White and Taylor GH-LCDs

Dichroic dyes of positive and negative dichroism are required for various configurations of the Heilmeier and Zanoni as well as the White and Taylor GH-LCDs with positive and negative contrast. They should be chemically, photochemically and electrochemically stable, as well as exhibit a high order parameter, a high dichroic ratio and good solubility in the host nematic matrix. 

The tetralins (181-183) collated in Table 3.23 are red liquid crystals with a transition moment orthogonal to the molecular long axis, see Figure 3.13. Since they are liquid crystalline themselves they are very soluble in nematic host mixtures. Such mixtures exhibit high negative dichroic ratios and can be used in White and Taylor GH-LCDs with positive contrast. Furthermore, mixtures containing an additional anthraquinone dye of positive dichroic ratio can be used to switch from one colour to another under the action of an electric field. 

Figure 3.15 Schematic representation of a White and Taylor guest-host liquid crystal display (GH-LCD). ...

The first prototype GH-LCDs based on the chiral nematic phase change effect investigated initially by White and Taylor also used indophenol dyes. 

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