MXPA98002476A - Coating compositions for revel electrodes - Google Patents

Abstract

The present invention relates to a method apparatus for reducing accumulation of organic pigment from the surface of an electrode member in a developing unit of an electrotoxic printing apparatus, by providing a coating composition comprising a lubricating polymer and a material inorganic, at least one portion of the electro member

Description

COATING COMPOSITIONS FOR DEVELOPMENT ELECTRODES BACKGROUND OF THE INVENTION The present invention relates to methods, processes and apparatus for developing images and more specifically to electrode members for use in a developing unit in electrophotographic copying or printing machines, or in digital imaging systems such as Xerox Corporation machines 220 and 230. Specifically, the present invention relates to methods and apparatus wherein at least a portion of an electrode member for developing unit is coated with a coating composition and in embodiments, a low coating. surface energy. In embodiments, the history of the electrode member, the cushioning and / or accumulation of organic pigment are controlled or reduced. In general, the electrophotographic printing or copying process includes charging a photoconductive member to a substantially uniform potential in order to sensitize its photoconductive member. The loaded portion of the photoconductive member is exposed to a light image of an original document that is reproduced. This records a latent electrostatic image on the photoconductive member. After the latent electrostatic image is recorded in REF: 26853 the photoconductive member, the latent image is revealed by carrying a developer in contact with it. Two-component and one-component developers are commonly used. A typical two-component developer comprises magnetic carrier granules having triboelectrically adhered organic pigment particles. A single component developer typically comprises organic pigment particles. Particles of organic pigment are attracted to the latent image by forming an image of organic pigment powder in the photoconductive member. The image of organic pigment powder is subsequently transferred to a copy sheet. Finally, the organic pigment powder image is heated to permanently fuse to the copy sheet in image configuration. One type of single-component developing system is a debugging system that uses a donor roller to transport organic pigment charged to the development zone. At least one and preferably a plurality of electrode members are closely spaced to the donor roll in the developing zone. An AC voltage (AC) is applied to the electrode members that form a cloud of organic pigment in the developing zone. The electrostatic fields generated by the latent image attract the organic pigment of the organic pigment cloud to reveal the latent image. Another type of a two-component development system is a development system without hybrid debugging, which employs a developer roller with magnetic brush to transport organic pigment that has triboelectrically adhering organic pigment. A donor roller is also used in this configuration to transport charged organic pigment to the developing zone. The donor roller and the magnetic roller are electrically derived from each other. The organic pigment is attracted to the donor roller from the magnetic roller. The electrically derived electrode members detach the organic pigment from the donor roller, forming a cloud of organic pigment powder in the developing zone, and the latent image attracts the organic pigment particles. In this way, the latent image recorded on the photoconductive member is revealed with organic pigment particles. Various types of development systems have previously been employed as illustrated by the following: US Pat. No. 4,868,600 issued to Hays et al., The subject of which is hereby incorporated by reference, describes an apparatus wherein a donor roller transports organic pigment to an opposite region from a surface on which a latent image is recorded. A pair of electrode members are placed in the space between the latent image surface and the roller and are electrically derived to release organic pigment from the donor roll to form a cloud of organic pigment. The organic pigment detached from the cloud reveals the latent image. The U.S. Patent No. 4No. 984,019 issued to Fol ins, the subject matter of which is hereby incorporated by reference, discloses a developing unit having a donor roller with adjacent electrode members disposed in a developing zone. A magnetic roller transports developer material to the donor roller. Particles of organic pigment are attracted from the magnetic roller to the donor roller. When the developing unit is inactivated, the electrode members are vibrated to remove contaminants. The U.S. Patent No. 5,124,749 issued to Bars, the subject matter of which is hereby incorporated by reference, describes an apparatus in which a donor roll advances organic pigment to an electrostatic latent image recorded on a photoconductive member wherein a plurality of electrode wires are place in the space between the donor roller and the photoconductor member. The wires are electrically derived to detach the organic pigment from the donor roller in order to form a cloud of organic pigment in the space between the electrode wires of the electrode and the photoconductive member. The cloud of dust reveals the latent image. A damping material is coated on a portion of the electrode wires in the position of connection to the electrode support members, for the purpose of damping the vibration of the electrode wires. The Patents of the U.S.A. Nos. 5,300,339 and 5,448,342 both to Hays et al., The subject of which of which is hereby incorporated by reference in their entirety, describe a roller for transporting coated organic pigment containing a core with a coating. The U.S. Patent No. 5,172,170 issued to Hays et al., The subject of which is hereby incorporated by reference in its entirety, discloses an apparatus in which a donor roller advances organic pigment to an electrostatic latent image recorded on a photoconductive member. The donor roll includes a dielectric layer disposed relative to the circumferential surface of the roll between adjacent grooves. Primarily because the adhesion force of the organic pigment particles is greater than the detachment force generated by the electric field of the electrode members in the developing zone, an organic pigment tends to accumulate in the electrode members. The accumulation of the organic pigment particles in the wire member causes a non-uniform development of the latent image, resulting in printing defects. This problem is aggravated by fines of organic pigment and any organic pigment components, such as high molecular weight, entangled and / or branched components, and disruptive discharge between the wire member and the donor roll. A specific example of organic pigment contamination results from revealing a document having solid areas that requires a large concentration of organic pigment to be deposited at a particular position in the latent image. Areas of the electrode member corresponding to high performance or areas of high concentration of organic pigment, tend to include higher or lower accumulation of organic pigment due to this different exposure to the yield of