Classifications

• • 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

Definitions

• the present invention relates to multicolor electrophotographic reproduction apparatus and methods and. more specifically, to the improved production of copy in selected colors.
• Brief Description of the Prior Art In U.S. Patent 4.045,218 an apparatus is described for producing color accented reproductions from originals of a single color. In ' this method, an original such as a letter is placed at a copier's exposure station and an indicator member adjusted to identify which lines are to be reproduced in which colors.
• the first ten lines of an original black-on-white letter may be desired to be reproduced in say red and the remainder.of the letter to be reproduced in its original color black.
• the patent discloses that the entire original may be exposed onto a primary charged photoconductor to produce a latent electrostatic image thereof and the portion to be reproduced in black is erased by an electroluminescent panel. The remaining image is then developed with red toner. The original is then again exposed onto the photoconductor but this time the information to be reproduced in red is erased and the electrostatic latent image developed with black: toner. The two toner images are then transferred to a copy sheet in registration with one another to provide the multicolored reproduction.
• three colors may be provided in the reproductions where three developer stations are used.
• the invention is directed to an electrophotographic reproduction method and apparatus for producing copies with color accenting, i.e.. in colors different from that of an original.
• signals are provided related to the desired color and position of an image area to be color accented.
• a plurality of image frames are used to reproduce the original and these image frames are developed with differently colored toners that are superimposed when transferred to a copy sheet to form a reproduction of the area to be color accented in a color different than that of the original.
• the charge level on one of these image frame(s) is reduced from its primary voltage to an intermediate level needed for the color accenting.
• Information not to be reproduced by color accenting is selectively erased entirely from this image frame.
• a three color copier using subtractive colored toners of cyan, magenta and yellow more than three image frames may be used to produce copy.
• the additional frames being used to provide intermediate charge levels needed for color accenting. For example, where up to six image frames are used to produce copy, three of the frames may be devoted to reproducing information near the primary charge level of Vo with selected areas erasable to a level below which will permit development. In a system constrained to use
• Vo allows for 3 . or 27 colors, i.e., 25 colors plus black and white.
• the charge level is reduced to one-half Vo on the selected image frame by exposure of a non-image information bearing light source through a half-tone screen.
• FIG. 1 is a perspective view of a multicolor electrophotographic reproduction apparatus for practice of the present invention.
• FIG. 2 is a schematic side view of the operating elements of the multicolor electrophotographic reproduction apparatus for practice of the present invention.
• FIG. 3 is a schematic illustration in cross- section of some of the elements forming a multi- layered photoconductive member for use in the apparatus of Fig. 2.
• FIG. 4 is a schematic illustrating a data input station and block diagrams of controls for control ⁇ ling the apparatus shown in Figs. 1 and 2.
• FIG. 5 is an illustration of a document that is to be reproduced with selected color accenting.
• FIG. 6 is an illustration of various image frames on the photoconductor used to produce a color accented copy.
• the apparatus 10 includes a closed loop, flexible image transfer member, or photoconductive web 12.
• the web 12. which may be of the type described in FIG. 3 is supported on rollers 5 - 8.
• the rollers are mounted on the copier frame (not 0 shown) with one of the rollers, for example roller 5. rotatively driven by a motor 16 to effect continuous movement of the web 12 in a clockwise direction about its closed loop path.
• the web has a plurality of sequentially spaced, nonoverlapping 5 image areas which pass successively through electrophotographic processing stations (charge, expose, develop, transfer, clean) located about the path of the web.
• the web also includes timing marks (or regularly spaced perforations) which are sensed 0 by appropriate means, such as timing signal generator 17 to produce timing signals. Such signals are sent to a computer controlled logic and control unit 31.
• the LCU 31 controls the entire electrophotographic process based on the 5 instantaneous location of the web in the travel path.
• An encoder 18 associated with the roller drive motor 16 also produces timing signals for the LCU. The signals from the encoder cause the LCU to fine tune the process timing.
