| 摘要 |
PURPOSE:To decrease light scattering and the quantity of the flare light to be emitted and to improve definition by decreasing the microforeign matter existing in a plastic light transmission body with which the refractive index changes continuously from the central part to the peripheral part as far as possible. CONSTITUTION:The microforeign matter of 0.1 to 25mum existing in the distributed refractive index plastic light transmission body with which the refractive index changes continuously from the central part toward the peripheral part is so decreased that the total sum of the number thereof attains <=1,000,000 pieces/g. The number thereof is preferably <=500,000 pieces/g, more preferably 100,000 pieces/g for applications where the definition is further required. The size and total number of the microforeign matter can be measured by a laser scattering type micrforeign matter counter. More specifically the produced distributed index plastic light transmission body is dissolved in a dust-free solvent in a clean room and the soln. prepd. in such a manner is irradiated with a laser. The scattering intensity of the light by the microforeign matter existing in the soln. is measured and the total sum is determined from the relation with the previously calibrated number of the microforeign matter. |
