US2877133A - Electrostatic photography - Google Patents

Electrostatic photography Download PDF

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Publication number
US2877133A
US2877133A US61724656A US2877133A US 2877133 A US2877133 A US 2877133A US 61724656 A US61724656 A US 61724656A US 2877133 A US2877133 A US 2877133A
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Prior art keywords
image
liquid
weight
latent electrostatic
developer
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Edward F Mayer
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General Dynamics Corp
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General Dynamics Corp
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    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00Developers
    • G03G9/08Developers with toner particles
    • G03G9/12Developers with toner particles in liquid developer mixtures
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ELECTROGRAPHY; HOLOGRAPHY
    • G03GELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00Developers
    • G03G9/08Developers with toner particles
    • G03G9/12Developers with toner particles in liquid developer mixtures
    • G03G9/135Developers with toner particles in liquid developer mixtures characterised by stabiliser or charge-controlling agents
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S101/00Printing
    • Y10S101/37Printing employing electrostatic force
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00Stock material or miscellaneous articles
    • Y10T428/29Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982Particulate matter [e.g., sphere, flake, etc.]

Description

March 10, 1959 E. F. MAYER 2,877,133

ELECTROSTATIC PHOTOGRAPHY Filed Oct. 22. 1956 FIG.]

PHOTOGRAPHIC ELEMENT BEARING LATENT ELECTROSTATIC LMAGE EICSUTD TDEQELOEETZ.

PIG.2.

PHOTOGRAPHIC ELEMENT BEARING LATENT ELECTROSTATIC IMAGE INVENTOR EDWARD I. MAYER Myra/44 3 ATTORNEY United States Patent ELECTROSTATIC PHOTOGRAPHY Edward F. Mayer, Cleveland, Ohio, assignor, by mesne assignments, to General Dynamics Corporation, San Diego, Calif., a corporation of Delaware Application October 22, 1956, Serial No. 617,246

6 Claims. (Cl. 117-37) This invention relates to the development of visual images in electrophotographic processes and to a novel composition of matter which has been found to be particularly suitable for the development of a visible image from a latent electrostatic image existing as a charge pattern in a layer of a material having a high resistance,

Among the prior art processes in which latent electrostatic images are formed on or in such layers and subsequently converted into a visual image by application of a finely divided opaque solid material suspended in air either as a dry powder or as a liquid mist are those described by C. F. Carlson in Patents 2,297,691 and 2,551,582 respectively. In other copending applications, Serial No. 380,285 filed September 15, 1953, and Serial No. 484,215 filed January 26, 1955, I have disclosed electrophotographic processes in which a latent electrostatic image is converted into a visual image by means of a suspension of solid opaque particles in a liquid. The present application is a continuation-in-part of a copending application, Serial No. 486,995, filed February 8, 1955,

disclosing one type of developer formulation.

in the form of powder clouds into intimate contact with the charge image to be rendered visible. Such developers are described in Walkup Patent 2,618,551; Wise Patent 2,618,552; Walkup Patent 2,638,416; Copely Patent 2,659,670; and Landrigan Patent 2,753,308, and consist essentially of pigmented resin particles based on specific resins. Other electroscopic powders known in the art are disclosed in Patent 2,297,691, and these include finely pulverized synthetic resins and natural gums and waxes as well as inorganic powdered materials such as aluminum bronze, talcum powder, minium, sulfur and carbon dust.

I have found that development based on liquid media instead of the above described dry processes offers important advantages. The time required for development of a visible image can be materially diminished and this is of importance in the design of apparatus which is to continuously produce legible copy. In addition, the use of liquid borne developers permits of a greater control in the developing process.

Essentially, the developer in my process comprises a liquid combination of mutually compatible ingredients, which when brought into contact with an element bearing an electrostatic charge pattern corresponding to the image to be reproduced, previously referred to as a latent electrostatic image, will deposit by electrostatic attraction a visible light and shadow pattern corresponding to the ice in this art may be employed in the developer. Thus talcum powder, carbon black and other pigments disclosed in Carlson above noted or any pigment which forms a dispersion with the other constituents of the developer may be used. The particle size of the specific opaque material will influence both the rate at which the image is developed and the density of the image. Particles between 0.1 and 10 microns are satisfactory for most purposes, with about 2 microns being preferred. Of the many pigments available, I prefer hardwood charcoal the particle size of which has been reduced sufficiently, to, for example, 2 microns or less by ball milling. Up to about 25% by Weight of the finely divided opaque powder may be incorporated in the composition, with between 10% and 20% by weight being a preferred range and 15% by weight producing particularly good results. The particle size and concentration chosen for any specific application is necessarily related to the sharpness or definition desired in the ultimate image.

