EP0625730A2 - Verfahren und Vorrichtung zum zwei Tonerbilder in einem Abbildungsdurchlauf zu Erzeugen - Google Patents

Verfahren und Vorrichtung zum zwei Tonerbilder in einem Abbildungsdurchlauf zu Erzeugen Download PDF

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Publication number
EP0625730A2
EP0625730A2 EP94107101A EP94107101A EP0625730A2 EP 0625730 A2 EP0625730 A2 EP 0625730A2 EP 94107101 A EP94107101 A EP 94107101A EP 94107101 A EP94107101 A EP 94107101A EP 0625730 A2 EP0625730 A2 EP 0625730A2
Authority
EP
European Patent Office
Prior art keywords
image
toner
polarity
exposure
electrostatic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP94107101A
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English (en)
French (fr)
Other versions
EP0625730A3 (de
EP0625730B1 (de
Inventor
Joseph Edward C/O Eastman Kodak Company Guth
W. Charles c/o Eastman Kodak Company Kasiske
Eric Carl C/O Eastman Kodak Company Stelter
Yee Seung c/o Eastman Kodak Company Ng
Frank Joseph c/o Eastman Kodak Company Koetter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eastman Kodak Co
Original Assignee
Eastman Kodak Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/065,246 external-priority patent/US5985499A/en
Priority claimed from US08/065,248 external-priority patent/US5485190A/en
Application filed by Eastman Kodak Co filed Critical Eastman Kodak Co
Priority to EP97100597A priority Critical patent/EP0774698B1/de
Publication of EP0625730A2 publication Critical patent/EP0625730A2/de
Publication of EP0625730A3 publication Critical patent/EP0625730A3/de
Application granted granted Critical
Publication of EP0625730B1 publication Critical patent/EP0625730B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/22Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/32Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the charge pattern is formed dotwise, e.g. by a thermal head
    • G03G15/326Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the charge pattern is formed dotwise, e.g. by a thermal head by application of light, e.g. using a LED array
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B41PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41JTYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J2/00Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed
    • B41J2/435Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material
    • B41J2/447Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using arrays of radiation sources
    • B41J2/45Typewriters or selective printing mechanisms characterised by the printing or marking process for which they are designed characterised by selective application of radiation to a printing material or impression-transfer material using arrays of radiation sources using light-emitting diode [LED] or laser arrays
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/01Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0142Structure of complete machines
    • G03G15/0147Structure of complete machines using a single reusable electrographic recording member
    • G03G15/0152Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member
    • G03G15/0157Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member with special treatment between monocolour image formation
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/01Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0142Structure of complete machines
    • G03G15/0147Structure of complete machines using a single reusable electrographic recording member
    • G03G15/0152Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member
    • G03G15/0163Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member primary transfer to the final recording medium
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00Apparatus for electrographic processes using a charge pattern
    • G03G15/04Apparatus for electrographic processes using a charge pattern for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material
    • G03G15/04036Details of illuminating systems, e.g. lamps, reflectors
    • G03G15/04045Details of illuminating systems, e.g. lamps, reflectors for exposing image information provided otherwise than by directly projecting the original image onto the photoconductive recording material, e.g. digital copiers
    • G03G15/04054Details of illuminating systems, e.g. lamps, reflectors for exposing image information provided otherwise than by directly projecting the original image onto the photoconductive recording material, e.g. digital copiers by LED arrays
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00Apparatus for electrophotographic processes
    • G03G2215/01Apparatus for electrophotographic processes for producing multicoloured copies
    • G03G2215/0167Apparatus for electrophotographic processes for producing multicoloured copies single electrographic recording member
    • G03G2215/017Apparatus for electrophotographic processes for producing multicoloured copies single electrographic recording member single rotation of recording member to produce multicoloured copy
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G2215/00Apparatus for electrophotographic processes
    • G03G2215/04Arrangements for exposing and producing an image
    • G03G2215/0497Exposure from behind the image carrying surface

