US3792964A - Electrostatic imaging system and apparatus therefor - Google Patents

Abstract

A copying machine having means for producing a fusible toner image on a copy substrate, includes a radiant energy light source (e.g., iodine quartz lamp) mounted to direct part of its rays onto the object that is to be copied to illuminate the latter, and part onto the surface of a rotating receiver roll to heat the surface thereof approximately to the fusing temperature of the toner. The copy substrate is passed beneath the receiver roll tangentially thereof by a transport which causes the toner image to engage the heated receiver surface with a minimal amount of pressure so that the toner is fused and fixed to the substrate. Various release agents may be applied to the roll surface to enhance fixing of the image.

Description

United States Patent [1 1 Chatter'i [4 1 Feb. 19,1974

'[22] Filed:

l l ELECTROSTATIC IMAGING SYSTEM AND APPARATUS THEREFOR [76] Inventor: Arun K. Chutterjl, 100 Kittelberger Pk., Webster, NY. 14580 June 5, 1972 [21] Appl. No.: 259,953

Primary Examiner-John J. Camby Attorney, Agent, or Firm-Shlesinger, Fitzsimmons &

Shlesinger w i 57 I ABSTRACT A copying machine having means for producing a fusible toner image on a copy substrate, includes a radiant energy light source (e.g., iodine quartz lamp) mounted to direct part of its rays onto the object that is to be copied to illuminate the latter, and part onto the surface of a rotating receiver roll to heat the surface thereof approximately to the fusing temperature of the toner. The copy substrate is passed beneath the receiver roll tangentially thereof by a transport which causes the toner image to engage the heated receiver surface with a minimal amount of pressure so that the toner is fused and fixed to the substrate. Various release agents may be applied to the roll surface to enhance fixing of the image.

9 Claims, 3 Drawing Figures ELECTROSTATIC IMAGING SYSTEM AND APPARATUS THEREFOR This invention relates to an electrostatic imaging system, and more particularly to improved process and apparatus for fixing the toner image developed by electrostatic copy processes and the like.

Many known copying systems such as for example, electrophotography, adherography, chemical copying including encapsulated imaging systems, etc. involve the basic steps of producing a latent image on a light sensitive surface or the like; developing a corresponding visible image on a reusable photoconductor or a copy substrate (paper, etc.) by using, for example, a developer containing a toner of either electroscopic or non-electrical attributes, for forming the final visible image on the copy substrate; and then fixing the toner image on the substrate. The step of producing latent image in systems of the type described, generally dictates that the associated machine or apparatus contain a light source and lens system for focusing an image of the matter that is to be copied onto the surface that is to develop the corresponding latent image. The subsequent developing, transferring and fixing steps for the visible image may be performed either as a batch or continuous operation.

Heretofore the fixing step has been achieved in different ways, for example through the use of solvent, vapor, heat, pressure, or combinations thereof, depending, in most cases, on the type of developer employed. The disadvantage of machines employing solvent and /or vapors for fixing purposes is that the air in the vicinity of the machine very often becomes polluted by excess of unused vapors developed by the machine; and if these vapors are inflammable, the threat of fire is increased unnecessarily. For these and other reasons it is now preferable, generally speaking, to use systems which rely upon heat, or a combination of heat and pressure, to fuse or fix a toner image.

The use of heat alone has been employed in various non-contact fusing systems in which the heat source remains spaced from, and does not actually contact the toner at the time that it fixes or fuses the toner to the substrate. Generally this method relies upon convection currents of air (sometimes forced) to transfer heat from a source thereof across the space separating the heat source from the toner image. Due to unavoidable loss of heat during this convective heat transfer operation, the total power requirement of the machine, as represented by the quantity of heat developed at the heat source, is substantially higher than the quantity of heat actually used to fix the image. A further disadvantage has been the difficulty in achieving consistently reliable coalescence of the toner particles in the image. One reason for this is that although the coalescence is effected by the properties of the toner itself, as well as the surface to which it is to be fixed, perhaps the most important factor is the thermal flux, or consistency of heat transfer between the heat source and the toner image. In this non-contact method, however, the existence of the air layer between the heat source and the image makes it extremely difficult efficiently to control this thermal flux, and consequently also makes it difficult to control proper coalescence of the toner particles.

