Satellite Formation in Transfer Gaps

Abstract

Toned electrophotographic images often exhibit toner satellites around alphanumeric characters and halftone dots. Among the electrophotographic subsystems, transfer is believed to be a frequent and even dominant source of such image artifacts. This paper reports on toner adhesion, detachment, and disruption as determined using a laboratory ultracentrifuge and an electrostatic detachment cell (ESD). The simplicity of this apparatus helps isolate factors contributing to satellite formation such as toner particle size, surface treatment, transfer gap (pre-nip or post-nip) and transfer electric field. Measurements have confirmed that surface-treatment can decrease adhesion and/or cohesion and increase the number, but not the spatial extent, of laterally displaced toners after gap-jumping. Results from both the ultracentrifuge and the ESD show that, even for highly surface-treated toner, only a small fraction of toner is removed by the normally-directed electrostatic forces encountered during transfer from photoconductor to paper. In contrast, relatively weak tangential forces cause toner to move laterally; suggesting an additional mechanism for satellite formation that need not involve gap jumping.