Image forming apparatus

An image forming apparatus, comprising:

• an image carrier configured by a positively charged single-layer electrophotographic photosensitive body;
• a charging device which is based on a contact charging method for charging a circumferential surface of the image carrier while making contact with the circumferential surface of the image carrier;
• and
• a transfer unit which transfers a toner image on the circumferential surface of the image carrier to a transfer receiving body by gripping the transfer receiving body with the image carrier,
• wherein the transfer unit includes an application unit to which a transfer bias is applied,
• a region having a volume resistivity of 107 to 109 Ω·cm exists between the image carrier and the application unit,
• the image carrier has a conductive base body and a photosensitive layer,
• the photosensitive layer contains a charge generation material, a charge transport material and a binding resin, and
• a yield point strain of the binding resin is 9 to 29%
• a yield point strain of the photosensitive layer is 5 to 25%,
• the charging device comprises a charging member for charging the circumferential surface of the image carrier while in a state of contact with the circumferential surface of the image carrier,
• the surface roughness of the charging member is 55 to 130 μm, in terms of an average distance (Sm) between asperity peaks on a cross-sectional curve, and the ten-point average roughness (Rz) is 9 to 19 μm, and
• the charging device performs charging so as to satisfy Formula (I) below:
• 960−60X≦Y≦600 (I)
• (in Formula (I), X indicates the power of ten of a volume resistance (Ω·cm) of a region having a highest volume resistance between the image carrier and the application unit, and Y indicates a surface potential (V) of the image carrier).