| 摘要 |
PURPOSE:To reduce irregularity in printed density, by a method wherein heating elements provided at a thermal head of a thermal printer are preheated to maintain the temperature of the element at a fixed value. CONSTITUTION:When a carriage 200 starts moving and the movement becomes substantially stable, a preheating current-passing pulse 202b having less power than that of printing current-passing pulse 202a is impressed on the thermal head at the moment a several-dot period before the start of the first printing 203 (printing of a part of letter H). Since the impressing of the pulse 202b results in heating only to a temperature of not higher than the melting point of a heat-fusible ink provided on a heat transfer ribbon, printing is not conducted. when the passing of an electric current for preheating is continued, a printing starting temperature 204c becomes constant. Once the thermal head reaches an equilibrium, the maximum temperature 204d of the heating element at the time of passing an electric current for printing becomes constant, so that no irregularity is generated in the printed density. In addition, when a continuous dot printing operation is conducted, the current-passing duration of the second and later current-passing pulses 202c for continuous printing is set to be 80% of that of the first printing current-passing pulse 202a, so that accumulation of heat in the heating element at the time of continuously passing an electric current is prevented. |
