US3836363A

US3836363A - Color electrophotography using a photoconductive layer on both sides of a multicolor screen

Info

Publication number: US3836363A
Application number: US00318352A
Authority: US
Inventors: T Plutchak
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1972-12-26
Filing date: 1972-12-26
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17

Abstract

A novel electrophotographic reproduction process for producing a plurality of multicolor prints from a single exposure of a color original. The process makes use of a novel color electrophotograhpic recording element which preferably comprises a pair of pan-sensitive photoconductive layers, each having a conductive electrode in electrical contact therewith, and a multicolor additive filter mosaic which is sandwiched between the conductive electrodes of the photoconductive layers during the reproduction process.

Description

United States Patent 1191 1111 3,836,363 Plutchak Sept. 17, 1974 COLOR ELECTROPHOTOGRAPHY USING 3,413,117 11/1968 Gaynor 96/1.2

A PHOTOCONDUCTIVE LAYER ON BOTH 3,458,309 7/1969 Gaynor 96/ 1.2

SIDES OF A MULTICOLOR SCREEN Inventor: Thomas Miles Plutchak, Webster,

Assignee: Eastman Kodak Company,

Rochester, NY.

Filedz Dec. 26, 1972 Appl. No.: 318,352

References Cited UNITED STATES PATENTS 6/1964 Land 96/80 X 12/1965 Tokumoto 96/l.24

ABSTRACT A novel electrophotographic reproduction process for producing a plurality of multicolor prints from a single exposure of a color original. The process makes use of a novel color electrophotograhpic recording element which preferably comprises a pair of pan-sensitive photoconductive layers, each having a conductive electrode in electrical contact therewith, and a multicolor additive filter mosaic which is sandwiched between the conductive electrodes of the photoconductive layers during the reproduction process.

14 Claims, 12 Drawing Figures PATENTEDSEPIYIQM Y 3.836.363

SHEEI S (If 5 COLOR ELECTROPHOTOGRAPHY USING A PI-IOTOCONDUCTIVE LAYER ON BOTH SIDES OF A MULTICOLOR SCREEN BACKGROUND OF THE INVENTION The present invention relates to color electrophotography and particularly to a process for making multiple color prints from a single exposure of a color original. It also relates to a novel recording element useful in color electrophotography.

Various electrophotographic color processes have been proposed for making color prints from a color original. See, for instance, the processes disclosed in R. M. Schafferts texton Electrophotography, Focal Press 1965, as well as the processes disclosed in US. Pats. Nos. 3,057,720; 3,150,976; 2,940,847; and 3,212,887. All of the processes disclosed in the above references, however, lack the capability of producing multiple fullcolor prints of a colored original from a single exposure of such original. All require that the electrophotographic recording element be imagewise exposed each time a color print is produced. This exposure requirement not only adversely affects the rate at which multiple prints can be produced, it also renders the original inaccessible until all prints have been made. Moreover, all of these processes involve multiple imagewise exposures of the recording element, which exposures must be precisely in registration in order for good quality prints to be made.

SUMMARY OF THE INVENTION It is, therefore, an important object of the present invention to provide an electrophotographic process in which a multitude of color prints can be made from an electrophotographic recording element which has been imagewise exposed only once to the color original.

It is another object of this invention to produce positive-appearing color prints from either positiveor negative-appearing originals.

Another object of the invention is to provide a novel electrophotographic process for making color prints of multicolor originals which process does not require the registration of multiple imagewise exposures which is characteristic of prior art methods.

Still another object of the invention is to provide a novel method of making color prints ofa color original electrophotographically.

A further object of the invention is to provide novel recording elements useful in the color electrophotographic process of the invention.

In accordance with the present invention, a novel electrophotographic recording element comprising a multicolor additive filter mosaic sandwiched between two photoconductive layers is utilized in carrying out the novel electrophotographic color process. At least one of the photoconductive layers of the recording element is substantially transparent to the visible or optical region of the electromagnetic spectrum, and each has an electrode or conductive layer in electrical contact'therewith. The mosaic is disposed between the respective electrodes of the photoconductive layers, and is laterally divided into a multitude of color filter elements which are constructed to effect selective transmission of predetermined portions of the visible electromagnetic spectrum substantially corresponding to its red, green, and blue regions. The photoconductive layers are spectrally sensitive at least to the colors transmitted by the various filter elements of the mosaic and preferably are pan-sensitive (i.e., sensitive to all visible electromagnetic radiation.)

To carry out the novel process, one photoconductive layer of the recording element is uniformly charged and imagewise exposed to a color original through the mosaic. The resulting electrostatic latent image is developed with an opaque electrographic toner. The other photoconductive layer is then uniformly charged, exposed, and developed three successive times, using red, green, and blue light to expose, and cyan, magenta, and yellow electrographic developer, respectively. The last three exposures are made through the opaque toner image-bearing surface of the first photoconductive layer and the mosaic. The resulting color image is then transferred to a receiver sheet. Multiple color prints of the color original can then be made with no additional exposure to the original by merely cleaning the residue of untransferred color developer, leaving the black toner image undisturbed, repeating the three successive cycles of uniform charging, exposing and color developing, and transferring the color image to a receiver sheet.

