Method And Device For Removing Developing Liquid

Abstract

A method and device used with an electronic photocopying apparatus and for removing any residual developing solution from a photosensitive member by the use of a corona discharger to thereby provide a perfect copy of an original image.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to means for a developing device used with an electronic photocopying apparatus, and more particularly to method and means for removing any excessive or residual developing solution from a photosensitive member during the process of development.

2. Description of the Prior Art

According to the prior art, it is generally the case with the development process effected by using a developing solution that a portion of such solution tends to stick not only to the electrostatic image formed on a photosensitive member but also to other areas of the photosensitive member. When the photosensitive member still having such residual developing solution thereon is subjected to the fixing process, the residual developing solution acts to form blots or stains in the reproduced image itself and the resultant copy becomes unsatisfactory in clarity or vividness.

To prevent such an unsatisfactory result, the prior art has employed means such as rollers for squeezing the residual developing solution on the photosensitive member or moisture absorbing means or the like to thereby remove such residual material. Such types of means, however, may also remove even the developing solution required to visualize the electrostatic image and the resultant image visualization may be greatly disturbed thereby. In this point, the use of such conventional squeezing rollers or moisture absorbing means cannot be considered an effective solution to the existing problem.

SUMMARY OF THE INVENTION

It is an object of the present invention to eliminate the above-described inconveniences and to remove only the unnecessary developing solution from a photosensitive member, thereby producing a vivid or clear reproduction of an original image.

It is another object of the present invention to remove any excessive developing solution from a photosensitive member by means of a corona discharger.

It is still another object of the present invention to provide an effective device which is capable of continuously carrying out the removal of the excessive developing solution.

It is yet another object of the present invention to provide all means that will be disclosed in the following detailed description.

According to the present invention, electric charges of a certain polarity are uniformly applied through corona discharging to the surface of developing solution in either direction with respect to the developed photosensitive member or to the developing device. As a result, the uniform electric charges of the same polarity in the surface of the developing solution repulse one another to thereby reduce the surface tension of the liquid. The electrically charged surface of the liquid is further concaved due to the coulomb force with respect to the electric charges of the opposite polarity produced on the photosensitive member. Thus, any residual liquid on the photosensitive member is forced to be completely swept out of the electrically charged area of the photosensitive member, whereby there is formed a perfect, flawless reproduction or copy of an original image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 are schematic views illustrating the operation of the present invention;

FIGS. 5 and 6 are fragmentary sectional views showing embodiments of the present invention; and

FIG. 7 shows another form of the present invention as applied to an electronic photocopying apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is shown the manner in which a photosensitive member 1 bearing thereon a negatively charged electrostatic latent image is developed by developing solution 2 so that positive toner 3 sticks to the latent image. If the developing solution 2 is then electrically charged uniformly by electrically charging means 10 such as corona discharger as shown in FIG. 2, the electric charges applied to the surface of the developing solution 2 will stick to the molecules of the liquid, which are thereby formed into ionized molecules. These ionized molecules of the liquid repel one another because they are of the same polarity, and strive to move with a force F.sub.H in parallel to the surface of the liquid. Thus, the portion of the liquid which has been electrically charged decreases its effective surface tension and provides a high degree of fluidity. Also, the electric charges E sticking to the liquid molecules in the surface of the developing solution produce a force F.sub.V which strives to depress or concave the liquid surface due to the coulomb force with respect to the corresponding electric charges E' on the photosensitive member 1. Consequently, as shown in FIG. 3, a concave develops very appreciably in that portion of the electrically charged liquid disposed right below the corona discharger 10. Therefore, the excessive portion of the liquid can be removed by removing that portion of the liquid forming the convex part of the liquid. Alternatively, removal of such excessive liquid portion can be accomplished by moving the corona discharger 10 along the surface of the liquid in the manner as shown in FIG. 4, to thereby force the excessive liquid to be displaced for removal.

FIG. 5 shows the present invention as applied to a photosensitive film with a mount for slide. In such a case where the surface of the photosensitive member takes a complicated contour, it is impossible to use the ordinary type of roller squeezing. In FIG. 5, the photosensitive film, the electrically charging means and the developing solution are designated by numeral 11, 10 and 13, respectively. In this embodiment, use is further made of a fixing infrared ray lamp 12, suction means 14 for sucking removed liquid, and a mount 15 for holding the photosensitive film 11. After subjected to the preceding processes, such as electric charging, exposure and development, the photosensitive film 11 is carried to the station provided with the shown electric charger, fixing lamp, etc. Thereupon the electric charger is moved to scan the photosensitive film so as to remove any residual excessive portion of the developing solution from the photosensitive film. Such residual liquid portion is brought to the junction area between the film and the mount and then sucked by the suction means 14 for removal. In this way the surface of the photosensitive film is now substantially dry and it is further subjected to heat radiation applied from the fixing infrared ray lamp 12 or to hot air applied from any other suitable means, whereby the film is completely fixed by heating. The quantity of heat required for this purpose may be very small. The suction means 14 for sucking the excessive liquid may take a tubular form, but a fully satisfactory result may be also achieved by the arrangement as shown in FIG. 6, in which a thin sheet 16 is disposed in contact with the junction between the film 11 and its mount 15 so that the liquid can follow the surface of the thin sheet or flow out due to the capillary effect.

