More?

CDs and DVDs store just so much information. And it’s never enough. That’s why, a team of researchers at Bayer is looking to produce media that can store lots more.

In particular, Bayer’s Central Research Division has high hopes for ‘photoaddressable polymers’ (PAPs), – molecules onto which data can be recorded by means of light.

Photoaddressable polymers (PAPs) consist of long-chain molecules whose primary cords have a large number of shorter side-chains attached to them. In their normal state, these side-chains are disordered and pointing in all directions. This changes as soon as a polarised laser beam (a laser beam that oscillates on only one plane) hits the polymer.

Then, the side-arms of the molecule chains become aligned exactly perpendicular to the polarisation of the light. Information can be deposited within the polymer according to the orientation of the side-chains. The advantage of this is that the arrangement of the side-chains is very stable and data can still be read by a polarised laser beam for a long time afterwards.

The result is an optical storage medium that is more efficient than conventional media like CDs.

With these polymers, Bayer’s chemists are aiming to produce two new kinds of data storage systems: PAP-DVDs and holo-disks.

The PAP-DVD is a storage medium in CD-format with about 60 times the storage capacity of conventional CDs.

The structure and principle of a PAP-DVD are somewhat different than those of a conventional DVD. The Makrolon disc is not coated with an inorganic metal alloy or a layer of dye, but with the photoaddressable polymer (PAP). It is written on, dot by dot, by a laser beam.

Bayer estimates that the PAP-DVD could become a reality by 2003. The potential storage capacity is currently estimated at about 30-40 gigabytes. By way of comparison, a conventional CD can store up to 0.65 gigabytes, while a DVD can store 4.7 gigabytes (on each side).

The second avenue of research is the development of the holo-disc: a system that stores the information in a PAP coating according to the principle of holography. One holo-CD would be able to store 1,500 times more data than a conventional CD.

Bayer’s scientists estimate that such a rewritable holographic disc would not go on the market before 2005.

Bayer are at www.bayer.com

General information on the subject of holography, including contacts, can be found at:

http://www.holografie.de

If you would like to know more about the physics and chemistry of Photoaddressable polymers, visit: http://www.ep4.phy.uni-bayreuth.de/ag_haarer/research/photo_poly/index.html