Patents biimidazoles

My colleagues and I developed a novel imaging system, which resulted in products for the prepress proofing industry that were successful for over 35 years. They were big earners because the research was done with an eye on establishing a strong patent position, and no effective competition came along. The photo-oxidants that were developed became enormously successful as photopolymerization initiators, which allowed DuPont to manufacture a series of novel products of importance to the printing and electronics industries. Now, some 40 years after this work was done, these biimidazole derivatives still appear to be initiators of choice and are found to play a role in current patents. 

Soon after our initial experiments, we realized that we had something unusual, with potentially important opportunities. We were able to obtain some foreign patents on the biimidazoles and were concerned that these might tip off others in this field, for there was considerable activity, as can be seen from a listing of biimidazole work as reported in Chemical Abstracts. By 1964, we filed our first application on the leucodye oxidation. By then, we had a sufficient head start on this chemistry that we became less concerned about competitive activities. 

In time, HABIs were to become important components of photopolymer systems as of December 2004, there were over 1000 U.S. patents, in which biimidazoles, lophine dimers, HABIs, and 2-o-chlorophenyl-imidazole derivatives were mentioned A word about patents. At Du Pont, the names of inventors are listed alphabetically, even though the lead inventor might have a name that was at the bottom of the alphabet. There were exceptions. Sometimes, one of the inventors would request the attorneys to list a lead inventor first. 

Unfortunately, only patents issued after 1975 can be searched electronically and searching for chemical structures is complicated by the fact that trivial names abound. In compiling a database for HABIs, I found different patents which identified lophine dimers, imidazole dimers, imidazolyl dimers, DYLUX , bisimidazoles, biimidazoles, etc. 

The Patent Office suspended prosecution of the application for several years while a structure determination was carried out. The structure of the o-bromophenyl dimer [2,2 -bis(o—bromophenyl)-4,4 5,5 -tetraphenyl-l,2 -biimidazole] was subsequently determined and submitted to the Patent Office, and the claims of the application were allowed. Consequently, the basic HABI patent, U.S. Patent 3,784,557 (to Lawrence Anthony Cescon), Phototropic 2,4,5-Triphenylimidazolyl Radicals and Dimers Thereof, did not issue until January 8,1974, nearly twelve years after the filing of the initial application. 

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