US2618551A - Developer for electrostatic images - Google Patents

Developer for electrostatic images Download PDF

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US2618551A
US2618551A US55645A US5564548A US2618551A US 2618551 A US2618551 A US 2618551A US 55645 A US55645 A US 55645A US 5564548 A US5564548 A US 5564548A US 2618551 A US2618551 A US 2618551A
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particles
electrostatically
powder
charged
core
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US55645A
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Lewis E Walkup
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Xerox Corp
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Xerox Corp
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Priority to US55645A priority Critical patent/US2618551A/en
Priority to GB5283/50A priority patent/GB686466A/en
Priority to FR1018653D priority patent/FR1018653A/en
Priority to CH292431D priority patent/CH292431A/en
Priority to DEB2977A priority patent/DE926587C/en
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/10—Developers with toner particles characterised by carrier particles
    • G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/08—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer
    • G03G15/0801—Apparatus for electrographic processes using a charge pattern for developing using a solid developer, e.g. powder developer for cascading
    • Y—GENERAL 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S101/00—Printing
    • Y10S101/37—Printing employing electrostatic force

Definitions

  • This invention relates to a developer for electrostatic images, with particular reference to the development of electrostatic images on plates such as used in electrophotographic processes where a sensitive layer .is charged electrostatically and then exposed to receive allatent electrostatic image which is developed by a developer that results in a powder image, the powder image .being then transferred to asheet of transfer material, and the invention has .for its purpose to afford a developer composed of electroscopic powder and a granular carrier .material that is more efiicient and not open to the objectionable characteristics that have been present in developers heretofore employed for this purpose, also which enables a reduction in the cost of the granular carrier material and makes possible carriers having magnetic properties,
  • the developers previously used comprise in general a mixture of a suitable pigmented or dyed electroscopic powderand a granular carrier material, which latter functions to carry and to generate triboelectric charges on the electroscopic powders as well as to remove excess powder .from uncharged or slightly charged or background areas of the plate, and it has been found that in some instances, the granular carrier material exhibits a tendency to adhere to the image bearing plate, thus preventing the proper functioning of the electroscopic powder and blocking theimage more or less, and it is ,a particular purpose of the invention to so form the granular carrier material that it is not likely to adhere to the charged or uncharged areas of the plate, and
  • Another purpose of the invention is to enable controlling the specific gravity of the granular carrier material in relation to the electroscopic developing powder whereby any desired relation between the specific .gravities oi the two components of the mixture may be had while maintaining a proper triboelectric charging relationship between-them.
  • the'invention comprises the utilization of a granular carrier material consisting of a core, base or interior composed of any selected material which may be of high specific gravity such as glass or steel beads, covered with and encased in a suitable covering which imparts the necessary tri'boelectric properties to the granular carrier material, so that it will properly charge the electroscopic powder when mixed therewith,
  • Such a high specific gravity granular carrier material may be produced by adhering anouter covering consisting of a selected triboelectric'resinous or other suitable substance to the core-or base particles of glass or steel beads or the like by first coating the core particles with an intermediate bonding layer, for example a liquid resin which contains a hydrochloric acid catalyst.
  • the coated core or base "particles are then added to the dry triboelectri'c resinoussubstance which adheres thereto and constitutes a covering that is fused or otherwise affixed to the core'or base particles, any remaining fines being separated by screening, and such coated granular carrier material is then mixed with the 'electroscopic powder to form the-developer.
  • the invention is carried out by employing an electroscopic powder such as a mixture of 20 parts Amberol F-7l, a phenol-formaldehyde resin manufactured by Resinous Products & Chemical Co., 222 West Washington Square, Philadelphia-5, Pa, and 1 part carbon black such as Raven Bead Carbon Black manufactured by Binney & Smith Co., 41 East 42nd Street, New York 7, N. Y.
  • the electroscopic powder is prepared by mixing the above ingredients and breaking them to a 16- mesh size or smaller, after which approximately 225 grams of the mixture are placed in a onehalf gallon capacity ball mill 'jar containing an aluminum scraper.
