DE1965293A1 - Electrophotographic imaging process - Google Patents

Description

Patent attorneys uipl.-ing. Jtvweickmann,

Dipl.-Ing. H. Weickmann, Dipl, -Phys. Dr. K. Fincke Dipl.-Ing. F. A. Weickmann, Dipl.-Chem. B. Huber

8 MUNICH 86, DEN

PO Box 860 820

MDHLSTRASSE 22, NUMBER 48 39 21/22

RANK XETROX LIMITED, Rank Xerox House, 538, Euston Road, London, 1T.W.1, England

Electrophotographic or electrostatographic imaging processes

The invention relates to electrostatic imaging and is particularly concerned with the development of electrostatic ones latent images and the removal of residual toner images from an image plate ©

The most advanced electrostatic imaging process is xerography, first described in US Pat. No. 2,297,691. This process is carried out with an electrophotographic image plate, which consists of a conductive base and a layer of a photoconductive insulating material. The plate surface is evenly charged electrostatically and then exposed to a Licht-Sohatten image. In the exposed parts of the surface it is discharged according to the intensity of the incident radiation, so that an electrostatic latent image is formed on the surface of the photoconductive layer, which corresponds to the light-shadow image. The electrostatic latent image is then developed by applying an electroscopic drawing material called "toner ^11. The developed image is also referred to as a" toner image "or" developed image ". Bs can be on the electrophotographic imaging plate

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fixed themselves or transferred to a sheet of paper or another image carrier and fixed on this o It is however, it is possible that after the image transfer there will still be a residual toner image on the surface of the photoconductive Sohioht adheres. Will use this picture before again If the image plate is not removed, it can at least partially be transferred to a copy sheet with the next image generated be o

Since certain photoconductive insulating materials such as amorphous selenium can be used repeatedly to form images, the electrophotographic process was automated, including a rotating electrophotographic imaging plate in the form of a cylindrical drum is used o one Apparatus suitable for automatically performing the process is disclosed, for example, in U.S. Patent 3,062,109 A very successful model of such a device is the Xerox 914 copier machine Corporation, Roohester, New York. In such a machine the individual process steps are carried out at different stations that are arranged around the image drum are · These stations are used sequentially for charging, exposure, development, image transfer and drum cleaning

In order to prevent a later transfer of the remaining images in such automatically working Masohinen, special Stations on the rotating electrophotographic drum are sequentially developed and cleaned and also charging with a polarity opposite that of the pre-exposure charging after image transfer and cleaning and the next Image generation performed. The charging of an electrophotographic image plate after the image transfer with this po « larity enables the rest to be removed more easily

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Toner particles from the image area, for example with a rotating fur brush. After cleaning the image plate the entire imaging cycle can be carried out again with it will.

The flat and drum-shaped optical plates are most widely used in electrophotography. The optical plate can be used but also have any other shape, for example it can be as a tape, sheet, foil or similar, as a metal strip, metal sheet, Metal roll, metal cylinder, metal drum, endless metal belt, endless Mobius strip, round disc or be trained differently. The electrically conductive picture plate « The substrate can consist of two or more layers according to the required properties of the entire image plate. In the following, an electrophotographic imaging plate is understood to mean any of the aforementioned configurations will. The shape of the plate surface determines the arrangement of the various electrophotographic process stations or the type of implementation of the individual process steps.

In addition to the preferred charging and exposure of the image plate, the electrostatic latent image can also be generated in other ways formed by the normal electrophotographic process and then transferred to the surface of another imaging plate by bringing both elements very close together and using an overlay process such as that disclosed in U.S. Patents 2,982,647, 2,825,814 and 2,937,943 is described. Furthermore, charge patterns corresponding to specially selected and shaped electrodes or electrode ^{combinations can be generated on an image surface using the "IESI M} discharge process, which is described in FIG

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U.S. Patents 2,023,731 and 2,919,967 is. Furthermore, the TJ.S, patents 3 001 849 described method as well as the electron beam recording according to U.S. patent 3 113 179 are used.

Xerography serves as an imaging method to explain the present invention. In the same way, however, an application of the invention to other electrostatographic imaging processes is also conceivable. Electrostatography is understood to mean the generation and use of a latent electrostatic charge pattern for the purpose of recording and reproducing image patterns in visible form «(see" Standard Definitions of Terms for Electrostatographic Devices ", IEEE Hr _β 224, November 1965, published by The Institue of Electrical and Electronics Engineers, Inc., 345 East 47 Street, Few York, NY 10017).

A process has established itself for image development that in the XT. S. Pat ent writing 2 618 551 and is suitable for automatically operating devices. It will a developer is used, which consists of toner and a granular carrier. Both substances are mixed and taken thereby triboelectrically · charges of opposite polarity on * Then this developer material is under the force of gravity via the electrophotographic image plate or the electrostatic one cascaded latent image. The carrier particles usually consist of small globules, but they can also be different Have shapes and, for example, as flat plates, cubic plague bodies, synthetic or natural · Faeern, metal shavings uswhere be trained. Except for the development of caecada are also still the magnetic brush development, the liquid development, the liquid bed development, the powder cloud development and other procedures known »

A widely used method for image plate cleaning

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in an automatically working reproduction machine is described in U.S. Patents 2,751,616 and 2,852,977. Here, a brush with Weiohen lasers with suitable triboelectric properties is used strength is sufficient to remove residual toner particles from the image plate. The remaining toner particles will be Wiped off the image plate with such a brush, as it were, learners can also whiten tissue or ribbons from them fibrous materials or sticky! laughs as well as other cleaning elements be applied"

However, the above-described options for cleaning the image plate and developing the image also have disadvantages. For example, an extensive apparatus for image plate cleaning required, which is disposed at a particular location on the optical disk _e Experience has shown that with increasing number of processing stations for the implementing of the electrophotographic process, the risk of the leakage of toner powder from the image forming area in the machine and thus the soiling of the machine increases »Many cleaning devices require more than one cycle of the image plate through the cleaning area, which means that cleaning the image plate takes longer and cleaning becomes a limiting factor for the time required for an image generation cycle different areas of the image plate, again requiring devices to ensure that the portion of the image plate used to reproduce the desired image is accurate to every process is aligned. For photoconductive substances, aioh has shown that with an increasing number of the necessary cleaning or development processes, the number of possible image creation processes for a given, acceptable image quality decreases.

