US3690756A

US3690756A - Color xerography

Info

Publication number: US3690756A
Application number: US126742A
Authority: US
Inventors: William A Smith
Original assignee: Xerox Corp
Current assignee: Northrop Grumman Systems Corp; Xerox Corp
Priority date: 1971-03-22
Filing date: 1971-03-22
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12
Also published as: DE2213998A1; FR2130718B1; IT950399B; GB1365753A; NL7203733A; BE781001A; CA963522A; FR2130718A1

Abstract

An electrostatographic reproduction apparatus cable of producing a polychromatic copy of a color original upon a copy material comprising: 1. LIGHT SCANNING MEANS FOR FORMING A LIGHT IMAGE OF THE COLOR ORIGINAL; 2. BEAM SPLITTING MEANS FOR SEPARATING THE LIGHT IMAGE INTO AT LEAST A FIRST AND SECOND LIGHT BEAM, WHICH ARE CONDUCTED ALONG DIFFERENT OPTICAL PATHS OF EQUAL LENGTHS THROUGH SEPARATE FILTERS OF DISSIMILAR COLORS; 3. A UNIFORMLY CHARGED PHOTOCONDUCTIVE AREA AT THE TERMINUS OF EACH OPTICAL PATH, EACH AREA BEING SIMULTANEOUSLY DISCHARGED IN IMAGEWISE CONFIGURATION BY THE LIGHT BEAM IMPINGING UPON IT; 4. MEANS FOR SEPARATELY DEVELOPING THE RESPECTIVE IMAGED AREAS WITH TONER COMPOSITIONS OF DIFFERENT COLORS TO FORM DEVELOPED IMAGES OF DIFFERENT COLORS; AND 5. MEANS FOR MOVING A COPY MATERIAL IN SEQUENTIAL CONTACT WITH THE DEVELOPED PHOTOCONDUCTIVE AREAS WHEREBY THE DEVELOPED IMAGES ARE TRANSFERRED THERETO IN SUBSTANTIALLY PERFECT REGISTRATION TO THEREBY FORM A COMPOSITE COLOR IMAGE.

Description

United States Patent Smith [451 Sept. 12, 1972 COLOR XEROGRAPHY [72] Inventor: William A. Smith, Webster, NY.

[73] Assignee: Xerox Corporation, Rochester,

22 Filed: March 22,1971

211 Appl.No.:126,742

52 US. (:1 ..3ss/4 51 1111.01. ..G03g 15/00 58 Field 6: Search .355/4, 32

[56] References Cited UNITED STATES PATENTS 2,986,466 5/1961 Kaprelian ..3ss/4 x 3,292,486 12/1966 Mey .355/4 Primary Examiner-Samuel S. Matthews Assistant Examiner-Kenneth C. Hutchison Attorney-James J. Ralabate, William Kaufman and Barry Kramer ABSTRACT An electrostatographic reproduction apparatus cable of producing a polychromatie copy of a color original upon a copy material comprising:

1. light scanning means for forming a light image of the color original;

2. beam splitting means for separating the light image into at least a first and second light beam, which are conducted along different optical paths of equal lengths through separate filters of dissimilar colors;

3. a uniformly charged photoconductive area at the terminus of each optical path, each area being simultaneously discharged in imagewise configuration by the light beam impinging upon it;

4. means for separately developing the respective imaged areas with toner compositions of different colors to form developed images of different colors; and

5. means for moving a copy material in sequential contact with the developed photoconductive areas whereby the developed images are transferred thereto in substantially perfect registration to thereby form a composite color image.

10 Claims, 4 Drawing Figures MIRROR 2 1 3! 34 E] 1 27 155] or gin 33 26 O [8 32 0 com 0 eopv INPUT I OUTPUT 35 SIDE 36 37 38 q e10:

United States Patent 1 [151 3,690,756 Smith [451 Sept. 12,1972

PATENTEIISEP I2 I972 SHEEI 2 BF 3 DRUM '3 (5h: Q 53fi LIGHT SPLITTER I SECTION ORIGINAL LIGHT SPLITTER "I SECTION B STEPS Tic, 3

