reference In Example 2-2, the opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26a to the area of the second electrode sheet 26a of this embodiment, is 63%.

[0171] The number of filaments 71 included in the filament aggregate 72 that constitutes the first electrode sheet 25a is not particularly limited. The filament aggregate 72 according to this embodiment includes six filaments 71, but it may have two to five filaments or seven or more filaments.

[0172] As shown in FIG. 21(a), the longitudinal direction S of a plurality of warp filament aggregates 72a and the longitudinal direction X of the first electrode sheet 25a are arranged to intersect. Also, the longitudinal direction T of a plurality of weft filament aggregates 72b and the longitudinal direction X of the first electrode sheet 25a are arranged to intersect. Specifically, the longitudinal direction S of a plurality of warp filament aggregates 72a forms an acute angle that is substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25a. Also, the longitudinal direction T of a plurality of weft filament aggregates 72b forms an acute angle that is substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25a. The fact that the angle is substantially 45° includes the case where the angle is 45° and also includes cases where the angle can be recognized as being substantially 45°.

[0173] However, the longitudinal direction S of a plurality of warp filament aggregates 72a may form an acute angle that is different from 45° with respect to the longitudinal direction X of the first electrode sheet 25a. Also, the longitudinal direction T of a plurality of weft filament aggregates 72b may form an acute angle that is different from 45° with respect to the longitudinal direction X of the first electrode sheet 25a.

[0174] As shown in Fig. 21(a), the intervals between the plurality of warp filament aggregates 72a according to this embodiment are arranged at substantially equal intervals. However, "substantially equal intervals" includes the case of equal intervals, and also includes the case where, even if they are not equal intervals, they can be recognized as substantially equal intervals. Also, the intervals between the plurality of weft filament aggregates 72b are also arranged at substantially equal intervals.

[0175] In this embodiment, the intervals between the plurality of warp filament aggregates 72a and the intervals between the plurality of weft filament aggregates 72b are set to be substantially the same. However, the intervals between the plurality of warp filament aggregates 72a and the intervals between the plurality of weft filament aggregates 72b may be different.

[0176] As shown in Fig. 22, a plating layer 33 is formed on at least a part of the surface of the twisted yarn 73 that constitutes the filament aggregate 72. In this embodiment, the plating layer 33 is formed on the surface of the filament 71 that is exposed to the outside among the surfaces of the twisted yarn 73.

[0177] When the plating layer 33 of the warp filament aggregate 72a and the plating layer 33 of the weft filament aggregate 72b come into contact, the warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected.

[0178] Also, in this embodiment, on a part of the surface of the filament 71 that constitutes the twisted yarn 73 and is exposed inside the twisted yarn 73, the plating layer 33 is not formed. Thereby, the surface of the filament 71 exposed inside the twisted yarn 73 is in a state of being exposed to the space inside the twisted yarn 73. On the other hand, in this embodiment, on another part of the surface of the filament 71 that constitutes the twisted yarn 73 and is exposed inside the twisted yarn 73, the plating layer 33 is formed. Thus, in this embodiment, the surface of the filament 71 exposed inside the twisted yarn 73 includes a portion where the surface of the filament 71 is exposed and a portion where the plating layer 33 is formed.

[0179] Where the plating layer 33 is not formed and the surface of the filament 71 is exposed, the structure is more movable than the portion where the plating layer 33 is formed. Thus, when stress is applied to the sensor sheet, the relatively freely movable filament 71 can absorb the stress.

[0180] This Reference In Example 2-2, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is about 20 μm. The metal constituting the plating layer 33 has Ni as the outermost layer and is formed of Cu on the innermost layer (on the filament 71 side). The twisted wire 73 is composed of six filaments 71.

[0181] In the same manner as in Sample 2-1, Reference Sample 2-2 of the sensor sheet 18 related to the first electrode sheet 25a and the second electrode sheet 26a of Example 2-2 is produced. Descriptions overlapping with those of Sample 2-1 are omitted.

[0182] ( Reference Modification 1 of Example 2-2) Next, with reference to FIG. 23, Reference Modification 1 of Example 2-2 will be described. As shown in FIG. 23, the plating layer 33 is formed on at least a part of the surface of the filament 71. In this Modification 1, the plating layer 33 is formed on the surface of each filament 71 except for the contact points where adjacent filaments 71 contact each other. In this Modification 1, the plating layer 33 is also formed on the surface of the filament 71 located inside the twisted wire 73 among the surfaces of the filaments 71.

[0183] ( Reference Modification 2 of Example 2-2) Next, with reference to FIG. 24, ReferenceA modification example 2 of Example 2-2 will be described. As shown in FIG. 24, a plating layer 33 is formed on the entire circumference of the surface of a plurality of filaments 71 constituting the twisted yarn 73. When the plating layers 33 formed on the surfaces of adjacent filaments 71 come into contact with each other, the adjacent filaments 71 are electrically connected to each other.

[0184] 2.1.7.3. Comparative Example 2-1 and Sample 2-3 (Comparative Example 2-1 and Sample 2-3) Next, referring to FIGS. 25 to 26, Comparative Example 2-1 will be described. As shown in FIG. 25, the first electrode sheet 25b according to Comparative Example 2-1 is a conductive cloth in which a plurality of filament aggregates 72 are woven. The plurality of filament aggregates 72 include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled without being twisted, and a plating layer 33 formed on at least a part of the surface of the untwisted yarn bundle 74. The filament aggregate 72 is formed in a flat shape in the thickness direction of the first electrode sheet 25b.

[0185] The first electrode sheet 25b according to this Comparative Example 2-1 is formed by weaving a warp 41 in which a plurality of filaments 71 are bundled without being twisted and a weft 42 in which a plurality of filaments 71 are bundled without being twisted to form a base fabric, and forming a plating layer 33 on the surface of this base fabric. However, the manufacturing method of the first electrode sheet 25b is not limited to the above method. Since the first electrode sheet 25b has substantially the same configuration as the second electrode sheet 26b, in the following description, overlapping descriptions will be omitted except when specifically mentioned.

[0186] As shown in FIG. 25(a), the first electrode sheet 25b of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The first electrode sheet 25b includes a first opening 34a that opens between the plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25b. The opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25b to the area of the first electrode sheet 25b in this Comparative Example 2-1, is about 20%.

[0187] As shown in Fig. 25(b), the second electrode sheet 26b of this embodiment is substantially the same as the first electrode sheet 25b except that it has a second opening 34b that opens between a plurality of filament aggregates 72, and thus redundant descriptions are omitted. The opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26b to the area of the second electrode sheet 26 of this embodiment, is approximately 20%.

[0188] The number of filaments 71 included in the filament aggregate 72 constituting the first electrode sheet 25b is not particularly limited. The filament aggregate 72 according to this embodiment includes six filaments 71, but it may also have two to five filaments or seven or more filaments. The plurality of filaments 71 included in the filament aggregate 72 are arranged in a state of being arranged in a single layer.

[0189] As shown in Fig. 26, a plating layer 33 is formed on at least a part of the surface of the untwisted yarn bundle 74 constituting the filament aggregate 72. In this embodiment, the plating layer 33 is formed on the entire circumference of the surface of the untwisted yarn bundle 74.

[0190] When the plating layer 33 of the warp filament aggregate 72a contacts the plating layer 33 of the weft filament aggregate 72b, the warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected.

[0191] As shown in FIG. 25(a), the longitudinal direction S of the plurality of warp filament aggregates 72a and the longitudinal direction X of the first electrode sheet 25a are arranged to intersect. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b and the longitudinal direction X of the first electrode sheet 25a are arranged to intersect. Specifically, the longitudinal direction S of the plurality of warp filament aggregates 72a is substantially at an acute angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25a. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b is substantially at an acute angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25a. The fact that the angle is substantially 45° includes the case where it is 45° and also includes cases where it can be recognized as being substantially 45°.

[0192] However, the longitudinal direction S of the plurality of warp filament aggregates 72a may be at an acute angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25a. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b may be at an acute angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25a.

[0193] In this sample 2-3, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is 10 to 20 μm. The metal constituting the plating layer 33 has a three-layer structure, with the outermost layer being Ni, the intermediate layer being Cu, and the innermost layer (on the filament 71 side) being Ni. The untwisted yarn bundle 74 is composed of six filaments 71.

[0194] In the same manner as in Sample 2-1, a sample 2-3 of the sensor sheet 18 related to the first electrode sheet 25b and the second electrode sheet 26b of Comparative Example 2-1 is produced. Descriptions overlapping with those of Sample 2-1 are omitted.

[0195] 2.1.7.4. Tensile Test of the First Electrode Sheet Next, with reference to FIG. 27, the tensile test performed on the first electrode sheet will be described. ReferenceThe first electrode sheets according to Examples 2-1 to 2-2 and Comparative Example 2-1 were cut into strip shapes of 150 mm × 20 mm to prepare test pieces. The thickness of the first electrode sheet is about 0.1 mm. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp 41 or the warp filament aggregate 72a is set to 45°.

[0196] The test piece is gripped by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is performed on the test piece 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 piece. The tensile testing machine is AGS-X 1 kN manufactured by Shimadzu Corporation. The tensile test is performed in the range where the strain is 0 to 20%. Fig. 27 shows a graph showing the change of stress with respect to strain.

[0197] Reference In Example 2-1 and Reference Example 2-2, in the region where the strain is 0 to 20%, the stress increased monotonically and very gently. Reference In Example 2-1 and Reference Example 2-2 do not have a yield point showing a maximum value in the section where the strain is 0.5 to 10% in the stress-strain curve in the tensile test.

[0198] Reference Example 2-1 shows a stress of about 0.4 MPa when the strain is 5%, and shows a maximum stress value of about 0.8 MPa when the strain is 20%. Therefore, in the tensile test Reference the maximum value of the stress in Example 2-1 is 1 MPa or less. Similarly, Reference Example 2-2 shows a stress of about 0.3 MPa when the strain is 5%, and shows a maximum stress value of about 0.5 MPa when the strain is 20%. Therefore, Reference also for Example 2-2, the maximum value of the stress in the tensile test is 1 MPa or less. Reference In Example 2-1 and Reference Example 2-2, in the stress-strain curve, the maximum value of the stress when the strain is 0 to 5% is 3 MPa or less, and the maximum value of the stress when the strain is 0 to 20% is 15 MPa or less.

[0199] Comparative Example 2-1 has a yield point where the stress-strain curve in the tensile test shows a maximum value in the strain range of 0.5 to 10%. In the region where the strain is from 0 to about 1%, the stress increased linearly and monotonically. When the strain was about 1%, the stress showed a maximum value of about 17 MPa and then decreased rapidly to about 12 MPa. Thus, in Comparative Example 2-1, before and after the strain of about 1%, the stress changed from an increasing trend to a decreasing trend. Thereafter, in the region where the strain was from about 1 to about 13%, the stress monotonically decreased from about 12 to about 10 MPa. Thereafter, in the region where the strain was from about 13 to 20%, the stress monotonically increased from about 10 to about 12 MPa. Thus, in Comparative Example 2-1, in the stress-strain curve, the maximum value of the stress at a strain of 0 to 5% is greater than 3 MPa, and the maximum value of the stress at a strain of 0 to 20% is greater than 15 MPa.

[0200] 2.1.7.5. Tensile Test of Sensor Sheet Next, the tensile test performed on the sensor sheet will be described. Test pieces are prepared by cutting out the sensor sheets according to Samples 2-1 to 2-2 and Sample 2-3 into strips of 90 mm × 20 mm. The thickness of the sensor sheet is about 1 mm. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp yarns 41 or the aggregate of warp filaments 72a constituting the first electrode sheet and the second electrode sheet is set to 45°.

[0201] Connect a wire to one end in the longitudinal direction of the first electrode sheet and connect it to a DC power supply. Connect a wire to the other end in the longitudinal direction of the first electrode sheet and connect it to a voltage measuring instrument.

[0202] Grip the test piece with a pair of chucks. The distance between the pair of chucks is 50 mm. Perform a tensile test on the test piece at a tensile speed of 1 mm / sec, and calculate the stress by dividing the load by the cross-sectional area of the test piece. Also, during the tensile test, calculate the DC resistance value (an example of the electrical resistance value) of the sensor sheet from the voltage of the DC power supply and the voltage drop of the sensor sheet. For the measurement of the DC resistance value, use a digital multimeter 2000 series manufactured by KEITHLEY.

[0203] As shown in FIG. 28, Sample 2-1 shows a stress of about 0.1 MPa when the strain is 5%, a stress of about 0.4 MPa when the strain is 20%, and a stress of about 1.3 MPa, which is the maximum value of the stress, when the strain is 30%.

[0204] Sample 2-2 shows a stress of about 0.1 MPa when the strain is 5%, a stress of about 0.4 MPa when the strain is 20%, and a stress of about 0.9 MPa, which is the maximum value of the stress, when the strain is 30%.

[0205] In the stress-strain curves of Sample 2-1 and Sample 2-2, the stress at a strain of 0 - 5% is 0.5 MPa or less, and the maximum value of the stress at a strain of 0 - 20% is 3 MPa or less.

[0206] In the stress-strain curves of Sample 2-1 and Sample 2-2, the stress at a strain of 0 - 5% is 0.5 MPa or less, and the maximum value of the stress at a strain of 0 - 20% is 3 MPa or less.

[0207] Sample 2-3 has a yield point showing a maximum value in the strain range of 0.5 - 10% in the stress-strain curve of the tensile test. In the region where the strain is from 0 to about 3%, the stress increased linearly and monotonically. At a strain of about 3%, the stress showed a maximum value of about 0.7 MPa and then rapidly decreased to about 0.6 MPa. Thus, in Sample 2-3, before and after the strain of about 1%, the stress changed from an increasing trend to a decreasing trend. Thereafter, in the region where the strain is from about 1 to about 13%, the stress decreased slightly. Thereafter, in the region where the strain is from about 13 to 30%, the stress increased monotonically from about 0.6 to about 1.7 MPa. Thus, in the stress-strain curve of Sample 2-3, the maximum value of the stress at a strain of 0 - 5% is greater than 0.5 MPa, and the maximum value of the stress at a strain of 0 - 20% is greater than 0.7 MPa.

[0208] When tensile forces are applied to Sample 2-1 and Sample 2-2, the first opening 34a of the first electrode sheet extends in the tensile direction and contracts in the direction intersecting the tensile direction. Fig. 29 shows the state in which the first opening 34a deforms, taking Sample 2-1 as an example. Thus, since the tensile forces are absorbed, it is considered that the change in stress is small. Note that the same applies to Sample 2-2, so the description thereof is omitted.

[0209] In Sample 2-1 and Sample 2-2, even when tensile forces are applied to the sensor sheet, at the portions where the warp 41 and the weft 42 intersect, the relative positions of the warp 41 and the weft 42 do not change significantly. Therefore, it is considered that the electrical connection state between the warp 41 and the weft 42 is maintained. Thus, in Sample 2-1 and Sample 2-2, it is considered that the DC resistance value hardly changes even when tensile forces are applied to the sensor sheet.

[0210] On the other hand, Sample 2-3 has a yield point where the strain shows a maximum value in the range of 0.5 to 5%. In Sample 2-3, in the range from 0% strain to the yield point, it is considered to elastically deform because the plating layer 33 formed at the portion where the warp 41 and the weft 42 intersect is maintained. Thereafter, at the yield point, it is considered that the plating layer 33 formed at the portion where the warp 41 and the weft 42 intersect is broken.

[0211] Thereafter, in the section where the stress hardly changes (the section where the strain is about 5 to about 15%), similar to Sample 2-1 and Sample 2-2, it is considered that the tensile forces are absorbed by the deformation of the first opening 34a and the second opening 34b.

[0212] Thereafter, when the strain becomes larger than about 15%, since the first opening ratio and the second opening ratio of Sample 2-3 are 20%, the first opening 34a and the second opening 34b are completely blocked, and it is considered that the tensile forces acting on the first electrode sheet and the second electrode sheet cannot be absorbed. Thus, it is considered that the stress increases.

[0213] 2.1.7.6. DC Resistance Value of Sensor Sheet Figure 30 shows a graph indicating the change in DC resistance value with respect to strain. Figure 30 shows the DC resistance value in the region where the strain is 0 to 30%.

[0214] For Sample 2-1, in the region where the strain was 0 to 30%, the DC resistance value was approximately 0.1 Ω and hardly changed. For Sample 2-2, in the region where the strain was 0 to 30%, the DC resistance value was approximately 0.2 Ω and hardly changed.

[0215] For Sample 2-3, in the region where the strain was 0 to approximately 3%, the DC resistance value was approximately 0.2 Ω and hardly changed. When the strain exceeded approximately 3%, the DC resistance value of Sample 2-3 increased monotonically and was approximately 0.44 Ω at a strain of 30%. Thus, for Sample 2-3, the DC resistance value changed from approximately 0.2 Ω to approximately 0.44 Ω.

[0216] In the process of assembling the sensor sheet 18 to the steering wheel 10, the sensor sheet 18 is assembled to the steering wheel 10 while being pulled and stretched. The sensor sheet 18 is fixed to the steering wheel 10 in the pulled and stretched state. Therefore, the sensor sheet 18 in the state assembled to the steering wheel 10 is maintained in a state where tension is applied. As time passes, it is assumed that the residual stress in the materials (such as metal and resin) constituting the sensor sheet 18 is relaxed and the tension applied to the sensor sheet 18 changes. If the tension changes, the electrical resistance value of the sensor sheet 18 may change.

[0217] As described above, a tensile force acts on the sensor sheet 18 and this tensile force may change over time. Therefore, when a tensile force is applied to the sensor sheet 18, if the DC resistance value of the sensor sheet 18 changes, the sensitivity of the sensor sheet 18 changes, which is not preferable.

[0218] Samples 2-1 and 2-2 are preferable because the DC resistance value hardly changes in the region where the strain is 0 to 30%.

[0219] On the other hand, Sample 2-3 is not preferable because the DC resistance value changes from about 0.2 to about 0.44 Ω in the region where the strain is 0 to 30%.

[0220] 2.1.8. Effects of this embodiment Next, the effects of this embodiment will be described. The sensor sheet 18 according to this embodiment includes an insulating sheet 24, first electrode sheets 25 and 25a, a first joint portion 36, second electrode sheets 26 and 26a, and a second joint portion 37. The insulating sheet 24 has a first surface 27 and a second surface 28, and is formed of a foam. The first electrode sheets 25 and 25a are disposed on the first surface 27 side of the insulating sheet 24 and have a first opening 34a penetrating therethrough. The first electrode sheets 25 and 25a have conductivity. The first joint portion 36 joins the insulating sheet 24 and the first electrode sheet 25. The second electrode sheets 26 and 26a are disposed on the second surface 28 side of the insulating sheet 24 and have a second opening 34b penetrating therethrough. The second electrode sheets 26 and 26a have conductivity. The second joint portion 37 joins the insulating sheet 24 and the second electrode sheets 26 and 26a. The sensor sheet 18 is configured not to have a yield point indicating a maximum value in the section where the strain is 0.5 to 10% in the stress-strain curve in the tensile test. The aperture ratio, which is the ratio of the opening area of the first opening 34a to the area of the first electrode sheets 25 and 25a, is 40% or more. The aperture ratio, which is the ratio of the opening area of the second opening 34b to the area of the second electrode sheets 26 and 26a, is 40% or more.

