IP Library › Granted Patent US 8,088,466
Granted Patent B2
US 8,088,466 · App. 12/705,218 · Granted Jan 3, 2012

Metal alloys for the reflective or the semi-reflective layer of an optical storage medium

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Quick Facts
Patent No.
US 8,088,466
App. No.
12/705,218
Granted
Jan 3, 2012
Kind
B2
Abstract

A silver-based alloy thin film is provided for the semi-reflective coating layer of optical discs. Alloy additions to silver include copper and a rare earth metal. These alloys have moderate to high reflectivity and reasonable corrosion resistance in the ambient environment.

Claims (28)

1. An optical storage medium, comprising:

a first layer having a pattern of features in at least one major surface;

a reflective layer;

a second layer having a pattern of features in at least one major surface; and

a semi-reflective layer including a metal alloy, said metal alloy including silver, copper, and an element R from the group consisting of terbium, thallium, thulium, ytterbium, gadolinium, and holmium;

wherein the relationship between the amounts of silver, copper, and the element R is defined by Ag x Cu y R z ; and

wherein x is between about 0.85 and about 0.9998, y is between about 0.0001 and about 0.10, and z is between about 0.0001 and about 0.05.

2. The medium of claim 1 , wherein the rare earth metal is terbium.

3. The medium of claim 1 , wherein the rare earth metal is thallium.

4. The medium of claim 1 , wherein the rare earth metal is thulium.

5. The medium of claim 1 , wherein the rare earth metal is ytterbium.

6. The medium of claim 1 , wherein the rare earth metal is gadolinium.

7. The medium of claim 1 , wherein the rare earth metal is holmium.

8. Apparatus for making an optical storage medium, the apparatus comprising, in combination:

a first layer having a pattern of features in at least one major surface;

means for sputtering a reflective layer onto the first layer;

a second layer having a pattern of features in at least one major surface;

a target comprising a metal alloy; and

means for sputtering a semi-reflective layer from the target onto the second layer;

wherein the metal alloy comprises silver, copper, and an element R from the group consisting of terbium, thallium, thulium, ytterbium, gadolinium, and holmium;

wherein the relationship between the amounts of silver, copper, and the element R is defined by Ag x Cu y R z ; and

wherein x is between about 0.85 and about 0.9998, y is between about 0.0001 and about 0.10, and z is between about 0.0001 and about 0.05.

9. The apparatus of claim 8 , wherein the rare earth metal is terbium.

10. The apparatus of claim 8 , wherein the rare earth metal is thallium.

11. The apparatus of claim 8 , wherein the rare earth metal is thulium.

12. The apparatus of claim 8 , wherein the rare earth metal is ytterbium.

13. The apparatus of claim 8 , wherein the rare earth metal is gadolinium.

14. The apparatus of claim 8 , wherein the rare earth metal is holmium.