Medium substrate, production method thereof and magnetic disk device
First Claim
1. A medium substrate for use as a substrate in magnetic recording mediums and the like, said medium substrate comprising silica (SiO2) glass having a purity of 99% or more as a main component, the silica glass being a sea component of phase-separated borosilicate glass having an islands-in-sea structure, and having on the surface thereof a continuous texture derived from the porous structure of the silica glass, the texture having a surface roughness Ra of 1 to 10 nm and a pore size of 5 to 250 nm.
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Abstract
A medium substrate comprising a borosilicate glass containing silica as a main component and having on the surface thereof a continuous texture derived from the porous structure, the medium substrate being used as a substrate in the production of a magnetic recording medium and other. The method for the production of the textured medium substrate is also disclosed, along with a magnetic recording medium using the medium substrate and a magnetic disk device.
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Citations
23 Claims
- 1. A medium substrate for use as a substrate in magnetic recording mediums and the like, said medium substrate comprising silica (SiO2) glass having a purity of 99% or more as a main component, the silica glass being a sea component of phase-separated borosilicate glass having an islands-in-sea structure, and having on the surface thereof a continuous texture derived from the porous structure of the silica glass, the texture having a surface roughness Ra of 1 to 10 nm and a pore size of 5 to 250 nm.
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10. A method for producing a medium substrate for use as a substrate in magnetic recording mediums and the like, said medium substrate comprising silica (SiO2) glass having a purity of 99% or more as a main component, the silica glass being a sea component of phase-separated borosilicate glass having an islands-in-sea structure, and having on the surface thereof a continuous texture derived from the porous structure of the silica glass, the texture having a surface roughness Ra of 1 to 10 nm and a pore size of 5 to 250 nm,
the method comprising the steps of: -
heat-treating a disk of borosilicate glass at a temperature of 500 to 750°
C. to cause phase separation, thereby forming the phase-separated borosilicate glass; and
treating the phase-separated borosilicate glass with an acid selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid and acetic acid to dissolve out an islands component from the phase-separated borosilicate glass and thereby render the borosilicate glass porous. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
Na2O 10 to 30% by weight, B2O3 10 to 30% by weight, and SiO2 50 to 80% by weight.
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13. A method for producing a medium substrate as recited in claim 12, wherein the sodium borosilicate glass comprises 10% by weight of Na2O, 30% by weight of B2O3 and 60% by weight of SiO2.
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14. The method for producing a medium substrate as recited in claim 10, wherein the borosilicate glass is lithium borosilicate glass formed starting from Li2O, B2O3 and SiO2.
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15. The method for producing a medium substrate as recited in claim 14, wherein the lithium borosilicate glass has the following composition:
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Li2O 5 to 30% by weight, B2O3 10 to 30% by weight, and SiO2 50 to 80% by weight.
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16. The method for producing a medium substrate as recited in claim 15, wherein the lithium borosilicate glass comprises 5% by weight of Li2O, 30% by weight of B2O3 and 65% by weight of SiO2.
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17. The method for producing a medium substrate as recited in claim 10, wherein the borosilicate glass is heat-treated at a temperature of 600 to 700°
- C. for 5 to 24 hours to control the pore size of the porous structure to the range from 5 to 250 nm.
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18. The method for producing a medium substrate as recited in claim 10, wherein after the borosilicate is heat-treated to cause phase separation, the acid treatment is performed while allowing a masking element to be present in the region exclusive of the landing zone of a magnetic head to selectively render the landing zone porous.
- 19. A magnetic recording medium comprising a substrate having applied thereon at least a magnetic recording layer, said substrate comprising silica (SiO2) glass having a purity of 99% or more as a main component, the silica glass being a sea component of phase-separated borosilicate glass having an islands-in-sea structure, and having on the surface thereof a continuous texture derived from the porous structure of the silica glass, the texture having a surface roughness Ra of 1 to 10 nm and a pore size of 5 to 250 nm.
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21. A method for producing a magnetic recording medium comprising a substrate having applied thereon at least a magnetic recording layer, in which said substrate comprises silica (SiO2) glass having a purity of 99% or more as a main component, the silica glass being a sea component of phase-separated borosilicate glass having an islands-in-sea structure, and having on the surface thereof a continuous texture derived from the porous structure of the silica glass, the texture having a surface roughness Ra of 1 to 10 nm and a pore size of 5 to 250 nm,
the method comprising the steps of: -
heat treating a disk of borosilicate glass at a temperature of 500 to 750°
C. to cause phase separation, thereby forming the phase-separated borosilicate glass; and
treating the phase separated borosilicate glass with an acid selected from the group consisting of nitric acid, sulfuric acid, hydrochloric acid and acetic acid to dissolve out an islands component from the phase-separated borosilicate glass, thereby producing said substrate.
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- 22. A magnetic disk device comprising a recording head part for recording information in a magnetic recording medium and a reproducing head part for reproducing the information, wherein the magnetic recording medium is a magnetic recording medium comprising a nonmagnetic substrate having provided thereon a magnetic recording layer and the substrate comprises silica (SiO2) glass having a purity of 99% or more as a main component, the silica glass being a sea component of phase-separated borosilicate glass having an islands-in-sea structure, and having on the surface thereof a continuous texture derived from the porous structure of the silica glass, the texture having a surface roughness Ra of 1 to 10 nm and a pore size of 5 to 250 nm.
Specification