[0221] The aperture ratio, which is the ratio of the aperture area of the first opening 34a to the area of the first electrode sheets 25, 25a, is 40% or more, and the aperture ratio, which is the ratio of the aperture area of the second opening 34b to the area of the second electrode sheets 26, 26a, is 40% or more. Therefore, the tensile force applied to the sensor sheet 18 can be absorbed by the deformation of the first opening 34a and the second opening 34b. As a result, the influence of the tensile force applied to the sensor sheet 18 can be reduced, and an increase in the electrical resistance value of the sensor sheet 18 can be suppressed. The aperture ratio is more preferably 50% or more, and even more preferably 60% or more, because it becomes easier to absorb the tensile force applied to the sensor sheet 18.

[0222] The sensor sheet 18 according to this embodiment is configured not to have a yield point that exhibits a maximum value in the range of 0.5 to 10% of strain in the stress-strain curve in the tensile test. As a result, in a region where the strain is relatively small, such as 0.5 to 10%, a large stress is not generated and a rapid change in stress is suppressed. As a result, the efficiency of the work of assembling the sensor sheet 18 to the steering wheel 10 can be improved. Further, since it does not have a yield point that exhibits a maximum value in the range of 0.5 to 5% of strain, when the sensor sheet 18 is slightly pulled, a large stress is not generated and the stress does not change, so the workability is further improved, which is more preferable.

[0223] In addition, the first electrode sheet 25a and the second electrode sheet 26a according to this embodiment are conductive fabrics in which a plurality of filament aggregates 72 are woven. The filament aggregate 72 includes a twisted wire 73 formed by twisting a plurality of filaments 71 and a plating layer 33 formed on at least a part of the surface of the twisted wire 73. The first electrode sheet 25a includes a first opening 34a that opens between a plurality of filament aggregates 72. The second electrode sheet 26a includes a second opening 34b that opens between a plurality of filament aggregates 72.

[0224] By forming the plating layer 33 on at least a part of the surface of the twisted wire 73 formed by twisting a plurality of filaments 71, a plurality of conductive paths are formed on the surface of the filament aggregate 72. Thus, even if a tensile force is applied to the sensor sheet 18 and some of the plating layers 33 are destroyed and some of the conductive paths are broken, the electrical connection can be maintained by the other conductive paths. Thereby, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0225] According to this embodiment, in the stress-strain curve in the tensile test, in the section where the strain is 0.5 to 10%, since the lattice composed of the warp 41 and the weft 42 is deformed into a rhombus shape, it is not only possible to deform without requiring a large load, but also the tensile strain on the warp 41 and the weft 42 themselves is suppressed at that time. Therefore, the strain applied to the plating layer 33 formed on the yarn is also small, and the destruction of the plating layer is suppressed. That is, by arranging the conductive cloth at an inclination of 45° with respect to the tensile direction, structural flexibility is exhibited. As a result, since the destruction of the plating layer 33 formed on the warp 41 or the weft 42 of the conductive cloth during extension is suppressed, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0226] The sensor sheet 18 according to this embodiment is configured such that the maximum value of the stress when the strain is 0 to 5% in the stress-strain curve is 0.5 MPa or less. Further, the sensor sheet 18 is configured such that the maximum value of the stress when the strain is 0 to 20% in the stress-strain curve is 3 MPa or less. Thereby, when a tensile force is applied to the sensor sheet 18, it is possible to suppress an excessively large stress from being applied to the first electrode sheets 25 and 25a. As a result, it is possible to suppress the structure of the first electrode sheets 25 and 25a from being destroyed, and thus it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0227] From the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, in the stress-strain curve, the maximum value of the stress of the sensor sheet 18 when the strain is 0 to 5% is preferably 0.5 MPa or less, more preferably 0.4 MPa or less, and even more preferably 0.3 MPa or less.

[0228] Similarly, from the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, in the stress-strain curve, the maximum value of the stress of the sensor sheet 18 when the strain is 0 to 20% is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1.5 MPa or less.

[0229] Further, the first electrode sheets 25 and 25a according to the present embodiment are configured such that in the stress-strain curve, the maximum value of the stress of the first electrode sheets 25 and 25a when the strain is 0 to 5% is 3 MPa or less. Further, the first electrode sheets 25 and 25a are configured such that in the stress-strain curve, the maximum value of the stress when the strain is 0 to 20% is 15 MPa or less.

[0230] From the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, in the stress-strain curve, the maximum value of the stress of the first electrode sheets 25 and 25a when the strain is 0 to 5% is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1 MPa or less.

[0231] Similarly, from the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, the maximum value of the stress when the strain is 0 to 20% is preferably 10 MPa or less, more preferably 7 MPa or less, and even more preferably 3 MPa or less.

[0232] By configuring the sensor sheet 18 or the first electrode sheets 25 and 25a as described above, when a tensile force is applied to the sensor sheet 18, it is possible to suppress an excessively large stress from being applied to the first electrode sheets 25 and 25a. Thereby, it is possible to suppress the structure of the first electrode sheets 25 and 25a from being destroyed, and thus it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0233] The plating layer 33 according to this embodiment is formed on at least a part of the surface of the twisted wire 73 and is not formed on at least a part of the inside of the twisted wire 73. As a result, inside the twisted wire 73, there are filaments 71 that are not fixed by the plating layer 33 and can move freely. As a result, even when a tensile force is applied to the sensor sheet 18, the stress can be absorbed by the freely movable filaments 71, so that an excessively large stress is prevented from being applied to the first electrode sheets 25, 25a and the second electrode sheets 26, 26a. As a result, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0234] (Embodiment 3-1) Next, Embodiment 3-1 will be described. Since Embodiment 3-1 has the same configuration as the configuration described in 1.1.1 to 1.1.5 of Embodiment 1-1, the descriptions in 1.1.1 to 1.1.5 are read as 3.1.1 to 3.1.5, and duplicate descriptions are omitted.

[0235] 3.1.6. Configuration of Electrode Sheets The first electrode sheet 25 and the second electrode sheet 26 are conductive cloths having conductivity. The first electrode sheet 25 and the second electrode sheet 26 have conductivity and flexibility. The first electrode sheet 25 and the second electrode sheet 26 have stretchability in the longitudinal direction X and the intersecting direction Y.

[0236] As shown in FIG. 31, the first electrode sheet 25 and the second electrode sheet 26 are conductive cloths in which a plurality of filament aggregates 72 are woven. The filament aggregate 72 includes a plurality of filaments 71 and a plating layer 33 formed on at least a part of the surface of the filament 71.

[0237] As shown in FIGS. 31(a) to 31(b), the first electrode sheet 25 and the second electrode sheet 26 are manufactured by forming a plating layer 33 on a base cloth in which a plurality of untwisted yarn bundles 74 are woven. Each untwisted yarn bundle 74 is formed by bundling a plurality of filaments 71 without twisting.

[0238] Examples of the resin constituting the filament 71 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 resin constituting the filament 71 is not limited to the above, and any resin can be appropriately selected. The second electrode sheet 26 has a similar configuration.

[0239] The plating layer 33 is formed on the surface of the base fabric in which a plurality of filament aggregates 72 are woven. The method for forming the plating layer 33 is not particularly limited. For example, electrolytic plating, electroless plating, electroless plating may be performed first and then electrolytic plating, or electrolytic plating may be performed first and then electroless plating. Any method can be appropriately selected.

[0240] As the metal constituting the plating layer 33 formed on the surface of the base fabric, any metal or alloy such as copper, nickel, tin, solder, etc. can be appropriately selected. The plating layer 33 formed on the surface of the base fabric may be composed of one metal species or a plurality of metal species. For example, only copper may be plated on the surface of the base fabric, only nickel may be plated on the surface of the base fabric, a copper plating layer made of copper may be formed on the surface of the base fabric, and a nickel plating layer made of nickel may be formed on the surface of this copper plating layer. The plating layer 33 formed on the surface of the base fabric may be formed by electrolytic plating or electroless plating. The second electrode sheet 26 has a similar configuration.

[0241] As shown in FIG. 31(a), the first electrode sheet 25 includes a first opening 34a that opens between a plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25. The first opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25 to the area of the first electrode sheet 25, is 1% or more and 40% or less.

[0242] As shown in FIG. 31(b), the second electrode sheet 26 includes a second opening 34b that opens between a plurality of filament aggregates 72. The second opening 34b penetrates the second electrode sheet 26. The second opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26 to the area of the second electrode sheet 26, is 1% or more and 40% or less.

[0243] 3.1.7. Examples, Comparative Examples, and Samples 3.1.7.1. Example 3-1 and Sample 3-1 (Example 3-1 and Sample 3-1) Referring to FIGS. 31 to 34, Example 3-1 will be described. As shown in FIG. 31(a), the first electrode sheet 25 according to Example 3-1 is a conductive cloth in which a plurality of filament aggregates 72 are woven. The plurality of filament aggregates 72 include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled without being twisted, and a plating layer 33 formed on at least a part of the surface of the untwisted yarn bundle 74. The filament aggregate 72 is formed in a flat shape in the thickness direction of the first electrode sheet 25b. However, since the first electrode sheet 25 and the second electrode sheet 26 have substantially the same configuration, duplicate descriptions will be omitted except where specifically mentioned.

[0244] The first electrode sheet 25 according to this Example 3-1 is formed by weaving a warp in which a plurality of filaments 71 are bundled without being twisted and a weft in which a plurality of filaments 71 are bundled without being twisted to form a base cloth, and forming a plating layer 33 on the surface of this base cloth. However, the manufacturing method of the first electrode sheet 25 is not limited to the above method.

[0245] As shown in Fig. 31(a), the first electrode sheet 25 of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The first electrode sheet 25 has a first opening 34a that opens between the plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25. In Example 3-1, the opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25 to the area of the first electrode sheet 25, is approximately 3%. Note that this opening ratio is the ratio of the total opening area of the plurality of first openings 34a formed in the target area of the first electrode sheet 25 to the area of the target area of the first electrode sheet 25. This opening ratio is calculated, for example, by specifying a 10 mm × 10 mm target area in the first electrode sheet 25, summing the areas of the first openings 34a within the target area, and dividing the total area by the area of the target area.

[0246] As shown in Fig. 31(b), the second electrode sheet 26 of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The second electrode sheet 26 of this embodiment has a second opening 34b that opens between the plurality of filament aggregates 72. The second opening 34b penetrates the second electrode sheet 26. In Example 3-1, the opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26 to the area of the second electrode sheet 26 of this embodiment, is approximately 3%.

[0247] The number of filaments 71 included in the filament aggregate 72 that constitutes the first electrode sheet 25 is not particularly limited. The filament aggregate 72 according to this embodiment includes 75 filaments 71, but it can be any number. Also, the same applies to the second electrode sheet 26 as to the first electrode sheet 25.

[0248] As shown in FIG. 32, a plating layer 33 is formed on at least a part of the surface of the untwisted yarn bundle 74 that constitutes the filament aggregate 72. When the plating layer 33 of the warp filament aggregate 72a comes into contact with the plating layer 33 of the weft filament aggregate 72b, the warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected.

[0249] As shown in FIG. 31(a), the longitudinal direction S of the plurality of warp filament aggregates 72a and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Specifically, the longitudinal direction S of the plurality of warp filament aggregates 72a is substantially at an acute angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b is substantially at an acute angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25a. The fact that the angle is substantially 45° includes the case where it is 45° and also includes cases where it can be recognized as being substantially 45°. Note that since the second electrode sheet 26 has the same configuration as the first electrode sheet 25, duplicate explanations are omitted.

[0250] When the longitudinal direction S of the warp filament aggregate 72a is parallel to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 0°), when the first electrode sheet 25 is stretched in the direction X in parallel, the warp filament aggregate 72a itself will be stretched, and a large load is required.

[0251] On the other hand, when the longitudinal direction S of the warp filament aggregate 72a is inclined at an angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 45°), when the first electrode sheet 25 is stretched in parallel with the direction X, the square or rectangular lattice (opening 34) composed of the warp filament aggregate 72a and the weft filament aggregate 72b is deformed into a rhombus shape, and the warp filament aggregate 72a or the weft filament aggregate 72b itself is not stretched, so a large load is not required. That is, when the acute angle is substantially 45°, structural flexibility is imparted. Furthermore, the higher the aperture ratio, the easier it is for the square or rectangular lattice to be deformed into a rhombus shape, and the structural flexibility is less likely to be impaired.

[0252] However, the longitudinal direction S of the plurality of warp filament aggregates 72a may be at an angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b may be at an angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25.

[0253] The number of filaments 71 constituting the warp filament aggregate 72a and the number of filaments 71 constituting the weft filament aggregate 72b may be the same or different. In the present Example 3-1, the number of filaments 71 constituting the warp filament aggregate 72a and the number of filaments 71 constituting the weft filament aggregate 72b are set to be substantially the same. Substantially the same includes the case where they are the same and also the case where they are not the same but can be recognized as substantially the same. The same applies to the weft filament aggregate 72b, so duplicate explanations are omitted. In the present Example 3-1, the number of filaments 71 is set to 75. However, the number of filaments 71 is not limited to the above number.

[0254] As shown in FIG. 32, a plating layer 33 is formed on at least a part of the plurality of filaments 71 that constitute the warp filament assembly 72a. For example, the plating layer 33 is formed on the surface of the filaments 71 exposed on the outer surface of the warp filament assembly 72a. The plating layer 33 is not formed on the surfaces of some of the filaments 71 located inside the warp filament assembly 72a. In the portions where the plating layer 33 is not formed, the surfaces of the filaments 71 are exposed. Since the same applies to the weft filament assembly 72b, redundant descriptions are omitted.

[0255] In the portion where the warp filament assembly 72a and the weft filament assembly 72b face each other and cross, the plating layer 33 is partially formed, and in the portion where the plating layer 33 is not formed, the surface of the filament 71 is exposed. In the region closer to the portion exposed to the outside among the portions where the warp filament assembly 72a and the weft filament assembly 72b face each other and cross, the plating layer 33 is formed, while in the portion closer to the inside, portions where the plating layer 33 is formed and portions where the plating layer 33 is not formed are mixed. Since the weft filament assembly 72b also has the same configuration as the warp filament assembly 72a, redundant descriptions are omitted.

[0256] As shown in Fig. 34, the cross-sectional area A1 of each warp filament aggregate 72a is larger than the opening area A2 of the first opening 34a in the state where no strain occurs in the first electrode sheet 25 shown in Fig. 33. The cross-sectional area A1 of the warp filament aggregate 72a refers to the cross-sectional area formed by the outer contour line of the warp filament aggregate 72a. The same applies to the weft filament aggregate 72b. Although not shown in detail, the cross-sectional area A1 of each weft filament aggregate 72b is larger than the opening area A2 of the first opening 34a in the state where no strain occurs in the first electrode sheet 25. Although not shown in detail, in the second electrode sheet 26, the cross-sectional area A1 of each warp filament aggregate 72a and the cross-sectional area A1 of each weft filament aggregate 72b are larger than the opening area A2 of the second opening 34b in the state where no strain occurs in the second electrode sheet 26.

[0257] As shown in Fig. 33, when viewed from the thickness direction of the first electrode sheet 25, the intersection area A3, which is the area of the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other, is larger than the opening area A2 of the first opening 34a shown in Fig. 33. Although not shown in detail, when viewed from the thickness direction of the second electrode sheet 26, the intersection area A3, which is the area of the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other, is larger than the opening area A2 of the second opening 34b.

[0258] In the present Embodiment 3-1, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is about 10 μm. The metal constituting the plating layer 33 is formed in a three-layer structure, with the outermost layer being Ni, the intermediate layer being Cu, and the innermost layer (on the filament 71 side) being Ni. The diameter of the warp filament aggregate 72a is 185 μm, and the diameter of the weft filament aggregate 72b is 185 μm. However, since the second electrode sheet 26 has substantially the same configuration as the first electrode sheet 25, redundant descriptions are omitted.

[0259] As shown in FIG. 4, the above-described first electrode sheet 25 is joined to the first surface 27 of the insulating sheet 24 via a first joining portion 36. Further, a second electrode sheet 26 having the same configuration as the first electrode sheet 25 is joined to the second surface 28 of the insulating sheet 24 via a second joining portion 37. The insulating sheet 24 is an ether-based polyurethane foam. The first joining portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first joining portion 36 is 50 μm. Since the first joining portion 36 and the second joining portion 37 are the same, duplicate explanations are omitted. In this way, the sensor sheet 18 according to Sample 3-1 is manufactured.

[0260] 3.1.7.2. Example 3-2 and Sample 3-2 (Example 3-2 and Sample 3-2) Subsequently, with reference to FIGS. 35(a) to 35(b), the configurations of the first electrode sheet 25a and the second electrode sheet 26a according to Example 3-2 will be described. In the first electrode sheet 25a according to the present Example 3-2, the number of filaments 71a constituting the warp filament aggregate 72aa is different from the number of filaments 71a constituting the weft filament aggregate 72ba. In the present Example 3-2, the number of filaments 71a constituting the warp filament aggregate 72aa is larger than the number of filaments 71a constituting the weft filament aggregate 72ba. However, the number of filaments 71a constituting the warp filament aggregate 72aa may be smaller than the number of filaments 71a constituting the weft filament aggregate 72ba.

[0261] In Example 3-2, the number of filaments 71a constituting the warp filament aggregate 72aa is set to about twice the number of filaments 71 constituting the weft filament aggregate 72ba. In Example 3-2, the number of filaments 71a constituting the warp filament aggregate 72aa is set to about 80, and the number of filaments 71 constituting the weft filament aggregate 72ba is set to about 40. However, the difference in the number of filaments 71a constituting the warp filament aggregate 72aa and the number of filaments 71a constituting the weft filament aggregate 72ba is not limited to the above.

[0262] The aperture ratio, which is the ratio of the aperture area of the first aperture 34a formed in the first electrode sheet 25a according to Example 3-2 to the area of the first electrode sheet 25a, is about 10%. Also, the aperture ratio, which is the ratio of the aperture area of the second aperture 34b formed in the second electrode sheet 26a to the area of the second electrode sheet 26a, is about 10%.

[0263] Since the second electrode sheet 26a has the same configuration as the first electrode sheet 25a, duplicate explanations are omitted.

[0264] In Example 3-2, the resin constituting the filament 71a is PET (polyethylene terephthalate), and the diameter of the filament 71a is about 10 μm. The metal constituting the plating layer 33 has a single-layer structure and is a Ni single layer. The diameter of the warp filament aggregate 72aa is about 180 μm, and the diameter of the weft filament aggregate 72ba is about 90 μm.

[0265] The configuration other than the above is the same as that of Example 3-1, so duplicate explanations are omitted.

[0266] Also, in Example 3-2, the insulating sheet 24 is an ether-based polyurethane foam. The first joint portion 36 is an acrylic-based adhesive. The thickness of the first joint portion 36 is about 50 μm. Since the first joint portion 36 and the second joint portion 37 are the same, redundant explanations are omitted. Except for the above, in the same manner as in Sample 3-1, a sample 3-2 of the sensor sheet 18 related to the first electrode sheet 25a and the second electrode sheet 26a of Example 3-2 is produced. Redundant explanations overlapping with those of Sample 3-1 are omitted.