Definitions

  • This invention relates to the formation of two or more toner images in a single frame or area of an image member. Although not limited thereto, it is particularly usable in a method and apparatus which forms accent color images on a single frame of an image member in a single pass.
  • U.S. Patent No. 5,001,028 to Mosehauer et al is representative of a number of references describing a process in which a photoconductive image member is uniformly charged and imagewise exposed to create an electrostatic image.
  • Toner is applied to the electrostatic image to create a toner image.
  • discharged area development is used.
  • the toner applied is of the same polarity as the electrostatic image. It deposits in the areas of lowest charge (the discharged areas) to form a toner image having a density which is greatest in the portions of the image receiving the greatest exposure.
  • the image member is, again, uniformly charged with a charge of the same polarity as the original charge and it is, again, imagewise exposed to form a second electrostatic image, generally in the portions of the image member not covered by the first toner image.
  • the second electrostatic image is toned, again with a toner of the same polarity as the charge to create a second toner image.
  • the process can be repeated with a third electrostatic image toned by a third color toner to create a three color image, etc.
  • the two (or more) color image is transferred in a single step to a receiving sheet and fused also in a single step.
  • the process has a number of advantages in accent color applications: It eliminates the troublesome and expensive steps usually used in registering images at transfer. If it uses separate exposure stations, it can produce accent color output at the same speed as single color output.
  • U.S. Patent No. 4,778,740 notes a problem observed in such systems that when the second electrostatic image includes discharged areas immediately next to the first toner image, the first toner has a tendency to migrate into the second image.
  • the solution suggested is to leave a one pixel gap from the first image in the second exposure. This can be accomplished in an electronic exposure system providing registration between the two exposures is very accurate. However, it requires excellent registration and leaves a thin, untoned area between the two images which can show up as a white streak or "halo".
  • U.S. Patent No. 5,025,292 shows a system, used commercially, in which a series of color separation images are formed on a single image member using liquid developing.
  • the first image is heated to dry it so it is fixed during the second exposure.
  • the second exposure is made through a transparent support in order to create an electrostatic image that, in fact, overlaps the first color image, which electrostatic image is toned to form overlapping color toner images.
  • This process is also carried out with discharged area development and the image member is recharged between images.
  • the charge from the first and/or second charging steps located next to the toner image will prevent movement of the toner into that space.
  • that charge is dissipated and the toner is now repelled by the charge still remaining underneath the toner into the space which is no longer protected by its own charge. We call this "toner blowoff".
  • Our solution to this problem is to discharge some of this charge repelling the first toner image.
  • second (and subsequent) exposures are used to discharge this charge, for example, by exposure through the base of the image member.
  • Some of such exposure is allowed or designed to overlap the first toner image, thereby discharging or reducing the charge on the photoconductor which would otherwise have a tendency to repel the toner. With that charge missing, the toner does not have a tendency to be repelled into the adjacent discharged areas of the second image.
  • Charge retained on the first toner image has a tendency to reduce overtoning by the second image in the overlapping areas. However, some overtoning is likely. According to a preferred embodiment, this effect is made less obvious by overlapping the lighter of the two images into the darker. This is easier to do if the second image is lighter, but it can also be accomplished if the first image is lighter.
  • the method uses an image member having a photoconductive layer and preferably having a transparent support.
  • a first electrostatic image is formed on the image member and is toned by applying a first dry toner of a first polarity and first color to form a first color toner image.
  • a second electrostatic image is formed on the image member in a charge also of the first polarity by imagewise exposure of the image member, preferably, through the transparent support.
  • the second electrostatic image is developed by the application of a second color toner also of the first polarity to form a second color toner image corresponding to exposed portions of the second electrostatic image.
  • the exposure also overlaps the first toner image to discharge portions of the image member under the toner image that adjoin the second electrostatic image.
  • the feature of exposure through the support can be used in process color imaging as well as accent color imaging. Exposure through the support has many advantages other than avoiding the earlier images. For example, there is often more room for a printhead writer assembly on the side of the image member opposite the toning station. The printhead is less likely to become dirty from airborn toner. Charged area development is easier to use.
