A switchable diffuse reflective film with high color purity is demonstrated using holographic-polymer dispersed liquid crystals (HPDLC). By recording a diffuse hologram directly into the LC/polymer film, the diffuse mode HPDLC exhibit viewing angles an order of magnitude larger than the conventional mode. A simple phenomenological model based on coupled-wave theory is developed to describe our observations.
We report the temperature dependent far-infrared spectrum of ultra-thin films of polyethylene oxide (PEO). Using the orientational specificity of infrared and far-infrared reflection–absorption spectroscopy and in-situ recrystallization, we find that during spin coating the PEO helices are initially in the plane of the film, but on crystallization reorient to be normal to the substrate. A splitting of the C–O torsional mode near 109 cm−1 is identified as arising from a distortion of the normal helical structure of PEO. Comparison with transmission spectra of cast films demonstrates the value of far-infrared reflection–absorption spectroscopy (FIRRAS) in the study of crystalline polymers in the far infrared.
Abstract— In this paper we determine the visual parameters required for effective, full‐color reflective displays. We analytically examine a number of contemporary liquid crystal (LC) technologies and associated optical configurations which hold promise for achieving reflective color displays. We conclude that reflective displays based on holographically formed polymer‐dispersed liquid crystals (H‐PDLCs) and polymer‐stabilized cholesteric‐texture liquid crystals (PSCT) are the most viable color‐capable reflective technologies to date.
A novel device for separation of color image components in image capture systems is described. The device is based upon temporal switching of HPDLC elements with tunable spectral passbands. The device may be operated as either a reflective RGB color separation mirror or a transmissive CMY color separation filter. A breadboard color image capture system using this device for color separation has been developed and tested as a proof of concept.
We describe a simplified procedure to assess the ambient performance for common types of mobile displays. The unique properties which allow for this simplification will be explained. Results will be presented showing the importance of front-ofscreen reflection for typical LCD and OLED screens currently used in smartphones and tablets.
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