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Treatment or cleaning is partially worn out, and the resulting scratches promote the absorption of toner particles, which results in a tinting of the background areas of the images produced.Finally, repeated passage of the image plate through the development or cleaning area leads to increased toner consumption and a deterioration in the toner concentration in the Developer _β Each of these phenomena mentioned above contributes to the deterioration of the image quality in the known reproduction machines «

Also the successfully used and well developed electrophotographic ones Reproductive machines therefore contain extensive cleaning devices on a special basis. driving station, which increase the toner consumption and the toner contamination of the machine, the service life of the pot conductor shorten and degrade the image quality

Various Versuohe have already been carried out to avoid the above-mentioned disadvantages, which, however, lead to unsatisfactory solutions. In the U.S. patent 2 484 782, for example, it is stated that to remove a residual toner image only a granular material, charged oppositely to the toner particles are cascaded across the electrophotographic imaging plate can. However, this process always requires a special process station and does not avoid the associated ones Naohteile. U.S. Patent 3,146,687 is a Process described in which various sectors of a round plate are sequentially applied to the electrophotographic process locations including the cleaning parts and the Development site must be passed · Here, however, there are several cleaning devices · and special mechanical devices required that the correct arrangement of the respective gen sector at each process station aichera-Älen, In the

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OBGINAl

U.S. Patent 3,108,895 is the erasure of a dielectric Described recording medium with an electrically conductive base, including the recording medium by a Mass of an electrically conductive, particulate dye is performed with the conductive base of the Recording medium is electrically connected. Here is however, the recording medium must again be passed through a special cleaning device

The object of the invention is therefore to provide the above-mentioned main parts of known reproduction machines to avoid and to create a process in which the image development and the image plate cleaning as possible with one device simultaneously in one and the same area of an electrostatographic recording medium, for example an electrophotographic image plate, can be carried out in one process step «. So that should improves the image quality of electrophotographic images and increases the utilization of the toner present in the developer “It is also intended to increase the service life of the photoconductive Insulating material layer of an electrophotographic image plate or the image material layer of another electrostatographic Extend the recording medium * Finally by avoiding mechanical devices, a simpler and more compact structure and quieter operation of a electrophotographic reproduction machine at lesser Toner contamination be possible »

for an electrophotographic or »electrostatographic ab-» Formation process in which a developing agent consisting of toner and carrier loaen is used and repeated by one image plate going through an imaging cycle a residual toner image after each image transfer

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is removed, this object is achieved according to the invention in that the developer substance is present in each case of a residual toner image on the image plate subsequent image generation cycle is brought to act on the image plate during image development in such a way that at the same time as the image develops, the remaining [toner image is removed

A better understanding of the invention and its further advantages and characteristics emerges from the following description preferred exemplary embodiments based on the figures

Figol is a side view of an electrophotographic reproduction machine, which works according to the method according to the invention,

2 shows a side view of a for carrying out the invention Process suitable developing and cleaning device and

3 shows a graphic representation of a preferred operating range the charging voltage and the lighting strength for the production of electrostatic latent images on a according to the method of the invention image plate to be processed

In Fig. 1 is an electrophotographic reproduction machine the known electrophotographic process stations contains, but works according to the development and purification process according to the invention. As an image carrier serves a rotating drum 10, which is provided with a photoconductive image material layer · While the surface 11 the drum is rotated through the imaging cycle they are first charged electrostatically with a corona discharge device 12. The charged area then arrives the exposure point 13, at which the I & oht-

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Shadow image is projected on them.

The charged and exposed surface of the drum, which now forms an electrostatic latent image corresponding to the projected one The original image then arrives in a device 14 which, according to the invention, has a development and drum cleaning system enables. The method according to the invention is carried out in the device 14 by adding a developer, which consists of tuner and carrier particles, is cascaded over the drum surface. This makes the electrostatic Image developed and at the same time, in a manner to be described, removal of one formed from toner particles remaining image that may still adhere to the drum after development. Both effects of this process step therefore take place in one and the same area of the drum surface

The development tray is the one provided with the developed image Drum surface then to an optionally provided electrode 15, which before the image transfer or »for its preparation causes the drum surface to be recharged · Then the developed image arrives at the transfer point 16, on which it is transferred to another image carrier 17 », for example on a sheet of paper · The one with the transferred Imaged paper sheet is then conveyed to a fixing device 18 having a heater or another Flxer is provided. This sheet transport takes place with a conveyor belt 19 · While the paper sheet 20 through the When the fuser is moved, the part of the electrophotographic drum from which the developed image is transferred becomes which, however, now only consists of remaining toner particles existing image carries through the image generation cycle turned further · The device shown in Plg.1 is behind the image transfer point 16 one with negative polarity working loading device 21 arranged with which the

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The polarity of the drum charge is reversed before cleaning. The known cleaning device would normally be at the point 22 The drum surface provided with the residual image is arranged at the discharge point 23 by leaching with Idcht completely discharged.

