CD-R

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A CD-R (from English : C ompact D isc R ecordable) is a write-once CD , with a commercially available burner can be described. Data, photos, videos or music can be stored on it and played with a CD drive . The as yet unwritten CD-R is often referred to as a blank CD .

Back of a CD-R
Blank reflective layer
Black (but infrared-permeable) CD-R compared to a standard blank
A stack of 50 with 700 MB CD-R blanks

construction

It consists of a transparent plastic carrier made of a polycarbonate manufactured using an injection molding process, in the surface of which there is a microscopically fine, spiral-shaped groove (“pregroove”). This minimal recess is used to guide a laser , which while writing (“burning”) the digital information changes the absorption properties and thus the reflectivity of a special organic dye layer ( called dye ) in the smallest areas, the so-called pits. These pits can then be read out again (by a weaker laser that does not change the color layer) by evaluating the changed reflectivity on an overlying (vapor-deposited) silver or gold layer by converting the reflected radiation intensity into an electrical signal. To protect the layers (color and reflection layer), a thin, transparent lacquer layer is applied to the metallic reflection layer (usually silver, less often gold) before the decorative print is made. Because silver tends to form black sulfide compounds, early silver-plated CD-Rs had a short life expectancy. This was significantly increased by vapor deposition of an aluminum layer behind the silver layer.

Sizes

The capacity of a CD-R is usually stated both in minutes (for audio CDs) and in MB (for data CDs).

  • 185 MB: 021 min ( mini CD )
  • 210 MB: 023 min (mini CD)
  • 550 MB: 063 min (no longer in production)
  • 610 MB: 071 min (very rare, is only produced by Taiyo Yuden and is no longer on the market, is only made available to developers)
  • 650 MB: 074 min (previously standard, now very rare, only available from a few manufacturers)
  • 700 MB: 080 min (standard)
  • 800 MB: 090 min
  • 870 MB: 099 min (relatively rare)
  • 900 MB: 100 min (relatively rare)

Depending on the quality and type of the blank and the burner, it is also possible to burn outside the area approved in the ATIP (overburn). However, this can lead to errors or loss of data in this area. Not all drives support overburning.

With sizes beyond the original 650 MB / 74 min, playback problems can occur in some CD drives because the track grooves are closer together in order to achieve the higher capacity. Up to the standardized 700 MB, however, this occurs almost exclusively with older CD players and drives.

The MultiLevel CD-R has three times the capacity of a normal CD-R, but it never went into series production.

History / the CD-R today

The CD-R was presented to the public in October 1988 after three years of development work by the Japanese company Taiyo Yuden .

The first CD-Rs for the entire market were produced in 1992 (after the CD-R and Photo CD were presented by Kodak and Philips at the Photokina) and cost around 20 marks. Some of the early manufacturers were Taiyo Yuden , Kodak, Maxell, and TDK . Since then, the CD-R has been continuously developed, so that today it can be burned at 56 times faster than the first CD-R. The improvements mainly concerned the colorants used on the CD-R, the design of the groove and the coating process.

Although the CD-R was originally developed in Japan , Taiwan has been producing the largest amount of CD-R since 1998 . Taiwanese manufacturing accounted for more than 70% worldwide (2003: 10.5 billion CD-Rs). Manufacturers from Taiwan include Daxon ( BenQ ), Ritek , Prodisc , and CMC Magnetics , but they have often outsourced a large part of CD production to Malaysia , Hong Kong or the People's Republic of China . Outside of Taiwan, Moser Baer India is the largest CD-R manufacturer.

CD-R sales have been falling continuously for years. While more than 850 million blank CDs and DVDs were sold in Germany in 2005, sales in 2016 were just 133 million. The reason is that data is increasingly being stored on USB sticks and in the cloud .

Dyes

There are currently three basic dye mixtures for CD-Rs:

  1. Cyanine dyes were first used by Taiyo Yuden for use as the recording layer in CD-Rs. Cyanine dyes canbe adapted relatively easilyto the wavelength of the semiconductor laser in the CD drive (wavelength: 780 nm) through chemical optimization. The cyanine dyes suitable for CD-R are green, turquoise or light blue. The first CD-Rs made with cyanine dyes were quite sensitive to high humidity and solar radiation. By improving the chemical composition and using light stabilizers, cyanines can be stabilized to such an extent that they are suitable for archiving (“metal-stabilized cyanine”, “super cyanine”).
  2. Azo dyes for use with optical media are deep blue. The use of azo and metal complex azo dyes was introduced by Mitsubishi Chemicals . In contrast to simple azo dyes, metal complex azo dyes are relatively stable to the effects of light and chemical agents. CD-Rs with azo dyes are produced by Mitsubishi Kagaku Media ( Verbatim ),among others.
  3. Phthalocyanine dyes appear on the CD-R in a silvery green, silver or gold color. The patents for this dye are held by Mitsui Chemicals and Ciba Specialty Chemicals . This dye is chemically and very stable to sunlight. CD-Rs manufactured today are mostly made with phthalocyanine dyes, as these are particularly economical to use and enable CD-R media with good recording and playback properties and good durability.

There were other, rather insignificant dyes in the past, for example formazan dyes developed by Kodak . The formazans could not establish themselves on the market and are no longer available.

The composition of the dye used cannot always be inferred from the color of the recording layer of the CD-R. Additional dye additives and the type of reflector material used (silver or gold) change the color impression. So it is not possible to conclude from the shimmering gold alone that it is a CD-R with a phthalocyanine dye and a golden reflective layer.

Furthermore, it is not possible to infer the durability of the CD-R directly from the dye used. Other factors such as reflectivity, surface protection or sealing play a bigger role. Since the reflectivity of an intact CD-R reaches a value that is above the minimum specified for CD-ROM and CD-DA , all intact CD drives can also read CD-Rs. However, since the typical reflectivity of CD-Rs is below the typical reflectivity of a CD, dusty drives first have problems reading CD-Rs before they can no longer read CDs.

See also

Individual evidence

  1. ↑ The capacity is given in binary (1 MB = 1024 KB)
  2. ↑ http://ceramni.jpn.org/file/soukai06/kouen_0602.pdf
  3. ↑ Mathias Brandt: Burned out! , Statista, April 20, 2017

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