EP0557858A1 - Bilderzeugungsverfahren und Apparat unter Verwendung eines Zwischenbildträgers - Google Patents

Bilderzeugungsverfahren und Apparat unter Verwendung eines Zwischenbildträgers Download PDF

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Publication number
EP0557858A1
EP0557858A1 EP93102383A EP93102383A EP0557858A1 EP 0557858 A1 EP0557858 A1 EP 0557858A1 EP 93102383 A EP93102383 A EP 93102383A EP 93102383 A EP93102383 A EP 93102383A EP 0557858 A1 EP0557858 A1 EP 0557858A1
Authority
EP
European Patent Office
Prior art keywords
image
toner
transfer
sheet
receiving sheet
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.)
Withdrawn
Application number
EP93102383A
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English (en)
French (fr)
Inventor
Muhammad c/o EASTMAN KODAK COMPANY Aslam
Lawrence Paul C/O Eastman Kodak Company Demejo
Alec Naftali c/o EASTMAN KODAK COMPANY Mutz
John Murray c/o EASTMAN KODAK COMPANY McCabe
Kevin Michael c/o EASTMAN KODAK COMPANY Johnson
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 US07/843,664 external-priority patent/US5253021A/en
Priority claimed from US07/843,666 external-priority patent/US5428430A/en
Application filed by Eastman Kodak Co filed Critical Eastman Kodak Co
Publication of EP0557858A1 publication Critical patent/EP0557858A1/de
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0105—Details of unit
    • G03G15/0131—Details of unit for transferring a pattern to a second base
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
    • G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
    • G03G15/1605—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using at least one intermediate support
    • G03G15/161—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using at least one intermediate support with means for handling the intermediate support, e.g. heating, cleaning, coating with a transfer agent

Definitions

  • This invention relates to the use of an intermediate in toner image formation.
  • the invention is particularly usable in forming a multicolor image on an intermediate by heat assisted transfer, in registration, of more than one single color toner image, and to the transfer and fusing of such multicolor image in a single step from the intermediate to a receiving sheet.
  • it is particularly usable with small, dry toner particles.
  • Two or more single color images are transferred in registration from an image member to a receiving sheet by heating the receiving sheet to an elevated temperature.
  • the temperature of the receiving sheet is sufficiently high that the toner sticks to the receiving sheet and to itself.
  • the receiving sheet is heated from inside a transfer drum to which it is secured.
  • the transfer drum and image member form a pressure nip with the combination of heat and pressure transferring the image.
  • This method is particularly useful in transferring extremely small, dry toner particles, for example, toner particles having a mean particle diameter of 5 microns or less.
  • a receiving sheet having a heat-softenable outer layer is used.
  • the receiving sheet is heated to a temperature which softens the outer layer and the first layer or layers of the toner images partially embed themselves in the heat-softened layer to assist in transfer of the first image or so. Further layers of toner from subsequent images or dense portions of the first image attach themselves to toner particles that are partially embedded. With extremely small, dry toner particles this method provides extremely efficient transfer with excellent resolution.
  • heat assisted transfer to a heat-softened layer provides the most efficient and highest resolution transfer of very small toner particles known in the prior art, it is not without problems.
  • relatively high pressures are desirable, for example, pressures of up to 500 pounds per square inch and higher. Heating is accomplished generally through the receiving sheet. Even if the receiving sheet is carried on a metallic drum, it is somewhat difficult to maintain the temperature of the thermoplastic layer within limits that will sinter the toner without overheating the image member or blistering the receiving sheet. Overheating of the image member can cause damage to it, including a reduction of its ability to hold a charge. Overheating of the toner image can cause sticking to the image member and/or spreading of the image.
  • the relief image is substantially reduced, the image is more permanently fixed and gloss can be increased by bringing the image into contact with a ferrotyping surface under conditions of heat and pressure which cause the image to be further embedded in the thermoplastic layer.
  • the ferrotyping surface is smooth and hard and has good release characteristics. For example, it can be made of nickel, stainless steel or other metals, with or without surface treating with silicones or the like. For highest quality imaging, the ferrotyping surface is left in contact with the image until the image and heat-softened layer have cooled below their glass transition temperatures, at which point it is separated without offset.
  • endless belts generally to fix regular toner images directly to paper, transparency stock, or the like has been known for many years; see, for example, U.S. 3,948,215; European Applications 0301585 and 0295901.
  • the toner image is left in contact with the web until the image is cooled below the glass transition temperature of the toner, at which point the receiving sheet can be separated without offset.
