DE2303819A1 - PHOTO-ELECTROSTATIC IMAGE TRANSFER PROCESS - Google Patents

Description

PATENT LAWYERS

DIPL -ING. MARTIN LICHT

11 2S4 Di? L.-Pr.YS. SEB. HERRMANN

11 o ¹ * January 26, 1973

_R / _Sch MÜNCHcN 2

THERESIENSTRASSE 33 _{; 3}

ADDRESSOORAPH-ÄULTIGRAFH CORPORATION 1200 Babbitt Road, Cleveland, Ohio 44117, V.St.A.

Photoelectrostatic image transfer process

The invention relates generally to photoelectrostatieches Image transfer method and in particular such a method in which the photoconductor is repeated in a single environment, where one or more high voltage electrodes and / or Bias electrodes used in image transfer is used.

Photoelectrostatic image transfer processes in which on a photoconductor by means of a powder (toner «) creates an image and then on a sheet of paper (plain paper) are known. In these image transfer processes, the photoconductor must be sensitized by a charge and then exposed to a pattern of light and shadow be to the charge image on the surface of the photoconductor to create. The charge image is created by developing with a

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Toner, i.e. an electroscopic powder, made visible. In many cases the developer equipment has a vo * - apannelectrode, which is between the conductive surface of the Photoconductor and the toner creates a voltage gradient. The need for such bias electrodes arises in a particular system such as, for example in U.S. Patent 3,598,580 entitled "Phot © electrostatic Copying Process Employing Organic Photoconduotors "by the applicant himself. Xn this known method the photoconductive layer is underexposed, and by the action of a biasing electrode on the developing ' lungsst at ion, the electric field in the underground area for the acceptance of toner becomes ineffective.

In the final stage of image transfer, the toner image developed at the development station must be transferred to the receiving sheet. Electrodes are also used at the transfer station to facilitate the transfer of toner particles from the photoconductive layer to the receiver sheet. Such electrodes can corona discharge electrodes that the receiver sheet a voltage having a polarity to that of the toner particles is opposite to give be f, so that the particle is given a movement torque in the direction of the recording sheet. A non-corona electrode which produces a field effect, for example a roller with an applied voltage, which also causes the powder to receive a moment of movement in the direction of the receiving sheet, can also be used.

The image reproduction methods described above require the Use of electrodes connected to high voltage sources. This in turn makes it necessary to design the photoconductor in such a way that it provides sufficient resistance to the influence of these high voltage gradients. The Photolei-

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230381η

It can, of course, take various forms. For the implementation of the procedure described here, he has expediently the Form of an endless ribbon. But it can also take the form of a Have web that is brought to the machine on reels, unwound from one reel and wound onto another reel. The coils are then arranged in a rotatable drum that part of the photoconductor lies on the surface of the primary drum. As the drum rotates, the photoconductor is fed through the various stations required for imaging.

A typical photo conductor has a carrier made of a polyester film, on which a conductive layer made of, for example, aluminum is applied. An excellent carrier is aluminized "Mylar". A film can be placed on this carrier can be applied from a photoconductive material. There is a full circle from the corona wire to charge the film required above earth} in order for the toner to be deposited in the correct pattern is a during its application Conductive path required, and a complete path to supply the energy for transferring the toner to the receiver sheet Requires a circle from the transfer electrode to earth.

In the case of such a photoconductor in the vicinity of one with electrodes, As described above, equipped device, the photoconductive layer must be uniform and continuous and must not have any holes that result in a direct connection between the conductive layer and the high-voltage source would. If this layer is too thin in places, has irregularities or flaws, then it comes to one Short-circuit with the electrode at the development station, which resulted in a build-up of toner on the photoconductive layer the same dimensions as those of the developer brush enables. Such an uncontrolled toner deposition

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smeared on the photoconductive layer at the short-circuit points parts of the image and thus makes the photoconductor unusable,

The main object of the invention is therefore a method for production of reproductions on plain paper using a photoconductor covering an enlarged area of process parameters.

In particular, the object of the invention is a duplication method for making reproductions on paper using high quality copies using a biasing technique can be obtained without the danger of shortening the useful life of the photoconductor.

