Sony & Toppan Printing, a large Japanese printing company, have developed a Blu-ray disc based on a paper substrate which promises to be more environmentally friendly and secure when destroyed than traditional discs.

The Blu-ray disc uses a blue laser to achieve a storage capacity of around 25GB, around five times that of current DVD discs. It is one of a number of new optical disc storage formats that are being targeted at areas such as high-definition video storage.

In a Blu-ray disc the recording layer on which the data is stored lies under a 0.1mm protective layer and on top of a 1.1mm thick substrate. The substrate is the basic surface on which a material adheres and is usually made of a polycarbonate plastic, but the new disc replaces this with paper. The result is a disc of which paper makes up approximately 51 percent of its weight, Sony says.

The disc is only a prototype at this stage and the companies are planning to reveal full details of their work at the Optical Data Storage 2004 conference scheduled to run from April 18 to April 21 in Monterey, California.

By replacing plastic with paper the companies hope to produce a more environmentally friendly and more secure disc, said Taro Takamine, a spokesperson for Sony in Tokyo.

"Oil is a limited resource but paper can be recycled," he says. "One of the initial advantages of the paper disc will be a decrease in the amount of raw material needed to produce a disc."

By replacing most of the plastic in a disc with paper it could also aid recycling of products such as magazines bundled with discs.

The paper disc can also be more easily cut with a pair of scissors and that will make it much easier for users to destroy discs in order to protect their data.

The next step for the two companies is to investigate mass production techniques and possibly realise another goal of the project: a cheaper Blu-ray disc. Blank Blu-ray discs are currently sold for around £18 each.