| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a charging roller free of occurrence of a white-striped uneven image in a portion brought into contact with a drum when the roller is used for producing numbers of images in an HH environment and then the roller is allowed to stand in an LL environment for ≥24 h while in contact with the drum. <P>SOLUTION: In the charging roller, an outermost surface layer of an electrically conductive covering member comprises a thermoplastic styrenic elastomer, a high-impact polystyrene (HIPS), and a highly electrically conductive carbon black having a DBP oil absorption of 300-500 cm<SP>3</SP>/100 g as an electrically conductive agent in an amount of ≥6.0 parts by mass based on 100 parts by mass of all the binder resins, wherein a ratio Tse/Tps between the mass Tse of the thermoplastic styrenic elastomer and the mass Tps of the high-impact polystyrene is 70:30 to 50:50, and a ratio (Rr/Ru) between the resistance (Rr) of the charging roller and the resistance (Ru) of an underlying roller freed of the outermost surface layer is 2.7 to 8.6 times. A process cartridge with the charging roller and an electrophotographic apparatus are also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
