Masashi IMAMURA’s research while affiliated with Nagoya University and other places

A self-organized patterning method for molecularly thin liquid polymer films on solid surfaces has been demonstrated. In contrast to conventional methods that prepattern solid surfaces and then use the patterns as templates for polymer films, this method utilizes self-organization of polymers induced by ultraviolet (UV) radiation through a mask, thereby directly patterning the polymer films and omitting the prepatterning process. Such UV irradiation locally modified the interaction between polymer films and solid surfaces. As a result, molecular flow occurred at the boundary between the irradiated and nonirradiated areas, leading to three-dimensional surface structures.

To create functionalized tribological surfaces utilizing the effect of nano-textures, we have proposed a method in which nanometer-thick perfluoropolyether lubricant films coated on solid surfaces were irradiated with 172 nm ultraviolet (UV) rays through a photo mask in nitrogen atmosphere. By measuring the thickness profiles of the lubricant films at the boundary of non-UV-irradiated and UV-irradiated areas, we found that lubricant molecules in the non-UV-irradiated area spread toward the UV-irradiated area with time and stable concave-convex film structures are obtained at the equilibrium state. We experimentally demonstrated that desirable three-dimensional lubricant textures can be formed using this UV-induced lubricant spreading (lubricant redistribution) phenomenon. The optimum conditions for forming lubricant textures are also discussed.

To tailor the characteristics of molecularly thin lubricant films, magnetic disk surfaces coated with nanometer-thick perfluoropolyether AM 3001 lubricant films were irradiated with 184.9 and 253.7 nm ultraviolet (UV) rays. We elucidated the effect of UV irradiation on the interactions between the lubricant and the magnetic disk surface via surface energy, bonded lubricant thickness and lubricant spreading measurements for films with and without UV irradiation. We found that UV irradiation decreased the dispersive and polar surface energies of the lubricant films by 20 and 80 percent, respectively ; increased bonded lubricant thickness ; and decelerated lubricant spreading. These results indicated that dispersion and polar interactions between lubricant molecules and the magnetic disk surface were strengthened by UV irradiation.

To tailor the characteristics of molecularly thin lubricant films, magnetic disk surfaces coated with nanometer-thick perfluoropolyether AM3001 lubricant films were irradiated with 184.9 and 253.7nm ultraviolet (UV) rays. We elucidated the effect of UV irradiation on the interactions between the lubricant and the magnetic disk surface via surface energy, bonded lubricant thickness and lubricant spreading measurements for films with and without UV irradiation. We found that UV irradiation decreased the dispersive and polar surface energies of the lubricant films by 20 and 80%, respectively; increased bonded lubricant thickness; and decelerated lubricant spreading. These results indicated that dispersion and polar interactions between lubricant molecules and the magnetic disk surface were strengthened by UV irradiation.

To tailor the characteristics of molecularly thin lubricant films, magnetic disk surfaces coated with nanometer-thick perfluoropolyether AM3001 lubricant films were irradiated with 172nm ultraviolet (UV) rays through a photo mask in nitrogen atmosphere. By measuring the time-dependent thickness profiles, we found that lubricant molecules in the non-UV-irradiated area spread toward the UV-irradiated area until the re-distributed lubricant thickness reaches an equilibrium state. We also confirmed that three-dimensional lubricant textures can be formed on magnetic disk surfaces utilizing the UV-induced film re-distribution phenomenon.

In this study, we investigated the effect of ultraviolet (UV) irradiation on the thickness stability of molecularly thin lubricant films over magnetic disk surfaces. Step-shaped multilayer (3.5-nm-thick) and monolayer (2-nm-thick) perfluoropolyether AM3001 films were dip-coated on magnetic disk surfaces, respectively, and then exposed to 172-nm UV rays through a photomask. We measured the time-dependent thickness profiles of the lubricant films in the UV-irradiated and non-UV-irradiated regions, respectively. By comparing the profiles, we found that for non-UV-irradiated multilayer films, lubricant thickness decreased with time due to the relaxation process, whereas for UV-irradiated multilayer films, the relaxation process was suppressed because of the increased intermolecular interactions. For monolayer films, the relaxation process was not observed regardless of UV irradiation.