Application of fluorescent whitening agent

The first theoretical explanation of fluorescence was in 1852, when Stokes proposed what later became known as Stokes' law.  In 1921 Lagorio observed that the visible fluorescence energy emitted by a fluorescent dye was lower than the visible light energy it absorbed, so he reasoned that a fluorescent dye had the ability to convert invisible ultraviolet light into visible fluorescence.  He also found that the whiteness of natural fibres could be increased by treating them with an aqueous solution of a fluorescent substance.  In 1929, Krais adopted Lagorio's proof of principle and dipped yellowish rayon into a solution of 6, 7-dihydroxy coumarin ligand and found that the whiteness of the rayon was significantly improved after drying.  

With the rapid development of fluorescent whitening agent, some people regard it as one of the three great achievements of dye industry in the late 20th century, together with the advent of reactive dye and organic pigment DPP.  

Many industries are beginning to use fluorescent brighteners, such as paper, plastics, leather, detergents.  At the same time, fluorescent brighteners are also used in many high-tech fields, such as fluorescence detection, dye lasers, anti-counterfeiting printing, etc., and even the high sensitivity film used in aerial photography to improve the sensitivity of photographic latex, will also use fluorescent brighteners.  

In China, fluorescent whitening agent is first divided into printing and dyeing auxiliaries, and then divided into dye products.  Because of its unique properties and a large amount of demand, it has been separated in the two industries, become a separate class of fine chemical products.  The first largest user of fluorescent whitening agent in China is detergent, the second largest user is paper, and the third largest user is textiles.