organic pigment. When subsequently trying to reveal another different image, the accumulation of organic pigment in the electrode member can lead to differential development of the newly developed image, which corresponds to areas of greater or lesser accumulation of organic pigment of the electrode members. The result is a band obscured or lightened in the position corresponding to the solid area of the previous image. This is particularly evident in areas of intermediate density, since these are the areas most sensitive to differences in development. These particular image defects caused by accumulation of organic pigment in the electrode wires in the developing zone, they are referred to as wire story. Wire contamination results when fused organic pigment is formed between the electrode member and the donor member due to organic pigment fines and any organic pigment components, such as high molecular weight, entangled and branched components, and the disruptive stress of the pigment. voltage between the wire member and the donor roller. The history of the wire is a change in the ability of, revealed because the pigment components or the organic pigment, adhere to the upper part of the electrode member. Accordingly, there is a specific need for electrode members in the developing zone of a developing unit of an electrophotographic copying or printing machine, which provide a diminished tendency for accumulation of organic pigment, in this way to decrease the history primarily of wire and wire contamination, especially in high performance areas, and decrease the production of unwanted surface static charges from which contaminant may not be released. One possible solution is to change the electrical properties of the wire. However, attempts to decrease the build-up of organic pigment in the developing wire by changing its electrical properties may result in interference with the function of the wire and its ability to produce the formation of the organic pigment dust cloud. Therefore, there is a specific need for electrode members that have a decreased tendency to accumulate organic pigment and also retain their electrical properties in order to avoid interference with their operation. There is also an additional need for electrode members having superior mechanical properties including durability against severe wear of the receiving electrode when repeatedly brought into contact with hard rotating donor roller surfaces. SUMMARY OF THE INVENTION Examples of objects of the present invention include: An object of the present invention is to provide an apparatus for reducing accumulation of organic pigment from electrode members in the developing zone of a developing unit in an electrophotographic printing apparatus. with many of the advantages indicated here. Another object of the present invention is to provide an apparatus for reducing adhesion of organic pigment to electrode members. Another object of the present invention is to provide an apparatus comprising electrode members having an interior surface energy. Still another object of the present invention is to provide an apparatus comprising electrode members having increased mechanical strength. Still another object of the present invention is to provide an apparatus comprising electrode members having superior electrical properties. The present invention has as an additional objective to provide an apparatus comprising electrode members having smooth or uniform areas. Many of the above objects have been met or satisfied by the present invention, in embodiments, including: an apparatus for revealing a latent image recorded on a surface, comprising: wire supports; a donor member spaced from the surface and adapted to transport organic pigment to an opposite region of the surface; an electrode member placed in the space between a surface and the donor member, the electrode member is spaced closely from the donor member and is electrically derived to release organic pigment from the donor member, thereby allowing the formation of a cloud of organic pigment of the space between the electrode member and the surface with the organic pigment detached from the cloud of organic pigment that reveals the latent image, wherein opposite end regions of the electrode member are connected to wire supports adapted to support the end regions opposites of the electrode member; and a coating composition at least in a portion of unconnected regions of the electrode member, wherein the coating composition comprises a polymer, a lubricant and an inorganic material. Modalities further include: an electrophotographic process comprising: a) forming a latent electrostatic image on a charge retentive surface, b) applying organic pigment in the form of a cloud of organic pigment to the latent image, to form an image revealed in the load retentive surface, wherein the organic pigment is applied using a developing apparatus comprising wire supports; a donor member spaced on the surface which is adapted to transport organic pigment to an opposite region on the surface; an electrode member placed in the space between the surface and the donor member, the electrode member is spaced closely from the donor member and is electrically derived to release organic pigment from the donor member thus allowing the formation of a cloud of organic pigment in the space between the electrode member and the surface with organic pigment evolved from the organic pigment cloud revealing the latent image, wherein opposite end regions of the electrode member are connected to the wire supports adapted to support the opposite end regions of the electrode member; and a low surface energy coating composition at least in a portion of unconnected regions of the electrode member, wherein the coating composition comprises a polymer, a lubricant and an inorganic material; c) transferring the organic pigment image from the charge retentive surface to a substrate; and d) fixing the organic pigment image to the substrate. The present invention provides electrode members that in modalities have a diminished tendency to accumulate organic pigment and that also in modalities, retain their electrical properties in order to avoid interference with their operation. The present invention further provides electrode members which, in embodiments, have superior mechanical properties including durability against severe wear to the electrode member when repeatedly brought into contact with surfaces of hard rotating donor rollers. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing aspects of the present invention will be apparent as the following description is advanced with reference to the drawings wherein: Figure 1 is a schematic illustration of an embodiment of a developing apparatus useful in an electrophotographic printing machine . The Fi < Jura 2 is an enlarged schematic illustration of an electrode member and donor roll representing one embodiment of the present invention. Figure 3 is a fragmentary schematic illustration of a developing housing comprising a donor roller and an electrode member from a different angle than that illustrated in Figure 2. Figure 4 is an enlarged schematic illustration of an electrode member supported by mounting means in an embodiment of the present invention. Figure 5 is an illustration of wire contamination and wire history.

