DE2262774A1 - DEVICE FOR REMOVING ELECTRICAL POTENTIAL FROM AN ELECTRICALLY CONDUCTIVE LAYER OF A RECORDING FOIL - Google Patents

Description

DR. EEHG CIPL .-: NG .. 3TAPF

PATENT LAWYERS
8 MUNICH 86, POST BOX 860245

Dr. Berg Dipl.-Ing. Stapf, 8 Munich 86, PO Box £ 3 0245 · * "> ^{h ε} ti '"^''* p

Our sign β MÖNCHEN 80

Our ref. 23 25 O Mauerkircherstraße 45

Attorney's File No. 23258

Kabushikl Kaisha Ricoh Tokyo / Japan

Device for removing electrical potential from an electrically conductive layer of an on = drawing film

The present invention relates to a device for removing electrical potential from an electrically conductive layer of a recording film _9, in particular for a device for producing electrophotographic images in which the distance between the charging station and the development station for the recording film is smaller than the length of the recording film ₉ .or for a device for converting an electrostatic _s latent image into a visible image with a toner or developer eines..anderen "

Tologrammo: BERGSTAPFPATENT Munich Baniton: Bayeriacha Varolnabanlt IMünchon 4231CD

TELEX: 05 24 SSO BERG <J Hypo-Bonit Munich 3E9 2323

PoqicÄoc :; Munich 653 43

3Ö9S2 7 / ÜS3

Various devices are currently used for making electrophotographic images. To get a copy of To produce an original, these devices have either an electrophotographic copier and others Devices in which a recording film with a photoconductive layer on an electrically conductive Layer is electrically charged, exposed to the image of an original and then developed, or they have facilities which are used to develop an electrostatic latent image that is different from electrical Charge and exposure of an image of the original is generated. You can also make a copy of a Original facilities are used in which an electrostatic latent image is developed by charging and exposing an image of the original and formed on a recording sheet having a dielectric layer is transferred to an electrically conductive layer; furthermore, in certain facsimile systems, facilities for Development of an electrostatic, latent image is used, which is generated from electrical signals and on a Recording film is recorded or transferred with an electrically conductive layer. With such devices and facilities it has become common to adjust the distance between the charging station in which a bias of the recording sheet for charging the same or for transferring the image, and the development station, in which the electrostatic latent image is transformed into a visible one

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Image is converted to minimize »to increase the operating speed of the device and to thereby obtaining a small, compact device.

The reduction in the distance between the charging station and the development station can, however, be disadvantageous. If the Distance is smaller than the length of the recording film, connects the electrically conductive layer of each recording film, which is moved along this path, so to speak electrically, the two stations, which leads to the fact that insufficient development is carried out. The copies produced can then adhere to their base Developer may be dirty, or the image is, as it depends on the charge of the electrically conductive layer, not properly trained at all.

An example of such a hindrance or impairment of development is described with reference to Pig. 1 and 2. In Fig. 1, a number of endless conveyor belts 3 made of electrically conductive rubber are pulled over pairs of rollers 1 and 2; the roller 1 is made of metal or electrically conductive rubber and is grounded so as to serve as a counter electrode during development. A suction chamber ¹ I ,. which has suction openings 4a on its upper side, is arranged between the upper and lower strand of the endless belt 3, with a recording film A1 conveyed through the upper strand of the belt 3 being drawn to the latter by the suction effect

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so that the film is conveyed evenly. The suction chamber 4 is connected to a corresponding suction pump, not shown , via a line hb.

A transparent platen for an original is arranged above the suction chamber H parallel to the upper run of the conveyor belt 5. An original 6 lies on the platen 5 and is moved in the direction of the arrow b synchronously with the movement of the recording film Al, which is fed on the upper run of the conveyor belt 3 in the direction of an arrow a, so that the image through a lens 7, the is arranged between the platen 5 and the belt 3, while an exposure is projected onto the recording film.

