Patent ID: 9086647
Filing Date: 2015-07-21
Classification: G03G

Abstract:
1. A developing device, comprising: a developer bearing member, which is disposed opposite to an electrostatic latent image bearing member and which bears thereon a developer for developing an electrostatic latent image formed on the electrostatic latent image bearing member and conveys the developer to a developing region, wherein the developer comprises a toner and a carrier, the toner comprising: a toner base comprising a binder resin and a colorant; and an external additive, wherein the external additive comprises coalescent particles each made up of a plurality of coalescing primary particles, wherein a work function Wc of the carrier and a work function Ws of the developer bearing member satisfy a relationship of the following formula (1): and wherein said developing device satisfies at least one of the following conditions a), b) and c): a) the coalescent particles have a particle size distribution index expressed by the following formula (2): where in the formula (2), in a distribution diagram in which particle diameters (nm) of the coalesced particles are on the horizontal axis and cumulative percentages (% by number) of the coalesced particles are on the vertical axis and in which the coalesced particles are accumulated from the coalesced particles having smaller particle diameters to the coalesced particles having larger particle diameters, Db b) the coalescent particles satisfy the following formula (3): where in the formula (3), Nx denotes the number of broken or collapsed particles in 1,000 of the coalescent particles, where the broken or collapsed particles are selected by stirring 10.5 g of the coalescent particles and 49.5 g of the carrier placed in a 50 mL-bottle by use of a rocking mill, which is manufactured by Seiwa Giken Co., Ltd., under conditions of 67 Hz and for 10 minutes, and then observing the stirred coalescent particles through a scanning electron microscope, and c) the coalescent particles satisfy the following formula (3-1): where in the formula (3-1), Nx denotes the number of broken or collapsed particles in 1,000 of the coalescent particles, where the broken or collapsed particles are selected by stirring 10.5 g of the coalescent particles and 49.5 g of the carrier placed in a 50 mL-bottle by use of a rocking mill, which is manufactured by Seiwa Giken Co., Ltd., under conditions of 67 Hz and for 10 minutes, and then observing the stirred coalescent particles through a scanning electron microscope.