Image forming apparatus

摘要

An image forming apparatus includes an image bearing member (1) for bearing an electrostatic image; a developer carrying member (10) for carrying a developer and for forming a developing zone with the image bearing member, wherein the developer is externally added with additive having a charging polarity opposite from that of the developer; voltage applying means (12) for applying a developing voltage to the developer carrying member. A size of area S (V x sec) of a region in a waveform of the developing voltage in which the additive receives force toward said image bearing member and an amount of additive W (% by wt.) in the developer satisfy: -26.5W + 386 ≤ S ≤ -26.5W + 511.