DETAILED DESCRIPTION For a general understanding of the features of the present invention a description thereof will be made with reference to the drawings. Figure 1 shows a developing appus that is used in an electrophotographic printing machine such as the one illustrated and described in US Pat. No. 5,124,749 the description of which is hereby incorporated by reference in its entirety. This patent describes the details of the main components of an electrophotographic printing machine and how these components interact. The present application is concentrated in the development unit of the electrophotographic printing machine. Specifically, after a latent electrostatic image has been recorded on a photoconductive surface, a photoreceptor band advances the latent image to the developing station. At the development station, a developing unit processes the latent image that is recorded on the photoconductive surface. Now with reference to Figure 1, in a preferred embodiment of the invention, the developing unit 38 reveals the latent image recorded on the photoconductive surface 10. Preferably, the developing unit 38 includes the donor roller 40 and the electrode member or members of electrode 42. The electrode members 42 are electrically derived from the donor roll 40 to release organic pigment, so as to form a cloud of organic pigment powder in the space between the donor roll 40 and the photoconductive surface 10. The latent image It attracts organic pigment particles from the organic pigment dust cloud that forms an image of organic pigment powder. The donor roller 40 is mounted, at least partially, in the chamber of the developer housing 44. The chamber in the developer housing 44 stores a supply of developer material. The developer material is a developer material of two components of at least carrier granules having particles of organic pigment that adhere to it triboelectrically. A magnetic roller disposed within the chamber of the housing 44 conveys the developer material to the donor roller 40. The magnetic roller 46 is electrically derived from the donor roller, such that the organic pigment particles are attracted from the magnetic roller to the magnetic roller. donor roller. More specifically, the developing unit 38 includes a housing 44 that defines a chamber 76 for storing a supply of two-component developer material (pigment and carrier). The donor roller 40, the electrode members 42 and the magnetic roller 48 are mounted in the chamber 76 of the housing 44. The donor roller can be rotated either in the "for" or "against" direction with respect to the direction of movement of the band 10. In Figure 1, the donor roller 40 is shown rotating in the direction of arrow 68. Similarly, the magnetic roller can be rotated either in the "for" or "against" direction with respect to the direction of the movement of the band 10. In Figure 1, the donor roller 46 is illustrated rotating in the direction of arrow 92. The donor roller 40 is preferably made from anodized aluminum or ceramic. The developing unit 38 also has electrode members 42 that are disposed in the space between the band 10 and the donor roller 40. A pair of electrode members are shown to extend in a direction substantially plel to the longitudinal axis of the donor roller. The electrode members are made from one or more thin stainless steel or tungsten electrode members (ie 50 to 100 μm in diameter) that are spaced closely from the donor roll 40. the distance between the electrode members and the roll The donor is from about 0.001 to about 45 μm, preferably from 10 to about 25 μm, or the thickness of the organic pigment layer of the donor roller. The electrode members are self-spaced from the donor roller by the thickness of the organic pigment in the donor roller. For this purpose, the ends of the electrode members supported by the upper parts of the end-containing blocks also support the donor roller for rotation. The ends of the electrode members are connected in such a way that they are slightly on a tangent to the surface, including the organic pigment layer of the donor structure. Mounting the electrode members in this manner renders them insensitive to roller wear due to their own spacing. As illustrated in Figure 1, an alternating electric shunt is applied to the electrode members by a source of AC voltage or voltage (AC) 78. The applied CA establishes an alternating electrostatic field between the electrode members and the donor roller. effective to detach organic pigment from the photoconductive member of the donor roller and form a cloud of organic pigment with respect to the electrode members, the height of the cloud is such that it is not substantially in contact with the band 10. The magnitude of the AC voltage (AC) ) is relatively low and is in the order of about 200 to about 500 peak at a frequency that is in the range of about 9 KHz to 15 KHz. A supply with DC bypass (DC) 80 that applies approximately 300 volts to the donor roll 40 establishes an electrostatic field between the photoconductive member of the band 10 and the donor roll 40 to attract the organic pigment particles detached from the cloud surrounding the members electrode to the latent image recorded on the photoconductor member. At a spacing in the range of about 0.001 μm to about 45 μm between the electrode members and the donor roll, an applied voltage of about 200 to about 500 volts produces a relatively large electrostatic field without risk of disruptive air discharge. A cleaning blade 82 removes all of the organic pigment from the donor roller 40 after development, such that the magnetic roller 46 meters fresh organic pigment into a clean donor roller. The magnetic roller 46 doses a constant amount of organic pigment having a substantially constant charge on the donor roll 40. This ensures that the donor roll provides a constant amount of organic pigment having a substantially constant charge in the developing space. Instead of using a cleaning blade, the combination of the donor roller spacing, ie the spacing between the donor roller and the magnetic roller, the compressed pile height of the developer material on the magnetic roller, and the magnetic properties of the magnetic roller , in conjunction with the use of a conductive magnetic developer material, achieve the deposition of a constant amount of organic pigment that has a substantial charge on the donor roller. A DC bypass supply (DC) 84 which applies approximately 100 volts to the magnetic roller 46, establishes an electrostatic field between the magnetic roller 46 and the donor roller 40, such that an electrostatic field is established between the donor roller and the roller magnetic, which causes organic pigment particles to attract from the magnetic roller to the donor roller. The dosing blade 86 is positioned closely adjacent the magnetic roller 46, to maintain the compressed stack height of the developer material on the magnetic roller 46 at the desired level. The magnetic roller 46 includes a non-magnetic tubular member 88 preferably made from aluminum and having its rough outer circumferential surface. An elongate magnet 90 is placed inside of and spaced from the tubular member. The magnet mounts stationary. The tubular member rotates in the direction of the arrow 92, to advance the developing material adhering to it at the point of attachment defined by the donor roller 40 and the magnetic roller 46. The organic pigment particles are attracted from the carrier granules in the magnetic roller to the donor roller.

