TRANSFER POINT TRAILING EDGE TONER DUST SUPPRESSION

摘要

Charged toner is transferred from an image member (such as an image cylinder or belt) to a web of imagable material (typically paper), preferably utilizing a rotating conductive impression cylinder. The toner, having a first polarity, is applied to the image member. The paper web, typically by contact with the impression cylinder, is moved into contact with the image member so that the toner transfers from the image member to the web under pressure. Even despite a high speed of movement of the web (e.g. 200 feet per minute or more), toner back scatter is substantially prevented by applying an electrical bias of the first polarity to the impression cylinder so as to impose an electric force field on the toner particles of sufficient intensity to overcome aerodynamic drag forces which would separate particles from the image areas between the impression cylinder and the image member. While the applied potential is typically between about 100-600 volts, in order to take care of all speeds and all types of toners and all types of printer geometries, a fixed potential of about 750 volts may be utilized. Where the image member is an image cylinder, a nip is provided between the cylinders at which, or immediately adjacent to, toner transfer takes place.