P‐81: In‐Situ Spectroscopy of Holographically formed Polymer Dispersed Liquid Crystal Materials for High Performance Reflective Display Applications

Warren, Gregory L.; Sarkar, Mousumi De; Qi, Jun; Crawford, Gregory P.

doi:10.1889/1.1832005

Cited by 7 publications

(4 citation statements)

References 12 publications

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“…The shrinkage results in a polarization sensitive diffraction since the optical axis is on average along the same direction for all droplets, therefore making diffraction efficiency sensitive to the input polarization. However, in our experiment, the shrinkage was only about 2% which is significantly smaller than the reported data, which are usually 5% ∼ 10% [48,157]. The smaller polymerization shrinkage reduces the PDL remarkably.…”

Section: Polarization Dependencecontrasting

confidence: 84%

Holographic Polymer‐Dispersed Liquid Crystals: Materials, Formation, and Applications

Liu

Sun

2008

Advances in OptoElectronics

108

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By combining polymer-dispersed liquid crystal (PDLC) and holography, holographic PDLC (H-PDLC) has emerged as a new composite material for switchable or tunable optical devices. Generally, H-PDLC structures are created in a liquid crystal cell filled with polymer-dispersed liquid crystal materials by recording the interference pattern generated by two or more coherent laser beams which is a fast and single-step fabrication. With a relatively ideal phase separation between liquid crystals and polymers, periodic refractive index profile is formed in the cell and thus light can be diffracted. Under a suitable electric field, the light diffraction behavior disappears due to the index matching between liquid crystals and polymers. H-PDLCs show a fast switching time due to the small size of the liquid crystal droplets. So far, H-PDLCs have been applied in many promising applications in photonics, such as flat panel displays, switchable gratings, switchable lasers, switchable microlenses, and switchable photonic crystals. In this paper, we review the current state-of-the-art of H-PDLCs including the materials used to date, the grating formation dynamics and simulations, the optimization of electro-optical properties, the photonic applications, and the issues existed in H-PDLCs.

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Section: Polarization Dependencecontrasting

confidence: 84%

Holographic Polymer‐Dispersed Liquid Crystals: Materials, Formation, and Applications

Liu

Sun

2008

Advances in OptoElectronics

108

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“…For acrylates as H-PDLC hosts, we observed a progressive blue shift of the reflection notch during real-time monitoring of grating formation. , We attribute the blue shift to polymer shrinkage during the curing process. According to the Bragg relation, an expected increase of the polymer refractive index due to curing should red shift the notch; thus, any blue shift observed gives a low estimate of the amount of shrinkage.…”

Section: Resultsmentioning

confidence: 74%

Switchable Holographic Polymer-Dispersed Liquid Crystal Reflection Gratings Based on Thiol−Ene Photopolymerization

et al. 2003

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Holographic reflection gratings in polymer-dispersed liquid crystals (H-PDLCs) were formed by thiol−ene photopolymerization. Using UV laser light and a single prism, electrically switchable reflection gratings in blue, green, yellow, and red colors were fabricated. Results indicate that thiol−ene polymers function as better hosts for H-PDLC than multifunctional acrylate as matrixes. These differences are the result of a much different temporal structure development caused by fundamental differences in the polymerization propagation mechanism: a step-growth addition mechanism for the thiol−ene system compared to a chain-growth addition mechanism in multifunctional acrylates. Morphology studies by TEM support these conclusions, as striking differences in droplet shape and uniformity are observed. Discrete nematic droplets with a nearly spherical shape were seen. Thiol−ene polymers offer lower switching fields, higher diffraction efficiencies, better optical properties, and higher thermal stabilities. The response times of the thiol−ene gratings were five times slower than those of acrylates.

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“…[10] Warren et al investigated the degree of shrinkage according to urethane acrylate functionality. [25] Recently, Schulte et al used fluoro-substituted acrylate monomers and found that the presence of fluorine atoms at the LC/polymer interface of the HPDLC gratings may lower the anchoring strength and the switching voltage. [26] Most HPDLCs need much higher switching voltages than conventional PDLCs due to their very small and irregularly shaped domains.…”

Section: Introductionmentioning

confidence: 99%

Surfactant Effects on Morphology and Switching of Holographic PDLCs Based on Polyurethane Acrylates

Woo

Kim

2006

ChemPhysChem

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Effects of octanoic acid (OA) on the morphology, diffraction efficiency, and electro-optic properties of the transmission mode of holographic polymer-dispersed liquid crystals (HPDLC) are studied. Droplet size decreases with increasing OA content (0-9 %), and this leads to a monotonic increase in off-state diffraction with increasing OA content. However, on-state diffraction decreases with increasing applied voltage and shows a minimum at 6 % OA, for which minimum switching voltage (5 V microm(-1)) and maximum contrast ratio (10) are obtained. Rise time and decay time decrease with increasing OA content. Interposition of OA between polymer and LC droplet is theoretically predicted by the spreading coefficient (lambda>0) calculated on the basis of the solubility parameter, while the coalescence behavior of droplets is described by a dimensionless group (gamma d rho / mu(2)) called coalescence number.

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P‐81: In‐Situ Spectroscopy of Holographically formed Polymer Dispersed Liquid Crystal Materials for High Performance Reflective Display Applications

Cited by 7 publications

References 12 publications

Holographic Polymer‐Dispersed Liquid Crystals: Materials, Formation, and Applications

Holographic Polymer‐Dispersed Liquid Crystals: Materials, Formation, and Applications

Switchable Holographic Polymer-Dispersed Liquid Crystal Reflection Gratings Based on Thiol−Ene Photopolymerization

Surfactant Effects on Morphology and Switching of Holographic PDLCs Based on Polyurethane Acrylates

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