With continued reference to Figure 1, an auger, indicated generally by the reference number 94, is located in the chamber 76 of the housing 44. The auger 94 is rotatably mounted in the chamber 76, for mixing and transporting developer material. The auger has blades that extend spirally outward from an arrow. The blades are designed to advance the developer material in the axial direction substantially parallel to the axis longitudinally of the arrow. As successive latent electrostatic images are revealed, the organic pigment particles inside the developer become depleted. An organic pigment spout (not shown) stores a supply of organic pigment particles which may include organic pigment particles and carrier. The organic pigment spout is in communication with the chamber 76 of the housing 44. As the concentration of organic pigment particles in the developer decreases, fresh organic pigment particles are delivered to the developer in the chamber from the organic pigment spout. In one embodiment of the invention, the auger in the housing chamber mixes the fresh organic pigment particles with the remaining developer, such that the resulting developer is substantially uniform with the concentration of the optimized organic pigment particles. In this way, a substantially constant amount of organic pigment particles are present in the chamber of the developing housing, or in the organic pigment particles having a constant charge. The developer in the chamber of the developing housing is magnetic and can be electrically conductive. By way of example, in one embodiment of the invention, wherein the organic pigment includes carrier particles, the carrier granules include a ferromagnetic core having a thin layer of magnetite overcoated with a non-conductive layer of resinous material. The organic pigment particles can be generated from a resinous material, such as a vinyl polymer, mixed with a coloring material, such as chromogenic black. The developer may comprise from about 90 to about 99% by weight of a carrier and from 10% to about 1% by weight of organic pigment. However, a person skilled in the art will recognize that any other suitable developers may be employed. In an alternate embodiment of the present invention, developer of a component comprising organic pigment without carrier may be employed. In this configuration, the magnetic roller 46 is not present in the developer housing. This embodiment is described in more detail in the U.S. patent. No. 4,868,600 the description of which is hereby incorporated by reference. One embodiment of the developing unit is further illustrated in Figure 2. The developing apparatus 34 comprises an electrode member 42 which is disposed in the space between the photoreceptor (not shown in Figure 2) and the donor roller 40. The electrode 42 it may comprise one or more stainless steel or thin tungsten electrode members (i.e. about 50 to about 100 μm in diameter) that are lightly placed on or near the donor structure 40. The electrode member is closely spaced from the donor member. The distance between the wire (s) and the donor roll is about 0.001 μm to about 45 μm and preferably about 10 to about 25 μm or the thickness of the organic pigment layer 43 in the donor roll. The wires as illustrated in Figure 2, are self-spaced from the donor structure by the thickness of organic pigment in the donor structure. The opposite ends or end regions of the electrode member are supported by support members 54 which can also support the donor structure for rotation. In a preferred embodiment, the ends of the electrode member or opposite end regions are connected such that they are slightly below a tangent to the surface, including a layer of organic pigment, of the donor structure. Mounting the electrode members in this way makes them insensitive to roller wear due to their self spacing. In an alternative mode to that illustrated in Figure 1, the metering blade 86 is replaced by a combined loading and dosing blade 86 as illustrated in Figure 3. The loading and dosing device in combination may comprise any convenient device for depositing. a monolayer of organic pigment well loaded onto the donor structure 40. For example, it may comprise an apparatus such as that described in the US Patent No. 4,459,009 wherein the contact between the weakly charged organic pigment particles and a triboelectrically active coating that is contained in a loading roller, results in well-charged organic pigment. Other charging and dosing devices in combination can be employed, for example a conventional magnetic brush used with a two-component developer cloud can also be formed to deposit the organic pigment layer on the donor structure, or a donor roller only used with a one-component developer .

