Method of forming gradated images by thermal printer and thermal head for thermal printers

摘要

A method of forming a gradated image by using a thermal printer wherein a thermal head having a plurality of lined-up heating elements scans in one direction and the surface of thermal paper is fed in a secondary scanning direction intermittently and synchronously with the scanning movement of the thermal head. The method comprising the steps of setting a feed amount of the thermal paper to a level which is not greater than 1/2 of the length of arrangement of the heating elements, advancing the thermal paper to the position where the sections formed between the preceding printing sections become the subsequent printing sections. New image element information is given to such heating elements that are not opposed to the sections formed between the preceding printing section of the thermal paper while giving to such heating elements that are opposed to the sections formed between the preceding printing section of the thermal paper image element information which is the same as the already-printed image element information in an adjacent heating element. The heating elements are actuated by modulated signals, which are made by modulating a signal representative of the density of an image to a plurality of pulse signals having a pulse width sufficiently smaller than the pulse width of the pulse current. A thermal head for thermal printers having a plurality of heating elements provided on a substrate is further disclosed.