Charging roll for electrophotographic machine

A charging roll for an electrophotographic machine, comprising:

• a shaft body;
• an elastic body layer, formed on an outer peripheral surface of the shaft body;
• and
• a surface layer, formed on an outer peripheral surface of the elastic body layer, wherein
• at least one groove extending in a direction within ±46° relative to a circumferential direction is regularly formed in an axial direction on the outer peripheral surface of the elastic body layer;
• the groove has a groove width w1 of 4 μm or more and 30 μm or less;
• the groove has a groove depth of 2 μm or more and 12 μm or less;
• a planar part being a portion of the outer peripheral surface of the elastic body layer other than the groove has a width w2 of 4 μm or more and 30 μm or less;
• an angle θ of the direction in which the groove extends relative to the circumferential direction and a ratio w2/w1 of the groove width w1 of the groove to the width w2 of the planar part has a relationship represented by relationships (A) to (C) below;
• the surface layer comprises a binder polymer and roughness forming particles;
• and
• the roughness forming particles are respectively arranged on the planar part and on the groove of the elastic body layer;
• (A) when −5°≤θ≤+5°, 0.7≤w2/w1≤1.3;
• (B) when −22°≤θ<−5° or +5°<θ≤+22°, 1.0≤w2/w1≤2.0;
• (C) when −46°≤θ<−22° or +22°<θ≤+46°, 1.2≤w2/w1≤2.6.