The opaque solid particles are dispersed or suspended in a liquid vehicle possessing a high resistance. In order to avoid discharge of the latent electrostatic image, a liquid with a resistivity of about at least 10 ohm centimeters is necessary. Liquids which I have found suitable include carbon tetrachloride, kerosene, benzene, toluene, and other hydrocarbons and substituted hydrocarbons having a boiling point between about 70 C. and 200 C.

In order to minimize settling or clumping or agglomeration of the particles, a third ingredient is included in the developer composition. I have found that a silica aerogel (Santocel No. 54, a product of Monsanto Chemical Company) formed by dehydrating normal silica gel and replacing the water of hydration with air, without destruction of the gel structure, is particularly suitable. Amounts of up to about 20% by weight of the gel have been found satisfactory, between about 5 and 15% by weight being preferred.

The several ingredients may be formed into the desired suspension in various ways. For example, the high resistance liquid and the opaque powder may be mixed during the ball milling of the powdered material and the silica aerogel added to the mixture. Alternatively the ingredients may merely be blended by mixing them at one time in a Waring type blender. Once the finely divided powder is dispersed in the high resistance liquid it may be readily maintained uniformly suspended by occasional hand-stirring, since the aerogel functions as a suspending agent in the mixture.

Compositions comprehended within the above description have been found to be particularly useful in the roller electrophotographic process described in my aforesaid copending patent applications. One difficulty encountered in forming the latent electrostatic image into a visual image has been the tendency of the liquid developer heretofore employed to ride up on the developer roll in insufficient amounts and as a result-to produce low contrast images. By employing the combination of ingredients herein disclosed I have found that a developer of suitable viscosity results, free from the difficulties previously encountered.

The following examples will further illustrate the preparation and use of developers in accordance with my invention.

Example I A developer was prepared by ball milling for 7 hours, 1 part by weight of charcoal and 1 part by weight of Solvesso 150, a mixture of polyalkyl benzenes boiling at 365 F. to 415 F. and having a flash point of 150 F., manufactured by The Standard Oil Company of Ohio. At the end of this time the particle size of the charcoal was reduced to between 1 and microns and the average particle size was 2 microns. The contents of the ball mill were discharged and any adherent pigment was rinsed from the balls by flushing them with additional Solvesso. The dispersion of solid particles was diluted with additional Solvesso until the relative proportions by weight of charcoalzvehicle was about 1:8. One part by weight of silica aerogel was added to each parts by weight of the mixture and the resulting composition was charged into a Waring type blender and mixed for 10 minutes. The developer when applied to a plate bearing an electrostatic image produced a sharp image after 2 seconds contact and was readily transferred to a newsprint web which served as a permanent record medium.

Example II The process of Example I was repeated except that the developer composition prepared contained 2 micron particle-size charcoal, Solvesso 150, and silica aerogel (Santocel No. 54) in the relative proportion by weight of 1:7:2. The image was developed by flowing the liquid developer over an applicator roller which lightly contacted a rotating cylinder bearing an electrostatic image. The image formed rapidly and reproduced the details of the original object electrostatically photographed.

While I have disclosed specific examples in which the finely divided solid opaque material is charcoal and the liquid vehicle in which it was dispersed was an alkyl benzene mixture, it will be understood that many other media and pigments may be used in combination without departing from the spirit and scope of my invention.

In the single sheet of drawing accompanying this application, I have shown by way of illustration two of the possible ways of applying developer compositions to a surface bearing a latent electrostatic image. Figure 1 illustrates the method of Example I in which developer is applied by a roller applicator to a plate bearing a latent electrostatic image. Figure 2 is a showing of one method of applying the liquid developer compositions to a rotating cylinder bearing a latent electrostatic image as described in Example II, above. It will be readily apparent to others skilled in the art that the liquid may be brought into physical contact with surfaces bearing latent electrostatic images in many other ways, including: immersion of the surface in a pool of developer, or flowing of developer over the image-bearing surface, in addition to the two methods illustrated.

Having now described my invention in accordance with the patent statutes, I claim:

1. A process for developing a visible image of a latent electrostatic charge image in a high resistance material which comprises: applying a liquid developer consisting essentially of a finely divided opaque solid electrostatically attractable powder of which the particle size is not greater than 10 microns dispersed in a liquid having a specific resistivity of at least about 10 ohm centimeters and containing up to about by weight of a silica aerogel 5 suspended therein, to the material bearing the electro- 6 static charge image for a time suflicient to develop the desired visible image.