  • Another advantage of exposure through the support is that a simple and accurate mount can be designed for the printhead writer assembly.
  • FIG. 1 is a side schematic of an image forming apparatus.
  • FIGS. 2a-2f are side schematic sections illustrating the steps of an image forming method.
  • FIGS. 3-7 are side schematic sections illustrating various aspects of an image forming methods.
  • FIGS. 8, 12, 13 and 14 are perspective views of portions of an LED printhead writer assembly.
  • FIGS. 9-11 and 15 are side views of an LED printhead writer assembly with FIG. 10 showing an alternative embodiment to FIGS. 9 and 15.
  • FIGS. 2a-2f show a method of forming two dry and unfixed toner images on the same area or frame of an image member 1.
  • the toners do not have to be of different color, a multicolor application is the most attractive use of this process, and the description will be in terms of color. Further, for illustration, a two color image will be described, but the same process can be used to form three or more images which can be of different color.
  • an image member 1 includes a support 3 and a photoconductive layer 5. It is a typical image member used in electrophotography. If the support 3 is not conductive, it will contain a conductive layer between the support and the photoconductive layer 5. It can be much more complex than illustrated, including charge generation layers, charge transport layers, barrier layers and protective overcoat layers. For purposes herein, however, it is conveniently illustrated as a support with a photoconductive layer.
  • the photoconductive layer 5 is uniformly charged with a charge of a first potential, for example, a negative potential.
  • a first potential for example, a negative potential.
  • an electrostatic image is created on image member 1 by imagewise exposing the charged photoconductive layer 5, for example, by exposing it with an LED printhead writer 7.
  • the electrostatic image is toned by the application of dry toner having a charge of the first polarity, in this instance, a negative charge, to create a first toner image.
  • This toner is preferably of a first color, for example, black.
  • the image member 1 is then charged again with a charge of the first polarity, that is, a negative charge.
  • a second electrostatic image is formed on the image member by imagewise exposing the image member 1, for example, with another or the same LED printhead writer 7.
  • the second electrostatic image is toned by the application of a second toner of the first polarity.
  • the second toner adheres to the image member in the exposed portions of the second electrostatic image to create a second toner image, which can be of a second color, for example, red.
  • the image member 1 now has black toner in the exposed portions of the first image and red toner in the exposed portions of the second image and no toner where there has been no exposure thus far. Additional images can be placed in the areas that have not yet been exposed using toners of different colors to create three or more color images.
  • the process can be used with ordinary optical copiers, it is preferably used with electronic printers and copiers.
  • the step illustrated in FIG. 2d in which the image member is recharged before the second exposure can, in theory, be eliminated. That is, the image member in its condition shown in FIG. 2c, contains charge in the unexposed areas which could be used to form the second electrostatic image. However, it is found that less overtoning results if the image member is recharged to assure that both the toned areas and the untoned areas are placed at approximately an even charge so that the next toner image will accumulate only in the exposed areas of the second electrostatic image.
  • the second charging step can also be used to compensate for variations in the materials in the two toning steps.
  • FIG. 3 illustrates a problem we encountered with the exposure creating the second electrostatic image, which exposure is also shown in FIG. 2e.
  • toner at an edge 11 of the first toned image has a tendency to move into exposed areas of the second electrostatic image that adjoin it. That is, toner along the edge 11 of the first toner image has a tendency to move to the left, as shown in FIG. 3, when the second electrostatic image includes exposed areas directly adjoining it. Note that toner along the right edge 13 of the first toner image does not move because there is no exposed portion of the second electrostatic image adjoining it.
  • FIG. 4 A first solution to this problem is illustrated in FIG. 4.
  • the second exposure comparable to that shown in FIG. 2e, is preferably made through the support 3. This exposure is allowed to overlap under the first image, as shown in FIG. 4, dissipating the charge under the portion of the image which has a tendency to lose toner. At this point, the toner in the first image is not repelled by the charge underneath it, which no longer exists, and has no reason to move into the adjacent exposed area, as shown at edge 11 in FIG. 4.
  • the second toner image is applied, as in FIG. 2f, the toner then adheres to the discharged areas with good image density up to the original edge of the first toner image.
  • the exposure may cause some overtoning. For this reason, the darker image should be exposed to conform to the desired final image and the lighter image expanded where it is intended to border the darker image.
