| 摘要 |
<p>PURPOSE:To provide a negatively chargeable developer having reduced dependence of the amount of charge on environmental conditions, excellent developing and transferring properties, a high hardness and good durability by using a coated carrier contg. specific hydrophilic silica particles in its coating layer. CONSTITUTION:The negatively chargeable developer contains a carrier which is obtained by coating the surfaces of magnetic particles with a silicone-based polymer. The coated carrier contains hydrophilic silica particles having a <20, preferably <=15 hydrophobicity in the coating layer, where the value of wettability by methanol is referred to as hydrophobicity. When a carrier is hydrophobic, the difference between the ranks of electrification of the toner and the carrier becomes smaller and, accordingly, the amount of charge of the toner becomes smaller. The subject carrier contains hydrophilic and weakly and negatively chargeable silica particles and, therefore, adsorbs water molecules at a high humidity the same as the toner does and also the rank difference of electrification of carrier is shifted to the plus side the same as the toner is. Therefore, the difference between the ranks of electrification of the carrier and the toner is unchanged and an almost constant amount of charge is maintained irrespective of environmental temp.</p> |
