| 摘要 |
PURPOSE:To obtain a toner which has the strength to withstand the stress in a developing device and can prevent the increase in the starting torque of the developing device by coating a crosslinked high-polymer film consisting of an epoxy resin and polyamide resin on porous magnetite particles calcined at a specific temp. CONSTITUTION:The granules of the commercially marketed iron oxide red, etc. prepd. by adding about the same weight of water thereto to form a slurry, then granulating the slurry to about 20mu diameter with a spray dryer are calcined for one hour at 700-800 deg.C to prepare the porous particles which remain porous as the crystal growth of the magnetite particles does not progress thoroughly. Such porous particles are pulverized and classified to obtain the particles having the particle size ranging 63-149mu and 0.73g/cc bulk specific gravity. The crosslinked high-polymer consisting of the epoxy resin and polyamide resin is coated on such particles at 1-6wt%, by which the carrier for an electrophotographic developer is obtd. The carrier which has high strength, can prevent the increase in the starting torque of a developing device and can widen the allowance of the toner concn. is thus obtd. |