  • the amount of exposure overlap that is desirable is dependent upon the materials used and is empirically determinable by those skilled in the art. It is preferable that the amount of overlap be designed into the exposure for the lighter image. Either the first or second image may be the lighter image. Initially, however, a dark first image and a light second image will be discussed.
  • the overlap is accomplished with an appropriate algorithm, as explained below, combining the first and second images and expanding the exposure to adjacent pixels of the lighter image, where those pixels are adjacent pixels of the darker image.
  • the overlap can extend for as little as a single pixel and have an advantageous effect on the tendency of the toner to move into the second electrostatic image. Note that this approach has an additional advantage of preventing a white line between images when exposure registration is less than perfect. If different printheads are used for the exposures (see FIG. 1), the system provides productivity not possible with transfer station registration. However, multiple printheads increase exposure registration problems. Such registration problems can produce a white line between adjacent images. This approach fills in any such white line.
  • FIG. 5 shows an extended version of FIG. 4 in which electronic signals making up the first and second electrostatic images are fully combined for the second exposure to expose the entire area underneath the first toner image.
  • This approach is appropriate for a first image that is always darker than the second image and, it is the easiest electronically. It has the advantage of assuring that there is no tendency of any of the first toner image to migrate into the exposed portions of the second electrostatic image. It also eliminates the charge on the photoconductor that has a tendency to repel the first toner image, thereby reducing the tendency of the first toner image to be scavenged by the second toning step (FIG. 2f). However, overtoning becomes more noticeable with this approach and may limit the colors with which it is usable.
  • a relatively simple algorithm can be used.
  • the image is scanned or stored in the form of an imagewise bit map. Adjacent colors can be detected by comparing adjacent pixels in the incoming data from the scanner or the previously stored bitmap. If, for instance, a first pixel is to be light in the second color and a second pixel is to be dark in the first color, then the second pixel is also exposed in the second exposure (in addition to being exposed in the first exposure). This "grows" the second color into the adjacent first color. The algorithm then compares the second pixel to the third pixel and extends the overlap, as required.
  • the algorithm is much simpler.
  • the second image is added to the first image, with or without the second image being reduced in intensity where it overlies the first image.
  • exposure under the first image has a tendency to improve the holding power of the first image and thereby reduces the scavenging effect.
  • it has a tendency to reduce the overall charge associated with the first image when the second image is toned, thus, it may have a tendency to increase overtoning.
  • the amount of this overtoning is dependent upon the amount of charge that remains across the toner itself in the first image.
  • the second image can be toned using a toning bias set to prevent toning of areas with an excess of 200 volts potential.
  • the intensity of the overlapping exposure can be reduced so that the photoconductor retains a greater portion of the residual charge.
  • the first image can be allowed to be overtoned and the system used with the lighter image the expanded, overtoning one. This latter approach is preferred. Adjacency of images is most commonly desired where one of the colors is substantially lighter than the other. For example, a black image next to a dark blue or a dark red image is much more rare in practice than is a black image or a dark red or a dark blue image next to a light yellow, light blue, light orange or light pink image.
  • the dark image is laid down first, its exposure is made to conform accurately to its desired appearance in the final image, that is, unexpanded.
  • the reverse can also be done. That is, the expanded light color can be laid down first with the dark color second. In either case, the second exposure is under a portion of the first toner image.
  • gray scale exposure may be used.
  • a black toner can be used to produce a range of image density from dark black to light gray. With the black station placed first, nearly all images would be processed so that the black image is produced unexpanded and all other colors adjacent it are expanded into it. However, it is within the skill of the art to recognize the unusual occurrence of a low density black (light gray) pixel next to a much higher density pixel of a color of intermediate darkness like red. In this instance, the black image would be expanded and the red image not expanded.
  • a first step in such an algorithm in examining two pixels of different color is to first determine which is the lighter. That portion of the lighter image is then expanded.
  • This approach preferably uses an extensive lookup table, it is not complicated and is within the skill of the art.
  • the pixel-by-pixel algorithm for overlapping images mentioned earlier for the case of the darker first image can be used if the second image is darker.
  • the embodiment in FIG. 5 has the advantage of reducing scavenging of the first image by holding the first image to the image member with greater force during the second toning step. However, it requires excellent registration of the second exposure to prevent a second color border on portions of the first image that are not intended to be adjacent the second image.
