At Japan's largest annual IT trade show CEATEC (Combined Exhibition of Advanced Technologies) that's taking place from October 6 - 10 this year, TDK presented a 10-layer optical disc with a storage capacity of 320 GB.

"As the number of recording layers increases, signals on each layer weaken, making it necessary to improve the transmittance. This time, the company enhanced the transmittance by readjusting the composition of used materials, it said. The transmittance of the outermost layer, which requires the highest transmittance, is more than 90%, while that of the disc prototyped in 2006 was 80 to 90%.

The symbol error rate of the new optical disc is less than 10^-4, which the company considers as the threshold of commercial viability. When data is being written on the disc, the output of the laser is less than 30mW, which is the maximum output of commercially available blue-violet lasers, on a film surface of each layer, TDK said."