CA1295652C - Method of high resolution electrostatic transfer of a high density image to a nonporous and nonabsorbent conductive substrate - Google Patents

Abstract

METHOD OF HIGH RESOLUTION
ELECTROSTATIC TRANSFER OF A HIGH
DENSITY IMAGE TO A NONPOROUS AND
NONABSORBENT CONDUCTIVE SUBSTRATE

Abstract of the Invention A method of fabricating a toned pattern on an isolated nonabsorbent receiving surface is disclosed wherein a charged electrostatic latent image area is established on an electrostatically imageable surface, and is transferred to the receiving surface across a gap of between about 1 mil and about 20 mils filled with a liquid formed at least partially of a nonpolar insulating solvent in which are suspended charged toner particles.

Description

Background of the Invention This invention relates generally to a method of high resolution electrostatic transfer of a high density image to a nonporous, nonabsorbent receiving surface. More specifically, it pertains to the method of transfer and the method of creating a latent image on an electrostatically imageable surface that may be repeatedly used to produce high resolution and high density images on receiving surfaces such as printed circuit boards. Density as used herein with respect to nonconductive images refers to the number of individual images per unit surface area.
The production of conductive wiring patterns on an insulating substrate employing a dry film resist lS by use of photoimaging and other techniques to produce a printed circuit board typically employs a five step process. Regardless of whether a tenting method or a hole-plugging method is employed, the five distinct 5tep8 have included 1aminating or coating a ~;

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~29~ 2 photosensitive dry film resist on at least one conductive surface of an insulating substrate, forming a wiring pattern on the dry film resist by use of artwork or a phototool and exposing the dry film resist to actinic radiation through the transparent areas of the phototool, developing the circuit board by removing the unexposed portions of the negative working dry film resist, etching the conductive substrate from the circuit board in all non-imaged areas no-t beneath the desired conductive wiring pattern which is still covered with the dry film resist~ and finally stripping or removing the dry film resist covering the desired wiring pattern from the non-etched portions of the conductive substrate. This five step process must be repeated for ~15 each circuit board produced.
During the exposure step in the standard dry film process, sufficient radiation exposure levels and exposure times are desired to produce straight sidewalls in the~dry film resist that are the result of a pattern ~2~0;~ f the cross-linking of polymers in the dry film. These straight sidewalls should be normal to the conductor ;surface~. Practically, however, in the standard negative working dry film photoresist print and etch process either~ under~expos`ure occurs, producing a sidewall edge ~25~ that undercuts the desired resist pattern, or overexposure~occurs, producing a sidewall edge in the dry~film photoresist that increases the width of the dry film photoresist at the base of the resist and the surface of the condu~tor causing a foot. Both of these condi~tions vary the width of the ultimate conductive pattern from that which is desired, beyond the planned and engineered tolerance or overage of the line widths in the conductor surface.
The~development step during this process deally should develop away the unexposed negative ~,-: :

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working dry film resist to produce an edge in the dry film resist on the conductor surface that is equal in width to the pattern on the phototool and normal to the conductor surface. Practically, however, either underdevelopment or overdevelopment of the dry film photoresist occurs. Underdevelopment produes a buildup of resist residue in the sidewall zone or developed channels that is sloped toward the adjacent sidewall resulting in smaller spaces between the adjacent lines than is desired. When overdevelopment occurs the unexposed film resist edge is undercut, producing larger than desired spacing between adjacent lines.
Additionally, there is the potential or some rounding at the top of the resist surace sidewall edges.
This inability to accurately reproduce the phototool in the dry film resist affects the fine line resolution and reproduction characteristics of the reproduced circuit pattern. As circuit boards have become more complex and stacking of multiple boards has become prevalent, the need for higher density, finer r~esolytion circult patterns has evolved. Resolution has ~been viewed as the ability to reliably produce the smallest line and space between adjacent lines that can be reliably~carried through the aforementioned five step 25~ ~ processing. The thinness or smallness of the lines that can~survive development and the narrowness of the gap or space between the adjacent lines in the circuit pattern :: :
have led to ine line resolution and reproduction standards~in the~printed circuit board industry calling for about 3.1 mil line and space dimensions or the development of about 6.3 line pairs per millimeter.
These~standards are used to define the desired density of the c~ircuit board.
; The attempt to apply the principles of xerography to transfer developed electrostatic latent 1mages from a photoconductor's electrostatically imaged ::: ~

surface to a receiver surface with high resolution and high density images has encountered difficulty. The major source of this difficulty stems from the fact that circuit boards consist of a nonporous or nonabsorbent substrate, such as metal, like copper, or a plastic, like the polyester film sold under the tradename of MYLAR. This nonporous and nonabsorbent receiving surface causes the image being transferred, especially when attempted with a liquid toner, to become distorted or '~squished~l>
Xerographic techniques solved the problem of transferring an image to absorbent receiving surfaces, such as paper, by transferring the images formed by toner particles across a gap. The gap has either been an air or a combination air-liquid gap. Attempts to translate this gap transfer technology to nonporous substrates, however, resulted in image "squish" and the realization that the gap space and the voltage must be ~ carefully controlled to produce an acceptable trans~ferred toner image with the proper resolution and density. If the voltage and the gap space or distance between the photoconductor or the electrostatically -~ imageable surface and the ~of}~e receiving surface are not carefully controlled, electrical arcing across the gap will occur. This can cause pin-holes in the transferred toner image by permanently damaging the electrostatically imageable surface. This is especially significant in print and etch applications used to manufacture printed circuit boards.
Also, it has been found with nonporous receiving substrates that both the photoconductor or electrostatically imageable surface and the receiving surace must be stationary at the point of transfer of the toner image to achieve a transferred image of high resolution.

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An additional problem is presented in transferring the developed latent image electrostatically to a nonabsorbent substrate, such as copper. The metal or copper surface forming the receiving surface, as well as the electrostatically imageable surface, is uneven so that the spacing between the electrostatically imageable surface and the receiving surface mus~ be sufficient to avoid contact between the uneven surfaces of the photoconductor and the receiving surface.
These problems are solved in the process of the present invention by providing a method of making a transfer of a developed electrostatic latent image from an electrostatically imageable surface across a liquid-filled gap to a nonabsorbent receiving surface associated with conductive means to produce multiple printed circuit boards ~; with a desired conductive pattern from a single persistent ;~ ~ latent image. The electrostatically imageable surface may be elther a photoconductor or a permanent master.

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`~ ' i6~2 Summary of the Invention It is an object of the present inYention to provide a method for achieving non-contact high resolution electrostatic transfer of a developed high density electrostatic latent image directly to a nonabsorbent substrate associated with conductive means.
It is another object of the present invention to obtain the high density electrostatic latent image through the use of a dry film resist that serves a~ a permanent and reuseable master.
- It is another object o~ the present invention that the method of slectrostatic transfer can be ~` utilized with a photoconductor or a permanent master as the electrostatically imageable surface.
It is another object of the present invention to transfer the developed high density image from the electrostatically imageable surface acros~ a liquid-filled gap to a receiving surface so that the liquid serves as the tran-~fer medium.
It i~ still another obiect of the present invention to provide a method that permit~ the latent image and the trans~erred image to be capable of resol~ing about 3.1 mil line and space.
It is a feature of the present invention that the guality of the image density, the thickne~ or : ~ height of the toner particles forming the image and the thickness of the layer of liquid serving as th~ tran~fer mediu~ in the gap between the electrostatically imaged surface and the receiving surface are controlled by the spacinq of the gap and the voltaqe applied to create the electric fieLd between the : ~ electrosta~ically imageable surface and the conductive means associated with the receiving surface.

