US 3851964 A
An electrophotographic copying machine employs a method of contact transfer of developed electrostatic images. A moving photoconductive surface is charged and exposed to a pattern of light and shade as done in known electrophotographic processes, and the latent image is developed with a liquid developer which carries a toner which is tacky-that is, one that has adhesive properties. The developed image with the toner in tacky state is contacted with sheet material such as paper, which has greater affinity for the tacky toner than the photoconductive surface from which the image is transferred. After the image is transferred to the sheet material the toner quickly loses its tackiness and dries to a hard scuff-resistant surface. Transfer of the tacky toner may be facilitated by heating the sheet material before contact is made between it and the developed image.
Description (OCR text may contain errors)
United States Patent [191 Smith et al. Dec. 3, -1974 1 1 CONTACT TRANSFER ELECTROSTATIC 3,592,642 7/1971 Kaupp 96/14 R COPYING APPARATUS 3,698,314 10/1972 Grier 96/l.4 X 3,716,360 2/1973 Fukushima ct a1. 96/1 LY X Inventors: Ian Edward Smith, Lockleys; Peter John Hastwell, Elizabeth Grove; Marinus Cornelus Vermeulen, Valley View, all of Australia Assignee: Savin Business Machines Corporation, Valhalla, N.Y.
Filed: May 14, 1973 Appl. N0.: 359,651 I Related US. Application Data  Division of Ser. No. 155,108, June 21, 1971.
 US. Cl. 355/10, 96/1 LY, 96/1.4, 117/37 LE, 118/D1G. 23
 Int. Cl. G03g 15/14, (303g 15/10 [58} Field of Search 355/10, 3 R; 96/1 LY, 1.4; 117/37 LE; 118/DIG. 23
 References Cited UNITED STATES PATENTS 3,176,653 4/1965 Hansen 118/637 3,275,436 9/1966 Mayer 96/1.4
3,493,412 2/1970 Johnston et al... 96/1.4 X
3,591,276 7/1971 Byrne 355/3 R Primary E.\'aniiner-Robert P. Greiner Attorney, Agent, or Firm-Shenier & OConnor 5 7 ABSTRACT An electrophotographic copying machine employs a method of contact transfer of developed electrostatic images. A moving photoconductive surface is charged 1 image is transferred. After the image is transferred to the sheet material the toner quickly loses its tackiness and dries to a hard scuff-resistant surface. Transfer of the tacky toner may be facilitated by heating the sheet material before contact is made between it and the developed. image.
7 Claims, Drawing Figures PATENTEU 553 74 SHEEI 1 OF 5 PATENTEL E 3 74 SIEEI 2 OF 5 PATENTEL DEC 74 SHEET 3 0F 5 PATENIEL EEC 31974 SHEET 5 0F 5 i r 1 I/III/IIIIIIII- rlllllllllIl/III, 1114' i CONTACT TRANSFER ELECTROSTATIC COPYING APPARATUS This is a division of application Ser. No. 155,108, filed June 21,1971.
BACKGROUND OF THE INVENTION Electrostatic reproduction processes are well known to the art. In the well-known Xerox system a photoconductive surface carried by a drum is electrostatically charged by a corona discharge device. The photoconductive surface which may be of selenium or the like is an insulator in the drak and a conductor in the light. The image to be reproduced is focused onthe photo conductive surface. When the light strikes the photoconductive surface the charge leaks away in the illuminated areas leaving the dark areas to form the image. The latent image in the form of electrostatic charges on the photoconductive surface is" then developed by a toner. This toner must be in the form of a dry powder. The dry toner particles are then transferred by an electrostatic charge to sheet material such asordinary paper and are usually formed from thermoplastic resins. The toner particles are then fixed by heat on the ordinary paper and the image appears in its final form. The necessity of using heat to fix the toner particles prevents high-speed operation of the Xerox system. Furthermore, the dry toners are slightly abrasive and sooner or later they scratch and mar the selenium surface of the drum which is the heart of the Xerox machine. The dry toner also causes mechanical problems since the toner particles become air-borne and permeate the bearings of the machine. This requires frequent cleaning, which is an onerous task. The dry toners have inherent dielectrophoretic properties which prevent theirfilling in large black areas. This is easily observed by viewing any copy which has a large, black-area made on the Xerox'machin'e.
In the Electrofax method, a sheet of paper is covered with a photoconductive such as zinc oxide. The latent electrostatic image can be developed eithenby a dry toner or by a liquid in which a toner is suspended. A liquid developer comprises finely divided pigment particles having an average size no larger than about twenty microns and probably much smaller 'toabout an average size of about five microns, suspended in a relatively non-conductive light hydrocarbon such as benzene, zylene, hexane, naphtha, cyclohexane, or the like. The final image, of course, in the Electrofax process, appears on the photoconductor-coated surface and is not transferred to ordinary paper. It has been realized for some time bythose skilled in the art that it would be desirable to use liquid developers in a transfer process. No one has found a way, however, to accomplish this conveniently. In U.S. Pat. No. 3,251,688 issued May 17, 1966, to Mihajlov, one attempt at the employment of liquid developers in a transfer process is shown. Mihajlov applies a film of liquid developer over the photoconductive surface. He then exposes the photoconductive surface and the developer simultaneously to a pattern of light and shadow. He then attempts to developer and makes the roller of conductive rubber or the like. v
In all of the processes of the prior art in which transfer of an image is made from a photoconductor to ordinary paper, there is a loss of definition according to the application of pressure which distorts the developed image or through the difficulty of attaining effective transfer of development particles to a new location and the effective fixing of the same. Difficulty is also experienced when the same photoconductive surface is used repetitively, and images produced on it successively are transferred to another medium. The problem is that the photoconductive surface becomes soiled. This soiling is not very great when dry toners are used but in a method such as that of Mihajlov, the liquid toner will adhere to some extent to the photoconductive surface and gradually becomeunuseable.
