Thermal paper roll has a big defect is that the document with thermal paper roll is easily faded after a period. Its color fading is because thermal paper roll uses a kind of special dye. Leuco dye on the surface of thermal paper roll is colorless at room temperature, it will turn into another color when it is at a high temperature because of chemical reaction. However, this kind of new structure is not very stable, it will return to the former color when it meets suitable condition, like crystal violet lactone, which meets acid substance will become colorful, when it meets alkaline substance, it will return to colorless. After printing a shopping receipt, it will meet many kinds of chemicals in the process of storing, even isolation and high temperature, all of them will lead to color fading of receipt with thermal paper roll.

In order to solve this problem, many manufacturers of thermal paper roll production will add another protective coating on the dye layer too prevent it from contacting with chemical substance, so document with thermal paper roll will be stored for a longer time. However, this kind of method will increase the cost of thermal paper roll, therefore, some manufacturers are still using common thermal paper roll without protective coating.