DE2615624A1 - MULTI-LAYER PHOTO RECEPTOR ELEMENTS - Google Patents

Description

Multilayer photoreceptor elements

The present invention relates to composite photoreceptor elements, photoconductive elements, an imaging method and a method to form an electrostatic latent image.

The present invention relates to the field of xerography and, more particularly, to a system which includes a photoreceptor with a sta- ' bilen middle layer used. The field of xerography concerns the use of a photosensitive element which contains a photoconductive insulating layer that is initially uniform is electrostatically charged in order to sensitize its surface. The plate is then activated with electromagnetic Rays such as light, X-rays or the like are exposed, thereby reducing the charge in the exposed Areas of the photoconductive insulator is scattered and a latent electrostatic image in the unexposed areas remains. The electrostatic latent image can then be developed and visualized by finely dispersing it, electroscopically

609846/0870

marked particles on the surface of the photoconductive insulating layer to be abandoned. This concept was originally described by Carlson in US Pat. No. 2,297,691 and is now in US Pat many related patents in the field have been developed.

The use of glassy selenium has been discussed by Bixby in U.S. Pat 2,970,906; this material remains the most widely used photoconductor in commercial xerography because it is a Can hold and retain electrostatic charge for a relatively long time when not exposed to light and because it is relatively sensitive to light compared to other photoconductive materials.

Both Ullrich (US Pat. No. 2,803,542) and Mayer et al (US Pat. No. 2,822,300) describe one way of evaluating the properties of the To improve vitreous selenium by adding elemental arsenic in amounts up to about 50% by weight. Arsenic concentrations of more than about 10% by weight cause an increased spectral response in the yellow-red range or band of the electromagnetic Spectrum.

Paris in US Pat. No. 2,803,541 describes two-layer photoreceptor structures, the layers of selenium and selenium-arsenic alloys exhibit. An improved photosensitivity is achieved in that a coating of vitreous selenium tellurium on a Layer of selenium is applied. However, this structure does not show adequate abrasion resistance in the operation of automatic machines xerographic machines and also shows a high rate of dark decay. Protective organic and inorganic coatings have been developed to improve abrasion resistance, but one The main problem with these coatings is their ability or inability to perform properly under a variety of different environmental conditions to work.

Sechak in U.S. Patent 3,655,377 describes a three-layer

809846/0870 - 3 -

Structure, i.e. a three-layer photoreceptor composed of a top Layer of an arsenic-selenium alloy for abrasion resistance, temperature stability and improved dark decay rate; a second layer of a selenium-tellurium alloy to provide panchromatic light response; and one thick bottom layer of xerographic grade selenium or consists of arsenic-selenium mixed with halogen. Sechak does not describe the element of the invention, i.e. a ternary alloy as a middle class. Sechak, on the other hand, describes a binary alloy as a middle layer. Sechak also does not acknowledge the problem that with the loss of electrical properties of a three-layer photoreceptor associated with aging at elevated temperatures i.e. 46.1 ° C (115 ° F) and above.

Chiou in US Pat. No. 3,861,913 describes a xerographic plate which that of a photoconductive substrate, a charge transport layer and a charge generating layer consisting essentially of 5 to 35% by weight tellurium and 0.5 to 20% by weight arsenic, is built up, the majority of the remainder being vitreous selenium. This patent specification does not describe either the three-layer element according to the invention, nor this patent recognizes the problem with the loss of electrical Properties of a three-layer photoreceptor related to aging at elevated temperatures, i.e., 46.1 ° C (115 ° F) and above is.

It has been found that when a three-layer photoreceptor is used, which consists of a top layer of an arsenic-selenium alloy; consists of a second or middle layer of a selenium-tellurium alloy and a third layer of vitreous selenium or arsenic-selenium, the electrical properties of the photoreceptor change to a large extent when accelerated aging by heat or when stored at elevated temperatures for a long period of time worsen. It is assumed that part of the tellurium present in the middle layer ^{migrates from this middle layer into:} the neighboring upper or lower layer,

609846/0870 - 4 -

so that it leads to the above-mentioned lowering of the electrical properties comes. In contrast, it has now been found that by adding arsenic to the middle layer, an arsenic-tellurium-selenium alloy for the middle layer is formed, the three-layer photoreceptor one Deterioration of the electrical properties can be prevented if this is accelerated aging by heat or by storage at temperatures above exposed to room temperature for a long period of time. It is believed that the addition of arsenic increases the migration of the tellurium from this middle layer is prevented and thus the maximum capacity of the three-layer photoreceptor is maintained for much longer can be.

It is therefore an object of the present invention to provide a system in which a system composed of three layers Photoreceptor can be used to overcome the above disadvantages.

It is another object of the present invention to provide a three layer photoreceptor with greatly improved stability of electrical properties at elevated temperatures for a prolonged period Create period.