Another heat fusing method of the non-contact variety heretofore employed has involved the use of a radiant energy source to fix a toner image by radiant heat, rather than through a convective heat transfer operation. Prior such radiant heat transfer operations, however, have not been satisfactory since they have also resulted generally in much higher power requirements than needed to produce the heat actually employed to fix an image, and have also had the problem of inefficient or faulty toner coalescence.

It is known that coalescence of toner particles in a heat fixing process can be improved by application of pressure to the heat toner image, which also enables the temperature of the process to be reduced, as com pared to the non-contact, heat-only method. However, what has been overlooked heretofore is that the glass transition temperature of a polymer, which is a basic component of typical electrostatic process toner, is increased by the application of pressure. Thus fixing systems employing both heat and pressure are little more efficient than the heat-only systems, since any power saved through reduction in the fixing temperature ambient is exhausted in generating the necessary pressure required by the operation. Moreover, with such systems undesirable change in texture of the image bearing substrate also results from the application of too much pressure.

In an effort to increase the rate of image fixing or toner coalescence without increasing the power input, it has been customary heretofore also to employ special or low melting toners. This, however, often results in undesirable offsetting and consequent blurring of the image. Also, undesirable caking or blocking of tiner in the dispenser units or toner containers during transport from one place to another is apt to occur. Further contributing to the high power input per copy, or fixed image output, in prior such devices has been the necessity heretofore to employ, particularly in the case of images fixed by heat fusing operation, one light source for supplying the illumination necessary for the development stage of the latent image, and a separate light or heat source for use in the toner image fusing or fixing stage of the system.

It is an object of this invention to provide an improved copying process in which a toner image is developed and fused on a copy substrate more rapidly and with less power consumption than heretofore was possible.

Another object of this invention is to provide novel copying apparatus that employs a single energy source for providing both the light for developing the latent image, and energy for the toner image fixing stage of the apparatus.

A further object of this invention is to provide improved copying apparatus of the type described that operates more rapidly and with less power consumption per copy than prior such apparatus.

Still another object of this invention is to provide a novel method of employing radiant energy for fixing a toner image on a copy substrate or the like.

Still another object of this invention is to provide an improved copying system in which the image fixing rate can be selected for low, moderate and high speed operation to integrate the fixing stage of the process with copy subsystem such as, for example, duplicators, online printers, etc.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawing.

In the drawing:

FIG. 1 is a schematic side elevation view of a machine made in accordance with one embodiment of this invention for practicing the electrostatic imaging process disclosed herein;

FIG. 2 is an enlarged fragmentary elevational view taken at right angles to the view in FIG. 1, and illustrating fragmentarily and schematically the discharge sides of the receiver roll and associated transport mechanism which form part of the image fixing system in this machine; and

FIG. 3 is a wiring diagram illustrating one manner in which the paper jam control circuit in the machine may be wired for operation.

Referring now to the drawing by numerals of reference, denotes generally a copying machine of the electrostatic variety comprising a document supporting platen 12, which may be made in known manner, from non-glare glass, or the like. Mounted beneath platen 12 are one or more collimating lenses 13 for directing light through the platen 12 to the document thereon as noted herafter. A copy lens 14, which is mounted beneath the platen 12, is used to direct an image of the document onto the periphery of a photoreceptor drum 16, which is mounted to rotate beneath lens 14 in the direction indicated by arrow 17, and which is coated in the usual manner around its periphery with a lightsensitive photoconductor such as, for example, selenium or an alloy thereof.

Mounted adjacent drum 16 and the portion of its periphery that registers with lens 14 is a conventional charging corona unit 20, which may be controlled by logic circuitry (not illustrated) contained in a nearby unit 21. Mounted adjacent drum 16 in advance of the corona unit 20 is the usual cleaning subsystem 22; and adjacent this is the usual cleaning corona 24. Units 22 and 24 can also be controlled by circuitry in logic unit 21.