  • the jar is filled to approximately three-quarters :its capacity with diamter balls and the mixture ball milled for about four hours, after which it 'is removed from the ball mill jar and iused'on a hot plate under suitable heating lamps or by other suitable means.
  • the mixture is then cooled and broken into approximately Iii-mesh size particles, following which it is micropulverized to an average size of from 1 to 20 microns substantially as disclosed in copending application Ser. No. 24,674, filed May 1, 1948.
  • an electroscopic powder and granular carrier combination should be selected in which the powder is triboelectrically positive to the granular carrier, and to develop a latent image comprised of positive electrostatic charges, an electroscopic powder and granular carrier should beselected in which thepowder is tr-iboelectrically negative to the granular carrier.
  • This triboelectric relationship between the powder and granular carrier depends on their relative positions in a triboelectric series in which the materials are arranged in such a way that each material is charged with positive electricity When contacted with any material below it in the series and with negative electricity when contacted with any material above it in the series.
  • Example 1 A suitable granular carrier material for use with plates carrying a negative electrostatic charge is made by using 200 parts glass beads and a covering consisting of 40 parts Vinylite VYLF (a vinyl chloride-vinyl acetate copolymer produced by Bakelite Corporation, 30 East 42nd Street, New York, N.
  • Vinylite VYLF a vinyl chloride-vinyl acetate copolymer produced by Bakelite Corporation, 30 East 42nd Street, New York, N.
  • Durite X221 a phenol-furfural and phenol-formaldehyde thermosetting resin and molding compound manufactured by The Borden Company, Chemical Division, Philadelphia, Pa
  • Durez 12763 a phenol-formaldehyde molding compound and resin material manufactured by Durez Plastics llz Chemical Inc., North Tonawanda, N. Y.
  • said covering being bonded to the glass bead base or core particles by a resin adhesive intermediate coating consisting of 16 parts Durez 8286 (a phenol-formaldehyde molding compound and resin manufactured by Durez Plastics & Chemical Inc., North Tonawanda, N. Y.) catalyzed with 1.5 cc.
  • the core particles are first coated with the liquid bonding resin containing the catalyst, and then mixed with the dry covering material, which adheres to the bonding resin on the core particles, andis then fused thereto in any suitable manner. any remaining fines being removed by screening.
  • the final granular carrier particles are preferably smaller than 30-mesh, i. e. an outer diameter of approximately 0.023 inches, and larger than 50-mesh, i. e. an outer diameter of approximately 0.012 inches, in size, and the electroscopic powder is preferably mixed with the granular carrier material in the proportion of 6 to 170.
  • Example 2 Another granular carrier material suitable for use with negatively charged plates consists of 200 parts of glass bead core particles covered with 40 parts Saran B115 (a vinylidene chloride resin manufactured by Dow Chemical Co., Midland, Mich.), 16 parts Durite X221, and 16 parts Durez 12763, the covering being adhered to the glass bead core or base particles by a resin bonding agent consisting of 16 parts Bakelite BR7534 (a resin material manufactured by Bakelite Cor- 4 poration, 30 East 42nd Street, New York, N. Y.) to which has been added a catalyst consisting of 1.5 cc. of a 50% hydrochloric acid.
  • Saran B115 a vinylidene chloride resin manufactured by Dow Chemical Co., Midland, Mich.
  • Durite X221 16 parts
  • Durez 12763 the covering being adhered to the glass bead core or base particles by a resin bonding agent consisting of 16 parts Bakelite BR7534 (a resin material manufactured by Bakelite Cor- 4 poration, 30 East 42
  • This granular carrier material is produced in the same manner as already described, by first applying the liquid bonding resin and catalyst to the core particles, and then adding the core particles coated with the bonding resin to the dry covering material, which imparts the necessary triboelectric properties to the core particles.
  • This granular carrier material when in its final form is preferably of a size smaller than 30-mesh and larger than 50-mesh, and the electroscopic powder is preferably mixed With(. such granular carrier material in the proportion of 10 to 240.
