US3556784A - Electrostatic image development - Google Patents

Abstract

A PROCESS IN WHICH AN ELECTROSTATIC IMAGE-BEARING INSULATING SHEET IS BROUGHT INTO CONTACT WITH A COVER SHEET BY A PAIR OF ROLLS FORMING A LINE OF CONTACT AT WHICH THE DEVELOPMENT TAKES PLACE. A BEAD OF LIQUID DEVELOPER IS PLACED BETWEEN THE SHEETS AND AS THE SHEETS ARE MOVED AS A UNIT BETWEEN THE ROLLS, THE BEAD IS WIPED ACROSS THE SHEET AND IMAGES ARE DEVELOPED IN ACCORDANCE WITH THE POTENTIAL APPLIED TO THE ROLL IN CONTACT WITH ITS RESPECTIVE SHEET. THE PROCESS INCLUDES THE FOLLOWING EMBODIMENTS: THE ELECTROSTATIC IMAGE INDUCED ON THE COVER SHEET CAN BE DEVELOPED; THE ELECTROSTATIC IMAGE ON THE INSULATING SHEET CAN BE DEVELOPED WITH SIMULTANEOIUS TRANSFER OF THE DEVELOPER PARTICLES TO THE COVER SHEET; THE ELECTROSTATIC IMAGE ON THE INSULATING SHEET CAN BE DEVELOPED AND SIMULTANEOUS PHYSICALLY TRANSFERRING THE TONER PARTICLES TO THE COVER SHEET; AND THE ELECTROSTATIC IMAGE ON THE INSULATING LAYER CAN BE DEVELOPED WITH SIMULTANEOUS DEVELOPMENT OF THE ELECTROSTATIC IMAGE INDUCED ON THE COVER SHEET.

Description

' Jan. 19,. 1971 G, H, ,ROBINSON T A1. 3,556,784`

vELECIROS'IA'IIC IMAGE DEVELOPMENT Original Filed July 24, 1963' GENE H ROB/NS/V JAMES G. JPV/S A TTOR/VEYS United States Patent O 3,556,784 ELECTROSTATIC IMAGE DEVELOPMENT Gene H. Robinson and James G. Jarvis, Rochester, N.Y.,

assignors to Eastman Kodak Company, Rochester, N.Y,

a corporation of New Jersey Continuation of application Ser. No. 297,263, July 24,

1963. This application Sept. 21, 1966, Ser. No. 581,116 Int. Cl. G03g 13/16, 13/10, 15/10 U.S. Cl. 96-1.4 14 Claims ABSTRACT OF THE DISCLOSURE A process in which an electrostatic image-bearing insulating sheet is brought into contact with a cover sheet by a pair of rolls forming a line of contact at which the development takes place. A bead of liquid developer is placed between the sheets and as the sheets are moved as a unit between the rolls, the bead is wiped across the sheet and images are developed in accordance with the potential applied-to the roll in contact with its 'respective sheet. The process includes the following embodiments: the electrostatic image induced on the cover sheet can be developed; the electrostatic image on the insulating sheet can be developed with simultaneous transfer of the developer particles to the cover sheet; the electrostatic image on the insulating sheet can be developed and simultaneous physically transferring the toner particles to the cover sheet; and the electrostatic image on the insulating layer can be developed with simultaneous development of the electrostatic image induced on the cover sheet.

This application is a continuation of copending application Ser. No. 297,263, filed July 24, 1963, and now abandoned.

This invention relates to electrostatic printing and more particularly to improved processes employing liquid developers for converting electrostatic images into positive prints.

Processes for forming an electrostatic image on an insulating sheet are well known, for example, by xerography. Processes employing liquid developers for subsequently converting such electrostatic images into visual records are also well known. Such liquid developers comprise a nely divided solid or toner dispersed in a liquid having a high electrical resistance. The liquid developer is applied to the sheet carrying the electrostatic image by immersion of the sheet in the liquid developer or by owing the liquid developer over the sheet.

However, in all such processes a layer of the suspending liquid from the liquid developer is left on the electrostatic image-bearing sheet along with the toner particles. The presence of this layer of the suspending liquid is undesirable from several standpoints. That part which remains in the non-image areas with some suspended toner may produce background fog as the solvent is evaporated; fortunately, this is not too serious a problem, but in any case the present invention corrects it. A more serious trouble arises from the liquid which stays in the image areas along with the desired toner particles. This liquid tends to hinder the transfer of the toner particles to a permanent record media. If the permanent record rnedium is absorbent, too much of the suspending liquid is absorbed thereby without a sufficient quantity of the toner particles being transferred. If the permanent record medium is not absorbent, the pressure that is applied between the two layers produces a flood of the suspending liquid which tends to wash the toner particles otf of the image areas of the insulating sheet.