  • the embodiment shown in FIG. 4 has the advantage of curing registration problems where the two images interface but does not add to the registration problems where the images are not adjoining.
  • the support 3 must be transparent to the exposing radiation.
  • a conductive layer 9 generally positioned between the support 3 and the photoconductive layer or layers 5 must also be transparent. Both transparent supports and transparent conductive layers are well known in the art. Transparency is generally obtained in a conductive layer by use of a normally nontransparent material but by making the layer extremely thin. Thin layers of nickel, tin, cuprous iodide and other conductive materials are usable for this application.
  • the charge underneath the first toner can also be dissipated by front exposure providing the material making up the first toner image is chosen to be transparent to the activating radiation of the second exposure.
  • This is a known procedure for providing overlapping toner images.
  • an infrared laser is used for the activating radiation with an appropriately sensitized photoconductive material in the photoconductive layer 5.
  • the toner is then chosen from materials that are opaque to visible light and provide the appropriate color but which are transparent to the activating radiation.
  • Exposure from the front while feasible, is especially less desirable than exposure through the support in an accent color application, because it restricts the design of the toners and the color order in which they are laid down.
  • exposure through the, support, as shown in FIG. 1, can also be used when it is desirable to overlap toner images, for example, in process color applications when the toners of the earlier images partially block subsequent exposures.
  • the first toner image is formed of small particles which, it is well known, hold well to the image member.
  • the second toner image is formed of larger toner particles which, it is well known, have better aerodynamics for projection toning.
  • the first toner image is formed of small size, dark toner particles, for example, black toner particles having a mean particle diameter of 8 microns. Exposure is through the base with desired overlapping, as shown in either FIG. 4 or FIG. 5, to create a second electrostatic image but without movement of the first toner image. According to FIG.
  • the second electrostatic image is toned with larger, light color toner particles, for example, yellow, light blue, orange or pink toner particles having a 12 micron mean diameter which behave well using projection toning to provide a second toner image which may overlap the first toner image.
  • light color toner particles for example, yellow, light blue, orange or pink toner particles having a 12 micron mean diameter which behave well using projection toning to provide a second toner image which may overlap the first toner image.
  • FIG. 7 illustrates another feature that reduces the tendency toward toner blowoff as well as scavenging.
  • the image member is blanket exposed with radiation to which the image member is sensitive through its transparent support 3 to as much as possible eliminate negative charge from the first electrostatic image on the image member.
  • the toner is then held on the image member by surface forces and compensating positive charge (electron holes) that move through the photoconductive layer attracted by the negative charge still remaining on the toner itself.
  • this step would be somewhat overwhelmed by the charge in the second charging step, it still reduces the tendency of the toner to blowoff in the second exposure step. This is apparently due to the holes remaining near the surface of the photoconductive layer, despite the second charging step. With the overlapping second exposure (FIGS. 4 and 5), more holes are attracted toward the surface to further help hold toner or keep it from moving.
  • FIG. 1 shows an apparatus for producing two color images in which the second exposure is through the base.
  • an image member 1 is in the form of an endless belt trained about a series of rollers, including a tension roller 16 and a drive roller 18, to continuously move through a series of electrophotographic stations well known in the art.
  • Image member 1 is charged by a charging device 10 to uniform potential, for example, a negative potential. It is imagewise exposed by an exposure device, for example, LED printhead 7 to create a first electrostatic image.
  • the first electrostatic image is toned at a first toning station 15 by the application of toner having a polarity the same as the original charging station 10, for example, a negative polarity and having a small particle size, for example, 8 microns. Toner is, thus, applied to the areas discharged by exposure station 7.
  • the image member is recharged by an additional charging station 20 which evens up the charge of the first polarity on the image member at a predetermined level. This level need not be the same as the charge applied by station 10. However, before recharging, the image member is exposed to overall blanket radiation through its Support by erase lamp 19. As described above, this causes the toner to be more firmly held to the image member, despite charge from the charging station 20.