SUMMARY OF THE INVENTION One object of our invention is to provide a novel method of contact transfer of developed electrostatic images from the surface of a photoconductor to sheet material such as paper.
Another object of our invention is to provide a novel method of contact transfer of electrostatic images developed by a liquid developer to ordinary paper or the like.
Another object of our invention is to provide a novel methodof contact transfer .of a liquid toner developed electrostaticimage from the photoconductive surface in an expedient and simple manner without the use of an electrostatic field.
Still another object of our invention is to provide a method of contact transfer of liquid toner developed electrostatic images while maintaining high resolution.
A further object of our invention is to provide a method of contact transfer of a liquid toner developed electrostatic image from a photoconductive surface to a copy sheet while maintaining the photoconductive surface in a clean condition.
Another object of our invention is to provide a photoconductive surface having less affinity for the developed electrostatic image than for the paper to which it is to be transferred.
Another object of our invention is to provide an improved liquid toner or developer which can readily be applied to a latent electrostatic image on a photoconductive surface from which it can readily be transferred to a second surface such as ordinary paper or the like.
A further object of our invention is to provide a novel liquid toner or developer which is non-sticky when first deposited,'becomes sticky or tacky after deposit so it can be transferred while tacky and loses its tackiness and remains firmly bonded to the surface to which it is transferred.
Another object of our invention is to provide a toner which can be transferred while tacky to a dry surface and then cured to provide a scuff-free and abrasionresistant final image.
Still another object of our invention is to provide a developer or toner which when tacky will have greater affinity for paper than the photoconductive surface on which the image was developed.
A further object of our invention is to provide novel apparatus for carrying out our novel method.
bled in a machine for making charge device which is well known in the art. The original which is to be copied or reproduced is projected upon the charged surface; Where light strikes, the charge is conducted to ground through the .photoconductor leaving a pattern of charges such as electrons faithfully reproducing the image in a latent fashion.
The latent image is then developed with a liquid toner having transient adhesive or tacky properties. The toner composition has low adhesion for the imageforming surface and high-adhesion for the copy surface. The tacky or adhesive properties are transient and the final image exhibits high resolution and isscufffree. While our. invention contemplates the use of ordinary paper, other appropriate sheet material such as thin sheetsof plastic,.aluminum foil or the like may be used if desired. The copy paper may be coated with a thin film of synthetic resin for which the toner particles suspended in the developer liquid have affinity. This procedure will permit a wider variety of developer'liqui'ds to be used. Thiseliminates the criticality or close limits of components in the confection of the developer liquids.
BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numer als are used to indicate like parts of the various views:
FIG. 1 is a diagrammatic sectional view of a photocopier adapted to carry out the method of our invention and embodying one form of the apparatus of our invention.
' FIG. 2 is a diagrammatic view showing the driving train for the photocopier'shown in FIG. 1.
FIG. 3 is a circuit diagram showing the control circuit for the photocopier shown inFlG. l.
FIG. 4 is a diagrammatic sectional view similar to that shown in FIG. 1 showing another embodiment of apparatus involving our invention and capable of carrying out the process of our invention;
FIG. 5 is a diagrammatic view similar to that shown in FIG. 1 of apparatus adapted to make a printing roller by the process of our invention.
FIG. 6 is a diagrammatic view showing the-printing roller made by the apparatus shown in FIG. 5 assemrapid succession.