After this discharge at the discharge point 23, the drum surface is then ready for recharge and exposure, although the remaining image from the previous imaging cycle still exists on it. The renewed image generation is nevertheless possible if the method according to the invention is used «in known electrophotographic devices an additional cleaning step would be required before recharging and exposing the image surface «

A preferred embodiment of the method according to the invention consists of a cascading of developer, which consists of toner and carrier particles, over the surface the photoconductive image stabilizer layer provided with the remaining toner image. While the developer substance over the When the plate surface is cascaded, electrostatic latent images are developed and, surprisingly, images are made remaining toner particles from the previous imaging cycle removed by the interaction of mechanical, triboelectric and electrostatic processes It is assumed that that the developer particles physically abut the residual toner particles and from the surface of the photoconductive ones Push the layer away so that it can be electrostatically attracted to the toner-free areas of the carrier parts. This creates a cleaning effect. The surprising property of the coecadation process, one simultaneous removal of residual toner particles and the associated development of electrostatic latent images to enable, so comes with the method according to the invention for exploitation

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A preferably Ausführungsungaform a device for simultaneous cascading development and picture plate cleaning is shown in Figo2, in it the developer 24 at point 25 over the surface 11 of the drum or cascaded through the development and cleaning zone.

The process of simultaneous developing and cleaning may be improved by the guide of an electrode parallel to the electrophotographic image plate _or the electrode may be made of a solid plate, a grid, a BsLhe of wires or a plurality of points close to the optical disk surface to be formed and is connected to a voltage source , which creates an electric field of predetermined polarity between it and the photoconductive image material. The electrode is preferably connected to a voltage whose polarity corresponds to that of the electrostatic image charges on the image plate.

In the device shown in FIG. 2, there is an electrode 26 arranged near the image plate surface 11. Furthermore is a Guide plate 27 is provided with which the flow of the developer as well as the formation of toner clouds at the lower end of the development and cleaning zone is influenced · Except for this Effect, the guide plate 27 also supports the development in the same way as the development and cleaning electrode » since it can also be biased.

When using the method according to the invention in automatically operating reproduction machines of the type shown in FIG Art as well as in other electrostatographic devices several variables occur which directly influence the operating characteristics.

One of these variables is the angle at which the

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cascading developer to the surface of the photoconductive Shift is performed. For those shown in Pig »1 and 2 Apparatus can be seen to be the portion of the electrophotographic drum over which the developer cascades is bent. A tangent to the drum surface forms a different angle along this arc with the horizontal. At each point on the drum surface, the developer flows under a certain one Angle. However, since it is composed of a particulate mixture, the carrier particles and the toner particles move as well as their combinations at any point on the curved drum surface or a flat plate surface other embodiments in directions and at angles, which are slightly different from the values as determined by the plate surface and the electrode ο The However, the bulk of the developer follows the direction and angle of the image plate and at a given point Electrodeβ

In another embodiment of the invention, the developing agent can cascaded via a flat plate made up of a conductive base and a photoconductive base Insulation layer consists. The flat image plate and its associated Electrodes can be inclined up to 90 ° to the horizontal at any angle. The flat image plate can be applied in the usual way, i.e. the developer will.over the surface of the photoconductive layer cascaded. It is also a cascading of the developer material Possible over the electrode that is parallel and close to the surface of the photoconductive layer, but in a corresponding manner other, i.e. the inverted inclination is arranged. It has been found that an optimal developing and cleaning effect occurs when the electrophotographic image plate or the electrode forms an angle with respect to the horizontal which is in the region of the above. 70 ° with the usual Sohräglage

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until oa. 70 ° "with an inverted inclined position. Optimal development and cleaning therefore results when the image plate and electrode are arranged vertically. A preferred angular range between the electrode and the horizontal extends from approx. 60 ° to approx. 60 ° inverted. A satisfactory one The development and cleaning effect results when the angle between the electrode and the horizontal is approx. »20 ° to approx. 20 ° inverted, the lower limit value is approximately the angle of inclination of the respective arrangement associated electrode with respect to the horizontal, at which the developer begins to flow over the uncharged plate or, in the case of an inverted position, over the electrode surface. This flow occurs at an angle that is slightly less than the angle of inclination when the developer is already at an initial speed o With these g However, at angular values the flow of developer material is unstable and there is only a slight development and cleaning effect. It is further noted that although the optimum operating area of a vertical arrangement or ₀ great angle values corresponding to that, however, at very low angular values the conventional Kaskadierungsanordnung is more effective than the inverted assembly. Maximum cleaning action occurs within the development and cleaning zone near the photoconductive layer, where the activity of the developer is greatest.