  • a magnetic scavenger 27 is positioned to attract any carrier inadvertently picked up by the image member in the first toning step. The position of scavenger 27 before toning station 25 is to prevent carrier used in station 15 from carrying dark toner into station 25.
  • the image member 1 is then imagewise exposed by a second exposure station, for example, a second LED printhead 17 which is positioned inside image member 1 and exposes image member 1 through its transparent support to create a second electrostatic image.
  • the second electrostatic image is toned by a second toning station 25 which applies toner preferably of a color different than that applied by station 15 to create a second toner image on the image member, preferably with toner of a larger particle size, for example, 12 microns, thereby forming a two color or multicolor image on the image member.
  • a receiving sheet is fed from a receiving sheet supply 29 into overlying contact with the two color toner image.
  • the two color toner image is transferred to the receiving sheet at a conventional biased roller electrostatic transfer station 31 and the receiving sheet separates from the image member as the image member goes around a small roller 24.
  • the receiving sheet is transported by a vacuum transport 33 to a fuser 35 where the two color image is fixed to the receiving sheet.
  • the receiving sheet is ultimately deposited in an output tray 37.
  • the image member is cleaned by cleaning device 39 so that the process can be continued.
  • This apparatus doubles the speed of doing two color images, compared to conventional approaches in which the images are formed on separate frames and transferred in registration. It also avoids the complexity of registering two image transfers with the attendant complex receiver handling.
  • Toning stations 15 and 25 are preferably constructed as in U.S. Patent No. 5,001,028, Mosehauer issued March 19, 1991.
  • the first toning station 15 is spaced from the image member 1 by an amount less than the nap of the magnetic brush.
  • the brush thus, directly contacts the image member, providing a high quality dense image.
  • the second toning station 25 is spaced from image member 1 by enough that the nap does not directly contact image member 1.
  • An AC component on the bias on station 25 helps provide the density desired in the second image despite the gap between the nap and the image member.
  • FIGS. 8-15 show the details of a linear printhead writer assembly 50 suitable for use as either printhead 7 or printhead 17 in FIG. 1.
  • its construction makes it particularly adaptable to backside location and is, therefore, particularly usable as printhead 17 in FIG. 1.
  • linear printhead writer assembly 50 includes a linear source of radiation, for example, a linear LED array 52 (FIGS. 9 and 15), a linear focusing means, for example, a linear lens 54 such as a conventional Selfoc® (trademark of Hitachi, Ltd.) lens and a suitable support housing.
  • the LED array is supported on support tiles 64 (FIG. 8) which, in turn, are supported on a mother board 62 which, in turn, is supported on a baseplate 60.
  • the baseplate 60 is fixed with respect to a pair of support or datum plates 56 and 58 which are positioned at each of the baseplate ends.
  • the lens 54 is fixed to a lens support 55 to which is affixed a pair of end supports 67 and 69 using a thermal compensating means which will be described below.
  • End supports 67 and 69 each contain screw holes 76 which are positioned in alignment with oversized holes 66 in support plates 56 and 58 (FIG. 8). Screws 65, each with an oversized washer 68 (FIGS. 9 and 15) are inserted through holes 66 and into screw holes 76. The screws 65 can be moved within holes 66 to position lens 54 with respect to LED array 52 for final factory adjustment of those two components.
  • a single positioning bar 70 is mounted between support plates 56 and 58.
  • the LED array 52, the lens 54 and the positioning bar 70 are all elongated parallel to a Z axis. (Orthogonal X, Y and Z axes are shown in FIG. 8.)
  • the upper surface of positioning bar 70 contacts image member 1, as shown in FIGS. 9 and 15, to control the distance (in a Y direction) between image member 1 and lens 54 and LED array 52.
  • Both factory and field adjustment of positioning bar 70 is accomplished by mounting positioning bar 70 eccentrically on a shaft 74.
  • Shaft 74 is mounted on support plates 56 and 58.
  • a knob 72 is used to rotate shaft 74 to rotate bar 70. Because of the eccentric mounting of bar 70 with respect to shaft 74, the top surface of bar 70 moves toward and away from LED array 52 as bar 70 is rotated.
  • lens 54 Focusing of lens 54 with respect to both conjugates is best shown by reference to FIG. 15, in which unnecessary details are eliminated.
  • writer assembly 50 is mounted in a suitable fixture for adjusting focus (see, for example, U.S. Patent No. 4,928,139, which patent is hereby incorporated by reference herein).
  • Lens 54 is moved in the fixture until LED array 52 is imaged, by lens 54, at a desired linear exposure locus 78, which locus is also parallel to the Z axis. This movement is accomplished by movement of screws 65 within oversized holes 66 in plates 56 and 58. When the proper focus is obtained, the screws 65 are tightened to fix lens 54 with respect to LED array 52 and plates 56 and 58.
  • Factory adjustment of positioning bar 70 can be accomplished at the same time by rotating knob 72 to rotate positioning bar 70 around eccentric shaft 74.
  • a length of web for example, a web having the same thickness as the proposed image member 1, can he tensioned across bar 70 to help in determining whether the appropriate side of the web is positioned in exposure locus 78 as the knob 72 is rotated. Determination of focus can also be done with appropriate instrumentation, known in the art.
