Capacitive-coupling sensor and method for producing the same
A capacitive-coupling sensor includes: a detection electrode layer that generates capacitance between the detection electrode layer and an object to be detected; a shield electrode layer; and an insulating layer disposed between the detection electrode layer and the shield electrode layer. The insulating layer includes a thermoplastic elastomer, and the insulating layer has a thermal conductivity of 0.3 W/m·K or more and a volume resistivity of 1×10 12 Ω·cm or more. When the detection electrode layer and the shield electrode layer are made of conductive cloths, the conductive cloth for the detection electrode layer is placed on a front surface of the insulating layer and the conductive cloth for the shield electrode layer is placed on a back surface of the insulating layer forming a laminate. The laminate is pressed in a front-back direction under heating to fuse the insulating layer to the conductive cloths, producing the capacitive-coupling sensor.
1. A capacitive-coupling sensor, comprising:
a detection electrode layer that generates capacitance between the detection electrode layer and an object to be detected;
a shield electrode layer; and
an insulating layer disposed between the detection electrode layer and the shield electrode layer, wherein
the detection electrode layer surrounds an entire circumference of the insulating layer,
the insulating layer includes a thermoplastic elastomer,
the insulating layer has a thermal conductivity of 0.3 W/m·K or more and a volume resistivity of 1×10 12 Ω·cm or more, and
the capacitive-coupling sensor is disposed in a steering wheel.
2. The capacitive-coupling sensor according to claim 1 , wherein the insulating layer includes an inorganic filler.
3. The capacitive-coupling sensor according to claim 2 , wherein the inorganic filler includes particles having a thermal conductivity of 20 W/m·K or more.
4. The capacitive-coupling sensor according to claim 2 , wherein the inorganic filler includes flame retardant particles.
5. The capacitive-coupling sensor according to claim 4 , wherein the flame retardant particles are magnesium hydroxide.
6. The capacitive-coupling sensor according to claim 1 , wherein a type A durometer hardness of the insulating layer is 35 or more and less than 90.
7. The capacitive-coupling sensor according to claim 1 , wherein the insulating layer has a tensile strength of 0.1 MPa or more and a breaking elongation of 100% or more.
8. The capacitive-coupling sensor according to claim 1 , wherein the thermoplastic elastomer is one or more selected from a styrene-based elastomer and an olefin-based elastomer.
9. The capacitive-coupling sensor according to claim 1 , wherein at least either of the detection electrode and insulating layers or the shield electrode and insulating layers are fixed to each other without using an adhesive.
10. The capacitive-coupling sensor according to claim 1 , wherein both the detection electrode and insulating layers as well as the shield electrode and insulating layers are fixed to each other without using an adhesive.
11. The capacitive-coupling sensor according to claim 1 , wherein the detection electrode layer is made of conductive rubber or a conductive cloth.
12. The capacitive-coupling sensor according to claim 1 , wherein the shield electrode layer is made of a conductive cloth.
13. The capacitive-coupling sensor according to claim 1 , wherein
the detection electrode layer and the shield electrode layer are made of conductive cloths, and
at least part of the conductive cloths is embedded in the insulating layer.
14. The capacitive-coupling sensor according to claim 1 , wherein
the steering wheel includes a heater layer, and
the shield electrode layer is disposed on a heater layer side.
15. The capacitive-coupling sensor according to claim 14 , wherein the shield electrode layer and the heater layer are fixed to each other without using an adhesive.
16. A method for producing the capacitive-coupling sensor according to claim 13 , the method comprising:
placing the conductive cloth that serves as the detection electrode layer on a front surface of the insulating layer and placing the conductive cloth that serves as the shield electrode layer on a back surface of the insulating layer to form a laminate; and
fusing the insulating layer to the conductive cloths by pressing the laminate in a front-back direction under heating.
17. The capacitive-coupling sensor according to claim 2 , wherein the inorganic filler has at least either of magnesium oxide particles and aluminum oxide particles.
18. The capacitive-coupling sensor according to claim 1 , wherein:
at least one of the detection electrode layer and the shield electrode layer is made of a conductive cloth; and
the conductive cloth is a woven fabric or a non-woven fabric of polyester fibers plated with copper or nickel.
19. A steering wheel comprising the capacitive-coupling sensor according to claim 1 , a core, and a heater layer disposed between the capacitive-coupling sensor and the core, wherein
in the capacitive-coupling sensor,
the insulating layer includes an inorganic filler including particles having a thermal conductivity of 20 W/m·K or more, the thermoplastic elastomer of the insulating layer is one or more selected from a styrene-based elastomer and an olefin-based elastomer, and
at least part of the detection electrode layer and the shield electrode layer is embedded in the insulating layer.
20. The capacitive-coupling sensor according to claim 1 , wherein the insulating layer is a flexible layer that is a thickest layer in the capacitive-coupling sensor.