Thesis (M.Sc.)--Chulalongkorn University, 1997

The dependence of the toner charge-to-mass ratio (q/m) in the two-component developer of electrophotography was investigated on shaking time, toner concentration (T/C), carrier sizes, carrier coated materials, and carrier core particles to acquire relationship to the print qualities in terms of image density, background density, tone reproduction, and resolution. Four different sizes of the fluorine/acrylate coated spherical ferrite carriers of 100, 70, 60 and 50 mum, other four different coated materials: acrylate, silicone, fluorine/silicone, and un-coated, and the fluorine/acrylate coated irregular iron carrier were used with two types of toner resin: 14 mum red toner containing styrene/acrylate resin and 8 mum cyan toner containing polyester resin. The q/m measurement by a blow-off method showed that the red toner was of positive charge while the cyan toner was of negative charge with these carriers. The toner q/m values changing by the shaking time and decreasing by the increasing T/C were more affected by the larger carrier which has less surface area per mass than does the smaller carrier. The fluorine/acrylate coated ferrite carriers gave an useful range of q/m to these toners in a latitude of T/C by producing high print density without background fog. The carrier giving too low q/m to the toner produced fog on the background, and the carrier giving too high q/m produced low print density. The T/C latitude corresponding to the red toner q/m range of 15-20 muC/g and the cyan toner q/m range of 15-25 muC/g was wider when a carrier size was smaller. Additionally, the T/C latitude of the larger toner was wider than that of the smaller toner.