• the LCU 31 has a digital computer, preferably a microprocessor.
• the microprocessor has a stored program responsive to the input signals for sequentially actuating, then de-actuating the work stations as well as for controlling the operation of many other machine functions.
• microprocessors such as one or more INTEL model 8086 microprocessor (which along with others can be used in accordance with the invention), is a conventional skill well understood in the art. This disclosure is written to enable a programmer having ordinary skill in the art to produce an appropriate control program for the microprocessor. The particular details of any such program would, of course, depend on the architecture of the designated microprocessor.
• LCU 31 logic and control unit 31 which interfaces with the apparatus 10.
• the LCU 31 consists of temporary data storage memory 42, central processing unit 43. timing and cycle control unit 44. and stored program control 46. Data input and output is performed sequentially under program control. Input data are applied either through input signal buffers 50 to a input data processor 41 or to interrupt signal processor 45. The input signals are derived from various switches, sensors, and analog-to-digital converters. The output data and control signals are applied to storage latches 47 which provide inputs to suitable output drivers 48, directly coupled to leads. These leads are connected to the various work stations, mechanisms and controlled components associated with the apparatus.
• a multicolored original document sheet D to be reproduced is placed, image side down, on a 5 transparent glass platen 20 supported by the copier frame.
• Exposure lamps 22, such as xenon flash tubes, are located beneath the platen 20 within the frame. The lamps flood the document sheet with light and a reflected image of the document sheet is 0 transmitted via mirror 24, lens 26, and mirror 28 in focus to an area 30 lying in the plane of the web 12.
• the original document could, of course, be a transparency illuminated from the back side thereof.
• the document sheet D is illuminated, for example, four times in succession to form four separate electrostatic latent image frames of the document.
• a red filter 32R, a green filter 32G, o o ⁇ a blue filter 32B is inserted into the light path to form color separation images at the area 30.
• a fourth filter comprising a neutral density filter 32N for providing what is known as a skeletal black image is inserted during a fourth exposure of the 5 original or may be used for coloring areas to be developed in black.
• the timing of the flash of lamps 22 and the insertion of the colored filters are controlled by the LCU and related to the travel of the web 12 to expose adjacent, nonoverlapping 0 areas of the web to the color separation images and the skeletal black image.
• One or more corona charging units exemplified by corona charger 34, is located upstream of the exposure area 30, and applies a generally uniform primary electrostatic charge, of say negative polarity, to the web 12 as it passes the charger and before it enters the exposure area.
• a programmable power supply may be provided to selectively apply to each image frame a predetermined generally uniform electrostatic primary charge level Vo suitable for developing the particular color toner used to develop that image frame.
• the photoconductive properties of the web cause the primary charge in the exposed areas of the web to be discharged in that portion struck by the exposure light. This forms latent imagewise charge patterns on the web in the exposed areas corresponding to the respective black and color separation images. Travel of the web then brings the areas bearing the latent images into a development area 36.
• the development area has a plurality of magnetic brush development stations, corresponding to the number of formed black and color separation images, in juxtaposition to. but spaced from, the travel path of the, web.
• Magnetic brush development stations are well known; for example, see U.S. Patent 4.473,029 to Fritz et al and 4.546,060 to Miskinis et al.
• the color separation images are red. green, blue and a skeletal black image is also to be provided
• the toner particles are agitated in the respective developer stations to exhibit a triboelectric charge of opposite polarity to the latent imagewise charge pattern.
• Backup rollers 38C, 38M, 38Y, and 38B located on the opposite side of web 12 from the development area, are associated with respective developer stations 36C, 36M, 36Y and 36B.
• Actuators 40C, 40M. 40Y and 40B selectively move respective backup rollers into contact with the web 12 to deflect the web from its travel path into operative engagement with respective magnetic brushes.
• the charged toner particles of the engaged magnetic brush are attracted to the oppositely charged latent imagewise pattern to develop the pattern.
