A Noble Photo-Grafting Technique of Perfluoropolyether Molecular Chains to the Carbon Overcoat Free

The technique of enhancing adhesion of PFPE (perfluoropolyether) lubricants to the carbon overcoat of magnetic media discs by irradiation with far-UV (185 nm) was reported some time ago.[1] It was later suggested that photoelectrons emanating from the carbon layer was responsible for the observed efficacy.[2] Capture of these low energy electrons by PFPE molecular chains would lead to detachment of a fluoride anion and formation of a radical center on the polymer backbone. Adhesion occurs when the radical center reacts with the carbon layer. Most recently this mechanism was challenged, and photo-cleavage of a CF₂O unit from the molecular chain thus generating two radical chain fragments was proposed as the primary happening.[3] In either case the reaction commences at a point randomly selected on the molecular chain. The UV-curing process was not adopted into the production process until recently. The process is now being used for such lubricant mixtures as A20H/Z-dol and A20H/Z-tetraol. In these mixtures, however, an electro- or photo-chemistry involving the phosphazene moiety of A20H appears to play a major role.[4] One negative issue with the far-UV curing process is production of ozone if oxygen is present.