SAN JOSE, CALIF. - To help compact disc replicators produce better polycarbonate substrates, GE Plastics in Pittsfield, Mass., announced a proprietary molding technology it calls managed heat transfer. GE Plastics developed MHT jointly with engineers at GE's Corporate Research and Develop-ment Center in Schenectady, N.Y., by building on patents developed during the past eight years. This technology aims at three keys to the CD industry: better pit replication, lower stress, and reduced clouding, with the possibility for improvement in cycle times.
The demand for discs with increased storage capacity means that the pits, which contain the information, are much closer together. Also, the substrates are much thinner, 0.6 millimeter, which also means greater molding processing challenges.
MHT uses a thermal insulating layer on the mold's surface, just behind the stamper, allowing the skin layer to relax and flow more uniformly from center to edge. It also allows more uniform cooling.
At Replitech International 1996 in San Jose, GE Plastics said the technology produces a CD with better pit geometry and appears to be independent of mold temperature and cycle time. It also broadens the processing window.