  • assembly 50 When the assembly 50 is inserted in the image forming apparatus shown in FIG. 1, assembly 50 is fixed to the mechanism plates of the apparatus. As shown in FIG. 15, assembly 50 is positioned so that the positioning bar 70 intersects the path of image member 1 and, thus, lightly pushes the image member away from its normal path, for example, its path between rollers 16 and 18 in FIG. 1. If toning stations 15 and 25 have parts which control the position of image member 1, then bar 70 would intersect the path of image member 1 between the developing stations. Thus, the positioning bar 70 partially defines the path of image member 1.
  • Positioning bar 70 has the function of moving the lateral position of image member 1 to assure proper location of the sensitive part of image member 1 with respect to the exposure locus 78. Note that this positioning structure is not dependent upon the use of springs to urge the printhead assembly against backing members or the image member itself.
  • the printhead assembly is fixed with respect to the mechanism plates of the apparatus. Extremely accurate positioning of the printhead in the apparatus is also not critical providing bar 70 intersects the path of image member 1.
  • Positioning bar 70 is shown in the FIGS. as adjustable as a unit from one end by rotation as described.
  • eccentric mounts at each end can be provided which would allow field adjustment of each end of bar 70 with respect to the exposure locus. This is ordinarily not necessary, since skew adjustment of lens 54 in the factory (using screws 65) assures a parallel relation between the exposure locus 78 and bar 70.
  • FIG. 10 illustrates an, alternative embodiment in which two positioning bars 70 and 80 are positioned on opposite sides of lens 54 and both contact image member 1.
  • This structure is very similar to the embodiment shown in FIGS. 8, 9 and 15. It has the advantage of precisely determining the location of image member 1 without regard to orientation of the assembly 50 in the apparatus.
  • the embodiments shown in FIGS. 8, 9 and 15, however, have the advantage of simplicity and also have no danger of being overconstrained, a condition that can occur with two positioning bars. Note that either of the positioning bars can be adjustable, or both can be adjustable, depending upon the amount of adjustment desired.
  • image member 1 when in contact with positioning bar 70, will have a slight break to it because the direct mounting for assembly 50 assumes intersection by positioning bar 70 with the path of image member 1 so that the path of image member 1 can be controlled by positioning bar 70.
  • Positioning bar 70 is shown as being rotatable only to adjust its spacing from lens 54. However, it could also be a roller rotatable with the image member 1. This has the advantage of reducing friction between the bar 70 and the image member 1, but it makes the eccentric mount of the bar somewhat more complicated.
  • FIGS. 11-14 illustrate a thermal compensation device for lens 54.
  • lens 54 is fixed to lens support 55 which, in turn, is secured to end supports 67 and 69.
  • the LED array As the LED array is used, it gradually heats up the lens and the lens support.
  • the lens and lens support can be made of similar materials and expand together.
  • the housing for example, baseplate 60, does not necessarily expand at the same rate. Thus, it is conventional to provide a thermal compensation coupling between the housing and the lens support.
  • lens support 55 has a pair of pins 82 at each end.
  • the pins have an axis oriented in the X direction (FIG. 8) and generally transverse to the longitudinal orientation of the lens support 55 (Z direction).
  • the pins are inserted in oversized holes 84 in end supports 67 and 69, as best seen in FIG. 11. Thermal expansion in the Z direction would cause a buckling of lens support 55 if not compensated for. Such thermal expansion is permitted by the looseness of fit between pins 82 and oversized holes 84.
  • a dampener 90 for example, a spring or elastomer, which is positioned to resiliently resist movement of pins 82 in the Z direction away from the center of the lens support 55.
  • the dampeners 90 are held in end supports 67 and 69 by spring loaded shoulder screws 86.
  • they are rubber shock absorbers which can be loosened or tightened by screws 86 to vary their force on pins 82.
  • Lens support 55 is secured to each of end supports 67 and 69 using a shoulder screw, not shown, secured in a hole 96 in lens support 55 through an oversized hole 98 in the end support.
  • the shoulder screw is tightened against a spring that fits between it and a shoulder of the end support.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Printers Or Recording Devices Using Electromagnetic And Radiation Means (AREA)
  • Color Electrophotography (AREA)
  • Discharging, Photosensitive Material Shape In Electrophotography (AREA)
  • Exposure Or Original Feeding In Electrophotography (AREA)
  • Combination Of More Than One Step In Electrophotography (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Control Or Security For Electrophotography (AREA)
EP19940107101 1993-05-20 1994-05-06 Verfahren zum Erzeugen zweier Tonerbilder übereinander Expired - Lifetime EP0625730B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP97100597A EP0774698B1 (de) 1993-05-20 1994-05-06 Bilderzeugungsapparat mit Belichtung durch bandförmigen Bildträger