It is another object of the invention to provide a method of exposure of a new PR to create.

It is another object of the invention to provide a new photoreceptor.

The above objects and others are thereby achieved in accordance with the present invention achieves that a photoreceptor composed of three layers is provided. The three-layer photoreceptor consists of one top layer made of an arsenic-selenium alloy; a second or middle layer made of an arsenic-tellurium-selenium alloy that forms the Decrease in the electrical properties of the photoreceptor under accelerated aging conditions due to heat or during storage

609846/0870 - 5 -

prevent preservation of the photoreceptor at temperatures above room temperature for an extended period of time; and a lower layer of vitreous selenium or an arsenic-selenium alloy or an arsenic-selenium alloy mixed with halogen. This Multi-layer photoreceptor may be deposited or vapor deposited onto a standard xerographic base material in accordance with known techniques will.

The advantages of the improved photoreceptor of the present invention will be will become apparent upon consideration of the following description of the present invention, particularly when taken in conjunction is taken into account with the accompanying drawings:

1 is a schematic illustration of a cross-sectional view of one of the embodiments of a multilayer xerographic photoreceptor as provided in the present invention;

Fig. 2, 3 and 4 show sensitivity curves, at the beginning and after the accelerated aging by heat, a multi-layered photoreceptor, which has a top layer of arsenic-selenium, a middle layer made of a binary alloy of tellurium-selenium and a base layer an arsenic-selenium alloy doped with a halogen. The middle class does not contain any Arsenic;

Figures 5, 6, 7 and 8 show sensitivity curves of a multilayered Apparatus according to the present invention.

Fig. 1 shows a schematic drawing of one of the embodiments of the present invention consisting of a multilayer xerographic PR. The multi-layered one, i.e. three-layered one Structure is referred to as a "three layer" photoreceptor. The photoreceptor 4 can be self-supporting or can comprise a known carrier element 5, which is either electrical

609846/0870 " ⁶ "

can be insulating or electrically conductive. Preferably, the carrier element 5 is a known electrical carrier such as brass, aluminum, nickel, steel or any other suitable material. The carrier element 5 can be of any known thickness, can be brittle or flexible, and can be of any desired thickness Form, such as a sheet, or film, fabric, plate, cylinder, drum or any other suitable shape. The carrier element can also consist of any other suitable material, such as, for example, metallized Paper, plastic sheets coated with a thin layer of a metal, such as aluminum or copper oxide or made of glass coated with a thin layer of chromium or tin oxide. If desired, the photoreceptor can also be formed on an electrically insulating substrate and with the help of xerographic processes that are in the field the xerography for photoreceptors with insulating backs electrically charged will. As indicated above, element 5 can in some cases be omitted entirely.

Layer 1 can consist of a first layer of vitreous selenium or a vitreous arsenic-selenium alloy. Layer 1 preferably consists of a vitreous arsenic-selenium alloy, which contains up to about 3 wt .-% arsenic. Layer 1 can contain from about 0.1 to about 2.0 weight percent arsenic. In particular contains Layer 1 contains up to about 1% by weight arsenic, and in particular layer 1 contains up to about 0.5% by weight arsenic, with the balance being selenium is. If layer 1 is either vitreous selenium or an arsenic-selenium alloy layer 1 can also contain a halogen additive (dopant). The preferred halogen additive is mainly from chlorine, bromine and iodine. The halogen additive is preferably in concentrations of about 5 parts per million present to about 10,000 parts per million. Layer 1 can be from about 10 to about 300 µ thick, preferably from about 40 to 100 µ thick thick and in particular from about 52.0 to 68.0 µ thick, in very preferred cases the layer is 60 / U thick. * are known

609846/0870 - 7 -

Layer 2, which represents the second or middle layer, can consist of a second layer of vitreous arsenic-tellurium-selenium alloy which covers the first layer 1. Middle layer 2, which is the second layer of vitreous arsenic-tellurium-selenium alloy, can contain from about 0.1 to about 40.0% by weight arsenic and from about 1.0 to about 50.0% by weight tellurium and from about 50.0 to 90.0 weight percent selenium. Preferably, the arsenic-tellurium-selenium alloy of layer 2 contains from about 3.0 to about 5.0 weight percent arsenic and from about 15.0 to about 25.0 weight percent tellurium, the remainder being selenium is formed. It has been found that an arsenic content in the range of about 3.0 to 5.0 weight percent in the alloy of layer 2 is particularly desirable. The most preferred composition of layer 2 is about 4.0% by weight arsenic, about 20.5% by weight tellurium, and about 75.5% by weight selenium. It is important and thus the critical point, that layer contains arsenic 2, since the presence of arsenic causes the photoreceptor its electrical properties in accelerated aging by heat or at elevated temperatures, ie, above 46.1 ⁰ C (115 ° F ) maintains.

