BD-RE

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Storage medium BD-RE
Single-layer blank (25 GB) from Panasonic (cartridge version)
General
Type	Optical storage medium
capacity	25 GByte (single layer) 50 GByte (double layer)
size	12 cm or 8 cm (diameter)

The BD-RE is the rewritable format of the Blu-ray Disc and is in contrast to the write-once BD-R . The abbreviation RE stands for Recordable Erasable . Current single-layer blanks are available with a storage capacity of 25 gigabytes . The double-layer variant offers 50 GB.

Rewriting is possible through the use of phase change technology . In contrast to the DVD ± RW , it can be rewritten at least 1000 times and offers greater data security, but does not come close to the DVD-RAM for both properties . Some manufacturers are already promoting BD-REs that should be rewritable up to 10,000 times. The service life of the data is given as 30 to 50 years.

In the future there will also be media with a storage capacity of 27 GB per shift.

In addition to discs with a diameter of 12 cm, there are also 8 cm discs. The capacity of the 8 cm disks is 7.8 GByte (single layer) or 15.6 GByte (double layer).

construction

A BD-RE that can be written on from one side is composed of seven layers. Starting from the labeled side in the direction of the laser , the first layer is the substrate (the carrier layer), which consists of polycarbonate . It has an incorporated groove surface that spreads in a spiral shape from the center to the edge. A silver alloy layer is applied to the substrate, which is responsible for the reflection of the laser. On top of this layer is a dielectric layer made of zinc sulfide and silicon dioxide . This is followed by the writable layer (also called phase change layer). This can be composed of a germanium - tellurium - antimony or indium - silver- tellurium-antimony alloy. Another dielectric layer follows, followed by a polycarbonate or silicone cover layer. Usually a protective layer (hard coat layer) made of plastic resin is applied over it, which makes the use of cartridges superfluous.

The structure is summarized:

1. Carrier layer
2. reflective layer
3. dielectric layer
4. rewritable layer
5. dielectric layer
6. final top layer
7. Protective layer

Schematic structure

In the case of a double-layer BD-RE, the outer dielectric layer is followed by a spacer layer (spacing layer) and the second rewritable layer, surrounded by two dielectric layers. The structure then looks like this:

1. Carrier layer
2. reflective layer
3. dielectric layer
4. rewritable layer
5. dielectric layer
6. Distancing layer
7. dielectric layer
8. rewritable layer
9. dielectric layer
10. final top layer
11. Protective layer

File system

The preferred file system for the BD-RE is UDF version 2.5. In principle, any file system can be used, but systems other than UDF 2.5 can rarely achieve the intended 1000 rewrite processes.

See also

• Blu-ray Disc (General)
• BD-R (Writable Blu-ray Disc)

literature

• Hartmut Gieselmann: Burner in blue. In: c't ISSN  0724-8679 , 23rd year, issue 15, 2006, pp. 114-121. also available online

Web links

Commons : Blu-ray Disc  - collection of pictures, videos and audio files

• blu-raydisc.com - Official website of the Blu-ray Disc Association.