抄録
Rate of fading of fluorescent brightening agents, 1, 2-bis (5-methylbenzoxazolyl) ethylene (1) and its derivatives, increases with an increase in their concentrations both in solution and on polymer film. Such fading behavior is discussed from the standpoints of photoreaction and physical state of the dyes in substrates.
Two kinetic models of the photoreaction process are proposed by assuming the simultaneous trans-cis isomerization and photodimerization; kinetic model (I) postulates that the photoreactions proceed only through the singlet excited state and kinetic model (II) assumes that dye (1) isomerizes through both its singlet and triplet state, but dimerizes only through its triplet excited state. The results obtained by solving the derived rate laws are compared with the experimental results for the ethanol solutions. The fading curve, characteristic fading curve and other experimental results can be well accommodated by the kinetic model (II).