  • Preventing offset by cooling in contact with the web eliminates the need for offset preventing liquids which have a degrading effect on a high-quality image.
  • a problem in using a web system, especially an endless belt system, in a productive image forming apparatus is associated with the time required for the belt and image to cool while maintained in contact. If the fixing device is slowed down to below the speed of the transfer station to allow cooling, then the mismatch of speeds between the transfer station and the fixing device must be accommodated. In general, this requires either a full frame distance in the in-track direction between the transfer station or drum and the fixing device, or loop or other mechanism for absorbing the difference in speeds.
  • Belt fixing devices create other non-trivial problems. For example, belt tracking must be controlled. The belts are expensive and difficult to replace. If the belt has a seam the timing of the apparatus must be controlled to prevent the seam appearing in the middle of an image. The convenient availability of different textures is accomplished generally by exchanging belts, a task which is time consuming and especially difficult if the apparatus is hot. The belt has very limited room inside it for cooling structure.
  • An intermediate transfer member (sometimes herein called an "intermediate") has been used in both single color electrophotography and multicolor electrophotography.
  • U.S. Patent 4,931,839 shows the use of an intermediate conductivity intermediate web to accumulate several single color toner images by separate electrostatic transfer from a photoconductive web. The multicolor image formed on the intermediate is electrostatically transferred to a receiving sheet and later fed to a separate fixing station. See also, U.S. 4,657,373; U.S. 4,068,937; U.S. 3,893,761; U.S. 4,453,820; and U.S. 4,542,978.
  • the intermediate has a silicone rubber or other compliant surface which is used because of its affinity to toner at the first transfer step.
  • the image and, in some instances, the receiving sheet are preheated so that transfer and fusing can be accomplished in a single step.
  • the intermediate is generally cooled before it returns to the original image member to pick up additional images for fear of damage to a photoconductor or other sensitive portion of the original image member.
  • a number of references show single color transfer to an intermediate and then a combined step including simultaneous fixing and transfer under heat and pressure from the intermediate to a receiving sheet. See, for example, U.S. 4,657,373; U.S. 4,068,937; U.S. 3,893,761; U.S. 4,453,820; and U.S. 4,542,978.
  • the intermediate has a silicone rubber or other compliant surface which is used because of its affinity to toner at the first transfer step.
  • the image and, in some instances, the receiving sheet are preheated so that transfer and fusing can be accomplished in a single step.
  • the intermediate is generally cooled before it returns to the original image member to pick up additional images for fear of damage to a photoconductor or other sensitive portion of the original image member.
  • U.S. Patents 4,588,279; 4,455,079; and 4,518,976 maintain the receiving sheet in contact with the intermediate until the image has cooled before separation.
  • silicone rubber is generally used for the intermediate in order to accomplish pressure transfer without heat at the first or original transfer.
  • U.S. Patent 4,910,558 shows an intermediate drum which is internally heated and covered with compressible silicone rubber. A receiving sheet is preheated to the temperature of boiling water and pressure is used at both transfers.
  • U.S. Patent 4,912,514 shows an intermediate web with a conductive base and a fluoride coating with separate rapid heating components opposite the original transfer from a photoconductive drum and opposite a combination transfer-fusing position where the single image is transferred to and fused to a receiving sheet.
  • the first transfer is said in the reference to involve fusing the toner on a photosensitive drum until it transfers to and is temporarily fixed on the surface of the intermediate.
  • U.S. Patent 4,531,825 shows an intermediate roller having a heat conductive core with a silicone or fluoride resin coating.
  • the original image member has a soft backing providing a larger nip for the first transfer and the transferred image is fused and transferred to a preheated receiving sheet in a single step.
  • U.S. Patent 4,992,833 shows an intermediate sheet or web to which a single toner image is transferred by means not described. After the transfer the image is fused to the intermediate and kept warm until overlaid with a receiving sheet. The receiving sheet and intermediate are cooled together before separation. The intermediate is cleaned for reuse.
  • Japanese Kokai 1-179181 shows a combination of heat and electric field used to transfer a toner image to a receiving sheet carried by either a drum or belt.
  • the image is fixed while the receiving sheet is still on the drum or belt by pressure contact with a heated roller.
  • a small particle toner image is formed on an image member.
  • the image is transferred to a transfer surface of a conductive, preferably metallic, intermediate member by a combination of heat and electrostatic field.
  • a plurality of different color, single color toner images are formed on one or more image members with small, dry toner particles, i.e., toner particles averaging less than 5 microns in diameter (for example, about 3.5 microns).
  • the toner images are transferred in registration by contact with a metallic intermediate.
