US3244546A - Electrostatic image reproduction - Google Patents

Description

April 5, 1966 J. E. CRANCH 3,244,546

ELECTROSTATIC IMAGE REPRODUCTION Filed Jan. 4, 1963 POWER SUPPLY INVENTOR. JOHN E. CRANCH ATTORNEY United States Patent 3,244,546 ELECTROSTATIC IMAGE REPRODUCTION John E. Cranch, Penfield, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a'corporation of New York Filed Jan. 4, 1963, Ser. No. 249,484 11 Claims. (Cl. 117-175) This invention relates to electrostatic method and apparatus for reproducing images.

Various electrostatic methods are known for reproducing images from original copy usually dependent on optical or electrical properties of the original. Thus the art of xerography as, for example, disclosed in US. Patent 2,297,691 to Chester F. Carlson utilizes optical presentation of light or other forms of activating radiation to selec tively discharge a previously charged photoconductive insulating member to form an electrostatic latent image corresponding to the original. The latent image can then be made visible by development with an electroscopic powder as is well known in the art. Another electrostatic reproduction method termed xeroprinting is disclosed, for example, in Schatfert U.S. Patent 2,576,- 047. This latter method employs images in the form of insulating material supported on a relatively conductive support. Reproduction is non-optical in that an applied charge is retained only in the insulating image areas which may then bedeveloped. Yet another method of electrostatically reproducing images is disclosed in Ebert US. Patent 2,647,464 in which the relative differences in electrical conductivity between the support sheet and the printing inks comprise a basis for selectively charging an insulating layer. In this latter method, the image member is placed in contact with a dielectric during charging to form an electrostatic image and subsequently the insulator is developed as in the manner of Xerography to render a visible and useful reproduction.

Now in accordance with the instant invention, there has been discovered that images contained on a support sheet can be electrostatically reproduced without optics and without regard to distinctive electrical properties between printing material if any, and the support sheet. Rather, it has been found that where the images are represented by surface impressions or indentations or raised or depressedareas, they are per se capable of being electrically reproduced. The advantages are many. In particular, a novel image master is defined for reproduction systems. Such a master can easily and simply be reproduced without optics and in the presence of complete ambient illumination. I

It is, therefore, an object of this invention to define a novel master for electrostatic printing.

It is another object of the instant invention to provide a novel method of electrostatic printing.

It is a further object of the invention to provide a novel method of electrostatic printing which is not dependent on optical exposure.

It is still a further object of the invention to provide novel method and apparatus for electrostatic printing which reproduces images on a support sheet without dependency on electrical properties of printing inks, if any, of which the image may be comprised.

It is a still further object of the invention to provide a novel method of electrostatic printing for reproducing images comprised of surface impressions or indentations in a support surface.

Further objects and features of the invention will become apparent while reading the following description in connection with the drawings wherein:

FIG. 1 is a plan view of an original copy image on a support sheet reproducible in accordance with the invention;

FIG. 2 is a sectional view taken substantially along line 2-2 of FIG. 1 and showing the image impressions in exaggerated relation for purposes of illustration;

FIGS. 3(a) through (d) illustrate an embodiment of steps in carrying out the process of the invention;

FIG. 4 illustrates an alternative step for the embodiment of FIG. 3; and,

FIG. 5 illustrates an apparatus operable in accordance with the invention.

It has been found that when an image is comprised of surface impressions, indentations or the like on its support prepared by such means as letter press, typewriter, sharp implement or the like as will be further defined herein, they will, by the process of the invention, reproduce faithfully in image configuration.

Referring now to the drawings, there is illustrated in FIGS. 1 and 2, the images A and H each designated 10, formed as surface impressions on a support sheet 11 which may be a suitable, relatively smooth, relatively conductive material such as paper, conductive plastic, or the like having substantially homogeneous bulk resistivity of about between 10 -10 ohm cm. Obviously, although the image areas are considered herein to be impressed, it should be realized that in accordance with the process it makes no difference whether the impressed portions represent image or non-image areas or if master surfaces are formed by selectively embossing either image or nonimage areas.

