Phase change technique

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With the phase change or phase change technology (based on the English term) it is possible to produce rewritable optical data carriers based on phase change materials. It is used, for example, on rewritable CDs, DVDs or Blu-ray discs. In the semiconductor industry, too, this technology is increasingly supplementing the familiar flash memory chips in the form of phase-change random access memory .

history

Over time, the phase change technology was used in various storage solutions. These are listed below in historical order according to the year of manufacture (and not the year of specification):

1995: PD (Phasewriter Dual) from Panasonic , stores 650 MB (megabytes).
1996: CD-RW (Compact Disc ReWriteable) from Philips , Sony , Hewlett-Packard , Mitsubishi Chemical and Ricoh , initially 650 MB, later 700 MB storable.
1998: DVD-RAM (DVD - Random Access Memory) from the manufacturer consortium DVD Forum , initially 2.6 GB (gigabytes), today up to 9.4 GB can be stored.
1999: DVD ± RW (DVD - ReWriteable) from the manufacturer consortium DVD + RW Alliance , initially 4.6 GB, today up to 9.4 GB storable.
2004: UDO (Ultra Density Optical) from Plasmon , storable 28 GB.
2004: PDD (Professional Disc for Data) from Sony , storable 20.5 GB.
2006: BD-RE (Blu-ray Disc ReWriteable) from Sony , initially 25 GB, today up to 50 GB can be stored.

The transition from one generation of phase change technology to the next has always been a safe investment because the newer generation has a certain downward compatibility with the older generation. Three examples:

  • The first generation of DVD-RAM drives could also read PD media.
  • Commercially available DVD devices can also read and write CD-RWs.
  • BD devices can read and write all DVD-RAM, DVD-RW and CD-RW.

technology

The phase change technique does not require any special playback devices. For example, a typical CD-ROM or DVD-ROM drive can also read media based on phase change technology (such as CD-RW or DVD-RW and DVD-RAM) with only minimal technical changes, because the encoding is very similar to that of pure ROM media. While with pressed CD-ROMs and DVD-ROMs the data is stored in pits or non-recessed areas (lands) in the plastic layer, with media using phase change technology, it is successive reflective and non-reflective points.

When writing, a relatively high-energy laser beam causes amorphous zones at certain points on the surface, which reflect the light of the reading laser more poorly. A somewhat lower-energy laser is used to erase, under the influence of which the surface material becomes crystalline again and reflects better. As a rule, germanium-antimony-tellurium or silver-indium-antimony-tellurium alloys are used.

In 2009, TÜV Rheinland provided Panasonic products with a 50-year archiving certificate.

literature

  • Bernd Steinbrink: Light bits. Phase change storage technology: a storage technology with a future. In: c't. ISSN  0724-8679 , 12th year (1995), edition 2, pages 76ff., Also available online . A good basic article that explains not only the story, but also the technology of the dual phase writer in pictures.
  • Stephan Becker: Finely burned. In: c't. ISSN  0724-8679 , Volume 15 (1998), Issue 25, Pages 190-195, also available online . The article presents the history and technical differences up to 1998, i.e. without UDO, PDD and BD-RE.
  • Hartmut Gieselmann: Blue memory. Professional data backup of the next generation. In: c't. ISSN  0724-8679 , Volume 21 (2004), Edition 6, Pages 196ff., Also available online . This article covers UDO and PDD and also shows relevant differences to MO and DVD-RAM.

Web links

Individual evidence

  1. ↑ The world's first Blu-ray Disc with TÜV Rheinland certificate comes from Panasonic. Archive data securely for over 50 years. In: panasonic.de. September 2009, archived from the original .