US3795443A

US3795443A - Xerographic development

Info

Publication number: US3795443A
Application number: US00755461A
Authority: US
Inventors: Geldern R Heine; A Amidon
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1968-08-26
Filing date: 1968-08-26
Publication date: 1974-03-05
Anticipated expiration: 1991-03-05

Abstract

A method and apparatus for developing an electrostatic charge pattern with an ultrasonically generated uncharged droplet mist. The apparatus comprises an ultrasonic transducer which is energized from a power source and which has the capability of generating uncharged droplet mist particles from a liquid material. The droplet mist so created is brought into contact with the electrostatic charge pattern to effect its development without regard to image or charge polarity.

Description

United States Patent 1191 Heine-Geldern et al.

[ XEROGRAPHIC DEVELOPMENT [75] Inventors: Robert V. Heine-Geldern, Pittsford;

Alan B. Amidon, Penfield, both of NY.

[73] Assignee: Xerox Corporation, Rochester, NY.

22 Filed: Aug. 26, 1968 21 Appl. No.: 755,461

52 us. 01. 355/10 51 161.131 ..G03g 13/10 581 Field 61 Search...; 95/ 13; 355/3, 10, 16, 17

[56] References Cited UNITED STATES PATENTS 2,690,394 9/1954 Carlson ..355/1O 3,165,299 1/1965 Balamuth 259/1 3,166,418 1/1965 Gundlach..... 355/17 X 3,166,420 1/1965 Clark 355/17 X 36 I POWER SUPPLY 1 51 Mar. 5, 1974 3,178,281 4/1965 Jaruis 96/12 FOREIGN PATENTS OR APPLICATIONS 1,107,746 3/1968 Great Britain 355/10 Primary Examiner John M. Horan Assistant ExaminerT. Mauro [5 7 ABSTRACT 11 Claims, 4 Drawing Figures POWER SUPPLY POWER SUPPLY PAIENTEUMAR 51914 3.195.443 SHEET 1 BF 2 POWER a POWER SUPPLY SUPPLY POWER N SUPPLY 22 POWER SUPPLY INVENTORS ROBERT V. HElNE-GELDERN ALAN B. AMIDON BY A M A T TORNE VS s msms PAIENTEUHAR 51974 SHEEF 2 if 2 IN VENTORS ElNE-GELDERN AMIDON FiG.

POWER SUPPLY POWER SUPPLY ATTORNEYS XEROGRAPHIC DEVELOPMENT This invention relates to method and apparatus for developing xerographic images and particularly, to the development of such images by means of ultrasonically generated liquid mists.

In the process of xerography, for example, as disclosed in Carlson U.S. Pat. No. 2,297,691, issued Oct. 6, I942, a xerographic plate comprising a layer of photoconductive insulating material on a conductive backing is given a uniform electric charge over its surface and is then exposed to the subject matter to be reproduced, usually by conventional projection techniques. This exposure discharges the plate areas in accordance with the radiation intensity that reaches them, and thereby creates an electrostatic latent image on or in the photoconductive layer. Development of the latent image is usually effected with an electrostatically charged, finely-divided material such as an electroscopic powder that is brought into surface contact with the photoconductive layer and is held thereon electrostatically in a pattern corresponding to the electrostatic latent image. Thereafter, the developed xerographic image is usually transferred to a support surface to which it may be affixed by any suitable means. Where the xerographic plate comprises a consumable material as is known in the art, the developed image may be affixed directly thereto without the necessity of transfer.

Various development systems are known in the art including cascade, powder cloud, liquid, magnetic, brush and the like, each of which employ large quantities of electroscopic powder particles that are preferentially charged in transport to one polarity or the other for presentation to the electrostatic latent image. Each of these prior development systems are characterized in that large masses of material are continuously transported to effect charging of the individual powder particles and to present the charged particles to the latent image. In any practical apparatus embodiment, it has therefore been necessary to provide equipment for material transport. In addition, because of associated dust generation, it has been necessary to design and extend the equipment whereby to closely contain the dust as to prevent its escape and otherwise contaminate the apparatus with which it is being employed. At the same time, these prior systems in order to triboelectrically charge the powder particles, have inherently required some form of positive charging mechanism associated therewith, e. g. the cascade system utilizes carrier beads for triboelectric charging and which serve also for the purpose of transporting the charged particles into contact with the image surface.

