Abstract: A cross-linked rubber obtained by crosslinking a rubber composition containing a conjugated diene rubber and an inorganic filler, wherein when a loss tangent value of a non-interface component forming, of the cross-linked rubber ingredient, a portion other than an interface with the inorganic filler is represented as L(m) and a loss tangent value of an interface component forming, of the cross-linked rubber ingredient, an interface portion with the inorganic filler is represented as L(i), each loss tangent value being measured using an atomic force microscope in a state in which sinusoidal vibrations of 5 kHz are applied to the cross-linked rubber, the cross-linked rubber has a ratio L(i)/L(m) of 0.85 or less.

Abstract: A cross-linked rubber obtained by crosslinking a rubber composition containing a conjugated diene rubber and an inorganic filler, wherein when a loss tangent value of a non-interface component forming, of the cross-linked rubber ingredient, a portion other than an interface with the inorganic filler is represented as L(m) and a loss tangent value of an interface component forming, of the cross-linked rubber ingredient, an interface portion with the inorganic filler is represented as L(i), each loss tangent value being measured using an atomic force microscope in a state in which sinusoidal vibrations of 5 kHz are applied to the cross-linked rubber, the cross-linked rubber has a ratio L(i)/L(m) of 0.85 or less.

Abstract: An unsaturated nitrile-conjugated diene copolymer having at least 0.03 mole, per 100 moles of the monomeric units constituting the molecule, of an alkylthio group having 12 to 16 carbon atoms, which include at least three tertiary carbon atoms, and having a sulfur atom which is directly bound to at least one of the tertiary carbon atoms; said copolymer having a Mooney viscosity of 15 to 65. This copolymer is produced by copolymerizing an unsaturated nitrile and a conjugated diene in the presence of a free-radical initiator by using as a molecular weight modifier an alkylthiol compound having the above-mentioned alkylthio group. The copolymer is used as a rubber composition having incorporated therein a sulfur-containing vulcanizer.