The middle layer 2 may preferably also comprise a glassy arsenic-tellurium-selenium alloy having a halogen additive. The halogen additive can be made of the same material and have the same concentration as was described for layer 1.

Layer 2 can be from about 0.1 to about 2.0 , n thick, preferably from 0.1 to 1.0, u thick, in particular from 0.1 to 0.1, i / U thick; the preferred thickness is 0.3, u.

Layer 3, i.e. the top or third layer, consists of a layer made of a vitreous arsenic-selenium alloy, which on Layer 2 is arranged. Layer 3 preferably consists of one Arsenic-selenium alloy containing from about 0.1 to 40.0% by weight of arsenic and in particular from about 0.1 to 5.0% by weight of arsenic and in particular contains from about 0.1 to about 3.0 weight percent arsenic, wherein

609846/0870

the rest consists of selenium. Layer 3 can be doped with a halogen. The halogen addition can be the same material and can be used in the same concentration as described for layers 1 and 2.

Layer 3 can be from about 0.1 to about 5.0 µ thick, in particular from about 1.0 to 4.0 / U thick, and preferably has a thickness of about 3.0, u.

Element 4 can comprise a photoconductive element. The element can have a carrier 5 and a first layer 1 made of vitreous Have selenium, which supports 5 covered. The cover layer 1 can be a second layer 2 made of a vitreous arsenic-tellurium-selenium alloy be. Cover layer 2 can be a third layer made of a vitreous arsenic-selenium alloy. The first layer can be from about 40 to 100, u thick and can contain up to about 1.0 wt .-% arsenic, in particular up to about 0.5 wt .-% arsenic, the remainder being selenium. The second layer 2 of arsenic-tellurium-selenium can be from about 0.1 to about 1.0 µm thick

and can be up to about 40.0 wt% and up to 50.0 wt% tellurium, preferably up to about 5.0 wt% arsenic and up to contain about 25.0% by weight tellurium, the remainder being selenium. The third layer 3 of the arsenic-selenium alloy can be from about 0.1 to about 5.0 / U thick and can be up to about 40.0% by weight arsenic, preferably up to about 5.0% by weight arsenic, the remainder being selenium. All three layers, i.e. layers 1, 2 and 3 can be doped with a halogen. Preferably, a halogen is selected, such as chlorine, bromine or Iodine at a preferred concentration of from about 5 parts per million to about 10,000 parts per million.

When substrate 5 is electrically conductive, it is generally during charging in known xerographic devices grounded to facilitate the application of an even layer of charge to layer 3. Charging PR 4 is easily achieved in a variety of ways, for example * arsenic

609846/0870 - 9 -

wisely by rubbing layer 4 with a soft brush or with fur or in particular by using corona charging methods and devices such as those described by Vyverberg in U.S. Patent 2,836,725 and by Walkup in U.S. Patent 2,777 to be discribed. Charging is generally carried out in the absence of actinic rays, i.e. rays that affect the photoreceptor 4 make electrically more conductive in the parts hit by rays. After charging, the next step can be taken exposing the photoreceptor according to known xerographic techniques be in the form of a pattern of electromagnetic actinic rays. , being the areas struck by the light of the photoreceptor 4 are discharged, in contrast to the exposed areas, so that a latent electrostatic image is formed on or in the surface of the photoreceptor.

Other Methods of Forming a Latent Image on the Photoreceptor 4 are known and consist in the fact that such a charge pattern is first applied to a separate photoconductive insulating layer is formed according to known xerographic reproduction methods, and then this charge pattern on the layer 3 of the photoreceptor 4 is transferred by bringing both layers into close contact, and then a strike through process as used, for example, by Carlson in US Pat. No. 2,982,647 and by Walkup in US Pat. No. 2,825,814 and US Pat

2 9 37 943 has been described. Also, charge patterns, the selected shaped electrodes, or combinations of electrodes are formed on layer 3 by the "TESI" discharge technique as described by Schwertz in the US Pat

3,023,731 and 2,919,967 or by methods such as those described by Walkup in U.S. Patents 3,001,848 and 3,001,849, and also by preferred electron beam recording techniques which are well known and those of Glenn in U.S. Patent 3,113,179 be described, for example.

The latent image is then made generally visible, i.e. it is developed by applying the latent image with finely divided,

609846/0870 -10-

marked material, which is generally electrostatically charged with a polarity that corresponds to the polarity of the latent electrostatic image is opposite, is brought into contact by placing such a material in surface contact with layer 3 is brought so that the material is held thereon in an image pattern similar to that of the latent image is equivalent to.

Any suitable development system can be used to develop the latent images on the photoreceptors of the present invention and there are very many such systems in the literature.

