LU81412A1 - COLORED ELECTROPHOTOGRAPHIC PRINTING METHOD AND APPARATUS - Google Patents

Description

The present invention relates to a color printing apparatus and, more particularly, to a color printing apparatus operating on the basis of electrostatic principles rather than on the conventional principles adopted in photography or graphic printing.

Systems for full color printing are known by adopting electrostatic techniques, but it has been found that most of these systems are complex, expensive, unreliable and unable to provide images of the desired quality.

The invention relates to an electrophotographic color printing method and apparatus in which an elongated substrate such as a strip of paper, a fabric, a sheet of synthetic resin or the like receives an impression of several images of different colors to form a picture ; polychrome composite.

1 This apparatus comprises several independent stations for printing images through which the substrate passes.

I;

In one embodiment of the invention, each image printing station comprises an electrophotographic sleeve | phique. On this sleeve, a latent image is formed corresponding to one of the color images of the composite image. A "toner" is applied to the image thus formed, then it is transferred to the substrate and fixed there.

In another embodiment of 1: invention, each image printing station comprises two eco-photographic sleeves; ; ‘On one of the two sleeves, a latent image is formed corresponding to a G & S X ΙΠ.3 £ [es in color of the composite image. A "toner" is applied to the image thus formed, then it is projected; optically on the second sleeve. Apply a toner to the image projected on the second sleeve, then transfer it - 3 - in 3 es d *. * Ux the orDC · »of realization, elc-! E> ;: They are provided to exactly match the images transferred to the substrate in each station.

The monochrome image formed in each station can be obtained by projection from a color image, 1 from a transparent color image or the like using. different color filters, etc., or we can train it! by "laser transcription".

The image can be formed (and receive a "toner")! on the sleeve before or after mounting the latter in the i i> I image printing station.

Preferably, the image printing stations are aligned and operate independently of each other so that it is possible to obtain, at each station, different conditions to ensure optimum transfer.

The image applied in each station is fixed on the substrate before the latter has moved this image to the next station i. Toner, voltages, temperatures and settings | analogues of any position can be different from | those of all other positions. This system of independent posts; dants put in alignment offers great flexibility and allows! get the best results.

! The electrophotographic sleeves consist of a photoconductive coating deposited on a conductive substrate.

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In the embodiment in which the toner received image is transferred from a first to a second sleeve, then to the substrate, the first sleeve is transparent so that an appropriate source of rayon energy "'Ent can be directed via this sleeve on a second. This second sleeve is loaded before receiving the projected image of the first sleeve, then a "toner" is applied to it when it has received the image ... 4 - the moving substrate, thus ensuring the transfer of all of the received toner image. Then, the process is repeated for the different colors at the different respective stations. These images are fixed between these posts.

Density measurements can be made at any station and the information collected can be sent back to previous stations to modify the parameters of the printing conditions.

The embodiment of the apparatus in which two sleeves are used at each station is particularly useful for forming multiple or repeated copies of a color image on an elongated substrate, since the image having received the toner and formed on the first sleeve remains on the latter. The embodiment of the apparatus in which a single sleeve is used at each station is particularly useful for forming a monochrome copy of an image or an object. However, each type of device can be used for i all applications and one can adopt one or the other! version when the input information to be printed is digital information supplied by a computer.

In the embodiment of the apparatus in which a single sleeve is used at each station, the image having i! * received the toner must be adjusted to the desired color and, of course, it must not be fixed on the sleeve. In the embodiment of the apparatus in which two sleeves are used at each station, the image having received the toner and formed on the first sleeve need not necessarily be adjusted to the desired color which is to be printed and, moreover , it can optionally be fixed on the first sleeve.

- J - I οι-s of 1 a loi'.Trition of images lütcntcs on1 sleeves elect. r ο ρ] i o t o rap! not a word. qu es by "trance Γ ipt ï 011 laser", we use digital information provided by a memory and corresponding to the desired polychrome copy, in order to modulate a laser beam which scans the surface of each sleeve having been previously loaded.

Both embodiments can be adopted to form repeated color images on an elongated substrate or to form one or more color copies on an elongated substrate.

In the accompanying drawings: FIG. 1 is a schematic view of an embodiment of an apparatus according to the invention; Figure 2 is a schematic view of another embodiment of an apparatus according to the invention; Figure 3 is- a schematic view illustrating a method of producing an electrophotographic sleeve used according to the invention; Figure 4 is another schematic view illustrating a second method of producing an electrophoto-graphic sleeve used according to the invention; and Figure 5 is a schematic representation of an entire system for forming color copies using the method and apparatus of the present invention.

