Toshiba has announced that it has perfected the manufacture of double layered 30GB HD-DVD-R discs, doubling the previous capacity.

The new design was approved by the DVD Forum's Steering Committee on 14 September, and the discs will be available in the spring of next year. It allows for 15GB of data to be stored on each layer on the disc.

Toshiba's move is important because capacity is one of the chief advantages of the rival Blu-Ray system. However, there will be no Blu-Ray DVD-R specification until at least October.

The new technique uses a specially developed organic dye which penetrates the DVD substrate in a similar way to traditional DVDs. Toshiba believes that the new technique can be built into current manufacturing systems at little extra cost.