THERMAL PRINTER

PURPOSE:To keep a printing density constant without the reduction of the life of a thermal head and the performance of an ink ribbon and the influence of an ambient temperature by disposing a preheating mechanism before a printing part. CONSTITUTION:A preheating mechanism 2 consisting of a heating roller 21 rotating in a paper feed direction and a guide roller 22 pressing recording paper 3 against the heating roller 21 is provided in the vicinity of a printing part 1 on the side of feeding the recording paper 3. The heating roller 22 is made of a good heat conductive material, such as copper and aluminum, and provided with a heat source, such as an infrared heater 21a, inside. The surface of the roller is heated up to a predetermined high temperature in accordance with an ambient temp.. The printing surface of the recording paper 3 is brought into contact with the surface of the heating roller 21, and the recording paper 3 is heated, supplied to the printing part 1, and passed through between a thermal head 12 and a platen roller 11. At this time, a printing current is applied to a heating element 12a to heat it selectively to transfer an ink on the recording paper 3. In this manner, the life of the thermal head is extended, a thermal efficiency in preheating is improved regardless of the thickness of the ink ribbon, and an energy is less consumed.