LlGI-ITSPLITTER l SECTION A LIGHT SPLITTER "'2 SECTION MIRROR 3 MIRROR 4 MIRROR I MIRROR "2 COLOR XEROGRAPHY This invention relates to polychromatic electrostatographic imaging and, more particularly, a xerographic system wherein an original is light scanned, .and the resultant light beam is separated into at least two parts which are sent through separate filters and used to simultaneously discharge in imagewise configuration separate charged photoconductive areas. The imagewise discharged photoconductive areas are developed with toner compositions of different colors and the developed images are successively transferred in registered configuration onto a copy material which may be a stack of separate sheets or a continuous copyweb. In one embodiment, separate photoconductive surfaces are placed at the terminus of each optical path. The size and location of the photoconductive surfaces are such that the copy material traveling from one surface to another, receives superimposed toner images of different color thereby producing a color reproduction of the original. By employing photoconductive surfaces of different circumferences, each surface can be driven by the same drive means at the same lineal speed, the copy material can likewise move at one and the same speed, and critical timing problems, which would arise if three photoconductor surfaces of the same circumference were used, are obviated.

The electrostatographic system of this invention may suitably include three photoconductive areas, each being discharged in imagewise configuration representative of a single color component of the original, and developed with toner of a primary color, whereby when all three developed images are superimposed on the copy material, a full color reproduction of the original is created.

The formation and development of latent electrostatic images on an electrostatographic imaging surface is well known. The basic electrostatographic process, as taught by C. F. Carlson in U.S. Pat. No. 2,297,691, involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light and developing the resulting latent electrostatic image by depositing on the image a finely-divided electroscopic material referred to in the art as toner. The toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the latent electrostatic image. This powder image may then be transferred to a support surface such as paper. The transferred image may subsequently be permanently affixed to the support surface as by heat. The powder image may be fixed to the photoconductive layer if elimination of the powder image transfer step is desired. Other suitable fixing means such as solvent or overcoating treatment may be substituted for the foregoing heat fixing step.

Prior to the present invention, it was known that a color original could be reproduced electrostatographically by sequential exposure of one or more charged photoconductive surfaces to light images representing the proportionate amount of a color in the original copy. Sequential development of the imaged surfaces with toners of different primary colors gives the desired full color reproduction.

In order to achieve a full color reproduction of :the color original using this method, it is required that three light images be formed and it is critical that the images be superimposed upon each other on the copy material in near-perfect registry. This requiresthree exposures and elaborate mechanical drive arrangements to synchronize the movements of the copy material and the three sequentially imaged photoconductive surfaces.

The electrostatographic preparation of a color copy employs the same principles used in lithography for substractive color printing. This involves formation of three .or more light images, each image representing the proportionate amount of a colored toner to be used in developing the exposed photoconductive surface. To do this, requires separation of the colors of the original. Color separation is effected through the absorption and transmission characteristics of the transparent ink films printed on a white paper original. The yellow ink in the original reflects almost as much red and green as the paper, but almost completely absorbs blue. Thus, yellow controls where blue reflects from the white paper. A blue filter transmitting only its third of the spectrum is the correct filter to use to provide correct filter separation tone values for a yellow toner. The desired effect is to record only where the blue light comes from the original. When a positive is made from this negative, it will be a record of the minus-blue (yellow) of the copy.

The magenta ink on the original absorbs green light without disturbing the reflectance of the red and blue light by the paper. A green filter which transmits its own third of the spectrum will be the proper filter to record the red areas of the original. When a positive is made from this negative with magenta toner, it will record the minus-green (red) areas of the original.

The blue ink (cyan) in the original absorbs red light without disturbing the reflectance of the green and blue light. A red filter which transmits its own third of the spectrum is used to control the red light reflected by the copy. Developing the resultant negative with cyan ink will give a positive which is a record of the blue areas in the original.

The fact that the described process entails three sequential light scanning steps to sequentially expose the photo-conductive surfaces is obviously disadvantageous from several standpoints. Since the light source must be energized three times for each full color reproduction, the number of copies which can be made from a given light source is concomitantly reduced by a factor of three and the power requirement for each copy is increased by the same factor. The copy output capability is significantly and adversely affected since the exposure time is a rate limiting factor for any given electrostatographic copying system.

In view of the importance of color reproduction capabilities and the emphasis on copy system speed and efliciency, there is an existing need for a color reproduction process which avoids the deficiencies of known processes.

Accordingly, an object of this invention is to provide an electrostatographic apparatus which has the capacity to conveniently produce color images using one or more photoconductive areas to transfer different color images of a color original to a copy material.

It is another object of this invention to provide a color reproduction system which employs an improved optical system which does not depend upon multiple light scanning of a color original to form color separation images on a photoconductive surface.

ls another object to provide means of accomplishing this objective without the requirement for elaborate drive trains to impart critically timed non-synchronous movement to separate photoconductive surfaces. Still further, it is an object of this invention to produce color images electrostatographically using a plurality of photoconductive areas moving at a single lineal speed synchronously with the moving copy material. Other objects will be apparent from the ensuing description of this invention in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic representation of one copying system of this invention employing three separate photoconductive surfaces imaged simultaneously by a single light scanning of an original document.

