DE2200450A1 - Process for the cyclical production of an electrostatic copy - Google Patents

Description

Rochester, NY 14 603
V.St.A.

Process for the cyclical production of an electrostatic copy

The invention relates to a method for the cyclical production of an electrostatic copy of an original image by means of an electrostatic recording medium and a donor element covered with a toner layer.

As is known, a recording medium, e.g. a drum, electrostatically charged by means of a corotron fed with direct current and then with a Image pattern are irradiated, whereby the charges on its surface are selectively dissipated and a latent electrostatic Image in the form of the remaining charges is created. It is also known that the latent image can be formed by deposition of a pigmented material can be converted into a visible image. Fine soot particles or others can be used for this purpose Pigment substances are applied to the recording medium, so that they are attracted and bound by the remaining charges, so that a visible image of the one to be copied Image emerges. It is also known to transfer the visible image from the record carrier to an image carrier, at · =

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for example a sheet of paper, to be transferred and melted on it, so that a permanent copy is created. Such a method is exemplified by US patent specification 3,062,095 known.

According to US Pat. No. 2,895,847, a donor element can be used which is coated with a layer of the pigmented Material is covered. The surface of the recording medium can with this material, hereinafter also referred to as toner, are touched so that the latent image is developed. From US Pat. No. 3,232,190 it is known to have such a Development also to be carried out in such a way that there is a distance between the donor element and the recording medium.

The devices and types of methods for performing such dispensing element spacing development are complicated and require compliance with very small tolerance ranges for the respective distance. The creation of a layer toner with uniform properties also poses several problems.

The object of the invention is to provide a method for the cyclical production of an electrostatic copy, which is characterized by simpler implementation and simply structured devices.

A method of the type mentioned is designed according to the invention to achieve this object in such a way that a relative weak electrostatic charge is applied to the recording medium that the toner layer the recording medium is opposed at a distance that allows parts of the toner to transition, so that the toner layer is balanced is that a relatively strong electrostatic charge is applied to the recording medium and an exposure is carried out with the image to be copied, and that the balanced toner layer the recording medium in one of the

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Enabling transfer of toner to the electrostatic latent image Distance is compared so that a visible, transferable to an image carrier on the recording medium Toner image is created.

This method significantly improves the technique of electrostatic recording. Carrying out the development with a distance between the recording medium and the donor element is a much simpler device possible, at the same time the formation of a uniform toner layer on the donor element is guaranteed. The tolerances of the required between the donor element and the recording medium Distances are greater than in known arrangements. As will be described later, some elements can be electrostatic Image generation fulfill double functions, so that overall a lower cost for an image generation device arises.

The invention is preferably carried out with contactless development, but it can also be carried out in such a way that that the donor element actually touches the recording medium. This latter embodiment avoids the problem a uniform distance between the donor element and the recording medium, but at the same time more Problems such as the presence of agglomerates of the toner on the donor element and / or uneven layering avoided on the donor element by the invention »

An apparatus for carrying out the method according to the invention may, for example with a donor element in the form of a roll working ^ of a charging device zvm applying the toner on their Oberfläehe is assigned _o This can be realized for instance by egg "toner bath _s dowell passing the supply roll is rotated. The toner bath is removed from the dispenser roll, which is done within the operating cycle by a control device of the copier

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is adjustable. The dispenser roll also has a cleaning device for cleaning their surface within a predetermined part of the operating cycle and a corotron for Corona charging of the toner on its surface. Furthermore, a recording medium is for example for the copy production provided in the form of a drum with an associated drive device. The dispenser roll and the drum-shaped recording medium are preferably identical Diameter and are rotated at the same speed in mutually opposite directions at the same time. in the The following describes an embodiment in which the recording medium is clockwise and the donor element turned counterclockwise. The recording medium is equipped with a discharge corotron and a cleaning device Mistake. Furthermore, a charge corotron is used to charge the recording medium and an exposure device is used to generate it an electrostatic latent image, a developing area for visualizing the latent images, and an image transfer device for transferring a toner image to an image carrier, for example a sheet of paper, a glass plate, a plastic layer, etc. is provided. The charge corotron can be a double corotron or there are two separate ones Corotrons are provided, one of which is the surface of the recording medium with relatively low power with direct current for example, with a voltage of 75 to 100 volts, while the other corotron works with relatively higher power and generates a charging potential of, for example, 400 to 500 volts DC voltage.

