Thermal printing method for preventing degrading of print quality due to fluctuation in transport speed of recording sheet

摘要

A thermal printing method for printing an image line by line on a recording material by driving an array of heating elements of a thermal head while transporting the recording material relative to the thermal head. Heating data for recording a subject line to print is corrected in accordance with heat accumulation amounts of the heating elements. Surface temperatures of the respective heating elements are estimated on the basis of corrected heating data. A frictional force that will be generated between the thermal head and the recording sheet on recording the subject line is calculated on the basis of the estimated surface temperatures. The heating elements start being driven to record the subject line at a time shifted by a time shifting amount from a standard time. The time shifting amount is determined depending upon the frictional force so as to eliminate influence of fluctuations in transport speed of the recording sheet on the printed image.