Two years ago, TDK already presented a Blu-ray disk with a 200 GB capacity. During the upcoming CEATEC conference, held in Japan on the 6th of October till the 10th, the company will show its latest prototype, which is capable of storing up to 320 GB of data. The secret behind this high capacity is the usage of ten layers, each with a 32 GB capacity. The usage of additional layers however makes it more difficult to read and write a disc. To keep the readability on the disc's outer layer above 90%, special materials are used. The L0 layer uses a silicium-copper alloy, while the layers L1 up to L9 are made of bismut and germaniumoxide. By varying the materials, TDK was able to keep each layer unique enough to identify it with a laser.
Last year, Pioneer was already capable of producing a 500 GB optical disc, spread over sixteen layers. Pioneer's model however could only be read, while TDK's disc can also be written to using Blu-ray burners. To read the TDK disc, a 405 nm blue laser is required, combined with a lens aperture of 0,85 (NA). Both specifications equal those found in conventional Blu-ray players. To burn the new disc however, a laser capacity of between 13 mW and 28 mW is required, which means not all of the current-generation Blu-ray burners will support writing data to the disc.
It's still unclear when we are to expect the first 320 GB Blu-ray discs at the local retailer.