Image forming apparatus, retransfer printer and image forming method

An image forming apparatus comprising:

• a platen roller;
• a thermal head configured to be brought into or out of contact with the platen roller in a relative movement;
• an ink ribbon conveyance mechanism configured to convey an ink ribbon including a plurality of color ink layers;
• a transfer film conveyance mechanism configured to convey a transfer film on which a plurality of transfer frames are formed at a predetermined pitch in a longitudinal direction and demarcated by frame marks having light transmissivity lower than that of another part of the transfer film;
• a line sensor arranged to extend in a width direction of the transfer film across end portions of the frame marks in the width direction;
• and
• a controller configured to, when forming color images on a selected one of the transfer frames by making the ink ribbon conveyance mechanism and the transfer film conveyance mechanism respectively convey the ink ribbon and the transfer film such that the color ink layers on the ink ribbon sequentially face the selected transfer frame on the transfer film, and by bringing the thermal head into press contact with the platen roller with the ink ribbon and the transfer film, interposed in between, adjust positions of the images to be formed on the selected transfer frame, in the width direction based on light-reception information outputted from the line sensor.