Improved red color with cholesteric liquid crystals in Bragg reflection mode

The helical pitch of the cholesteric liquid crystal (CLC) can be adjusted to reflect the colors red, green, and blue. Additive mixing of these colors in displays results in multicolor images and it is easy to use pure primary blue and green colors, but the red color is in general very unsaturated. W...

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Bibliographic Details
Published in:Optical Engineering 2002-03, Vol.41 (3), p.638-646
Main Authors: Kipfer, Peter, Klappert, Rolf, Herzig, Hans Peter, Grupp, Joachim, Da¨ndliker, Rene´
Format: Article
Language:English
Subjects:
cholesteric texture
color generation
liquid crystals
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Summary:The helical pitch of the cholesteric liquid crystal (CLC) can be adjusted to reflect the colors red, green, and blue. Additive mixing of these colors in displays results in multicolor images and it is easy to use pure primary blue and green colors, but the red color is in general very unsaturated. We show by simulations that this poor red color performance is due to reflection sidebands on the smaller wavelength side of the normal red Bragg reflection band. We discuss five approaches to improve the red color performance, namely, two types of spectral filtering (dyes or filters), a very low birefringence CLC, a gradient in the birefringence of the CLC, and the use of a bluish reflector. The two methods of spectral filtering are also experimentally tested. ©
ISSN:0091-3286
1560-2303
DOI:10.1117/1.1447229