Paper feed roller

A paper feed roller for use in a paper feeding unit in an electrophotographic image forming device, the paper feed roller comprising:

• an elastic layer composed of thermosetting polyurethane containing a plasticizer,
• wherein an addition amount of the plasticizer in the elastic layer is within a range of 10 to 50 pts. mass based on 100 pts. mass of the thermosetting polyurethane, and
• wherein a surface residual charge on a surface of the elastic layer is within a range of 90 to 170 V, where the surface residual charge is a value determined by single-point measurement of a surface potential on the surface of the elastic layer, a way of the measurement including:
• rotating the paper feed roller in a circumferential direction at a rotation speed of 70 rpm in an environment at 23° C. and 53% RH,
• electrifying the surface of the elastic layer by applying 100 μA of corona current by use of a corotron under such a condition that a distance between a core part of the corotron and the surface of the elastic layer are 10 mm, while rotating the paper feed roller, and
• measuring the surface potential at a center point on the paper feed roller in a roller axis direction under such a condition that a distance between a probe of a surface electrometer and the surface of the elastic layer are 1 mm in a position where the paper feed roller is rotated by 90 degrees from a position where the surface of the elastic layer is electrified.