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I t is another feature of the pre~ent invention that the conductive backing material or the sub~trate supporting the ~lectrostatically imageable surface i~
electrically grounded and the conductive means associated with the receiving surface is electrically isolated from It is still another feature of the present invention that ~he developed laten ma~e i~ tran~ferred di~ectly from the elec~ro~tatically ima~eable ~urface to the nonabsorbent receiving surface through a nonconductive dielectric in~ulating fluid by the migration of the individual toner par ticles compr ising the toned image through the liquid to the conductive receiving surface.
It is yet another feature o th~ pre~erl~
inven~cion that the distance or spa~i~g of the gap between the electros~atically imageable ~urfae~ and the receiving surface is between about 1 mil and about 20 mils and the di~tance i~ mai~tained by the use between the two surfaces o~ ~pacer mean~ which ar~
electr ically isolated from ground .
It i9 still another feature of the pre~Rnt invention ~hat conven~ional photoconauc~ors or per2~anellt ma~ter may be u~ed a~ th~ electro~tatically imageable ur~ac~ ~o produce large quantltl~ of printed csircuit board~ by eliminating the need for a dry film or llquid 25 ~ photoc~ t for each circuit board copy.
It is yet another feature o~ the pre~ent invention that the tran~fer of the electro!Ytatic latent image to the receivlng surface is accomplished by directly applying D.C. voltage to the conductive means associated with . ~ the receiving surface, rather than corona charging.

:: : It is a further feature of the pre3ent ~ invention witb a photocondu~tor used a~ the - electrostatically imageable surface that an additional 3 5 expo~u~e is required to produce each additional latent image.

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~5~52 It is an advantage of the method of the present invention that high resolution .transfer of the toner particles forming the developed latent image is obtained on the receiving surface without image distortion.

It is another advantage of the present invention that there is no damage or abrasion to the electrostatically imageable surface during the process so that the surface may be continually reused.
It is still another advantage of the present invention that high resolution transfer is achieved because there is no contact between the ~eveloped toner particles on the electrostatically imageable surface and " the receiving surface.
It is yet another advantage of the present invention that the power requirements can b~ reduced to accomplish the electrostatic transfer because of the use of direct applied voltage, rather than corona charging which causes air ionization.
;~ 20 It is still another advantage o~ the present invention that a faster and lower cost method of making ; printed circuit boards is achieved because o~ the j~ elimination of the repeated exposure and development steps required of dry film or liquid photoresist3 for each circuit board.
These and other objects, ~eatures and a;dvantages are obtained by the use of the method of : fabr icating a toned pattern on an isolated nonabsorbent . surface by first establishing a developed :~ 30 electrostatic latent image on an el~ctrostatically :,:
imageable sur~ace, developing the latent image with charged toner particles, and then transferring charged : ~ toner particles across a liquid filled gap comprised at least pa~tially of a nonpolar insulating solvent to : .

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create an imaged area on a ~eR~#eb~we receiving surface while the gap is maintained between at least about 1 mil and about 20 mils at the point of transfer of the toner particles forming the image.

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~rief Descri~ion of_the Drawin~s - The objects, features and advantages of the invention will become apparent upon consideration of the following detailed disclosure of the invention, especially when it is taken in conjunction with the accompanying drawings wherein:
FIGURE 1 is a diagrammatic illustration o~ th~
prior art print and etch printed circuit board fabrication steps:
FIGURE 2a is a diagrammatic i.llustration of the process of the present inven~ion employing a perma~ent master that is reusable to produce multiple copies of a desired conductive wiring pattern on an in~ulating dielectric layer by the migration of charged toner particles from the master acro~s a liquid-filled gap to a conductive receiving surface;
FIGURE 2b is an enlarged diagrammatic illustration of the migration of the charged toner particles across a liquid filled gap to ~he conductive receiving surface of Fig. 2a.
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Detailed Desceiption of the Preferred Embodiment FIGU~E 1 shows the standard five step process that has been previously employed in the production of printed circuit boards. Each one of the circuit boards produced has routinely required the application of a dry film to a conductive substrate, such a~ copper, that is laminated to a nonconductive substrate, such a fiberglass epoxy, with pressure and heat. A mask is then applied over the dry film to permit selective exposure from a light source or other source of actinic radiation to produce the desired pattern. Development takes place by removing the uncros~-linked dry ~ilm, leaving only cross-linked dry film with the desired pattern. Etching with an acid etchant removes th~
conduc~ive copper substrate from between the areas of cross-linked dry film. Finally, stripping the dry film fro~ the remaining conductive copper substrate exposes the desired circuit pattern. Thi~ i~ commonly known as the print and etch process.
: 20 In the process of the present invention, however, a permanent master is produced with the use of ~\ a photosensitive material or coating, such as a dry film or liquid photoresist over a conduc~ive substrate.
Thereafter, dry film or liquid photore3ist iq not ~ 25 employed to produce the desired conductive wiring :~ patterns from the permane~t master on the product circuit boards or other receiving surfaces.
The permanent master ls usad as an electro-statically imageable surface as shown in FIGURE 2. A
conductive backing has a photo~ensitive material, such as a dry fllm or liquid photoresist, applied to it on at - least one side. This photosensitLve material undergoes a change in resistivity upon exposure to actinic radiation because of the cross-linking of the polymers in the mater ial. A persistent image is formed on the 3~

photosensitive material by actinicly radiating through a mask or by "writing" the desired pattern with a digital laser pen. ~ither method produces electro~tatic contrasts or differences in the resistivity between imaged and non-imaged areas on the photosensi~ive material. The electrostatically imageable surface is isolated ~rom ground and charged with a corona charging device to produce the charged latent image.
The electrostatically imageable surface is then developed by the application, through surface adsorption, of a liquid comprised at least partially of a nonpolar insulating solven that serves a~ a liquid carrier for toner particles that are charged oppo~itely ~` to the charge of the electrostatically imag~able surface. Thi~ application can be accomplished by flooding, dipping or spraying the electrostatically imageable surface. The charged toner particle~ are directed to the latent image area of the electrostaticalLy i~ageable surface to form or develop the latent image.
Thus developed, the image i5 formed on the electro~tatically imageable surfac~ according to the .~ persistent latent image's pattern on the permanent master. The developed image thu is ready for transfer to an electrically isolated receiving surface to produce a circ~it board with the de~ired conductive wiring pattern.
: The receiving surface is first coated with a liquid that comprises at lea~t part~ally a nonpolar insulating solvent. The ~olvent is the same as or an equivalent to that which iS appLied to the elec:trostatically imageable surace and m~y be applied : by sponge, squeegee, rubber roller or other means capable of applying a thin continuou~ film. The solvent should preferably have a high resistivity and a low viscosity to permit the charged toner particles to 6~2 ~igrate or flow through the solvent from the charged electrostatic latent image area on the electrostatically imageable surface to the receiving surface.
, The solvents are generally mixtures o~ Cg-Cll or Cg-Cl2 branched aliph~tic hydrocarbons ~old und~r the tradename Isopar G and Isopar H, r~spectively, manufactured by the Exxon Corporation, or equivalent~
thereof. The electrical resistivity i~ preferably on the order of at least about 109 ohm-centimeter~ and the dielectric constant preferably is le~ th~n about 3 1/2. The use of nonpolar insulating olvent~ with these characteristics help~ to ensure that the pattern of charged toner particle3 is not dis~ipated.
After a D.C. voltage optimally betw~en about 200 to about 1200 volt~ i~ applied to the : receiving surface to establish an ele~tric field b~tween the electrostatically imageable sur~ac~ and th~
receiving surface, the surfaces are moved close enough together to create a completely liquid transfer medium by the contact of the two layers of ~: nonpolar in~ulating ~olvent. The fir t liquid surface of the first layer o~ nonpolar in~ulating ~olvent on the `~ elect~oqtatically imageable surface and the second ligui~ 3ur~ace of the second layer of nonpolar in~ulating solvent on the conductive receiver surface join ::~ogether to fill the gap between th~ two surface~, ~ The voltage necessary to e~tablish the electric fieLd ;~ : between the electro~tatically imageable ~urfac~ and the receiving surface operably can be between 30~ about 200 to about 3500 volt~, but i~ preferably between ~: about 200 and about 1500 volts and optimally i3 a~
stated aboYe. The ability to transfer a high re~olution image is a function of the combined actor~ o~ ths toner, the liquid carrier, the gap spacing and 'che :

