A group headed by Toshiba says it has successfully developed the way to make single-recording, high-definition DVDs using existing DVD production methods.

It is the latest move against rivals Sony in a tit-for-tat war to be the format of choice for future DVDs.

Hitachi Maxell and Mitsubishi Chemical Corp said the HD-DVD-R disc, which can only record once, uses a special dye.

The organic dye is especially sensitive to narrow wavelengths of blue lasers needed to put data onto high-def DVDs.

Both Toshiba and Sony have been pushing different DVD formats which has so far split movie studios and technology firms.

Toshiba is promoting its HD-DVD format, while Sony is touting its Blu-ray Disc (BD) technology.

"By combining our cumulative know-how in high-density optical disc technology with the breakthrough of the new dye, we have tested and proven the manufacturability of HD-DVD-R discs," said Norio Ota from Hitachi Maxell.

He added that the discs would be ready in time for the release of its HD-DVD recorders and PCs with HD-DVD drives, early in 2006.

Sony said Blu-ray-based write-once discs could be available as early as the end of 2005.

More sensitive

The developers, two of Japan's top makers of optical disc media, say it is the first time a mass-production process has been successfully demonstrated using current DVD production line methods.

This is important because it means next-generation HD-DVD disc formats will not require entirely new production facilities, which could be costly.

The organic dye was developed by Hayashibara Biochemical Laboratories, a key manufacturer of dyes for DVD-R discs.

Current DVD-R DVDs use a photosensitive organic dye as the data storage medium in their recording layer.

The next generation of DVD players use blue laser light which has a shorter wavelength than red light used for current DVDs and CDs.

In a comment aimed at the rival Sony-led format, senior Toshiba researcher Hisashi Yamada said the breakthrough had been possible because the HD-DVD format was based on the same disc structure and design as current DVDs.

Avoiding war

Toshiba and Sony both have big name backers in the technology and entertainment industries.

Discs that can be recorded onto once only are extremely important to the industries which rely on optical disc technology.

They account for 87% of the current recordable DVD-R market, according to Toshiba, compared to re-writeable discs (DVD-RW) which can be recorded onto multiple times.

DVD-Rs are cheaper to produce, and to buy, and are most commonly used for storing or backing up digital data, like images or film.

Both Toshiba and Sony want to avoid a format war, but say their technology is the most suitable and robust for the next generation of DVDs which will store much more data.

The two groups had been in talks to develop a hybrid format, but no compromise has so far been reached.

High-definition images are extremely crisp when viewed on suitable equipment, and offer 3D-like quality pictures.

Films and games in high-definition formats will start to appear for sale next year, and will be an extremely lucrative market for the entertainment and software industry.

Sony's PlayStation 3 will come with a BD drive for high-definition discs.

Players compatible for the formats are already on sale in Japan, but will not hit western markets until next year.

In May, TDK, one of the manufacturers in Sony's BD camp, said it had produced a four-layer BD which means it can hold 100Gb of data.

Earlier that month, Toshiba had introduced a three-layer HD-DVD disc capable of storing 45Gb.