Fluorescent dyes:-
by : Rahul Sharma
Fluorescent dyes:-
Anisotropic fluorescent dyes based on perylene-esters and perylene-di-imides, combining good solubility with high light fastness, as a means of improving brightness and contrast, are a more recent advance [68]. Using a mixed isomer of 3,9 and 3,10-bis (4-n-pentyl-bicyclo (2.2.2.) oct-l-yl) perylene dicarboxylate (structure 12) in aliquid crystal resulted in an intense emission spectrum at 510-525 nm when irradiated with u.v. light at 340 nm [69], Further, the fluorescence peak at 380 nm, due solely to the liquid crystal host, was quenched in the presence of the dye. This behaviour is attributed to an energy transfer between host and fluorescent dye giving a more efficient excitation than direct excitation of the dye. A major advantage of an LCD cell based on this system is that under bright ambient lighting conditions, such as direct sunlight, the stronger will be the fluorescence emission [70]. Such fluorescent displays also exhibit a wider viewing angle than conventional displays.
