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

Sensor sheet and method for manufacturing the same

[0001] The present invention relates to a sensor sheet and a method for manufacturing the sensor sheet.

[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 touched the steering wheel.

[0003] Japanese Patent Application Laid-Open No. 2019-68414

[0004] The sensor sheet described in Patent Document 1 has an issue with the reliability of the sensor detection accuracy. For example, when the sensor sheet is attached to a steering wheel, the sensor sheet is stretched while being wrapped around the steering wheel, which causes a problem that the conductive path of the first electrode sheet changes due to tensile stress, changing the electrical resistance value of the first electrode sheet.

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

[0006] One aspect of the present invention comprises: an insulating sheet having a first surface and a second surface and formed of a foam; a conductive first electrode sheet arranged on the first surface side of the insulating sheet and having a first opening passing therethrough; a first joint joining the insulating sheet and the first electrode sheet; a conductive second electrode sheet arranged on the second surface side of the insulating sheet and having a second opening passing therethrough; and a second joint joining the insulating sheet and the second electrode sheet; the first electrode sheet and the second electrode sheet are conductive cloths woven with a plurality of filament assemblies, the plurality of filament assemblies comprising a plurality of filaments and a plating layer formed on at least a portion of the surface of the filaments; the first electrode sheet has the first openings opening between the plurality of filament assemblies; and the second electrode sheet has second openings opening between the plurality of filament assemblies; a stress-strain curve in a tensile test is configured so as not to have a yield point showing a maximum value in the strain range of 0.5 to 10%; an opening ratio, which is the ratio of the opening area of ​​the first openings to the area of ​​the first electrode sheet, is 1% or more and 50% or less; The sensor sheet has an opening ratio, which is the ratio of the opening area of ​​the second opening to the area of ​​the second electrode sheet, of 1% to 50%.

[0007] Another aspect of the present invention is a method for manufacturing a sensor sheet, comprising the steps of: forming a filament assembly by bundling a plurality of filaments; forming a base fabric by knitting the plurality of filament assemblies; forming a conductive fabric by plating the base fabric; and forming a sensor sheet by joining the conductive fabric to the first surface of an insulating sheet made of an elastomer having a first surface and a second surface.

[0008] According to one aspect of the present invention, when a tensile force is applied to the sensor sheet, the first opening of the first electrode sheet and the second opening of the second electrode sheet deform, reducing the opening areas of the first opening and the second opening. This causes new conductive paths to form between the multiple filament assemblies that were previously separated by the first opening. Similarly, new conductive paths to form between the multiple filament assemblies that were previously separated by the second opening. This prevents changes in electrical resistance even when a tensile force is applied to the sensor sheet.

[0009] Furthermore, the sensor sheet according to one aspect of the present invention is configured so that the stress-strain curve in a tensile test does not have a yield point showing a maximum value in the strain range of 0.5 to 10%, which prevents the plating layer from breaking in the strain range of 0.5 to 10%, thereby preventing changes in the electrical resistance of the sensor sheet.

[0010] According to another aspect of the present invention, there are sensor sheets in which adjacent filaments are electrically connected by contacting each other with plating layers formed on their surfaces, and adjacent filaments are not formed with plating layers on their surfaces and are free to move relative to each other. As a result, when a tensile force is applied to the sensor sheet, the stress is absorbed by the filaments that can move relative to each other, preventing excessive stress from being applied to the sensor sheet. As a result, the electrical connection of the sensor sheet is maintained by the electrically connected filaments, preventing changes in the electrical resistance of the sensor sheet.

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

[0012] 5(a) is a partial enlarged plan view showing the first electrode sheet of Example 1-1, and (b) is a partial enlarged plan view showing the second electrode sheet of Example 1-1. FIG. 5(a) is a partial enlarged plan view showing the first electrode sheet of Example 1-1. FIG. 5(b) is a partial enlarged plan view showing the warp filament assembly of Example 1-1. FIG. 5(a) is a partial enlarged plan view showing the first electrode sheet of Example 1-2, and (b) is a partial enlarged plan view showing the second electrode sheet of Example 1-2. FIG. 5(a) is a partial enlarged plan view showing the first electrode sheet of Comparative Example 1-1, and (b) is a partial enlarged plan view showing the second electrode sheet of Comparative Example 1-1. FIG. 5(b) is a graph showing the relationship between stress and strain in a tensile test on a first electrode sheet. FIG. 5(b) is a graph showing the relationship between stress and strain in a tensile test on a sensor sheet. 5(a)-5(d) are cross-sectional views of a first electrode sheet according to a modification of Example 1-2, taken along line CC in FIG. 5(a). 5(b)-5(d) are cross-sectional views of a first electrode sheet according to a modification of Example 1-2, taken along line CC in FIG. 5(a). 5(b)-5(d) are cross-sectional views of a first electrode sheet according to a modification of Example 1-2, taken along line CC in FIG. 5(a). 5(c)-5(d) are cross-sectional views of a first electrode sheet according to a modification of Example 1-2, taken along line CC in FIG. 5(a). 19(a) is a partially enlarged plan view showing the first electrode sheet of Embodiment 2-1, and (b) is a partially enlarged plan view showing the second electrode sheet of Example 2-1. It is a cross-sectional view taken along line CC in FIG. 19. It is a partially enlarged plan view showing the first electrode sheet of Embodiment 2-2, and (b) is a partially enlarged plan view showing the second electrode sheet of Example 2-2. It is a cross-sectional view taken along line DD in FIG. 21.21(a) is a cross-sectional view of a first electrode sheet of a modified example (1) of Example 2-2, corresponding to line D-D in FIG. 21 . 21(b) is a cross-sectional view of a first electrode sheet of a modified example (2) of Example 2-2, corresponding to line D-D in FIG. 21 . 21(a) is a partially enlarged plan view showing a first electrode sheet of Comparative Example 2-1, and (b) is a partially enlarged plan view showing a second electrode sheet of Comparative Example 2-1. 21(b) is a cross-sectional view taken along line E-E in FIG. 25 . 21(b) is a graph showing the relationship between stress and strain when a tensile test is performed on a first electrode sheet. 21(b) is a graph showing the relationship between stress and strain when a tensile test is performed on a sensor sheet. 21(b) is a partially enlarged plan view showing a first electrode sheet of a sensor sheet according to Embodiment 2-1, when a tensile test is performed on the sensor sheet. 21(b) is a graph showing the relationship between DC resistance and strain when a tensile test is performed on a sensor sheet. 21(a) is a partially enlarged plan view showing a first electrode sheet of Example 3-1, and (b) is a partially enlarged plan view showing a second electrode sheet of Example 3-1. 21(b) is a cross-sectional view taken along line C-C in FIG. 31(a). 36A and 36B are partially enlarged plan views showing the first electrode sheet of Example 3-1; (a) is a partially enlarged plan view showing the first electrode sheet of Example 3-1; (b) is a partially enlarged plan view showing the second electrode sheet of Example 3-2; (a) is a partially enlarged plan view showing the first electrode sheet of Comparative Example 3-1; and (b) is a partially enlarged plan view showing the second electrode sheet of Comparative Example 3-1. A cross-sectional view taken along line D-D in FIG. 36; (b) is a graph showing the relationship between stress and strain in a tensile test on a first electrode sheet; and (c) is a graph showing the relationship between stress and strain in a tensile test on a sensor sheet. For Sample 3-2, (a) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 0%, (b) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 10%, (c) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 20%, and (d) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 30%. 10 is a graph showing the relationship between the rate of change in DC resistance and the strain of the sensor sheet, and the relationship between the rate of change in DC resistance and the number of repetitions when a 10% elongation tensile test is repeatedly performed on the sensor sheet.44. FIG. 44 is a graph showing the relationship between the rate of change in DC resistance value and the number of repetitions when a 20% elongation tensile test is repeated on a sensor sheet. FIG. 44 is a partially enlarged plan view showing a first electrode sheet of Embodiment 3-2. FIG. 44 is a cross-sectional view taken along line E-E in FIG. 44. FIG. 44 is a cross-sectional view taken along line F-F in FIG. 44. FIG. 44 is a plan view showing a sensor sheet of Embodiment 3-2, which is a plan view schematically showing a weave pattern of a plurality of warp filament assemblies and a plurality of weft filament assemblies. FIG. 44 is a cross-sectional view corresponding to the cross-section taken along line E-E in FIG. 44, showing a first electrode sheet of Embodiment 3-3. FIG. 44 is a cross-sectional view corresponding to the cross-section taken along line F-F in FIG. 44, showing a first electrode sheet of Embodiment 3-3. FIG. 44 is a partially enlarged plan view showing a first electrode sheet of Embodiment 3-4. FIG. 44 is a partially enlarged plan view showing a first electrode sheet of Embodiment 3-5. FIG. 44 is a partially enlarged plan view showing a first electrode sheet of Embodiment 3-6. FIG. 44 is a partially enlarged plan view showing a first electrode sheet of Embodiment 3-7. FIG. 44 is a plan view showing a sensor sheet of Embodiment 3-8. FIG. 44 is a plan view showing a sensor sheet of Embodiment 3-9. 59(a) is a partially enlarged plan view showing the first electrode sheet of Example 4-1, and (b) is a partially enlarged plan view showing the second electrode sheet of Example 4-1. FIG. 59(a) is a partially enlarged plan view showing the first electrode sheet of Example 4-2, and (b) is a partially enlarged plan view showing the second electrode sheet of Example 4-2. FIG. 59(b) is a graph showing the relationship between stress and strain in a tensile test on a first electrode sheet. FIG. 59(b) is a graph showing the relationship between stress and strain in a tensile test on a sensor sheet. Regarding sample 4-2, (a) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 0%, (b) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 10%, (c) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 20%, and (d) is a partially enlarged plan view of the first electrode sheet at an elongation rate of 30%. It is a graph showing the relationship between the rate of change in DC resistance value and strain of a sensor sheet. It is a graph showing the relationship between the rate of change in DC resistance value and the number of repetitions when a 10% elongation tensile test is repeated on a sensor sheet.67. (a) is a graph showing the relationship between the rate of change in DC resistance value and the number of repetitions when a 20% elongation tensile test is repeated on a sensor sheet. (a) is a partially enlarged plan view showing a first electrode sheet of a modified example of Embodiment 4-1, and (b) is a partially enlarged plan view showing a second electrode sheet of a modified example of Embodiment 4-1. (b) is a partially enlarged cross-sectional view taken along line D-D in FIG. 67. (c) is a partially enlarged plan view showing a first electrode sheet when a tensile test is performed on a modified example of Embodiment 4-1. (d) is a partially enlarged cross-sectional view corresponding to the cross-sectional view along line B-B in FIG. 57, showing a sensor sheet according to Embodiment 4-2. (e) is a partially enlarged cross-sectional view showing a sensor sheet according to Embodiment 4-2. (f) is a cross-sectional view corresponding to the cross-sectional view along line B-B in FIG. 57, showing a sensor sheet according to Embodiment 4-3. (f) is a partially enlarged cross-sectional view showing a sensor sheet according to Embodiment 4-3. (g) is a cross-sectional view corresponding to the cross-sectional view along line B-B in FIG. 57, showing a sensor sheet according to Embodiment 4-4.

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

[0014] The sensor sheet is attached to, for example, the steering wheel of a vehicle, and detects whether or not the occupant's hand (fingers, palm, back of the hand, etc.) is in contact with or approaching the steering wheel.

[0015] 1.1.2 Overall Configuration of Steering Wheel 10 First, the structure of the steering wheel 10 will be described with reference to Figures 1 and 2. As shown in Figure 1, the steering wheel 10 includes a core portion 11, a ring portion 12, and multiple (three in this embodiment) connection 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. The cross section of the ring portion 12 perpendicular to the axis is formed in a circular shape, for example, as shown in FIG.

[0017] 1.1.3 Detailed Configuration of Steering Wheel 10 The detailed configuration of the steering wheel 10 will be described with reference to Figures 1 and 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 forms the center 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 its axis. Here, the cross section of the core body 16 perpendicular to its axis is not limited to a circular shape, but can be any shape such as an elliptical shape, an egg shape, a U-shape, a C-shape, or a polygonal shape. The core body 16 in this embodiment is formed from a metal such as aluminum or magnesium and is conductive. Materials other than metals can also be used as the material of the core body 16.

[0019] The resin inner layer material 17 covers the outer surface of the core body 16 along the entire circumference of the ring shape of the core body 16 and along the entire circumference of the circular cross section of the core body 16. In this embodiment, the cross section of the resin inner layer material 17 is circular. If the core body 16 has a U-shaped cross section, the resin inner layer material 17 is filled not only on the radially outer side of the cross section of the core body 16 along the axis-perpendicular to the core body 16, but also in the U-shaped recess of the core body 16. The resin inner layer material 17 is injection molded on the outer surface of the core body 16 and directly bonded to the outer surface of the core body 16. The cross section of the resin inner layer material 17 along the axis-perpendicular to the core body 16 is not limited to a circular shape, but can be any shape, such as an oval, elliptical, or polygonal shape. The resin inner layer material 17 is molded, for example, from a foamed resin. For example, a foamed urethane resin is used for the resin inner layer material 17. Note that a non-foamed resin may also be used for the resin inner layer material 17.

[0020] A sensor sheet 18 is wrapped around the outer surface of the resin inner layer material 17. The sensor sheet 18 forms a C-shape when wrapped 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 outer surface of the sensor sheet 18 (the surface of the sensor sheet 18 opposite the resin inner layer material 17) around the entire ring-shaped circumference of the sensor sheet 18. In other words, as will be described later, the skin material 19 also functions as a covering for the first electrode sheet 25 when the first electrode sheet 25 is exposed on the first surface 27 of the insulating sheet 24. The skin material 19 is formed by injection molding, and is wrapped around and joined to the outer surface of the sensor sheet 18. The skin material 19 is formed from, for example, a urethane resin. The outer surface of the skin material 19 forms a design surface. The material of the skin material 19 is not particularly limited, and it is preferable to use, for example, a non-foamed urethane resin or a slightly foamed urethane resin.

[0022] As another embodiment of the cover material 19, leather or cloth may be used for the cover material 19, which is wrapped around the outer surface of the sensor sheet 18 and bonded to the outer surface of the sensor sheet 18. An adhesive or glue may be used to bond the cover material 19 to the sensor sheet 18, and the cover material 19 may be sewn to cover the periphery of the steering wheel. The outer surface of the cover material 19 forms a decorative surface. The material of the cover material 19 is not particularly limited, and any material can be selected, such as leather (natural leather, synthetic leather, etc.), cloth, rubber, or resin, but leather (natural leather, synthetic leather, etc.) is preferred for the cover material 19.

[0023] 1.1.4. Overall Configuration of Sensor Sheet 18 The overall configuration of the sensor sheet 18 of embodiment 1-1 will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the sensor sheet 18 is formed into an elongated shape in the longitudinal direction X as a whole. The sensor sheet 18 includes a sheet main body 20 formed into an overall rectangular shape. The sheet main body 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, arrow X indicates the longitudinal direction of the sensor sheet 18, arrow Y indicates the intersecting direction intersecting the longitudinal direction, and arrow Z indicates the thickness direction of the sensor sheet 18.

[0024] A seat recess 21 is formed in the pair of long side edges 20a of the seat main body 20, recessed inward in the transverse direction Y that intersects with the longitudinal direction X. The seat recess 21 is formed in a position that includes an overlapping region of the pair of long side edges 20a of the seat main body 20 in the transverse direction Y. However, the seat recess 21 may be formed in only one of the pair of long side edges 20a.

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

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

[0027] 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 formed in layers.

[0028] The first electrode sheet 25 is disposed on the first surface 27 side of the insulating sheet 24. More 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 to but 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 , the first electrode sheet 25 has a recess 30 recessed inward in the transverse direction Y at a position corresponding to the sheet recess 21 of the sensor sheet 18. The first electrode sheet 25 has an extension 31a extending from a long side edge of the first electrode sheet 25 along the longitudinal direction X in an extension direction E1 that intersects the longitudinal direction X, and an extension 31b extending in the extension direction E2. A core wire 32a exposed from an end of an electric wire 32 is connected to the extensions 31a and 31b. The core wire 32a and the extensions 31a and 31b are electrically connected by a known method such as soldering, brazing, or ultrasonic welding. In the following description, when the extensions 31a and 31b are not to be distinguished from each other, they may be referred to as extensions 31.

[0030] 4 , the second electrode sheet 26 is disposed on the second surface 28 side of the insulating sheet 24. More 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 to but 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 be the same shape and size, or may be similar shapes with one being slightly larger than the other. In this embodiment, the first electrode sheet 25 and the second electrode sheet 26 have approximately the same configuration.

[0032] The second electrode sheet 26 has substantially the same configuration as the first electrode sheet 25, and therefore, in the following description, overlapping descriptions may be omitted.

[0033] The insulating sheet 24 is flexible and can be stretched in the planar direction. The insulating sheet 24 may be formed of, for example, a foamed resin or an elastomer as a main component. Therefore, the insulating sheet 24 is flexible.

[0034] When the insulating sheet 24 is formed with a foamable resin as its main component, the insulating sheet 24 can be manufactured from, for example, a resin or elastomer foam. Elastomers include cross-linked rubber and thermoplastic elastomers. Examples of the elastomer include 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 resin foam, melamine foam, polymethacrylimide foam, and fluororesin foam.

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

[0036] Furthermore, the insulating sheet 24 may contain rubber, resin, or other materials other than thermoplastic elastomer. For example, if 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, the insulating sheet 24 may contain a flexibility-imparting component such as a plasticizer. Furthermore, the insulating sheet 24 may be composed mainly of a reactive curing elastomer or a thermosetting elastomer.

[0037] Furthermore, a material with good thermal conductivity is preferable for the insulating sheet 24. Therefore, the insulating sheet 24 may be made of a thermoplastic elastomer with high thermal conductivity, or may contain a filler that can increase thermal conductivity. The insulating sheet 24 may also have a foam structure with fine air layers. Furthermore, the insulating sheet 24 may have perforations (regular physical holes, such as perforations) or slits (slits, notches).

[0038] The first electrode sheet 25 is disposed on a first surface 27 of the insulating sheet 24, i.e., on the upper surface side of the insulating sheet 24 (the upper surface in FIG. 4 ), and the second electrode sheet 26 is disposed on a second surface 28 of the insulating sheet 24, i.e., on the lower surface side of the insulating sheet 24 (the lower surface in FIG. 4 ). At least the first electrode sheet 25 constitutes a detection electrode. The first electrode sheet 25 and the second electrode sheet 26 are conductive. 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 are flexible and configured to be extensible in the planar direction.

[0039] 1.1.5. Bonding Structure of First Electrode Sheet 25 and Second Electrode Sheet 26 with Insulating Sheet 24 As shown in FIG. 4 , the first electrode sheet 25 is bonded to the first surface 27 of the insulating sheet 24 by a first bonding portion 36. The material constituting the first bonding portion 36 is not particularly limited and can be appropriately selected from any material, such as an acrylic adhesive, a silicone adhesive, a urethane adhesive, or a rubber adhesive. Also, as shown in FIG. 4 , the second electrode sheet 26 is bonded to the second surface 28 of the insulating sheet 24 by a first bonding portion 36. The material constituting the second bonding portion 37 is the same as that of the first bonding portion 36, so a redundant description will be omitted.

[0040] 1.1.6. Configuration of the Electrode Sheet The configuration of the electrode sheet will be described with reference to FIGS. 5(a) to 5(b) and 9(a) to 9(b). The first electrode sheets 25, 25a shown in FIGS. 5(a) to 5(b) and the second electrode sheets 26, 26a shown in FIGS. 9(a) to 9(b) are conductive cloths. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a are flexible while being conductive. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a are stretchable in the longitudinal direction X and the transverse direction Y.

[0041] The first electrode sheet 25 and the second electrode sheet 26 are conductive cloths woven with a plurality of filament assemblies 72. The filament assemblies 72 include a plurality of filaments 71 and a plating layer 33 formed on at least a portion of the surface of the filaments 71.

[0042] 5(a) to 5(b) and 9(a) to 9(b), the first electrode sheets 25, 25a and the second electrode sheets 26, 26a are manufactured by forming a plating layer 33 on a base fabric woven with a plurality of untwisted bundled yarns 74. Each untwisted bundled yarn 74 is formed by bundling a plurality of filaments 71 together in an untwisted state.

[0043] Examples of resins that can be used to form the filaments 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 that can be used to form the filaments 71 are not limited to the above, and any resin can be selected as appropriate. The second electrode sheet 26 also has a similar configuration.

[0044] The method for forming the plating layer 33 is not particularly limited, and may be, for example, electrolytic plating, electroless plating, electroless plating followed by electrolytic plating, or electroless plating followed by electrolytic plating; any method can be selected as appropriate.

[0045] The metal constituting the plating layer 33 formed on the surface of the base fabric can be selected from any metal or alloy, such as copper, nickel, tin, or solder. The plating layer 33 formed on the surface of the base fabric can be composed of one metal type or multiple metal types. For example, the surface of the base fabric can be plated with only copper, or only nickel, or a copper plating layer made of copper can be formed on the surface of the base fabric, and then a nickel plating layer made of nickel can be formed on the surface of this copper plating layer. The plating layer 33 formed on the surface of the base fabric can be formed by electrolytic plating or electroless plating. The second electrode sheet 26 has a similar configuration.

[0046] 5( a) and 9(a), the first electrode sheet 25, 25a has first openings 34a that open between the multiple filament assemblies 72. The first openings 34a penetrate the first electrode sheet 25. A first opening ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25, 25a to the area of ​​the first electrode sheet 25, 25a, is 1% or more and 40% or less.

[0047] 5(b) and 9(b), the second electrode sheet 26, 26a has second openings 34b that open between the multiple filament assemblies 72. The second openings 34b penetrate the second electrode sheet 26. A second opening ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26, 26a to the area of ​​the second electrode sheet 26, 26a, is equal to or greater than 1% and equal to or less than 40%.

[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 Example 1-1 will be described with reference to FIGS. 5 to 8. 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 assemblies 72. The plurality of filament assemblies 72 include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled together in an untwisted state, and a plating layer 33 formed on at least a portion of the surface of the untwisted yarn bundle 74. The filament assemblies 72 are 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 warp yarns in which a plurality of filaments 71 are gathered together in an untwisted state and weft yarns in which a plurality of filaments 71 are gathered together in an untwisted state to form a base fabric, and then forming a plating layer 33 on the surface of this base fabric. However, the method for manufacturing 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 assemblies 72a and a plurality of weft filament assemblies 72b. The first electrode sheet 25 includes first openings 34a that open between the plurality of filament assemblies 72a. The first openings 34a penetrate the first electrode sheet 25. In this Example 1-1, the aperture ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25 to the area of ​​the first electrode sheet 25, is approximately 3%. Note that this aperture ratio is the ratio of the total opening area of ​​the plurality of first openings 34a formed in a target area of ​​the first electrode sheet 25 to the area of ​​the target area of ​​the first electrode sheet 25. This aperture ratio is calculated, for example, by identifying a 10 mm × 10 mm target area on the first electrode sheet 25, adding up the areas of the first openings 34a within the target area, and dividing the total area by the area of ​​the target area.

