Developing device and developing method

A developing device comprising:

• a first toner carrying member for carrying toner on its peripheral surface, the first toner carrying member being capable of rotating while keeping out of contact with an image carrying member;
• a second toner carrying member for carrying toner on its peripheral surface, the second toner carrying member being capable of rotating while keeping out of contact with the image carrying member and being located downstream from the first toner carrying member in the rotating direction of the image carrying member;
• a developer carrying member for carrying toner composed of toner and carriers on its peripheral surface and for supplying the toner to the first toner carrying member and the second toner carrying member, the developer carrying member being located opposite to the first toner carrying member and the second toner carrying member;
• a first voltage application unit for applying an AC bias voltage to the first toner carrying member;
• and
• a second voltage application unit for applying an AC bias voltage to the second toner carrying member;
• wherein the AC bias voltage applied to the second toner carrying member has an average absolute value that is smaller than an average absolute value of the AC bias voltage applied to the first toner carrying member.

A developing method comprising the steps of:

• carrying a developer that is composed of toner and carriers on a peripheral surface of a developer carrying member;
• supplying the toner of the developer from the peripheral surface of the developer carrying member to a plurality of toner carrying members that are placed along a rotating direction of an image carrying member and out of contact with the image carrying member, so that the toner carrying members carry the toner on their peripheral surfaces;
• and
• applying AC bias voltages to the toner carrying members so as to cause the toner carried by the toner carrying members to stick to an electrostatic latent image formed on the image carrying member by the effect of electric fields induced by a voltage of the electrostatic latent image and the AC bias voltages applied to the respective toner carrying members;
• wherein the amount of developing toner sticking onto the image carrying member immediately after the image carrying member has passed a development area in an upstream side in the rotating direction of the image carrying member is larger than the amount of developing toner sticking on the image carrying member immediately after the image carrying member has passed a development area in a downstream side in the rotating direction of the image carrying member.

A developing method comprising the steps of

• carrying a developer composed of toner and carriers on a peripheral surface of a developer carrying member located opposite to a first toner carrying member and a second toner carrying member;
• supplying the toner from the peripheral surface of the developer carrying member to the first toner carrying member and to the second toner carrying member that are capable of rotating while keeping out of contact with an image carrying member, the second toner carrying member being located downstream from the first toner carrying member in the rotating direction of the image carrying member, so that the first toner carrying member and the second toner carrying member carry the toner on their peripheral surfaces;
• applying an AC bias voltage to the first toner carrying member;
• and
• applying an AC bias voltage to the second toner carrying member;
• wherein an average voltage value of the AC bias voltage applied to the second toner carrying member has a smaller absolute value than an average voltage value of the AC bias voltage applied to the first toner carrying member.