"A day after the announcement of a HD DVD-R disk format, Pioneer Corp. and Mitsubishi Kagaku Media Co. Ltd. jointly announced development of write-once disk for the Blu-ray Disc format.

The partners said they intend to propose the disk as the BD-R format to the Blu-ray Disc Association.

Mitsubishi Kagaku Media was one of the developers of the HD DVD-R disk. It developed a separate organic die to be used in the BD format disk, a company spokesman said.

Pioneer, which led development of the write-once DVD format, said it also intends to take the lead in developing a write-once disk for the BD format. Pioneer and Mitsubishi Chemical Media have been collaborating on disk development since last autumn as the drive and media makers.

The BD disk has a recording layer on its reflective layer. The recording layer was formed by spin coating the organic die. The layer is covered with a 0.1-mm-thick cover file. The single-layer disk has a capacity of 25 Gbytes. Disk jitter is 6 percent, and the reflection rate is 40 percent, which is almost the same level of BD-ROM disk, according to Mitsubishi Chemical Media.

The partner will present more detail at the ISOM/ODS '05 show in Hawaii next month. "