Image forming apparatus

An image forming apparatus comprising:

• an image bearing member;
• a rotatable developing roller which includes an electroconductive layer containing an electroconductive agent and which carries a liquid developer containing toner and a carrier liquid, said developing roller developing an electrostatic latent image formed on said image bearing member, at a developing portion;
• an electrode portion, provided with a predetermined interval from said developing roller on a side upstream of the developing portion with respect to a rotational direction of said developing roller, for forming a potential difference between itself and said developing roller;
• an electroconductive roller, provided on a side upstream of said developing portion and downstream of said electrode portion with respect to the rotational direction of said developing roller, for urging said developing roller;
• first voltage applying means for generating a potential difference between said developing roller and said electrode portion;
• second voltage applying means for generating a potential difference between said developing roller and said electroconductive roller;
• current detecting means for detecting a current flowing through between said developing roller and said electroconductive roller;
• and
• a controller capable of controlling said first voltage applying means,
• wherein said controller controls said first voltage applying means so that by calculating information on a toner concentration in the liquid developer between said electroconductive roller and said developing roller from a detection result by said current detecting means when a predetermined potential difference is formed between said developing roller and said electroconductive roller in a state in which the liquid developer is applied onto said developing roller, the toner concentration is a target value.