The printing method of the invention consists in forming, by electrophotographic means, a different toner image on each of the electro-graphic tographic sleeves of a group, the toner image formed on each sleeve corresponding to one of the images. in color-s of the composite copy in color, this vtiurnal marriage on its own axis and it enters directly into - 6 - that the latter, or it has the office of medium of projection through which 11 image of rent thus formed is projected onto a second graphic electrophoto sleeve where it receives a “toner”, this last toner image then being transferred directly from the second sleeve onto the moving substrate.

One of the important aspects of the invention resides in the fact that the apparatus comprises several image printing stations, each of these stations being controlled independently according to the various parameters required to obtain the printing or the printing. image required on the substrate.

* Figure 1 shows a device generally designated by the reference numeral 10 for the formatior of a color copy by the indirect transfer process.

This device comprises several stations, two of which are illustrated in 12 and 14. Each of these stations is intended to apply an impression of a different color on a substrate 16 which, as shown in the drawing, enters the station 12 located on the left, to then leave the latter and enter the station 14 located on the right. For a full color printing, at least three and usually four colors are usually provided, namely blue-green, magenta, yellow and black \ consequently, it should be considered that the usual apparatus of invention will include four posts of this type. In the case of fabrics, it can usually be expected that the items will be provided r in a number corresponding to that of the colors and shades of the fabric because ·, as a rule, composite colors are * not obtained by · mixed.

In plague 12 is shown an image projecting apparatus 1b comprising a main sleeve 20 which, in this case, is in the form of an electrophotographic support strip · on rollers 22 and 24; an illuminated optical projector 26 watertight. .- - / - prim ipal 20, tarnli. "qu1 i 1 <.- st (. '.'. îii.u to project any 11th image conveyed on tape control through a lens or a system of 2S projection.

Preferably, the strip 20 conveys an image in the form of a chromatic selection in digital code which has been applied to this strip as will be described with reference; more particularly in Figures 3 and 4 · It can be stipulated here that the strip is formed of a material or of an electrophoto-graphic member comprising a transparent polyester substrate coinpor-; Both an ohmic layer and a coating of photoconductive material on its outer face. The photoconductive material consists of an inorganic compound, preferably cadmium sulfide, which has been projected onto the substrate in the form of a microcrystalline, transparent deposit with a high quantum yield of the type described in the patent. United States of America No. 4 * 025,339.

The process for forming a coating on this substrate is also described in this patent.

At station 12, there is a second sleeve 30 extending and rotating between the rollers 32 and 34 · The lower strand (· of this sleeve is exposed to image 30 which has been projected by the t.

lens system 28, while its upper strand comes f; engage on the underside of the substrate 16. The speed of the substrate moving from left to right, as well as the speed 1 "wj; of the sleeve 30 are chosen so that the movement is ♦ synchronized. The rollers 32 er 34 can be driven to achieve this movement., The sleeve being in the form of a band, i 'The material of which the second sleeve 30 is made, is the same as that of the main sleeve 20: therefore, this sleeve is an organ electrophotographic with photoconductive coating! applied to the outside.

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In the present specification, it is assumed that there are control elements ensuring the movement of the sleeves, rollers, substrate and cylinders as required and under appropriate control.

An electrostatic corona discharge device is arranged at 38 in order to charge the lower surface of the second sleeve 30 immediately before it enters the zone of the bundle 36. It will be understood that the lower strand of the second sleeve moves from right to left . At 40, there is provided a device preferably containing a type of toner which is compatible with the type of substrate 16. For example, if the substrate 16 is paper, the "toner" used with the apparatus 40 will be suitable for transfer to paper. This toner may or may not be dielectric, while its color and composition will be determined by the conditions required for printing.

The image now developed moves around the roller 32 and it joins the underside of the substrate 16 as the latter moves through the station 12.

Polarization plates 42, 44 are disposed respectively above and below the substrate 16, while the upper strand of the sleeve 30 and the substrate 16 combined pass between these plates. These plates 42, 44 are connected to a source of power.

