US Patent 7537530 Golf ball with negative hardness gradient core

A golf ball including an inner core having a first outer surface and a geometric center, the inner core having a hardness of 35 to 55 Shore C; an outer core layer adjacent the inner core having a second outer surface and an inner surface, the outer core layer having a hardness of 55 to 90 Shore C; and a cover layer; wherein the hardness of the first outer surface is substantially the same as or lower than the hardness of the geometric center to define a first negative hardness gradient, and the hardness of the second outer surface is substantially the same as or lower than the hardness of the inner surface to define a second negative hardness gradient.