Various other objects of the invention, as well as its advantages, will become apparent to those skilled in the art from the ensuing detailed description of preferred embodiments, reference being made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section of a color electrophotographic recording element useful in carrying out the novel process of the invention;

FIGS. 2 (a) through 2 (h) schematically illustrate the sequential steps of the inventive process;

FIGS. 3 and 4 illustrate various other forms which the novel recording element of the invention may take; and

FIG. 5 illustrates an automatic electrophotographic apparatus for carrying out the inventive process.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A novel electrophotographic recording element 10 suitable for use in producing color prints in accordance with the present invention is illustrated in FIG. 1. As

shown, recording element 10 comprises a trichromatic filter mosaic 11 which is sandwiched between the conductive coatings 12 and 12 (a) of a pair of pan-sensitive

photoconductive layers

13 and 14, respectively. The conductive coatings, as well as their respective photoconductive layers, are substantially transparent to the visible portion of the electromagnetic spectrum. Preferably, each photoconductive layer is approximately ten microns thick and comprises an aggregated organic photoconductor containing 4,-4-diethylamino-2,2- dimethyltriphenylmethane as the organic photoconductor, a polycarbonate binder such as Lexan (a General Electric Company trade name), and 4-(4- dimethylaminophenyl)-2,o-dilphenylthiapyrylium fluoroborate and 4-(4-dimethylaminophenyl)-2-(4- ethoxyphenyl)-6-phenylthiapyrylium fluoroborate as sensitizer dyes.

Mosaic 11 preferably comprises a transparent support 15 having a trichromatic layer '16 disposed thereon. Trichromatic layer 16 is laterally divided into a multitude of additive color filter elements, R, G, and

B. which correspond to red, green, and blue filter elements, respectively. Such filter elements are contiguously arranged and may take the forms of minute dots, squares, triangles, or other geometric configurations, or, alternatively, be in the form of narrow lines (e.g., 0.002 inch in width) which extend in one dimension across the entire recording element. Preferably, the colored portions are orderly arranged to the extend that, for any given area, the number of red, green, and blue portions will be substantially equal. Red filter element R is constructed to be selectively transparent to the red region of the visible spectrum, being relatively opaque to the blue and green regions. Similarly, green filter element G transmits a high percentage of green light, but relatively little red and blue light, and blue filter element B transmits a high percentage of blue light, but relatively little red and green light. Mosaic 11 is preferably produced photographically on Eastman Color Print Film (a trademark of Eastman Kodak Company) using master grids produced by a scanning apparatus manufactured by K. S. Paul Company. The polyethylene terephthalate film base serves as support and the colored filter elements are formed in the emulsion layer of the film.

To use the recording element described above to produce color prints, the novel process illustrated schematically in FIGS. 2 (a) through 2 (h) is carried out. As will be noted, the conductive layers 12 and 12 (a) are connected to a reference voltage, preferably ground potential, during the process. The first step of the process is to uniformly charge one of the photoconductive layers of the recording element, layer 13, for instance, to several hundred volts. For purposes of illustration, the uniform charge is shown to be of a positive polarity. Such uniform charging can be accomplished, for instance, by advancing the recording element at a uniform rate in close proximity to a conventional corona charging unit. The uniformly charged photoconductive layer 13 is then imagewise exposed to the color original. White light, such as provided by a xenon lamp, is used to illuminate the original and imagewise exposure of layer 13 is effected through the color mosaic and the other photoconductive layer (i.e., layer 14). The effects of such exposure are illustrated in FIG. 2 (a) wherein the charge-dissipating effects of various colors comprising the color original are shown. As illustrated, the red portions of the color original serve to dissipate charge on the uniformly charged photoconductor only in those areas opposite the red filter elements of the mosaic. Such charge dissipation is, of course, effected due to the increase in conductivity of the photoconductive layer 13 with exposure, and by the connection of conductive layer 12 to a lower potential (ground) than that corresponding to the initial charge. Similarly, charge is dissipated from the uniformly charged photoconductor by the green portion of the color original only in those areas opposite the green filter elements of the mosaic. When the uniformly charged photoconductive layer is exposed, through the mosaic, to cyan light, charge is dissipated in those areas opposite both the green and blue filter elements of the mosaic, since cyan has green and blue components. In those areas where no light strikes the photoconductor, the uniform charge, of course, remains unaltered. Where white light strikes the uniformly charged photoconductive surface through the mosaic, the charge is dissipated uniformly from layer 13 in all exposed areas.

Upon being imagewise exposed to the color original, through the mosaic 11, those areas of the photoconductor where charge was dissipated are developed with a black or opaque electrographic toner. See FIG. 2 (b). Such development can be effected by any of the wellknown electrographic development techniques (i.e., cascade, liquid, magnetic brush, etc., development) using positively charged electroscopic toner. Following such development, photoconductive layer 14 is successively uniformly charged and flood exposed to the three additive colors of the recording element mosaic. The sequence or order of the colored flood exposures is immaterial. Following each charge and exposure step, a different colored electrographic developer is applied to the resulting electrostatic image, the particular color of such developer being predominantly spectrallyabsorptive of the exposing color preceding such development. For instance, as shown in FIG. 2 (c), upon forming a black toner image on photoconductive layer 13 of the recording element, photoconductive layer 14 is uniformly charged (e.g., by a corona charger) and flood exposed, through the color mosaic, to red light. See FIG. 2 (c). In those areas of the uniformly charged photoconductive layer 14 opposite the red filter elements of the mosaic which are exposed to the red light, the uniform charge is dissipated. Note charge on some areas of layer 14 opposite the red filter elements of the mosaic will not be dissipated; these areas correspond to those areas shielded from exposure to red light by the black toner image previously formed on layer 13. Since red light is absorbed by the blue and green filter elements of the mosaic, charge on the photoconductive surface of layer 14 opposite these filter elements remain also. The resulting electrostatic image is then developed with a cyan colored electrographic toner c, (cyan being predominantly spectrally absorptive of red light and transmissive of other colors), producing the result schematically illustrated in FIG. 2 (d). Note, as shown in the drawings, color toner development is effected only in those areas on the photoconductive surface where charge is dissipated.

