PRINTING"

BACKGROUND OF THE INVENTION

In the apparel and related industries it is customary to use a so-called marker for cutting of materials or fabrics. The marker comprises a sheet of paper on which are printed in essence lines defining the contours of various pieces of fabric forming various parts of a garment which is made by sewing together such pieces of fabric. The marker is laid over a stack formed by a number of fabric layers, or in certain cases over a single fabric layer/ and the fabric is cut through the marker by a cutter which follows precisely the contour lines printed thereon. For each fabric stack cutting a new marker is required because the marker is destroyed in the process and therefore it is economically necessary to -use -cheap paper for the marker, particularly since in many instances up to 100 or even more markers are needed to cut the number of stacks or quantity of fabric for the required number of garments.

There are various methods of imprinting the contour lines on the markers and one such method is as follows. By appropriate electronic data manipulation the contour line configuration for a specific garment is stored as a programme in a computer which operates a plotter as is well known in the art. The output from the plotter is a sheet of paper containing thereon a printout of the contour lines and such plotter output is then used as a duplicating master for generating a number of

copies which then serve as markers.

Marker generation by copying from the duplicating master is carried out as follows. The plotter printout is produced by signal addressed styli contacting a dielectric paper and forming an electrostatic charge pattern thereon corresponding to the information to be printed that is the contour lines. The dielectric paper surface is then contacted with a liquid toner as. is well known in the art, that is electroscopic marking particles dispersed in a so-called carrier liquid, whereby such electroscopic marking particles or toner material becomes attracted by said electrostatic charges and forms pattemwise deposits on the dielectric paper surface. The toner material is of a composition adapted to form hectographic printing deposits that is to say it contains alcohol soluble dyes and thus the plotter output becomes a hectographic duplicating master for the generation of copies therefrom or markers by hectographic or so-called spirit duplication, as is well known in the art. In the process of duplication, the hectographic master is usually mounted on or passed over a rotating cylinder; the copy paper is moistened with alcohol or a mixture of water and alcohol and is brought into intimate contact with the printing surface of the master whereby the alcohol in the copy paper dissolves some of the spirit soluble dye contained in the printing deposits on said printing surface and such dissolved dye becomes absorbed by the moistened copy paper forming a dye image thereon. Upon evaporation of the alcohol the dye image becomes fixed to the copy paper. Subsequent copies are made by repeating the steps of moistening the copy paper and contacting it with the printing surface of the master.

It has been found in practice that by the above described method in many instances it is not possible to produce the required number such as up to 100 markers from one dielectric paper base hectographic master because such masters due to the nature of the dielectric paper base and hectographic toner deposit formed thereon show severe copy density deterioration after only about 15 or so copies. Thus in those instances where more than about 15 markers are required it is necessary to produce in the plotter further duplicating masters on dielectric paper, which is time consuming and expensive, in view of the high cost of the dielectric paper. Thus there is need for increasing substantially theru b r of copies or markers which can be generated from one and the s.ame ^■ dielectric paper base output produced in the plotter.

It is known to develop a latent electrostatic image on a dielectric sheet by a coloured toner and to electrically transfer the toner to a first and even to a second surface but this only involves transferring a single developed image at a time. Such a method is shown in the specification of Australian Letters Patent No. 469,940 and the corresponding United States Patent No. 3,862,848.

SUMMARY OF THE INVENTION

It is therefore the object of this invention to provide a method of and means for producing an inexpensive duplicating master which is capable of generating in excess of 100 copies or markers.

Another object of this invention is to provide a duplicating master which is produced by a method whereby the dielectric paper comprising the plotter output can be reused many times.

A further object of this invention is to provide a method of and means for producing copies or markers from a dielectric paper comprising the plotter output where such dielectric paper ca be reused many times.

A still further object of this invention is to provide a method of ^' and means for producing copies or markers from a dielectric paper comprising the plotter output whereby such copies or markers can themselves be used as duplicating masters if so desired for the generation of a limited number of further copies or markers and where such dielectric paper can be reused many times.