  • the metallic intermediate is heated to a temperature sufficient to sinter the toner at least where it touches the intermediate and where toner particles touch each other.
  • An electrical field is applied, enhancing transfer of the toner to the intermediate to form a multicolor toner image.
  • the multicolor image can be transferred from the intermediate to a receiving sheet.
  • transfer efficiency comparable to that with a heat softenable receiver is achieved but without the sensitivity to heat and pressure variations of the prior process. Risk of damage to the image member from heat and pressure is substantially reduced.
  • This object is accomplished by apparatus in which a toner image is formed on an image member and transferred to an intermediate sheet.
  • the toner image is overlaid with a receiving sheet, and a combination of heat and pressure is used to transfer and fix the toner image to the receiving sheet in a single step.
  • the intermediate and receiving sheet are allowed to cool while separated from the pressure applying means and are separated from each other only after such cooling.
  • the invention provides remarkable results in a method and apparatus in which a series of single color, different color toner images are formed on one or more image members. These images are transferred in registration to a surface of an intermediate sheet.
  • the surface to which the images are transferred is hard and smooth. For example, it is preferably a metal surface of an entirely metal sheet.
  • the images are transferred by heating the intermediate sheet to a temperature sufficient to at least sinter portions of the toner image and applying an electric field urging transfer.
  • a multicolor image is formed on the intermediate sheet.
  • a receiving sheet is overlaid the multicolor toner image and the intermediate and receiving sheet are fed as a sandwich between pressure members in the presence of sufficient heat and pressure to transfer and fix the multicolor toner image to the receiving sheet.
  • the receiving sheet and intermediate are allowed to cool as a unit separate from the pressure members and then are separated.
  • the intermediate can be heated for two transfers predominantly from a single source and the pressure applied for the fixing step at ordinary machine speed but the combination of the intermediate sheet and receiving sheet can be allowed to cool (or be actively cooled) at a slower speed. This allows the cooling to be accomplished without inordinately enlarging the apparatus. It provides the space and heat conservation of transfixing with the offset preventing advantages associated with cooling before separation without either slowing the main apparatus or elongating the intermediate.
  • the intermediate sheet can be wrapped around a transfer drum and recycled past one or more image members. This provides the registration advantages of a drum not usually obtainable in transfixing devices that require cooling before separation.
  • Fig. 1 is a side schematic of a multicolor image forming apparatus.
  • Fig. 2 is a side schematic of a portion of the apparatus shown in Fig. 1 illustrating the separation of intermediate and receiving sheets.
  • Figs, 3,4 and 5 are side schematics of alternative image forming apparatus.
  • Figs. 1, 3, 4 and 5 illustrate alternative image forming apparatus using toner image transfer intermediates.
  • each of the intermediates is conductive and image transfer to the intermediates is accomplished in the presence of heat and an electric field according to a process described more thoroughly below.
  • the image on the intermediate is transferred and fused in a single step to a receiving sheet and the receiving sheet and intermediate are maintained in contact until the image is cooled sufficiently for separation without offset.
  • the method and apparatus disclosed herein can be used with receiving sheets made of ordinary paper, transparency stock, highly finished paper and the like. However, the best results are obtained if the receiving sheet has a heat-softenable thermoplastic outer surface to which the image is transferred.
  • an image member upon which electrostatic images can be formed can be of a variety or type including a drum or a belt.
  • an image member 1 is a drum which includes a photoconductive outer surface and which is rotatable past a series of stations.
  • the stations include a charging station 3 which uniformly charges the photoconductive surface.
  • a series of electrostatic images are formed by a suitable exposure means, for example, a laser 4, to create a series of electrostatic images on the photoconductive surface of image member 1.
  • Each of the electrostatic images is toned by one of toning stations 5, 6, 7 or 8 to create a series of toner images.
  • Toning stations 5, 6, 7 and 8 include toners of different colors, so that the series of electrostatic images are turned into a series of different color toner images.
  • the electrostatic images could be formed by other methods, for example, non-electrophotographically by imagewise ion deposition.
  • An intermediate sheet 20 is fed out of an intermediate sheet supply 33 to the periphery of a transfer drum 2 where it is held by a vacuum, gripping fingers or other means.
  • Drum 2 (which could also be an endless belt) is rotated a number of times to bring intermediate sheet 20 through transfer relation with the toner images carried on image member 1.
  • Each toner image is transferred to intermediate sheet 20 on a separate revolution of drum 2 to overlay the toner images in registration to form a multicolor toner image. This transfer is assisted by heat from lamp 24 and an electrical field from a source of potential 12 urging transfer of the toner images to the intermediate sheet 20.
