Bibliographic Details
| Title: |
POLISHING LIQUID COMPOSITION FOR MAGNETIC-DISK SUBSTRATE |
| Document Number: |
20110240594 |
| Publication Date: |
October 6, 2011 |
| Appl. No: |
13/133736 |
| Application Filed: |
December 18, 2009 |
| Abstract: |
There is provided a polishing composition for a magnetic disk substrate that can reduce scratches, nanoprotrusion defects, and substrate surface waviness after polishing. The polishing composition for a magnetic disk substrate that contains: a copolymer that has a constituent unit derived from a monomer having a solubility of 2 g or less in 100 g of water at 20° C. and a constituent unit having a sulfonic acid group, and has a saturated hydrocarbon chain as the main chain thereof, or a salt of the copolymer; an abrasive; and water. |
| Inventors: |
Hamaguchi, Takeshi (Wakayama, JP); Doi, Haruhiko (Wakayama, JP) |
| Claim: |
1. A polishing composition for a magnetic disk substrate, comprising: a copolymer that has a constituent unit derived from a monomer having a solubility of 2 g or less in 100 g of water at 20° C. and a constituent unit having a sulfonic acid group, and has a saturated hydrocarbon chain as the main chain thereof, or a salt of the copolymer; an abrasive; and water. |
| Claim: |
2. The polishing composition for a magnetic disk substrate according to claim 1, wherein the constituent unit derived from a monomer having a solubility of 2 g or less in 100 g of water at 20° C. is a constituent unit represented by the general formula (1) or (2): [chemical expression included] wherein R1 and R3 are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R2 is a hydrogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, or an aryl group, and R4 is a hydrocarbon chain having 1 to 22 carbon atoms. |
| Claim: |
3. The polishing composition for a magnetic disk substrate according to claim 1, wherein the constituent unit having a sulfonic acid group is represented by the general formula (3): [chemical expression included] wherein R5 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R6 is an aryl group having one or more sulfonic acid groups. |
| Claim: |
4. The polishing composition for a magnetic disk substrate according to claim 1, wherein the molar ratio of the constituent unit derived from a monomer having a solubility of 2 g or less in 100 g of water at 20° C. to the constituent unit having a sulfonic acid group in all the constituent units constituting the copolymer is 5/95 to 95/5. |
| Claim: |
5. The polishing composition for a magnetic disk substrate according to claim 1, wherein the copolymer has a weight-average molecular weight of 1000 to 100000. |
| Claim: |
6. The polishing composition for a magnetic disk substrate according to claim 1, wherein the abrasive satisfies the following conditions (a) and (b): (a) an average particle diameter measured at a detection angle of 90° by dynamic light scattering is of 1 to 40 nm; and (b) ΔCV (ΔCV=CV30−CV90) is 0 to 10%, where ΔCV is a difference between values of coefficients of variation (CVs), i.e., CV30 and CV90, CV30 is obtained by dividing a particle size standard deviation measured at a detection angle of 30° by dynamic light scattering by an average particle diameter measured at a detection angle of 30° by dynamic light scattering and multiplying the result by 100, and CV90 being obtained by dividing a particle size standard deviation measured at a detection angle of 90° by dynamic light scattering by an average particle diameter measured at a detection angle of 90° by dynamic light scattering and multiplying the result by 100. |
| Claim: |
7. The polishing composition for a magnetic disk substrate according to claim 1, wherein the abrasive satisfies the following conditions (c) and (d): (c) a sphericity measured by observation with a transmission electron microscope is 0.75 to 1; and (d) a value of surface roughness (SA1/SA2) is 1.3 or greater, where surface roughness (SA1/SA2) is obtained by dividing a specific surface area (SA1) measured by a sodium titration method by a specific surface area (SA2) converted from an average particle diameter (S2) measured by observation with a transmission electron microscope. |
| Claim: |
8. The polishing composition for a magnetic disk substrate according to claim 1, further comprising a heterocyclic aromatic compound, the heterocyclic aromatic compound comprising two or more nitrogen atoms in the heterocycle thereof. |
| Claim: |
9. The polishing composition for a magnetic disk substrate according to claim 1, wherein the magnetic disk substrate is a Ni—P-plated aluminum alloy substrate. |
| Claim: |
10. The polishing composition for a magnetic disk substrate according to claim 1, wherein the magnetic disk substrate is a glass substrate. |
| Claim: |
11. A method for producing a magnetic disk substrate, comprising the step of polishing a substrate to be polished by using the polishing composition according to claim 1. |
| Current U.S. Class: |
216/22 |
| Current International Class: |
11; 09 |
| Accession Number: |
edspap.20110240594 |
| Database: |
USPTO Patent Applications |
