Color fastness to light is also called light fastness or light fastness. The main factors affecting fading under sunlight include light, molecular structure of dyes, dye aggregation state and dyeing depth, and fiber properties.
Light is the most important factor causing dye fading. The chromophore group of dye undergoes photo-oxidation or photo-reduction reaction under the irradiation of ultraviolet light and visible light, resulting in fading of fabrics.
The light fastness of dyes is also related to its molecular structure. 70%~75% of the molecular structure of reactive dyes are azo type, and the rest are anthraquinone type and phthalocyanine type. The light fastness of azo type is generally poor, and the light fastness of anthraquinone type and phthalocyanine type is better.
The aggregated structure of the dye also has an effect on its light fastness. The existing state of dyes on fibers is mainly in molecular form, aggregate form and the mixture of these two forms. The dyes that exist in the form of molecules fade faster, and the aggregates of dyes are more likely to transfer energy due to the strong internal molecular force, and light fading mainly occurs on the surface, so dyed fabrics in the initial stage. Basically unchanged.