| 摘要 |
PURPOSE: To obtain high translucent performance and a region where a refractive index changes continuously by specifying the diameter of a core including a refractive index distribution region formed in the light transmission body contg. nonpolymerizable compds, having a high refractive index and low refractive index. CONSTITUTION: The diameter of the core including the refractive index distribution region formed in light transmission body contg. at least >=2 kinds of the nonpolymerizable compds. varying in the refractive index from each other and contg. the nonpolymerizable compds. having the refractive index higher than the refractive index of the polymers and the refractive index lower than the refractive index of the polymers is specified to <=70% of the outside diameter of the clad. For example, the polymer A contg. the nonpolymerizable compd. C is introduced by a gear pump into the inner part 2 of a composite spinning mouthpiece and the polymer B contg. the nonpolymerizable compd. D into the outer part 3. The respective polymers A, B are thereafter extruded from an inner discharge hole 2 and an outer discharge hole 3, respectively to form a core-and-sheath type composite rod-shaped body within the composite spinning mouthpiece 6. The composite rod state of the core-and-sheath type is then heated for a specified period of time at the viscosity at which spinning is possible and at the temp. at which the polymers do not foam at the time of discharge the rod from the mouthpiece. |