! mentation 46 by means of which an electric field is established between the plates in order to polarize the particles of "toner" which must pass from the upper strand of the sleeve 30 on the underside of the substrate 16. Although the transfer of the toner image can be carried out mechanically by pressure, it is preferable to provide a small space between the upper strand of the sleeve 30 and the substrate 16 so that there is no wear on the surface of the sleeve 30 "nor any risk of formation - Q -

Loi-.sque 1 * printing has been made and if it is assumed that it is or is intended to provide a single color, the band moves around the roller 34 and passes through a cleaning station in 48 where the toner which can remain on the sleeve 30 is removed so that, when this area of this second sleeve 30 passes through the charging apparatus 3-S, it is again clean.

Assuming that the substrate 16 consists of a fabric and that the toner supplied by the apparatus 40 is an electrostatic mordant, after formation of the impression, the substrate 16 passes into a tank 50 where the dye to be absorbed by the mordant is conveyed as indicated in 52. The substrate 16 passes over the rollers 54 and 56 while circulating in the dye tank 50 It will be understood that, in the case of a fabric, the mordant constituting the toner will normally not contain pigment, but that it will simply include the type of chemical that adheres or is absorbed by the fibers of the fabric to absorb the dye 52. In the case of paper or other substrate, the toner will be pigmented and there will have no i dye tank, but the substrate 16 will pass through one or more fixing elements, as will be described below, to arrive! then to the next station.

Continuing the description of the position 12, when j j; the substrate has received the dye, it is brought into a rinsing tank 5 & by breaking on the rollers 00 and 62 where all the coding agent is removed by rinsing. At station 12, a drying apparatus, ’(not shown) can be installed following the rinsing tank.

Box 64 represents an optical transducer reacting to the density of the impression formed at station 12. This transducer emits a signal in relation to the density, signal i • υ - the intensity of the source here * ecl ai iae in the projector 26. binds, so you can adjust the intensity of the image obtained at station t 12.

Station 14 is identical in all respects to station 12 therefore, it is not necessary to describe it in detail. The only difference lies in the color of the dye S2 'contained i |: in the tank 50'. The parameters that constitute the polarization i.01 Γ i provided by the power source 46 ', the type of mordant in I -; the toner application apparatus 40 'and the characteristics of the signals emitted at 64 * and at 66' may be different in; ‘Due to the different color involved.

FIG. 2 illustrates a second embodiment of a printing apparatus 70 which, for the illustration, comprises four stations 72, 74> 76 and 7§.

The substrate S0 follows a straight path without being deviated as is the case in the apparatus 10. At the first station, there is provided a main sleeve 82 mounted on a roller; 84. The main sleeve 82 is an electrophotographic member but it has a cylindrical shape instead of the oval shape shown in FIG. 1. This sleeve can be produced in the same way as the sleeve 20, with the exception that in this case I transparency is not essential. Preferably, the man-! chon S2 includes a coating of the same type of photoconductive material as that described above, this coating being applied I * i on a thin metal cylinder whose cylindrical shape is maintained on the roller 84 by suitable elements, j * The post image printing 72 comprises a secondary station 8c applying an electrestate charge i that, a station! secondary imaging station 88, secondary toner application station 90, secondary image transfer station 92, secondary image fusion station 94 and secondary station -

In use, the sleeve S2 passes through the secondary station for applying electrostatic charge S6 which can be in the form of a corona discharge device where this sleeve receives a uniform electrostatic charge. The sleeve 82 then passes through the secondary ima training station; S8 where a latent electrostatic image is formed there by projection, by "laset transcription" or by other suitable means. Marks (not shown) are also marked on the sleeve at a specific location located near the image in this secondary station. These markers can be in the form of a grid of points or in the form of a series of points arranged next to the image, as well as a series of points arranged in the longitudinal direction of the image. The tracking points can be formed in the same way as the image, i.e. by projection, laser, etc.

After having formed the latent image and the marks on the sleeve 82, the latter passes through the secondary toner application station 90 where the latent image is developed.

This secondary station 90 can comprise a certain quantity of liquid toner 98 enclosed in a container 100 and applied to the surface of the sleeve 82 by a roller 102. The image having received the toner, but not fixed is then brought to the secondary station of image transfer 92 where it is transferred to the underside of the substrate 80. This transfer is carried out practically without contact using a high-efficiency field obtained between the sleeve 82 and the substrate 80 by means of electrode 104 and 106 connected to an appropriate power source 108 The substrate 80 carrying the toner image then passes through the secondary image fixing station 94 which may consist of a hot air flotation bar where the image is fixed in permanently on the substrate »Any toner remaining - 12 - 9θ · This secondary station may include a pad filled with nIsopar (not shown) or another suitable cleaning tlui.de t.-n depending on the toner used . The cleaning fluid is applied ultrasonically to the sleeve 82. This sleeve S2 is then ready to possibly undergo a new charge, a new image formation, etc.