FIG. 2 is a graphic illustration of the travel of two points on the copy material relative to three imaged photoconductive surfaces, moving at the same lineal speed.

FIG. 3 is a graphic illustration of the image inversions and reversals at the several mirrors and light splitters in the light path, showing that by the system given in FIG. 1, the three images arrive in phase with respect to both each other and the original.

FIG. 4 is a schematic representation of another embodiment of this invention in which a single photoconductive surface is simultaneously imaged in three separate areas with color separation images of the original copy.

These and other objects are accomplished in accordance with this invention by the provision of an optical system which uses the light image produced by a single scanning of a color original to simultaneously form color separation images on three different photoconductive areas. The light image formed by scanning the original copy is passed through a focusing lens assembly separated by beam splitters into at least three light beams which are color filtered and conducted along optical paths of equal lengths to expose separate photoconductive areas and thereby record the respective color separation images.

An essential part of the present invention is that a single light scanning of the original copy can be employed to simultaneously produce three or more color separation images on three or more separate photoconductive areas, thus overcoming the difficulties inherent in known reproduction systems which required a separate light scanning step for each color separation image. The choice of specific beam splitting devices, color filters or photoconductors is not a critical part of the present invention. Thus, monochromatic beam splitters can be used to concurrently separate the light beam into parts and produce one color separation image or the beam splitting and color filtration functions can be performed by separate beam splitting and filter devices. Similarly, conventional commercial subtractive printing processes which divide the color spectrum into thirds and produces three color separation images can be used herein, but other modifications involving a lesser or greater number of color separations are also useful. Similarly, the color separation images can be used to image separate areas on one photoconductive surface or three separate photoconductive surfaces.

The present invention will be further described in connection with the drawings. In FIG. 1 is depicted an imaging system of the invention in which an optical system with two light splitters and three color filters is used to form three color separation images on three separate photoconductive surfaces.

A color original depicted by reference numeral 1 is moved, in the direction shown, past exposure lamps 2 producing a light beam image which passes through slit 3 along path 4 through focusing lens 5 and along path 6 to light splitter No. 1 shown generally by reference numeral 7. At point 8 the beam is split into 2 parts shown generally by reference numerals 9 and 10. The part of the light beam conducted along path 10 proceeds to light splitter No. 2 shown generally by reference numeral 11. At point 12 the beam is separated and conducted along paths 13 and 14 respectively.

The beam conducted along path 13 impinges upon mirror No. 4 shown by reference numeral 15. The reflected light follows path 16 through blue filter 17 to give one color separation image which impinges upon photoconductive drum 18 at point 19. As Drum No. 3 rotates in the direction shown, point 19 passes developer station shown generally by reference numeral 20 whereat yellow toner is supplied to the imaged drum surface. Further rotation of drum 3 past the developer station brings the developed imaged drum to point 38 at which the image is transferred to the copy material shown generally by line 35.

Returning now to the other part of the light beam emitted by light splitter No. 2. The light proceeds along path 14 to mirror No. 3 shown by reference numeral 21. The reflected light proceeds along path 22 to mirror No. 2 shown by reference numeral 23. The reflected light proceeds along path 24 through green filter 25 to give a second color separation image which impinges at point 27 on Drum No. 2 shown by reference numeral 26. As Drum No. 2 rotates in the direction shown, the remaining charge on its surface cause it to attract red toner at developer station 28 thus producing a developed image on the surface of the drum for transfers to copy material 35 at point 37.

The other part of the light beam emitted by light splitter No. 1 is used to discharge Drum No. 1 in imagewise fashion. Thus, the beam proceeds along path 9 to mirror No. 1 shown by reference numeral 29 whereat it is reflected along path 30 through red color filter 31 to form the third color separation image on the surface of Drum No. 1 (reference numeral 32) at point 33. As Drum No. l is rotated in the direction shown, it passes developer station 34 whereat it is developed with blue toner in imagewise fashion corresponding to the blue component of color original 1. Further rotation past developer station 34 brings the developed image to point 36 at which it is to be transferred to copy material 35.