[0051] 5(b), the second electrode sheet 26 of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The second electrode sheet 26 of this embodiment includes second openings 34b that open between the plurality of filament assemblies 72. The second openings 34b penetrate the second electrode sheet 26. In this Example 1-1, the opening ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26 to the area of ​​the second electrode sheet 26 of this embodiment, is approximately 3%.

[0052] There is no particular limitation on the number of filaments 71 included in the filament assembly 72 that constitutes the first electrode sheet 25. The filament assembly 72 according to this embodiment includes 75 filaments 71, but the number may be any number.

[0053] 6, a plated layer 33 is formed on at least a portion of the surface of the twisted wires 73 that make up the filament assembly 72. The plated layer 33 of the warp filament assembly 72a and the plated layer 33 of the weft filament assembly 72b come into contact with each other, thereby electrically connecting the warp filament assembly 72a and the weft filament assembly 72b.

[0054] As shown in FIG. 5( a), the longitudinal direction S of the multiple warp filament assemblies 72a and the longitudinal direction X of the first electrode sheet 25 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 25 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 25. 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 25a. The angle being substantially 45° includes cases where the angle is 45° and also cases where it can be determined that the angle is substantially 45°.

[0055] When the longitudinal direction S of the warp threads 41 is parallel to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 0°), stretching the first electrode sheet 25 parallel to the direction X results in the warp threads 41 themselves being stretched, requiring a large load.

[0056] On the other hand, when the longitudinal direction S of the warp threads 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°), stretching the first electrode sheet 25 parallel to the longitudinal direction X causes the square or rectangular lattice formed by the weft threads 42 and the warp threads 41 to deform into a diamond shape, and the warp threads 41 or the weft threads 42 themselves are not stretched, so no large load is required. In other words, 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 deform into a diamond shape, and structural flexibility is less likely to be impaired.

[0057] However, the longitudinal direction S of the multiple warp filament assemblies 72a may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25. Furthermore, the longitudinal direction T of the multiple weft filament assemblies 72b may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25.

[0058] The number of filaments 71 constituting the warp filament assembly 72a and the number of filaments 71 constituting the weft filament assembly 72b may be the same or different. In this embodiment 1-1, the number of filaments 71 constituting the warp filament assembly 72a and the number of filaments 71 constituting the weft filament assembly 72b are set to be substantially the same. "Substantially the same" includes cases where they are the same, and also includes cases where they are not the same but can be recognized as being substantially the same. The same applies to the weft filament assembly 72b, so a duplicated description will be omitted.

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

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

[0061] A plating layer 33 is formed on at least a portion of the surface of the filament 71 that is exposed to the internal space 80. The surface of the filament 71 is exposed in the internal space 80 where the plating layer 33 is not formed.

[0062] 6, a plating layer 33 is formed on at least a portion of the non-exposed portion 81 where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect. On the other hand, the surface of the filament 71 exposed in the non-exposed portion 81 has no plating layer 33 formed thereon, and the surface of the filament 71 is exposed in that portion.

[0063] At the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect with each other, a plating layer 33 is formed on at least a portion of the portion where the filaments 71 exposed on the outer surface of the warp filament aggregate 72a and the filaments exposed on the outer surface of the weft filament aggregate 72b face each other, and the outer surface of the filaments 71 is exposed in the portion where the plating layer 33 is not formed.

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

[0065] The cross-sectional area A1 of each warp filament assembly 72a shown in FIG. 8 is larger than the opening area A2 of the first opening 34a shown in FIG. 7 when the first electrode sheet 25 is not distorted. The cross-sectional area A1 of the warp filament assembly 72a refers to the cross-sectional area formed by the outline of the warp filament assembly 72a. The same applies to the weft filament assembly 72b below. Although not shown in detail, the cross-sectional area A1 of each weft filament assembly 72b is larger than the opening area A2 of the first opening 34a when the first electrode sheet 25 is not distorted. Although not shown in detail, in the second electrode sheet 26, the cross-sectional area A1 of each warp filament assembly 72a and the cross-sectional area A1 of each weft filament assembly 72b are larger than the opening area A2 of the second opening 34b when the second electrode sheet 26 is not distorted.

[0066] As shown in Fig. 7, an intersection area A3, which is the area of ​​the portion where the warp filament aggregate 72a and the weft filament aggregate 72b intersect with each other, when viewed from the thickness direction of the first electrode sheet 25, is larger than the opening area A2 of the first opening 34a shown in Fig. 7. Furthermore, although not shown in detail, as 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 with each other, is larger than the opening area A2 of the second opening 34b.

[0067] The same applies to the weft filament assembly 72b as above, so a duplicated description will be omitted.

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

[0069] As shown in FIG. 4 , the first electrode sheet 25 described above is bonded to a first surface 27 of an insulating sheet 24 via a first bonding portion 36. A second electrode sheet 26 having a configuration similar to that of the first electrode sheet 25 is bonded to a second surface 28 of the insulating sheet 24 via a second bonding portion 37. The insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first bonding portion 36 is 50 μm. The first bonding portion 36 and the second bonding portion 37 are identical, so a redundant description will be omitted. In this manner, a sample 1 of a sensor sheet 18 relating 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, the configurations of the first electrode sheet 25a and the second electrode sheet 26a according to Example 1-2 will be described with reference to FIGS. 9(a) and 9(b). In the first electrode sheet 25a according to this Example 1-2, the number of filaments 71 constituting the warp filament assembly 72a is different from the number of filaments 71 constituting the weft filament assembly 72b. In this Example 1-2, the number of filaments 71 constituting the warp filament assembly 72a is greater than the number of filaments 71 constituting the weft filament assembly 72b. However, the number of filaments 71 constituting the warp filament assembly 72a may be less than the number of filaments 71 constituting the weft filament assembly 72b.

[0071] In this Example 1-2, the number of filaments 71 constituting the warp filament aggregate 72a is set to approximately twice the number of filaments 71 constituting the weft filament aggregate 72b. However, the difference between 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] The second electrode sheet 26a has the same configuration as the first electrode sheet 25a, and therefore a duplicated description 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 approximately 10 μm. The metal constituting the plating layer 33 is a single layer of Ni. 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.

[0074] The configuration other than the above is the same as in Example 1-1, so a duplicated description will be omitted.

[0075] In addition, in this sample 1-2, the insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive. The thickness of the first bonding portion 36 is approximately 50 μm. The first bonding portion 36 and the second bonding portion 37 are identical, so a duplicated description will be omitted. Except for the above, sample 1-2 of the sensor sheet 18 relating to the first electrode sheet 25a and the second electrode sheet 26a of Example 1-2 is produced in the same manner as sample 1-1. A duplicated description of sample 1-1 will be omitted.

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

[0077] 10( a), the first electrode sheet 25b of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The first electrode sheet 25b includes first openings 34a that open between the plurality of filament assemblies 72a. The first openings 34a penetrate 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 openings 34a formed in the first electrode sheet 25b to the area of ​​the first electrode sheet 25b, is 20%.

[0078] 10(b), the second electrode sheet 26b of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The second electrode sheet 26b of this embodiment includes second openings 34b that open between the plurality of filament assemblies 72a. The second openings 34b penetrate 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 openings 34b formed in the second electrode sheet 26b to the area of ​​the second electrode sheet 26 of this embodiment, is 20%.

[0079] In this 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 middle layer being Cu, and the innermost layer (on the filament 71 side) being Ni. The diameter of the warp filament aggregate 72a is approximately 70 μm, and the diameter of the weft filament aggregate 72b is approximately 70 μm.

[0080] The configuration other than the above is the same as that of embodiment 1-1, so a duplicated description will be omitted.

[0081] In Comparative Example 1-1, the insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first bonding portion 36 is 50 μm. The first bonding portion 36 and the second bonding portion 37 are identical, so a duplicated description will be omitted. Sample 1-3 of the sensor sheet 18 including the first electrode sheet 25b and the second electrode sheet 26b of Sample 1-3 is produced in the same manner as Sample 1-1. A duplicated description of Sample 1-1 will be omitted.

[0082] 1.1.7.4. Tensile Test of First Electrode Sheet Next, with reference to FIG. 11 , a 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 measuring 150 mm x 20 mm to prepare test specimens. The thickness of the first electrode sheet varied between Examples 1-1 to 1-2 and Comparative Example 1-1, but was approximately 0.1 mm. The angle between the longitudinal direction of the test specimen and the longitudinal direction of the warp filament assembly 72a was set to 45°.

[0083] The test specimen is held by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is performed on the test specimen at a tensile speed of 1 mm / sec, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test specimen. The tensile tester is an AGS-X 1 kN model manufactured by Shimadzu Corporation. The tensile test is performed in a strain range of 0 to 20%. Figure 11 shows a graph showing the change in stress versus strain.

[0084] In Examples 1-1 and 1-2, the stress increased slowly and monotonically in the strain range of 0 to 20%. In Examples 1-1 and 1-2, the stress-strain curve in the tensile test does not have a yield point showing a maximum value in the strain range of 0.5 to 10%.

[0085] Example 1-1 exhibits a stress of approximately 1.4 MPa when the strain is 5%, and a stress of approximately 7.5 MPa when the strain is 20%. Example 1-2 exhibits a stress of approximately 0.9 MPa when the strain is 5%, and a stress of approximately 5.9 MPa when the strain is 20%. The first electrode sheets 25, 25a according to the sample examples and sample examples have a maximum stress of 3 MPa or less when the strain is 0 to 5%, and a maximum stress of 15 MPa or less when the strain is 0 to 20%.

[0086] Comparative Example 1-1 has a yield point with a maximum value in the 0.5 to 10% strain range in the stress-strain curve in the tensile test. In the 0 to approximately 1% strain range, the stress increased monotonically and linearly. At approximately 1% strain, the stress reached a maximum value of approximately 17 MPa and then rapidly decreased to approximately 12 MPa. Thus, in Comparative Example 1-1, the stress changed from an increasing trend to a decreasing trend before and after the strain reached approximately 1%. Thereafter, in the approximately 1 to approximately 13% strain range, the stress decreased monotonically from approximately 12 to approximately 10 MPa. Thereafter, in the approximately 13 to 20% strain range, the stress increased monotonically from approximately 10 to approximately 12 MPa. Thus, in Comparative Example 1-1, the maximum stress in the 0 to 5% strain range was greater than 3 MPa, and the maximum stress in the 0 to 20% strain range was greater than 15 MPa in the stress-strain curve.

[0087] 1.1.7.5. Tensile Test of Sensor Sheet Next, we will explain the tensile test performed on the sensor sheet. Test pieces were prepared by cutting the sensor sheets of Samples 1-1 to 1-2 and Sample 1-3 into 90 mm x 20 mm strips. The thickness of the sensor sheet varied between Samples 1-1 to 1-2 and Sample 1-3, but was approximately 1 mm. The angle between the longitudinal direction of the test piece and the longitudinal direction of the warp filament assembly 72a constituting the first electrode sheet and the second electrode sheet was set to 45°.

[0088] An electric wire is connected to one longitudinal end of the first electrode sheet and connected to a DC power supply, and an electric wire is connected to the other longitudinal end of the first electrode sheet and connected to a voltage measuring instrument.

[0089] The test piece is held 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, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test piece. During the tensile test, the DC resistance value (an example of an electrical resistance value) of the sensor sheet is calculated from the voltage of the DC power supply and the voltage drop across the sensor sheet.

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

[0091] Sample 1-1 exhibits a stress of approximately 0.5 MPa at a strain of 5%, and a maximum stress of approximately 2.6 MPa at a strain of 20%. Sample 1-2 exhibits a stress of approximately 0.3 MPa at a strain of 5%, and a maximum stress of approximately 1.5 MPa at a strain of 20%. In the stress-strain curves of Samples 1-1 and 1-2, the maximum stress values ​​are 0.5 MPa or less at strains of 0 to 5%, and 3 MPa or less at strains of 0 to 20%.

[0092] In the stress-strain curves of Samples 1-1 and 1-2, the stress is 0.5 MPa or less when the strain is 0 to 5%, and the maximum stress is 3 MPa or less when the strain is 0 to 20%.

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

[0094] When a tensile force is applied to Samples 1-1 and 1-2, the first openings 34a in the first electrode sheet expand in the tensile direction and contract in a direction intersecting the tensile direction. Figure 13 shows the deformation of the first openings 34a using Sample 1-2 as an example. As shown in Figure 13(a), the first openings 34a are open at an elongation rate of 0%. However, as the elongation rate increases to 10% (see Figure 13(b)), 20% (see Figure 13(c)), and 30% (see Figure 13(d)), the gaps between the fibers of the conductive cloth decrease, and at an elongation rate of 30%, the first openings 34a almost disappear. This change in fiber shape allows for easy elongation, which is thought to reduce the stress generated during elongation. In other words, the presence of the first openings 34a is thought to contribute to the structural flexibility of the fibers. The above configuration is similar for the second electrode sheet, so a description thereof will be omitted. The same is true for Sample 1-1, so a description thereof will be omitted.

[0095] In addition, since the opening ratio of sample 1-2 is larger than that of sample 1-1, the opening area decreases due to a change in the spatial arrangement of the entire filament 71 when stretched, thereby exhibiting structural flexibility in terms of expansion and contraction, and therefore generating less stress than sample 1-1.

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

[0097] In Samples 1-1 and 1-2, when a tensile force is applied to the sensor sheet, it is believed that the tensile force is absorbed by the gradual deformation of the first openings 34a. As a result, the relative positions of the warp filament aggregates 72a and the weft filament aggregates 72b do not change significantly at the intersections between the warp filament aggregates 72a and the weft filament aggregates 72b, and therefore the electrical connection between the warp filament aggregates 72a and the weft filament aggregates 72b is maintained. As a result, in Samples 1-1 and 1-2, it is believed that the DC resistance value changes very little even when a tensile force is applied to the sensor sheet.

[0098] Furthermore, Samples 1-1 and 1-2 do not have a yield point with a maximum value in the strain range of 0.5 to 5%. This is thought to be because Samples 1-1 and 1-2 do not experience a significant change in the structure of the plating layer 33 formed on the first electrode sheet and the second electrode sheet in the strain range of 0.5 to 5%. This suppresses changes in the electrical resistance value of the sensor sheet 18.

[0099] On the other hand, Sample 1-3 has a yield point that shows a maximum value in the strain range of 0.5 to 5%. In Sample 1-3, it is believed that the plating layer 33 formed at the intersection of the warp filament aggregate 72a and the weft filament aggregate 72b is maintained in the strain range from 0% to the yield point, causing elastic deformation. It is believed that the plating layer 33 formed at the intersection of the warp filament aggregate 72a and the weft filament aggregate 72b is then destroyed at the yield point.

[0100] Thereafter, in the section where the stress does not change much (the section where the strain is approximately 5 to approximately 15%), it is thought that the tensile force is absorbed by the deformation of the first opening 34a and the second opening 34b, as in Sample 1-1 and Sample 1-2.

[0101] Thereafter, when the strain becomes larger than about 15%, the first openings 34a and the second openings 34b are completely blocked because the first opening ratio and the second opening ratio of Sample 1-3 are 20%, and it is believed that the tensile force acting on the first electrode sheet and the second electrode sheet can no longer be absorbed, which is believed to increase the stress.

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

[0103] The test piece is held 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 wires is measured. The DC resistance value is used to calculate the rate of change in DC resistance based on the following formula (1). The DC resistance value is measured using a 2000 series digital multimeter manufactured by Keithley Corporation. The above test is performed on Samples 1-1 to 1-2 and Sample 1-3.

[0104]

[0105] 13 is a graph showing the change in DC resistance value with strain. The DC resistance value change of Sample 1-1 increased in the strain range of 0 to approximately 2%, and at a strain of approximately 2%, the DC resistance value change was approximately 5%. Thereafter, the DC resistance value change decreased in the strain range of approximately 2 to approximately 5%, and the DC resistance value change was approximately 0%. Thereafter, at a strain of approximately 25% or more, the DC resistance value change gradually increased, and at a strain of 30%, the DC resistance value change was approximately 7%. Thus, the DC resistance value change of Sample 1-1 was 10% or less in the strain range of 0 to 30%.

[0106] The DC resistivity change rate of Sample 1-2 increased in the strain range of 0 to approximately 3%, and at a strain of approximately 3%, the DC resistivity change rate was approximately 10%. Thereafter, the DC resistivity change rate decreased in the strain range of approximately 3 to approximately 5%, and reached approximately 0%. Thereafter, even at a strain of 30%, the DC resistivity change rate was approximately 0%. Thus, the DC resistivity change rate of Sample 1-2 was 10% or less in the strain range of 0 to 30%.

[0107] The DC resistance change rate of Sample 1-3 was approximately 2% in the strain range of 0 to approximately 3%. Thereafter, in the strain range of approximately 3 to 30%, the DC resistance change rate monotonically increased, reaching approximately 130% at a strain of 30%. Thus, the DC resistance change rate of Sample 1-3 was greater than 10% in the strain range of 0 to 30%, and the resistance change during extension was significantly greater than that of Samples 1-1 and 1-2.

[0108] 1.7.7. Change in DC Resistance of Sensor Sheet at 10% Elongation Next, the change in DC resistance of the sensor sheet at 10% elongation was measured. To measure the change in DC resistance of the sensor sheet described above, the sensor sheet was stretched 10% relative to the reference length (50 mm) before the tensile force was applied to the sensor sheet, then returned to the reference length, and again stretched 10%. This test was repeated a predetermined number of times. The number of repetitions in this test was 1, 5, and 10. The change in DC resistance was calculated based on the above formula (1) for the DC resistance values ​​at this time. The above test was performed on Samples 1-1, 1-2, and 1-3.

[0109] 15 shows a graph showing the relationship between the number of repetitions of the extension test and the rate of change in DC resistance. For Sample 1-1, the rate of change in DC resistance at the first measurement was approximately 0%. Thereafter, as the number of repetitions increased, the rate of change in DC resistance increased to approximately 36% after one repetition, approximately 48% after five repetitions, and approximately 57% after ten repetitions. After ten repetitions, the rate of change in DC resistivity for Sample 1-1 was 60% or less.

[0110] For Sample 1-2, the DC resistivity change rate at the initial measurement was approximately 14%, which was larger than that of Sample 1-1. However, the DC resistance change rate did not increase significantly with increasing number of repetitions, being approximately 9% after one repetition and approximately 15% after five repetitions. After 10 repetitions, the DC resistance change rate for Sample 1-2 was approximately 30%. After 10 repetitions, the DC resistance change rate for Sample 1-2 was 50% or less.

[0111] The rate of change in DC resistance value of Sample 1-3 at the initial measurement was approximately 0%, which was the same as that of Sample 1-1. However, as the number of repetitions increased, the rate of change in DC resistance value increased to approximately 61% after one repetition, approximately 89% after five repetitions, and approximately 115% after ten repetitions, and was therefore greater than that of Samples 1-1 and 1-2.

[0112] As described above, it was found that the sensor sheets of Samples 1-1 and 1-2 showed smaller changes in DC resistance value than Sample 1-3, even when the 10% elongation test was repeated.

[0113] 1.1.7.8. Rate of change in DC resistance value of sensor sheet when stretched by 20% Next, for Samples 1-1 to 1-2 and Sample 1-3, the rate of change in DC resistance value when the sensor sheet is stretched by 20% is measured.

[0114] 16 shows a graph showing the relationship between the number of repetitions of the extension test and the rate of change in DC resistance. For Sample 1-1, the rate of change in DC resistance at the first measurement was approximately 0%. Thereafter, the rate of change in DC resistance increased as the number of repetitions increased, to approximately 35% after one repetition and approximately 91% after five repetitions. After 10 repetitions, the rate of change in DC resistance was approximately 137%.

[0115] The DC resistivity change rate of Sample 1-2 at the first measurement was about 10%, which was larger than that of Sample 1-1, but the DC resistivity change rate did not increase much with increasing number of repetitions, about 27% after 1 repetition and about 32% after 5 repetitions. After 10 repetitions, the DC resistivity change rate of Sample 1-2 was about 55%.

[0116] The DC resistance change rate of Sample 1-3 at the first measurement was about 0%, which was the same as that of Sample 1-1. However, it showed about 114% after one repetition and exceeded 200% after five repetitions.

[0117] As described above, it was found that the sensor sheets of Samples 1-1 and 1-2 showed smaller changes in DC resistance value than Sample 1-3, even when the 20% elongation test was repeated.

[0118] 1.1.7.9 Modification 1 of Embodiment 1-1 As shown in FIG. 17 , the cross-sectional shape of the filament 71 according to Modification 1 of Embodiment 1-1 is formed into a hexagonal shape. However, the cross-sectional shape of the filament 71 may be a triangle, a rectangle, a pentagon, or a polygon with seven or more sides. Furthermore, the cross-sectional shape of the filament 71 does not have to be a regular polygon. Furthermore, the cross-sectional shapes of the multiple filaments 71 do not have to be of one type; for example, some may be formed into a rectangle and the other parts may be formed into a pentagon.

[0119] 1.1.7.10 Modification 2 of Embodiment 1-1 As shown in Fig. 18, the cross-sectional shape of the filament 71 according to Modification 2 of Embodiment 1-1 may be non-circular, for example, may be elliptical. In addition, the cross-sectional shape of the filament 71 may be any shape, such as a track shape or an irregular shape with a different maximum diameter of the inscribed circle.

[0120] Furthermore, the cross-sectional shape of the plurality of filaments 71 does not have to be of one type. For example, some may be formed in a polygonal shape and other parts may be formed in an oval shape.

[0121] 1.1.8. Effects of the Present Embodiment Next, the effects of the present embodiment will be described. The sensor sheet 18 according to this embodiment includes an insulating sheet 24, a first electrode sheet 25, a first bonding portion 36, a second electrode sheet 26, and a second bonding 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, is disposed on the first surface 27 side of the insulating sheet 24, and has a first opening 34a extending therethrough. The first bonding portion 36 bonds the insulating sheet 24 and the first electrode sheet 25. The second electrode sheet 26 is conductive, is disposed on the second surface 28 side of the insulating sheet 24, and has a second opening 34b extending therethrough. The second bonding portion 37 bonds the insulating sheet 24 and the second electrode sheet 26. The first electrode sheet 25 and the second electrode sheet 26 are conductive cloths woven with a plurality of filament assemblies 72. The plurality of filament assemblies 72 include a plurality of filaments 71 and a plating layer 33 formed on at least a portion of the surface of the filaments 71. The first electrode sheet 25 includes first openings 34a that open between the plurality of filament assemblies 72. The second electrode sheet 26 includes second openings 34b that open between the plurality of filament assemblies 72. The sensor sheet 18 is configured so that a stress-strain curve in a tensile test does not have a yield point that shows a maximum value in the strain range of 0.5 to 10%. The aperture ratio, which is the ratio of the opening area of ​​the first openings 34a to the area of ​​the first electrode sheet 25, is 1% or more and 50% or less. The aperture ratio, which is the ratio of the opening area of ​​the second openings 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 18, the first openings 34a of the first electrode sheet 25 deform, reducing the opening area of ​​the first openings 34a. This forms a new conductive path 72 between the multiple filament assemblies that were previously separated by the first openings. This prevents changes in the electrical resistance value even when a tensile force is applied to the sensor sheet 18. The same applies to the second openings 34b of the second electrode sheet 26.