[0267] 3.1.7.3. Comparative Example 3-1 and Sample 3-3 (Comparative Example 3-1 and Sample 3-3) Next, referring to FIGS. 36(a) to 36(b), Comparative Example 3-1 will be described. The warp filament aggregate 72ab and the weft filament aggregate 72bb according to Comparative Example 3-1 include six filaments 71b.

[0268] As shown in FIG. 36(a), the first electrode sheet 25b of this embodiment includes a plurality of warp filament aggregates 72ab and a plurality of weft filament aggregates 72bb. The first electrode sheet 25b has a first opening 34a that opens between the plurality of warp filament aggregates 72ab and the plurality of weft filament aggregates 72bb. The first opening 34a penetrates the first electrode sheet 25b. The opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25b to the area of the first electrode sheet 25b in this Comparative Example 3-1, is 20%.

[0269] As shown in FIG. 36(b), the second electrode sheet 26b of this embodiment is substantially the same as the first electrode sheet 25a except that it has a second opening 34b that opens between the plurality of warp filament aggregates 72ab and the plurality of weft filament aggregates 72bb, so redundant explanations are omitted. The opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26b to the area of the second electrode sheet 26 of this embodiment in this Comparative Example 3-1, is 20%.

[0270] In Comparative Example 3-1, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is 10 to 20 μm. The metal constituting the plating layer 33 has a three-layer structure, with the outermost layer being Ni, the intermediate layer being Cu, and the innermost layer (on the side of the filament 71b) being Ni. The diameter of the warp filament aggregate 72a is about 70 μm, and the diameter of the weft filament aggregate 72b is about 70 μm.

[0271] As shown in FIG. 37, the plating layer 33 is formed on at least a part of the surface of the untwisted yarn bundle 74b constituting the warp filament aggregate 72ab and the weft filament aggregate 72bb. In this embodiment, the plating layer 33 is formed on the entire circumference of the surface of the untwisted yarn bundle 74b.

[0272] When the plating layer 33 of the warp filament aggregate 72ab comes into contact with the plating layer 33 of the weft filament aggregate 72bb, the warp filament aggregate 72ab and the weft filament aggregate 72bb are electrically connected.

[0273] Since the configuration other than the above is the same as that of Example 3-1, duplicate explanations are omitted.

[0274] Also, in Comparative Example 3-1, the insulating sheet 24 is an ether-based polyurethane foam. The first joint portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first joint portion 36 is 50 μm. Since the first joint portion 36 and the second joint portion 37 are the same, duplicate explanations are omitted. In the same manner as in Sample 3-1, a sample 3-3 of the sensor sheet 18 related to the first electrode sheet 25b and the second electrode sheet 26b of Comparative Example 3-1 is produced. Duplicate explanations with Sample 3-1 are omitted.

[0275] 3.1.7.4. Tensile Test of the First Electrode Sheet Next, with reference to FIG. 38, the tensile test performed on the first electrode sheet will be described. The first electrode sheets according to Examples 3-1 to 3-2 and Comparative Example 3-1 were cut into strips of 150 mm × 20 mm to prepare test pieces. The thickness of the first electrode sheet is about 0.1 mm, although it is different in Examples 3-1 to 3-2 and Comparative Example 3-1. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a is set to 45°.

[0276] The test piece is gripped by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is performed on the test piece 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 piece. The tensile testing machine is AGS-X 1 kN manufactured by Shimadzu Corporation. The tensile test is performed in the range where the strain is 0 to 20%. FIG. 38 shows a graph showing the change of stress with respect to strain.

[0277] In Examples 3-1 and 3-2, in the region where the strain was 0 to 20%, the stress increased gently and monotonically. Examples 3-1 and 3-2 do not have a yield point showing a maximum value in the section where the strain is 0.5 to 10% in the stress-strain curve in the tensile test.

[0278] Example 3-1 showed a stress of about 1.4 MPa when the strain was 5% and a stress of about 7.5 MPa when the strain was 20%. Example 3-2 showed a stress of about 0.9 MPa when the strain was 5% and a stress of about 5.9 MPa when the strain was 20%. The first electrode sheets 25 and 25a according to Examples 3-1 and 3-2 have a maximum stress value of 3 MPa or less when the strain is 0 to 5% and a maximum stress value of 15 MPa or less when the strain is 0 to 20%.

[0279] Comparative Example 3-1 has a yield point where the stress-strain curve in the tensile test shows a maximum value in the strain range of 0.5 to 10%. In the region where the strain is from 0 to about 1%, the stress increased linearly and monotonically. At a strain of about 1%, the stress showed a maximum value of about 17 MPa and then decreased rapidly to about 12 MPa. Thus, in Comparative Example 3-1, before and after the strain of about 1%, the stress changed from an increasing trend to a decreasing trend. Thereafter, in the region where the strain is from about 1 to about 13%, the stress decreased monotonically from about 12 to about 10 MPa. Thereafter, in the region where the strain is from about 13 to 20%, the stress increased monotonically from about 10 to about 12 MPa. Thus, Comparative Example 3-1 has a maximum stress value in the stress-strain curve greater than 3 MPa when the strain is from 0 to 5% and greater than 15 MPa when the strain is from 0 to 20%.

[0280] 3.1.7.5. Tensile Test of Sensor Sheet Next, the tensile test performed on the sensor sheet will be described. Test pieces are prepared by cutting out the sensor sheets according to Samples 3-1 to 3-2 and Sample 3-3 into strips of 90 mm × 20 mm. The thickness of the sensor sheet is about 1 mm although it is different for Samples 3-1 to 3-2 and Sample 3-3. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a constituting the first electrode sheet and the second electrode sheet is set to 45°.

[0281] Connect an electric wire to one end of the longitudinal direction of the first electrode sheet and connect it to a DC power supply. Connect an electric wire to the other end of the longitudinal direction of the first electrode sheet and connect it to a voltage measuring instrument.

[0282] Grip the test piece with a pair of chucks. The distance between the pair of chucks is 50 mm. Perform a tensile test on the test piece at a tensile speed of 1 mm / sec, and calculate the stress by dividing the load by the cross-sectional area of the test piece. Also, during the tensile test, calculate the DC resistance value (an example of the electrical resistance value) of the sensor sheet from the voltage of the DC power supply and the voltage drop of the sensor sheet.

[0283] Fig. 39 shows the stress-strain curve in the tensile test conducted on the sensor sheet. Fig. 39 shows the graph in the region where the strain is 0 to 20%. The stress of Samples 3-1 to 3-2 increased monotonically in the region where the strain is 0 to 20%. Samples 3-1 and 3-2 do not have a yield point showing a maximum value in the interval where the strain is 0.5 to 10% in the stress-strain curve of the tensile test.

[0284] Sample 3-1 shows a stress of about 0.5 MPa when the strain is 5%, and shows a maximum stress of about 2.6 MPa when the strain is 20%. Sample 3-2 shows a stress of about 0.3 MPa when the strain is 5%, and shows a maximum stress of about 1.5 MPa when the strain is 20%. Samples 3-1 and 3-2 have a maximum stress value of 0.5 MPa or less when the strain is 0 to 5% and a maximum stress value of 3 MPa or less when the strain is 0 to 20% in the stress-strain curve. Samples 3-1 and 3-2 have a stress of 0.5 MPa or less when the strain is 0 to 5% and a maximum stress value of 3 MPa or less when the strain is 0 to 20% in the stress-strain curve.

[0285] Sample 3-3 has a yield point showing a maximum value in the interval where the strain is 0.5 to 10% in the stress-strain curve of the tensile test. In the region where the strain is from 0 to about 3%, the stress increased linearly and monotonically. When the strain is about 3%, the stress shows a maximum value of about 0.7 MPa and rapidly decreases to about 0.6 MPa. Thus, in Sample 3-3, before and after the strain is about 3%, the stress changed from an increasing trend to a decreasing trend. Thereafter, in the region where the strain is about 1 to about 13%, the stress slightly decreased. Thereafter, in the region where the strain is about 13 to 20%, the stress increased monotonically from about 0.6 to about 0.8 MPa. Thus, Sample 3-3 has a maximum stress value of more than 0.5 MPa when the strain is 0 to 5% and a maximum stress value of more than 0.7 MPa when the strain is 0 to 20% in the stress-strain curve.

[0286] When tensile forces are applied to Sample 3-1 and Sample 3-2, the first opening 34a of the first electrode sheet extends in the tensile direction and contracts in the direction intersecting the tensile direction. Fig. 40 shows the state in which the first opening 34a is deformed, taking Sample 3-2 as an example. As shown in Fig. 40(a), the first opening 34a is open in the state with an elongation rate of 0%. However, as the elongation rate increases to 10% (see Fig. 40(b)), 20% (see Fig. 40(c)), and 30% (see Fig. 40(d)), the gaps between the fibers of the conductive cloth decrease, and in the state with an elongation rate of 30%, the first opening 34a almost disappears. Due to such a change in the fiber shape, it can be easily stretched, so it is considered that the stress generated during stretching is small. That is, it is considered that the presence of the first opening 34a contributes to the expression of the structural stretchability and flexibility of this fiber. The above configuration is the same for the second electrode sheet, so the description is omitted. Note that the same applies to Sample 3-1, so the description is omitted.

[0287] In Samples 3-1 and 3-2, when a tensile force is applied to the sensor sheet, it is considered that the tensile force is absorbed as the first opening 34a gradually deforms. As a result, at the intersection of the warp filament assembly 72a and the weft filament assembly 72b, since the relative positions of the warp filament assembly 72a and the weft filament assembly 72b do not change significantly, it is considered that the electrical connection state between the warp filament assembly 72a and the weft filament assembly 72b is maintained. Thus, in Samples 3-1 and 3-2, it is considered that the DC resistance value hardly changes even when a tensile force is applied to the sensor sheet.

[0288] Also, Samples 3-1 and 3-2 do not have a yield point showing a maximum value in the strain range of 0.5 to 5%. This is considered to be due to the fact that in Samples 3-1 and 3-2, in the strain range of 0.5 to 5%, there is no significant change in the structure of the plating layer 33 formed on the first electrode sheet and the second electrode sheet. Thereby, the change in the electrical resistance value of the sensor sheet 18 is suppressed.

[0289] On the other hand, Sample 3-3 has a yield point where the strain shows a maximum value in the range of 0.5 to 5%. In Sample 3-3, in the range from 0% strain to the yield point, it is considered that elastic deformation occurs because the plating layer 33 formed at the intersection of the warp filament aggregate 72a and the weft filament aggregate 72b is maintained. Thereafter, at the yield point, it is considered that the plating layer 33 formed at the intersection of the warp filament aggregate 72a and the weft filament aggregate 72b is broken.

[0290] Thereafter, in the section where the stress does not change much (the section where the strain is about 5 to about 15%), it is considered that the tensile force is absorbed by the deformation of the first opening 34a and the second opening 34b, similar to Sample 3-1 and Sample 3-2.

[0291] Thereafter, when the strain becomes larger than about 15%, since the first opening ratio and the second opening ratio of Sample 3-3 are 20%, the first opening 34a and the second opening 34b are completely blocked, and it is considered that the tensile force acting on the first electrode sheet and the second electrode sheet cannot be absorbed. As a result, it is considered that the stress increases.

[0292] 3.1.7.6. Change rate of DC resistance value of sensor sheet Next, the change rate of the DC resistance value was measured for the sensor sheet. The sensor sheet was cut out into a strip shape of 90 mm × 20 mm to prepare a test piece. The angle formed by the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a was set to 45°.

[0293] The test piece is gripped by a pair of chucks. The distance between the pair of chucks is 50 mm. A tensile test is carried out on the test piece at a tensile speed of 1 mm / sec. Wires are connected to both ends of the first electrode sheet, and the DC resistance value between the two wires is measured. For the DC resistance value at this time, the DC resistance value change rate is calculated based on the following formula (1). The measurement of the DC resistance value uses a digital multimeter 2000 series manufactured by KEITHLEY. The above test is carried out for samples 3-1 to 3-2 and sample 3-3.

[0294]

Number

[0295] Figure 41 is a graph showing the change of the DC resistance value change rate with respect to strain. The DC resistance value change rate of sample 3-1 increased in the range of strain from 0 to about 2%, and in the state where the strain was about 2%, the DC resistivity change rate was about 5%. Thereafter, it decreased in the range of about 2 to about 5%, and the DC resistivity change rate became about 0%. Thereafter, when the strain was about 25% or more, the DC resistance value change rate increased gently, and the DC resistance value change rate was about 7% when the strain was 30%. Thus, the DC resistance value change rate of sample 3-1 was 10% or less in the range of strain from 0 to 30%.

[0296] The DC resistance value change rate of sample 3-2 increased in the range of strain from 0 to about 3%, and in the state where the strain was about 3%, the DC resistivity change rate was about 10%. Thereafter, it decreased in the range of about 3 to about 5%, and the DC resistivity change rate became about 0%. Thereafter, the DC resistance value change rate was also about 0% when the strain was 30%. Thus, the DC resistance value change rate of sample 3-2 was 10% or less in the range of strain from 0 to 30%.

[0297] The change rate of the DC resistance value of Sample 3-3 was approximately 2% in the range where the strain was 0 to approximately 3%. Subsequently, in the range where the strain was approximately 3 to 30%, the change rate of the DC resistance value increased monotonically, and at a strain of 30%, it became approximately 130%. Thus, the change rate of the DC resistance value of Sample 3-3 was greater than 10% in the range where the strain was 0 to 30%, and the resistance change during extension was extremely large compared to Sample 3-1 and Sample 3-2.

[0298] 3.1.7.7. Change Rate of DC Resistance Value of Sensor Sheet at 10% Extension Next, the change rate of the DC resistance value at 10% extension was measured for the sensor sheet. The sensor sheet was cut into a strip shape of 90 mm × 20 mm to prepare a test piece. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a was set to 45°.

[0299] The test piece was gripped by a pair of chucks. The distance between the pair of chucks was 50 mm. A tensile test was performed on the test piece at a tensile speed of 1 mm / sec. Wires were connected to both ends of the first electrode sheet, and the DC resistance value between the two wires was measured. Based on the following formula (1), the change rate of the DC resistance value was calculated for the DC resistance value at this time. For the measurement of the DC resistance value, a digital multimeter 2000 series manufactured by KEITHLEY was used. The above test was performed on Samples 3-1 to 3-2 and Sample 3-3.

[0300] When measuring the change rate of the DC resistance value of the above-mentioned sensor sheet, after extending the sensor sheet by 10% with respect to the reference length (50 mm) in the state before applying a tensile force to the sensor sheet, it was returned to the reference length, and the test of extending it by 10% again was repeated a predetermined number of times. The number of repetitions in this test was 1 time, 5 times, and 10 times. Based on the above formula (1), the change rate of the DC resistance value was calculated for the DC resistance value at this time. The above test was performed on Samples 3-1 to 3-2 and Sample 3-3.

[0301] Figure 42 shows a graph showing the relationship between the number of repetitions of the elongation test and the change rate of the DC resistance value. For Sample 3-1, the change rate of the DC resistance value at the first measurement was approximately 0%. Subsequently, as the number of repetitions increased, the change rate of the DC resistance value increased, reaching approximately 36% at 1 repetition, approximately 48% at 5 repetitions, and approximately 57% at 10 repetitions. At 10 repetitions, the change rate of the DC resistivity of Sample 3-1 was 60% or less.

[0302] For Sample 3-2, the change rate of the DC resistivity at the first measurement was approximately 14%, which was larger than that of Sample 3-1. However, as the number of repetitions increased, the change rate of the DC resistance value did not increase significantly, being approximately 9% at 1 repetition and approximately 15% at 5 repetitions. It was approximately 30% at 10 repetitions. At 10 repetitions, the change rate of the DC resistance value of Sample 3-2 was 50% or less.

[0303] For Sample 3-3, the change rate of the DC resistance value at the first measurement was equivalent to that of Sample 3-1, approximately 0%. However, as the number of repetitions increased, the change rate of the DC resistance value increased more than that of Sample 3-1 and Sample 3-2, reaching approximately 61% at 1 repetition, approximately 89% at 5 repetitions, and approximately 115% at 10 repetitions.

[0304] As described above, it was found that the sensor sheets related to Samples 3-1 and 2 had a smaller change in the DC resistance value compared to Sample 3-3 even when the 10% elongation test was repeated.

[0305] 3.1.7.8. Change Rate of DC Resistance Value of Sensor Sheet at 20% Elongation Subsequently, for Samples 3-1 to 3-2 and Sample 3-3, the change rate of the DC resistance value when the sensor sheet was elongated by 20% was measured.

[0306] Figure 43 shows a graph showing the relationship between the number of repetitions of the elongation test and the change rate of the DC resistance value. For Sample 3-1, the change rate of the DC resistance value at the first measurement was approximately 0%. After that, at 1 repetition, it was approximately 35%, and at 5 repetitions, it was approximately 91%. As the number of repetitions increased, the change rate of the DC resistance value increased. At 10 repetitions, the change rate of the DC resistance value was approximately 137%.

[0307] For Sample 3-2, the change rate of the DC resistivity at the first measurement was approximately 10%, which was larger than that of Sample 3-1. However, at 1 repetition, it was approximately 27%, and at 5 repetitions, it was approximately 32%. As the number of repetitions increased, the change rate of the DC resistance value did not increase much. At 10 repetitions, the change rate of the DC resistance value of Sample 3-2 was approximately 55%.

[0308] For Sample 3-3, the change rate of the DC resistance value at the first measurement was approximately 0%, which was the same as that of Sample 3-1. However, it showed approximately 114% at 1 repetition and exceeded 200% at 5 repetitions.

[0309] As described above, it was found that the sensor sheets related to Samples 3-1 and 2 had a smaller change in the DC resistance value compared to Sample 3-3 even when the 20% elongation test was repeated.

[0310] 3.1.8. Operational Effects of this Embodiment Next, the effects of the present embodiment will be described. The sensor sheet 18 according to this embodiment includes an insulating sheet 24, first electrode sheets 25 and 25a, a first joint portion 36, a second electrode sheet 26, and a second joint portion 37. The insulating sheet 24 has a first surface 27 and a second surface 28 and is formed of a foam. The first electrode sheets 25 and 25a are conductive and are disposed on the first surface 27 side of the insulating sheet 24 and have a first opening 34a that penetrates therethrough. The first joint portion 36 joins the insulating sheet 24 and the first electrode sheets 25 and 25a. The second electrode sheet 26 is conductive and is disposed on the second surface 28 side of the insulating sheet 24 and has a second opening 34b that penetrates therethrough. The second joint portion 37 joins the insulating sheet 24 and the second electrode sheet 26. The first electrode sheets 25 and 25a and the second electrode sheet 26 are conductive cloths in which a plurality of filament aggregates 72 are woven. The filament aggregate 72 includes a plurality of filaments 71 and a plating layer 33 formed on at least a part of the surface of the filament 71. The first electrode sheets 25 and 25a include a first opening 34a that opens between the plurality of filament aggregates 72, and the second electrode sheet 26 includes a second opening 34b that opens between the plurality of filament aggregates 72. The sensor sheet 18 is configured not to have a yield point that exhibits a maximum value in the range of strain from 0.5% to 10% in the stress-strain curve in the tensile test. The opening ratio, which is the ratio of the opening area of the first opening 34a to the area of the first electrode sheets 25 and 25a, is 1% or more and 40% or less. The opening ratio, which is the ratio of the opening area of the second opening 34b to the area of the second electrode sheets 26 and 26a, is 1% or more and 40% The following or less.

