Coumarin optical brighteners are the third largest class of optical brighteners. The chemical structure of coumarin is shown below.
Coumarin itself has very strong fluorescence. By introducing various substituents at the 3- and 7-positions, it can become a practical coumarin optical brightener. Early commercialized varieties are now being phased out due to their poor fastness properties. These are being replaced by more complex substituents at the 3- and 7-positions, particularly heterocyclic groups. These products have higher whiteness and improved light fastness.
A typical example of coumarin optical brighteners is Uvitex WGS (C.1. Fluorescent Brightener 52).
This variety is known as optical brightener SWN in China. Despite its poor light fastness, its strong fluorescence has led to its widespread use for whitening wool fibers since its launch in 1954.
Details TDS can refer to optical brightener SWN
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