| 摘要 |
PURPOSE:To prevent the conductive layer of a developing roller from being peeled and to obtain a high-definition image without a faulty part in the long term by providing an elastic layer and the conductive layer provided on the surface of the elastic layer on the developing roller and satisfying a specified relation between the elongation of the material of the elastic layer and the elongation of the material of the conductive layer. CONSTITUTION:The developing roller 12 is provided with the elastic layer 12b and the conductive layer 12c provided on the surface of the layer 12b. Supposing that the elongation of the material of the layer 12b is Le%, the elongation of the material of the layer 12c is Ll%, the relation of 0.5<=Ll/Le<=5.0 is satisfied. When the ratio of the elongation of the material of the layer 12b to that of the layer 12c is within a range satisfying the relation, the layer 12c can follow up the deformation of the layer 12b caused by the press-contact of the developing roller 12 with a developer thin layer forming means and an electrostatic latent image holding body. Thus, the conductive layer 12c of the developing roller 12 is prevented from being peeled and the high-definition image without the faulty part is obtained in the long term. |
