Despite angle dependence and polarization se-along an average preferred direction in a given plane. This preferred direction, indicated by a unit vector called lectivity, the color of cholesteric liquid-crystal (CLC) polysiloxane films can be quantified by standard colorim-the director, n, rotates slightly from one plane to the next, forming a helix structure that may be right-handed or left-etry. A new fractured form of the film called ''flakes'' makes it possible to use the Center of Gravity Color Mix-handed depending on the constituents of the molecule. 3 A typical model is shown in Fig. 1. It is the periodicity ing Principle to predict the chromaticity of CLC color mixtures. A complete color gamut can be produced by of the helix that leads to the constructive interference colors of CLCs. The distance it takes the director to rotate layering CLC films, mixing CLCs physico-chemically, and mixing CLC flakes. แญง 1998 John Wiley & Sons, Inc. Col Res Appl, through 360ะ is called the pitch P of the CLC helix. The pitch multiplied by nV n , the average refractive index of 23, 210-220, 1998
the molecular layers, gives the wavelength of selective Key words: cholesteric liquid crystals; CLC flakes; polyreflections, l 0 , which may range from the ultraviolet siloxanes; color through the visible to the infrared. 4 The width of the reflected wavelength band for visible-reflecting CLCs (l 0 ranging from 380-780 nm) can typically range from 10-* Correspondence to: E. M. Korenic the defects or other discontinuities are referred to as do-