Zumer S

Director configurations and configuration transitions in PDLC material

The molecular anchoring strength for the liquid crystal E7 (EM Chemicals) confined to spherical cavities dispersed in the polyurethane TU5OA (CONAP) is measured. The anchoring strength values result from a study of the radial-to-axial configuration transition when perpendicular anchoring conditions exist at the polymer/liquid crystal interface. This transition is also a function of droplet radius, temperature, and the strength of any external fields present. A study of field-induced configuration transitions provides values for the reduced local electric fields inside droplets. Computer simulated pictures of nematic droplets are formed to identify director configurations.

High-Intensity Color Projection For Automotive Displays

A new type of low-loss, high-intensity projector is described for possible use in full-color reflective head-up or other automotive displays. The device is based on light shutters made from polymer dispersed liquid crystals (PDLC) which avoid the use of light-absorbing polarizers. Voltage-controlled Rayleigh scattering from PDLC shutters placed in parallel additively mix three primary colors produced by dielectric dichroic mirrors from white light, providing for arbitrary colors of the outgoing light. High-intensity and low heat dissipation due to the scattering-induced light attenuation that is possible from refractive index-matched PDLC shutters yields bright color and high-intensity large-scale projection. The light intensity yield exceeds that of conventional electrically-controlled light modulators by at least a factor of two. With the addition of an active matrix PDLC shutter, this system can replace the CRT in high information content automotive displays.

Captured liquid crystalline order in polymer networks

Orientationally ordered polymer networks are prepared in spherical and cylindrical geometries by isothermal photopolymerization of diacrylate molecules dissolved in a nematic liquid crystal. Optical polarizing microscopy textures reveal that the network memorizes the nematic director field. Diacrylate concentrations of 2% by weight suffice to create a stable network embedded in the anisotropic liquid crystal environment for temperatures as high as 150 degree(s)C. Polymer networks that are formed under various surface conditions, applied electric fields, and geometrical constraints are characterized with optical polarizing microscopy.