For example, the system of cascade development has received widespread commercial attention and application; it exists generally made of a developer material that flows according to gravity and consists of two components of the type, as described by Walkup in U.S. Patent 2,638,416, the material being over the latent image bearing PR flows. The two components consist of an electroscopic powder called "toner" and a granular one Material called "carrier material" that mixes triboelectric charges of opposite polarity to win. During development, the toner component, which is charged generally opposite to that of the latent image, is deposited on the electrostatic latent image so that it makes the image visible.

Other typical development systems are, for example, magnetic brush development, as described in the following patents, for example, by Giamo in U.S. Patent No. 2,930,351j to Simmons et al in U.S. Patent 2,791,949; by Hall et al in U.S. Patent 3,015,305; Liquid development e.g. by Carlson in U.S. Patents 2,221,776, 2,551,582,

2,690,394; 2,761,416 and 2,928,575 to Thompson in U.S. Patent

3,064,622 to Gundlach in U.S. Patents 3,068,115 and 3,084,043 and Metcalfe in U.S. Patents 2,907,674, 3,001,888, 3,032,432 and 3,078,231; Skid development, e.g. by Mayo in the US PS

609846/0870

- 11 -

261562A

- 11 2 895 847 and others.

Once the development is complete, it can do little Adhering toner image can be transferred to another carrier surface, on which it is then applied by solvent vapors, heat or other suitable measures can be fixed to make the image usable indefinitely, or the loose powder image can be fused directly onto the photoreceptor, either as a result of development or by a subsequent separate one Procedural integrity.

Fig. 2 shows a sensitivity curve of a three-layer photoreceptor element with a topmost layer about 3.0µ thick and composed of an alloy of about 0.5 wt% arsenic and 99.5 wt% selenium, one Middle layer of about 0.3 / U thickness, which consists of an alloy of about 25 wt .-% tellurium and 75 wt .-% selenium and a lower layer about 60.0 , n thickness, which consists of an alloy of about 0 , 33 wt .-% arsenic and 99.66 wt .-% selenium, doped with 20 parts chlorine per million. As indicated, this photoreceptor does not contain arsenic in the middle or second layer. This element is exposed to the action of a helium-neon laser which emits activating rays at 6328 8. The surface potential in volts is given on the left-hand side of this curve. The relative irradiation with laser energy is given in microwatts below the curve. The above element was first charged to a surface potential of 800 volts and gradually discharged by progressively irradiating the photoreceptor with larger amounts of activating rays, measured in microwatts, using a helium-neon laser emitting activating rays at 6328 8. After a number of exposures the element was severely discharged, ie to about 110 volts. The original sample was then subjected to accelerated aging by exposure to heat at 51.7 ° C (125 ° F) for 7 days. The element was charged again to a surface potential of 800 volts and step-

609846/0870 - 12 -

wise to the action of activating rays under the same Conditions as originally exposed. After the same number of exposures and under the same conditions as originally were used, the element was discharged to approximately 700 volts. These results are in the upper curve in FIG. 2 specified.

3, which likewise shows a sensitivity curve of a three-layer element which is similar to the element which was described in connection with FIG. 2 and which also has no arsenic in the middle layer. Eas element was first irradiated, then subjected to accelerated aging by 3-day heating at 51.7 ⁰ C (125 ° F) and then subjected to accelerated aging by heating for 7 days at 51.7 ⁰ C (125 ° F).

Fig. 4 illustrates a similar element, as indicated in Fig. 3 and under the same conditions, except that the element is first irradiated and then subjected to accelerated aging by 7-day exposure to heat of 51.7 ⁰ C (125 ° F).

Fig. 5 shows standard sensitivity curves of an inventive Element, the values determined at the beginning and after 7 days of accelerated aging by exposure to heat of 51.7 C (125 F) became. The element shown in Fig. 5 is an element which has a top layer of about 3.0 µ thick consisting of a Alloy of 0.5 wt .-% arsenic and 99.5 wt .-% selenium consists, a Middle layer of about 0.65, u thickness, made of a ternary alloy from about 3.5 wt .-% arsenic and 20.5 wt .-% tellurium, the remainder being selenium, and a bottom layer of about 60, u thickness, made of an alloy of about 0.33 wt .-% Arsenic and 99.66 wt .-% selenium, which with 20 parts of chlorine is doped per million. The element was first charged to a surface potential of 800 volts, then through Irradiation with activating rays, i.e. microwatts from one

609846/0870 - 13 -

Helium-neon laser that emits activating rays at 6328 8, unload. The element was first discharged to a surface potential of about 75 volts. After an accelerated Aging by heating at 51.7 ° C (125 ° F) for 7 days, the same element was also brought to a surface potential discharged from about 75 volts.

