Color thermal printer and color thermal printing method

摘要

The printer has a conveyor roller pair and three thermal heads to record yellow, magenta and cyan images onto a recording sheet. The conveyor roller pair receives forward tension Ff from the forward tension roller pairs located near the thermal heads to pull the recording sheet with tension. A backward tension roller pair is provided to generate backward tension Fb to cancel forward tension Ff so that the recording sheet is conveyed at a stable conveyance speed. The coefficient of friction between the thermal head and the recording sheet is varied depending on the temperature, humidity and so force. Backward tension Fb is equal to Ef.alpha in consideration of the correction value alpha to correct variation in the coefficient of friction.