US Patent 7086966 Golf ball

Golf ball 1 has a core 2, a mid layer 3 and a cover 4. The mid layer 3 is composed of a matrix of which base material is a rubber or a synthetic resin, and solid particles which are dispersed in the matrix. Hardness (Shore D) Hm of the matrix is greater than hardness Hg of the solid particles. Difference between both hardness (Hm−Hg) is 5 or greater. Particle size D of the solid particles is 0.5 mm or greater. A ratio “D/T”, i.e., a ratio of the particle size D to the thickness T of the mid layer is 0.1 or greater. A proportion of the solid particles occupied in the mid layer 3 is 3% by weight or greater and 40% by weight or less. Hardness Hm of the matrix is 30 or greater. Hardness Hg of the solid particle is 40 or less.