The double corotron or the two corotrons for electrostatic Charging of the recording medium, the exposure device and the image transfer device as well as the toner bath and the corotron discharge for the donor element are all controlled by a two-phase control device which operates in accordance with the operations of the donor roll and the recording drum. The development

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Charging device for the recording medium and its cleaning device preferably work independently of the two-phase control, so that the surface of the recording medium is cleaned before it with the charge corotron is charged regardless of the respective working phase of the operating cycle.

The operating cycle controlled by the cyclically operating control device preferably runs in two phases. Every phase of the operating cycle corresponds to a complete revolution of the recording medium, which is evaluated by a scanning device will. During the first phase, the cyclic control device is in its "phase 1" state. During this Phase, the charging corotron of the recording medium is switched on for low power, while the! Corotron is switched on for high Power is off. The exposure device is also switched off. The corotron of the donor element is switched on during phase 2 to clean the surface of the dispenser roll for cleaning after the development of the prepare latent image. The toner bath or the associated container is in an "upper" position, as well is to be regarded as the normal position. The image transmission device is turned off, and this condition will also be the same in the following referred to as normal state or idle state.

During the first cyclic rotation or phase 1 of the operating cycle, the donor element is rotated through the toner bath, its surface being coated with toner. It should be noted that the cyclic control device is in a very specific phase of the operating cycle and in accordance with the rotational position of the Operating components for the respective function to be performed is timed accordingly. Works during phase 1 the discharge corotron of the donor company in such a way that the old toner is removed and new or fresh toner is on the The surface of the donor element has been applied kamio Das

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Charge corotron can, if desired, corona charge the new toner layer during phase 1 of the operating cycle can be used, or alternatively it is used to charge the toner layer during the entire operation. For the recording drum, the discharge corotron and the cleaning device operate without dependence on the cyclic Control, since the surface of the recording medium must always be cleaned before the corona charging takes place. While In phase 1, the corotron is switched on for low charge strength, so that a correspondingly weak charge is applied to the surface of the recording medium is applied. This charge preferably has a charge opposite the charge on the toner layer polarity opposite to that of the donor element. While the toner roll with fresh toner layer and the recording drum are rotated past each other with a weak corona charge, part of the toner layer is transferred from the dispenser roll to the Transferring the recording drum, namely in the zone in which the development of a latent image normally takes place would. If the surface of the recording medium appears in the normal development zone, it is therefore with a uniform, weak electrostatic charge. This uniform electrostatic charge has an attraction onto the surface of the dispenser roll, which is evenly spaced from it. Because the layer of toner on the dispenser roll cannot have a uniform thickness, the electrostatic charge on the recording medium removes the toner from the thick areas of this layer. The amount of toner transferred in this way depends on the thickness of the toner layer and thus the distance between the toner on the donor roll and the surface of the recording medium and the strength of the charge on the recording medium.

Such toner is transferred to the recording medium, which adheres only weakly to the donor element or which has formed lumps and / or agglomerates that affect the recording medium closer than the normal toner layer. Since the

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"Trapped" toner on the recording medium at the switched off Image transfer device is moved past, it comes into the area of influence of the discharge corotron and then to the cleaning device, where it is removed again from the recording medium.

In the normal development zone “where part of the toner layer is transferred to the recording medium, a toner layer remains on the donor roll, which has a uniform thickness Has. This thickness can correspond to the strength of the weak corona charge on the surface of the recording medium and can be set depending on the distance between the two elements.