Further, such processes require a relatively large quantity of liquid developer. This is disadvantageous both economically and safetywise. The suspending liquid is sometimes ilammable or toxic and it is most often volatile.

Still further, if an immediate visual inspection of the image is desired, and if the print must be handled, time is consumed while Waiting for the layer of suspending liquid to evaporate.

It is an object of the present invention to provide a process for developing an electrostatic image employing a minimum quantity of liquid developer.

It is another object of the present invention to develop electrostatic images with liquid developer Without permitting any appreciable layer of the suspending liquid to deposit on the image-bearing sheet, in either the nonimage areas or the image areas.

It is an incidental object of the invention that it permits theA use of suspending liquids which are less volatile, which in turn reduces the dangers of fire and toxicity, and extends the choice of suspending liquids.

It is an object of one embodiment of the present invention to provide simultaneous development and transfer in one step instead of two or more steps.

It is a further object of such embodiment of the invention to provide for the simultaneous formation of a positive print on the receiving sheet and a reverse-reading negative print on the recording layer, or a reverse of this, by the proper selection of materials.

It is a still further object of the present invention to provide for the formation of a right-reading print or, if desired, a wrong-reading print (for example, for use in xeroprinting plates) by ree'x, contact, or projection printing of a negative or a positive, by proper choice of charged toner particles, proper transfer paper, and proper voltages. Such versatility is not only available but is convenient with the present invention.

These obejcts are accomplished by the invention in all of its embodiments by wiping an electrostatic image with a bead of liquid developer. This is strictly a wiping action in which the bead reaches an area of the image and immediately thereafter is wiped olf; it is not a spreading action. Simple spreading would have little or no advantage over immersion or ilowing of the developer over the image.

The preferred method according to the invention of providing such highly desirable wiping action employs two rollers or their equivalents to bring the electrostatic imagebearing insulating sheet into contact with a cover sheet, between which sheets, adjacent the line of contact, is positioned a bead or pod of liquid developer. The sheets are then squeezed between the rollers, wiping the bead across both sheets, and suiicient pressure is applied so that substantially no liquid gets past the rollers. Toner is deposited and liquid is wiped off in one operation. The process includes the following different preferred embodiments:

(l) A process for developing an electrostatic image induced on the cover sheet,

(2) A process for developing an electrostatic image on the insulating sheet and simultaneously transferring the developer particles to the cover sheet which contains a resin layer softened by a carrier liquid, e.g., cyclohexane in the liquid developer,

(3) A process for developing an electrostatic image on the insulating sheet and simultaneously physically transferring the toner particles to the cover sheet, and

(4) A process for developing an electrostatic image on the insulating layer and simultaneously developing an electrostatic image induced on the cover sheet.

Each of the above species of the invention has certain advantages in addition to those stated above. In each of the above species of the invention a direct print is produced. It is desirable to have such a choice of processes, because it is sometimes necessary to reproduce from a negative and sometimes from a positive document and because a choice of reflex, projection, or contact exposures is often desirable. It is an object of the invention to provide positive, right-reading prints regardless of the nature of the document to be reproduced and the desired type of exposure,

An essential feature of the invention is that as the electrostatic image-bearing sheet and the cover sheet are brought into contact, sufficient pressure is applied so that substantially none of the suspending liquid passes beyond the line of contact. There is no spreading of a liquid layer as is required in diffusion transfer processing of silver halide photographic films, and as is commonly used in cameras with built-in processing. According to the present invention a narrow bead of liquid developer moves across the image, leaving nothing noticeable except the imagewise distributed toner particles. Development (and/ or transfer) is complete at the rollers.

While it may be true that a minute quantity of the suspending liquid must theoretically get past the line of contact, such quantity is so inappreciable that it is not noticeable. The liquid is either immediately absorbed by the sheets or immediately evaporated upon separation of the sheets without leaving any apparent residue. That is, if there is any developer (liquid plus toner) left after the wiping action, it is so small that the toner is invisible, i.e., not noticeable. When the solvent is gone, by absorption or evaporation, there is no toner visible. As a practical matter there is effectively no liquid left and no toner left except in the image areas.