Figure 4 illustrates an enlarged view of a preferred embodiment of the electrode member of the present invention. The electrode wires 45 are placed within the electrode member 42. The anchor portions 55 of the electrode members are the portions of the electrode member that anchor the electrode member to the support member. The mounting sections 56 of the electrode member are the sections of the electrode members between the electrode member and the mounting means 54. Organic pigment particles are attracted to the electrode members, primarily via electrostatic traction. Organic pigment particles adhere to the electrode members due to the adhesion strength of the organic pigment being greater than the detachment force generated by the electric field of the electrode member. In general, the adhesion force between an organic pigment particle and an electrode member is represented by the general expression Fad = q2 / kr2 + W where Fad is the adhesion force, q is the charge in the pigment particle organic, k is the effective dielectric constant of the organic pigment and any dielectric coating, and r is the separation of the particle from its image charge within the wire that depends on the thickness, dielectric constant and coating conductivity. The element W is the adhesion force due to short range adhesion forces, such as van der Waals forces and capillaries. The force necessary to detach or remove particles from the electrode member is supplied by the electric field of the wire during the middle of its period of AC, qE, plus effective forces resulting from mechanical movement of the electrode member and by bombardment of the wire by pigment organic in the cloud. Since the adhesion force is quadric in q, the adhesion forces will be larger than the forces of detachment. Figure 5 contains an illustration of wire contamination and wire history. A photoreceptor 1 is placed near the wire 4 and contains a sub-revealed image 6, which is subsequently revealed by organic pigment originating from the donor member 3. The wire contamination occurs when the fused organic pigment 5 is formed between the wire 4 and the donor member 3. The problem is aggravated by fines of organic pigment and any organic pigment components, such as high molecular weight, entangled and / or branched components, and voltage disruptive discharging between the wire member and the roller donor The history of wire is a change in the developing ability because the organic pigment 2 or the organic pigment components adhere to the upper part of the wire 4, the upper part of the wire is the part of the wire that faces the photoreceptor . In order to avoid the organic pigment defects associated with wire contamination and wire history, the electrical properties of the electrode member can be changed, thereby changing the adhesion forces in relation to the peel forces. However, these changes in the electrical properties of the electrode member can adversely affect the ability of the electrode member to adequately provide a cloud of organic pigment, which is essential to reveal a latent image. The present invention is directed to an apparatus for reducing the unacceptable accumulation of organic pigment in the electrode member while maintaining the desired electrical and mechanical properties of the electrode member. The electrode member of the present invention is coated with a coating of material that reduces the significant attraction of organic pigment particles to the electrode member, which can result in organic pigment build-up. However, the coating of material does not interfere adversely with the mechanical or electrical properties of the electrode member.

Materials that have these qualities include compositions with low surface energy. The composition of low surface energy decreases the accumulation of organic pigment, by ensuring electrical continuity to load the wires and eliminate the possibility of load accumulation. In addition, the low surface energy materials as described herein, do not interfere with the electrical properties of the electrode member and do not adversely affect the ability of the electrode to produce a cloud of organic pigment powder. Still further, the electrode member retains its rugged mechanical properties, allowing the electrode member to remain durable during severe wear to the electrode member when repeatedly brought into contact with hard rotating donor roll surfaces. Also, the electrode member maintains a "smooth" surface after the coating is applied. A smooth surface includes surfaces having surface roughness of less than about 5 microns, preferably from about .01 to about 1 micron. Examples of suitable low surface energy compositions include both inorganic and organic materials. In a preferred embodiment of the invention, both organic and inorganic materials are used together in a coating composition. In embodiments, the coating composition comprises a polymer, a lubricant and an inorganic material. Examples of suitable polymeric materials include polymers having for example the physical properties of high strength, low surface energy, high lubricity and wear resistance. Although any polymer having the above characteristics is suitable for use as a coating composition, preferred examples of polymers include epoxy resins; formaldehyde resins such as phenol formaldehyde resins and melamine formaldehyde resins; alkyd resins; polysulfones such as polyether sulfone; polyethers; polyimides such as polyetherimide, polyamide imide which is sold for example under the trademark Torlon ™ 7130 available from Amoco; polyketones, such as those sold for example under the trademark Kaden ™ E1230 available from Amoco, polyether ether ketone sold, for example, under the brand name PEEK 450GL30 from Victrex, polyaryl ether ketone; polyamides such as polyphthalamide sold, for example, under the Amodel ™ brand available from Amoco; poliparabanic acid; and silicone resins. Particularly preferred examples of polymers include thermoset polymers and thermoplastic polymers, particularly a thermoplastic alloy, a relatively high temperature stable thermoplastic, a relatively low temperature thermofix such as epoxy polymers, polyamides, polyimides, polysulfones, formaldehyde resins, polyketones, polyesters, resins formaldehyde and its mixtures. The polymer or polymers are present in the coating composition in a total amount of about 25 to about 95% by weight, and preferably about 50 to about 90% by weight of the total composition. Mixtures of thermoplastic or thermoplastic materials can also be used. The total composition, as used herein, refers to the total amount by weight of polymer, lubricant and inorganic material, wherein the inorganic material comprises for example one or more reinforcers and / or one or more electrically conductive fillers. In a preferred embodiment, a lubricant is present in the coating composition. The primary purpose of the lubricant is to provide a non-adherent nature to the upper surface of the coating, such that the organic pigment does not adhere to the electrode member. The lubricant preferably has the characteristics of relatively low porosity, relatively low coefficient of friction, thermal stability, relatively low surface energy, and has the ability to be relatively inert to chemical attack. Preferred examples of suitable lubricants include organic material such as for example fluoroplast materials including TEFLON ™ type materials such as tetrafluoroethylene (TFE) polymers and fluorinated ethylene-propylene (FEP) polymers such as for example polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), perfluorovinylalkylether