Thin films can be observed by various microscopic interference techniques. Unfortunately these methods provide only a limited indication of the film coverage especially on irregular surfaces. Most films are invisible to more convention microscopy. By using a very simple staining technique, these films can be clearly observed by fluorescent microscopy. The technique is applicable to almost any polymeric film on any inorganic surface.This technique was applied to a variety of xerographic carriers to visualize the coating. Changes in processing can be clearly observed. Film thickness down to hundreds of angstroms can be readily observed. Thin discrete films become apparent in this technique and it is ideal for observing powder-coating processes. The technique is applicable to a variety of other applications involving thin films on small irregular surfaces.The technique was used to measure the coating available for charging on a carrier surface. The carrier charge was proportional to the fluorescent intensity of the polymer on the surface and not the total amount of polymer present.
Thomas J. Budny, "Fluorescent Staining Technique for Visualizing Thin Films" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP18), 2002, pp 644 - 647, https://doi.org/10.2352/ISSN.2169-4451.2002.18.1.art00053_2