Internal release agents for electrophotographic toners

Abstract

Continuous improvements in printer resolution place greater demands on toner performance. As the pel size becomes smaller, the requirements for edge definition and the elimination of hot offset increasingly become limiting factors in determining print quality. Edge definition, resolution, and offset can be addressed to some extent by improved charge control for narrower charge distribution and elimination of wrong size toner. Another contribution to the offset lies in the adhesion of toner to the fuser roll and subsequent redeposition on the paper where it is not intended. This study evaluates wax internal release agents to determine which combinations of waxes and additives, including block copolymers and polydimethylsiloxane oils, provide the best release properties. Primarily the focus is on polyethylene and polypropylene waxes. There is little effect of polyethylene wax molecular weight on peel strength. Lowest peel strength is with polyethylene wax and polydimethylsiloxane oil. Lowest offset with little effect on tribocharging is with polypropylene wax and polydimethylsiloxane oil. Release properties are controlled by the distribution of release agent between surface and bulk as well as the dynamics of migration from the bulk to the surface. X-ray photoelectron spectroscopy is suggested as a sensitive means for further analysis of these effects.