Now in accordance with the instant invention, it has been discovered that some liquids, generally, but not always, characterized as being electrically conductive, when ultrasonically generated into a fine mist in the vicinity of an electrostatic charge pattern, will deposit an image selectively on that pattern to effect its development. By chemically coloring the liquid, as by dyes, the selective deposition produces an image reproduction which optionally can subsequently be transferred from or fixed directly on the image bearing surface. The mists so generated have been found to be characterized by general immobility and relative, although not complete, stagnation as to make unnecessary the use of complex apparatus for effecting its containment. At the same time, the development by this means is effected without the necessity of external charging mechanisms and without utilizing a carrier or transport mechanism. In fact, the particles so generated are generally considered to be uncharged in that at most only insignificant charges have been detected while the mist has been found to deposit ona latent image without preferential regard to the image polarity. In addition, whereas such prior systems generally experience difficulty in developing solid areas without the benefit of external control means such as a development electrode, it has been found that the ultrasonically generated mists of the invention hereof tend to deposit in solid areas with equal facility to line copy without the benefit of external controls.

It is therefore an object of the invention to provide novel method and apparatus for developing xerographic latent images.

It is a further object of the invention to provide novel method and apparatus in which ultrasonically generated liquid mists are effective for developing xerographic latent images.

These and other objects as well as the various features, advantages and limitations of the invention will become apparent from the following description and drawings, in which:

FIGS. 1, 2 and 3 exemplify different apparatus embodiments for effecting development in accordance with the invention hereof; and,

FIG. 4 is an optional apparatus variation as may be incorporated into the other apparatus embodiments hereof.

Referring first to FIG. 1, there is shown a continuous xerographic plate 10 which may be of the consumable type, e. g. well-known forms of Zinc oxide in a suitable binder, and advanced continuously-from a supply roll 11 over suitable guide rolls l2 and 13 and onto a takeup roll M being driven continuously by means of motor 15. As the plate advances from the supply roll, it is first uniformly charged by means of a corona discharge device 20 having an electrode 21 connected to a potential source 22 which provides a potential above corona threshold for the electrode 21.

The uniformly charged xerographic plate is advanced to an exposure station designated 25 whereat an optical image of a copy sheet 26 is illuminated by lamps LMP-l and LMP-2 and imaged by means of objective lens 27 to selectively discharge the xerographic plate in the areas subjected to illumination. Slit exposure methods can be incorporated in order to expose the xerographic plate during its continuous advance or optionally full frame exposure can be employed by momentarily interrupting movement of the xerographic plate. To prevent or minimize developer retention in the nonimage areas, these areas should preferably be discharged to a maximum.

Following exposure the xerographic plate is ad'- vanced until the latent image formed on exposure passes a development zone designated 30, as will be described below, whereat an ultrasonically generated liquid mist deposits or adheres selectively in the charged areas of the image to effect its development. Some additional wetting of the surface may occur and can subsequently be removed. After development, the xerographic plate advances past a fusing station 31 whereat the liquid deposited on the plate surface is subjected to an over heater 32 that is effective to dry the liquid image before its windup onto takeup roll 14.

For effecting the mist generating vibrations at development zone 30 there is provided an ultrasonic transducer 35 of a type commercially available and energized from a power source 36. Secured to the horn tip 37 of the transducer extending generally perpendicular to the axis thereof is a mist generating flat plate 38. Liquid developer 40, as will be described below, is contained in a generally open container 41 having an orifice outlet connection 42 to which is connected a length of conduit 43 which terminates in a nozzle 44 angularly disposed to the surface of plate 38. Container 41 maintains a sufficient head above the nozzle for ensuring a constant flow through the conduit and to effect discharge from the nozzle against the vibrating surface of plate 38.

The ultrasonic vibrations are transmitted to plate 38 and are effective in breaking up the liquid stream striking the surface of plate 38 into fine droplets in a manner to generate a fog or mist in close proximity thereto. It has been found that when the liquid is broken up into mist droplets sizes generally in the range of up to 200 microns that these droplets will generally deposit selectively on the charged areas of xerographic plate 10. Droplet size varies with the generator frequency such that higher frequencies produce the smaller size. With constant vibration generated from the transducer 35 it has been noticed that the mist generated is relatively stagnant with very little dropout. In order to collect miscellaneous or stray droplets which inadvertently drop out, or at shutdown, there is provided a receiver 45 supported generally below the mist area and which is effective in collecting dropoff therefrom.