The above objects and other advantages are accomplished in accordance with this invention by employing electrostatic duplication for the generation of copies or markers and by producing the elctrostatic duplicating master and in certain instances by produc¬ ing the copies or markers by image transfer from a reusable plotter output, as will be described in mere detail in the following.

DESCRIPTION OF THE INVENTION

In the well known art of electrostatic printing or duplication it is customary to employan electro¬ static master having a printing-surface which comprises

relatively conductive background or non-image areas and relatively insulative or dielectric image or printing areas corresponding to the information to be printed. The conductive or relatively conductive background area may be the surface of a metal plate or coated paper or a photoconductive recording member or the like whereas the image areas which will be referred to henceforth as primary image deposits can be formed by deposits of dielectric material. In the process of duplication such electrostatic master is usually placed over a conductive support member such as a rotating cylinder which is connected to the terminal of one polarity of a high tension DC power supply whereas the terminal

of the other polarity of such power supply is connected to corona or electrostatic field generating means positioned near the printing surface of said electro¬ static master to apply electrostatic charge to the primary image deposits contained thereo . ^' Subsequently electroscopic marking particles generally referred to as toner material which may be of dry powder type or of liquid dispersed type as is well known in the art, henceforth referred to as secondary toner, are applied to the printing surface- Such toner material is attracted to the charged primary image deposits and forms a toner material deposit there.on which toner deposits will be referred to henceforth as the secondary image deposit. Such secondary image deposit is then transferred electro- statically or by other means such as pressure as is well known in the art onto a receiving member such as a sheet of plain copy paper on which such transferred secondary image deposit is subsequently affixed by solvent evaporation, heat fusion, pressure or other means. Subsequent copies are generated in like manner by recharging the primary image deposits, forming secondary image deposits thereon and transferring the secondary image deposits to consecutive copy sheets.

It should be noted that in certain instances it is not necessary to recharge the primary image deposits following the electrostatic transfer therefrom of the secondary image deposits onto the copy paper as the corona or electrostatic field generating means can be constructed to operate in such manner that after one initial step of applying electrostatic charge to the primary image deposits to attract secondary toner material thereto for the formation of the secondary image deposit which is to be t ansferred to the first

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copy sheet, the electrostatic field applied during the step of transferring the secondary image deposits to a copy sheet also effects recharging of or maintaining of charge on the primary image for attraction thereto of secondary toner material to form secondary image deposits for transfer onto a subsequent copy sheet.

The electrostatic master referred to in the foregoing is prepared in accordance with this invention as follows. The plotter output that is the dielectric paper containing on its surface an electrostatic charge pattern corresponding to the information to be printed that is the contour lines is contacted with primary toner material which is dielectric or insulative and is attracted by said electrostatic charges. The pattemwise deposits formed by such primary toner on the dielectric paper surface are transferred electro¬ statically or by other means onto -an electrically conductive or relatively conductive coating contained on at least one side of a paper sheet and are affixed thereto to form primary dielectric image deposits on said conductive surface and thereby to produce an electro¬ static duplicating master.

The primary toner material comprises dielectric or insulative electroscopic marking particles which may be applied in the form of dry powder by known toning methods or such electroscopic marking particles may be in liquid dispersed form. Such primary toner material may consist of insulative and preferably thermoplastic polymeric substances such as polystyrene, acrylics, ketone resins, epoxy, polyethylene and the like, waxes, and colouring matter such as pigments may also be included provided they do not lower the insulative

properties of the toner material. In the case of liquid toners other substances such as dispersing agents and charge directors or polarity control agents can also be included. It is however important that such primary toner is capable of forming on the dielectric paper toner deposits which can be transferred to the con¬ ductive coating on the master base paper virtually completely so that as little as possible residue remains on the dielectric paper surface.

