Electrophotographic Photosensitive Member

The present invention relates to in general an electrophotographic photosensitive member for use in an electrophotographic copying machine, and more particularly to a photosensitive member for use in a wet electrophotographic process and provided with means for preventing the developing solution from flowing past the sides of the photosensitive member.

The photosensitive members are used in the electrophotographic processes as disclosed in U.S. Pat. Nos. 2,221,776, 2,297,691 and 2,357,809 in which the surface of the photosensitive member consisting of a support made of electrically conductive material and a photoconductive layer is charged uniformly, the light image of an original to be reproduced is projected upon the charged surface so as to produce an electrostatic latent image, the latent image is developed by the toner and the toner image is transferred to a recording medium such as paper and is fixed. There has been known an electrophotographic photosensitive member of the type disclosed in U.S. Pat. No. 3,234,019, which has a protective layer applied to the surface of the photosensitive member.

There has been known the electrophotographic photosensitive member of the type used in an electrophotographic process disclosed in U.S. Pat. No. 3,438,706, assigned to the same applicant and in which the surface of an insulating layer overlaid upon a photoconductive layer is uniformly charged, an electrostatic latent image is produced by projecting the light image of an original to be reproduced while contemporaneously applying the charge with the polarity opposite to that of the charge previously applied or AC corona discharge, the whole surface is illuminated so as to enhance the contrast of the electrostatic latent image, the latent image thus formed is developed, transferred and fixed. In addition to the electrophotographic processes of the type described, various processes have been proposed and used in practice with various types of photosensitive members.

The present invention is applied to a photosensitive member capable of being used repetitively in a wet electrophotographic process. The photosensitive members for use in the wet electrophotographic process are in the forms of a flat sheet, a cylinder and an endless belt as shown in FIGS. 1A, 1B and 1C. In general, the photosensitive members such as 3A, 3B and 3C consist of photoconductive layers such as 1A, 1B and 1C and supports such as 2A, 2B and 2C. When these photosensitive members are used in wet electrophotographic processes in which developing solution is caused to flow over one of the surfaces of the photosensitive member, the member is immersed in the developing solution, or the developing solution is sprayed over the surface of the photosensitive member, the developing solution tends to flow over the side edges of the photosensitive member so that the image quality is degraded and the machine is corroded by the developing solution, thus causing breakdown.

Therefore, a primary object of the present invention is to provide an improved electrophotographic photosensitive member which may prevent the developing solution from flowing out from the side edges thereof.

It is another object of the present invention to provide an improved electrophotographic photosensitive member provided with means for preventing the developing solution from flowing over the side edges of the photosensitive member, said means being formed in a portion outside of an image forming portion of the member.

It is another object of the present invention to provide an improved electrophotographic photosensitive member provided with means for preventing the developing solution from flowing over the side edges of the photosensitive member and collecting the excess developing solution to a predetermined position.

An electrophotographic photosensitive member in accordance with the present invention is provided with grooves or ridges in suitable dimensions formed along the side edges of the member so that the excess developing solution used in the wet electrophotographic processes may be collected from the image forming surface into the grooves or toward the bases of the ridges, thereby preventing the developing solution from flowing further toward the side surfaces. The excess developing solution collected in the grooves or toward the bases of the ridges flows toward a suitable reservoir or the like.

The present invention will become more apparent from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings in which:

FIGS. 1A, 1B and 1C are schematic perspective views of the conventional electrophotographic photosensitive members;

FIG. 2 is a perspective view of an improved electrophotographic photosensitive member in accordance with the present invention for use in a wet electrophotographic process in which the developing solution is cascaded over the flat surface of the photosensitive member;

FIG. 3 is a diagrammatic sectional view illustrating an improved cylindrical electrophotographic photosensitive member in accordance with the present invention for use in a wet process in which the photosensitive member is immersed in the developing solution;

FIG. 4 is a schematic sectional view illustrating an improved cylindrical electrophotographic photosensitive member used in a wet process in which the developing solution is sprayed over the surface of the photosensitive member; and

FIGS. 5A and 5B are perspective views illustrating improved electrophotographic photosensitive members in the form of endless belts used in a wet process in which the developing solution is cascaded over the surface of the photosensitive member.

Referring to FIG. 2, an electrophotographic photosensitive member generally designated by 23 comprises a photoconductive member 21 and a support 22 and is provided with grooves 24 formed along the opposite side edges of the photosensitive member 23. The developing solution from a container 25 is cascaded over the surface of the photosensitive member 23 while a roller 26 rotating in the direction opposite to the direction indicated by X is advanced in the direction indicated by Y, thereby developing the electrostatic latent image formed upon the surface of the photosensitive member 23. In this case, the developing solution is spread over the surface by the roller 26 and collected into the grooves 24 from which the developing solution flows into a receptacle 27.

Referring to FIGS. 3 and 4, cylindrical photosensitive members generally designated by 33 and 43 comprise photosensitive members 31 and 41 and supports 32 and 42 disposed on drums 38 and 48, respectively, and such structures will be referred to as "photosensitive drums" hereinafter. The photosensitive drums 38 and 48 are provided with annular grooves 34 and 44 formed along the lateral side edges thereof, respectively. In the photosensitive drum 38, the outer walls 39 of the grooves 34 are made lower than the peripheral surface of the photosensitive drum 38 because the latter is used in a wet process in which the drum 38 is partly immersed in the developing solution. In case of the photosensitive drum 48 which is used in a wet process in which the developing solution is sprayed over the peripheral surface of the drum 48, the outer walls 49 of the grooves 44 may be in flush with the peripheral surface of the drum 48.

The photosensitive drum 38 rotates in the direction indicated by Z and the developing solution at the top of the drum may flow into the grooves 34, from which the developing solution returns to a developing solution reservoir 37. In case of the photosensitive drum 48, the excess developing solution sprayed from a developing solution tank 45 is also collected into the grooves 44, from which the developing solution may flown into a receptacle 47.

Electrophotographic photosensitive members in the form of endless belts illustrated in FIGS. 5A and 5B and generally designated by 53A and 53B each comprise a photosensitive layer and a support and are provided with grooves 54A and 54A', and ridges 54B and 54B' respectively. Excess developing solution may be collected into the grooves 54A and 54A' to flow into a receptacle 57A in FIG. 5A and the solution may be made to flow along the ridges 54B and 54B' into a receptacle 57B in FIG. 5B.

In case of the photosensitive druus 38 and 48 and the photosensitive members in the form of endless belts 53A and 53B, scrapers 30, 40, 50A and 50B made from felt or the like may be interposed between the grooves or ridges and the receptacles or reservoir so as to effectively collect the developing solution to the desired portions.

In addition to the embodiments described hereinabove with reference to FIGS. 2 through 5B, the present invention may be applied to many other electrophotographic photosensitive members used in wet processes. The developing solution may be prevented from flowing toward the side edges thereof by providing the grooves or ridges along the side edges of the photosensitive members, so that the damage to the image may be prevented and that the breakdown of the copying machines may be also prevented. Since the excess developing solution may be removed from the surface of the photosensitive member, the electrostatic latent images may be developed with a uniform quantity of developing solution so that the better quality images may be produced.