COC gives new CDs a sweeter sound. (In Brief).

The new hybrid Super Audio CD (SACD) format from Sony/Philips not only promises to bring back the "warm" sound of vinyl records, it also represents the breakthrough of cyclo-olefin copolymer (COC) into the CD market. SACDs use new recording technology that increases the resolution of digital music by more closely following the original analog waveform. According to Sony, the result is more faithful to the original. SACDs can hold more than four times more information than a CD.

Only Sony Music in Japan, Sonopress in Germany, and Crest National in Hollywood, Calif, have SACD production lines up and running. Sony's Terre Haute, Ind., plant should be making SACDs soon.

Unlike the DVDs on which movies are recorded, a hybrid SACD (which includes a conventional CD layer to play on standard equipment) is not symmetrical in the placement of the metal and plastic layers. As a result, it is more vulnerable to warpage caused by moisture absorption, which would render the CD portion unusable, explains Robert Freedman, senior v.p. for technical operations at Crest National. Polycarbonate reportedly does not have the moisture resistance needed to keep the disc flat, but COCs do. Sony's SACD project director David Kawakami says COCs offer low birefringence. COC also helps SACDs function by absorbing less laser light.

To use PC rather than convert to COC would require sputtering an additional barrier layer of silicon oxide onto the exposed face of the SACD to prevent moisture absorption and maintain flatness. That extra step is very expensive and very slow, says Freedman. Sonopress reportedly started out using this method but then converted to COC. Sony Japan is also using COC. The COC resins being used are Zeonex and Zeonor from Zeon Chemicals in Japan (U.S. office in Louisville, Ky.). Ticona in Summit, N.J., another maker of COCs, had no comment at press time. Zeon [phone], www.zeonchemicals.com