Thermal transfer printing apparatus and thermal transfer printing method

A thermal transfer printing apparatus that includes a thermal head and a platen roll and forms an image on printing paper by causing the thermal head to heat an ink ribbon including a plurality of consecutive ink layers, each of which includes sequential panels of a yellow layer, a magenta layer, and a cyan layer and thereby transfer ink while transporting, between the thermal head and the platen roll, the ink ribbon and the printing paper that are superimposed on each other, the thermal transfer printing apparatus comprising:

• a sensor detecting ink content of the ink layers;
• and
• a controller controlling energy applied to the thermal head during image formation based on a result of the detection of the sensor, wherein
• the sensor is provided between the thermal head and an ink ribbon collecting unit collecting a used ink ribbon, and
• the sensor detects ink content in a printed region used for formation of an image on the printing paper and ink content in a non-printed region that is not used for image formation.