Bis-azo dyes for thin film polarizers and synthesis method

Abstract

A dichroic bis-azo biphenyl dye of the following formula: The substituents R1, R2, R3, R4 are alkyl (CnH2n+1) or alkenyl (CnH2n−1) groups with n=1-18. At least one substituent among R1R2R3R4 is different from the other substituents. A benzidine-free method of making a dichroic bis-azo biphenyl dye is provided in which the biphenyl portion of the dye is formed from different first and second mono-azo dyes by a cross-coupling reaction, which may be a Suzuki reaction. A polarizer is formed from a photoaligned layer of the bis-azo biphenyl dye on a substrate and exhibits a dichroic ratio of at least 40. Chemical modification of the photoaligned bis-azo biphenyl dye layer creates a broad-band thin film polarizer with low light scattering and high thermal and photo tolerances.

Dependencies are inferred from the claim text.