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With dimethyl 2,2'-azobis(isobutyrate); butyl 3-mercaptopropionate; at 95℃; for 8 - 28h; |
A polymerization chamber having an inner surface of polyvinylidene fluorine and having an inner diameter of 18.5 mm and a length of 17 cm was prepared. A mixed solution was prepared by adding, to a mixture of 80 parts by weight of 2, 2, 2-trifluoroethyl methacrylate and 20 parts by weight of <strong>[13642-97-2]pentafluorophenyl methacrylate</strong>, dimethylazobisisobutyrate as a polymerization initiator in an amount of 0.1 mol% of all the monomers and Compound (2-9) as a chain transfer agent in an amount of 0.09 mol%. Thus prepared, the solution was purged with nitrogen for 5 minutes, and then filtered through a PTFE membrane filter (Whatman' s Model 6784-1302) . This was fed into the polymerization chamber, and sealed up with a Teflon stopper. Next, the polymerization chamber was kept horizontal, and rotated at 2000 rpm, in which the monomers were thermally polymerized at 950C for 2 hours. This is a clad. Next, a mixed solution was prepared by adding, to a mixture of 76.2 parts by weight of 2, 2, 2-trifluoroethyl methacrylate and 23.8 parts by weight of <strong>[13642-97-2]pentafluorophenyl methacrylate</strong>, dimethylazobisisobutyrate as a polymerization initiator in an amount of 0.1 mol% of all the monomers and Compound (2-9) as a chain transfer agent in an amount of 0.09 mol%. Thus prepared, the solution was purged with nitrogen for 5 minutes, and then filtered through a PTFE membrane filter (Whatman's Model 6784-1302) . This was injected into the hollow area of the clad. Then, the polymerization chamber was kept horizontal, and rotated at 2000 rpm, in which the monomers were thermally EPO <DP n="27"/>polymerized at 95C for 2 hours. This is the first layer of a core. Next, as in Table 1 below, other core layers up to the 10th layer were laminated on it, in the same manner as that for the formation of the first core layer. This was further heated at 95C for 6 hours, and a preform having an outer diameter of 18.5 mm and a hole diameter of 3 mm was finally obtained. The amount of the constitutive materials to be fed into the reactor was so controlled that the thickness of the clad could be 1.5 mm and the thickness of each core layer could be constant, 0.625 mm. Thus obtained, the preform was dried at 250C and under a reduced pressure of -0.1 MPa (as intended for full vacuum, corresponding to about 3 mmHg as calculated) for 100 hours, and then its hollow was connected to a degassing device. In that condition, this was thermally stretched in an electric furnace having an inner temperature of 2000C under a reduced pressure of -4 KPa. Its hollow was lost, and 130 m of POF having an outer diameter of 470 μm was obtained. Thus obtained, the POF was analyzed for its refractive index profile with a two-flux transmission interference microscope (Mizojiri Optics' Model TD-20) . Thus obtained, the refractive index profile data were processed for g-power approximation, and the refractive index profile coefficient, g, was 2. The transmission loss through the POF at a light source wavelength of 650 nm was measured, and it was 94 dB/km. EPO <DP n="28"/> |