The object of the invention is also, in particular, a copying method in which higher bias electrodes are used at the various stations Voltage can be used and in which a photoconductor with a resistive layer through which the photoconductor during the process is protected against harmful effects.

Another object of the invention is a method in which a photoconductor having a resistive layer in contact with the photoconductive layer is used to connect to the individual stages of the process where high voltage bias electrodes are required, short circuits through the photoconductive Shift to be avoided.

Another object of the invention is a photoconductor comprising a conductive support, a photoconductive layer and a resistive layer in contact with the photoconductive layer, so that short-circuit currents through irregularities in the photoconductive Shift to be avoided.

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According to the preferred embodiment of the method according to Invention for the production of reproductions by means of a Photoconductor, a photoconductor constructed in a certain way is charged by means of a conventional corona electrode. Of the charged photoconductor is then exposed to a pattern of light and shadow, so that a corresponding Charge pattern is generated. The charge pattern on the photoconductor is developed by using a suitable Means such as a magnetic brush applies a toner, i.e., an electroscopic powder, thereon while a potential gradient is applied to the conductive support of the photoconductor and the magnetic brush. That in this Way on the photoconductor developed image is then under the influence of a transfer electrode which creates a field between the Surface of the powder image on the photoconductor and the sheet, for example a sheet of paper, onto which the image is transferred is to be generated, transferred to the recording sheet.

According to the invention, the photoconductor is formed so that he in its passage through the individual stages of the process against the influence of the various high-voltage electrodes Is resistant without it being necessary that the photoconductive layer itself is extremely uniform and coherent. To this end, according to the invention the photoconductive layer is brought into contact with a protective resistive layer, so that an impedance »wipe the Developer brush and earth or the reference potential is created. The resistance of the photoconductor is in its dark state about 10 to 10 cm. The resistance of the

protective resistive layer should be in the range of 10 to

10 JCL * cm.

It was found that the value of the resistance for the current

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delimiting layer a puncture of the speed with which the photoconductor passes the development brush or electrode, and the applied bias. In general it can be stated that the layer has a time constant which prevents a loss of bias at the point where the photoconductive layer has a crack or a hole / must have.

In general, such a protective resistive layer must satisfy the requirement that its electrical resistance is high enough to prevent the formation of short-circuit currents and so high that it does not cause a loss of bias on the photoconductive surface and thus the localized assumption prevented by toner. In addition, the protective layer must have such a high dielectric strength that the voltage breakdown is prevented. On the other hand, the resistance must be so low that only a negligible atroma-restricting effect is produced during normal charging, development and transfer under the influence of high-voltage electrodes. The protective layer must lie between the electrode and the conductive layer and can therefore either be applied to the photoconductive layer or be arranged between the conductive layer and the photoconductive layer.

In the drawings is:

Figure 1 is an elevation of a duplicating device for performing the method according to the invention,

Figure 2 is a circuit diagram showing the various electrodes to which the photoconductor is exposed,

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FIG. 3 shows a schematic cross section through a photoconductor according to the invention,

FIG. 4 shows a schematic cross section through another embodiment a photoconductor according to the invention and

Figure 5 is a schematic illustration of the operation of the photoconductor according to the invention.

Figure 1 shows a copier 10, which can be used to carry out of the method according to the invention is suitable. The photoelectrostatic Copying device 10 is housed in a housing 12 and has a feed station 14 through which the to be reproduced Originals are imported on. At the lower part of the housing there is a joint 16 of cut pieces Sheets from which the individual recording sheets 17 »to which the toner images are to be transferred are fed. the Sheets 17 are guided through a fixing station 18 and placed on a receiving tray 20 in front of the housing 12.

In the front part of the housing there is a designated 22 Photoconductor in the form of an endless belt. The education the photoconductor 22 is critical to the successful implementation of the method according to the invention, as follows described in more detail. It has a polyester carrier 24 and a conductive layer 26 thereon. In direct contact with the Conductive layer 26 is the protective resistive layer 30, on which the next layer is the photoconductive Layer 32 is applied. The resistance layer 30 can, however, as mentioned, also applied to the photoconductive layer 32 will. The endless belt 22 is taut over a number of rotatable rollers 34, 36, 38 and 40 which are about parallel horizontal ones

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Axes a, b, c and d are rotatably mounted, guided. One of the rolls, for example, the roller 40 is pivoted to two arms 42 and 42 ^montierfc _'w | ^d fld g ^{ß it} can slid ^{out of the} path of movement of the endless belt / and serve as a voltage control for this band. Another of these rollers, for example roller 36, is driven by a drive mechanism consisting of a motor 44, gears 4ia and 4ib and a chain 46 via the shaft b.

