Philips CDR880 - CD-Recording Disc Details; CD-Recording Disc Structure; Disc Dimensions; CD-R Disc Structure Details

BASICS CDR/RW
2 CD-Recording discs
2.1 The CD-Recording discs
Both CD-R and CD-RW discs have the same basic structure
but with significant differences. The CD-R disc has a dye-
based recording layer, with a reflectivity of 40 - 70%, while the
CD-RW disc has a phase-change recording layer with a
reflectivity of 15 - 25%. Both discs have an additional reflec-
ting layer: golden for the CD-R, which accounts for that disc's
distinctive appearance, and silver (aluminium) for the CD-RW.
2.1.1 Dimensions
In figure 1, 2 and 3 the dimensions of the unrecorded,
partially recorded and recorded disc are drawn.
Layout_of_an_Unrecorded_Disc
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intormation_Area
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Area
Figure 1
Layout of the unrecorded disc
The most important difference between the conventional disc
and the recordable disc is the beginning of the Information
Area. Between diameter 44.7 and 46 mm there is the
information of temporary table of contents of the disc:
PCA en PMA. See figure 2. The meaning of the PCA and
PMA are explained in chapter 2.5: "Data organization".
Layout_of_a_Partially Recorded_Disc
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B47 :
LLL LLL LLL LLL ZEEE. LLLLLLLLLLLL LLL
7
\ rogram_Area Recordable_User_Area_+
PCA | Lead-n Lead-Out Area
PMA
Figure 2
Layout of the partially recorded disc
The line above the disc surface indicates the recorded part.
After the fixing up of the disc the temporary table of contents
is moved to the Lead-in Area of the disc. See figure 3.
Layout_of_a_Recorded_Disc
4
EEE LLL
|
]
Program_Area
>|
|
lead-in Lead-Out
Area Area
Figure 3
Layout of the recorded disc
The line above the disc surface indicates the recorded part.
2.1.2 The structure
The PC-substrate of the CD-Recording disc is basically the
same as for a conventional pre-recorded CD.
In a pre-recorded CD, the reflection layer contains a spiral
shaped track consisting of depressions, the so called: "pits”.
The aluminium reflection layer on top of this substrate
contains the same pit pattern.
In the CD-Recording disc, the reflection layer contains a spiral
shaped groove instead of pits. Later on the pits will be
recorded ‘under’ this groove. On a blank disc, the groove is
important because it enables rotational speed control, radial
tracking control and time indication on the disc (see chapter
2.5, "Data organization").
Between the substrate and the grooved surface of the
reflective layer (gold or aluminium) is the sensitive layer (an
organic dye material). Additionally a protective coat and a
label are used. A cross-section of a CD-R discis drawn in
figure 4. The substrate layer is of polycarbonate material:
PC-substrate; the golden reflective layer is called
AU-reflective layer;
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A cross section of the CD-R disc
& PH I Li PS Service disc systems