tetrafluoroethylene copolymer (PFA TEFLONMR), polyether sulfone and its copolymers; and inorganic materials such as molybdenum disulfide, boron nitride, titanium diboride, graphite and the like. In embodiments, a lubricant or blends of lubricants are present in a total amount of from about 3 to about 50% by weight and preferably about 5 to about 25% by weight of the total coating composition. In embodiments, the coating composition comprises an inorganic material. An aggregate inorganic filler can improve the strength of the composition as well as tailor other properties such as color and electrical and thermal conductivities of the polymer matrix. The aggregate filler can also help in forming a smooth surface for the coating composition. Preferred inorganic materials include conductive fillers and reinforcements. Examples of electrically conductive fillers include metal oxides such as tin oxide, titanium oxide, zirconium oxide, magnesium oxide and the like. Another preferred filler is carbon black, graphite or the like, with surface treatment of compounds such as for example siloxane, silane, fluorine or the like. Specifically preferred treated carbon blacks include fluorinated carbons such as those described in U.S. patent application. Serial No. 08 / 635,356 co-pending filed on April 19, 1996, the description of which is hereby incorporated by reference in its entirety. More than one electrically conductive filler may be present in the reverse composition. In preferred embodiments, one or more electrically conductive fillers are present in a total amount from about 2% by weight to about 25% by weight and preferably about 5 to 12.5% by weight of the total composition. Examples of reinforcements include materials that have the ability to increase the strength, hardness, and / or abrasion resistance of the polymer and / or thermoplastic or thermoplastic material. Examples of suitable reinforcements include carbon blacks, and furnace and thermal blacks; and further include metal oxides such as zinc oxide, silicon dioxide, titanium dioxide and the like; carbonates such as magnesium carbonate and calcium carbonate and the like and other materials such as hydrated silicas and their mixtures. In preferred embodiments, one or more reinforcements are present in a total amount of from about 2 to about 25% by weight and preferably about 5 to about 12.5% by weight of the total composition. The composition may comprise a polymer, lubricant and reinforcement; a polymer lubricant and electrically conductive filler; or a polymer lubricant, reinforcement and electrically conductive filler. In preferred embodiments, the polymer is a thermoplastic or thermoplastic material, particularly a high temperature stable thermoplastic or a low temperature thermofix; the lubricant is FEP, PFA, PTFE and / or MoS2; the electrically conductive filler, if present, is carbon black; and the reinforcement, when present, is silicon dioxide or titanium dioxide. The resulting matrix includes the properties of all elements of the composition, including having high lubricity and low surface energy of the lubricant, having a high total wear resistance due to the polymer component and reinforcements, and having a smooth surface and superior properties. electrical because the inorganic component includes the reinforcers and / or the inorganic filler (s). The coating composition material is preferably present in an amount from about 5 to about 95% by weight of the total solids, and preferably from about 10 to about 40% by weight of total solids. Total solids refer to the total amount by weight of the coating composition, solvent, optical fillers and optional additives contained in the coating solution. The volume resistivity of the coated electrode for example is approximately l "10 ohm-cm, and preferably 10"5 to 10" 1 ohm-cm. The surface roughness is less than about 5 microns and preferably from about 0.01 to about 1 micron. The coating has a relatively low surface energy of about 5 to about 35 dynes / cm, preferably about 10 to about 25 dynes / cm. In a preferred embodiment of the invention, the coating composition is applied over at least a portion of the non-aggregated regions of the electrode member. The non-aggregated region of the electrode member is the entire outer surface region of the electrode, minus the region where the electrode is connected to the mounting members 54 and minus the anchoring area (55 in Figure 4). It is preferred that the coating covers the portion of the electrode member that is adjacent to the donor roll. In another preferred embodiment of the invention, the coating composition is coated over an entire area of the electrode member that is located in a central portion of the electrode member and extends to an area adjacent to the unconnected portion of the electrode member. . This area includes all the surface of the electrode member minus the anchoring area (55 in Figure 4). In an alternate embodiment, the entire length of the electrode member is coated with the coating material, including the anchoring area 55 and the mounting area 56. In embodiments, at least a portion refers to the unconnected region that is coated , or from about 10 to about 90% of the electrode member. The organic pigment can accumulate anywhere on the electrode member, but will not affect the development unless it accumulates along the electrode member near the donor roll or at the closest length to the photoreceptor. Therefore, it is preferred that the material coating cover the electrode member over the entire length corresponding to the donor roller, and over the entire length corresponding to the photoreceptor. The coating composition can be deposited at least on a portion of the electrode member by any convenient, known method. These deposition methods include liquid and powder coating, dip coating and spraying, and plasma deposition of RF and ion beam assisted plasma. In a preferred deposition method, the composition coating is coated on the electrode member with dip coating. After coating, the coating composition is preferably dried in the air and cured at a convenient temperature to set the specific composition material. Curing temperatures are in the range of about 37.8 ° C (100 ° F) to about 760 ° C (1400 ° F) and preferably about 48.9 ° C (120 ° F) to about 648.9 ° C (1200 ° F). The average thickness of the coating is from about 1 to about 30 μm and preferably from about 2 to about 10 μm in thickness. If the coating is applied only to a portion of the electrode member, the coating thickness may or may not taper or thin out at points farther from the midpoint of the electrode member. Therefore, the thickness of the coating can decrease at points further away from the midpoint of the electrode. The electrode members of the present invention, the embodiments of which have been described herein, exhibit superior performance in terms of wear resistance and decreased accumulation of organic pigment on the surface of the electrode member, while also maintaining electrical properties, which stimulate the development of the development of the organic pigment cloud without accumulation of charge. In addition, the electrode members present exhibit superior mechanical properties such as durability against donor roller surfaces, which are typically made of strong materials such as ceramics. All patents and applications referred to herein are incorporated specifically and fully by reference in this specification. The following examples further define and describe embodiments of the present invention. Unless otherwise indicated, all parts and percentages are given by weight.