In carrying out the process of the invention, there is employed an electrographic plate 12 comprising a dielectric layer 13 supported on a conductive support 14 which may be any convenient conductive material to which the dielectric layer will make contact or bond including various forms of metal such as aluminum or the like. The dielectric is preferably of about 1 to 10 mils in thickness and may be any convenient form of insulating material such as Lucite 45, Mylar, or Teflon being respectively an isobutyl polymeric ester, a resin film' of polyethylene terephthlate and a tetrafiuorethylene polymer each of the E. I. du Pont de Nemours 8: Co., chlorinated rubber, Amberol F-71 which is believed to be a phenolic resin manufactured by Rohm and Haas Co., Staybelite ester No. 10, being a glyceryl ester of hydrogenated resin manufactured by the Hercules Powder Co., polystyrene, polyethylene, Pliofilm, being a rubber hydrochloride of the Goodyear-Tire and Rubber Co., ethyl cellulose, various combinations of Parlon and Rezyl, which are, respectively, chlorinated rubber and alkyd resin products of Hercules Powder Co. and Americal Cyanamid Co., certain resin blends made up of various combinations of the above-named resins, and various other materials which possess dielectric properties. Obviously, where it is convenient to practice the invention in the dark, the dielectric may also include the well-known photoconductive insulators such as vitreous selenium, zinc oxide in a suitable binder, etc. This affords the advantage of enabling erasure of electrostatic images or portions of the image simply by exposing the plate to general illumination. It also allows one to add information by optical means either prior to or following image formation as disclosed for example in the Carlson patent cited above and in Byrne et al. US. Patent 3,057,719.

The first step in one embodiment of the process, as illustrated in FIG. 3a, is .to pass the electrographic plate 12 past a suitable charging device With the substrate 14 maintained at ground potential. The charging device may be a corona generator 15, such as disclosed in Carlson US. Patent 2,588,699, Walkup US. Patent 2,777,957, or any other suitable means known in the art as more fully described below for applying a uniform potential of a selected polarity as, for example, positive onto the surface of the dielectric layer 13. As shown,

there is illustrated a corona generating device energized from a source of high potential 16 that applies potential in the range of about 2,000 to 10,000 volts to a corona generating electrode 17 which emits corona of a selected polarity to deposit a uniform charge onto the surface of a dielectric 13. The applied charge on the surface of dielectric member 13 may be on the order of 400 to 800 volts as is conventional in the xerographic art or may be as low as 20 or 30 volts. The voltage selected will depend to some extent on the preselected system of utilizing the electrostatic image once formed.

The next step in this embodiment of the process is illustrated in FIG. 3b in which the original image hearing member 11 is placed in surface contact against the previously charged dielectric layer 13. When in this position, the sandwich is passed past the potential generating device 15 to place a charge of opposite polarity to that applied in FIG. 3a, in this case negative, onto the backside of the image bearing member. The negative charge applied in the illustration in FIG. 3b is usually of a magnitude approximately suflicient to produce a net neutralizing effect at the interface contact between the image bearing member 11 and the insulating layer 13. The magnitude of the applied negative charge will therefore be a function to some extent of the magnitude of the initial charge applied to the surface of layer 13 as well as the conductivity and thickness of the material of which image member 11 is comprised. Hence the applied negative charge usually is of an order of magnitude effective to produce a neutralizing force at the interface in the areas of physical contact. For example, if an initial charge of approximately 600 volts is applied on the surface of layer 13 and member 11 is comprised of a highly conductive paper in close contact against the surface, a negative charge of approximately 600 volts will effect the desired result. Complete neutralization however, is not essential such that a 20 to 30 volt differential can produce a developable image if a sufiiciently sensitive developing system is used to the extent that background may possess potentials in their range or higher.

Following the application of opposite polarity charge, the image member is removed as in FIG. 3c from the contact relation with layer 13' and for reasons as will be explained, there remains on the surface of layer 13 a charge potential 20 in pattern configuration corresponding to the original copy. Thereafter, as illustrated in FIG. 3d, electroscopic powder developer 2-1 charged to a polarity in accordance with the result to be obtained is presented in any convenient manner such as by cascade, powder cloud, magnetic brush, brush, or any other means known in the art over the dielectric surface to effect development. Where it is desired that the developed image comprise an image developed corresponding to areas of charge, it is usual to pass in contact therewith a developer which is triboelectrically charged to a polarity opposite to the retained charge whereby the developer is attracted and adheres to the charged areas of the image pattern. Where it is preferred that a developed image corresponding to uncharged areas result, it is usual to employ a developer charged to the same polarity as the image charge pattern such that the developer is repelled by the charges and deposits on the nonimage areas, with the charged areas remaining absent of developer. In FIG. 3d of the drawing, the developer material 21 has been permitted to flow part way across the face of the plate 12 making visible those portions of the image areas 20 contacted by developer 21. As herein illustrated, developer 21 may comprise a two-component developer of a type disclosed in Wise Patent 2,618,552 to cascade across the plate surface from a hopper 22 into a receiver bin 23. To enhance develop ment of large solid areas of charge, a closely spaced development electrode may be employed as disclosed, for

4i example, in Gundlach U.S. Patent 2,777,418 or Ulrich U.S. Patent 3,011,475.