The above-mentioned different species are provided by varying the polarity of charge on the toner particles, the type of cover paper and the type of susupending liquid in the liquid developer, and the use and amount ofpotential applied to the transfer sheet and to the electrostatic image-bearing sheet.

The present invention will be more fully understood from the following detailed description of iive examples described with reference to the accompanying drawing in which:

FIGS. 1-5 are diagrammatic views through a xerographic sheet, a cover sheet, a bead of liquid developer, and a set of rollers, showing the position of electrical charges during the processes of Examples 1-5 of the present invention, and

FIG. 6 is a diagrammatic view of a pod of liquid developer attached to a sheet of electrostatic printing material.

The present invention will be described in detail by way of Examples 1-5, which correspond to FIGS. 1-5. These examples will be limited to a xerographically produced electrostatic image. Some of the advantages of the invention are directed particularly thereto, i.e., those advantages concerned with the production of a positive print regardless of the nature of the document to be reproduced (negative or positive) and whether the desired type of exposure is reflex, projection, or contact. However, the remaining advantages of the invention are not limited thereto. An electrostatic image can be produced on an insulating sheet by other than the use of a photoconductive insulating sheet as used in xerography. And such electrostatic images can be developed by the process of the present invention to achieve the advantages inherent in this process as discussed above.

EXAMPLE NO. 1

FIG. l shows a simultaneous positive-positive development and transfer'process. The term positive-positive means that the document to be reproduced is a positive and that the print produced by the process is also a positive. This embodiment of the invention is directed to the production of a positive print from a positive transparency by projection exposure. A zinc-oxide-in-resin-binder xerographic sheet 10 (4 in. x l1 in.) bearing a negatively charged wrong-reading electrostatic image 11 is brought into contact with a clay-coated paper receiving sheet 12 (4 in. x 11 in.) by means of two grounded conductive rollers 14 and 16. The rollers 14 and 16 are mounted to rotate in the direction indicated by the arrows. A bead 18 of liquid developer containing about 10 ml. of a negative toner developer is positioned between the two sheets as shown in FIG. l. The developer was made by dispersing about 0.1 g. Sherwin-Williams Solefast green lithographic ink in about ml. of cyclohexane. A positive electrostatic image 13 is induced on the receiving sheet 12. FIG. 1 exaggerates the production of the induced charge on the receiving sheet. The induced charge is obtained when the two sheets are brought into close proximity. This is also true for the subsequent figures described below. The negatively charged toner particles are attracted to the positive electrostatic image 13 on the receiving sheet 12 to produce a right-reading positive print thereon.

The receiving sheet in this embodiment and the following embodiments can be any type of paper, preferably absorptive. Conductive material, such as metal foil and the like, can also be used.

The bead 18 in this embodiment of the invention as well as in all of the following embodiments can be replaced with a pod made from, for example, a photographic dry mounting tissue rolled into cylindrical form and heat sealed at the ends. Other materials which can be used for making pods include an aluminum foil-paper laminate, aluminum foil, aluminum foil sealed with wax, and heat-sealed polyethylene. This feature of the invention will be described more fully hereinafter with reference to FIG. 6.

EXAMPLE NO. 2

FIG. 2 shows a zinc-oxide-in-resin-binder xerographic sheet 20 which has been negatively charged and reflex exposed through a right-reading negative to provide an electrostatic image 21 thereon. The xerographic sheet 20` is brought into contact with a clay-coated paper receiving sheet 22 between which sheets a bead 28 of liquid developer is introduced. About 10 ml. of bead of liquid developer was used. It was made by dispersing 1.0 g. of black lithographic ink (Sleight and Hellmuth Tri Dim B) in 100 ml. of cyclohexane. The two sheets are brought into contact by means of two conductive rollers 14 and 16. The roller 14 behind the receiving sheet 22 is grounded and the roller 16 behind the zinc oxide resin sheet 20 is held at 700 volt positive with respect to ground. The liquid developer described above provides toner particles having a negative charge. As the xerographic sheet 20 and the receiving sheet 22 pass between the rollers 14 and 16, the toner particles are electrically attracted to the uncharged areas of the xerographic sheet 20 and are then transferred to the receiving sheet 22, as shown by the arrows 25. A right-reading positive print is thus produced on the receiving sheet 22. Although the theory of this embodiment is not completely understood, we believe this to be a physical, rather than an electrical, transfer of the toner particles.