It should be noted that the conditions for the best developing and Reinigungewirkung in a device can be realized in which the flow of the carrier is not only duroh produced gravity but also or only duroh other means, which are arranged close to the image plate and from "turning aside from the device shown in the figures ar-

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Working · However, these options require a more complicated one Construction and are simple in terms of cost, size of the machine and its construction in connection with the method according to the invention to be carried out less desirable

Another variable is the voltage difference between the developing and cleaning electrode and the irradiated and the non-irradiated background or image area parts of the image plate o The electrode voltage V must be so much lower and of the same polarity as the voltage Y. of the non-irradiated image areas of the image plate be that the field generated by the electrostatic latent image is intensified and a uniform deposition of toner occurs in the image area parts. The voltage V should be sufficiently high and of the same polarity as the voltage Vi. be areas of the background, so that the voltage difference Δ V = V - V ^ zwisohen background areas of the image plate and the electrode prevents substantially complete toner deposition in the background surfaces without the toner deposition in the image surface parts impairing ₀

The voltage values V_ and Vv ₁ are determined by the initial charge voltage at the beginning of the imaging cycle. The background voltage V ^ is the potential which remains in the exposed areas of the surface of the photoconductor after their partial discharge by the impinging Idoht during the exposure. This relationship is described in more detail below. It shows SiOH that a preferential area for the initial charging zwisohen above. +800 and above «+700 volts. An optimum range is AWI sohen about +300 and above +500 volts,

The optimal ones lie in accordance with these voltage ranges

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Voltage values V, which lead to a good development and cleaning effect, in the range of approx. +150 "to approx. +500 volts, preferably in the range from approx. +150 to approx. ₀ +300 volts.

It should be noted that a negative initial charge, a negative electrostatic latent image and a negative electrode voltage can also be used ₀ Above or below the preferred ranges given, a satisfactory development and cleaning effect occurs the cleaning effect. In the case of voltages above the preferred areas, a satisfactory development and cleaning effect occurs, but at the same time the cascaded carrier particles can stick to the photoconductor »

This adhesion of the carrier particles occurs when the electrostatic Attractive forces that the image plate exerts on the toner and the toner on the carrier particles together are greater are all the mechanical forces, for example gravity, which accelerate the carrier particles. Will the concentration of the toner in the developer is reduced, the carrier particles adhere to the surface of the image plate, causing them can be scratched if it is passed through sealing devices in the other process steps.

Another variable size of the method according to the invention is the flow rate of the developer. Maximum Cleaning action occurs when the activity of the developer is at its greatest. That is why it is as large as possible Dwell time of the developer near the image plate is desirable. The development and cleaning effect per unit of time increases with increasing flow. As a general As a rule, the cleaning effect is better with increasing flow rate, although the developer

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1365293

shows a developing and cleaning effect at each flow value. The loading service of the remaining image is impaired also the development and cleaning effect and can therefore determine the selection of the flow rate. the Charge served is the amount of charge per unit area of the Image plate surface and should not be confused with the image tone density, which will be described later. In any Pail are said to be composed of latent images with higher initial charge density developed images with correspondingly higher flow velocities of the developer material or getting cleaned. At lower flow velocities, the percentage value of the cleaning effect is proportional the flow velocity, regardless of the initial charge density o At higher flow values (grams of developer per second and unit of plate width) are developed after charging to a lower initial charge density Images more fully cleaned.

It has also been found that the particle size of the toner is an essential factor in the process according to the invention. It interferes with the effectiveness of the electrostatic transfer of the toner to the electrostatic latent image and the transfer of the residual toner from the image plate back to the carrier particles. Both processes have been shown to be more effective with larger toner particles more complete coverage of the carrier parts, as a result of which less free carrier part surface remains, which is essential for a cleaning effect. The smaller toner particles can also be more difficult to remove from the optical disk surface. It is therefore advantageous to use toner having a particle size distribution in which relatively small toner particles occur in a minimal amount. Toner particles can be sorted according to their size in a classifier for fine, dry powder, for example in the model

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Sharpies K8 Super Classifier manufactured by the Sharpies Company, 424 West Fourth Street, Bridgeport, Pennsylvania. At the scale used, the toner particles are measured in microns. Toners having an average particle size predominantly about 10 to about 20 microns and a negligible number of particles less than 5 microns provide results similar to those of about 4 to about 7 microns in a $ 50.00 some portion less than 5 microns in size are preferable. Toner types in both of the specified size ranges show a developing and cleaning effect similar to that of toner. particles up oa _o are preferable to 3 microns in size and a 90 $ strength by weight fraction of particles of less than 5 microns in size in the range of approx. 2 The smaller toner particles also have a developing and cleaning effect, but a more rapid accumulation of a toner film on the machine parts occurs with them.

Another influencing factor is the toner concentration of the developer mixture. It influences the development and cleaning action mainly during development. There is also a cleaning effect, but if the toner concentration is too high, the residual images to be cleaned are rüokentwiekelt just as quickly as they are cleaned.The limiting value of the concentration is on the one hand the ability to develop (i.e. sufficient toner to develop electrostatic latent images), and on the other hand the cleaning «Opportunity. These limit values for the toner concentration are determined by the degree of quality of the copy to be produced. The toner concentration is advantageously expressed as mass per surface unit of the surface of the carrier parts. The inventive method shows satisfactory results at a toner concentration of the above. 0 _f 1 to oa. 0.4 milligrams of toner per the above-mentioned carrier part surface. With toner concentrations of less than ale oa · O ₁ 1 mg / om? also occurs

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a development in the more extensive and unexposed areas of the image plate is noticeable, but it falls The uniformity of the image surface tinting decreases quickly · With higher Concentrations occurs a reduced cleaning effect on. This can be attributed in part to an increase in the residual toner bound as a residual image. It is Furthermore, it is to be assumed that with a higher toner concentration a stronger reverse development of the residual image occurs. A preferable one The range of the toner concentration in the developer / substance mixture is between approx. 0.2 and approx. 0.3 mg / cm. These Values show that the most precise control possible of the toner concentration is preferred in automatic reproduction machines is to strive for. Further, with a higher toner concentration, an impact effect of the toner and occurs toner agglomeration, both phenomena can significantly degrade the image quality.

