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Birefringence–An important property of plastic substrates for magneto‐optical storage disks
Author(s) -
Siebourg W.,
Schmid H.,
Rateike F. M.,
Anders S.,
Grigo U.,
Löwer H.
Publication year - 1990
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760301804
Subject(s) - materials science , birefringence , magneto optical , property (philosophy) , composite material , optoelectronics , magneto , optics , mechanical engineering , physics , philosophy , epistemology , quantum mechanics , rotor (electric) , magnetic field , engineering
Birefringence is an important substrate property for optical data storage media. The basic definitions of birefringence and its relation to the chemical nature of polycarbonate are outlined. The polarizability of the monomer unit, expressed in the rheo‐optical constant and the degree of remaining polymer chain orientation, determines the level of birefringence in polycarbonate disk substrates. Based on this theory, the theory of blending materials with positive and negative rheo‐optical constants Is developed, and the current work with polycarbonate/polystyrene blends is reviewed. The biggest disadvantage of the reviewed system Js that only binary systems with low LCST (lower critical solution temperature) (<240°C) can be formulated. Finally, we report on successful development work of a single‐phase blend of a modified polycarbonate with a special styrene‐acrylonitrile copolymer. The experimental results are compared with the theoretical expectations, and the implications on the injection molding of disk substrates are discussed.