Image forming apparatus and method that charges latent image carrier

An image forming apparatus comprising:

• a latent image carrier which rotates in a predetermined movement direction and carries an electrostatic latent image on a surface thereof;
• a first charging unit which charges the latent image carrier with a surface potential having the same polarity as a charged polarity of toner at a first charge position;
• a second charging unit which supplies a charge having a reverse polarity of the charged polarity of the toner toward the surface of the latent image carrier at a second charge position located on a downstream side of the first charge position in a movement direction of the latent image carrier;
• a latent image forming unit which forms the electrostatic latent image on the surface of the latent image carrier at a latent image formation position located on the downstream side of the second charge position in the movement direction of the latent image carrier by lowering a surface potential of an image region, where the toner is attached, on the surface of the latent image carrier and by allowing a surface potential of a non-image region, where no toner is attached, to be different from the surface potential of the image region;
• a toner carrying roller which is formed in a roller shape, is disposed to face the latent image carrier with a predetermined gap therebetween at a development position located on the downstream side of the latent image formation position, in the movement direction of the latent image carrier, and carries a toner layer containing both a contact toner which comes in direct contact with the surface of the toner carrying roller and a non-contact toner which comes in contact with the contact toner and does not come in contact with the surface of the toner carrying roller;
• an electric field forming unit which develops the electrostatic latent image by the toner at the development position by generating an alternating electric field as a toner fly electric field between the latent image carrier and the toner carrying roller;
• a transfer unit which transfers a toner image formed by developing the electrostatic latent image to a transfer medium at a transfer position located on the downstream side of the development position in the movement direction of the latent image carrier;
• and
• a cleaning unit which removes attachments attached on the surface of the latent image carrier, and is charged with the reverse polarity of the charged polarity of the toner, on the downstream side of the transfer position and the upstream side of the second charge position in the movement direction of the latent image carrier.

An image forming method comprising:

• charging a rotating latent image carrier with a surface potential having the same polarity as a charged polarity of toner at a first charge position;
• supplying a charge having a reverse polarity of the charged polarity of the toner toward the surface of the latent image carrier at a second charge position located on a downstream side of the first charge position in a movement direction of the latent image carrier;
• forming an electrostatic latent image on the surface of the latent image carrier at a latent image formation position located on the downstream side of the second charge position in the movement direction of the latent image carrier by lowering a surface potential of an image region, where the toner is attached, on the surface of the latent image carrier and by allowing a surface potential of a non-image region, where no toner is attached, to be different from the surface potential of the image region;
• disposing a toner carrying roller, which is formed in a roller shape and carries a toner layer containing both a contact toner which comes in direct contact with the surface of the toner carrying roller and a non-contact toner which comes in contact with the contact toner and does not come in contact with the surface of the toner carrying roller, to face the latent image carrier with a predetermined gap therebetween at a development position located on the downstream side of the latent image formation position in the movement direction of the latent image carrier;
• developing the electrostatic latent image by the toner at the development position by generating an alternating electric field as a toner fly electric field between the latent image carrier and the toner carrying roller;
• transferring a toner image formed by developing the electrostatic latent image to a transfer medium at a transfer position located on the downstream side of the development position in the movement direction of the latent image carrier;
• and
• removing attachments attached on the surface of the latent image carrier with a cleaning unit that is charged with the reverse polarity of the charged polarity of the toner, on the downstream side of the transfer position and the upstream side of the second charge position in the movement direction of the latent image carrier.