Golf ball 2 has spherical core 4 , cover 6 situated on the external side of the core 4 , and paint layer 8 situated on the external side of the cover 6 . The cover 6 has a Shore D hardness of no greater than 61. The paint layer 8 has a Martens hardness of no greater than 2.0 mgf/μm 2 . The base polymer of the paint layer 8 is a polyurethane obtained by a reaction of a polyol with a polyisocyanate. The polyisocyanate contains a buret-modified form of hexamethylene diisocyanate. The cover 6 has a thickness of 0.3 mm or greater and 1.0 mm or less. The paint layer 8 has a thickness of 5 μm or greater and 40 μm or less.
1. A golf ball comprising a core, a cover situated on the external side of the core, and a paint layer situated on the external side of the cover, wherein
the cover has a Shore D hardness of no greater than 61,
the paint layer has a Martens hardness of no less than 0.01 mgf/μm 2 and no greater than 2.0 mgf/μm 2 ,
the base polymer of the paint layer is a polyurethane obtained by a reaction of a polyol having a weight-average molecular weight of 50 to 2,000 with a polyisocyanate, and
the base polymer of the cover is at least one member selected from the group consisting of a polyurethane, an ionomer resin, a polyamide, a polyester, a polystyrene and a polyolefin.
2. The golf ball according to claim 1 , wherein the base polymer of the paint layer is a polyurethane obtained by a reaction of a polyol with a polyisocyanate, and the NCO/OH ratio in the polyurethane is 1.0/1.0 to 1.4/1.0.
3. The golf ball according to claim 1 , wherein the paint layer has a thickness of 5 μm to 40 μm.
4. The golf ball according to claim 1 , wherein the cover has a Shore D hardness of no greater than 55.
5. The golf ball according to claim 1 , wherein the cover has a thickness of 0.3 mm to 1.0 mm.
6. The golf ball according to claim 1 , wherein the amount of compressive deformation of the core is 1.8 mm to 4.0 mm, as measured under a condition in which the initial load is 98 N and the final load is 1,274 N.
7. The golf ball according to claim 1 , wherein the core has a center and a mid layer situated on the external side of the center, and the surface of the center has a JIS-C hardness of 60 to 95.
8. The golf ball according to claim 1 , wherein the core has a center and a mid layer situated on the external side of the center, and the amount of compressive deformation of the center is 1.5 mm to 5.0 mm, as measured under a condition in which the initial load is 98 N and the final load is 1,274 N.
9. The golf ball according to claim 1 , wherein the core has a center and a mid layer situated on the external side of the center, and the center has a diameter of 30 mm to 41.5 mm.
10. The golf ball according to claim 1 , wherein the core has a center and a mid layer situated on the external side of the center, and the center has a weight of 25 g to 42 g.
11. The golf ball according to claim 1 , wherein the core has a center and a mid layer situated on the external side of the center, and the base polymer of the mid layer is at least one selected from the group consisting of an ionomer resin, a styrene block-containing thermoplastic elastomer, a thermoplastic polyester elastomer, a thermoplastic polyamide elastomer, a thermoplastic polyurethane elastomer and a thermoplastic polyolefin elastomer.
12. The golf ball according to claim 1 , wherein the core has a center and a mid layer situated on the external side of the center, and the mid layer has a Shore D hardness of 40 to 75.
13. The golf ball according to claim 1 , wherein the core has a center and a mid layer situated on the external side of the center, and the mid layer has a thickness of 0.3 mm to 2.5 mm.
14. The golf ball according to claim 1 having an amount of compressive deformation of 2.0 mm to 3.5 mm, as measured under a condition in which the initial load is 98 N and the final load is 1,274 N.
15. The golf ball according to claim 1 , wherein the polyisocyanate contains a buret-modified form of hexamethylene diisocyanate.
16. The golf ball according to claim 15 , wherein the percentage of the buret-modified form relative to the total amount of the polyisocyanate is no less than 20% by weight.
17. The golf ball according to claim 16 , wherein the percentage of the buret-modified form relative to the total amount of the polyisocyanate is no less than 50% by weight.
18. The golf ball according to claim 1 , wherein the cover has a Shore D hardness of no greater than 58, when the base polymer of the cover is the ionomer resin.
19. The golf ball according to claim 1 , wherein the cover has a Shore D hardness of no greater than 45, when the base polymer of the cover is the polyurethane.
20. A golf ball comprising a core, a cover situated on the external side of the core, and a paint layer situated on the external side of the cover, wherein
the cover has a Shore D hardness of no greater than 61,
the paint layer has a Martens hardness of no less than 0.01 mgf/μm 2 and no greater than 2.0 mgf/μm 2 ,
the base polymer of the paint layer is a polyurethane obtained by a reaction of a polyol having a weight-average molecular weight of 50 to 2,000 with a polyisocyanate, and
the base polymer of the cover is at least one member selected from the group consisting of a polyurethane, an ionomer resin, a polyamide, a polyester, a polystyrene and a polyolefin, wherein the Shore D hardness of the cover and the Martens hardness of the paint layer represent a compatible softness such that the deforming of the paint layer follows the deforming of the cover.
21. The golf ball according to claim 1 , wherein the paint layer has a Martens hardness of no less than 0.12 mgf/μm 2 and no greater than 2.0 mgf/μm 2 .
22. The golf ball according to claim 20 , wherein the paint layer has a Martens hardness of no less than 0.12 mgf/μm 2 and no greater than 2.0 mgf/μm 2 .