Abstract: A disc-shaped recording medium having transcription characteristics for fine signals simultaneously with resonance characteristics and stiffness which are characteristics contrary to the transcription characteristics. At least a recording layer and a light transmitting layer are sequentially formed on a substrate and light is illuminated from a light transmitting layer side to record and/or reproduce information signals. The substrate includes a core layer formed of a resin composition comprised of a mixture of two or more resin sorts. The resin composition has tan?, as an index indicating the internal loss, equal to not less than 0.015 as a system in its entirety. The resin composition constituting the core layer is a compounded resin of the incompatible system and is of an islands-sea structure.

Abstract: An aromatic polycarbonate which has high durability and is excellent in color tone, transparency and mechanical strength, especially an aromatic polycarbonate which has high durability and stability when it is used under high temperature and high humidity conditions for a long time, and production method and use thereof. In the aromatic polycarbonate which has a sodium element content of 100 ppb or less and a content of each of Ni, Pb, Cr, Mn and Fe of 70 ppb or less and the method of producing a polycarbonate by polycondensing an aromatic dihydroxy compound and a carbonic acid diester, the above aromatic polycarbonate is produced by controlling 1) the content of sodium element contained in each of the above raw materials to 52 ppb or less, 2) the content of each of Fe, Cr, Mn, Ni and Pb to 40 ppb or less and 3) the amount of a specific catalyst to a specific value based on the content of Fe contained in the raw materials.

Abstract: A resin composition comprising 100 parts by weight of a resin component selected from (a) an aromatic polycarbonate resin (A-1 component) obtained by melt polymerization and, when measured for fluorescent spectrum at an exciting wavelength of 320 nm, having a relative fluorescence intensity of 4×10−3 or less at 465 nm relative to a standard substance, (b) a resin mixture of said A-1 component and a styrene-based resin (A-2 component), and (c) a resin mixture of said A-1 component and an aromatic polyester resin (A-3 component), and 5 to 200 parts by weight of a reinforcing filler. This resin composition gives a molded article superior in wet heat fatigue and various physical properties.

Abstract: A disc-shaped recording medium having transcription characteristics for fine signals simultaneously with resonance characteristics and stiffness which are characteristics contrary to the transcription characteristics. At least a recording layer and a light transmitting layer are sequentially formed on a substrate and light is illuminated from a light transmitting layer side to record and/or reproduce information signals. The substrate includes a core layer formed of a resin composition comprised of a mixture of two or more resin sorts. The resin composition has tan&dgr;, as an index indicating the internal loss, equal to not less than 0.015 as a system in its entirety. The resin composition constituting the core layer is a compounded resin of the incompatible system and is of an islands-sea structure.