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~ ' voltage applied. Generally, a greater gap spacing requires a higher voltage to effect a high quality, high resolution image ~ransfer.
~ uniform spacing across this gap i~ maintained by the use of spacer strips or gap spacers, seen in FIGURE 2, which are electrically isolated from ground.
The developed image from the electrostatically imageable surface is transferred across the gap through the liquid medium to the receiving surface to form an imaged area in a pattern similar to that of the phototool where the transferred toner particle~ are present and non-imaged areas where the particles are absent.
The transfer of the developed image across the liquid-filled gap takes place at the poin o~ transfer by maintaining a first plane taken through the electrostatically imageable surface parallel to a second plane taken through the receiving surface.
The electro~tatically ima~eable surface and th~
receiving surface at the point of transfer should have no relative motion occuring betw~en them, although the point of transfer could be a stationary or rolling point of transfer. A dr~m or web, or a ~` stationa~y flat sur~ace could be employed f~r the electro~tatically ima~eable surface, transferring the developed image acros~ the gap to a flat and stationary, or a moving receiving surface. The moving receiving surface could be a rolling drum of a web or other appropriate means. The electrostatically imageable and ; receiving surfaces must be held in place at the point of ; ~ transfer, such as by a vacuum, or alternately could be accomplished by magnetically or electrostatically holding the surfaces in place across the gap.
3s This gap between the electrostatically ~; imageable surface and the receiving surface is preferably maintained between at least about 3 mils d~

(~003 inch) and about 10 mils (.OLO inch) by the use of spacer strips of the desired thickness, although high quality images have been transferred across gaps as large as about 20 mils (.02 inch). By maintaining the gap greater than about 3 mils, the inconsistencies or irregularities in the two surfaces are separated sufficiently to prevent any contact from occurring between the two surfaces and any possible abra~ion or scratching from occurring to the surface of the master or electrostatically imageable sur~ace.
The spacer strips or gap spacers are selected from either conductive materials, ~uch a~ metal, or nonconductive materials, such as polyester film sold under the tradename MYLAR, or cellophane. The strip~
must be electrically isolated from ground and be o uniform thickness. The uniform thickne~ insures that a uniform gap spacing i5 obtained between the electrostatically imageable surface and the receiving surface9 The spacer strips preferably should be plàced outside o~ the image area.
By applying the first and second layers of nonpola~ insulating solvent in sufficient thickness to ' the e.lectrostatically imageable surface and the . receiving surface to flll the gap therebe ween, the first liquid surface and tne second liquid surfac~ of the first and second layer3 of the nonpolar insulating solvent join together to form a continuous liquid transfer medium at the point of transfer of the charged toner particles between l:he electrostatically imageable surfac~ and the receiving surface. By traveling through a continuous sea of liquid transfer medium, there are no Yurface ten~ion forces which the charged toner particles must ~ 2~ ~ ~5 overcome that could hinder their migration from the electrostatically imageable surface to the conductive receiving surface. The charged toner particle~ are directed through the liquid transfer medium formed by the joining of the two layers o~ nonpolar insulating solvent at this point o~ trans~er by the electric field that is applied at the point of transfer~
As is diagrammatically illustrated in FIGURES 2a and 2b, the charged toner particles with their predetermined `
charge, migrate from the oppositely charged cross-linked imaged area with the photosensitive material on the electrostatically imagea~le surface to the receiving surface as individual or grouped particles.
As shown, the receiving surface is a conductive layer of copper laminated on to an insulating dielectric layer, such as a fiberglass epoxy. The applied electric transfer field causes the toner particles to migrate through the liquid transfer medium of the nonpolar insulating solvent and attach to the conduc~ive receiving surface to create imaged areas where the toner particles are present and non-imaged areas where they are absent.
Since the photosen~itive material, such aQ a dry fil~ or liquid photoresistJ on the electrostatically imageable surface acts as a master electrostatic image plate, and the resistivity differenc~ between the imaged and non-imaged areas on the electrostatically imageable surface remain3 relatively constant in mo~t in~tance~
for sustained per iods of time dependent upon the photoresist used, multiple copies c~n be made by the electrostatic transfer method. To repeat the proc:edure, excess nonpolar insulating solvant and excess toner particles on the electrostatically imageable surface should be removed, such as by r ins ing, followed by a physical wiping or squeeging. Any residual electric charge o~ the electrostatlcally imageable ar~a should be j~,~ ..

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discharged, such as by charging the photosensitive material ls surface with an alter~atirlg current corona.
The desired electrostatic latent image pattern remains in the photosensitive material by using the S ma~erial~s ability to retain differences in resis~ivity for relatively long per iods of time after havin~ been exposed to actinic radiation to form cross-linked imaged areas of increased resistivity and non-imaged areas unexposed to the actinic radiation which remain the less resistive or background areas. The photosensitive material, such as a dry film resist~ typically i3 formed of polymers which becoma cross-linked to form the imaged areas of greater electrical resistivity ~hat may be an order of magnitude more dielectric than the background or une~posed areas. These imaged areas are the only areas of increased resistivity that hold a high voltage charge when charged by a V.C. charge corona, if the conductive backing is electrically grounded. The non-imaged or background areas with the les~er electrical re~istivity very rapidly release or leak the charge through the grounded conductive backing. The charged toner particles suspended in the nonpolar insulating solvent are oppositely charged to these latent imaged area~ so that the charged toner particles are attracted to them. This then permit~ the transfer of these charged toner particles from the electrostatically imageable surface across the liquid gap to the receiving surface as previously described.
described.
Once the toner image i~ formed by the toner particles in the imaged area on a receiving surface, the particles are fused to the - receiving sur~ace by heating, as illustrated diagrammatically in F~GURE 2. The heat can be provided either by the use of an oven or directed warm air through an air slot so that the heat is supplied for a finite period of time sufficient to reach the temperature at which the binder or pol~mer orming the toner particles will solvate in the liquid which is entrained within the transferred image. The fusing, for example, can occur for about 15 to about 20 seconds at a temperature greater than about 100C and up to about 180C. `
Thereafter in the instance of copper circuit boards the non-imaged areas are etched to produce the desired conductive wiring pattern in the unetched conductive receiver surface which i~ overcoated with the toner particles. The etching step utilizes a solution that cannot remove the conductor material ~rom the areas of the conductiYe receiving sur~ace protected by the toner par icle~, but doe~ attack and remove the conductor material from the areas unprotected by the toner particles. The particula~ type of etchant employed depends, in part, on the conductor material being etched and the type of resist being used, 50 that both acid and very mild alkaline etchin~ solutions are possible for use. For example, when the conductlve receiving surface is copper, an etchant comprising acidic.cupric chloride i preferably used.
The final step in the electrostatic transfer .:
proce~s to form the copy is the stripping step. Dur~ng this step the toner particles are appropriately removed or stripped from the imaged area~, such a~ by rinsing with methylene chloride, acetone, a~ alkallne aqueous solution ox other suitable ~olution.
: In order to exemplify the re-qults achieved, the ~: ~ follow:ing examples are provided without any intent to limit the scope of the instant invention to the ~: ~ discussion therein. The example~ are intended to illustrate the manner in which a permanent ma~ter with a persistent conductive latent image on the ~ -6~;~

electrostatically imageable surface can be obtained and how the gap spacing and voltage levels can be varied to achieve successful electrostatic image transfer. The examples also illustrate, whether a photoconductor or a permanent master is used as the electrostatically imageable surface, how succe~sful electro~t~tic image transfer can be achieved without the need for the application of a dry film or liquid resist to each conductive receiving surface prior to the tran~fer of the developed latent image from the electrostatically imageable surface.

