Patent ID: 8411121

Claim:
A thermal printhead for progressively printing a pattern of dots on a thermosensitive paper moving in one direction, comprising: a substrate; and a plurality of resistor elements on the substrate arranged in a substantially straight line extending in a direction perpendicular to a moving direction of the thermosensitive paper, the plurality of resistor elements each corresponding to respective one of the dots constituting the pattern to be printed onto the thermosensitive paper, each of the resistor elements having at least one heat transfer area that will be in contact with the thermosensitive paper upon printing the dot, wherein the heat transfer area of each of the resistor elements is shaped to have a sag in a plan view in at least one of two boundary lines that define the heat transfer area along the moving direction of the thermosensitive paper, the sag being positioned in a substantially middle portion of a length of the boundary line, to adjust a shape to be printed onto the thermosensitive paper by the heat transfer area of the resistor elements.