DE1522645A1 - Xerographic copying process - Google Patents

Description

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Docket 8184

Xerographic.es copying process

The usual type of xerographic copier uses a photoconductor attached to a drum. As a photoconductor is z. B. Selenium used, which is applied to a conductor is. The photoconductor layer is first charged in the dark by ion precipitation with the aid of a corona discharge device. The charged surface on the drum is then transmitted to an optical Station, in which the document with the help of a slot-shaped optics is applied to the surface of the drum in the form of a latent electrostatic image. This electrostatic Image is then developed by using a toner that contains a carrier material is mixed, is applied to the electrostatic image, so that the toner particles from the charged surfaces be attracted so that a visible image on the drum arises. A sheet of paper is then in contact with the inked

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th picture brought and ions of suitable polarity are on the back of the paper sheet in order to transfer the powder image from the drum onto the paper. The colored paper then passes through a heating station in which the toner is heated to such an extent that it becomes sticky and bonds to the paper.

A disadvantage of this type of copier is that the photoconductor layer on the drum wears off because the remaining toner particles must be removed from the drum by mechanical means. As a result, the quality of the copies deteriorates with increasing wear and tear and the photoconductor drum needs to be replaced from time to time. Do you want make multiple copies with this known copier, so must a new electrostatic latent image on the for each copy Photoconductor layer are generated. After the initial heating-up time the machine therefore no longer saves time per copy when making multiple copies.

There is a need for electrophotographic copying machines, capable of making multiple copies of one document, without regenerating the electrostatic latent image for each copy must become. In addition, the image quality of this electrostatic latent image should not decrease as the number of copies increases.

The purpose of the invention is to use the known Xerox copying process in this way to perfect that from a latent electrostatic image

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multiple copies can be made. The inventive method also has the advantage that the photoconductor layer when Copying does not wear out because the photoconductor is not directly connected to it comes into contact with the toner and copy paper.

The invention relates to a xerographic copying process in which the photoconductive layer is applied to an insulating layer is. The invention is characterized in that the latent electrostatic image at the interface between the photoconductive Layer and the insulating layer is formed and that for manufacturing of the copy (s) the outer surface of the insulating layer is colored.

The invention will be explained in more detail below with reference to the drawings will.

Pig. 1 shows an example of a Xerox copier which

works according to the method according to the invention, ™

Figures 2A, 2B, 2C

2D and 2E illustrate the preferred embodiment of the copying process according to the invention and

Figures 3A, 3B

and Fig. 3C illustrate something different according to the invention

Xerox copying process,

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A more detailed description of a system in which the present Novel processes can be used first on hand of Fig. 1. There two rotatable drums 1 and 2 are shown. The drums are rotatably mounted and are not supported by one here. showed facility turned. There is a on the drums photoconductive belt 2, which is transported by them and its exact condition further below in connection with FIGS. 2 and 3 is described. Drums 1 and 2 rotate the belt in the direction of arrow 5 · There is one in operative connection with belt 2 Double corona charger 4. This consists of two corona dischargers, which are on either side of the tape. The shield 5 the left corona discharge device is grounded, and its electrodes 6 are due to positive potential. The shield 7 of the right corona discharge device is also grounded, and its electrodes 8 are at negative potential. One for use with the present A dual corona charger suitable for this method is described in U.S. Patent 2,922,885. By using the double corona charger 4, uniform, same, but opposite Charges applied to the opposite sides of the belt 2.

The portion of the belt 2 that has been charged is then used by the Corona charging device 4 brought from into an exposure station 9. There, a document 10 to be reproduced is imaged by means of the lens 11 on the previously charged area on the belt 2. on this creates a latent electrostatic image of the document 10 on belt 2. This electrostatic latent image is scrolling

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then past a magnetic brush tinting station 12 where a toner is on the tape is applied to the electrostatic latent image in conventional way to develop. The magnetic brush can be a be conventional device. In Pig. 1 it is a rotatable cylinder 1> shown, in which magnets are embedded that form tufts which are rotated by a toner supply container 15. One detailed description of one in Pig's system. I usable magnetic brush is contained in U.S. Patent 2,890,968.

The toned image is then moved around the drum 20 and in intimate Brought into contact with an output sheet 16, which can consist of the usual paper. A paper supply 17 is located in a magazine 18, and the sheets are by means not shown in intimate contact with the belt 2 past and in operative connection with the Corona unit 19 transported. The shield 21 of the corona unit

19 is grounded and its corona generating electrodes 22 are applied a positive corona generation potential. The corona unit I9 positive ions are applied to the back of the sheet 16 in such a way that the toner is attracted to the sheet 16 from the belt 2. This is a traditional toner transfer process, that is described in U.S. Patent 2,576,0A7. Inside the drum

20 is a conductive spindle 23 which is grounded. The senior Spindle 23 forms an electric field between the corona unit 19 and is designed so that the positive ions from the Corona unit I9 is drawn off to the spindle and on the sheet 16 be deposited.

