An object of the present invention is to provide a golf ball striking a good balance between flight distance on driver shots and spin rate on approach shots, and excellent in stain resistance and shot feeling. The present invention provides a golf ball comprising a paint film, wherein a base resin of the paint film contains a polyurethane obtained by a reaction between a polyisocyanate composition and a polyol composition containing a urethane polyol having a polyether diol with a number average molecular weight in a range from 800 to 3,000 as a constituent component, and the following requirements are satisfied:
Mp≦200×X−75
Mp≦100
Minm−Moum>40
Moum−Mc<5
Tinm≧Toum>Tc>Tp
(Tinm×Minm)/(Toum×Moum)>2.0
(Toum×Moum)/(Tc×Mc)<3.0
(Tc×Mc)/(Tp×Mp)>10.0
[where Mp, Minm, Moum, and Mc represent a 10% elastic modulus (kgf/cm.sup.2) of the paint film, inner intermediate layer, outer intermediate layer and cover, respectively; Tp, Tinm, Toum, and Tc represent a thicknesses (mm) of the paint film, inner intermediate layer, outer intermediate layer and cover, respectively; and X represents a molar ratio (NCO/OH) of a NCO group in the polyisocyanate composition to a OH group in the polyol composition.].

In a golf ball having a core, envelope layer, intermediate layer and cover, the (core diameter)/(ball diameter) value falls within a particular range, the core has a specific hardness profile, the intermediate layer is formed primarily of an ionomer resin material including a high-acid ionomer resin, and the Shore C hardness relationships among the core center and surface hardnesses and the surface hardnesses of the envelope layer-encased sphere, intermediate layer-encased sphere and ball satisfy the following conditions: (1) core surface hardness<surface hardness of envelope layer-encased sphere<surface hardness of intermediate layer-encased sphere>ball surface hardness, (2) (surface hardness of envelope layer-encased sphere)−(core center hardness)≥28.

Also, the intermediate layer and cover have respective thicknesses which satisfy the condition: (3) cover thickness<intermediate layer thickness.

This ball enables mid-level and skilled amateur golfers to achieve superior distances on driver shots and on iron shots, and moreover has a soil yet good feel at impact.

Golf balls having covers made of thermoplastic polyurethane compositions are provided. Multi-piece golf balls can be made. Polyurethane primer coatings and polyurethane top-coatings are applied to the thermoplastic polyurethane cover. Isocyanate-rich and polyol-rich polyurethane coatings can be applied. In one embodiment, multi-functional imine and amine compounds can be used to treat the golf ball. The resulting coating may contain polyurethanes, polyureas, and hybrids, copolymers, and blends thereof. The cover composition and surface coatings can further include catalysts, ultraviolet (UV)—light stabilizers, and other additives. Heat is used to cure the coatings. The coating methods have many benefits and the finished balls have good physical properties.

Methods for coatings for golf balls, particularly golf balls having thermoplastic polyurethane covers, and the resulting finished balls are provided. The coating is preferably a topcoat comprising a polyurethane composition containing optical brighteners. The topcoat composition preferably comprises a low concentration of optical brighteners. For example, the concentration of optical brightener can be in the range of 0.01 to about 0.20 weight %. The optical brighteners provide the desired brightness to the golf ball without sacrificing color stability. Multi-piece golf balls having inner cores, outer cores, inner covers, and intermediate layers can be made. The finished ball with the topcoat has many advantageous physical and playing performance properties.

The presently disclosed subject matter is directed to a golf ball providing improve play characteristics. The disclosed golf ball includes an outer cover comprising a plurality of divots. The disclosed golf ball further includes a central core comprising one or more lightweight materials, such as aerogel. The combination of the lightweight core and the unique divots enable the golf ball to go farther and straighter when hit by the golfer, thereby providing increased performance.

A golf ball manufacturing method includes an inner layer molding step of molding an inner layer that includes an outer surface with a recess, an inner film formation step, after the inner layer molding step, of coating the outer surface of the inner layer with inner film paint to form an inner film, an inner film removal step, after the inner film formation step, of removing the inner film except for a portion thereof covering a surface of the recess to obtain an inner ball that includes the inner layer and the inner film, and a cover layer molding step, after the inner film removal step, of molding a cover layer that includes an outer surface with dimples on an outer circumferential side of the inner ball to obtain a golf ball. The inner layer and inner film are different colors, and the cover layer is transparent or semi-transparent.

An object of the present invention is to provide a golf ball having improved spin performance on wedge shots under a wet condition such as rain by controlling the formulation of the paint film. The present invention provides a golf ball comprising a golf ball body and a paint film covering the golf ball body, wherein the paint film contains a base resin and a porous filler, and the porous filler contains SiO.sub.2 as a constituent in an amount of 50 mass % or more.

A method for producing a golf ball of the present invention includes the steps of: forming a first coating film on a surface of a covering having a plurality of dimples; and forming a second coating film on a surface of the first coating film. The second coating film is formed of a second coating material composition containing a polyurethane coating material and a solvent having a boiling point of 80° C. or less. An elastic recovery rate of the second coating film is 50% or more. In the golf ball of the present invention obtained by the method, an edge ratio which is a ratio of a film thickness of the second coating film in an edge portion of the dimple to a film thickness of the second coating film in a central portion of the dimple is 50% or more.

An object of the present invention is to provide a golf ball having high visibility and excellent orientation at shot. The present invention provides a golf ball comprising a core and a cover disposed outside of the core, wherein a surface of the golf ball has a first region with a first color and a second region with a second color, the first color has hue H1 represented by H value in HSL color space, the second color has hue H2 represented by H value in HSL color space, and the H1 and the H2 satisfy the following mathematical formula (1): 60<|H1−H2|<300 (1).

An object of the present invention is to provide a golf ball having high visibility and little uncomfortableness at shot. The present invention provides a golf ball comprising a core and a cover disposed outside of the core, wherein a surface of the golf ball has a first region with a first color and a second region with a second color, the first color has hue H1 represented by H value in HSL color space, the second color has hue H2 represented by H value in HSL color space, and the H1 and the H2 satisfy a specific mathematical formula.