Image-Forming Device Sequential Toner Transfer

The patent applies preliminary action by transferring the black developer image first before other colored developer images. This sequential arrangement ensures that the black toner is transferred to the transfer recipient before any colored toner, preventing the colored toner from being reverse-transferred onto the black toner layer. The development sequence is specifically arranged as: black developer → colored developers, which is the reverse of the conventional approach and directly addresses the reverse transfer problem.

The patent segments the developer images by color and transfers them sequentially to the transfer recipient. Each developer image (black, red, green, blue) is transferred in a separate step, allowing the cleaning device to recover waste developer from each image bearing member independently. This segmentation prevents mixed waste developer from different colors from being recovered together, thus avoiding color mixing while maintaining effective waste developer recovery.

The patent uses preliminary action by transferring the black developer image first, creating a stable base layer on the transfer recipient. Subsequent colored developer images are then transferred onto this black layer. This sequence ensures that even if waste developer has high charge capability, it cannot displace the already-transferred black toner, as the black toner forms the foundational layer. The sequential transfer process prevents color mixing while maintaining image quality.