Above the photoconductor 22 is a pivoting frame made up of a pair of L-shaped parts 48 and 49 * of those in FIG only one, 48, is shown. These parts are around peg 52 rotatably attached to the frame 50 and are secured by tie rods 54 and 56 held at a distance from each other. This scaffolding can be in its operative position, in which it is above the flat part 58 of the path of movement of the belt 22 over the rollers 34 and 38 is located, can be pivoted.

A corona discharge device is located on the underside of the frame 47 60, which has a fine wire electrode 62 stretched within a shield 64. The corona discharge device extends between the parts 48 and 49 and is attached to the pull rod 56 so that that it is in the operative position at a distance of 1.27 to 0.95 cm (1/2 to 3/8 of an inch) above the photoconductor 22, when this runs over the roller 38. At this station the photoconductor 22 receives an electrostatic charge.

On the underside of the frame 47 is a pair of rollers 66 and 68, which are rotatably mounted about shafts e and f, over the part of the path of movement of the belt 22 between the rollers 34 and 38. These waves e and f run, as shown in the drawing, parallel to the waves a and c, are between the WaI-

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zen 34 and 38 arranged and extend over the full width of the belt 22. The endless belt 22 is thus both from below as it runs between the two sets of rollers 34/38 and 66/68 as well as supported from above, so that a tight, flat exposure plane 58 is created.

An elongated radiation source 72 is located in one Reflector housing 74, which extends over the entire width of the photoconductor belt and represents the source of radiant energy for photoconductor 22. The reflector housing is in the cut-out part 76 of the L-shaped frame part 48 attached. The roller assembly also serves to convey the original to be reproduced into intimate contact with the photoconductor 22 over the entire exposure plane 58.

The roller 34 is the developer device 80 through which the Toner on the photoconductive layer 32 of the photoconductor 22 carrying the latent image, after this ungsstation from the loading light 58 has leaked, is applied, assigned. The developer has a tray 82 that holds a developer powder contains. This powder can be a conventional mixture of iron and electroscopic thermoplastic carrier particles Powder particles such as those used in magnetic brush developers. Construction and operation of magnetic brush developers are known and do not need to be described here. When installing the developer device, it must be compared to the others Parts of the copier are isolated. The trough rests on a frame or platform 86 made of a highly insulating material plastic material, such as an acrylic or polystyrene resin or equivalent, and this platform is in turn carried by the frame of the device. A drive motor is used to drive the magnetic brush device 80 85 provided. The circuit diagram and the control devices

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the device of Figure 1 are described in more detail below, A negative voltage that is equal to or slightly greater than the voltage in the underground area is expediently applied to the developer. created. A more detailed description of this developer and exposure technique can be found in US Pat. No. 3,598,580 Applicant herself.

Instead of a magnetic brush device, another suitable developer device can be used for developing the image with the toner. for example, a cascade development system using conductive glass beads and using the developer electrode at the area where the powder falls on the photoconductor can be used.

The transfer of the image to the receiving sheet takes place in the transfer station 88, to which the receiving sheet 17 is fed from the pile 16 via the feed wheel 90 in chronological relation to the supply of the image on the surface of the photoconductor to the transfer station. An adjustable pressure device 92, which consists of a roller 9 ^ rotatably mounted in an insulating bearing 96, presses against the roller 36. The bearing 96 is arranged in a yoke 98 which is pivotably mounted at 100 on a frame 99.

One end of the yoke 98 is on a threaded one Post 101 attached. This post is attached at one end to the housing 12, while the other end rotates into the Yoke engages. There is a threaded nut 102 at the bottom of the post and the post 101 will by a coil spring I08, which is between the yoke 98 and the Nut 102 is held in a compressed state, surrounded. Adjusting the nut 102 will compress the spring and thus the force with which the yoke and the roller 94 at the roller 36 are pressed, increased or decreased.

