Patent ID: 7826758

Claim:
An image forming apparatus comprising: an image bearing member; and a developer carrying member which carries a developer including a toner and a carrier, the developer carrying member developing with the developer an electrostatic image formed on the image bearing member, the developer carrying member being applied with alternating voltage so that an alternating electric field is formed between the developer carrying member and the image bearing member, wherein, in a graph whose axis of abscissa illustrates an electric field intensity to which the carrier is subjected and whose axis of ordinate illustrates a permittivity of the carrier, when: a slope of the graph at an electric field intensity Ed=|(Vp 2 −VL)/X| is given as K 1 ; and a slope of the graph at an electric field intensity Eb=|(Vp−VL)/X| is given as K 2 , a relation |K 1 |<|K 2 | is satisfied, where: VL represents a potential [V] of the electrostatic image at which a maximum density is obtained; Vp 1 represents, out of peak potentials in the alternating voltage, a peak potential [V] that provides such a potential difference from the VL potential that moves the toner toward the image bearing member; Vp 2 represents, out of peak potentials in the alternating voltage, a peak potential [V] that provides such a potential difference from the VL potential that moves the toner toward the developer carrying member; and X represents a closest distance [m] between the image bearing member and the developer carrying member, and wherein the carrier comprises a porous core filled with a resin.