|
Polymer-Dispersed Liquid Crystal(PDLC) films are newly
developed electro optical maerials. It can be used as a display
application. Since its fabrication is much simpler than that of
the traditional TN-LCD, it is now being researched and
delevloped actively for a display application. In addition to
being used as a display material, it can be used to store
holographic gratings. This thesis studies the temperature
dependence of the PDLC-grating formation. Firstly, we study the
phase separation effect using light scattering technique at
various temperatures. Then, we measured the temperature
dependence of the first-order diffracted beam intensities as a
function of time. Finally, we investigated the PDLC morphologies
using Scanning Electron Microscope(SEM). The result shows that
when the content of the liquid crystal in the mixture is ~20wt%,
no liquid crystal droplets are formed. In other words, phase
separation doesn't occur. The dynamical measurement of the
first-other diffracted beam shows that,during the initial phase
grating formation, a thermal grating effect dominated. Later, it
was offset by polymerization effect. When the liquid crystal
content is 40wt%, the thermal grating effect was quickly
quenched by the diffusions of both liquid crystal and monomer
molecules due to phase separation. All these results have good
correlations with morphologies observed by SEM.
|