The control variable of the cyclic control device for the phase is maintained for one complete revolution of the recording medium, which rotates simultaneously with the donor roll. When the control device determines that this rotation has ended, the transition iron from phase 1 to phase 2 _O begins. During the associated position of the "movable components to one another, phase 1 ends in time and phase 2 begins with the introduction of phase 2 controller output control quantity _o is the YQPzmgswsIs © = ser change point of the phases such that _p correspond to the corona charging of the recording medium "

At the beginning of phase 2 of the operating cycle, the corona charging is switched from low power to relatively high power. If the region relatively strong charge reaches the exposure region _g the Beliehtungsvorrichtung is turned on. As a result, a latent electrostatic image is created on the surface of the application drum. In phase 2 the container for the toner bath is removed from the dispenser element so that the even © TonerseMcht βμϊ of the surface of the donor element cannot be disturbed »" The toner bath is used for a complete rotation of the dispenser roll

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held in this position. The discharge corotron for the donor roll is switched on for one revolution during phase 1 and then turned off during phase 2, but the turn-on and turn-off are controlled so that they do not disturb the even toner layer. The charge corotron for the toner layer on the dispenser roll can be cyclical can be turned on and off if desired. However, it can also be switched on regardless of cyclical operation being held.

If the timing and phasing in described Manner are carried out, the beginning of a latent image on the record carrier and the beginning of the uniform layer of toner on the donor element in the development zone, and the electrostatic latent image is developed during the rotation of both elements. When the developed image reaches the image transfer device, this is switched on and the image that is now visible is transferred to the image carrier.

During the dispenser roll two revolutions together with the recording medium carries out, this fulfills a double function. The is effective during an operating phase or revolution Recording medium as a pretensioned roller, which creates a uniform layer of toner on the donor roller. During the In the subsequent operating phase, the recording medium serves as a normal recording element for generating an electrostatic one latent image.

The invention is illustrated below with reference to one in the figure exemplary device described for their implementation. The figure shows an electrostatic recording device, in which a dispenser roll 10 in the illustrated arrow direction 11 and a recording medium 12 in are rotated in the direction of arrow 13 and have a distance from one another, which is shown at E. An engine with associated Gear 14 drives the recording medium via tapes

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and the dispenser roll over tapes 16. Preferably, the Recording medium 12 and the dispenser roll 11 with matching Speed and similar in time, but rotated in opposite directions.

Distributed in the direction of the circumference of the recording drum, the devices are arranged for generating an electrostatic Record or copy an original document or image. To discharge or neutralize Toner that settles on the surface of the recording drum whose cleaning is still in progress, a discharge corotron or a corotron A fed with alternating voltage is provided. the The surface of the drum 12 is cleaned with a cleaning device B. The device C contains one or more Corotrons, which are used to apply an electrostatic charge to the surface of the recording drum. As already described, a duplex corotron can be provided here, which has at least two different charge strengths can generate. This duplex arrangement, under the control of the cyclic controller 20, can have a relatively low corona charge generate during phase 1 of the operating cycle and a relatively high corona charge during phase 2 of the operating cycle.

The device D is used for exposure and can be a platen or some other device for holding an original document. There is also a source of light in it and / or an optical system is provided, which an image of the original image on the surface of the recording drum projected to form an electrostatic latent image by dissipating electrostatic charges from the surface of the recording medium in accordance with the original image.

The exposure is controlled by the cyclic controller 20. During phase 1 of the operating cycle, the exposure device is turned off, so the relatively weak

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Corona charge on the surface of the recording drum applied by the corotron B was kept uniform and the function of the pre-tensioned roller can be fulfilled. During phase 2 of the operating cycle, the exposure device turned on by the cyclic controller 20, so that the electrostatic latent image by selective Derivation of the relatively strong charges from the surface of the recording medium can be generated.

The area of small distance between the recording drum 12 and the donor roll 10 is designated by E. In this In the area, the layer of toner on the donor roll is made even and smoothed, with a limited attraction of the low electrostatic charge on the recording medium is used in phase 1 of the operating cycle. During the Phase 2 the electrostatic latent image is developed through the even and smooth layer of toner on the donor roll .

The now visible image, which is created by the transfer of toner in a distribution corresponding to the latent electrostatic image was generated by the donor roll on the recording medium, can be on an image carrier, for example a sheet of paper or another material, for which the image transfer device F is intended. If desired, the image transmission device F can be controlled independently of the operating phases. Every second revolution of the Record carrier, the visible image is transferred to its image carrier, for example during phase 2 of the operating cycle. During phase 1, the image carrier can be used to remove the toner, which is used to form the uniform The layer of toner has been removed from the dispenser roll. This is through the discharge corotron A and through the cleaning device B reduces the amount of work to be done, but uses twice the amount of paper. Preferably, therefore the image transfer device was kept off during phase 1 of the cycle of operation while it was in phase is switched on.

