Charging roller featuring specified ratio of storage elastic modulus and dynamic viscoelasticity values and process cartridge and electrophotographic apparatus featuring the same

摘要

Charging roller has at least a support member and a conductive covering member, the charging roller where a value of tan δ expressed in a ratio of a storage elastic modulus and a loss elastic modulus by dynamic viscoelasticity in a cross sectional direction of the charging roller at 25° C. is 0.2 or more in a range of 1 to 20 kHz and 0.2 or less in a range of 1 to 10 Hz, or a charging roller where the conductive covering member is constructed of two or more layers and a value of tan δ in at least one layer other than a surface layer is 0.2 or more at 10 Hz in a range of 10 to 50° C. and a value of tan δ in a cross sectional direction of the whole charging roller is 0.2 or less at 10 Hz in a range of 10 to 50° C.