[0123] The opening ratio of the first opening 34a is preferably 1% or more and 50% or less. With an opening ratio of 50% or less, when the first opening 34a is deformed in a direction that reduces the opening area, the multiple filament assemblies 72 tend to come into contact with each other. Because the multiple filament assemblies 72 tend to come into contact with each other in this way, the opening 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 even more preferably 1% or more and 30% or less. The opening ratio of the second opening 34b is the same as that of the first opening 34a.

[0124] Furthermore, the sensor sheet according to this embodiment is configured so that the stress-strain curve in a tensile test does not have a yield point showing a maximum value in the 0.5 to 10% strain range. This prevents the plating layer from breaking in the 0.5 to 10% strain range, thereby preventing changes in the electrical resistance of the sensor sheet. Furthermore, in the relatively small strain range of 0.5 to 10%, large stress is not generated and sudden changes in stress are suppressed. This results in improved efficiency in assembling the sensor sheet 18 to the steering wheel 10. Furthermore, the absence of a yield point showing a maximum value in the 0.5 to 5% strain range prevents large stress from being generated and changes in stress when the sensor sheet 18 is slightly stretched, which is more preferable because it further improves workability.

[0125] When a tensile force is applied to the sensor sheet 18, the first openings 34a of the first electrode sheet 25 deform, and the opening area of ​​the first openings 34a decreases. In other words, the filaments 71 are stretchable by changing the spatial arrangement of the entire filament 71, without tensile strain concentrating on the filaments 71 themselves. That is, the reduction in the opening area accompanying the change in the spatial arrangement of the entire filament 71 exhibits structural flexibility for expansion and contraction, so the extension strain applied to the filaments 71 themselves is small and damage to the plating layer 33 formed on the filaments 71 can be suppressed. Therefore, even when a tensile force is applied to the sensor sheet 18, changes in the electrical resistance value can be suppressed.

[0126] The opening ratio of the first opening 34a is preferably 1% or more and 50% or less. With an opening ratio of 50% or less, when the first opening 34a is deformed in a direction that reduces the opening area, the multiple filament assemblies 72 tend to come into contact with each other. Because the multiple filament assemblies 72 tend to come into contact with each other in this way, the opening 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 even 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 so that the maximum stress value in the stress-strain curve is 0.5 MPa or less when the strain is 0 to 5%. Furthermore, the sensor sheet 18 is configured so that the maximum stress value in the stress-strain curve is 3 MPa or less when the strain is 0 to 20%. This prevents excessively large stress from being applied to the first electrode sheets 25, 25a when a tensile force is applied to the sensor sheet 18. As a result, damage to the structure of the first electrode sheets 25, 25a can be prevented, and changes in the electrical resistance value of the sensor sheet 18 can be prevented.

[0128] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or the stress applied to the second electrode sheets 26, 26a, the maximum stress value of the sensor sheet 18 at a strain of 0 to 5% in the stress-strain curve is preferably 0.5 MPa or less, more preferably 0.4 MPa or less, and even 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 the second electrode sheets 26, 26a, the maximum stress value of the sensor sheet 18 at a strain of 0 to 20% in the stress-strain curve is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1.5 MPa or less.

[0130] The first electrode sheets 25, 25a according to this embodiment are configured so that the maximum stress of the first electrode sheets 25, 25a is 3 MPa or less when the strain is 0 to 5% on the stress-strain curve. The first electrode sheets 25, 25a are configured so that the maximum stress of the first electrode sheets 25, 25a is 15 MPa or less when the strain is 0 to 20% on the stress-strain curve. The same applies to the second electrode sheets 26, 26a.

[0131] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or the stress applied to the second electrode sheets 26, 26a, the maximum value of the stress of the first electrode sheets 25, 25a or the second electrode sheets 26, 26a at a strain of 0 to 5% in the stress-strain curve 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, 25a or the stress applied to the second electrode sheets 26, 26a, the maximum value of the stress of the first electrode sheets 25, 25a or the second electrode sheets 26, 26a at a strain of 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 test piece of 20 mm x 90 mm is gripped and a tensile test is carried out at a tensile speed of 1 mm / s.

[0134] The cross-sectional shape of the filaments 71 may be non-circular or polygonal. This forms irregular spaces between the multiple filaments 71. As the filaments 71 move within these spaces, the tensile force applied to the sensor sheet 18 is absorbed, preventing excessive stress from being applied to the sensor sheet 18. As a result, changes in the electrical resistance of the sensor sheet 18 can be prevented.

[0135] Furthermore, in the filament assembly 72 according to this embodiment, the portions where the plating layers 33 formed on the surfaces of adjacent filaments 71 come into contact with each other and are electrically connected are also present on the outer surfaces of the plurality of filaments 71 located inside the bundled untwisted yarn wire 74. Therefore, even if the plating layers 33 formed on the outer surfaces of the filaments 71 located on the surface of the untwisted yarn wire 74 break when a tensile force is applied to the sensor sheet 18, there are still plating layers 33 formed on the outer surfaces of the plurality of filaments 71 located inside the untwisted yarn wire 74. As a result, the plating layers 33 formed on the outer surfaces of the plurality of filaments 71 located inside the untwisted yarn wire 74 come into contact with each other, thereby suppressing changes in the electrical resistance value even when a tensile force is applied to the sensor sheet 18.

[0136] Furthermore, the filament assembly 72 according to this embodiment includes an internal space 80 formed at least partially between adjacent filaments 71. The filaments 71 can move freely within the internal space 80, so that when a tensile force is applied to the sensor sheet 18, the filaments 71 can absorb the stress by moving within the internal space 80. This prevents excessive stress from being applied to the sensor sheet 18, thereby preventing changes in the electrical resistance value of the sensor sheet 18.

[0137] Furthermore, in the filament assembly 72 according to this embodiment, multiple filaments 71 are arranged in both the planar direction of the sheet surface of the first electrode sheet 25 and the normal direction to the sheet surface. An internal space 80 is formed at least partially between adjacent filaments 71 in the planar direction and at least partially between adjacent filaments 71 in the normal direction. This allows the filaments 71 to move in the planar direction and the normal direction, thereby efficiently absorbing stress applied to the sensor sheet 18 by the filaments 71. As a result, changes in the electrical resistance of the sensor sheet 18 can be suppressed.

[0138] Furthermore, a plating layer 33 is formed on at least a portion of the surface of the filament 71 that is exposed to the internal space 80, and the portion of the surface of the filament 71 that is exposed to the internal space 80 but does not have the plating layer 33 formed thereon is exposed. This allows the filament 71 exposed to the internal space 80 to move freely without being restrained by the plating layer 33. As a result, the filament 71 is able to move within the internal space 80, and therefore can efficiently absorb the stress applied to the sensor sheet 18 by the filament 71. As a result, changes in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0139] Furthermore, a plating layer 33 is formed on at least a portion of the non-exposed portion 81 where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect, thereby electrically connecting the warp filament aggregate 72a and the weft filament aggregate 72b and forming a conductive path for the sensor sheet 18.

[0140] Furthermore, a plating layer 33 is formed on at least a portion of the surface of the filament 71 exposed to the outer surface of the filament assembly 72. The surface of the filament 71 is exposed where the plating layer 33 is not formed. Because the plating layer 33 is formed on at least a portion of the surface of the filament 71 exposed to the outer surface of the filament assembly 72, the plating layer 33 formed on one filament 71 contacts the plating layer 33 formed on the surface of another filament 71, electrically connecting the filaments 71 to each other. Furthermore, the portion of the surface of the filament 71 where the plating layer is not formed allows the filament 71 to move relatively freely, thereby absorbing the tensile force applied to the sensor sheet 18. This prevents excessive stress from being applied to the sensor sheet 18, thereby preventing changes in the electrical resistance of the sensor sheet 18.

[0141] The multiple filament assemblies 72 in this embodiment include warp filament assemblies 72a and weft filament assemblies 72b, and at the portions where the warp filament assemblies 72a and the weft filament assemblies 72b intersect with each other, a plating layer 33 is formed on at least a portion of the portion where the filaments 71 exposed on the outer surface of the warp filament assemblies 72a and the filaments 71 exposed on the outer surface of the weft filament assemblies 72b face each other, and the outer surfaces of the filaments 71 are exposed in the portions where the plating layer 33 is not formed.

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

[0143] In addition, the manufacturing method of the sensor sheet 18 in this embodiment includes the steps of: forming a filament assembly 72 by bundling a plurality of filaments 71; forming a base cloth by knitting the plurality of filament assemblies 72; forming a conductive cloth by plating the base cloth; and forming the sensor sheet 18 by joining the conductive cloth to the first surface 27 of an insulating sheet 24 made of an elastomer and having a first surface 27 and a second surface 28.

[0144] According to the above-described method for manufacturing the sensor sheet 18, there are some filaments 71 that are electrically connected by contacting each other with the plating layers 33 formed on their surfaces, and some filaments 71 that are not formed with the plating layers 33 and are free to move relative to each other. As a result, when a tensile force is applied to the sensor sheet 18, the stress is absorbed by the filaments 71 that are free to move relative to each other, preventing excessive stress from being applied to the sensor sheet 18. As a result, the electrical connection of the sensor sheet 18 is maintained by the electrically connected filaments 71, preventing changes in the electrical resistance of the sensor sheet 18.

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

[0146] 2.1.6. Configuration of Electrode Sheets The first electrode sheets 25, 25a and the second electrode sheets 26, 26a will be described with reference to Figures 19 and 21. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a are conductive cloths that are electrically conductive. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a are flexible while being electrically conductive. The first electrode sheets 25, 25a and the second electrode sheets 26, 26a are stretchable in the longitudinal direction X and the transverse 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 wires 73. Each twisted wire 73 is formed by twisting a plurality of filaments 71.

[0148] Examples of resins that can be used to form the filaments 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 that can be used to form the warp threads 41 and the weft threads 42 are not limited to those mentioned above, and any resin can be selected as appropriate. The second electrode sheet 26 also has a similar structure.

[0149] The method for forming the plating layer 33 is not particularly limited, and may be, for example, electrolytic plating, electroless plating, electroless plating followed by electrolytic plating, or electroless plating followed by electrolytic plating; any method can be selected as appropriate.

[0150] The metal constituting the plating layer 33 formed on the surface of the base fabric can be selected from any metal or alloy, such as copper, nickel, tin, or solder. The plating layer 33 formed on the surface of the base fabric can be composed of one metal type or multiple metal types. For example, the surface of the base fabric can be plated with only copper, or only nickel, or a copper plating layer made of copper can be formed on the surface of the base fabric, and then a nickel plating layer made of nickel can be formed on the surface of this copper plating layer. The plating layer 33 formed on the surface of the base fabric can be formed by electrolytic plating or electroless plating. The second electrode sheet 26 has a similar configuration.

[0151] 2.1.7. Examples, Comparative Examples, and Samples 2.1.7.1. Example 2-1 and Sample 2-1 Example 2-1 and Sample 2-1 Example 2-1 and Sample 2-1 will be described with reference to FIGS. 19 and 20. As shown in FIG. 19(a), the first electrode sheet 25 of this Example 2-1 includes multiple warp threads 41 and multiple weft threads 42. The first electrode sheet 25 is formed by weaving the warp threads 41 and the multiple 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. The first electrode sheet 25 and the second electrode sheet 26 have substantially the same configuration, and therefore, in the following description, redundant explanations will be omitted unless otherwise noted.

[0152] The first electrode sheet 25 has first openings 34a that open between two adjacent warp threads 41 among the multiple warp threads 41 and two adjacent weft threads 42 among the multiple weft threads 42. The first openings 34a penetrate the first electrode sheet 25. In this Example 2-1, the opening ratio, which is the ratio of the opening area of ​​the first openings 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 multiple first openings 34a formed in a 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 on the first electrode sheet 25, adding up the areas of the first openings 34a within the target area, and dividing the total area by the area of ​​the target area.

[0153] 19(b), the second electrode sheet 26 of this 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 has second openings 34b that open between two adjacent warp threads 41 of the plurality of warp threads 41 and two adjacent weft threads 42 of the plurality of weft threads 42. In this Example 2-1, the opening ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26 to the area of ​​the second electrode sheet 26, is approximately 63%.

[0155] 19( a), the longitudinal direction S of the multiple warp threads 41 and the longitudinal direction X of the first electrode sheet 25 are arranged to intersect. Furthermore, the longitudinal direction T of the multiple 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 multiple warp threads 41 forms an acute angle of substantially 45° with the longitudinal direction X of the first electrode sheet 25. Furthermore, the longitudinal direction T of the multiple weft threads 42 forms an acute angle of substantially 45° with the longitudinal direction X of the first electrode sheet 25. The angle being substantially 45° includes the case where it is 45° and also includes the case where it can be recognized as being substantially 45°.

[0156] When the longitudinal direction S of the warp threads 41 is parallel to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 0°), stretching the first electrode sheet 25 parallel to the direction X results in the warp threads 41 themselves being stretched, requiring a large load.

[0157] On the other hand, when the longitudinal direction S of the warp threads 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°), stretching the first electrode sheet 25 parallel to the longitudinal direction X causes the square or rectangular lattice formed by the weft threads 42 and the warp threads 41 to deform into a diamond shape, and the warp threads 41 or the weft threads 42 themselves are not stretched, so no large load is required. In other words, 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 deform into a diamond shape, and structural flexibility is less likely to be impaired.

[0158] However, the longitudinal direction S of the plurality of warp threads 41 may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25. Furthermore, the longitudinal direction T of the plurality of weft threads 42 may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25. The second electrode sheet 26 is similar to the first electrode sheet 25, and therefore a redundant description will be omitted.

[0159] As shown in Fig. 19(a), the plurality of warp threads 41 according to this embodiment 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 being substantially equal. Note that the intervals between the plurality of warp threads 41 may be different from one another.

[0160] In addition, the plurality of weft yarns 42 according to this embodiment 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 being substantially equal. Note that the intervals between the plurality of weft yarns 42 may be different from one another.

[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, and therefore a duplicated description will be omitted.

[0162] 20 , a plated layer 33 is formed on at least a part of the warp thread 41. The plated layer 33 may be formed on the entire surface of the warp thread 41, or may be formed on only a part of the surface of the warp thread 41.

[0163] Furthermore, a plated layer 33 is formed on at least a portion of the weft yarn 42. The plated layer 33 may be formed on the entire surface of the weft yarn 42, or the plated layer 33 may be formed on only a portion of the surface of the weft yarn 42.

[0164] In this embodiment, the plating layer 33 formed on the surface of the warp thread 41 comes into contact with the plating layer 33 formed on the surface of the weft thread 42, thereby electrically connecting the warp thread 41 and the weft thread 42.

[0165] In this 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 middle layer being Cu, and the innermost layer (on the filament 71 side) being Ni.

[0166] As shown in FIG. 4 , the first electrode sheet 25 described above is bonded to a first surface 27 of an insulating sheet 24 formed primarily from a foamable resin via a first bonding portion 36. The insulating sheet 24 is an ether-based polyurethane foam. The insulating sheet has a thickness of approximately 1.0 mm. The first bonding portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first bonding portion 36 is 50 μm. A second electrode sheet 26 having a configuration similar to that of the first electrode sheet 25 is bonded to a second surface 28 of the insulating sheet 24 via a second bonding portion 37. The first bonding portion 36 and the second bonding portion 37 are identical, and therefore a redundant description will be omitted. In this manner, a sensor sheet sample 2-1 corresponding to the first electrode sheet 25 and the second electrode sheet 26 of Example 2-1 is produced.

[0167] 2.1.7.2. Example 2-2 and Sample 2-2 (Example 2-2 and Sample 2-2) Next, the configurations of the first electrode sheet 25a and the second electrode sheet 26a according to Example 2-2 will be described with reference to FIGS. 21(a) and 21(b). The first electrode sheet 25a according to this embodiment is a conductive cloth woven with a plurality of filament assemblies 72. The plurality of filament assemblies 72 include a stranded wire 73 formed by twisting a plurality of filaments 71 together, and a plating layer 33 formed on at least a portion of the surface of the stranded wire 73. The plurality of filament assemblies 72 also include a warp filament assembly 72a and a weft filament assembly 72b. In the following description, when the warp filament assembly 72a and the weft filament assembly 72b are not distinguished from each other, they may be referred to as filament assemblies 72. Note that, of the symbols used below, the same symbols as those used in the previous embodiment represent the same components as those in the previous embodiment, unless otherwise specified.

[0168] The first electrode sheet 25a according to this embodiment is formed by weaving twisted wires 73 constituting warp threads formed by twisting a plurality of filaments 71 together with twisted wires 73 constituting weft threads formed by twisting a plurality of filaments 71 together to form a base fabric, and then forming a plating layer 33 on the surface of this base fabric. However, the method for manufacturing the first electrode sheet 25a is not limited to the above method. The first electrode sheet 25a and the second electrode sheet 26a have substantially the same configuration, and therefore, in the following description, redundant explanations will be omitted unless otherwise noted.

[0169] 21(a), the first electrode sheet 25a of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The first electrode sheet 25a includes first openings 34a that open between the plurality of filament assemblies 72a. The first openings 34a penetrate the first electrode sheet 25a. In this Example 2-2, the opening ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25a to the area of ​​the first electrode sheet 25a, is 63%.

[0170] 21(b), the second electrode sheet 26a of this embodiment is substantially the same as the first electrode sheet 25a except that it is provided with second openings 34b that open between the multiple filament assemblies 72, and therefore a duplicated description will be omitted. In this Example 2-2, the opening ratio, which is the ratio of the opening area of ​​the second openings 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 assembly 72 constituting the first electrode sheet 25a is not particularly limited. The filament assembly 72 according to this embodiment includes six filaments 71, but may include two to five filaments, or seven or more filaments.

[0172] As shown in Fig. 21(a) , the longitudinal direction S of the multiple warp filament assemblies 72a and the longitudinal direction X of the first electrode sheet 25a 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 25a intersect with each other. Specifically, the longitudinal direction S of the multiple warp filament assemblies 72a forms an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25a. 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 25a. The phrase "the angle is substantially 45°" includes cases where the angle is 45° and also cases where it can be determined that the angle is substantially 45°.

[0173] However, the longitudinal direction S of the multiple warp filament assemblies 72a may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25a. Also, the longitudinal direction T of the multiple weft filament assemblies 72b may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25a.

[0174] As shown in Fig. 21(a), the plurality of warp filament assemblies 72a according to this embodiment 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 being substantially equal. Furthermore, the plurality of weft filament assemblies 72b are also arranged at substantially equal intervals.

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

[0176] 22 , a plating layer 33 is formed on at least a portion of the surface of the stranded wire 73 that constitutes the filament assembly 72. In this embodiment, the plating layer 33 is formed on the surface of the filaments 71 that are exposed to the outside of the surface of the stranded wire 73.

[0177] The plated layer 33 of the warp filament aggregate 72a and the plated layer 33 of the weft filament aggregate 72b come into contact with each other, thereby electrically connecting the warp filament aggregate 72a and the weft filament aggregate 72b.

[0178] Furthermore, in this embodiment, of the surfaces of the filaments 71 constituting the stranded wire 73, a portion of the surface of the filaments 71 exposed inside the stranded wire 73 is not formed with the plating layer 33. As a result, the surface of the filaments 71 exposed inside the stranded wire 73 is exposed to the space inside the stranded wire 73. Meanwhile, in this embodiment, of the surfaces of the filaments 71 constituting the stranded wire 73, the other portion of the surface of the filaments 71 exposed inside the stranded wire 73 is formed with the plating layer 33. Thus, in this embodiment, the surface of the filaments 71 exposed inside the stranded wire 73 includes a portion where the surface of the filaments 71 is exposed and a portion where the plating layer 33 is formed.

[0179] The portion where the plating layer 33 is not formed and the surface of the filament 71 is exposed is configured to be more flexible than the portion where the plating layer 33 is formed. As a result, when stress is applied to the sensor sheet, the stress can be absorbed by the filament 71, which is relatively flexible.

[0180] In this Example 2-2, the resin constituting the filament 71 is PET (polyethylene terephthalate), and the diameter of the filament 71 is approximately 20 μm. The metal constituting the plating layer 33 is formed such that the outermost layer is Ni and the innermost layer (on the filament 71 side) is Cu. The stranded wire 73 is composed of six filaments 71.

[0181] Sample 2-2 of the sensor sheet 18 according to Example 2-2, which is the first electrode sheet 25a and the second electrode sheet 26a, is produced in the same manner as Sample 2-1. Descriptions that overlap with Sample 2-1 will be omitted.

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

[0183] (Modification 2 of Example 2-2) Next, Modification 2 of Example 2-2 will be described with reference to Fig. 24. As shown in Fig. 24, a plating layer 33 is formed on the entire periphery of the surface of a plurality of filaments 71 that make up a stranded wire 73. The plating layers 33 formed on the surfaces of adjacent filaments 71 come into contact with each other, thereby electrically connecting the adjacent filaments 71 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, Comparative Example 2-1 will be described with reference to FIGS. 25 and 26. As shown in FIG. 25, the first electrode sheet 25b according to Comparative Example 2-1 is a conductive cloth woven with a plurality of filament assemblies 72. The plurality of filament assemblies 72 include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled together in an untwisted state, and a plating layer 33 formed on at least a portion of the surface of the untwisted yarn bundle 74. The filament assembly 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 Comparative Example 2-1 is formed by weaving warp yarns 41, each of which is formed by gathering a plurality of untwisted filaments 71, and weft yarns 42, each of which is formed by gathering a plurality of untwisted filaments 71, to form a base fabric, and then forming a plating layer 33 on the surface of this base fabric. However, the method for manufacturing the first electrode sheet 25b is not limited to the above method. The first electrode sheet 25b has substantially the same configuration as the second electrode sheet 26b, and therefore, in the following description, redundant explanations will be omitted unless otherwise noted.

[0186] 25(a), the first electrode sheet 25b of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The first electrode sheet 25b includes first openings 34a that open between the plurality of filament assemblies 72a. The first openings 34a penetrate the first electrode sheet 25b. In this comparative example 2-1, the opening ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25b to the area of ​​the first electrode sheet 25b, is approximately 20%.

[0187] 25(b), the second electrode sheet 26b of this embodiment is substantially the same as the first electrode sheet 25b except for the provision of second openings 34b that open between the multiple filament assemblies 72, and therefore a redundant description will be omitted. The opening ratio, which is the ratio of the opening area of ​​the second openings 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 assembly 72 constituting the first electrode sheet 25b is not particularly limited. The filament assembly 72 according to this embodiment includes six filaments 71, but may include two to five, or seven or more filaments. The multiple filaments 71 included in the filament assembly 72 are arranged side by side in a single layer.

[0189] 26, a plating layer 33 is formed on at least a portion of the surface of the untwisted yarn bundle 74 that constitutes the filament assembly 72. In this embodiment, the plating layer 33 is formed on the entire periphery of the surface of the untwisted yarn bundle 74.

[0190] The plated layer 33 of the warp filament aggregate 72a and the plated layer 33 of the weft filament aggregate 72b come into contact with each other, thereby electrically connecting the warp filament aggregate 72a and the weft filament aggregate 72b.

[0191] As shown in Fig. 25(a) , the longitudinal direction S of the multiple warp filament assemblies 72a and the longitudinal direction X of the first electrode sheet 25a 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 25a intersect with each other. Specifically, the longitudinal direction S of the multiple warp filament assemblies 72a forms an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25a. 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 25a. The phrase "the angle is substantially 45°" includes cases where the angle is 45° and also cases where it can be determined that the angle is substantially 45°.

