Sony will release next month in Japan the world's first BD-R XL discs with a capacity of 128GB, just in time for the first 4K satellite broadcasts in the country.

The price of the "BNR4VAPJ4" disc is expected to be about 1,500 yen ($13.4) per disc, with sony to also offer 3-pack and 5-pack options for 3,900 yen ($34.8) and 6,000 yen ($53.5), respectively.

Until now, BDXL recordable discs featured 3 recording layers and a maximum capacity of 100GB. Sony says that adding an extra recording layer required a combination of "unique" materials in order to ensure a strong signal from all four layers of the new disc, even at 4X burning speeds.

Besides the accurate and stable "burning" of the data marks on the disc while recording, optimizing the reflectivity and transmittance of each recording layer is required in order to achieve reliable playback. Sony reduced the recording marks by about 78.5% as compared to the shortest mark length of a 2-layer disc structure, which is translated to a shortest recording mark length of 0.117Myuemu. Each recording layer has a capacity of 32GB.

In terms of reliability and data longevity, Sony used a newly resin material as an intermediate layer and adopted dielectric materials for each layer of the disc.

The new disc is compatible with all major Blu-ray disc recorders. Besides Sony, Sharp is set to launch on November 24 a new AQUOS 4K recorder featuring a built-in tuner.