FORMATION OF PROTECTIVE LAYER FOR OPTICAL DISK

摘要

PURPOSE:To obtain the protective layer which does not peel and crack in high- temp. and high-humidity environment by forming the protective layer to be provided between a substrate and a recording layer under a specific sputtering pressure by using silicon oxynitride having a specific compsn. CONSTITUTION:The protective layer 2 consisting of the silicon oxynitride having the refractive index at 830nm wavelength ranging 1.8 to 2.1 is provided between the plastic substrate 1 and the recording layer 3. The sputtering gaseous pressure P (mTorr) when the refractive index at 83-nm wavelength after oxygen is removed from the silicon oxynitride is destinated n0 is adjusted to the ranges of equation I and equation II at the time of forming the layer 2 by a sputtering method. The crack resistance degrades if the gaseous pressure P is higher than the range of the equation II and the peeling resistance degrades if the pressure is lower than this range. The barrier property to oxygen and water degrades if the pressure is higher than the range of the equation I and the formation of the stable sputtered film is difficult if the pressure is lower than this range. The protective layer having the excellent environmental resistance is obtd. in this way.