Christopher C. Bowley

Diffusion kinetics of formation of holographic polymer-dispersed liquid crystal display materials

The underlying physical phenomena behind the increased reflection/diffraction efficiency of holographically formed polymer-dispersed liquid crystal gratings formed from blended oligomers are investigated. Using parameters determined by in situ diffraction measurements during grating formation, a phenomenological diffusion model shows that a composition modulation in the polymer network results in blended oligomer systems. Scanning electron microscope studies reveal polymer morphologies consistent with this hypothesis.

Optical strain characteristics of holographically formed polymer-dispersed liquid crystal films

The optical strain characteristics of a reflective holographic-polymer dispersed liquid crystal are investigated. A spectral blueshift and induced polarization dependence are observed to occur with increasing strain. The spectral dependence on strain is explained by the Poisson contraction of the material and the polarization dependence is largely attributed to elongation of liquid crystal droplets. The material has potential use as an optical strain gauge.

Electro-Optic Investigations of H-PDLCs: The Effect of Monomer Functionality on Display Performance

We investigate the effect of monomer functionality on the electro-optic performance of holographically-formed polymer dispersed liquid crystals. Oligomers of functionality 2, 3 and 6 are mixed to yield oligomers of intermediate functionality. Reflection efficiency and critical field peaks are reported for effective functionality ∼4.5. SEM studies allow us to correlate these results to polymer morphology.

Model of the Fast-Switching, Polymer-Stabilized IPS Configuration

A significant improvement in the dynamic response times of IPS mode LCDs is achieved through polymer-stabilization. The improvement is a result of the introduction of a low-density, stabilizing polymer network that causes the LC director to favor the zero-field orientation. We report on the effect of the polymer concentration and network orientation on the electro-optic performance of our novel polymer-stabilized IPS mode cells. Furthermore, we present a detailed model derived using elastic continuum theory to explain our observations.

Advances in Holographic Polymer Dispersed Liquid Crystal Technology

We discuss recent advances in reflective holographically-formed polymer dispersed liquid crystal materials in the context of their suitability for reflective display applications. A dual-domain phenomenon resulting in a broadened reflection peak is presented. A simple phenomenological model is developed to explain this unusual effect The effect of monomer functionality on the reflectance characteristics of these materials is also discussed. Monomers of effective functionality ∼4.5 yield the brightest holograms, however, the data suggests that these systems are currently far from optimal.

Improvement in holographically formed polymer-dispersed liquid crystal performance through acrylated monomer functionality studies

We investigate the effect of monomer blends on the performance of holographically-formed polymer dispersed liquid crystals (H-PDLCs). Difunctional, trifunctional, and hexafunctional urethane acrylate resins are mixed in different ratios to yield monomers characterized by an effective functionality. Reflection H-PDLCs are formed using the different blends. Reflection efficiency and voltage response are measured. Monomer blends prepared with trifunctional/hexafunctional constituents are formed to yield H-PDLCs with higher reflection efficiency than their difunctional/hexafunctional counterparts, but require higher voltages to switch. Scanning electron microscope investigations are also undertaken.

Effect of Monomer Functionality on Performance of Holographically-Formed Polymer Dispersed Liquid Crystals

Abstract Reflection gratings are formed holographically in polymer dispersed material. The effect of polymer functionality on the reflective display performance characteristics of these materials is investigated. Commercial urethane resins of functionality 2, 3, and 6 are used as base materials to create integer and half-integer effective functionalities from 2 to 6. Our results reveal an optimum reflectance at an effective functionality of 4.5.

A model of the fast-switching polymer-stabilized in-plane-switching configuration

— A significant improvement in the dynamic response times of IPS-mode LCDs is achieved through polymer stabilization. The improvement is a result of the introduction of a low-density stabilizing polymer network that causes the LC director to favor the zero-field orientation. We report on the effect of the polymer concentration and network orientation on the electro-optic performance of our novel polymer-stabilized IPS-mode cells. Furthermore, we present a detailed model derived using elastic continuum theory to explain our observations.

Electro‐optic investigations of holographically formed PDLCs: The effect of monomer functionality on display performance

— We investigated the effect of monomer functionality on the electro-optic performance of holographically formed polymer-dispersed liquid crystals. Oligomers of functionality 2, 3, and 6 are mixed to yield oligomers of intermediate functionality. Reflection efficiency and critical field peaks are reported for an effective functionality of ∼4.5 SEM studies, allowing us to correlate these results to polymer morphology.