Light induced gradient refractive index materials |
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| Authors: | Hüseyin Esen Celine C Barghorn Xavier Allonas |
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| Affiliation: | 1. Polymer Engineering Department, Engineering Faculty, Yalova University, Yalova, Turkey;2. Laboratoire de Photochimie et d'Ingenierie Macromoleculaires, University of Haute Alsace, ENSCMu, Mulhouse Cedex, France |
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| Abstract: | Controlled and patterned variation of refractive index (wavefront) across a lens surface was obtained via the use of “phase mask”. Gradient interpenetrating network was selected to screen the acrylate and epoxy monomer to obtain necessary refractive index change over the lens surface. The best photoinitiator system was determined to give a stable and transparent wavefront as a mixture of 2 wt% Irgacure 250 (I 250), 1 wt% Isopropylthoxanthone (ITX) and 0.5 wt Irgacure 184 (I 184). It is found that a dipropylene glycol diacrylate (SR 508) and a triethylene glycol dimethacrylate (TGDM) improved the stability of the transparent wavefront because of higher Tg of the network. Haze problem, a consequence of diffusion of one monomer to other network because of the rate differences, was eliminated with IPN composed of TGDM (an acrylate with slow polymerization rate) and bis (3,4‐epoxy cyclohexylmethyl)adipate (BECMA, an epoxy with fast polymerization rate). A high refractive index additive, bromonaphthalene, resulted the best wavefront with lens power when incorporated into BECMA and TGDM IPN. Copyright © 2015 John Wiley & Sons, Ltd. |
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