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The pressure in the area is expedient during the transmission from about 0.36 to 17 * 8 kg / cm linear contact (about 2 pounds to about 100 pounds per ruler contact inch).

Figure 2 shows the eohematically the belt 22 as it runs around the Rollers 34, 36 and 38 through the charging station 60, the developer station 8o and the transfer station 92 associated electrodes. The power supply of the device of FIG. 1 can be seen from the circuit diagram of FIG. The two of them Poles of a 115V AC power source connected lines IiO and 112 supply the high voltage circuits.

The high voltage circuits 114, 116 and 118 are individually over the Power supply lines. The circuit 114 provides the voltage for the Charger 60, circle 116 the voltage for the transfer roller 94 and the circle 118 the variable voltage for the developer device 80.

The corona wire 62 is via line 120 to the negative pole of the high voltage circuit 114 is connected so that a voltage in the range of 4000 to 6000 V is applied to the fine wire 62 and a corona emission is generated from this. When the photoconductor 22 passes the wire 62 in the charging station 60, is its surface is electrostatically charged.

While the belt 22 continues to run steadily from the charging station 60, becomes a graphic original through the loading station 14 introduced and brought into intimate contact with the charged surface of the photoconductor 22 via the rollers 66 and 68, as described in connection with FIG. At the exposure station 58 is applied to the photoconductor by the electromagnetic Radiation source 72 applied a pattern of light and shadow.

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After leaving the exposure station, the belt moves to the next station, i.e. development station 80, where toner is applied to the the latent image bearing surface of the photoconductor is applied. As described above, it has proven to be useful to carry out development in the presence of a field between the developer particles and the charge image. This is it is necessary that the developer via the line 122 to the negative pole of the high voltage circuit 118 with variable Voltage is connected. It is useful to give the developer a negative potential in an area that is the same or something is greater than the voltage in the subsurface area of the photoconductor 22, created. The bias voltage applied to the brush is in the range of 150 to 500 V.

The powder image generated in the developer device 80 is transferred to the receiving sheet 17, which is taken from the stack 16 by means of the feed roller 90 (FIG. 1) in chronological order to the arrival of the Powder image is supplied to the transfer station, transferred. A transfer roller 94 is pressed against the roller jJ6 and effected the transfer of the powder image to the receiving sheet 17. The transfer roller 94 cooperating with the roller 36 effects the transfer of the powder to the receiver sheet, which passes between these rollers.

When the apparatus of Figure 1 is used for duplication i.e. when the powder image is to be transferred from the surface of the photoconductor 22 and then the latent image again is to be dusted and transferred, it becomes necessary between the surface of the powder image and that fed from the stack 16 Copy paper to create a field. To one for a reproduction To create a suitable environment, a field is applied between the two rollers 36 and 94 of the transfer zone, by moving the metallic shaft 124 of the roller 94 with the high-

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23Ό3819

Tensioned DC voltage circuit 116 connects, wherein a field of the same polarity as that of the electrostatic charges is generated in the latent image parts. The core 124 is thus connected to the negative pole of the source 116 via the conductor 126. The voltage applied to the conductive core of the roller 124 is in the range of 1000 to 3000 V, preferably in the range of 1200 to 2000 V, and the pressure is in the range of 0.14 to 0.56 kg / cm ^{2 of} contact area (from 2 to 8 pounds per square inch contact area).

FIG. 3 is a schematic cross section showing the structure of the Photoconductor 22 on which the successful implementation of the reproduction process in the device 10 is illustrated.

In order for the photoconductor to be sufficiently flexible and strong that it is used in the device 10 in the form of an endless belt can be, the carrier 24 is preferably made of a polyester film. The photoconductor 22 can, however, also be a different one Shape, for example the shape of a web, which is wound onto spools on suitable carriers and from these in suitable Lengths to be applied to supports ^ around sequentially the process to be subjected to.

