This material is a glassy thermotropic chiral nematic liquid crystalline composition with low molar mass, which is used for forming optical devices with clear transparent films that selectively reflect visible and near-infrared circular-polarized light, but do not absorb light in the visible region.
This material can be used in circular polarizing filters, selective reflectors, beam splitters, beam apodizers or notch filters.
Currently, low molecular weight liquid crystal materials have many limitations including durability, effective temperature, mesophase stability, and amenability to processes for device fabrication. It is also difficult to synthesize materials with the correct optical properties. The materials of the present invention overcome these limitations. They are simultaneously capable of forming mesophase and vitrification characteristics at temperatures above the ambient. They can form both right-handed and left-handed helical structures and exhibit solubility characteristics which enable their processing into clear glassy thin films for use as optical devices. They form clear transparent films that absorb no light in the visible and exhibit selective reflection of visible and near infrared circular-polarized light whose wavelength can be varied by changes in the structure and concentration of the chiral moiety in the liquid crystalline composition. For this purpose, the extent of the conjugated unsaturation and length of the flexible link is chosen to ensure the composition exhibits adequate helical twisting power. This invention describes the synthesis, properties, and device formation of glassy thermotropic chiral nematic liquid crystalline compositions which can comprise either a single pure low mass compound of a cycloaliphatic radical to which a nematogenic moiety and a chiral moiety are attached. Or alternatively, the composition can comprise mixtures of such low molar mass compounds, or mixtures of low mass chiral and nematogenic liquid crystalline compounds.The US patents that cover this disclosure are #5,378,393 and #5,514,296.