It was found that the addition of small amounts of a dry These solid and hydrophobic lubricants are effective in influencing the impact and agglomeration of the toner can. Such lubricants are metal salts of fatty acids such as zinc stearate and other substances such as ζ · Β. colloidal fumed Silio components such as "Oab-0-Sil" available from Cabot Corporation, or various mixtures of these materials. A large number of lubricants are in the Belgian patent 727 561 mentioned · The preferred concentration values of the lubricant are in the range from approx. 0.1 to approx. 1 $, based on the weight of the toner.

The other component of the developer is the granular one Carrier, which by mixing with the toner particles a Frictional electrical charge with one polarity opposite that of the toner particles receives · The carrier parts ohen can be any shape you want, for example that of a flaohen one To have flat holes, a cube, a ball hole. Of the

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Fabric can be made of any suitable material such as ZeB * glass, plastic, Metal or another granular substance "consist" of carrier particles with an average size of approx. 30 to approx. 1000 microns show satisfactory results · The size of the carrier parts is preferably in the range of approx. 100 to about 600 microns.

Another variable size that has the development and cleaning effect influenced in the method according to the invention is in the formation of the latent electrostatic image by charging and exposure the voltage to which the photoconductive First shift. This initial charge voltage is often called the initial potential of the loto conductor or referred to as the initial surface potential. Surprisingly, it turns out that the cleaning effect in the the Eestbild-bearing parts of the image plate is affected by the initial charge. The rate of discharge of the image plate in the parts covered by the remaining toner image can be smaller than in the uncovered parts Parts o The cover by the rest of the toner image prevents the incidence of light and thus the discharge of the covered ! Smile parts of the photoconductive layer during image exposure and the discharge during subsequent electrophotographic processes Process steps These remaining charge images can then be developed backwards, creating the remaining image is amplified on the optical disc. It was found, however, that with an initial charge voltage of less than approx. +700 volts or below approx. +500 volts for optimal results the transfer of remaining images to subsequent copies is prevented

It has also proven advantageous to use an image plate provided with a residual image with a polarity opposite that of the charge of the latent electrostatic image before the image surface for a near

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The following image generation is recharged · This charge is negative if the initial charge was positive. A negative charge after the image transfer indicates an effective one Reduction of the binding force for the ioner and thus supports the relatively uncomplicated toner removal during development and cleaning procedures. With the one shown in Fig.1 Device, this negative charge is made at the charging point 21. Choosing other toner and Carriers with triboelectric properties which are opposite to those of the substances described above, facilitates of course, the use of charges of opposite polarity in a device for carrying out the invention Procedure;

The initial charge voltage is also important in connection with the relative exposure level during image exposure. In electrophotographic reproduction, relative exposure is a unit of measurement of the amount of light that reaches the exposed parts of the surface of the image plate and discharges it. The relative exposure is expressed by an "f" number. This number indicates the relative aperture of the optics of a conventional projection apparatus, it has the Value Ρ /!), If P is the focal length of the optics and D the effective Diameter of the aperture is. With a constant light source, all optics produce theoretically with the same f-number Images of the same brilliance from one and the same object, regardless of the focal length of the optics or the durometer the aperture. When the image is exposed in an electrophotographic Reproduction machine uses a conventional projection device, for such embodiments of the electrophotographic process the relative exposure is then constant. It can, however Another embodiment can also be used in which an adjustable diaphragm opening differs accordingly Exposure values is provided. Here should-

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different charging voltages are used accordingly will. The values of the relative exposure and the charging voltage determine when the method according to the invention is used the quality of the ultimately transmitted image. Fig.3 shows the relationship between the charging voltage and the relative exposure. As has already been explained in connection with other variable quantities, a unsatisfactory developing and cleaning effects occur if the charge is in the background areas of the image is so strong that residual toner images cannot be removed from these areas. The line applies in Fig. 3 30 for such maximum charging voltages and corresponding exposure values for a certain setting of the others Sizes that still have a satisfactory cleaning effect occurs. It has also already been shown that the initial charge voltage must be so high that the dark parts of the image area of the electrostatic latent image can be fully developed upon image development. The line 31 in Figure 3 applies to minimum charging voltages and corresponding lighting values, in which images of satisfactory quality are developed.

A preferred range for the initial charge voltage on the surface of the photoconductor is between the above. +200 and +700 volts. An optimal range is between the above. +300 and +500 volts. Correspondingly, an exposure range of the above <> applies f / 8 to oa. f / 5 »6. However, background voltages can also occur with charging and exposure outside these ranges can be generated, the satisfactory developing and cleaning effects as well as good copy quality, depending on the respective setting of the other variable sizes which depends on the operating values »

Lines 30 and 31 in Pig x 3 enclose with the envelope 32 tin

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contains voltages and exposure values at which a satisfactory development and cleaning effect as well good copy quality occurs. It should also be noted that the dashed line 33 represents the lower part of the envelope and indicates that when the electrophotographic imaging plate is slightly charged and the exposure is low, the electrostatic latent image is insufficient for acceptable copy quality.

In this way it is easy to demonstrate that the background voltage VV and the image surface tension V. in connection with a predetermined electrode voltage V and when using the advantageous process according to the invention lead to the generation of copies which meet normal commercial requirements meet or exceed.

It should be noted that only a representative Example of an approximate operational area of a development and cleaning device is shown and that the values shown there only for a given setting of the other variable quantities apply »changes of each the other values or a combination of these values can lead to changes in the values shown in FIG. 3 or those shown Lead curves for the charging voltage as a function of the relative exposure.