Thus it can be seen from the description of the system shown in FIG. 1 that the light beam resulting from the single scanning of a color original, after passage through primary color filters, is used to simultaneously image Drum No. 1, Drum No. 2 and Drum No. 3, each of which is then developed with a color toner whose color is determined by the concepts of subtractive color printing processes. Accordingly, Drum No. 1 after imaging through a red filter and development with blue pigment is imbued with a developed image corresponding to the blue components of the color original. Likewise, Drum No. 2, after imaging through a green filter and development with a red pigmented toner, has a red image corresponding to the red component of the color original. Similarly, the Drum No. 3 after imaging through a blue filter and development with yellow toner, as described above, has an image corresponding to theyellow components of the color original. As the copy material moves along the path between copy input point 35 and output point 39, it comes in sequentialcontact with Drums Nos. 1, 2 and 3 at

points

36, 37 and 38 respectively. In the embodiment shown in FIG. l the drums are rotated at the same lineal speed and by virtue of difference in circumference of the respective drums, the respective images are superimposed upon the web thus giving the desired color reproduction. The manner in which this is accomplished can be readily comprehended from the following detailed description of the movement of each drum as the copy material moves at a single rate of speed between the

points

35 and 39.

Again referring to FIG. 1, the light beam produced by scanning the color original is simultaneously conducted along optical paths of equal lengths to impinge upon the three photoconductive drums which are caused to rotate at the same lineal speed during imaging, development, transfer, etc. concomitantly, the copy material is moved along the indicated path at a speed which is equal to the speed at which the drums are moving. In the time that it takes for a point on a copy material to move between points 35 and 36 (a distance which is shown in FIG. 1 as X,), Drum No. l is moved one half revolution, so that the first point to be imaged at point 33 and the point on the copy material, simultaneously reach transfer station 36. By imparting a charge to the copy material using a conventional charging means such as a corotron (not shown in FIG. 1,), the developed image corresponding to the blue components of the color original is transferred to the copy material as it and Drum No. 1 move in synchronous relationship past point 36. The blue imaged copy material continues to move along the path between points 36 and 37 (shown in FIG. 1 as X Drum No. 2 (shown by reference numeral 26) which is imaged simultaneously with the imaging of Drum No. l is rotated one half revolution by the time the copy material reaches point 37. Since the drums are being simultaneously rotated at the same lineal speed, the lineal distance between imaging point 27 and transfer point 37 of Drum No. 2 must be equal to the sum of one half the circumference of Drum No. l and the distance X in order that the copy material and the first image point of Drum No. 2, reach point'37 simultaneously. If this condition is met, then the developed'red image of Drum No. 2 is transferred to the copy material in perfect registry with the blue toner-developed image previously deposited at point 36. The transfer is effected by imparting a suitable charge by conventional means to the copy material whereby the toner on Drum No. 2 is electrostatically attracted from the drum surface to the copymaterial.

As the copy material continues to move along its path from point 37, it arrives'at point 38 on Drum No. 3. Since the imaging of Drum No. 3 was simultaneous with the imaging of the other two drums, and, by definition, all drums-are moving at the same lineal speed, the size of Drum No. 3 must be such that one half its:circumference is equal to the distance which the copy web moves in traversing its path between points 35 and38. If this condition is met, then the material will have moved with its two previously imparted images to point 38 in the time that it takes for Drum No. 3 to make one half revolution whereby the'image which is imparted at point 19 and developed at developer station 20 reaches point 38 at the proper time to enable superimposition of the yellow image in perfect registry with the other images. Thus, the copy material after being charged by conventional means, receives the yellow developed image in perfect registry with the other two imagesat point 38. As will be obvious from the foregoing discussion, the distance between points 37 and 38 (shown as X in FIG. 1) must be such that the sum of X and one half the circumference of Drum No. 2 is equal to one half the circumference of Drum No. 3.

After full imaging by the afore-described process the copy material is conducted past a fixing station (not shown) to permanently affix the images thereto and is then collected in a collection station (not shown) at point 39.

Subsequent to image transfer, each drum is cleaned and recharged by conventional means (not shown) in preparation for future reproduction cycles.

. By referring to FIG. 2 which shows the relative movement of two points from start to finish along the copying path versus two points on the respective photoconductive surfaces, one can see graphically the movement of the copy material relative to the movement of the respective drums. Here again, the copy web moves at the same lineal speed as the drum surfaces. In step 1 a first point on the copy material is positioned at the input side of the copy material path. The leading edge of the image indicated by an X is in the 12 oclock position shown respectively by the reference numerals 51A, 51B and 51C. In step 2 the leading edge of the copy material (indicated by. a check mark) has moved the distance X bringing it into contact with Drum No. 1, while the trailing edge of the copy material, indicated by a circle appears at point 50. Simultaneously, Drum No. l rotates one half revolution thereby bringing the leading edge of the image (X) in contact with the leading edge of the copy material.

