Phase transition mode liquid crystal display device

A phase transition mode liquid crystal display device comprising:

• a liquid crystal mixture comprised of a nematic liquid crystal mixed with at least one of a cholesteric liquid crystal and a chiral nematic liquid crystal, the liquid crystal mixture having a thermally established psuedo-focal-conic state in which the liquid crystal mixture exhibits in the absence of an electric field a light-scattering characteristic effective for use as the display background;
• and means including electrodes arranged to define a pattern of picture elements against the display background and coacting with the liquid crystal mixture for selectively applying electric fields to the liquid crystal mixture to display selected picture elements, said means comprising means for applying a relatively strong electric field to the liquid crystal mixture in the regions of selected picture elements to transform the selected picture element regions to a homeotropic light-transmitting state and for applying a relatively weak electric field to the liquid crystal mixture in the regions of non-selected picture elements to transform the non-selected picture element regions to a focal-conic light-scattering state;
• whereby the light-scattering states of the display background and the non-selected picture element regions exhibit a generally similar appearance which contrasts with that of the light-transmitting state of the selected picture element regions.

A method of producing a display background for use in a phase transition mode liquid crystal display device, comprising the steps of:

• providing a liquid crystal mixture comprised of a nematic liquid crystal mixed with at least one of a cholesteric liquid crystal and a chiral nematic liquid crystal;
• sealing the liquid crystal mixture between a pair of substrates to form a cell;
• heating the cell to a temperature above the clearing temperature of the liquid crystal mixture;
• and
• cooling the heated cell to transform the liquid crystal mixture into a stable pseudo-focal-conic light-scattering state effective for use as a display background in a phase transition mode liquid crystal display device.