1. Field of the Invention
This invention relates to an electrophotographic apparatus for visualizing latent images by means of liquid development, and more particularly to an electrophotographic apparatus which prevents image quality from being deteriorated because of contamination by the developing liquid during continuous image formation. The invention is particularly effective for multi-color reproduction.
2. Description of the Prior Art
Electrophotographic apparatus of the image transfer type in which visible images may be formed on a photosensitive medium and transferred to ordinary paper to provide copies thereof has become widely popular because of its operating cost. Such apparatus, when used with liquid developer, can provide good half-tone reproduction and has been in great use for such purpose.
On the other hand, for the purpose of multi-color reproduction, there is a method known whereby color-resolved images of an original to be copied are applied to a photosensitive medium and each of these color-resolved images is individually reproduced and superposed one upon another to thereby provide a final multi-color reproduction. Particularly in a multi-color copying apparatus which may produce multi-color copies through an image transfer to ordinary paper or like medium, it is preferred and widely practised that a single photosensitive medium be exposed to image lights of different colors through a single optical system in order to ensure proper registration between different color images of the original as they are superposed one upon another. The apparatus of such type suffers from the problem that the necessity for different color developments to be effected successively on a single photosensitive medium tends to cause mixture of the different colors during development, and this is particularly so in the case of liquid development. More specifically, in the case of liquid development, after one color development has been completed, some of the developing liquid remains deposited on the photosensitive medium even if that particular color developing means ceases to operate and with the movement of the photosensitive medium, such deposited developing liquid flows along the surface of the photosensitive medium to mix with a developing liquid from a subsequent color developing device when another color development occurs, thus causing mixture of colors.
Such mixture might affect the toner density in the subsequent steps even in the case of single color development. This must be avoided to secure high quality of images.