ON THE FORMATION OF WHITE SPOTS IN ELECTROPHOTOGRAPHY

White spots observed in electrophotography were investigated. Magnetic toners were prepared by the conventional toner preparation method and applied to a laser printer and copiers produced by Canon Co., Japan. White spots were found to be generated during the development step. To ner particles constituting the white spots were analyzed by scanning e lectron microscopy and energy dispersive x-ray spectroscopy. It was co ncluded that white spots were caused by either silica-induced toner ag glomerates, or the agglomerates fused together by frictional heating d uring charging of toner particles on the magnetic roller.