Golf ball

Abstract

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.

1 . 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) of the paint film in a state of being formed on the surface of the golf ball body measured by the following measuring condition 1 is plotted as a vertical axis against a measuring frequency (Hz) as a horizontal axis, and that an elastic modulus of the paint film in the state of being formed on the surface of the golf ball body measured by the following measuring condition 2 ranges from 0.040 GPa to 0.600 GPa:
 <Measuring condition 1>   Measuring apparatus: “TI950 Tribo Indenter” available from Hysitron, Inc.   Indenter specification: Berkovich type   Test load (maximum indenting load): 100 μN   Frequency: 1 Hz, 10 Hz, 105 Hz   Measuring environment: 23° C., RH 50%, in the atmosphere;   <Measuring condition 2>   Measuring apparatus: “TI950 Tribo Indenter” available from Hysitron, Inc.   Indenter specification: Berkovich type   Maximum indenting depth: 300 nm   Measuring environment: 23° C., RH 50%, in the atmosphere.   
     
     
         2 . The golf ball according to  claim 1 , wherein the linear approximation curve has the slope in a range from 0.0020 to 0.0040. 
     
     
         3 . The golf ball according to  claim 1 , wherein the storage modulus of the paint film in the state of being formed on the surface of the golf ball body at the measuring frequency of 1 Hz ranges from 0.100 GPa to 0.850 GPa. 
     
     
         4 . The golf ball according to  claim 1 , wherein the storage modulus of the paint film in the state of being formed on the surface of the golf ball body at the measuring frequency of 10 Hz ranges from 0.200 GPa to 1.000 GPa. 
     
     
         5 . The golf ball according to  claim 1 , wherein the storage modulus of the paint film in the state of being formed on the surface of the golf ball body at the measuring frequency of 105 Hz ranges from 0.300 GPa to 1.200 GPa. 
     
     
         6 . The golf ball according to  claim 1 , wherein a hardness of the paint film in the state of being formed on the surface of the golf ball body measured by the above measuring condition 2 ranges from 0.001 GPa to 0.020 GPa. 
     
     
         7 . The golf ball according to  claim 1 , wherein the paint film has a thickness in a range from 5 μm to 50 μm. 
     
     
         8 . The golf ball according to  claim 1 , wherein a base resin constituting the paint film is a polyurethane obtained through a reaction between a polyol composition and a polyisocyanate composition. 
     
     
         9 . The golf ball according to  claim 8 , wherein the polyisocyanate composition contains an isocyanurate-modified product of hexamethylene diisocyanate, a biuret-modified product of hexamethylene diisocyanate and an isocyanurate-modified product of isophorone diisocyanate. 
     
     
         10 . The golf ball according to  claim 8 , wherein the polyol composition contains a urethane polyol. 
     
     
         11 . The golf ball according to  claim 8 , wherein in a reaction between the polyol composition and the polyisocyanate composition, a molar ratio (NCO/OH) of an isocyanate group (NCO group) in the polyisocyanate composition to a hydroxyl group (OH group) in the polyol composition ranges from 0.15 to 1.20. 
     
     
         12 . The golf ball according to  claim 1 , wherein the golf ball body comprises a core and a cover covering the core. 
     
     
         13 . The golf ball according to  claim 12 , wherein the golf ball body further comprises at least one intermediate layer between the core and the cover. 
     
     
         14 . The golf ball according to  claim 13 , wherein a hardness difference (intermediate layer-cover) between the intermediate layer and the cover ranges from 10 to 60 in Shore D hardness. 
     
     
         15 . The golf ball according to  claim 13 , wherein a Shore D hardness ratio (intermediate layer/cover) of the intermediate layer to the cover ranges from 1.1 to 5. 
     
     
         16 . The golf ball according to  claim 13 , wherein the intermediate layer has a material hardness ranging from 50 to 80 in Shore D hardness. 
     
     
         17 . The golf ball according to  claim 12 , wherein a hardness difference (Hs−Ho) between a surface hardness Hs of the core and a center hardness Ho of the core ranges from 10 to 50 in Shore C hardness. 
     
     
         18 . The golf ball according to  claim 17 , wherein the surface hardness Hs of the core ranges from 60 to 100 in Shore C hardness. 
     
     
         19 . The golf ball according to  claim 17 , wherein the center hardness Ho of the core ranges from 40 to 80 in Shore C hardness.