Patent ID: 7153224

Claim:
A multi-piece solid golf ball comprising a solid core consisting of a center core and an outer core, an inner cover layer and an outer cover layer, wherein the solid core is molded from a rubber composition comprising 100 parts by weight of a base rubber composed of (a) 20 to 100 wt % of a polybutadiene having a cis-1,4 content of at least 60% and a 1,2 vinyl content of at most 2%, having a viscosity η at 25° C. as a 5 wt % solution in toluene of up to 600 mPa·s, being synthesized using a rare-earth catalyst, in combination with (b) 0 to 80 wt % of a diene rubber other than component (a), (c) 10 to 60 parts by weight of an unsaturated carboxylic acid or a metal salt thereof or both, (d) 0.1 to 5 parts by weight of an organosulfur compound, (e) 5 to 80 parts by weight of an inorganic filler, and (f) 0.1 to 5 parts by weight of an organic peroxide; the center core has a JIS-C hardness of 40 to 60 on its center and a JIS-C hardness of 55 to 75 on its surface and the difference therebetween is at least 10, the outer core is harder than the surface hardness of the center core, the cross-sectional hardness of 1 mm outside from the border between the center core and the outer core is from 65 to 85 on a JIS-C hardness, a surface of the outer core has a JIS-C hardness of 75 to 95, the inner cover layer has a Shore D hardness of 50 to 80, the outer cover layer has a Shore D hardness of 35 to 60, and the outer cover layer has a lower Shore D hardness than the inner cover layer.