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A liquid toner was prepared for use by prepar ing the following raw mater ial~ in the amount~
shown in a high speed disperser:

% Raw Mater ial ~ ~
ISOPAR*EI 1248.6 solvent-carrLer UNIREZ*7059 439.2 alcohol insoluble ~UNION CAM~) maleic modified r os in e~ ter Allied AC 307.8 linear polyethylene : Polyethylene 6A
BAKELITE* 1584 .0 ethylene-DPD 6169 ethylacryla'ce (UNION CARBID~) copo1ymer 20~6 ~hock-: 15 cooled suspension in : I SOPAR H
phthalocyanine229~2 coloring agent -green pigment :: * *
Alkali Blu~ G 158.4 coloring agent -: 20 ~ ~ pigmen :
6~ These componentwere mixed a~ a ~peed of 8000 rpm for 10 minu~es while maintaining the temperature of : the mixtur~ between 160 an~ 220F
, 606 Gram~ of an amphipathic graft copolymer ~25; ~ Sy3te!D was prepared by mixing 1û4.3 gra~ o~ lauryl methacryl~e and 4~.7 g~am~ of m~thyl m~hacrylate, both ava~lable~ from Roh~a and ~aas, and 3.0 gram3 o~ azobi~
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obutonitrile:, av~ilabl~ from DuPont a~ V~z~*64.
Next loa.2: grams of an amphipathlc copolymer 30 :~ ~ ~ stabi~llzer: wa~ prepared according to the procedure described hereafter. In a 1 li~er reaction fla~k equipped with a ~tirrer, a thermometer and a r~flux condensor i~ placed 4ao gram~ of petroleum ether (b.p.
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90-120C) and the same is the heated at atmospheric pressure to a moderate rate of reflux. A solution is made of 194 grams lauryl methacrylate, 6.0 grams o glycidyl methacrylate and 3.0 grams of benzoyl peroxide paste (60 percent by wt. in dioctyl phthalate) and placed in a 250 ml. dropping funnel attached to the reflux condensor. The monomer mixture is allowed to drip into the refluxing solvent at such a rate that it requires 3 hours for the total amount to be added.
After refluxing 40 minutes at atmospheric pressure beyond the final addition of monomer, 0.5 grams of lauryl dimethyl amine is added and the refluxing is continued at atmospheric pressure for another hour.
Then 0.1 gram hydroquinone and 3.0 grams methacrylic asid are added and refluxing continued under a nitrogen ~blanket until about 52 percent esterification of the glycidyl groups is effected (about 16 hours). The resulting product is slightly viscous straw-colored ~liquid.
20 ~ 345.8 Grams of ISOPAR H from Exxon Corporation was added to the 108.2 grams of the amphipathic copolymer stabilizer and the aforementioned quantities of lauryl methacrylate, methyl methacrylate and azobis isobutnitrile to form the 606 grams of amphipathic graft ~25 ~ copolymer system. Polymerization was effected by heating this solution to about 158F under a nitrogen atmospher~e for about 4 to about 20 hours.
606 Grams of additional ISOPAR H was added to t~e above solution and mixing was continued for 10 ~3~0 ~ minutes at 8000 RPM while the temperature was maintained between about 160F and 180F.
~; Finally, 3578 grams of ISOPAR H was added, the mixer speed reduced to 1000-2000 RPM, and mixing :
continued for 30 minutes. During this last step, the temperatura of the mixture was maintained between ~ 120F and 140 F.

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Next a liquid toner concentrate was prepared b~
combining the following in ~ static attritor-type mill:

Maeer ial ~ Descr lption Predispersion Mix 1022.7 liquid toner predispersion Car nauba wax 5 8 . 3 wax polymer dispersion 83.3 amphipathic polym~r dispersion as prepared is~ Ex. XI
of Kos~l (U. S . Patent No. 3 ,900 ,412~
Neocryl S-1004 62.4 amphipathic polymer disper~ion available ~rom Polyvinyl Chemical Industries, Div. of Beatr ice 730 Main St.
Wilmington, MA 01887 ~SOPAR H ~94 .5 . solvent-carr ier The~e component~ were milled for three hours at 300 Rli?M and a temp~rature of about 75F to create a toner conc~trat~. The toner concentrat~ was futher diluted to about 1 to about 2 percent ~olids to create 2S the working solution for u~e in el~ctrostatic ~maging.
A cadmium ~ulfide photoconductor overcoated with a M~LAR poly~ r ~ilm layer (typical of the NP
proce~ type) wa~ corona charged and then light expo~ed to a circuit trac~ pattern ~om about 0.75 to ab~ut 2.70 micro~ou1e~/sqllare cerl~ime~er in a Canon*Model 1824 copi~r ~o create a charged la~ent image. The cha~ged latent image wa3 developed by appLying the liquid toner to ~he ov~rcoated cadmium sulf ide photoconductor tha~ i~
th~ elecJcro- sta~ically imageable ~ur~ac~. The electro~tatically imageable surface o~ this photoconductor i~ mounted o~er an inner aluminum ~ub~tral e drum. ~he drum was removed * Trade-mark B

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from the copier. A high voltage power source had its ground lead connected to the interior of the drum and its positive lead connected to the copper surface of the conductive receiving surface. Cellophane spacer strips or gap spacers were used between the drum and the conductive surface. The conduc~ive surface was coated with a liquid that included the nonpolar insulating solvent that was squeegeed onto the conductive surface.
The electrostatically imageable surface of the drum was coated during the development step. 1000 Volts D.C.
current was applied and the gap was set at 10 mils.
The cadmium sulfide drum was manually rolled across the spacer strips to create points of transfer of ; the latent image from the electrostatically imageable surface to the conductive receiving surface of copper.
The image transfer was successful with the image possessing excellent resolution and good density.

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Example 2 The cadmium sulfide photoconductor drum of Example 1 was cleaned and dried and reimaged as in Example I. The liquid transfer medium was applied to . the conductive receiving surface. 500 volts of D.C.
voltage was applied and the same gap space was set as in Example 1. The image transfer was successful, but the amount of the transferred toner particles forming the transferred imaye was less than the amount in Example 1 and was very light over the entire image area. There appeared to be insufficient voltage applied to transfer the majority of the toner particles over a 10 mil gap.

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Example 3 The same steps and liquid transfer medium as employed in Example 2 were repeated. The conductive receiving surface was wetted with the liquid transfer medium by applying to the conductive receiving surface with a squeegee. The spacer strips were set at 3 mils to achieve a uniform 3 mil separation between the two sur~aces and a voltage of 1000 volts was employed.
A clear high resolution image with good density was obtained but some void areas appeared in the image.
The image was uniform and distinct.