[0311] When a tensile force is applied to the sensor sheet 18, the first opening 34a of the first electrode sheets 25 and 25a deforms so that the opening area of the first opening 34a decreases. Also, a new conductive path is formed between the plurality of filament aggregates 72 that were separated by the first opening 34a. Thereby, even when a tensile force is applied to the sensor sheet 18, it is possible to suppress a change in the electrical resistance value. The same applies to the second opening 34b of the second electrode sheets 26 and 26a.

[0312] The aperture ratio of the first opening 34a is preferably 1% or more and 40% or less. When the aperture ratio is 40% or less, when the opening area of the first opening 34a is deformed in a direction of decreasing, it becomes easier for the plurality of filament aggregates 72 to come into contact with each other. Thus, since it becomes easier for the plurality of filament aggregates 72 to come into contact with each other, the aperture ratio of the first opening 34a is preferably 1% or more and 40% or less, more preferably 1% or more and 30% or less, and still more preferably 1% or more and 20% or less. However, the same applies to the second opening 34b.

[0313] The sensor sheet 18 according to this embodiment is configured not to have a yield point showing a maximum value in the range of strain of 0.5 to 10% in the stress-strain curve in the tensile test. Thereby, in a region where the strain is relatively small, such as 0.5 to 10%, generation of a large stress is suppressed and a rapid change in stress is suppressed. As a result, the efficiency of the work of assembling the sensor sheet 18 to the steering wheel 10 can be improved. Further, since it does not have a yield point showing a maximum value in the range of strain of 0.5 to 5%, when the sensor sheet 18 is slightly pulled, a large stress is not generated and the stress does not change, so the workability is further improved, which is more preferable.

[0314] When a tensile force is applied to the sensor sheet 18, the first opening 34a of the first electrode sheet 25 is deformed so that the opening area of the first opening 34a decreases. That is, without the tensile strain concentrating on the filament 71 itself, the spatial arrangement of the entire filament 71 changes, so that it is stretchable. That is, due to the decrease in the opening area accompanying the change in the spatial arrangement of the entire filament 71, structural stretching flexibility is exhibited, so the stretching strain applied to the filament 71 itself is small, and damage to the plating layer 33 formed on the filament 71 can be suppressed. Therefore, even when a tensile force is applied to the sensor sheet 18, a change in the electrical resistance value can be suppressed.

[0315] Further, since the sensor sheet 18 according to the present embodiment is configured not to have a yield point showing a maximum value in the strain range of 0.5 to 10% in the stress-strain curve in the tensile test, it is possible to suppress the plating layer 33 from breaking in the strain range of 0.5 to 10%. Thereby, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0316] The sensor sheet 18 according to the present embodiment is configured such that the maximum value of the stress at a strain of 0 to 5% in the stress-strain curve is 0.5 MPa or less. Further, the sensor sheet 18 is configured such that the maximum value of the stress at a strain of 0 to 20% in the stress-strain curve is 3 MPa or less. Thereby, when a tensile force is applied to the sensor sheet 18, it is possible to suppress an excessively large stress from being applied to the first electrode sheets 25, 25a. As a result, it is possible to suppress the structure of the first electrode sheets 25, 25a from being destroyed, and thus it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0317] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or from the viewpoint of reducing the stress applied to the second electrode sheets 26, 26a, in the stress-strain curve, the maximum value of the stress of the sensor sheet 18 at a strain of 0 to 5% is preferably 0.5 MPa or less, more preferably 0.4 MPa or less, and even more preferably 0.3 MPa or less.

[0318] Similarly, from the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or from the viewpoint of reducing the stress applied to the second electrode sheets 26, 26a, in the stress-strain curve, the maximum value of the stress of the sensor sheet 18 at a strain of 0 to 20% is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1.5 MPa or less.

[0319] Further, the first electrode sheets 25 and 25a according to this embodiment are configured such that the maximum value of the stress in the stress-strain curve is 3 MPa or less when the strain is 0 to 5%. Further, the first electrode sheets 25 and 25a are configured such that the maximum value of the stress in the stress-strain curve is 15 MPa or less when the strain is 0 to 20%. The same applies to the second electrode sheets 26 and 26a.

[0320] From the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, or from the viewpoint of reducing the stress applied to the second electrode sheets 26 and 26a, in the stress-strain curve, the maximum value of the stress of the first electrode sheets 25 and 25a, or the second electrode sheets 26 and 26a when the strain is 0 to 5% is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1 MPa or less.

[0321] Similarly, from the viewpoint of reducing the stress applied to the first electrode sheets 25 and 25a, or from the viewpoint of reducing the stress applied to the second electrode sheets 26 and 26a, the maximum value of the stress of the first electrode sheets 25 and 25a, or the second electrode sheets 26 and 26a when the strain is 0 to 20% is preferably 15 MPa or less, more preferably 10 MPa or less, and even more preferably 7 MPa or less.

[0322] The stress-strain curve of the sensor sheet 18 according to this embodiment is a stress-strain curve obtained by gripping a test piece of 20 mm × 90 mm and performing a tensile test at a tensile speed of 1 mm / s.

[0323] The sensor sheet 18 according to this embodiment is configured such that the direct current resistor change rate defined by Equation (1) is 50% or less when the strain in the tensile test is 20%.

[0324]

Equation

[0325] According to this embodiment, even when the sensor sheet 18 is stretched, it is possible to suppress a change in the DC resistance value. Thereby, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18. The DC resistance value change rate is preferably 50% or less, more preferably 30% or less, and even more preferably 11% or less.

[0326] The sensor sheet 18 according to this embodiment is configured such that the DC resistance value change rate defined by Equation (1) is 150% or less after repeating the test of returning the strain to 0% after applying a strain of 20% ten times.

[0327]

Equation

[0328] According to this embodiment, even when the operation of returning the sensor sheet 18 to its original dimensions is repeated after stretching the sensor sheet 18, it is possible to suppress a change in the DC resistance value. Thereby, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18. The DC resistance value change rate is preferably 150% or less, more preferably 140% or less, and even more preferably 100% or less.

[0329] The cross-sectional area of each of the plurality of filament aggregates 72 according to this embodiment is larger than the opening area of the first opening 34a in a state where no strain is generated in the first electrode sheets 25 and 25a. As a result, the ratio of the filament aggregate 72 in the unit area increases, so that a large number of conductive paths are formed in the first electrode sheets 25 and 25a. As a result, even when a tensile force is applied to the sensor sheet 18 and some of the plurality of conductive paths are damaged, it is possible to leave conductive paths that can be electrically conductive. Thereby, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18. Further, the cross-sectional area of each of the plurality of filament aggregates 72 is larger than the opening area of the second opening 34b in a state where no strain is generated in the second electrode sheets 26 and 26a. The operational effects are the same as those of the first electrode sheets 25 and 25a, so the description thereof is omitted.

[0330] In addition, the plurality of filament aggregates 72 according to this embodiment include a warp filament aggregate 72a and a weft filament aggregate 72b, and the area of the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other is larger than the opening area of the first opening 34a in a state where no strain is generated in the first electrode sheets 25, 25a. Note that, also for the second electrode sheets 26, 26a, the area of the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other is larger than the opening area of the second opening 34b in a state where no strain is generated in the second electrode sheets 26, 26a.

[0331] At the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other, the warp filament aggregate 72a and the weft filament aggregate 72b are electrically conductive. Therefore, at the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect each other, in addition to the plating layer 33 being formed on the portion exposed to the outside, the more the area where the plating layer 33 is formed in the inner portion (inside the intersection), the easier it is for the warp filament aggregate 72a and the weft filament aggregate 72b to be electrically conductive. Therefore, according to this embodiment, even when a tensile force is applied to the sensor sheet 18, the electrical conduction between the warp filament aggregate 72a and the weft filament aggregate 72b can be maintained. As a result, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0332] The sensor sheet 18 according to this embodiment further includes conductive second electrode sheets 26, 26a on the second surface 28 of the insulating sheet 24. By providing the second electrode sheets 26, 26a, the sensor sheet 18 can be electromagnetically shielded, so that the sensitivity of the sensor sheet 18 can be improved.

[0333] The plurality of filament aggregates 72 according to this embodiment includes a warp filament aggregate 72a and a weft filament aggregate 72b. The warp filament aggregate 72a and the weft filament aggregate 72b include an untwisted yarn bundle 74 in which a plurality of filaments 71 are gathered without being twisted, and a plating layer 33 formed on at least a part of the surface of the untwisted yarn bundle 74.

[0334] Since the filament aggregate 72 is the untwisted yarn bundle 74, the plurality of filaments 71 constituting the filament aggregate 72 are configured to be relatively freely movable. Therefore, even when a tensile force is applied to the sensor sheet 18, the plurality of filaments 71 constituting the untwisted yarn bundle 74 can move to absorb stress. As a result, excessive stress is prevented from being applied to the sensor sheet 18, so that a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0335] In the filament aggregate 72 according to this embodiment, portions where the plating layers 33 formed on the surfaces of adjacent filaments 71 are electrically connected to each other by contacting each other are also present on the outer surfaces of the plurality of filaments 71 located inside the untwisted yarn bundle 74 formed in a bundle shape. Therefore, when a tensile force is applied to the sensor sheet 18, even if the plating layer 33 formed on the outer surface of the filament 71 located on the surface of the untwisted yarn bundle 74 is broken, there is still the plating layer 33 formed on the outer surfaces of the plurality of filaments 71 located inside the untwisted yarn bundle 74. As a result, the plating layers 33 formed on the outer surfaces of the plurality of filaments 71 located inside the untwisted yarn bundle 74 contact each other, so that a change in the electrical resistance value can be suppressed even when a tensile force is applied to the sensor sheet 18.

[0336] (Embodiment 3-2) Next, Embodiment 3-2 will be described with reference to FIGS. 44 to 47. Among the reference numerals used after Embodiment 3-2, those identical to the reference numerals used in the previous embodiments represent the same components and the like as those in the previous embodiments unless otherwise specified.

[0337] 3.2.1. Configuration of the first electrode sheet 25c As shown in FIG. 44, the first electrode sheet 25c according to Embodiment 3-2 includes a warp filament aggregate 72a and a weft filament aggregate 72b. As described above, the warp filament aggregate 72a and the weft filament aggregate 72b each include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled without being twisted, and a plating layer 33 formed on the surface of the untwisted yarn bundle 74. Although not shown in detail, the sensor sheet 18 according to this embodiment includes a second electrode sheet on the second surface side of the insulating sheet 24. Since the configuration of the second electrode sheet is substantially the same as that of the first electrode sheet 25c, redundant description is omitted.

[0338] As the metal constituting the plating layer 33, any metal or alloy such as copper, nickel, tin, solder, etc. can be appropriately selected. Since the metal constituting the plating layer 33 is the same as that in Embodiment 3-1, redundant description is omitted.

[0339] In this embodiment, the metal species that constitute the plating layer 33 of the plurality of warp filament aggregates 72a and the metal species that constitute the plating layer 33 of the plurality of weft filament aggregates 72b are the same. However, the metal species that constitute the plating layer 33 of the plurality of warp filament aggregates 72a and the metal species that constitute the plating layer 33 of the plurality of weft filament aggregates 72b may be different. Also, the metal species that constitute the plating layer 33 of the plurality of warp filament aggregates 72a may be different in the direction in which the plurality of warp filament aggregates 72a are arranged. Further, the metal species that constitute the plating layer 33 of the plurality of weft filament aggregates 72b may be different in the direction in which the plurality of weft filament aggregates 72b are arranged. Additionally, at least two of the plurality of warp filament aggregates 72a may have different metal species that constitute the plating layer 33 formed on the plurality of filaments 71 that make up each warp filament aggregate 72a. Moreover, at least two of the plurality of weft filament aggregates 72b may have different metal species that constitute the plating layer 33 formed on the plurality of filaments 71 that make up each weft filament aggregate 72b.

[0340] By varying the metal species, the properties (electrical properties, chemical properties, mechanical properties, etc.) of the plating layer 33 of the plurality of warp filament aggregates 72a and the properties (electrical properties, chemical properties, mechanical properties, etc.) of the plurality of weft filament aggregates 72b can be made different. Examples of electrical properties include the electrical resistance value. Examples of chemical properties include the ionization tendency, affinity, etc. Examples of mechanical properties include the friction coefficient, strength, elongation rate, etc. The aperture ratio, which is the ratio of the aperture area of the first opening 34a formed in the first electrode sheet 25c of this embodiment to the area of the first electrode sheet 25c, is 30% or more. However, the value of the aperture ratio is not particularly limited and may be less than 30%.

[0341] As shown in FIG. 44, each warp filament aggregate 72a includes a plurality of filaments 71. The number of filaments 71 that make up one warp filament aggregate 72a is not particularly limited.

[0342] As shown in FIG. 44, each weft filament assembly 72b includes a plurality of filaments 71.

[0343] As shown in Fig. 47, the longitudinal direction S of the multiple warp filament assemblies 72a and the longitudinal direction X of the first electrode sheet 25c intersect with each other. Furthermore, the longitudinal direction T of the multiple weft filament assemblies 72b and the longitudinal direction X of the first electrode sheet 25c intersect with each other. Specifically, the longitudinal direction S of the multiple warp filament assemblies 72a forms an acute angle of substantially 45° with the longitudinal direction X of the first electrode sheet 25c. Furthermore, the longitudinal direction T of the multiple weft filament assemblies 72b forms an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25c. The same applies to the second electrode sheet.

[0344] As shown in FIG. 45 , a plating layer 33 is formed on at least a portion of the surface of each filament 71 constituting the warp filament aggregate 72a. The plating layer 33 may be formed on the entire surface of each filament 71 constituting the warp filament aggregate 72a, or the plating layer 33 may be formed on only a portion of the surface of each filament 71 constituting the warp filament aggregate 72a. In this embodiment, the plating layer 33 is formed on the surface of each filament 71 except for warp filament contact points 71aa where adjacent filaments 71 contact each other. In this embodiment, the plating layer 33 is also formed on the surface of the filaments 71 located in the inner region of one warp filament aggregate 72a. Adjacent filaments 71 are electrically connected by the plating layer 33 in the region exposed on the surface of the first electrode sheet 25c.

[0345] As shown in Fig. 46, a plating layer 33 is formed on at least a part of the surface of each filament 71 that constitutes the weft filament aggregate 72b. The plating layer 33 may be formed on the entire surface of each filament 71 that constitutes the weft filament aggregate 72b, or the plating layer 33 may be formed on a part of the surface of each filament 71 that constitutes the weft filament aggregate 72b. In this embodiment, the plating layer 33 is formed on the surface of each filament 71 except at the weft filament contact points 71ab where adjacent filaments 71 contact each other. In this embodiment, the plating layer 33 is also formed on the surface of the filaments 71 located in the inner region of one weft filament aggregate 72b. Adjacent filaments 71 are electrically connected by the plating layer 33 in the region exposed on the surface of the first electrode sheet 25c.

[0346] Also, in this embodiment, the plating layer 33 is formed on the surface of each filament 71 except at the weft filament contact points 71ab where the filaments 71 that constitute the warp filament aggregate 72a and the filaments 71 that constitute the weft filament aggregate 72b contact each other. The warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected by the plating layer 33.

[0347] 3.2.2. Relationship between the first electrode sheet 25c and the narrow portion 35 3.2.2.1. As shown in Fig. 47, in the first electrode sheet 25c, the region sandwiched between two recesses 30 formed at overlapping positions in the crossing direction Y is a narrow portion 35 that is narrower in the crossing direction Y than other portions. In the narrow portion 35, the occupied area when a plurality of warp filament aggregates 72a are projected in the thickness direction Z of the narrow portion 35 is larger than the occupied area when a plurality of weft filament aggregates 72b are projected in the thickness direction Z of the narrow portion 35.

[0348] 3.2.2.2. In the narrow portion 35, the interval between adjacent weft filament aggregates 72b is smaller than the interval between adjacent warp filament aggregates 72a.

[0349] 3.2.2.3. The number of filaments 71 that make up the warp filament aggregate 72a in the narrow portion 35 is larger than the number of filaments 71 that make up the warp filament aggregate 72a in a portion different from the narrow portion 35.

[0350] 3.2.2.4. The number of filaments 71 that make up the weft filament aggregate 72b in the narrow portion 35 is larger than the number of filaments 71 that make up the weft filament aggregate 72b in a portion different from the narrow portion 35.

[0351] The configurations described in the above 3.2.2.1. to 3.2.2.4. are independent of each other. It is possible to have all of the configurations described in 3.2.2.1. to 3.2.2.4., or to have at least one selected from the configurations described in 3.2.2.1. to 3.2.2.4. Also, the configurations described in 3.2.2.1. to 3.2.2.4. may be omitted.

[0352] 3.2.3. Relationship between the first electrode sheet 25c and the extension portion 31 As described above, in the first electrode sheet 25c of this embodiment, the longitudinal direction S of the plurality of warp filament aggregates 72a is at an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25c, and the longitudinal direction T of the plurality of weft filament aggregates 72b is at an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25c. FIG. 47 schematically shows, by a pattern in which a lattice pattern is inclined at an angle of 45° obliquely, the extending directions of the plurality of warp filament aggregates 72a and the plurality of weft filament aggregates 72b of the first electrode sheet 25c.

[0353] 3.2.3.1. As shown in FIG. 47, in the extension portions 31a, 31b of the first electrode sheet 25c, the angle α formed by the extension direction E1 of the extension portion 31a formed on the left side of FIG. 47 and the longitudinal direction S of the plurality of warp filament aggregates 72a is smaller than the angle β formed by the extension direction E1 of the extension portion 31a and the longitudinal direction T of the plurality of weft filament aggregates 72b.

[0354] 3.2.3.2. As shown in FIG. 47, at the extension portion 31 of the first electrode sheet 25c, the angle α formed by the extension direction E2 of the extension portion 31b formed on the right side of FIG. 47 and the longitudinal direction S of the plurality of warp filament aggregates 72a is larger than the angle β formed by the extension direction E2 of the extension portion 31b and the longitudinal direction T of the plurality of weft filament aggregates 72b. The same applies to the second electrode sheet.

[0355] 3.2.3.3. At the extension portion 31 of the first electrode sheet 25c, the occupied area when the plurality of warp filament aggregates 72a are projected in the thickness direction Z of the extension portion 31 is larger than the occupied area when the plurality of weft filament aggregates 72b are projected in the thickness direction Z of the extension portion 31.

[0356] 3.2.3.4. At the extension portion 31 of the first electrode sheet 25c, the interval between adjacent filaments 71 of the weft filament aggregate 72b is smaller than the interval between adjacent filaments 71 of the warp filament aggregate 72a.