  • Intermediate sheet 20 is preferably conductive.
  • it can be made entirely of nickel from 3 to 10 mils in thickness.
  • the surface of intermediate sheet 20 receiving the toner cages is made hard and smooth.
  • Drum 2 is also preferably metallic, allowing good conduction of heat from lamp 24 and also of the bias from potential source 12.
  • image member 1 can include a compliant layer underneath suitable photoconductive and conductive layers.
  • image member 1 can be an aluminum drum to which is attached a thin compliant silicone rubber or other material and on top of which is stretched a web or sheet photoconductor having a grounded conductive backing layer. Transfer from image member 1 to intermediate sheet 20 can also be assisted by moderately heating image member 1 internally. However, as will be described later, this does not appear to be necessary using a metallic intermediate.
  • a wedge or skive 15 is activated and moved into contact with drum 2 to separate intermediate sheet 20 therefrom.
  • a receiving sheet 10 is fed from a receiving sheet supply 22 into overlying relation with the image on intermediate sheet 20 as these sheets enter a nip 79 between pressure rollers 32 and 34.
  • At least one of the pressure rollers, for example, roller 32 is heated internally by a lamp 36 and sufficient pressure is applied between the rollers to effect transfer of the multicolor toner image to the receiving sheet.
  • Intermediate 20 and receiving sheet 10 form a sandwich which is fed by rollers 32 and 34 onto a transport 40 for transport away from heating lamps 36 and 24.
  • the sandwich can be stopped while it cools or moved much slower by transport 40 allowing cooling at a slower speed which greatly shortens the path required for such cooling.
  • sheets 20 and 10 can be cooled by a forced air cooling mechanism 49 located inside transport 40.
  • a cooling mechanism can also be located on the opposite side of the sandwich. Much greater flexibility in cooling is available with the sandwich not forced to move at the same speed as drum 2 and rollers 32 and 34.
  • transport 40 includes a transport roller 46.
  • transport 40 moves the leading edges of receiving sheet 10 and intermediate sheet 20 past transport roller 46 the leading edge of sheet 20 is sensed by an optical or other suitable sensor 83.
  • a separation pawl 75 is actuated by a solenoid 80 in response to sensor 83 to rotate clockwise into the leading portion of intermediate sheet 20 prior to arrival of the leading edge of receiving sheet 10.
  • Pawl 75 substantially deflects intermediate sheet 20 from its path. The toner image having cooled below its glass transition temperature no longer holds these sheets together and the stiffness or beam strength of the receiving sheet 10 causes the two sheets to separate with the receiving sheet going above separation pawl 75 and the intermediate sheet 20 going below.
  • the receiving sheet 10 progresses on to be further treated. For example, it can be texturized at a station, not shown, or cut at a cutting station 60 and ultimately placed in an output hopper 62. Meanwhile, intermediate sheet 20 proceeds into transport rollers 85 which ultimately feed it along a path back to intermediate sheet supply 33.
  • receiving sheet 10 has a heat-softenable thermoplastic outer layer on its bottom side as seen in Fig. 1.
  • the thermoplastic outer layer can be preheated by any suitable means, for example, by passing between a pair of rollers 95, one of which is heated or by a suitable shoe contacting the backside of receiving sheet 10 immediately before it enters nip 79.
  • the thermoplastic outer layer is heated to its softening point either by the preheating device or by contact with intermediate 20 or by rollers 32 and 34 or a combination of these.
  • the toner image is at least partially embedded in the thermoplastic layer as the sheets 10 and 20 pass between rollers 32 and 34 with any toner not so embedded leveled by pressure and heat in the same process.
  • drum 2 is moving at full machine speed at all times, for example, four inches per second.
  • Pressure rollers 32 and 34 also would operate at the same speed as drum 2. This allows these rollers to be positioned adjacent drum 2 without a slack box or loop between drum 2 and rollers 32 and 34.
  • Transport 40 can then be operated at one inch per second or slower or be stopped allowing the sandwich to cool adequately without slowing drum 2. With rollers 32 and 34 positioned close to drum 2, most of the heat passed to intermediate 20 by drum 2 is not lost. The overall result is a much more compact and heat-efficient apparatus than if a fusing belt were used for both the fixing and cooling steps. (Compare, for example, the structure shown in Fig. 5.)
  • intermediate sheet 20 and receiving sheet 10 can be fed into nip 79 with pressure rollers 32 and 34 permanently urged together, better results are obtained if these rollers are separated and moved together as the beginning of receiving sheet 10 reaches the center of the nip.
