Patent Publication Number: US-7211358-B2

Title: Image cylinder sleeve for an electrophotographic machine and method for producing same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Reference is made to the following commonly assigned application, the disclosure of which is incorporated herein by reference: 
     U.S. patent application Ser. No. 10/836,756, filed on Apr. 30, 2004, by Edward T. Miskinis, et al., entitled, “PHOTOCONDUCTIVE MEMBER FOR AN ELECTROPHOTOGRAPHIC MACHINE AND METHOD OF FORMING SAME”. 
     FIELD OF THE INVENTION 
     The present invention relates to image cylinders for electrophotographic machines. More particularly, the present invention relates to an image cylinder sleeve of an electrophotographic machine, and a method of producing same. 
     BACKGROUND OF THE INVENTION 
     Electrophotographic machines, such as, for example, copiers and printers, produce images by forming a latent image charge pattern on a photoconductive surface. The photoconductive surface carries the latent image through a developing station wherein pigmented toner particles are drawn by electrostatic attraction onto the latent image charge pattern on the photoconductive surface. An electric field is applied to transfer the image from the photoconductive surface onto either an intermediate transfer member or an image substrate, such as, for example, a piece of paper. Thereafter, the image is fixed, such as, for example, by fusing, to the image substrate. 
     In some electrophotographic machines, the photoconductive surface may be disposed upon an endless-loop belt. In other electrophotographic machines, the photoconductive surface is disposed on a cylindrical roller or drum, variously referred to as the image cylinder, photoconductive drum or photoconductive roller. Generally, the photoconductive drum includes an inner roller or mandrel over which a photoconductive sleeve is disposed. The mandrel is typically constructed of aluminum. The photoconductive sleeve is typically constructed from a metal substrate, such as, for example, nickel, onto which a photoconductive layer is applied. 
     Typically, the photoconductive sleeve is mounted to the inner roller or mandrel by an air mounting process, as is more particularly described hereinafter. Generally, the air mounting process is very sensitive to the surface characteristics of the inside surface of the photoconductive sleeve. A photoconductive sleeve having a relatively rough inside surface is difficult to air mount or may be incompatible with the air mounting process, whereas a photoconductive sleeve having a relatively smooth inside surface is compatible with the process of air mounting and is relatively easy to air mount. 
     However, several of the manufacturing processes used to produce the photoconductive sleeve, including, for example, the nickel plating process, the surface of the mandrel used in the plating process, the grain structure of the plated nickel, the acid etching process by which the nickel surface is cleaned, and other manufacturing processes, cause the inside surface of the photoconductive sleeve to be undesirably if not unacceptably rough for use in an air mounting process. Since it is the inside surface of the photoconductive sleeve that must be machined or smoothed, the use of conventional processes such as, for example, grinding or polishing, may be somewhat labor intensive, time consuming, and costly. 
     Therefore, what is needed in the art is a photoconductive sleeve for a photoconductive roller that is compatible with an air mounting process, and a method of manufacturing same. 
     SUMMARY OF THE INVENTION 
     The present invention provides a photoconductive member, such as, for example, a photoconductive sleeve, that has an improved compatibility with an air-mounting process by which the photoconductive member is operably associated with a mandrel. 
     The invention includes, in one form thereof, a photoconductive member having an inside and outside surface. An inner smoothing layer is disposed over the inside surface of the substrate. The inner smoothing layer improves the compatibility of the photoconductive member with the air-mounting process. 
     An advantage of the present invention is that the inner smoothing layer improves the compatibility of the photoconductive member with the air-mounting process. 
     Another advantage of the present invention is that the inner smoothing layer is formed at least in part by processes used to form other parts and/or layers of the photoconductive member and therefore additional processes may not be required. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become apparent and be better understood by reference to the following description of one embodiment of the invention in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram of one embodiment of an electrophotographic machine having one embodiment of a photoconductive drum or image cylinder of the present invention; 
         FIG. 2  is an exploded view of the photoconductive drum of  FIG. 1 ; 
         FIGS. 3 and 4  illustrate an exemplary air-mounting process by which a photoconductive sleeve is mounted to a mandrel; 
         FIG. 5  is a cut-away cross-sectional view of the photoconductive sleeve of  FIG. 2 ; and 
         FIG. 6  is a process diagram illustrating one embodiment of a process of the present invention for producing a photoconductive member in accordance with the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
     Referring now to  FIG. 1 , there is shown a schematic diagram of one embodiment of an electrophotographic machine having one embodiment of a photoconductive roller of the present invention. Machine  10  includes photoconductive drum  20 , transfer roller  22 , writer or latent-image forming station  24 , toning station  26 , pre-cleaning station  28 , cleaning station  30 , and charging station  32 . 
