Optical brighteners refer to materials that emit light when stimulated by ultraviolet light. They are also known as optical brightening agents, fluorescent brightening agents, or fluorescent whitening agents. These dyes absorb light in the UV and violet region (usually 340–370 nm) of the electromagnetic spectrum.
The purpose of optical brighteners is to provide an intense source of visible light, specifically the blue spectrum, for use in applications such as fibers, coatings, inks, and detergents. A major use for optical brighteners is in printing applications. In the case of ink jet printers, they act as a time-dispersing printer ink emulsion, applying ink quickly to paper in a coated drum where it is then removed after use. For flatbed scanners, the device acts as a time-dispersing bleaching agent between the scanned images and the carrier paper. Finally, in the case of LED and plasma screens, the brightening agent shifts the phosphor concentration of charged particles in a semiconductor array, thereby generating light.
There are two different kinds of optical brighteners used in clothes today, namely fluorescein and quantum fluorescence. Fluorescein works by adding extra energy to certain wavelengths of ultraviolet light to create the light that we see when looking at dyed clothes. Quantum fluorescing uses the principles of excitation-fresco-disruption to give off an extra bright light. There are two different types of fluorescent dyes used for clothes-one uses monochromatic (a single color), while the other uses multicolor dyes. The type that is used in most clothes is monochromatic because it creates brightness when the light strikes a surface and is the least expensive. Multicolor dyes are used in clothes that are very bright but are usually used in specialty shops or museums where people want to be able to see their clothes for different situations.
Various companies are focused on increasing the production capacity of optical brighteners. In July 2019, BASF SE, a Germany-based multinational chemical company, announced to increase production capacity for Tinopal CBS optical brighteners at the company's Monthly site.