| 摘要 |
PURPOSE:To improve the C/N ratio and to reduce the variation with time by forming groups concentrically or spirally on the surface of foaming resin. CONSTITUTION:For instance, a polyvinyl chloride plate 2 having 0.2g/cm<3> density and an independent air bubble structure is heated up to 100 deg.C. Then an electrocasting stamper which forms spiral groups 3 centering on a rotary shaft is pressed and at the same time cooled. Thus the group 3 is fixed on the surface 2 of the polyvinyl chloride. Then Al is vapor deposited on the surface 2 to form a reflecting layer 1. The vertical angle of the group 3 is set between 130 deg. and 170 deg.. The recording bits are read by an LD of 3mw, and the C/N ratio is set at 55dB. It is known that the variation of the C/N ratio is limited within a range of the experimental error at 60 deg.C with 80% humidity and after 1,000hr. The foaming resin uses an expanded plastic base material such as the thermosetting resin like polystyrene, polyvinyl chloride, etc. that has preferably >=1.5 foaming factor. The layer 1 uses a metal or an alloy of Al, Ti, Cr, etc. |