[0357] 3.2.3.5. The number of filaments 71 constituting the warp filament aggregate 72a at the extension portion 31 of the first electrode sheet 25c is larger than the number of filaments 71 constituting the warp filament aggregate 72a in a portion different from the extension portion 31.

[0358] 3.2.3.6. The number of filaments 71 constituting the weft filament aggregate 72b at the extension portion 31 of the first electrode sheet 25c is larger than the number of filaments 71 constituting the weft filament aggregate 72b in a portion different from the extension portion 31.

[0359] The configurations described in 3.2.3.1. to 3.2.3.6. above are independent of each other. It may include all of the configurations described in 3.2.3.1. to 3.2.3.6., or may include at least one selected from the configurations described in 3.2.3.1. to 3.2.3.6. Also, the configurations described in 3.2.3.1. to 3.2.3.6. may be omitted. The same applies to the second electrode sheet.

[0360] 3.2.4. Bending Test When the first electrode sheet 25c is subjected to a bending test at an angle of 135° using a clamp with a load of 50 g and R0.38 mm in accordance with JIS P8115:2001, it is preferable that the increase rate of the electrical resistance value after 1000 cycles is 50% or less, more preferably that the increase rate of the electrical resistance value after 2000 cycles is 50% or less, even more preferably that the increase rate of the electrical resistance value after 5000 cycles is 50% or less, and particularly preferably that the increase rate of the electrical resistance value after 10000 cycles is 50% or less. Thereby, the sensor sheet 18 in which an increase in the electrical resistance value is suppressed even when an external force is applied can be obtained.

[0361] 3.2.5. Operational Effects of this Embodiment Subsequently, the operational effects of this embodiment will be described. The first electrode sheet 25c related to the sensor sheet 18 of this embodiment is a conductive cloth including a plurality of warp filament aggregates 72a having a plurality of filaments 71 and a plurality of weft filament aggregates 72b having a plurality of filaments 71. A plating layer 33 made of metal is formed on the surface of each filament 71.

[0362] According to this embodiment, when an external force is applied to the sensor sheet 18, even if the plating layer 33 peels off and the conductive path from one end to the other end of one filament 71 is interrupted, the possibility that the conductive paths of other filaments 71 remain intact increases. Also, even when the conductive path between one filament 71 and another filament 71 is interrupted, the possibility that the conductive path between any other filaments 71 remains intact increases. As a result, even when an external force is applied to the sensor sheet 18, the possibility that the conductive paths between the plurality of filaments 71 constituting the sensor sheet 18 remain intact can be increased, so that an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18 can be suppressed.

[0363] In addition, the plurality of warp filament aggregates 72a according to this embodiment are arranged side by side at equal intervals from each other, and the plurality of weft filament aggregates 72b are arranged side by side at different intervals from each other. The strength of the first electrode sheet 25c can be improved by the plurality of warp filament aggregates 72a arranged at equal intervals, and the stretchability of the first electrode sheet 25c can be improved by the plurality of weft filament aggregates 72b arranged at different intervals from each other.

[0364] Adjacent filaments 71 constituting the warp filament aggregate 72a according to this embodiment are electrically connected by the plating layer 33 in a region exposed on the surface of the first electrode sheet 25c. Thereby, a plurality of filaments 71 constituting the warp filament aggregate 72a can be electrically connected to each other.

[0365] Adjacent filaments 71 constituting the weft filament aggregate 72b according to this embodiment are electrically connected by the plating layer 33 in a region exposed on the surface of the first electrode sheet 25c. Thereby, a plurality of filaments 71 constituting the weft filament aggregate 72b can be electrically connected to each other.

[0366] As shown in FIG. 45, in this embodiment, the filaments 71 constituting the warp filament aggregate 72a are in contact with each other at warp filament contact points 71aa (an example of filament contact points). Further, as shown in FIG. 46, the filaments 71 constituting the weft filament aggregate 72b are in contact with each other at weft filament contact points 71ab (an example of filament contact points). Also, as shown in FIGS. 45 and 46, the filaments 71 constituting the warp filament aggregate 72a and the filaments 71 constituting the weft filament aggregate 72b are in contact with each other at warp and weft filament contact points 71ac (an example of filament contact points). According to this embodiment, except for the warp filament contact points 71aa, the weft filament contact points 71ab, and the warp and weft filament contact points 71ac, a plating layer 33 is formed on the surfaces of the plurality of filaments 71. Thereby, even when an external force is applied to the sensor sheet 18, the possibility that the conductive paths of the plurality of filaments 71 constituting the sensor sheet 18 continue can be increased. Thereby, it is possible to suppress an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18.

[0367] 3.2.6.1. The first electrode sheet 25c according to this embodiment has a narrow portion 35 that is narrower in width than other portions in the crossing direction Y that crosses the longitudinal direction X of the first electrode sheet 25c. In the narrow portion 35, the occupied area when the plurality of warp filament aggregates 72a are projected in the thickness direction Z of the narrow portion 35 is larger than the occupied area when the plurality of weft filament aggregates 72b are projected in the thickness direction Z of the narrow portion 35. According to this embodiment, by making the occupied area of the plurality of warp filament aggregates 72a in the narrow portion 35 larger than the occupied area of the plurality of weft filament aggregates 72b, the strength of the narrow portion 35 can be improved.

[0368] 3.2.6.2. In the narrow portion 35 according to this embodiment, the interval between adjacent filaments 71 that constitute the plurality of weft filament aggregates 72b is smaller than the interval between adjacent filaments 71 that constitute the plurality of warp filament aggregates 72a. Since the narrow portion 35 is very easy to deform, a relatively large force is likely to be applied, and the plating layer 33 is likely to peel off. According to this embodiment, by making the interval between the filaments 71 that constitute the plurality of weft filament aggregates 72b smaller than the interval between the filaments 71 that constitute the plurality of warp filament aggregates 72a, the conductive path between the filaments 71 that constitute the weft filament aggregate 72b can be maintained.

[0369] 3.2.6.3. The number of the plurality of filaments 71 that constitute the warp filament aggregate 72a in the narrow portion 35 according to this embodiment is larger than the number of the plurality of filaments 71 that constitute the warp filament aggregate 72a in a portion different from the narrow portion 35. According to this embodiment, by making the number of the plurality of filaments 71 that constitute the warp filament aggregate 72a in the narrow portion 35 larger than that in other portions, the strength of the narrow portion 35 can be improved.

[0370] 3.2.6.4. The number of the plurality of filaments 71 that constitute the weft filament aggregate 72b in the narrow portion 35 according to this embodiment is larger than the number of the plurality of filaments 71 that constitute the weft filament aggregate 72b in a portion different from the narrow portion 35. According to this embodiment, by making the number of the plurality of filaments 71 that constitute the weft filament aggregate 72b in the narrow portion 35 larger than that in other portions, the strength of the narrow portion 35 can be improved.

[0371] 3.2.6.5. According to this embodiment, extension portions 31a and 31b are provided which extend in the extension directions E1 and E2 from the long side edges along the longitudinal direction X of the first electrode sheet 25c. In the extension portions 31a and 31b, the occupied area when a plurality of warp filament aggregates 72a are projected in the thickness direction Z of the extension portions 31a and 31b is larger than the occupied area when a plurality of weft filament aggregates 72b are projected in the thickness direction Z of the extension portions 31a and 31b. Thereby, by making the occupied area of the plurality of warp filament aggregates 72a larger than that of the plurality of weft filament aggregates 72b, the strength of the extension portions 31a and 31b can be improved.

[0372] 3.2.6.6. In the extension portion 31a according to this embodiment, the angle α formed by the extension direction E1 of the extension portion 31a and the longitudinal direction S of the plurality of warp filament aggregates 72a is smaller than the angle β formed by the extension direction E1 of the extension portion 31a and the longitudinal direction T of the plurality of weft filament aggregates 72b. According to this embodiment, the longitudinal direction S of the plurality of warp filament aggregates 72a can be arranged along the extension direction E1 of the extension portion 31a. Thereby, the strength of the extension portion 31a can be improved.

[0373] 3.2.6.7. In the extension portion 31b according to this embodiment, the angle α formed by the extension direction E2 of the extension portion 31b and the longitudinal direction S of the plurality of warp filament aggregates 72a is larger than the angle β formed by the extension direction E2 of the extension portion 31b and the longitudinal direction T of the plurality of weft filament aggregates 72b. Thereby, the longitudinal direction T of the plurality of weft filament aggregates 72b can be arranged along the extension direction E2 of the extension portion 31b. Thereby, the strength of the extension portion 31b can be improved.

[0374] 3.2.6.8. In the extension part 31 according to this embodiment, the interval between adjacent filaments 71 that constitute the weft filament aggregate 72b is smaller than the interval between adjacent filaments 71 that constitute the warp filament aggregate 72a. Since the extension part 31 is very easy to deform, a relatively large force is likely to be applied, and the plating layer 33 is likely to peel off. According to this embodiment, by making the interval between adjacent filaments 71 that constitute the weft filament aggregate 72b smaller than the interval between adjacent filaments 71 that constitute the warp filament aggregate 72a, the conductive path between the filaments 71 that constitute the weft filament aggregate 72b can be maintained.

[0375] 3.2.6.9. The number of a plurality of filaments 71 that constitute the warp filament aggregate 72a in the extension part 31 according to this embodiment is larger than the number of a plurality of filaments 71 that constitute the warp filament aggregate 72a in a part different from the extension part 31. According to this embodiment, by making the number of a plurality of filaments 71 that constitute the warp filament aggregate 72a in the extension part 31 larger than that in other parts, the strength of the extension part 31 can be improved.

[0376] 3.2.6.10. The number of a plurality of filaments 71 that constitute the weft filament aggregate 72b in the extension part 31 according to this embodiment is larger than the number of a plurality of filaments 71 that constitute the weft filament aggregate 72b in a part different from the extension part 31. According to this embodiment, by making the number of a plurality of filaments 71 that constitute the weft filament aggregate 72b in the extension part 31 larger than that in other parts, the strength of the extension part 31 can be improved.

[0377] 3.2.6.11. The aperture ratio, which is the ratio of the aperture area of the first opening 34a of the first electrode sheet 25c according to this embodiment to the area of the first electrode sheet 25c, is 30% or more. Thereby, the stretchability of the first electrode sheet 25c can be improved.

[0378] The configurations described in the above 3.2.6.1. to 3.2.6.11. are independent of each other, and all of the configurations described in 3.2.6.1. to 3.2.6.11. may be provided, or at least one selected from the configurations described in 3.2.6.1. to 3.2.6.11. may be provided. Also, the configurations described in 3.2.6.1. to 3.2.6.11. may be omitted. The same applies to the second electrode sheet.

[0379] (Embodiment 3-3) Subsequently, with reference to FIGS. 48 to 49, the first electrode sheet 25d of Embodiment 3-3 will be described. FIG. 48 also shows a partially enlarged view of the enlarged region R1.

[0380] As shown in FIG. 48, in this embodiment, at least a part of the plurality of filaments 71 that make up the plurality of warp filament aggregates 72a has a warp filament facing surface 71ba (an example of a filament facing surface) that faces each other. In this embodiment, a plating layer 33 is formed on the warp filament facing surface 71ba.

[0381] Among the plurality of filaments 71 that make up the warp filament aggregate 72a, the plating layer 33 formed on the warp filament facing surface 71ba of one filament 71 and the plating layer 33 formed on the warp filament facing surface 71ba of another filament 71 adjacent to one filament 71 are in contact. Thereby, the plurality of filaments 71 that make up the warp filament aggregate 72a are electrically connected to each other.

[0382] Further, FIG. 49 also shows a partially enlarged view of the enlarged region R2. As shown in FIG. 49, in this embodiment, at least a part of the plurality of filaments 71 constituting the weft filament aggregate 72b has a weft filament facing surface 71bb facing each other. In this embodiment, a plating layer 33 is formed on the weft filament facing surface 71bb. By the plating layers 33 formed on the weft filament facing surfaces 71bb of adjacent filaments 71 constituting the weft filament aggregate 72b coming into contact with each other, the plurality of filaments 71 constituting the weft filament aggregate 72b are electrically connected to each other.

[0383] In a portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect and overlap, the filament 71 exposed on the outer surface of the warp filament aggregate 72a and the filament 71 exposed on the outer surface of the weft filament aggregate 72b have warp and weft filament facing surfaces 71bc (an example of a filament facing surface) facing each other. In this embodiment, a plating layer 33 is formed on the warp and weft filament facing surface 71bc. Thus, the warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected.

[0384] In this embodiment, among the plurality of filaments 71 constituting the warp filament aggregate 72a, at least a part of the plurality of filaments 71 located inside the warp filament aggregate 72a has a warp filament facing surface 71ba facing each other, and a plating layer 33 is formed on the warp filament facing surface 71ba.

[0385] Since the plating layer 33 is formed on the warp filament facing surface 71ba of the filament 71 located inside the warp filament aggregate 72a, even when an external force is applied to the sensor sheet 18, the direct application of the external force to the warp filament facing surface 71ba is suppressed. As a result, the possibility of the plating layer 33 formed on the facing surface remaining is increased. Thereby, even when an external force is applied to the sensor sheet 18, the possibility of the conductive path of the warp filament aggregate 72a constituting the sensor sheet 18 remaining can be increased, so that an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18 can be suppressed.

[0386] In this embodiment, among the plurality of filaments 71 constituting the warp filament aggregate 72a, the plating layer 33 formed on the warp filament facing surface 71ba of one filament 71 and the plating layer 33 formed on the warp filament facing surface 71ba of the other filament 71 are in contact with each other. According to this embodiment, since the conduction path between one filament 71 and the other filament 71 can be made to continue, an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18 can be suppressed. Note that, for the weft filament aggregate 72b as well, the same operational effects as those of the warp filament aggregate 72a can be obtained, and thus redundant explanations are omitted.

[0387] In this embodiment, one of the plurality of filaments 71 constituting the warp filament aggregate 72a and one of the plurality of filaments 71 constituting the weft filament aggregate 72b are provided with warp and weft filament facing surfaces 71bc facing each other, and a plating layer 33 is formed on the warp and weft filament facing surface 71bc.

[0388] Since the warp and weft filament facing surface 71bc is entirely located inside the first electrode sheet 25d, even when an external force is applied to the sensor sheet 18, the possibility of the conductive path between the filaments 71 that make up the warp filament assembly 72a that makes up the sensor sheet 18 and the filaments 71 that make up the weft filament assembly 72b can be increased. Therefore, an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18 can be suppressed.

[0389] In this embodiment, the plating layer 33 formed on the warp filament facing surface 71ba of one filament 71 that makes up the warp filament assembly 72a and the plating layer 33 formed on the warp filament facing surface 71ba of one filament 71 that makes up the weft filament assembly 72b are in contact. According to this embodiment, since the conduction path between the warp filament assembly 72a and the weft filament assembly 72b can be maintained, an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18 can be suppressed. Note that for the weft filament assembly 72b, the same effects as those of the warp filament assembly 72a can be obtained, so redundant explanations are omitted.

[0390] If the state where the user's hand is in contact with the steering wheel 10 continues, the steering wheel is placed in a high-temperature and high-humidity state. If the high-temperature and high-humidity state continues for a long time, the plating layer 33 formed on the surface of the filament 71 exposed on the outer surfaces of the warp filament aggregate 72a and the weft filament aggregate 72b may be damaged. According to this embodiment, since the plating layer 33 is formed on the warp filament facing surface 71ba, the weft filament facing surface 71bb, and the warp and weft filament facing surface 71bc, even if the plating layer 33 formed on the surface of the filament 71 exposed on the outer surfaces of the warp filament aggregate 72a and the weft filament aggregate 72b is damaged, the plating layer 33 formed on the warp filament facing surface 71ba, the weft filament facing surface 71bb, and the warp and weft filament facing surface 71bc is less likely to be damaged. Thereby, an increase in the electrical resistance value of the sensor sheet 18 can be suppressed. Note that the second electrode sheet also has the same operational effects as described above, so redundant explanations are omitted.

[0391] (Embodiment 3-4) Next, referring to FIG. 50, Embodiment 3-4 will be described.

[0392] (a) In the first electrode sheet 25e of this embodiment, the number of filaments 71 constituting the plurality of warp filament aggregates 72a is different in the direction in which the plurality of warp filament aggregates 72a are arranged.

[0393] (b) Also, in this embodiment, the intervals between adjacent warp filament aggregates 72a are different in the direction in which the plurality of warp filament aggregates 72a are arranged.

[0394] (c) In this embodiment, the number of filaments 71 constituting the plurality of warp filament aggregates 72a is different in the direction in which the plurality of warp filament aggregates 72a are arranged. By thus making the strengths of the plurality of warp filament aggregates 72a different from each other, it is possible to easily partially change the strength of the first electrode sheet 25e.

[0395] (d) In this embodiment, the plurality of warp filament aggregates 72a are arranged side by side at intervals, and the intervals between adjacent warp filament aggregates 72a are different in the direction in which the plurality of warp filament aggregates 72a are arranged. By changing the intervals between the plurality of warp filament aggregates 72a in this way, the stretchability of the first electrode sheet 25e can be easily changed.

[0396] The configurations described in the above (a) to (d) are independent of each other, and all of the configurations described in (a) to (d) may be provided, or at least one selected from the configurations described in (a) to (d) may be provided. Also, the configurations described in (a) to (d) may be omitted. Note that the second electrode sheet can have the same configuration as the first electrode sheet 25e, so overlapping explanations are omitted.

[0397] (Embodiment 3-5) Next, referring to FIG. 51, Embodiment 3-5 will be described.

[0398] (e) In the first electrode sheet 25f of this embodiment, the number of the plurality of filaments 71 constituting the plurality of weft filament aggregates 72b is different in the direction in which the plurality of weft filament aggregates 72b are arranged.

[0399] (f) Also, in this embodiment, the intervals between adjacent weft filament aggregates 72b are different in the direction in which the plurality of weft filament aggregates 72b are arranged.

[0400] (g) In this embodiment, the number of the plurality of filaments 71 constituting the plurality of weft filament aggregates 72b is different in the direction in which the plurality of weft filament aggregates 72b are arranged. By making the strengths of the plurality of weft filament aggregates 72b different in this way, it is possible to easily partially change the strength of the first electrode sheet 25f.

[0401] (h) In this embodiment, the plurality of weft filament aggregates 72b are arranged at intervals, and the intervals between adjacent weft filament aggregates 72b are different in the direction in which the plurality of weft filament aggregates 72b are arranged. By changing the intervals between the plurality of weft filament aggregates 72b in this way, the stretchability of the first electrode sheet 25f can be easily changed.

[0402] The configurations described in (e) to (h) above are independent of each other, and all of the configurations described in (e) to (h) may be provided, or at least one selected from the configurations described in (e) to (h) may be provided. Also, the configurations described in (e) to (h) may be omitted. Note that the second electrode sheet can have the same configuration as the first electrode sheet 25f, so duplicate explanations are omitted.

[0403] (Embodiment 3-6) Next, referring to FIG. 52, Embodiment 3-6 will be described.