[0192] However, the longitudinal direction S of the multiple warp filament assemblies 72a may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25a. Also, the longitudinal direction T of the multiple weft filament assemblies 72b may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25a.

[0193] In Sample 2-3, the resin constituting the filaments 71 is PET (polyethylene terephthalate), and the diameter of the filaments 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 middle 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] Sample 2-3 of the sensor sheet 18 according to the first electrode sheet 25b and the second electrode sheet 26b of Comparative Example 2-1 is fabricated in the same manner as Sample 2-1. Descriptions that overlap with Sample 2-1 will be omitted.

[0195] 2.1.7.4. Tensile Test of First Electrode Sheet Next, with reference to FIG. 27 , a tensile test performed on the first electrode sheet will be described. The first electrode sheets according to Examples 2-1 to 2-2 and Comparative Example 2-1 were cut into strips measuring 150 mm x 20 mm to prepare test specimens. The thickness of the first electrode sheet was approximately 0.1 mm. The angle between the longitudinal direction of the test specimen and the longitudinal direction of the warp threads 41 or warp filament assembly 72a was set to 45°.

[0196] The test specimen is held by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is performed on the test specimen at a tensile speed of 1 mm / sec, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test specimen. The tensile tester is an AGS-X 1 kN model manufactured by Shimadzu Corporation. The tensile test is performed in a strain range of 0 to 20%. Figure 27 shows a graph showing the change in stress versus strain.

[0197] In Examples 2-1 and 2-2, the stress increased very slowly and monotonically in the strain range of 0 to 20%. In Examples 2-1 and 2-2, the stress-strain curve in the tensile test does not have a yield point showing a maximum value in the strain range of 0.5 to 10%.

[0198] Example 2-1 exhibits a stress of approximately 0.4 MPa at a strain of 5%, and a maximum stress of approximately 0.8 MPa at a strain of 20%. Therefore, the maximum stress value of Example 2-1 in the tensile test is 1 MPa or less. Similarly, Example 2-2 exhibits a stress of approximately 0.3 MPa at a strain of 5%, and a maximum stress value of approximately 0.5 MPa at a strain of 20%. Therefore, the maximum stress value of Example 2-2 in the tensile test is also 1 MPa or less. In the stress-strain curves of Examples 2-1 and 2-2, the maximum stress value at strains of 0 to 5% is 3 MPa or less, and the maximum stress value at strains of 0 to 20% is 15 MPa or less.

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

[0200] 2.1.7.5. Tensile Test of Sensor Sheet Next, we will explain the tensile test performed on the sensor sheet. Test pieces were prepared by cutting the sensor sheets of Samples 2-1 to 2-2 and Sample 2-3 into 90 mm x 20 mm strips. The thickness of the sensor sheet was approximately 1 mm. The angle between the longitudinal direction of the test piece and the longitudinal direction of the warp threads 41 or warp filament assemblies 72a that constitute the first electrode sheet and the second electrode sheet was set to 45°.

[0201] An electric wire is connected to one longitudinal end of the first electrode sheet and connected to a DC power supply, and an electric wire is connected to the other longitudinal end of the first electrode sheet and connected to a voltage measuring instrument.

[0202] The test piece is held 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, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test piece. During the tensile test, the DC resistance value (an example of an electrical resistance value) of the sensor sheet is calculated from the voltage of the DC power supply and the voltage drop across the sensor sheet. The DC resistance value is measured using a 2000 series digital multimeter manufactured by Keithley Corporation.

[0203] As shown in FIG. 28, sample 2-1 exhibits a stress of approximately 0.1 MPa when the strain is 5%, a stress of approximately 0.4 MPa when the strain is 20%, and a maximum stress of approximately 1.3 MPa when the strain is 30%.

[0204] Sample 2-2 exhibits 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 maximum stress of about 0.9 MPa when the strain is 30%.

[0205] In the stress-strain curves of Samples 2-1 and 2-2, the stress is 0.5 MPa or less when the strain is 0 to 5%, and the maximum stress is 3 MPa or less when the strain is 0 to 20%.

[0206] In the stress-strain curves of Samples 2-1 and 2-2, the stress is 0.5 MPa or less when the strain is 0 to 5%, and the maximum stress is 3 MPa or less when the strain is 0 to 20%.

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

[0208] When a tensile force is applied to Sample 2-1 and Sample 2-2, the first opening 34a of the first electrode sheet expands in the tensile direction and contracts in a direction intersecting the tensile direction. Figure 29 shows the state in which the first opening 34a deforms, using Sample 2-1 as an example. This is thought to absorb the tensile force, resulting in a small change in stress. Note that the same applies to Sample 2-2, so a description thereof will be omitted.

[0209] In Samples 2-1 and 2-2, even when a tensile force is applied to the sensor sheet, the relative positions of the warp threads 41 and the weft threads 42 do not change significantly at the intersections of the warp threads 41 and the weft threads 42, and therefore it is believed that the electrical connection between the warp threads 41 and the weft threads 42 is maintained. As a result, in Samples 2-1 and 2-2, it is believed that the DC resistance value changes very little even when a tensile force is applied to the sensor sheet.

[0210] On the other hand, Sample 2-3 has a yield point that shows a maximum value in the strain range of 0.5 to 5%. In Sample 2-3, it is believed that the plating layer 33 formed at the intersection of the warp yarns 41 and weft yarns 42 is maintained in the strain range from 0% to the yield point, causing elastic deformation. It is believed that the plating layer 33 formed at the intersection of the warp yarns 41 and weft yarns 42 is then destroyed at the yield point.

[0211] Thereafter, in the section where the stress does not change much (the section where the strain is approximately 5 to approximately 15%), it is thought that the tensile force is absorbed by the deformation of the first opening 34a and the second opening 34b, as in Sample 2-1 and Sample 2-2.

[0212] Thereafter, when the strain becomes larger than about 15%, the first openings 34a and the second openings 34b are completely blocked because the first opening ratio and the second opening ratio of Sample 2-3 are 20%, and it is believed that the tensile force acting on the first electrode sheet and the second electrode sheet can no longer be absorbed, which is believed to increase the stress.

[0213] 2.1.7.6 DC Resistance of Sensor Sheet Figure 30 shows a graph showing the change in DC resistance with respect to strain. Figure 30 shows the DC resistance in the strain range of 0 to 30%.

[0214] Sample 2-1 showed almost no change in DC resistance at about 0.1Ω in the strain range of 0 to 30%. Sample 2-2 showed almost no change in DC resistance at about 0.2Ω in the strain range of 0 to 30%.

[0215] For Sample 2-3, the DC resistance value remained almost unchanged at approximately 0.2 Ω in the strain range of 0 to approximately 3%. When the strain exceeded approximately 3%, the DC resistance value of Sample 2-3 increased monotonically, reaching approximately 0.44 Ω at a strain of 30%. Thus, the DC resistance value of Sample 2-3 changed from approximately 0.2 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 attached to the steering wheel 10 while being pulled and stretched. The sensor sheet 18 is fixed to the steering wheel 10 in a pulled and stretched state. Therefore, the sensor sheet 18 attached to the steering wheel 10 is maintained in a state in which tension is applied. Over time, residual stress in the material (metal, resin, etc.) that constitutes the sensor sheet 18 is expected to relax, causing a change in the tension applied to the sensor sheet 18. 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, if a tensile force is applied to the sensor sheet 18, the DC resistance value of the sensor sheet 18 changes, which is undesirable because it changes the sensitivity of the sensor sheet 18.

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

[0220] 2.1.8. Effects of the Present Embodiment Next, the effects of the present embodiment will be described. The sensor sheet 18 according to the present embodiment includes an insulating sheet 24, first electrode sheets 25, 25a, a first bonding portion 36, second electrode sheets 26, 26a, and a second bonding 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, 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, 25a are conductive. The first bonding portion 36 bonds the insulating sheet 24 and the first electrode sheet 25. The second electrode sheets 26, 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, 26a are conductive. The second bonding portion 37 bonds the insulating sheet 24 and the second electrode sheets 26, 26a. The sensor sheet 18 is configured so that a stress-strain curve in a tensile test does not have a yield point showing a maximum value in the strain range of 0.5 to 10%. 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, 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, 26a, is 40% or more.

[0221] 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, 25a, is 40% or more, and 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, 26a, is 40% or more. Therefore, the first opening 34a and the second opening 34b can deform to absorb the tensile force applied to the sensor sheet 18. This reduces the effect of the tensile force applied to the sensor sheet 18, thereby suppressing an increase in the electrical resistance of the sensor sheet 18. The aperture ratio is more preferably 50% or more, and even more preferably 60% or more, because it makes it easier to absorb the tensile force applied to the sensor sheet 18.

[0222] The sensor sheet 18 according to this embodiment is configured so that the stress-strain curve in a tensile test does not have a yield point showing a maximum value in the strain range of 0.5 to 10%. This prevents large stress from occurring and suppresses sudden changes in stress in the relatively small strain range of 0.5 to 10%. As a result, the efficiency of assembling the sensor sheet 18 to the steering wheel 10 can be improved. Furthermore, since the sensor sheet 18 does not have a yield point showing a maximum value in the strain range of 0.5 to 5%, when the sensor sheet 18 is slightly stretched, large stress is not generated and the stress does not change, which is more preferable because it further improves workability.

[0223] Furthermore, the first electrode sheet 25a and the second electrode sheet 26a according to this embodiment are conductive cloths woven with a plurality of filament assemblies 72. The filament assembly 72 includes a stranded wire 73 formed by twisting a plurality of filaments 71 together, and a plating layer 33 formed on at least a portion of the surface of the stranded wire 73. The first electrode sheet 25a includes first openings 34a that open between the plurality of filament assemblies 72. The second electrode sheet 26a includes second openings 34b that open between the plurality of filament assemblies 72.

[0224] By forming a plating layer 33 on at least a portion of the surface of the stranded wire 73 formed by twisting multiple filaments 71, multiple conductive paths are formed on the surface of the filament assembly 72. As a result, even if a tensile force is applied to the sensor sheet 18 and some of the plating layers 33 are destroyed, causing some conductive paths to break, electrical connection can be maintained through the other conductive paths. This makes it possible to suppress changes in the electrical resistance value of the sensor sheet 18.

[0225] According to this embodiment, in the stress-strain curve in a tensile test, the lattice consisting of the warp threads 41 and weft threads 42 deforms into a diamond shape in the strain range of 0.5 to 10%, which not only enables deformation without requiring a large load, but also suppresses the extension strain on the warp threads 41 and weft threads 42 themselves, thereby reducing the strain applied to the plating layer 33 formed on the threads and suppressing damage to the plating layer. In other words, by arranging the conductive cloth at an angle of 45° with respect to the tensile direction, structural flexibility is achieved, which suppresses damage to the plating layer 33 formed on the warp threads 41 or weft threads 42 of the conductive cloth during extension, thereby suppressing changes in the electrical resistance of the sensor sheet 18.

[0226] The sensor sheet 18 according to this embodiment is configured so that the maximum stress value in the stress-strain curve is 0.5 MPa or less when the strain is 0 to 5%. Furthermore, the sensor sheet 18 is configured so that the maximum stress value in the stress-strain curve is 3 MPa or less when the strain is 0 to 20%. This prevents excessively large stress from being applied to the first electrode sheets 25, 25a when a tensile force is applied to the sensor sheet 18. As a result, damage to the structure of the first electrode sheets 25, 25a can be prevented, and changes in the electrical resistance value of the sensor sheet 18 can be prevented.

[0227] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a, the maximum value of the stress of the sensor sheet 18 at a strain of 0 to 5% in the stress-strain curve 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, 25a, the maximum stress value of the sensor sheet 18 at strains of 0 to 20% in the stress-strain curve is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1.5 MPa or less.

[0229] The first electrode sheets 25, 25a according to this embodiment are configured so that the maximum stress of the first electrode sheets 25, 25a is 3 MPa or less when the strain is 0 to 5% on the stress-strain curve, and the maximum stress of the first electrode sheets 25, 25a is 15 MPa or less when the strain is 0 to 20% on the stress-strain curve.

[0230] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a, the maximum value of the stress of the first electrode sheets 25, 25a at a strain of 0 to 5% in the stress-strain curve 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, 25a, the maximum value of the stress at a strain of 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, 25a as described above, it is possible to prevent excessively large stress from being applied to the first electrode sheets 25, 25a when a tensile force is applied to the sensor sheet 18. This prevents the structure of the first electrode sheets 25, 25a from being destroyed, and therefore prevents changes in the electrical resistance value of the sensor sheet 18.

[0233] The plating layer 33 in this embodiment is formed on at least a portion of the surface of the stranded wire 73, but is not formed on at least a portion of the interior of the stranded wire 73. This allows the filaments 71 to be freely movable within the stranded wire 73 without being fixed by the plating layer 33. As a result, even when a tensile force is applied to the sensor sheet 18, the freely movable filaments 71 can absorb the stress, thereby preventing excessive stress from being applied to the first electrode sheets 25, 25a and the second electrode sheets 26, 26a. As a result, changes in the electrical resistance of the sensor sheet 18 can be prevented.

[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 of 1.1.1 to 1.1.5 will be read as 3.1.1 to 3.1.5, and overlapping descriptions will be omitted.

[0235] 3.1.6. Structure of Electrode Sheets The first electrode sheet 25 and the second electrode sheet 26 are conductive cloths. The first electrode sheet 25 and the second electrode sheet 26 are conductive and flexible. The first electrode sheet 25 and the second electrode sheet 26 are stretchable in the longitudinal direction X and the transverse direction Y.

[0236] 31 , the first electrode sheet 25 and the second electrode sheet 26 are conductive cloths woven with a plurality of filament assemblies 72. The filament assemblies 72 include a plurality of filaments 71 and a plating layer 33 formed on at least a portion of the surface of the filaments 71.

[0237] 31(a) and 31(b), 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 untwisted bundled yarns 74. Each untwisted bundled yarn 74 is formed by bundling a plurality of filaments 71 together in an untwisted state.

[0238] Examples of resins that can be used to form the filaments 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 that can be used to form the filaments 71 are not limited to the above, and any resin can be selected as appropriate. The second electrode sheet 26 also has a similar configuration.

[0239] The plated layer 33 is formed on the surface of a base fabric woven with a plurality of filament assemblies 72. The method for forming the plated layer 33 is not particularly limited, and any method can be appropriately selected, for example, electrolytic plating, electroless plating, electroless plating followed by electrolytic plating, or electroless plating followed by electrolytic plating.

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

[0241] 31( a), the first electrode sheet 25 has first openings 34a that open between the multiple filament assemblies 72. The first openings 34a penetrate the first electrode sheet 25. A first opening ratio, which is the ratio of the opening area of ​​the first openings 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] 31( b), the second electrode sheet 26 has second openings 34b that open between the multiple filament assemblies 72. The second openings 34b penetrate the second electrode sheet 26. A second opening ratio, which is the ratio of the opening area of ​​the second openings 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 Example 3-1 will be described with reference to FIGS. 31 to 34. As shown in FIG. 31(a), the first electrode sheet 25 according to Example 3-1 is a conductive cloth woven with a plurality of filament assemblies 72. The plurality of filament assemblies 72 include an untwisted bundled yarn 74 in which a plurality of filaments 71 are bundled together in an untwisted state, and a plating layer 33 formed on at least a portion of the surface of the untwisted bundled yarn 74. The filament assemblies 72 are formed in a flat shape in the thickness direction of the first electrode sheet 25b. However, because the first electrode sheet 25 and the second electrode sheet 26 have substantially the same configuration, redundant description will be omitted unless otherwise noted.

[0244] The first electrode sheet 25 according to this Example 3-1 is formed by weaving warp yarns in which a plurality of filaments 71 are gathered together in an untwisted state and weft yarns in which a plurality of filaments 71 are gathered together in an untwisted state to form a base fabric, and then forming a plating layer 33 on the surface of this base fabric. However, the method for manufacturing 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 assemblies 72a and a plurality of weft filament assemblies 72b. The first electrode sheet 25 includes first openings 34a that open between the plurality of filament assemblies 72a. The first openings 34a penetrate the first electrode sheet 25. In this Example 3-1, the aperture ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25 to the area of ​​the first electrode sheet 25, is approximately 3%. Note that this aperture ratio is the ratio of the total opening area of ​​the plurality of first openings 34a formed in a target area of ​​the first electrode sheet 25 to the area of ​​the target area of ​​the first electrode sheet 25. This aperture ratio is calculated, for example, by identifying a 10 mm × 10 mm target area on the first electrode sheet 25, adding up the areas of the first openings 34a within the target area, and dividing the total area by the area of ​​the target area.

[0246] 31(b), the second electrode sheet 26 of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The second electrode sheet 26 of this embodiment includes second openings 34b that open between the plurality of filament assemblies 72. The second openings 34b penetrate the second electrode sheet 26. In this Example 3-1, the opening ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26 to the area of ​​the second electrode sheet 26 of this embodiment, is approximately 3%.

[0247] There is no particular limitation on the number of filaments 71 included in the filament assembly 72 that constitutes the first electrode sheet 25. The filament assembly 72 according to this embodiment includes 75 filaments 71, but the number may be any number. The second electrode sheet 26 is similar to the first electrode sheet 25.

[0248] 32, a plated layer 33 is formed on at least a portion of the surface of the untwisted yarn bundle 74 that constitutes the filament assembly 72. The plated layer 33 of the warp filament assembly 72a and the plated layer 33 of the weft filament assembly 72b come into contact with each other, thereby electrically connecting the warp filament assembly 72a and the weft filament assembly 72b.

[0249] As shown in FIG. 31( a), the longitudinal direction S of the multiple warp filament assemblies 72a and the longitudinal direction X of the first electrode sheet 25 intersect. Furthermore, the longitudinal direction T of the multiple weft filament assemblies 72b and the longitudinal direction X of the first electrode sheet 25 intersect. Specifically, the longitudinal direction S of the multiple warp filament assemblies 72a forms an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25. 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 25a. The phrase "the angle is substantially 45°" includes cases where the angle is 45° and also cases where it can be determined that the angle is substantially 45°. The second electrode sheet 26 has a configuration similar to that of the first electrode sheet 25, and therefore a redundant description will be omitted.

[0250] 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°), stretching the first electrode sheet 25 parallel to the direction X results in the warp filament assembly 72a itself being stretched, requiring a large load.

[0251] On the other hand, when the longitudinal direction S of the warp filament assemblies 72a is inclined at an angle of 45° relative to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 45°), stretching the first electrode sheet 25 parallel to the direction X causes the square or rectangular lattice (openings 34) formed by the warp filament assemblies 72a and the weft filament assemblies 72b to deform into a diamond shape. This does not require a large load because the warp filament assemblies 72a or the weft filament assemblies 72b themselves are not stretched. In other words, when the acute angle is substantially 45°, structural flexibility is imparted. Furthermore, the higher the opening ratio, the easier it is for the square or rectangular lattice to deform into a diamond shape, and structural flexibility is less likely to be impaired.

[0252] However, the longitudinal direction S of the multiple warp filament assemblies 72a may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25. Furthermore, the longitudinal direction T of the multiple weft filament assemblies 72b may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25.

[0253] The number of filaments 71 constituting the warp filament assembly 72a and the number of filaments 71 constituting the weft filament assembly 72b may be the same or different. In this Example 3-1, the number of filaments 71 constituting the warp filament assembly 72a and the number of filaments 71 constituting the weft filament assembly 72b are set to be substantially the same. "Substantially the same" includes cases where they are the same, as well as cases where they are not the same but can be recognized as being substantially the same. The same applies to the weft filament assembly 72b, so redundant explanations will be omitted. In this 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 Figure 32, a plating layer 33 is formed on at least some of the filaments 71 that make up the warp filament assembly 72a. For example, the plating layer 33 is formed on the surfaces of the filaments 71 that are 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. The same applies to the weft filament assembly 72b, so a duplicated description will be omitted.

[0255] At the portion where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect, a plated layer 33 is formed in part, and the surface of the filament 71 is exposed in the portion where the plated layer 33 is not formed. At the portion where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect, the plated layer 33 is formed in the region closer to the portion exposed to the outside, while in the portion closer to the inside, there is a mixture of portions where the plated layer 33 is formed and portions where the plated layer 33 is not formed. Note that the weft filament aggregate 72b has the same configuration as the warp filament aggregate 72a, so a duplicated description will be omitted.

[0256] The cross-sectional area A1 of each warp filament assembly 72a shown in FIG. 34 is larger than the opening area A2 of the first opening 34a shown in FIG. 33 when the first electrode sheet 25 is not distorted. The cross-sectional area A1 of the warp filament assembly 72a refers to the cross-sectional area formed by the outline of the warp filament assembly 72a. The same is true for the weft filament assembly 72b. Although not shown in detail, the cross-sectional area A1 of each weft filament assembly 72b is larger than the opening area A2 of the first opening 34a when the first electrode sheet 25 is not distorted. Although not shown in detail, in the second electrode sheet 26, the cross-sectional area A1 of each warp filament assembly 72a and the cross-sectional area A1 of each weft filament assembly 72b are larger than the opening area A2 of the second opening 34b when the second electrode sheet 26 is not distorted.

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

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

[0259] As shown in FIG. 4 , the first electrode sheet 25 described above is bonded to a first surface 27 of an insulating sheet 24 via a first bonding portion 36. A second electrode sheet 26 having a configuration similar to that of the first electrode sheet 25 is bonded to a second surface 28 of the insulating sheet 24 via a second bonding portion 37. The insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first bonding portion 36 is 50 μm. The first bonding portion 36 and the second bonding portion 37 are identical, so a redundant description will be omitted. In this manner, a sensor sheet 18 according to sample 3-1 is produced.

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

[0261] In this Example 3-2, the number of filaments 71a constituting the warp filament aggregate 72aa is set to approximately twice the number of filaments 71 constituting the weft filament aggregate 72ba. In this Example 3-2, 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 between 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] In this Example 3-2, the aperture ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25a to the area of ​​the first electrode sheet 25a, is approximately 10%. Also, the aperture ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26a to the area of ​​the second electrode sheet 26a, is approximately 10%.

[0263] The second electrode sheet 26a has the same configuration as the first electrode sheet 25a, and therefore a duplicated description will be omitted.

[0264] In this Example 3-2, 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 single layer of Ni. The diameter of the warp filament aggregate 72aa is approximately 180 μm, and the diameter of the weft filament aggregate 72ba is approximately 90 μm.

[0265] The configuration other than the above is the same as in Example 3-1, so a duplicated description will be omitted.

[0266] In addition, in this Example 3-2, the insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive. The thickness of the first bonding portion 36 is approximately 50 μm. The first bonding portion 36 and the second bonding portion 37 are identical, so a duplicated description will be omitted. Except for the above, Sample 3-2 of the sensor sheet 18 relating to the first electrode sheet 25a and the second electrode sheet 26a of Example 3-2 is produced in the same manner as Sample 3-1. A duplicated description of Sample 3-1 will be omitted.

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

[0268] 36( a), the first electrode sheet 25b of this embodiment includes a plurality of warp filament assemblies 72ab and a plurality of weft filament assemblies 72bb. The first electrode sheet 25b includes first openings 34a that open between the plurality of warp filament assemblies 72ab and the plurality of weft filament assemblies 72bb. The first openings 34a penetrate the first electrode sheet 25b. In this comparative example 3-1, the opening ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25b to the area of ​​the first electrode sheet 25b, is 20%.

