The present invention provides a golf ball having excellent rebound characteristics and flight performance, while maintaining good durability and appearance. The present invention relates to a golf ball comprising a center, an intermediate layer and a cover, the intermediate layer comprises an outermost layer and a second layer adjacent to the underside of the outermost layer, and the cover has many dimples on the surface thereof, wherein the second layer is formed from thermoplastic resin and has a thickness of 0.5 to 2.0 mm, the outermost layer is formed from thermosetting or thermoplastic resin and has a thickness of 1 to 100 μm, the intermediate layer has depressions on the surface thereof at the position and shape corresponding to the dimples through the cover, and the cover is formed from thermoplastic resin and has a thickness of 0.1 to 0.8 mm in land portion having no dimple.
1. A method of making a golf ball comprising a core having a center and an intermediate layer formed on the center, and a cover covering the core, the intermediate layer having at least two layers comprising an outermost layer and a second layer adjacent to the underside of the outermost layer, and the cover has many dimples formed in the surface thereof, the method comprising the steps of:
(a) forming a spherical center,
(b) (i) forming the second layer of the intermediate layer on the center by using two core intermediate half molds having a semi-spherical cavity to form a spherical core intermediate,
(ii) forming the outermost layer of the intermediate layer on the core intermediate by using two core half molds having a semi-spherical cavity to form a spherical core
(c) (i) molding a cover composition, formed from polyurethane-based thermoplastic elastomer, into a semi-spherical half-shell for the cover,
(ii) covering the core with two of the half-shells and placing the covered core in a golf ball half mold having a semi-spherical cavity and many projections corresponding to the shape of the dimples in the cavity,
(iii) press molding the covered core under heating to mold a golf ball with a cover having a thickness at the bottom of each dimple that differs from the thickness in land portions by no more than 0.2 mm and simultaneously form depressions in the surface of the intermediate layer at positions corresponding to the dimples in the cover, and
(d) after cooling, opening the mold to take out a molded golf ball.
2. A method of making a golf ball comprising a core having a center and an intermediate layer formed on the center, and a cover covering the core, the intermediate layer consists of at least two layers comprising an outetmost layer and a second layer adjacent to the underside of the outermost layer, and the cover has and having many dimples formed in the surface thereof, the method comprising the steps of:
(a) forming a spherical center,
(b) (i) forming the second layer of the intermediate layer on the center by using two core intermediate half molds having a semi-spherical cavity to form a spherical core intermediate,
(ii) forming an outermost layer of the intermediate layer on the core intermediate by a coating system to form a spherical core,
(c) (i) molding a cover composition, formed from polyurethane-based thermoplastic elastomer, into a semi-spherical half-shell for the cover,
(ii) covering the core with two of the half-shells and placing the covered core in a golf ball half mold having a semi-spherical cavity and many projections corresponding to the shape of the dimples in the cavity,
(iii) press molding the covered core under heating to mold a golf ball with a cover having a thickness at the bottom of each dimple that differs from the thickness in land portions by no more than 0.2 mm and simultaneously form depressions in the surface of the intermediate layer at positions corresponding to the dimples in the cover, and
(d) after cooling, opening the mold to take out a molded golf ball.
3. The method according to claim 1 or 2 , wherein
the dimples are formed in the surface of the cover prior to the application of a finish coating to the surface of the cover,
the second layer of the intermediate layer is formed from thermoplastic resin, and has a thickness of 0.5 to 2.0 mm,
the outermost layer of the intermediate layer is formed from thermosetting resin or thermoplastic resin, and has a thickness of 1 to 100 μm,
the intermediate layer has depressions in the surface thereof at positions and having shapes corresponding to the dimples through the cover, and
the cover is formed from thermoplastic resin and has a thickness of 0.1 to 0.8 mm in land portion having no dimple.
4. The method according to claim 3 , wherein the depressions in the surface of the outermost layer of the intermediate layer have a depth of 5 to 95%, based on the depth of the dimple.
5. The method according to claim 1 or 2 , wherein
the second layer of the intermediate layer is formed from ionomer resin,
the outermost layer of the intermediate layer is formed from a two-pack curable epoxy resin, and
the polyurethane-based thermoplastic elastomer is polyurethane-based thermoplastic elastomer formed by using cycloaliphatic diisocyanate.