An optimal embodiment of the invention results when the parameters are set within the optimal range of each variable variable. The optimal conditions are given, for example, in an electrophotographic process with electrode and cascading development as well as with a vertical arrangement of photoconductor and electrode, if the electrode voltage is in the range of oa · + 150 to oa »+300 volts, the toner part size oa · 10 to oa · 20 microns with a reasonable number of particles with

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less than 5 microns in size, the toner concentration is about 0.2 to about 0.3 mg / cm, the carrier particle size is in the range of about 250 to 300 microns, the The initial charge voltage is approx. +300 to approx. +500 volts and the relative exposure intensity is in the range of the above. f / 8 to ca · f / 5 »6 lies. In addition, still other preferred embodiments can be implemented, with parameter settings can be made in any possible combination of the various optimal values.

Except for the preferred cascading development other types of development can also be carried out, such as they are known for the electrostatographic process According to one embodiment of the invention, the simultaneous development and cleaning can also be carried out in such a way that that the image plate provided with the latent electrostatic image is moved past a magnetic brush ,. The brush is composed of magnetic carrier particles to which the toner particles are electrostatically adhered Toner particles electrostatically onto the image area parts of the Image plate transfer · At the same time, residual toner images in the background area are removed by the electrostatic and mechanical action of the magnetic bristles of the brush removed. It should be noted that in the background text of the image plate, where the greatest possible discharge has taken place during other process steps, the force of attraction between the image plate and the remaining toner particles is less than the forces of attraction between the bristles of the brush and then the residual toner particles «, Therefore, these residual toner particles are easily removed with the magnetic brush, see above that this type of development represents an advantageous embodiment of the method according to the invention. Magnetic brush process, which so far only for the development of electrostatic latent

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Images used are in the UoS. Patents 2,846,333 and 3,064,622. It should be noted that the supply of toner particles in a magnetic brush assembly either essentially of magnetic or non-magnetic © :! Toner particles or from a liquid suspension magnetic shear or non-magnetic toner particles can exist.

Another embodiment of the method according to the invention works with a fur brush that is in contact with and close to the image plate carrying the electrostatic latent image a supply of toner particles is arranged for the development of electrostatic latent images »Here a triboelectric occurs Interaction between the toner particles and the fabric of the bristles so that the toner particles stick to them adhere and be transferred to the picture surface »This will develop the picture. At the same time remove the bristles triboelectrically and mechanically residual toner particles essentially the same area of the picture surface. " A fur brush development, suitable for practicing the process of the invention is disclosed in U.S. Patent 2 902 974.

* According to a further embodiment of the invention, a Amount of developer material be arranged in contact with the image area, and the image area is through the developer material moved through. During this process, the toner remains, which has a charge opposite to that of the image area parts owns, stick in the image area parts, whereby the image becomes visible β at the same time becomes in the same area of the picture surface a residual toner image remaining from the previous imaging cycle by the combination of electrostatic attraction of the toner to the carrier parts and the impact of the developer on the remaining Toner particles removed. Similar to the cascading process this process has only been used for development so far

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turned, but the inventive method also brings the "advantages described with it" in the French Patent specification 1 511 809 describes a development process with a C-shaped development housing which is used to carry out of the method according to the invention is suitable and in which the image plate is moved through a developer material will·

Another embodiment of the invention is that the image plate with the electrostatic latent image through a liquid bed of the developer material is passed through For this purpose, a quantity of developer material can be brought into a quasi-liquid state by causing a gas flow upwards direction is passed through it, whereby the particles are suspended in the gas flow «. An amount of developer can also be brought into this state by mechanical vibration, so that some of the moving leil * * are suspended · As the image plate moves through this bed of fluid, the same effect as with the other embodiments of the method according to the invention Achieved »A plush bed development is in the U.S. patents 3 008 826 and 3 393 663. She also became so far only used for development, but not for cleaning image plates, as is the case with the invention of the Pail «

The $ r.fiafi "* ngo method can be applied to any electrostatographic imaging in which a latent Stieohea image is present on an image plate. .. ·. * -ΆΡΛ photoconductive insulating material. A preferred white

xlml for this layer is amorphous selenium, since it enables a *. ·, £ ähöh » image quality, has relatively high sensitivity and the possibility of receiving and storing thermal charges of different voltages and poles * - rl'fe & 1i6n offers. Any suitable photoconductive insulating material

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shift can in the implementation of the invention; ^s .i «^ must be used. It turns out, however, that better results are obtained if the image surface is made fairly smooth. Typical suitable photoconductive insulating layers consist of amorphous selenium, alloys of sulfur, arsenic or tellurium with selenium, selenium doped with substances such as thallium, oadmium sulphide, oadmium salenide etc., particulate photoconductive substances such as zinc sulphide, zinc cadmium sulphide, zinc oxide produced by the Irench process, cadmthalocyanine, phthalocyanine , Gadmium selenide, zinc silicate, oadmium sulfoselenide, linear quinacridones, etc. dispersed in a non-conductive, inorganic, film-forming binder such as a vitreous material or a binder such as epoxy resin, silicone resin, alkyd resin, styrene-butadiene resin, wax or the like. Other typical photoconductive insulating materials are mixtures , Copolymers, terpolymers, etc. of lotoconductors and non-photoconductive substances that are either copolymerizable or miscible together and form solid solutions. Organic photoconductive substances of this type are anthracene, polyvinylanthracene, anthraquinone, oxadiazole derivatives such as 2,5-bis (p-aminophenyol-1), 1,3,4-oxadiazolj 2-phenylbenzoxazole; and charge-transferring complex substances which are formed by combining synthetic resins such as polyvinyl carbazole, phenol aldehydes, epoxies, phenoxides, polycarbonates, etc. with a Lewis acid, for example tetrachlorophthalic anhydride 2,4,7-trinitrofluorenonium metal chlorides such as aluminum, zinc oxide, iron carbonates -; ^ W. iB {Dimethylamino) benzophenonj Ohloranil, Piorinsäure "1 _f .3 _s 5-urinitrobenzene, 1-chloranthraquinone, bromoal, 4-nitrobenzaldehyde, 4-nitrophenol, acetic anhydride, maleic anhydride, boron triochloric acid, maleic acid, maleic acid, and mixtures of these Fabrics «

