A golf ball 2 includes a core 4 , an envelope layer 6 , a mid layer 8 and a cover 10 . A thickness Tm of the mid layer 8 is less than 1.2 mm. A thickness Tc of the cover 10 is less than 0.6 mm. The sum of the thicknesses Tm and Tc is equal to or less than mm. A hardness Hs of the envelope layer 6 is 50 or greater. A hardness Hm of the mid layer 8 is 30 or greater and 60 or less. A hardness Hc of the cover 10 is less than 40. The hardness Hs, the hardness Hm, and the hardness Hc satisfy the following formula (1). Hs≧Hm≧Hc (1) The base material of the envelope layer 6 is ionomer resin. The base material of the midlayer 8 is polyurethane. The base material of the cover 10 is polyurethane.
1. A golf ball comprising a core, an envelope layer positioned outside the core, a mid layer positioned outside the envelope layer and a cover positioned outside the mid layer, wherein,
a thickness Tm of the mid layer is less than 1.2 mm,
a thickness Tc of the cover is less than 0.6 mm,
the sum of the thickness Tm and the thickness Tc is equal to or less than 1.7 mm,
a Shore D hardness Hc of the cover is less than 40, and
the Shore D hardness Hs of the envelope layer, the Shore D hardness Hm of the mid layer, and the Shore D hardness He of the cover satisfy the following formula (2):
Hs>Hm>Hc (2);
wherein the base material of the cover is polyurethane;
wherein the base material of the mid layer is polyurethane;
wherein the base material of the envelope layer is ionomer resin;
wherein a difference between the hardness Hs of the envelope layer and the hardness Hm of the mid layer is equal to or greater than 10 and equal to or less than 29;
wherein a difference between the hardness Hs of the envelope layer and the hardness Hc of the cover is equal to or greater than 19 and equal to or less than 41; and
wherein a difference between the hardness Hm of the mid layer and the hardness Hc of the cover is equal to or greater than 9 and equal to or less than 21.
2. The golf ball according to claim 1 , wherein the Shore D hardness Hs of the envelope layer is equal to or greater than 50.
3. The golf ball according to claim 1 , wherein the Shore D hardness Hm of the mid layer is equal to or greater than 30 and equal to or less than 60.
4. The golf ball according to claim 1 , wherein the core has a diameter of 35.0 mm or greater and 42.0 mm or less.
5. The golf ball according to claim 1 , wherein a difference between a surface hardness H 2 and a central hardness H 1 of the core is equal to or greater than 5 and equal to or less than 35 according to measurements by a JIS-C type hardness scale.
6. The golf ball according to claim 5 , wherein the difference between a surface hardness H 2 and a central hardness H 1 of the core is equal to or greater than 12 and equal to or less than 35 according to measurements by a JIS-C type hardness scale.
7. The golf ball according to claim 1 , wherein the core has a diameter of 39.5 mm or greater and 41.2 mm or less.
8. The golf ball according to claim 1 , wherein an amount of compressive deformation D 1 of the core is equal to or greater than 2.3 mm and equal to or less than 6.0 mm;
an amount of compressive deformation Ds of a spherical body including the core and the envelope layer is equal to or greater than 2.0 mm and equal to or less than 3.8 mm;
an amount of compressive deformation Dm of a spherical body including the core, envelope layer and mid layer is equal to or greater than 1.8 mm and equal to or less than 3.8 mm; and
an amount of compressive deformation Db of the golf ball is equal to or greater than 1.8 mm and equal to or less than 3.8 mm.
9. The golf ball according to claim 1 , wherein the sum of the thickness Tm and the thickness Tc is equal to or less than 1.2 mm.
10. The golf ball according to claim 9 , wherein the sum of the thickness Tm and the thickness Tc is equal to or less than 0.9 mm.