Optical materials.

Optical materials are probably the future in recording. They become more and more important in movie and data distribution and in recording technology for private use. Expectations are that media as DVD will soon make videotape obsolete. As optical material we consider following media

• Audio CD
• Photo CD
• CD ROM
• CD-R (recordable)
• CD-RW (rewritable)
• DVD

Optical materials use lasertechnology to detect the changes in optical quality of the surface of the disc.

The discs consists mainly of a polycarbonate substrate coated with a reflective layer (gold, silver or aluminium). A plastic coating protects the top of this layer against all kinds of damages. On top of this the label is placed. The polycarbonate contains pits which are located against the reflective layer.When the appropriate laser passes along the pits, the interruptions in reflection,which occur, are decoded and the information becomes available.

Optical media have large storage capacities which makes them ideal for the storage for moving images, computerprograms and largesize databases.

The preservation of photographic materials is being influenced by the condition of the support and the reflective layer. This condition can be affected by temperature, humidity, light, UV-radiation, chemical pollutants and even ordinary use. Discs can be ruined by writing on it with inappropriate writing-materials, by using solvents, gluing labels or peeling them off and by exposure to dust and dirt.

One does still not know how long these media will survive. There is still a lot of research to be done in that area. Another problem is the obsolescence of the hardware and software needed for reading these materials. Adequate solutions will be necessary in the long run.