HEAT-RESISTANT PLASTIC OPTICAL FIBER

PURPOSE:To give the optical fiber having high heat resistance and to prevent the optical fiber from deterioration of light conducting characteristic at high temp. by constituting the optical fiber of core consisting of a copolymer comprising specified 6-membered ring anhydride, unsatd. carboxylic acid, aromatic vinyl compd. and methyl methacrylate, and a shell consisting of polymer having low refractive index. CONSTITUTION:The optical fiber is constituted of core consisting of copolymer comprising 3-20wt% 6-membered ring anhydride unit expressed by the formula, 5wt% unsatd. carboxylic acid unit, aromatic vinyl compd. unit, and methyl methacrylate (MMA) unit, and shell consisting of a polymer having lower refractive index than the core. The total of the content of the MMA unit and the aromatic vinyl compound unit is regulated to >=75wt%, and the weight ratio of the MMA unit to the aromatic vinyl compd. unit is regulated to 0.5-1.2. Further, a polymer of MMA or a copolymer of MMA with a fluorine compd. having >=90 deg.C softening point is used for the shell material. Said core polymer is compatible satisfactorily with the polymer of the shell consisting essentially of MMA, and a core-shell structure is formed forming a completely transparent compatible region.