A golf ball 2 includes a spherical core 4 and a cover 6 positioned outside the core 4 . The core 4 is obtained by crosslinking a rubber composition including 2-naphthalenethiol. The difference between: a hardness H(5.0) at a point which is located at a distance of 5 mm from the central point of the core 4 ; and a hardness Ho at the central point is 6.0 or greater. The difference between: a hardness H(12.5) at a point which is located at a distance of 12.5 mm from the central point; and the hardness H(5.0) is 4.0 or less. The difference between a hardness Hs at the surface of the core 4 and the hardness H(12.5) is 10.0 or greater. The difference between the hardness Hs and the hardness Ho is 22.0 or greater. There is no zone in which a hardness decreases from the central point to the surface.
1. A golf ball comprising a core and a cover positioned outside the core, wherein
a difference between: a JIS-C hardness H(5.0) at a point which is located at a distance of 5 mm from a central point of the core; and a JIS-C hardness Ho at the central point is equal to or greater than 6.0,
a difference between: a JIS-C hardness H(12.5) at a point which is located at a distance of 12.5 mm from the central point; and the hardness H(5.0) is equal to or less than 3.0,
a difference between a JIS-C hardness Hs at a surface of the core and the hardness H(12.5) is equal to or greater than 10.0,
a difference between the hardness Hs and the hardness Ho is equal to or greater than 22.0,
there is no zone in which a hardness decreases from the central point toward the surface,
the core is formed by crosslinking a rubber composition including a base rubber and an organic sulfur compound, and the organic sulfur compound is 2-naphthalenethiol,
the rubber composition includes the base rubber in an amount of 100 parts by weight, and 2-naphthalenethiol in an amount which is not less than 0.2 parts by weight and not greater than 2.0 parts by weight, and
the JIS-C hardness Ho at the central point of the core is equal to or less than 60.0.
2. The golf ball according to claim 1 , wherein
the hardness Ho is equal to or greater than 40.0, and
the hardness Hs is equal to or greater than 78.0 but equal to or less than 95.0.
3. The golf ball according to claim 1 , wherein the hardness H(5.0) is equal to or greater than 63.0 but equal to or less than 73.0.
4. The golf ball according to claim 1 , wherein the hardness H(12.5) is equal to or greater than 64.0 but equal to or less than 76.0.
5. The golf ball according to claim 1 , wherein an amount of compressive deformation CD of the golf ball is equal to or greater than 2.5 mm but equal to or less than 4.0mm.
6. The golf ball according to claim 1 , wherein the JIC-C hardness H(12.5) is not less than 64.0 and not greater than 72.0.
7. The golf ball according to claim 1 , wherein a difference between: the JIS-C hardness H(12.5) and a JIS-C hardness H(10.0) at a point which is located at a distance of 10 mm from a central point of the core, is equal to or less than 1.0.
8. The golf ball according to claim 1 , wherein a JIS-C hardness H(15.0) at a point which is located at a distance of 15 mm from a central point of the core, is greater than a JIS-C hardness H(10.0) at a point which is located at a distance of 10 mm from a central point of the core.