The effect of dye structure on the dyeing and optical properties of dichroic dyes for PVA polarizing film

The dyeing behaviour and optical properties of four novel dyes in PVA polarizing films were determined in terms of the linearity, hydrogen bonding ability, intermolecular interaction and transition moment. The linearity and H-bonding ability of the dyes were the dominant factors in terms of both the substantivity and orientation in PVA films, which, in turn, determined the dichroic ratios of the polarizing films. Dye adsorption and optical anisotropy of the dyes were further affected by the substituents within the dyes. The difference in the electrostatic interactions of the substituent within the dyes also had an influence on dye-uptake. Moreover, charge transfer within the dye molecules was reflected in higher dichroic ratios of the dyed polarizing film.