Glass substrate for magnetic recording medium, magnetic recording medium, and method of manufacturing the same

• US 6,395,634 B1
• Filed: 03/31/2000
• Issued: 05/28/2002
• Est. Priority Date: 03/31/1999
• Status: Expired due to Term

• Current Assignee: Hoya Corporation
• Original Assignee: Hoya Corporation
• Inventors: Miyamoto, Takemi
• Primary Examiner(s): Zarabian, Amir
• Assistant Examiner(s): Pyonin, Adam
• Application Number:
  US09/540,888
• Time in Patent Office: 788 Days
• Field of Search: 438/481,478,691,690,756,723,743 428/1.32 218/80,97 65/30.14,30.1
• US Class Current: 438/691
• CPC Class Codes: C03C 15/00 Surface treatment of glass, not in the form of fibres or filaments, by etching etching or surface-brightening compositions, in general C09K13/00
• CPC Class Codes: C03C 19/00 Surface treatment of glass, not in the form of fibres or filaments, by mechanical means sand-blasting, grinding, or polishing glass B24
• CPC Class Codes: C03C 2204/08 Glass having a rough surface
• CPC Class Codes: C03C 3/083 containing aluminium oxide or an iron compound
• CPC Class Codes: G11B 5/7379 Seed layer, e.g. at least one non-magnetic layer is specifically adapted as a seed or seeding layer
• CPC Class Codes: G11B 5/73921 Glass or ceramic substrates
• CPC Class Codes: G11B 5/8404 manufacturing base layers

Abstract

In a method of manufacturing a glass substrate for a magnetic recording medium for forming a predetermined roughness, a principal surface of the glass substrate is precisely polished by the use of polishing material containing free abrasive grain. Remaining stress distribution for a portion of a polishing trace due to the free abrasive grain is generated on the surface of the glass substrate. A surface process is performed for at least the principal surface of the glass substrate by the use of hydrosilicofluoric acid. A portion having relatively high remaining distortion in the generated remaining stress distribution is decided as an island portion. The glass substrate is heated after precisely polishing before performing the surface process by the use of the hydrosilicofluoric acid.

Claims

1. A method of manufacturing a glass substrate for a magnetic recording medium for forming a predetermined roughness, comprising the steps of:

precisely polishing a principal surface of the glass substrate by the use of polishing material containing free abrasive grain,

generating remaining stress distribution for a portion of a polishing trace due to the free abrasive grain on the surface of the glass substrate,

performing a surface process for at least the principal surface of the glass substrate by the use of hydrosilicofluoric acid, and

deciding a portion having relatively high remaining distortion in the generated remaining stress distribution as an island portion,

the glass substrate being heated after precisely polishing before performing the surface process by the use of the hydrosilicofluoric acid.

4. A method as claimed in any one of the claim 1 or 2, wherein:

heating temperature in the heating process step falls within the range between 30°

C. and 180°

C.

5. A method as claimed in any one of the claim 1 or 2, wherein:

the heating process is carried out by the use of at least one selected from the group consisting of hot water, heated sulfuric acid, heated glycerin, and heated phosphoric acid.

6. A method as claimed in any one of the claim 1 or 2, wherein:

the glass substrate contains at least alkali metal oxide and alkali earth oxide, and

content of the alkali earth oxide is not exceeding 3 mol %.

7. A method as claimed in claim 6, wherein:

the glass constituting the glass substrate contains SiO₂ between 58 and 75 weight %, Al₂O₃ between 5 and 23 weight %, Li₂O between 3 and 10 weight %, and Na₂O between 4 and 13 weight % as main components.

8. A method as claimed in claim 7, wherein:

the glass contains SiO₂ between 62 and 75 weight %, Al₂O₃ between 5 and 15 weight %, Li₂O between 4 and 10 weight %, Na₂O between 4 and 12 weight %, and ZrO₂ between 5.5 and 15 weight % as main components, and

weight ratio of Na₂O/ZrO₂ falls within the range between 0.5 and 2.0 while weight ratio of Al₂O₃/ZrO₂ falls within the range between 0.4 and 2.5.

9. A method as claimed in any one of claim 1, 2, 3, 4, 5, 6 or 7, wherein:

a chemical strengthening process is carried out after the surface process using a hydrosilicofluoric acid.

10. A method of manufacturing a magnetic recording medium, wherein:

at least a magnetic layer is formed on the principal surface of the glass substrate manufactured by the method claimed in any one of claim 1 or 2.

2. A method of manufacturing a glass substrate for a magnetic recording medium for forming a predetermined roughness, comprising the steps of:

precisely polishing a principal surface of the glass substrate by the use of polishing material containing free abrasive grain,

generating remaining stress distribution for a portion of a polishing trace due to the free abrasive grain on the surface of the glass substrate,

chemically processing at least the principal surface of the glass substrate, and

deciding a portion having relatively high remaining distortion in the generated remaining stress distribution as an island portion,

the glass substrate being heated by dipping the glass substrate in heated solvent after precisely polishing but before chemically processing the principal surface.

3. A method as claimed in claim 2, wherein:

the chemical surface process comprises any one of an etching process by the use of solution containing hydrofluoric acid, solution containing hydrosilicofluoric acid, and alkali solution.