Furthermore, the method according to the invention can only be used as a cleaning method be performed. There are some advantages

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8 ORIGINAL

le egg simultaneous development, "for example the lesser one Hasciiiiien size, a. "Better keeping the machine clean and longer screen life. However, the application of the invention only to optical disk cleaning is also new, as no cleaning system "is known, which uses developer as a cleaning element and all in one Operational age works

The method according to the invention can thus be used as a development method or as a cleaning process in an electrostatographic Method can be used that works with two respective cycles. In such a method, the Development performed on the first cycle and the imaging plate cleaning performed on the second cycle for removal only residual toner images from the image area is used. In contrast to a device with two processing stations a method operating with two cycles achieves all the advantages of the invention, but with "5" in each case second cycle requires a slightly more complicated drive mechanism associated with electrical control circuits

The foregoing description of embodiments of the invention has focused primarily on an electrophotographic process It should be noted, however, that the The invention also applies to any other electrostatographic process can be used

The following examples serve for further specific explanation the inventive method of simultaneous image development and image plate cleaning in one and the same Area of a picture provided with an electrostatic latent image.3p "lTfcte. Proportions and percentages relate on weight ^ unless otherwise stated. The following examples represent preferred embodiments of the method according to the invention.

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The charge density of electrostatic latent images was mentioned above as a factor influencing development and cleaning effects. In practice, the charge density of a photoconductive image layer cannot easily be measured, which is particularly true of automatic reproduction machines. The charge density in the non-irradiated part of an electrostatic latent image is approximately proportional to the image density of the original image above a certain lower limit voltage, the image density D = log 1 / R and R being the ratio of W reflected light to incident light. The following examples show standard values for image density. For example, in a very densely toned area of an original image in which only 1/10 of the incident light is reflected, the value R equals 1/10 and * log 1 / R, ie the image density, equals 1. An image density of 1.3 occurs when about 1/20 of the incident light is reflected. Dioht values in the range of approx. 1.2 to 1.5 or more appear to the eye as very dense blackening. The image density is therefore a value which is suitable for comparing the quality of electrophotographic or other copies with the original image.

" Example I

A 10 χ 10 cm image plate with selenium as the more photoconductive one Layer is charged to a surface tension of oa · +500 volts, exposed and developed. The developed image is transferred to a sheet of paper, its mean density is oa. 1.3. The image plate still carrying the remaining image is then taken from a distance of about 25 cm or the like. 30 seconds irradiated with a 300 watt photoflood lamp long after each image development and image transmission. This will make the Discharge photoconductive layer. This cycle is then repeated several times. The developer material consists of glass carrier

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particles of oa. 250 microns medium size and Xerox 914- Toner with a toner concentration of the above. 0.3 mg / cm. The developer flow rate is about 0.8 g / oai Plate width see with an overall flow of 25 »50 or 100 g. A developing electrode in the form of a 10 χ 10 cm flat stainless steel plate carries a bias of approx. +100 volts and is arranged parallel to the selenium surface at a distance of about 1.5 mm. The development and imaging plate cleaning is carried out with different electrode angles in conventional and inverted position. The data obtained therefrom show that an optimal development and cleaning effect occurs at an electrode angle close to the vertical (90 °) and that a good cleaning effect in the range of approx. 60 ° of conventional inclination until oa. 60 ° inverted inclination is possible.

Example II

An electrophotographic image plate and a developer mixture according to Example I are used. The plate is charged as in Example I and exposed to light for image generation; the density of the transferred, developed image is approx. 1.3 Example I with an electrode angle of 75 °, a developer flow rate of oa · β g / om see bet ICO _& - total flow is used. The electrode voltage is changed from VCi to approx. +1200 volts. A good development and cleaning effect occurs in the range of oa · +200

: ■■ & * +700 volts. Pur this setting of the operating values i? i, i; there is a certain adhesion of the carrier parts in the case of elec-

Sound above +1200 volts

Example III
Am ft2pi.e.? Device 914 from Xerox Corporation, Roohester, New

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York, is equipped with a device for carrying out the method according to the invention. The development and cleaning housing contains an electrode arrangement with a length of 6.35 μm (from the beginning to the end of the development zone measured on the sheet parallel to the drum surface) and a distance to the drum surface of the above, 2 mm. The drum surface is coated with an amorphous selenium layer as a photoconductor. The electrode assembly rests on the edges of the drum, thereby avoiding adjustment problems. Furthermore, a conductive lead connected as an electrode is arranged directly below the development and cleaning electrode in order to avoid excessive losses at the lower end of the development and cleaning zone. A corotron is arranged behind this zone and in front of the image transfer point, which promotes the image transfer. The development agent mixture consists of non-coated, bleached glass grains with an average size of the above. 250 microns and made from Xerox 9H toner with an average particle size of about 12 to about 15 microns. It also contains 1.8 i "of the toner weight of zinc stearate Sohmiermittel. The electrode voltage is approx. +200 volts. This embodiment of the invention enables continuous production of continuously toned and half-toned images as well as line drawings with high quality and little background drawing in more than 50,000 cycles. The image quality is improved if the toner concentration is kept at or above 0.28 mg / cm of the carrier particle surface. The toner consumption and the toner efficiency are excellent, more than 15,000 copies of 21.5 χ 28 cm in size can be made per pound of toner · The absence of a cleaning brush extends the life of the photoconductive layer caused by toner movement, can be omitted in this embodiment, so that the reproduction machine works cleaner overall.

