Patent ID: 8384750

Claim:
A printing apparatus comprising: a thermal head provided with a line head including a plurality of heater elements arranged in a linear fashion; conveying units that convey a printing medium in a sub-scanning direction which is in an orthogonal relation with the line head of the thermal head; and a control unit that controls the conveying units and the thermal head; said control unit carrying out an application process for causing the respective heater elements constituting the line head of the thermal head to selectively generate heat in each one of application periods which are repeated successively, to form printed dots on the printing medium which is conveyed by the conveying unit in the sub-scanning direction of the thermal head and as a result carry out printing, wherein each application period is set as a fixed period of time ranging from a main heating start point which shows when application of a main pulse for main heating which causes the printing medium to develop color starts at the line head of the thermal head to a next main heating start point, to cause successive printed dots to be formed on the printing medium in the sub-scanning direction of the thermal head; and the control unit carries out application of a sub pulse for auxiliary heating which, when applied independently, cannot cause the printing medium to develop color, but, when applied so as to compensate main heating by the main pulse as applied in a next application period can cause the printing medium to develop color, with respect to each of the heater elements constituting the line head of the thermal head in accordance with a following constraint (A): (A) the sub pulse is applied in a current application period wherein the printing medium is not caused to develop color, irrespective of whether the next application period wherein the main pulse for main heating is applied to cause the printing medium to develop color starts immediately after the current application period wherein the printing medium is not caused to develop color.