| 摘要 |
PURPOSE: To reduce the influence of moisture absorption of a medium by specifying the changing ratio of the dimension after 5 hours to the dimension after 0.5 hour as the reference in the area from the center of the optical recording medium substrate to specified distance and from the surface to specified depth of the medium at specified temp. and humidity. CONSTITUTION: When the medium is stored in an environment at 60 deg.C and 90%RH, in the area whose distance from the center of the substrate of the optical information recording medium is, for example, <20mm and in the area whose depth from the substrate surface is, for example, 100μm, it is necessary that the dimension L1 after 0.5 hour storage and the dimension L2 after 5 hours storage are in the relation (L1 -L2 )/L1 <=1.0×10<-3> . As for an acryl resin to satisfy this condition, for example, such a material having >110 deg.C glass transition temp., <1.0% water absorption in used, and a molded substrate which is annealed at temp. within ±30 deg.C of the glass transition temp. is used. As for an inorg. thin film, Al, metal, metal essentially comprising Al or silicon oxide is used. |