[0269] 36(b), the second electrode sheet 26b of this embodiment is substantially the same as the first electrode sheet 25a except that it has second openings 34b that open between the plurality of warp filament assemblies 72ab and the plurality of weft filament assemblies 72bb. Therefore, a duplicated description will be omitted. In this comparative example 3-1, the opening ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26b to the area of ​​the second electrode sheet 26 of this embodiment, is 20%.

[0270] In this 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 middle layer being Cu, and the innermost layer (on the filament 71b side) being Ni. The diameter of the warp filament aggregate 72a is approximately 70 μm, and the diameter of the weft filament aggregate 72b is approximately 70 μm.

[0271] 37, a plating layer 33 is formed on at least a portion of the surface of the untwisted yarn bundle 74b that constitutes the warp filament aggregate 72ab and the weft filament aggregate 72bb. In this embodiment, the plating layer 33 is formed on the entire periphery of the surface of the untwisted yarn bundle 74b.

[0272] The plated layer 33 of the warp filament aggregate 72ab and the plated layer 33 of the weft filament aggregate 72bb come into contact with each other, thereby electrically connecting the warp filament aggregate 72ab and the weft filament aggregate 72bb.

[0273] The configuration other than the above is the same as in Example 3-1, so a duplicated description will be omitted.

[0274] In addition, in this comparative example 3-1, the insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first bonding portion 36 is 50 μm. The first bonding portion 36 and the second bonding portion 37 are identical, so a duplicated description will be omitted. Sample 3-3 of the sensor sheet 18 relating to the first electrode sheet 25b and the second electrode sheet 26b of comparative example 3-1 is produced in the same manner as sample 3-1. A duplicated description of sample 3-1 will be omitted.

[0275] 3.1.7.4. Tensile Test of First Electrode Sheet Next, with reference to FIG. 38 , a 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 150 mm x 20 mm strips to prepare test specimens. The thickness of the first electrode sheet varied between Examples 3-1 to 3-2 and Comparative Example 3-1, but was approximately 0.1 mm. The angle between the longitudinal direction of the test specimen and the longitudinal direction of the warp filament assembly 72a was set to 45°.

[0276] The test specimen is held by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is performed on the test specimen at a tensile speed of 1 mm / sec, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test specimen. The tensile tester is an AGS-X 1 kN model manufactured by Shimadzu Corporation. The tensile test is performed in a strain range of 0 to 20%. Figure 38 shows a graph showing the change in stress versus strain.

[0277] In Examples 3-1 and 3-2, the stress increased slowly and monotonically in the strain range of 0 to 20%. In Examples 3-1 and 3-2, the stress-strain curve in the tensile test did not have a yield point showing a maximum value in the strain range of 0.5 to 10%.

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

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

[0280] 3.1.7.5. Tensile Test of Sensor Sheet Next, we will explain the tensile test performed on the sensor sheet. Test specimens were prepared by cutting the sensor sheets of Samples 3-1 to 3-2 and Sample 3-3 into 90 mm x 20 mm strips. The thickness of the sensor sheet varied between Samples 3-1 to 3-2 and Sample 3-3, but was approximately 1 mm. The angle between the longitudinal direction of the test specimen and the longitudinal direction of the warp filament assembly 72a constituting the first electrode sheet and the second electrode sheet was set to 45°.

[0281] An electric wire is connected to one longitudinal end of the first electrode sheet and connected to a DC power supply, and an electric wire is connected to the other longitudinal end of the first electrode sheet and connected to a voltage measuring instrument.

[0282] The test piece is held 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, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test piece. During the tensile test, the DC resistance value (an example of an electrical resistance value) of the sensor sheet is calculated from the voltage of the DC power supply and the voltage drop across the sensor sheet.

[0283] Figure 39 shows the stress-strain curves in the tensile test performed on the sensor sheet. Figure 39 shows a graph of the strain range of 0 to 20%. The stress of Samples 3-1 and 3-2 increased monotonically in the strain range of 0 to 20%. Samples 3-1 and 3-2 do not have a yield point showing a maximum value in the strain range of 0.5 to 10% in the stress-strain curves in the tensile test.

[0284] Sample 3-1 exhibits a stress of approximately 0.5 MPa at a strain of 5%, and a maximum stress of approximately 2.6 MPa at a strain of 20%. Sample 3-2 exhibits a stress of approximately 0.3 MPa at a strain of 5%, and a maximum stress of approximately 1.5 MPa at a strain of 20%. In the stress-strain curves of Samples 3-1 and 3-2, the maximum stress is 0.5 MPa or less at strains of 0 to 5%, and the maximum stress is 3 MPa or less at strains of 0 to 20%. In the stress-strain curves of Samples 3-1 and 3-2, the maximum stress is 0.5 MPa or less at strains of 0 to 5%, and the maximum stress is 3 MPa or less at strains of 0 to 20%.

[0285] The stress-strain curve of Sample 3-3 in the tensile test showed a maximum yield point in the strain range of 0.5 to 10%. In the strain range of 0 to approximately 3%, the stress increased monotonically and linearly. At a strain of approximately 3%, the stress reached a maximum of approximately 0.7 MPa and then rapidly decreased to approximately 0.6 MPa. Thus, in Sample 3-3, the stress changed from an increasing trend to a decreasing trend before and after a strain of approximately 3%. Thereafter, the stress slightly decreased in the strain range of approximately 1 to approximately 13%. Thereafter, the stress monotonically increased from approximately 0.6 to approximately 0.8 MPa in the strain range of approximately 13 to 20%. Thus, in the stress-strain curve of Sample 3-3, the maximum stress value was greater than 0.5 MPa in the strain range of 0 to 5%, and the maximum stress value was greater than 0.7 MPa in the strain range of 0 to 20%.

[0286] When a tensile force is applied to Samples 3-1 and 3-2, the first openings 34a in the first electrode sheet expand in the tensile direction and contract in a direction intersecting the tensile direction. Figure 40 shows the deformation of the first openings 34a using Sample 3-2 as an example. As shown in Figure 40(a), the first openings 34a are open at an elongation rate of 0%. However, as the elongation rate increases to 10% (see Figure 40(b)), 20% (see Figure 40(c)), and 30% (see Figure 40(d)), the gaps between the fibers of the conductive cloth decrease, and at an elongation rate of 30%, the first openings 34a almost disappear. This change in fiber shape allows for easy elongation, which is thought to reduce the stress generated during elongation. In other words, the presence of the first openings 34a is thought to contribute to the structural flexibility of the fibers. The above configuration is similar for the second electrode sheet, so a description thereof will be omitted. The same is true for Sample 3-1, so a description thereof will be omitted.

[0287] In Samples 3-1 and 3-2, when a tensile force is applied to the sensor sheet, it is believed that the tensile force is absorbed by the gradual deformation of the first openings 34a. As a result, the relative positions of the warp filament aggregates 72a and the weft filament aggregates 72b do not change significantly at the intersections between the warp filament aggregates 72a and the weft filament aggregates 72b, and therefore the electrical connection between the warp filament aggregates 72a and the weft filament aggregates 72b is maintained. As a result, in Samples 3-1 and 3-2, it is believed that the DC resistance value changes very little even when a tensile force is applied to the sensor sheet.

[0288] Furthermore, Samples 3-1 and 3-2 do not have a yield point with a maximum value in the strain range of 0.5 to 5%. This is thought to be because Samples 3-1 and 3-2 do not experience significant changes in the structure of the plating layer 33 formed on the first electrode sheet and the second electrode sheet in the strain range of 0.5 to 5%. This suppresses changes in the electrical resistance of the sensor sheet 18.

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

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

[0291] Thereafter, when the strain becomes larger than about 15%, the first openings 34a and the second openings 34b are completely blocked because the first opening ratio and the second opening ratio of Sample 3-3 are 20%, and it is believed that the tensile force acting on the first electrode sheet and the second electrode sheet can no longer be absorbed, which is believed to increase the stress.

[0292] 3.1.7.6. DC Resistance Change Rate of Sensor Sheet Next, the DC resistance change rate of the sensor sheet was measured. The sensor sheet was cut into a 90 mm x 20 mm strip to prepare a test piece. The angle between the longitudinal direction of the test piece and the longitudinal direction of the warp filament assembly 72a was set to 45°.

[0293] The test piece is held 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 wires is measured. The DC resistance value is used to calculate the rate of change in DC resistance based on the following formula (1). The DC resistance value is measured using a 2000 series digital multimeter manufactured by Keithley Corporation. The above test is performed on Samples 3-1 to 3-2 and Sample 3-3.

[0294]

[0295] 41 is a graph showing the change in DC resistance value with strain. The DC resistance value change of Sample 3-1 increased in the strain range of 0 to approximately 2%, and at a strain of approximately 2%, the DC resistance value change was approximately 5%. Thereafter, the DC resistance value change decreased in the strain range of approximately 2 to approximately 5%, and the DC resistance value change was approximately 0%. Thereafter, at a strain of approximately 25% or more, the DC resistance value change gradually increased, and at a strain of 30%, the DC resistance value change was approximately 7%. Thus, the DC resistance value change of Sample 3-1 was 10% or less in the strain range of 0 to 30%.

[0296] The DC resistivity change rate of Sample 3-2 increased in the strain range of 0 to approximately 3%, and at a strain of approximately 3%, the DC resistivity change rate was approximately 10%. Thereafter, the DC resistivity change rate decreased in the strain range of approximately 3 to approximately 5%, and reached approximately 0%. Thereafter, even at a strain of 30%, the DC resistivity change rate was approximately 0%. Thus, the DC resistivity change rate of Sample 3-2 was 10% or less in the strain range of 0 to 30%.

[0297] The DC resistance change rate of Sample 3-3 was approximately 2% in the strain range of 0 to approximately 3%. Thereafter, in the strain range of approximately 3 to 30%, the DC resistance change rate monotonically increased, reaching approximately 130% at a strain of 30%. Thus, the DC resistance change rate of Sample 3-3 was greater than 10% in the strain range of 0 to 30%, and the resistance change during extension was significantly greater than that of Samples 3-1 and 3-2.

[0298] 3.1.7.7. Change in DC resistance of sensor sheet at 10% elongation Next, the change in DC resistance of the sensor sheet at 10% elongation was measured. The sensor sheet was cut into a 90 mm x 20 mm strip to prepare a test piece. The angle between the longitudinal direction of the test piece and the longitudinal direction of the warp filament assembly 72a was set to 45°.

[0299] The test piece is held 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 wires is measured. The DC resistance value is used to calculate the rate of change in DC resistance based on the following formula (1). The DC resistance value is measured using a 2000 series digital multimeter manufactured by Keithley Corporation. The above test is performed on Samples 3-1 to 3-2 and Sample 3-3.

[0300] When measuring the rate of change in DC resistance of the sensor sheet described above, the sensor sheet is stretched by 10% relative to the reference length (50 mm) before applying a tensile force to the sensor sheet, then returned to the reference length, and again stretched by 10%. This test is repeated a predetermined number of times. The number of repetitions in this test is 1, 5, and 10. The rate of change in DC resistance is calculated based on the DC resistance value at this time using the above formula (1). The above test is performed on Samples 3-1 to 3-2 and Sample 3-3.

[0301] 42 shows a graph showing the relationship between the number of repetitions of the extension test and the rate of change in DC resistance. For Sample 3-1, the rate of change in DC resistance at the first measurement was approximately 0%. Thereafter, as the number of repetitions increased, the rate of change in DC resistance increased to approximately 36% after one repetition, approximately 48% after five repetitions, and approximately 57% after ten repetitions. After ten repetitions, the rate of change in DC resistivity for Sample 3-1 was 60% or less.

[0302] For Sample 3-2, the DC resistivity change rate at the initial measurement was approximately 14%, which was larger than that of Sample 3-1. However, the DC resistance change rate did not increase significantly with increasing number of repetitions, being approximately 9% after one repetition and approximately 15% after five repetitions. After 10 repetitions, the DC resistance change rate for Sample 3-2 was approximately 30%. After 10 repetitions, the DC resistance change rate for Sample 3-2 was 50% or less.

[0303] The rate of change in DC resistance value of Sample 3-3 at the initial measurement was approximately 0%, which was the same as that of Sample 3-1. However, as the number of repetitions increased, the rate of change in DC resistance value increased to approximately 61% after one repetition, approximately 89% after five repetitions, and approximately 115% after ten repetitions, and was therefore greater than that of Samples 3-1 and 3-2.

[0304] As described above, it was found that the sensor sheets of Samples 3-1 and 3-2 showed smaller changes in DC resistance value than Sample 3-3, even when the 10% elongation test was repeated.

[0305] 3.1.7.8. Rate of change in DC resistance value of sensor sheet when stretched by 20% Next, the rate of change in DC resistance value when the sensor sheet is stretched by 20% is measured for Samples 3-1 to 3-2 and Sample 3-3.

[0306] 43 shows a graph showing the relationship between the number of repetitions of the extension test and the rate of change in DC resistance. For Sample 3-1, the rate of change in DC resistance at the first measurement was approximately 0%. Thereafter, the rate of change in DC resistance increased as the number of repetitions increased, reaching approximately 35% after one repetition and approximately 91% after five repetitions. After 10 repetitions, the rate of change in DC resistance was approximately 137%.

[0307] The DC resistivity change rate of Sample 3-2 at the first measurement was about 10%, which was larger than that of Sample 3-1. However, the DC resistivity change rate did not increase significantly with increasing number of repetitions, being about 27% after one repetition and about 32% after five repetitions. After 10 repetitions, the DC resistivity change rate of Sample 3-2 was about 55%.

[0308] The DC resistance change rate of Sample 3-3 at the first measurement was about 0%, which was the same as that of Sample 3-1. However, it showed about 114% after one repetition and exceeded 200% after five repetitions.

[0309] As described above, it was found that the sensor sheets of Samples 3-1 and 3-2 showed smaller changes in DC resistance value than Sample 3-3, even when the 20% elongation test was repeated.

[0310] 3.1.8. Effects of the Present 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, 25a, a first bonding portion 36, a second electrode sheet 26, and a second bonding 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, 25a are conductive, are disposed on the first surface 27 side of the insulating sheet 24, and have a first opening 34a penetrating therethrough. The first bonding portion 36 bonds the insulating sheet 24 and the first electrode sheet 25, 25a. The second electrode sheet 26 is conductive, is disposed on the second surface 28 side of the insulating sheet 24, and has a second opening 34b penetrating therethrough. The second bonding portion 37 bonds the insulating sheet 24 and the second electrode sheet 26. The first electrode sheets 25, 25a and the second electrode sheet 26 are conductive cloths woven with a plurality of filament assemblies 72. The filament assemblies 72 include a plurality of filaments 71 and a plating layer 33 formed on at least a portion of the surface of the filaments 71. The first electrode sheets 25, 25a include first openings 34a that open between the plurality of filament assemblies 72, and the second electrode sheet 26 includes second openings 34b that open between the plurality of filament assemblies 72. The sensor sheet 18 is configured so that a stress-strain curve in a tensile test does not have a yield point that shows a maximum value in the strain range of 0.5 to 10%. The aperture ratio, which is the ratio of the opening area of ​​the first openings 34a to the area of ​​the first electrode sheets 25, 25a, is 1% to 40%. The aperture ratio, which is the ratio of the opening area of ​​the second openings 34b to the area of ​​the second electrode sheets 26, 26a, is 1% to 40%.

[0311] When a tensile force is applied to the sensor sheet 18, the first openings 34a of the first electrode sheets 25, 25a deform, reducing the opening area of ​​the first openings 34a. Furthermore, new conductive paths are formed between the multiple filament assemblies 72 that were previously separated by the first openings 34a. This prevents changes in the electrical resistance value even when a tensile force is applied to the sensor sheet 18. The same applies to the second openings 34b of the second electrode sheets 26, 26a.

[0312] The opening ratio of the first opening 34a is preferably 1% or more and 40% or less. With an opening ratio of 40% or less, when the first opening 34a is deformed in a direction that reduces the opening area, the multiple filament assemblies 72 tend to come into contact with each other. Because the multiple filament assemblies 72 tend to come into contact with each other in this way, the opening 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 even 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 so that the stress-strain curve in a tensile test does not have a yield point showing a maximum value in the strain range of 0.5 to 10%. This prevents large stress from occurring and suppresses sudden changes in stress in the relatively small strain range of 0.5 to 10%. As a result, the efficiency of assembling the sensor sheet 18 to the steering wheel 10 can be improved. Furthermore, since the sensor sheet 18 does not have a yield point showing a maximum value in the strain range of 0.5 to 5%, when the sensor sheet 18 is slightly stretched, large stress is not generated and the stress does not change, which is more preferable because it further improves workability.

[0314] When a tensile force is applied to the sensor sheet 18, the first openings 34a of the first electrode sheet 25 deform, and the opening area of ​​the first openings 34a decreases. In other words, the filaments 71 are stretchable by changing the spatial arrangement of the entire filament 71, without tensile strain concentrating on the filaments 71 themselves. That is, the reduction in the opening area accompanying the change in the spatial arrangement of the entire filament 71 exhibits structural flexibility for expansion and contraction, so the extension strain applied to the filaments 71 themselves is small and damage to the plating layer 33 formed on the filaments 71 can be suppressed. Therefore, even when a tensile force is applied to the sensor sheet 18, changes in the electrical resistance value can be suppressed.

[0315] Furthermore, the sensor sheet 18 according to this embodiment is configured so that the stress-strain curve in a tensile test does not have a yield point that shows a maximum value in the strain range of 0.5 to 10%, which prevents the plating layer 33 from breaking in the strain range of 0.5 to 10%, thereby preventing changes in the electrical resistance of the sensor sheet 18.

[0316] The sensor sheet 18 according to this embodiment is configured so that the maximum stress value in the stress-strain curve is 0.5 MPa or less when the strain is 0 to 5%. Furthermore, the sensor sheet 18 is configured so that the maximum stress value in the stress-strain curve is 3 MPa or less when the strain is 0 to 20%. This prevents excessively large stress from being applied to the first electrode sheets 25, 25a when a tensile force is applied to the sensor sheet 18. As a result, damage to the structure of the first electrode sheets 25, 25a can be prevented, and changes in the electrical resistance value of the sensor sheet 18 can be prevented.

[0317] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or the stress applied to the second electrode sheets 26, 26a, the maximum stress value of the sensor sheet 18 at a strain of 0 to 5% in the stress-strain curve 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 the second electrode sheets 26, 26a, the maximum stress value of the sensor sheet 18 at a strain of 0 to 20% in the stress-strain curve is preferably 3 MPa or less, more preferably 2 MPa or less, and even more preferably 1.5 MPa or less.

[0319] The first electrode sheets 25, 25a according to this embodiment are configured so that the maximum stress in the stress-strain curve is 3 MPa or less when the strain is 0 to 5%. The first electrode sheets 25, 25a are configured so that the maximum 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, 26a.

[0320] From the viewpoint of reducing the stress applied to the first electrode sheets 25, 25a or the stress applied to the second electrode sheets 26, 26a, the maximum value of the stress of the first electrode sheets 25, 25a or the second electrode sheets 26, 26a at a strain of 0 to 5% in the stress-strain curve 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, 25a or the stress applied to the second electrode sheets 26, 26a, the maximum value of the stress of the first electrode sheets 25, 25a or the second electrode sheets 26, 26a at a strain of 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 when a test piece of 20 mm x 90 mm is gripped and a tensile test is carried out at a tensile speed of 1 mm / s.

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

[0324] However, the difference in DC resistance before and after stretching is the difference obtained by subtracting the initial DC resistance before stretching from the DC resistance after stretching.

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

[0326] The sensor sheet 18 of this embodiment is configured so that the DC resistance change rate defined by equation (1) is 150% or less after a test in which the strain is increased to 20% and then returned to 0% is repeated 10 times.

[0327] However, the difference in DC resistance before and after stretching is the difference obtained by subtracting the initial DC resistance before stretching from the DC resistance after stretching.

[0328] According to this embodiment, even when the sensor sheet 18 is repeatedly stretched and then restored to its original dimensions, it is possible to suppress changes in the DC resistance value, thereby suppressing changes in the electrical resistance value of the sensor sheet 18. The rate of change in the DC resistance value 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 multiple filament assemblies 72 in this embodiment is larger than the opening area of ​​the first opening 34a when the first electrode sheet 25, 25a is not distorted. This increases the proportion of the filament assemblies 72 per unit area, thereby forming many conductive paths in the first electrode sheet 25, 25a. As a result, even if a tensile force is applied to the sensor sheet 18 and some of the multiple conductive paths are damaged, it is possible to leave electrically conductive paths. This prevents changes in the electrical resistance of the sensor sheet 18. Furthermore, the cross-sectional area of ​​each of the multiple filament assemblies 72 is larger than the opening area of ​​the second opening 34b when the second electrode sheet 26, 26a is not distorted. The effects are similar to those of the first electrode sheets 25, 25a, so a description thereof will be omitted.

[0330] The multiple filament assemblies 72 according to this embodiment include warp filament assemblies 72 a and weft filament assemblies 72 b, and the area of ​​the intersections between the warp filament assemblies 72 a and the weft filament assemblies 72 b is larger than the opening area of ​​the first opening 34 a when the first electrode sheets 25, 25 a are not distorted. Note that, for the second electrode sheets 26, 26 a, the area of ​​the intersections between the warp filament assemblies 72 a and the weft filament assemblies 72 b is also larger than the opening area of ​​the second opening 34 b when the second electrode sheets 26, 26 a are not distorted.

[0331] At the intersections of the warp filament aggregates 72a and the weft filament aggregates 72b, the warp filament aggregates 72a and the weft filament aggregates 72b are electrically conductive. Therefore, at the intersections of the warp filament aggregates 72a and the weft filament aggregates 72b, the plating layer 33 is formed on the exposed portions. Furthermore, the greater the area where the plating layer 33 is formed, even in the inner portions (inside the intersections), the more likely the warp filament aggregates 72a and the weft filament aggregates 72b are to be electrically conductive. Therefore, according to this embodiment, even when a tensile force is applied to the sensor sheet 18, electrical conductivity between the warp filament aggregates 72a and the weft filament aggregates 72b can be maintained. As a result, changes in the electrical resistance 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 including the second electrode sheets 26, 26a, the sensor sheet 18 can be electromagnetically shielded, thereby improving the sensitivity of the sensor sheet 18.

[0333] The plurality of filament assemblies 72 according to this embodiment include a warp filament assembly 72 a and a weft filament assembly 72 b. The warp filament assembly 72 a and the weft filament assembly 72 b each include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled together in an untwisted state, and a plating layer 33 formed on at least a portion of the surface of the untwisted yarn bundle 74.

[0334] Because the filament assembly 72 is an untwisted yarn bundle 74, the multiple filaments 71 that make up the filament assembly 72 are configured to move relatively freely. Therefore, even if a tensile force is applied to the sensor sheet 18, the multiple filaments 71 that make up the untwisted yarn bundle 74 move, making it possible to absorb the stress. This prevents excessive stress from being applied to the sensor sheet 18, thereby preventing changes in the electrical resistance value of the sensor sheet 18.