     Generally, photoconductive drum  20  is rotated in the direction of arrow  34  past charging station  32 , which charges the outer photoconductive surface of photoconductive drum  20  to a uniform potential. Writer or latent-image forming station  24  selectively discharges the outer surface of photoconductive drum  20  to form thereon a latent charge image corresponding to the image to be printed or reproduced. As photoconductive drum  20  rotates through or past toning station  26  toner particles are electrostatically drawn to the outer surface of photoconductive drum  20  thereby developing the latent charge image. The developed image carried on the outer surface of photoconductive drum  20  is then transferred to transfer roller  22  and, from there, to an image substrate (not shown) that is brought into engagement with transfer roller  22 . The outer surface of photoconductive drum  20  is then conditioned by a pre-cleaning station  28  and cleaned by cleaning stations  28  and  30 , and the above-described cycle repeats. 
     Referring now to  FIG. 2 , an exploded view of photoconductive drum  20  is shown. Photoconductive drum  20  includes inner roller or mandrel  40  and one embodiment of an outer photo conductive sleeve  42  of the present invention. Mandrel  40  is typically constructed of metal, such as, for example, aluminum, and has a hard outer surface (not referenced) that is machined to a very smooth surface, such as, for example, by turning and/or polishing. 
     Photoconductive sleeve  42  is disposed upon and surrounds at least a portion of the outer surface of mandrel  40 . Typically, photoconductive sleeve  42  is air mounted onto mandrel  40  and an interference fit exists or is formed therebetween. 
     More particularly, mandrel  40  includes an air inlet  44  and, as shown in  FIGS. 3 and 4 , nose piece  46  and main body  48 . Nose  46  is tapered and has a maximum diameter portion that has a diameter that is substantially equal to or slightly larger than the inside diameter of photoconductive sleeve  42  and which forms a seal with the inside surface of photoconductive sleeve  42 . A supply of pressurized air is connected to air inlet  44  (see  FIG. 2 ). Mandrel  40  is constructed (details are well known to one of ordinary skill in the art and thus are not shown) such that the pressurized air is channeled into a clearance formed between nose piece  46 , a chamfered portion (not referenced) of body  48 , and the inside surface (not referenced) of photoconductive sleeve  42 . The pressurized air causes photoconductive sleeve  40  to temporarily expand and/or deflect outward, thereby forming gap G ( FIG. 3 ) between the outer surface of body  48  and the inside surface of sleeve  42  that facilitates the sliding of photoconductive sleeve  42  over and onto body  48 . 
     When photoconductive sleeve  42  is in the desired position over body  48  of mandrel  40 , the air pressure supplied to mandrel  40  is removed and photoconductive sleeve  42  returns to its normal and undeflected inside diameter, as shown in  FIG. 4 . An interference fit is thereby formed between the inside surface of photoconductive sleeve  42  and the outer surface of body  48  of mandrel  40 , and the outer surface of photoconductive sleeve  42  conforms to and/or takes the shape of the outer surface of body  48  of mandrel  40 . 
     The process of air mounting is particularly sensitive to the characteristics of the inside surface of photoconductive sleeve  42 . More particularly, in order to facilitate the air mounting process, the inside surface of photoconductive sleeve  42  must be relatively smooth. The smooth inside surface lowers insertion force, i.e., the force required to slide the sleeve over or relative to the mandrel. In order to be compatible with the air mounting process, the inside roughness of photoconductive sleeve  42  is preferably less than approximately 1.0 roughness average and less than approximately 2.0 roughness peak-to-peak, and more preferably from approximately 0.5 to approximately 0.20 roughness average and from approximately 1.5 to approximately 0.5 roughness peak-to-peak. However, sleeves typically have an inside roughness of approximately 0.5 roughness average and approximately 3.0 roughness peak-to-peak. 