[0404] In the first electrode sheet 25g of this embodiment, the number of filaments 71 constituting the warp filament aggregate 72a and the number of filaments 71 constituting the weft filament aggregate 72b are different. Thereby, the strength of the warp filament aggregate 72a and the strength of the weft filament aggregate 72b can be made different. As a result, it is possible to easily partially change the strength of the first electrode sheet 25. The number of filaments 71 constituting the warp filament aggregate 72a may be more than the number of filaments 71 constituting the weft filament aggregate 72b. Also, the number of filaments 71 constituting the warp filament aggregate 72a may be less than the number of filaments 71 constituting the weft filament aggregate 72b. Note that the second electrode sheet can have the same configuration as the first electrode sheet 25g, so duplicate explanations are omitted.

[0405] (Embodiment 3-7) Next, referring to FIG. 53, Embodiment 3-7 will be described. In the first electrode sheet 25h of this embodiment, the weft filament aggregate 72b includes a twisted yarn 73 formed by twisting a plurality of filaments 71, and a plating layer 33 formed on the surface of the twisted yarn 73. The twisted yarn 73 is formed by twisting a plurality of filaments 71.

[0406] According to this embodiment, plating is performed in a state where pressure contact between the warp filament aggregate 72a and the weft filament aggregate 72b is ensured by the weft filament aggregate 72b including the twisted yarn 73. Therefore, it is possible to suppress an increase in the electrical resistance value of the sensor sheet 18 by improving the pressure contact at each contact point between the plurality of warp filament aggregates 72a and the plurality of weft filament aggregates 72b.

[0407] However, the warp filament aggregate 72a may include a twisted yarn 73 and a plating layer 33, and the weft filament aggregate 72b may include an untwisted yarn bundle 74 and a plating layer 33. However, since the second electrode sheet also has the same configuration as the first electrode sheet 25h, redundant description will be omitted.

[0408] (Embodiment 3-8) Next, referring to FIG. 54, Embodiment 3-9 will be described. In the sensor sheet 18 of this embodiment, the two sheet extension portions 22 formed on the sensor sheet 18 are formed in parallel. That is, the two sheet extension portions 22 extend in the same extension direction E1. The extension portion 31 formed on the first electrode sheet 25h also extends in the same extension direction E1.

[0409] In this embodiment, the angle α formed by the longitudinal direction S of the plurality of warp filament aggregates 72a of the first electrode sheet 25i and the extension direction E1 of the extension portion 31 is smaller than the angle β formed by the longitudinal direction T of the plurality of weft filament aggregates 72b of the first electrode sheet 25f and the extension direction E1 of the extension portion 31.

[0410] According to this embodiment, the longitudinal direction S of the plurality of warp filament aggregates 72a can be arranged along the extending direction E1 of the extension part 31. Thereby, the strength of the extension part 31 can be improved. Note that the second electrode sheet can also have the same configuration as the first electrode sheet 25f, so overlapping explanations are omitted.

[0411] (Embodiment 3-9) Referring to FIG. 55, Embodiment 3-9 will be described. In the sensor sheet 18 of this embodiment, two first electrode sheets 25j and 25k are arranged along the longitudinal direction X of the insulating sheet 24 on the first surface 27 of the insulating sheet 24. Although not shown in detail, two second electrode sheets are arranged along the longitudinal direction X of the insulating sheet 24 on the second surface 28 of the insulating sheet 24.

[0412] In this embodiment, the longitudinal direction S1 of the plurality of warp filament aggregates 72a of the first electrode sheet 25j arranged on the left side of FIG. 55 and the longitudinal direction S2 of the plurality of warp filament aggregates 72a of the first electrode sheet 25k arranged on the right side of FIG. 55 are orthogonal to each other. Also, the longitudinal direction T1 of the plurality of weft filament aggregates 72b of the first electrode sheet 25j arranged on the left side of FIG. 55 and the longitudinal direction T2 of the plurality of weft filament aggregates 72b of the first electrode sheet 25k arranged on the right side of FIG. 55 are orthogonal to each other.

[0413] In this embodiment, the angle α formed by the longitudinal direction S1 of the warp filament aggregate 72a of the first electrode sheet 25i and the extending direction E1 of the extension part 31 is smaller than the angle β formed by the longitudinal direction T1 of the weft filament aggregate 72b of the first electrode sheet 25j and the extending direction E1 of the extension part 31.

[0414] Also, the angle α formed by the longitudinal direction S2 of the plurality of warp filament aggregates 72a of the first electrode sheet 25k and the extending direction E2 of the extension part 31b is smaller than the angle β formed by the longitudinal direction T2 of the plurality of weft filament aggregates 72b of the first electrode sheet 25j and the extending direction E2 of the extension part 31b.

[0415] According to this embodiment, the longitudinal direction S1 of the plurality of warp filament aggregates 72a can be arranged along the extending direction E1 of the extension part 31a. Thereby, the strength of the extension part 31a can be improved. Further, the longitudinal direction S2 of the plurality of warp filament aggregates 72a can be arranged along the extending direction E2 of the extension part 31b. Thereby, the strength of the extension part 31b can be improved. Note that since the second electrode sheet can have the same configuration as the first electrode sheet 25i, redundant descriptions are omitted.

[0416] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the gist thereof.

[0417] As shown in FIG. 56, the first electrode sheet 25 may be disposed on the first surface 27 of the insulating sheet 24, and the second electrode sheet 26 may not be disposed on the second surface 28 of the insulating sheet 24.

[0418] (Embodiment 4-1) Next, Embodiment 4-1 will be described. Since Embodiment 4-1 has the same configuration as that described in 1.1.1 to 1.1.4 of Embodiment 1-1, the descriptions in 1.1.1 to 1.1.4 are read as 4.1.1 to 4.1.4, and redundant descriptions are omitted.

[0419] 4.1.5. Bonding structure between the first electrode sheet 25 and the second electrode sheet 26 and the insulating sheet 24 FIG 58 As shown in the figure, on the first surface 27 side of the insulating sheet 24, the insulating sheet 24 and the first electrode sheet 25 are joined by a first joining portion 36 interposed between the insulating sheet 24 and the first electrode sheet 25. The material constituting the first joining portion 36 is not particularly limited, and can be appropriately selected from any materials such as acrylic adhesives, silicone adhesives, urethane adhesives, rubber adhesives, and the like. Also, FIG 58As shown in [Fig.], on the side of the second surface 28 of the insulating sheet 24, the insulating sheet 24 and the second electrode sheet 26 are joined by a second joint portion 37 interposed between the insulating sheet 24 and the second electrode sheet 26. Since the material constituting the second joint portion 37 is the same as that of the first joint portion 36, duplicate explanations are omitted.

[0420] 4.1.6. Protection portion 60 Fig. 57 ~FIG. 58 As shown in [Fig.], a first protection portion 61 is disposed on the surface (outer surface) of the first electrode sheet 25. The first protection portion 61 is formed to cover the surface of the first electrode sheet 25 in a layered manner. Also, a second protection portion 62 is disposed on the surface (outer surface) of the second electrode sheet 26. The second protection portion 62 is formed to cover the surface of the second electrode sheet 26 in a layered manner. In the following description, when the first protection portion 61 and the second protection portion 62 are not distinguished, they may be described as the protection portion 60.

[0421] The protection portion 60 is configured to include a resin material or a rubber material. The material for forming the protection portion 60 is not particularly limited, and any material such as polyolefins such as polyethylene and polypropylene, polyesters such as polybutylene terephthalate and polyethylene terephthalate, polyamides such as nylon 6 and nylon 6,6, polyurethane, and silicone polymers can be appropriately selected. However, acrylic-based materials, urethane-based materials, and silicone-based materials are preferred.

[0422] In addition to the resin material, the protection portion 60 may include additives such as antioxidants or may include fillers or the like.

[0423] The first protection portion 61 disposed on the first electrode sheet 25 and the second protection portion 62 disposed on the second electrode sheet 26 may be formed of the same material or may be formed of different materials.

[0424] The first electrode sheet 25 and the first protection part 61 may be configured to be integrated with the first electrode sheet 25 by the adhesiveness of the first protection part 61. Further, the first protection part 61 may be heat-sealed to the first electrode sheet 25 to integrate the first electrode sheet 25 and the first protection part 61. Further, the first electrode sheet 25 and the first protection part 61 may be integrated by adhering them with an adhesive. The adhesive may be a known adhesive, or the same material as the material constituting the above-described first joint part 36 may be applied.

[0425] Regarding the configuration for integrating the second electrode sheet 26 and the second protection part 62, it may be the same as or different from the configuration for integrating the first electrode sheet 25 and the first protection part 61.

[0426] 4.1.7. Configuration of Electrode Sheet The first electrode sheet 25 and the second electrode sheet 26 will be described. The first electrode sheet 25 and the second electrode sheet 26 are conductive cloths having conductivity. The first electrode sheet 25 and the second electrode sheet 26 have conductivity and flexibility. The first electrode sheet 25 and the second electrode sheet 26 have stretchability in the longitudinal direction X and the crossing direction Y.

[0427] Figure 59 As shown in the figure, the first electrode sheet 25 and the second electrode sheet 26 are conductive cloths in which a plurality of filament aggregates 72 are woven. The filament aggregate 72 includes a plurality of filaments 71 and a plating layer 33 formed on at least a part of the surface of the filament 71.

[0428] Figure 59 (a) to Figure 59 (b) As shown, the first electrode sheet 25 and the second electrode sheet 26 are manufactured by forming a plating layer 33 on a base cloth in which a plurality of untwisted yarn bundles 74 are woven. Each untwisted yarn bundle 74 is formed by gathering a plurality of filaments 71 without being twisted.

[0429] Examples of the resin constituting the filament 71 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 resin constituting the filament 71 is not limited to the above, and any resin can be appropriately selected. The second electrode sheet 26 has a similar configuration.

[0430] The plating layer 33 is formed on the surface of the base fabric in which a plurality of filament aggregates 72 are woven. The method of forming the plating layer 33 is not particularly limited. For example, electrolytic plating, electroless plating, electroless plating may be performed after electrolytic plating, or electrolytic plating may be performed after electroless plating, and any method can be appropriately selected.

[0431] As the metal constituting the plating layer 33 formed on the surface of the base fabric, any metal or alloy such as copper, nickel, tin, solder, etc. can be appropriately selected. The plating layer 33 formed on the surface of the base fabric may be composed of one metal species or a plurality of metal species. For example, only copper may be plated on the surface of the base fabric, only nickel may be plated on the surface of the base fabric, a copper plating layer made of copper may be formed on the surface of the base fabric, and a nickel plating layer made of nickel may be formed on the surface of this copper plating layer. The plating layer 33 formed on the surface of the base fabric may be formed by electrolytic plating or electroless plating. The second electrode sheet 26 has a similar configuration.

[0432] Figure 59 As shown in Fig. (a), the first electrode sheet 25 includes a first opening 34a that opens between a plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25. The first opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25 to the area of the first electrode sheet 25, is 1% or more and 40% or less.

[0433] Figure 59As shown in (b), the second electrode sheet 26 includes a second opening 34b that opens between a plurality of filament aggregates 72. The second opening 34b penetrates the second electrode sheet 26. The second opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26 to the area of the second electrode sheet 26, is 1% or more and 40% or less.

[0434] 4.1.8. Examples and Samples 4.1.8.1. Example 4-1 and Sample 4-1 (Example 4-1 and Sample 4-1) Figure 59 ~Figure 60 Referring to Figures 59 As shown in (a), the first electrode sheet 25 according to Example 4-1 is a conductive fabric in which a plurality of filament aggregates 72 are woven. The plurality of filament aggregates 72 include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled without being twisted, and a plating layer 33 formed on at least a part of the surface of the untwisted yarn bundle 74. The filament aggregate 72 is formed in a flat shape in the thickness direction of the first electrode sheet 25. However, since the first electrode sheet 25 and the second electrode sheet 26 have substantially the same configuration, duplicate descriptions are omitted except where specifically mentioned.

[0435] The first electrode sheet 25 according to this Example 4-1 is formed by weaving a warp filament aggregate 72a in which a plurality of filaments 71 are bundled without being twisted and a weft filament aggregate 72b in which a plurality of filaments 71 are bundled without being twisted to form a base fabric, and forming a plating layer 33 on the surface of this base fabric. However, the manufacturing method of the first electrode sheet 25 is not limited to the above method.

[0436] Figure 59As shown in (a), the first electrode sheet 25 of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The first electrode sheet 25 includes a first opening 34a that opens between the plurality of filament aggregates 72. The first opening 34a penetrates the first electrode sheet 25. In Example 4-1, the opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25 to the area of the first electrode sheet 25, is approximately 3%. Note that this opening ratio is the ratio of the total opening area of the plurality of first openings 34a formed in the target area of the first electrode sheet 25 to the area of the target area of the first electrode sheet 25. This opening ratio is calculated, for example, by specifying a 10 mm × 10 mm target area in the first electrode sheet 25, summing the areas of the first openings 34a within the target area, and dividing the total area by the area of the target area.

[0437] Figure 59 As shown in (b), the second electrode sheet 26 of this embodiment includes a plurality of warp filament aggregates 72a and a plurality of weft filament aggregates 72b. The second electrode sheet 26 of this embodiment includes a second opening 34b that opens between the plurality of filament aggregates 72. The second opening 34b penetrates the second electrode sheet 26. In Example 4-1, the opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26 to the area of the second electrode sheet 26 of this embodiment, is approximately 3%.

[0438] The number of filaments 71 included in the filament aggregate 72 that constitutes the first electrode sheet 25 is not particularly limited. The filament aggregate 72 according to this embodiment includes 75 filaments 71, but can be any number. Also, the same applies to the second electrode sheet 26 as to the first electrode sheet 25.

[0439] Figure 60As shown, a plating layer 33 is formed on at least a part of the surface of the untwisted yarn bundle 74 that constitutes the filament assembly 72. When the plating layer 33 of the warp filament assembly 72a contacts the plating layer 33 of the weft filament assembly 72b, the warp filament assembly 72a and the weft filament assembly 72b are electrically connected.

[0440] Figure 59 (a) As shown, the longitudinal direction S of the plurality of warp filament assemblies 72a and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Also, the longitudinal direction T of the plurality of weft filament assemblies 72b and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Specifically, the longitudinal direction S of the plurality of warp filament assemblies 72a is substantially at an acute angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft filament assemblies 72b is substantially at an acute angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25a. The fact that the angle is substantially 45° includes the case of 45° and also includes cases where it can be recognized as being substantially 45°. Note that since the second electrode sheet 26 has the same configuration as the first electrode sheet 25, duplicate explanations are omitted.

[0441] When the longitudinal direction S of the warp filament assembly 72a is parallel to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 0°), when the first electrode sheet 25 is stretched parallel to the direction X, the warp filament assembly 72a itself will be stretched, and a large load is required.

[0442] On the other hand, when the longitudinal direction S of the warp filament aggregate 72a is inclined at an angle of 45° with respect to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 45°), when the first electrode sheet 25 is stretched in parallel to the direction X, the square or rectangular lattice (first opening 34a) composed of the warp filament aggregate 72a and the weft filament aggregate 72b is deformed into a rhombus shape, and the warp filament aggregate 72a or the weft filament aggregate 72b itself is not stretched, so a large load is not required. That is, when the acute angle is substantially 45°, structural flexibility is imparted. Further, the higher the aperture ratio, the easier it is for the square or rectangular lattice to be deformed into a rhombus shape, and the structural flexibility is less likely to be impaired. The same applies to the second electrode sheet 26, so redundant explanations are omitted.

[0443] However, the longitudinal direction S of the plurality of warp filament aggregates 72a may be at an angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25. Also, the longitudinal direction T of the plurality of weft filament aggregates 72b may be at an angle different from 45° with respect to the longitudinal direction X of the first electrode sheet 25.

[0444] The number of the plurality of filaments 71 constituting the warp filament aggregate 72a and the number of the plurality of filaments 71 constituting the weft filament aggregate 72b may be the same or different. In this Example 4-1, the number of the plurality of filaments 71 constituting the warp filament aggregate 72a and the number of the plurality of filaments 71 constituting the weft filament aggregate 72b are set to be substantially the same. Substantially the same includes the case where they are the same and also the case where they are not the same but can be recognized as substantially the same. The same applies to the weft filament aggregate 72b, so redundant explanations are omitted. In this Example 4-1, the number of the filaments 71 is set to 75. However, the number of the filaments 71 is not limited to the above number.

[0445] Figure60 As shown in 60 , a plating layer 33 is formed on at least a part of the plurality of filaments 71 that constitute the warp filament aggregate 72a. For example, the plating layer 33 is formed on the surface of the filaments 71 exposed on the outer surface of the warp filament aggregate 72a. Among the filaments 71 located inside the warp filament aggregate 72a, the plating layer 33 is not formed on the surface of some of the filaments 71. In the portion where the plating layer 33 is not formed, the surface of the filament 71 is exposed. Since the same applies to the weft filament aggregate 72b, redundant explanations are omitted. However, the plating layer 33 may be formed on the surface of each filament that constitutes the plurality of filaments 71.

[0446] In the portion where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and cross, the plating layer 33 is formed in part, and in the portion where the plating layer 33 is not formed, the surface of the filament 71 is exposed. Among the portions where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and cross, the plating layer 33 is formed in the region closer to the portion exposed to the outside, and the plating layer 33 is not formed in the portion closer to the inside. Note that since the weft filament aggregate 72b has the same configuration as the warp filament aggregate 72a, redundant explanations are omitted.

[0447] In this Example 4-1, the resin that constitutes the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is about 10 μm. The metal that constitutes the plating layer 33 is formed in a three-layer structure, with the outermost layer being Ni, the intermediate layer being Cu, and the innermost layer (on the side of the filament 71) being Ni. The diameter of the warp filament aggregate 72a is about 185 μm, and the diameter of the weft filament aggregate 72b is about 185 μm.

[0448] Figure 58As shown, the above-described first electrode sheet 25 is joined to the first surface 27 of the insulating sheet 24 via a first joint portion 36. Further, a second electrode sheet 26 having the same configuration as the first electrode sheet 25 is joined to the second surface 28 of the insulating sheet 24 via a second joint portion 37. The insulating sheet 24 is an ether-based polyurethane foam. The first joint portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first joint portion 36 is 50 μm. Since the first joint portion 36 and the second joint portion 37 are the same, duplicate explanations are omitted.

[0449] The first protective portion 61 is disposed on the outer surface of the first electrode sheet 25 and integrated with the surface of the first protective portion 61. The first electrode sheet 25 and the first protective portion 61 are integrated by an acrylic adhesive. The resin constituting the first protective portion 61 is an acrylic adhesive. The thickness of the first protective portion 61 is about 50 to 100 μm. Since the first protective portion 61 and the second protective portion 62 are the same, duplicate explanations are omitted.

[0450] In this way, a sample 4-1 of the sensor sheet 18 according to the first electrode sheet 25 and the second electrode sheet 26 of Example 4-1 is produced.