DESCRIPTION OF THE PREFERRED EMBODIMENT- conductive layer 16. Drum 14 is made of conductive,
material and carries a photoconductive layer 16 wewin' describe in greaterdetail hereinafter. Mounted on t t JP I of the housing 12 is a carriage 18' adapted to reciprocate on suitable bearings 20. The carriage 18 supports a transparent plate 22 on which an original 24 to be copied is mounted. The reciprocating carrier 18 is adapted to move the original back and forth past the light 26 (also identified as L1) which illuminates the copy. The movement of the carriage 18 is synchronized with the rotation of the drum 14 such that the peripheral speed of the drum and the linear motion'of the carriage 18 are identical. As copy passes by the lens 28 the image is focused upon the surface of the photoconductive layer 16. A mirror 30 which may be a prism if desired directs the image at right angles to the surface of the photoconductive layer 16. The limits of the path of trav'elof the carriage are determined by limit switch LS1 in the direction to the right as viewed inFIG. land limit switch LS2 as viewed to the left in FIG. I. It is unders'tood, of course, that switch LS2 is positioned much further to the left, a part of the support being shown broken away because of space limitations on the drawing. Drum 14 is mounted onthe shaft 32 and its surface is in contact'with rollers 33, '34, and 35, which arcpositioned in a tank 36 containing the developer liquid 38 of our invention. 1
A motor M2 is adapted to drive an agitator 40 to keep the developer liquid agitated so that the insoluble components of the developer will remain dispersed throughout the developer liquid. A shaft 42 carries roll of paper 44 or other flexible sheet material to which the copy is to be transferred. A motor M3 drives a centrifugal fan 46 to furnish'air to an elongated nozzle 48 adjacent the periphery of the drum '14 to remove excess developer liquid from the surface 16 of the drum. Aplurality of hot air manifolds 50,, 52, 54 and 56 are controlled by respective valves connected to a supply of hot air (not shown). Hot air from manifold 50 is directed against the surface 16 of the periphery drum l4. Manifold'52'directs hot air to the side of the paper which is to receive the transfer from the drum. Manifold 54 directs hot air on the opposite side of the paper. Manifold 56 directs hot air to the finished transfer after it has been severed from the roll by knife 60 operated by solenoid 52; Paper is drawn from the roll 44 by takeoff roller 62 and the cut sheet is then moved by delivery roll 64. As will be pointed'out hereinafter the positions of the respective valves controlling the hot air may be varied depending upon the particular composition of'the developing liquid being used. The use of hot Xerographic prints in t air manifolds are beneficial but not absolutely essential for the practicing of our method. They are particularly useful where high-speed operation'and a rapid reproduction rate is desired. A corona discharge device 66 (K) is positioned adjacent the photoconductor surface of the drum to charge its surface in the dark. A cleaning roller 68, which may be wet if desired, removes anyresidual toner which may be inadvertently left on the surface of the drum.
Shielded light 70 (L2) insures that a residual electrostatic charge is conducted to ground before the surface of the drum is recharged.
Referring now to FIG. 2 the moving parts of our photocopier are driven from a prime mover to be indicated by the reference numeral and a motor M1. The motor. 100 drives a shaft 32 which carries for rotation therewith, a first-gear wheel 102, a second-gear wheel 104 and a pinion 106. A shaft 31 carries a pinion 108 for rotation therewith. A pinion 110 which is loosely mounted on shaft 31 engages a rack 112 which is carried by and secured to the carriage 18. A clutch C1 is secured to shaft 31 for rotation therewith. A pinion 114 is mounted on a side shaft 39 for rotation therewith. Pinion 107 is driven by shaft 31 and drives pinion 109 which drives pinion 111 to drive shaft 39. Pinion 114 is in engagement with the pinion 116 which is mounted for rotation with shaft-.29 which shaft carries a clutch C2. It will be seen clutch C1 rotates in one direction and-clutch C2 rotates in the opposite direction. When clutch Cl is energized it will vengage the loosely mounted pinion 110 and drive the rack 112 in one direction. When clutch C2 is energized it will engage the pinion 110 and drive the rack 112 in the opposite direction. The pinion 108 is driven from the gear 102 to gear chain 120. The pinion 106 drives the pinion 122 through a gear chain 124. This drives the roller 34. R01- lers 33 and 35 are driven through intermediate gears 123, 124, 125, 126 and 127. The developer applying rollers 33, 34 and 35 rotate in the same direction. The ratio of the gear chain and pinions is such that peripheral speed of the rollers 33, 34and 35 is the same as the peripheral speed of the drum 16'. A takeoff roller 62-is mounted on a shaft 61 for rotation therewith. A clutch C3 is mounted on the shaft 61 for rotation therewith. The shaft 61 carries a pinion 128 loosely so that the pinion may rotate freely. The pinion 128 isdriven by gear chain 130 from the. gear wheel 104. When the clutch C3 is energized the takeoff roller will rotate. A pinion 132 is driven from the pinion 128 by a gear chain 134. It rotatescontinuously and is mounted on the shaft 63which carriesthe delivery roller 64.
Referring again to FIG. 1 the paper on which copy is to be made passes from theroll 44 over printing roller 43 mounted on a shaft'41. The shaft is carried by a pair of links 45 pivotally mountedon a shaft 47. When the arcuate solenoid S1 is energized the links move downwardly to bring the paper into contact with the rotary drum to effect the transfer of the developed image to the paper.
Referring now to FIG. 3, which shows the control circuit for our copier, at the start of an operation limit switches LS1 and LS2 are in the positions shown in the drawing. The carriage 18 is to the right as viewed in FIG. 1. An original sheet to be copied is placed upon the transparent plate 22. The machine is energized by closing switch TS. The main lines 200 and 202 are connected across an appropriate source of potential. The closing of the switch TS energizes the main motor M1, the blower motor M3 and the agitator motor M2. It also energizes the erasing light L2. To start the operation of the copier, push button PB is pressed just momentarily. This completes a circuit through the relay winding IR and closes normally open relay contacts 1R1, 1R2 and 1R3. The contact 1R1 completes a holding circuit through LS2 and maintains the relay winding 1R in energized condition. The circuit through contacts 1R2 energizes clutch C1 and drives the carriage to the left as viewed in FIG. 1. The circuit through contacts 1R3 energizes the light L1 and the corona discharge device K. The original passes by the light and an image of it is focused upon the moving drum by the lens 28 and the mirror or prism 30. A latent electron image is impressed upon the photoconductor surface 16 as is known in the art. This latent image is later developed by the developing liquid owing to the movement of adhesive toner particlessuspended in the developing liqend of a cycle of operations.