upon transfer onto the conductive coating the primary toner deposits can be affixed thereto by application of heat or warm air whereby the thermo¬ plastic dry or liquid toner materials are caused to melt and adhere to the conductive coating and it will be realised that if such materials are applied from liquid dispersion the carrier liquid or solvent may be evaporated prior to or during such heat fixing step. In the case of liquid toners it is also possible to use so-called self-fixing toner materials which affix the toner deposit to the conductive coating upon evaporation of the carrier liquid or solvent. Accordingly in order to attain good adhesion or bonding it is also necessary for such primary toner materials to be compatible with the substance forming the conductive coating on the masts base paper. Furthermore it is also necessary for such primary toner material to be so selected that the fused or fixed primary image deposits on said conductive coating are solvent resistant that is to say they are not dissolved or swelled or tackified or otherwise affected by the carrier liquid of the secondary toner in those instances where such secondary toner is of the liquid type.

As has been stated earlier, in the process of ' duplication the electrostatic master surface is charged uniformly whereby the dielectric image deposits contained thereon acquire electrostatic charges for the attraction of secondary toner material thereto whereas the back¬ ground or non-image areas remain free of such charges.

Accordingly the coating on t e paper base of the *• ^* duplicating master must be sufficiently conductive to .prevent the background or non-image areas thereon from accepting electrostatic charges of sufficient magnitude to attract secondary toner material thereto which may form o jectionable fog or stain in such background areas. Such conductive coating may comprise a water soluble quaternary ammonium polymer or other such like materials as are commonly used in the preparation of conductive or relatively conductive coatings in electrostarographic recording members and such paper base may also contain on at least one side thereof a so-called carrier barrier coating as is also well known in the art to prevent or reduce solvent absorption by the paper base of solvent in case the secondary toner is of liquid type to enable immediate reuse of the master without completely drying same if so desired for the generation of a subsequent copy. Generally however the duplicating master is dried with heat or warm air prior to reuse for the generation of a subsequent copy.

The second<ary toner may be of the dry or liquid type and such toner material should have very good electrostatic transfer properties that is to say upon transfer onto the copy paper it should leave no residue on the dielectric image deposits contained on the master surface or if some residue is left thereon it should not impair the*;dielectric properties or affect the subsequent charge acceptance thereof which is particularly

import-ant in those instances where such secondary toner material contains electrically conductive pigments such as carbon black and the like. The composition of the secondary toner material should be of the kind which allows for the secondary toner deposits upon transfer onto the copy paper to be affixed thereto by pressure, heat, warm air, solvent evaporation or other preferred methods.

The conductive coated paper for the duplicating master ca be of inexpensive type however it should be so selected with regards its thickness and bulk as well as solvent resistance that it can withstand, mechanical fatigue and recycling during the process of duplication for the required run length.

The copy paper type is usually determined by economic considerations and MG (machine glazed) paper and other similar cheap grades of paper have be-en found suitable.

It has been stated in the foregoing that after transfer of dielectric primary toner deposits from the dielectric paper plotter output onto the conductive coated paper it is important that virtually no residue remains on the dielectric paper. This is necessary to permit reuse of the expensive dielectric paper in that we have found that the dielectric paper can be reused many times in the plotter provided its dielectric properties are not affected or not substantially affected by the formation thereon and subsequent transfer therefrom of primary toner deposits. In those instances where after transfer some residue of primary ^' toner remains on the dielectric paper surface, upon reuse of such dielectric paper the slight primary toner residue

remaining on its surface does not affect significantly the electrostatic pattern formed thereon by the signal addressed styli because such residue is itself dielectric and accordingly may only slightly affect the level of charges formed by said styli and correspondingly it may affect only slightly the quantity of primary toner material attracted thereto upon retoning, however when the primary deposits formed during retoning are transrerred onto the conductive coating on the paper base master we have found that even very slight traces of such residue remaining from the preceding toning step on the dielectric paper surface will also transfer onto the conductive coating and produce an ob ectionable "ghost" image corres¬ ponding to the preceding pattern on the dielectric paper which during the process of duplication will attract secondary toner material and thus will be reproduced on the copies generated from such master. In order to pre-ven the transfer of such slight primary toner .residue from the dielectric paper we found it necessary to affix it thereto prior to reuse of such dielectric paper by applying heat or warm air to at least one side thereof.

