http://patft.uspto.gov/netacgi/nph-...&RS=TTL/Cyanine

"
5. The optical recording medium of claim 1, wherein said transition metal M is selected from the group consisting of Fe, Co, Ni, Cu and Pt.

6. The optical recording medium of claim 5, wherein said transition metal M is Cu.
"


TDK 藍 was using Cu.............