Thermal paper is a special type of paper that is manufactured by coating a high-quality base paper with a "thermal coating" (a heat-sensitive color-changing layer). Although there are over a dozen chemicals used in this color-changing layer, at least the following compounds are used: a colorless dye, which has a wide variety of types and the most commonly used is fluorescent compounds; a developer that makes up less than 20% of the total, commonly used are bisphenol and p-hydroxybenzoic acid; an intensifier that makes up less than 10% of the total, which contains benzenesulfonamide-type compounds; fillers that make up less than 50% of the total, commonly used are calcium carbonate (particles); a binder that makes up less than 10% of the total, such as polyvinyl acetate; and stabilizers such as diphenylphthalate. Therefore, the manufacturing process is difficult and requires high technical requirements.