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Title: Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

Abstract

Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

Inventors:
 [1];  [1];  [2]
  1. Rochester, NY
  2. Pittsford, NY
Publication Date:
Research Org.:
The University of Rochester (Rochester, NY)
Sponsoring Org.:
USDOE
OSTI Identifier:
908441
Patent Number(s):
7,042,617
Application Number:
10/405,163
Assignee:
The University of Rochester (Rochester, NY) OAK
DOE Contract Number:
FC03-92SF19460
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION

Citation Formats

Kosc, Tanya Z, Marshall, Kenneth L, and Jacobs, Stephen D. Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system. United States: N. p., 2006. Web.
Kosc, Tanya Z, Marshall, Kenneth L, & Jacobs, Stephen D. Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system. United States.
Kosc, Tanya Z, Marshall, Kenneth L, and Jacobs, Stephen D. Tue . "Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system". United States. doi:. https://www.osti.gov/servlets/purl/908441.
@article{osti_908441,
title = {Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system},
author = {Kosc, Tanya Z and Marshall, Kenneth L and Jacobs, Stephen D},
abstractNote = {Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue May 09 00:00:00 EDT 2006},
month = {Tue May 09 00:00:00 EDT 2006}
}

Patent:

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  • Composite or layered flakes having a plurality of layers of different materials, which may be dielectric materials, conductive materials, or liquid crystalline materials suspended in a fluid host and subjected to an electric field, provide optical effects dependent upon the angle or orientation of the flakes in the applied electric field. The optical effects depend upon the composition and thickness of the layers, producing reflectance, interference, additive and/or subtractive color effects. The composition of layered flakes may also be selected to enhance and/or alter the dielectric properties of flakes, whereby flake motion in an electric field is also enhanced and/ormore » altered. The devices are useful as active electro-optical displays, polarizers, filters, light modulators, and wherever controllable polarizing, reflecting and transmissive optical properties are desired.« less
  • Doped electrically actuatable (electrically addressable or switchable) polymer flakes have enhanced and controllable electric field induced motion by virtue of doping a polymer material that functions as the base flake matrix with either a distribution of insoluble dopant particles or a dopant material that is completely soluble in the base flake matrix. The base flake matrix may be a polymer liquid crystal material, and the dopants generally have higher dielectric permittivity and/or conductivity than the electrically actuatable polymer base flake matrix. The dopant distribution within the base flake matrix may be either homogeneous or non-homogeneous. In the latter case, themore » non-homogeneous distribution of dopant provides a dielectric permittivity and/or conductivity gradient within the body of the flakes. The dopant can also be a carbon-containing material (either soluble or insoluble in the base flake matrix) that absorbs light so as to reduce the unpolarized scattered light component reflected from the flakes, thereby enhancing the effective intensity of circularly polarized light reflected from the flakes when the flakes are oriented into a light reflecting state. Electro-optic devices contain these doped flakes suspended in a host fluid can be addressed with an applied electric field, thus controlling the orientation of the flakes between a bright reflecting state and a non-reflecting dark state.« less
  • Flakes or platelets of polymer liquid crystals (PLC) or other birefringent polymers (BP) suspended in a fluid host medium constitute a system that can function as the active element in an electrically switchable optical device when the suspension is either contained between a pair of rigid substrates bearing transparent conductive coatings or dispersed as microcapsules within the body of a flexible host polymer. Optical properties of these flake materials include large effective optical path length, different polarization states and high angular sensitivity in their selective reflection or birefringence. The flakes or platelets of these devices need only a 3-20.degree. rotationmore » about the normal to the cell surface to achieve switching characteristics obtainable with prior devices using particle rotation or translation.« less
  • The motion of highly dielectric polymer cholesteric liquid crystal (PCLC) flakes suspended in a host fluid can be controlled with an ac electric field. The electric field acts to induce a dipole moment on the flake due to interfacial, or Maxwell-Wagner, polarization. Theoretical modeling of PCLC flakes as oblate spheroids shows that the flakes will reorient to align one of the two major axes parallel to the electric field. The theory also supports the observed dependence of the particle reorientation time on the electric-field magnitude, frequency, and particle shape. A PCLC flake's orientation determines its ability to reflect light ofmore » a specific wavelength and circular polarization. The ability to switch the position of PCLC flakes with an electric field has implications for electro-optic devices and display applications.« less
  • Compositions in accordance with the invention comprise a polymer and flake reinforcing material distributed throughout the polymer in an effective amount to structurally reinforce the polymer. Individual flakes of the flake material (a) are less than or equal to 1,000 Angstroms in thickness, (b) have an aspect ratio greater than or equal to 100, and (c) are preferably significantly randomly oriented throughout the polymer. A novel apparatus for shear grinding a platy solid material into such individual flakes comprises a cylindrical shearing drum and a shear grinder received therein. The shearing drum has a longitudinal axis and an internal surfacemore » formed about a first predetermined radius of curvature. The cylindrical drum is supported for rotation about its longitudinal axis. The shear grinder has an external surface formed about a second predetermined radius of curvature. The second radius of curvature is slightly less than the first radius of curvature.« less