Photopolymers for laser imaging and holographic recording: Design and reactivity of photosensitizers

One of the most difficult problems encountered currently in the design of photosensitive systems in the field of UV curing and in the area of imaging science (such as 3-D stereolithography, photopolymers in laser-to-plate imaging systems, holographic recording films, or holographic optical elements) is to extend the spectral sensitivity of the photoinitiating system to the visible light emission, The design of efficient photosensitizer/photoinitiator combinations is partly based on a better understanding of the basic mechanism that is involved. The time-resolved laser absorption spectroscopy combined with steady state experiments appears as a very convenient tool to improve the efficiency of photoinitiating systems. The discussion centers on the excited state processes in selected examples of efficient photosensitive systems for laser-induced polymerization reactions that are of great practical use, e.g., in holographic recording or laser imaging.