Patent ID: 7471909

Claim:
An image forming apparatus, comprising: an image bearing member including a photoconductive layer having a capacitance per unit area which is equal to or larger than 1.7×10 −6 (F/m 2 ); and a developing device, which develops an electrostatic latent image formed on said image bearing member using a developer containing toner and a carrier to form a toner image on said image bearing member, said developing device including a developer carrying member, which carries the developer, a development bias voltage being applied to said developer carrying member, wherein the following Expression 1 is satisfied:  Q M  ≥ 0.95 × Vcont ( M S ) × ( L t 2 ⁢ ɛ 0 ⁢ ɛ t + Ld ɛ 0 ⁢ ɛ d ) ( Expression ⁢ ⁢ 1 ) where Q/M (C/g) indicates a quantity of electric charge per unit weight of the toner image formed on said image bearing member, Vcont (V) indicates a potential difference between a direct current component of the development bias voltage and a surface potential of said image bearing member with respect to a maximum density portion of the toner image formed on said image bearing member, M/S (g/m 2 ) indicates a toner weight per unit area of the maximum density portion of the toner image formed on said image bearing member, L t (m) indicates a thickness of a toner layer in the maximum density portion of the toner image formed on said image bearing member, L d (m) indicates a thickness of the photoconductive layer, ε t indicates a relative permittivity of the toner layer, ε d indicates a relative permittivity of the photoconductive layer, and ε 0 (F/m) indicates a vacuum permittivity.