EXAMPLE NO. 3

A zinc-oxide-in-resin-binder xerographic sheet 30 has been negatively charged and projection exposed through a right-reading positive transparency to produce an electrostatic image 31 thereon. The xerographic sheet 30 is brought into contact with a clay-coated paper receiving sheet 32 by means of a pair of conductive rollers 14 and 16. A bead 38 of liquid developer is positioned between the sheets as shown in FIG. 3. About 10 ml. of liquid developer containing positively charged toner particles is used. The rollers 14 and 16 are grounded. A positivepolarity electrostatic image 33 is induced on the receiving sheet 32. As the xerographic sheet 30 and the receiving sheet 32 pass between the rollers 14 and 16, the toner particles are attracted to the electrostatic image 31, as shown by the arrows 35. A right-reading positive print is produced on the xerographic sheet 30. The developer is made according to the following procedure:

Ten grams of Amberlac D-96 (Rohm and Haas), a modied maleic anhydride rosin resin, were dissolved in 10 g. of Solvesso 100, the composition of which is given in U.S. Pat. No. 2,899,335, by heating the mixture at elevated temperature. Ten grams of Nigrosine, Spirit Iet (General Aniline and Film) and 20 ml. of additional Solvesso solvent were added to the resin solution. After 65 hours of milling in a micro mill, 25 ml. of Solvesso `was added and the mixture milled further for 36 hours.

Fifteen rnl. of Solvesso solvent, used to rinse out the mill, was added to the liquid developer.

EXAMPLE NO. 4

FIG. 4 shows a negative-positive process in which a zinc-oxide-in-resin-binder xerographic sheet 40` was negatively charged and projection exposed through a rightreading negative transparency to produce the electrostatic image 41 thereon. The xerographic sheet 40 was brought into contact with a clay-coated paper receiving sheet 42 by means of two conductive rollers 14 and 16. The roller 14 behind the receiving sheet 42 is grounded and the roller 16 behind the xerographic sheet 40 is biased to 120 volt positive with respect to ground. A bead 48 of liquid developer is positioned between the two sheets as shown in FIG. 4. The liquid developer is provided with negatively charged toner particles. About l ml. of liquid developer is used and is made by dispersing 0.1 g. of Sherwin William Solefast green negatively charged toner particles in 100 ml. of cyclohexane. As the sheets 40 and 42 are passed between the rollers 14 and 16, the toner particles are attracted to the uncharged areas of the xerographic sheet 40, and to the induced positive electrostatic image 43 on the receiving sheet 42, as indicatedby the arrows 45. A positive right-reading print is produced on the xerographic sheet 40 and a wring-reading negative print is produced on the receiving sheet 42.

EXAMPLE NO. 5

FIG. 5 shows a simultaneous positive-positive development and transfer process. A zinc-oxide-in-resin-binder xerographic sheet 50 has been negatively charged and projection exposed through a wrong-reading positive transparency to provide an electrostatic image 51 thereon. A receiving sheet 52 is provided which carries a layer of a mixture of styrene-butadiene and silicone resins. The two sheets are brought into contact by means of two rollers 14 and 16 as shown in FIG. 5. A bead 58 of liquid developer containing positively charged toner particles was introduced between the two sheetsgAbout ml. of a liquid developer comprising 0.l g. of Sleight and Hellmuth 7048 cyan lithographic ink in 100 ml. of cyclohexane was used. The cyclohexane solvent softens the styrenebutadiene and silicone resin layer in the receiving sheet 52, but does not attack the styrene alkyd resin in the xerographic sheet 50. As the sheets 50 and 52 pass between the rollers 14 and 16, the toner particles are attracted to the negative electrostatic image 51, as indicated by the arrows 55. They are then physically transferred to the softened, tacky, resinous, receiving sheet 52, to yield a right-reading positive print thereon.