When the electrostatic field is applied to transfer the primary toner deposits from the dielectric paper onto the conductive coating on the paper base master such field induces on the dielectric paper surface an overall electrostatic charge of a greater or lesser magnitude, depending on the configuration and materials employed, and such charge remains for some time on-the dielectric paper surface after the transfer step and after the conductive coated paper base master has been separated therefrom. Prior to reusing such dielectric paper in the plotter it is necessary to neutralize such overall charge thereon otherwise such charge will attract

primary toner to the dielectric paper surface causing an overall background stain or fog thereon and consequently also on the master and the copies generated therefrom. Such overall charge may be neutralized for instance by subjecting the dielectric paper after the transfer step to an overall AC corona discharge or other static eliminator means. Surprisingly we have found that if during the step of affixing after transfer slight residue of primary toner onto the dielectric paper as disclosed in the foregoing the heat or warm air is applied to the reverse side of such dielectric paper that is to the side opposite to that containing the dielectric coating such heat or warm air will also neutralize the residual overall electrostatic charge whereas if such heat or warm air is applied to the front surface that is to the dielectric coating on such paper no charge neutralization or no complete charge neutral-' ization occurs.

In those instances where only a few markers or copies are required and thus it may not be economical to produce a master on conductive coated paper, we have found that the primary image deposit can be advantageously transferred directly from the dielectric paper onto the copy paper to generate a marker and the primary image deposit can be affixed to the copy paper by heat or warm air while the dielectric paper can be reused as disclosed in the foregoing.

We have also found surprisingly that if the di¬ electric primary toner deposit is transferred from the dielectric paper directly onto the copy paper such as machine glazed or other such like cheap paper such copy paper can itself be used as an electrostatic duplicating

master for the generation of further copies or markers. The image quality of the copies or markers obtainable from such copy paper base master depends mainly on the conductivity of such copy paper which in absence of 5 any special conductive coating depends on its moisture content, the nature of chemicals contained therein and ■*, the nature of the paper base itself. If the moisture content is low, the resistivity of the paper may be sufficiently high to accept electrostatic charges during 10 the process of duplication not only on the dielectric primary image deposits contained thereon but also in the non-image areas and this results in attraction of the secondary toner thereto with consequent fog or stain formation of greater or lesser density on the copies or l* ⁵ markers generated therefrom. In those instances however where the moisture content of the copy paper -is relatively high or its conductivity per se is relatively high, good quality and virtually fog-free copies or markers can be generated. In those instances where the secondary toner ⁰ is of the liquid type, it is preferable to dry the master by means of heat or warm air after transfer therefrom and - prior to reuse for the generation of a subsequent copy particularly where the paper base of the master .comprises cheap grade solvent absorbent paper. Such drying or 5 solvent evaporating has been found to be of advantage in reducing the fog level on the subsequent copy or marker generated from such master in that residual solvent in the master base paper increases its resistivity and thus allows the background areas to accept electrostatic 0 charges and to attract secondary toner in background areas. The number of copies or markers which can be generated from such copy paper base master depends mainly on its thickness and bulk which determine to what extent it can withstand mechanical fatigue and recycling during

the process of duplication.

It will be realised that in those instances where only a few copies or ^' markers are required and where such copies are generated by direct transfer from the dielectric paper plotter output onto copy paper as disclosed in the foregoing, the toner used for the formation of image deposits on the dielectric paper need not be of the dielectric type and any suitable transferable toner can be used to produce visible images on the copies or markers. It should be noted however that the toner must be so selected that the residue remaining after transfer on the dielectric pape. does not affect its dielectric properties and thereby impair its reusability as may be the case for instance if such toner contains carbon black or other such li!<e conductive pigments or materials.

