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7 March 2016 Feasibility study on the use of liquid crystal/dye cells for digital signage
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Proceedings Volume 9770, Advances in Display Technologies VI; 977004 (2016) https://doi.org/10.1117/12.2212302
Event: SPIE OPTO, 2016, San Francisco, California, United States
Abstract
Elongated dye molecules orient themselves with surrounding liquid crystal molecules. We propose to incorporate such a guest-host cell in a screen of a projection display. This configuration might be applied for digital signage to be installed on building walls. Dual-mode operation is realized by the bias applied to the cell. In display-mode, the dye molecules are oriented in parallel to the substrate of the cell. When excited by ultra-violet light, photoluminescence (PL) is generated. Because it is mostly perpendicular to the long axis of the molecule, it exits the cell efficiently. In powerharvesting mode, they are oriented vertically. The PL generated by ambient light is directed to edge surfaces where solar cells are mounted. In experiment, we fabricated a cell with commonly-available materials (coumarin 6 and a nematic liquid crystal). Anti-parallel alignment condition was adopted. We recorded PL spectra from the cell for the two excitation conditions. First, the center of the cell was irradiated by a 1.69mW blue laser beam. Second, the whole cell was uniformly exposed to the light from a fluorescent lamp at illuminance of 800lx. From the measured spectra for these cases, the contrast of luminance is calculated to be 3.2 ×105 . This factor is improved to 5 7.5×105 by attaching a polarizer sheet on the cell surface. The optical power reaching its edge surfaces is measured and it roughly agrees with the prediction by a simple model neglecting self-absorption. Development of phosphor materials with a large Stokes shift is desired to boost performance of the proposed system.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Shunsuke Itaya, Nada Dianah Binti M. Azumi, Masamichi Ohta, Shintaro Ozawa, and Ichiro Fujieda "Feasibility study on the use of liquid crystal/dye cells for digital signage", Proc. SPIE 9770, Advances in Display Technologies VI, 977004 (7 March 2016); https://doi.org/10.1117/12.2212302
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