Image forming apparatus having a plurality of developing devices

摘要

An image forming apparatus is provided with an optical system for forming a first electrostatic latent image and a second electrostatic latent image on a rotatable photosensitive member, a first developing device accommodating a first developer for developing the first electrostatic latent image, and a second developing device accommodating a second developer for developing the second electrostatic latent image. The second developing device is located downstream from the first developing device in a direction of rotation of the photosensitive member and is provided with a developing roller having a magnetic force. The second developer differs in color from the first developer and has a magnetism greater than the first developer. The second developer is transported to the second electrostatic latent image along a periphery of the developing roller. The image forming apparatus is further provided with a collector provided in the second developing device and having a collecting member confronting the developing roller. The first developer mixed in the second developer is moved toward and collected by the collecting member under the influence of an electric field formed between the collecting member and developing roller. Alternatively, the photosensitive member can act as a collector for collecting first developer mixed in the second developer.