The electric charges required for the charge-squeezing should desirably be of a polarity which will never malaffect the reproduction of an original image, and in this sense the negative polarity is preferred for the primary charges while the positive polarity is preferred for the use with a positive developing toner. The illustrated embodiment of FIG. 5 shows the surface of the film to be developed as facing downward, whereas such surface of the film may face either downward or upward as desired.

In addition to the described embodiments in which the electrically charging means is moved to thereby force any excessive developing solution to be removed, there occurs to mind a system which utilizes the fact that the surface tension of the developing solution is extremely decreased due to the neutralization of the electric charges or to the repulsion therebetween, whereby the solution may be removed by its own weight. Such a system, as shown in FIG. 7, for example, may comprise a corona discharger 10 disposed adjacent to the outlet portion of a developing device in the direction of movement of a photosensitive member a, so that the residual portion of the developing solution b sticking to the photosensitive member a is electrically charged with a polarity for reducing the sticking force, whereby that residual portion of the developing solution b drops on the developing device 21 from its own weight.

The developing device 21 may be so arranged that the photosensitive member a is directly dipped in the body of developing solution b, but such arrangement may result in an inconvenience that the developing solution b sticks to both surfaces of the photosensitive member a. Therefore, as shown in FIG. 7, a pump 22 is disposed within the developing device 21 to inject the developing solution b through a nozzle 23 onto the image-bearing surface of the photosensitive member a. Further, an arcuate developing electrode 24 is extended from the nozzle means to define a wedge-shaped flow passage 26 through cooperation with the photosensitive member a, so that turbulent flow of the developing solution b is provided in the wedge-shaped flow passage 26. This arrangement always ensures only the image-bearing surface of the photosensitive member to be effectively exposed to fresh developing solution.

The corona discharger 10 has therein filaments 25 of tungsten or like material having a diameter in order of 5/100 to 10/100 mm and disposed perpendicularly to the path of the photosensitive member a. A high voltage is applied from a power source 27 to the corona discharger 10 to cause corona discharge.

In the example shown in FIG. 7, the photosensitive member a is moved first downwardly and then upwardly depicting a U-shaped path along a rotating drum 28. In such a vertical U-shaped path of the photosensitive member a, there are sequentially provided an electrically charging means 29, an optical system 30 for forming an optical frame on the photosensitive member, a developing device 21, a corona discharger 10 and a drier 31. However, the present invention may also applicable to a lateral type arrangement in which the photosensitive member follows a laterally U-shaped path, or a circular type arrangement in which the photosensitive member is moved entirely circularly around the rotating drum, or a flat type arrangement in which the photosensitive member is moved horizontally in one direction.

As has been described above, the present invention eliminates the direct contact between the image-bearing surface of the phtosensitive member and the squeezing rollers which has existed in the prior art device, and this results in a perfect or flawless image reproduction having a highly excellent resolving effect. Moreover, as compared with the conventional device using squeezing rollers, the device of the present invention achieves highly efficient removal of any residual developing solution from the photosensitive member, which in turn leads to a lesser production or evaporation of the solvent during the drying process, and accordingly to a greater hygienical advantage. Furthermore, the removal of the developing solution form the photosensitive member is accomplished independently of the surface conditions thereof, and this means a highly stable removing effect which also means the elimination of any mechanical adjustment for such removal.

Claims

What is claimed is:

1. A method of removing excessive developing liquid from the surface of a photosensitive member comprising:

applying corona discharge from a corona discharger to said surface of the photosensitive member bearing said excessive developing liquid to deposit electric charge of a predetermined polarity uniformly thereon, and drawing off excessive developing liquid from said surface of the photosensitive member.

2. A method of removing excessive developing liquid as in claim 1 wherein said excessive developing liquid is drawn off said photosensitive member by suction.

3. A method of removing excessive developing liquid as in claim 1 wherein said excessive developing liquid is drawn off by sucking developing liquid at a predetermined height above said surface of the photosensitive member.