• the logic and control unit 31 selectively activates the actuators in relation to the passage of the image areas containing corresponding latent color separation images through the development area 36. That is, as the area containing the latent red color separation image reaches the development station 36C. actuator 40C moves the backup roller 38C to deflect the web so that the latent charge image is developed by attracting cyan toner particles from the station 36C. As soon as the image area leaves the effective development area of the station 36C, the actuator 40C returns the backup roller 38C to its nondefleeting position. Thus., as the areas containing the green and blue color separation images and the neutral density latent image pass the developer station 36C, no development takes place. A similar cycle is accomplished by the logic and control unit 31 for the developer stations 36M.
• the red latent color separation image is developed only with cyan toner particles
• the green latent color separation image is developed only with magenta toner particles
• the blue latent color separation image is developed only with yellow toner particles
• the neutral density latent image is developed only with black toner.
• a transfer roller 68 includes a compliant insulating surface thereon and is biased to a potential suitable for transfer of the developed image on the first image sector to the copy sheet S and to tack copy sheet S to roller 68.
• Roller 68 is driven by a stepper motor 19 which receives actuating signals from the LCU 31.
• Roller 68 may also be a biased vacuum roller or a roller with sheet clamping mechanisms to clamp the sheet to it. Continued movement of web 12 and synchronized rotation of roller 68 brings the lead edge of copy sheets back into transferable relationship with the web as the lead edge of the next toner image arrives at roller 68. At this point, sheet S remains tacked to roller 68 and the second toner image is transferred in superimposed registration with the first toner image on sheet S. The process is repeated until toner images on each of the first three image sectors have been transferred to the same surface of sheet S and the leading edge of copy sheet has been brought back into transferable relationship with the fourth toner image on the web.
• a corona charging station 70 and a rear erase lamp 71 may be located upstream of the cleaning unit 66 to neutralize any charge remaining on the web and thus reduce the adherence forces of the toner to the web.
• a document sheet such as document sheet D (see FIG. 5) having composite information comprised of line-type information in areas A. B and C and multicolor continuous-tone information in areas E and F.
• the document sheet D is placed face up on a digitizing tablet 52 and registered against an appropriate corner (or centered relative to a predetermined edge) as shown in FIGS. 1, 4 and 5.
• a wand 53 is associated with the tablet and used by the operator to determine the format of the original and the locations of the various parts of the image information.
• the operator calls up a special program for accomplishing this task via inputs of a code on a keyboard 51 which is part of the control panel.
• the operator presses a for at input button 57 and moves the wand in turn to points e, f (or just point g which contains the coordinates of e and f) on the digitizing tablet to define the format of the document D.
• Transducers may be located beneath the sheet to produce signals relating the position of the points touched relative to the registered upper left corner of the sheet.
• the tablet may be of the known sonic type wherein a spark formed by a wand creates sound waves in the air which are sensed by microphones placed along the sides of the tablet or wherein a sensor is placed in the wand and sources at known points on the sides of the tablet emit sonic signals (see. for example. U.S. patents Nos. 4.012,588 in the name of Davis et al and 4.124.838 in the name of Kiss).
• a digitizer controller 54 knowing the times of emitting of the signals and their receipt can through triangulation principles calculate the location of a point on the platen relative to a known point such as the upper-left corner shown.
• the operator inputs the desired color for the information appearing in area A by de ⁇ pressing an accent input button 58 and one of the 25 color buttons 61 in the apparatus' menu of available colors and moves the wand to four or more points to define an imaginary rectangle or other area which encloses the information in area A and encloses no other information.
• the LCU is programmed to recognize that the area is bordered by the straight lines joining adjacent points and the coordinates for the rectangular area to be selectively colored are thus stored in temporary memory.
• the LCU may be programmed to recognize two diagonally opposite points as defining a rectangle.
