SAN JOSE, CALIF. - The advent of digital versatile discs is the driving force behind the development of new and improved polycarbonate resins used in the molding of optical discs. Several large players in the optical disc industry featured the processability of their PC materials in conjunction with molding machinery manufacturers at Replitech International 1996, molding the 0.6-millimeter substrates required for DVD.
Bayer Corp. of Pittsburgh recently developed the first generation of a PC designed to address the tightened molding parameters of DVD. Makrolon DP1-1265 offers DVD replicators a wider processing window, Ramesh Pisipati, industry manager for optical memory products, said at the show, held June 4-6 in San Jose.
Although Bayer developed the product with DVD in mind, Jon Newcome, process specialist for Bayer, said DP1-1265 has other applications for molding CDs and CD-ROMs as well. And, he added, the new material does not preclude the standard-grade Mak-rolon CD2005-MAS140 from being used in difficult CD molding applications.
Pisipati said DP1-1265 provides lower birefringence or stress, something that becomes more critical to control as cycle times become faster - currently less than four seconds for CD molding applications.
``Molding is still the single-longest unit in the CD manufacturing operation,'' Pisipati said. ``As you cycle faster, you're putting more emphasis on the performance of the material. We want to improve the productivity in standard CD molding as well as looking down the road at DVD molding.''
GE Plastics of Pittsfield, Mass., announced the introduction of its continuous-improvement, optical-quality Lexan OQ RDX PC for the CD industry. The company claims the resin may result in lower cycle times, because it can be processed at higher temperatures compared with standard Lexan OQ resin.
Dow Plastics of Midland, Mich., also is focusing on the new digital technology. T.J. Wainerdi, senior market development manager, said, ``We are currently working on a number of products, including developments in resins and resin technology to support our customers in areas such as DVD technology.
``The rapid evolution of the optical disc as the digital format for multimedia applications now requires a substrate resin that offers optical, physical and rheological properties necessary to achieve reduced cycle times, increased pit density, purity and reduces disc substrate thickness,'' Wainerdi said.
Dow Plastics has an experimental PC optical grade called XU 73109.01L for CD and DVD manufacturing.
Wainerdi said the market for optical disc media and packaging is growing about 20 percent annually.
International demand for both general-purpose and high-impact grades of polystyrene for optical media cases is expected to reach 700 million pounds by 1998, as disc manufacturers continue to support the PS jewel box as the primary CD enclosure.
Dow Plastics introduced its first generation of PS for the thin-walled jewel box, the XU70268.00.
``Traditionally, the jewel box has been clear with an opaque tray,'' said development engineer Amy Waier.
``The industry is now looking for materials that will allow the use of clear trays with greater toughness, especially as manufacturers of CD-ROM increase their use of jewel boxes as their enclosure of choice.''
Wainerdi said demand for the clear tray is driven by the need for yet another surface on the packaging for advertising. Wainerdi said about 70 percent of all CD-ROMs, excluding game software, are packaged in jewel boxes.