Next, photoconductive layer 14 bearing the cyan colored toner particles is uniformly charged and flood exposed to green light. Again, flood exposure is effected through the mosaic and the black toner-bearing photoconductive layer of the recording element. See FIG. 2 (e). Upon developing those areas in which charge is dissipated, with a magenta colored electrographic developer M, the result is as illustrated in FIG. 2 (f).

Finally, photoconductive layer 14, hearing the cyan and magenta colored toner particles, is uniformly charged and flood exposed, through the mosaic and layer 13 to blue light. See FIG. 2 (g). Upon developing those areas in which charge is dissipated with a yellow electrographic developer Y, a full color print 19 of the original is provided on the recording element surface. This color image can then be electrostatically transferred to a paper receiving sheet and fixed thereon, permitting the recording element to be recycled through the process steps illustrated in FIGS. 2 (c) 2 (h) to produce multiple color prints.

The operability of the process described above is illustrated by the following examples in which a color print comprised of two of the three primary additive colors, red and blue, is produced.

EXAMPLE 1 A bichromatic filter mosaic was made photographically on Eastman Color Print Film by repetitively scanexposing the film to red and blue light using the aforementioned K. S. Paul Scanner. This mosaic was then employed in the recording element illustrated in FIG.

One photoconductive layer of the recording element (e.g., layer 13) was uniformly and positively charged to approximately 600 volts using a conventional gridcontrolled corona charger. This layer was then contact exposed with white light from a xenon arc source to a color original through the bichromatic mosaic for approximately 20 seconds. Those areas of the photoconductive layer on which charge was dissipated by the exposure to the original were developed with a liquid black electrographic developer and rinsed with lsopar G, a Humble Oil Company trade name for an isopraffinic hydrocarbon using a positive 550 volts bias on a development electrode and a negative 150 volts bias on the rinse electrode. A conductive development elec trode and rinse electrode were positioned approximately 0.02 inch from the surface of the photoconductor during the development and rinse steps.

The other photoconductive layer (layer 14 in FIG. 1) was then uniformly charged to a positive polarity of approximately 600 volts, using a grid-controlled charger. This layer was subsequently flooded uniformly with red light through the black toner deposit on layer 13 and the mosaic for approximately 50 seconds. The areas that were discharged by the red light flood exposure were then developed with a cyan colored liquid electrographic developer and rinsed with lsopar G using a positive 550 volts bias on the development electrode and a negative 150 volts bias on the rinse electrode. Layer 14 was then uniformly charged, flood exposed, and developed a second time in exactly the same manner as the first time, except that this time a blue light flooding exposure of about 100 seconds duration and a yellow developer were used. The blue light was obtained by modulating a xenon are light source with a dichroic cut-off filter which effectively blocked wavelengths longer than about 677 nanometers and a Wratten Filter 478 (an Eastman Kodak Company trade name). The red light used for the uniform flooding exposure was obtained by modulating the xenon arc source with a dichroic cut-off filter which effectively blocked wavelengths longer than about 725 nanometers and a Kodak Wrattan Filter 70.

The resulting two-color image was transferred to a receiver sheet while it was moist by rolling the receiver sheet into contact with the image using a conducting rubber roller that was electrically biased to approximately minus 1,000 volts. The receiver in this case was a clay-coated paper which had been made conductive and which had been given a thin (approximately 5- micron) insulating coating of polyvinyl butyral resin and titanium oxide particles. The resulting print was a two-color reproduction of the original containing green, cyan, yellow, and white areas corresponding to black, blue, yellow, and white areas, respectively, in the original. The print was lacquered with a solution containing a clear styrene-butadiene polymer to protect it and to give a glossy finish. This process demonstrated the production of positive color prints from a positive color original.

EXAMPLE 2 Photoconductive layer 14 used in Example 1 was cleaned, but the black toner deposit on photoconductive layer 13 was left undisturbed. The operations performed on layer 14 in Example l were then repeated. The resulting two-color image was then transferred and lacquered to produce a second color print which was identical to the first.

This process was repeated two more times to produce a total of three additional color reproductions of the original with no further exposure to the original. Although only three additional color reproductions were made, it was apparent that any desired number of additional color reproductions could have been made with no further exposure to the original and with each additional color reproduction being identical to the first.

EXAMPLE 3 Photoconductive layer 14 of the recording element used in Examples I and 2 was cleaned, but the black toner deposit on photoconductive layer 13 was left undisturbed. Layer 14 was then uniformly charged, floor exposed with red through the black image on layer 13 and the mosaic, developed with cyan developer, and rinsed as in Example l, except that the development electrode bias and the rinse electrode bias were both positive 550 volts; consequently, during the development and rinse steps, layer 14 recharged to approximately positive 550 volts. Layer 14 was then flood exposed using blue light through the black image on layer 13 and the mosaic, and developed with yellow developer in the manner described in Example 1, except that both development and rinse electrode biases were +500 volts.

The two-color image was transferred and lacquered as in Example 1, and the resulting print was again a reproduction of the original. The process used in making this print was, however, somewhat simpler than the process used in Examples 1 and 2, since in this example, layer 14 was recharged during the cyan development step and the associated rinse step making it possible to omit the subsequent corona charging step.

EXAMPLE 4 Photoconductive layer 13 in FIG. 1 was uniformly charged to approximately -600 volts using a gridcontrolled corona charger. Layer 13 was then contact exposed to the color original through a two-color mosaic (red and blue) for approximately seconds using white light that was modulated with a Kodak Wratten Filter 28 and a dichroic cut-off filter that effectively blocked wave-lengths longer than about 725 nanometers. Those areas of layer 13 that were not discharged by the exposure to the original were developed with black electrographic developer and rinsed with lsopar G, using a --75 volt bias on the development electrode and a 775 volt bias on the rinse electrode.

