Abstract: The present invention discloses a polycyclic norbornene-based ring-opening polymer which comprises(A) 90-5% by mol of a repeating unit represented by the following formula [I] or the alkyl-substituted derivative thereof, and(B) 10-95% by mol of at least one repeating unit selected from a repeating unit represented by the following formula [II], the alkyl-substituted derivative thereof, a repeating unit represented by the following formula [III], the alkyl-substituted derivative thereof, or the alkylidene-substituted derivative thereof, and which has an intrinsic viscosity [.eta.] of 0.01-20 dl/g as determined in toluene at 25.degree. C., the hydrogenation products thereof, and a process for production thereof ##STR1## wherein ------ denotes a single bond or a double bond.

Abstract: There are disclosed a polycyclic norbornene or its derivative hydrogenated copolymer which containsa repeating unit represented by the following formula [I] or the alkyl-substituted derivative thereof (A),a repeating unit represented by the following formula [II] or the alkyl-substituted derivative thereof (B) and, as desired,5-85% by mole of at least one repeating unit (C) selected from a repeating unit represented by the following formula [III], the alkyl-substituted derivative thereof, a repeating unit represented by the following formula [IV], the alkyl-substituted derivative and the alkylidene-substituted derivative thereof, and a process for producing the polycyclic norbornene or its derivative ring-opening hydrogenated copolymer ##STR1## wherein ------ represents either a single bond or a double bond.

Abstract: There are disclosed a polycyclic norbornene or its derivative ring-opening hydrogenated copolymer which contains 90-10% by mole of a repeating unit represented by the following formula [I] or the alkly-substituted derivative, at least a repeating unit represented by the following formula [II] or the alkly-substituted derivative thereof and, as required, a repeating unit represented by the following formula [III], the alkyl-substituted derivative thereof or the alkylidene-substituted derivative thereof, has an intrinsic viscosity [.eta.] of 0.01-20 dl/g as determined in toluene at 25 .degree. C., and in which at least 50% of the (C C) linkages constituting the main chain are single bonds, and the production of said hydrogenation product ##STR1## wherein represents either a single bond or a double bond.

Abstract: A molding material suitable as an optical material and an optical recording medium formed of the molding material are disclosed. The molding material comprises a hydrogenated product of a polymer formed by ring-opening polymerization of a norbornene-type monomer, the hydrogenated product having a number average molecular weight (Mn) of 20,000 to 50,000, a weight average molecular weight (Mw) of 40,000 to 80,000 and a molecular distribution (Mw/Mn) of not more than 2.5 and having a volatile content of not more than 0.3% by weight.