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Optical Brightener

Dec 06, 2023

In 1929, P. Krais discovered that 6,7-dihydroxycoumarin can emit fluorescence under ultraviolet light, and fabrics can have a whitening effect after being immersed in its aqueous solution. The earliest commercially available optical brightener was a derivative of 4,4′-bisazilaminostilbene-2,2′disulfonic acid produced by Bayer Company in Germany in 1940. Since then, many fluorescent whitening agents have been developed, forming a series of dyes of their own.


Fluorescent whitening agents are commonly known as "white dyes", also known as optical brightening agents, or whitening agents for short. A colorless organic compound that fluoresces when illuminated by ultraviolet light. Its whitening effect is to use the optical complementary color principle, so that after the yellowing substance is treated with the fluorescent whitening agent, it can not only reflect visible light, but also absorb ultraviolet light other than visible light and convert it into purple-blue or cyan visible light for reflection. . Organic substances that can improve the whiteness of fabrics, paper, etc. The whitening agent can absorb ultraviolet light with a wavelength of 330 to 360 nanometers, and the reflected light is blue-violet light with a wavelength of 400 to 440 nanometers, which is complementary to the yellow light originally reflected by the fabric that is still yellowing after bleaching. Therefore, Add to form white, making the fabric white. After whitening treatment, part of the ultraviolet light is also converted into visible light and reflected, and the total amount of reflection is increased than that without treatment, so the brightness of the treated fabric also increases, making the white fabric whiter and the colored fabric increased in brightness. Fluorescent whitening is different from chemical bleaching in that it will not damage the color and strength of the fabric. However, for fabrics and papers with dark background colors, if they are directly treated with a whitening agent without bleaching, good results will not be obtained.

  Whitening agents are mainly used in the textile printing and dyeing industry to improve the whiteness and luster of various natural and synthetic fiber fabrics. In recent years, its application in papermaking, plastics, leather, soap, synthetic detergents and other daily necessities industrial sectors has also grown rapidly.
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