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Proceedings Paper

Feasibility study on the use of liquid crystal/dye cells for digital signage
Author(s): Shunsuke Itaya; Nada Dianah Binti M. Azumi; Masamichi Ohta; Shintaro Ozawa; Ichiro Fujieda
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Paper 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.

Paper Details

Date Published: 7 March 2016
PDF: 10 pages
Proc. SPIE 9770, Advances in Display Technologies VI, 977004 (7 March 2016); doi: 10.1117/12.2212302
Show Author Affiliations
Shunsuke Itaya, Ritsumeikan Univ. (Japan)
Nada Dianah Binti M. Azumi, Ritsumeikan Univ. (Japan)
Masamichi Ohta, Ritsumeikan Univ. (Japan)
Shintaro Ozawa, Ritsumeikan Univ. (Japan)
Ichiro Fujieda, Ritsumeikan Univ. (Japan)

Published in SPIE Proceedings Vol. 9770:
Advances in Display Technologies VI
Liang-Chy Chien; Sin-Doo Lee; Ming Hsien Wu, Editor(s)

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