Two cycles of uniform charging, flood exposing, and developing were performed on layer 14 in the same manner as in Example 1, except that the red flooding exposure was for approximately 25 seconds and the blue flooding exposure was for approximately seconds and was made using a Kodak Wratten Filter 50.

The two-color image was then transferred to a receiver sheet and lacquered in the same manner as in Example 1. The resulting print was a two-color, negative-to-positive reproduction of the color original containing green, cyan, yellow and white areas corresponding to white, red, blue and black areas, respectively.

EXAMPLE Photoconductive layer 14 of the recording element illustrated in FIG. 1 and used in Example 4 was cleaned, with the'black toner deposit on layer 13 was left undisturbed. Two cycles of uniform charging, flood exposing and developing were then performed on layer 14 in the same manner as in Example 4.

The two-color image was then transferred to a receiver sheet in the manner described in Example 1, but inthis case the receiver sheet was bond paper which had been pre-wet with lsopar G. The transfer was essentially complete and the resulting print was a negative-to-positive reproduction of the original.

EXAMPLE 6 The operations described in Example 5 were repeated, but in this example dry bond paper was used as the receiver sheet. The transfer was very good, although not as complete as in Example 5, and the resulting print was again va negative-to-positive reproduction of the original.

Although the examples above illustrate a two-color system, the extension to a full-color system is straightforward. lt merely requires that the mosaic have green filter elements as well as red and-blue filter elements, and it requires that an additional cycle of uniform charging, green uniform flooding exposure, and magenta development be performed.

The method used in making each of the developers used in the above, examples is to disperse a small amount of an appropriately colored concentrate into a isoparaffinic hydrocarbon, such as Isopar G (a General Electric tradename). Each of the developers, therefore, is basically a suspension of the color concentration in a isoparaffinic hydrocarbon. The black concentrate comprised carbon black, such as Cabot ELF-O (a Cabot Corporation tradename), and Monsastral Blue (a DuPont trade name) pigment as colorants in cyclohexane, with a soya-modifled alkyd resin, and an oilsoluble phenol-formaldehyde resin as additional ingredients. The cyan concentrate comprised Monastral Blue pigment as the colorant in Solvesso (a Standard Oil Company trade name for certain hydrocarbon solvents) with a soya-modified alkyd resin, an oil-soluble phenol-formaldehyde resin, a small amount of a solution of cobalt naphthenate containing 6 percent cobalt and a small amount of aluminum stearate as additional ingredients. The yellow concentrate can have the same formulation as the cyan concentrate, except that the colorant is Permanent Yellow HR (an American Hoechst trade name) pigment, and no Uversol Cobalt Liquid is used. A magenta concentrate can comprise a precipitate formed from Astraphloxine FF (made by Eastman Kodak Company), phosphotungstic acid and phosphomolybic acid. All of these developers intrinsically carry a positive charge.

An alternate method of making a positive-to-positive reproduction is to charge negatively throughout the process and, after each exposure step, develop the areas that were not discharged with the appropriate developer. An alternate method of making a negative-topositive reproduction is to uniformly charge layer 13 to one polarity (e.g., positive) prior to the imagewise exposure step, and then charge to the opposite polarity (e.g., negative) throughout the remainder of the process. The blank development step would then be performed such that the areas that were discharged during the exposure to the original would be developed. The cyan, magenta and yellow development steps would be performed such that the areas that were not discharged during the exposure to the original would be developed.

As indicated in the examples, a variety of receiver sheets may be used. Preferred receiver sheets are baryta paper that has been made conductive, polyethylene-encased baryta paper that has a conducting layer on its surface, and specially treated or coated bond papers.

Any mosaic containing appropriately colored filters of sufficiently small dimension can be used as the filter mosaic. The ratios of the individual color filter elements of the mosaic can be altered to suit the spectralresponse of the photoconductive material comprising the recording element. This technique can be used to compensate for a photoconductive material that has significantly more sensitivity in some regions of the spectrum than in others.

The photoconductive layer on which the full-color reproduction is finally formed can be made separable from the other part of the recording element and whiteappearing. In FIG. 3, a two-part recording element is depicted, the separable photoconductive portion being supported by a transparent support 20. This layer also could then serve as the final support for the print thus eliminating the need to transfer to a receiver. As shown in FIG. 4, the recording element can comprise three separable elements which are brought together during the reproduction process. Preferably, each element has its own supporting layer (i.e., layers 15,-21, and 22). When using a twoor three-part recording element, it is not necessary for the second photoconductive layer to be brought into position until after imagewise exposure of the first photoconductive layer. Moreover, the second photoconductive layer need not be optically transparent.

One of the several advantages of the process of this invention is that, unlike color electrophotographic processes requiring multiple imagewise exposures of the original to produce a single color print, there are inherently no registration problems involved. This simplifies machine design and reduces the complications of producing a colored electrophotographic print.

Another advantage of this invention is that good color rendition is possible by merelyoverlapping the subtractively colored toners any'desired degree. Various techniques can be used to obtain the overlapping of the subtractively colored toners required for the best possible color rendition. One technique for obtaining the desired amount of overlap is to design the recording element and the colored light flooding sources so that the black toner deposits on the first photoconductive layer and the filter mosaic are not imaged sharply on the second photoconductive layer during the uniform flooding exposures. One way that this unsharp imaging can be accomplished is to use exposure sources for the uniform colored light flooding steps that are physically broad and that provide diffuse illumination, and to use in conjunction with these exposure sources a sandwichstructure recording element where the second photoconductive layer is spaced appropriately far away from the first photoconductive layer and the color mosaic. The spacing between the photoconductive layers, the distance from the flood exposure sources to the recording element, and the shapes and dimensions of the flood exposure sources is adjusted to give the optimum unsharpness, i.e., the optimum overlap of the colorants, for any color mosaic that is employed. Another technique that can be used to obtain the desired overlapping of the colorants would be to introduce a certain amount of smearing during the transfer step.