By still another embodiment in accordance with the invention, the step illustrated in FIG. 3b above is omitted and the step of FIG. 4 employed instead. In this embodiment, as described in connection with FIG. 3a, a charge of either polarity is first uniformly applied onto the surface of the dielectric 13. After charging, the image bearing member 11 is placed against the charged dielectric to effect areas of contact and areas of spacing, with the latter representing the image areas 10. When in this position, the top surface of the image hearing member is shorted to the substrate 14 which can be effected by any suitable means such as by advancing an electrically connected roller 18 across the surface in the manner illustrated in FIG. 4. The roller is preferably pliable and may contain a fluid conductor on its surface in order that uniformity of contact be made with all portions of the top surface of sheet 11, particularly where the surface becomes irregular by virtue of the image impressions. Either simultaneously with or after shorting, the image bearing member is peeled away in the manner illustrated in FIG. 30. The image charges remaining may then be developed in the manner of FIG 3a. When the image support is highly conductive, localized shorting may be effective. However, by rolling in the manner described, the process is operable over a wide latitude of master conductivities. A hand method of shorting the image member to the substrate is for the operator to place his hands with one against the top surface of member 11 and the other in contact with substrate 14.

By yet another embodiment, the precharging step illustrated in FIG. 3a can be eliminated and the image bearing member 11 placed directly onto the insulating surface of layer 13. In this embodiment, without precharging the dielectric, a charge is applied through the back of the image bearing member as described above of either polarity to create a selectively deposited uniform potential on the surface of the dielectric. It has been found in this instance that the space between the raised image areas, as compared to the other areas of member 11 in closer propinquity with the dielectric surface prevents charge from being deposited on the dielectric surface in the areas correspondent to the image areas. At the same time, in all other areas thereof, there is deposited a. uniform charge density. By this means, then, it is possible to present a powder of opposite polarity charge across the plate surface to attract developer to the charged non-image areas producing a reversed image formation of the original or alternatively, to pass a powder charged to the same polarity as that produced in the non-image areas to be repelled into the uncharged areas of image giving a right-reading positive image.

It is apparent that the image indentations or impressions on the image bearing member create a gap between the image bearing member and the dielectric surface in the areas correspondent to the image, While there is substantially contact in the non-image areas. It has been found that the minimum depth of image impression bears a direct relationship to the fidelity of the final reproduction. If the impression is too shallow, charge deposits result in the image areas as well as in the background areas. Adequate difference is achieved with impressions on the order of about 7/10 mils and above without any real limitation to the upper limit of impression depth as long as the edge of the image is reasonably defined. Thus, where a typewriter is used to form the indentations, it should be operated preferably without a ribbon with the paper supported against a relatively soft platen. Normal pressure in typing with a ribbon will usually only produce impression depths of less than 7/10 mils; whereas, without a ribbon, depths of about 1.3 mils are achieved which can be increased to about 2.5 mils with heavy pressure and with a soft platen.

While the exact mechanism by which the present invention operates is not known or established, the following theories are believed to possess considerable merit. Both theories suppose that to insure optimum operation of the invention, both the original to be copied and electrographic plate to be used should meet certain requirements and specifications. It appears that the original to be copied must comprise an image supporting material which is a relatively good conductor and that the image be idented sufficiently to provide an adequate air gap from the insulating surface against which the image member is to be placed. The surface texture of the copy should be smooth without irregularities or surface indentations that are likely to reproduce in the same manner as the impressed images thereon.

It is believed that when an original of this type is placed upon an electrographic plate of the type disclosed heretofore and subjected to an electrical discharge as previously stipulated, those areas of a previously charged electrographic plate directly below the background portion of the original become discharged as compared to those areas directly below the image indentations. Likewise, where the precharge of the dielectric is omitted, areas of the dielectric below the background become charged whereas areas below the image do not. Consequently, an electrostatic image of the original is formed on the electrographic plate to form an electrostatic pattern of charge which can be rendered visible by presenting an electrically charged powder material thereto.

