Solid golf ball

1. A solid golf ball comprising at least one layer of a core, and at least one layer of a cover formed on the core, wherein

at least one layer including the inmost layer of the core is formed by vulcanizing a rubber composition comprising a base rubber, a co-crosslinking agent, a vulcanization initiator and a filler,

the core has a center hardness in JIS-C hardness of 40 to 60, a surface hardness in JIS-C hardness of 80 to 95 and a hardness difference (B−A) between a hardness in JIS-C hardness at a distance of 5 mm from the center point of the core (B) and the center hardness (A) of not less than 1 to less than 10;

wherein the rubber composition for the core comprises at least one organic sulfur compound selected from the group consisting of bis(pentachlorophenyl)disulfide and bis(pentabromophenyl)disulfide

wherein the rubber composition for the core comprises further at least one hydroquinone compound selected from the group consisting of compounds which are represented by the following formula (5):

wherein R 1 to R 4 are independently a hydrogen or a substituent selected from the group the group consisting of a halogen group (F, Cl, Br, I), alkyl group, carboxyl group (—COOH) or ester thereof (—COOR), formyl group (—CHO), acyl group (—COR), halogenated carbonyl group (—COX), sulfo group (—SO 3 H) or ester thereof (—SO 3 R), halogenated sulfonyl group (—SO 2 X), sulfino group (—SO 2 H), alkylsulfinyl group (—SOR), carbamoyl group (—CONH 2 ), halogenated alkyl group, cyano group (—CN), alkoxy group (—OR) and combinations thereof; and

the hydroquinone compound is present in an amount within the range of 0.002 to 5 parts by weight, based on 100 parts by weight of the base rubber.

2. The solid golf ball according to claim 1 , wherein the organic sulfur compound is present in the rubber composition for the core in an amount of from 0.05 to 5.0 parts by weight based on 100 parts by weight of the base rubber.

3. The solid golf ball according to claim 1 , wherein the organic sulfur compound is present in the rubber composition for the core in an amount of from 0.1 to 3.0 parts by weight based on 100 parts by weight of the base rubber.

4. The solid golf ball according to claim 1 , wherein the core has a center hardness in JIS-C hardness of 45 to 59, a surface hardness in JIS-C hardness of 82 to 90 and a hardness difference (B−A) between a hardness in JIS-C hardness at a distance of 5 mm from the center point of the core (B) and the center hardness (A) of not less than 1 to 8.

5. The solid golf ball according to claim 1 , wherein the core has a center hardness in JIS-C hardness of 45 to 55, a surface hardness in JIS-C hardness of 83 to 89 and a hardness difference (B−A) between a hardness in JIS-C hardness at a distance of 5 mm from the center point of the core (B) and the center hardness (A) of 2 to 8.

6. The solid golf ball according to claim 1 , wherein the core has a hardness in JIS-C hardness at a distance of 5 mm from the center point of the core (B) of 41 to 69.

7. The solid golf ball according to claim 1 , wherein the core has a hardness in JIS-C hardness at a distance of 5 mm from the center point of the core (B) of 50 to 67.

8. The solid golf ball according to claim 1 , wherein the core has a hardness in JIS-C hardness at a distance of 10 mm from the center point of the core of 55 to 85.

9. The solid golf ball according to claim 1 , wherein the core has a hardness in JIS-C hardness at a distance of 10 mm from the center point of the core of 65 to 75.

10. The solid golf ball according to claim 1 , wherein the core has a hardness in JIS-C hardness at a distance of 15 mm from the center point of the core 60 to 90.

11. The solid golf ball according to claim 1 , wherein the core has a hardness in JIS-C hardness at a distance of 15 mm from the center point of the core 75 to 85.