Burns, Doane, Swecker & Mathis
Optical urethane resins and plastic lenses comprising the same
 Optical urethane resins according to the present invention are each obtained by reacting an active hydrogen compound with an isocyanate compound containing as a stabilizer a phenolic compound. Owing to their low yellowness, high light transmittance and optical-strain-free quality, these resins are useful as optical materials for plastic lenses or the like which are required to be colorless, transparent and uniform. 
Mitsui Toatsu Chemicals, Inc.
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Hiroyuki Koju Masahiko Teruyuki
Yamashita Okazaki Kusumoto Nagata