TDK has developed a prototype optical disc that can hold up to 320GB of information - that's more than six times the current highest-capacity media available.

The 12cm disc has 10 recording layers, each of which can store 32GB. In comparison a Blu-ray Disc can hold 25GB on each layer, and a dual-layer disc is the highest capacity generally available at present.

As more layers are added to a disc it becomes more difficult to reliably read and write data because the laser has to shine through the layers. To help get around this, TDK engineers created a disc that uses clearer plastic so that more light can be shone through.

The disc improves on a 200GB prototype that was shown by TDK in 2006, but holds less data than a 400GB prototype disc that was presented by Pioneer last year. The Pioneer disc packed 16 recording layers onto a conventional 1.1mm thick, 12cm disc.

All three prototypes have something in common: their manufacturers have announced no plans to commercialise the discs. Their use in Blu-ray Disc players and recorders would require standardisation efforts at the Blu-ray Disc Association and likely minor hardware changes in disc drives. So for now they serve as an indicator to where optical disc technology stands in the research laboratory.