EXAMPLES EXAMPLE 1 Wire preparation to be coated A stainless steel wire with a thickness of approximately .0762 mm (3 mils) is cleaned to remove obvious contaminants. A dip coating apparatus consists of a glass cylinder with a diameter of 2.54 cm (1") by 38.1 cm (15") in length, sealed at one end to maintain the liquid coating material, was used for coating by immersion of the wire. A cable connected to an engine type NSH-12R from Bodine Electric Company is used to raise and lower a wire support that holds the wire tight during the coating process. The immersion speed and removal of the wire support inside and outside the coating solution are regulated by a motor control apparatus of B &B Motors and Control Corporation (NOVA PD DC motor speed control). After coating, a displaced device with motor is used to screw the wire around its axis, while receiving external heating to allow controlled evaporation of solvent. When the coating was dry and / or non-flowable, the coated wire is heated in a through-flow oven using a schedule of times and temperatures to complete either the drying or curing / post-curing of the coating. The general procedure may include: (A) cleaning and degreasing the wire with a suitable solvent, for example acetone, alcohol or water, and making it rough if necessary, for example with sandpaper; (B) the coating material can be adjusted to the proper viscosity and solids content by adding solids or solvent to the solution; and (C) the wire is immersed in and removed from the coating solution, dried and cured / post-cured if necessary and immersed again, if required. The coating thickness and uniformity are a function of the extraction speed and viscosity of the solution (solid contents in most solvent-based systems) and a drying program consistent with uniform solidification of coating. EXAMPLE 2 Preparation of coating composition solutions A .0635 mm (2.5 mil) stainless steel wire can be prepared by lightly grit blasting, sanding or rubbing the wire surface with steel wool, degreasing with acetone and then rinsing with - Isopropyl alcohol and dry. The clean wire can be primed with Whitford P-51 or Dow Corning 1200 primer using any convenient technique such as conventional dip / spin or spray methods. The coating material is XYLANM ™ (1052 wb / black) supplied by Whitford Corporation, West Chester, Pennsylvania, which contains liquids such as carbon black, lubricants such as molybdenum disulfide and polytetrafluoroethylene in a thermofix matrix. the viscosity can then be adjusted with deionized water to 30 to 45 Zahn Cup No. 2, immediately (a few seconds) before spraying. This dispersion can then be coated with immersion on an electrode as described in example 1. Optional evaporation or air drying of the coating is optional; however, to achieve optimum release, the cure time is preferably about 10 minutes at about 343.3 ° C (650 ° F). The coating can be polished to obtain a smooth and dry thickness with a thickness of 2 to 3 microns. EXAMPLE 3 A stainless steel wire of .0635 mm (2.5 mils) can be prepared by light attack with shot, degreased with acetone and then rinsed with isopropyl alcohol, followed by a wash with mild sodium hypochlorite solution, a rinsing of water, dry alcohol rinse, and dried. A primer is optional in this example. "XILANMR High Lubricty Blue" can be used as the coating material. This coating material is supplied by Whitford Corporation and contains calcium carbonate as reinforcement and lubricants such as polytetrafluoroethylene in a thermoset matrix. This coating composition can be applied to the electrode wire according to the procedures set forth in example 1. The recommended dip temperature, preferably it is between 21.1 to 26.6 ° C (70 and 80 ° F) and the viscosity of application solution is between about 20 and 30 seconds using a Zahn No. 2 assembly. If a thinner coating is desired, water may be employed as a diluent. The coated wire can be air dried for about 2 minutes at room temperature (about 25 ° C) and then baked for about 20 minutes at about 93.3 ° C (200 ° F) This coating is expected to be mild and have high lubricity. EXAMPLE 4 A wire according to Example 1 was degreased as in Example 2 or optionally degreased with steam.A light sanding or grit attack as in Example 2 is followed by a dry alcohol wash.A primer application is optional , but if one is used, XI primer N ^ P-501 is recommended.The coating suspension used was Whitford XILAN1411 1052 DF / 880 BLACK COATING, and the constituents include molybdenum disulfide, polytetrafluoroethylene and spinel of manganese ferrite black in a thermoset polymer matrix.The viscosity of coating solution was approximately 32 seconds Zahn cup.The coating may have to be diluted with solvent e Whitford 99B to obtain the desired dry thickness. This dispersion is then used to dip the electrode as described in Example 1. Immediately after the coating, the coating is preferably instantaneously evaporated for about 5 minutes at about 93.3 ° C (200 ° F) followed by curing for about 15 minutes at approximately 204.4 ° C (400 ° F). The resulting smooth coating was less than 5 microns thick, exhibited high temperature stability, wear resistance and demonstrated adequate lubricity. EXAMPLE 5 The procedure set forth in Example 4 is repeated except that ferrite can be replaced with a highly conductive carbon black in order to increase the electrical conductivity within a range of about 10"to about 10" 1, and preferably about 10"5 to approximately 10" 1 ohms-cm.

