| 摘要 |
PROBLEM TO BE SOLVED: To improve adhesion with a recording film and also prevent corrosion of recording film and metal dies during the molding by processing polycarbonate including impurity with an organic solvent such as aceton, etc., to obtain high purity polycarbonate with extremely less amount of impurity contents and by using such polycarbonate for the disk substrate. SOLUTION: Amount of impurity can be reduced by extracting polycarbonate powder including impurity obtained by an ordinary methods using an organic solvent such as aceton, etc. Low molecule element is set to 3wt.% or less, while inreactive bisphenol is set to 20ppm or less and methylene chloride is set to 20ppm or less. Here, if low molecule element exceeds 3wt.% or inreactive bisphenel exceeds 20ppm, contact property of the disk substrate and recording film is lowered. When methylene chloride really exceeds 20ppm, a recording film is easily corroded and moreover metal dies during the molding is corroded, shortening the operation life of stamber. |