Still another advantage of the novel process of the invention is that one photoconductive recording element can be used without the need for cleaning the photoconductive surface between the production of each of the three successive subtractively colored images.

In FIG. 5, apparatus for carrying out the novel process of the invention automatically is schematically illustrated. As shown, the novel recording element 10 has a closed-loop configuration, being in the form of a cylinder 30. The components of the apparatus are best described in connection with the description of the operation of the apparatus which follows.

Cylinder 30 is rotatably mounted by means not shown and is driven in the direction indicated by the arrow. As cylinder 30 passes the corona charging station32, a uniform electrostatic charge is laid down on photoconductive layer 13 of the recording element. Following such charging, layer 13 is imagewise exposed to a color original 34 which is advanced from a supply roll 36 at the same linear rate as that at which cylinder 30 moves. Original 34 is maintained in contact with the outer surface of photoconductive layer 14 by

rollers

38 and 40, and, following imagewise exposure, is wound upon take-up roll 42. lmagewise exposure is effected by activating a source of white light 44 (i.e., a source having the additive colors of the mosaic 11 present, preferably in substantially equal amounts). As shown, such imagewise exposure of photoconductive layer 13 is effected through the other layers of the recording element, including photoconductive layer 14 and mosaic 11. Such imagewise exposure serves to selectively dissipate the uniform charge on layer 13, leaving behind a latent electrostatic image.

Upon being imagewise exposed, the electrostatic image-bearing portion of layer 13 of the recording element is advanced past an electrostatic development station 46, shown for purposes of illustration as being of the magnetic brush variety, where an opaque or black toner is selectively applied to the surface of layer 13. By properly controlling the electrical potential of the brush and the polarity of the toner particles, either the background or image areas of the electrostatic image are developed.

Following development with opaque toner, the surface of photoconductive layer 14 is successively uniformly charged, flood exposed and developed three times by

corona charging stations

50, 52, and 54,

flood exposure stations

56, 58, and 60, and

development stations

62, 64, and 66.

Flood exposure stations

56, 58, and 60 comprise sources of right light, green light, and blue light, respectively.

Development stations

62, 64, and 66 are, like development station 46, of the magnetic brush variety, comprising reservoirs containing cyan, magenta and yellow colored toner particles, re-

spectively. These stations serve to produce a full-color image on the surface of layer 14 in precisely the same manner as described above with reference to FIGS. 2 (0) through 2 (h).

The color image formed on layer 14 is then transferred to an appropriate receiving sheet 68 by a conventional corona transfer station 72. Receiving sheet 68 is advanced from a supply roll 69 to a take-up roll 70 along a path which comes into contact with the periphery of cylinder 30 at the transfer station. The transferred image is then permanentized by a roller fusing apparatus 74, and the residue of colored toner particles is removed from the surface of layer 14 by a soft fur brush, or the like. To make multiple copies of the same color original, the opaque toner image is left undisturbed and cylinder 30 is repetitively recycled past the various processing stations.

This invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. A process for producing a multicolored image from a multicolored original using a recording element comprising (a) a first pan-sensitive photoconductive layer having an optically transparent, electrically conductive layer in electrical contact with one surface thereof; (b) a second pan-sensitive photoconductive layer having an optically transparent, electrically conductive layer in electrical contact with one surface thereof; and (c) a multicolored filter mosaic disposed between the conductive layers, at least the first photoconductive layer being optically transparent and the multicolored mosaic being divided into a multitude of color filter elements, some of such filter elements being predominantly transparent to a first additive color, and others being predominantly transparent to a second additive color, said process comprising the steps of:

a. uniformly charging the first photoconductive layer of the recording element;

b. imagewise exposing the first photoconductive layer to the multicolored original, such imagewise exposure being effected through the mosaic using an exposure source comprising light of at least said first and second additive colors, thereby forming a first electrostatic image on the first photoconductive layer in accordance with the image of the multicolored original as attenuated by the mosaic;

c. applying a first electroscopic toner to the first electrostatic image to produce a first toner image on a surface of the first photoconductive layer, such first electroscopic toner being opaque to the first and second additive colors to which the mosaic is transparent;

d. uniformly charging the second photoconductive layer;

e. exposing the second photoconductive layer to light of said first additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the first additive color to form a second electrostatic image;

f. applying a second electroscopic toner to the second electrostatic image to produce a second toner image on a surface of the second photoconductive layer, such second electroscopic toner being of a color which is predominantly spectrally absorptive of said first additive color;

g. uniformly charging that surface of the second photoconductive layer bearing the second toner image;

h. exposing the second photoconductive layer to light of said second additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the second additive color to form a third electrostatic image which is superimposed on the second toner image; and

. applying a third electroscopic toner to the third electrostatic image to produce a third toner image on that surface of the second photoconductive layer bearing the second toner image, such third electroscopic toner being of a color which is predominantly spectrally absorptive of said second additive color, whereby a multicolored image is formed ofthe color original, such color image comprising the superimposed second and third toner images.

