M-DISC™ DATA LAYER STABILITY
The Data Layer
The M-DISC™ data layer is a nano-scale, multi-layer structure consisting of metals and other inorganicmaterials. It is substantially different from the conventional organic dye-based disc in that it was designed
from the beginning to last for centuries without the failure points common to conventional Blu-rays andDVDs. Oxidation of the nano-scale data layer in the M-DISC™ during long-term storage is the only potential
cause of data loss that is a concern as long as the polycarbonate substrate survives.
The materials used in the M-DISC™ data layer are extremely resistant to oxidation. Even so, if enoughoxidation occurs over the centuries, the M-DISC™ could still become unreadable at some point in time.
Determining the maximum rate of oxidation is the key to determining the lifetime of the M-DISC™.

Measuring Longevity
Measuring M-DISC™ performance to directly determine the longevity is a challenge. When somethingchanges very slowly, taking meaningful measurements requires a long period of time. The data layer isso resistant to oxidation that observable changes in an M-DISC™ stored under normal conditions are still
barely detectable after months. One way to deal with this challenge is to make a worst-case estimate of thelifetime using well-known theories and data and then test the results against measured data to see if theestimate is useful. Oxidation of the metal layers is the probable failure mechanism. Theorists agree that theoxidation of metals like those used in the M-DISC™ proceeds logarithmically. The bare metal forms a thin,nano-scale oxide layer very quickly. This oxide layer then protects the rest of the metal layer from furtheroxidation. If this is the correct physical model for oxidation of the M-DISC™ data layer, the M-DISC™
reflectivity over time should look like the curve shown in Figure 1. Most of the change in reflectivity would
occur in the first few months after the disc is manufactured.

Greater than 10,000 Years
A worst-case scenario for failure in the data layer would be a critical loss in reflectivity as the metals in theM-DISC™ slowly oxidize. Failure would occur when the reflectivity dropped below the minimum specification of

18%. Figure 1 shows the reflectivity curve we would expect to see due to oxidation if the M-DISC™ data layers
reach a reflectivity of 18% after 10,000 years. The curve shows that if the M-DISC™ was readable for only 10,000years, we would expect to see it lose more than 3% reflectivity

32

after aging only 50 days. A 3% change
is easily measureable. Of course, if thereflectivity changed at a slower rate,
the M-DISC™ could be expected tolast even longer. The actual observedreflectivity change is less than 1% after
300 to 350 days (as shown with the3035282630242502,000

Days

graph inset into Figure 1) indicating
theactualperformanceofthe

4,000

20M-DISC™ data layer is significantly
better than our worst-case scenario.

15The obvious conclusion is that thedata on an M-DISC™ should be

10

readable for greater than 10,000

02,0004,000years when stored in an ordinary, dry,room-temperature environment.

6,000

8,000

10,000Years
Figure 1

Polycarbonate: Stable for 1,000 Years
Since it is doubtful that the polycarbonate substrate materials can endure for that length of time, the substratematerials must be the actual weak link in the M-DISC™ structure. Studies of the long-term durability ofpolycarbonate concluded that the substrate materials in Blu-rays and DVDs should be reliable for atleast 1,000 years. Therefore, a lifetime estimate of at least 1,000 years, limited by the durabilityof the polycarbonate substrate, is very reasonable.

M-DISC

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