  • Example 3 Another ranular carrier material suitable for use with negatively charged plates is produced in a similar manner by using 200 parts of glass beads for the base or core particles, which are covered with 40 parts Pliolite (a butadiene polymer manufactured by Goodyear Tire & Rubber Co., Akron, Ohio), 8 parts Durez 12763, and 8 parts Durite X221, the covering being adhered to the base or core particles by a resin bonding agent consisting of 16 parts Bakelite BR7534 to which has been added a catalyst consisting of 2 cc. of a 50% hydrochloric acid.
  • Pliolite a butadiene polymer manufactured by Goodyear Tire & Rubber Co., Akron, Ohio
  • Durez 12763 8 parts
  • Durite X221 8 parts
  • the covering being adhered to the base or core particles by a resin bonding agent consisting of 16 parts Bakelite BR7534 to which has been added a catalyst consisting of 2 cc. of a 50% hydrochloric acid.
  • the size of the final granular carrier particles are the same as stated above in connection with Examples #1 and #2, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 6 to 225.
  • Example 4 A suitable granular carrier material for use with a positively charged plate is made by using 500 parts of steel beads for the base or core particles, which are covered with 60 parts Melmac 401 (a thermosetting, melamine-type synthetic resin manufactured by American Cyanamid Co., Plastics Division, New York 20, N. Y.), 40 parts Vinylite VYNS, and 5 parts Nigrosine Base 10 (a black dye manufactured by the Calco Chemical Division of the American Cyanamid Company, Boundbrook, N. J.) adhered to the core or base particles by a bonding agent consisting of 15 parts Bakelite BR7534, to which has been added a catalyst consisting of 1 cc. of a 50% hydrochloric acid.
  • Melmac 401 a thermosetting, melamine-type synthetic resin manufactured by American Cyanamid Co., Plastics Division, New York 20, N. Y.
  • Vinylite VYNS a black dye manufactured by the Calco Chemical Division of the American Cyanamid Company, Boundbrook, N. J.
  • the granular carrier particles are the same size as stated above, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 8 to 300.
  • Example 5 Another granular carrier material suitable for use with positively charged plates is produced by applying the same covering as specified in the last mentioned Example #4 to a base or core particles consisting of parts of glass beads, and adhering th covering to the core particles by a bonding agent consisting of 16 parts Bakelite BR7534 to which has been added a catalyst consisting of 1.5 cc. of a 50% hydrochloric acid.
  • the granular carrier particles are the same size as stated above, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 10 to 230.
  • Example 6 Another satisfactory granular carrier material for use with a positively charged plate is produced by using carborundum for the base or core particles, covering the same with 60 parts Melmac 4'01, 40 parts Vinylite VYNS, and 5 parts Nigrosine Base 10, adhered to the core or base particles by a bonding agent consisting of parts Bakelite BR7534 to Which has been added a catalyst consisting of 1 cc. of a 50% hydrochloric acid.
  • This granular carrier material is preferably of a size smaller than -mesh and larger than SO-mesh, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 8 to 300.
  • Example 7 Another satisfactory granular carrier material for use in printing from a plate carrying a negative charge is made by using 200 parts of glass beads for the core or base particles, covering the same with parts Pliolite, 8 parts Durez 12763, and 8 parts Durite X221, adhered to the base particles by a bonding agent consisting of 15 parts Bakelite Eli/753 i to which has been added a catalyst consisting of 2 cc. of a hydrochloric acid.
  • the size of the granular carrier material is the same as stated in the precedin examples, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 6 to 225.
