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Proceedings Paper

Determination of nematics material parameters by measurements of Fredericksz transitions in crossed electric and magnetic fields in wedge cell
Author(s): Jerzy Kedzierski; Zbigniew Raszewski; Marek Andrzej Kojdecki; Emilia Miszczyk; Pawel Perkowski; Wiktor Piecek; Ludwika Lipinska
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Paper Abstract

Wedge cells of the wedge angle of order of few milliradians were used to measure the threshold voltages for the Freedericksz transition in electric and magnetic fields crossed. A nematic liquid crystal, PCB, filling cells was of planar orientation enforced by the treatment of the flat boundary plates, covered with poly(amic acid) PM9. A system of interference fringes appeared in each cell placed in normally incident light between analyzer and polarizer crossed. In the vicinity of each fringe a cell could be considered as a flat-parallel one and hence it was equivalent to the system of flat cells of different precisely determined thickness. Threshold voltages, parameterized by magnetic field magnitudes were interpreted as the eigenvalues of the boundary eigenvalue problem for the operator of the second derivative; the interaction between the nematics and the substrates was assumed very strong with the anchoring direction parallel to the cell boundaries. The resulting formulae were used to determine the anisotropy of diamagnetic susceptibility and the splay elastic constant of PCB after the threshold magnitudes measured. The estimates of material parameters agreed well with those determined by the composite method.

Paper Details

Date Published: 1 September 2004
PDF: 5 pages
Proc. SPIE 5565, XV Conference on Liquid Crystals, (1 September 2004); doi: 10.1117/12.581095
Show Author Affiliations
Jerzy Kedzierski, Military Univ. of Technology (Poland)
Zbigniew Raszewski, Military Univ. of Technology (Poland)
Marek Andrzej Kojdecki, Military Univ. of Technology (Poland)
Emilia Miszczyk, Radom Univ. of Technology (Poland)
Pawel Perkowski, Military Univ. of Technology (Poland)
Wiktor Piecek, Military Univ. of Technology (Poland)
Ludwika Lipinska, Institute of Electronic Materials Technology (Poland)

Published in SPIE Proceedings Vol. 5565:
XV Conference on Liquid Crystals
Jozef Zmija, Editor(s)

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