We have developed cholesteric LCDs, the reflective color of which is controlled by UV exposure. The chirality of a photo-sensitive chiral material doped in cholesteric mixture is reduced with increase of UV exposure energy. The colors of cholesteric LC cells rendered by UV exposure were vivid and bistable switching was achieved in any color area of the cholesteric LCDs as shown in the figures. The liquid crystal mixtures were prepared by using three kinds of materials, typical cholesteric LC, nematic LC and newly developed photo-sensitive chiral dopant to show blue color before UV exposure. The color range variable by UV exposure can be controlled by varying the concentration of photo-sensitive chiral dopant, which depends on the ratio of main cholesteric LC and nematic host. Full color cholesteric LCDs could be achieved by optimizing UV exposure energy and concentration ratio of three kinds of materials. The details of experimental conditions and electro-optical properties of the full color cholesteric LCDs will be discussed.

*This work was financially supported by Chisso Corporation Korea and "NURI" program of the Ministry of Education and Human Resources Development.