| 摘要 |
PURPOSE: To prevent yellowing at the time of the molding of an optical element composed of a transparent thermoplastic resin by adding a specific amt. of at least one or more kind of a surfactant out of cationic, anionic, nonionic and amphoteric surfactants to a thermoplastic resin to perform molding in an inert gas atmosphere. CONSTITUTION: An injection molding machine 1 is used and the temp. of the cylinder 2 thereof is set to 250 deg.C as the highest temp. to perform molding. At the time of molding, nitrogen gas is continuously discharged as inert gas from the lowermost part of the resin supply part 3 of the molding machine to set the nitrogen vol. occupying ratio in the cylinder 2 and the resin supply part 3 to 99vol.%. 0.05-20.00wt.% of at least one or more kind of a surfactant among cationic, anionic, nonionic and amphoteric surfactants to a thermoplastic resin to be kneaded therewith and the kneaded resin is molded. As the thermoplastic resin, polystyrene is especially pref. but polymethyl methacrylate or polycarbonate may be used. |
