HABI Photoinitiators in Photopolymer Films Developed for Holographic Applications

HABI PHOTOINITIATORS IN PHOTOPOLYMER FILMS DEVELOPED FOR HOLOGRAPHIC APPLICATIONS 

292 Hickory Dr, Kermett Square, PA 19348-1550, USA E-mail thomas.felder usa. dupont. com 

The advent of commercially available lasers in the late 1960 s sparked research efforts at DuPont into many new areas. In one of the early successes of this effort, E.F. Haugh in 1972 patented a unique application for photopolymers, as holographic media [1], 

Researchers at DuPont reasoned that differences in refractive index could be created on a submicron scale in dry photopolymer films, that such refractive index differences could function as diffraction gratings, and that lasers could be used to produce these structures. In initial experiments, photopolymers were exposed using lasers beams diffracted by commercial gratings, and polymerized structures in exposed photopolymers confirmed that very high spatial resolution was possible [2]. This work led to the development and commercialization of holographic photopolymer film from DuPont. 

Bis-imidazole photoinitiators are well-suited to photopolymer holographic films because these photoinitiators are sensitive, can be stored indefinitely, can be sensitized to all visible wavelengths, and are readily compatible with binder systems. It was the coincident development of bis-imidazole photoinitiators which catalyzed the rapid growth of photopolymer films in DuPont, holographic films in particular. The ready sensitization of bis-inudazoles has been exploited in a wide variety of holographic photopolymer films sensitized to all major visible commercial lasers, including panchromatic sensitization for the production of fiill-color 

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