[0451] 4.1.8.2. Example 4-2 and Sample 4-2 (Example 4-2 and Sample 4-2) Subsequently, with reference to FIGS. 61 (a) to FIGS. 61 (b), the configuration of the first electrode sheet 25a and the second electrode sheet 26a according to Example 4-2 will be described. In the first electrode sheet 25a according to this Example 4-2, the number of filaments 71a constituting the warp filament aggregate 72aa is different from the number of filaments 71a constituting the weft filament aggregate 72ba. In this Example 4-2, the number of filaments 71a constituting the warp filament aggregate 72aa is larger than the number of filaments 71a constituting the weft filament aggregate 72ba. However, the configuration may be such that the number of filaments 71a constituting the warp filament aggregate 72aa is smaller than the number of filaments 71a constituting the weft filament aggregate 72ba.

[0452] In Example 4-2, the number of filaments 71a constituting the warp filament aggregate 72aa is set to be approximately twice the number of filaments 71a constituting the weft filament aggregate 72ba. In Example 4-2, the number of filaments 71a constituting the warp filament aggregate 72aa is set to approximately 80, and the number of filaments 71 constituting the weft filament aggregate 72ba is set to approximately 40. However, the difference in the number of filaments 71a constituting the warp filament aggregate 72aa and the number of filaments 71a constituting the weft filament aggregate 72ba is not limited to the above.

[0453] The aperture ratio, which is the ratio of the aperture area of the first aperture 34a formed in the first electrode sheet 25a according to Example 4-2 to the area of the first electrode sheet 25a, is approximately 10%. Also, the aperture ratio, which is the ratio of the aperture area of the second aperture 34b formed in the second electrode sheet 26a to the area of the second electrode sheet 26a, is approximately 10%.

[0454] Since the second electrode sheet 26a has the same configuration as the first electrode sheet 25a, duplicate explanations are omitted.

[0455] In Example 4-2, the resin constituting the filament 71a is PET (polyethylene terephthalate), and the diameter of the filament 71a is approximately 10 μm. The metal constituting the plating layer 33 has a single-layer structure and is a Ni single layer. The diameter of the warp filament aggregate 72a is approximately 180 μm, and the diameter of the weft filament aggregate 72b is approximately 90 μm.

[0456] Since the configuration other than the above is the same as that of Example 4-1, duplicate explanations are omitted.

[0457] Also, in Example 4-2, the insulating sheet 24 is an ether-based polyurethane foam. The first joint portion 36 is an acrylic-based adhesive. The thickness of the first joint portion 36 is about 50 μm. Since the first joint portion 36 and the second joint portion 37 are the same, duplicate explanations are omitted. The first protective portion 61 is disposed and integrated on the surface of the first protective portion 61 on the outer surface of the first electrode sheet 25a. The first electrode sheet 25a and the first protective portion 61 are integrated by an acrylic-based adhesive. The resin constituting the first protective portion 61 is an acrylic-based adhesive. The thickness of the first protective portion 61 is about 50 to 100 μm. Since the first protective portion 61 and the second protective portion 62 are the same, duplicate explanations are omitted.

[0458] Except for the above, in the same manner as in Sample 4-1, a sample 4-2 of the sensor sheet 18 related to the first electrode sheet of Example 4-2 is produced. Duplicate explanations with Sample 4-1 are omitted.

[0459] 4.1.8.3. Tensile Test of the First Electrode Sheet Next, with reference to FIG. 62 the tensile test performed on the first electrode sheet will be described. The first electrode sheets according to Examples 4-1 to 4-2 were cut out into strips of 150 mm × 20 mm to prepare test pieces. The thickness of the first electrode sheet is different in Examples 4-1 to 4-2, but is about 0.1 mm. The angle formed by the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a is set to 45°.

[0460] The test piece is gripped by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is performed on the test piece 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 piece. The tensile testing machine is AGS-X 1 kN manufactured by Shimadzu Corporation. The tensile test is performed in the range where the strain is 0 to 20%. FIG. 62 shows a graph showing the change of the stress with respect to the strain.

[0461] In Example 4-1 and Example 4-2, in the region where the strain was 0 to 20%, the stress increased gently and monotonically. Example 4-1 and Example 4-2 do not have a yield point showing a maximum value in the range of 0.5 to 10% of strain in the stress-strain curve in the tensile test.

[0462] Example 4-1 showed a stress of about 1.4 MPa when the strain was 5%, and showed a stress of about 7.5 MPa when the strain was 20%. Example 4-2 showed a stress of about 0.9 MPa when the strain was 5%, and showed a stress of about 5.9 MPa when the strain was 20%. For the first electrode sheets 25, 25a according to Example 4-1 and Example 4-2, the maximum value of the stress when the strain is 0 to 5% is 3 MPa or less, and the maximum value of the stress when the strain is 0 to 20% is 15 MPa or less.

[0463] 4.1.8.4. Tensile Test of Sensor Sheet Next, the tensile test performed on the sensor sheet will be described. Test pieces are prepared by cutting out the sensor sheets according to Samples 4-1 to 4-2 into strip shapes of 90 mm × 20 mm. The thickness of the sensor sheet is about 1 mm, although it is different for Samples 4-1 to 4-2. The angle formed by the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a constituting the first electrode sheet and the second electrode sheet is set to 45°. In this test, a configuration in which the first protection part 61 and the second protection part 62 were excluded from the configurations of Samples 4-1 to 4-2 described above was used as the test piece.

[0464] Connect an electric wire to one end in the longitudinal direction of the first electrode sheet and connect it to a DC power supply. Connect an electric wire to the other end in the longitudinal direction of the first electrode sheet and connect it to a voltage measuring instrument.

[0465] Grip the test piece with a pair of chucks. The distance between the pair of chucks is 50 mm. Perform a tensile test on the test piece at a tensile speed of 1 mm / sec, and calculate the stress by dividing the load by the cross-sectional area of the test piece. Also, during the tensile test, calculate the DC resistance value (an example of the electrical resistance value) of the sensor sheet from the voltage of the DC power supply and the voltage drop of the sensor sheet.

[0466] Figure 63 shows the stress-strain curve in the tensile test performed on the sensor sheet. Figure 63 shows the graph in the region where the strain is 0 to 20%. The stress of Samples 4-1 to 4-2 increased monotonically in the region where the strain was 0 to 20%. Samples 4-1 and 4-2 do not have a yield point showing a maximum value in the stress-strain curve in the interval where the strain is 0.5 to 10%.

[0467] Sample 4-1 shows a stress of about 0.5 MPa when the strain is 5%, and shows a maximum stress of about 2.6 MPa when the strain is 20%. Sample 4-2 shows a stress of about 0.3 MPa when the strain is 5%, and shows a maximum stress of about 1.5 MPa when the strain is 20%. Samples 4-1 and 4-2 have a maximum stress value of 0.5 MPa or less when the strain is 0 to 5% and a maximum stress value of 3 MPa or less when the strain is 0 to 20% in the stress-strain curve.

[0468] Samples 4-1 and 4-2 have a stress of 0.5 MPa or less when the strain is 0 to 5% and a maximum stress value of 3 MPa or less when the strain is 0 to 20% in the stress-strain curve.

[0469] When a tensile force is applied to Samples 4-1 and 4-2, the first opening 34a of the first electrode sheet extends in the tensile direction and contracts in the direction intersecting the tensile direction. Figure 64 shows the state in which the first opening 34a is deformed, taking Sample 4-2 as an example. Figure 64 As shown in (a), in the state where the elongation rate is 0%, the first opening 34a is open, but when the elongation rate is 10% (see Figure 64 (b)), 20% (see Figure 64 (c)), 30% (see Figure 64(d) As the reference increases, the gaps between the fibers of the conductive cloth decrease, and in the state of 30% elongation, the first opening 34a almost disappears. Due to such a change in the fiber shape, it can be easily stretched, so it is considered that the stress generated during stretching is small. That is, it is considered that the presence of the first opening 34a contributes to the expression of the structural expansion and contraction flexibility of this fiber. Since the above configuration is the same for the second electrode sheet, the description is omitted. Note that the same applies to Sample 4-1, so the description is omitted.

[0470] In Samples 4-1 and 4-2, when a tensile force is applied to the sensor sheet, it is considered that the first opening 34a gradually deforms, thereby absorbing the tensile force. As a result, at the intersection of the warp filament aggregate 72a and the weft filament aggregate 72b, the relative positions of the warp filament aggregate 72a and the weft filament aggregate 72b do not change significantly, so it is considered that the electrical connection state between the warp filament aggregate 72a and the weft filament aggregate 72b is maintained. Thereby, in Samples 4-1 and 4-2, it is considered that the DC resistance value hardly changes even when a tensile force is applied to the sensor sheet.

[0471] 4.1.8.5. DC Resistance Value Change Rate of Sensor Sheet Next, the DC resistance value change rate was measured for the sensor sheet. The sensor sheet was cut into a strip shape of 90 mm × 20 mm to prepare a test piece. The angle formed by the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a was set to 45°. In this test, a configuration in which the first protection part 61 and the second protection part 62 were excluded from the configurations of Samples 4-1 to 4-2 described above was used as the test piece.

[0472] Grip the test piece with a pair of chucks. The distance between the pair of chucks is 50 mm. Conduct a tensile test on the test piece at a tensile speed of 1 mm / sec. Connect electric wires to both ends of the first electrode sheet and measure the DC resistance value between the two electric wires. Calculate the DC resistance value change rate based on the following formula (1) for the DC resistance value at this time. The measurement of the DC resistance value uses a digital multimeter 2000 series manufactured by KEITHLEY. Conduct the above test on samples 4-1 to 4-2.

[0473] [Number]

[0474] Figure 65 is a graph showing the change of the DC resistance value change rate with respect to strain. The DC resistance value change rate of sample 4-1 increased in the range of strain from 0 to about 2%, and in the state where the strain was about 2%, the DC resistivity change rate was about 5%. Then, it decreased in the range of about 2 to about 5%, and the DC resistivity change rate became about 0%. After that, when the strain was about 25% or more, the DC resistance value change rate increased gently, and the DC resistance value change rate was about 7% when the strain was 30%. Thus, the DC resistance value change rate of sample 4-1 was 10% or less in the range of strain from 0 to 30%.

[0475] The DC resistance value change rate of sample 4-2 increased in the range of strain from 0 to about 3%, and in the state where the strain was about 3%, the DC resistivity change rate was about 10%. Then, it decreased in the range of about 3 to about 5%, and the DC resistivity change rate became about 0%. After that, the DC resistance value change rate was also about 0% when the strain was 30%. Thus, the DC resistance value change rate of sample 4-2 was 10% or less in the range of strain from 0 to 30%.

[0476] 4.1.8.6. DC resistance value change rate of the sensor sheet at 10% elongation Next, the change rate of the DC resistance value at 10% elongation was measured for the sensor sheet. The sensor sheet was cut into a strip shape of 90 mm × 20 mm to prepare a test piece. The angle formed between the longitudinal direction of the test piece and the longitudinal direction of the warp filament aggregate 72a was set to 45°. In this test, a configuration obtained by excluding the first protection part 61 and the second protection part 62 from the configurations of the above-described samples 4-1 to 4-2 was used as the test piece.

[0477] The test piece is gripped by a pair of chucks. The distance between the pair of chucks is 50 mm. A tensile test is performed on the test piece at a tensile speed of 1 mm / sec. Electric wires are connected to both ends of the first electrode sheet, and the DC resistance value between the two electric wires is measured. Based on the following formula (1), the change rate of the DC resistance value is calculated for the DC resistance value at this time. For the measurement of the DC resistance value, a digital multimeter 2000 series manufactured by KEITHLEY is used. The above test is performed on samples 4-1 to 4-2.

[0478] When measuring the change rate of the DC resistance value of the above-described sensor sheet, the sensor sheet is extended by 10% with respect to the reference length (50 mm) in the state before applying a tensile force to the sensor sheet, then returned to the reference length, and a test of extending by 10% again is repeated a predetermined number of times. The number of repetitions in this test is 1 time, 5 times, and 10 times. Based on the above formula (1), the change rate of the DC resistance value is calculated for the DC resistance value at this time. The above test is performed on samples 4-1 to 4-2.

[0479] Figure 66 shows a graph showing the relationship between the number of repetitions of the extension test and the change rate of the DC resistance value. For sample 4-1, the change rate of the DC resistance value at the first measurement was about 0%. Thereafter, as the number of repetitions increased, the change rate of the DC resistance value increased to about 36% at 1 repetition, about 48% at 5 repetitions, and about 57% at 10 repetitions. At 10 repetitions, the change rate of the DC resistivity of sample 4-1 was 60% or less.

[0480] Sample 4-2 had a DC resistivity change rate of approximately 14% during the first measurement, which was larger than that of Sample 4-1. However, during the first repetition, it was approximately 9%, and during the fifth repetition, it was approximately 15%. As the number of repetitions increased, the DC resistance value change rate did not increase significantly. During the tenth repetition, it was approximately 30%. At the tenth repetition, the DC resistance value change rate of Sample 4-2 was 50% or less. As described above, it was found that the sensor sheets according to Samples 4-1 and 2 had small changes in the DC resistance value even when the 10% elongation test was repeated.

[0481] 4.1.8.7. DC Resistance Value Change Rate of Sensor Sheet at 20% Elongation Subsequently, for Samples 4-1 to 4-2, the DC resistance value change rate when the sensor sheet was elongated by 20% was measured. In this test, a configuration obtained by excluding the first protection part 61 and the second protection part 62 from the configurations of Samples 4-1 to 4-2 described above was used as a test piece.

[0482] Figure 67 shows a graph showing the relationship between the number of repetitions of the elongation test and the DC resistance value change rate. For Sample 4-1, the DC resistance value change rate during the first measurement was approximately 0%. Subsequently, during the first repetition, it was approximately 35%, and during the fifth repetition, it was approximately 91%. As the number of repetitions increased, the DC resistance value change rate increased. At the tenth repetition, the DC resistance value change rate was approximately 137%.

[0483] For Sample 4-2, the DC resistivity change rate during the first measurement was approximately 10%, which was larger than that of Sample 4-1. However, during the first repetition, it was approximately 27%, and during the fifth repetition, it was approximately 32%. As the number of repetitions increased, the DC resistance value change rate did not increase significantly. At the tenth repetition, the DC resistance value change rate of Sample 4-2 was approximately 55%. As described above, it was found that the sensor sheets according to Samples 4-1 and 2 had small changes in the DC resistance value even when the 20% elongation test was repeated.

[0484] 4.1.9. Modification Example of Embodiment 4-1 Figure 68 ~Figure 70Referring to 68 , a modification of Embodiment 4-1 will be described. In this modification, the configurations of the first electrode sheet 25c and the second electrode sheet 26c are different from those in Sample 4-1. As shown in Fig. 68 (a), the first electrode sheet 25c of this modification includes a plurality of warp threads 41 and a plurality of weft threads 42. The first electrode sheet 25c is formed by weaving the warp threads 41 and the plurality of weft threads 42. Each warp thread 41 is composed of a single filament 71 and a plating layer 33 formed on the surface of the filament 71, and each weft thread 42 is also composed of a single filament 71 and a plating layer 33 formed on the surface of the filament 71.

[0485] The first electrode sheet 25c has a first opening 34a that opens between two adjacent warp threads 41 among the plurality of warp threads 41 and two adjacent weft threads 42 among the plurality of weft threads 42. The first opening 34a penetrates the first electrode sheet 25c. The opening ratio, which is the ratio of the opening area of the first opening 34a formed in the first electrode sheet 25c to the area of the first electrode sheet 25c in this modification, is approximately 63%.

[0486] Fig. 68 (b), the second electrode sheet 26c of this modification includes a plurality of warp threads 41 and a plurality of weft threads 42. The second electrode sheet 26c is formed by weaving the warp threads 41 and the plurality of weft threads 42. Each warp thread 41 is composed of a single filament 71, and each weft thread 42 is also composed of a single filament 71.

[0487] The second electrode sheet 26c has a second opening 34b that opens between two adjacent warp threads 41 among the plurality of warp threads 41 and two adjacent weft threads 42 among the plurality of weft threads 42. The opening ratio, which is the ratio of the opening area of the second opening 34b formed in the second electrode sheet 26c to the area of the second electrode sheet 26c in this modification, is approximately 63%.

[0488] Fig. 68As shown in (a), the intervals between the plurality of warp threads 41 according to this modified example are arranged at substantially equal intervals. However, "substantially equal intervals" includes cases where the intervals are equal, and also includes cases where the intervals are not equal but can be recognized as substantially equal. Also, the intervals between the plurality of warp threads 41 may be different.

[0489] Also, the intervals between the plurality of weft threads 42 according to this modified example are arranged at substantially equal intervals. However, "substantially equal intervals" includes cases where the intervals are equal, and also includes cases where the intervals are not equal but can be recognized as substantially equal. Also, the intervals between the plurality of weft threads 42 may be different.

[0490] Figure 68 As shown in (b), the configuration of the second electrode sheet 26 is the same as that of the first electrode sheet 25, so duplicate explanations are omitted.

[0491] Figure 69 As shown, a plating layer 33 is formed on at least a part of the warp thread 41. The plating layer 33 may be formed on the entire surface of the warp thread 41, or may be formed on a part of the surface of the warp thread 41.

[0492] Also, a plating layer 33 is formed on at least a part of the weft thread 42. The plating layer 33 may be formed on the entire surface of the weft thread 42, or may be formed on a part of the surface of the weft thread 42.

[0493] In this modified example, the plating layer 33 formed on the surface of the warp thread 41 and the plating layer 33 formed on the surface of the weft thread 42 come into contact with each other, so that the warp thread 41 and the weft thread 42 are electrically connected.

[0494] When a tensile force is applied to this modified example, the first opening 34a of the first electrode sheet 25c extends in the tensile direction and contracts in the direction intersecting the tensile direction. Figure 70This shows the state in which the first opening 34a is deformed in this modification example. As a result, since the tensile force is absorbed, it is considered that the change in stress is small. Note that the same applies to the second electrode sheet 26c, and thus redundant explanations are omitted.

[0495] The configuration other than the above is the same as that of Sample 4-1, and thus redundant explanations are omitted.

[0496] 4.1.10. Operational effects of this embodiment Subsequently, the operational effects of this embodiment will be described. The sensor sheet 18 according to this embodiment includes an insulating sheet 24 having a first surface 27 and a second surface 28, a first electrode sheet 25 made of conductive cloth disposed on the first surface 27 side of the insulating sheet 24, a first joining portion 36 that joins the first surface 27 of the insulating sheet 24 and the inner surface of the first electrode sheet 25, and a first protection portion 61 disposed on the outer surface of the first electrode sheet 25 to protect the outer surface of the first electrode sheet 25.

[0497] According to this embodiment, since the first electrode sheet 25 is protected from external forces by the first protection portion 61, it is possible to suppress damage to the conductive path of the first electrode sheet 25. Thereby, a change in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0498] Further, the sensor sheet 18 according to this embodiment includes a second electrode sheet 26 made of conductive cloth disposed on the second surface 28 side of the insulating sheet 24, a second joining portion 37 that joins the second surface 28 of the insulating sheet 24 and the inner surface of the second electrode sheet 26, and a second protection portion 62 disposed on the outer surface of the second electrode sheet 26 to protect the outer surface of the second electrode sheet 26.

