| abstract |
(57) Abstract: [PROBLEMS] To provide a rubber composition most suitable for forming the outermost layer of a developing roll or the like for the purpose of preventing toner filming. SOLUTION: The rubber composition comprises fluororubber as a matrix component, and particles formed from the release agent are dispersed in the fluororubber matrix, wherein the release agent is a reactive silicone oil and a reactive fluorooil. At least one of which the particles formed from the release agent are reactively fixed in the fluororubber matrix, and the particle size of the particles having a particle size of 1 μm or more is measured. When accumulated, the particle size of the particles at the point where the cumulative cross-sectional area is 90% of this total cumulative area is 30 μm or less. |