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 253.7 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%, 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.