     Since it is the inside surface of the photoconductive sleeve that must be smoothed, the use of conventional processes such as, for example, grinding or polishing, may be somewhat more difficult, time consuming, and costly. Further, in order to avoid undesirable imaging artifacts, the process or processes that might be used to smooth the inside surface of the photoconductive sleeve must not affect the smoothness of the outside photoconductive surface/coating of the photoconductive sleeve. 
     The present invention provides a photoconductive sleeve having an inside surface smoothness that is compatible with the air mounting process, and a method of producing such a photoconductive sleeve that utilizes existing processes and manufacturing methods and potentially requires no additional processes. 
     As best shown in  FIG. 5 , photoconductive sleeve  42  includes substrate  50 , outer smoothing layer  52 , outer barrier layer  54 , charge generating layer (CGL)  56 , charge transport layer (CTL)  58 , inner smoothing layer  62 , and inner barrier layer  64 . Substrate  50  is constructed of metal, such as, for example, nickel, and has a thickness of, for example, from approximately 50 to approximately 200 microns (μ), and preferably from approximately 100 to approximately 150μ. Outer smoothing layer  52  is a layer of a polymer material and has a thickness of, for example, from approximately 2 to 4μ thick. Outer barrier layer  54  is a layer of a nylon material and has a thickness of, for example, from approximately 0.25 to 1.5μ thick. CGL layer  56  is a layer of hydrolyzed polyvinyl acetate material and has a thickness of, for example, from approximately 0.2 to 1.0μ. CTL layer  58  is a layer of polycarbonate material and has a thickness of, for example, from approximately 20 to 30μ thick. 
     Charge generating layer  56  and charge transport layer  58  are each formed by an entrapped-air dipping process. Generally, an entrapped-air dipping process is a process by which one end of sleeve  42  is capped or sealed in an air tight manner and the opposite, open end of sleeve  42  is dipped into a vat or tub of material. The outside surface of sleeve  42  is coated by the coating material. However, the air entrapped within sleeve  42  precludes to a substantial extent the coating material from entering into the open end of sleeve  42 . The inside surface of sleeve  42  is left substantially uncoated. Thus, charge generating layer  56  and charge transport layer  58  are not formed or disposed upon the inside surface of substrate  50 . Inner smoothing layer  62  is, however, formed and disposed upon the inside surface of substrate  50 . 
     Inner smoothing layer  62  is a layer of polymer material disposed upon or over substrate  50 . Inner smoothing layer  62  can be formed of the same or a different polymer than outer smoothing layer  62 . Inner smoothing layer  62  is generally formed to a thickness that provides photoconductive sleeve  42  with an inside surface that is compatible with (i.e., of a sufficient smoothness) an air mounting process. More particularly, inner smoothing layer  62  is formed to a thickness that is sufficient to fill or substantially fill most or substantially all voids and other roughness on the inner surface of substrate  50  and thereby smooth the inside surface of photoconductive sleeve  42 . 
     Inner barrier layer  64  is optionally formed upon and/or over inner smoothing layer  62 . Inner barrier layer  64  is formed of a layer of nylon, and can be of the same or a different nylon material from which outer barrier layer  54  is formed. Inner barrier layer  64  supplements, when desired and/or necessary, the thickness of inner smoothing layer  62  to thereby ensure that most or substantially all voids and other roughness on the inner surface of substrate  50  are filled and thereby smooth the inside surface of photoconductive sleeve  42 . 
     Referring now to FIG  6 , one embodiment of a process of the present invention for producing photoconductive sleeve  40  is shown. Process  200  generally includes outer smoothing layer formation  202 , outer barrier layer formation  204 , CGL formation  206 , CTL formation  208 , inner smoothing layer formation  210  and inner barrier layer formation  212 . 
     Outer smoothing layer formation  202  places outer smoothing layer  52  upon and/or over substrate  50 , such as, for example, by one of a normal dipping process or an entrapped-air dipping process. A normal (non-entrapped-air) dipping process coats the inside surface of substrate  50  with the same material from which outer smoothing layer  52  is formed and thereby results in the formation of inner smoothing layer  62  on and/or over the inside surface of substrate  50 . Thus, using a normal (non-entrapped-air) dipping process causes the simultaneous formation of outer smoothing layer  52  and inner smoothing layer  62 . Although shown as separate processes in  FIG. 6 , outer smoothing layer formation  202  and inner smoothing layer formation  210  are the same or simultaneous processes when outer smoothing layer formation  202  is conducted via a normal dipping process. 
