Patent ID: 7463849

Claim:
An image forming apparatus, comprising: a photosensitive member being movable in a predetermined direction; a charging roller that charges a surface of the photosensitive member with a predetermined potential, the charging roller being disposed so as to come into contact with the surface of the photosensitive member; and a static pre-eliminator that eliminates static electricity from the surface of the photosensitive member by irradiating the surface of the photosensitive member with light, the static pre-eliminator being located on an upstream side of the charging roller in a direction of movement of the photosensitive member; wherein an arrangement and an exposure amount of the static pre-eliminator are set to satisfy E≦ 0.025×exp( t /τ) where τ is a residual time constant of a photo carrier generated in the photosensitive member by the static pre-eliminator, t is a time period from a time when the photosensitive member passes through the static pre-eliminator to a time when the photosensitive member is charged by the charging roller, and E is a normalized exposure amount of the static pre-eliminator which is obtained by normalizing the exposure amount of the static pre-eliminator by half-value exposure amount of the photosensitive member.