  • a developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby bein electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostaticallycharged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
  • a developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably 6 adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coatin of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
  • a developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specificgravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles havin a triboelectric relationship of opposite polarity, the powder particles thereby being elec trostatically charged through triboelectric action by mixing with the granular carrier material to m-ovably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded
  • a developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a glass bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to remove said charged powder particles from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
  • a developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a carborundum core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to remove said charged powder particles from uncharged areas of the el ctrostatic latent image surface when cascaded there
  • a developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a steel bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostaticallycharged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to remove said charged powder particles from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
  • a resin coating permanently bonded on said core said coating and powder particles having a tribeelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
  • an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically attractable material
  • the improvement comprising developing the image by cascading thereacross a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a glass bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged
  • an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically-attractable material
  • the improvement comprising developing the image by cascading ther across a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a steel bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract
  • an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically-attractable material
  • the improvement comprising developing the image by cascading thereacross a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a carborundum core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectri'c relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus
  • an electrophotographic process the steps of which comprise imposing an electrostatic charge 011 the photoconductive insulating surface of an electrophotographic plate havin a photoconductive insulating layer on a conductive backing, exposing the charged surface to a light image to yield an electrostatic latent image and developing the electrostatic latent image, the improvement comprising developing the image by cascading thereacross a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mix ing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by
  • a developer for electrostatic latent images comprising a mixture of loose movable particles of electrostatically attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity and particle size grossly higher than the specific gravity and particle size of the powder particles and a coating permanently bonded on said core and having a triboelectric relationship of opposite polarity to the powder, the powder material being mcvably and electro statically secured on the surface of said coated granular particles,

Description

Patented Nov. 18, r 1952 11 DEVELQPER FOR ELECTROSTATIC IMAGES Lewis E. Walkup, Columbus, Ohio, assignor, by mesne assignments, to The Haloid Company,
Rochester, -N. Y., a corporation of New York No Drawing. Application October 20, I948, Serial No. 55,645
13 Claims.
This invention relates to a developer for electrostatic images, with particular reference to the development of electrostatic images on plates such as used in electrophotographic processes where a sensitive layer .is charged electrostatically and then exposed to receive allatent electrostatic image which is developed by a developer that results in a powder image, the powder image .being then transferred to asheet of transfer material, and the invention has .for its purpose to afford a developer composed of electroscopic powder and a granular carrier .material that is more efiicient and not open to the objectionable characteristics that have been present in developers heretofore employed for this purpose, also which enables a reduction in the cost of the granular carrier material and makes possible carriers having magnetic properties,
The developers previously used comprise in general a mixture of a suitable pigmented or dyed electroscopic powderand a granular carrier material, which latter functions to carry and to generate triboelectric charges on the electroscopic powders as well as to remove excess powder .from uncharged or slightly charged or background areas of the plate, and it has been found that in some instances, the granular carrier material exhibits a tendency to adhere to the image bearing plate, thus preventing the proper functioning of the electroscopic powder and blocking theimage more or less, and it is ,a particular purpose of the invention to so form the granular carrier material that it is not likely to adhere to the charged or uncharged areas of the plate, and
to insure the removal of substantially all of the granular carrier material from the plate, leaving only the electroscopic powder particles which are attracted and retained by the charged areas.
Another purpose of the invention is to enable controlling the specific gravity of the granular carrier material in relation to the electroscopic developing powder whereby any desired relation between the specific .gravities oi the two components of the mixture may be had while maintaining a proper triboelectric charging relationship between-them.
In general, the'invention comprises the utilization of a granular carrier material consisting of a core, base or interior composed of any selected material which may be of high specific gravity such as glass or steel beads, covered with and encased in a suitable covering which imparts the necessary tri'boelectric properties to the granular carrier material, so that it will properly charge the electroscopic powder when mixed therewith,
while maintaining such a relative specific gravity as to insure against adherence of the granular carrier material to the charged plate.
Such a high specific gravity granular carrier material may be produced by adhering anouter covering consisting of a selected triboelectric'resinous or other suitable substance to the core-or base particles of glass or steel beads or the like by first coating the core particles with an intermediate bonding layer, for example a liquid resin which contains a hydrochloric acid catalyst. The coated core or base "particles are then added to the dry triboelectri'c resinoussubstance which adheres thereto and constitutes a covering that is fused or otherwise affixed to the core'or base particles, any remaining fines being separated by screening, and such coated granular carrier material is then mixed with the 'electroscopic powder to form the-developer.
