Patent ID: 7773928

Claim:
A transfer-separation device comprising: an intermediate transfer unit that is in a shape of an endless belt, onto which a toner image is primarily transferred from an image carrier; a secondary transfer roller that is in contact with a surface of the intermediate transfer unit where the toner image is carried via a recording medium, the secondary transfer roller including a core and a resistance layer, wherein the resistance layer includes an inner layer formed outside the core and a surface layer formed outside the inner layer, and a resistance of the surface layer, which is a surface resistance between two separate surface portions on the surface layer, is configured to be higher than a resistance of the inner layer, which is a volume resistance between the core and the outer surface of the surface layer; a repulsive roller that is located opposite to the secondary transfer roller and, with the secondary transfer roller, forms a secondary transfer nip through which the intermediate transfer unit and the recording medium pass; a transfer unit that applies a bias voltage of a polarity identical to a polarity of the toner image to the repulsive roller to generate a transfer electric field, and secondarily transfers the toner image onto the recording medium; and a charge-eliminating and separating member that is located downstream of the secondary transfer nip in a conveying direction of the recording medium, and eliminates charge from a surface of the recording medium to separate the recording medium from the intermediate transfer unit, wherein a resistance of the repulsive roller is greater than a resistance of the secondary transfer roller, and the surface resistance of the secondary transfer roller is equal to or greater than 10 6.5 ohm.