     Conversely, when outer smoothing layer formation  202  is conducted via an entrapped-air dipping process, the coating of the inside surface of substrate  50  with the material from which outer smoothing layer  52  is formed is substantially precluded. Thus, inner smoothing layer formation  210  is not simultaneous with or the same process as outer smoothing layer formation  202  when outer smoothing layer formation  202  is an entrapped-air dipping process. Rather, inner smoothing layer formation  210  is a completely separate process when outer smoothing layer formation  202  is an entrapped-air dipping process. 
     Outer barrier layer formation  204  places outer barrier layer  54  upon and/or over outer smoothing layer  52  by, for example, a normal or entrapped-air dipping process. A normal (non-entrapped-air) dipping process coats inner smoothing layer  62  with the same material from which outer barrier layer  54  is formed and thereby results in the formation of inner barrier layer  64  on and/or over inner smoothing layer  62 . Thus, using a normal (non-entrapped-air) dipping process causes the simultaneous formation of outer barrier layer  54  and inner barrier layer  64 . Although shown as separate processes in  FIG. 6 , outer barrier layer formation  204  and inner barrier layer formation  212  are the same or simultaneous processes when outer barrier layer formation  204  is conducted via a normal dipping process. 
     Conversely, when outer barrier layer formation  204  is conducted via an entrapped air dipping process, the coating of inner smoothing layer  52  with the material from which outer barrier layer is formed is substantially precluded. Thus, inner barrier layer formation  212  is not simultaneous with or the same process as outer barrier layer formation  204  when outer barrier layer formation  204  is an entrapped-air dipping process. Rather, inner barrier layer formation  212  is a completely separate process when outer barrier layer formation  204  is an entrapped-air dipping process. 
     It should be particularly noted that the thicknesses of outer smoothing layer  52  and/or outer barrier layer  54  can, if desired, be increased by respective entrapped-air dipping processes and can use the same or a different material than used in any preceding non entrapped-air formation processes  202 ,  204 , respectively. 
     CGL formation process  206  places CGL layer  56  upon and/or over outer barrier layer  54  by, for example, an entrapped-air dipping process. Similarly, CTL formation process  208  places CGL layer  56  upon and/or over CGL layer  56  by, for example, an entrapped-air dipping process. 
     In the embodiments shown, photoconductive sleeve  24  is configured as a cylindrical member. However, it is to be understood that the photoconductive member can be configured in other geometrical shapes. 
     In the embodiments shown, the photoconductive sleeve of the present invention includes an inner smoothing layer that is shown and described as being a specific layer of material. However, it is to be understood that the photoconductive sleeve of the present invention can be alternately configured with an inner smoothing layer that is formed from the same material as and/or by the same processes as one or more of the other layers that are formed upon and/or over the outer surface of the substrate of the photoconductive sleeve, such as, for example, the outer barrier layer or other suitable layers of material that are applied onto and/or over the outer surface of the substrate. 
     While this invention has been described as having a preferred arrangement, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the present invention using the general principles disclosed herein. Further, this application is intended to cover such departures from the present disclosure as come within the known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims. 
     PARTS LIST 
     
         
           10 . Machine 
           20 . Photoconductive member or drum 
           22 . Transfer Roller 
           24 . Writer Station 
           26 . Toning Station 
           28 . Precleaning Station 
           30 . Cleaning Station 
           32 . Charging Station 
           40 . Mandrel 
           42 . Photoconductive Sleeve 
           44 . Air Inlet 
           46 . Nose Piece 
           48 . Main Body 
           50 . Substrate 
           52 . Outer Smoothing Layer 
           54 . Barrier Layer 
           56 . Charge Generating Layer 
           58 . Charge Transfer Layer 
           62 . Inner Smoothing Layer 
           64 . Inner Barrier Layer 
           200 . Process 
           202 . Outer Smoothing Layer Formation 
           204 . Barrier Layer Formation 
           206 . Charge Generating Layer Formation 
           208 . Charge Transfer Layer Formation 
           210 . Inner Smoothing Layer Formation 
           212 . Inner Barrier Layer Formation 
         G Gap