74 posts? 76 and 7S have the same secondary stations and operate in the same way as station 72. Of course, the color * of the toner is different. In addition, these stations also include electro-optical sensors 110, * 112 and 114 connected to servo systems 116, 118 and 120 respectively. These servo systems are connected to the roller control systems on which the sleeves are mounted. The control systems (not shown) can be adjusted to change the speed of rotation of the rollers and they can also be moved laterally by driving the rollers in the same movement (i.e. along their axis of rotation) .

In use, the sensors 110, 112 and 114. detect the marks appearing on the substrate near the imag which has been deposited there at the first printing station then, via the servo mechanisms, they regulate the speed of rotation and the axial position of the sleeves at the respective stations so than the images that were deposited there from the second? of the third and fourth sleeves, are in exact location with the image transferred from the first sleeve.

When the substrate 80 has passed through stations 72 to 7S, it can be brought to a finishing station 124 where a glazing compound is applied thereto (for example, with a roller) to obtain a brilliant final copy.

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From there, the substrate i> 0 jv.-ut be .-- r-ené to cutters in lonj ", guillotines, folding machines, rolls of al ii.-entat ion, etc., none of these devices not being represented, ais it is assumed that they have a structure adapted to the substrate that they receive.

Figure 3 shows a roller 196 made of transparent electrophotographic material from which the sleeve 20 (such as that used in Figure 1) is made. This material can be welded or otherwise fixed to form a strip indicated at 20, either before or after the application of the image. The image can be projected optically onto the main strip 20 and, for this purpose, a load is applied, then the image formation, the application of the toner and the fixing are carried out. However, it is preferable to apply the image digitally so that it is not necessary to provide a screen and also so as to avoid the problems posed by the optical projection elements.

A suitable polychrome image is scanned and its colors are selected, then transformed into bits which can be introduced into an electronic memory, as indicated in 198. This memory is then used to actuate a scanning mechanism of the galvanometer type in order to create deviations in a light beam emitted by a low power laser such as, for example, a helium-neon laser 200. By means of reflective elements 202 and 204, the laser projects its modulated beam onto the surface of the electrophot- ograph of the lQo roll in 20ό as this material is unwound.

By means of appropriate commands, the reflective elements 202 and 204 can correct and compensate for the conversion taking place. between the continuous flow of bits and the application on a surface as the beam rotates forward and towards 11 year · 5 era. The material is first charged in $ 20. it * ”- · / - 14 • fixed semi-permanently and the length of material obtained at that time can be cut from the roll 190, to be transformed into a sleeve 20 in the form of a strip by welding the ends one to the other.

FIG. 4 represents another device which can be used to form a sleeve 20 such as that used in FIG. 1. This sleeve 20 is in the form of a thin cylinder of metal or of a similar material comprising a coating of the photoconductive material described, this cylinder being mounted on a mandrel 214, which is driven. A laser 216 of the same type as that shown in 200 in FIG. 3 and which is supplied from an electronic memory 217, directs a modulated light beam 218 consisting of bits digitized on a movable mirror 220 mounted on a driven guide bar 222 such that the digitized bits are properly deposited on the surface of the sleeve 20 to produce the desired image representing a single color of a composite image. A corona discharge device 224 is designed to charge this surface, while a device 226 is provided for applying a toner to the image after it has been deposited. The reference figure | rence 228 represents a toner fixing device installed on the opposite side in the illustration of FIG. 4j this device being intended to fix the toner image on the sleeve 20 semi-permanently.

When the sleeve 20 has received the toner and the image is fixed thereon, it is removed from the mandrel 114 and installed in an apparatus.

Figure S is a schematic representation of the assembly of a system 301 comprising the apparatus of Figure 2 for the purpose of forming color copies from transparent color plates.

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A transparent color plate, a color copy of which must be taken, is placed on a flat table scanner 401 in which the image is quickly scanned (approximately 15 seconds) and resolved into its information components, for example, color type, density, shade and location. This information is conveyed, via a mini-computer 403, either in a permanent memory 405, or in an intermediate memory 107.

