Patent ID: 8218199

Claim:
An image forming apparatus, comprising: an image-data acquisition portion for acquiring image data; an image formation portion for forming an image onto a sheet forwarded in a predetermined forwarding direction based on image data acquired by the image-data acquisition portion, the image formation portion including: a photosensitive drum that forms and electrostatic latent image on a surface thereof; a development roller that is given a voltage and supplies the photosensitive drum with toner to thereby reveal an electrostatic latent image formed on the surface of the photosensitive drum; and a transfer portion that transfers a toner creating a revealed image formed on the surface of the photosensitive drum onto the sheet by giving the sheet a polarity reversed from the polarity of the toner; a control portion for controlling the image formation portion; an image-formation condition storage portion for storing in advance: a first image formation condition that is a suitable value for forming an ordinary toner image having no bar code on the sheet, the first image formation condition concerning at least one of a frequency of an alternating voltage applied to the development roller, a surface potential of the photosensitive drum, a direct-current voltage applied to the development roller and a transfer current supplied to the transfer portion, and a second image formation condition that is a suitable value for forming a toner image having a bar code on the sheet, the second image formation condition concerning at least one of a frequency of an alternating voltage applied to the development roller, a surface potential of the photosensitive drum, a direct-current voltage applied to the development roller and a transfer current supplied to the transfer portion, the second image formation conditions being different from the first image formation condition; wherein the control portion allows the image formation portion to form a toner image onto the sheet based on image data acquired by the image-data acquisition portion: at the first image formation condition when the image data includes no sub-image data indicating a bar code, and at the second image formation condition when the image data includes sub-image data indicating a bar code.