| 摘要 |
PROBLEM TO BE SOLVED: To provide a developing roll by which the inclination of developingγis made to be steep even when the surface of the roll is worn with the lapse of time and also toner is saturated at developing potential being low potential of <=150 V and whose durability is improved, and a developing device provided therewith. SOLUTION: This developing roll 10 is successively provided with a core shaft 1, an elastic layer 2 and a surface layer 3, and its volume resistance at an initial stage is set to <=1.5×104Ωcm, its capacitance at the initial stage is set to >=1.5×10-4 F/m2, and besides, the volume resistance after the 75% of the surface layer 3 is worn is set to <=1.5×106Ωcm, and also the capacitance after the 75% of the surface layer 3 is worn is set to >=1.0×10-6 F/m2. The JIS-A hardness of the roll 10 is desirably 25 to 50. The thickness of the surface layer of the roll 10 is desirably <=30μm, and the ASKER-C hardness of the roll 10 including the surface layer is desirably <=55 (303 g load). |