Mounted adjacent drum 16 at its side remote from units 20, 22 and 24 to apply developer to the drum face after the latent document image has been produced thereon, is the development subsystem 26. This system operates in known manner to apply an electroscopic developer, which comprises carrier particles and toner particles, to the latent image on drum 16. The toner image thus formed is then transported by drum 16 over a paper substrate, which is fed from a paper supply 28 by conventional paper transports 30 and 31 beneath drum l6 and over a transfer corona 32, which is mounted in the usual manner beneath drum 16 to effect transfer of the toner image from the drum to the upper surface of the paper substrate. A transport 33 then conveys the toner image-bearing substrate into the image fixing subsystem of the machine.

This image fixing stage or subsystem comprises a rotating cylinder or receiver roll 40 (FIGS. 1 and 2), which is mounted in the machine to be rotated about a stationary axis beneath a radiant energy source defined by a pair of lamps 41. Roll 40 is designed to be rotated selectively at desired speeds of from about less than one rpm to about 100 rpm by an electric dipole motor 42 (FIG. 2), or the like, which has its armature drivingly connected to roll 40 as by a belt 43 (FIG. 2). The outer peripheral surface of the receiver roll 40 should have a relatively high reflectivity factor, for example, at least about 0.2 and preferably about 0.6 or higher, when the radiant energy source 41 is located externally of the receiver roll as in the illustrated embodiment; and the transmissivity of its outer peripheral surface should be less than about 0.5. This prevents undesirable heat dissipation from the outside to the inside of the roll. In the event that the radiant energy source or emitter, on the other hand, is placed within the receiver roll, the transmissivity of the receiver surface facing the radiant energy source or emitter should be relatively high, for example, at least about 0.5 and preferably about 0.6 or higher. In all cases the receiver roll should be manufactured from a material that will have satisfactory thermal stability at the operating temperature of the fixing subsystem of the copier for example, aluminum, nickel, platinum, carbon steel, stainless steel, copper and the like, sintered glass, glazed ceramic, polysulfones, glass bonded mica and the like, polyarnides, glass fiber or asbestos filled phenol formaldehyde, glass filled nylons, reinforced fluroplastics, regular and filled polyphenylenes, flexible and filled silicones, etc.

The radiant energy emitters or lamps 41 should be capable of emitting light having wave lengths of from about 0.3 microns to about 10 microns. Typically the lamps may be of the iodine quartz variety, orany other capable of emitting light in the range of the abovenoted wave lengths. Mounted on the machine at the side of the lamps remote from the receiver roll 40 is a reflector 45 (FIG. 1), which partially circumscribes the lamps to reflect radiant energy therefrom back toward the receiver roll 40. The reflector 45 is intended to minimize the loss of radiation to areas other than the receiver surface, and for this reason may have any configuration suitable for this purpose. The operating surface ofa reflector should have a high factor of reflectivity; and it has been found that surfaces such as enamel, porcelain, aluminum, and the like may be employed for this purpose.

A bundle 46 of fiber optics comprising glass or plastic materials (FIG. 1) is mounted at one end in the reflector 45 and at its opposite end in a further reflector 48, which is mounted adjacent one of the collimating lenses 13. These fibers have highly polished ends embedded in an array in a molded plastic circumscribed by reflector 48, and function as a light pipe to convey or transmit light from the lamps 41 to the registering lens 13, thereby to provide the illumination necessary to project onto drum 16 an image of the document on platen 12. If both lenses 13 are employed, a second pipe 46' and illuminator unit 48 are employed to direct light through this second lens 13 onto the platen as shown in FIG. 1.

Preferably the fiber optic bundle 46 is conveniently assembled in a hard-pack arrangement, meaning that the fiber optic bundle is constructed so that cladding fills its voids. To avoid any imperfections at the illuminating end due to the discontinuities created bythe cladding material, it is preferable to allow some deliberate cross talk, which means leakage of light from one fiber to another. Typically a light pipe of the type described may comprise Fiberscope, made by American Optical Co., and consisting of a focusing objective with a length of armored, coherent fiber image bundle connecting it to an eye piece at the other end; or a Magnifiber consisting of a coherent, tapered fiber bundle; or similar such products.

