Fluorescent brightening agents (FBA) sometimes called optical brightening agent (OBA) or fluorescent whitening agents are fluorescent white dyes that absorb ultraviolet region (340 370 nm), light of electromagnetic region emit back visible blue light region (420 470 nm). Its suitable for cellulose, nylon, polyester, silk, wool, paper and other polymers. Optical Brightening Agents are 'colourless dyes' which are capable of absorbing invisible ultra violet light and remitting visible 'blue' light
Texlile fibres, detergents, printing paste, polymer, paper, plastics and coatings in the raw state possess aesthetically undesirable creamish cast. The reason of this in case of natural materials is the presence of the natural dyes and pigments and in the case of man-made fibers this is attributable to thermal decomposition. The coloring matter, whether it is natural or present as a contaminant in the fiber is generally decolorized by different bleaching methods. But still they retain a faint, creamy colour. Excessive bleaching can degrade the substrate extremely. Tinting with bluing agents or optical brightening agents can compensate this residual yellowness. Materials treated with these agents appear less yellow. Therefore chemical treatments are become necessary to neutralize the yellow tint of the textile fibers. Optical brightening agents are also used in polymer and cosmetic industries.
Virtually all white fabrics have OBA incorporated or applied during processing. Commercial laundry detergents contain OBA(s) to 'top-up', maintain or increase the level of OBA on the fabric.