2. The process according to claim 1 wherein some of the filter elements of the mosaic layer of the recording element are predominantly transparent to a third additive color and wherein the exposure source used in the imagewise exposing step further comprises light of the third additive color to which the mosaic layer is transparent, and said process further comprises the steps of:

j. uniformly charging the second photoconductive layer bearing the superimposed second and third toner images;

it. exposing the second photoconductive layer to light of said third additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic layer which are predominantly transparent to said third additive color to form a fourth electrostatic image which is superimposed on the second and third toner images; and

. selectively applying a fourth electroscopic toner to the fourth electrostatic image to produce a third toner image on that surface of the second photoconductive layer bearing the superimposed second and third toner images, such fourth electroscopic toner being of a color which is predominantly spectrally, absorptive of the third additive color, whereby a multicolored image is formed of the color original, such multicolored image being comprised of the superimposed second, third, and fourth toner images. 3. The process according to claim 1 further comprising the step of transferring the toner image to a receiving member.

4. The process according to claim 2 wherein the first, second, and third additive colors are red, green, and blue; and thecolors of the electroscopic toners which are applied following the red, green, and blue flood exposures are cyan, magenta, and yellow, respectively.

5. The process according to claim 4 wherein the first, second, third, and fourth toners are applied to those areas on the photoconductive surfaces where charge is dissipated during the exposure steps.

6. The process according to claim 4 wherein the first, second, third, and fourth toners are applied to those areas on the photoconductive surfaces where electrostatic charge remains after the exposure steps.

7. The process according to claim 4 wherein the first toner is applied to those areas on the first photoconductive layer where charge is dissipated during the imagewise exposure step and wherein the second, third and fourth toners are applied to those areas on the second photoconductive layer where charge remains after the subsequent exposure steps, whereby a negative multicolored image is provided on the second photoconductive layer.

8. The process according to claim 4 wherein the first toner is applied to those areas on the first photoconductive layer where charge remains after the imagewise exposure step and wherein the second, third and fourth toners are applied to those areas on the second photoconductive layer where charge is dissipated during the subsequent exposure steps, whereby a negative multicolored image is provided on the second photoconductive layer.

9. The process according to claim 4 wherein the first photoconductive layer is uniformly charged to one polarity prior to being imagewise exposed to the multicolored original and the second photoconductive layer is uniformly charged to an opposite polarity each time prior to being subsequently exposed.

10. A process for producing a multicolored image from a multicolored original using a recording element comprising (a) a first pan-sensitive photoconductive layer having an optically transparent, electrically conductive layer in electrical contact with one surface thereof, (b) a second pan-sensitive photoconductive layer having an optically transparent, electrically conductive layer in electrical contact with one surface thereof, and (c) a trichromatic additive colored mosaic comprising red, green, and blue filter elements positioned between the conductive layers of the first and second photoconductive layers, said process comprising the steps of:

a. uniformly charging the first photoconductive layer of the recording element;

b. imagewise exposing the first photoconductive layer to the multicolored original, such imagewise exposure being effected through the multicolored mosaic using an exposure source comprising a mixture of red, green, and blue light, thereby forming a first electrostatic image on the first photoconductive layer in accordance with the image of the multicolored original;

c. selectively applying an opaque electroscopic toner to the first electrostatic image-bearing surface of the first photoconductive layer to produce an opaque toner image;

d. successively uniformly charging, exposing, and applying toner particles to the second photoconductive layer using red, green, and blue light to expose followed by the application of cyan, magenta, and yellow colored electroscopic toner, respectively, such exposures to red, green and blue light being made through the opaque toner image and the multicolored mosaic.

11. A color electrophotographic recording element comprising:

a. first and second optically transparent, pansensitive photoconductive layers, each having an optically-transparent conductive layer electrically associated therewith; and

b. a trichromatic additive multicolored mosaic comprising red, green, and blue filter elements disposed between the conductive layers of the first and second photoconductive layers.

12. A separable color electrophotoconductive recording element comprising:

a. a first optically transparent, pan-sensitive photoconductive layer having an optically transparent electrode in electrical contact with one surface thereof;

b. a second pan-sensitive photoconductive layer having an optically transparent electrode in electrical contact with one surface thereof; and

c. a multicolor additive filter mosaic layer disposed between the electrodes of the first and second photoconductive layers.

13. A process for producing a multicolored image from a multicolored original using a multi-layered recording element comprising first and second pansensitive, photoconductive layers, each having an optically transparent, electrically conductive layer in electrical contact with one surface thereof; and a multicolored filter mosaic disposed between such conductive layers, the conductive layers and the photoconductive layers being optically transparent, and the multicolored mosaic being divided into a multitude of color filter elements, some of such filter elements being predominantly transparent to a first additive color, and others being predominantly transparent to a second additive color, said process comprising the steps of:

a. uniformly charging the first photoconductive of the recording element;

b. imagewise exposing the first photoconductive layer to the multicolored original, such imagewise exposure being effected through the mosaic and the second photoconductive layer using an exposure source comprising light of at least said first and second additive colors, thereby forming a first electrostatic image on the first photoconductive layer in accordance with the image of the multicolored original as attenuated by the mosaic;

. applying a first electroscopic toner to the first electrostatic image to produce a first toner image on a surface of the first photoconductive layer, such first electroscopic toner being opaque to the first and second additive colors to which the mosaic is transparent;

d. uniformly charging the second photoconductive layer;

e. exposing the second photoconductive layer to light of said first additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated fillayer ter elements of the mosaic which are predominantly transparent to the first additive color to h. exposing the second photoconductive layer to light of said second additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the second additive color to form a third electrostatic image which is superimposed on the second toner image; and

. applying a third electroscopic toner to the third electrostatic image to produce a third toner image on that surface of the second photoconductive layer bearing the second toner image, such third electroscopic toner being of a color which is predominantly spectrally absorptive of said second additive color, whereby a multicolored image is formed of the color original, such color image comprising the superimposed second and third toner images,

