Golf ball
A golf ball 2 includes a core 4 , a mid layer 6 , and a cover 8 . A hardness H75 at a point to which a distance from a central point of the core 4 is 75% of a radius of the core 4 is greater than a hardness H0 at the central point of the core 4 . A difference D1=(H75−H0) is not less than 10.0 and not greater than 27.0 in Shore C hardness. A hardness Hs at a surface of the core 4 is greater than the hardness H75. A difference D2=(Hs−H75) is not less than 0 and not greater than 6.5 in Shore C hardness. The hardness H75 is less than a Shore C hardness HmC of the mid layer 6 . A Shore D hardness HmD of the mid layer 6 is greater than a Shore D hardness Hc of the cover 8.
1. A golf ball comprising a spherical core, a mid layer positioned outside the core, and a cover positioned outside the mid layer, wherein
a hardness H75 at a point to which a distance from a central point of the core is equal to 75% of a radius of the core is greater than a hardness H0 at the central point of the core, and a difference D1=(H75−H0) between the hardness H75 and the hardness H0 is not less than 10.0 and not greater than 27.0 in Shore C hardness,
a hardness Hs at a surface of the core is greater than the hardness H75, and a difference D2=(Hs−H75) between the hardness Hs and the hardness H75 is not less than 0 and not greater than 6.5 in Shore C hardness,
the hardness H75 is less than a Shore C hardness HmC of the mid layer, and
a Shore D hardness HmD of the mid layer is greater than a Shore D hardness Hc of the cover,
wherein a ratio (D2/D1) of the difference D2 to the difference D1 is not greater than 0.25 in Shore C hardness.
2. The golf ball according to claim 1 , wherein a hardness H25 at a point to which a distance from the central point of the core is equal to 25% of the radius of the core is greater than the hardness H0, and a difference D3=(H25−H0) between the hardness H25 and the hardness H0 is not less than 7.0 in Shore C hardness.
3. The golf ball according to claim 1 , wherein a difference D4=(H50−H25) between a hardness H50 at a point to which a distance from the central point of the core is equal to 50% of the radius of the core and the hardness H25 is not less than −3.0 and not greater than 3.0 in Shore C hardness.
4. The golf ball according to claim 1 , wherein the hardness H75 is greater than the hardness H50, and a difference D5=(H75−H50) between the hardness H75 and the hardness H50 is not less than 6.0 in Shore C hardness.
5. The golf ball according to claim 1 , wherein a difference D6=(HmC−H75) between the hardness HmC and the hardness H75 is not less than 7.0 in Shore C hardness.
6. The golf ball according to claim 1 , wherein the hardness HmC is greater than the hardness Hs, and a difference D7=(HmC−Hs) between the hardness HmC and the hardness Hs is not less than 4.0 in Shore C hardness.
7. The golf ball according to claim 1 , wherein a difference D8=(HmD−Hc) between the hardness HmD and the hardness Hc is not less than 20.0 in Shore D hardness.
8. The golf ball according to claim 1 , wherein the core is formed from a rubber composition, and the rubber composition of the core includes (a) a base rubber, (b) a co-crosslinking agent that is an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof, (c) a crosslinking initiator, and (d) an unsaturated fatty acid and/or a metal salt thereof (except the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and the metal salt thereof).
9. The golf ball according to claim 8 , wherein a number of carbon atoms of a fatty acid component of the unsaturated fatty acid and/or the metal salt thereof (d) is not less than 4 and not greater than 33.
10. The golf ball according to claim 8 , wherein the unsaturated fatty acid and/or the metal salt thereof (d) has one or two carbon-carbon double bonds.