4. A method of removing excessive developing liquid as in claim 1 wherein said excessive developing liquid is drawn off by moving said corona discharger relative to said photosensitive member.

5. A method of removing excessive developing liquid as in claim 4 wherein said relative movement is in a direction whereby said developing liquid is dripped off.

6. A method of removing excessive developing liquid from the surface of a photosensitive member bearing an electrophotographic image visualized with toner of one polarity comprising:

applying corona discharge from a corona discharger to said surface of the photosensitive member to deposit electric charge of the same polarity as said one polarity of said toner uniformly thereon, and drawing off excessive developing liquid from said surface of the photosensitive member.

7. A method of removing excessive developing liquid as in claim 6 wherein said excessive developing liquid is drawn off said photosensitive member by suction.

8. A method of removing excessive developing liquid as in claim 6 wherein said excessive developing liquid is drawn off by sucking developing liquid at a predetermined height above said surface of the photosensitive member.

9. A method of removing excessive developing liquid as in claim 6 wherein said excessive developing liquid is drawn off by moving said corona discharger relative to said photosensitive member.

10. A method of removing excessive developing liquid from the surface of a photosensitive member comprising:

applying corona discharge from a corona discharger to said photosensitive member to decrease the effective surface tension of said developing liquid thereon and to provide same with a high degree of fluidity and

drawing off excessive developing liquid.

11. A method of removing excessive developing liquid from the surface of a photosensitive member comprising:

applying corona discharge from a corona discharger to said photosensitive member to depress the surface of developing liquid thereon, and

drawing off at least a portion of the developing liquid displaced by the depression of said surface.

12. In a copying device, an apparatus for removing excessive developing liquid from the surface of a photosensitive member comprising:

corona discharge means positioned relative to said photosensitive member bearing said excessive developing liquid for depositing electric charge of a predetermined polarity uniformly thereon, and

means for drawing off excessive developing liquid from said surface of the photosensitive member.

13. In a copying device, an apparatus as in claim 12 wherein said means for drawing off excessive developing liquid includes vacuum suction means for forcibly sucking removable developing liquid from said surface of the photosensitive member.

14. In a copying device, an apparatus as in claim 12 wherein said means for drawing off excessive developing liquid includes means causing relative movement between said corona discharge means and said photosensitive means.

15. In a copying device, an apparatus as in claim 14 further comprising means establishing said relative movement between said photosensitive means and said corona discharge means in a direction whereby said developing liquid is dripped off.

16. In a copying device, an apparatus for removing excessive developing liquid from the surface of a photosensitive member bearing an electrophotographic image visualized with toner of one polarity comprising:

corona discharge means positioned relative to said photosensitive member for depositing electric charge of the same polarity as said one polarity of said toner uniformly thereon, and

means for drawing off excessive developing liquid from said surface of the photosensitive member.

17. In a copying device, an apparatus as in claim 16 wherein said means for drawing off excessive developing liquid includes vacuum suction means for forcibly sucking removable developing liquid from said surface of the photosensitive member.

18. In a copying device, an apparatus as in claim 16 wherein said means for drawing off excessive developing liquid includes means causing relative movement between said corona discharge means and said photosensitive means.

19. In a copying device, an apparatus for removing excessive developing liquid from the surface of a photosensitive member comprising:

corona discharge means positioned relative to said photosensitive member for decreasing the effective surface tension of said developing liquid thereon and providing same with a high degree of fluidity, and means for drawing off excessive developing liquid.

20. In a copying device, an apparatus for removing excessive developing liquid from the surface of a photosensitive member comprising:

corona discharge means positioned relative to said photosensitive member for depressing the surface of said developing liquid, and means for drawing off at least a portion of the developing liquid displaced by the depression of said surface.

21. A method of removing excessive developing liquid from the surface of a photosensitive member comprising:

applying corona discharge from a corona discharger to said photosensitive member to subject said surface bearing said excessive developing liquid to electric charge of a predetermined polarity, and

drawing off excessive developing liquid from said surface of said photosensitive member.

22. A method of removing excessive developing liquid as in claim 21, wherein said corona discharge is a DC corona discharge.

23. In a copying device, an apparatus for removing excessive developing solution from the surface of a photosensitive member comprising:

corona discharge means positioned relative to said photosensitive member for subjecting said surface bearing said excessive developing liquid to electric charge of a predetermined polarity, and

means for drawing off excessive developing liquid from said surface of the photosensitive member.

24. In a copying device, an apparatus according to claim 23, wherein said corona discharge means generates a DC corona discharge.