Coumarin and Thiocoumarin Dyes for Guest–Host Type Liquid Crystal Displays

Abstract To realize bright and pure colors in Guest–Host type Liquid Crystal Displays (GH-LCDs), the solubilities and/or absorption coefficients of dichroic dyes which are dissolved in liquid crystals are the most important properties. We have found that a mixture of coumarin and anthraquinone dyes was very useful because it had a large absorption coefficient and little fluorescence. On the other hand, substitution of a sulfur atom for an oxygen atom of the coumarin dye contributes to increase its solubility to liquid crystals, particularly at low temperatures.