| US 7,580,660 B2 | ||
| Developing roller, process for producing developing roller, process cartridge and image forming apparatus | ||
| Tadashi Sato, Suntou-gun (Japan); Yosuke Ata, Suntou-gun (Japan); Saki Tominaga, Suntou-gun (Japan); and Momosuke Takaichi, Nagareyama (Japan) | ||
| Assigned to Canon Kabushiki Kaisha, Tokyo (Japan) | ||
| Filed on Oct. 09, 2008, as Appl. No. 12/248,292. | ||
| Application 12/248292 is a continuation of application No. PCT/JP2008/057651, filed on Apr. 15, 2008. | ||
| Claims priority of application No. 2007-111784 (JP), filed on Apr. 20, 2007. | ||
| Prior Publication US 2009/0041499 A1, Feb. 12, 2009 | ||
| Int. Cl. G03G 15/08 (2006.01) | ||
| U.S. Cl. 399—286 | 6 Claims |
| 1. A developing roller comprising:
a conductive shaft member;
a conductive elastic layer formed around the shaft member in a thickness of 0.5 mm to 6.0 mm; and
a surface layer,
wherein the elastic layer contains carbon black and silicone rubber serving as a binder for the carbon black, the carbon black
is in a content of 7% by mass to 17% by mass based on the mass of the elastic layer, the carbon black in the elastic layer
has at least two peaks in its particle size number distribution, a minimum diameter peak center in the particle size number
distribution is within the range of 10 nm to 40 nm,
the elastic layer has density within the range of 1.01 g/cm3 to 1.07 g/cm3, and
where a ratio of carbon atoms to silicon atoms (C/Si) in the vicinity of the surface of the elastic layer is represented by
X, the ratio of carbon atoms to silicon atoms at a depth of 100 μm from the surface of the elastic layer by Y, and the ratio
of carbon atoms to silicon atoms at a depth of 200 μm from the surface of the elastic layer by Z,
the X, the Y and the Z satisfy the relationships of the following expressions:
1.50≧X/Y≧1.10, and
1.10≧Y/Z≧1.02.
|