The first proposed theory with either embodiment is that the dielectric breakdown value of the air is substantially greater than the field occasioned by the potential applied in the impressed areas. This prevents charge migration :therebelow when charging the backside of the image member in contact against the dielectric. On the other hand, the field in the non-impressed areas, or areas of higher capacitance, under the same applied potential, exceeds the critical stress for air ionization. It is believed that this ionized air transfers charge from the image bearing member to either neutralize the precharge on the electrographic plate where the precharge has been performed or effect a charge application thereon where the precharge has been omitted. The second theory supposes that no charge transfer occurs until separation of the image bearing member from the dielectric particularly when applying charge to a fairly low potential. On separation, there occurs a charge breakdown as the areas of contact pass through a critical separation distance while in those indented areas, no charge breakdown occurs since the air gap initially exceeds the threshold distance below which charge breakdown would otherwise occur because of the potentials present. Thus, it is known, for example, as more fully described in Byrne US. Patent 3,057,719 that as an air gap reaches a critical value on separation, charge breakdown can destroy the effective electrostatic fields in the areas in which it occurs. In either case, and for whatever the reason a charge pattern is known to remain clearly distinguishing the impressed from the unimpressed areas of the original.

Whatever may be the exact mechanism by which the present invention effects reproduction of images, it is certain that the adoption of the steps described above will result in such reproduction in a rapid and satisfactory manner. Whatever the phenomenon that takes place, it has been found and shown that surface impressions in the image bearing member can be reproduced in the form of an electrostatic latent image on an electrographic plate. Preferably, conductive inks or other conductive printing materials should generally be avoided in the impressed areas of the original copy particularly Where the impression depth is relatively shallow. That is, since it is assumed that the image support has sufiicient conductivity to reach equipotential, any inking material should not fill the impression although the impression can be partially occupied. The particular apparatus or technique employed in applying charge toform the electrostatic image on the electrognaphic plate is not critical and many variations in design and application are pos sible. Methods which can and have been used include producing a corona discharge from wires or needles and passing the electrographic plate through the discharge area: induction as by covering the electrographic plate assembly with a metal plate connecting the metal plate to a voltage source; and other methods of producing electric fields in the vicinity of the plate copy assembly.

In the step of developing an electrostatic image, it has been found that various resinous powders are very satisfactory. These powders should be caused to selectively assume electric charge of the same or opposite polarity as the polarity of charge on the electrographic plate. This may be done by means of devices which spray electric charges or may be effected by triboelectric action in the mixture of developer material and a carrier material. In the two-component developer, the particular materials chosen are selected in accordance with their relative position in the triboelectric series, wherein it may be ascertained that the developer component will assume the proper polarity of charge upon triboelectric reaction with the carrier material. The particular powdered carriers used in the present method are not critical to this operation, the only requirement being that the powder be charged with the appropriate polarity dependent upon the image to be reproduced as stipulated above.

Once the powder image is developed onto an electrographic plate, it may be treated in any one of several ways depending upon ultimate use to which it is to be put. For example, the developed image may be fused directly to the electrographic plate to form permanent copy. Other applications may require the image to be transferred to a second surface and this is conveniently done electrostatically by placing the transfer material over the image and applying an electrostatic charge to the back of the material of polarity opposite to the polarity of charge on the powder. Other transfer methods may be used, of course, as for example, various chemical transfer methods or methods involving hygroscopic or adhesive action.

Referring now to FIG. 5, there is illustrated a form of automatic apparatus embodying the principles described above and particularly including the process step described above in connection with FIG. 4. In accordance with the apparatus hereof, the electrographic plate 12 is in the form of a rotatable cylinder being continually rotated at a uniform rate by means of a motor 25. Image sheet 11 is contained on a supply roll 26, (not yet contaming any images thereon) and wherefrom, it is drawn between an impression cylinder 27 and a pliable platen 28 both driven by motor 2%. The impression cylinder includes a wrapped around flexible sheet 30 containing bossed images 31 that are effective to indent or impress he image areas into the image sheet 11 moving therepast.

Surface 13 is charged by means of a corona generating device 15, after which the sheet 11 now containing the recessed images corresponding to images 31, passes over guide roll 32 into contact with surface 13. After a short period of superposed travel, the image sheet is then separated from the drum by passing over a grounded guide roll 33, similar to roller 18 described above, after which it passes over guide roll 4% onto take-up roll 41 driven by motor 2% through a slip-clutch 42 in order to maintain the linear speed of the web synchronous with the peripheral movement of the drum.

