Kao Corporation

Kenichi Suenaga

Toshiya Hagihara

Yoshiaki Oshima

Shigeo Fujii

Kazuhiko Nishimoto

Masahiko Suzuki

Makoto Suzuki

A polishing composition for a hard disk substrate includes alumina particles, silica particles, and water. The volume median diameter of secondary particles of the alumina particles measured by a laser beam diffraction method is 0.1 to 0.8 &#x3bc;m. The volume median diameter of primary particles of the silica particles measured by transmission electron microscope observation is 40 to 150 nm. The standard deviation in number-basis particle size of the primary particles of the silica particles measured by the transmission electron microscope observation is 11 to 35 nm. The polishing composition for a hard disk substrate can preferably reduce the embedding of alumina abrasive grains into the substrate without impairing the productivity.

Polishing composition for hard disk substrate

The present invention preferably provides a polishing composition for a hard disk substrate, containing aluminum oxide particles and water, wherein secondary particles of the aluminum oxide particles have a volume-median particle size of from 0.1 to 0.7 &#x3bc;m, and particles having particle sizes of 1 &#x3bc;m or more of the aluminum oxide particles are contained in an amount of 0.2% by weight or less of the polishing composition; and a method for manufacturing a hard disk substrate using the polishing composition. By using the polishing composition and the method for manufacturing a substrate of the present invention, for example, a hard disk substrate suitable for high recording density can be provided in high productivity.

A polishing composition for memory hard disk containing 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 in the range of particle sizes of from 40 to 100 nm satisfy the following formula (1): V&#x2267;0.5&#xd7;R+40 (1), wherein the particle size is determined by observation with a transmission electron microscope (TEM). The polishing composition of the present invention can be even more suitably used for the manufacture of a substrate for precision parts such as substrates for memory hard disks.

Polishing composition

A method for manufacturing a substrate, a polishing process for a substrate, a method of reducing microwaviness for a substrate, each including the step of polishing a substrate to be polished with a polishing composition containing an abrasive and water with a polishing pad of which surface member has an average pore size of from 1 to 35 &#x3bc;m; and a method of reducing scratches for a substrate, comprising the step of polishing a substrate to be polished with a polishing composition comprising an abrasive, an oxidizing agent, an acid, a salt thereof, or a mixture thereof and water, with a polishing pad of which surface member has an average pore size of from 1 to 35 &#x3bc;m. The method for manufacturing a substrate can be used for finish polishing of a memory hard disk or for polishing of a semiconductor element.

Method for manufacturing substrate

A polishing composition for a substrate for memory hard disk, comprising silica particles in an aqueous medium, wherein the silica particles satisfy a specified relationship between an average particle size of the silica particles on the number basis and a standard deviation on the number basis, wherein the average particle size is obtained by a determination by transmission electron microscope (TEM) observation, and wherein a particle size and a cumulative volume frequency in a range of particle sizes of from 60 to 120 nm satisfies a specified relationship; a method of reducing microwaviness of a substrate for memory hard disk, comprising the step of polishing the substrate for memory hard disk with the polishing composition; and a method for manufacturing a substrate for memory hard disk, comprising the step of polishing a Ni&#x2014;P plated substrate for memory hard disk with the polishing composition. The method can be suitably used for the manufacture of a substrate for precision parts, such as a substrate for memory hard disk.

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Wakayama, Japan

Kenichi Suenaga