Japanese public broadcaster Nippon Hoso Kyokai (NHK), working with Sony, has developed a prototype 1-inch disk drive that is thinner and has more storage capacity than similar drives on the market today.

NHK, Sony, and the University of Tokyo are developing the slim, high-capacity drives for use in portable devices such as mobile phones, according to Eiichi Miyashita, a senior research engineer at NHK's Science and Technical Research Laboratories (STRL). Mini hard drives are often used in portable music players as well, such as Apple Computer's iPod.

The new drives are 2.5 millimeters thick and store 10GB of data. This makes them half the thickness of the 1-inch drives sold by Hitachi Global Storage Technologies (HGST). The highest capacity 1-inch drives currently on sale store 6GB.

A number of Japanese cell phone makers plans to start selling phones in Japan in the first half of next year with tuners to receive digital terrestrial broadcasts. A 10GB drive would be enough to store about 100 minutes of programming, Miyashita said.

NHK and its partners have so far developed working prototypes of the drives. Miyashita declined to say when the drives are expected to go on sale.

Sony is providing technical support for the disk development, but declined to say whether it has plans to commercialize the technology.

"It's such a small disk technology. ... It's much more like a research and development project," said Sony spokesman David Yang.

Part of the secret behind the high capacity of the disks is the use of a perpendicular recording technology, Miyashita said.

Perpendicular recording is a method of storing information using magnetic fields to represent each bit. In disks that are commercially available today, the bits, or magnetic fields, lay flat on the disk surface. In drives using perpendicular recording, the bits stand vertically, or perpendicular to the disk. Because the bits take less space, more can be packed on the disk.

Several companies have announced that they will sell drives using perpendicular recording technology, including HGST, Toshiba, and Fujitsu.

NHK and Sony are also developing 0.85-inch disks using perpendicular recording technology, Miyashita said.