Electro-Optical Devices from Polymer-Stabilized Liquid Crystal Molecule

KSU.254A

Abstract: The electro-optic device (KSU.254A) includes a liquid crystal cell, and at least one electrode arranged to selectively electrically bias the liquid crystal (LC) cell.  The polymeric network is disposed at an inside surface of the LC cell and extends partway into the LC cell, leaving at least a portion of the LC cell substantially free of the polymeric network. 

The related preparation method (KSU.254B) involves a chiral or cholesteric liquid crystal, a photoreactive monomer, and a photoinitiator disposed in a liquid crystal cell.  A principal surface of the LC cell is illuminated with UV light - selected to have a non-uniform ultraviolet light intensity profile in the liquid crystal cell.  This generates a polymer network having a density corresponding to the non-uniform ultraviolet light intensity profile.  The polymer network biases the LC toward a selected helical alignment direction.  In some embodiments, the illuminating includes illuminating with first and second UV light intensity profiles to produce surface and volume polymer network components. 

By using polymer to stabilize or modify the liquid crystal (LC) phase structures, two modes of electro-optical switching are possible:   at a low applied voltage the molecules rotate in the plane parallel to the substrates and can give high modulation of the transmitted light intensity due to the field-induced tilt of the optical axis; while at a high applied electric field the molecules are switched in the direction perpendicular to the substrates.  The polymer content in the composite can vary from a few percent (polymer stabilization type) to as high as possible (polymer dispersed type) as long as the polymer does not interfere with the switching of LC molecules.

Applications:

Spatial light modulators for applications such as optical waveguides, optical beam scanners, computer-generated holograms, adaptive optics for flat panel displays, switchable windows, sunglasses, for example

Advantages:

Fast (sub-millisecond) switching – device is ready for applications in current form.

Inventors:  Lachezar Komitov, Liang-Chy Chien, Sang Hwa Kim