[0335] In the filament assembly 72 according to this embodiment, the portions where the plating layers 33 formed on the surfaces of adjacent filaments 71 come into contact with each other and are thereby electrically connected are also present on the outer surfaces of the plurality of filaments 71 located inside the bundled non-twisted yarn wire 74. Therefore, even if the plating layers 33 formed on the outer surfaces of the filaments 71 located on the surface of the non-twisted yarn wire 74 break when a tensile force is applied to the sensor sheet 18, there are still plating layers 33 formed on the outer surfaces of the plurality of filaments 71 located inside the non-twisted yarn wire 74. As a result, the plating layers 33 formed on the outer surfaces of the plurality of filaments 71 located inside the non-twisted yarn wire 74 come into contact with each other, thereby suppressing changes in the electrical resistance value 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 Figures 44 to 47. Of the symbols used in embodiment 3-2 and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components as those in the previous embodiments, unless otherwise specified.

[0337] 3.2.1. Configuration of First Electrode Sheet 25c As shown in FIG. 44, the first electrode sheet 25c according to embodiment 3-2 includes a warp filament assembly 72a and a weft filament assembly 72b. As described above, the warp filament assembly 72a and the weft filament assembly 72b include an untwisted bundled wire 74 in which a plurality of filaments 71 are bundled together in an untwisted state, and a plating layer 33 formed on the surface of the untwisted bundled wire 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. The configuration of the second electrode sheet is substantially the same as that of the first electrode sheet 25c, and therefore a redundant description will be omitted.

[0338] Any metal or alloy such as copper, nickel, tin, solder, etc. can be appropriately selected as the metal constituting the plating layer 33. The metal constituting the plating layer 33 is the same as that in embodiment 3-1, so a duplicated description will be omitted.

[0339] In this embodiment, the metal type constituting the plated layer 33 of the plurality of warp filament assemblies 72a is the same as the metal type constituting the plated layer 33 of the plurality of weft filament assemblies 72b. However, the metal type constituting the plated layer 33 of the plurality of warp filament assemblies 72a may be different from the metal type constituting the plated layer 33 of the plurality of weft filament assemblies 72b. Furthermore, the metal type constituting the plated layer 33 of the plurality of warp filament assemblies 72a may be different in the direction in which the plurality of warp filament assemblies 72a are arranged. Furthermore, the metal type constituting the plated layer 33 of the plurality of weft filament assemblies 72b may be different in the direction in which the plurality of weft filament assemblies 72b are arranged. Furthermore, at least two of the plurality of warp filament assemblies 72a may have different metal types constituting the plated layers 33 formed on the plurality of filaments 71 constituting each warp filament assemblies 72a. Furthermore, at least two of the multiple weft filament assemblies 72b may have different metal types constituting the plating layer 33 formed on the multiple filaments 71 constituting each weft filament assembly 72b.

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

[0341] As shown in Fig. 44, each warp filament assembly 72a includes a plurality of filaments 71. The number of filaments 71 constituting one warp filament assembly 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 is true for the second electrode sheet.

[0344] As shown in Figure 45, a plating layer 33 is formed on at least a portion of the surface of each filament 71 constituting the warp filament assembly 72a. The plating layer 33 may be formed on the entire surface of each filament 71 constituting the warp filament assembly 72a, or the plating layer 33 may be formed on only a portion of the surface of each filament 71 constituting the warp filament assembly 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 assembly 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 Figure 46, a plating layer 33 is formed on at least a portion of the surface of each filament 71 constituting the weft filament assembly 72b. The plating layer 33 may be formed on the entire surface of each filament 71 constituting the weft filament assembly 72b, or the plating layer 33 may be formed on only a portion of the surface of each filament 71 constituting the weft filament assembly 72b. In this embodiment, the plating layer 33 is formed on the surface of each filament 71 except for 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 assembly 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] In this embodiment, a plating layer 33 is formed on the surface of each filament 71, except for a weft filament contact point 71ab where the filaments 71 constituting the warp filament aggregate 72a and the filaments 71 constituting the weft filament aggregate 72b come into contact with each other. The warp filament aggregate 72a and the weft filament aggregate 72b are electrically connected by the plating layer 33.

[0347] 47 , the region of the first electrode sheet 25c sandwiched between two recesses 30 formed at overlapping positions in the transverse direction Y is defined as a narrow portion 35 that is narrower in the transverse direction Y than the other portions. In the narrow portion 35, the area occupied by the plurality of warp filament assemblies 72a projected in the thickness direction Z of the narrow portion 35 is larger than the area occupied by the plurality of weft filament assemblies 72b projected in the thickness direction Z of the narrow portion 35.

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

[0349] 3.2.2.3 The number of the filaments 71 constituting the warp filament assembly 72 a in the narrow width portion 35 is greater than the number of the filaments 71 constituting the warp filament assembly 72 a in a portion other than the narrow width portion 35 .

[0350] 3.2.2.4 The number of the filaments 71 constituting the weft filament assembly 72b in the narrow width portion 35 is greater than the number of the filaments 71 constituting the weft filament assembly 72b in a portion other than the narrow width portion 35.

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

[0352] 3.2.3 Relationship between First Electrode Sheet 25c and Extension 31 As described above, in the first electrode sheet 25c of this embodiment, the longitudinal direction S of the multiple warp filament assemblies 72a forms 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 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. Fig. 47 schematically shows a lattice pattern inclined at 45° with respect to the extension direction of the multiple warp filament assemblies 72a and the multiple weft filament assemblies 72b of the first electrode sheet 25c.

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

[0354] 47, in the extension portion 31 of the first electrode sheet 25c, the angle α formed between the extension direction E2 of the extension portion 31b formed on the right side of Fig. 47 and the longitudinal direction S of the multiple warp filament assemblies 72a is larger than the angle β formed between the extension direction E2 of the extension portion 31b and the longitudinal direction T of the multiple weft filament assemblies 72b. The same is true for the second electrode sheet.

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

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

[0357] 3.2.3.5. The number of the filaments 71 constituting the warp filament assembly 72a in the extension portion 31 of the first electrode sheet 25c is greater than the number of the filaments 71 constituting the warp filament assembly 72a in the portion other than the extension portion 31.

[0358] 3.2.3.6. The number of the filaments 71 constituting the weft filament assembly 72b in the extension portion 31 of the first electrode sheet 25c is greater than the number of the filaments 71 constituting the weft filament assembly 72b in the portion other than the extension portion 31.

[0359] The configurations described in 3.2.3.1 to 3.2.3.6 above are independent of each other, and all of the configurations described in 3.2.3.1 to 3.2.3.6 may be included, or at least one selected from the configurations described in 3.2.3.1 to 3.2.3.6 may be included. 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 a radius of 0.38 mm in accordance with JIS P8115:2001, the increase in electrical resistance after 1,000 cycles is preferably 50% or less, more preferably 50% or less, after 2,000 cycles, even more preferably 50% or less, after 5,000 cycles, and particularly preferably 50% or less, after 10,000 cycles. This makes it possible to obtain a sensor sheet 18 in which an increase in electrical resistance is suppressed even when an external force is applied.

[0361] 3.2.5. Effects of the Present Embodiment Next, the effects of the present embodiment will be described. The first electrode sheet 25c of the sensor sheet 18 of the present embodiment is a conductive cloth including a plurality of warp filament assemblies 72a each having a plurality of filaments 71, and a plurality of weft filament assemblies 72b each having a plurality of filaments 71. A metal plating layer 33 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 severed, the conductive paths of the other filaments 71 are likely to continue. Also, even if the conductive path between one filament 71 and another filament 71 is severed, the conductive path between any of the other filaments 71 is likely to continue. As a result, even when an external force is applied to the sensor sheet 18, the conductive paths between the multiple filaments 71 that make up the sensor sheet 18 are likely to continue, which makes it 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.

[0363] Furthermore, in this embodiment, the plurality of warp filament assemblies 72 a are arranged side by side at equal intervals, and the plurality of weft filament assemblies 72 b are arranged side by side at unequal intervals. The strength of the first electrode sheet 25 c can be improved by the plurality of warp filament assemblies 72 a arranged at equal intervals, while the stretchability of the first electrode sheet 25 c can be improved by the plurality of weft filament assemblies 72 b arranged at unequal intervals.

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

[0365] Adjacent filaments 71 constituting the weft filament assembly 72b according to this embodiment are electrically connected to each other in the region exposed on the surface of the first electrode sheet 25c by the plating layer 33. This allows the multiple filaments 71 constituting the weft filament assembly 72b to be electrically connected to each other.

[0366] As shown in FIG. 45 , in this embodiment, the filaments 71 constituting the warp filament assembly 72a contact each other at a warp filament contact point 71aa (an example of a filament contact point). Also, as shown in FIG. 46 , the filaments 71 constituting the weft filament assembly 72b contact each other at a weft filament contact point 71ab (an example of a filament contact point). Also, as shown in FIGS. 45 and 46 , the filaments 71 constituting the warp filament assembly 72a and the filaments 71 constituting the weft filament assembly 72b contact each other at a warp-to-warp filament contact point 71ac (an example of a filament contact point). According to this embodiment, a plating layer 33 is formed on the surfaces of the multiple filaments 71, except for the warp filament contact point 71aa, the weft filament contact point 71ab, and the weft-to-warp filament contact point 71ac. This increases the likelihood that the conductive paths of the multiple filaments 71 constituting the sensor sheet 18 will remain intact even when an external force is applied to the sensor sheet 18. This prevents an increase in the electrical resistance 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 than other portions in a transverse direction Y that intersects with the longitudinal direction X of the first electrode sheet 25c. In the narrow portion 35, the area occupied by the multiple warp filament assemblies 72a when projected in the thickness direction Z of the narrow portion 35 is larger than the area occupied by the multiple weft filament assemblies 72b when projected in the thickness direction Z of the narrow portion 35. According to this embodiment, by making the area occupied by the multiple warp filament assemblies 72a in the narrow portion 35 larger than the area occupied by the multiple weft filament assemblies 72b, the strength of the narrow portion 35 can be improved.

[0368] 3.2.6.2 In the narrow width portion 35 according to this embodiment, the spacing between adjacent filaments 71 constituting the plurality of weft filament assemblies 72b is smaller than the spacing between adjacent filaments 71 constituting the plurality of warp filament assemblies 72a. Because the narrow width portion 35 is prone to large deformation, it is prone to being subjected to a relatively large force, which makes it easy for the plating layer 33 to peel off. According to this embodiment, by making the spacing between the filaments 71 constituting the plurality of weft filament assemblies 72b smaller than the spacing between the filaments 71 constituting the plurality of warp filament assemblies 72a, it is possible to maintain the conductive paths between the filaments 71 constituting the weft filament assemblies 72b.

[0369] 3.2.6.3 The number of filaments 71 constituting the warp filament assembly 72a in the narrow width portion 35 according to this embodiment is greater than the number of filaments 71 constituting the warp filament assembly 72a in a portion other than the narrow width portion 35. According to this embodiment, by increasing the number of filaments 71 constituting the warp filament assembly 72a in the narrow width portion 35 compared to other portions, the strength of the narrow width portion 35 can be improved.

[0370] 3.2.6.4 In this embodiment, the number of filaments 71 constituting the weft filament assembly 72b in the narrow width portion 35 is greater than the number of filaments 71 constituting the weft filament assembly 72b in a portion other than the narrow width portion 35. According to this embodiment, by increasing the number of filaments 71 constituting the weft filament assembly 72b in the narrow width portion 35 compared to other portions, the strength of the narrow width portion 35 can be improved.

[0371] 3.2.6.5. According to this embodiment, the first electrode sheet 25c has extensions 31a, 31b extending in extension directions E1, E2 from its long side edge along the longitudinal direction X. In the extensions 31a, 31b, the occupied area of ​​the multiple warp filament assemblies 72a when projected in the thickness direction Z of the extensions 31a, 31b is larger than the occupied area of ​​the multiple weft filament assemblies 72b when projected in the thickness direction Z of the extensions 31a, 31b. This makes the occupied area of ​​the multiple warp filament assemblies 72a larger than the occupied area of ​​the multiple weft filament assemblies 72b, thereby improving the strength of the extensions 31a, 31b.

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

[0373] 3.2.6.7 In the extension portion 31b according to this embodiment, the angle α between the extension direction E2 of the extension portion 31b and the longitudinal direction S of the plurality of warp filament assemblies 72a is larger than the angle β between the extension direction E2 of the extension portion 31b and the longitudinal direction T of the plurality of weft filament assemblies 72b. This allows the longitudinal direction T of the plurality of weft filament assemblies 72b to be aligned with the extension direction E2 of the extension portion 31b. This improves the strength of the extension portion 31b.

[0374] 3.2.6.8 In the extension portion 31 according to this embodiment, the spacing between adjacent filaments 71 that make up the weft filament assembly 72b is smaller than the spacing between adjacent filaments 71 that make up the warp filament assembly 72a. Because the extension portion 31 is prone to large deformation, it is prone to being subjected to relatively large forces, which can easily cause the plating layer 33 to peel off. According to this embodiment, by making the spacing between adjacent filaments 71 that make up the weft filament assembly 72b smaller than the spacing between adjacent filaments 71 that make up the warp filament assembly 72a, it is possible to maintain the conductive paths between the filaments 71 that make up the weft filament assembly 72b.

[0375] 3.2.6.9 The number of filaments 71 constituting the warp filament assembly 72a in the extension portion 31 according to this embodiment is greater than the number of filaments 71 constituting the warp filament assembly 72a in a portion other than the extension portion 31. According to this embodiment, by making the number of filaments 71 constituting the warp filament assembly 72a in the extension portion 31 greater than in other portions, the strength of the extension portion 31 can be improved.

[0376] 3.2.6.10 The number of filaments 71 constituting the weft filament assembly 72b in the extension portion 31 according to this embodiment is greater than the number of filaments 71 constituting the weft filament assembly 72b in a portion other than the extension portion 31. According to this embodiment, by making the number of filaments 71 constituting the weft filament assembly 72b in the extension portion 31 greater than in other portions, the strength of the extension portion 31 can be improved.

[0377] 3.2.6.11 The opening ratio, which is the ratio of the opening area of ​​the first openings 34a of the first electrode sheet 25c to the area of ​​the first electrode sheet 25c, is 30% or more. This can improve the stretchability of the first electrode sheet 25c.

[0378] The configurations described in 3.2.6.1 to 3.2.6.11 above are independent of each other, and all of the configurations described in 3.2.6.1 to 3.2.6.11 may be included, or at least one selected from the configurations described in 3.2.6.1 to 3.2.6.11 may be included. 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) Next, a first electrode sheet 25d of embodiment 3-3 will be described with reference to Figures 48 and 49. Figure 48 also shows a partially enlarged view of region R1.

[0380] 48, in this embodiment, at least some of the filaments 71 constituting the warp filament assemblies 72a have warp filament facing surfaces 71ba (an example of a filament facing surface) that face each other. In this embodiment, a plating layer 33 is formed on the warp filament facing surfaces 71ba.

[0381] Of the multiple filaments 71 constituting the warp filament assembly 72a, the plated layer 33 formed on the warp filament-facing surface 71ba of one filament 71 is in contact with the plated layer 33 formed on the warp filament-facing surface 71ba of another filament 71 adjacent to the one filament 71. This electrically connects the multiple filaments 71 constituting the warp filament assembly 72a.

[0382] 49 also shows a partially enlarged view of region R2. As shown in FIG. 49, in this embodiment, at least some of the filaments 71 constituting the weft filament assembly 72b have weft filament facing surfaces 71bb that face each other. In this embodiment, a plating layer 33 is formed on the weft filament facing surfaces 71bb. The plating layers 33 formed on the weft filament facing surfaces 71bb of adjacent filaments 71 constituting the weft filament assembly 72b come into contact with each other, thereby electrically connecting the filaments 71 constituting the weft filament assembly 72b.

[0383] At the portion where the warp filament assembly 72a and the weft filament assembly 72b intersect and overlap, the filaments 71 exposed on the outer surface of the warp filament assembly 72a and the filaments 71 exposed on the outer surface of the weft filament assembly 72b have opposing warp and weft filament facing surfaces 71bc (an example of a filament facing surface) that face each other. In this embodiment, a plating layer 33 is formed on the warp and weft filament facing surfaces 71bc. This electrically connects the warp filament assembly 72a and the weft filament assembly 72b.

[0384] In this embodiment, of the multiple filaments 71 that constitute the warp filament aggregate 72a, at least some of the multiple filaments 71 located inside the warp filament aggregate 72a have warp filament facing surfaces 71ba that face each other, and a plating layer 33 is formed on the warp filament facing surfaces 71ba.

[0385] The plating layer 33 is formed on the warp filament facing surface 71ba of the filaments 71 located inside the warp filament assembly 72a, so that even when an external force is applied to the sensor sheet 18, the external force is prevented from being directly applied to the warp filament facing surface 71ba. As a result, the plating layer 33 formed on the facing surface is more likely to survive. This increases the likelihood that the conductive paths of the warp filament assembly 72a that constitutes the sensor sheet 18 will survive even when an external force is applied to the sensor sheet 18, thereby preventing an increase in the electrical resistance of the sensor sheet 18 when an external force is applied to the sensor sheet 18.

[0386] In this embodiment, of the multiple filaments 71 constituting the warp filament assembly 72a, the plating layer 33 formed on the warp filament-facing surface 71ba of one filament 71 is in contact with the plating layer 33 formed on the warp filament-facing surface 71ba of another filament 71. According to this embodiment, a conduction path between one filament 71 and another filament 71 can be maintained, thereby suppressing an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18. Note that the weft filament assembly 72b also provides the same effects as the warp filament assembly 72a, so a redundant description will be omitted.

[0387] In this embodiment, one filament 71 of the multiple filaments 71 constituting the warp filament assembly 72a and one filament 71 of the multiple filaments 71 constituting the weft filament assembly 72b have warp and weft filament opposing surfaces 71bc that face each other, and a plating layer 33 is formed on the warp and weft filament opposing surfaces 71bc.

[0388] Since the warp and weft filament opposing surfaces 71bc are located inside the first electrode sheet 25d as a whole, even when an external force is applied to the sensor sheet 18, it is possible to increase the likelihood that a conductive path will remain between the filaments 71 that make up the warp filament aggregate 72a and the filaments 71 that make up the weft filament aggregate 72b that make up the sensor sheet 18, thereby preventing an increase in the electrical resistance value of the sensor sheet 18 when an external force is applied to the sensor sheet 18.

[0389] In this embodiment, the plating layer 33 formed on the warp filament-facing surface 71ba of one filament 71 constituting the warp filament assembly 72a is in contact with the plating layer 33 formed on the warp filament-facing surface 71ba of one filament 71 constituting the weft filament assembly 72b. According to this embodiment, a conduction path can be maintained between the warp filament assembly 72a and the weft filament assembly 72b, thereby suppressing an increase in the electrical resistance of the sensor sheet 18 when an external force is applied to the sensor sheet 18. Note that the weft filament assembly 72b also provides the same effects as the warp filament assembly 72a, so a redundant description will be omitted.

[0390] When a user's hands remain in contact with the steering wheel 10, the steering wheel is exposed to high temperatures and humidity. If high temperatures and humidity continue for a long period of time, the plating layers 33 formed on the surfaces of the filaments 71 exposed on the outer surfaces of the warp filament assemblies 72a and weft filament assemblies 72b may be damaged. According to this embodiment, the plating layers 33 are formed on the warp filament facing surfaces 71ba, weft filament facing surfaces 71bb, and weft filament facing surfaces 71bc. Therefore, even if the plating layers 33 formed on the surfaces of the filaments 71 exposed on the outer surfaces of the warp filament assemblies 72a and weft filament assemblies 72b are damaged, the plating layers 33 formed on the warp filament facing surfaces 71ba, weft filament facing surfaces 71bb, and weft filament facing surfaces 71bc are less likely to be damaged. This prevents an increase in the electrical resistance of the sensor sheet 18. The second electrode sheet also provides the same effects as described above, and therefore a redundant description will be omitted.

[0391] (Embodiment 3-4) Next, embodiment 3-4 will be described with reference to FIG.

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

[0393] (b) In this embodiment, the intervals between adjacent warp filament assemblies 72a vary in the direction in which the multiple warp filament assemblies 72a are arranged.

[0394] (c) In this embodiment, the number of filaments 71 constituting the warp filament assemblies 72a varies in the direction in which the warp filament assemblies 72a are arranged. By varying the strength of the warp filament assemblies 72a in this manner, it is possible to easily vary the strength of the first electrode sheet 25e in parts.

[0395] (d) In this embodiment, the plurality of warp filament assemblies 72 a are arranged side by side with intervals therebetween, and the intervals between adjacent warp filament assemblies 72 a vary in the direction in which the plurality of warp filament assemblies 72 a are arranged. By varying the intervals between the plurality of warp filament assemblies 72 a in this manner, the stretchability of the first electrode sheet 25 e can be easily changed.

[0396] The configurations described in (a) to (d) above are independent of each other, and all of the configurations described in (a) to (d) may be included, or at least one selected from the configurations described in (a) to (d) may be included. Furthermore, the configurations described in (a) to (d) may be omitted. The second electrode sheet may also have the same configuration as the first electrode sheet 25e, and therefore, redundant explanations will be omitted.

[0397] (Embodiment 3-5) Next, embodiment 3-5 will be described with reference to FIG.

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

[0399] (f) In this embodiment, the intervals between adjacent weft filament assemblies 72b vary in the direction in which the multiple weft filament assemblies 72b are arranged.

[0400] (g) In this embodiment, the number of filaments 71 constituting the weft filament assemblies 72b varies in the direction in which the weft filament assemblies 72b are arranged. By varying the strength of the weft filament assemblies 72b in this manner, it is possible to easily vary the strength of the first electrode sheet 25f partially.

[0401] (h) In this embodiment, the plurality of weft filament assemblies 72 b are arranged side by side at intervals, and the intervals between adjacent weft filament assemblies 72 b vary in the direction in which the plurality of weft filament assemblies 72 b are arranged. By varying the intervals between the plurality of weft filament assemblies 72 b in this manner, the stretchability of the first electrode sheet 25 f 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 included, or at least one selected from the configurations described in (e) to (h) may be included. Furthermore, the configurations described in (e) to (h) may be omitted. The second electrode sheet may also have the same configuration as the first electrode sheet 25f, and therefore, redundant explanations will be omitted.

[0403] (Embodiment 3-6) Next, embodiment 3-6 will be described with reference to FIG.

[0404] In the first electrode sheet 25g of this embodiment, the number of filaments 71 constituting the warp filament assembly 72a is different from the number of filaments 71 constituting the weft filament assembly 72b. This allows the strength of the warp filament assembly 72a to be different from the strength of the weft filament assembly 72b. As a result, it is easy to partially vary the strength of the first electrode sheet 25. The number of filaments 71 constituting the warp filament assembly 72a may be greater than the number of filaments 71 constituting the weft filament assembly 72b. Furthermore, the number of filaments 71 constituting the warp filament assembly 72a may be less than the number of filaments 71 constituting the weft filament assembly 72b. Note that the second electrode sheet can also have a configuration similar to that of the first electrode sheet 25g, and therefore a redundant description will be omitted.

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

[0406] According to this embodiment, plating is performed while ensuring pressure between the warp filament aggregate 72a and the weft filament aggregate 72b by the weft filament aggregate 72b including the twisted wire 73. This further improves the contact pressure at the contact points of the plurality of warp filament aggregates 72a and the plurality of weft filament aggregates 72b, thereby preventing an increase in the electrical resistance of the sensor sheet 18.