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The donor roll 10 is assigned a discharge corotron (alternating voltage corotron) L, which is switched on by the signal of the control device 20 corresponding to phase 2. It causes a discharge of the toner still present on the surface of the donor roll after the development of the latent image in area E. This toner can be discharged before cleaning the surface of the dispenser roll and before reloading it with a new layer of toner. During phase 1, the discharge corotron L is normally switched off. In order to facilitate the cleaning of the surface of the dispenser roll, a doctor blade 21 is mounted in the toner bath device M. The toner container contains toner 22 and is pivotably arranged so that the toner bath can be pivoted away from the surface of the dispenser roll during phase 2. During phase 1 it is in its normal or rest position, ie it is arranged in the upper position so that the lower part of the dispenser roll 10 is moved through the toner bath when the roll is rotated. The arrows 23 show the direction in which the toner container can be pivoted away from the lower surface of the dispenser roller 10.

The dispenser roll is also a charging corotron N for application associated with an electrostatic charge on the toner present on it. This is done before the toner layer in the Development area E is introduced.

The cyclic controller 20 may include an arrangement that converts its output signal from phase 1 to phase 2 and then switches back to phase 1 for each revolution made by the recording drum and the dispenser roll is carried out. The cyclic control device can contain, for example, a flip-flop, which is responsive to the rotation the recording drum responds. However, another suitable two-stage switching device can also be provided be. The drive wheel 24 is provided with a display device 25 which, at each revolution of the recording drum

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passes an evaluation device 26, which is a sensor that generates a pulse when the display device 25 passes generated. Both elements are arranged at a short distance from one another. The pulse can be sent to the cyclic control device 20 are supplied via line 30. The flip-flop or the two-stage switching device of the cyclic control device can be switched from one of its states to the other if a pulse is supplied at a time. Each of these impulses indicates one revolution of the recording drum and the donor roll. In this way, the control device can through the respective rotational position of the recording drum and the dispenser roll can be controlled so that a cycle two revolutions is equivalent to.

The output signal of the control device corresponding to phase 1 20 on line 32 is fed to the charge corotron C and effects the low power charge. That of phase 2 The corresponding output signal on the line 35 is fed to the charge corotron C and causes the strong charge. Further it becomes the exposure device D to switch it on, the toner container M to remove it from the donor roll, the discharge corotron L to discharge the toner on the surface of the donor roller and the image transfer device F for Image transfer is applied after the development of the electrostatic latent image.

During the first rotation of the recording drum and the donor roll it is on the entire surface of the recording drum applied charge stronger than stray charges and those charges that are the background of the latent electrostatic Image during the second rotation of the recording drum and the donor roll, so that those in the background areas Any stray charges that are still present do not attract and / or bind toner from the toner layer of the donor roll, so that the background of the developed image remains clear. Because the recording drum and the donor roll have the same diameter

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and are rotated at the same speed, both surfaces run on exactly corresponding ones with each rotation Make over. This removes the normally required tight tolerances for development by far of the donor element to the recording medium enlarged.

The first rotation within the operating cycle can also be referred to as a blind rotation, while the second rotation phase referred to as copy rotation. The sensor 26 can work mechanically, electrically or electronically, the same applies also for the cyclically operating control device 20. The display device 25 can be any suitable element that the sensor 26 responds.

According to another embodiment of the invention, the corotron C can be a single corotron, which is a uniform Applies charge to the surface of the recording drum during both phases of the operating cycle. The exposure device D can fulfill a double function, for which purpose it provides uniform lighting on the entire charged body during phase 1 Lets the surface of the recording medium act so that background lighting is stimulated. This will make the Corona charge derived from the surface of the recording drum, so that toner is held in the uneven toner layer on the surface of the donor roll, which by the Background charges of the latent image would be trapped during the next phase if it is not removed beforehand.

During phase 2, the surface of the recording drum can be provided with the same charge as in phase 1, however the exposure device works in such a way that an image to be copied is projected and thus a latent electrostatic one Image is generated on the recording drum. This latent image can then be developed.

