Recent Developments of long Wavelength Photoinitiators for Radical Polymerization

Abstract

Since the 1960’s, UV light for radical polymerization initiation has gained industrial importance in several applications.1 For curing with light, the most important parameter is the penetration depth of light into the curable formulation. It is responsible for generating sufficient layer thickness and is corresponding with longer wavelength of the used light. Therefore, photoinitiators with red-shifted absorption spectra allow the use of visible light LEDs what results in a higher penetration depth of light. Our recent work regarding long wavelength photoinitiators included tetrakisbenzoylgermane2 and -stannane3 derivatives that show the desired red-shift in their absorption. Selected substances were characterized regarding their initiation properties. Generally, outstanding photoreactivity at defined wavelengths, as well as good photobleaching behavior and storage stability have been found.