The recording film Al has an insulating layer 8, electrical conductive layers 9 and 10, one on top of layer 8 and the other on its bottom, as shown in Figure 3, is arranged, and a further electrically conductive layer 11, which is on the electrically conductive layer 10 is arranged. The recording film A1 is attached to the endless belt 3 via a pair of rollers 12 and 13 fed in the direction of arrow a.

Left above the upper run of the belt 3 is in Fig.l a charging station 16 is arranged, which is a charging device 'with a wire electrode 15 to which a high voltage

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(i.e. a negative charge as shown) is impressed by an energy source 1 * J. The recording film Al is electrically charged evenly over the entire surface. The electrically conductive layer 9 of the recording film Al is grounded via the roller 1. But since that's electric Conductive tape is not a perfect conductor, as is the electrically conductive layer for other reasons brought into a position during a charging process in which they have an electrical potential with a higher absolute value (a negative charge, as shown) has a ground or reference potential.

After the recording sheet Al is electrically charged, there is an electrostatic latent image of the original recording on it or the original image applied, with an optical image of the original recording by means of them a lens is projected. The recording film A1 with an 'electrostatic latent image formed on it is transferred to a development station via a hold-down roller 18 supplied.

The development station 18 has a container 19 with a certain amount of descaling fluid; a number of guide plates 20 and 21 are vertically spaced in two Rows arranged in relation to one another are accommodated in the container 19. A pair of take-off and nip rollers 22 and 23 are in Pig.l on the right above the container 19 and are

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pressed against each other. The recording sheet Al takes
the toner supplied by the developer liquid,
which has a charge opposite to the electrostatic latent image (a positive charge as shown), whereby the latent image becomes visible as the film is moved along its path between the guide plates 20 and 21. The recording sheet is then withdrawn from the unloading station, being squeezed by rollers 22 and 23.

The distance between the charging station 14 and the developing station 18 is shorter than the length of the recording sheet A1. As a result, the recording sheet Al, their
electrically conductive layer in the charging station I ¹ I is brought to an electrical potential (a negative charge, as shown) with a higher absolute value than the reference potential, exposed to the influences of the electric field, while it is exposed to both the charging station 14 and the development station 18 is promoted. Through this
more toner than necessary is then added to the electrostatic latent image and the background can become dirty; moreover, the toner can adhere to the electrically conductive layer itself and stain the underside of the copy.

In Fig.2 is a photosensitive drum 26 with a photoconductive Layer 25 on a drum body 24 made of metal

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tall or other electrically conductive material carried by shaft 26a and rotated in the direction of arrow c; Its entire surface is electrically uniformly charged by a charging device 29 with a wire electrode 28 _s on which a bias voltage (which, as shown, causes a negative charge) from an energy source 27 is impressed.

To the left of the photosensitive drum 26, an optical exposure system 35 is angeordent in Figure 2, which has a projection lens 32, a reflector 33 and a slot portion J> with a slot S for projecting the image of an original recording or an original image 31, on a Support plate 30 is. The photosensitive drum 26, which is electrically charged during the rotation, is exposed to an image of the original recording or the original image projected by means of the optical system 35 and then carries an electrostatic latent image formed on it of the original recording.

A transfer roller 36 made of electrically conductive rubber is arranged under the photosensitive drum 26 and is pressed against it. A bias (which, as shown creates a positive charge), which generates a charge opposite to the photoconductive layer 25, In order to improve the result of the image transfer, an energy source 37 is used to impress on the roller 36, since the roller 36 is housed in a loading station 36a

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is brought.

A recording sheet A2 is fed between the photosensitive drum 26 and the transfer roller 36 via a pair of feed rollers 38 and 39. As shown in FIG. ¹ *, the recording film A2 has an insulating layer hl which is applied to an electrically conductive layer ^ O. As long as the insulating layer 41 of the film A2 is pressed by the transfer roller 36 against the periphery of the photosensitive drum 26, the electrostatic, latent image on the photoconductive layer 25 is transferred to the insulating layer Hl of the film A2.

