Japan's Matsushita Electric Industrial has developed a two-sided optical rewritable disc that can store 100GB. The technology used would make DVD compatibility difficult, but Matsushita hopes the format will be used for the next generation of DVD discs. The disc could store more than two hours of high-definition video and could also be used for data. Matsushita said it would present its research on Friday at the International Symposium on Optical Memory in Taipei, Taiwan. Mainstream DVDs store about 4.7GB per disc. Matsushita's disc is dual-layer and double-sided, with a capacity of 50GB on each side. The company used a set of violet lasers with a wide numerical aperture (NA) of 0.85, which helps focus the light more tightly, and a thin 0.1 nanometer (nm) cover layer on the disc, the company said. The same technology has also been used by Hitachi in a development project and in the DVR-Blue recordable disc format created by Sony and Phillips Electronics. DVR-Blue and other methods using blue or violet lasers aren't compatible with current DVDs, but they factor in the debate over the next-generation recordable DVD standard. Other companies are also working on ultra high capacity discs. Constellation 3D expects its partners, including Plasmin, to next year ship products based on its Fluorescent Multi-layer Disc (FMD) technology, which in its first generation will allows CD-sized discs to store up to 100GB of data. Second-generation FMD technology, using blue lasers, is expected to increase this figure to 1 terabyte. See the Hardware News Section for full coverage. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the Chips Central forum Let the editors know what you think in the Mailroom. And read other letters.