uid to the charged portions of the drum. The air knife blows excess developingliquid from the drum. As. the carriage 18 moves to the left it strikes limitswitch LS2. Thisswitch now moves downwardly from the position shown in FIG. 3 to break the holding circuit through lRland thus opens the circuits through 1R2 and 1R3. The opening of the circuit through 1R2 de-energizes clutch C1. The opening of the circuit through 1R3 deenergizes the corona charging circuit K and deenergizes the illuminating lamp L1. A circuit is now made through'winding 2R. The energization for winding 2R closes circuit through 2R1, 2R2, 2R3 and 2R4. The closing of the circuit through 2R1 completes a holding circuit and maintains the winding 2R energized, the circuit now being completed from main 200 through winding 2R through contacts 2R1 through normally closed contacts 3R1 to the other side of the line 202. The closing of contacts 2R2 energizes clutch C2 through normally closed (in the position shown) limit switch LS1 and drives the carriage 18 in the reverse direction. The closing of contacts 2R3 energizes solenoid S1 to draw the printing roller 43 downwardly against the action of the spring 49. The tacky toned image is then transferred to the paper. The clutch C3 is also energized so the take-off roller 62 will rotate to draw the paper from the roll and pass it to the right through the delivery rollers 64. As can be seen by reference to FIG. 1 both the rollers 62 and 64 have backup rollers against which they hear. The closing of contacts 2R4 partially completes a circuit through winding 3R. When the carriage on its return to the right strikes limit switch LS1 it moves it from its normal position shown in FIG. 3 upwardly. This completes a circuit'through winding 3R. Energization of winding 3R closes the contacts through 3R2 and energizes solenoid S2 which operates the cutting knife 60. It also breaks the holding circuit through winding 2R. This permits contacts 2R1, 2R2, 2R3 and 2R4 to reassume their open positions. When contacts 2R4 are broken the relay winding 3R is de-energized and contacts 3R2 are opened to de-energize winding of solenoid S2. It will be understood, that while we have described the cycle for a single operation, successive cycles to any desired number may be initiated by a sequencing means'known to the art, whereby the cycle will be repeated as desired to make multiple copies automatically. This can be easily accomplished by having a sequencing switch act to close the circuit through PB completed by a synchronous brush instead of by a push button. It is to be understood, of course, that the limit switches are biased by the appropriate means such as springs to assume the positions shown in FIG. 3
Referring now to FIG. 4, we have shown a modified form of the machine'shown in FIG. 1. Instead of adrum carrying'a photoconductive layer we provide a belt 300 having a photoconductive layer 16. The belt is passed around a pair of conductive drums 302 and 304. The sheet material to which the image is to be transferred passes from roll 44 over guide roll 306 under guide roll 308 around the belt 300 carrying the photoconductive layer 16 and then over guide roll 310 to takeoff roller 62.
In the fonn of the invention shown in FIG. 4 an elongated manifold 53 heats the rear side of the copy paper by hot air delivered to the manifold and controlled by a valve. The cleaning roll in the form of the invention shown in FIG. 4 is disposed in a tank 69 containing at the I y The belt may belt.
which is flexible and conductive such as wire mesh, fi bers of synthetic resin impregnated with conductive material and woven'into a belt, or flexiblemetallic screen, or the like. The photoconductive layer will be described more fully hereinafter. It will be recognized be made of any appropriate material.
that the arrangement shown in FIG. 4 is-essentially the.. same as that shown in FIG. 1, except that a belt is usedv instead of a drum. Since the imaging station is removed from the transfer station, it is not-necessary to use a solenoidSl to bring the copy paper into contact with the drum.
'Referring now to FIG. 5, the arrangement is quite similar to that shown in FIG. 1, except that instead of transferring a toned image from the photoconductive layer-l6 to sheet material, the transfer is made onto a conductive drum 400 mounted on a shaft 402. The transferred image indicated at 403 is fixed by a radiant heater 404. v
Referring now to FIG. 6, the-drum 400 having the image 403 thereon is mounted on a shaft 406. The toner-formed image 403' is' non-conductive so that when it is'charg'ed bythe corona, discharge from corona discharge device 60 only the image will retain the charge. The charge elsewhere on drum 400 will be conducted to ground since it is conductive. Accordingly, when the chargedimage is subjected to the developer solution as fed by the rolls 33, 34 and 35 from the toner liquid in the tank 36, the drum will act as aprinting drum and transfer the freshly toned portion of the image 403 on the paper drawn from the roll 44. ltwill be observed that this operation may take'place in broad daylight since 'no photoconductive phenomenon is involved. The charge is retained on the non-conductive image formed by the toner particles and the charge upon the image will pick up toner andtransfer the toner image to a portion of the roll of paper or other sheet materials. It is to beunderstood, of course, that the printing drum 400 may be .provided with a cleaning roller 68.
The developer according to the present invention is so arranged that it is more adhesive in respect of the surface to which it is to be transferred than it is to the surface on which the latent image is produced. Accordingly, when the latent image is developed it can readily be transferred to the copy sheet because of its greater affinity for it.