The photoconductor 22 has a flexible carrier 24 made of a polyester or another plastic such as cellulose acetate, cellulose triacetate, cellulose acetate butyrate, polyurethane elastomers, fluorocarbon polymers such as the copolymer of hexafluoropropylene and Tetrafluoroethylene, cellulose propionate, xthyl cellulose, polyamide, polymethyl methacrylate, polyethylene, ethylene / vinyl acetate copolymer, Polyvinyl fluoride, polypropylene, polyester terephthalate, polytetrafluoroethylene, Polystyrene, polyvinyl alcohol, polyvinyl chloride, vinylidene chloride / vinyl chloride copolymer, polycarbonate and rubber

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hydrochloric !, on. The preferred substrate is a polyester terephthalate film known as "Mylar", the has the greatest dimensional accuracy.

The resistance of polyester films is high, i.e. lies within that Range from 10 to 10 ^ -O- · cm. Because of their high resistance These polyesters alone are not suitable as a carrier to which the photoconductive material can be applied directly because it what is essential is that the carrier has a resistance in the range of 10 XL »cm to the resistance of metal.

The conductivity of the sole 26 is achieved by a thin uniform metallized layer, for example Aluminum or copper, by vapor deposition with a thickness in the range of 0.00013 to 0.013. mm (0.005 mil to 0.50 mil). Also other methods of achieving conductivity can be applied. For example, a metal-containing semiconductor compound can be used in a film-forming binder dispersed and the semiconductor and binder are brought into solution together to form a coating solution. Since the Most semiconductors are not readily soluble in organic solvents, they are formed with other compounds solubilizing complexes combined. Suitable semiconductor materials are cupric and silver halides, halides of Bismuth, gold, indium, iridium, lead, nickel, palladium, rhenium, tin, tellurium and wolfrati. The semiconductors are through Complex formation is solubilized and then dispersed in a binder such as polyvinyl acetate, and the mixture is made into cyclohexanone or other more suitable ketones dissolved.

In direct contact with the conductive layer is next the protective resistive layer 30 is applied. Such Resistance schioht must mainly meet the requirement that

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their electrical resistance is high enough to prevent short circuits due to voids or irregularities in the photoconductive Prevent layer. Their dielectric strength must be so high that the voltage does not collapse, when exposed to strong fields. The resistance of the resistance layer should, however, be sufficiently low that will only have negligible effects on normal charging, exposure and development such as those used to produce a Image are required. A suitable protective layer can be film-forming using any of the following Materials are trained »

Methyl cellulose

Hydroxypropyl methyl cellulose ethyl acrylate / acrylic acid / styrene terpolymer

Copolymer of methyl vinyl ether and maleic anhydride

Polyvinyl alcohol

The above materials are dissolved in a suitable solvent, which in some cases may be water, and if necessary a hardener must be used.

The resistive protective layer is applied in such an amount that the thickness of the dry film is in the range of 5 to 15M- * preferably in the range from 6 to 10 µ. In general, however, the thickness of the film can be in the range of 2 to 50 µm lie.

After the resistive scMAzschicht is applied, excess Solvent is evaporated therefrom and the film is brought to a dry state, the photoconductive layer 32, which a photoconductive pigment, such as zinc oxide, cadmium sulfide, cadmium selenide, can be in a resin as a binder,

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brings. The photoconductive layer can, however, also be an organic photoconductive system to which many different aromatic Hydrocarbons include as described in U.S. Patent 3,287,199. These photoconductors include aromatic hydrocarbons, such as naphthalene, anthracene, benzanthrene, chrysene, peradlphenylbenzene, diphenylanthracene, pera-terphenyl and peraquaterphenyl as well as sexiphenylj heterocyclic compounds such as oxidiazolej triazole? Imidazolones and imidazothionej N-arylpyrazolones; hydrated imidazoles; and other connections. The organic photoconductive substances can be obtained from a solution or together with a film-forming binder, such as a natural resin, for example shellac, or a synthetic resin, such as a coumarone resin, or a Binders, such as cellulose ethers, vinyl polymers, polyacrylates, are applied to the carrier.

Another extremely suitable group of photoconductive ones Materials make up the organic polymeric photoconductors. The polymeric substances that are found to be used to carry out the Process according to the invention have proven useful are the vinyl polymers and in particular vinyl carbazole and vinyl copolymers, which contain vinyl carbazole units. If the photoconductor is an organic polymer, it serves as his own film-forming agent, and the use of your own binder is not required. Excellent results are achieved with photoconductive materials such as polyvinyl carbazole and poly (N-vinylbenzocarbazole).

