Synthesis and Characteristic of Dichroic Dyes for Liquid Crystal Display

Abstract

Dichroic dyes of great practical value for liquid crystal displays (LCD) have been reviewed from the view point of the synthetic design. The function of dichroic guest dyes for LCD is dependent on the structure of substituent group and its position on chromophore. Some examples of the synthesis of anthraquinone, naphthoquinone and azo dyes with positive dichroism are shown. Dyes with negative dichroism are also described. Dyes for polarizing film are classified into two categories, i.e. for polyvinylalcohole matrix and for polyester matrix. Hydrophilic polyazo dyes with sulfonic acid groups are used in the former film, and for polyester matrix, hydrophobic dyes with long rod-like struture have been developed.