Disk rot is a phrase that describes the tendency of a CD or DVD or other optical disc to become unreadable due to physical or chemical deterioration. The cause of this effect varies from the oxidation of the reflective layer, to the abrasion and physical abrasion of the surface or edges of the disc, including visible scratches, to other types of contaminants, ultraviolet damage and the removal of the adhesive bonds used. to attach layers of discs.
Video Disc rot
Cause
In the CD, the reflective layer immediately falls under a thin protective layer of shellac, and is also exposed at the edges of the disc. The tape that protects the edge of an optical disc can usually be seen without enlargement. Uncommonly thick uniform; thickness variations are usually seen. The reflective layer is usually aluminum, which readily reacts with some commonly-discovered chemicals such as oxygen, sulfur, and certain ions carried by condensed water. In regular use, the surface layers of aluminum oxide form very quickly when the aluminum surface is exposed to the atmosphere; it serves as a passive for bulk aluminum with regards to many, but not all, contaminants. The CD reflective layer is so thin that this passivation is less effective. In the case of CD-R and CD-RW media, materials used in the reflective layer are more complex than simple aluminum layers, but can also cause problems if contaminated. A thin layer of protective lacquer is equal to 0.25-0.5 mm.
DVDs have different structures from CDs, using plastic discs above the reflecting layer. This means scratches on one of the DVD surfaces may not reach the reflective layer and expose it to environmental contamination and may cause corrosion, possibly progressive corrosion. Each type of optical disc has a different susceptibility to contamination and corrosion of its reflective layer; Furthermore, the writable and rewritable versions of each type of optical disc are quite different as well. Finally, discs made with gold as a reflective layer are much less susceptible to corrosion problems, although not less susceptible to physical damage to the coating. Because the price is cheaper, the industry has adopted an aluminum reflective coating as the standard for factory-supplied optical discs.
Maps Disc rot
Decay disc signs
On the CD, decay becomes visually visible in two ways:
- When the CD is held with a strong light, the light shines through several holes with a pin prick.
- The disc color change, which looks like a coffee stain on the disk. See also bronzing CD.
In an audio CD, decay leads to random or skipped audio or even the inability to play a track.
Variant
Laser rot
Rotting lasers are the display of video and audio artifacts during LaserDiscs playback, and their progressives deteriorate over time. This is most often associated with oxidation in the aluminum layer with poor quality adhesives used to hold the pieces of the disc together. One-sided video disks do not seem to suffer from laser decay while two-sided disks. The name "laser rotting" is not a name; although the disc degradation does not involve a laser player, "rot" refers to the laser disk itself.
Laser rot is characterized by the appearance of colored spots appearing in the video output of the laser disc during playback. Speckles increase in volume and frequency as the disk continues to decrease. Much of the initial production of the DiscoVision Disc Disc MV has severe laser decay. Also, in the 1990s, LaserDiscs manufactured by the Sony DADC plant in Terre Haute, Indiana was plagued by laser decay.
HD-DVD Rotation
Many HD-DVDs, especially those manufactured by Warner Bros. between 2006 and 2008, developed decay not long after production. Rotted discs are also more common on double-sided HD-DVDs than single-sided HD-DVDs.
See also
- Data is decomposed, similar concepts
- Bronzing CD
- DVD-D and Flexplay, a single-use optical disc format designed to become unplayable after a limited time
- M-Disc, an optical disc format that is claimed to have a lower decay rate than conventional DVD
References
External links
- Mac Observer article
- "CD Bronzing" article, with PDO replacement information, in Classical.net - How manufacturing problems can cause disk quality degradation
- "Using CD for Data Storage" article, with extensive footnotes.
- A bad DVD rod feeds into the movie collection
- Blu-ray decays on copy of The Prestige on AVS Forums
Source of the article : Wikipedia
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