| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyethersulfone resin film improved in color tone, esp. in the degree of yellowing, by adding hypophosphorous acid and/or phosphorous acid to a polyethersulfone resin soln., then casting the soln. onto a carrier, and peeling the resultant film from the carrier. SOLUTION: A polyethersulfone resin having repeating units represented by the formula: [-Ph-SO2 -Ph-O-] (wherein Ph is phenyl) is dissolved in a solvent (e.g. N,N-dimethylformamide. N-methyl-2-pyrrolidone methylene chloride, or chloroform) to give a resin soln. having a viscosity of 15 P or lower. After 50-200 ppm hypophousphorous acid and/or phosphorous acid is added to the soln., it is cast on a carrier, dried by evaporating the solvent, and peeled. Thus is stably produced a polyethersulfone resin film which exhibits a low degree of yellowing, an excellent clarity, a good surface smoothness and a high thickness accuracy and is suitable as an optical film. |