Fig. 6, 7 and 8, in which the element / both in Fig., As well as in Fig. 8, it was heat-aged and test values at the beginning, after three days at 51.7 ⁰ C (125 ° F) and read after seven days at 51.7 ° C (125 ° F). As FIGS. 6, 7 and 8 indicate, none of the elements loses any significant amount of their sensitivity or electrical properties after an accelerated aging process under the action of heat. The same results were obtained as shown in Figure 7, except that the element in Figure 7 was tested initially and after accelerated aging by heating to 51.7 ° C (125 ° F) for 7 days .

It has been found that when using a three-layer photoreceptor, that of a top layer made of an arsenic-selenium alloy, a second or middle layer made of a selenium-tellurium alloy and a third or lowermost layer consists of vitreous selenium or arsenic-selenium, the electrical properties this three-layer photoreceptor after accelerated aging by exposure to heat for an extended period of time at elevated temperatures, such as above 46.1 C (115 F), deteriorate significantly. It is believed, that part of the tellurium in the middle layer of this three-layer photoreceptor from the middle layer into the adjacent upper and lower layers of the photoreceptor migrate, causing a reduction in the electrical properties of the photoreceptor comes. In contrast, it has been found that when arsenic is added to the middle layer of the three-layer photoreceptor, one ternary alloy of arsenic-tellurium-selenium was used as the middle layer, reducing the electrical properties

609846/0870 - 14 -

by accelerated aging under the influence of heat over a longer period of time, as may be for example above 46.1 ⁰ C (115 ° F), prevents ie at temperatures that are above room temperatures. It is believed that the addition of arsenic prevents the tellurium from migrating out of the middle layer so that the maximum capacity of the three layer photoreceptor is substantially increased.

The three-layer photoreceptor of the present invention can be made by any suitable method. A typical procedure is for example vacuum evaporation, in which each photoconductive layer is successively applied to the corresponding base material is vaporized. In this process, the bottom or first layer of selenium or an arsenic-selenium alloy, the middle or second layer of an arsenic-tellurium-selenium alloy and the top or third layer of one Arsenic-selenium alloy in separate process steps under vacuum conditions, which vary between about 10 ~ to 10 ~ Torr, evaporates. In another embodiment of this method the three photoreceptor layers are continuously vacuum evaporated, i.e., one after the other, in the same vacuum chamber, without breaking the vacuum, by successively three separate sources of selenium or selenium-arsenic for that bottom or first layer, made of arsenic-tellurium-selenium for the middle or second layer and arsenic-selenium for the top or third layer.

Another typical process is, for example, coevaporation, in which the appropriate amount of material for each of the alloy layers is placed in separate heated crucibles kept under vacuum conditions with a source temperature of each alloy component being controlled, so that the appropriate percentage of the alloy is obtained. This process is described in U.S. Patent 3,940,903.

Another typical method for evaporation is for example

609846/0870 -15-

wise evaporation under relaxation and vacuum conditions that are similar to those in coevaporation, wherein a powder mixture such as arsenic, tellurium and selenium is selectively mixed into one heated crucible, which is kept at a temperature of about 400 ° C to 600 ° C. The fumes emitted by the When this mixture is heated, it is placed on top of a substrate, which is fixed above the crucible, vaporized.

In all the above methods is desired that the substrate on which the photoconductive material is vapor-deposited, being maintained at a temperature of about 50 ⁰ C to about 80 ⁰ C. If necessary, a water-cooled roller or other suitable cooling device can be used to guarantee a constant substrate temperature. In general, a selenium base or massive layer thickness of about 60 µ is obtained if evaporation is carried out for about an hour at a vacuum of about 5 10 Torr
is carried out.

about 5 χ 10 ~ Torr and at a crucible temperature of about 280 ° C

The following U.S. patents to Ullrich (U.S. Patent 2,803,542), Mayer et al (U.S. Patent 2,822,300), Dessauer et al (U.S. Patent 2,901,348), Schaffert (US Pat. No. 2,963,376), Bixby (US Pat. No. 2,970,906) and Blakney et al (US Pat. No. 3,077,386) describe vacuum evaporation processes, all of which are used to form alloy layers in accordance with the present invention Invention are suitable. The crucibles used for evaporation of the photoreceptor layers can be made from any inert material, such as quartz, molybdenum, stainless steel, which is coated with silicon monoxide or any other equivalent material. The selenium to be evaporated or the selenium alloy to be evaporated is in a Temperature between its melting point and boiling point evaporates.

The photoreceptor of the present invention has the ability to generate electrical Properties even under the conditions of accelerated aging by the influence of heat or during a long period

609846/0870 - 16 -

Period of time at temperatures above room temperature, ie at temperatures above 46.1 ⁰ C (115 ° F). The photoreceptor of the present invention has also improved dark decay properties. In addition, the sensitivity curves and the increase in the mottling index, ie the gradual charging of the photoreceptor, show that the photoreceptor according to the invention retains its electrical properties under the conditions of accelerated aging by the influence of heat or for a long period of time at temperatures above room temperature, ie above temperatures of 46.1 C (115 ° F), hardly loses. The mottling indices clearly show that the photoreceptor according to the invention after accelerated aging by the influence of heat has essentially the same sensitivity, ie electrical properties, as before the treatment, ie originally.