The recording film A2 on which the electrostatic latent image has been transferred is separated from the periphery of the photosensitive drum 26 by a separation means k2 and fed through a pair of conveying rollers ¹ 13 and the developing station Hk 18th The development station 18 is constructed in exactly the same way as the development station shown in FIG. 1, so that it no longer needs to be described in detail.

Since the distance between the charging station 36a and the development station 18 is smaller than the length of the recording film A2 in this case too, a part of the electrically conductive layer kO is still impressed with a bias voltage (which produces a positive charge, as shown), while another Part of the film already in the discharge

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station is introduced after the electrostatic, latent Image (with a negative charge as shown) has been transferred to this. As long as the recording film A2 simultaneously through both the loading station 36a and Also the development station 18 is pulled, the toner (with a positive charge, as shown) in the 'developer liquid prevented from adhering to the recording sheet A2, and in the worst case, the latent Image not developed at all.

The voltage impressed on the electrically conductive layers 9 and 40 should now be removed in that electrically conductive rubber is used as the material for the conveyor roller HH and this roller is then grounded. However, since the electrically conductive layers 9 and ¹ JO themselves are not perfect conductors, it is very difficult to completely remove the electrical potential with this arrangement.

The invention is therefore intended to provide a device for removing the electrical potential from an electrically conductive one Create a layer of a recording film, ■ the in an apparatus for creating an electrophotographic image in which the distance between the charging station and the developing station for a recording sheet is shorter than the length of the recording sheet and in the detrimental influences of the voltage that

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the electrically conductive layer of the recording film in the Iiadestation was impressed during * the development in the developing station are eliminated, even if the recording sheet is simultaneously used by both the loading station as well as being pulled through the development station.

According to the invention an apparatus is provided in which the electrically conductive layer of the recording film (in the conveying direction) in front of the development station a bias voltage is first impressed, which has an opposite charge generated like the voltage that is impressed on the electrically conductive layer of the recording film in the charging station will; then alternating bias voltages are impressed on the electrically conductive layer, which are continuously increasing Generate changing charges and their absolute values continuously decrease, whereby the electrical potential of the electrical conductive layer can be reduced essentially to the reference potential. This device enables it is necessary to develop electrostatic latent images on recording sheets properly and produce very good copies to produce even if the recording sheets have a length that is greater than the distance between the charging station and the development station.

The invention thus provides a device that is used in devices for the production of electrophotographic Images used xierden in which the distance between

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the loading station and the developing station for the recording sheet is shorter than the length of the recording film. In the device the voltage that one is electrical conductive layer of the recording film is embossed, essentially at the level of the earth potential or a reference voltage immediately before the development station reduced by first impressing a bias voltage on the electrically conductive layer of the recording film will have an opposite charge as the bias generated by the electrically conductive layer in the charging station (in the conveying direction) in front of the Entificklungsstation is imprinted; then the electrically conductive layer of the recording film are alternately biased imprinted with changing polarities and with continuously decreasing absolute values, creating the conditions under which the recording sheet is developed.

The invention is explained in more detail below with the aid of a preferred exemplary embodiment, for which purpose the attached Drawings are taken into account. Show it:

Fig.l and 2 are sectional views of equipment for the production of electrophotographic images in which the invention may be incorporated;

Fig.3 and h are sectional views of recording films, the

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can be used in connection with the invention;

5 shows a sectional view of an embodiment of the device according to the invention for removing electrical potential from the electrically conductive layer of Recording sheet; and

FIG. 6 is a graph showing how the electrical potential is removed ^{by means of the device shown in FIG. 1 *.}

An embodiment of the invention is referred to on FIGS. 5 and 6 described. In Fig. 5 is the same development station as shown in Fig.l; in both figures the corresponding parts are with the same Reference numerals denoted. Of course, in the development station 18 instead of the wet developer shown one of the known dryer developers can also be used. A recording sheet is used as the recording sheet A shown with an electrically conductive layer. However, one of those shown in FIGS. 3 and M can also be used Recording foils are used.

