Semiconductive roller, method for manufacturing the same and image forming apparatus

1. A semiconductive roller comprising:

a conductive support; and

a semiconductive elastic layer disposed on a circumferential surface of the conductive support, the semiconductive elastic layer containing at least an epichlorohydrin rubber, an acrylonitrile-butadiene rubber, and a conducting agent and having a foam structure, wherein a mixing ratio of the epichlorohydrin rubber to the acrylonitrile-butadiene rubber ranges from 80/20 to 20/80 by mass,

wherein, when the semiconductive roller is immersed in pure water for 30 minutes, a chlorine ion content derived from the semiconductive elastic layer per unit area of the semiconductive elastic layer is approximately not more than 0.06 μmol/cm 2 ,

wherein no electricity has been run through the semiconductive roller before the semiconductive roller is immersed in the pure water for 30 minutes, and

wherein a volume resistivity of the semiconductive roller ranges from greater than 7 logΩ·cm to 13 logΩ·cm at 20° C.,

the semiconductive roller being manufactured by a process comprising a cleaning process that comprises immersing the semiconductive elastic layer into pure water for approximately not less than 30 minutes for cleaning.

2. The semiconductor roller according to claim 1 , wherein the semiconductive roller is a transfer roller used in an image forming apparatus.

3. An image forming apparatus comprising:

an image carrier;

a charging unit that charges a surface of the image carrier;

an electrostatic latent image forming unit that forms an electrostatic latent image on the charged surface of the image carrier;

a developing unit that develops the electrostatic latent image on the surface of the image carrier with toner to form a toner image; and

a transfer unit including the semiconductive roller according to claim 1 , the transfer unit transferring the toner image formed on the surface of the image carrier to a transfer medium.

4. A method for manufacturing the semiconductive roller according to claim 1 , the method comprising:

kneading a rubber composition containing at least an epichlorohydrin rubber, an acrylonitrile-butadiene rubber, and a conducting agent;

forming the kneaded rubber composition into a substantially roll shape;

heating the rubber composition for vulcanization and foaming to form a semiconductive elastic product having a substantially roll shape;

polishing a circumferential surface of the semiconductive elastic product having a substantially roll shape; and

cleaning the semiconductive elastic product having the polished circumferential surface, wherein

the semiconductive elastic layer is placed on an outer circumferential surface of the conductive support to form the semiconductive roller,

wherein the semiconductive elastic product having the polished circumferential surface is immersed into pure water for approximately not less than 30 minutes for the cleaning.

5. The semiconductive roller according to claim 1 , wherein a surface hardness of the semiconductive roller, determined as Asker-C hardness in accordance with JIS K-7312, is in a range of 10° to 70°.

6. The semiconductive roller according to claim 1 , wherein a thickness of the semiconductive elastic layer is in a range of 2 to 12 mm.