During use it is generally desirable to apply an additive or release agent to the outer periphery of the rotating receiver roll 40 to prevent toner from sticking to the receiver surface, and otherwise to help fix the toner to the substrate. Mounted for this purpose in the frame adjacent one side of the receiver roll 40 is a container or reservoir 50 having, for example, an arcuate applying surface that extends longitudinally of roll 40 for applying thereto a chemical additive or release agent. This additive may be in the form of certain waxes, polymers, commercial slip agents, metal salts of long chain fatty acids and/or mixtures thereof. The release agent may be dispensed in a conventional manner from the illustrated reservoir 50 onto the surface of the rotating receiver roll; or it may be applied in any suitable manner such as, for example, by a sponge, blade, wick, etc. when it is liquid form. If the release agent initially is in a solid state, it may be necessary to melt it before applying it to the roll; or it could be packed, for example, in a porous tube the pores of which are disposed in closely spaced, confronting relation to the receiver surface, so that upon the application of heat from, for example, the radiant energy emitters 41 or receiver roll 40 to the porous tube, the release agent will become molten and flow through the pores onto the surface of the rotating roll.

Rotatably mounted coaxially of each other in a stationary transport frame 52 beneath the receiver roll 40 are a plurality of axially spaced, steel discs 53. Secured around the periphery of each disc 53 coaxially thereof is a neoprene ring 54, which has rolling, very light, tangential engagement with the underside of the receiver roll 40 frictionally to be driven thereby, when the receiver roll is rotated. After transfer of a toner image on a paper substrate, or the like, the substrate is fed by transport 33, toner side up, into the nips between the rings 54 and receiver roll 40 to be advanced thereby beneath roll 40, and into the nip of the discharge transport 56. During this operation the heated surface of the roll 40 fixes the image to the substrate. However, this image fixing operation takes place, in essence, without the application of any pressure on the toner image at the time that the latter contacts the heated roll 40. The reason for this is that the rings 54 barely engage roll 40 for example, only with enough pressure to insure that a substrate passing between roll 40 and rings 54 will be gripped thereby and transported beneath the roll to its discharge side.

Mounted on frame 52 adjacent the substrate entrance and discharge sides, respectively, of the roll 40 are two sets of microswitches S1 and S2, whic have operating arms positioned beneath the plane in which the paper substrate normally travels during its advance beneath roll 40.

As shown schematically in FIG. 3, switches S1 are connected in parallel with each other, and in series with a time delay relay TDl between the power lines L1 and L2, which supply AC power to the machine when the main switch 60 is closed. Relay TDl controls a set of normally-open, time-delayed-closing contacts TDl-l that are connected in series with switches S2 and the operating coil of a relay cCR2 between L1 and L2. The switches S2 are connected in series with each other between switch TDl-l and relay CR2. Relay CR2 controls normally closed contacts CR2-1, which are connected between L1 and L2 through the forward" operating coil of motor 42, and the normally open contacts, which are connected between L1 and L2 through the reverse operating coil of motor 42. Another time delay relay TD2 is connected in series with CR2-2 between L1 and L2, and controls a normally open, time-delayed-closing switch TD2-1 that is in series with a power disconnect solenoid 61 between L1 and L2..

As a substrate is fed into the nip beneath roll 40 it closes switches S1 and energizes relay TDl. If the substrate emerges at the discharge side of roll 40 before contacts TDl-l close, it will open one or both of switches 52 to prevent energization of relay CR2. If, however,.a substrate jams and begins to pile up at the entrance side of roll 40, and consequently does not pass through the nip to close one of the switches S2 before contacts TDl-l close (e.g., within a few seconds), then CR2 will be energized to open contacts CR2-1 and close contacts CR2-2 thereby to reverse the rotation of motor 42. This causes roll 40 to rotate in a reverse direction so that it tends positively to back up or unjam the loaded substrate. The closing of switch CR2-2 also energizes the time delay relay TD2, which, within a few seconds after the rotation of roll 42 has been reversed, energizes solenoid 61, which is used to operate any conventional power interrupting means (not illustrated) for the machine.

After passing beneath roll 40, a substrate may be fed by transport 56 to a conventional sorter and bin 58 in known manner. For duplication purposes the machine may also include logic controls 60and a duplex station 61 which form no part of this invention.

