Abstract
A fluorescent brightening agent of a stilbene type C. I. FBA 24 (FBN) was found to enhance the fading rate of a blue direct azo dye C. I. (DB15) in aqueous solution, on the irradiation with a high pressure mercury lamp. On the other hand, DB15 depressed the fading of FBN. Fading of both DB15 and FBN was depressed in aqueous solution by the irradiation using a low mercury lamp. Similar effect was also observed in the measurement on cotton fabric, on the irradiation with a high pressure mercury lamp, whereas FBN depressed the fading of the dye on the irradiation with a low pressure mercury lamp. These effects were found in the concentration range of the dye bath of FBN higher than 1×10-5 mol/l. The dye accelerated the fading of FBN at the early stage of the reaction when exposed to a low pressure mercury lamp, a high pressure mercury lamp or a xenon lamp.
