Abstract: Ribbon (22) in thermal printing has an outer layer which adheres to printed characters at intermediate temperatures, lower than printing temperatures. The printhead (7) has a column of electrodes (9) which sweep across the character area. Lift-off is accomplished by the pattern control (40) controlling the current source (38) to provide rapid, square wave pulses displaced in phase 180 degrees at adjoining electrodes (9). The high level of the pulses is about that of the level at printing, and the pulses are sufficiently rapid so that their net effect is to raise the outer layer ribbon (22) to the intermediate temperature. At areas corresponding to underlines of characters, duration of the up period is longer. Good, long term reliability is achieved by the significant erase level being very close to the print level.

Abstract: An electrode drive configuration for a resistive ribbon thermal printer utilizes as a feedback a monitored signal representative of an internal ribbon voltage at the print point. A monitoring contact is preferably located on the opposite side of the printhead from the drive signal return contact and the feedback signal is used to cancel the effects voltage drop variations in the common return portion of the drive signal path.