DESCRIPTION OF THE DRAWINGS

In order that the invention may be more fully understood, reference will now be made to the drawings in which

FIG. 1 illustrates a preferred method for the production of a plotter master by transfer of primary toner deposits from the surface of a dielectric record¬ ing member to a receptor surface, such as a conductive paper surface which forms the receiving member, whereas FIG. 2 illustrates the use of such master to produce copies on a plain low cost paper web, the thus produced copies being markers as herein defined.

Referring now to FIG. 1 in detail, dielectric recording member 1, in web form, is fed from feed reel 2, -the dielectric coated side of recording member 1

being on the lower side thereof, to contact recording nibs 3. Contact of the dielectric surface of dielectric recording member 1 with recording nibs 3 is maintained by pressure applied by grounded backing member 4 which contacts the rear relatively conductive surface of dielectric recording member 1. The electrostatic latent image impressed on the dielectric surface of dielectric recording member 1 is toned by the application of liquid dispersed toner from toner fountain 5, forming a first developer station, excess toner being returned to toner tank 6. Toned dielectric recording member 1 then passes over guide roller 7, which may advantageously be the primary drive roller, to pass face up over delivery tray 8. The previous description refers to known equipment such as for instance a Versatec plotter.

To effect transfer of the primary toner deposit from the dielectric recording member 1 to a receiving member such as a conductive paper web, toned dielectric recording member 1 passes from delivery tray 8 over guide roller 9 and enters the nip between transfer roller pair 10 and 11 which form a first transfer station- Simultaneously copy paper 12 is fed from feed roller 13 to pass through the nip between transfer roller pair 10 and 11 in contact with the toned dielectric surface of dielectric recording member 1. A directional electro¬ static field applied in know -manner between transfer roller pair 10 and 11 causes transfer of the toned image deposit from the surface of dielectric recording member 1 to receiving member 12. Dielectric recording member 1 then passes over guide roller 14 and fuser roller 15 to take-up reel 16. Receiving member 12 passes around fuser roller 17 to take-up reel 18. Receiving member 12 after transfer of the dielectric image thereto and fusing of same thereon

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constitutes a master from which markers can be produced.

FIG. 2 illustrates the process steps involved in the production of markers from dielectric masters prepared for instance as described in relation to

FIG. 1. The dielectric master 12 of FIG. 1 is fed from feed reel 16 over a series of guide rollers 22 to charging station comprising semi-conductive charging roller 23 which contacts the image bearing surface of dielectric master 20 and grounded backing roller 24 which contacts the back surface of dielectric master 12. A voltage of 100-2000 volts is applied to semi- conductive roller 23, which preferably has a conductive central spindle, to impress an electrostatic charge on the dielectric image deposit on the surface of dielectric master 12. Such charge may be positive or negative as desired, depending on the polarity of the secondary toner- The toning unit σomprisies guide rollers 25 and 26, toner tank 27, toner applicator roller 28 and developing plate 29. Toner contained in tank 27 which forms a second developer station, is lifted by toner applicator roller 28 which rotates in the direction shown -to flow across developing plate 29 , which is positioned in relation to guide rollers 25 and 26 to cause the surface of dielectric master 12 to contact the toner on developing plate 29. Solvent limiting roller 30 rotating in the direction shown and spaced apart from the dielectric master surface 12 a distance generally within the range 1-20 mils, may be used if desired to restrict the amount of dispersant liquid from the toner which is carried out bv the master.

The toned dielectric master 12 next enters the nip between a pair of trans fer rollers 31 and 32 , which form a second transfer station , at which position it contacts copy web 33 . Copy web 33 is contained initially on feed reel 34 , from which it passes over guide rollers 35 and 36 to enter the nip between transfer rollers 31 and 32. A directional electrostatic field is applied in known manner between trans fer rollers 31 and 32 to trans fer copy toner contained on the image areas of dielectric master 12 to copy web 33 . Transfer vo ltage is of the order 100-2000 volts of a polarity dependent on the polarity of the copy toner . Dielectric master 12 is finally re-reeled on take-up reel 37 whereas copy web 33 passes over guide roller 38 , which may be heated if desired to fuse the toner deposit contained on copy web 33 , and finally is re- reeled on take-up reel 18 .

