Electrically conductive rubber composition, transfer roller, and image forming apparatus

A transfer roller which is made from an electrically conductive rubber composition comprising a tubular body having:

• a roller resistance of not less than 106.5Ω and not greater than 109Ω as measured at an application voltage of 1000 V in an environment at a temperature of 23° C. and a relative humidity of 55%;
• and
• an ASKER-C hardness of not greater than 40 degrees as measured with a load of 500 gf (≈4.9 N) in an environment at a temperature of 23° C. and a relative humidity of 55% by a measurement method,
• the electrically conductive rubber composition comprises:
• a rubber component;
• a crosslinking component for crosslinking the rubber component;
• and
• a foaming component for foaming the rubber component,
• wherein the rubber component includes at least a styrene butadiene rubber, an ethylene propylene diene rubber and an epichlorohydrin rubber,
• wherein the foaming component includes sodium hydrogen carbonate as a foaming agent and citric acid as a foaming assisting agent,
• wherein the sodium hydrogen carbonate is present in a proportion of not less than 0.1 parts by mass and not greater than 5 parts by mass based on 100 parts by mass of the rubber component, and
• wherein the citric acid is present in a proportion of not less than 0.1 parts by mass and not greater than 0.5 parts by mass based on 100 parts by mass of the rubber component on an anhydride basis.