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The sheet 16 carrying the toned image is then passed under a heat fusing unit 24 which is conventional Facility acts, soft the toner sticks, and after it cools down therefore, a fixed copy of the document 10 is produced, which is then transported by a device (not shown here) into an output magazine 25 will. ·

Now the tape 2 is rotated so that the part that was previously tinted Has worn image, passes the dual corona charger 26. This consists of two corona discharge devices, their shields 27 and 28 are grounded and their electrodes 29 and 30 on AC voltages are. In the arrangement described here are the shields 27 and 28 transparent to allow light from the floodlights 31 and 52 it can penetrate.

The floodlights 31 j 52 and the double kotona unloading device 26 are turned on if no further copies of the electrostatic latent images are to be made, as described below will see. When the tape is exposed by the floodlights 32 and 33 so the photoconductor becomes conductive, and the corona discharge device 26 is caused to neutralize any charge on the pattern in order to create a new electrostatic latent image can be.

Now the tape runs past a toner cleaning brush 33, which the Remaining toner removed from the belt 2. The rest of the toner

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is removed from the belt 2 regardless of whether the electrostatic latent image has been erased by the floodlights 31 and 32 and the corona unit 26. Then the belt passes the corona unit 4 again and the process is repeated. As already stated, when multiple copies are desired, the electrostatic latent image is not erased by means of the floodlights 31 and 32 and the double corona unit 26. The electrostatic latent image is then passed through the double corona charging unit 4, which is now out of service ■%, and then that is at the exposure station 9 past also out of service back to tint station 12. The electrostatic latent image is then toned again, and the above The process described is repeated to make another copy. The final copy is then followed by the erasure of the electrostatic latent image.

As previously described, the system uses a double corona discharge device to create a uniform, same but opposite Charge patterns on opposite sides of the belt 2. Of course, it should be understood by those skilled in the art that other means can also be used to produce a uniform, same but opposite Charge is used on the opposite surfaces of the belt could become.

It could e.g. B. conductive rollers that operate at relatively high voltages opposite polarity, in contact with the opposite sides of the tape to be unrolled, thereby making the required To generate charge on the belt.

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Figures 2 and 3 illustrate methods according to the invention, at which can make multiple copies of a single electrostatic latent image. The preferred embodiment is in Pig. 2, while FIG. 3 shows another possible embodiment shows. According to FIG. 2, an arrangement consisting of a photoconductive layer 35 on a dielectric layer is shown used. Photoconductor 35 can be any conventional photoconductor be, such as B. zinc cadmium sulfide, zinc oxide, selenium, etc. That Dielectric 36 must and should have good insulating properties also be quite resilient, because that in the development Tinting agent used in the electrostatic image is applied to the dielectric.

The charge patterns generated during the five steps of the preferred method are shown in FIG. 2. In FIG. 2A, a charge on the surface 37 of the Pnouoieiuers and the surface 3 <3 of the dielectric applied. The charges shown here are uniform and equal, but of opposite polarity. Next up In the process step, the photoconductor is uniformly exposed. The result is the charge pattern shown in Fig. 2B. The one before positive charges present on the surface 37 of the photoconductor are now to the interface 39 between photoconductor and dielectric hiked. The previously on the surface 38 of the dielectric 36 existing negative charges remain. In the third process step, the layer sequence is carried out by a double corona charger or by conductive rollers in such a way that one

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Charge with the same but opposite polarity as that of the first charge (2A) is applied to surfaces 37 and 38. The results are shown in FIG. 2C, where the previously applied to surface 38 existing negative charges are neutralized and a uniform negative charge on the surface 37 of the photoconductor. The positive charge pattern on the interface 39 remains unaffected. The layer sequence prepared in this way is used in the fourth process step illuminated by the illumination of a document to be copied. It therefore, the electrostatic latent image shown in FIG. 2D is produced. Where light falls on the photoconductor 35 ′, the charges on its surface and those existing at the interface 39 neutralize Charges to each other, and in the dark areas they remain Charges on the surface of the photoconductor unaffected. An observation of the in Flg. 2D shown electric field 4i shows but that it remains essentially in the photoconductor 35 and that one very small part of the electric field is available for tinting stands. Thus, if element 36 were made relatively thin, it would obviously a portion of the electric field extends above surface 38. However, this electric field would have the known edge effect. A better electric field distribution is obtained by means of the fifth step in which the charge is removed from the surface 37 of the photoconductor, so that the latent electrostatic image only occurs at the interface 38. When removing the charge pattern from the surface 37 * as shown in FIG. 2E shows, that emerging from the charge pattern at the interface 38 is the same electric field 4.1 about the electric field that one

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free body in space is assigned. It has no edge effect (see Fig. 2E), and a substantial electric field extends above the surface of the photoconductor 55 .and the dielectric 36, which can be developed by conventional means.

