A new composite carrier based on magnetic particles and a phenol resin has been developed for application to long life electrophotographic developers. The carrier, composed of core particles and a resin shell, is quite spherical in shape with a narrow particle size distribution in the range of 10-200 mum in diameter. The carrier core can either be made up of magnetic fine particles such as ferrites and magnetites, or of non-magnetic particles such as hematites with 90 wt% or high loading. The core particles were prepared by dispersing magnetic or non-magnetic fine particles in an aqueous solution of phenol and formaldehyde in the presence of ammonia as condensation catalyst. The surface of the core particles was then coated with a silicone resin. The composite carrier thus prepared exhibited excellent charging and charge-holding properties that greatly exceeded those of commercial ferrite based carriers. [References: 19]
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