The electrostatic image then remaining on the drum surface is developed by means of a developing unit 41?. In the developing unit, developing material is carried up by a conveyor 44 driven by suitable drive means from motor 45 and is released onto chute 46 wherefrom it cascades down over the drum surface. Toner component 47 of developer 48 that is consumed in developing is stored in dispenser 49 and is released in amounts controlled by gate 50.

Thereafter the powder image is electrostatically transferred to a support surface web 60 by means of a second corona generating device 61 similar to corona generating device 15, mentioned above. The support surface to which the powder image is transferred may be of any convenient type such as paper and is obtained from a supply roll 62 and is fed over guide rolls 63 and 64 to be directed into surface contact with the drum in the immediate vicinity of the transfer corona generating device 61. After transfer, the support surface is separated from the drum surface and is guided through a suitable fusing apparatus 65 which may be an adaptation of the type disclosed in Crumrine US. Patent 2,852,651 whereby the powder image is permanently affixed to the support surface. Thereafter, the support surface is fed onto a take- -up roll d6 that is also driven by motor 25 through a suitable slip-clutch 67.

After transfer, the drum surface is brushed clean by cleaning brush 68 driven also by motor 25 whereby residual developing material remaining on the drum is removed.

It should be appreciated in connection with the appara tus of FIG. 5 that it can be adapted to be operable consistent with the embodiments above other than FIG. 4 and it can also be adapted to produce from and onto individual cut sheets instead of a continuous web as illus trated.

It will be appreciated that a new and useful method and apparatus for reproducing copy has been described. Throughout the specification and claims, the word copy is used to describe material to be reproduced. It is again pointed out for purposes of emphasis that no light-sensitive steps are performed. The operation is based entirely upon electrical principles as has already been pointed out and explained. It will be apparent that the present method provides for the reproduction of either a positive or negative of the copy being reproduced. This is so since the operation of novel steps is to produce charge areas corresponding to the depressed areas of the copy and areas having little or no charge which correspond to the smoothsurfaced areas of the copy. By selecting a developer charge of the required polarity, either the charged areas or the non-charged areas can be developed, thus producing copy as desired and without regard to the form of the original. In a second embodiment, charge may be applied directly through the areas of surface contact of copy and the dielectric. Development form may similarly be optional.

Since many changes could be made in the above construction and many apparently widely different embodiments of this invention can be made without departing from the scope thereof, it is intended that all matter contained in the drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A method of forming a reproduction comprising the steps of (a) impressing an image to be reproduced to a depth of about at least 7/10 mils in the surface of a relatively conductive paper sheet image support;

(b) placing the image support into overlying contact with a member having an insulating surface;

() applying a charge potential onto the back of the image support while in said last recited relation; and,

(d) removing the image support from the position of contact with the insulating member whereby a derelopable charge remains on the surface of said insulating member in areas corresponding to areas of contact adjacent to areas of spacing formed by the image impressions of the image support.

2. The method according to claim 1 which comprises the additional step of presenting electroscopic developer material to the remaining charges on said insulating material to render a visible reproduction of said image.

3. A method of forming a reproduction comprising the steps of:

(a) typewriting copy with an absence of ribbon to form image depths of about 7/l0 to 2 /2 mils in the surface of a relatively conductive paper sheet;

(b) placing the paper sheet containing the typed impressions in overlying contact wtih a member having an insulating surface;

(c) applying a charge potential onto the back of the paper while in said last recited relation; and,

(d) removing the paper from the position of contact with the insulating member whereby a developable charge remains on the surface of said insulating member in areas corresponding to areas of contact adjacent to areas of spacing formed by the typed impressions of the paper.

4. The method according to claim 3 which comprises the additional step of presenting electroscopic developer material to the remaining charges on said insulating material to render a visible reproduction of said image.

5. A method of forming a reproduction comprising the steps of:

(a) impressing an image to be reproduced to a depth of about at least 7/10 mils in the surface of a relatively conductive paper sheet image support;

(b) applying a uniform charge potential onto a sur face of an insulating member;

(c) placing the image support into overlying surface contact with said charged insulating member;

(d) applying a reference potential to the back of said support while in said last recited relation adapted to effect surface discharge of said insulating member in areas of contact with said image support; and,

(e) removing the image support from the position of contact with the insulating member whereby a developable charge remains on the surface of said insulating member in areas corresponding to areas of spacing formed by the image impressions of the image support.

