An object of the present invention is to provide a golf ball having good spin performance on approach shots and good shot feeling as well as excellent stain resistance by precisely controlling physical properties of a paint film actually formed on a surface of a golf ball body. The present invention provides a golf ball comprising a golf ball body and a paint film formed on a surface of the golf ball body, wherein the paint film is such that a linear approximation curve obtained by a least square method has a slope in a range from 0.0015 to 0.0045 when a storage modulus (GPa) thereof measured by a nanoindentation method is plotted as a vertical axis against a measuring frequency (Hz) as a horizontal axis, and that an elastic modulus thereof measured by a nanoindentation method ranges from 0.040 GPa to 0.600 GPa.

A golf ball 2 includes a main body 4 and a paint layer 6 positioned outside the main body 4. The main body 4 includes a spherical core 8, a mid layer 10 positioned outside the core 8, and a cover 12 positioned outside the mid layer 10. The paint layer 6 includes an inner layer 14 and an outer layer 16 positioned outside the inner layer 14. When an indentation depth (nm) is measured on a cross-section along a plane passing through a central point of the golf ball 2 when a force of 30 mgf is applied to the cross-section in a direction perpendicular to the cross-section, an indentation depth Di on a cross-section of the inner layer 14 is lower than an indentation depth Do on a cross-section of the outer layer 16.

A golf ball 2 includes a main body 4 and a paint layer 6 positioned outside the main body 4. The main body 4 includes a spherical core 8, a mid layer 10 positioned outside the core 8, and a cover 12 positioned outside the mid layer 10. An indentation depth, measured when the paint layer 6 in a cross-section along a plane passing through a central point of the golf ball 2 is pressed by a force of 30 mgf in a direction perpendicular to the cross-section, is not less than 300 nm and not greater than 3000 nm. The paint layer 6 preferably has a thickness of not less than 5 m and not greater than 50 m.

A golf ball paint composition includes primarily a urethane paint containing polyol as a base resin and polyisocyanate as a curing agent. Two types of polyester polyol are used as the polyol, and the composition has an elastic work recovery of at least 70%. The paint composition has a high self-repairing ability and is of high quality as a golf ball paint. Golf balls coated with this composition are able to maintain a good durability, in addition to which they have an excellent abrasion resistance and an excellent ball appearance.

Golf balls having an initial velocity greater than 255 ft/sec and/or an overall distance of greater than 320 yards are disclosed. The golf balls comprise one or more core layers, one or more cover layers, and optionally one or more intermediate layers disposed between the core and the cover. At least one layer is optionally formed from a composition comprising from 2 wt % to 50 wt % of a plasticizer, based on the total weight of the composition.

Low compression multi-piece golf balls having a solid core comprising at least one layer made of a plasticized thermoplastic composition are provided. Preferably, the ball has a compression of less than 60 and more preferably less than 50. The ball includes a cover in addition to the core sub-assembly. For example, two-piece and three-piece golf balls may be made. The plasticized thermoplastic composition preferably comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. Preferably, a fatty acid ester such as butyl oleate is used as the plasticizer. In two-layered core constructions, the outer core layer is preferably formed from a thermoset composition such as polybutadiene rubber. The core layers may have different hardness levels. The core structure and resulting ball have relatively good resiliency at given compressions.

The present invention is directed to thermoset rubber compositions comprising from 1 phr to 20 phr of a zinc ionomer. The thermoset rubber composition is used to form at least one layer of a one-piece, two-piece, or multi-layer golf ball.

A golf ball includes a unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The core is formed from a substantially homogenous rubber composition. The golf ball also includes an inner cover layer and an outer cover layer. The soft transition region has a thickness of up to 4 mm and a negative hardness gradient of about 5 Shore C to about 15 Shore C. The unitary core has an overall negative hardness gradient of up to 20 Shore C.

A golf ball resin composition includes (A) (I) an olefin-C.sub.3-8 ,-unsaturated carboxylic acid copolymer or a metal neutralization product thereof and/or (II) an olefin-C.sub.3-8 ,-unsaturated carboxylic acid-C.sub.3-8 ,-unsaturated carboxylic acid ester terpolymer or a metal neutralization product thereof; (B) isocyanuric acid or a haloisocyanuric acid; and (C) a fatty acid or a fatty acid metal salt. When this resin composition is used as a cover material, the paint film adhesion between the cover material and various types of paint, including urethane-based paints, is excellent, enabling various properties of the golf ball to be improved.

The present invention is directed to thermoset rubber compositions comprising from 1 phr to 20 phr of a zinc ionomer. The thermoset rubber composition is used to form at least one layer of a one-piece, two-piece, or multi-layer golf ball.