Multi-layered golf balls having at least one layer made of a foamed silicone composition are provided. Multi-layered golf balls having at least one layer made of non-foamed silicone elastomer composition also are provided. For example, three-piece, four-piece, and five-piece golf balls containing different core and cover structures can be made. The foamed silicones have good thermal stability and durability without sacrificing resiliency. The non-foamed silicone elastomers have high elongation, tensile strength, chemical/fluid-resistance, and weatherability properties. These compositions can be used to form any layer, for example, core, intermediate, or cover, in the golf ball.

A golf ball 2 includes a core 4, a mid layer 6, a cover 8, and dimples 10. A difference DH in hardness between a surface and a central point of the core 4, a thickness Tm and a hardness Hm of the mid layer 6, a thickness Tc and a hardness Hc of the cover 8, and an amount of compressive deformation Sb meet the following mathematical formulas.

(DH*Hm)/(Hc*Tc)>80

((Sb*Tc)/(Hc* Hm*Tm))*1000>0.75

An area ratio So of dimples 10 and a ratio Rs of a number of the dimples 10 each having a diameter of equal to or greater than 9.60% but equal to or less than 10.37% of a diameter of the golf ball 2 meet the following mathematical formula (3).

Rs≧−2.5*So+273   (3)

In a golf ball having a core and a cover of at least one layer encasing the core, the core is a product molded under heat from a rubber composition which includes (A) a base rubber, (B) an unsaturated carboxylic acid and/or a metal salt thereof, and (C) an organic peroxide. Letting the content of component (B) in the rubber composition per 100 parts by weight of component (A) be X parts by weight and the concentration of volatile substances from component (B) within the core be A wt %, the value A/X is 0.0123 or less. This golf ball has a low energy loss, enabling a high initial velocity to be obtained.

A rubber composition for golf balls includes (A) a base rubber, (B) two different metal salts of α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms, (C) a metal salt in which at least one bonding site is a fatty acid of 9 or more carbon atoms, and (D) a crosslinking initiator. Letting component (B) include (B-1) an unsaturated metal carboxylate in a high compounding weight and (B-2) an unsaturated metal carboxylate in a low compounding weight, the ratio (B-2)/(B-1) is from 4 to 20 wt % and the ratio (B-2)/(C) is from 20 to 115 wt %. By using this rubber composition in a golf ball core, the golf ball can be endowed with both good spin properties and good durability on impact.

A golf ball includes a core having an outer surface and a geometric center; an inner cover layer, and an outer cover layer. The inner cover layer includes an ionomeric material and has a material hardness of about 60 Shore D or greater. The outer cover layer is formed from a polyurea or polyurethane and has a material hardness of about 60 Shore M or greater. The outer surface of the core has a hardness of about 68 to 92 Shore C. The geometric center of the core has a hardness of about 45 to 85 Shore C. The core outer surface hardness is greater than the geometric center hardness by about 5 to 21 Shore C to define a positive hardness gradient. The core also has a volume weighted average hardness, H.sub.V, of about 70 to 80, where

[00001]${\stackrel{\_}{H}}_V=\frac{I_V}{V_c}.$

In a golf ball having a core and a cover of at least one layer, the core and/or at least one layer of the cover are formed of a resin composition that includes (A) 100 parts by weight of a thermoplastic resin, and (B) 1 to 30 parts by weight of a compound having a fluorene skeleton, or a derivative thereof. This resin composition for golf balls has an improved injection-moldability and thus enables the ball to achieve both a reduced spin rate and a good durability (scuff resistance).

Provided is a golf ball is excellent in flight distance performance, approach performance, and feel at impact. A ball 2 includes a core 4, a mid layer 6, and a cover 8. The core 4 includes an inner core 10 and an outer core 12. The cover 8 includes an inner layer cover 10 and an outer layer cover 12. An inner core volume Vc, a mid layer volume Vm, a mid layer hardness Hm, an inner layer cover volume Vinc, an inner layer cover hardness Hinc, an outer layer cover volume Vouc, an outer layer cover hardness Houc, and a ball volume V meet the following relational expressions (a) to (g): (a) Vc/V<0.07, (b) Hm>Hinc>Houc, (c) Hm−Houc>25, (d) Vm>Vinc>Vouc, (e) (Vm+Vinc+Vouc)/V<0.30, (f) Vm/Vouc>1.50, and (g) (Vm*Hm)/(Vouc*Houc)>3.0.

A golf ball 2 has a large number of dimples 10 on a surface thereof. The contours of the dimples 10 are non-circular. A standard deviation of areas of the dimples 10 is equal to or less than 1.7 mm.sup.2. A ratio of a total area of the dimples 10 relative to a surface area of a phantom sphere of the golf ball 2 is equal to or greater than 80%. By comparting lines CS obtained by projecting sides of a regular dodecahedron, which is inscribed in the phantom sphere, onto the phantom sphere, a surface of the phantom sphere can be divided into 12 units Ut each of which meets the following mathematical formula (I):
−2≦(Nt/12)−Nu≦2  (I),
where Nt represents the total number of the dimples 10 and Nu represents the number of the dimples 10 on one unit.

A golf ball of one aspect of the present invention includes a spherical core, one or more cover members to cover the core, and a coating layer to coat a cover member configuring an outermost layer of the one or more cover members. A plurality of dimples is formed in the cover member. Shore-D hardness of the cover member is equal to or larger than 50. A 10% modulus of the coating layer is equal to or smaller than 160 kgf/cm.sup.2. Roughness is produced on a surface of the coating layer after applying a coating material over the cover member of the outermost layer A maximum height Rz of the coating layer is equal to or larger than 3 μm.

An object of the present invention is to provide a golf ball having excellent color development stability. The present invention provides a golf ball comprising a core and a cover covering the core, wherein the cover is formed from a resin composition containing a first base resin and a fluorescent pigment, and the fluorescent pigment has a number-based cumulative median size of 2.5 μm or more.