| 摘要 |
PURPOSE:To maintain uniformity of density of printed dots and enhance printing quality, by preheating a heating element not supplied with an electric current for printing, at the time of printing. CONSTITUTION:At the start of printing, each of the heating element is in a thermal equibrium state. The heating element used for printing is supplied with a driving pulse with a width t1 to perform printing, while the heating element 1a not used for printing at this time is supplied with a printing pulse with a width t3 to heat the element to a temperature Ta, which is set to be not higher than the transferring temperature of a printing ribbon. The temperature of the heating element at the next printing period is either Ta (where the element has been used in the preceding- time printing) or Tb (where the element has not been used in the preceding-time printing). Accordingly, in the next printing, the heating element is driven with a printing pulse width t2 where the temperature thereof is Ta or is driven with a printing pulse width (t2+t4) where the temperature thereof is Tb, whereby a suitable dot can be printed. When not printing, the heating element is supplied with a printing pulse with a width t4 to heat the element to the temperature Ta, only when the temperature of the element is Tb. By carrying out the same treatment in the subsequent printing operations, it is made possible to print suitably. |
