The present invention provides an improved elastic material which is free
of roller abrasion when used in development rollers and overcomes
disadvantages of the conventional silicone rollers of deterioration in
the abrasion resistance, an elastic roller employing such elastic
materials, and an electrophotographic apparatus and electrostatic
recording apparatus incorporating such rollers. The elastic material
satisfies a relationship represented by the following equation:
log{(TbEb).sup.-1}.ltoreq.-0.0011(Hd).sup.2+0.1154(Hd)-5.6 where Tb is
the tensile strength (N/mm.sup.2), Eb is the tension fracture elongation
(%) and Hd is the Asker C hardness (.degree.).Further, the present
invention provides a novel developer carrier for use with an imaging
apparatus and an imaging apparatus incorporating the developer carrier.
The developer carrier includes an electrically conductive elastic layer
and is arranged in contact with, or in the proximity of, an imaging body.
In the developer carrier, the conductive elastic layer satisfies the
equation: 0.01.ltoreq.ST/Hd.ltoreq.2.0 where S is the compressive
permanent set (%), T is the thickness of the elastic layer (mm), and Hd
is the Asker C hardness (.degree.).