  • Fig. 3 shows an alternative embodiment of the structure shown in Fig. 1 in which image member 1 and drum 2 are identical in construction and operation with that in Fig. 1.
  • the pressure rollers 32 and 34 have been replaced by a single articulatable pressure roller 32 which moves into pressure applying relationship with drum 2 after all images have been transferred to intermediate sheet 20.
  • intermediate sheet 20 leaves the transfer nip with image member 1 after the final single color image has been transferred to it producing the desired multicolor image, it approaches nip 79 established between drum 2 and heated pressure roller 32.
  • a receiving sheet 10 is fed from receiving sheet supply 22 into overlying relation with the toner image as it enters nip 79.
  • pressure roller 32 is moved toward drum 2 with sufficient force to fuse the multicolor toner image to receiving sheet 10 as in the Fig. 1 embodiment.
  • receiving sheet 10 is preferably preheated by a suitable shoe or heated rollers, especially if receiving sheet 10 has a thermoplastic outer layer.
  • the sandwich of intermediate sheet 20 and receiving sheet 10 is separated by articulatable skive 15 as in Fig. 1 and transported for cooling and separation by transport 40, also as in Fig. 1.
  • This embodiment has the advantage of fewer parts and more compactness. It also further conserves heat since intermediate sheet 20 has had no chance to cool by leaving drum 2 at all before the fusing step as in Fig. 1. For highest quality work with this embodiment, care must be taken to not disturb an exposure operation on image member 1 in creating further electrostatic images when articulatable heated roller 32 is moved into contact with receiving sheet 10. Although this can be accommodated by beginning the exposure of the next image after roller 32 is applying pressure to the receiving and intermediate sheets, movement of roller 32 away from drum 2 at the completion of the fixing may also have an effect on such exposure. Again, careful timing can prevent a injurious affect on the electrostatic image; for more details for such high-quality work, see U.S. Patent 5,021,835, mentioned above.
  • Fig. 4 shows still another embodiment similar to the structure shown in Figs. 1-3.
  • image member 1 has been replaced by four image members 101, 102, 103 and 104, known generally in the art.
  • Each of these image members can have a photoconductive outer surface or other means for forming electrostatic images.
  • each of the image members is uniformly charged by charging device 113 and is exposed by a suitable exposure device, for example, lasers 115, 116, 117 and 118 to create a single electrostatic image on each image member.
  • Each electrostatic image is toned by one of toning stations 105, 106, 107 and 108.
  • Each of the toning stations contains a different color toner to provide a different color toner image on each image member.
  • the image members are continuously cleaned before charging by suitable cleaning devices 109.
  • Image member 1 is continuously cleaned by a suitable cleaning device 9.
  • An intermediate sheet 20 which is the same as the intermediate sheets used in Figs. 1-3 is fed from intermediate supply 33 onto a large transfer drum 102 where it is held by vacuum, gripping fingers, or other suitable means.
  • intermediate sheet 20 is heated by a lamp 24 inside transfer drum 102 to a temperature sufficient to raise the temperature of the toner images on each of the image members above their glass transition temperatures at least where the toner particles contact intermediate sheet 20 or each other. Transfer is further assisted by an electrostatic field between intermediate sheet 20 through drum 102 from voltage source 12. As in Figs. 1-3, some width of the nips can be obtained by compliant backing layers on image members 101 through 104.
  • Each of the different color toner images are transferred from their respective image members to the outside surface of intermediate sheet 20 in registration to form a multicolor image.
  • the multicolor image is then transferred and fixed to a receiving sheet 10 fed from receiving sheet supply 22 into overlying relation with the image on intermediate sheet 20 by heated pressure roller 32 substantially as in the Fig. 3 embodiment.
  • the receiving and intermediate sheets are separated from drum 102 as a sandwich by permanent skive 15 and picked up by transport device 40 as in Fig. 3.
  • This embodiment creates a three or four color image on less than a single revolution of drum 102 and can therefore be four times as fast as the Figs. 1-3 structure. It has the known disadvantage of more difficulty in maintaining registration between images for highest quality work compared to the single transfer position embodiment shown in Figs. 1-3. As with the other embodiments, for highest quality work, receiving sheet 10 has a heat-softenable outer layer. Although it is not absolutely necessary that pressure roller 32 be articulatable, it is still preferred for best overlaying of the leading edges of the sheets.
  • Fig. 5 illustrates use of an endless belt intermediate which does not have the advantages of separate intermediate sheets illustrated in Figs. 1-4, but can utilize the advantages of a conductive intermediate with electrostatic and heat assisted transfer. Like the Figs. 1-4 embodiments, it illustrates the transfer process to be described below. Since it does not include a separate intermediate sheet, it is useful for comparison purposes only with respect to that feature.
