Color thermal printing method

Abstract

A color thermal printing method capable of preventing a color registration shift and shading is unable with a color thermosensitive recording sheet having cyan, magenta, and yellow thermosensitive coloring layers, respectively formed on a base in this order. A thermal sensitivity becomes lower the nearer the thermosensitive coloring layer is to the base. The thermosensitive coloring layer having a lower sensitivity is printed at an earlier timing to make the centers of three color print areas coincident with each other. According to a preferred embodiment, a preliminary pressed running section is provided in front of each print area. In the preliminary pressed running section, a thermal head is preheated and pressed against a color thermosensitive recording sheet. In order to reduce a change in the friction coefficient between the preliminary pressed running section and the print area, the heat energy for the preheating is set to a bias heat energy having a level just under a coloring energy. This bias heat energy having a level just under a coloring energy changes with color so that the preliminary pressed running section is set differently for each color. During the preliminary pressed running operation, a pulse motor for driving a platen drum is driven by the same predetermined number of drive pulses for all three colors.