Figure 4 illustrates another embodiment of a Photoconductor 130 according to the invention. The carrier is the same as that in the photoconductor illustrated by FIG and consists of a carrier film 13 ^ · on which a conductive Metal layer I36 and the photoconductive layer 138 applied are. The protective resist-

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Stand layer I4o applied. The photoconductors 130 of Figure 4 and 22 of Figure 3 differ in that the former has the resistive layer over the photoconductive layer lies. Apart from the arrangement of the protective resistance layer 14o, the structure of the photoconductor 130 is the same as that of the photo guide 22.

The following examples illustrate the manufacture of special photoconductors for the practice of the new duplication process according to the invention.

example X

On a carrier made of an aluminized Mylar film in which the ifylar film was 0.076 mm (3 mils) thick and the aluminized one conductive layer had a thickness of 0.00005 mm (0.002 mils), a resistive protective layer was composed of the following composition aung applied:

Parts

Polyvinyl alcohol 1

Water 9

polymeric quaternary amine salt 0.5

(ECR-34 from Dow Chemical

Company)

The polyvinyl alcohol solution was applied to the aluminized mylar film Applied in such an amount that after the water has evaporated from the coating, a layer 6 μ thick is obtained became.

After applying the protective resistive layer it was a photoconductive coating produced as follows «

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5 g of poly (N-vinyl-7H-benzo / € / -carbazole) were dissolved in 65 g of chlorobenzene. To the solution was added 0.5 β of 2,4,7-trinitrofluorenone ( ¹ Jp -type acid, 10 # of the weight of the polymer as solids). The solution was applied in such an amount that after evaporation of the solvent a photoconductive layer with a thickness of about 0.005 to 0.008 mm (about 0.2 to 0.3 mils) was obtained.

The finished photoconductor was suitably formed into an endless belt and around the rollers. ^ 4, 36, 38 and 40 placed. The tape was made as described in US Pat. No. 3,533,692. This US patent describes a method of continuously grounding the conductive layer 2.6 to the conveyor rollers through the use of conductive connections which penetrate the mylar layer and create a conductive connection between this layer and the rollers.

Example 2

The photoconductor of this example was made as in Example 1, with the exception that the following recipe was used for the protective resistive layer:

Parts

Methyl cellulose 0.20

(METHOCEL MC of the Dow
Chemical Corporation)

Quaternary ammonium salt 0.06 (ARQUAD C-50 of the Armor
Industrial Chemical)

Water ΙΌ

This protective resistive coating was applied in such an amount that a dry film thickness of 6 μ was obtained,

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Example 3

The photoconductor of this example was made as in Example 1, with the exception that the following recipe is used for the production of the protective resistive layer became:

Parts

Hydroxypropylmethylcellulose 2.4 (METHOCEL 65HG from Dow Chemical Company)

U FORMITE 700 1.2

(Rohm and Haas Company) Organic Quaternary Amine Salt 1.0 (ARQUAD C-50 from Armor Industrial Chemical)

Methanol 8

Water? 8

Hydrochloric acid (to adjust the pH to 4.5)

The solution was applied in an amount such that one dry coat thickness of 5 μ was obtained. Before applying the photoconductive coating, the film was left in an oven overnight be cured at 100Ϊ.

Example 4

The photolelter of this example was made like that Photoconductor of Example 1, except that the following is used for the production of the protective resistive layer Recipe was used:

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Parts

Diisocyanate resin 5 * 2

(DDI of the General Mills. Company)

Modified amine - 4.8

(A-IOO of General Mills

Company)

Organic quaternary amine salt 2.0 (ARQUAD 2HT 75 of the Armor Industrial Chemical)

Toluene 58

The resistive coating had to be cured in an oven held at 100T for 2k hours. The solution was applied to the aluminized Mylar film in such an amount that a dry layer thickness of 10 μ was obtained.

