Patent ID: 8606152

Claim:
An image forming apparatus to form an image in a single pass manner, comprising: a plurality of image carriers; a transfer belt to receive developer images from the respective image carriers; a plurality of primary transfer rollers disposed to be offset from the image carriers along the transfer belt, respectively; a backup roller disposed adjacent to a last one of the primary transfer rollers disposed most-downstream in a rotating direction of the transfer belt; and a secondary transfer roller to transfer the developer images from the transfer belt to a printing medium, the secondary transfer roller being disposed opposite to the backup roller to interpose the transfer belt therebetween, wherein the backup roller has a resistance in a range of 10 to 50 MΩ, and where, when a distance between a center of the last primary transfer roller and a center of the image carrier corresponding thereto is A and a distance between the center of the last primary transfer roller and a center of the backup roller is B, a following inequality is satisfied: 2A<B<6A.