With development of the technology, the thermal paper is using widely in Food Industry, Travel, Bank, Merchandise, Medical Treatment, etc. More and more factories prepare the thermal paper making machine line for producing thermal paper roll for market needing.

For the thermal paper coating machine line, there are three important elements to lead the thermal paper quality.

The thermal paper coating chemical is mainly elements, as it will influence the ink color rendering and shelf life.

Although there are more than a dozen kinds of chemical used in this color-changing layer, there are at least the following compounds: leuco dyes, which has a wide variety of dyes, and fluorescent compounds are the most commonly used; Phenol and p-hydroxybenzoic acid(BPA/BPS); sensitizer account for less than 10%, which contains benzenesulfonamide compounds; fillers account for less than 50%, commonly used calcium carbonate (particles)--CACO3 90; adhesives account for less than 10%, such as polyvinyl acetate; stabilizers, such as dibenzoyl terephthalate; lubricants, etc. Therefore, the process is difficult and the technical requirements are high.

The principle of thermal paper

When thermal paper is placed in an environment above 70°C, the thermal coating begins to change color. The reason for its discoloration also starts from its composition.

There are two main heat-sensitive components in the thermal paper coating: one is leuco dye or leuco dye; the other is the color developer. This type of thermal paper is also called two-component chemical type thermal recording paper.

Commonly used as leuco dyes are: crystal violet lactone (CVL) of trityl phthalide system, fluorane system, colorless benzoyl methylene blue (BLMB) or spiropyran system and other substances.

Commonly used dispersants are: polyvinyl alcohol L-3266, polyvinyl alcohol GL-05, polyvinyl alcohol KL-03 (produced by Japan Synthetic Chemicals).

Commonly used top coat and base coat additives are: gohsefimer Z-200, polyvinyl alcohol T-350, polyvinyl alcohol N-300.

Commonly used as color reagents are: p-hydroxybenzoic acid and its esters (PHBB, PHB), salicylic acid, 2,4-dihydroxybenzoic acid or aromatic sulfone.

When the thermal paper is heated, the colorless dye and the developer reacts chemically to produce color, so when the thermal paper is used to receive a signal on a fax machine or print directly with a thermal printer, the graphics and text will be displayed. Since there are many kinds of leuco dyes, the colors of the handwriting that appears are different, such as blue, purple, black and so on.