[0499] According to this embodiment, since the second electrode sheet 26 is protected from external forces by the second protection portion 62, it is possible to suppress damage to the conductive path of the second electrode sheet 26. Thereby, it is possible to suppress a decrease in the shielding performance of the sensor sheet 18.

[0500] The first protective part 61 and the second protective part 62 according to this embodiment are configured to include a resin material. Thereby, the strength of the first protective part 61 and the second protective part 62 is improved. In addition, the operation of arranging the first protective part 61 on the surface of the first electrode sheet 25 can be easily performed, and the operation of arranging the second protective part 62 on the surface of the second electrode sheet 26 can be easily performed.

[0501] The first protective part 61 according to this embodiment is formed in a layer shape that covers the outer surface of the first electrode sheet 25. Thereby, since the outer surface of the first electrode sheet 25 can be surely covered, the first electrode sheet 25 can be further protected. As a result, it is possible to further suppress a change in the electrical resistance value of the sensor sheet 18.

[0502] Also, the second protective part 62 is formed in a layer shape that covers the outer surface of the second electrode sheet 26. Thereby, since the outer surface of the second electrode sheet 26 can be surely covered, the second electrode sheet 26 can be further protected. As a result, the shielding performance of the sensor sheet 18 can be further improved.

[0503] The conductive cloth constituting the first electrode sheet 25 according to this embodiment has a plurality of filament aggregates 72 woven therein. The first protective part 61 is formed on the outer periphery of the filament aggregate 72. Thereby, since the filament aggregate 72 can be protected by the first protective part 61, it is possible to further suppress a change in the electrical resistance value of the sensor sheet 18.

[0504] The first joint part 36 according to this embodiment is interposed between the insulating sheet 24 and the first electrode sheet 25. Thereby, the insulating sheet 24 and the first electrode sheet 25 can be surely joined.

[0505] The conductive fabric constituting the first electrode sheet 25 according to this embodiment has a plurality of filament aggregates 72 woven therein, and the filament aggregate 72 includes a plurality of filaments 71. The conductive fabric has a first opening 34a that opens between the plurality of filament aggregates 72. The opening ratio, which is the ratio of the opening area of the first opening 34a to the area of the first electrode sheet 25, is 3% or more. Thereby, when an external force is applied to the first electrode sheet 25, the first opening 34a deforms to absorb the external force. Thereby, it is possible to suppress an excessive large stress from being applied to the first electrode sheet 25, and thus it is possible to suppress the conductive path of the first electrode sheet 25 from being damaged. As a result, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0506] The insulating sheet 24 according to this embodiment is made of a foamed elastomer. Thereby, the flexibility of the insulating sheet 24 can be improved. As a result, when an external force is applied to the sensor sheet 18, the insulating sheet 24 deforms to absorb the external force. Thereby, it is possible to suppress an excessive large stress from being applied to the first electrode sheet 25, and thus it is possible to suppress the conductive path of the first electrode sheet 25 from being damaged. As a result, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0507] The conductive fabric according to this embodiment has a plurality of filament aggregates 72 woven therein, and the filament aggregate 72 includes a plurality of filaments 71 and a plating layer 33 formed on at least a part of the surface of the filament 71. By the plating layers 33 formed on the surfaces of the plurality of filaments 71 coming into contact with each other, the plurality of filaments 71 are electrically connected. Thereby, the conduction path of the first electrode sheet 25 is formed.

[0508] The plating layer 33 is formed on the surface of each of the plurality of filaments 71. Thus, even when an external force is applied to the sensor sheet 18 and the relative positions of the plurality of filaments 71 fluctuate, the plating layer 33 formed on the surface of each filament 71 facilitates the formation of a conduction path. As a result, it is possible to suppress a change in the electrical resistance value of the sensor sheet 18.

[0509] (Embodiment 4-2) Next, 71 ~ 72 Referring to 71 Embodiment 4-2 will be described. As shown in

[0510] As shown in 72 the first joint portion 36 according to this embodiment includes a first exposed joint portion 36a exposed on the outer surface of the first electrode sheet 25. The first exposed joint portion 36a is formed in a layer on the outer surface of the first electrode sheet 25. The first exposed joint portion 36a also serves as a first protection portion 61 that protects the first electrode sheet 25. Thereby, compared with the case where the first protection portion 61 is separately arranged and fixed to the first electrode sheet 25 in addition to the first joint portion 36, the manufacturing process of the sensor sheet 18 can be simplified.

[0511] According to this embodiment, the first joint portion 36 is inserted into the first opening 34a of the first electrode sheet 25 to form a first inserted joint portion 36b, and the first exposed joint portion 36a and the first inserted joint portion 36b can be made into a continuous shape. Thereby, when the first joint portion 36 is laminated on the first surface 27 of the insulating sheet 24, the first electrode sheet 25 is disposed on the first joint portion 36, and the first electrode sheet 25 is pressed toward the insulating sheet 24, the first inserted joint portion 36b enters into the first opening 34a of the first electrode sheet 25, and further, by covering the first electrode sheet 25, the first exposed joint portion 36a is formed, and this first exposed joint portion 36a can be used as a first protection portion 61 for protecting the first electrode sheet 25.

[0512] Since the opening ratio of the first opening 34a according to this embodiment is 3% or more, the first joint portion 36 can be easily inserted into the first opening 34a. Thereby, the sensor sheet 18 according to this embodiment can be easily manufactured. Note that the opening ratio of the first opening 34a is preferably 5% or more, more preferably 10% or more, so that the first joint portion 36 can be more easily inserted into the first opening 34a.

[0513] Also, as shown in FIG. 71 The second joint portion 37 according to this embodiment includes a second exposed joint portion 37a exposed on the outer surface of the second electrode sheet 26. The second exposed joint portion 37a is formed in a layer shape on the outer surface of the second electrode sheet 26. The second exposed joint portion 37a also serves as a second protection portion 62 for protecting the second electrode sheet 26. The configuration related to the second joint portion 37 and the second electrode sheet 26 is the same as the configuration related to the first joint portion 36 and the first electrode sheet 25, so redundant descriptions are omitted.

[0514] Among the reference numerals used in and after Embodiment 4-2, those same as the reference numerals used in the previous embodiments represent the same components as those in the previous embodiments unless otherwise specified.

[0515] (Embodiment 4-3) Next, FIGS. 73 ~FIGS. 74Referring to FIG., Embodiment 4-3 will be described. 73 As shown in FIG. 73 , the first electrode sheet 25 according to this embodiment is disposed on the first surface 27 of the insulating sheet 24. The first electrode sheet 25 may be in contact with the first surface 27 of the insulating sheet 24 over the entire surface, or may be in partial contact. Thereby, a first direct region 38 in which no first bonding portion 36 is interposed is formed between the insulating sheet 24 and the first electrode sheet 25 due to their direct contact (see FIG. 74 ).

[0516] The first bonding portion 36 is disposed on the outer surface of the first electrode sheet 25. Thereby, a portion of the first bonding portion 36 that is exposed on the outer surface of the first electrode sheet 25 is defined as a first exposed bonding portion 36c. The first exposed bonding portion 36c is formed in a layer on the outer surface of the first electrode sheet 25. The first exposed bonding portion 36c also serves as a first protection portion 61a that protects the first electrode sheet 25.

[0517] As shown in FIG. 74 The first electrode sheet 25 includes a first opening 34a. The first bonding portion 36 penetrates into the first opening 34a. A portion of the first bonding portion 36 that penetrates into the first opening 34a is defined as a first penetrating bonding portion 36d. The first penetrating bonding portion 36d penetrates through the first electrode sheet 25 and is continuous with the first exposed bonding portion 36c. As described above, since the first exposed bonding portion 36c also serves as the first protection portion 61a, the first penetrating bonding portion 36d is continuous with the first protection portion 61a.

[0518] According to this embodiment, the first joint portion 36 is inserted into the first opening 34a of the first electrode sheet 25 to form a first inserted joint portion 36d, and the first exposed joint portion 36c and the first inserted joint portion 36d can have a continuous shape. Thereby, when the first joint portion 36 is laminated on the first surface 27 of the insulating sheet 24, the first electrode sheet 25 is disposed on the outer surface of the first joint portion 36, and the first electrode sheet 25 is pressed toward the insulating sheet 24, the first inserted joint portion 36d penetrates into the first opening 34a of the first electrode sheet 25, and further, by covering the first electrode sheet 25, the first exposed joint portion 36c is formed, and this first exposed joint portion 36c can be used as a first protection portion 61a for protecting the first electrode sheet 25.

[0519] Also, as shown in FIG. 73 The second electrode sheet 26 according to this embodiment is disposed on the second surface 28 of the insulating sheet 24. The second electrode sheet 26 may be in contact with the second surface 28 of the insulating sheet 24 over the entire surface, or may be in partial contact. Thereby, by the insulating sheet 24 and the second electrode sheet 26 being in direct contact, a second direct region 39 is formed in which no second joint portion 37 is interposed between the insulating sheet 24 and the second electrode sheet 26.

[0520] The second joint portion 37 is disposed on the outer surface of the second electrode sheet 26. Thereby, a portion of the second joint portion 37 that is exposed on the outer surface of the second electrode sheet 26 is defined as a second exposed joint portion 37c. The second exposed joint portion 37c is formed in a layer shape on the outer surface of the second electrode sheet 26. The second exposed joint portion 37c also serves as a second protection portion 62a for protecting the second electrode sheet 26. The configuration related to the second joint portion 37 and the second electrode sheet 26 is the same as the configuration related to the first joint portion 36 and the first electrode sheet 25, and thus redundant descriptions are omitted.

[0521] The rest is the same as in Embodiment 4-2, and redundant descriptions are omitted.

[0522] According to this embodiment, the first electrode sheet 25 is placed on the first surface 27 of the insulating sheet 24, and the first joint portion 36 formed in a layered manner is placed on the first electrode sheet 25. Next, the first joint portion 36 is pressed toward the insulating sheet 24. Then, the first joint portion 36 enters into the first opening 34a of the first electrode sheet 25 to become the first intrusion joint portion 36d. The first intrusion joint portion 36d is in contact with the first surface 27 of the insulating sheet 24 within the first opening 34a. The insulating sheet 24 and the first electrode sheet 25 are joined by the first intrusion joint portion 36d within the first opening 34a. Note that the operational effects of the second joint portion 37 and the second electrode sheet 26 are the same as those of the first joint portion 36 and the first electrode sheet 25, so overlapping explanations are omitted.

[0523] (Embodiment 4-4) Next, referring to FIG. 75 Embodiment 4-4 will be described. As shown in FIG. 75 The sensor sheet 18 according to this embodiment is different from Embodiment 4-1 in that the second electrode sheet 26 is not arranged on the second surface 28 side of the insulating sheet 24. Since the rest is the same as in Embodiment 4-1, overlapping explanations are omitted.

[0524] Although not shown in detail, the sensor sheet 18 according to Embodiment 4-2 and Embodiment 4-3 may also be configured such that the second electrode sheet 26 is not arranged on the second surface 28 side of the insulating sheet 24.

[0525] The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the gist thereof.

Claims

1. An insulating sheet (24) having a first surface (27) and a second surface (28) and formed of a foam, A conductive first electrode sheet (25) disposed on the first surface side of the insulating sheet and having a first through-opening (34a), A first bonding portion (36) for bonding the insulating sheet and the first electrode sheet, A conductive second electrode sheet (26) disposed on the second surface side of the insulating sheet and having a second through-opening (34b), A second bonding portion (37) for bonding the insulating sheet and the second electrode sheet, and The first electrode sheet and the second electrode sheet are conductive cloths in which a plurality of filament aggregates (72) are woven, The plurality of filament aggregates include a plurality of filaments (71) and a plating layer (33) formed on at least a part of the surface of the filaments, The first electrode sheet includes the first opening that opens between the plurality of filament aggregates, The second electrode sheet includes the second opening that opens between the plurality of filament aggregates, In the stress-strain curve in the tensile test, it is configured not to have a yield point showing a maximum value in the section where the strain is 0.5 to 10%, The opening ratio, which is the ratio of the opening area of the first opening to the area of the first electrode sheet, is 1% or more and 50% or less, The opening ratio, which is the ratio of the opening area of the second opening to the area of the second electrode sheet, is 1% or more and 50% or less, The filament aggregate further has an internal space (80) formed in at least a part between adjacent filaments, and is a sensor sheet (18).

2. The sensor sheet according to claim 1, wherein in the stress-strain curve, the maximum value of the stress when the strain is 0 to 5% is 0.5 MPa or less.

3. The sensor sheet according to claim 1, wherein in the stress-strain curve, the maximum value of the stress when the strain is 0 to 20% is 3 MPa or less.

4. The sensor sheet according to claim 1, wherein in the stress-strain curve, the maximum value of the stress when the strain is 0 to 5% is 5 MPa or less.

5. The sensor sheet according to claim 1, wherein the first electrode sheet is configured such that the maximum value of the stress in the stress-strain curve is 10 MPa or less when the strain is 0 to 20%.

6. The sensor sheet according to any one of claims 1 to 5, wherein the stress-strain curve is a stress-strain curve obtained by gripping a test piece of 20 mm × 90 mm and performing a tensile test at a tensile speed of 1 mm / s.

7. The sensor sheet according to any one of claims 1 to 5, wherein the cross section of the filament is non-circular.

8. The sensor sheet according to claim 7, wherein the cross section of the filament is polygonal.

9.

9. The sensor sheet according to any one of claims 1 to 5, wherein the plurality of filaments are arranged in the plane direction of the sheet surface of the first electrode sheet and in the normal direction of the sheet surface.

10.

10. The sensor sheet according to claim 9, wherein the internal space is formed in at least a part between the filaments adjacent to each other in the plane direction and in at least a part between the filaments adjacent to each other in the normal direction.

11.

11. The plating layer is formed on at least a part of the surface of the filament exposed to the internal space,

11. The part of the surface of the filament exposed to the internal space where the plating layer is not formed has the surface of the filament exposed. The sensor sheet according to any one of claims 1 to 5.

12. The plurality of filament aggregates include a warp filament aggregate and a weft filament aggregate,

12. The plating layer is formed on at least a part of the non-exposed portion (81) where the warp filament aggregate and the weft filament aggregate face each other and cross each other. The sensor sheet according to any one of claims 1 to 5.

13.

13. The plating layer is formed on at least a part of the surface of the filament exposed to the outer surface of the filament aggregate,

13. The part of the surface of the filament exposed to the outer surface of the filament aggregate where the plating layer is not formed has the surface of the filament exposed. The sensor sheet according to any one of claims 1 to 3.

14.

14. The plurality of filament aggregates include a warp filament aggregate (72a) and a weft filament aggregate (72b), In a portion where the warp filament aggregate and the weft filament aggregate intersect each other, the plating layer is formed on at least a part of a portion where the filament exposed on the outer surface of the warp filament aggregate and the filament exposed on the outer surface of the weft filament aggregate face each other, and the outer surface of the filament is exposed in a portion where the plating layer is not formed. The sensor sheet according to any one of claims 1 to 5.

15. The plating layer is a single layer made of nickel or a plurality of layers including a layer made of copper and a layer made of nickel. The sensor sheet according to any one of claims 1 to 5.

16. The sensor sheet further includes A protective portion (60) disposed on the outer surface of the first electrode sheet to protect the outer surface of the first electrode sheet. The sensor sheet according to any one of claims 1 to 5.

17. The first joint portion is interposed between the insulating sheet and the first electrode sheet. The sensor sheet according to claim 16.

18. The first joint portion includes an exposed joint portion (36a) exposed on the outer surface of the first electrode sheet, The exposed joint portion is disposed on the outer surface of the first electrode sheet and also serves as a protective portion for protecting the outer surface of the first electrode sheet. The sensor sheet according to any one of claims 1 to 5.

19. When the insulating sheet and the first electrode sheet are in direct contact, there is a direct region (38) where the first joint portion is not interposed between the insulating sheet and the first electrode sheet. The sensor sheet according to any one of claims 1 to 5.

20. The plurality of filament aggregates include a warp filament aggregate and a weft filament aggregate, The area of the portion where the warp filament aggregate and the weft filament aggregate intersect each other is larger than the opening area of the first opening in a state where no distortion occurs in the first electrode sheet. The sensor sheet according to any one of claims 1 to 5.

21. The first electrode sheet is formed to be long in the longitudinal direction, The first electrode sheet, The first electrode sheet includes an extension portion (31) extending in the extension direction from the long side edge along the longitudinal direction of the first electrode sheet, In the extension part, when the plurality of warp filament aggregates are projected in the thickness direction of the extension part, the occupied area is larger than the occupied area when the plurality of weft filament aggregates are projected in the thickness direction of the extension part. The sensor sheet according to claim 20.

22. The first electrode sheet is formed to be long in the longitudinal direction. The first electrode sheet is provided with an extension part extending in the extension direction from the long side edge along the longitudinal direction of the first electrode sheet. In the extension part, the angle α formed by the extension direction of the extension part and the longitudinal direction of the warp filament aggregate is smaller than the angle β formed by the extension direction of the extension part and the longitudinal direction of the weft filament aggregate. The sensor sheet according to claim 20.

23. The first electrode sheet is formed to be long in the longitudinal direction. The first electrode sheet is provided with an extension part extending in the extension direction from the long side edge along the longitudinal direction of the first electrode sheet. In the extension part, the angle α formed by the extension direction of the extension part and the longitudinal direction of the warp filament aggregate is larger than the angle β formed by the extension direction of the extension part and the longitudinal direction of the weft filament aggregate. The sensor sheet according to claim 20.

24. The first electrode sheet is formed to be long in the longitudinal direction. The first electrode sheet is provided with an extension part extending in the extension direction from the long side edge along the longitudinal direction of the first electrode sheet. In the extension part, the interval between adjacent filaments among the plurality of filaments constituting the weft filament aggregate is smaller than the interval between adjacent filaments among the plurality of filaments constituting the warp filament aggregate. The sensor sheet according to claim 20.

25. The first electrode sheet is formed to be long in the longitudinal direction. The first electrode sheet has a narrow-width part (35) that is narrower in width than other parts in the direction intersecting the longitudinal direction of the first electrode sheet. In the narrow-width part, when the plurality of warp filament aggregates are projected in the thickness direction of the narrow-width part, the occupied area is larger than the occupied area when the plurality of weft filament aggregates are projected in the thickness direction of the narrow-width part. The sensor sheet according to claim 20.

26. The first electrode sheet is formed to be long in the longitudinal direction. The first electrode sheet It has a narrow-width portion that is narrower in width than other portions in a direction intersecting the longitudinal direction of the first electrode sheet, In the narrow-width portion, the distance between adjacent filaments among the plurality of filaments constituting the weft filament aggregate is smaller than the distance between adjacent filaments among the plurality of filaments constituting the warp filament aggregate. The sensor sheet according to claim 20. [

27. ] The first electrode sheet is formed to be long in the longitudinal direction, The first electrode sheet, It has a narrow-width portion that is narrower in width than other portions in a direction intersecting the longitudinal direction of the first electrode sheet, The number of the plurality of filaments constituting the warp filament aggregate in the narrow-width portion is larger than the number of the plurality of filaments constituting the warp filament aggregate in a portion different from the narrow-width portion. The sensor sheet according to claim 20.

Images