Photofading of monoazo disperse dyes on polyester and polyamide substrates,

Six monoazo disperse dyes were applied to nylon and polyester substrates and irradiated under aerobic and anaerobic conditions. The dyes underwent reductive fading under both sets of conditions, with few exceptions. Exposing nylon films containing disperse dyes and a vinylsulfonyl copper¯phthalocyanine (CuPc) dye, when immersed in aerated or O2-saturated water, led to a decrease in the rate of reductive fading compared with exposures involving disperse dyes without the CuPc dye. Singlet oxygen generated by the photosensitization of CuPc dye suppressed the reductive fading of disperse dyes. Nylon had a greater tendency to give light-induced reduction and oxidation of disperse dyes than polyester, depending upon the properties of the adsorbed dye. High lightfastness in disperse dyes requires 1O2-suppressed reduction, due to self-photosensitization during exposures involving aerobic conditions.