Thermal printer and thermal head control method

Abstract

A thermal printer has a thermal head, which includes plural heating elements arranged in a main scanning direction. The heating elements are driven while the thermal head and a color thermosensitive recording sheet are moved relatively in a sub scanning direction perpendicular to the main scanning direction. The heating elements apply bias heat energy and image heat energy to the recording sheet, thermally to record an ink dot on the recording sheet. The bias heat energy is determined to heat the recording sheet substantially to a temperature at which the recording sheet starts being colored. The image heat energy is determined in accordance with image data of a halftone image. Density correcting heat energy is additionally applied to the recording sheet through heating elements located in end positions in the thermal head. The heating elements of the end positions are so located that heat escapes therefrom fastest of the plural heating elements. The correcting heat energy is determined to make the heating elements of the end positions as hot as heating elements in a middle position. The density of the ink dot is regularized with reference to the main scanning direction.