Electro-optical behavior of polymer cholesteric liquid crystal flake/fluid suspensions in a microencapsulation matrix

Kenneth L. Marshall; Erin Kimball; Shari McNamara; Tanya Z. Kosc; Anka Trajkovska-Petkoska; Stephen D. Jacobs

doi:10.1117/12.559627

15 October 2004 Electro-optical behavior of polymer cholesteric liquid crystal flake/fluid suspensions in a microencapsulation matrix

Kenneth L. Marshall, Erin Kimball, Shari McNamara, Tanya Z. Kosc, Anka Trajkovska-Petkoska, Stephen D. Jacobs

Author Affiliations +

Proceedings Volume 5518, Liquid Crystals VIII; (2004) https://doi.org/10.1117/12.559627
Event: Optical Science and Technology, the SPIE 49th Annual Meeting, 2004, Denver, Colorado, United States

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 mV_rms/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).

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Kenneth L. Marshall, Erin Kimball, Shari McNamara, Tanya Z. Kosc, Anka Trajkovska-Petkoska, and Stephen D. Jacobs "Electro-optical behavior of polymer cholesteric liquid crystal flake/fluid suspensions in a microencapsulation matrix", Proc. SPIE 5518, Liquid Crystals VIII, (15 October 2004); https://doi.org/10.1117/12.559627

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