1. Field of the Invention
The present invention relates to an image forming apparatus including copiers, printers, facsimiles and the like, specifically, to an image forming apparatus in which development is accomplished by the liquid developing unit. Also, the present invention relates to the liquid developing unit.
2. Description of Related Art
An electrophotographic image forming apparatus includes, for example, an image forming apparatus comprising a liquid developing unit that supplies a liquid toner to a photosensitive drum on which an electrostatic latent image is formed so as to develop the electrostatic latent image. This liquid developing unit includes a developing roller for supplying the liquid toner to the photosensitive drum. The liquid toner in a tank is drawn by an application roller, and at the same time, the toner on the circumferential surface of the application roller whose amount is regulated by a doctor blade is supplied to the developing roller.
In addition, spiral-shaped grooves extending continuously in the axial direction are formed on the foregoing circumferential surface of the application roller. These grooves convey dust, paper chips and the like that enter the contact area between the application roller and the doctor blade in the axial direction to remove them (Refer to Japanese Unexamined Patent Publication No. 2002-278296, for example).
However, in the foregoing apparatus, since the liquid toner in the tank is drawn only by means of the application roller, and the drawn liquid toner needs to be leveled so that the amount thereof is even on the circumferential surface, it is disadvantageously hard to supply the developing roller with the liquid toner.
Therefore, the present inventors tried to develop an apparatus additionally provided with a pick-up roller for drawing the liquid toner from the tank in the previous stage to the application roller. However, applying the invention disclosed in the above-identified Japanese Unexamined Patent Publication to a liquid developing unit including such a pick-up roller for supplying the liquid toner to the application roller causes the following problem.
Although forming spiral-shaped grooves in the circumferential surface of the application roller makes it possible to remove foreign objects entered the contact area between the application roller and the doctor blade, in such a case, the liquid toner supplied from the pick-up roller to the application roller is conveyed in the axial direction. As a result, the liquid toner fails to be evenly supplied along the axial direction of the application roller. Accordingly, it is impossible to supply the liquid toner evenly along the axial direction of the developing roller and the photosensitive member, which results in degraded quality of the image transferred from the photosensitive member to the paper.