Effect of Ultraviolet Irradiation on Adhesion of Nanometer-Thick Lubricant Films Coated on Magnetic Disk Surfaces

Abstract

By measuring force-distance curves with an environmental scanning probe microscope (SPM), we quantitatively evaluated the effect of ultraviolet (UV) irradiation on the adhesive properties of nanometer-thick perfluoropolyether (PFPE) Z03 films coated on magnetic disks. The experimental results indicated that UV irradiation shows negligible influence on the adhesion of the disk surface and on the adhesion of the mobile fraction contained in the UV-irradiated Z03 films. The effect of UV irradiation on the adhesion of Z03 films is essentially achieved by its effect that improves the bonding of the Z03 molecules to the disk surfaces. As the bonding ratio increased with UV irradiation, the adhesive force measured on the 2-nm-thick PFPE Z03 films initially decreased, but it increased after reaching a minimum at a bonding ratio of about 0.6. This is possibly attributed to the increase of the meniscus force caused by decreased mobile lubricant thickness and the decrease of the van der Waals force between the SPM probe and the sample surfaces caused by increased bonded lubricant thickness.

Fabricating Nanometer-Thick Simultaneously Oleophobic/Hydrophilic Polymer Coatings via a Photochemical Approach

“…More recently, as shown in Scheme , Nakakawaji proposed that both the excitation of the substrate and the excitation of the PFPE contribute to the bonding between PFPE and the substrate under UV irradiation. Regardless of the exact mechanism that requires further investigation, our results are in line with the previous reports − showing that UV irradiation results in the covalent bonding between Z-03 and the silica substrate.…”

“…Indeed, it has been reported extensively in the past 25 years that UV will induce covalent bonding between PFPEs and solid substrates. − It is beyond the scope of the current paper to comprehensively review the previous results on this topic. Here we only briefly discussed the key findings.…”

Analysis of elastic contact due to meniscus adhesion force

“…筆者ら の動的吸着力の測定実験では， 半径が 1 および 2 mm のガラス球を用いており， また Tani らの論文 Tagawa, 2012, Tani, et al, 2013)では半径 1.82 mm のガラス球を， Zhang らの実験 (Zhang, et al, 2007) (Zhang, et al, 2011 Iteration number Penetration  [10 nm]…”