In this embodiment of the invention the resin used in the receiving sheet S2 must be softened and rendered tacky by the cyclohexane or other organic solvent in the developer, whereas the resin in the zinc oxide recording layer must be insoluble in the solvent. The receiving sheet 52 used in this example was zinc oxide in binder coated on a suitable substrate. The binder was a mixture of a silicone resin and styrene-butadiene resin, The proportions may range from 5:95 to 50:50. The

preferred ratio in the styrene-butadiene is 70:30%. The silicone is an organo polysiloxane resin having the recurring moieties represented by the structural formula:

all .it

wherein x is an integer from 6 to 40, and R is a methyl or phenyl radical, so chosen that both radicals on any given silicon atom are identical and the molar ratio of methyl to phenyl radicals varies from 4:1 to 1:4. The Zinc oxide material, in this case, served as a filler to give proper tackiness in the receiving sheet 52, and the pigment-to-binder ratio was 4:1. The Zinc oxide xerographic layer 50 contained a cross-linked styrenated alkyd resin, Styresol 4440, Reichold Chemicals, which is not attacked by cyclohexane.

FIG. 6 shows a pod 60 of liquid developer 62 attached to a sheet `64 of electrostatic printing material. The .term electrostatic printing material is herein defined, for purposes of the present patent application, as including both an insulating sheet capable of storing an electrostatic image and a transfer sheet of conductive material such as paper, because the pod 60 can be attached to either an insulating sheet to be provided with an electrostatic image or to the cover sheet. The pod 60 is used as an alternative to the bead of liquid developer described above. The material of which the -pod is constructed must be non-absorptive and must rupture under pressure to release the liquid developer 62. The sheet 64 to which the pod 60 is attached may be either the electrostatic image-bearing sheet or the receiving sheet, both of which are described above. In one embodiment the pod is given sufficient strength so as not to rupture under` normal packing and handling conditions. In this way the pod can be manufactured, attached to the sheet of electrostatic printing material, for example, by the use of an adhesive, packed, and stored for later use. Various types of pod construction are possible. In one type, for example, one end of the sheet of electrostatic printing material is rolled back onto itself to form a liquid developer container, which is filled with liquid developer and sealed at the ends to provide an integral pod and sheet construction.

In all of the embodiments described above with reference to FIGS. 1-5, the rollers 14 and 1-6 can be re` placed by any other suitable means for applying pressure to the xerographic sheet and the receiving sheet as they are brought into contact. In some of the alternative arrangements, a roller is used in co-operation with a flat surface; in another device, two at surfaces are used in co-operation with means for pulling the two sheets therebetween. In all such systems, in order to produce prints of highest quality (e.g., minimum background) it is necessary that suflicient pressure be applied to the sheets to prevent any excess developer from going past the point of contact. By excess is meant any portion of the liquid developer other than those toner particles which have been electrically attracted to one or the other of the sheets. This pressure is sufficient to ensure physical transfer of the toner particles, in those embodiments wherein such physical transfer is to take place. The bead of liquid developer is continually pushed or forced ahead of the line of contact. Development is complete at the line of contact of the sheets.

The sheet materials may be moved lbetween the pressure rollers by manual or mechanical rotation of the rollers to cause frictional engagement between the rollers and the sheet materials or by manual or automatic pulling of the sheets through the rollers.

Although the present invention is particularly useful with zinc oxide, other photoconductive materials can be used including vitreous selenium, and organic photoconductors, such as anthracene, triphenylamines, polyvinyl carbazoles, etc. The cover sheet or transfer sheet in the transfer processes can be any type of paper, preferably non-absorptive, or any other conducting material, such as metal foil 'and the like. The liquid developer, when used as a bead, is introduced between the sheets from any suitable container such as, for example, a col lapsible tube.

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

We claim:

1. In a process for developing an electrostatic image on one surface of an insulating sheet and simultaneously reproducing said electrostatic image as a positive rightreading image on a facing surface of a cover sheet, the steps of forming a line of contact transversely of said sheets and at which said sheets are pressed into engagement, positioning a liquid developer comprising a liquid carrier and charged tone particles suspended therein which have a polarity of charge the same as said electrostatic image between said sheets at the line of contact, moving said sheets as a unit relative to said line of contact to simultaneously wipe said liquid developer across said surfaces while holding said cover sheet and the outside surface of said insulating sheet at electrical ground potential, whereby an electrostatic image is induced on said cover sheet which has a polarity opposite to that on said insulating sheet, maintaining sufficient pressure on said sheets while bing moved to prevent any substantial amount of said carrier from being left on said surfaces while said toner particles are attracted to and deposited on said induced electrostatic image, and separating said sheets.

2. The process according to claim 1 wherein said cover sheet is held at electric ground potential and the outside surface of said insulating sheet is held at a bias potential of the polarity opposite to that of said electrostatic image, whereby said toner particles are electrically attracted to the non-image areas on said insulating sheet and are physically transferred to said cover sheet at said line of contact.

