Patent ID: 7273425

Claim:
A solid golf ball, comprising a solid core, a cover layer that encloses the core, and a plurality of dimples formed on an outside surface of an outermost layer of the cover, wherein the solid core is formed of a rubber composition composed of 100 parts by weight of a base rubber that includes 60 to 100 parts by weight of a polybutadiene rubber having a cis-1,4 bond content of at least 60% and synthesized using a rare-earth catalyst, 0. 1 to 5 parts by weight of an organosulfur compound, and an unsaturated carboxylic acid or a metal salt thereof, an organic peroxide and an inorganic filler; the solid core has a deformation, when subjected to loading from an initial load of 10 kgf to a final load of 130 kg, of 2.0 to 3.5 mm, and has the hardness distribution shown in the table below; the cover layer is formed primarily of a thermoplastic or thermoset polyurethane material and has a thickness of 0.5 to 2.5 mm, a Shore D hardness at the surface of 50 to 70 and a flexural rigidity of 50 to 300 MPa; the surface hardness of the core is from 1 to 15 Shore D hardness units lower than the surface hardness of the cover; and the golf ball has a deformation, when subjected to loading from an initial load of 10 kgf to a final load of 130 kgf, of 2.0 to 2.9 mm Hardness Distribution in Solid Core Shore D hardness Center 35 to 55 Region located 5 to 10 mm from center 39 to 58 Region located 15 mm from center 48 to 66 Surface 50 to 68 Hardness difference between center and surface 5 to 20 and wherein the solid golf ball has a hardness difference between any two places in the region of the solid core located 5 to 10 mm from the core center of not more than ±2 Shore D hardness units.