Machine Design

New Resin Brings 15-Gbyte Optical Disc

Polycyclohexylethylene (PCHE) resin will make possible 15-Gbyte data densities for next-generation optical media. The new resin is said to have higher light transmittance with lower birefringence, water absorption, melt viscosity, and specific gravity than traditional polycarbonates. The refractive index of PCHE is 1.51 and its light transition spreads across a full spectrum, extending down to the ultraviolet range of 300 nm.

The 300-nm transmittance range lets next-generation, high-density optical media technologies switch from red lasers to much shorter wavelengths — violet, blue, and green. The shorter wavelengths can read more densely spread pits on the disc surface. PCHE layers are ultimately expected to surpass the 15-Gbyte capacity obtained by U.K.based Plasmon Data Systems Ltd. during molding trials.

PCHE also has low inherent moisture, less than 0.01%; an important factor in maintaining extreme flatness during disc manufacturing. The new resin may help thwart disc piracy as well. Materials currently used to replicate optical media are often unmonitored. MediaShield, Dow Plastic's PCHE/anitpiracy program, involves creating an independent legal entity to track the PCHE supply and secure its use for legitimate replication only.

Dow Plastics, Box 1206, Midland, MI 48674, (800) 441-4369,


TAGS: Materials
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