Via the software, this computer provides instructions in order to balance the colors by adjusting the size of the points, the location and, if necessary, the energy of exposure, thus taking into account the print toner characteristics. This ability to adjust the color balance also allows the operator to access and, therefore, to deliberately adjust colors by command response from a computer terminal 409 ·

This terminal 409 makes it possible to select the scale, that is to say the magnification factor, to prune the image, to adjust the intensity of the colors and to pass to an alphanumeric command 1 by means of a keyboard.

On order, the information provided by the computer 403 is introduced into an image training module I

411, the characteristic of which is to include a laser system producing simultaneously the four chromatic selections on the four sleeves 413 * 415 * 417 and 419 · These sleeves are electrostatically charged, while the aforementioned lasers form there images which receive then a toner, these sleeves then being able to transfer the wet toner images onto a sheet of blank paper 421. The transfer is practical - - 16 -

When the image is completely transferred, the paper is glossy to make the toner transparent and fix the image on the paper below a high gloss finish.

Various modifications can be envisaged without losing the spirit and the scope of the invention as defined in the claims below, i ï t

Claims (25)

1. Apparatus for printing a composite image at least once on a mobile substrate, this image being made up of impressions identifying different images having different colors, characterized in that it comprises: A. several stations 'printing of images which are each of substantially the same construction and which are intended to give a different color impression on a substrate, B. elements for moving an elongated substrate from one station to another 'e through the device, C. each station including: i. a rotary sleeve having an image as a component of a composite image, a. this sleeve being a graphic electrophotc organ comprising an external coating of photoconductive material, b. this image being a toner image? formed electrostatically on this outer coating, r £; I ii. elements for transferring the toner image to a surface of the substrate while the latter | move through this post, f iii. elements for fixing the image on the surface of the substrate before the latter moves to the next station, in order to obtain an impression of a certain T color, as well as XV, elements for remove uoux. excess toner not transferred and possibly remaining on the surface of the substrate. - 1 8 - 2. Apparatus according to resells icntion 1, characterized in that the sleeve is designed to rotate in a position of juxtaposition relative to the substrate and at a peripheral speed equal to the linear speed of the substrate moving through a station, which comprises elements for the aforementioned transfer directly from the sleeve to the surface of the substrate as the latter passes through this station. 3 · Apparatus according to claim 2, characterized in that the sleeve is in the form of a cylinder. 4. Apparatus according to claim 2, characterized in that the elements ensuring the transfer are elements producing an electric field with a view to establishing, between the sleeve and the substrate, an electrical polarization efficiently displacing the toner from the sleeve on the substrate. 5. Apparatus according to claim 2, characterized in that the element removing any excess toner is a cleaning apparatus located near the sleeve after the place where the transfer is carried out. 0. Apparatus according to claim 2, characterized in that the fixing element comprises a heating device located near the surface of the substrate after the place where the transfer is effected in the aforementioned station. 7 · Apparatus according to claim 2, characterized 'î ·! * in that the cylinder is formed from a small thickness of metal to which the coating of photoconductive material is directly adhered. 8. Apparatus according to claim 2, characterized in that the charging of the fixed toner image is carried out in ambient light. 9. Apparatus according to claim 4j characterized in that the elements producing the electric field are cons- - JM. " - J.0. Apparatus according to claim 1, characterized in that the transfer element 115 u: - tone age on the substrate comprises a second rotary sleeve which is also an electrophotographic organ, elements for charging! At j a progressive part of the second sleeve in the dark, the! the first sleeve being spaced from the second, while it comprises j I elements with a view to optically projecting the image of t-oner of the ii * first on the second sleeve in order to expose the loaded part to form a latent image therein, elements in order to apply! latent toner on the second sleeve, which is! designed to bring its toner image into juxtaposition relation with the substrate as the latter passes through the station, as well as elements in order to carry out the transfer from the second sleeve. 11. Apparatus according to claim 10, characterized in that one of the sleeves is a strip. 12. Apparatus according to claim 10, characterized in that the two sleeves are bands. : 13. Apparatus according to claim 10, character ized in that the elements ensuring the transfer are elements! elements producing an electric field and establishing, between the second sleeve and the substrate, an electrical polarization effectively displacing the toner from the second sleeve on the substrate. . 