Referring now to FIG. 2, the xerographic plate is similarly processed for charging, exposing, and fusing in a manner described above with reference to FIG. 1. At the development zone 30, a quantity of liquid 50, from which the mist is to be generated, is contained in an open container 51. An ultrasonic generator 52 is supported with its horn tip 53 extending upward through a sealing gasket 54 into the liquid body and below the top surface thereof. With the generator energized and its horn tip supported extending to within approximately one-fourth inch below the liquid surface, generally about one thirty-second inch to one-sixteenth inch, a mist is generated generally in the form of an inverted elliptic paraboloid. Under the appropriate operating conditions, affecting droplet size as aforesaid, reproductions were obtained with the mist depositing selectively in the charged image areas of the xerographic plate 10.

While the xerographic plates of the above described embodiments have been considered on the basis of consumable materials comprising xerographic plate 10, rendering unnecessary the requirement to transfer the developed image, it should be apparent that such a transfer can be effected as will now be described in connection with FIG. 3. This embodiment employs a xerographic plate in the form of a cylindrical drum mounted for rotation via motor 59 and comprising a photoconductive insulating layer 60, such as vitreous selenium or the like, on a conductive substrate 61 such as aluminum. brass or other known conductive materials. The apparatus is shown adapted for slit exposure in which an original image, such as microfilm 65 illuminated by lamp LMP-3 and advanced via a motor 66 for projection by objective lens 67 through a slit aperture 68. The latent image is developed similarly as in FIG.

l or 2 above after which the drum advances the developed image through a transfer station designated 70. Transfer is effected onto an absorbent web type support surface, such as an absorbent paper 71, drawn from a supply roll 72 and urged against the imagebearing drum surface as it passes about resilient roller 73. After transfer, the image-bearing web 71 is passed through a heating unit 74 which dries the image for effecting its permanent formation after which the web is wound onto take up roll 75. With certain developer compositions such as solvent type inks, heating unit 74 may not be required.

Following transfer, the xerographic drum is wiped clean by means of a felt cotton fabric drawn from a supply roll 81 over guide rolls 82 and 83 to pass in wiping contact against the drum surface before being wound onto take up roll 84.

In FIG. 4, there is shown apparatus adapted to any of the embodiments above described in which the ultrasonically generated mist may be further subjected to an externally applied field in passing through an aperture in a conductive plate 91 biased to a desired potential from power supply 92. With this latter arrangement, the sensitivity of the ultrasonically generated droplets can be further enhanced by applying a potential of desired polarity on the order of 300 to 3,000 volts to render it increasingly selective in its deposition to an image charge.

It is known in the-art, as for example disclosed in Lang patent U. S. Pat. No. 3,103,3l0, that the size of droplets atomized by sonic energy is a function to a large degree of the particular frequency at which generation is effected. It has been found in accordance with the invention hereof that the ultimate image resolution obtained on development is related to the droplet size which in turn is proportioned to the generating frequency. For these purposes, therefore, frequencies on the order of 20 kilocycles and above produce acceptable resolution and resolution is substantially enhanced as the frequency is increased. Optimum resolution is effected with very fine particle size produced at frequency ranges on the order of to 200 megacycles. Even at the above given lower frequencies, however, resolution can be enhanced by interposing a fine screen which is effective in further breaking up or reducing thedroplet size. The mesh should be sufficient so as not to be choked off by the larger droplets.

The following examples exemplify the invention:

EXAMPLE I A developer liquid comprising about 99.0 percent Isopar G, isoparaffinic hydrocarbon marketed by the Humble Oil and Refining Co. and containing minute percentages of about 0.89 percent Ethyl Cellosolve marketed by Union Carbide Chemical Co.; about 0.05 percent of Zeco 19, a hydrocarbon resin marketed by the Ziegler Chemical Co.; about 0.04 percent Colidex carbon pigment marketed by Columbian Carbon Co.; and about 0.02 percent 55-D-5 plasticizer marketed by Rohm and Haas Co. was used as the developer and generated as a mist at a frequency of at least 20 kilocycles and above to produce acceptable image reproductions on a selenium photoconductor.

EXAMPLE II A fluorescent pigment comprising Velva-glo type, P- l500-G-310 yellow, marketed by the Radiant Color Company and dispersed in tap water was generated as a mist at frequencies of at least kilocycles and likewise produced acceptable image quality on both selenium photoconductors and commercial forms of zinc oxide paper.

EXAMPLE Ill Rhodamine 6G in tap water likewise generated ultrasonically as a mist at frequencies of at least 20 kilocycles produced acceptable reproductions of the same zinc oxide paper employed in Example II, but failed to produce an acceptable reproduction when used in conjunction with an image-bearing selenium plate. The reason for the inoperability with the latter is not fully understood.

