| 1. |
- Kim, Sang Hwa, et al.
(author)
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Effects of polymer concentration and localization on the electro-optical performance of cholesteric flexoelectro-optical devices
- 2005
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In: Proceedings of the SPIE. - 0277-786X. ; 5741, s. 15-22
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Journal article (peer-reviewed)abstract
- We discussed the effect of polymer concentration and localization on flexoelectro-optical device using short pitch cholesterics oriented in uniform lying helix texture. By using a small concentration of photoreactive liquid crystal monomer with various concentrations and selecting the illumination conditions, we have been able to create a localized polymeric network at both substrate surfaces. We can stabilized the two switching modes and eliminating at the same time the effect of the residual birefringence of the polymeric network in the field-unwound state of the sample. The device has two operating modes: amplitude and phase modulation mode, respectively. The amplitude modulation mode is a fast in-plane switching of the device optic axis that enables to achieve a 100 % modulation of the transmitted light intensity whereas the phase mode gives a continuous change of the refractive index and thus of the phase shift of the transmitted light.
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| 2. |
- Kim, Sang Hwa, et al.
(author)
-
Short pitch cholesteric electro-optical device stabilized nonuniform polymer network
- 2005
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In: Appl.Phys.Lett.. - : AIP Publishing. - 0003-6951. ; 86
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Journal article (peer-reviewed)abstract
- We have developed a method for stabilization of the uniform lying helix (ULH) texture of short pitch cholesterics in an electro-optical device, based on the flexoelectro-optic effect in such a texture. By using a small concentration of photoreactive liquid crystal monomer (less than 5 wt. %) and selecting the illumination conditions, we were able to create a nonuniform polymeric network in the liquid crystal bulk (localized essentially at both substrate surfaces) which stabilized efficiently the amplitude and the phase modulation modes of the device. Most importantly, the effect of the residual birefringence of the polymeric network in the field-unwound state of the device was eliminated resulting thus in a substantial improvement of device performance. ©2005 American Institute of Physics doi:10.1063/1.1897057
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| 3. |
- Komitov, Lachezar, 1944, et al.
(author)
-
Electro-optical devices from polymer-stabilized liquid crystal molecules
- 2005
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Patent (other academic/artistic)abstract
- Electrooptical devices are described which comprise first and second spaced-apart surfaces defining a gap; a chiral or cholesteric liq. crystal material disposed in the gap; and a polymeric network disposed in the gap, the polymeric network being .ltorsim.5 wt. % of the liq. crystal and biasing the liq. crystal material toward a substantially uniformly lying helix texture. The polymeric network may extend only partway into the liq. crystal cell leaving at least a portion of the liq. crystal cell substantially free of the polymeric network. Methods for producing the devices are described which entail disposing a chiral or cholesteric liq. crystal, a photoreactive monomer, and a photoinitiator in a liq. crystal cell; and illuminating a principal surface of the liq. crystal cell with UV light selected to have a nonuniform intensity profile in the liq. crystal cell, the illuminating cooperating with the photoinitiator to polymerize at least a portion of the photoreactive monomer near the principal surface to generate a polymer network having a d. corresponding to the non-uniform a UV light intensity profile, the polymer network biasing the liq. crystal toward a selected helical alignment direction.
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