Fluorescent whitening agent, also known as optical whitening agent, abbreviated as whitening agent, is a fluorescent dye that excites fluorescence under ultraviolet light irradiation. It is mainly used in the textile printing and dyeing industry to improve the whiteness and enhance the luster of various natural and synthetic fiber fabrics. In recent years, its application in papermaking, plastics, leather, soap, synthetic detergents, and other daily necessities industries has also grown rapidly. Its characteristic is the ability to convert ultraviolet light into visible light of blue, blue-violet, or red, producing optical whitening effects. It also generates fluorescence due to the excitation of incoming light, resulting in a fluorescent effect similar to that of fluorspar for the dyed material. The function of fluorescent whitening agents is to significantly improve the whiteness of paper and make it visually pleasing, which cannot be achieved by any chemical bleaching agent. Therefore, fluorescent whitening agents are widely used in the whitening treatment of high-grade paper. Fluorescent Chemicalbook whitening agents are organic compounds that can enhance the whiteness of fiber fabrics and paper. Whitening agents can absorb ultraviolet light with a wavelength of 330-360 millimicrons, and the reflected light with a wavelength of 400-440 millimicrons is blue purple light, which complements the yellow light originally reflected from the fabric that still turns yellow after bleaching treatment. Therefore, when added together, it becomes white, making the fabric pure white. After whitening treatment, a portion of ultraviolet light is also reflected back into visible light, resulting in an increase in total reflection compared to untreated fabric. As a result, the brightness of the treated fabric also increases, making the white fabric cleaner and the colored fabric more vibrant. Fluorescent whitening is different from chemical bleaching in that it does not damage the color and strength of fabrics. However, for fabrics, papers, etc. with dark background colors, if they are treated directly with whitening agents without bleaching, they cannot achieve good results.