In its simplest aspect we may give the photoconductive surface low adhesion by treating the same to provide a silicone or a urethane film. Similarly it is feasible to treat paper with a medium which will give the paper a physical affinity for the toner, that is, the developed toner image. In a similar manner it is possible to cool the photoconductive surface and heat the copy paper. This temperature differential will'have the effect of enhancing the affinity of the developed image with a copy a er. p To make a photoconductive surface for the'druml4 or the conductive belt 300 which will have a low affinity for the developed image we proceed ina number of different ways to accomplish this result.
EXAMPLE 1 Prepare a mixture as follows:
r 1,000 gms. of Zinc Oxide '80 gms. of short oil (safflower) oxidizing alkyd resin. 2l0 gms. of unmodified melamine formaldehyde resin solution in butanol having a solids content of about 58% and a specific gravity of about L02.
I mls. of Butanol 480 mls. of Toluol 300 mls. of Chlorothenc Dyes may be added to the above mixture, as is well known. in the art, to obtain the required photosensitivity. This mixture is then ballmilled for l2 hours. it is then diluted with the following solution:
300 mls. of Chlorothene 300 mls. of Toluene 300 mls. of I Butanol I 1.2 gms. of Cobalt Naphthenate (as a dryer). 2.4 gms. of Lead Naphthenate (as a dryer).
This mixture is then appliedto the drum or thebelt and cured. After curing,athin film of an emulsion of a silicone resin together withan appropriate catalyst such as lead monoxide, benzoyl peroxide or the like, is mixed in a light hydrocarbontboiling range 60 C 140 C) and is applied over the photoconductive surfeet per minute.
EXAMPLE 2 Zinc Oxide shortoil (safflower) oxidizing alkyd resin. unmodified melamine formaldehyde resin solution in butanol having a solids content of about 58% and a specific gravity of about 1.02. an emulsion of silicone resin ballmilled with an appropriate catalyst such as lead monoxide, benzoyl peroxide or the like. hydrocarbon solvent having 1 a boiling range between l00 C and I20 C. Toluol Terpineol of of gms. 6 gms.
l9 gms. of
8 gms. of
40 mls. of
IO mls. l0 mls.
of of The above mixture is then ballmilled with dyes to ob-" tain the required photosensitivity as is known in the art and diluted with:
40 mls. of hydrocarbon solvent having a boiling ran e between 100 C and 70 mls. of Toluol 0.2 gms. of Cobalt Naphthenate used 0.8 gms. of Lead Naphthenate as 1.6 gms. of Zirconium Octoate dryers lt will be observed that the silicone resin is now combined with the photoconductive zinc oxide and a binder EXAMPLE 3 100 gms. of 27 gms. of
Zinc Oxide short oil (safflower) oxidizing alkyd resin.
an emulsion of silicone resin ballmilled with an appropriate catalyst such as lead monoxide. benzoyl peroxide, or the like. hydrocarbonsolvent having a boiling range between 100 C and 120 C. Terpineol 20 gms. of
10 mls. of
10 mls. of
The above mixture is then ballmilled with dyes to obtain'the required photosensitivity as is known in the-art and diluted with:
40 mls. of hydrocarbon solvent having a boiling range between 100 C and 120 C.
10 mls. of Toluol l0 mls; of Terpineol 0.2 gms, of Cobalt Naphthenate used 0.8 gms. of Lead .Naphthenate as 1.6 gms. of Zirconium Octoate dryers This mixture is then applied to a substrate and cured.
' EXAMPLE 4 A 1,000 gms. of Zinc Oxide 415 gms. of Polyurethane Alkyd Resin 400 mlsv of Toluol 400 mlsv of hydrocarbon solvent having a boiling range between 100C and 120 C.
Dyes are added to obtain the required photosensitivity and the mixture is then ballmilled as in EXAM- PLE 1. it is then diluted with:
300 mls. of Toluene 300 mls. of hydrocarbon solvent having a boiling range between 100 C and 120 C. I 300 mls. of Chlorothene 3 grns. of suitable dryers such as Cobalt Naphthenate, Lead Naphthcnate and Zirconium Octoate.
The mixture is then coated on the substrate and cured as before. g
It will be observed that in the above examples the photoconductive'material which is coated on the drum or the belt substrate is compounded so that the photoconductive layer will have a reduced adhesion for the tacky toner.
Ordinarily, it is more desirable to be able to employ untreated paper as the copy sheet to which the tacky tonered imageis to be transferred. However, it is also contemplated by our invention that a paper treated to have special affinity for the tacky toner can be employed. For example, we have treated the paper with a solution of an acid maleic-modified vinyl chloride and vinyl acetate copolymer. The solvent is evaporated and it will be found that the paper thus treated has a special affinity for the tacky tonered image.
Another example of a coating for paper is a solution of a vinyl-toluene butadiene copolymer resin. These resins are available from the Goodyear Tire and Rubber Company and sold under the trademark PLlO- LITE. They are soluble and aliphatic solvents and films are formed by simple evaporation of the solvents. A paper coated with PLlOLlTE resin exhibits affinity for the tacky tonered image. Another example of a coated paper is one coated with a solution of polyvinyl butyral. This synthetic resin is dissolved in alcohol to form a 4% solution. It is then applied to the paper to form a thin continuous film. The affinity for the toner in each case of the paper coated with the examples given above was such that transfer took place from the photoconductive layer to the paper. It is of interest to note that the pressure to effect the transfer is very slight. As a matter of fact if too much pressure is used it was found that the transfer of the tonered image from the photoconductor to the paper was less effective.