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Example 4 The same steps and liquid trans~er medium were employed as in Example 3, but the gap spacers were 3 mil thickness to establish the 3 mil gap between the electrostatically imageable surface and the conductive receiving surface. 200 Volts D~Co current was applied to establish the electric field. A very clear high resolution image was transferred from the electrostatically imageable surface to the conductive receiving surface, which exhibited good reflectance imaga density. The density of the pad areas and line traces, however, was somewhat less than that achieved in Example 3 because all of the toner particles apparently were not transerred.

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Example 5 ~he sama steps and liquid transfer medium were employed as used in Example ~, but the liquid was squeegeed on. The gap spacers were 1 mil thick to establish a 1 mil gap between the electrostatically imageable surface and the conductive receiving surface.
1000 Volts D.C. was applied to create the electric field. The transferred image had good image density, but there were many ho}low spots due to arcing. Some 10 ~ image distortion was present,~apparently due to the closeness of the two surfaces and the resultant "squishing" of the toner particles. The use of a system, such as a~vacuum hold-down system, which permits the receiving substrate to be held rigidly flat would have reduced the image distortion. Most of the transferred image was not distorted.

~: : :

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A 4 " x 5 " electr ically conductive substrate of copper mounted on a glass epoxy supporl: sub~trate known as FR 4, was selected a~ the conductive substrate for use in making the electrostatically imageable sur~ace of the permarlent master. The copper substrate wa~ checked for need of leaning or degreasing. If necessary, the subqtrate can be cleaned with methyl chlor ide, methylene chloride or trichloroethylene to promote good adhesion of the photoresist to tha cleaned.su~a~ during the ~ s~bsequent lamlnation step. In this particular instance .' cleaning wa~ not nece~ary. DuPont Riston 215 dry film photoresist was laminated to the substrate a~ the : photo~ensitive materi.~l. The lamination was :15 ac~omplished with the u~e of a We~tern Magnum Moa~l XRL-360 laminator made by Dynachem o~ T~stin, CA. The : lamination wa~ car~ied out a~ a roll te~peratu~e o~
: about:220~ and a ~peed of about ~ix feet per minute.
A~protectiv~ top layer of approxima~ely .OOl inch thick ~20 :polyethyl~ne terephthalat~, hereafter PET, film was ; eetained~:over the dry film photore~ist of the copper/Riston 215 laminate.
The laminat~ was expo~ed to actinic radiation :: through a negati~re~:phototool u~ing the Optic Beam*5050 25 : expo~ure unit manufactured by Optical Radiation Corpo~ation. The exposure was accomplished aft¢r the : laminate cooled to room temperature foLlowing ~he lamina~ing proce~ The expo~ure lev~l wa3 app~oximat~ly 250 mil~ijoules~or abou~ 60 ~e~ond~ The ~30~ phototool wa~ a Microcopy Test Targ~ T~10 resolution te~t chart:, wlth group~ of bar~ varylng from 1.0 oycle~
or line pair~ par ~ mater to 18 cy~les or l~n~ pairc p~r millimeter, sold by Photographic Science~ Inc.
,, ~ ~ * Trade-mar}c :: : :: :

:: ~
,-~2~i6~2 The exposed electrostatically imageable surface was then allowed to cool to room temperature for about 30 minutes, thereby permitting cross-linking in the dry film to complete. The protective layer of PET film was peeled away. The copper substrate was grounded and the electrostatically imageable surface was corona charged so that the imaged area received a positive charge.
After a short delay o~ about a second or more to allow background areas to discharge, the charged persistent-image was then electrophotographically developed with liquid toner of Example 1. Excess toner particles were rinsed from the developed permanent master with Isopar H
solvent carrier without allowing ~he toner to dry. The developed persistent image on the electrostatic master was then ready ~or transfer to a conductive receiving surface.
The electrostatic master thus formed was laid ~ ~ flat on a generally flat working surface. MYLAR~
; ~ ~ polyester spacer strips were placed along a pair of 20~ parallel and opposing edges of the master outside of the developed image area to a thickness of about 10 mils.
A flexible conductive receiving surface of 1/2 ounce copper foil laminated to a 1 mil thick Kapton~
; polyimlde insulating layer was wrapped around and 25~ secured~by lap taping the edges to a 1 1/2 inch diameter dr~um.~ The receiving surface was wet with a layer of Isopar H solvent carrier by immersing the cylinder.
Alternatively, the receiving surface could be coated by ~; pouring the li~uid thereover.
An electri~al potential of about 1000 volts was established to create~an electric field across an approximately 10 mil gap. The conductive receiving surface of copper foil was charged with positive polarity with respect to the electrically conductive copper substrate of the master for use with the negatively charged toner particles.

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The l l/2 inch diameter drum with the conductive receiving surface secured thereto was rolled over the spacer strips on the edges of the master. As the roller passed over the master at each discrete point of transfer the toner particles were ~ransferred from the master to the conductive receiving surface. The ; transferred image displayed excellent resolution up to about 3.6 line pairs per millimeter. It appeared as though 100% of the toner particles were transferred to the conductive receiving surface.
The conductive receiving surface was then exposed to a fan for up to about 30 seconds to dry the non-imaged areas that comprise the background areas.
The non-imaged areas should be dried while the imaged areas remain wet so the polymers in the toner particles ~;~ can solvate in ~he solvent carrier and not run outside of the imaged areas. An air knife can also be used to effect the drying of the non-imaged areas.
The transferred image on the conductive 20 ~ receiving~surface was then fused by placing in an oven for~ about~30 seconds. The temperature of the oven prior to~;~opening was about 180C. The fusing is ;accomplished through a temperature ramping that effectively~occurs when the oven door is opened to place 25~ the conductive receiving surface inside because of the resultant temperature~drop within the oven, The oven tempera~ure~gradually increases to the approximate 180C~temperature level after the oven door is closed again.;~ ~

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The permanent master of Example 6 was cleaned and dried. The same liquid toner and the same charging technique were employed to electrophotographically develop the charged persistent image as in Example 6.
The developed electrostatic master was laid on a generally flat working surface and MYLAR~ polyester spacer strips were used as in Example 6 to create a thickness of about 15 mils. A flexible copper foil conductive receiving surface was mounted about the 1 1/2 inch drum and wetted as described in Example 6. An electrical potential of about 1000 volts was established as in Example 6 to create the electric field.
The 1 1/2 inch diameter drum was rolled over the spacer strips on the edges of the master to effect the transfer of the toner particles to the conductive receiving surface. The transferred image displayed excellent~resolution up to about 5.0 line pairs per millimeter with very slight distor~tion. It appeared as ;~20~ though~about 70-8~0% of the toner particles were tr~ansferred to the conductive receiving surface.
The transferred image was then dried and fused as ~in~Example 6. ~

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Example 8 The permanent master of Example 6 was cleaned and dried. The same liquid toner and the same charging technique were employed to electrophotographically develop the charged persistent image as in Example 6.
The developed electrostatic master was laid on a generally flat working surface and MYLAR~ polyester spacer strips were used as in Example 6 to create a thickness of about 20 mils. A flexible copper foil conductive receiving surface was mounted about the 1 1/2 inch drum and wetted as described in Example 6. An electrical potential of about 1000 volts was established as in Example 6 to create the electric field.
The 1 1/2 inch diameter drum was rolled over the spacer strips on the edges of the master to e-ffect the transfer of the toner particles to the conductive recelving~surface. The transferred image displayed excellent~resolutlon up to about 4.0;1ine~pairs per millimeter with slight distortion. It appeared as 20 ~ though about 50-60% of the toner~particles were transferreù~to the c~onductive~rece1ving surfaae~
The trans~ferred image was~then dried and fused as~in Example 6.~

