Depth-resolved characterization of UV cured coatings by confocal Raman and two-photon microscopy

UV cured coatings can be characterized very effectively by confocal Raman microscopy, real-time IR spectroscopy and two-photon laser scan microscopy. The first two vibrational spectroscopic methods for chemical imaging and kinetics of curing conversion, respectively, can help to optimize UV formulations and curing conditions, e.g. UV dosage or temperature. In contrast, two-photon laser scan confocal microscopy can be used to monitor changes in refractive indices and intrinsic or tracer fluorescence with three-dimensional spatial and fast temporal resolution. This technique is well suited to analyze buried interfaces to substrate and other coating layers and to visualize distribution of fillers. In this regard, aluminum flakes in metallic coatings can be investigated without additional sample preparation as a function of their individual orientation and size. With this information, one can optimize the process of coating formation yielding improved coloristic properties. Illustrative examples will be presented to elucidate the perspective of these techniques in coatings characterization.