Claims
- 1. A glass substrate for a magnetic disk, comprising:a glass substrate having an information recording surface which is formed in the surface of the glass substrate, wherein the surface part of the glass substrate is substantially free from a chemical strengthening layer, and wherein said glass substrate contains a rare earth element which increases the mechanical strength of the glass substrate, the rare earth element being selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb and Lu and being contained in an amount of 3 to 10 weight % on the basis of conversion to Ln2O3 (Ln=rare earth element), and a transition metal oxide.
- 2. The glass substrate for a magnetic disk according to claim 1, wherein the transition metal oxide is CoO.
- 3. A glass substrate for a magnetic disk according to claim 1, wherein the glass substrate containsSiO2: 50 to 80 weight %, B2O3: 0 to 15 weight %, R2O (the R=alkali metal element): 0 to 20 weight %, Ln2O3 (Ln=rare earth element): 3 to 10 weight %, Al2O3: 0.5 to 15 weight %; and CoO: 1 to 30 weight % on the basis of oxide conversion.
- 4. The glass substrate for a magnetic disk according to claim 1, wherein the rare earth element is selected from the group consisting of Gd and Er.
- 5. The glass substrate for a magnetic disk according to claim 1, wherein the transition metal oxide is an oxide of a transition metal element selected from the group consisting of titanium, vanadium, chrome, manganese, cobalt, nickel, copper, gold and silver.
- 6. The glass substrate for a magnetic disk according to claim 1, wherein the transition metal oxide is CoO and is contained in an amount of 1 to 30 weight %.
- 7. The glass substrate for a magnetic disk according to claim 1, wherein Ln2O3 is selected from the group consisting of Gd2O3 and Er2O3.
- 8. The glass substrate for a magnetic disk according to claim 1, wherein the glass substrate has a transmittance of 10% or less to light having a wavelength of 300 to 2000 nm measured when a thickness of the glass substrate is 0.635 nm.
- 9. A glass substrate for a magnetic disk, comprising:a glass substrate having an information recording surface which is formed in the surface of the glass substrate, wherein the glass substrate contains a rare earth element which increases the mechanical strength of the glass substrate, the rare earth element being selected from the group consisting of La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Er, Tm, Yb and Lu and being contained in an amount of 3 to 10 weight % on the basis of conversion to Ln2O3 (Ln=rare earth element), and a transition metal oxide.
- 10. The glass substrate for a magnetic disk according to claim 9, wherein the transition metal oxide is CoO.
- 11. The glass substrate for a magnetic disk according to claim 9, wherein the rare earth element is selected from the group consisting of Gd and Er.
- 12. The glass substrate for a magnetic disk according to claim 9, wherein the transition metal oxide is CoO and is contained in an amount of 1 to 13 weight %.
- 13. The glass substrate for a magnetic disk according to claim 12, wherein the surface part of the glass substrate is substantially free from a chemical strengthening layer.
- 14. The glass substrate for a magnetic disk according to claim 9, wherein Ln2O3 is selected from the group consisting of Gd2O3 and Er2O3.
- 15. The glass substrate for a magnetic disk according to claim 9, wherein the glass substrate has a transmittance of 10% of less to light having a wavelength of 300 to 2000 nm measured when a thickness of the glass substrate is 0.635 nm.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9-198184 |
Jul 1997 |
JP |
|
Parent Case Info
This application is a continuation of U.S. Ser. No. 09/795,085, filed Mar. 1, 2001, now U.S. Pat. No. 6,577,472, which is a continuation of U.S. Ser. No. 09/121,531, filed Jul. 24, 1998, now abandoned.
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Continuations (2)
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Number |
Date |
Country |
Parent |
09/795085 |
Mar 2001 |
US |
Child |
10/408444 |
|
US |
Parent |
09/121531 |
Jul 1998 |
US |
Child |
09/795085 |
|
US |