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AssigneeHoffmann-La Roche Inc.
InventorsRichard Buchecker, Jurg Funfschilling, Martin Schadt
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Small-pitch cholesteric liquid crystal mixtures are temperature compensated. They are particularly useful when no, or only a slight, temperature dependence of the selective reflection is permissible, because a considerable temperature dependence would interfere with or render wanted effects impossible. They are composed of a nematic liquid crystal doped with at least two chiral additives satisfying the following conditions: (1) a(c.sub.1 B.sub.1 +c.sub.2 B.sub.2)=b(c.sub.1 A.sub.1 +c.sub.2 A.sub.2) and (2) 1/.lambda..sub.o (T)=a(c.sub.1 A.sub.1 +c.sub.2 A.sub.2)+aT(c.sub.1 B.sub.1 +c.sub.2 B.sub.2)+bT(c.sub.1 A.sub.1 +c.sub.2 A.sub.2) where .lambda..sub.o denotes the mean value of the wavelength band of the selective reflection c.sub.1 c.sub.2, . . . denote the concentrations of the chiral dopants and A.sub.1,B.sub.1 are coefficients of a progression.
A liquid crystal layer containing a liquid crystal composition with a central wavelength of selective reflection .lambda..sub.o wherein
Dependencies are inferred from the claim text.