In each of the above examples, development was completed in approximately ten seconds after subjecting the image bearing plate to the ultrasonically generated liquid mist. The aqueous developers in particular evidenced no preference as to polarity of charge on which it deposited although it preferentially deposited selectively in the charged as opposed to the uncharged areas. Other liquids than those named can of course be used as for example disclosed in U. S. Pat. Nos. 2,784,109; 2,890,174; 2,899,335; 2,892,709; 2,913,353; 2,907,674; 3,032,432; and French patent No. 1,212,255.

ln addition to developing charge patterns formed from charging and exposing a xerographic plate in the manner described above, the ultrasonically generated mist of the invention hereof was found effective in developing images formed without prior application of an external charge to the plate surface which has previously been stored in a cool dark environment in the manner described in Metcalfe Great Britain patent No. 935,621. Specifically, employing a commercial grade of zinc oxide paper and subjecting it to high intensity illumination without previously and without initially charging the surface thereof produced a good quality reproduction when exposed to an ultrasonically generated mist in accordance with the invention hereof. Developer compositions included those described in the aforesaid Metcalfe Australian patent. Greater uniform wetting of the surface occurs with this embodiment than the others and which can subsequently be cleared as by blowing over the surface by a fan or the like.

By the above description, there is disclosed novel method and apparatus whereby ultrasonically generated liquid mists are effective in developing electrostatic images for the reproduction of copy. Good results have been obtained rendering unnecessary the need for charging the particles triboelectrically or otherwise for presentation to the image to be developed. At the same time. the generated mist is easily contained being a relatively stagnant immobile mass as compared to prior art techniques for effecting similar development. Whereas development has been emphasized with regard to developing charge patterns formed directly on a photoconductive surface, it is not intended to limit the invention thereby. Rather, the invention is operable with any charge-bearing dielectric surface and is likewise operable for developing on an intermediate sheet such as paper imposed between the mist formation and the charge-bearing surface as is known in the art. This latter alternative makes unnecessary the cleaning of the photoconductivc surface following image transfer as is otherwise required for reuse. Likewise, the invention is;

not to be regarded as limited to developing only graphic patterns formed by a direct light exposure, but is intended to include charge patterns formed by whatever means including charge transfer techniques disclosed for example in U. S. Pat. Nos. 2,285,814; 2,919,967; and 3,015,304.

Since many changes could be made in the above construction and many apparently different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the drawings and specification shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A method of developing a charge differential image pattern on a support comprising,

ultrasonically generating an uncharged droplet mist of charge-depositable liquid material without further treating said mist to impart a charge thereto, and

subjecting a support bearing a charge differential pattern to said uncharged mist for a controlled time period to produce a developed image thereon.

2. The method according to claim 1 in which said mist comprises an aqueous suspension.

3. The method according to claim 1 in which the droplets comprising said mist are of a size predominantly in the range of less than 200 microns.

4. The method according to claim 1 in which the mist generating frequency is at least 20 kilocycles.

5. A method of image reproduction comprising,

forming a charge pattern of the original of said image on the surface of a dielectric member,

ultrasonically generating a droplet mist of uncharged charge-depositable liquid material, and

presenting the charge bearing dielectric surface into contact with said uncharged mist droplets for a controlled time period to produce a developed image thereon.

6. A method of image reproduction comprising,

placing an imaging sheet in superposed contiguous relation overlying the charge pattern on said surface, ultrasonically generating a droplet mist of uncharged charge-depositable liquid material without further treating said mist to impart a charge thereto, and

presenting the imaging sheet on the charge bearing dielectric surface into contact with said uncharged mist for a controlled time period to produce a de-- veloped image on said sheet.

7. Apparatus for forming a xerographic reproduction comprising in combination,

a xerographic plate,

means to form an image charge pattern on the surface of said plate,

ultrasonic generating means,

a source of liquid developer material,

means to present controlled quantities of liquid from said source into transducing contact with said ultrasonic generating means whereby said contacting liquid is formed into an uncharged mist-like atmosphere in the absence of other means adapted to impart a charge to said mist, and

means to support the image bearing plate in said uncharged misst'lilse atmospl'iere for a controlled time period to produce a developed image thereon.