  • image member 1 is constructed as in Fig. 1 and creates a series of different color single color toner images. These images are transferred in registration to an intermediate 220 which is an endless belt made of electroformed nickel. The nickel surface can be covered with a very thin layer of a suitable silicone or fluoride to enhance its release capabilities.
  • the single color toner images are transferred in registration to intermediate 220 under the influence of an electric field from a source of potential 12 and after being heated by contact with intermediate 220. The transfer is performed in a nip 279 between intermediate 220 and image member 1 where image member 220 is backed by a metallic roller 202 having a lamp 224 for heating both roller 202 and intermediate belt 220.
  • a multicolor image is formed on intermediate belt 220 which is transferred at a second roller 234 to receiving sheet 10 fed from receiving sheet supply 22.
  • Receiving sheet 10 is pressed by a pressure roller 232 against intermediate 220 where intermediate 220 is backed by roller 234.
  • Pressure roller 232 is articulatable toward roller 234 after the multicolor image has been formed on intermediate belt 220.
  • Receiving sheet 10 maintains contact with intermediate belt 220 while it is cooled by forced air cooling mechanism 249 along a flat section of the belt travel.
  • the belt is passed around a small roller 242 after the image is sufficiently cool for separation from intermediate belt 220, at which point the stiffness of receiving sheet 10 causes it to separate and pass onto cutter 60 and output tray 62.
  • belt 220 may be too large for efficiency with single multicolor images. Accordingly, several multicolor images can be made at the same time by, for example, making two or three images of the same color at a time and placing two or three images on belt 220 before the next three images of a different color are formed and transferred to belt 220. Belt 220 would then be, for example, two images in length. Alternatively, belt 220 could be one or two ledger-size images in length and two or four letter-sized images in length and operate at full efficiency in each mode; see, for example, U.S. Patent 4,712,906, Bothner et al.
  • receiving sheet 10 can have a thermoplastic outer layer which improves both resolution and gloss in the final image.
  • the temperature of the heat softenable layer cannot be allowed to get too hot for risk of injury to the photoconductor from which it is being transferred.
  • the toner may get hot where it contacts the photoconductor and fuse to the photoconductor ruining transfer efficiency.
  • Controlling the temperature is challenging through a receiving sheet which also contains a certain amount of moisture. The moisture can turn into steam if the temperature gets above 100°C and blister the sheet while if the temperature is much below 100°C, consistent softening of the thermoplastic layer is difficult to achieve.
  • Preheating the photoconductor can help, but it can only be heated to a temperature that does not damage it.
  • an intermediate which is highly thermally conductive for example, one made entirely of nickel or of nickel coated stainless steel, requires less energy to heat than a receiving sheet with lower thermal conductivity. Its temperature is much easier to control.
  • the conductive intermediate does not have the affinity for toner that a softened thermoplastic coated receiving sheet has, transfer of the first layer or layers is somewhat more difficult.
  • a thermally and electrically conductive intermediate is used which is heated high enough to heat the toner it touches to its glass transition temperature and an electrical field is also impressed between the intermediate and the image member, transfer efficiency comparable to that with thermoplastic coated receivers is obtained. With most toners, transfer efficiencies of 90-96% are obtained. With some toners, transfer efficiencies of 99% and higher are obtained.
  • these transfers are obtained at pressures as low as 50 pounds per square inch and lower with a quality comparable to that with the thermoplastic coated receiver at 600 pounds per square inch. This provides substantial improvement in the life of the image member as well as making manufacture and design of apparatus easier. In highest quality work, the high pressure transfer is more susceptible to perturbations that could alter the motion of the image member during exposure adversely affecting an image.
  • metal intermediates Although stainless steel, nickel and aluminum and other metals are preferred for the intermediate, they may be covered with a very thin layer of a conductive release material which has sufficient carbon or other particles in it to make it both heat and electrically conductive.
  • a conductive release material which has sufficient carbon or other particles in it to make it both heat and electrically conductive.
  • Materials suitable as surface treatments for metal intermediates include low surface energy polymers such as silicones and fluoropolymers containing metal salts as filler particles, like aluminum oxide and carbon, and metal/polymer alloys such as electro-deposited nickel/fluoropolymer coatings. In general, as shown by the examples below, remarkable results are achieved without such release materials.
  • This particular process is especially useful in transferring toner particles less than 5 microns in mean particle diameter, because such toner particles are virtually impossible to transfer with high efficiency using an electric field alone. As described above, this is due to greater effect on small particles of van der Waals and other similar adhesive forces than the force from an electric field. For that reason, some sort of heat assist is necessary with such fine particles.
