Abstract: A thermal printer for forming an image on a sheet includes a thermal head having a plurality of linearly arranged thermal elements. A total number of thermal elements to be energized to form the line image is determined. A difference between the total thermal elements to be energized to form the line image, and previous number of the thermal elements that were energized to form a previous line image is calculated. The thermal elements are then driven for a period of time which is a function of the difference between the total number and the previous number that was calculated.

Abstract: The past print data of plural heating resistance elements adjacently disposed are stored and latched in first latching circuit, the present print data is stored and latched in second latching circuit, and corresponding to the latched outputs of these first and second latching circuits, when the heating resistance elements have printed in the past and when the heating resistance elements adjacently to both sides of each heating resistance element are presently used in printing, it is controlled so as to shorten the driving time. As a result, blurring of the print due to excessive temperature rise of the heating resistance elements may be suppressed. Hence, the printing quality may be enhanced.

Abstract: A thermal printer for forming an image on a sheet, with the image having a plurality of line image data. The thermal printer includes a thermal head having a plurality of linearly arranged thermal elements for forming the image. The total number of the thermal elements to be driven is determined. The thermal elements are driven for a predetermined time period in accordance with the line image data if the number of thermal elements to be driven is not greater than a predetermined value. If the total number of the thermal elements to be driven is greater than the predetermined value, then the predetermined time period is divided into a number of fractional time periods and the thermal elements are intermittently driven for each of the fractional time periods. The predetermined value is determined to avoid sticking between the thermal head and a thermosensitive sheet due to excess heat.