Transfer-separation device and image forming apparatus

An image forming apparatus comprising:

• an image carrier that carries a toner image;
• and
• a transfer-separation device that includes
• an intermediate transfer unit that is in a shape of an endless belt, onto which a toner image is primarily transferred from the 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 106.5 ohm.