Patent ID: 7575301

Claim:
An image forming apparatus, comprising: an ejection head which ejects droplets having electro rheological effects onto a recording medium; a holding device which holds the recording medium, the holding device being disposed at a position facing an ejection side surface of the ejection head, the recording medium interposing between the ejection head and the holding device; a pair of electrodes which is disposed on the holding device, the pair of electrodes comprising a first electrode and a second electrode; and a voltage application device which applies a voltage to the pair of electrodes, wherein: when a specific voltage is applied to the pair of electrodes by the voltage application device, an electric field strength having substantially arcuate lines of electric force between the pair of electrodes is applied to the droplets deposited over the entire surface of the recording medium wherein the electric filed strength on the recording medium takes a value at which the droplets deposited on the recording medium do not cause interference with each other while an electric field strength in the ejection side surface of the ejection head is not large enough to affect a droplet ejection of the ejection head, wherein the electric field strength is a function of the voltage and an arrangement of said pair of electrodes including disposing said first electrode and said second electrode at a specific distance, the electric field strength being configured such that the electric field strength in the ejection side surface of the ejection head is not large enough to affect droplet ejection of the ejection head, and wherein the specific distance is a range determined according to the equation: K - K 2 - E A ⁢ ⁢ 0 2 ⁢ h A 2 E A ⁢ ⁢ 0 < x < K - K 2 - E B ⁢ ⁢ 0 2 ⁢ h B 2 E B ⁢ ⁢ 0 , where x represents half the specific distance, K represents a constant proportionate to the voltage applied to the first and second electrodes, E A0 represents a first electric field strength threshold above which droplets deposited on the recording medium do not cause interference with each other, E B0 represents a second electric field strength threshold below which droplet ejection of the ejection head is not affected by the electric field strength, h A represents a height of the droplets deposited on the recording medium with reference to a center plane of the electrodes, and h B represents a height of the ejection side surface of the ejection head with reference to the center plane of the electrodes.