  • the electric field appears to substitute for the thermoplastic layer on the receiver of the prior heat assisted systems, with the substantial improvements noted.
  • an aluminum drum was covered first with a 33 mil thick polycarbonate sheet of 87 shore A hardness and then with an inverse composite organic photoconductor element.
  • the photoconductor element included conventional conductive and photoconductive layers on a support.
  • the photoconductive layers were charged to between -400 and -450 volts and exposed for two seconds through a .7 neutral density filter.
  • the discharged areas of the photoconductor were toned with a magnetic brush at a bias of 45 volts with positively charged cyan toner.
  • Three cyan toner images so formed were transferred on top of each other to a nickel sheet wrapped around a metallic drum.
  • the examples were repeated under varying heat, pressure, and electric field conditions. The results are tabulated as follows:
  • the pressure is given in pounds per linear inch. A pressure of 20 pounds per linear inch corresponds roughly to a peak pressure of 200 pounds per square inch in such a nip.
  • the electrical field is created by biasing the metallic transfer drum and grounding the conductive layer of the photoconductive element. The toners are
  • the percent of toner transferred was measured by transferring both the transferred image(s) and the residual image on the photoconductor to separate receiving sheets.
  • the reflection density of the images on the receiving sheets was measured by an X-rite densitometer and compared.
  • Examples 16-24 were all carried out with a field of -450 volts, pressure of 20 pounds per linear inch and at 4 inches per second.
  • Toners #2, 5 and 6 are powder compositions which comprise core particles of small particle size that are coated with minute transfer-assisting particles of colloidal silica, colloidal polymer or colloidal alumina.
  • the core particles, of which a thermoplastic binder polymer is the major component, are pigmented and contain an ionic charge control agent.
  • the transfer-assisting particles can be from 0.01 to 0.2 microns in size and are uniformly distributed upon the surface of the toner. They are the subject of cofiled patent application Serial No. 07/843,664.
  • the binder polymer is a low molecular weight styrene-butyl acrylate copolymer, such as Piccotoner 1221* polymer supplied by Hercules Co.
  • the pigment is bridged aluminum phthalocyanine.
  • the core particles of 3.5 microns average diameter are made by the evaporative limited coalescense process disclosed in U.S. Patent No. 4,833,060, which patent is incorporated herein by reference.
  • the core particles of the toner have an overcoat which makes up about 3 wt.% of the coated particles and which is formed by coating the particles with an aqueous dispersion of the selected colloidal-size material. Following are examples of useful procedures and materials for coating the core particles.
  • Toner #2 To a 40-g portion of the core toner particles in a blender is added dropwise 29.2g of an aqueous colloidal dispersion of silica containing 4% solids by weight. The latter is prepared by dilution of Nalcoag 1060* silica, a 50% by weight dispersion of silica having an average particle size of about 0.060 microns. After agitation for about 30 min., the coated toner is dried at room temperature.
  • Toner #5 A 40-g portion of core toner particles in a blender is treated with a mixture of 50g of a monodisperse latex of styrenesodium styrenesulfonate copolymer (2.4% solids by weight; average particle size about 0.1 microns) and 7g of water. After brief further agitation, the coated toner is dried for 30 min. under vacuum in a microwave oven at 30% power to prevent fusion of the toner particles.
  • Toner #6 As in Toner #2 above, 24g of an aqueous dispersion of aluminum oxide containing 5% solids by weight (Aluminum Oxid C*, from Degussa Corp.) diluted with 16g of water is added to 40g of the core toner particles in a blender. After brief further agitation, the coated toner is dried as with Toner #5, above.
  • Aluminum Oxid C* aluminum oxide containing 5% solids by weight
  • the glass transition temperature of the toners be fairly low, for example, between 55 and 70°C. Good transfer can be obtained less than 10° above this glass transition temperature. Although good transfer can also be obtained at 90 or 100°C, using these higher temperatures is more likely to damage the image member if the temperature is poorly controlled.
  • Toner #2 in the above examples has a glass transition temperature about 60°C.
  • the method will work at higher pressures, there are substantial system advantages to maintaining the pressure below 300 psi and less. The method will work at 100 psi.
  • the nickel sheet was removed, overlaid with a high quality laser print paper receiving sheet and fed by hand through a pair of fusing rollers, both of which were heated.
  • the sheets were allowed to cool and were then separated with the three images stored in overlapping relation on the receiving sheet. Measurements to determine transfer efficiency were done with these images.
