A compact disc is constructed of 5 separate layers…
1. First a thick, soft, clear plastic layer.
This layer comprises the majority of the CD's thickness and weight.
It serves two purposes. First, it protects the data layer from
damage on the play side and Secondly it acts as a lens to focus the
CD player's laser onto the data layer so it can more easily read the
data (much the way lenses in spectacles help eyes focus on the words
on a page).
2. Next the data layer is where the music and
any other information are stored. It's the layer that the CD player
"reads" in order to create the music, graphics, etc. The
data layer is molded or pressed into the top of the clear plastic
layer. The data in the data layer is arranged in tracks that spiral
like the grooves on a vinyl record (except CDs are read from the "inside
out", the opposite of vinyl records).
3. Now a reflective, metallic layer is located
on top of the data layer. It allows the disc to function like a
mirror, reflecting the CD player's laser back to the detector in the
CD player after it reads the data layer It's this layer that gives
the CD's play side a shiny appearance.
4. A thin, hard protective layer is an
ultra-thin plastic coating that is added to provide some protection
for the reflective and data layers, while also forming a surface
upon which the label information can be printed.
5. Finally the label layer is printed on top of
the protective layer. It contains the title, graphics, band and
other information to identify the contents of the disc. (label
side).
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