2. A process for developing a visible image of a latent electrostatic charge image in a high resistance material which comprises: applying a liquid developer consisting essentially of a finely divided opaque solid electrostatically attractable powder of which the particle size is not greater than 10 microns dispersed in a liquid having a specific resistivity of at least about 10 ohm centimeters and containing up to about 20% by weight of a silica aerogel suspended therein, to the material bearing the electrostatic charge image for a time sufiicient to develop the desired visible image, and transferring the visible image to a permanent record medium.

3. A process for developing a visible image of a latent electrostatic charge image in a high resistance material which comprises: applying a liquid developer consisting essentially of finely divided charcoal particles up to 10 microns in size dispersed in a liquid having a specific resistivity of at least about 10 ohm centimeters and containing up to about 20% by weight of a silica aerogel suspended therein, to the material bearing the electrostatic charge image for a time sufiicient to develop the desired visible image.

4. A process for developing a visible image of a latent electrostatic charge image in a high resistance material which comprises: applying to the material bearing the electrostatic charge image a liquid developer consisting essentially of a charcoal powder approximately 2 microns in size, dispersed in a liquid having a specific resistivity of at least about 10 ohm centimeters and containing up to about 20% by weight of a silica aerogel suspended therein, for a time suflicient to develop the desired visible image.

5. A process for developing a visible image of a latent electrostatic charge image in a high resistance material which comprises: preparing a liquid developer consisting essentially of a finely divided opaque solid electrostatically attractable powder of which the particle size is not greater than 10 microns dispersed in a liquid having a specific resistivity of at least about 10 ohm centimeters and containing up to about 20% by weight of a silica aerogel suspended therein, and applying the liquid developer to a material bearing a latent electrostatic charge image for a time sufiicient to develop the desired visible image.

6. A process for developing a visible image of a latent electrostatic charge image in a high resistance material which comprises: preparing a liquid developer consisting essentially of between 10 and 20% by weight of a finely divided opaque solid electrostatically attractable powder of which the particle size is not greater than 10 microns dispersed in a liquid having a specific resistivity of at least about 10 ohm centimeters and containing up to about 25% by weight of the dispersion of a silica aerogel suspended therein and applying the liquid developer to a material bearing a latent electrostatic charge image for a time sufi-lcient to develop the desired visible image.

References Cited in the file of this patent Walkup Mar. 5, 1957 OTHER REFERENCES Industrial and Engineering Chemistry, vol. 33, No. 9, September 1941, pp. 1169-1173.

Claims (1)

