Image forming apparatus

An image forming apparatus, comprising:

• a photosensitive member having a surface on which an amorphous silicon photosensitive layer is formed;
• a charging device that charges the surface of the photosensitive member to a prescribed surface potential;
• an exposure device that performs exposure with respect to the surface of the photosensitive member so as to form an electrostatic latent image thereon;
• a developing device including:
• a developer carrying member that is arranged to be opposed to the photosensitive member and carries a two-component developer including a toner and a carrier,
• the developing device causing the toner to adhere to the electrostatic latent image formed on the photosensitive member so as to form a toner image thereon;
• a development voltage power supply that applies, to the developer carrying member, a development voltage obtained by superimposing an alternating-current voltage on a direct-current voltage, and
• a control portion that controls the charging device, the exposure device, the developing device, and the development voltage power supply,
• wherein
• when a surface potential of the photosensitive member during image formation is indicated as V0 and a direct-current component of the development voltage to be applied to the developer carrying member as Vdc, and a potential difference V0−Vdc between the photosensitive member and the developer carrying member has a first potential difference in a direction in which the toner is moved from the developer carrying member to the photosensitive member and a second potential difference in a direction in which the toner is moved from the photosensitive member to the developer carrying member, the control portion adjusts V0 or Vdc so that the first potential difference and the second potential difference are equal in value and opposite in polarity, and
• when a first development current that flows between the photosensitive member and the developer carrying member at the first potential difference is indicated as |Ia| and a second development current that flows between the photosensitive member and the developer carrying member at the second potential difference as |Ib|, the second development current |Ib| satisfies Expression (1) below:
• 1.9×10−2≥|Ib|/N≥5.7×10−3[μA/mm] (I)
• where N denotes an axial length [mm] along which a magnetic brush on the developer carrying member is in contact with the photosensitive member.