IL33418A - Process for transferring electrostatic charge images to a dielectric layer - Google Patents

Description

PROCESS FOR TRANSFERRING ELECTROSTATIC CHAROE IMAGES TO A ELECTRIC LAYER This invention is with a prooese electrophotographic production of of the type in electrostatic charge images transferred from a conductor layer carried on a conductive support onto a dioleotrio layer provided with a conduotive which layer is in virtual contact with the photoconductor the layers are separated from one another and the transferred latent charge image is developed by photographic dry or liquid development if subsequently The numerous hitherto known processes of this type substantially all have in with the layers in an external electric field applied to transfer the The external electric field may be produced by direct or alternating voltage or by a corona discharge on the reverse side of one or both dielectric Depending on the nature of the process there may bo an exactly gap of 50 to 200 μ between the two or they may be in virtual or an intimate oontaot may be produced between them by applying high mechanical exists in the oase of the superposition of two surfaoes without the application of additional external pressure perpendicular to these two in virtual there is always a thin air film the thiokneee of whioh depends on the smoothness of the two surfaoes in the present is about 1 This small air gap can be eliminated only by mechanical pressure or evacuation of the surrounding whereby the state of the oalied is These known processes have the disadvantage under the action of the external charges are transferred to the reoGiving material not only in the image areas but also the Due to overlapping of the external field with the field produced by the latent charge sufficient differentiation between image and areas is not so that copies with an intensely background are obtained upon Performing that process while maintaining a constant air gap of about to 200 μ involves the further d sadvantage that an unsharp is obtained which is particularly disadvantageous the reproduction of snail character text attempts have been made to the disturbing blackening of the background but a fully satisfactory solution has not hitherto It has been for prior to the image to charge the layer of the receiving material homogeneously by means of a corona discharge in a sense opposite to that of the charge The charge images obtained thereby have charges of opposite sense in the image and After they thus have an exoess charge of the same polarity as the toner of the and firmly to one the copies obtained are not free from sinoe the due to friction on the easily tends to reverse charge in case of a charge of the same and also sinoe a oertain fraction of every toner has a charge opposite to the oharge In another modification in which the receiving material is charged with the same polarity as the latent charge image and a voltage of the same polarity is applied to the reverse eide of the receiving copies are obtained the background of which is more intensely than in the case of material which has not been Also in the known processes operating with an intimate contact of the with the application of mechanical distinot blackening of the background cannot be apart from the fact that the photoconductor layer is very soon mechanically which is a substantial advantage particularly in the case of a continuous working method intended to operate at a high The process of the present invention is of the type above referred to and in it the photoconduotor layer consists entirely or substantially of organic charge transfer coraplexee or contains suoh complexes and is oapable of charged in a thickness of 8 to 15 μ to 800 to and is so exposed to that image areas have a voltage of at lea3t about 500 volte and tho areas of afc about According to a preferred the difference on the conduotor layer between areas and the image areas is between about 500 The use of the specified photoconductor layers ie relatively si ple in that it requires neither the application of an external electric field nor tho application of pressure for achieving copies of good Photoconductor layers based upon charge transfer complexes are known particularly from German Patent Specification They are combinations of such compounds as contain a photoconductive substance with an electron donor function and also an activator with an electron acceptor The compounds include particularly such as have at least one aromatic or heterocyclic ring which may be Suoh include aromatic suoh as thiazole derivatives and others polymers of one or more suoh as vinyldibenzof and the being particularly Suitable activators include particularly compounds strongly polar such as a acid anhydride or oarboxyl group or a quinone Further details are to be found in the German suitable the purposes of the invention are compounds such as particularly 4 or compounds such as and the The proportion of the activator with respect to the conductive substance vary within wide small relative amounts being often In it is to ratios of 1 of the two the proportion of the activator being about to calculated on 1 of the The photoconductive material is produced in known charged and exposed to The dielectric material used be such in the charged state during the image it does not exhibit a marked charge a loss which markedly the image which requires a speoifio of about 10 ohms x Very suitable is a support made from a conductive paper having a top coating of an polystyrene or cellulose According to another optional feature of the the support materials of the photoconductor layer and the dielectric layer may be earthed during virtual Images a particularly contrast are obtained this but production is also possible without such Virtual contact of two layers can be produced in the simplest way by conveying the material without any outer pressure over two rollers and against a drum carrying the photoconductor To establish the paper tension necessary for the transport is The rollers conveying the material as well ae the drum carrying the photocond are The rendering visible of the transferred latent charge image is performed according to the known methods of dry or liquid A farther advantage of invention even with the application of the liquid dispersion which is advantageous for many images with a very good contrast and 3urpri8ingly free from scumming are apparatus for carrying out prooess of the invention is illustrated by way of example in the accompanying the single figure of which is a sectional elevation of an apparatus for the continuous production of Referring to the a metal drum 1 earthed via its shaft carries an organic pho oconductor layer 2 which is charged negatively with reference to earth to about volts by means of a corona fed from a direct voltage An original 6 conveyed synchronously and in a direction opposite to the direction of rotation of the drum as shown by the to lamps 5 through a slit and is reproduced by means of an objective 7 onto photoconductor receiving material drawn from a roll 8 by means of transport rollers 10 and conveyed over earthed metal rollers 11 into virtual contact with photoconductor The resulting transferred latent charge image is developed in the illustrated embodiment with a liquid dispersion developer 13 which is contained in a trough 12 and is sprayed through a nozzle The material first runs over a roller 16 and is then in the developer and freed from the part of the adhering developer liquid by means of squeeze rollers 17 and 18 drying of the copy is by heat radiators For circulating the developer there 1B a 14 for cleaning the squeeze roller a scraper The finished copies are taken up in a roll The process of the invention in any known differing the adapt it to practical Instead of the described dispersion dry development by the cascade or another process may be The organic photoconductor layer may instead to a metal foil or a metallized synthetic plastics film which is then fixed on the When using as material a resiatanoe layer having a hydrophilizable the production of printing platen is possible in the conventional The production of t charge image on the electrophotographic layer may be performed by any known by deposition of metal pins having a sufficiently high electric impulse voltage or by other According to the process of the in general any photoconductor layers consisting entirely or substantially of organic charge transfer complexes or containing such can be but the following layers have proved particularly A layer consisting of 1 of fluorenone and a molar ratio of calculated on the monomer unit of the polyvinyl A layer consisting of by weight of part by weight of and 26 parts by weight of polyvinyl acetate Registered Trade A layer consisting of by weight of part by weight of and 26 parts by weight of polyvinyl acetate The invention is illustrated the ollowing Example A photoconduotor as described under above was applied 75μ thick a layer thickness of a Voltmeter was film was fixed on a ana charged to volts by of a corona the aluminium layer been earthed at one By means of a photographic an original was reproduced from a synchronously and oppositely drum via a elit diaphragm onto the photoconduotor Exposure of original was per ormed w h two green lamps The volts in the image areas and 300 volts in the After the transfer of the charge image to the the voltage as determined was volts in the image areas and below 10 volte in the After rendering visible the transferred latent charge e by means of a liquid a oop of good contrast and free from scumming was A photoconduotor layer made from fluorenone and in a molar ratio of t calculated on the monomer unit of the polyvinyl was applied to an aluminium The layer had a of ooated aluminium foil was fixed as described in Example 1 and charged to volts by means of a corona Exposure to light was carried out as desoribed in Example 1 The charge value determined was 700 volts in the areas 220 volts in the After the transfer of the charge image in virtual contact to the the voltage in the image areas of the layer was voltage determined in the areas was in the range 0 to After rendering visible the transferred charge image by means of a dry mixture per cent by weight of and a magnetic full black copies free from scumming were insufficientOCRQuality