3. The process according to claim 1 wherein said toner particles have a polarity of charge opposite to that of said electrostatic image, whereby an electrostatic image of the same polarity as said toner particles is induced on said cover sheet and said toner particles are attracted to and deposited on said electrostatic image on said insulating sheet at said line of contact.

4. The process according to claim 1 wherein said cover sheet is held at electrical ground potential and the outside surface of said insulating sheet is held at a bias potential of a polarity opposite to that of said electrostatic image, whereby an image of a polarity opposite to that of said electrostatic image is induced on said cover sheet and said toner particles are attracted to and deposited on said induced image and are also attracted to and deposited on the non-image areas of said insulating sheet at said line of contact.

5. The process according to claim 1 wherein said cover sheet is provided with a resin layer which is softened and rendered tacky by said liquid developer, and said toner particles have a polarity of charge opposite to that of said electrostatic image, whereby said toner particles are electrically attracted to said electrostatic image and are then physically transferred to said tacky receiving sheet at said line of contact.

6. The method of forming on an image receiving web a visual record of a latent electrostatic image on an image support member comprising placing an individual droplet of developer comprising particulate electrically charged toner suspended in a non-conductive liquid carrier on said Crt image support member, simultaneously establishing a line of intimate physical contact between successive portions of said image receiving web and said image support member and advancing said line, said developer advancing in front of said line of intimate physical contact and between said image receiving web and said image support member to deposit said toner particles on said image receiving web in image configuration at said line of intimate physical contact, and separating said web from said image support member bearing a developed image.

7. The method according to claim 6 wherein said particulate toner comprises a solution of resin in a solvent therefor and said liquid carrier comprises a non-polar organic liquid.

8. The method according to claim 6 wherein said particulate tone comprises a solution of resin in a solvent therefor and including the additional step of fixing said tone particles deposited on said image receiving web by eliminating the solvent therefrom.

9. The method of depositing toner particles on an image receiving web in conformity with a latent electrostatic image on an image support member comprising placing an individual droplet of developer comprising electrically charged toner particles suspended in a non-conductive liquid carrier onto said support member, bringing successive portions of said web into intimate contact with successive portions of said support member by rolling a cylindrical roller across said web and simultaneously advancing said developer before the line of contact between said web and Said support member, and separating said web from said image support member.

10. The method according to claim 9 wherein said roller is electrically conductive.

11. The method according to claim 9 wherein said roller is electrically conductive and an electrical bias is applied to said roller.

12. A method for forming on an image receiving web a visual record of a latent electrostatic image on an image support member comprising advancing developer comprising electrically charged toner particles suspended in a non-conductive liquid carrier across said support member by establishing a line of intimate physical contact between successive portions of said web and said support member whereby toner particles are selectively deposited on said web in image configuration, and separating said web from said support member.

13. A method for Xerographic image reproduction comprising applying an electrostatic charge of one polarity to the surface of a Xerographic plate, exposing said plate to a pattern of light and shadow, placing an individual droplet of developer comprising electrically charged particles suspended in a nonconductive liquid carrier on the said plate, establishing a line of intimate physical contact between successive portions of said plate and an image receiving web and advancing said developer in front of said line of contact whereby printing of a visible record of said latent electrostatic image is effected on said web, and separating said web from said xerographic plate.

14. The method of developing a visible record of a latent electrostatic image residing on an image support member comprising:

(a) establishing a line of intimate contact between a leading area of an image receiving web and the image support member at an individual bead of liquid developer on said image support member;

(b) advancing said line of intimate contact:

(l) to establish pressure contact between successive areas of said web and said image support member, and,

(2) to distribute and move said liquid developer across the surface of said support member in advance of said line of intimate contact; and

(c) separating successive areas of said web from said support member;

9 wherein said liquid developer comprises electrically charged particulate toner suspended in a non-conductive liquid carrier.

References Cited UNITED STATES PATENTS 2,907,674 10/ 1959 Metcalfe et al. 117-37 3,063,859 11/1962 Heckscher 117-17.5 3,172,043 6/ 1965 Metcalfe et al 96-1 10 3,234,019 2/1966 Hall 96-1.3 3,240,596 3/1966 Medley et al. 96-1.4 3,247,825 4/1966 Johnson 118-637 CHARLES E. VAN HORN, Primary Examiner U.S. C1. X.R.

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