14. A process for producing a multicolored image from a multicolored original using a separable recording element comprising (a) a first pan-sensitive, optically transparent photoconductive layer having an electrically conductive, optically transparent layer in electrical contact with one surface thereof, (b) a second pan-sensitive photoconductive layer having an electrically conductive, optically transparent layer in electrical contact with one surface thereof, and (c) a multicolored mosaic divided into a multitude of color filter elements, some of such filter elements being predominantly transparent to a first additive color, and others being predominantly transparent to a second additive color, said process comprising the steps of:

a. uniformly charging the first photoconductive layer of the recording element;

. applying a first electroscopic toner to the first electroscopic image to produce a first toner image on a surface of the first photoconductive layer, such first electroscopic toner being opaque to the first and second additive colors to which the mosaic is transparent;

d. uniformly charging the second photoconductive layer;

e. exposing the second photoconductive layer to light of said first additive color, such exposure being effected through the first toner image borne by th surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the first additive color to form a second electrostatic image;

applying a second electroscopic toner to the second electrostatic image to produce a second toner image on a surface of the second photoconductive layer, such second electroscopic toner being of a color which is predominantly spectrally absorptive of said first additive color;

of said second additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the second additive color to form a third electrostatic image which is superimposed on the second toner image; and

applying a third electrostatic toner to the third electrostatic image to produce a third toner image on that surface of the second photoconductive layer bearing the second toner image, such third electroscopic toner being of a color which is predominantly spectrally absorptive of said second additive color, whereby a multicolored image is formed of the color original, such color image comprising the superimposed second and third toner images.

P041050 UNITED sTATEs. PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 4 3,83 Dated September Inventofls) Thomas Miles Plutchak It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 8, the word "extend" should read --extent--.

Column 6, line 23, the word "floor" should read --flood--;

and on 'line 2 4, after "red" the word --light--should be added.

Column 8, line 6 the word "blank" should read --black--.

Column 13, line 16, the word "electrophotoconductive" after "color" should read --electrophotographic--.

Signed and sealed this 8th day of April 19-75.

(SEAL) test. c. MARSHALL DANN RUTH C. I'TASON Commissioner of Patents Arresting Officer and Trademarks gggg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION mm No. 3,836,363 Dated p b r 17, 197M Inventofls) Thomas Miles Plutchak It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 8, the word "extend" should read --eXtent--.

Column 6, line 23, the word "floor" should read ----flood--;

and online 2 1, after "red" the word --light--should be added.

Column 8,' line 6 the word "blank" should read -black--.

Column 13, line 16, the word "electrophotoconductive'" after "color" should read -e1ectrophotogr'aphic-.

Signed and sealed this 8th day of April 1975.

(SEAL) fittest: C. MARSHALL DANN RUTH C. MAS-ON Commissioner of Patents Attesting Officer and Trademarks