[0407] However, the warp filament assembly 72a may include twisted wires 73 and a plated layer 33, and the weft filament assembly 72b may include untwisted bundled wires 74 and a plated layer 33. However, the second electrode sheet also has the same configuration as the first electrode sheet 25h, and therefore a redundant description will be omitted.

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

[0409] In this embodiment, the angle α between the longitudinal direction S of the multiple warp filament assemblies 72a of the first electrode sheet 25i and the extension direction E1 of the extension portion 31 is smaller than the angle β between the longitudinal direction T of the multiple weft filament assemblies 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 assemblies 72a can be arranged along the extension direction E1 of the extension portion 31. This can improve the strength of the extension portion 31. Note that the second electrode sheet can also have a configuration similar to that of the first electrode sheet 25f, and therefore a redundant description will be omitted.

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

[0412] In this embodiment, the longitudinal direction S1 of the multiple warp filament aggregates 72a of the first electrode sheet 25j arranged on the left side of Fig. 55 is perpendicular to the longitudinal direction S2 of the multiple warp filament aggregates 72a of the first electrode sheet 25k arranged on the right side of Fig. 55. Also, the longitudinal direction T1 of the multiple weft filament aggregates 72b of the first electrode sheet 25j arranged on the left side of Fig. 55 is perpendicular to the longitudinal direction T2 of the multiple weft filament aggregates 72b of the first electrode sheet 25k arranged on the right side of Fig. 55.

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

[0414] Furthermore, the angle α between the longitudinal direction S2 of the multiple warp filament assemblies 72a of the first electrode sheet 25k and the extension direction E2 of the extension portion 31b is smaller than the angle β between the longitudinal direction T2 of the multiple weft filament assemblies 72b of the first electrode sheet 25j and the extension direction E2 of the extension portion 31b.

[0415] According to this embodiment, the longitudinal direction S1 of the plurality of warp filament assemblies 72a can be arranged along the extension direction E1 of the extension portion 31a, thereby improving the strength of the extension portion 31a. Furthermore, the longitudinal direction S2 of the plurality of warp filament assemblies 72a can be arranged along the extension direction E2 of the extension portion 31b, thereby improving the strength of the extension portion 31b. Note that the second electrode sheet can also have a configuration similar to that of the first electrode sheet 25i, and therefore a redundant description will be omitted.

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

[0417] As shown in Figure 56, a configuration may be adopted in which a first electrode sheet 25 is arranged on a first surface 27 of an insulating sheet 24, and a second electrode sheet 26 is not arranged on a 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 the configuration described in 1.1.1 to 1.1.4 of embodiment 1-1, the descriptions of 1.1.1 to 1.1.4 will be read as 4.1.1 to 4.1.4, and overlapping descriptions will be omitted.

[0419] 4.1.5. Bonding Structure of the First Electrode Sheet 25 and the Second Electrode Sheet 26 with the Insulating Sheet 24 As shown in FIG. 57 , the insulating sheet 24 and the first electrode sheet 25 are bonded to each other on the first surface 27 side of the insulating sheet 24 by a first bonding portion 36 interposed between the insulating sheet 24 and the first electrode sheet 25. The material constituting the first bonding portion 36 is not particularly limited and can be appropriately selected from any material, such as an acrylic adhesive, a silicone adhesive, a urethane adhesive, or a rubber-based adhesive. Also, as shown in FIG. 57 , the insulating sheet 24 and the second electrode sheet 26 are bonded to each other on the second surface 28 side of the insulating sheet 24 by a second bonding portion 37 interposed between the insulating sheet 24 and the second electrode sheet 26. The material constituting the second bonding portion 37 is the same as that of the first bonding portion 36, and therefore, a redundant description will be omitted.

[0420] 57 , a first protective portion 61 is disposed on the surface (outer surface) of the first electrode sheet 25. The first protective portion 61 is formed by covering the surface of the first electrode sheet 25 in a layered manner. Furthermore, a second protective portion 62 is disposed on the surface (outer surface) of the second electrode sheet 26. The second protective portion 62 is formed by covering the surface of the second electrode sheet 26 in a layered manner. In the following description, when there is no need to distinguish between the first protective portion 61 and the second protective portion 62, they may be referred to as protective portion 60.

[0421] The protective portion 60 is made of a resin material or a rubber material. The material for the protective portion 60 is not particularly limited, and any suitable material can be selected, 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, with acrylic, urethane, and silicone materials being preferred.

[0422] The protective portion 60 may contain additives such as antioxidants, fillers, etc., in addition to the resin material.

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

[0424] The first electrode sheet 25 and the first protective portion 61 may be configured to be integrated with the first electrode sheet 25 by the adhesiveness of the first protective portion 61. Alternatively, the first electrode sheet 25 and the first protective portion 61 may be configured to be integrated with the first electrode sheet 25 by heat-sealing the first protective portion 61 to the first electrode sheet 25. Alternatively, the first electrode sheet 25 and the first protective portion 61 may be configured to be integrated with each other by bonding them with an adhesive. The adhesive may be a known adhesive, or the same material as the material constituting the first bonding portion 36 described above may be used.

[0425] The structure in which the second electrode sheet 26 and the second protective portion 62 are integrated may be the same as or different from the structure in which the first electrode sheet 25 and the first protective portion 61 are integrated.

[0426] 4.1.7. Configuration of Electrode Sheets 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 that are electrically conductive. The first electrode sheet 25 and the second electrode sheet 26 are flexible while being electrically conductive. The first electrode sheet 25 and the second electrode sheet 26 are stretchable in the longitudinal direction X and the transverse direction Y.

[0427] 58 , the first electrode sheet 25 and the second electrode sheet 26 are conductive cloths woven with a plurality of filament assemblies 72. The filament assemblies 72 include a plurality of filaments 71 and a plating layer 33 formed on at least a portion of the surface of the filaments 71.

[0428] 58(a) and 58(b), 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 untwisted bundled yarns 74. Each untwisted bundled yarn 74 is formed by bundling a plurality of filaments 71 together in an untwisted state.

[0429] Examples of resins that can be used to form the filaments 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 that can be used to form the filaments 71 are not limited to the above, and any resin can be selected as appropriate. The second electrode sheet 26 also has a similar configuration.

[0430] The plated layer 33 is formed on the surface of a base fabric woven with a plurality of filament assemblies 72. The method for forming the plated layer 33 is not particularly limited, and any method can be appropriately selected, for example, electrolytic plating, electroless plating, electroless plating followed by electrolytic plating, or electroless plating followed by electrolytic plating.

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

[0432] 58( a), the first electrode sheet 25 has first openings 34a that open between the multiple filament assemblies 72. The first openings 34a penetrate the first electrode sheet 25. A first opening ratio, which is the ratio of the opening area of ​​the first openings 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] 58( b), the second electrode sheet 26 has second openings 34b that open between the multiple filament assemblies 72. The second openings 34b penetrate the second electrode sheet 26. A second opening ratio, which is the ratio of the opening area of ​​the second openings 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) Example 4-1 will be described with reference to FIGS. 58 and 59. As shown in FIG. 58(a), the first electrode sheet 25 according to Example 4-1 is a conductive cloth woven with a plurality of filament assemblies 72. The plurality of filament assemblies 72 include an untwisted yarn bundle 74 in which a plurality of filaments 71 are bundled together in an untwisted state, and a plating layer 33 formed on at least a portion of the surface of the untwisted yarn bundle 74. The filament assemblies 72 are 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, redundant description will be omitted unless otherwise noted.

[0435] The first electrode sheet 25 according to this Example 4-1 is formed by weaving a warp filament assembly 72a in which a plurality of filaments 71 are gathered together in an untwisted state and a weft filament assembly 72b in which a plurality of filaments 71 are gathered together in an untwisted state to form a base fabric, and then forming a plating layer 33 on the surface of this base fabric. However, the method for manufacturing the first electrode sheet 25 is not limited to the above method.

[0436] As shown in FIG. 58( a), the first electrode sheet 25 of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The first electrode sheet 25 includes first openings 34a that open between the plurality of filament assemblies 72a. The first openings 34a penetrate the first electrode sheet 25. In this Example 4-1, the aperture ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25 to the area of ​​the first electrode sheet 25, is approximately 3%. Note that this aperture ratio is the ratio of the total opening area of ​​the plurality of first openings 34a formed in a target area of ​​the first electrode sheet 25 to the area of ​​the target area of ​​the first electrode sheet 25. This aperture ratio is calculated, for example, by identifying a 10 mm × 10 mm target area on the first electrode sheet 25, adding up the areas of the first openings 34a within the target area, and dividing the total area by the area of ​​the target area.

[0437] 58(b), the second electrode sheet 26 of this embodiment includes a plurality of warp filament assemblies 72a and a plurality of weft filament assemblies 72b. The second electrode sheet 26 of this embodiment includes second openings 34b that open between the plurality of filament assemblies 72. The second openings 34b penetrate the second electrode sheet 26. In this Example 4-1, the opening ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26 to the area of ​​the second electrode sheet 26 of this embodiment, is approximately 3%.

[0438] There is no particular limitation on the number of filaments 71 included in the filament assembly 72 that constitutes the first electrode sheet 25. The filament assembly 72 according to this embodiment includes 75 filaments 71, but the number may be any number. The second electrode sheet 26 is similar to the first electrode sheet 25.

[0439] 59, a plated layer 33 is formed on at least a portion of the surface of the untwisted yarn bundle 74 that constitutes the filament assembly 72. The plated layer 33 of the warp filament assembly 72a and the plated layer 33 of the weft filament assembly 72b come into contact with each other, thereby electrically connecting the warp filament assembly 72a and the weft filament assembly 72b.

[0440] As shown in FIG. 58( a), the longitudinal direction S of the multiple warp filament assemblies 72a and the longitudinal direction X of the first electrode sheet 25 intersect. Furthermore, the longitudinal direction T of the multiple weft filament assemblies 72b and the longitudinal direction X of the first electrode sheet 25 intersect. Specifically, the longitudinal direction S of the multiple warp filament assemblies 72a forms an acute angle of substantially 45° with respect to the longitudinal direction X of the first electrode sheet 25. 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 25a. The phrase "the angle is substantially 45°" includes cases where the angle is 45° and also cases where it can be determined that the angle is substantially 45°. The second electrode sheet 26 has a configuration similar to that of the first electrode sheet 25, and therefore a redundant description will be 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°), stretching the first electrode sheet 25 parallel to the direction X results in the warp filament assembly 72a itself being stretched, requiring a large load.

[0442] On the other hand, when the longitudinal direction S of the warp filament assemblies 72a is inclined at a 45° angle relative to the longitudinal direction X of the first electrode sheet 25 (when the acute angle is substantially 45°), stretching the first electrode sheet 25 parallel to the direction X causes the square or rectangular lattice (first openings 34a) formed by the warp filament assemblies 72a and the weft filament assemblies 72b to deform into a diamond shape. This does not require a large load because the warp filament assemblies 72a or the weft filament assemblies 72b themselves are not stretched. In other words, when the acute angle is substantially 45°, structural flexibility is imparted. Furthermore, the higher the opening ratio, the more easily the square or rectangular lattice deforms into a diamond shape, and structural flexibility is less likely to be impaired. The second electrode sheet 26 is similar to the first electrode sheet 25, so a redundant description will be omitted.

[0443] However, the longitudinal direction S of the multiple warp filament assemblies 72a may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25. Furthermore, the longitudinal direction T of the multiple weft filament assemblies 72b may form an acute angle other than 45° with respect to the longitudinal direction X of the first electrode sheet 25.

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

[0445] As shown in Figure 59, a plating layer 33 is formed on at least some of the multiple filaments 71 that make up the warp filament assembly 72a. For example, the plating layer 33 is formed on the surfaces of the filaments 71 that are 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. The same applies to the weft filament assembly 72b, so redundant explanations will be omitted. However, the plating layer 33 may be formed on the surface of each filament that makes up the multiple filaments 71.

[0446] At the portion where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect, a plated layer 33 is formed in part, and the surface of the filament 71 is exposed in the portion where the plated layer 33 is not formed. At the portion where the warp filament aggregate 72a and the weft filament aggregate 72b face each other and intersect, the plated layer 33 is formed in the region closer to the portion exposed to the outside, and the plated layer 33 is not formed in the portion closer to the inside. Note that the weft filament aggregate 72b has the same configuration as the warp filament aggregate 72a, so a duplicated description will be omitted.

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

[0448] As shown in Figure 57, the first electrode sheet 25 described above is bonded to a first surface 27 of an insulating sheet 24 via a first bonding portion 36. A second electrode sheet 26 having a configuration similar to that of the first electrode sheet 25 is bonded to a second surface 28 of the insulating sheet 24 via a second bonding portion 37. The insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive manufactured by Nogawa Chemical Co., Ltd. The thickness of the first bonding portion 36 is 50 µm. The first bonding portion 36 and the second bonding portion 37 are identical, so a repeated description will be omitted.

[0449] The first protective portion 61 is disposed on the surface of the first protective portion 61 on the outer surface of the first electrode sheet 25, and they are integrated together. The first electrode sheet 25 and the first protective portion 61 are integrated together with an acrylic adhesive. The resin that makes up the first protective portion 61 is an acrylic adhesive. The thickness of the first protective portion 61 is approximately 50 to 100 μm. The first protective portion 61 and the second protective portion 62 are identical, so a redundant description will be omitted.

[0450] In this manner, a sample 4-1 of the sensor sheet 18 relating 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) Next, the configurations of the first electrode sheet 25a and the second electrode sheet 26a according to Example 4-2 will be described with reference to FIGS. 60(a) and 60(b). In the first electrode sheet 25a according to Example 4-2, the number of filaments 71a constituting the warp filament aggregate 72aa differs from 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 greater 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 less than the number of filaments 71a constituting the weft filament aggregate 72ba.

[0452] In this Example 4-2, the number of filaments 71a constituting the warp filament aggregate 72aa is set to approximately twice 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 set to approximately 80, and the number of filaments 71a constituting the weft filament aggregate 72ba is set to approximately 40. However, the difference between 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] In this Example 4-2, the aperture ratio, which is the ratio of the opening area of ​​the first openings 34a formed in the first electrode sheet 25a to the area of ​​the first electrode sheet 25a, is approximately 10%. Also, the aperture ratio, which is the ratio of the opening area of ​​the second openings 34b formed in the second electrode sheet 26a to the area of ​​the second electrode sheet 26a, is approximately 10%.

[0454] The second electrode sheet 26a has the same configuration as the first electrode sheet 25a, and therefore a duplicated description will be omitted.

[0455] In this 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 single layer of Ni. 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] The configuration other than the above is the same as in Example 4-1, so a duplicated description will be omitted.

[0457] In this Example 4-2, the insulating sheet 24 is an ether-based polyurethane foam. The first bonding portion 36 is an acrylic adhesive. The thickness of the first bonding portion 36 is approximately 50 μm. The first bonding portion 36 and the second bonding portion 37 are identical, so a duplicated description will be omitted. The first protective portion 61 is disposed on the surface of the first protective portion 61 on the outer surface of the first electrode sheet 25a, and they are integrated. The first electrode sheet 25a and the first protective portion 61 are integrated with an acrylic adhesive. The resin that constitutes the first protective portion 61 is an acrylic adhesive. The thickness of the first protective portion 61 is approximately 50 to 100 μm. The first protective portion 61 and the second protective portion 62 are identical, so a duplicated description will be omitted.

[0458] Except for the above, Sample 4-2 of the sensor sheet 18 relating to the first electrode sheet of Example 4-2 is produced in the same manner as Sample 4-1. Explanations overlapping with Sample 4-1 will be omitted.

[0459] 4.1.8.3. Tensile Test of First Electrode Sheet Next, with reference to FIG. 61 , a tensile test performed on the first electrode sheet will be described. The first electrode sheets according to Examples 4-1 and 4-2 were cut into strips measuring 150 mm x 20 mm to prepare test specimens. The thickness of the first electrode sheet varied between Examples 4-1 and 4-2, but was approximately 0.1 mm. The angle between the longitudinal direction of the test specimen and the longitudinal direction of the warp filament assembly 72a was set to 45°.

[0460] The test specimen is held by a pair of chucks. The distance between the pair of chucks is 70 mm. A tensile test is performed on the test specimen at a tensile speed of 1 mm / sec, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test specimen. The tensile tester is an AGS-X 1 kN model manufactured by Shimadzu Corporation. The tensile test is performed in a strain range of 0 to 20%. Figure 61 shows a graph showing the change in stress versus strain.

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

[0462] Example 4-1 exhibits a stress of approximately 1.4 MPa when the strain is 5% and a stress of approximately 7.5 MPa when the strain is 20%. Example 4-2 exhibits a stress of approximately 0.9 MPa when the strain is 5% and a stress of approximately 5.9 MPa when the strain is 20%. The first electrode sheets 25, 25a according to Examples 4-1 and 4-2 have a maximum stress of 3 MPa or less when the strain is 0 to 5%, and a maximum stress of 15 MPa or less when the strain is 0 to 20%.

[0463] 4.1.8.4. Tensile Test of Sensor Sheet Next, we will explain the tensile test performed on the sensor sheet. Test specimens were prepared by cutting the sensor sheets of Samples 4-1 to 4-2 into 90 mm x 20 mm strips. The thickness of the sensor sheets varied between Samples 4-1 to 4-2, but was approximately 1 mm. The angle between the longitudinal direction of the test specimen and the longitudinal direction of the warp filament assembly 72a constituting the first electrode sheet and the second electrode sheet was set to 45°. Note that in this test, the test specimens used were the configurations of Samples 4-1 to 4-2 described above, excluding the first protective section 61 and the second protective section 62, respectively.

[0464] An electric wire is connected to one longitudinal end of the first electrode sheet and connected to a DC power supply, and an electric wire is connected to the other longitudinal end of the first electrode sheet and connected to a voltage measuring instrument.

[0465] The test piece is held 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, and the stress is calculated by dividing the load by the cross-sectional area of ​​the test piece. During the tensile test, the DC resistance value (an example of an electrical resistance value) of the sensor sheet is calculated from the voltage of the DC power supply and the voltage drop across the sensor sheet.

[0466] Figure 62 shows the stress-strain curves in the tensile test performed on the sensor sheet. Figure 62 shows a graph of the strain range of 0 to 20%. The stress of Samples 4-1 and 4-2 increased monotonically in the strain range of 0 to 20%. Samples 4-1 and 4-2 do not have a yield point showing a maximum value in the strain range of 0.5 to 10% in the stress-strain curves in the tensile test.

[0467] Sample 4-1 exhibits a stress of approximately 0.5 MPa at a strain of 5%, and a maximum stress of approximately 2.6 MPa at a strain of 20%. Sample 4-2 exhibits a stress of approximately 0.3 MPa at a strain of 5%, and a maximum stress of approximately 1.5 MPa at a strain of 20%. In the stress-strain curves of Samples 4-1 and 4-2, the maximum stress values ​​are 0.5 MPa or less at strains of 0 to 5%, and 3 MPa or less at strains of 0 to 20%.

[0468] In the stress-strain curves of Samples 4-1 and 4-2, the stress is 0.5 MPa or less when the strain is 0 to 5%, and the maximum stress is 3 MPa or less when the strain is 0 to 20%.

[0469] When a tensile force is applied to Samples 4-1 and 4-2, the first openings 34a in the first electrode sheet expand in the tensile direction and contract in a direction intersecting the tensile direction. Figure 63 shows the deformation of the first openings 34a using Sample 4-2 as an example. As shown in Figure 63(a), the first openings 34a are open at an elongation rate of 0%. However, as the elongation rate increases to 10% (see Figure 63(b)), 20% (see Figure 63(c)), and 30% (see Figure 63(d)), the gaps between the fibers of the conductive cloth decrease, and at an elongation rate of 30%, the first openings 34a almost disappear. This change in fiber shape allows for easy elongation, which is thought to reduce the stress generated during elongation. In other words, the presence of the first openings 34a is thought to contribute to the structural flexibility of the fibers. The above configuration is similar for the second electrode sheet, so a description thereof will be omitted. The same is true for Sample 4-1, so a description thereof will be omitted.

[0470] In Samples 4-1 and 4-2, when a tensile force is applied to the sensor sheet, it is believed that the tensile force is absorbed by the gradual deformation of the first openings 34a. As a result, the relative positions of the warp filament aggregates 72a and the weft filament aggregates 72b do not change significantly at the intersections between the warp filament aggregates 72a and the weft filament aggregates 72b, and therefore the electrical connection between the warp filament aggregates 72a and the weft filament aggregates 72b is maintained. As a result, in Samples 4-1 and 4-2, it is believed that the DC resistance value changes very little even when a tensile force is applied to the sensor sheet.

[0471] 4.1.8.5. DC Resistance Change Rate of Sensor Sheet Next, the DC resistance change rate of the sensor sheet was measured. The sensor sheet was cut into 90 mm x 20 mm strips to prepare test pieces. The angle between the longitudinal direction of the test piece and the longitudinal direction of the warp filament assembly 72a was set to 45°. In this test, the test pieces used were the configurations of the above-mentioned samples 4-1 to 4-2, excluding the first protective portion 61 and the second protective portion 62, respectively.

[0472] The test piece is held 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 wires is measured. The DC resistance value is used to calculate the rate of change in DC resistance based on the following formula (1). The DC resistance value is measured using a 2000 series digital multimeter manufactured by Keithley Corporation. The above test is performed on Samples 4-1 and 4-2.

[0473]

[0474] 63 is a graph showing the change in DC resistance value with strain. The DC resistance value change of Sample 4-1 increased in the strain range of 0 to approximately 2%, and at a strain of approximately 2%, the DC resistance value change was approximately 5%. Thereafter, the DC resistance value change decreased in the strain range of approximately 2 to approximately 5%, and the DC resistance value change was approximately 0%. Thereafter, at a strain of approximately 25% or more, the DC resistance value change gradually increased, and at a strain of 30%, the DC resistance value change was approximately 7%. Thus, the DC resistance value change of Sample 4-1 was 10% or less in the strain range of 0 to 30%.

[0475] The DC resistivity change rate of Sample 4-2 increased in the strain range of 0 to approximately 3%, and at a strain of approximately 3%, the DC resistivity change rate was approximately 10%. Thereafter, the DC resistivity change rate decreased in the strain range of approximately 3 to approximately 5%, and reached approximately 0%. Thereafter, even at a strain of 30%, the DC resistivity change rate was approximately 0%. Thus, the DC resistivity change rate of Sample 4-2 was 10% or less in the strain range of 0 to 30%.

[0476] 4.1.8.6. Rate of change in DC resistance of sensor sheet at 10% elongation Next, the rate of change in DC resistance of the sensor sheet at 10% elongation was measured. The sensor sheet was cut into 90 mm x 20 mm strips to prepare test pieces. The angle between the longitudinal direction of the test piece and the longitudinal direction of the warp filament assembly 72a was set to 45°. In this test, the test pieces used were the configurations of the above-mentioned samples 4-1 to 4-2, excluding the first protective portion 61 and the second protective portion 62, respectively.

[0477] The test piece is held 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 wires is measured. The DC resistance value is used to calculate the rate of change in DC resistance based on the following formula (1). The DC resistance value is measured using a 2000 series digital multimeter manufactured by Keithley Corporation. The above test is performed on Samples 4-1 and 4-2.

