Dichroic and spectral properties of anthraquinone-based azo dyes for PVA polarizing film

Dichroic dyes with broad absorption bands are advantageous for the production of neutral gray polarizing films. For this purpose, anthraquinone-based azo dyes were synthesized to have a conjugated bichromophore design and this was applied to PVA polarizing films. The spectral and dichroic properties of the polarizing films were examined and compared to the films produced with a general disazo dichroic dye. The polarizing films with anthraquinone-based azo dyes had wider absorption bands, but lower dichroic ratios compared to the films with a general disazo dichroic dye. It was found that the alignment between the transition moments of the anthraquinone and azo chromophores is an important factor for the dichroic properties of anthraquinone-based azo dyes.

► Anthraquinone-based azo dyes had broad absorption band by bichromophore system.
► Anthraquinone as an acceptor induced broad and bathochromic absorption of azo groups.
► The substituted position influenced direction of transition moment in anthraquinone.
► The discrepancy between wavelengths of maximum absorption and dichroic ratio.