In addition, the height of the convex-shaped mark can be controlled by changing the irradiation time of a laser light.

"Currently, two values are realized by the existence of the convex-shaped mark," Fujifilm said. "But, for the future, it might become possible to realize four values by using four states of the mark (2x recording capacity) and eight values by using eight states of the mark (3x recording capacity)."

Furthermore, Fujifilm used a two-photon absorption material with a high light transmittance. The light transmittance of a prototype with 20 recording layers was 87%. Based on this result, the company estimates that about 50% light transmittance will be ensured with 100 layers. With existing BD technologies, transmittance is lowered to about 65% with four layers, it said.

"In the future, it will be possible to realize a 15-Tbyte optical disc (25 Gbytes/layer x 3 (eight values) x 100 layers x 2 (two sides)," Fujifilm said.

Low cost

As for the low cost, Fujifilm simplified the manufacturing process by using "Web coating" to form the recording, ultraviolet curable resin and adhesive material layers and sticking them together. In the case of BD, spin coating and sputtering have to be conducted for each layer.

"It takes 147 seconds to form a four-layer BD," the company said. "With our method, it takes only 58 seconds to form eight layers."

The competitors of the new disc are hard disk drives (HDDs) and magnetic tapes. The former is expensive, but its access speed is as fast as several milliseconds. The latter is inferior to HDDs in terms of access speed but has a cost (including maintenance) about 1/3 that of HDDs.

Therefore, HDDs are used mainly for saving and handling specific files with small sizes while magnetic tapes are used mainly for the backup of large-size data with high transmission speeds. On the other hand, the two-photon absorption disc has a cost as low as that of a magnetic tape and a fast access speed, Fujifilm said. The access speed is about several ten to hundred milliseconds.

The problem for the commercialization of the disc is the low reflectance ratio (0.5%) of playback signals. The ratio is only 1/40 that of BD (20%). Fujifilm confirmed writing and reading with the 17PP encoding technology, which is also used for BD.

"We will continue the development of the disc with help from drive makers," the company said.

Fujifilm developed the adhesive material layer in collaboration with Lintec Corp. Fujifilm will show a panel explaining the latest results at Inter BEE 2012, which will take place from Nov 14 to 16, 2012, Chiba Prefecture, Japan.