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Birefringence Properties of Polymeric Substrate Materials
Published online by Cambridge University Press: 29 November 2013
Extract
Depending upon the nature of the application, three materials currently dominate the optical substrate market today. Polycarbonate (PC), the most commonly used material, is typically used in disks with diameters up to 120 mm. For larger diameters, the inherent birefringence exhibited by PC interacts with the read laser and results in errors in the read-back signal. For 200 mm and greater, both polymethylmethacrylate (PMMA) and glass are used. Because PMMA is low in inherent birefringence, it is widely used for 200 mm video disks, an application which takes advantage of the manufacturing economies of the injection molding process. For larger diameter data storage disks, however, glass is used because it does not have the disadvantage of relatively high moisture absorption or the low heat resistance of PMMA.
This article will deal with the state-of-the-art in materials used for polymeric substrates. It will focus primarily on polycarbonate and the most significant substrate property currently confronting the field, namely birefringence. Other constraints placed by optical storage technology on the substrate material will be discussed along with new materials and research activities aimed at circumventing some of the current limitations.
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- Optical Storage Materials
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- Copyright © Materials Research Society 1990
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