1. A PROCESS FOR DEVELOPING A VISIBLE IMAGE OF A LATENT ELECTROSTATIC CHARGE IMAGE IN A HIGH RESISTANCE MATERIAL WHICH COMPRISES: APPLYING A LIQUID DEVELOPER CONSISTING ESSENTIALLY OF A FINELY DIVIDED OPAQUE SOLID ELECTROSTATICALLY ATTRACTABLE POWDER OF WHICH THE PARTICLE SIZE IS NOT GREATER THAN 10 MICRONS DISPERESED IN A LIQUID HAVING A SPECIFIC RESISTIVITY OF AT LEAST ABOUT 109 OHM CENTIMETERS AND CONTAINING UP TO ABOUT 20% BY WEIGHT OF A SILICA AEROGEL SUSPENDED THEREIN, TO THE MATERIAL BEARING THE ELECTROSTATIC CHARGE IMAGE FOR A TIME SUFFICIENT TO DEVELOP THE DESIRE VISIBLE IMAGE.
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Cited By (35)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2986521A (en) * 1958-03-28 1961-05-30 Rca Corp Reversal type electroscopic developer powder
US2991754A (en) * 1959-02-06 1961-07-11 Rca Corp Developing apparatus
US3001888A (en) * 1957-09-25 1961-09-26 Metcalfe Kenneth Archibald Method of developing an electrostatic image
US3053688A (en) * 1959-04-13 1962-09-11 Rca Corp Electrostatic printing
US3058914A (en) * 1957-10-01 1962-10-16 Commw Of Australia Non-inflammable liquid developers for electrostatic images
US3078231A (en) * 1959-05-13 1963-02-19 Commw Of Australia Controlled developer for use in electro-photography and electro-radiography
US3080251A (en) * 1958-03-13 1963-03-05 Xerox Corp Method of xerographic development
US3080318A (en) * 1958-03-13 1963-03-05 Xerox Corp Three-component xerographic toner
US3096198A (en) * 1958-12-22 1963-07-02 Ibm Method for developing latent field images with liquid inks
US3102045A (en) * 1957-06-28 1963-08-27 Metcalfe Kenneth Archibald Production of patterns on cloth or similar substances
US3129115A (en) * 1961-04-17 1964-04-14 Xerox Corp Xerographic developing apparatus
US3135695A (en) * 1961-02-20 1964-06-02 Eastman Kodak Co Liquid developers for electrostatic photography
US3241957A (en) * 1961-06-08 1966-03-22 Harris Intertype Corp Method of developing electrostatic images and liquid developer
US3276896A (en) * 1959-04-13 1966-10-04 Rca Corp Electrostatic printing
US3290251A (en) * 1963-12-16 1966-12-06 Dennison Mfg Co Electrostatic latent image developing compositions containing an ether
US3311490A (en) * 1958-09-23 1967-03-28 Harris Intertype Corp Developing electrostatic charge image with a liquid developer of two immiscible phases
US3336906A (en) * 1965-06-09 1967-08-22 Fairchild Camera Instr Co Apparatus for immersion development
US3399140A (en) * 1965-09-07 1968-08-27 American Photocopy Equip Co Liquid developer for electrostatic printing
US3405683A (en) * 1963-06-22 1968-10-15 Azoplate Corp Apparatus for the development of latent electrostatic images
US3417019A (en) * 1962-12-27 1968-12-17 Eastman Kodak Co Xerographic development
US3519566A (en) * 1966-11-07 1970-07-07 Dow Chemical Co Method of making electrophotographic developer for etch resist image patterns
US3622368A (en) * 1967-08-22 1971-11-23 Ricoh Kk Method for developing electrostatic latent images by utilizing coupling reaction
US3639052A (en) * 1968-07-09 1972-02-01 Matsushita Electric Ind Co Ltd Apparatus for electrophotographically producing an image on a single sheet of microfilm
US3810193A (en) * 1968-09-30 1974-05-07 Secretary Supply Australia Bitting card for data recording
US3839071A (en) * 1969-12-29 1974-10-01 Honeywell Inc Printing method
US3850830A (en) * 1970-12-03 1974-11-26 Fuji Photo Film Co Ltd Liquid developer containing extender body particles
JPS5119339B1 (en) * 1970-07-31 1976-06-16
US4014856A (en) * 1972-07-12 1977-03-29 Agfa-Gevaert, N.V. Liquid electrophotographic developers
US4021586A (en) * 1970-10-08 1977-05-03 Canon Kabushiki Kaisha Method of and means for the development of electrostatic images
US4035071A (en) * 1974-10-24 1977-07-12 Ricoh Co., Ltd. Developing process and apparatus for electrophotography
US4230782A (en) * 1978-05-15 1980-10-28 Xerox Corporation Migration imaging system with meniscus development
US4241159A (en) * 1974-02-26 1980-12-23 Agfa-Gevaert N.V. Electrophotographic liquid developer comprising acrylic or methacrylic acid ester of hydrogenated abietyl alcohol polymer
US4345015A (en) * 1975-07-07 1982-08-17 Oce-Van Der Grinten N.V. Dispersion-heat process employing hydrophobic silica for producing spherical electrophotographic toner powder
EP0078018A2 (en) * 1981-10-27 1983-05-04 Coulter Systems Corporation Method and apparatus for developing electrostatic latent images
US4656966A (en) * 1986-08-04 1987-04-14 Eastman Kodak Company Method and apparatus for developing electrographic images uses molecular sieve zeolite

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2682478A (en) * 1950-09-11 1954-06-29 Technicolor Motion Picture Method of forming television screens
US2784109A (en) * 1950-09-18 1957-03-05 Haloid Co Method for developing electrostatic images

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2682478A (en) * 1950-09-11 1954-06-29 Technicolor Motion Picture Method of forming television screens
US2784109A (en) * 1950-09-18 1957-03-05 Haloid Co Method for developing electrostatic images

