INFLUENCE OF MOLD TEMPERATURE ON TRANSCRIPTION AND SIGNAL DETERIORATION OF INJECTION-MOLDED SUBSTRATES FOR OPTICAL DISKS

In order to analyze the mechanism of the transcription in injection-molding and signal deterioration of optical discs, the relationship between the mold temperature and the surface roughness of the polycarbonate and amorphous polyolefin substrate has been studied. The results obtained are as follows; (1) When the mold temperature is low, microscopic flow marks more than 5 nm deep are formed on the surface of the injection-molded substrate, and the molding transcription drops. (2) When the mold temperature is high, the flow marks disappear, and at the same time the molding transcription improves. The surface roughness of the substrate of 3.2 nm in R(max) is nearly equal to that of the stamper of 2.7 nm in R(max). (3) The signal deterioration of the optical disc strongly depends on the surface roughness of the substrate. That is, the noise power becomes lower when the surface becomes smoother.