If a photoreceptor does not have the ability to be evenly charged and to hold a surface potential evenly, it is not a photoreceptor for use in cycling. The photoreceptor of the present invention has excellent and uniform charging properties and has the ability to uniformly maintain a surface potential. Three-layer photoreceptors without arsenic in the middle or second layer, ie a middle layer made of arsenic-tellurium-selenium, lose their ability to be evenly charged and a uniform surface potential under accelerated aging conditions due to the influence of heat or over a longer period of time maintain elevated temperatures, that is, at temperatures above 46.1 ⁰ C (115 ° F).

The following examples specifically define the present invention with regard to the method of making a three-layer photoreceptor element according to the present invention. Those given in the description in the examples and claims Percentages relate to weight, unless stated otherwise. The examples given below are intended to the various preferred embodiments for manufacture

609846/0870 - 17 -

a three-layer photoreceptor. The photoreceptor alloying elements, which were described in the description and examples, i.e. arsenic, tellurium and selenium are all xerographic grade High purity materials (arsenic and selenium 99.999 wt% purity and tellurium 99.99 wt% purity), as they can be obtained from Canadian Copper Refiners,

example 1

An oxidized aluminum substrate, i.e. an aluminum roller with a thin coating of aluminum oxide, approximately 8,638 cm (3 3/8 in inch) in diameter and 26.29 cm (10 3/8 inches) long is placed in a vacuum chamber. A starting alloy for the first or bottom layer of the three-layer photoreceptor is made by adding elemental selenium spheres about 0.1524 cm (1/16 inch) to 0.457cm (3/16 inch) in diameter in a silica-coated stainless steel evaporator boat will. The evaporation boat is located approximately 6 inches below the surface of the platen.

A starting alloy for the second or middle layer of the Three layer photoreceptor is made by taking pellets about 0.1524 cm (1/16 inch) to 0.457 cm (3/16 inch) in diameter elemental arsenic, tellurium and selenium in a ratio of 20.5% by weight tellurium, 4.0% by weight arsenic and 75.5% by weight selenium in one second, silicon-coated stainless steel boat weighed in which will be placed next to the first silicon coated stainless steel boat.

A base alloy for the third or top layer of the The three-layer photoreceptor is made by placing pellets about 0.88 cm (3/8 inch) to 1.27 cm (1/2 inch) in diameter, elemental arsenic and selenium in a ratio of 0.5% by weight, arsenic and 99.5% by weight selenium in a chromium-II-oxide or chromium-III-oxide boat which in addition to the first two with silicon

609846/0870

oxide coated stainless steel boats. Each boat is directly connected to a source of electrical power, which is designed so that the temperature of the respective boats can be controlled. The board is then turned on Vacuum of about 10 torr is evacuated while the roller is rotated at about 10 revolutions per minute. The first boat to do the Contains selenium, is heated to a temperature of about 310 C. over a period of about 35 minutes to form a layer of vitreous selenium about 60 µ thick on the Form aluminum roller. The source of electricity for the first boat, which contains the selenium, is maintained around any deposit of the other materials that are vaporized on the boat to prevent. Without breaking the vacuum, the roller speed increases increased to about 30 revolutions per minute. The temperature of the second boat that made the arsenic-tellurium-selenium alloy contains, is gradually increased to a temperature of 450 ° C over a period of about 8.5 minutes and held at that temperature for about 1 minute to form an arsenic-tellurium-selenium alloy coating of about 0.3, u Thickness to form on the first or bottom selenium layer. The power source connected to the second boat is retained. The roller speed is set to 30 revolutions per minute.

The temperature of the third boat that made the arsenic-selenium alloy contains, is gradually increased to 350 ° C over a period of about 10 minutes and about 7 minutes at this Maintained a 3.0, u thick surface layer of an arsenic-selenium alloy on the middle layer of the temperature To form arsenic-tellurium-selenium alloy. At the end of this period, the vacuum chamber is cooled to room temperature, the vacuum interrupted and the roller containing the three-layer photoconductor removed from the chamber.

Example 2

The roller containing the three-layer photoreceptor according to Example 1

609846/0870

- 19 -

is then raised to a positive potential by the method described by Carlson in US Pat. No. 2,588,699 loaded. The corona charge unit is held at approximately 7,500 volts, with the roller at a pick-up potential of charges about 850 to 900 volts. An analog signal obtained from a written document is converted into a Helium-neon laser given the activating rays at around 6328 Ä, with the intensity of the laser in accordance is modulated with the video information for the reel. This way the reel is presented with a pictorial representation which forms an electrostatic latent image thereon. This process is described by Mason in U.S. Patent 3,870,816. The roller that bears the electrostatic latent image is then developed by using an electroscopically marked material is applied over the photoconductive surface of the roller by the cascade method. The developed image will transferred to a sheet of paper and melted by the action of heat to make it permanent. The final image shows a good resolution, high density and is an excellent copy of the original.