Example 5

The photoconductor of this example was made according to that in Example 1 described method, with the exception that the following recipe for the protective resistive layer was used:

Parts

Ethyl acrylate / acrylic acid / styrene terpolymer
Weight ratio 69: 8

: 23 2.1

Epoxy resin 0.5

(EPON 836 of the Shell
Chemical Corporation)

Organic quaternary amine salt 0.5 (ARQUAD 2 HT 75 from Armor Industrial Chemical)

n-butanol 2

Toluene 3

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The resistive coating of this example had to be cured ^{at IQO 0} C for 24 hours. It was applied in an amount such that the dry draw thickness was 0.127 mm (5 mils).

Example 6

The photoconductor of this example was made according to the procedure described in Example 1, except that the following recipe was used for the protective resistance layer:

Parts

Copolymer of methyl vinyl ether and maleic anhydride 10 (GANTRY AN 419 der General Analine and Film)

1,5-pentanediol 1.27

Dibutyl phthalate 1.0

Organic quaternary amine

salt 4.9

(ARQUAD G-50 of the Armor

Chemical Company)

Tetrahydrofuran 90

The resistive coating was applied in such an amount that a dry film thickness of 6 μ was obtained. The coating required hardening at 100 * C for 24 hours »

Example 7

The photoconductor of this example was made according to the procedure described in Example 1, except that the order of the layers was changed so that the photoconductive layer was directly on the aluminized mylar film and the polyvinyl alcohol coating was applied as the last layer, so that the photoconductive layer between the conductive Layer and the resistive layer lay.

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In the photoconductors produced in the examples, the photoconductive layers had the following electrical properties:

At- dark resistance
play of the photoconductive layer

Resistance of the ^ protective layer

speed

. Humid

1O ¹ - * 1O ¹⁵ Ohm * cm 2 χ 10 Ohm'cm below 10 ¹¹ Ohm-cm

M. It If Il It

Il It H ti

ti ti

below 10 η η

11 η

ti

"6 x 10 ^M 8 χ 10 ^{12 tt} 2 χ 10 ¹ - ⁵

It

As can be seen from the above list, the Resistance depending on the humidity. In each of the examples, however, the resistive layer met above that specified Humidity range their purpose.

When using the photoconductor in the related with In the devices described in FIG. 1, the photoconductive layer was reduced to approximately 80 V by means of the corona discharge device 60 charged.

At the exposure station, the photoconductor was exposed to a pattern of light and shadow for so long that the voltage in areas hit by light dropped to about 300 volts. Of the Photoconductor with the latent, the pattern of light and shadow The corresponding image ran on to the developer brush, where the toner was applied. The magnet burst facility was included

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the negative PoX of a DC voltage source and the other pole this source was connected to earth, giving the developer a negative potential in the area that is equal or something was higher than the voltage in the underground area, in the present example about 300 V, was applied.

The brush was of a source of the same polarity as that electrically bias the sensitizing charge. The toner became selective in this environment drawn to the picture surfaces to the exclusion of the underground areas, which have a fairly considerable level of tension 300 V. The presence of the protective resistance layer 30 prevented short circuits due to the voltage of the magnetic brush to earth via irregularities or holes in the photoconductive layer 32.

FIG. 5 illustrates the effect of the photoconductor 22 according to FIG of the invention under conditions where the photoconductive layer 32 has cracks or discontinuities. As through this drawing As illustrated, the resistive layer 30 acts as a resistor 14o between the photoconductive layer 32 and the vapor deposited Metal layer 26.

As shown in Figure 5, the photoconductor 22 passes under the developer brush 85, by which the developer mixture 84 is carried. Those parts of the photoconductive surface that are not were struck by light and therefore still had the charge applied by the corona discharge device 60, toner particles attracted 84 * from the developer mixture 84, so that a visible image was created on the surface. When the brush is over the hole l42 in the photoconductive layer 32 which is the size may have a pinprick or some other irregularity so that the surfaces immediately below the airfoil 42

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are directly exposed to the high voltage source 118, runs, prevents the layer 30, which has the effect of a resistor 14o, a current flow which would otherwise result from a direct Connection of the high voltage source 118 to the conductive layer 26 and from there to earth would result. Such a direct one The connection would result in a loss of prestress and the parts 84 * would extend over the surface 32 over the Separate the entire length of the applicator roller 85. The result of such an uncontrolled deposition of toner in the area of the The brush-blackened area could be up to 1.3 cm (one-half inch) wide and extend over the whole Extend transverse dimension of the photoconductor. The attraction and deposition of toner across the width of the photoconductor in the manner described can be referred to as a "shorting bar". Using the Photoconductor according to the invention, as illustrated in FIG. 5, the occurrence of such a short-circuit bar completely prevented, even if the photoconductive layer has the hole designated 142. By preventing a short circuit prevents the receiver sheet from attracting a band of toner.