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Example 9 The permanent master of Example 6 was cleaned and dried. The same liquid toner and the same charging technique were employed to electrophotographically develop the charged persistent image as in Example 6.
; The developed electrostatic master was laid on a generally flat working surface and MYLAR~ polyester spacer strips were used as in Example 6 to create a thickness of about 25 mils. A flexible copper foil conductive receiving surface was mounted about the 1 1/2 inch drum and wetted as described in Example 6. An electrical potential of about 1500 volts was established as in Example 6 to create the electric field.
The 1 1/2 inch diameter drum was rolled over ~15 the spacer strips on the edges of the master to effect the transfer of the toner particles to the conductive ~; ~ receiving surface. The transferred image was distorted and inconsistent. It appeared as though about 30-40~ of the toner particles were transferred to the conductlve ~20 receiving surface.
The transferred image was then dried and fused as in Example 6.

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Example lO

The permanent master of Example 6 was cleaned and dried. The same liquid toner and the same charging technique were employed to electrophotographically develop the charged persistent image as in Example 6.
; The developed electrostatic master was laid on a generally flat working surface and MYLAR~ polyester spacer strips were used as in Example 6 to create a thickness of about 5 mils. A flexible copper foil conductive receiving surface was mounted about the l l/2 inch drum and wetted as described in Example 6. An electrical potential of about 800 volts ~Jas established as in Example 6 to create the electric field.
The l l/2 inch~diameter drum was rolled over 15 ~ ~ the spacer strips on the edges of the master to effect the transfer o~ the toner particles to the conductive rea~eiving surface. The transferred image displayed excellent resolution up to about 5.6 line pairs per mi~llimeter with a consistent image pattern. It appeared ;20 ~ as~though~about 50~ of the toner particles were transferred to the sonductive receiving surface.
The~transferred image was then dried and fused as~ in Example~6.

12 ~ 5 ~?2 While ~he preerred method in which the principles of the present inven~ion have been incorporated is shown and described above, it i9 to be understood that the present invention is not to be limited to the particular detail~ or methods thu~
presented~ but, in fact, widely different mean~ and methods may be employed in the practice of the ~roader aspect of this invention.
For example, to effect tran~fer the electric field established between the electro~tatically imageable surface and the receiving surface can be charged with either positive or neg ~ive polarity, depending upon the charge of the toner particle~, to dir@ct the charged toner particle~ acr~s~ ~he liquid medium. Charged toner particle~ of negative polarity will be attracted to a positively char~ed receivin~ surface or will be repelled by a negative back charging of the electrostatically i~ageable surface. If charged toner of po~itive poLarity ar~ u~ed, they will be attracted to a negatively charged receiving ~urface or repelled by a positive back ~, char~ing of~the electro~tatically imageable surface.
The nonpolar insulating solvent can equally well be minarsl spirit~, a long a~ it po3se~se~ high re~istivity and low viscosity.
The gap spacing can equally well employ a web-to-web arrangement that will hold the electro~tatically imageable surface and th~
receiving sur~ace at the desired ~i tance.
The electric field can be e~tablished in se~reral way~. For example, with a conductive receiver surface, such as the copper laminate, or in the case of a dielectric material, such as MYL~R polye~ter fil~, backed by a conductive surface the electric fieid is creat ed by direct charging. Where a dielectric 65~2 _3~_ receiving surface, such as MYIJAR polyester film, i~ used front or back charging via conventional corona charging or roller charging can be employed.
The electrostatically imageable surface can be a photoconductor, such aY a cadmium sulfide surface with a MYLAR polyester film or a polystyrene or a polyethylene overcoating, a selenium photoconductor surface, or suitable organic photoconductor~ such a~
carbazole and carbazole derivative~, polyvinyl carbazole and anthracene. Where the electrostatically imagaable surface uses a persistent latent imag~ aQ a permanent ma~ter, the surface can be zinc oxide, or organi~
photoconductors developed with toner which i~ fu~ed onto the ma~ter, or a dry film or liquid photore~ist.
The type of photosensitive ma erial applied to : the conductive backing to make the permanent master may vary as long as lt is permanently imageable and possesse~ the correct resistivity characteri~tic~ For example, where dry film re~ist~ are u3~d, the films may : be aqueous, semi-aqueou~ or ~olvent based.
Photoconductive in~ulating films of zinc oxid~ disp~rsed in a re~in binder may also be u~ed.
The procs~ disc:Losed herein ha~ b~en di3cussed :~ in th~ context of producing printed cirs::uit board~. It 25; shoul~ be no~ed, however, that the electrostatis: ima~e tran3fer process from a permanent maater is equally well acceptable for us~ in the production of labe}s, high speed produc'cion of documents and photochemical :~ machining or milling.
3 ~ ~ The scop~ of the appended claim 1~ intended to encompass all obvious changes in the details, mat~rials and arrangements of par ts which will occur to one of skill in the art upon a reading of the disclosure.

~ .

12~5i652 SUPPLEMENTARY DISCLOSURE

In the examples given above, the receiving surface is a conductor. However, regardless of whether the receiving surface is conductive or non-conductive, the key in effecting a transfer is establishing a sufficient electric field between the electrostatically imageable surface and the receiving surface. Instead of being a conductor, the ; receiving surface may be a dielectric material positioned atop a conductive supporting substrate. In the latter case, the transfer of the electrostatic latent image to the receiving surface is accomplished by directly applying D.C.
voltage to the conductive supporting surface~

It is a feature of this invention that high resolution transfer of the toner particles is obtained due to the electrical lines of force or pathways of toner transport being substantially straight and parallel, thereby giving the more uniform pile height between the centre and the edge of image.

Thls aspect of the invention is illustrated in Figs. 3a ~ and 3b of the drawings of this Supplementary Disclosure, wherein:
:
Flgure 3a is a diagrammatic illustration of the process of the present invention employing a permanent master that is :

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reusable to produce multiple copies of a desired pattern on an insulating dielectric layer by -the migration of charged toner particles from the master across a liquid-filled gap to a non-conductive receiving surface having an underlying conductive supportive substrate; and Figure 3b is an enlarged diagrammatic illustration of the migration of charged toner particles across a liquid-filled gap to the non-conductive receiving surface of Figure 3a.

The procedure illustrated in Figs. 3a and 3b ls similar to that described in relation to Figs. 2a and 2b, except that the voltage is applied to the conductive supporting surface.
The receiving surface which lies on top of the supporting conductive surface possesses the characteristics of being resistant to the nonpolar insulating solvent used to coat it, temperature stable, dimensionally stable and have good toner release characteristics. Suitable receiving surfaces include dielectrics such as silicone, polyethylene terephthalate, or polyvin~l fluoride positioned over a supporting conductive substrate such as copper or aluminum, conductive metals, or conductive silicone elastomer. Polytetrafluoroethylene could be used in place of silicone, although fluorosilicone could also be used. Conductive silicone or conductive fluoro-silicone, mear~ir~g silicone or fluorosilicone filled with a conductive or semiconductive material, could be laminated ~, A

1~95~52 over a metal electrode or to a flexible heat resistant polymer film, such as that sold under the tradename KAPTON by E.I. Du Pont de Nemours, ~with an underlying conductive base.
With these receiving surfaces, the developed image would be transferred thxough a liquid-filled gap, a~ cussed previou~ly and hereaf~er, dried and then tran~ferred in a : second step by heating the re~eiving sur~ace.

