ELECTROSTATIC CHARGE IMAGE DEVELOPER AND IMAGE FORMING METHOD

摘要

PROBLEM TO BE SOLVED: To obtain a developer having excellent electrification characteristics and developing characteristics to accurately develop a latent image, and to form an image of excellent quality without causing deposition of a carrier, irregular density or toner fog. SOLUTION: This developer consists of a toner and a carrier comprising core particles each coated with a resin layer. The toner has 3-9μm vol. average particle size and shows a specified particle size distribution. The toner particles are coated with an external additive of 20-100nm particle size by >=20% coating rate and with an external additive of 7-20nm average particle size by >=40% coating rate. The core particles of the carrier are magnetic particles produced by mixing 100 pts.wt. of a ferrite component expressed by formula (MO)100-x (Fe2 O3 )x and 0.01 to 10 pts.wt. of oxides of elements selected from IA, IIA, IIIA, IVA, VA, IIIB, IVB and VB groups in the periodical table, granulating the obtd. compsn. and sintering. The carrier contains Si by 500 to 5000ppm. In formula, M is Li, Mg, Ca or Mn and x is 45 to 95(mol%).