• the LCU may also be programmed to receive inputs regarding other geometrical shapes. This information is outputted on the display 55 showing the relative position of the area A on the display, indicating the desired color accent for area A. and also illustrates the format of the document sheet D.
• Area C on the other hand is desired to be reproduced in a color, for example, a particular shade of orange that is included within the menu.
• a color for example, a particular shade of orange that is included within the menu.
• 0 identifies the rectangular area C using the digitizer and depresses the button assigned for this color.
• Inputs from the digitizer and the color select buttons are inputted into the LCU through 5 interrupt signal processor 45 and are stored in temporary memory 42.
• the operator next takes the document sheet D and places it on the exposure platen (using feeder 15 for example) so that the side to be reproduced 0 faces the exposure lamps and registers the sheet with the appropriate corner (or centers it against a registration edge).
• the stored program control on the LCU has a program for compensating for the reversal of the sheet vis-a-vis the location of 5 areas when the sheet is face-up versus the location of these areas when the sheet is turned over for exposure.
• format input may not be needed where the same point on the sheet is registered when the sheet is both face up and face down.
• each color frame subsequent to exposure is passed between two linear illumination elements which extend across the width of the photoconductive web 12 transverse to the direction of web movement.
• a first illumination element 80 coupled to drivers 48 comprises LED's (light emitting diodes) 81 whose illumination is picked up by optical fibers 82 at one end thereof and carried to linear banks or holders where the fibers are aligned and spaced from a gradient index lens array 86 such as a Selfoc (trademark of Nippon Sheet Glass Co.. Ltd.) array.
• This array focuses illumination exiting the fibers onto a photoconductive surface of web 12.
• a linear array of LED's may be located proximate the web to expose the web directly or through a Selfoc lens without use of optical fibers.
• the photoconductive web 12 comprises a transparent support 90. a halftone screen 91. a conductive layer 92, and a photoconductive layer 93.
• the integral screen photoconductor may have the dot pattern that is printed therein rotated on adjacent frames so as to avoid moire patterns.
• key points or coordinates associated with the original document D have corresponding coordinates associated with each image frame 87 (designated by the x' , y' axes) which relate to the coordinates of the original and which are used to enable illumination from respective portions on the linear exposure element 80 (y" axes) at respective times established by corresponding x' abscissa coordinates.
• the second linear exposure element 85 is an electroluminescent light panel which is also coupled to drivers 48.
• the illumination from the panel as controlled by the drivers 48, is such in this embodiment as to image a screen pattern onto the photoconductive surface of each image frame.
• the screen 91 is preferably formed of rows of dots.
• the dots may be colored such as magenta to operate with a complementary-colored (green) screen exposure light source of electroluminescent panel 85 which provides an exposure of the screen pattern on the photoconductive surface from the rear of the web.
• the screen may be of "hard” or "soft” dots or may be comprised of lines or other shapes.
• the screen is preferably formed of "hard" dots or lines to form more uniform dots or lines over an image frame where the electro ⁇ luminescent panel may be providing nonuniform output over its length.
• the panel 85 in response to signals from the drivers is capable of generally uniformly outputting two levels of light throughout its linear length.
• the first level is a relatively low level that is adapted to image a screen pattern on an image frame of the photoconductor to screen all image areas thereof.
• the level of screen exposure will be relatively low and reduce the primary voltage level V to a new level only about 60 volts or so from its normal level of about
• the second level illumination level is the relatively higher one and is adapted to not only image a screen pattern on an image frame but will reduce the average charge level of the image frame to one-half Vo.
• the black frame is the first to be exposed to illumination from the document sheet D and is exposed through the neutral density filter 32N.
• those LED's 81 providing illumi ination to the upper (as viewed in FIG. 4, lower as viewed in FIG. 2) linear exposure element between the ordinates corresponding to y 0. y.1 and y4.
• y_b are all turned on to substantially erase all charge on the portion of this image frame between abscissa lines corresponding to xo and x,1, and 4, and xb respectively, to erase the charge areas on this frame reproducing the information in rectangles A and C. respectively.
