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INTRODUCTION
Radiation curing has now become a well-accepted technology which has found its main
apilications in various industrial sectors where ultrafast cure and high quality product are required
Ultraviolet (UV) or electron beam (EB) curing is indeed unique in that it achieves, selectively in the
exposed areas, a quasi-instantaneous transformation of a liquid resin into a solid polymer.The ability to tailor polymer properties, together with very high cure rates, has resulted in the technique being adopted worldwide in an ever increasing number of end uses. The radcure market, which has long been restricted to the coating industry for producing fast-drying varnishes and printing inks, has
progressively invaded new sectors of applications, mainly in microelectronics, photoimaging,
adhesives and composites. Today, the UV curing technology has gained a predominant position in
some specific industrial s ctors, such as in the graphic arts, the coating of optical fibres and laserstereolithography.
During the last decade, great progress has been achieved in the chemistry of radiation curable
systems, with the development of ever more efficient photoinitiators (for a comprehensive up to date
review, see reference 7), and highly reactive new monomers and oligomers for both clear and
pigmented formulations. There is presently a large choióe of commercially available products, thus
allowing one to select the proper formulation components in order to meet the cure speed and product properties requirements for the particular application considered. This is the main reason why research and development in radiation curing has shifted over the years from basic chemistry toward the application sector, taking full advantage of the remarkable performance of radiation curable systems. This tendancy is best illustrated by the fact that the proportion of "chemistry" papers presented at RadTech conferences has dropped from 50% to 25%, over the past 10 years, with a concomitant increase of the "applications" papers. As a result of the nice work accomplished by, chemists, today's trend in radiation curing appears thus to be rather toward the development of new end-uses, than new products.
In this paper, we will first outline some of the important requirements which are presently
imposed to radiation curing chemistry, before reporting the progress made in these areas with respect to both the photoinitiators and the monomers. Special attention has been directed toward the chemistry of hght-induced curing, as this sector still covers more than 90% of the radiation curing market . However, since the main difference between UV and EB curing lies in the imtiation step, any progress made in the development of new monomers and oligomers is likely to be directly applicable to EB formulation.
