Patent ID: 7352381

Claim:
A thermal printhead comprising: a plurality of main heat-producing resistor sections formed on a substrate and arranged at predetermined intervals in a primary scanning direction; a plurality of auxiliary heat-producing resistor sections each of which is spaced from a respective one of the main heat-producing resistor sections by a predetermined distance in a secondary scanning direction which is perpendicular to the primary scanning direction; a plurality of first electrodes each connecting, in series, at least one of the main heat-producing resistor sections and the corresponding auxiliary heat-producing resistor section which are, arranged in the secondary scanning direction; a plurality of second electrodes for energizing the series circuits of the main heat-producing resistor sections and the auxiliary heat-producing resistor sections connected in series by the first electrodes, printing being performed by heating a printing recording medium by the main heat-producing resistor sections while transferring the printing recording medium in the secondary scanning direction; and a glaze layer including a bulging portion and formed on the substrate, the bulging portion including a top surface and an inclined surface, the inclined surface being positioned downstream from the top surface in the secondary scanning direction and gradually reducing height from the substrate while extending downstream in the secondary scanning direction; wherein the distance between each of the main heat-producing resistor sections and a corresponding one of the auxiliary heat-producing resistor sections in the secondary scanning direction is larger than length of the main heat-producing resistor section in the secondary scanning direction; wherein each of the auxiliary heat-producing resistor sections is positioned upstream from each of the main heat-producing resistor sections in the secondary scanning direction; wherein each of the main heat-producing resistor sections is provided on the inclined surface of the bulging portion; and wherein each of the auxiliary heat-producing resistor sections is provided on the top surface or the inclined surface of the bulging portion at a position higher than each of the main heat-producing resistor sections.