It is not necessary that the developer deposit a toner in a tacky or sticky condition. The developer may be such that the tonered image is non-tacky at first then becomes tacky or adhesive so it can be transferred in a tacky state and then as the solvent evaporates, dries or cures and loses its stickiness and remains firmly bonded to the surface to which it was transferred.
According to our invention the adhesive toner comprises a relatively large amount of a high molecular weight polymer adapted to form a continuous pigmented polymer matrix exhibiting high cohesion and tackiness. In general, high molecular weight polymers are dissolved in a suitable solvent. The solution of the high molecular weight polymer is pigmented with a suitable pigment such as microlith black and the solution suspended in a lowpower solvent or diluent with the aid of a dispersing agent. The high molecular weight polymer may be one which has a low adhesion for the image forming surface and a high affinity for the copy surface. Alternatively the high molecular weight polymer may have low adhesion for both surfaces and a tackifier is combined with the polymer to create the high adhesion for the copy paper. The main characteristic of the high molecular weight polymer, however, is that it is generally insoluable in the diluent which we employ in making our developer fluid. The diluent which we prefer is that manufactured by the Standard Oil Company of New Jersey and sold under the trademark ISOPAR G. This is an isomerized paraffinic hydrocarbon having a specific gravity of .75 at 60 F. This product is substantially percent pure isoparaffm. It
has a boiling range from 157 C to 177 C. lSOPAR H" is a similar product and has a boiling range from 177 C to 188 C. This is disadvantageous in that it takes a longer period of time for the copies to dry. The feature which characterizes the diluent is that it has low solubility for the solution of the-high molecular weight polymer which is suspended throughout the diluent by a suitable dispersing agent. ISOPAR G has a kauributanol number of 27. This is true of ISOPAR E which has an initial boiling point of 116 C and a final boiling point of 143 C. lSOPAR E, however, is dangerous to use since it has a flash point of 50 F. The flash point of ISOPAR G" is F, and it is therefore a safe diluent. Because the tacky toner particles must migrate through the diluent under the influence of an electrostatic charge, the diluent must possess a low surface tension. ISOPAR is low in surface tension and high in interfacial tension. This accounts for its excellent demulsibility. Though other diluents which have low solvent power for the tacky toner organosol can be High Molecular Manufacturer Weight Resins Trademark Vinyl-toluene/acrylate Goodyear Tire PLIOLITE VTAC copolymer & Rubber Co.,
Akron. Ohio Styrene/acrylatc Goodyear Tire .PLIOLITE AC copolymer & Rubber Co.
Styrene copolymer Goodyear Tire PLIOLITE S-5A" Butadienc-styrene copolymer" Phillips Petroleum Co.
SOLPRENE" Solutions of this resin in solvents having kauri-butanol values of 36 and higher i dry rapidly to form tough. hard film with good adhesion. Furthermore, a solution of this resin will not dissolve in ISOPAR G" (which is one of our diluents] which has a kauri-butnnol number of 27,
" SOLPRENE 303" is a solution-polymerized copolymer in the ratio of 52/48 with partial block distribution of the styrene along the molecular chain. SOLPRENE I205 is a copolymer of butadiene and styrene in the ratio of 75/25 manufactured by the solution polymerization process.
These resins are readily soluble in hydrocarbon solvents having high kauri-butanol numbers of 50 or more. An appropriate solvent is the hydrocarbon solvent manufactured by Standard OilCompany of New Jersey and sold-under the-trademark SOLVESSO 100;" It'has an initial boiling point of 159C and a final boiling point or end point of 182 C. It consists'largely of aromatic hydrocarbons and has a kauri-butanol number of 9 l. It is to be understood that any appropriate solvent may be employed. However, since some of the solvent for the resin will be present in the developer solution, its end point should below.
As-is pointed out above, ISOPAR G'has' an end point of 177 C. SOLVESSO 100 has an endpoint of 182 C. SOLVESSO 150" could be used, if desired, but it has an end point of 212 C. The particular solvent is not critical as long as it is a solvent for the high molecular weight resin and can be evaporated at convenient temperatures from the final developer solution.
While the high molecular weight resins we employ exhibit tackiness upon drying, that is, when they are almost dry, it is desirable to increase the tackiness. This is done by adding aresinwhich has tacky properties to the solution of the high molecular polymer. The resin which is added for tackiness, as is the case with high molecular weight resins, must be soluble in the solvent for the high molecular weight resin and substantially insoluble in the diluent which is being used for the developerliquid.
We have found that appropriate tackifier resins are as follows:
Manufacturer Trademark 6 of hydrogenated rosin Theseprovide performance qualities comparable to those achieved by pure terpene resins. t
These polymers have iodine numbers of about 130. but the double bonds are structurally protected and not easily cross-linked or oxidized. They behave much like terpene resins and provide good wetting properties and adhesion to a wide variety of surfaces.
' The high molecular weight resins may be plasticized to render them tacky by modifying agents. These are:
Plasticizers for High Molecular Weight Resins Manufacturer Trademark Dibutyl phthalatc Celanese Corp. of America Celanese Corp. of America Dioctyl phthalate Dimetliyl phthalate Diethyl phthalate Di-isobutyl phthalate Di-iso-octyl phthalate Monsanto Chemi- "AROCLOR I254 Tricresyl phosphate Plastics Co.
