Hybrid lubricant film with high bonding ratio and high coverage
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TECHNICAL PAPER
Hybrid lubricant film with high bonding ratio and high coverage Hiroshi Tani1
•
Yuki Uesaraie2 • Reguo Lu1 • Shinji Koganezawa1 • Norio Tagawa1
Received: 11 October 2019 / Accepted: 4 March 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A hybrid lubricant film was prepared from the perfluoropolyether (PFPE) lubricant (Moresco DDOH), with a single end group, and a PFPE film obtained by depositing the HT170 film via photoelectron-assisted chemical vapor deposition (PACVD). The frictional properties of the prepared film were evaluated using a pin-on-disk tester and compared with those of a Z-tetraol dip-coated film. This hybrid lubricant film showed a considerably high bonding ratio of * 100% after Vertrel rinsing and lower surface energy than those of Z-tetraol. The frictional coefficient of only the PACVD-treated HT170 film was considerably high. However, the hybrid lubricant film without the mobile fraction showed a friction coefficient equivalent to that of the Z-tetraol film having a mobile fraction of 40%.
1 Introduction The flying height of magnetic head sliders has been reduced to increase the aerial density of hard disk drives (HDDs). To reduce magnetic spacing between the head element and the magnetic layer of the disks, the thickness of the perfluoropolyether (PFPE) lubricant film should be decreased. The head flying stability in the near contact regime is affected by the interaction between the slider surface and lubricant film on a disk surface, resulting in lubricant pickup. Additionally, in the picked-up lubricant, a meniscus bridge may form between the air-bearing surface of the slider and disk surface. Shimizu et al. reported that the slider surface, with the small polar surface energy, treated with fluorine-ion implantation decreased touchdown power. They concluded that the fluorine-ion implantation treatment reduced the slider–lubricant interaction, decreasing the slider touchdown height (Shimizu et al. 2010). Sakane et al. (2006) found that the meniscus bridge of lubricant molecules with polar end groups was formed between the slider surface and disk surface at the slider touch down and take off. Their results confirmed that an ideal chemically bonded lubricant that does not have polar end groups increases the head–disk clearance, & Hiroshi Tani [email protected] 1
Kansai University, Suita-shi, Osaka 564-8680, Japan
2
Graduate School of Kansai University, Suita-shi, Osaka 564-8680, Japan
because a meniscus bridge does not form on this lubricant film. Therefore, disks with extremely low polar surface energies and high chemical bonding ratios will exhibit a wide head–media clearance. Moreover, it is necessary to achieve extremely low surface energy and high chemical bonding by using a lubricant film with a smaller thickness than the actual lubricant thickness, otherwise the head–disk clearance is reduced. On the other hand, a lubricant film with high thermal stability is required for heat-assisted
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