|
Liquid crystals have had a large presence in the display industry for several decades, and they continue to remain at the
forefront of development as the industry delves into flexible displays and electronic paper. Among the emerging
technologies trying to answer this call are polymer cholesteric liquid crystal (PCLC) flakes. The motion of PCLC flakes
suspended in a host fluid is controlled with an electric field, whereby the flakes reorient to align parallel with the applied
field. A PCLC device easily switches from a bright state, where light of a given wavelength and polarizationis selectively
reflected, to a dark, non-reflective state. The device returns to a bright state when the flakes relax to their original
orientation after removal of the applied field. Progress has been made in addressing several key device issues: the need to
switch flakes back to a reflective state quickly, the development of bistability, the ability to produce flexible devices, and
the necessity to produce both high brightness and a large contrast ratio. Improvements in the technology have been made
by addressing the optical, mechanical, chemical, and electrical features and characteristics of the PCLC flake/fluid host
system. The manufacture of "custom" flakes by the process of formation of specific flake shapes, the addition of dopants,
or the formation of layered flake composites results in particles with improved reflectivity and response times along with
the ability to respond to both AC and DC fields. Specially designed driving waveforms provide a new means for
controlling flake motion. PCLC flake micro-encapsulation allows for the possibility of flexible and potentially bistable
devices. Here we report on the wide variety of approaches toward improving PCLC flake devices and their results.
|
