While both methods employ a heated printer head, thermal-transfer printers require an ink ribbon, while direct thermal printers do not need any ink sources for printing.
Direct-thermal and thermal-transfer printing share many similarities. Both techniques use a heated print head to print on the blank label. The main difference between the two techniques is the use of a printing ribbon in thermal-transfer printing, which is not required with direct-thermal methods.
Direct thermal printing uses heat to activate thermosensitive paper labels. The heated print head comes in direct contact with the label. When heated, the thermosensitive label reacts and darkens, creating the desired print. One important consideration when choosing this method is that this print is unstable and prone to fading over time, especially when stored in hot or humid conditions. Scratches can also produce enough heat to create marks on the label and affect the quality of the print.
In contrast to direct thermal printing, thermal-transfer methods use a ribbon to print information on labels. The heated print head is used to melt the ink coating of the ribbon, transferring it to the label. Since the label itself is not reactive, the print produced by this method is much more stable and a lot more durable. Thermal-transfer labels are usually made from a thermoplastic film, but can be made of paper material as well.