To maintain the necessary image fixing temperature, a temperature controller of any desired design (not illustrated) is employed selectively to energize the emitter lamps 41, so as to maintain a desirable temperature at the nip formed between the receiver 40 and the paper transport, as defined by the neoprene rings 54.

This controller includes a thermocouple (not illustrated), which is mounted adjacent the outer surface of the receiver roll 40 to detect its temperature, and to effect deenergization of lamps 41 whenever the surface temperature of the roll exceeds a predetermined value, and to reene'rgize the lamps when this temperature falls below a predetermined value.

Tests have indicated that, for rates of from anywhere from one to one hundred copies per minute, a toner image can be completely and satisfactorily fixed or fused upon a single pass of a substrate beneath the heated receiver roll 40. For example, a source of radiant energy comprising at least one iodine-quartz lamp and its associated reflector were mounted above a receiver roll comprising a solid aluminum cylinder having reflectivity of about 0.6. The aluminum roll was driven by a l/20th horsepower dipole motor having a rated torque of one foot pound. The thermocouple forming part of the temperature controller maintained the receiver surface within approximately plus or minus five degrees of 362 Fahrenheit. A thin film of a fluorcarbon lubricant dispersed in light oil, for example thetype sold by Pennwalt Corporation under the trademark Whitcon 50", was applied to the outer surface of the receiver roll; and a conventional toner comprising a copolymer of polystyrene and n-butyl methacrylate and carbon black was used in the developer. Even after continuous rotation of the receiver roll and operation of the emitter lamp for approximately one hour, the surface temperature of the receiver adjacent the nips still registered approximately 360 Fahrenheit. During this interval, when no image was being fixed the lamp was energized only about 60 per cent of the time, as opposed to 90 per cent when images were being fixed. Further tests indicated that, when the receiver roll was set to rotate at lower speed (fewer copies) the temperature controller could be adjusted to lower the receiver temperature required (at the nips) to effect satisfactory fixing of the toner images. Similarly, when a toner having a lower melting temperature was employed, the amount of radiant energy emitted by the lamp could be lowered through adjustment of the temperature controller without inhibiting the fixing operation.

In addition to Whitcon 50, the following materials were found to produce excellent results when used as a release agent on roll 40: a fluoropolymer lubricant; a non-silicone aerosol spray sold by Gilbralter Industries, Inc. under the trademark Surfak; an N, N-ethylene bis-stearamide made by Cincinnati Milacron of New Brunswick, New -lersey; and a fatty acid ester sold by the s ame company under the trademark A d vawax 146. i

The toner particles used with this invention usually comprise a coloring pigment or dye selected to a suit a desired color of the resultant image, together with one or more thermoplastic resin binder materials for imaging polymers such as, for example, polystyrene, poly-n-butyl methacrylate, poly-i-butyl methacrylate, polyvinyl butyral, epoxy resins, amide resins, polymeric esterification products of polyols and dicarboxylic acids and/or diols and dicarboxylic acids, and the like. The coloring pigment or dye is present in the amount of approximately 7 percent, by weight, of the imaging polymer.

From the foregoing it will be apparent that the instant invention permits substantial reduction in power requirements per copy for copying machines using electroscopic toners of the type described. The use of a radiant energy emitter, in combination with a transport which conveys a toner image into substantially pressureless contact with a heated fixing roll, obviates much of the power heretofore wasted in machines of the type in which the fixing roll was heated inductively or convectionally, or in which both heat and pressure were employed in the fixing operation to improve coalescence of the toner particles. As previously noted, toners of the type described comprise a very high proportion by weight of polymeric, resins, the glass transition temperatures of which are raised by the application of pressure, so that in effect, fixing processes which rely upon heat and pressure are partially selfdefeating. For this reason the neoprene rings that transport the toner-coated substrate beneath the receiving roll 40 of this invention, are barely in contact with this roll, so that they do not apply any significant pressure to the substrates advanced thereby beneath the roll during the fixing operation.

Having thus described my invention, what I claim is:

1. Copying apparatus of the type in which a heat fusible toner image is produced on the surface of a copy substrate, including a rotatable receiver,

means for transporting a substrate with a toner image thereon tangentially past a curved surface on said receiver to cause substantially pressureless contact between said toner image and said curved surface, and

a radiant energy emitter mounted adjacent said receiver to direct radiant energy onto said curved surface to heat the latter sufficiently to effect fusion of said toner upon contact thereof with said curved surface.

