Crystal violet lactone and ODB-2 for thermal papers
Nowadays, thermal paper can be seen everywhere, it is widely used on POS receipt, lottery and gaming, tags and labels and other applications. Thermal paper comprises a base paper and a layer of heat-sensitive chemicals which include color former, color developer, sensitizers, ect. At present, the 2-phenylamino-3-methyl-6-dibutylaminofluorane (ODB-2) and crystal violet lactone are most leuco dyes used as color former in thermal papers. 2-phenylamino-3-methyl-6-dibutylaminofluorane (ODB-2) is leuco dye which show black in case of pressure or heating. Crystal violet lactone (CVL) is leuco dye which present blue color under pressure or heating.
Crystal violet lactone is a leuco dye, mostly called CVL (CAS No.: 1552-42-7). It is a slightly yellowish crystalline powder, soluble in nonpolar or slightly polar organic solvents. Crystal violet lactone is first used in carbonless copy papers, and it is also widely used in thermal paper. Under the heating or pressure condition, the color former crystal violet lactone (CVL), developers and others are dispersed by poly-vinyl alcohol or others as texturizers and coated on the paper. The mechanism of color development is the melt mixing of dyes and developers by heating.
The color reaction of thermal paper is reversible, the colored products will decompose themselves, the color of the handwriting will gradually fade more and more light, until the natural fade to the handwriting completely disappeared in the white paper. In certain, the rate of fading is also related to the thermal sensitive paper itself.