Each of the transfer rollers 10 and 11 of FIG . 1 and 31 and 32 of FIG . 2 is preferably constructed by cast coating of soft polyurethane elastomer coating over a conductive metal spindle . The polymethane should preferably be of Duro eter har-dness within the range 18-30 Shore _: ^* A. Such elas tomeric coatings have been found to be of sufficient resilience to compensate for minor surface irregularities and to be of such resist¬ ivity that they limit the trans fer current flow to a safe level , such as 20-50 microamps /meter of length at an applied DC voltage of 500 volts . The elastomer coating is normally 3-5 millimeters in thickness .

In the drawings transfer field s upply units are designated T while charging fields are produced by units des ignated Cl and C2 , the unit Cl being a

is .

pattern-determining unit . Fusing stations are design¬ ated by Fl .

The dielectric master 12 can be wound from the take-up reel 18 to a separate supply reel and then to a further take-up reel instead of transferring the reels and master as illustrated in the drawinσs .

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Examples

The following Examples will serve to further illustrate the invention.

Example 1

The primary transferrable dielectric liquid toner was prepared as follows:- _.

Ketone resin, cyclohexanone formaldehyde, type 100 grams

Graphthol Red 1630-1 pigment 20 grams

FOA2 50 grams Zirconium Octoate (6% metal) 5 grams

Isoparaffinic hydrocarbon 400 grams were ball milled for 96 hours to form the toner concentrate. The primary liquid toner was made up by dispersing 20 to 50 grams of the above concentrate in 1000 grams of isoparaffinic hydrocarbon.

In the above formulation the Graphthol Red 1630-1 pigment is made by Sandoz and the FOA2 is a fuel additive made by DuPont.

A secondary transferrable black liquid toner was prepared as follows :-

Microlith Black CT 50 grams

Microlith Blue 4GT 25 grams

Pentalyn H 15 grams

Paraffin Wax, melting point 60°C, 20 grams Zirconium Octoate (6% metal) 5 grams

Isoparaffinic hydrocarbon 400 grams were ball milled for 96 hours to form the toner concentrate. The secondary liquid toner was made up by dispersing 10 to 20 grams of the abov ^' concentrate i 1000 grams of isoparaffinic hydrocarbon.

In the above formulation the Microlith Black CT and Microlith Blue 4GT are made by Ciba-Geigy and the Pentalyn H is a pentaerythritol ester of rosin made by Hercules Inc.

A commercially available dielectric paper with a thickness of 0.003 inch having a surface resistivity of 7x10 ohms/cm on its dielectric coated side was fad at the speed of 0.6 inches per second through a plotter having signal addressed styli with a writing potential of 400 volts negative which formed on the dielectric paper latent electrostatic images of about 250 volts negative. The dielectric paper surface was then con¬ tacted with the above disclosed primary liquid toner to form primary dielectric toner deposits thereon. Immed¬ iately after toning, that is while the image bearing di¬ electric paper surface was still wet, the dielectric paper was contacted with the conductive coated side of the paper base for the master and'the sandwich was passed through a pair of rollers to effect electrostatic transfer of the primary dielectric toner deposits from the di¬ electric paper onto the conductive coating of the paper base master. The conductive coated paper was 0.003 inch thick, the surface resistivity of the conductive coated

*"" O side was less than 10° ohms/c . The roller located behind the dielectric paper was of metal and keptat ground potential whereas the roller located behind the conductive coated paper comprised a metal cylinder having a- se conductive ^" rubber coating thereon and to effect electro- static transfer a potential of 700 to 1000 volts negative in relation to ground was applied to said metal cylinder. A very slight residue remained after transfer of the di¬ electric paper.

After transfer the dielectric paper was passed over a heated roller in such.'manner that the reverse side, that is the side opposite to the dielectric coated side, contacted the roller surface which was kept at a temperature of about 120°c whereby the slight primary

toner residue on the dielectric paper became affixed thereto and the overall electrostatic charge of about 20 volts induced thereon during the step of transfer has been completely neutralized.

