Golf ball 2 has a spherical core 4 , a mid layer 6 covering this core 4 , a reinforcing layer 8 covering this mid layer 6 , and a cover 10 covering this reinforcing layer 8 . Base polymer of the mid layer 6 includes an ionomer resin as a principal component. The mid layer 6 has a hardness Hm as measured with a Shore D type hardness scale of equal to or greater than 55. Base polymer of the reinforcing layer 8 is a thermosetting resin. Base polymer of the cover 10 includes a thermoplastic polyurethane elastomer as a principal component. The cover 10 has a thickness Tc of equal to or less than 0.6 mm. The cover has a hardness Hc as measured with a Shore D type hardness scale of equal to or less than 54. Ratio (Tr/Tc) of the thickness Tr of the reinforcing layer to the thickness Tc of the cover is 0.005 or greater and 3.0 or less.
1. A golf ball which comprises a spherical core, a mid layer positioned outside of the core, a reinforcing layer positioned outside of the mid layer, a cover positioned outside of the reinforcing layer and a paint layer positioned outside of the cover, wherein a principal component of the base polymer of said mid layer being an ionomer resin,
said mid layer having a hardness as measured with a Shore D type hardness scale of equal to or greater than 55,
a base polymer of said reinforcing layer is a thermosetting resin, wherein the thermosetting resin is a two component cured epoxy resin obtained by curing a bisphenol A type epoxy resin with a polyamide amine curing agent or a denatured product of the polyamide amine curing agent,
a principal component of the base polymer of said cover being a thermoplastic polyurethane elastomer which includes a polyurethane component, and a polyester component or a polyether component,
a curing agent in the polyurethane component being an alicyclic diisocyanate,
said cover having a thickness Tc of equal to or greater than 0.1 mm and equal to or less than 0.3 mm,
said cover having a hardness as measured with a Shore D type hardness scale of equal to or less than 54, and
a ratio (Tr/Tc) of the thickness Tr of said reinforcing layer to the thickness Tc of said cover being 0.005 or greater and 3.0 or less.
2. The golf ball according to claim 1 , wherein said reinforcing layer has a tensile strength of 150 kgf/cm 2 or greater and 500 kgf/cm 2 or less.
3. The golf ball according to claim 1 , wherein said reinforcing layer has a pencil hardness of 4 B or greater and 3 H or less.
4. The golf ball according to claim 1 , wherein a ratio (Tr/Tc) of the thickness Tr of said reinforcing layer to the thickness Tc of said cover is 0.020 or greater and 3.0 or less.
5. The golf ball according to claim 1 , wherein the alicyclic diisocyanate is 4,4′-dicyclohexylmethane diisocyanate.
6. The golf ball according to claim 1 , wherein the ratio of epoxy equivalent of bisphenol A type epoxy resin and amine active hydrogen equivalent of the curing agent is 1.0/1.4 or greater and 1.0/1.0 or less.