Example 3

A roller as made in Example 1 is placed in a Xerox X200 fax machine and a line copy is placed in one Black and white original image on known printing paper is produced. This image also shows good resolution and high density.

Example 4

A roller as it was produced in Example 1, and according to Example 1 is charged with a black-on-white line copy original image that was printed on known printing paper is present, exposed. The source of exposure is a 15 watt

609846/0870 -20-

Cold white fluorescent lamp used by General Electric No. F15T8CW - to create a latent electrostatic image create. The roller, which has the electrostatic latent image, is then developed by an electroscopically marked Material is added over the photoconductive surface of the roller using the cascade method. The developed image will transferred to a sheet of paper and brought to the melt by the action of heat in order to make it permanent. That The final image shows good resolution and high density and is an excellent copy of the original.

- 21 -

609846/0870

Claims (1)

- 21 claims Multi-layer photoreceptor elements consisting of a) a first layer of vitreous selenium; b) a second layer made of a vitreous arsenic-tellurium-selenium alloy, which covers the first selenium layer, and c) a third layer made of a vitreous arsenic-selenium alloy, which covers the second layer of the arsenic-tellurium-selenium alloy. 2. Element according to claim 1, characterized in that g e k e η η - draw is thick. draws that the first layer is from about 40.0 to 100.0 .u 3. Element according to claim 2, characterized in that the first layer from about 52.0 to 68.0 / is thick. 4. Element according to claim 3, characterized in that the first layer is about 60 u thick. 5. Element according to claim 1, characterized in that the second layer from about 0.1 to about 1.0, u is thick. 6. Element according to claim 5, characterized in that g e k e η η - draw is thick. indicates that the second layer is from about 0.1 to 0.5, u 7. Element according to claim 6, characterized in that g e k e η η draws that the second layer is 0.3, u thick. 8. Element according to claim 1, characterized in that g e k e η n- draw is thick. draws that the third layer from about 0.1 to 5.0 / 609846/0870 " ²² " 9. Element according to claim 8, characterized in that g e k e η η - drawing is thick. indicates that the third layer is from about 1.0 to 4.0, u 0O. Element according to Claim 9, characterized in that the third layer is about 3.0 , n thick. 11. Element according to claim 1, characterized in that the first layer of vitreous selenium contains up to about 3.0% by weight arsenic. 12. Element according to claim 1, characterized in that the first layer of vitreous selenium contains up to about 1.0% by weight arsenic. 13. Element according to claim 1, characterized in that g e k e η η ζ It is possible that the first layer of vitreous selenium contains up to about 0.50% by weight arsenic. 14. Element according to claim 1, characterized in that the first layer of vitreous selenium contains a halogen additive. 15. Element according to claim 14, characterized in that that the halogen additive is selected from the group consisting of chlorine, iodine and bromine. 16. Element according to claim 14, characterized in that the halogen additive in a concentration amount from about 5 parts per million to about 10,000 parts per million is present. 17. Element according to claim 1, characterized in that the second layer of the arsenic-tellurium-selenium Alloy from about 0.1 to about 40.0% by weight arsenic and contains from about 1.0 to about 50.0 weight percent tellurium. 609846/0870 " ²³ 18. Element according to claim 1, characterized in that the second layer consists of an arsenic-tellurium-selenium alloy contains from about 3.0 to about 5.0 weight percent arsenic and from about 15.0 to about 25.0 weight percent tellurium. 19. Element according to claim 1, characterized in that the second layer consists of the arsenic-tellurium-selenium alloy contains about 4.0% by weight arsenic and about 20.5% by weight tellurium. 20. Element according to claim 1, characterized in that the second layer consists of the arsenic-tellurium-selenium alloy contains a halogen additive. 21. Element according to claim 1, characterized in that g e k e η nzeichne t that the third layer of the arsenic-selenium alloy contains from about 0.1 to about 40.0 wt .-% arsenic. 22. Element according to claim 1, characterized in that the third layer consists of the arsenic-selenium alloy contains from about 0.1 to about 5.0 weight percent arsenic. 23. Element according to claim 1, characterized in that g e k e η η draw t that the third layer of the arsenic-selenium alloy contains about 0.1 to about 3.0 wt .-% arsenic. 24. Element according to claim 1, characterized in that the third layer consists of the arsenic-selenium alloy contains a halogen additive. 25. Photoconductive elements consisting of a) a carrier material; b) a first layer of vitreous selenium which covers the carrier material; c) a second layer made of a vitreous arsenic-tellurium-selenium alloy, which covers the first layer of selenium; and 609846/0870 - 24 - d) a third layer made of a vitreous arsenic-selenium alloy, covering the second arsenic-tellurium-selenium alloy. 26. Element according to claim 25, characterized in that the first layer of vitreous selenium
