Patent ID: 7081912

Claim:
An image forming apparatus comprising: an organic EL array exposure head for writing an image on an image carrier, said organic EL array exposure head comprising: a long transparent substrate, an array of organic EL elements aligned just like pixels aligned in at least one row, and a barrier plate formed with optical holes for preventing crosstalk of light, where crosstalk of light is a phenomenon that fluxes of light emitted from the light-emitting parts of adjacent organic EL elements are immixed at the condensing position of light from the light-emitting part of either organic EL element, wherein said barrier plate is arranged on the output side of said array of the organic EL elements on a side of said transparent substrate that is opposite to a side where said array of the organic EL elements is arranged, plus lenses are arranged at positions of said holes of said barrier plate, respectively, said image forming apparatus is a color image forming apparatus of a tandem type having at least two image forming stations each comprising a charging means, an exposure head, a developing means with toner, and a transfer means which are arranged around an image carrier, wherein said color image forming apparatus forms a color image by passing a transfer medium through the respective stations, and said image forming apparatus satisfies both the following relations:  Φ T - Φ L  ≤ 0.2 ⁢ ⁢ eV ( 1 )  Φ T - Φ B  ≥ 0.5 ⁢ ⁢ eV ( 2 ) wherein φ L is the work function of the material for said plus lenses, φ B is the work function of the material of said barrier plate, and φ T is the work function of the material of toner.