1. The concept of thermosensitive cash register paper

Thermosensitive cash register 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 thermosensitive cash register paper is a special coated processing paper. It is a kind of information paper which is composed of paper and other carriers, recessive colorless dyes, developer, sensitizer, adhesives, etc. as thermal chromogenic coatings.

2. Use of thermosensitive cash register paper

Thermosensitive cash register paper is mainly used in the following aspects: fax machine, communication, medical treatment, measurement system, such as electrocardiograph, thermal instrumentation, computer network terminal printing, trademark, signature (POS), etc., of which 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, advantages of fast image generation and convenient barcode labels, thermal cash register paper has been growing rapidly in the field of barcode recording information and bill printing.

3. Classification of thermosensitive cash register paper

Functionally, the heat-sensitive cash register paper can be divided into ordinary heat-sensitive cash register paper and three heat-resistant cash register paper. Three-proof heat-sensitive paper is coated with a protective layer on the thermochromic layer to give three-proof heat-sensitive paper better waterproof, oil-proof and friction-proof properties, mainly for high-end market. Thermosensitive cash register paper can be divided into two main types in structure. One is the physical thermosensitive cash register paper, which uses heat to physically colour the coloured pigments to achieve the recording effect. This kind of thermal paper can be divided into melt transparent type, melt transfer printing type and thermal sublimation type. Among them, melt transparent thermal paper is representative. It is widely used in medical electrocardiogram and electroencephalogram. The other is chemical heat-sensitive silver paper, which achieves the purpose of colouring by chemical reaction under the action of heat. It is the most widely used product in the market at present. This kind of heat-sensitive paper can be divided into two-component metal compound chromogenic heat-sensitive paper and two-component colorless dye heat-sensitive paper.

4. Principle of color rendering of thermal paper

The color rendering principle of melt transparent thermosensitive cash register paper is to coat a layer of opaque wax on the black base paper as a surface layer. Through the action of hot pen, opaque wax material is melted and transparent, and the color of the bottom of the base paper is exposed to form an image. Metal compound chromogenic thermosensitive silver 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, so that heavy metals can be reduced and free chromogenic.The colour developing principle of colourless dye-based thermosensitive silver paper is based on the mixing of colourless dyes with colour developing agents containing inner aliphatic rings. Under the action of heat, the chromogenic agent reacts with the colorless dye to produce color by heating and melting.