Simultaneously, the image is formed on Drums No. 2 and No. 3; however, in view of the larger size of the latter, the leading edges of the images have not yet reached the path of copy travel. 'Thus, in the case of Drum No. 2 the leading edge has rotated approximately one quarter a revolution to point 52 and in the case of Drum No. 3 the leading edge has rotated approximately one eighth of a revolution to point 53. In all three/cases the trailing edges of the images shown by a dot are located in the 12 o'clock position of the drum.

In step No. 3 the leading edge of the copy moves the distance X; as Drum No. 2 rotates a further quarter of a revolution bringing the leading edge of the image thereon into contact with the leading edge of the copy at point 54. During: the travel'of the copy past Drum No. 1 it receives the: image :of thatdrum as both'the drum and the copy move in contact with each other at the same lineal speed. Accordingly, by the time the leading edge of the copy reaches Drum No. 2 it has received the image present on the left half of Drum No. 1. Meanwhile continuing its rotation at the same lineal speed, both the leading and trailing edges of the image on Drum No. 3 have still not reached the copy path although they have approached it to a greater degree than in step 2.

In step 4 it can be seen that the leading edge of the copy has traversed the distance between the centers of rotation of Drums Nos. 2 and 3. Thus the leading edge of the copy is in contact with the leading edge of the image on Drum No. 3 whereas the trailing edge of the copy has moved past the point of contact with Drum No. 2. As Drum No. 3 continues to rotate and the copy continues to move, the image on Drum No. 3 is transferred to the copy material.

In step 5 the trailing edge of the copy has reached the transfer point of Drum No. 3 thus traversing the distance X between the centers of rotation of Drums Nos. 2 and 3. The simultaneous continued rotation of Drum No. 3, brings the trailing edge of the image to the point of transfer of the image to the copy thus completing the transfer of the images in registration with each other on the copy material.

It is a requirement of the present invention that the optical path between the color original and the three photoconductive surfaces be identical. Once either the optical path length or the size of the drums to be used are decided upon, then the other can be determined.

It is important not only that the images arrive at the three drum surfaces simultaneously but also that they be in phase with each other. FIG. 3 shows the inversions and reversals which occur as the light beam passes through the lens and various light splitters and mirrors shown in the system represented in FIG. 1. Like numerical designations are used in both FIG. 1 and FIG. 3 to designate various light splitters, mirrors and drums. It can be seen by following the image of the letter E through the separate light paths that the reversals and inversions occasioned by the light splitters and mirrors in each path cause the respective images to arrive at the copy in phase with each other.

FIGS. 1, 2 and 3 show an embodiment of the present invention in which three separate photoconductive surfaces are simultaneously imaged by the single light scanning of an original document. The present invention also encompasses systems in which a single continuous photoconductive surface is simultaneously imaged in three areas with a color separation image and each imaged area is separately developed with color toner. The separation images can then be sequentially transferred in registry to a copy material by known means to produce a full color reproduction of the color original. A schematic representation of such a system is shown in FIG. 4.

Referring now to FIG. 4, a color original shown by reference numeral 100 is in position over scanning station 101 consisting of slit 102, lamps 103 and focusing lens 104. In the optical path of lens 104 is monochromatic light splitter No. 1 shown by reference numeral 105, monochromatic light splitter No. 2 (106) and mirror 107. Photoconductive belt 108 travels around top guide roller 109 and bottom guide roller 110, in the direction shown, from charging station 111, to

exposure stations

112, 113 and 114 respectively, and

past developer stations

115, 116 and 117 where powder images are formed by attraction of toner to the charged portions of the photoconductive belt. Copy material (for example, a sheet of paper) is fed into the nip 118 formed between top guide roller 109 and copy roll 119. Transfer of the powder image from the photoconductive belt to the sheet of the support material is effected by means of the corona transfer device 119a that is located at or immediately after the line of contact between the support material and the photoconductive belt. In operation, the electrostatic field created by the corona transfer device is effective to tack the support material electrostatically to the belt surface, whereby the support material moves synchronously with the belt while in contact therewith. Simultaneously with the tacking action, the electrostatic field is effective to attract the toner particles comprising the powder image from the photoconductive belt and cause them to adhere electrostatically to the surface of the support material.

