LUMINESCENT CHOLESTERIC LIQUID CRYSTAL DISPLAY

The present invention concerns the technology liquid crystals displays. In particular, a new liquid crystals display based on a cholesteric non absorbent material, doped with one or more than one dicroic coloring (anisotropic photoluminescent molecules). The cell geometry is a conventional with a liquid-crystalline mixture film sandwiched between two plain transparent surfaces. The film thickness is typically between 1 and some tens of microns and an electric field perpendicular to plain surfaces is applied on the film. In the equilibrium state and in absence of external fields, a planar orientation of the coloring molecules causes an absorption of photons of a low wave-length and a consequent emission of photons with higher wave-length. The display appears, hence, coloured and luminous in presence of an opportune external illumination. In case of an applied electric field to the cell, the light absorption and luminescence are absent. The film, hence, appears transparent. The luminescence colour can be determined in a broad range and the main electro-optical characteristics of the display (time of response, resolution, contrast) are comparable with those of a conventional passive display with nematic liquid crystal. The proposed device doesn't need polariz or color filters. The here represented informations are visible on two display faces, vision angle is almost 180° because the light is emitted in all directions. This technological approach is compatible with all active and passive address techniques of liquid crystal displays and with some intrinsically bistable displays.