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Principle of thermal paper

Thermal paper is placed above 70 ℃ environment, the thermal coating began to change color. But also about the reasons for its color from its ingredients.
The thermosensitive thermal paper coating composition mainly two: one is called leuco dye or leuco dye; the other is color-developing agent. Such thermal paper is also known as two-component chemical-type thermal recording paper.
Used as the leuco dye mainly: crystal violet lactone trityl alkylbenzene phthalocyanine System (CVL), fluoran system, colorless benzoyl methylene blue (BLMB) or spiropyran system and other substances.
Common dispersants are mainly: polyvinyl alcohol L-3266, polyvinyl GL-05, polyvinyl alcohol KL-03 (Nippon Synthetic Chemical production).
Commonly used auxiliaries topcoat and undercoat layer mainly: gohsefimer Z-200, polyvinyl alcohol T-350, polyvinyl N-300.
Commonly used as a color-developing agent mainly: para-hydroxybenzoic acid and its esters (PHBB, PHB), salicylic acid, 2,4-dihydroxybenzoic acid or an aromatic sulfone and other substances.
Heat, colorless dye and color developing agent to produce a chemical reaction in case of color thermal paper, then use thermal paper to print the received signal or direct thermal printer for printing on the fax machine, the graphic is displayed. Because colorless dye used for many varieties, so there are different colors show handwriting, blue, purple, black and so on.