Nematic Liquid Crystal Hosts of Positive Dielectric Anisotropy

Nematic Liquid Crystal Hosts of Positive Dielectric Anisotropy 

The first nematic guest-host prototype nematic GH-LCD reported by Heilme-ier and Zanoni contained methyl red (157) as the dichroic dye dissolved in 4-butoxybenzoic acid as the nematic liquid crystal host. Other hosts investigated later included 4-methoxycinnamic acid and 4-ethoxy-4-aminoben-zonitrile (28), see Table 3.4. The melting point of these three single components is very high. Therefore, prototype GH-LCDs had to be operated and evaluated at very high temperatures. Thermal decomposition of the mixtures led sequentially to lower contrast, homeotropic orientation due to decomposition products and finally device breakdown. However, these initial experiments were sufficient to demonstrate the feasibility of this display type. 

The advent of the apparently superior White and Taylor device retarded the development of better guest-host materials and mixtures for this device type. 

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