8. Apparatus for forming a xerographic reproduction comprising in combination,

a xerographic plate, means to form an image charge pattern on the surface of said plate, a source of liquid developer material,

ultrasonic generating means supporting at least partially within. said liquid source below the liquid level thereof and operable at frequencies of at least kilocycles whereby a quantity of liquid is transformed above said source into an uncharged mistlike atmosphere in the absence of other means adapted to impart a charge to said mist, and

means to support the image bearing plate in said uncharged mist-like atamosphere for a controlled time period to produce a developed image thereon.

9. A method of image reproduction comprising,

forming without the use of an external applied charge, a charge pattern of the original on a solid surface which has previously been stored in a cool dark environment,

ultrasonically generating a droplet mist of uncharged charge-depositable liquid material having a droplet size of less than about 0.5 micron without further treating said mist to impart a charge thereto, and

presenting the latent image bearing solid surface into contact with said uncharged mist for a controlled time period to produce a developed image thereon. 10. A method of developing a charge differential image pattern on a support comprising, ultrasonically vibrating a quantity of liquid developer material to generate an uncharged droplet mist of the liquid developer material, and

subjecting said support proximate to said uncharged droplet mist of said liquid developer material, said droplet mist being attracted to said support in accordance with the differential charge pattern to produce a developed image.

11. A method of image reproduction comprising,

forming a differential charge pattern over a support,

ultrasonically vibrating a quantity of liquid developer material to generate an uncharged droplet mist of the liquid developer material, and

Claims

1. A method of developing a charge differential image pattern on a support comprising, ultrasonically generating an uncharged droplet mist of chargedepositable liquid material without further treating said mist to impart a charge thereto, and subjecting a support bearing a charge differential pattern to said uncharged mist for a controlled time period to produce a developed image thereon.

5. A method of image reproduction comprising, forming a charge pattern of the original of said image on the surface of a dielectric member, ultrasonically generating a droplet mist of uncharged charge-depositable liquid material, and presenting the charge bearing dielectric surface into contact with said uncharged mist droplets for a controlled time period To produce a developed image thereon.

6. A method of image reproduction comprising, forming a charge pattern of the original of said image on the surface of a dielectric member, placing an imaging sheet in superposed contiguous relation overlying the charge pattern on said surface, ultrasonically generating a droplet mist of uncharged charge-depositable liquid material without further treating said mist to impart a charge thereto, and presenting the imaging sheet on the charge bearing dielectric surface into contact with said uncharged mist for a controlled time period to produce a developed image on said sheet.

7. Apparatus for forming a xerographic reproduction comprising in combination, a xerographic plate, means to form an image charge pattern on the surface of said plate, ultrasonic generating means, a source of liquid developer material, means to present controlled quantities of liquid from said source into transducing contact with said ultrasonic generating means whereby said contacting liquid is formed into an uncharged mist-like atmosphere in the absence of other means adapted to impart a charge to said mist, and means to support the image bearing plate in said uncharged mist-like atmosphere for a controlled time period to produce a developed image thereon.

8. Apparatus for forming a xerographic reproduction comprising in combination, a xerographic plate, means to form an image charge pattern on the surface of said plate, a source of liquid developer material, ultrasonic generating means supporting at least partially within said liquid source below the liquid level thereof and operable at frequencies of at least 20 kilocycles whereby a quantity of liquid is transformed above said source into an uncharged mist-like atmosphere in the absence of other means adapted to impart a charge to said mist, and means to support the image bearing plate in said uncharged mist-like atamosphere for a controlled time period to produce a developed image thereon.

9. A method of image reproduction comprising, forming without the use of an external applied charge, a charge pattern of the original on a solid surface which has previously been stored in a cool dark environment, ultrasonically generating a droplet mist of uncharged charge-depositable liquid material having a droplet size of less than about 0.5 micron without further treating said mist to impart a charge thereto, and presenting the latent image bearing solid surface into contact with said uncharged mist for a controlled time period to produce a developed image thereon.

10. A method of developing a charge differential image pattern on a support comprising, ultrasonically vibrating a quantity of liquid developer material to generate an uncharged droplet mist of the liquid developer material, and subjecting said support proximate to said uncharged droplet mist of said liquid developer material, said droplet mist being attracted to said support in accordance with the differential charge pattern to produce a developed image.

11. A method of image reproduction comprising, forming a differential charge pattern over a support, ultrasonically vibrating a quantity of liquid developer material to generate an uncharged droplet mist of the liquid developer material, and subjecting said support proximate to said uncharged droplet mist of said liquid developer material, said droplet mist being attracted to said support in accordance with the differential charge pattern to produce a developed image.