The conventional thermal paper utilizes an electron-donating colorless dye and an electron-accepting
developer, which react to give colored image. To improve the image stability, various kind of methods
have been proposed. However, there has been no study on the prediction of the image stability. We
found that under some defined condition of thermal acceleration test,Arrhenius Plot of the fading gives
a straight line, and that the predicted value gives good coincidence with the value obtained by actual
aging. This report presents the outline of the method for prediction and the coincidence of the result of
the test method with that obtained by actual aging.