• the electroluminescent light panel 85 is turned on to its low level and illuminates a screen pattern over this entire image frame.
• the cyan frame is the next to be exposed to illumination from the document sheet D and is exposed through a red filter 32R. As this frame passes between the linear exposure elements. selected LED's provide illumination between the ordinate line pairs corresponding to y . y . y , y and y . y . commencing with the 2 3 4 5 abscissa lines corresponding with x . x commodity and
• ⁇ ne first magenta frame is the next to be exposed to illumination from the document sheet D and is exposed through a green filter 32G. As this frame passes between the linear illumination elements, selected LED's provide illumination between the ordinate line pairs corresponding to y . y and y . y . commencing with the abscissa lines x , x . respectively, and terminating with the abscissa lines x , x ,
• the yellow frame is the next to be exposed to illumination from the document sheet D and is exposed through a blue filter 32B.
• selected LED's provide illumination between the ordinate line pair corresponding to y , y commencing with the abscissa line corresponding to x and terminating with the abscissa line corresponding to x . This being done to erase all charge information on areas in this frame reproducing information in rectangle B.
• the electroluminescent light panel 85 is illuminated at its low level for this image frame, too.
• a fifth image frame to be developed with magenta toner is also provided with a primary charge and is also exposed to document D by flashlamps 22. As this frame passes between the linear illumination elements, selected LED's are illuminated to erase all charge information but for the information in areas on this frame reproducing information in rectangle C.
• the electroluminescent panel 85 is turned on at its high level for this frame to reduce the charge level at unexposed areas of this frame in rectangle C to a level of one-half Vo
• the five image frames are serially developed with respective colored toners (the fifth image frame being developed with magenta toner in this example) and the developed images thereon transferred in register to receiver sheet S. With the apparatus shown in FIG. 2, the first four image frames are transferred using transfer roller 68 and the fifth image frame transferred using. transfer charger 25. Alternatively all image frames may be transferred using transfer roller 68.
• the developed images are fixed and delivered to hopper 64 or accessory finishing unit 69.
• the resulting copy sheet includes reproductions of the photographs E and F which are reproduced in 4 colors and halftone screened to reduce contrast.
• the reproduction of area A originally in black is reproduced in red through combination or super position of magenta and yellow colored toners.
• the reproduction of area B is in black using only black toner.
• the reproduction of area C is in orange comprising a combination of a substantially V charge level in the yellow developed frame and one-half V charge level to one of the magenta developed frames.
• the screening of all information will be particularly beneficial to large solid areas which tend to appear mottled and of non-uniform color when developed without such screening.
• the apparatus as described herein is adapted to provide transfer of up to seven image frames, four devoted to images having charge levels averaging about V and three devoted to images having charge levels averaging about one-half V .
• additional f ames at still another voltage level may be provided for.
• the invention also contemplates the use of a light source which can accurately•reduce charge levels in selected areas of an image frame based on color accenting desired.
• a one half Vo level can be established on selected areas of the first magenta frame while leaving other areas on the same frame at substantially V then the use of additional frames beyond three and four may be dispensed with.
• variable output light sources with variable aperture arrays such as mechanically movable masks or alternatively electrically actuated masks such as PLZT arrays may be used to control screen illumination.
• PLZT is an abbreviation for a lead lanthanum zirconate titanate electro-optical material whose optical properties can be changed by an electric field.
• Illuminating panels or aperture arrays need not be linear, but can be areal and cover the area of the frame so that as a respective frame of the photoconductive web underlies the panel array illumination may then be selectively provided.
• the green colored light content of the LED's may be used to image a screen pattern on the electrostatic charge on the photoconductor in accordance with the requirements of the areas requiring selective screening and reduction of the average charge level to say one-half V .
