Patent ID: 7280788

Claim:
An image forming apparatus using a tandem method for a first transfer procedure, the image forming apparatus comprising: a plurality of image bearing members for carrying images of respective colors; an intermediate transfer member rotatably disposed so as to face the image bearing members; a plurality of first transfer devices for forming a full-color toner image on the intermediate transfer member by transferring color toner images formed on the image bearing members to the intermediate transfer member; a second transfer device for transferring the full-color toner image formed on the intermediate transfer member to a recording sheet; and a charge amount adjustment section for adjusting a charge amount of toner particles constituting the full-color toner image so as to reduce non-uniformity in a charge amount of toner particles of the full-color toner image on the intermediate transfer member per unit area, wherein the charge amount adjustment section suppresses a range of the non-uniformity in the charge amount of the toner particles of the full-color toner image on the intermediate transfer member per unit area to be less than 0.025 μC/cm 2 , further comprising: sensors for detecting thickness of a full-color toner image on the intermediate transfer member, and a controller adapted to activate the charge amount adjustment section when determining, based on the detection results of the sensors, that the range of non-uniformity in the charge amount of the full-color toner image on the intermediate transfer belt per unit area is 0.025 μC/cm 2 or more, wherein development conditions are set such that the amount of the toner particles supplied to the image bearing members is smaller than 0.4 mg/cm 2 and the charge amount of the toner particles at such time is smaller than −20 μC/g.