Contact Charging Characteristics of Styrene-Butyl Methacrylate Containing Dodecametallophosphate Salts

Abstract

Dodecatungstophosphate and dodecamolybdophosphate tetraalkylammonium salts, [R4N]3[PO4(MO3)12] where M is W or Mo, are reported to function as charge control additives in toner powders used for electrophotographic printing. With these salts the toner develops a positive contact charge (against iron powder) and the charge is reported to have improved uniformity and stability. We now find that the dodecatungstophosphate and dodecamolybdophosphate salts with a stearylammonium cation induce a negative contact charge to the styrene-co-butyl methacrylate copolymer powder when it is charge activated with metal beads, and the beads acquire the positive countercharge. Thus, a simple change in the structure in the cation of the salt reverses the sign of the charge. X-ray photoelectron spectroscopy (XPS) analysis of these powders reveals that the stearylammonium cation content on the surface is 60 times greater than the bulk content. XPS analysis of the metal beads after contact with and removal of each of the powders shows N and W or Mo signals for the presence of both ions from the salt which were originally added to the powder. Also, the cation content on the beads is in excess of the anion content and this ion imbalance must contribute to the resulting positive charge on the beads. © 1992, American Chemical Society. All rights reserved.