6. The method according to claim 5 which comprises the additional step of presenting electroscopic developer material to the remaining charges on said insulating material to render a visible reproduction of said image.

7. Apparatus for the reproduction of copy comprising in combination:

(a) image impression forming means capable of impressing an image of copy to be reproduced to a depth of about at least 7/1() mils in the surface of a relativeiy conductive flexible support material;

(b) a supply source containing a quantity of relatively conductive flexible image support material in which impressions are to be made by said impression forming means;

(c) support means supporting a member hav ng a layer of insulating material;

(d) charging means adapted to apply a uniform charge potential onto the surface of the insulating material of said member;

(e) means to advance a predetermined quantity of image support material from said source of supply into impression relation with said image impression means to form an image therein and then into superposed contacting relation with the charged surface of said insulating member;

(f) means to apply a reference potential to the imagebearing support material while in said last-recited relation adapted to effect surface discharge of said insulating member in areas of contact with said image support;

(g) separating means to separate the image support from said superposed relation whereby a developable charge remains on the surface of said insulating material in areas corresponding to areas of spacing formed by the image impressions of the image support material; and,

(h) developing means adapted to present electroscopio material to the remaining charges on said insulating material to render a visible reproduction of said image.

8. Apparatus according to claim 7, in which said impression forming means comprises (a) an image member of pre-formed substantially permanent embossed images;

(b) a cylindrical member adapted for rotation sup porting said image member about its periphery;

(c) a resilient platen supported in light pressure engagement with the image member on said cylinder; and,

(d) means to rotate said cylinder whereby the image support advanced by said advance means passes between said image member and said platen to receive an image impression therein.

9. Apparatus according to claim 8 in which said means to apply a reference potential comprises grounding means.

10. Apparatus according to claim 9 in which said grounding means comprises a conductive roller adapted for rolling contact with said image support.

11. Apparatus for the reproduction of copy comprising in combination:

(a) image impression forming means capable of impressing an image of copy to be reproduced to a depth of about at least 7/ 10 mils in the surface of a relatively conductive flexible support material;

(b) a supply source containing a quantity of relatively conductive flexible image support material in which impressions are to be made by said impression forming means;

(c) support means supporting a member having a layer of insulating material;

(d) means to advance a predetermined quantity of image support material from said source of supply into impressing relation with said image impression forming means and then into superposed contacting relation with said insulating member;

(e) charging means adapted to apply a charge potential onto the back surface of the image support while in said last recited relation to efiect a surface charge on said insulating member in areas of contact with said image support;

(f) separating means to separate the image support from said superposed relation whereby a developable charge remains on the surface of said insulating material in areas corresponding to areas of contact adjacent the areas of spacing formed by the image irn pressions of the image support material; and,

(g) developing means adapted to present electroscopic material to the remaining charges on said insulating material to render a visible reproduction of said image.

References Cited by the Examiner UNITED STATES PATENTS 2,576,047 11/1951 Schaifert 11717.5 X 2,633,796 4/1953 Pethick 101-212 2,912,586 11/1959 Gundlach 25049.5 3,015,304 1/1962 Carlson et al. 118-637 X 3,145,655 8/1964 Hope et al. 117-17.5

WILLIAM D. MARTIN, Primary Examiner.

G. L. HUBBARD, Assistant Examiner.

Claims (2)

1. A METHOD OF FORMING A REPRODUCTION COMPRISING THE STEPS OF: (A) IMPRESSING AN IMAGE TO BE REPRODUCED TO A DEPTH OF ABOUT AT LEAST 7/10 MILS IN THE SURFACE OF A RELATIVELY CONDUCTIVE PAPER SHEET IMAGE SUPPORT; (B) PLACING THE IMAGE SUPPORT INTO OVERLYING CONTACT WITH A MEMBER HAVING AN INSULATING SURFACE; (C) APPLYING A CHARGE POTENTIAL ONTO THE BACK OF THE IMAGE SUPPORT WHILE IN SAID LAST RECITED RELATION; AND, (D) REMOVING THE IMAGE SUPPORT FROM THE POSITION OF CONTACT WITH THE INSULATING MEMBER WHEREBY A DEVEL-

2. THE METHOD ACCORDING TO CLAIM 1 WHICH COMPRISES THE ADDITIONAL STEP OF PRESENTING ELECTROSCOPIC DEVELOPER MATERIAL TO THE REMAINING CHARGES ON SAID INSULATING MATERIAL TO RENDER A VISIBLE REPRODUCTION OF SAID IMAGE.

Images