• areas of o the photoconductor are required to be substantially erased of charge such as areas in an image frame to be selectively erased or interframe and edge areas of the photoconductor the current level to the LED's may be adjusted to provide light outputs in the red color.
• Control programs are known for illuminating a linear light source lying transverse to the direction of movement of a photoconductor for providing selective erase of charge from interframe and edge areas in accordance with encoded signals to the LCU determining the timing for illuminating a light source, at say. when the interframe area is positioned to be exposed to the light from the light source.
• An apparatus thus providing currents to selected LED's at levels suitable for generating light of a color to which the screen is transparent, for providing selective erase, and providing different currents to the LED's for generating light of a color to which the screen is not transparent, for providing selective screening, allows for the elimination of the need for an additional light source to provide the erase function.
• the invention is not limited to the use of a photoconductor with an integral screen.
• the screen may be separate from the photoconductor and when it is so, may be positioned adjacent the surface of the photoconductor that is to be developed.
• the image may be scanned upon the electrostatically charged photoconductor and may be imaged thereon using either a scanning reflection or transmission exposure of the original or using light which has been electronically generated from say a bit stream.
• segments of the original are scanned by a light source and the light modulated by the document is imaged upon the photoconductor.
• the information contents of a document are digitized into electrical signals by a suitable electronic image "reading" device and these signals used to modulate a light source such as a laser or LED arrangement which are then imaged upon the photoconductor.
• the image for the screen itself would be imaged upon the photo- conductor independently of the imaging source by the techniques described herein or their equivalent, however the selective erase function provided by the LED's could be incorporated into an electronic imaging device.
• the advantage to this would allow the electronic imaging source to be fed by a black only bit generator; yet 25 or more colors are available for accenting.
• Additional color levels may be provided for by incorporating a multicolor screen within the photoconductor and using multicolor illumination to illuminate a screen pattern on the image frames.
• light modulated only with a screen pattern is still considered to be "non-image information bearing light.”
• a screen may be used comprising a 60% dot magenta screen with a 30% dot cyan screen placed so that the dots of the two colored screens do not overlap.
• the charge level on the frame is reduced to 30* of V ; i.e., a 70* discharge level.
• the charge level on the frame is reduced to 60% of V ; i.e.. a 40% discharge level. With both lights on the charge on the image frame would be reduced to a level below which development can occur or 100% discharged. With no lights on. there is no discharge and the charge on the image frame remains at V .
• four discharge levels are possible
• modifications may include the use of a high percentage dot screen over a non-image bearing light source and repeated exposure of the photoconductor layer through the screen by the light source.
• the screen frequency can be varied in the direction of film motion by varying the frequency of light pulses exposing the photoconductor layer under the dot screen.
• the effective percent dot exposure is directly proportional to the frequency.
• I2B more than 22 colors in a two color apparatus.
• illumination sources or even charging devices which can be accurately controlled without use of a' screen may be used to reduce the charge to a predetermined percentage of V on a desired
• a high-resolution addressable light source may be used to synthesize a screen-like pattern.
• a photoconductor may be exposed to an image of an original, be developed and transferred to a copy sheet, the photoconductor cleaned, and the next exposure of the original be on the same photoconductor-ductor portion.
• signals from the LCU based on the menu colors selected determines the number of image frames to be exposed to the original document.
• the stored program control 46 stores the information regarding, for each color selected, the number of image frames needed to produce that color and how many of such frames are to be at about the average V level and how many that are to be at the averag a e one-half Vo level
• the selective erase light source and the screen light source locations are not critical other than each being locatable between the primary charging station and the development station.

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• Color Electrophotography (AREA)

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• 1986
  • 1986-12-15 EP EP19870900521 patent/EP0250556B1/de not_active Expired
  • 1986-12-15 JP JP62500088A patent/JPH0670725B2/ja not_active Expired - Lifetime
  • 1986-12-15 WO PCT/US1986/002674 patent/WO1987003708A1/en active IP Right Grant

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