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Claims (15)

Claims 1 ^. Process for the cyclical production of an electrostatic Copy of an original image by means of an electrostatic recording medium and one covered with a layer of toner Donor element, characterized in that there is a relatively weak electrostatic charge on the recording medium is applied that the toner layer to the recording medium is compared in a transition of parts of the toner allowing the distance, so that the Toner layer is compensated that a relatively strong electrostatic charge is applied to the recording medium and exposure is carried out on the image to be copied, and that the balanced toner layer dem Opposed recording media at a distance that enables the transfer of toner to the latent electrostatic image is, so that a visible, transferable to an image carrier toner image on the recording medium arises. 2. The method according to claim 1, characterized in that a drum-shaped recording medium and a dispenser roll be used that the recording medium and the dispenser roll each through a two revolutions comprehensive Operating cycle are performed that during the first rotation toner is applied to the surface of the donor roll and the surface of the recording medium is provided with the weak charge that it is coated with toner Donor surface and the surface of the recording medium are rotated past each other that the thereby on the Recording medium transferred toner is removed from the recording medium and that during the second rotation the strong charge applied to the recording medium and the exposure and development of the generated electrostatic latent image. 209830/1027 3. The method according to claim 2, characterized in that the developed image on during the second revolution an image carrier is transferred and cleaning of the surface of the recording drum is performed. 4. Electrostatic reproduction device for performing the method according to one of claims 1 to 3, characterized characterized in that a recording medium (12) and a dispensing element (10) are provided with matching dimensions are that the recording medium (12) a device (C) for electrostatic charging with a first Strength is assigned that a drive device (14, 15 »16) for moving the recording medium (12) and the dispenser element (10) is provided at a small distance past one another, and that the recording medium (12) has a device (C) is assigned to charge with a second strength. 5. Reproduction device according to claim 4, characterized in that that the recording medium (12) is assigned an image transmission device (F). 6. reproduction device according to claim 4, characterized in that that the weak charge has a direct potential of 70 to 100 volts and the strong charge has a direct potential from 400 to 500 volts. 7. reproduction device according to claim 4, characterized in that that a display device (25, 26) for displaying the passage of the entire surfaces of the recording medium (12) and the dispenser element (10) is provided past one another. 209830/1027 8. Reproduction device according to one of claims A to 7, characterized in that a drum-shaped recording medium (12) and a dispenser roll (10) are provided, which are rotatably mounted past one another that the drive device (14, 15, 16) the recording drum (12) and the dispenser roll (10) uniformly with coincident Speed rotates that a control device (20) by the rotation of the recording drum (12) and the donor element (10) is controllable and a first, a first phase of the operating cycle characterizing and a second, a The second phase of the operating cycle supplies a signal that indicates that a device (μ) for applying toner (22) on the surface of the dispenser roll (10) during the first phase of the operating cycle and that the device (C) for weak charging of the recording medium (12) in the first phase of the operating cycle, the device (C) can be switched on for strong charging of the recording medium (12) in the second phase of the operating cycle. 9. Reproduction device according to claim 8, characterized by a cleaning device (B) for removing amount of toner bound by the weak electrostatic charge on the surface of the recording drum (12). 10. Reproduction device according to claim 8, characterized in that that the device (C) for strong electrostatic charging of the recording drum (12) an in Direction of movement of the drum surface arranged exposure device (D) is arranged downstream. 11. Reproduction device according to claim 10, characterized in that that the recording drum (12) and the dispenser roll (10) with a part of their surface in a small Distance (E) to each other are arranged. 209830/1027 12. Reproduction device according to claim 11, characterized in that that an operable during the second phase of the operating cycle image transmission device (F) on the Recording drum (12) is arranged. 13. Reproduction device according to one of claims 4 to 12, characterized in that the device (C) for weak electrostatic charging of the recording drum (12) an exposure device (D) in the direction of movement of the Recording drum (12) is arranged downstream, which ensures uniform illumination of the charged recording drum (12) causes. 14. Reproduction device according to claim 13, characterized in that that the device (C) for electrostatically charging the recording drum (12) is a corotron. 15. Reproduction device according to claim 14, characterized in that that a second krotron (C) is provided for strong electrostatic charging of the recording drum (12) is. 2098 30/1027 Lee rse it