The development of the electrostatic latent image of Fig. 2E can preferably be done with a magnetic brush. ■

FIG. 3 shows another exemplary embodiment of the novel electrophotographic process, namely FIG. 3 shows a three-part layer sequence which consists of a dielectric 42, a photoconductor 43 and a dielectric 44. As a first process step, the surfaces 45 and 46 of the dielectric layers are provided with a uniform charge of the same but opposite polarity. In the second step, the thus charged sequence of layers of photoconductor and dielectric is illuminated with light from the document to be reproduced, and the charge pattern shown in FIG Interface 48 represent the latent electrostatic image appearing. The charges on the surfaces 45 and 46 of the dielectric elements are not affected by this exposure. An observation of the electric fields associated with the latent electrostatic image shows that the fields 49 remain completely in the photoconductor 43 and that no part of the electric field extends beyond the surfaces 45 or 46 of the dielectrics. If the dielectrics 45 and _Q 46 were made relatively thin, but would openly

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visibly part of the electric field from the latent image up to extend beyond the surface of the dielectric 45 or 46. at its development, this field pattern would exhibit the well-known edge effect. The third step is the electrostatic latent image made usable by taking the charge from one of the surfaces 45 and 46 is eliminated. According to Fig. JC, the shift sequence is between an insulating roller and a conductive roller moved therethrough the. The insulating roller acted on surface 45 and the conductive one Roll onto surface 46. The consequence is that the electrical Field from the charge pattern illustrated in Fig. ^ C extends beyond the surface 46 of the dielectric. The electric Field 50 arises because of the positive charges appearing on surface 45 and the negative ones appearing on the upper interface Charges neutralize each other and therefore the electric field associated with the positive charges at the lower interface 48 Assumes a pattern that applies to a free body in space.

The method described with reference to FIG. 3 produces a negative one Image, while the embodiment shown in Figure 2 gives a positive image, which is usually more desirable.

In the preferred embodiment, there was a uniform charge pattern applied to the surfaces 37 and 38 of the same but opposite polarity. The expert should take it for granted be clear that instead of z. B. a double corona charger to generate this same but opposite

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To use charge pattern, the lower corona unit through a metal plate directed towards the surface 38 of the dielectric 36 could replace. The procedural steps remained unchanged, but the same If the metal plate rests against the surface 38 of the dielectric, the toner would have to be applied to the surface 37 of the photoconductor which would expose the abrasion and wear and tear.

In summary it can be said, therefore, that in the preferred exemplary ™ guide for a positive electrostatic latent image in a photoconductor is prepared separately from the surface thereof.

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Claims (5)

Claims 1. Xerographic copying process in which the photoconductive Layer is applied to an insulating layer, characterized in that the latent electrostatic image on the Interface between the photoconductive layer and the insulating one Layer is formed and that the outer surface of the insulating layer is colored to produce the copy (s) will. 2. Xerographic copying process according to claim 1, characterized in that that the outer surfaces of the photoconductive and insulating layers are uniformly of opposite polarity be charged so that the photoconductive layer is exposed uniformly, so that the charge on the surface of the photoconductive layer to the interface between the photoconductive and the insulating layer flows off so that the outer surfaces are opposite to the first charge Polarity are charged evenly, that the photoconductive layer is exposed to the pattern to be copied and that then see the residual charge from the surface of the photoconductor Will get removed. 3. Xerographic copying process according to claim!, Characterized in that the photoconductive layer between two insulating Layers is embedded that the outer surfaces of the two iso- 909840/13 18 Docket 31ö4 ' The photoconductive layers are charged uniformly with the opposite polarity to that of the photoconductive layer to be copied Pattern is exposed and that the charge is removed from the outer surface of one of the insulating layers. 4 ·. Arrangement.zur performing one of the methods according to claims w 1 to j5, characterized in that corona discharge devices or rollers which are under tension are provided for applying the uniform charges. 5. Arrangement for performing one of the methods according to the claims 1 to 4, characterized in that the photoconductive layer and the insulating layer (s) form a tape over two Roles is guided. Docket 8184 909840/1318 $ &