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

[0479] Figure 65 shows a graph showing the relationship between the number of repetitions of the extension test and the rate of change in DC resistance. For Sample 4-1, the rate of change in DC resistance at the first measurement was approximately 0%. Thereafter, as the number of repetitions increased, the rate of change in DC resistance increased to approximately 36% after one repetition, approximately 48% after five repetitions, and approximately 57% after ten repetitions. After ten repetitions, the rate of change in DC resistivity for Sample 4-1 was 60% or less.

[0480] For Sample 4-2, the DC resistivity change rate at the initial measurement was approximately 14%, which was larger than that of Sample 4-1. However, the DC resistance change rate did not increase significantly with increasing number of repetitions, being approximately 9% after one repetition and approximately 15% after five repetitions. After 10 repetitions, it was approximately 30%. After 10 repetitions, the DC resistance change rate of Sample 4-2 was 50% or less. As described above, it was found that the sensor sheets of Samples 4-1 and 4-2 showed little change in DC resistance even when the 10% elongation test was repeated.

[0481] 4.1.8.7. Rate of change in DC resistance of sensor sheet at 20% elongation Next, for Samples 4-1 and 4-2, the rate of change in DC resistance when the sensor sheet was elongated by 20% was measured. In this test, the test specimens used were the same as those of Samples 4-1 to 4-2 described above, except that the first protective portion 61 and the second protective portion 62 were removed.

[0482] Figure 66 shows a graph showing the relationship between the number of repetitions of the extension test and the rate of change in DC resistance. For Sample 4-1, the rate of change in DC resistance at the first measurement was approximately 0%. Thereafter, the rate of change in DC resistance increased as the number of repetitions increased, to approximately 35% after one repetition and approximately 91% after five repetitions. After 10 repetitions, the rate of change in DC resistance was approximately 137%.

[0483] For Sample 4-2, the DC resistivity change rate at the initial measurement was approximately 10%, which was larger than that of Sample 4-1. However, the DC resistance change rate did not increase significantly with increasing number of repetitions, being approximately 27% after one repetition and approximately 32% after five repetitions. After 10 repetitions, the DC resistance change rate for Sample 4-2 was approximately 55%. As described above, it was found that the sensor sheets of Samples 4-1 and 4-2 showed little change in DC resistance even when the 20% elongation test was repeated.

[0484] 4.1.9. Modification of Embodiment 4-1 A modification of Embodiment 4-1 will be described with reference to FIGS. 67 to 69. This modification differs from Sample 4-1 in the configuration of the first electrode sheet 25c and the second electrode sheet 26c. As shown in FIG. 67(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. 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.

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

[0486] 67( b), the second electrode sheet 26c of this modified example 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. The warp thread 41 is composed of one filament 71, and the weft thread 42 is also composed of one filament 71.

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

[0488] As shown in Figure 67(a), the multiple warp threads 41 in 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 being substantially equal. Furthermore, the intervals between the multiple warp threads 41 may be different.

[0489] Furthermore, the plurality of weft yarns 42 according to this modification 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 being substantially equal. Furthermore, the intervals between the plurality of weft yarns 42 may vary.

[0490] As shown in FIG. 67(b), the configuration of the second electrode sheet 26 is the same as that of the first electrode sheet 25, and therefore a duplicated description will be omitted.

[0491] 68, a plated layer 33 is formed on at least a part of the warp threads 41. The plated layer 33 may be formed on the entire surface of the warp threads 41, or may be formed on only a part of the surface of the warp threads 41.

[0492] Furthermore, a plated layer 33 is formed on at least a portion of the weft yarn 42. The plated layer 33 may be formed on the entire surface of the weft yarn 42, or the plated layer 33 may be formed on only a portion of the surface of the weft yarn 42.

[0493] In this modified example, the plating layer 33 formed on the surface of the warp thread 41 comes into contact with the plating layer 33 formed on the surface of the weft thread 42, thereby electrically connecting the warp thread 41 and the weft thread 42.

[0494] When a tensile force is applied to this modified example, the first opening 34a of the first electrode sheet 25c expands in the tensile direction and contracts in a direction intersecting the tensile direction. Figure 69 shows the state in which the first opening 34a deforms in this modified example. This is thought to absorb the tensile force, resulting in a small change in stress. Note that the same applies to the second electrode sheet 26c, so a redundant explanation will be omitted.

[0495] The configuration other than the above is the same as that of sample 4-1, so a duplicated description will be omitted.

[0496] 4.1.10. Effects of the Present Embodiment Next, the effects of the present 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 and arranged on the first surface 27 side of the insulating sheet 24, a first bonding portion 36 that bonds the first surface 27 of the insulating sheet 24 to the inner surface of the first electrode sheet 25, and a first protective portion 61 that is arranged on the outer surface of the first electrode sheet 25 and protects the outer surface of the first electrode sheet 25.

[0497] According to this embodiment, the first electrode sheet 25 is protected from external forces by the first protective portion 61, which can prevent damage to the conductive paths of the first electrode sheet 25. This can prevent changes in the electrical resistance value of the sensor sheet 18.

[0498] In addition, the sensor sheet 18 in this embodiment is arranged on the second surface 28 side of the insulating sheet 24 and comprises a second electrode sheet 26 made of conductive cloth, a second joining portion 37 that joins the second surface 28 of the insulating sheet 24 to the inner surface of the second electrode sheet 26, and a second protective portion 62 that is arranged on the outer surface of the second electrode sheet 26 and protects the outer surface of the second electrode sheet 26.

[0499] According to this embodiment, the second electrode sheet 26 is protected from external forces by the second protective portion 62, which can prevent damage to the conductive paths of the second electrode sheet 26. This can prevent a decrease in the shielding performance of the sensor sheet 18.

[0500] The first protective portion 61 and the second protective portion 62 according to this embodiment are made to contain a resin material, thereby improving the strength of the first protective portion 61 and the second protective portion 62. Furthermore, the first protective portion 61 can be easily disposed on the surface of the first electrode sheet 25, and the second protective portion 62 can be easily disposed on the surface of the second electrode sheet 26.

[0501] The first protective portion 61 according to this embodiment is formed in a layer shape that covers the outer surface of the first electrode sheet 25. This ensures that the outer surface of the first electrode sheet 25 is covered, thereby further protecting the first electrode sheet 25. As a result, changes in the electrical resistance value of the sensor sheet 18 can be further suppressed.

[0502] Furthermore, the second protective portion 62 is formed in a layer shape that covers the outer surface of the second electrode sheet 26. This ensures that the outer surface of the second electrode sheet 26 is covered, thereby further protecting the second electrode sheet 26. 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 is woven from a plurality of filament assemblies 72. The first protective portion 61 is formed on the outer periphery of the filament assemblies 72. This allows the first protective portion 61 to protect the filament assemblies 72, further suppressing changes in the electrical resistance value of the sensor sheet 18.

[0504] The first bonding portion 36 according to this embodiment is interposed between the insulating sheet 24 and the first electrode sheet 25. This allows the insulating sheet 24 and the first electrode sheet 25 to be reliably bonded to each other.

[0505] The conductive cloth constituting the first electrode sheet 25 according to this embodiment is woven with a plurality of filament assemblies 72, each of which includes a plurality of filaments 71. The conductive cloth includes first openings 34a that open between the plurality of filament assemblies 72. The opening ratio, which is the ratio of the opening area of ​​the first openings 34a to the area of ​​the first electrode sheet 25, is 3% or more. This allows the first openings 34a to deform and absorb external forces when external forces are applied to the first electrode sheet 25. This prevents excessive stress from being applied to the first electrode sheet 25, thereby preventing damage to the conductive paths of the first electrode sheet 25. As a result, changes in the electrical resistance of the sensor sheet 18 can be prevented.

[0506] The insulating sheet 24 according to this embodiment is made of a foamed elastomer. This improves the flexibility of the insulating sheet 24. As a result, when an external force is applied to the sensor sheet 18, the insulating sheet 24 deforms and absorbs the external force. This prevents excessive stress from being applied to the first electrode sheet 25, thereby preventing damage to the conductive paths of the first electrode sheet 25. As a result, changes in the electrical resistance of the sensor sheet 18 can be prevented.

[0507] The conductive cloth according to this embodiment is formed by weaving a plurality of filament assemblies 72, and the filament assemblies 72 include a plurality of filaments 71 and a plating layer 33 formed on at least a portion of the surface of the filaments 71. The plating layers 33 formed on the surfaces of the plurality of filaments 71 come into contact with each other, thereby electrically connecting the plurality of filaments 71. This forms a conductive path in the first electrode sheet 25.

[0508] The plating layer 33 is formed on the surface of each of the filaments 71. As a result, even if an external force is applied to the sensor sheet 18 and the relative positions of the filaments 71 change, the plating layer 33 formed on the surface of each filament 71 makes it easier to form a conductive path. As a result, changes in the electrical resistance value of the sensor sheet 18 can be suppressed.

[0509] (Embodiment 4-2) Next, embodiment 4-2 will be described with reference to Figures 70 and 71. As shown in Figure 70, the first bonding portion 36 according to this embodiment includes a first exposed bonding portion 36a that is exposed on the outer surface of the first electrode sheet 25. The first exposed bonding portion 36a is formed in a layer on the outer surface of the first electrode sheet 25. The first exposed bonding portion 36a also serves as a first protective portion 61 that protects the first electrode sheet 25. This simplifies the manufacturing process of the sensor sheet 18 compared to when a first protective portion 61 is separately disposed and fixed to the first electrode sheet 25 in addition to the first bonding portion 36.

[0510] 71 , the first electrode sheet 25 has a first opening 34a. A first bonding portion 36 penetrates into the first opening 34a. The portion of the first bonding portion 36 that penetrates into the first opening 34a is a first penetrating bonding portion 36b. The first penetrating bonding portion 36b penetrates the first electrode sheet 25 and is continuous with the first exposed bonding portion 36a. As described above, the first exposed bonding portion 36a also serves as the first protective portion 61, and therefore the first penetrating bonding portion 36b is continuous with the first protective portion 61.

[0511] According to this embodiment, the first bonding portion 36 penetrates into the first opening 34a of the first electrode sheet 25 to form the first penetrating bonding portion 36b, and the first exposed bonding portion 36a and the first penetrating bonding portion 36b can be formed into a continuous shape. As a result, when the first bonding portion 36 is laminated on the first surface 27 of the insulating sheet 24, the first electrode sheet 25 is placed on this first bonding portion 36, and the first electrode sheet 25 is pressed against the insulating sheet 24, the first penetrating bonding portion 36b penetrates into the first opening 34a of the first electrode sheet 25 and further covers the first electrode sheet 25 to form the first exposed bonding portion 36a, and this first exposed bonding portion 36a can serve as the first protective portion 61 that protects the first electrode sheet 25.

[0512] Since the opening ratio of the first openings 34a in this embodiment is 3% or more, the first bonding portions 36 can easily enter the first openings 34a. This makes it easy to manufacture the sensor sheet 18 in this embodiment. Note that the opening ratio of the first openings 34a is preferably 5% or more, and more preferably 10% or more, so that the first bonding portions 36 can more easily enter the first openings 34a.

[0513] 70 , the second bonding portion 37 according to this embodiment includes a second exposed bonding portion 37a exposed on the outer surface of the second electrode sheet 26. The second exposed bonding portion 37a is formed in a layer on the outer surface of the second electrode sheet 26. The second exposed bonding portion 37a also serves as a second protective portion 62 that protects the second electrode sheet 26. The configuration of the second bonding portion 37 and the second electrode sheet 26 is the same as the configuration of the first bonding portion 36 and the first electrode sheet 25, and therefore a redundant description will be omitted.

[0514] Note that, among the symbols used in embodiment 4-2 and subsequent embodiments, the same symbols as those used in the previous embodiments represent the same components, etc. as in the previous embodiments, unless otherwise specified.

[0515] (Embodiment 4-3) Next, embodiment 4-3 will be described with reference to Figures 72 and 73. As shown in Figure 72, a first electrode sheet 25 according to this embodiment is disposed on a first surface 27 of an 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 in partial contact therewith. This brings the insulating sheet 24 and the first electrode sheet 25 into direct contact, thereby forming a first direct region 38 between the insulating sheet 24 and the first electrode sheet 25, where no first joint portion 36 is present (see Figure 73).

[0516] The first bonding portion 36 is disposed on the outer surface of the first electrode sheet 25. As a result, the 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 protective portion 61a that protects the first electrode sheet 25.

[0517] As shown in Figure 73, the first electrode sheet 25 has a first opening 34a. A first bonding portion 36 penetrates into the first opening 34a. The portion of the first bonding portion 36 that penetrates into the first opening 34a is a first penetrating bonding portion 36d. The first penetrating bonding portion 36d penetrates the first electrode sheet 25 and is continuous with the first exposed bonding portion 36c. As described above, the first exposed bonding portion 36c also serves as the first protective portion 61a, and therefore the first penetrating bonding portion 36d is continuous with the first protective portion 61a.

[0518] According to this embodiment, the first bonding portion 36 penetrates into the first opening 34a of the first electrode sheet 25 to form the first penetrating bonding portion 36d, and the first exposed bonding portion 36c and the first penetrating bonding portion 36d can be formed into a continuous shape. As a result, when the first bonding portion 36 is laminated on the first surface 27 of the insulating sheet 24, the first electrode sheet 25 is placed on the outer surface of this first bonding portion 36, and the first electrode sheet 25 is pressed against the insulating sheet 24, the first penetrating bonding portion 36d penetrates into the first opening 34a of the first electrode sheet 25 and further covers the first electrode sheet 25 to form the first exposed bonding portion 36c, and this first exposed bonding portion 36c can be used as the first protective portion 61a that protects the first electrode sheet 25.

[0519] 72 , 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 in partial contact therewith. This brings the insulating sheet 24 and the second electrode sheet 26 into direct contact, thereby forming a second direct region 39 between the insulating sheet 24 and the second electrode sheet 26, where no second joint portion 37 is present.

[0520] The second bonding portion 37 is disposed on the outer surface of the second electrode sheet 26. As a result, the portion of the second bonding portion 37 that is exposed on the outer surface of the second electrode sheet 26 is defined as a second exposed bonding portion 37c. The second exposed bonding portion 37c is formed in a layer on the outer surface of the second electrode sheet 26. The second exposed bonding portion 37c also serves as a second protective portion 62a that protects the second electrode sheet 26. The configuration of the second bonding portion 37 and the second electrode sheet 26 is the same as the configuration of the first bonding portion 36 and the first electrode sheet 25, and therefore a redundant description will be omitted.

[0521] Other than the above, the embodiment is the same as embodiment 4-2, so a duplicated description will be 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 bonding portion 36 formed in a layer is placed on the first electrode sheet 25. Next, the first bonding portion 36 is pressed toward the insulating sheet 24. As a result, the first bonding portion 36 penetrates into the first opening 34a of the first electrode sheet 25 to form a first penetration bonding portion 36d. The first penetration bonding portion 36d contacts 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 bonded by the first penetration bonding portion 36d within the first opening 34a. Note that the effects of the second bonding portion 37 and the second electrode sheet 26 are the same as the effects of the first bonding portion 36 and the first electrode sheet 25, and therefore, redundant description will be omitted.

[0523] (Embodiment 4-4) Next, embodiment 4-4 will be described with reference to Fig. 74. As shown in Fig. 74, the sensor sheet 18 according to this embodiment differs from embodiment 4-1 in that the second electrode sheet 26 is not disposed on the second surface 28 side of the insulating sheet 24. Other than the above, it is the same as embodiment 4-1, and therefore a duplicated description will be omitted.

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

[0525] The present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the spirit of the present invention.

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 opening (34a) extending therethrough; a first bonding portion (36) that bonds 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 opening (34b) extending therethrough; A second bonding portion (37) that bonds the insulating sheet and the second electrode sheet, the first electrode sheet and the second electrode sheet are conductive cloths woven with a plurality of filament assemblies (72); The filament assembly includes a plurality of filaments (71) and a plating layer (33) formed on at least a portion of the surface of the filaments, the first electrode sheet has the first opening that opens between the plurality of filament assemblies, the second electrode sheet has a second opening that opens between the plurality of filament assemblies, In a stress-strain curve in a tensile test, the material is configured so as not to have a yield point showing a maximum value in the range of 0.5 to 10% strain; an aperture ratio, which is a ratio of an opening area of ​​the first opening to an area of ​​the first electrode sheet, being 1% or more and 50% or less; The sensor sheet (18) has an opening ratio, which is the ratio of the opening area of ​​the second opening to the area of ​​the second electrode sheet, of 1% or more and 50% or less.

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

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

4. The sensor sheet according to claim 1 , wherein the first electrode sheet is configured so that in the stress-strain curve, the maximum stress at a strain of 0 to 5% is 5 MPa or less.

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

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 x 90 mm and conducting a tensile test at a tensile speed of 1 mm / s.

7. The sensor sheet according to claim 1 , wherein the cross section of the filament is non-circular.

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

9. The sensor sheet according to any one of claims 1 to 5, wherein the filament assembly further has an internal space (80) formed at least partially between adjacent filaments.

10. The sensor sheet according to claim 9 , wherein the filament assembly has the plurality of filaments arranged in a planar direction of a sheet surface of the first electrode sheet and in a normal direction to the sheet surface.

11. The sensor sheet according to claim 10 , wherein the internal space is formed at least partially between adjacent filaments in the planar direction and at least partially between adjacent filaments in the normal direction.

12. the plating layer is formed on at least a portion of the surface of the filament that is exposed to the internal space, The sensor sheet according to claim 9 , wherein a portion of the surface of the filament that is exposed to the internal space and on which the plating layer is not formed is an exposed surface of the filament.

13. the plurality of filament assemblies comprises a warp filament assembly and a weft filament assembly, The sensor sheet according to any one of claims 1 to 5, wherein the plating layer is formed on at least a portion of a non-exposed portion (81) where the warp filament aggregate and the weft filament aggregate face each other and intersect.

14. the plating layer is formed on at least a portion of the surface of the filament exposed to an outer surface of the filament assembly; The sensor sheet according to any one of claims 1 to 3, wherein a portion of the surface of the filament exposed on the outer surface of the filament assembly on which the plating layer is not formed is an exposed surface of the filament.

15. The plurality of filament assemblies include a warp filament assembly (72a) and a weft filament assembly (72b), The sensor sheet according to any one of claims 1 to 5, wherein at a portion where the warp filament aggregate and the weft filament aggregate intersect with each other, the plating layer is formed on at least a portion of the portion where the filaments exposed on the outer surface of the warp filament aggregate and the filaments exposed on the outer surface of the weft filament aggregate face each other, and the outer surfaces of the filaments are exposed in the portion where the plating layer is not formed.

16. The sensor sheet according to claim 1 , wherein the plating layer is a single layer made of nickel, or a multi-layer including a layer made of copper and a layer made of nickel.

17. moreover, The sensor sheet according to any one of claims 1 to 5, further comprising a joint (36) that joins the first surface of the insulating sheet and an inner surface of the first electrode sheet.

18. moreover, The sensor sheet according to claim 17, further comprising a protective portion (60) disposed on an outer surface of the first electrode sheet to protect the outer surface of the first electrode sheet.

19. The sensor sheet according to claim 17 , wherein the joint is interposed between the insulating sheet and the first electrode sheet.

20. The joint portion includes an exposed joint portion (36a) exposed on an outer surface of the first electrode sheet, The sensor sheet according to claim 17 , wherein the exposed joint portion is disposed on the outer surface of the first electrode sheet and also serves as a protective portion that protects the outer surface of the first electrode sheet.

21. The sensor sheet of claim 17, wherein the insulating sheet and the first electrode sheet are in direct contact with each other, so that a direct area (38) exists between the insulating sheet and the first electrode sheet without the joint being interposed therebetween.

22. The sensor sheet according to claim 17 , wherein the joint is interposed between the insulating sheet and the first electrode sheet.

23. the plurality of filament assemblies comprises a warp filament assembly and a weft filament assembly, The sensor sheet according to any one of claims 1 to 5, wherein an area of ​​the portion where the warp filament aggregate and the weft filament aggregate intersect with each other is larger than an opening area of ​​the first opening when no distortion occurs in the first electrode sheet.

24. The first electrode sheet is formed long in the longitudinal direction, The first electrode sheet is The first electrode sheet has an extension portion (31) extending in an extension direction from a long side edge along the longitudinal direction, The sensor sheet according to claim 23, wherein in the extension portion, an occupied area of ​​the plurality of warp filament assemblies when projected in a thickness direction of the extension portion is larger than an occupied area of ​​the plurality of weft filament assemblies when projected in the thickness direction of the extension portion.

25. The first electrode sheet is formed long in the longitudinal direction, The first electrode sheet is an extension portion extending in an extension direction from a long side edge along the longitudinal direction of the first electrode sheet; The sensor sheet according to claim 23, wherein in the extension portion, an angle α between the extension direction of the extension portion and the longitudinal direction of the warp filament assembly is smaller than an angle β between the extension direction of the extension portion and the longitudinal direction of the weft filament assembly.

26. The first electrode sheet is formed long in the longitudinal direction, The first electrode sheet is an extension portion extending in an extension direction from a long side edge along the longitudinal direction of the first electrode sheet; The sensor sheet according to claim 23, wherein in the extension portion, an angle α between the extension direction of the extension portion and the longitudinal direction of the warp filament aggregate is greater than an angle β between the extension direction of the extension portion and the longitudinal direction of the weft filament aggregate.

27. The first electrode sheet is formed long in the longitudinal direction, The first electrode sheet is an extension portion extending in an extension direction from a long side edge along the longitudinal direction of the first electrode sheet; The sensor sheet according to claim 23 , wherein in the extension portion, a distance between adjacent filaments among the plurality of filaments constituting the weft filament assembly is smaller than a distance between adjacent filaments among the plurality of filaments constituting the warp filament assembly.

28. The first electrode sheet is formed long in the longitudinal direction, The first electrode sheet is The first electrode sheet has a narrow portion (35) that is narrower than other portions in a direction intersecting the longitudinal direction of the first electrode sheet, The sensor sheet according to claim 23, wherein in the narrow width portion, an occupied area of ​​the plurality of warp filament assemblies projected in a thickness direction of the narrow width portion is larger than an occupied area of ​​the plurality of weft filament assemblies projected in the thickness direction of the narrow width portion.

29. The first electrode sheet is formed long in the longitudinal direction, The first electrode sheet is a narrow portion that is narrower than other portions in a direction intersecting the longitudinal direction of the first electrode sheet, 24. The sensor sheet according to claim 23, wherein in the narrow portion, a distance between adjacent filaments among the plurality of filaments constituting the weft filament assembly is smaller than a distance between adjacent filaments among the plurality of filaments constituting the warp filament assembly.

30. The first electrode sheet is formed long in the longitudinal direction, The first electrode sheet is a narrow portion that is narrower than other portions in a direction intersecting the longitudinal direction of the first electrode sheet, The sensor sheet according to claim 23 , wherein the number of the filaments constituting the warp filament assembly in the narrow width portion is greater than the number of the filaments constituting the warp filament assembly in a portion other than the narrow width portion.

31. forming a filament assembly by bundling a plurality of filaments; forming a base fabric by knitting a plurality of the filament assemblies; forming a conductive cloth by plating the base cloth; and forming a sensor sheet by joining the conductive cloth to a first surface of an insulating sheet made of an elastomer having a first surface and a second surface.