Bibliographic Details
| Title: |
Polishing composition for magnetic disk substrate |
| Document Number: |
20070254563 |
| Publication Date: |
November 1, 2007 |
| Appl. No: |
11/790615 |
| Application Filed: |
April 26, 2007 |
| Abstract: |
A polishing composition for a magnetic disk substrate of the present invention includes water, silica particles, and at least one or more selected from an acid, a salt of the acid, and an oxidizing agent. The silica particles are observed with a transmission electron microscope to measure a maximum diameter and a projected area of each particle, and a value obtained by dividing the area of a circle whose diameter is the maximum diameter of a silica particle by the projected area of the silica particle and multiplying the result by 100, is in the range of 100 to 130. |
| Inventors: |
Oshima, Yoshiaki (Wakayama, JP); Yamaguchi, Norihito (Wakayama, JP); Doi, Haruhiko (Wakayama, JP) |
| Claim: |
1. A polishing composition for a magnetic disk substrate comprising: water; silica particles; and at least one or more selected from the group consisting of an acid, a salt of the acid, and an oxidizing agent, wherein the silica particles have a value in the range of 100 to 130, wherein the value is obtained by dividing an area of a circle whose diameter is the maximum diameter of the silica particle by the projected area of the silica particle and multiplying the result by 100, when observed with a transmission electron microscope to measure the maximum diameter and the projected area of each particle. |
| Claim: |
2. The polishing composition according to claim 1, wherein in a graph of particle size versus cumulative volume frequency obtained by plotting a cumulative volume frequency (%) of the silica particles from a smaller particle size side against a particle size (nm) of the silica particles measured by transmission electron microscope observation, the cumulative volume frequency (V) and the particle size (R) satisfy the following formula (1): V≧0.5×R+40 (1) where R is in a range of 40 to 100 nm, and the cumulative volume frequency of the silica particles with a particle size of 15 nm is 20% or less. |
| Claim: |
3. The polishing composition according to claim 1, wherein the silica particles are colloidal silica. |
| Claim: |
4. The polishing composition according to claim 1, wherein an acid value of the polishing composition is 10 mgKOH/g or less. |
| Claim: |
5. The polishing composition according to claim 1, wherein a content of the oxidizing agent is 0.1 to 1 wt %. |
| Claim: |
6. The polishing composition according to claim 1, wherein the silica particles have a value in the range of 100 to 130, and the value is obtained by dividing an area of a circle whose circumference is a perimeter of the silica particle by the projected area of the silica particle and multiplying the result by 100, when observed with a transmission electron microscope to measure the perimeter and the projected area of each particle. |
| Claim: |
7. A method for manufacturing a magnetic disk substrate comprising: a step of polishing a substrate to be polished with a polishing composition comprising water, silica particles, and at least one or more selected from the group consisting of an acid, a salt of the acid, and an oxidizing agent, wherein the silica particles have a value in the range of 100 to 130, wherein the value is obtained by dividing an area of a circle whose diameter is the maximum diameter of the silica particle by the projected area of the silica particle and multiplying the result by 100, when observed with a transmission electron microscope to measure the maximum diameter and the projected area of each particle. |
| Claim: |
8. The method according to claim 7, wherein in a graph of particle size versus cumulative volume frequency obtained by plotting a cumulative volume frequency (%) of the silica particles from a smaller particle size side against a particle size (nm) of the silica particles measured by transmission electron microscope observation, the cumulative volume frequency (V) and the particle size (R) satisfy the following formula (1): V≧0.5×R+40 (1) where R is in a range of 40 to 100 nm, and the cumulative volume frequency of the silica particles with a particle size of 15 nm is 20% or less. |
| Claim: |
9. The method according to claim 7, wherein the silica particles are colloidal silica. |
| Claim: |
10. The method according to claim 7, wherein the substrate to be polished is polished at a polishing pressure of 11.7 to 20 kPa in the polishing step. |
| Claim: |
11. The method according to claim 7, further comprising a final polishing step of polishing the substrate to be polished at a polishing pressure of less than 11.7 kPa after polishing the substrate to be polished at a polishing pressure of 11.7 to 20 kPa in the polishing step. |
| Claim: |
12. The method according to claim 7, wherein the silica particles have a value in the range of 100 to 130, and the value is obtained by dividing an area of a circle whose circumference is a perimeter of the silica particle by the projected area of the silica particle and multiplying the result by 100, when observed with a transmission electron microscope to measure the perimeter and the projected area of each particle. |
| Current U.S. Class: |
451/60 |
| Current International Class: |
24; 24 |
| Accession Number: |
edspap.20070254563 |
| Database: |
USPTO Patent Applications |