Cited By (38)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3102045A (en) * 1957-06-28 1963-08-27 Metcalfe Kenneth Archibald Production of patterns on cloth or similar substances
US3001888A (en) * 1957-09-25 1961-09-26 Metcalfe Kenneth Archibald Method of developing an electrostatic image
US3212916A (en) * 1957-09-25 1965-10-19 Commw Of Australia Method of developing electrostatic image with foam liquid developer
US3058914A (en) * 1957-10-01 1962-10-16 Commw Of Australia Non-inflammable liquid developers for electrostatic images
US3080251A (en) * 1958-03-13 1963-03-05 Xerox Corp Method of xerographic development
US3080318A (en) * 1958-03-13 1963-03-05 Xerox Corp Three-component xerographic toner
US2986521A (en) * 1958-03-28 1961-05-30 Rca Corp Reversal type electroscopic developer powder
US3311490A (en) * 1958-09-23 1967-03-28 Harris Intertype Corp Developing electrostatic charge image with a liquid developer of two immiscible phases
US3096198A (en) * 1958-12-22 1963-07-02 Ibm Method for developing latent field images with liquid inks
US2991754A (en) * 1959-02-06 1961-07-11 Rca Corp Developing apparatus
US3053688A (en) * 1959-04-13 1962-09-11 Rca Corp Electrostatic printing
US3276896A (en) * 1959-04-13 1966-10-04 Rca Corp Electrostatic printing
US3078231A (en) * 1959-05-13 1963-02-19 Commw Of Australia Controlled developer for use in electro-photography and electro-radiography
US3135695A (en) * 1961-02-20 1964-06-02 Eastman Kodak Co Liquid developers for electrostatic photography
US3129115A (en) * 1961-04-17 1964-04-14 Xerox Corp Xerographic developing apparatus
US3241957A (en) * 1961-06-08 1966-03-22 Harris Intertype Corp Method of developing electrostatic images and liquid developer
US3301698A (en) * 1961-06-08 1967-01-31 Harris Intertype Corp Method and apparatus for simultaneously developing and fixing electrostatically formed images
US3417019A (en) * 1962-12-27 1968-12-17 Eastman Kodak Co Xerographic development
US3405683A (en) * 1963-06-22 1968-10-15 Azoplate Corp Apparatus for the development of latent electrostatic images
US3290251A (en) * 1963-12-16 1966-12-06 Dennison Mfg Co Electrostatic latent image developing compositions containing an ether
US3336906A (en) * 1965-06-09 1967-08-22 Fairchild Camera Instr Co Apparatus for immersion development
US3399140A (en) * 1965-09-07 1968-08-27 American Photocopy Equip Co Liquid developer for electrostatic printing
US3519566A (en) * 1966-11-07 1970-07-07 Dow Chemical Co Method of making electrophotographic developer for etch resist image patterns
US3622368A (en) * 1967-08-22 1971-11-23 Ricoh Kk Method for developing electrostatic latent images by utilizing coupling reaction
US3639052A (en) * 1968-07-09 1972-02-01 Matsushita Electric Ind Co Ltd Apparatus for electrophotographically producing an image on a single sheet of microfilm
US3810193A (en) * 1968-09-30 1974-05-07 Secretary Supply Australia Bitting card for data recording
US3839071A (en) * 1969-12-29 1974-10-01 Honeywell Inc Printing method
JPS5119339B1 (en) * 1970-07-31 1976-06-16
US4021586A (en) * 1970-10-08 1977-05-03 Canon Kabushiki Kaisha Method of and means for the development of electrostatic images
US3850830A (en) * 1970-12-03 1974-11-26 Fuji Photo Film Co Ltd Liquid developer containing extender body particles
US4014856A (en) * 1972-07-12 1977-03-29 Agfa-Gevaert, N.V. Liquid electrophotographic developers
US4241159A (en) * 1974-02-26 1980-12-23 Agfa-Gevaert N.V. Electrophotographic liquid developer comprising acrylic or methacrylic acid ester of hydrogenated abietyl alcohol polymer
US4035071A (en) * 1974-10-24 1977-07-12 Ricoh Co., Ltd. Developing process and apparatus for electrophotography
US4345015A (en) * 1975-07-07 1982-08-17 Oce-Van Der Grinten N.V. Dispersion-heat process employing hydrophobic silica for producing spherical electrophotographic toner powder
US4230782A (en) * 1978-05-15 1980-10-28 Xerox Corporation Migration imaging system with meniscus development
EP0078018A2 (en) * 1981-10-27 1983-05-04 Coulter Systems Corporation Method and apparatus for developing electrostatic latent images
EP0078018A3 (en) * 1981-10-27 1983-08-17 Coulter Systems Corporation Method and apparatus for developing electrostatic latent images
US4656966A (en) * 1986-08-04 1987-04-14 Eastman Kodak Company Method and apparatus for developing electrographic images uses molecular sieve zeolite

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