Claims (11)

Pate η ta η s g.rtte h β Method of making a reproduction of a Photoconductor, characterized in that one (a) A photoconductor composed of a conductive support, an organic photoconductive layer and a Carries a resistive layer preventing the passage of current in contact with the photoconductive layer, (b) applying an electrostatic charge to the photoconductor by means of a charging electrode, (c) on the charged layer by means of a pattern Light and shadow create an image, (d) developing the image by applying a toner to it while applying a bias Voltage gradients generated between the conductive carrier and the toner, (e) the toner image under the influence of a transfer electrode transmits to a recipient, (f) by arranging a reference electrode, a reference voltage for the electrodes in the above steps b, i and e creates, causing a loss of bias in the development stage through the resistive layer, the in the case of discontinuities in the photoconductive layer, the direct connection of the photoconductive layer interrupted with the reference electrode is prevented. 309832/1089 2. The method according to claim 1, characterized in that the resistance layer consists of a film-forming Material such as methyl cellulose, hydroxypropyl methyl cellulose, Polyvinyl alcohol, polyurea, ethyl acrylate / Acrylic acid / styrene terpolymer or methyl vinyl ether / taleinic anhydride copolymer, and a guiding agent. 3. The method according to claim 1, characterized in that that the thickness of the dried resistive layer is in the range of 2 to 50 μ. 4. The method according to claim 1 »characterized in that - that the resistance of the layer is in the range of 10 ¹¹ to 10 ¹ ^ ohm-cm. 5. The method according to claim X ₃ , characterized in that the latent electrostatic image is developed by applying a toner using a magnetic brush, wherein one develops (a) first a photoconductor made from a conductive carrier, that of an organic photoconductive layer and a current passage preventing resistive layer carries in contact with the photoconductive layer, produces, (b) connects the conductive support to a reference electrode, (c) applies a bias voltage to the magnetic brush and thereby a potential gradient between the conductive support and the toner creates where a loss of bias through the resistive layer, which is a direct link between the photographic 30 98 32 / I applicable layer and the reference electrode in the case of the Occurrence of discontinuities in the photoconductive Shift interrupts, is prevented. 6. The method according to claim 5, characterized in that that a bias voltage in the range of 50 to 300 volts is applied to the brush. 7. The method according to claim 5 *, characterized in that that the reference electrode is earth. 8. The method according to claim 1, characterized in that one copies of a graphic original manufactures by (a) A photoconductor made up of a conductive support, an organic photoconductive layer and a current passage carries preventive resistance layer in contact with the photoconductive layer, (b) on the photoconductive layer by means of an electrode applies an electrostatic charge, (c) creates a charge image on the layer with the charge by means of a pattern of light and shadow, (d) the charge image is developed by applying an electroscopic powder to it with a magnetic brush, while having a stress gradient between the conductive support and the electroscopic powder created by connecting the magnetic brush with an energy source, that creates a pre-potential for the developer, connects, 3098 3 2/1089 (e) the powder image under the influence of a transfer electrode transmits to a receiver, whereby one connects the transmission electrode with a voltage source, the a voltage gradient between the transmission part and creates, connects and biases the conductive support during transmission, (f) a reference voltage for provides the electrodes in steps b, d and e, (g) repeat steps d and e by making at least one further transmission to the receiver, wherein a loss of bias at the developer and transfer stations through the resistive layer, which is the direct connection of the photoconductive layer with the reference electrode in case of discontinuities interrupts in the photoconductive layer, is prevented. 9. The method according to claim 8, characterized in that the bias at the developer station is in the range of 50 to 300 volts. 10. The method according to claim 8, characterized that the bias voltage during transmission is in the range of 1000 to J5000 volts. 11. The method according to claim 8, characterized that the polarity of the applied voltage is the same as that of the electrostatic charge. 309832/1089 lee rs e ite