Spectral-Polarization Properties and Light Resistance of Polyvinyl-Alcohol Films Colored With Disazo Dyes

Abstract

Polarizers containing disazo dyes from the group of azobenzene-azonaphthalene have been developed. It has been established that their polarizing ability is determined by the mutual disposition of the azo group and electron-donor substituents in the naphthalene ring. On diazo coupling of γ acid into the α position relative to the oxy group, the M1 and M3 dyes are formed, the polarizing ability of which in uniaxially oriented polyvinyl-alcohol films is higher than in the M2 dye produced as a result of diazo coupling into the α position relative to the amino group. On irradiation by UV light, the dyes are subjected to photodestruction, which, in the case of M2, proceeds through trans-cis-isomerization. The rate of photodestruction depends on the aggregation of the dye molecules, and it increases in the presence of a free-radical initiator. The UV absorber (substituted benzotriazole) and the uniaxial orientation of the film retard this process.