Claims

2. The process according to claim 1 wherein some of the filter elements of the mosaic layer of the recording element are predominantly transparent to a third additive color and wherein the exposure source used in the imagewise exposing step further comprises light of the third additive color to which the mosaic layer is transparent, and said process further comprises the steps of: j. uniformly charging the second photoconductive layer bearing the superimposed second and third toner images; k. exposing the second photoconductive layer to light of said third additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic layer which are predominantly transparent to said third additive color to form a fourth electrostatic image which is superimposed on the second and third toner images; and l. selectively applying a fourth electroscopic toner to the fourth electrostatic image to produce a third toner image on that surface of the second photoconductive layer bearing the superimposed second and third toner images, such fourth electroscopic toner being of a color which is predominantly spectrally absorptive of the third additive color, whereby a multicolored image is formed of the color original, such multicolored image being comprised of the superimposed second, third, and fourth toner images.
3. The process according to claim 1 further comprising the step of transferring the toner image to a receiving member.
4. The process according to claim 2 wherein the first, second, and third additive colors are red, green, and blue; and the colors of the electroscopic toners which are applied following the red, green, and blue flood exposures are cyan, magenta, and yellow, respectively.
5. The process according to claim 4 wherein the first, second, third, and fourth toners are applied to those areas on the photoconductive surfaces where charge is dissipated during the exposure steps.
6. The process according to claim 4 wherein the first, second, third, and fourth toners are applied to those areas on the photoconductive surfaces where electrostatic charge remains after the exposure steps.
7. The process according to claim 4 wherein the first toner is applied to those areas on the first photoconductive layer where charge is dissipated during the imagewise exposure step and wherein the second, third and fourth toners are applied to those areas on the second photoconductive layer where charge remains after the subsequent exposure steps, whereby a negative multicolored image is provided on the second photoconductive layer.
8. The process according to claim 4 wherein the first toner is applied to those areas on the first photoconductive layer where charge remains after the imagewise exposure step and wherein the second, third and fourth toners are applied to those areas on the second photoconductive layer where charge is dissipated during the subsequent exposure steps, whereby a negative multicolored image is provided on the second photoconductive layer.
9. The process according to claim 4 wherein the first photoconductive layer is uniformly charged to one polarity prior to being imagewise exposed to the multicolored original and the second photoconductive layer is uniformly charged to an opposite polarity each time prior to being subsequently exposed.
10. A process for producing a multicolored image from a multicolored original using a recording element comprising (a) a first pan-sensitive photoconductiVe layer having an optically transparent, electrically conductive layer in electrical contact with one surface thereof, (b) a second pan-sensitive photoconductive layer having an optically transparent, electrically conductive layer in electrical contact with one surface thereof, and (c) a trichromatic additive colored mosaic comprising red, green, and blue filter elements positioned between the conductive layers of the first and second photoconductive layers, said process comprising the steps of: a. uniformly charging the first photoconductive layer of the recording element; b. imagewise exposing the first photoconductive layer to the multicolored original, such imagewise exposure being effected through the multicolored mosaic using an exposure source comprising a mixture of red, green, and blue light, thereby forming a first electrostatic image on the first photoconductive layer in accordance with the image of the multicolored original; c. selectively applying an opaque electroscopic toner to the first electrostatic image-bearing surface of the first photoconductive layer to produce an opaque toner image; d. successively uniformly charging, exposing, and applying toner particles to the second photoconductive layer using red, green, and blue light to expose followed by the application of cyan, magenta, and yellow colored electroscopic toner, respectively, such exposures to red, green and blue light being made through the opaque toner image and the multicolored mosaic.
11. A color electrophotographic recording element comprising: a. first and second optically transparent, pan-sensitive photoconductive layers, each having an optically-transparent conductive layer electrically associated therewith; and b. a trichromatic additive multicolored mosaic comprising red, green, and blue filter elements disposed between the conductive layers of the first and second photoconductive layers.
12. A separable color electrophotoconductive recording element comprising: a. a first optically transparent, pan-sensitive photoconductive layer having an optically transparent electrode in electrical contact with one surface thereof; b. a second pan-sensitive photoconductive layer having an optically transparent electrode in electrical contact with one surface thereof; and c. a multicolor additive filter mosaic layer disposed between the electrodes of the first and second photoconductive layers.
13. A process for producing a multicolored image from a multicolored original using a multi-layered recording element comprising first and second pan-sensitive, photoconductive layers, each having an optically transparent, electrically conductive layer in electrical contact with one surface thereof; and a multicolored filter mosaic disposed between such conductive layers, the conductive layers and the photoconductive layers being optically transparent, and the multicolored mosaic being divided into a multitude of color filter elements, some of such filter elements being predominantly transparent to a first additive color, and others being predominantly transparent to a second additive color, said process comprising the steps of: a. uniformly charging the first photoconductive layer of the recording element; b. imagewise exposing the first photoconductive layer to the multicolored original, such imagewise exposure being effected through the mosaic and the second photoconductive layer using an exposure source comprising light of at least said first and second additive colors, thereby forming a first electrostatic image on the first photoconductive layer in accordance with the image of the multicolored original as attenuated by the mosaic; c. applying a first electroscopic toner to the first electrostatic image to produce a first toner image on a surface of the first photoconductive layer, such first electroscopic toner being opaque to the first and second additive colors to which the mosaic is transparent; d. uniformly charging the second photoconductive layer; e. exposing the second photoconductive layer to light of said first additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the first additive color to form a second electrostatic image; f. applying a second elecroscopic toner to the second electrostatic image to produce a second toner image on a surface of the second photoconductive layer, such second electroscopic toner being of a color which is predominantly spectrally absorptive of said first additive color; g. uniformly charging that surface of the second photoconductive layer bearing the second toner image; h. exposing the second photoconductive layer to light of said second additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the second additive color to form a third electrostatic image which is superimposed on the second toner image; and i. applying a third electroscopic toner to the third electrostatic image to produce a third toner image on that surface of the second photoconductive layer bearing the second toner image, such third electroscopic toner being of a color which is predominantly spectrally absorptive of said second additive color, whereby a multicolored image is formed of the color original, such color image comprising the superimposed second and third toner images.
14. A process for producing a multicolored image from a multicolored original using a separable recording element comprising (a) a first pan-sensitive, optically transparent photoconductive layer having an electrically conductive, optically transparent layer in electrical contact with one surface thereof, (b) a second pan-sensitive photoconductive layer having an electrically conductive, optically transparent layer in electrical contact with one surface thereof, and (c) a multicolored mosaic divided into a multitude of color filter elements, some of such filter elements being predominantly transparent to a first additive color, and others being predominantly transparent to a second additive color, said process comprising the steps of: a. uniformly charging the first photoconductive layer of the recording element; b. imagewise exposing the first photoconductive layer to the multicolored original, such imagewise exposure being effected through the mosaic using an exposure source comprising light of at least said first and second additive colors, thereby forming a first electrostatic image on the first photoconductive layer in accordance with the image of the multicolored original as attenuated by the mosaic; c. applying a first electroscopic toner to the first electroscopic image to produce a first toner image on a surface of the first photoconductive layer, such first electroscopic toner being opaque to the first and second additive colors to which the mosaic is transparent; d. uniformly charging the second photoconductive layer; e. exposing the second photoconductive layer to light of said first additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the first additive color to form a second electrostatic image; f. applying a second electroscopic toner to the second electrostatic image to proDuce a second toner image on a surface of the second photoconductive layer, such second electroscopic toner being of a color which is predominantly spectrally absorptive of said first additive color; g. uniformly charging that surface of the second photoconductive layer bearing the second toner image; h. exposing the second photoconductive layer to light of said second additive color, such exposure being effected through the first toner image borne by the surface of the first photoconductive layer and through the mosaic, thereby selectively dissipating the uniform charge on the second photoconductive layer in those areas opposite those illuminated filter elements of the mosaic which are predominantly transparent to the second additive color to form a third electrostatic image which is superimposed on the second toner image; and i. applying a third electrostatic toner to the third electrostatic image to produce a third toner image on that surface of the second photoconductive layer bearing the second toner image, such third electroscopic toner being of a color which is predominantly spectrally absorptive of said second additive color, whereby a multicolored image is formed of the color original, such color image comprising the superimposed second and third toner images.