MAGNETIC TONER AND ELECTROPHOTOGRAPHIC METHOD

摘要

PURPOSE:To obtain a magnetic toner free from the degradation of image density even in the case of recycling by using a specific binding resin and making the ratio of BET specific surface area between before and after externally adding a flowability imparting agent to a specific value. CONSTITUTION:The magnetic toner is composed of at least a binding resin, a magnetic body and the flowability imparting agent. The binding resin is a copolymer made by copolymerizing at least monomers expressed by formulas I-IV. In the formula, R1 is H or CH3. R2 is 1-10C alkyl group. R3 is 16-25C alkyl group. The weight average molecular weight of the binding resin is 100000-500000 and the ratio between weight average molecular weight and number average molecular weight is 10-50. The ratio of BET specific surface area between before and after externally adding the flowability imparting agent is 1.05-1.5. The flowability imparting agent is composed of at least a hydrophobic silica having trimethylsiloxyl group.