Thermal paper, also known as thermal recording paper, thermal copy paper and thermal fax paper, was first developed by Minesota Mining Ink Character in 1951. Colorless dye two-component thermal paper is a kind of processing paper coated with special coatings. It is a kind of information paper which uses paper as carrier, recessive colorless dyes, developers, sensitizers, adhesives, etc. as thermal coatings.

The thermal printing paper rolls are mainly used in the following aspects: fax machine, communication, medical treatment, measuring system, such as electrocardiograph, thermal instrumentation, computer network terminal printing, trademark, signature (POS), etc. Among them, fax machine is the most widely used. With the rapid development of information technology, bill printer technology and bar code technology have been widely used. Because of its unique performance, the advantages of fast image generation and convenient bar code label, thermal paper has been growing rapidly in the field of bar code recording information and bill printing.

Functionally, thermal paper can be divided into ordinary thermal paper and three thermal-resistant paper. The three thermal-resistant paper is coated with a protective layer on the thermal layer to give three thermal-resistant paper better waterproof, oil-proof and friction-proof properties, mainly for high-end market.

Thermal paper can be divided into two main types: one is physical thermal paper, which uses heat to physically color colored pigments to achieve recording effect. This kind of thermal paper can be divided into melt transparent paper, melt transfer paper and heat sublimation paper. Among them, melt transparent thermal paper is representative, which is widely used in medical electrocardiogram and electroencephalogram. The chemical thermal paper, which can produce chemical reaction to achieve the purpose of chromogenic, is the most widely used product in the market at present. This kind of thermal paper can be divided into two-component metal compound chromogenic thermal paper and two-component colorless dye thermal paper.

The color rendering principle of molten transparent thermal paper is that a layer of opaque wax is coated on the black base paper as a surface layer, and the opaque wax material is melted and transparent by the action of hot pen, and the color of the base paper is exposed to form an image. Metal compound chromogenic thermal paper chromogenic principle is based on the mixture of heavy metal salts and reductants of fatty acids. Fatty acid salts are melted by heating and reacted with reductants to make heavy metals reductive and free chromogenic. The principle of colorless dye-based thermal paper is based on the reaction of colorless dye with colorless dye containing inner aliphatic ring and melting of colorless dye under the action of heat.