| http://www.w3.org/ns/prov#value | - With respect to a material constituting the conductive layer 211b placed around the rotary shaft 211a, for example, a rubber material, such as ethylene-propylene-diene-methylene copolymer rubber (EPDM), silicone rubber and urethane rubber, is used, and to such a rubber is dispersed carbon black, such as Ketchen black, acetylene black, and furnace black so that a volume resistivity value is set to
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