Pyrromethene dye and non-redox initiator system in a hydrophilic binder photopolymer

The bipyrromethene–BF2 complexes are dyes derived from pyrromethene. They have been studied in photopolymers with hydrophobic binder, where the dye can act as sensitizer and initiator at the same time. We introduce pyrromethene in a hydrophilic binder photopolymer to change the redox initiation system in photopolymers with xanthene dyes. In this way we avoid the use of triethanolamine as the redox initiator, typical in hydrophilic binder photopolymers, which is related to the existence of diffusion phenomena in the recorded hologram. Using a pyrromethene derived dye and 4,4′-azobis(4-cyanovaleric acid) as initiator we have obtained photopolymer layers with high thickness, good optical quality, absorption levels very close to xanthene dyes, and with the capability to record diffraction gratings with low noise level.