Application of Carbonless Paper/NCR Paper

Carbonless copy paper was invented by Lowell Schleicher and Barry Green of NCR Corporation in the United States in 1954. It is the first chemical pressure-sensitive recording paper. Microcapsules on the back of carbonless copy paper. Early microcapsules were prepared by precipitating water-soluble polymers (such as gelatin, gum arabic, and esterified cellulose) on the surface of organic microemulsion droplets containing dye precursors. The precipitation process is regulated by pH and temperature. The diameter of the microcapsule is about 3~8 μm (the size depends on the size of the microemulsion droplets). The current microcapsules are prepared by organic polymerization between the two phase interfaces (no longer the mechanism of polymer crosslinking and precipitation mentioned above), and this preparation method is more controllable. Common microcapsule "films" include polyurea, polyamide, phenolic resin, etc. Dye precursor in microcapsule. It is called a "precursor" because it must be colorless and must become a colored dye under certain conditions. Common carbonless copy paper can be selected from black, blue, orange, green, red, purple, etc., and correspondingly, the required dye precursors are also different. The color development of these dye precursors is regulated by pH. For example, the first dye precursor used: crystal violet lactone (CVL), under acidic conditions, the hybridization pattern of the central carbon changes from sp3 to sp2, the entire molecular structure becomes a planar aromatic structure, and its electronic excited state changes from the ultraviolet light region to the visible light region, that is, from colorless to colored.

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