METHOD FOR PRODUCING OPTICALT RANSMISSION BODY CONSISTING OF SYNTHETIC RESIN

摘要

PURPOSE:To obtain a uniform refractive index distribution over the entire part of a diameter by filling a monomer mixture composed of plural kinds having different polymer refractive indices and reactivity ratios into a prescribed vessel, heating the mixture to a specific temp. and polymerizing the mixture from the outside layer thereof toward the inside in the vessel. CONSTITUTION:The monomer mixture composed of such plural kinds as to attain >=1.1 or <=1/1.1 value of the formula when the reactivity ratio of an optional monomer Mi with respect to a monomer Mj in plural kinds of monomers having the different polymer refractive indices is designated as Rij, the reactivity ratijo of the monomer Mj with respect to the monomer Mi as Rji and themixing molar ratio of the monomers Mi and Mj as (Mi/Mj)m is filled into a polymerizing tube 1 and the temp. to be applied to the tube 1 is made >=50 deg.C, more preferably <=150 deg.C. The heating is progressively executed from one end of the tube 1. The copolymer contg. much monmer having the high monomer reactivity ratio is formed from near the inside wall of the tube 1 when the temp. of the polymerization system is increased by which the formation of the uniform refractive index gradient from the periphery toward the center of the tube is made possible. The copolymer is further thermally stretched and is made into a fiber, by which the optical near parabolic fiber having large NA is obted.