The support material with the powder image travels past fuser 120 and is taken up by copy take-off rolls 121. Just passed the nip formed by

rolls

109 and 119 in the direction of travel of the photoconductor is cleaning brush 122 and photoconductor discharge light 123.

The imaging system of FIG. 4 will simultaneously image photoconductor 108 at points 1 12, l 13 and 1 14, if the optical paths between these points and lens 104 are of identical length. Identity of optical paths can be achieved by positioning the photoconductor at the correct angle with respect to the vertical component of the optical path (i.e., 45).

Document moves passed slit 102 and reflects an image through slit 102 to lens 104. The light image hits monochromatic light splitter where the image is split into one color separation image which is directed to point 112 on photoconductor 108, and the remainder of the light image is transmitted to light splitter 106. Thus, for example, light splitter 105 can be chosen to split off the thirdof the spectrum which is transmitted by a blue filter while transmitting the remaining two-thirds to monochromatic light splitter 106. The image which is split off exposes photoconductor 108 at point 112 with a blue color separation image which will be developed with yellow toner.

The two-thirds of the spectrum which impinges upon monochromatic light splitter 106 is separated by the latter into two parts. For example, if light splitter 106 has the property of reflecting the red third of the spectrum, photoconductor 108 at point 113 will form the red color separation image of original copy 100 which should be developed with green color toner.

The remaining third of the spectrum is transmitted by light splitter 106 to mirror 107 where it reflects onto photoconductor 108 at point 114. Development of this image with red toner produces a record of the red components of the original copy.

To prepare a full color reproduction by the system of FIG. 4, the light source 103 is energized as the original copy is moved passed slit 102. Photoconductor 108 is caused to move in the direction shown passed charging station 1 1 l. The light image passing through lens 104 is split into color separation images which impinge upon photoconductor 108 at points 112, 1.13 and 114 respectively. As both the original document and the photoconductor continue to move, the charged photoconductor is discharged in imagewise configuration at the three points where light impinges upon it, thus forming three latent images on the photoconductor in the areas indicated by reference letters A, B and C.

As the imaged photoconductor continues to move in the indicated direction, the images pass in proximity-to

developer stations

115, 116 and 117. By suitable camming arrangements,-developer station 115 can .be activated to develop image A, developer station 116 can be activated to develop image B and developer station 117 can be activated to develop image C.

As the developedimages move toward copy roll 119, a sheet of copy material is fed into nip 1 18 by suitable feed means which keep the sheet on the copy roll for three revolutions of the latter. Preferably, a uniform charge'is imparted to the sheet to cause it to attract the toner image from the photoconductor. Simultaneous movement of the copy roll in contact with the three imaged areas of the photoconductor causes sequential transfer of the three developed images'to the copy sheet in perfect registration with each other. After three revolutions, the imaged copy sheet is removed from the copy roll by suitable take-off means and then conducted passed fuser station 120 to copy take-off rolls 121.

The color xerographic system of the present invention thus provides a simplified way for producing full color reproductions of a color original. It is based upon the simple concept that'two or more photoconductive surfaces moving at the same lineal speed can beimaged simultaneously, but transferred sequentially to a copy web if the photoconductive surfaces are of successively larger circumferences. Thus, in other words, this aspect of the present invention provides a method for storing the image on the second and following photoconductive surfaces while the first photoconductive surface contacts the copy material. The storage capacity is pro vided by the greater distance which the image must travel on the successively larger photoconductive surfaces. lt is an advantage of the present invention that conventional electrostatographic techniques, equipment and materials can be employed with simple modification to achieve the desired results. The apparatus in essence comprises a series of two or more reproducing stations in the path followed by the copy material. The components of each station are those required to make a monochromatic reproduction of an original, using equipment such as is well known in the art and commercially available.

Reference is made to U.S. Pat. No. 3,301,126 (Osborne et al.) and U.S.Pat. No. 3,062,109 (Mayo et al.) for disclosures of known techniquesand apparatus which can be readily modifiedfor use in the present invention. Each of the photoconductive surfaces used herein comprises a photoconductive layer on the conductive substrate which can be suitably formed in the shape of a drum or any othercontinuous surface. The surface may also include a'nonphotoconductive layer on the photoconductive surface astaught for'example in commonly assigned U.S. Pat. Nos. 3,146,145 (Kinsella) and 3,25 1,686 (Gundlach). As in the apparatus disclosed in the patents referred to, each photoconductive surface of the apparatus of thepresent invention must be subjected to the following operations to complete a reproduction cycle:

1. A photoconductive surface is imbued with a uniform electrostatic charge.

2. An exposure station at which the light beam'isprojected onto the photoconductive surface to dissipate the drum charge in exposed areas thereof and thereby form a latent electrostatic image of the copy to \be reproduced.

