Fluid dynamic bearing, spindle motor, and disk drive device

Abstract

[Object] To provide a fluid dynamic bearing filled with a lubricating oil composition containing a base oil and an ionic liquid, and to provide a spindle motor with evaporation being suppressed in the lubricating oil composition provided in the fluid dynamic bearing by incorporating the fluid dynamic bearing in the spindle motor, and thus occurrence of a read-write error in an HDD can be suppressed, and a disk drive device including the spindle motor. [Solution means] A fluid dynamic bearing filled with a lubricating oil composition containing a base oil and an ionic liquid, the ionic liquid including at least one cation selected from the group consisting of tetraalkylammonium cations and at least one anion selected from the group consisting of borate anions represented by Formulas (C-1) to (C-3): (where in the formula, R9 to R12 each independently represent a linear or branched alkyl group.)

Dependencies are inferred from the claim text.