14. Apparatus according to claim 13s characterized in that the elements producing an electric field comprise a power source and two metal plates located on the opposite faces of the sleeve and of the substrate at the right end where they meet. , this power source being j! connected to the aforementioned plates. - ο - # 15. Apparatus according to claim 10, characterized in that the toner is a mordant, while the fixing elements comprise a dye bath and a rinsing bath! downstream of the second sleeve, this station also comprising elements moving the substrate through this dye bath and; this rinsing bath. j, 16. Apparatus according to claim 10, caraeté- i ized in that there are provided elements for detecting the density of the impression obtained in the post in question by emitting a signal to adjust the intensity of l image projected to maintain this density at a predetermined value. 17. Apparatus according to claim 10, characterized in that the elements eliminating the excess toner comprise a cleaning device located near the second sleeve at a place coming after that where the substrate is detached from the sleeve during its movement . 18. Method for printing composite color images on an elongated substrate, characterized in that the color images are formed repeatedly and spaced along the substrate, each image consisting of several prints of different colors, characterized in that it! : consists of:; ^ A. provide several printing stations each designed to produce a print of a different color, B. provide, at each station, a sleeve of an electrophotographic material continuously rotating while simultaneously moving the substrate through this station, each sleeve comprising a respective toner image corresponding to a color of the composite image,. 1 ~ C. traiisî'û'i.T .The respective torn-r imago of each sleeve on the surface of the substrate as the latter passes through each station; and D. fix each toner image at its station after transfer to the substrate as the latter passes and before it enters the next station, and E. steps C are timed in each station so as to apply the toner images coincide. 19. The method of claim 18, characterized in that the toner image is transferred directly to the substrate. 20. The method of claim 18, characterized in that the toner image is transferred indirectly to the substrate by first projecting it optically onto a second sleeve. 21. The method of claim 18, characterized in that the toner image is formed initially on the sleeve, then projected onto a second sleeve of an electrophotographic material, exposed in the form of an image and added with toner on the second sleeve, then transferred directly from the latter onto the substrate. 22. Method according to claim lS, characterized in that the toner is pigmented. r i 23. The method of claim 18, characterized in that the toner is a dye mordant, while the fixing step is a coloring and rinsing step intended to pigment the fixed impression. 24 · A method according to claim lS, characterized in that the density of the toner image formed on the substrate is measured after fixing, this measurement being used to control the transfer. '-'. • ÿ. P -ni v.tnt la i-t vt.ï; ·.? i i: ;; l i on 18, caraclc- π ((1 rue le t i <'1 1 lit sur le substrat (--- 1- attend if it is not done electri queinent. 26. The following method, claim 18, characterized in that 1 · image of the main sleeve is formed before use by digitizing a composite image and memorizing the information thus obtained, modulation of a laser beam with the digitized information emitted by memory and transcription on the main sleeve, addition of a toner to this sleeve and fixing of the developed image obtained. 27. A method of forming a color copy of a color object, a color scene, a color image or the like on a substrate, characterized in that it consists of: A. providing several electrophotographic sleeves B. B. form a toner image electrophoto · graphically on each of these sleeves, the toner image of each sleeve corresponding to a color image different from the color copy, C. transfer the toner image from each sleeve on the substrate successively and in exact location. 28. The method of claim 27, character. i ized in that the toner images are transferred directly to the substrate. I 29 · A method according to claim 27, characterized in that the toner images are transferred indirectly. 30. The method of claim 27, characterized in that the toner images * are formed on the sleeve by first loading the latter, then forming i; latent electrostatic images by * laser transcription,: 'then applying a toner to the images thus formed. - 23 - * 31. An electrophotographic color printing apparatus for the formation of a polychrome copy on an elongated substrate, characterized in that it comprises: (a) several electrophotographic bodies of cylindrical shape arranged side by side and mounted to perform a movement of rotation on their longitudinal axis, (b) of the elements in order to form a toner image on each of these electrophotographic members, the toner image formed on each of these members corresponding to a · "color different from the full color copy, ( c) elements for moving the elongated substrate successively on each electrophotographic member, (d) elements for successively transferring the toner image of each electrophotographic member on the substrate, and (e) elements for adjusting the speed of; rotation and axial position of the electrophotographic member i to ensure exact registration of the toner images as they are transferred to the substrate. !: 3 ^. Process for forming a full color copy! of an image, a scene or the like, characterized in that it ij 'consists in: (· j * (a) transforming the image, the scene or the like into digital information, (b) using this digital information to form several separate latent electrostatic images, each image corresponding to a color of the composite image, of the scene or the like, (c) applying a toner to each latent electrostatic image thus formed with its new color, - - 4 - (d) transfer each of the toner inages successively to a substrate and by registering with each other in order to form a full color copy, and (e) the transfer of each image being followed by the fixing of this on the substrate before transferring the next image.