  • the transfer of the multicolor image formed on the intermediate to the receiving sheet is similar to transfusing or transfixing processes in the prior art.
  • ordinary fusing temperatures and pressures can be used for ordinary transfer to a paper receiving sheet.
  • the second transfer is best made to a receiving sheet having a heat-softenable thermoplastic outer layer.
  • that layer is preheated to its softening point.
  • Higher pressures are desired than with ordinary fusing, for example, pressures substantially in excess of 100 pounds per square inch.
  • the receiving sheet and the intermediate should be left in contact until both the image and the thermoplastic layer have cooled below their softening temperatures, as shown in Figs. 1-5.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Fixing For Electrophotography (AREA)
  • Color Electrophotography (AREA)
EP93102383A 1992-02-28 1993-02-16 Bilderzeugungsverfahren und Apparat unter Verwendung eines Zwischenbildträgers Withdrawn EP0557858A1 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US843664 1992-02-28
US843666 1992-02-28
US07/843,664 US5253021A (en) 1992-02-28 1992-02-28 Method and apparatus of transferring toner images made up of small dry particles
US07/843,666 US5428430A (en) 1992-02-28 1992-02-28 Image forming method and apparatus using an intermediate

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0775948A1 (de) * 1995-11-24 1997-05-28 Xeikon Nv Mehrfarben elektrostatographischer Drucker mit einem Umlauf
EP0800114A2 (de) * 1996-03-11 1997-10-08 Fuji Photo Film Co., Ltd. Bilderzeugungsverfahren und System
EP0871082A1 (de) * 1997-04-07 1998-10-14 Xeikon Nv Elektrostatographisches Druckgerät und Verfahren
EP1014219A2 (de) * 1998-12-23 2000-06-28 Xerox Corporation Drucksystem mit gleichzeitigen Übertragung und Fixierung

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1132215A (ja) 1997-07-10 1999-02-02 Fuji Photo Film Co Ltd 写真画像、その形成方法及び装置、並びにそのための記録媒体

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US4935788A (en) * 1988-06-16 1990-06-19 Xerox Corporation Multicolor printing system
US4992833A (en) * 1989-08-10 1991-02-12 Eastman Kodak Company Fixing method and apparatus having a transfer-fixing chilling drum
WO1991003771A1 (en) * 1989-09-11 1991-03-21 Eastman Kodak Company Toner fixing method and apparatus and image bearing receiving sheet
US5171653A (en) * 1991-09-06 1992-12-15 Xerox Corporation Electrostatic developing composition with carrier having external additive

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Publication number Priority date Publication date Assignee Title
US4935788A (en) * 1988-06-16 1990-06-19 Xerox Corporation Multicolor printing system
US4992833A (en) * 1989-08-10 1991-02-12 Eastman Kodak Company Fixing method and apparatus having a transfer-fixing chilling drum
WO1991003771A1 (en) * 1989-09-11 1991-03-21 Eastman Kodak Company Toner fixing method and apparatus and image bearing receiving sheet
US5171653A (en) * 1991-09-06 1992-12-15 Xerox Corporation Electrostatic developing composition with carrier having external additive

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PATENT ABSTRACTS OF JAPAN vol. 13, no. 460 (P-946)18 October 1989 & JP-A-01 179 181 ( CANON ) 17 July 1989 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0775948A1 (de) * 1995-11-24 1997-05-28 Xeikon Nv Mehrfarben elektrostatographischer Drucker mit einem Umlauf
EP0800114A2 (de) * 1996-03-11 1997-10-08 Fuji Photo Film Co., Ltd. Bilderzeugungsverfahren und System
EP0800114A3 (de) * 1996-03-11 1998-06-17 Fuji Photo Film Co., Ltd. Bilderzeugungsverfahren und System
US6155726A (en) * 1996-03-11 2000-12-05 Fuji Photo Film Co., Ltd. Image forming method and system
US6183933B1 (en) 1996-03-11 2001-02-06 Fuji Photo Film Co., Ltd. Image forming method and system
EP0871082A1 (de) * 1997-04-07 1998-10-14 Xeikon Nv Elektrostatographisches Druckgerät und Verfahren
US6052551A (en) * 1997-04-07 2000-04-18 Xeikon N.V. Electrostatographic printer and method
EP1014219A2 (de) * 1998-12-23 2000-06-28 Xerox Corporation Drucksystem mit gleichzeitigen Übertragung und Fixierung
EP1014219A3 (de) * 1998-12-23 2001-08-08 Xerox Corporation Drucksystem mit gleichzeitigen Übertragung und Fixierung

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