Image formation

摘要

A toner for image formation by back-exposure is constituted so that the value Fs determined by the equation Fs = 6/(dt. rho t.S), where dt is the volume-average particle diameter of the toner, rho t is the density of the toner and S is the specific surface area of the toner, is in the range 0.75 to 0.90, and the magnitude of the electrification as measured by a magnet blow-off method is in the range 10 to 40 mu C/g. The developer also uses a carrier, which has a magnetic susceptibility not less than 90 emu/g (at 1 k0e), a specific surface area in the range 1000 cm<2>/g to 1800 cm<2>/g, an electric resistivity from 10<2> to 10<6> OMEGA cm, and an average particle diameter of 20 to 45 mu m.