This tran fer o~ a liquid electrophotogxaphi¢ to~er acro~3 such a liquid-filled gap is dep~nd~nt upon the .~ 10 e~tablishment o~ a ~ufficien~ electric ield between th~
electro~tati~ally imageabl~ sur~ac2 and the receiving surface. It i8 not apparently dependenk upon the receiving ~urface being cla~sified a~ conductiv ,`~
Ex ~
lS A 1 mil thiok tran~par~nt heet of polyvinylfluoride, sold by DuPont und~r th~ trade~me T~D~A~, wa3 plac~d on a vacuu~ plate~ to which a D.C. potential wa~ appli~d. This heet;Wa~ th~ r~c~iYing ~ub~rate.
.
An electro~tatlcally imageable ~urface ~ mads by ;~ 20 lam~n~ting two on~^mil ~.00l inch3 thick ~i}~s of DuPont 210 ~: :
R dry ~ilm photor~3i~t ~o a 0.3 mil ~hick alu~izod : polyester film layer o~ about l0 mil thickn~s~ with a stan~ard ~ommercially available laminator, ~uch a~ Dy~achem~s : ~e~ern Magnum* Mod~l XRL-360. The 3uit~ble polye3t~r film : .

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can be that sold by DuPont under the tradename MYLAR. The electrostatically imageable surface was then exposed to about 50 millijoules per square centime~re of actinic radiation using a negative phototool on an Opti Beam Model 5050 exposure unit manufactured by Optical Radiation Corporation.
The phototool was an electrical circuit pattern. This exposed laminate, which serves as a permanent master, was allowed to cool and then was placed on the carrier web of a direct image transfer device.
In an automatic sequence, the permanent master was corona charged at +6500 volts to give the image area a positive charge, toned with a negative acting Olin Hunt premium toner, designated as 750/770 toner, by drawing it through a toner bath with about 1.5% solids in Exxon's ISOPAR
H* non-polar insulating solvent, and then placed over the receiving substrate on the vacuum platen.
About 800 volts D.C. was applied to the vacuum platen, which served as a conductive electrode, and the carrier web, with the toned permanent master, was brought close to, but not in~contact with, the receiving substrate. This was ~: :
accompiished by means of a transfer roller that traversed the back side of the carrier web while the receiving surface was .
kept in register to the electrostatically imageable surface.

The applied voltage created the electrostatic ~ield necessary to effect the electrostatic transfer across the fluid-filled gap.

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6~2 This gap was defined by one thickness of a suitable tape, such as Scotch Brand 810 Magic Transparent tape, placed on two opposing edges of the receiving surface of the transparent sheet of polyvinylEluoride on the vacuum platen to give a gap of approximately 2 mils. The gap was filled - with ISOPAR H non-polar insulating solvent.
Approximately 95% of the toner was transferred from the permanent master across the fluid-filled gap to the receiving surface. While the vacuum and 800 volt D.C. transfer potential were still applied to the vacuum platen, the wet toner image was partially dried on the receiving surface using a heat gun to prevent spreading of the image. A high resolution image was obtained on the receiving surface.
The process disclosed herein is equally well acceptable for use in the production of labels, high speed production of documents and photochemical machining or milling. It may ;~ ~ also be used to transfer an image to an absorbent substrate, such as paper. This may be effected by first heating the receiving surface, composed of a material such as silicone, and then by contact transfer from the intermediate silicone receiving surface to the absorbent substrate.

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Claims (56)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of fabricating a toned pattern on an isolated nonabsorbent receiving surface, comprising the steps of:
(a) establishing a charged electrostatic latent image area on an electrostatically imageable surface;
(b) developing the electrostatic latent image area by applying to the electrostatically imageable surface charged toner particles suspended is a liquid comprised at least partially of a nonpolar insulating solvent to form a first liquid layer with a first liquid surface, the charged toner particles being directed to the latent image area of the electrostatically imageable surface to form a developed latent image;
(c) applying to the nonabsorbent receiving surface a liquid comprised at least partially of a nonpolar insulating solvent to form a second liquid layer with a second liquid surface;

(d) establishing an electric field between the electrostatically imageable surface and conductive means associated with the receiving surface;
(e) placing the receiving surface adjacent to the electrostatically imageable surface so that a gap is maintained therebetween and the first liquid surface contacts the second liquid surface to create a liquid transfer medium across the gap;
(f) transferring the developed latent image from the electrostatically imageable surface at a point of transfer through the liquid to the receiving surface to form a transferred toner particle image in an imaged area and define non-imaged areas where toner particles are absent;
(g) maintaining the gap during transfer of the developed latent image between the electrostatically imageable surface and the receiving surface at the point of transfer between at least about 1 mil and about 20 mils,

2. The method according to claim 1 further comprising the steps of:
(a) etching the non-imaged areas of the receiving surface to remove the receiving surface from the non-imaged areas of the receiving surface on the conductor laminate; and (b) removing the toner particles from the imaged area of the receiving surface,

3. The method according to claim 2 further comprising maintaining the gap between the electrostatically imageable surface and the receiving surface at the point of transfer between at least about 3 mils and about 10 mils.

4. The method according to claim 1 further comprising maintaining at the point of transfer a first plane taken through the electrostatically imageable surface parallel to a second plane taken through the receiving surface.

5. The method according to claim 4 further comprising holding the receiving surface.
rigidly in place at the point of transfer.

6. The method according to claim 5 further comprising holding the receiving surface flat at the point of transfer.

7. The method according to claim 4 further comprising holding the receiving surface stationary at the point of transfer.

8. The method according to claim 7 further comprising holding the electrostatically imageable surface stationary at the point of transfer.

9. The method according to claim 7 further comprising moving the electrostatically imageable surface at the point of transfer in such a manner that there is no relative motion between the electrostatically imageable surface and the receiving surface at the point of transfer.

10. The method according to claim 4 further comprising moving the receiving surface.

11. The method according to claim 10 further comprising moving the electrostatically imageable surface at the point of transfer in such a manner that there is no relative motion between the electrostatically imageable surface and the receiving surface at the point of transfer.

12. The method according to claim 10 further comprising holding the electrostatically imageable surface stationary at the point of transfer.

13. The method according to claim 5 further comprising using a vacuum to hold the receiving surface in place.

14. The method according to claim 5 further comprising using a vacuum to hold the electrostatically imageable surface in place.

15. The method according to claim 5 further comprising magnetically holding the receiving surface in place.

16. The method according to claim 5 further comprising magnetically holding the electrostatically imageable surface in place.

17. The method according to claim 5 further comprising electrostatically holding the receiving surface in place.

18. The method according to claim 5 further comprising electrostatically holding the electrostatically imageable surface in place.

19. The method according to claim 2 further comprising fusing the transferred toner particle image with heat.

20. The method according to claim 19 further comprising fusing the transferred toner particle image in an oven.

21. The method according to claim 19 further comprising fusing the transferred toner particle image with directed air from an air slot.

22. The method according to claim 1 further comprising directing the charged toner particles across the gap through the liquid from the electrostatically imageable surface to the receiving surface by applying to the receiving surface a charge opposite in polarity to that of the charged toner particles.

23. The method according to claim 1 further comprising directing the charged toner particles across the gap through the liquid from the electrostatically imageable surface to the receiving surface by applying a back charge to the electrostatically imageable surface that is similar in polarity to the polarity of the toner particles.

