COUMARIN AND THIOCOUMARIN DYES FOR GUEST-HOST TYPE LIQUID-CRYSTAL DISPLAYS

To realize bright and pure colors in Guest-Host type Liquid Crystal Di splays (GH-LCDs), the solubilities and/or absorption coefficients of d ichroic dyes which are dissolved in liquid crystals are the most impor tant properties. We have found that a mixture of coumarin and anthraqu inone dyes was very useful because it had a large absorption coefficie nt and little fluorescence. On the other hand, substitution of a sulfu r atom for an oxygen atom of the coumarin dye contributes to increase its solubility to liquid crystals, particularly at low temperatures.