While the invention has been described in detail with reference to specific and preferred embodiments, it will be appreciated that various modifications and variations will be apparent to the skilled in the art. All these modifications and modalities that can easily occur to a person skilled in the art are intended within the scope of the appended claims. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (18)

1. CLAIMS 1. - An apparatus for revealing a latent image recorded on a surface, characterized in that it comprises: wire supports; a donor member spaced from the surface and adapted to transport organic pigment to an opposite region of the surface; an electrode member placed in the space between the surface and the donor member, the electrode member is spaced closely from the donor member and is electrically derived to release organic pigment from the donor member, thereby allowing the formation of a cloud of organic pigment in the space between the electrode member and the surface with the organic pigment evolved from the cloud of organic pigment revealing the latent image, wherein opposite end regions of the electrode member are connected to the wire supports adapted to support the regions at opposite ends of the electrode member; and a coating composition, at least in a portion of unconnected regions of the electrode member, wherein the coating composition comprises a polymer, a lubricant and an inorganic material.
2. 2. An apparatus according to claim 1, characterized in that the polymer is selected from the group consisting of epoxy polymers, polyamides, polyimides, polysulfones, formaldehyde resins, polyketones, polyesters and mixtures thereof.
3. 3. An apparatus according to claim 1, characterized in that the lubricant is selected from the group consisting of fluoroplastics, molybdenum disulfide, polyether sulfones, boron nitride, titanium diboride, graphite and mixtures thereof.
4. 4. An apparatus according to claim 3, characterized in that the fluoroplastic is selected from the group consisting of polytetrafluoroethylene, fluorinated ethylene-propylene copolymer, perfluorovinylalkylether tetrafluoroethylene copolymer and mixtures thereof.
5. 5. - An apparatus according to claim 1, characterized in that the inorganic material is selected from the group consisting of an electrically conductive filler, a reinforcement and their mixtures.
6. 6. - An apparatus according to claim 5, characterized in that the electrically conductive filler is selected from the group consisting of metal oxides, carbon black, graphite, surface-treated carbon black and mixtures thereof.
7. 7. - An apparatus according to claim 6, characterized in that the electrically conductive filler is selected from the group consisting of tin oxide, titanium oxide, zirconium oxide, magnesium oxide, fluorinated carbon and mixtures thereof.
8. 8. - An apparatus according to claim 5, characterized in that the reinforcement is selected from the group consisting of carbon black, thermal blacks, furnace blacks, metal oxides, carbonates, hydrated silicas and their mixtures.
9. 9. - An apparatus according to claim 8, wherein the reinforcement is selected from the group consisting of zinc oxide, silicon dioxide, titanium dioxide, magnesium carbonate, calcium carbonate and mixtures thereof.
10. 10. - An apparatus according to claim 1, characterized in that the polymer is a thermoset material, the lubricant is selected from the group consisting of polytetrafluoroethylene, molybdenum disulfide and mixtures thereof and wherein the inorganic material is selected from the group consisting of of carbon black, calcium carbonate and their mixtures.
11. 11. An apparatus according to claim 10, characterized in that the polymer is selected from the group consisting of epoxy polymers, polyamides, polyimides, polysulfones, formaldehydes, polyketones, polyesters and mixtures thereof.
12. 12. - An apparatus according to claim 1, characterized in that the composition is coated by immersion on the electrode wire.
13. 13. - An apparatus according to claim 1, characterized in that the coating composition is present from about 10 to about 90% of the electrode member.
14. 14. - An apparatus according to claim 1, characterized in that the coating composition has a thickness of about 1 μm to about 5 μm.
15. 15. - An apparatus according to claim 1, characterized in that the electrode member includes at least one wire with a thin diameter.
16. 16. - An apparatus according to claim 1, characterized in that the thin diameter wires have a diameter of about 50 to about 100 μm.
17. 17. - An apparatus according to claim 1, characterized in that the donor member is spaced closely from the donor member a distance of about 0.001 to about 45 μm.
18. 18. An electrophotographic process, characterized in that it comprises: a) forming a latent electrostatic image on a load retentive surface; b) applying organic pigment in the form of a cloud of organic pigment to the latent image, to form a revealed image on the retentive surface of charge, wherein the organic pigment is applied using a developing apparatus comprising wire supports; a donor member spaced on the surface and adapted to transport organic pigment to an opposite region on the surface; an electrode member placed in the space between the surface and the donor member, the electrode member is spaced closely from the donor member and is electrically derived to release organic pigment from the donor member, thereby allowing the formation of a cloud of organic pigment in the space between the electrode member and the surface with the organic pigment detached from the cloud of organic pigment that reveals the latent image, wherein opposite end regions of the electrode member are connected to the wire supports adapted to support the regions at opposite ends of the electrode member; and a low surface energy coating composition at least in a portion of unconnected regions of the electrode member, wherein the coating composition comprises a polymer, a lubricant and an inorganic material, - c) transferring the organic pigment image from the retentive surface of load to a substrate; and d) fixing the organic pigment image to the substrate.