The CD Recordable was originally named CD Write-Once (WO), a specification developed and published by Philips and Sony in 1988 in the 'Orange Book'. The first CD-Rs were produced in 1988. Generally, a CD-R, or 'blank CD' as it is commonly referred to, measures 1.2mm in thickness and 120 or 80mm in diameter. As per the 'Orange Book', a standard blank CD has a storage capacity of 74 minutes of audio or 650 MB of data. Some non-standard discs have capacities up to 79 minutes and 59 seconds, sold as 80 minute CD-Rs in the market. Unlike the familiar silvery-aluminum colored compact discs (CDs) such as the Audio or Video CD, a CD Recordable is specially constructed with an intermediate layer containing a chemical dye. This layer called the organic dye recording layer, is modified by a laser while writing information onto it and cannot be changed again. The organic dye recording layer is sandwiched between the polycarbonate substrate and the light reflective layer. The polycarbonate substrate is a transparent layer facing the underside of a CD-R, whereas the light reflective layer is an opaque layer on the top of the CD-R, usually used to write on text using felt pens. There are three basic chemical dyes used as the organic recording layer for manufacturing blank CDs. Each type differs in performance and durability from each other. The first type uses Cyanine dyes, the earliest developed and patented by Taiyo Yuden, that are green or light blue in color. These dyes are chemically unstable as compared to others, lasting only a few years, which makes them inappropriate medium for data archival. The second variety uses a dark blue colored 'Azo' dye, patented by Mitsubishi Chemicals. Azo dyes are relatively stable than Cyanine dyes and last for a lifetime spanning decades. The third kind of dye, the Phthalocyanine dye, is usually silver, gold, green or light green in color. This dye is the most chemically stable of all the three dyes and lasting at least a hundred years. It is patented by Mitsui Toatsu Chemicals (MTC) of Japan. The companies Taiyo Yuden, Kodak, Maxell, and TDK were the first companies to manufacture CD-Rs.