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Proceedings Paper

Electro-optical behavior of polymer cholesteric liquid crystal flake/fluid suspensions in a microencapsulation matrix
Author(s): Kenneth L. Marshall; Erin Kimball; Shari McNamara; Tanya Z. Kosc; Anka Trajkovska-Petkoska; Stephen D. Jacobs
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Paper Abstract

When flakes of polymer cholesteric liquid crystals (PCLC's) are dispersed in a fluid host and subjected to an applied electric field, their bright, polarization-selective reflection color is extinguished as they undergo field-induced rotation. Maxwell-Wagner (interfacial) polarization is the underlying physical mechanism for flake motion and results from the large difference in dielectric properties of the flake and fluid hosts. Flake reorientation times can be as short as 300 ms to 400 ms at exceedingly low driving fields (10 to 100 mVrms/μm) and are dependent on flake size and shape, fluid host dielectric constant and viscosity, and drive-filed frequency and magnitude. These attributes make this new materials system of special interest in electro-optical and photonics applications, where reflective-mode operation, polarization selectivity, and low power consumption are of critical importance (e.g., reflective displays). Until very recently, the electro-optical reorientation of PCLC flakes has been studied only in sandwich-type cells using glass substrates. In this work, we report on the dc field-induced reorientation behavior of PCLC flakes contained in confined spherical or near-spherical fluid-filled cavities formed by microencapsulation of the flake/fluid host dispersion in a water-borne flexible binder. This PCLC flake-fluid host/binder emulsion is coated onto either rigid or flexible condutive-coated substrates and then overcaoted (uniformly or patterned) using a conductive emulsion or paint that is either absorbing (black) or reflecting (silver). In addition to providing a unique environment to study flake motion, this device geometry also extends the application scope of the technology to conformal, electrically switchable coatings for large planar areas and flexible media for information display applications (e.g., electronic paper).

Paper Details

Date Published: 15 October 2004
PDF: 12 pages
Proc. SPIE 5518, Liquid Crystals VIII, (15 October 2004); doi: 10.1117/12.559627
Show Author Affiliations
Kenneth L. Marshall, Univ. of Rochester (United States)
Erin Kimball, Univ. of Rochester (United States)
Shari McNamara, Univ. of Rochester (United States)
Tanya Z. Kosc, Univ. of Rochester (United States)
Anka Trajkovska-Petkoska, Univ. of Rochester (United States)
Stephen D. Jacobs, Univ. of Rochester (United States)

Published in SPIE Proceedings Vol. 5518:
Liquid Crystals VIII
Iam-Choon Khoo, Editor(s)

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