The dielectric paper was reused 10 times where each reuse comprised the steps of feeding through the plotter, toning, transferring and heating, all carried out at the speed of 0.6 inches per second, as above disclosed. All 10 masters produced by reusing the di- electric paper were identical as far as master and copy image quality are concerned to the first master produced before reuse and to the copies generated therefrom. No "Ghost" images of preceding patterns nor background fog were evident.

The primary dielectric toner deposits transferred onto the conductive coating of the paper base master were fused thereto by passing at the speed of 0.6 inch per second the master over a heated roller in such manner that its reverse side contacted the roller surface which was kept at a temperature of about 120°C-

Copies were then generated from the thus prepared master at the speed of 45 feet per minute in the follow¬ ing manner. The master was passed over a metal roller held at ground potential and a corona generator held at 8 KV negative potential was positioned above such roller facing the conductive coated side of the.master whereby the dielectric primary image deposits contained thereon became electrostatically charged to a potential of about 200 volts negative. The secondary black toner as disclosed in the foregoing was then applied to the master surface to form secondary toner deposits on the

primary image deposits. The toned master was then contacted with Q.0024 inch thick machine glazed copy paper and the sandwich was passed through a pair of rollers to effect electrostatic transfer of the second- ary toner deposits from the master onto the copy paper.

The roller located behind the master was of metal and kept at ground potential whereas the roller located behind the copy paper comprised a metal cylinder having a semi-con¬ ductive rubber coating thereon and having a potential of about 500 volts negative applied to said metallic cylinder.

After transfer the copy paper was separated from the master. Warm .air was applied* to the copy paper to dry it and to affix the secondary toner deposits. The master was dried by passing it over a heated roller having a surface temperature of about 80-100°C.

The dry master was then reused to generate further copies in the same manner as above described. In excess of 100 copies were generated from the master and all copies showed good image quality.

Example 2

The primary dielectric toner deposit formed on the dielectric paper as disclosed in Example 1 was electro¬ statically transferred onto machine glazed copy paper, 0.0024 inch thick. To effect transfer a potential "of 1200 volts negative was applied to the metal cylinder.

The primary toner deposit transferred onto the copy paper was affixed -thereto by the application of warm air.

The affixed primary toner deposits formed a visible image of reddish colour on the copy paper. This produced a marker.

The dielectric paper was reused as disclosed in Example 1. j

Example 3

The dielectric paper was fed through the plotter ■and toned as disclosed in Example 1 except that the di¬ electric paper was toned with the secondary black toner of Example 1.

The black toner deposit thus formed on the di¬ electric paper was electrostatically transferred onto machine glazed copy paper, 0.0024 inch thick . To effect transfer of potential of 500 volts negative was applied to the metal cylinder.

The black toner deposit transferred onto the copy paper was affixed thereto by the application of warm air. This produced a marker.

The dielectric paper was reused .

Example 4

The primary toner deposit trans ferred onto the machine glazed 0 . 0024 inch thick copy paper of Example 2 was fused thereto by passing at the speed of 0 . 6 inch per second the copy paper over a heated roller in such manner that its reverse side contacted the roller surface which was kept at a temperature of about 120°c . This produced a duplicating mas ter on copy paper base .

The surface resistivity of the copy paper was about

The thus produced duplicating master was used in the electrostatic duplication process as disclosed in Example 1 except that to. effect transfer of the second¬ ary toner deposits from the master onto the copy paper a potential of about 600 volts negative was applied to the metallic cylinder.

In excess of 20 copies or markers of acceptable image quality were generated from the copy paper base master.

After each copy generation and preparatory to each reuse the master was dried as disclosed in Example 1.

There have been described new methods of producing inexpensive electrostatic duplicating masters from a reusable expensive dielectric paper and a method of generating copies from such master and from such di¬ electric paper. The methods and materials specifically disclosed herein are intended to only illustrate the present invention without limiting its scope in any way.