Abstract: A thermal head device operates while a recording medium is fed in its lengthwise direction for line-sequentially printing each image line along its widthwise direction. A platen has a plane tangential thereto to define a level of feeding pass of the recording medium in a printing zone thereof. A plurality of planar head segments are opposed to the printing zone of the platen in staggered relation to each other such that the head segments are arranged along a pair of parallel rows along the widthwise direction of the recording medium. The respective planar head segments have edge portions opposed to each other between the parallel rows in the printing zone, and are slanted relative to the tangential plane such that the respective edge portions are inclined away from the feeding pass of the recording medium.

Abstract: A thermal line head device operates while a recording medium is fed in a vertical direction for printing dots line-sequentially along a horizontal direction according to bit image data corresponding to dots. A plurality of longitudinal head segments have a plurality of heating elements effective to print dots according to the corresponding bit image data, and linearly arranged along a longitudinal edge portion of the segment and deviated from a longitudinal center portion of the segment. The head segment are arranged in staggered relation along upstream and downstream rows such that the longitudinal edge portions of segments are opposed adjacently to each other in parallel between the rows so that the heating elements are linearly arranged in the horizontal direction between the rows a given vertical spacing. A line memory stores bit image data and distributes the stored bit image data to the heating elements in synchronization with vertical feeding of recording medium through the given vertical spacing.