Toner for developing electrostatic image, image forming method and developing apparatus unit

摘要

A toner for developing an electrostatic image is constituted by at least toner particles and an additive. The toner particles have a shape factor SF-1 of 100-160, a phase factor SF-2 of 100-140 and a weight-average particle size of 4-10 mu m as measured by a Coulter counter. The toner contains particles having circle-equivalent diameters in a range of 0.6-2.0 mu m and satisfying the following conditions (i)-(iii): (i) a first value C1 of 3-50% by number as measured by a flow particle image analyzer after application of a ultrasonic wave of 20 kHz for 5 min., (ii) a second value C2 of 2-40% by number as measured by the flow particle image analyzer after application of a ultrasonic wave of 20 kHz for 1 min., and (iii) a value C of 105-150 obtained according to the following equation: C=(C1/C2)x100 The toner is effective in improving image-forming characteristics in a continuous image formation on a large number of sheets.