A golf ball 2 includes a main body 4 and a paint film 6. The paint film 6 includes an inner layer 14 and an outer layer 16. A modulus Min of the inner layer 14 is higher than a modulus Mout of the outer layer 16. A difference (Min−Mout) is not less than 25 kgf/cm 2 . The golf ball 2 has a plurality of dimples 18. A ratio So of a sum of areas of the dimples 18 relative to a surface area of a phantom sphere of the golf ball 2 and a ratio Rs of a number of the dimples 18 each having a diameter of not less than 9.60% and not greater than 10.37% of a diameter of the golf ball 2, relative to a total number of the dimples 18, satisfy the following mathematical formula (1). Rs ≥−2.5* So +273 (1)
1. A golf ball comprising a main body and a paint film positioned outside the main body, wherein
the paint film includes an inner layer and an outer layer positioned outside the inner layer,
a 10% modulus Min of the inner layer is higher than a 10% modulus Mout of the outer layer,
a difference (Min−Mout) between the modulus Min and the modulus Mout is not less than 25 kgf/cm 2 ,
the golf ball has a plurality of dimples on a surface thereof,
a ratio So of a sum of areas of the dimples relative to a surface area of a phantom sphere of the golf ball is not less than 81.0%,
a ratio Rs of a number of the dimples each having a diameter of not less than 9.60% and not greater than 10.37% of a diameter of the golf ball, relative to a total number of the dimples, is not less than 50%,
a dimple pattern of each hemisphere of the phantom sphere includes three units that are rotationally symmetrical to each other,
a dimple pattern of each unit includes two small units that are mirror-symmetrical to each other, and
the golf ball satisfies the following mathematical formula (1):
Rs≥− 2.5* So+ 273 (1).
2. The golf ball according to claim 1 , wherein the modulus Min is not less than 100 kgf/cm 2 .
3. The golf ball according to claim 1 , wherein the modulus Mout is less than 100 kgf/cm2.
4. The golf ball according to claim 1 , wherein
the inner layer has a thickness Tin of not less than 5 μm and not greater than 30 μm, and
the outer layer has a thickness Tout of not less than 5 μm and not greater than 30 μm.
5. The golf ball according to claim 1 , wherein
the inner layer is formed from a resin composition, and
a base resin of the resin composition is a polyurethane.
6. The golf ball according to claim 1 , wherein
the outer layer is formed from a resin composition, and
a base resin of the resin composition is a polyurethane.
7. The golf ball according to claim 1 , wherein the golf ball satisfies the following mathematical formula (2):
Rs≥− 2.5* So+ 278 (2).
8. The golf ball according to claim 7 , wherein the golf ball satisfies the following mathematical formula (3):
Rs≥− 2.5* So+ 283 (3).
9. The golf ball according to claim 1 , wherein
a ratio Rs′ of a number of the dimples each having a diameter of not less than 10.10% and not greater than
10.37% of the diameter of the golf ball, relative to the total number of the dimples, is not less than 50%, and
the golf ball satisfies the following mathematical formula (4):
Rs′≥− 2.2* So+ 245 (4).
10. The golf ball according to claim 9 , wherein the golf ball satisfies the following mathematical formula (5):
Rs′≥− 2.2* So+ 252 (5).
11. The golf ball according to claim 1 , wherein a depth of a deepest part of each dimple from a surface of the phantom sphere is not less than 0.10 mm and not greater than 0.65 mm.
12. The golf ball according to claim 1 , wherein a total volume of the dimples is not less than 450 mm 3 and not greater than 750 mm 3 .
13. The golf ball according to claim 1 , wherein a total number of the dimples is not less than 250 and not greater than 450.