from about 40.0 to about 100.0 µ thick. 27. Element according to claim 25, characterized in that the second layer of arsenic-tellurium-selenium · of about 0.1 to about 1.0 µ thick. 28. Element according to claim 25, characterized in that the third layer of arsenic-selenium of about 0.1 to about 5.0 µ thick. 29. Element according to claim 25, characterized in that the first layer of vitreous selenium
contains up to about 1.0% by weight arsenic. 30. Element according to claim 25, characterized in that the first layer of vitreous selenium
contains up to about 0.5% by weight arsenic. 31. Element according to claim 25, characterized in that the carrier material consists of an electrically
conductive material. 32. Element according to claim 25, characterized in that the second layer consists of the arsenic-tellurium-selenium alloy consists of up to about 40.0% by weight arsenic and up to about 50.0% by weight tellurium. 33. Element according to claim 25, characterized in that the second layer of the arsenic-tellurium-selenium alloy up to about 5.0 wt .-% arsenic and up to about
Contains 25.0% by weight tellurium. 609846/0870 " ²⁵ - 34. Element according to claim 25, characterized in that the third layer consists of the arsenic-selenium alloy Contains up to 40.0% by weight arsenic. 35. Element according to claim 25, characterized in that the third layer consists of the arsenic-selenium alloy contains up to about 5.0% by weight arsenic. 36. Element according to claim 25, characterized in that the first layer of vitreous selenium contains a halogen additive. 37. Element according to claim 25, characterized in that the second layer consists of the arsenic-tellurium-selenium alloy contains a halogen additive. 38. Element according to claim 25, characterized in that the third layer consists of the arsenic-selenium alloy contains a halogen additive. 39. Photoconductive element consisting of a) a conductive support; b) a 40 to 100 .mu.m thick first layer of vitreous arsenic-selenium, which contains from about 0.1 to 2.0 wt .-% arsenic; c) a 0.1 to 1.0 , n thick second layer of a vitreous arsenic-tellurium-selenium alloy containing from about 15.0 to 25.0% by weight of tellurium and from about 3.0 to 5, Contains 0% by weight arsenic, and which covers the first layer of arsenic-selenium, and d) a 0.1 to 5.0, u thick third layer of a vitreous Arsenic-selenium alloy which contains from about 0.1 to 3.0% by weight of arsenic, and which has the second layer of the arsenic-tellurium-selenium alloy covered. 40. Element according to claim 39, characterized in that the first layer of the vitreous arsenic 609846/0870 _{0 (} , 261S624 Selenium alloy is doped with a halogen. 41. Element according to claim 40, characterized in that the third layer consists of the vitreous Arsenic-selenium alloy is doped with a halogen. 42. Element according to claim 41, characterized in that the second layer consists of the vitreous Arsenic-tellurium-selenium alloy is doped with a halogen. 43. An imaging process, characterized in that one a) provides a photoconductive element which consists of a conductive substrate coated with a first layer of vitreous selenium of about 40 to 100 , u. Thickness, a second layer of a vitreous arsenic-tellurium-selenium alloy of about 0.1 to 1.0, u thickness, which covers the first layer of selenium, and a third layer of a vitreous arsenic-selenium alloy of about 0.1 to 5.0 µ thickness covering the layer of arsenic-tellurium-selenium; b) forming an electrostatic latent image on the element; and c) develops the image. 44. The method according to claim 43, characterized in that the first layer of vitreous selenium Contains arsenic. 45. The method according to claim 44, characterized in that the first layer consists of the vitreous arsenic-selenium alloy is doped with a halogen. 46. A method for forming an electrostatic latent image, characterized in that one a) creates a photoconductive element, which is a conductive carrier material, a first layer of vitreous selenium 609846/0870 -27- from about 40 to 100, u thickness, which covers the carrier material, a second layer of a vitreous arsenic-tellurium-selenium alloy of about 0.1 to 1.0 / U thickness, which forms the first selenium layer covered, and a third layer of a vitreous arsenic-selenium alloy of about 0.1 to 5.0, u thickness, which the second layer of the arsenic-tellurium-selenium alloy covered; b) electrostatically charges the element substantially uniformly; and c) the element with a pattern of activating electromagnetic Rays exposed to form an electrostatic latent image. 47. The method according to claim 46, characterized in that the first layer of vitreous selenium which contains arsenic. 48. The method according to claim 47, characterized in that that the first layer of the vitreous arsenic-selenium alloy is doped with a halogen. 609846/0870