3. A developing station at which a xerographic developing .material including toner particles having an electrostatic charge opposite tothat of the electrostatic latent image, is brought into contact with the photoconductive surface whereby the toner particles adhere to the electrostatic latent image to form a powdered image in the configuration of the copy being reproduced.

4. A transfer station at which the toner powder image is electrostatically attracted from the photoconductive surface to the copy web material.

5. Aphotoconductive cleaning and discharge station at which the photoconductive surface is brushed to remove residual toner particles remaining thereon after the image has been transferred to the copy web and at which the surface is exposed to a relatively bright light source to effect substantially. complete discharge of any residual electrostatic charge remaining thereon. Further, the apparatus of the present invention must comprise one or more stations at which the imaged copy web is subjected to treatment which permanently affixes the image thereto. This result can be accomplished in any of several ways depending upon the nature of the toner. If the toner is a pigmented thermoplastic material, fixation is readily accomplished by passing the imaged copy web through a fusing unit which causes the toner particle to momentarily melt and become permanently affixed to the copy web.

in order to obtain full color reproduction of a color original, the apparatus of this invention must have three separate photoconductive areas simultaneously imaged by light passing through different color filters and developed with a color toner, the color of which is dictated by the color of the filter. Colored toners are well known in the art. They are pigmented thermoplastic materials in particulate form. The thermoplastic material whichforms the matrix of the toner particles can be any homopolymer or copolymer previously used in electrostatographic reproduction processes. A commonly used material is a-copolymer of styrene anda acrylic acid ester containing percent styrene and 35 percent of the acrylate. Other suitable materials are disclosed in U.S. Pat. No. 3,502,582 (Clemens et al.) and U.S. Pat. No. 3,079,342 (Insalaco). Color imparting materials which can be used can be used can be chosen from those disclosedin U.S. Pat. No. 3,384,488 '(Talagen et .al.) For full color reproduction, toner compositions of three complimentary colors must be supplied to three separate photoconductive areas. Less than 'full color reproductioncan be achieved by using two photoconductive areas. Againitshould be noted that the choice of-thermoplastic material and coloring'for the toner composition is well within theskill of the art and does not comprise an aspect .of-thepresent invention.

The system described above may be modified in ways which will be obvious to those skilled in the art. Thus, the photoconductive surface may be a continuous belt traveling around two or more rollers between the various stations required for producing and transferring a developed electrostatic image to a copy material. Instead of one fusing step after all images are transferred to the copy material, it may be desired to improve copy quality by fixing each color separation image before the next is transferred to the copy material. Filters of other colors than those specifically employed hereinabove may be used. Similarly, other combinations of mirrors, light splitters and lenses may be substituted for those specifically shown in FIGS. 1 and 4. Such modifications, and others which are obvious to those skilled in the art, are encompassed by the present invention which is limited only by the appended claims.

What is claimed is:

1. An electrostatographic reproduction apparatus capable of continuously producing a polychromatic reproduction of a color original comprising: light scanning means for forming a light image of the color original, a single photoconductive surface, means for imparting a uniform charge to said photoconductive surface, optical means for separating the image formed by said light scanning means into at least two separation images, means for conducting said color separation images along different optical paths of equal length to different areas linearly arranged on said photoconductive surface whereby different areas on said surface are simultaneously imaged with different color separation images of the color original, means for separately developing each color separation image with a different marking material, the color of which corresponds to the separation image being developed by said marking material, and means for transferring and affixing the developed images in superimposed relationship onto a copy material.

2. The apparatus of claim 1 wherein three color separation images are separately formed and developed.

3. The apparatus of claim 2 wherein the color separation images are blue, green and red.

4. The apparatus of claim 3 wherein the blue, green and red separation images are respectively developed with yellow, magenta and cyan marking materials thereby producing a full color reproduction of original subject matter.

