Patent ID: 7155152

Claim:
An image forming method, comprising: forming an electrostatic latent image on an image bearing element; forming a toner image from the electrostatic latent image using toner; optically neutralizing a surface potential of the image bearing element that carries the toner image so as to create an optically neutralized surface on said image bearing element; controlling a surface potential of a transfer medium so that the toner is not transferred from the image bearing element to the transfer medium at an upstream of a contact area between the image bearing element and the transfer medium, while controlling a surface potential of a transfer medium so that the toner is transferred from the image bearing element to the transfer medium at a toner nip portion; and transferring a plurality of toner images of different colors from the image bearing element repeatedly to the transfer medium to form a superposed toner image on the transfer medium, wherein said step of controlling a surface potential includes applying a negative voltage to said transfer medium before said optically neutralized surface reaches said toner nip portion and applying a positive voltage to said transfer medium after said optically neutralized surface leaves said toner nip portions, wherein the surface potential of the transfer medium has same polarity as a toner potential on the image bearing element, and an absolute value of the surface potential of the transfer medium is equal to or greater than an absolute value of the toner potential.