1. Chapter VI, Digital Storage: Lesson II Disc Manufacturing

2. Making recordable Compact Disc (CD-R) media is a demanding multi-step process that requires high quality materials be handled under "super clean" conditions to meet strict manufacturing tolerances.

3. CD-R media have the following component layers:
A. Polycarbonate substrate (120mm diameter / 1.2mm thick) is the basic foundation on which all other layers are built
B. Recording layer (~100nm thick) is a disc that reacts to laser light energy during recording.
C. Reflective layer (~100nm thick) is a precious metal or alloy that reflects laser light back to a sensor during playback
D. Protective layer (~5 micrometers thick) is a lacquer based overcoat that helps protect the Disc from scratches
E. Label Printing layer (~10 micrometers thick) is the top most layer used for printing information and decoration on the Disc E D C B A

4. Compact Disc (CD) manufacture begins with high quality plastic resin, which is used to make the disc's substrate layer. Raw material is purified to remove residues and moisture before being moved into a clean room production environment.

5. During substrate molding, the resin is heated to a fluid state, then injected into the cavity between a smooth mold and a stamper. The stamper is used to form a spiral groove in the disc's substrate

6. This groove is an important feature of the recordable CD media.
It contains a sophisticated wave pattern called "wobble" that provides motor speed control and important timing information about the Disc. The groove and wobble pattern help guide a beam of laser light across the surface of the disc as digital information is recorded and played back.
Spiral Groove Wobble

7. Once discs pass quality control testing, they go through a process of dye coating. During dye coating, a specially formulated dyesolution is spin coated onto the substrate to produce the CD's recording layer.
Different dye formulas are used for different brands of CD media. The stability of these dyes and their ability to resist fading is the major factor in determining a CD's long term storage capability

8. After dye coating, the CD receives an edge washing to remove dye along the outside edge of the disc. The discs are then baked in ovens to remove any residual solvents used in dye coating and edge washing.

9. Originally, the CD's reflective layer was a metal layer made from either silver, gold/silver alloy, or pure gold. Gold/silver alloy is used to ensure the CD's stability and long life. When pure gold is used, even greater archival qualities are achieved.
Today most inexpensive CD’s reflective layers are made of alloys that contain little gold or silver to keep cost low.

10. Tests have shown Kodak CD-R Gold Ultima, which uses a pure gold reflective layer, to have a life expectancy of 200 years. Other Kodak media using gold and silver alloys have demonstrated archival capabilities of 100+ years.
Discs are then laser etched with a unique identification code and an optional bar code marking.

11. Next, the discs receive a spin coating of lacquer, the first of several layers that make up Kodak's unique Infoguard protective system. The coating is cured under ultra violet light to produce a super hard coating.

12. Quality control testing ensures that manufactured lots meet strict performance standards for a variety of record and playback systems.

13. Discs are then screen printed with product name and logo
Discs are then screen printed with product name and logo. Some discs receive an additional layer, a printable surface for thermal or inkjet printing.

14. CD media is made of a very strong polycarbonate material
CD media is made of a very strong polycarbonate material. However, this material is also relatively soft and easily scratched. Even though the KODAK INFOGUARD system offers significant protection, CDs should always be handled with care. This is true for both the recorded and the unrecorded disc

15. To ensure that your digital files are kept safe and secure for years to come, follow this simple handling and storage advice:                                
Always handle CDs by the edge or center.
Avoid touching the non-printed side of the CD.
Never use a ballpoint pen to label a CD.
The recording dye layer is very close to the labeling
surface. The pressure from a ballpoint pen can
damage this layer.
Do use a felt tip pen to label the CD.
Store the CD a protective case away from heat
and direct sun light.
Avoid bending or flexing the CD.
Often times attempts to clean a CD will do more
harm then good.
If the CD must be cleaned use mild soap and water.
Use an absorbent cloth to blot it dry. Avoid excessive rubbing!
Never use chemical solvents to clean the CD.
Remove light dust and dirt by brushing from the center out. Never wipe in a circular pattern!