I Some of the high molecular weight resins, such as PLIOLITE, VTAC,.' do not possess sufficient tackiness to effect complete transfer. We have seen that a tackifier resin may be added compatible with the high molecular weight resin to give the organosol the desired tackiness. This tackiness can be achieved by adding plasticizers to the high molecular weight resin. These plasticizers have the property ofimparting tackiness to the high molecular weight resin so that less or no tackifierresin may be employed.
In carrying out our invention, we first manufacture the organosol by dissolving a high molecular weight resin or amixture of high molecular weight resins in' an appropriate solvent.
EXAMPLE A The following formulation is prepared:
37.5 gms. PLIOLITE VTAC" 40.0 gms. "SOLPRENE 1205 100.0 gms. SOLVESSO As we have pointed out above, SOLVESSO 100 is an ideal solvent. Any other appropriate solvent such as tcrpineol can be employed. The above formulation is emulsified in a highspeed emulsifying mill, together with 1100 mls. of a diluent such as ISOPAR G. A quantity of this organosol is further diluted with ISO- PAR G to any desired extent to form a suspension. This suspension produces a tacky resin deposit on a negative polarity electrostatic surface charge.
The toner component is formulated'to be compatible with the resin organosol, since it must be physically attached to the resin developer aggregates or co-deposit at a rate in substantially the same proportion as the ratio of toner component to the organosol solids. If the toner component is not compatible with the organosol solution, it will act as a separate system and deposit at a greater rate than the organosol. This will pull the pigment out of the developer liquid, and the deposit will be predominantly pigment. This will result in low cohesion and poor transfer qualities.
The toner should have the same resin system as the organosol. 1n the example we are considering, the two resins used were PLIOLlTE VTAC" and SOLPRENE 1205." The pigment may be of any desired nature as, for example, carbon black, having a particle size on the average of 25 millimicrons. Any desired pigment may be used as, for example, reflex blue pigment with the carbon black. The pigment is advantageously coated with a modifying resin or a drying oil. A toner matching the organosol of this Example A is as follows:
100.0 gms. microlith black l2.5 gms. reflex blue 25.0 gms. PLIOLITE VTAC 25.0'gms. SOLPRENE 1205 Sufficient toluol was added to the above mixture to achieve the correct milling viscosity for milling in a triple-roll mill. After milling, the .mixturewas diluted with 600 mls. of lSOPAR G." This toner'is effective for negatively charged electrophotographic images.
The resin organosol and" the toner component are mixed in a high-speed emulsifying mill and the constituents milled together. The resin solutionprepared as described above was diluted with l 100 mls. ofISOPAR G" and milled for one minute. Then 120 mls. of the toner component were added and the mixture milled for three additional minutes. This concentrated adhesive toner was further diluted in a ratio of 50 mls. of toner to 200 mls. of ISOPAR G to produce a developer liquid. Adhesive or tacky toner in this developer liquid is readily deposited on a negative polarity surface charge. It will be understood that there is nothing critical in the method of mixing the components. The toner components may first be added to the mill with 1100 mls. of lSOPAR G" and then followed by mixing with the resin solution. Alternatively, the resin and the toner may be combined and then added to the mill with the diluent.
This adhesive toner developing liquid produced good image transfer between an organic photoconductor and an uncoated paper such as Velvet Book Opaque. It also produced good transfer between a zinc oxide resin photoconductor and a Velvet Book Opaque paper. A low density image was observed on the zinc oxide photoconductor after transfer. The photoconductive surface was a commercial zinc oxide photoconductor and not one of our special non-adhesive formulations as described above.
We then formulated another organosol component as follows:
EXAMPLE B 37.5 gms. PLIOLITE VTAC" 200 gms. BETAPRENE BC 100" which is a tackifler resin 100.0 gms. SOLVESSO 100" I The addition of the tackifier to the resin component and its incorporation into the developing fluid in the manner identical to that described above produced a developing fluid in which the image transfer from the organic photoconductor to the Velvet Book paper was less complete. On the other hand, when this toner was used with art paper, the transfer was more complete. it is to be understood, of course, that the photoconductors tested were not of the type of our invention having a low adhesion. When these toners were tested with photoconductors of our invention, the transfer of our tacky toner from the photoconductive surface to the paper was substantially'complete.
The amount of toner component combined with the organosol component changes the adhesive properties. With 120 mls. of toner component, optimum adhesive transfer properties were achieved. The toner component in the amount of 60 mls. produced a deposit of low optical density and there was greater sedimentation of the toner concentrate. A toner component of 240 mls. produced an optically dense deposit. The cohesion and adhesion were lowered with a resultant loss of transfer properties.
EXAMPLE C An organosol was formed as follows:
37.5 gms. SOLPRENE 303" 20.0 gms. PICCOLYTE ALPHA 10.0 gms. Polystyrene (melting point C; approximate molecular weight 400) 100.0 gms. SOLVESSO This resin mixture is milled in a high-speed emulsifying mill together with l 100 mls. of a diluent such as ISO- PAR G." This forms the resin solution or organosol.
