Tailoring primary processes for high performance photoinitiating systems usable under visible light

Optimization of holography recording in photopolymers was studied from the point of view of the photogeneration of radicals. On the basis of a dye/borate salt photoinitiating system, the effect of the primary events and their relative efficiency was investigated with respect to the final overall properties, such as the diffraction efficiency. Quenching of the dye excited states by the borate salts exhibits important differences depending on the dye used. Keeping in mind that both singlet and triplet states of the dyes can react and taking into account the viscosity of the matrix, the overall quantum yield of radicals released is evaluated. It is found that this quantum yield well correlates with the maximum rate of photopolymerization. More interestingly, the dose required to obtain a given diffraction efficiency was found to be also governed by the radical quantum yield, showing that the final property is directly governed by primary events