Golf ball
Golf ball 2 has a center 8 , a mid layer 10 , a cover 6 and dimples 12 . The mid layer 10 includes a styrene block-containing thermoplastic elastomer having a material hardness of less than 10, and an ethylene-(meth)acrylic acid copolymer-based ionomer resin having a material hardness of 50 or greater and 70 or less. This mid layer 10 has a hardness equal to or less than 50, and a thickness of equal to or less than 1.6 mm. The dimple has: a first side wall face 18 that has a curvature radius R 1 which is equal to or greater than a phantom curvature radius Rx; a second side wall face 20 that is positioned to the bottom side than the first side wall 18 face and has a curvature radius R 2 which is smaller than the phantom curvature radius Rx; and a bottom face 22 that is positioned to the bottom side than the second side wall face 20 and has a curvature radius R 3 which is equal to or greater than the phantom curvature radius Rx.
1. A golf ball comprising a spherical core, a cover covering said core and numerous dimples formed on the surface thereof,
said cover having a shore D hardness of equal to or greater than 50, and a thickness of equal to or less than 1.6 mm,
said dimple comprising: a first side wall face that has a curvature radius R 1 which is equal to or greater than a phantom curvature radius Rx; a second side wall face that is positioned to the bottom side than said first side wall face and has a curvature radius R 2 which is smaller than the phantom curvature radius Rx; and a bottom face that is positioned to the bottom side than said second side wall face and has a curvature radius R 3 which is equal to or greater than the phantom curvature radius Rx.
2. The golf ball according to claim 1 wherein ratio of depth of the first side wall face to depth of said dimple is 0.10 or greater and 0.50 or less.
3. The golf ball according to claim 1 wherein ratio of maximum diameter of the second side wall face to diameter of said dimple is 0.60 or greater and 0.95 or less.
4. The golf ball according to claim 1 wherein said core has a spherical center and a mid layer covering said center,
said mid layer having a Shore D hardness of 25 or greater and 55 or less, and a thickness of equal to or less than 1.6 mm,
surface hardness of said center being equal to or greater than Shore D hardness of the mid layer.
5. The golf ball according to claim 4 wherein ratio of the thickness of the cover to the thickness of said mid layer is 1.0 or greater and 2.0 or less.
6. The golf ball according to claim 4 wherein said mid layer comprises
20% by weight or greater and 60% by weight or less of a styrene block-containing thermoplastic elastomer having a material hardness of less than 10, and
40% by weight or greater and 80% by weight or less of an ethylene-(meth)acrylic acid copolymer-based ionomer resin having a material hardness of 50 or greater and 70 or less.