| 摘要 |
A polishing composition for a substrate for memory hard disk comprising water and silica particles, wherein the silica particles have a particle size distribution in which the relationship of a particle size (R) and a cumulative volume frequency (V) in a graph of particle size-cumulative volume frequency obtained by plotting a cumulative volume frequency (%) of the silica particles counted from a small particle size side against a particle size (nm) of the silica particles satisfies the above formula (1) and the above formula (2), and wherein a particle size at 90% of a cumulative volume frequency (D90) is within the range of 65 nm or more and less than 105 nm. By using the polishing composition of the present invention, there can be efficiently manufactured an Ni-P plated substrate for a disk polished to have an excellent surface smoothness, in which the micropits are effectively reduced.
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