초록 ▼

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

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 tanδ, 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.

대표청구항 ▼

1. An optical recording medium in which at least a recording layer and a light transmitting layer are sequentially formed on a substrate and in which the light is illuminated from the light transmitting layer side for recording and/or reproducing information signals, whereinsaid substrate has at lea

1. An optical recording medium in which at least a recording layer and a light transmitting layer are sequentially formed on a substrate and in which the light is illuminated from the light transmitting layer side for recording and/or reproducing information signals, whereinsaid substrate has at least a surface layer (skin layer) and a core layer, said core layer having an internal loss tanδ of not less than 0.015 as measured at 40° C. at 18 Hz pursuant to JIS K 7198. 2. The optical recording medium according to claim 1 wherein said core layer is a resin composition comprised of a mixture of two or more resins.3. The optical recording medium according to claim 2 wherein said resin composition is an incompatible composite resin material; andwherein said core layer is of an islands-sea structure. 4. An optical recording medium in which at least a recording layer and a light transmitting layer are sequentially formed on a substrate and in which the light is illuminated from the light transmitting layer side for recording and/or reproducing information signals,wherein said substrate has at least a surface layer (skin layer) and a core layer, said core layer having an internal loss tanδ of not less than 0.015 as measured at 40° C. at 18 Hz pursuant to JIS K 7198, wherein said core layer is a resin composition comprised of a mixture of two or more resins, wherein said resin composition is comprised of 50 to 90 wt% of an amorphous thermoplastic resin (component A) and a methyl methacrylate based resin (component B). 5. The optical recording medium according to claim 3 wherein said resin composition is comprised of 50 to 90 wt% of an amorphous thermoplastic resin (component A) and a methyl methacrylate based resin (component B).6. The optical recording medium according to claim 4 wherein said component A is an aromatic polycarbonate resin.7. The optical recording medium according to claim 5 wherein said component A is an aromatic polycarbonate resin.8. The optical recording medium according to claim 1 wherein said core layer is comprised of the resin composition and a filler.9. The optical recording medium according to claim 8 wherein said filler is graphite added in an amount of 5 to 15 wt% to said resin composition.10. The optical recording medium according to claim 1 wherein said substrate is of a structure of three or more layers comprised of the core layer sandwiched by surface layers each of which is a resin layer having the water absorption coefficient of not larger than 0.20% as measured under a condition of immersion in water at 23° C. for 24 hours pursuant to ASTM D 570.11. The optical recording medium according to claim 2 wherein said resin composition is comprised of 50 to 90 wt% of an amorphous thermoplastic resin (component A) and a methyl methacrylate based resin (component B).12. The optical recording medium according to claim 11 wherein said component A is an aromatic polycarbonate resin.