Multi-layered golf balls containing a dual-core structure are provided. The core structure includes an inner core (center) made from a foam or metal-containing composition, or it has a hollow shell construction, and the outer core layer is made of a thermoplastic composition. Preferably, the thermoplastic composition comprises: a) ethylene acid copolymer, b) plasticizer, and c) cation source. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. The core assembly preferably has a positive hardness gradient extending across the entire assembly. The core structure and resulting ball have relatively good resiliency at given compressions.

In a multi-piece solid golf ball having a core, a cover and an intermediate layer therebetween, the core, an intermediate layer-encased sphere and the ball have surface hardnesses which satisfy a specific relationship, and the intermediate layer and the cover have thicknesses which satisfy a specific relationship. Also, the core has a hardness profile in which the hardnesses at the core surface, core center, a position 5 mm from the core center, and a position midway between the surface and center of the core satisfy specific relationships. This golf ball, when used by mid- and high-level amateurs, enables the golfer to maintain an adequate distance on shots with a driver and achieve a good distance on iron shots, has a good spin performance on approach shots and has a good feel on impact. In addition, the ball has an excellent scuff resistance when struck with a grooved wedge.

Golf balls comprising a core having at least one layer and a cover having at least one layer are provided. At least one of the layers is made from a thermoplastic composition preferably comprising a telechelic ionomer derived from alkyl-cis-cyclooctene and cis-cyclooctene. The telechelic ionomer composition also may be used to form intermediate layers. Blends of telechelic ionomers and polybutadiene rubbers or ethylene acid copolymers can be prepared. The telechelic ionomer compositions can be used to make a cover layer having good impact durability and shear resistance and that also helps provide the ball with high resiliency.

In a golf ball including a core, an intermediate layer, and a cover, the relationship of the surface hardness between an intermediate layer-encased sphere and the ball satisfies a predetermined relational expression, and with an initial velocity of the ball and a deflection under a predetermined load applied to the ball optimized, and letting a value of (initial velocity of core?weight of core) be Ciw, a value of [(initial velocity of intermediate layer-encased sphere?initial velocity of core)?(weight of intermediate layer-encased sphere?weight of core)] be Miw, and a value of [(initial velocity of ball?initial velocity of intermediate layer-encased sphere)?(weight of ball?weight of intermediate layer-encased sphere)] be CViw, the expression of Ciw+Miw+CViw is optimized, and lift and drag coefficients at predetermined Reynolds numbers and spin rates of dimples are set to predetermined ranges.

Multi-piece golf balls having a multi-layered solid core and multi-layered cover are provided.

An object of the present invention is to provide a golf ball having excellent impact durability. The present invention provides a golf ball comprising a spherical core and at least one cover layer covering the spherical core, wherein the spherical core is formed from a core rubber composition containing (a) a base rubber, (b) an ,-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinkable compound having two or more polymerizable unsaturated bonds in the molecule, and (d) a crosslinking initiator.

Multi-layered golf balls containing a two-layered core assembly are provided. Preferably, at least one of the core layers is formed from a thermoplastic composition that comprises: a) thermoplastic non-acid polymer, and b) plasticizer. In one preferred embodiment, the inner core is made of a first thermoplastic composition comprising the non-acid polymer and plasticizer; and the outer core layer is made of a second thermoplastic composition. For example, an ethylene acid copolymer may be used to form the outer core layer. A fatty acid ester such as ethyl oleate is preferably used as the plasticizer. Suitable non-acid polymers include, for example, polyesters, polyamides, polyolefins, and polyurethanes. The core assembly has a relatively high resiliency at given compressions.

A golf ball 2 includes a core 4 and a cover 6 positioned outside the core 4. The cover 6 is formed in a mold having support pins by injection molding. A ratio (V/S) of a volume V (mm.sup.3) of the cover 6 to an amount of compressive deformation S (mm) of the core 4 is not less than 1000 and not greater than 1900. The cover 6 has a shore D hardness of not greater than 62. The golf ball 2 has a plurality of dimples 8 on a surface thereof. A total volume W of these dimples is not less than 490 mm.sup.3 and not greater than 620 mm.sup.3. A ratio (/P) of a latitude (degree) of each support pin to a total cross-sectional area P (mm.sup.2) of the support pins is not less than 0.35 and not greater than 0.60.

A golf ball 2 has a core 4, an inner cover 6, a main cover 8, and an outer cover 10. A product TH2 of a thickness T2 (mm) and a Shore C hardness H2 of the main cover 8 and a product THs of a value of 5% of a radius (mm) of the core 4 and a Shore C hardness Hs at a surface of the core 4 satisfy the following mathematical formula.

15(TH2THs)100

A product TH1 of a thickness T1 (mm) and a Shore C hardness H1 of the inner cover 6, a product TH3 of a thickness T3 (mm) and a Shore C hardness H3 of the outer cover 10, and the product TH2 satisfy the following mathematical formula.

0.25<((TH1+TH3)/2)/TH2<0.65

An object of the present invention is to provide a golf ball travelling a great flight distance on driver shots, having enhanced controllability on approach shots under a wet condition, and being excellent in stain resistance and shot feeling. The present invention provides a golf ball comprising a golf ball body having a cover, and a paint film covering the golf ball body, wherein a 10% elastic modulus of the paint film is 75 kgf/cm.sup.2 or less, a storage modulus (E.sub.150) at 150 C. of the paint film obtained by measuring dynamic viscoelasticity of the paint film is 1.010.sup.7 Pa or more, an indentation depth of the paint film measured with a nanoindenter in a state that the paint film is formed on the surface of the golf ball body is 1250 nm or more, and a material hardness of the cover is 50 or more in Shore D hardness.