| 摘要 |
PURPOSE:To enhance printing quality by making it possible to keep printing density always uniform, by providing a bias means for preliminarily supplying a predetermined bias current to each of the current supply electrodes of a current supply transfer type printing head. CONSTITUTION:A series circuit consisting of a diode 12 and a resistor 15, that of a diode 13 and a resistor 16 and that of a diode 14 and a resistor 17 are inserted between the collector of a transistor 11 and current supply electrode pins 1-3. Each of the diodes 12-14 is a reverse-current preventing one and each of the resistors 15-17 is a current limiting one. In this constitution, when the transistor 11 is preliminarily subjected to ON-control, a bias current is supplied to the pins 1-3 through the series circuits each consisting of the diode and the resistor even when drive transistors 8-10 are in an OFF-state. When this bias current is preset to a definite current value insufficient to perform printing, the preheating of an ink ribbon 4 is performed and printing density always constant is compensated. |