2. Copying apparatus as defined in claim 1, wherein said emitter produces light having wave lengths of from about 0.3 microns to about 10 microns, and said curved surface has a reflectivity of at least ap proximately 0.2 and preferably 0.6 or hgher.

3. Copying apparatus as defined in claim 2, wherein said curved surface has a transmissivity of less than 0.5.

4. Copying apparatus as defined in claim 1, wherein said receiver is a cylinder,

means is provided for rotating said cylinder about its axis, and said transporting means comprises resilient means having rolling engagement with said cylinder substantially tangentially thereof, and with just enough pressure to cause the rotation of said cylinder to be transmitted to said resilient means. 5. Copying apparatus as defined in claim 4, wherein said resilient means comprises a plurality of resilient rings mounted to rotate about a common axis adjacent said cylinder, and having the peripheral surfaces thereof-disposed in rolling engagement with the periphery of said cylinder at axially spaced points therealong. 6. Copying apparatus as defined in claim 4, wherein said rotating means comprises a reversible electric motor drivingly connected to said cylinder, and

switch means is positioned adjacent said nip to be responsive to a substrate jam at said nip to reverse the direction of rotation of said motor.

7. Copying apparatus as defined in claim 1, including a support,

means for projecting an image of an object on said support onto an adjacent, light-sensitive surface to form thereon a latent image of the object, when said object is illuminated, and

means for transmitting part of the energy from said emitter onto said support to illuminate the object thereon.

8. Copying apparatus as defined in claim 7, said light transmitting means comprises a bundle of fiber optics having one end facing said emitter, and its opposite end facing said support and the object thereon.

9. Copying apparatus as defined in claim 2, wherein said emitter comprises at least one iodine quartz lamp mounted in spaced confronting relation with said curved surface on said receiver.

Claims (9)

1. Copying apparatus of the type in which a heat fusible toner image is produced on the surface of a copy substrate, including a rotatable receiver, means for transporting a substrate with a toner image thereon tangentially past a curved surface on said receiver to cause substantially pressureless contact between said toner image and said curved surface, and a radiant energy emitter mounted adjacent said receiver to direct radiant energy onto said curved surface to heat the latter sufficiently to effect fusion of said toner upon contact thereof with said curved surface.

2. Copying apparatus as defined in claim 1, wherein said emitter produces light having wave lengths of from about 0.3 microns to about 10 microns, and said curved surface has a reflectivity of at least approximately 0.2 and preferably 0.6 or higher.

3. Copying apparatus as defined in claim 2, wherein said curved surface has a transmissivity of less than 0.5.

4. Copying apparatus as defined in claim 1, wherein said receiver is a cylinder, means is provided for rotating said cylinder about its axis, and said transporting means comprises resilient means having rolling engagement with said cylinder substantially tangentially thereof, and with just enough pressure to cause the rotation of said cylinder to be transmitted to said resilient means.

5. Copying apparatus as defined in claim 4, wherein said resilient means comprises a plurality of resilient rings mounted to rotate about a common axis adjacent said cylinder, and having the peripheral surfaces thereof disposed in rolling engagement with the periphery of said cylinder at axially spaced points therealong.

6. Copying apparatus as defined in claim 4, wherein said rotating means comprises a reversible electric motor drivingly connected to said cylinder, and switch means is positioned adjacent said nip to be responsive to a substrate jam at said nip to reverse the direction of rotation of said motor.

7. Copying apparatus as defined in claim 1, including a support, means for projecting an image of an object on said support onto an adjacent, light-sensitive surface to form thereon a latent image of the object, when said object is illuminated, and means for transmitting part of the energy from said emitter onto said support to illuminate the object thereon.

8. Copying apparatus as defined in claim 7, said light transmitting means comprises a bundle of fiber optics having one end facing said emitter, and its opposite end facing said support and the object thereon.

9. Copying apparatus as defined in claim 2, wherein said emitter comprises at least one iodine quartz lamp mounted in spaced confronting relation with said curved surface on said receiver.

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