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becomes the reproductive matohine described in Example III used with an initial voltage of oa. +400 Volts, a relative reference strength of approx. F / 6.3 »one Toner concentration of approx. 0.28 mg / cm, leaded glass carrier particles with a mean size of oa. 250 microns and an electrode voltage of approx. +125 volts · A satisfactory developing and cleaning effects for a large number of copies of excellent quality.

Example V

The reproduction machine described in Example III is used with a current flow of approx. 16 microamps for the transmission corotron to produce various test copies at different charging voltages and exposure values. Standard values are set for satisfactory operation and copy quality! "* The device must remove the remaining image if the density of the new image or the like is 1.3 and develop this new image in such a way that a density of the transferred image of approx. Furthermore, an image density of approximately 0.3 must be developed to a predetermined standard value of 0.2. The data obtained from various runs give an operating range which corresponds approximately to that shown in FIG Curve 30, which specifies the maximum charging voltage for a cleaning effect when the standard values specified here and the exposure values shown are met *, and curve 31> which specifies the maximum exposure for a development effect when the standard values specified here and the charging voltages shown are fulfilled low charging voltages and low exposure values, the ^{ready for operation: 11} -üaduroh limited, that a satisfactory maximum tint radiography cannot be achieved This means that the standard value for an image density of the

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carried picture of oa. 1.2 from a density of the generated Picture of oa. 1.3 cannot be achieved. In Iig «3 The dashed line 33 shows these limit values. The envelope 32 encloses an approximate operating range, the contains the appropriate values of charging voltage and relative exposure at which the device described if the other parameter values are set accordingly, works satisfactorily and produces copies that contain the fixed · = meet set standard values »

Although in the above description of preferred embodiments the invention certain substances and amounts of substance mentioned, other suitable materials and changes to the various process steps can also be provided be having satisfactory results and varying Quality grades can be achieved. Furthermore, additional Substances and procedures must be provided that have a synergetic, improving or otherwise favorable Have an effect on the respective properties of the invention. For example, various Photoconductive materials and different layer thicknesses are used, with a correspondingly different setting of the different operating sizes is required.

The Faohmann are aware of the above description numerous other embodiments of the invention are possible, all of which are encompassed by its basic concept.

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Claims (8)

Patent claims ο Electrophotographic or electrostatographic imaging aver: drive in which a developer consisting of toner and carrier particles is used and a residual toner image is to be removed from an image plate repeatedly running through an image generation cycle after the image transfer »characterized in that the developer is in the The image generation cycle following the presence of a residual toner image on the image plate (11) is brought to act on the image plate (11) during image development in such a way that the remaining toner image is removed at the same time as the image development. 2. The method according to claim 1, characterized in that the developer is brought into contact with the image plate (11) 3e method according to claim 1 or 2, characterized in that that the developer is guided past the image plate (11) will. 4. Method according to one of claims 1 to 3, characterized in that an electrostatic field is generated in the area of action of the development of the image plate (11) with an electrode (26) _e according to claim 4 »characterized in that the l the material is cascaded over the image plate (11) « 6; . "" .., Liii'en naoh claim 5 »characterized in that egg.'.' Image plate (11) and electrode (26) vertically aligned white · 009838 / U03 7 »Method according to claim 5, characterized in that the electrode (26) and the image plate (11) are arranged at an angle of + 60 ° to -60 ° with respect to the horizontal _e 8. The method according to any one of claims 4 "to 7, characterized in that that a voltage of 150 to 500 YoIt is connected to the electrode, 9e method according to claim 8, characterized in that a voltage of 150 to 500 volts is connected to the electrode will. 10 · Method according to one of the preceding claims, characterized characterized in that an image plate (11) with a photoconductive image material layer is used, which is before the Imaging is charged to a voltage between 200 and 700 volts « 11e method according to claim 10, characterized in that the photoconductive insulating layer is charged to a voltage of 300 to 500 volts. 12 · Method according to one of the preceding claims, thereby characterized in that in the developer material toner particles with a size of 10 to 20 microns with a proportion of at most 1?' Giner particle size less than 5 microns is used becomeε 13 · Method according to one of the preceding claims, characterized in characterized in that a developer with a toner concentration is used, which is 0.2 to 0.3 mg / cm of the carrier particle surface 009838 / U03 SAD original 14 * Method according to claim 13 »characterized in that carrier particles with an average G size of 100 to 300 microns can be used in the developer. Method according to one of Claims 1 to 4f, characterized in that carrier parts in the form of a magnetic brush are used for the development which applies the toner particles to the image plate (11) _{or the like} 16 »Method according to one of claims 1 to 4, characterized in that that the pasers of a fur brush are used as the carrier particles, which the toner particles on attach the image plate (11) « 17 »Method according to one of claims 1 to 4» characterized in that that the image plate (11) by a developer material is moved through. 18 "Procedure according to one of the An *,.-.- one 1 to 4" marked daduroh, that the image plate (11) moves a quasi-liquid amount of developer material will· 19 »Method according to claim 18, characterized in that the amount of developer is mechanically vibrated will· 20 · The method according to claim 18, characterized in that a gas flow to generate the quasi-liquid state through which the amount of developing agent is passed through will s 009838 / U03