The invention is carried out by employing an electroscopic powder such as a mixture of 20 parts Amberol F-7l, a phenol-formaldehyde resin manufactured by Resinous Products & Chemical Co., 222 West Washington Square, Philadelphia-5, Pa, and 1 part carbon black such as Raven Bead Carbon Black manufactured by Binney & Smith Co., 41 East 42nd Street, New York 7, N. Y. The electroscopic powder is prepared by mixing the above ingredients and breaking them to a 16- mesh size or smaller, after which approximately 225 grams of the mixture are placed in a onehalf gallon capacity ball mill 'jar containing an aluminum scraper. The jar is filled to approximately three-quarters :its capacity with diamter balls and the mixture ball milled for about four hours, after which it 'is removed from the ball mill jar and iused'on a hot plate under suitable heating lamps or by other suitable means. The mixture is then cooled and broken into approximately Iii-mesh size particles, following which it is micropulverized to an average size of from 1 to 20 microns substantially as disclosed in copending application Ser. No. 24,674, filed May 1, 1948.
It has been ascertained-that in order to develop a latent image comprised of negative electrostatic charges, an electroscopic powder and granular carrier combination should be selected in which the powder is triboelectrically positive to the granular carrier, and to develop a latent image comprised of positive electrostatic charges, an electroscopic powder and granular carrier should beselected in which thepowder is tr-iboelectrically negative to the granular carrier.
This triboelectric relationship between the powder and granular carrier depends on their relative positions in a triboelectric series in which the materials are arranged in such a way that each material is charged with positive electricity When contacted with any material below it in the series and with negative electricity when contacted with any material above it in the series. In the reproduction of high contrast copy such as letters, tracings, etc., it is desirable to select the electroscopic powder and granular carrier materials so that their mutual electrification is considerable, and the degree of such electrification is governed in most cases by the distance between their positions in the triboelectric series, that is, the greater distance they are removed from one another, the greater the mutual electrification, and the closer they are together in Example 1 A suitable granular carrier material for use with plates carrying a negative electrostatic charge is made by using 200 parts glass beads and a covering consisting of 40 parts Vinylite VYLF (a vinyl chloride-vinyl acetate copolymer produced by Bakelite Corporation, 30 East 42nd Street, New York, N. Y.), 8 parts Durite X221 (a phenol-furfural and phenol-formaldehyde thermosetting resin and molding compound manufactured by The Borden Company, Chemical Division, Philadelphia, Pa), and 8 parts Durez 12763 (a phenol-formaldehyde molding compound and resin material manufactured by Durez Plastics llz Chemical Inc., North Tonawanda, N. Y.), said covering being bonded to the glass bead base or core particles by a resin adhesive intermediate coating consisting of 16 parts Durez 8286 (a phenol-formaldehyde molding compound and resin manufactured by Durez Plastics & Chemical Inc., North Tonawanda, N. Y.) catalyzed with 1.5 cc. of a 50% hydrochloric acid. The core particles are first coated with the liquid bonding resin containing the catalyst, and then mixed with the dry covering material, which adheres to the bonding resin on the core particles, andis then fused thereto in any suitable manner. any remaining fines being removed by screening.
The final granular carrier particles are preferably smaller than 30-mesh, i. e. an outer diameter of approximately 0.023 inches, and larger than 50-mesh, i. e. an outer diameter of approximately 0.012 inches, in size, and the electroscopic powder is preferably mixed with the granular carrier material in the proportion of 6 to 170.
Example 2 Another granular carrier material suitable for use with negatively charged plates consists of 200 parts of glass bead core particles covered with 40 parts Saran B115 (a vinylidene chloride resin manufactured by Dow Chemical Co., Midland, Mich.), 16 parts Durite X221, and 16 parts Durez 12763, the covering being adhered to the glass bead core or base particles by a resin bonding agent consisting of 16 parts Bakelite BR7534 (a resin material manufactured by Bakelite Cor- 4 poration, 30 East 42nd Street, New York, N. Y.) to which has been added a catalyst consisting of 1.5 cc. of a 50% hydrochloric acid. This granular carrier material is produced in the same manner as already described, by first applying the liquid bonding resin and catalyst to the core particles, and then adding the core particles coated with the bonding resin to the dry covering material, which imparts the necessary triboelectric properties to the core particles.
This granular carrier material when in its final form is preferably of a size smaller than 30-mesh and larger than 50-mesh, and the electroscopic powder is preferably mixed With(. such granular carrier material in the proportion of 10 to 240.
