Humidity dependence of tribocharging of electrophotographic carriers coated with poly(vinylidene fluoride)-poly(methyl methacrylate) blends

In this study, the effect of humidity on the work function of ferrite carrier particles coated with blends of poly(vinylidene fluoride) and poly(methyl methacrylate) was investigated. Charging measurements made as a function of humidity using toner surface treated with hydrophobic and hydrophilic silica were analyzed using an extension of the surface state model of tribocharging. The carrier work function is a linear function of the ratio of poly(vinylidene fluoride) and poly(methyl methacrylate) in the carrier coating. In contrast to the work function of the surface treated toners used, the carrier work function is independent of humidity. The density of states of the charging sites on the carrier is large enough that the term containing it is much less than 1.0. Thus, unlike the toner, the carrier is in the so-called high density of states limit.