The toner component matching the Example C organosol was made as follows: 200 gms. microlith black 25 gms. reflex blue 50 gms. PLIOLITE S-5D 75 gms. SOLPRENE 1205" These were placed in a triple-roll mill and sufficient toluol was added to dissolve the 'mix and produce good milling viscosity. The mix was then diluted with 1200 mls. of lSOPAR G" in a high-speed emulsifying-mill. The resin mix was added to l 100 mls. of ISOPAR G in a high-speed emulsifying mill, to which was then added mls. of the toner component Type C. This produced a developing liquid of our invention which exhibited low adhesion for both the organicand zinc oxide photoconductors and high adhesion for bond paper, Velvet Book paper, and art paper.
it will be observed that in each case the toner component is compatible with the organosol, so that the high molecular weight polymer nucleates or attaches to the toner component. In order to achieve this, the pigment must be wetted with a material which allows compatibility with the high molecular weight polymer. After the toner component is milled, it is tested for its electrophoretic properties. The tests varied depending on the type of pigment employed. Some tests showed that toner components deposit both on negatively and positively charged electrostatic surfaces. A toner component of this nature may still be useful, if it is combined with the organosol, since in this case the toner charge control is supplied by the high molecular weight resin.
An example of this follows:
EXAMPLE D An organosol was confected as before from the following:
37.5 gms. PLIOLITE VTAC 20.0 gms. BETAPRENE 80100 100.0 gms. SOLVESSO 100 I The matching toner component was made as follows:
' 50 gms. carbon black (particle size millimicrons) .50 gms. BETAPRENE BC-lOO" 25 gms. SOLVESSO 100" Cowles-dissolver. The solution was then-added to 1 100 mls. of ISOPAR G in a high-speed emulsifying mill and milled for three minutes.
The resultant-adhesive toner concentrate was diluted in the ratio of 50 mls. concentrate to 200 mls. of ISO- PAR G to produce an adhesive developing liquid. This adhesive developing liquid produced a deposit on negatively charged zinc oxide photoconductor which was then transferred completely to uncoated bond paper. This formulation is characterized by a high-yield electrophoreti c deposition on anegative polarity charged surface.'The pigment to resin ratio of this toner is approximately 1:6. i I
It will beseen that a high molecular weight polymer may form a solution which may be then suspended in a diluent having low solvent power. PLIOLITE VTAC" acting by itself exhibits good adhesion to most surfaces. We can modify the adhesive properties by using other high molecular weight polymers which in themselves have a lower adhesion for most surfaces. Adhesion can be increased by adding tackifier resins which impart additional adhesion to high molecular weight polymers. Plasticizers may be added to modify the adhesive properties, if such be desired.
The pigment component acts to reduce sedimentation of the toner concentrate. Our tacky toners generally comprise relatively large aggregates and consequently suffer greater sedimentation than liquid toners of the prior art. This, however, does not present practical problems as long as the sediment is flocculent, since such flocculent sediment is easily redispersed by mechanical agitationrlt is for this reason that we have shown an agitator in out developer tank.
It will be observed that, in general, we employ a high" molecular weight polymer which has a low adhesion forthe image-forming surface and a high adhesion for the copy surface. We add another high molecular weight polymer which acts as a dispersingagent to produce optimum resin deposit and the required electrostatic charge polarity. These resins in solution form an organosol. If the high molecular weight polymer does not have suff ciently high adhesion, we may add a tackifier or a plasticizer which creates a high adhesion for the copy paper. The resins and plasticizers which are chosen must be insoluble in the diluent which suspends the organosol and the toner formulation.
It will be seen that wehave accomplished the objects of our invention. We have provided a novel method of contact transfer of developed electrostatic images from the surface of a photocon'ductor to sheet material such as paper. Our novel method enables such contact transfer with a liquid developer to untreated paper. Our transfer method of a developed electrostatically formed image utilizes the tackiness of the toner and does not depend on an electrostatic field. We have provided a method of contact transfer of a liquid toner developed electrostatic image from a photoconductive surface to a copy sheet while maintaining the conductive surface in a clean condition. We have provided a liquid developer which has greater affinity for the copy paperthan the photoconductive surface on which the image was formed. We have provided a photoconductive surface which has less affinity for the developed electrostatic image than for the paper to which it is to be transferred. We have provided a novel developing sticky when first deposited, which becomes sticky or tacky after deposit, so that it can be transferred in its tacky condition, and which then loses its tackiness so that it remains firmly bonded to the surface to which it is transferred. We have provided a novel apparatus for carrying out our novel method. We have provided a novel sheet material having a special affinity for a tacky toner developed image.
It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope-of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.
Having thus described our invention, what we claim is:
1. In an electrophotographic apparatus a conductive carrier, a photoconductive surface supported by said carrier, means for charging said photoconductive surface, means for exposing said charged surface to a pattern of light and shade of an image to be reproduced to I ductive surface to transfer the developed image thereto, and means for heating said sheet material before said sheet material arrives at the contacting means.
2. Apparatus as in claim 1 in which said means for heating said sheet material is positioned to direct heat against the rear of said sheet material.-
' 6. Apparatus as in claim 1 including means for heating said transferred image on said sheet material to fix the same thereto.
7. Apparatus as in claim 1 in which said photoconductive surface has less affinity for the tacky image than said sheet material.
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