Polishing composition
AssigneeNissan Chemical Industries, Ltd.
InventorsIsao Ota, Tohru Nishimura, Gen Yamada
Life of this patent
Estimating the term…
Abstract
For aluminum disks and glass-made hard disks, those disks having a mean waviness of less than 3 Å are being desired in order to increase the density of memory capacity. The present invention provides polishing compositions that can give smoothly polished surfaces for the disks. The polishing compositions are polishing compositions for aluminum disks or substrates having silica on the surface thereof, which contain colloidal silica particle groups having different particle size distributions and have a SiO2 concentration of 0.5 to 50% by weight.
Claims7
A polishing composition containing a silica sol for an aluminum disk, comprising:
- a colloidal silica particle group having a monomodal numerical particle size distribution with primary particle sizes of 80 to 120 nm as observed on a transmission electron microscope being 90% or more of the total particle number, and having a mean particle size Da (particle size measured with the nitrogen adsorption method) in the range of 65 to 100 nm (referred to as colloidal silica particle group (a) hereinafter),
- a colloidal silica particle group having a monomodal numerical particle size distribution with primary particle sizes of 20 to 40 nm as observed on a transmission electron microscope being 90% or more of the total particle number, and having a mean particle size Dc (particle size measured with the nitrogen adsorption method) in the range of 15 to 25 nm (referred to as colloidal silica particle group (c) hereinafter), and
- a colloidal silica particle group having a monomodal numerical particle size distribution with primary particle sizes of 5 to 15 nm as observed on a transmission electron microscope being 90% or more of the total particle number, and having a mean particle size Dd (particle size measured with the nitrogen adsorption method) in the range of 8 to 12 nm (referred to as colloidal silica particle group (d) hereinafter),
- wherein said composition has a SiO2 concentration of 0.5 to 50% by weight, a water dispersed stable silica sol with the weight ratio of said colloidal silica particle group (a), said colloidal silica particle group (c) and said colloidal silica particle group (d) of W(a):W(c):W(d)=1:0.05 to 9.0:0.01 to 1.4, and the ratio Of Dc/Da of 0.15 to 0.38 and the ratio of Dd/Dc of 0.26 to 0.80.
A polishing composition for a substrate with silica on the surface, comprising:
- a colloidal silica particle group having a monomodal numerical particle size distribution with primary particle sizes of 80 to 120 nm as observed on a transmission electron microscope being 90% or more of the total particle number, and having a mean particle size Da (particle size measured with the nitrogen adsorption method) in the range of 65 to 100 nm (referred to as colloidal silica particle group (a) hereinafter),
- a colloidal silica particle group having a monomodal numerical particle size distribution with primary particle sizes of 20 to 40 nm as observed on a transmission electron microscope being 90% or more of the total particle number, and having a mean particle size Dc (particle size measured with the nitrogen adsorption method) in the range of 15 to 25 nm (referred to as colloidal silica particle group (c) hereinafter), and
- a colloidal silica particle group having a monomodal numerical particle size distribution with primary particle sizes of 5 to 15 nm as observed on a transmission electron microscope being 90% or more of the total particle number, and having a mean particle size Dd (particle size measured with the nitrogen adsorption method) in the range of 8 to 12 nm (referred to as colloidal silica particle group (d) hereinafter),
- wherein said composition a SiO2 concentration of 0.5 to 50% by weight, a water dispersed stable silica sol with the weight ratio of said colloidal silica particle group (a), said colloidal silica particle group (c) and said colloidal silica particle group (d) of W(a):W(c):W(d)=1:0.05 to 9.0:0.01 to 1.4, and has the ratio of Dc/Da of 0.15 to 0.38 and the ratio of Dd/Dc of 0.26 to 0.80.
Dependencies are inferred from the claim text.