Image forming apparatus and method of developing an electrostatic latent image

An image forming apparatus, comprising a latent image bearing member, and a developing unit which comprises:

• a developer bearing member disposed adjacent to said latent image bearing member to define a developing zone therebetween, said developer bearing member being configured to carry a two-component developer including a toner and a carrier on its surface and to convey the developer to said developing zone, so that the latent image on said latent image bearing member is developed with the toner in said developing zone;
• and
• a developer regulating member configured to regulate the amount of the developer carried and conveyed by the developer bearing member toward said developing zone;
• wherein that portion of said toner which has a particle diameter of 2.0-4.0 μm accounts for 30-70% of a total number thereof, and
• wherein said developer regulating member is directly grounded so that when said developer bearing member is applied with a bias voltage, an electric field is formed between the developer regulating member and said developer bearing member, whereby toner deposits on said developer bearing member are transferred to said developer regulating member.