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US65248 1993-05-20
US08/065,246 US5985499A (en) 1993-05-20 1993-05-20 Method and apparatus for forming two toner images in a single frame
US65246 1993-05-20
US08/065,248 US5485190A (en) 1993-05-20 1993-05-20 Printhead writer assembly engageable with a web image member

Related Child Applications (2)

Application Number Title Priority Date Filing Date
EP97100597A Division EP0774698B1 (de) 1993-05-20 1994-05-06 Bilderzeugungsapparat mit Belichtung durch bandförmigen Bildträger
EP97100597.0 Division-Into 1997-01-15

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EP0625730A2 true EP0625730A2 (de) 1994-11-23
EP0625730A3 EP0625730A3 (de) 1995-01-11
EP0625730B1 EP0625730B1 (de) 1997-07-30

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EP97100597A Expired - Lifetime EP0774698B1 (de) 1993-05-20 1994-05-06 Bilderzeugungsapparat mit Belichtung durch bandförmigen Bildträger
EP19940107101 Expired - Lifetime EP0625730B1 (de) 1993-05-20 1994-05-06 Verfahren zum Erzeugen zweier Tonerbilder übereinander

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EP (2) EP0774698B1 (de)
JP (1) JPH0798529A (de)
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0785478A2 (de) 1996-01-17 1997-07-23 Eastman Kodak Company Verfahren um Tonerbilder aus zwei unterschiedlichen Tonermaterialen zu erstellen
US5700611A (en) * 1995-12-07 1997-12-23 Eastman Kodak Company Method for forming overlapping toner images
US5748218A (en) * 1996-01-17 1998-05-05 Eastman Kodak Company Method for forming toner images with two distinct toners

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6826775B2 (ja) * 2016-10-25 2021-02-10 株式会社リコー 画像形成装置

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JPS60247264A (ja) * 1984-05-23 1985-12-06 Japan Steel Works Ltd:The 多色電子写真装置
US4778740A (en) * 1986-03-31 1988-10-18 Matsushita Electric Industrial Co., Ltd. Color electrophotographic method and apparatus
EP0380132A2 (de) * 1989-01-27 1990-08-01 Oki Electric Industry Co., Ltd. Verfahren und Gerät zur Erzeugung von mehrfarbigen Bildern
US5001028A (en) * 1988-08-15 1991-03-19 Eastman Kodak Company Electrophotographic method using hard magnetic carrier particles
US5053821A (en) * 1987-10-06 1991-10-01 Seiko Epson Corporation, A Corporation Of Japan Electrophotographic image forming apparatus using photoconductive toner

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JPS60247264A (ja) * 1984-05-23 1985-12-06 Japan Steel Works Ltd:The 多色電子写真装置
US4778740A (en) * 1986-03-31 1988-10-18 Matsushita Electric Industrial Co., Ltd. Color electrophotographic method and apparatus
US5053821A (en) * 1987-10-06 1991-10-01 Seiko Epson Corporation, A Corporation Of Japan Electrophotographic image forming apparatus using photoconductive toner
US5001028A (en) * 1988-08-15 1991-03-19 Eastman Kodak Company Electrophotographic method using hard magnetic carrier particles
EP0380132A2 (de) * 1989-01-27 1990-08-01 Oki Electric Industry Co., Ltd. Verfahren und Gerät zur Erzeugung von mehrfarbigen Bildern

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PATENT ABSTRACTS OF JAPAN vol. 10, no. 119 (P-453) (2176) 6 May 1986 & JP-A-60 247 264 (NIPPON SEIKOSHO K.K.) 6 December 1985 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5700611A (en) * 1995-12-07 1997-12-23 Eastman Kodak Company Method for forming overlapping toner images
EP0785478A2 (de) 1996-01-17 1997-07-23 Eastman Kodak Company Verfahren um Tonerbilder aus zwei unterschiedlichen Tonermaterialen zu erstellen
US5748218A (en) * 1996-01-17 1998-05-05 Eastman Kodak Company Method for forming toner images with two distinct toners

Also Published As

Publication number Publication date
DE69427833T2 (de) 2002-04-04
DE69404550T2 (de) 1998-02-12
DE69427833D1 (de) 2001-08-30
EP0625730A3 (de) 1995-01-11
EP0774698A2 (de) 1997-05-21
DE69404550D1 (de) 1997-09-04
EP0625730B1 (de) 1997-07-30
EP0774698A3 (de) 1998-04-22
EP0774698B1 (de) 2001-07-25
JPH0798529A (ja) 1995-04-11

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