In Figure 5, the recording sheet A is electrically conductive layer to which a bias voltage is applied in a charging station (not shown) is »by a number of removing the electrical potential

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Pairs of rollers 45 and 46, 47 and 48, 49 and 50 and 51 'and

52 conveyed through before it is fed to the development station. The rollers 46, 48, 50 and 52 that oppose press the rollers 45, 47, 49 or 51, they touch electrically conductive layer of the recording sheet and are made of metal or electrically conductive rubber; the rollers 45, 47, 49 and 51 are made of a suitable one Isolation material produced.

The rollers 46, 48, 50 and 52 connected to an energy source

53 are switched on, represent the devices according to the invention, by means of which a bias is impressed or is created. A bias voltage (which creates a positive charge, as shown in Figure 6 at point Q is), which creates an opposite charge as a voltage (which creates a negative charge, like on the Point P is shown in Fig.6), which is connected to the electrical The conductive layer of the recording film is embossed in the charging station is embossed on a first roller 46. A bias (as shown at location R in Figure 6) that creates an opposite charge and which has a somewhat smaller absolute value than the voltage which is impressed on the first roller 46 Embossed on the second roller 48 via a resistor 54. A bias (as shown at point S in Figure 6) that creates an opposite charge and has a slightly smaller absolute value than the

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Voltage that is impressed on the second cave is impressed on the third cave 50 via resistors 55 and 56. Eventually there is a bias voltage (as shown at point T in Figure 6) which creates a charge opposite to the voltage impressed on roller 50 and which has an absolute value well below the level of the ground or reference voltage is, through resistors 5 '* »57 and 5.Ö. embossed on the fourth roller 52.

In this way, biases are applied to the different charges and which have continuously decreasing absolute values, by means of the rollers Ί6, 48, '* 9 and 50 alternately the electrically conductive layer of the recording film A impressed, so that the electrical potential of the electroconductive layer of the recording film A is required Has cargo with a required value. As a result, the influences of the voltage impressed on the charging station are at the development carried out in the development station eliminated even if the recording sheet Λ such Has length that it is pulled through both the loading station and the development station. This can the recording film can be developed flawlessly without that the background of the image or the underside of the film is soiled, and at the same time a toner image rail of an ont.inmlen density is generated.

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Of course, rolls 46, 48, 50 and 52 can also be used be replaced by electrodes of the appropriate shape and design; furthermore is the number of lumps or electrodes or the number of levels in which the absolute value the preload is continuously reduced to the number shown and described in the embodiment limited.

I'a.t outi.ni.s

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BATH ORIGINAL

Claims (3)

-Ib- _?
Claims -T262 774 Device for removing an electrical potential from an electrically conductive layer of a recording film, in particular for devices for producing electrophotographic scanners Images in which the distance between the charging station and the developing station for the recording sheet is smaller than the length of the recording sheet, thereby characterized in that by means of a device which impresses biases on an electrically conductive First layer of the recording film (A) (in the conveying direction) in front of the development station (18) is pre-tensioned is applied, which generates an opposite charge than the bias voltage in the charging station (16 or 29) is embossed on the electrically conductive layer, and that alternating bias voltages, the different charges and their absolute values continuously decrease, embossed on the electrically conductive layer of the recording film (A) until the electrical potential of the electrically conductive layer immediately before the development station (18) is reduced substantially to the level of the reference or ground potential. 2. Apparatus according to claim 1, characterized in that the device which impresses the stresses a number of electrically conductive rollers (46, 48, 50, 52) connected to a power source (53). , 17 309827/1053 226277 / + 3. Apparatus according to claim 1, characterized geke η η t draws that the device impressing the biases a number of electrically conductive lumps (46, 48, 50 and 52) aui'vreist, which are connected to a number of resistors (54 to 58) and an energici ^ uel! e (.53) are switched on. 0 9827/105 3 -. ■ BAD OBiGlNAi