Claims (5)

What we claim is:

1. · A process for the electrophotographic production of copies by trans erring electrostatic charge images from a photo-conductor layer oarried on a conductive support onto a dieleotrio layer provided with a conductive support, which layer is in virtual contact (as hereindefined) with the photoconductor layer, separating the layers from one another and developing the transferred latent charge image by electrophotographic dry or liquid development and, if desired, subsequently fixing the same, i which process the photoconductor layer consists entirely or substantially of organic charge transfer oomplexes or contains such complexes and is capable of being charged in a thickness of 8 to 15μ to 800 to 1,600 volts, and is so exposed to light that the image areas have a voltage of at least about 500 volts and the non-image areas of at most about 3 volts*

2. * A process as claimed in claim 1 , wherein the photoconductor layer is so exposed to light that the voltage difference on the photoconlucto layer between the non-image areas and the image areas is between about 500 and 900 volts*

3. A process as claimed in claim 1 or 2, wherein the support materials of the photoconductor layer and the dielectric layer are earthed during virtual contact*

4. · A process as claimed in any one of claims 1-3, wherein the photoconductor layer consists of 2,4,7-trinitro-9-fluorenone and a polymer of one or more vinylheterooycllo oompounds in a ratio pf about 0.7 to 1.3 mols of the fluorene to 1 mol of the monomer vinyl compound.

5. * A process as claimed in claim 1 , substantially as described in either of the Examples herein and with reference to the accompanying drawing.