Y. Kawakami, Y. Cho
Jul 1, 2006
Citations
0
Influential Citations
5
Citations
Journal
Macromolecular Symposia
Abstract
Well-defined transmission holographic gratings with high diffraction efficiency were fabricated by irradiating a mixture of dipentaerythritol penta-/hexafunctional acrylates, 1-vinyl-2-pyrrolidone and 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane or 1,3-bis[2-(1,2-epoxycyclohex-4-yl)ethyl]-1,1,3,3-tetramethyldisiloxane in the absence (photo-polymer systems, 30:10:60 in weight ratio; 80 or 55% efficiency) or presence (holographic polymer dispersed liquid crystal systems: 45:9:36:10 in weight ratio; 83 or 67% efficiency) of commercial liquid crystalline compound E 7 with diphenyliodonium hexafluorophosphate and 3,3'-carbonylbis(7-diethylaminocoumarin) photo-initiating system by Nd:YAG laser (λ=532 nm). When the ratio of dipentaerythritol penta-/hexaacrylate and 1,3-bis(3-glycidoxypropyl)-1,1,3,3-tetramethyldisiloxane was changed to 50:40 in photo-polymer system, the diffraction efficiency increased to 84%. They had smooth surface morphologies with regulated spacing. In polymer dispersed liquid crystal system, the same ratio of dipentaerythritol penta-/hexaacrylate and siloxane-containing epoxides gave the best results. 1,5-Bis(3-glycidoxypropyl)-1,1,3,3,5,5-hexamethyltrisiloxane and 1,5-bis[2-(1,2-epoxycyclohex-4-yl)ethyl]-1,1,3,3,5,5-hexamethyltrisiloxane gave. high diffraction efficiency with 10% E7 (97% and 75%). The trisiloxane derivatives gave gratings with considerably or moderately reduced angular deviation (0.83, 0.66 degree for trisiloxane from 1.2, 0.7 degree for disiloxane derivatives, respectively for signal beam, and 0.76, 0.70 degree from 1.1,1.0 degree for the reference beam at 32 degree of external incident angle) from Bragg profile, namely 5.2 and 4.5% volume shrinkage for trisiloxane, and 7.5, 5.6% for disiloxane derivatives, respectively. Gratings with diffraction efficiency over 95% with the narrowest angular selectivity of 4.0 degree was obtained when trimethylolpropane triacrylate was used together with 1,5-bis[2-(1,2-epoxycyclohex-4-yl)ethyl]-1,1,3,3,5,5-hexamethyltrisiloxane (50: 40) and 5% E7. These gratings were actually used to store real images.