24. The method according to claim 1 further comprising forming the electrostatically imageable surface in a photoconductor selected from the group consisting of selenium, cadmium sulfide, cadmium sulfide overcoated on mylar and organic photoconductors.

25. The method according to claim 2 further comprising forming a persistent latent image on the electrostatically imageable surface.

26. The method according to claim 25 further comprising forming the persistent latent image in an electrostatically imageable surface selected from the group consisting of a dry film photoresist, a liquid photoresist, zinc oxide and organic photoconductors.

27. The method according to claim 2 further comprising applying between about 200 to about 3500 volts to the receiving surface to form the electric field,

28. The method according to claim 2 further comprising applying between about 200 to about 1500 volts to the receiving surface to form the electric field.

29. The method according to claim 2 further comprising applying between about 200 to about 1200 volts to the receiving surface to form the electric field.

30. A method of fabricating a toned pattern on an isolated nonabsorbent conductive receiving surface, comprising the steps of:
(a) establishing a charged electrostatic latent image area on an electrostatically imageable surface the electrostatically imageable surface having a first plane passing therethrough;
(b) developing the electrostatic latent image area by applying to the electrostatically imageable surface charged toner particles suspended in a liquid comprised at least partially of a nonpolar insulating solvent to form a first liquid layer with a first liquid surface, the charged toner particles being directed to the latent image area of the electrostatically imageable surface to form a developed latent image;
(c) applying to the conductive receiving surface a liquid comprised at least partially of a nonpolar insulating solvent to form a second liquid layer with a second liquid surface;
(d) establishing an electric field between the electrostatically imageable surface and the conductive receiving surface;
(e) placing the conductive receiving surface adjacent to the electrostatically imageable surface and the first plane so that a gap is maintained therebetween and the first liquid surface contacts the second liquid surface to create a liquid transfer medium across the gap, the conductive receiving surface further having a second plane passing therethrough;
(f) transferring the developed latent image from the electrostatically imageable surface at a point of transfer through the liquid to the conductive receiving surface to form a transferred toner particle image in an imaged area and define non-imaged areas where toner particles are absent;

(g) maintaining the gap during transfer of the developed latent image between the electrostatically imageable surface and the conductive receiving surface at the point of transfer between at least about 1 mil and about 20 mils and maintaining the first plane parallel to the second plane at the point of transfer;
(h) fusing the transferred toner particle image to the conductive receiving surface;
(i) etching the non-imaged areas of the conductive receiving surface to remove the conductive receiving surface from the non-imaged areas of the conductive receiving surface on the conductor laminate;
and (j) removing the toner particles from the imaged area of the conductive receiving surface.

31. The method according to claim 1 further comprising forming the electrostatically imageable surface is a photoconductor selected from the group consisting of selenium, cadmium sulfide, cadmium sulfide overcoated on mylar and organic photoconductors.

32. The method according to claim 2 further comprising forming a persistent latent image on the electrostatically imageable surface.

33. The method according to claim 25 further comprising forming the persistent latent image in an electrostatically imageable surface selected from the group consisting of a dry film photoresist, a liquid photoresist, zinc oxide and organic photoconductors.

34. The method according to claim 2 further comprising applying between about 200 to about 3500 volts to the conductive receiving surface to form the electric field.

35. The method according to claim 2 further comprising applying between about 200 to about 1500 volts to the conductive receiving surface to form the electric field.

36. The method according to claim 2 further comprising applying between about 200 to about 1200 volts to the electrostatically imageable surface to form the electric field.

37. The method according to claim 4 further comprising holding the electrostatically imageable surface rigidly in place at the point of transfer.

38. The method according to claim 5 further comprising holding the conductive receiving surface flat at the point of transfer.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

39. A method of fabricating a toned pattern on a nonabsorbent receiving surface electrically isolated from ground, comprising the steps of:
(a) establishing a charged electrostatic latent image area on an electrostatically imageable surface;
(b) developing the electrostatic latent image area by applying to the electrostatically imageable surface charged toner particles suspended in a liquid comprised at least partially of a nonpolar insulating solvent to form a first liquid layer with a first liquid surface, the charged toner particles being directed to the latent image area of the electrostatically imageable surface to form a developed latent image of a predetermined pile height;
(c) applying to the nonabsorbent receiving surface a liquid comprised at least partially of a nonpolar insulating solvent to form a second liquid layer with a second liquid surface;
(d) establishing an electric field between the electrostatically imageable surface and the nonabsorbent receiving surface by connecting a D.C. voltage directly across a conductive electrode and the electrostatically imageable surface, the nonabsorbent receiving surface being positioned atop the conductive electrode which provides a supporting surface therefor;
(e) placing the nonabsorbent surface adjacent to the electrostatically imageable surface so that a gap is maintained therebetween and the first liquid surface contacts the second liquid surface to create a liquid transfer medium across the liquid-filled gap, the liquid-filled gap being of a depth greater than the pile height of the toner particles;
(f) transferring the developed latent image from the electrostatically imageable surface through the liquid to the nonabsorbent receiving surface to form a transferred toner particle image in an imaged area and define non-imaged areas where toner particles are absent;
(g) maintaining the gap during transfer of the developed latent image between the electrostatically imageable surface and the nonabsorbent receiving surface between at least about 1 mil and about 20 mils.

40. The method according to claim 39 further comprising maintaining the gap between the electrostatically imageable surface and the nonabsorbent receiving surface at the point of transfer between at least about 3 mils and about 10 mils.

41. The method according to claim 39 further comprising maintaining at a point of transfer a first plane taken through the electrostatically imageable surface parallel to a second plane taken through the nonabsorbent receiving surface.

42. The method according to claim 41 further comprising holding the nonabsorbent receiving surface in register to the electrostatically imageable surface.

43. The method according to claim 42 further comprising holding the nonabsorbent receiving surface flat at the point of transfer.

44. The method according to claim 43 wherein at least one of the receiving surface or the electrostatically imageable surface is curved.

45. The method according to claim 41 further comprising holding the nonabsorbent receiving surface stationary at the point of transfer.

46. The method according to claim 45 further comprising holding the electrostatically imageable surface stationary at the point of transfer.

47. The method according to claim 41 further comprising moving the electrostatically imageable surface at the point of transfer in such a manner that there is no relative motion between the electrostatically imageable surface and the nonabsorbent receiving surface at the point of transfer.

48. The method according to claim 42 further comprising moving the nonabsorbent receiving surface.

49. The method according to claim 48 further comprising moving the electrostatically imageable surface at the point of transfer in such a manner that there is no relative motion between the electrostatically imageable surface and the nonabsorbent receiving surface at the point of transfer.

50. The method according to claim 48 further comprising holding the electrostatically imageable surface stationary at the point of transfer.

51. The method according to claim 43 further comprising using a vacuum to hold the nonabsorbent receiving surface in place.

52. The method according to claim 43 further comprising using a vacuum to hold the electrostatically imageable surface in place.

53. The method according to claim 43 further comprising magnetically holding the nonabsorbent receiving surface in place.

54. The method according to claim 39 further comprising forming a permanent image on the electrostatically imageable surface.

55. The method according to claim 54 further comprising forming the permanent latent image in the electrostatically imageable surface wherein the electrostatically imageable surface is selected from the group consisting of a dry film photoresist, a liquid photoresist, zinc oxide and organic photoconductors.

56. The method according to claim 39 further comprising applying between about 200 to about 3500 volts to the conductive electrode connected to the receiving surface to form the electric field.