5. An electrostatographic reproduction apparatus capable of continuously providing a polychromatic reproduction of a color original comprising:

a. light scanning means for forming a light image of the color original;

b. beam splitting means for separating the light image into at least a first and a second light beam, and then conducting said beams along different optical paths of equal lengths through separate filters of dissimilar colors;

c. a continuous photoconductive surface at the terminus of each optical path, each surface being of a predetermined different size and means for moving each surface at the same lineal speed;

. means for sequentially imparting a uniform charge to each surface, prior to imagewise discharge exposure of said surface to one of said light beams, and means for separately developing the respective image surfaces with differently colored marking compositions;

e. means for moving a copy web at the same lineal speed as said surface in sequential contact with the developed photoconductive surfaces whereby the developed images are transferred thereto in substantially perfect registration to thereby form a composite color image;

f. means for cleaning said photoconductive surface after image transfer; and,

g. means for permanently affixing the composite image to said copy web,

the perimeter of each succeeding photoconductive surface being equal to the sum of the perimeter of the immediately preceding photoconductive surface plus twice the distance separating the transfer points of the surfaces, measured along the copy web path.

6. The apparatus of claim 5 in which the lightimage is separated into three light beams which are conducted through filters of different complementary colors prior to impinging upon the photoconductive surfaces.

7. The apparatus of claim 5 wherein the photoconductive surfaces are drum-shaped.

8. The apparatus of claim 5 wherein the surfaces are exposed at 0 rotation and image transfer occurs at rotation.

9. The apparatus of claim 6 wherein the filters are red, blue and green.

10. An electrostatographic reproduction apparatus capable of continuously producing a polychromatic reproduction of a color original comprising:

a. light scanning means for forming a light image of the color original;

c. a photoconductive surface at the terminus of each optical path, each surface being of a predetermined different size and means for moving each surface at the same lineal speed;

f. means for cleaning said photoconductive surfaces after image transfer, and

g. means for permanently affixing the composite image to said copy web,

Claims

1. LIGHT SCANNING MEANS FOR FORMING A LIGHT IMAGE OF THE COLOR ORIGINAL;

3. UNIFORMLY CHARGED PHOTOCONDUCTIVE AREA AT THE TERMINUS OF EACH OPTICAL PATH, EACH AREA BEING SIMULTANEOUSLY DISCHARGED IN IMAGEWISE CONFIGURATION BY THE LIGHT BEAM IMPINGING UPON IT;

5. An electrostatographic reproduction apparatus capable of continuously providing a polychromatic reproduction of a color original comprising: a. light scanning means for forming a light image of the color original; b. beam splitting means for separating the light image into at least a first and a second light beam, and then conducting said beams along different optical paths of equal lengths through separate filters of dissimilar colors; c. a continuous photoconductive surface at the terminus of each optical path, each surface being of a predetermined different size and means for moving each surface at the same lineal speed; d. means for sequentially imparting a uniform charge to each surface, prior to imagewise discharge exposure of said surface to one of said light beams, and means for separately developing the respective image surfaces with differently colored marking compositions; e. means for moving a copy web at the same lineal speed as said surface in sequential contact with the developed photoconductive surfaces whereby the developed images are transferred thereto in substantially perfect registration to thereby form a composite color image; f. means for cleaning said photoconductive surface after image transfer; and, g. means for permanently affixing the composite image to said copy web, the perimeter of each succeeding photoconductive surface being equal to the sum of the perimeter of the immediately preceding photoconductive surface plus twice the distance separating the transfer points of the surfaces, measured along the copy web path.

6. The apparatus of claim 5 in which the light image is separated into three light beams which are conducted through filters of different complementary colors prior to impinging upon the photoconductive surfaces.

8. The apparatus of claim 5 wherein the surfaces are exposed at 0* rotation and image transfer occurs at 180* rotation.

9. The apparatus of claim 6 wherein the filters arE red, blue and green.

10. An electrostatographic reproduction apparatus capable of continuously producing a polychromatic reproduction of a color original comprising: a. light scanning means for forming a light image of the color original; b. beam splitting means for separating the light image into at least a first and a second light beam, and then conducting said beams along different optical paths of equal lengths through separate filters of dissimilar colors; c. a photoconductive surface at the terminus of each optical path, each surface being of a predetermined different size and means for moving each surface at the same lineal speed; d. means for sequentially imparting a uniform charge to each surface, prior to imagewise discharge exposure of said surface to one of said light beams, and means for separately developing the respective image surfaces with differently colored marking compositions; e. means for moving a copy web at the same lineal speed as said surface in sequential contact with the developed photoconductive surfaces whereby the developed images are transferred thereto in substantially perfect registration to thereby form a composite color image; f. means for cleaning said photoconductive surfaces after image transfer, and g. means for permanently affixing the composite image to said copy web, the perimeter of each succeeding photoconductive surface being equal to the sum of the perimeter of the immediately preceding photoconductive surface plus twice the distance separating the transfer points of the surfaces, measured along the copy web path.