Lightfastness fluorescent dyes

Di- and Triaryl Carbonium and Related Dyes. As a class, these dyes are bright and strong, hut are generally deficient in lightfastness. Consequently, they are used in outlets where brightness and cost-effectiveness. rather than permanence, arc paramount, for example, the coloration of paper. Many dyes of this class, especially derivatives of pyronines Ixamhcnes). arc among the most fluorescent dyes known. 

Fluorescent molecules span the entire region from the ultraviolet, through the visible, to the near infrared. Many dyes exhibit fluorescence, but to be of practical use, fluorescent dyes must satisfy certain requirements they must produce a pure color dictated by their absorption and emission spectra, they must have a high molar extinction, and most important, they must have a high quantum yield. These requirements are met by very few dyes. A disadvantage shared by many fluorescent dyes is their poor lightfastness, but there are some exceptions. 

Perylene, a parent pentacyclic aromatic compound, which exhibits a strong fluorescence has found application in laser dyes and organic light emitting diodes (see section 3.8.5.1). The esters of di-, tri- and tetra-carboxylic acids of perylene are lightfast, yellow to red fluorescent chromophores, exemplified by the diisobutyl ester of the... 

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