Matsushita Electric Industrial Co., Ltd. has developed a 4-layer Blu-ray Disc (BD) medium using Te-O-Pd film for inorganic recording layers. Total capacity reaches 100 GB with each layer having 25 GB storage capacity. This is the company's first report of four-layer BD discs. By revising a Te-O-Pd composite proportion, the company reportedly achieved durability that allows data playback after 100 years.
Te-O-Pd film is an inorganic material, which Matsushita considers the cornerstone of its multilayer technology focusing on the material's high transmittance that makes it easy to increase the number of layers and low solubility that gives minor impact to the environment. In Te-O-Pd, substance transmittance, crystallization speed and durability depend on a composition ratio of these three elements. Matsushita said it discovered a ratio that realizes "100-year durability" (a company spokesperson), while achieving transmittance needed to create a four-layer disc and fast crystallization required for 2x writing speed. The company is yet to determine commercialization schedule, but seems to have developed the disc aimed at long-term storage (archive) applications, in particular.
When replaying data, which was written at 2x speed, at 1x speed, the prototype disc marked a maximum jitter of 8.5%. In addition, calculation using acceleration test results showed that the jitter degrades by 2% after more than 100 years at a temperature of 30 degrees and a humidity of 85%, or after more than 1,000 years at 25 degrees and 55%.
As for BD-R multilayer disc technology, TDK Corp. realized 2x writing speed with a 100 GB, four-layer disc (25 GB per layer) in 2005, and 1x writing speed with a 200 GB, six-layer disc (33.3 GB per layer) in 2006.