Example 3 Another ranular carrier material suitable for use with negatively charged plates is produced in a similar manner by using 200 parts of glass beads for the base or core particles, which are covered with 40 parts Pliolite (a butadiene polymer manufactured by Goodyear Tire & Rubber Co., Akron, Ohio), 8 parts Durez 12763, and 8 parts Durite X221, the covering being adhered to the base or core particles by a resin bonding agent consisting of 16 parts Bakelite BR7534 to which has been added a catalyst consisting of 2 cc. of a 50% hydrochloric acid.
The size of the final granular carrier particles are the same as stated above in connection with Examples #1 and #2, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 6 to 225.
Example 4 A suitable granular carrier material for use with a positively charged plate is made by using 500 parts of steel beads for the base or core particles, which are covered with 60 parts Melmac 401 (a thermosetting, melamine-type synthetic resin manufactured by American Cyanamid Co., Plastics Division, New York 20, N. Y.), 40 parts Vinylite VYNS, and 5 parts Nigrosine Base 10 (a black dye manufactured by the Calco Chemical Division of the American Cyanamid Company, Boundbrook, N. J.) adhered to the core or base particles by a bonding agent consisting of 15 parts Bakelite BR7534, to which has been added a catalyst consisting of 1 cc. of a 50% hydrochloric acid.
The granular carrier particles are the same size as stated above, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 8 to 300.
Example 5 Another granular carrier material suitable for use with positively charged plates is produced by applying the same covering as specified in the last mentioned Example #4 to a base or core particles consisting of parts of glass beads, and adhering th covering to the core particles by a bonding agent consisting of 16 parts Bakelite BR7534 to which has been added a catalyst consisting of 1.5 cc. of a 50% hydrochloric acid.
The granular carrier particles are the same size as stated above, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 10 to 230.
Example 6 Another satisfactory granular carrier material for use with a positively charged plate is produced by using carborundum for the base or core particles, covering the same with 60 parts Melmac 4'01, 40 parts Vinylite VYNS, and 5 parts Nigrosine Base 10, adhered to the core or base particles by a bonding agent consisting of parts Bakelite BR7534 to Which has been added a catalyst consisting of 1 cc. of a 50% hydrochloric acid.
This granular carrier material is preferably of a size smaller than -mesh and larger than SO-mesh, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 8 to 300.
Example 7 Another satisfactory granular carrier material for use in printing from a plate carrying a negative charge is made by using 200 parts of glass beads for the core or base particles, covering the same with parts Pliolite, 8 parts Durez 12763, and 8 parts Durite X221, adhered to the base particles by a bonding agent consisting of 15 parts Bakelite Eli/753 i to which has been added a catalyst consisting of 2 cc. of a hydrochloric acid.
The size of the granular carrier material is the same as stated in the precedin examples, and the electroscopic powder is preferably mixed with such granular carrier material in the proportion of 6 to 225.
While the invention has been described in connection with certain specific materials, it is not confined to the details herein disclosed, and this application is intended to cover such modifications or departures as may come within the purposes of the improvements or the scope of the following claims.
I claim:
1. A developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby bein electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostaticallycharged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
2. A developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably 6 adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coatin of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
3. A developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specificgravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles havin a triboelectric relationship of opposite polarity, the powder particles thereby being elec trostatically charged through triboelectric action by mixing with the granular carrier material to m-ovably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
4. A developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a glass bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to remove said charged powder particles from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
5. A developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a carborundum core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to remove said charged powder particles from uncharged areas of the el ctrostatic latent image surface when cascaded thereacross.
. 6. A developer for electrostatic latent images comprising a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a steel bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, a resin coating permanently bonded on said core and an intermediate adhesive coat bonding said coating to the core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostaticallycharged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to remove said charged powder particles from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
7. In an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically attractable material, the improvement comprising developing the ima e by cascading thereacross a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
8. In an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically attractable material, the improvement comprising developing the image by cascading thereacross a dry mixture of loose movable particles of electrostaticallyattractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and
a resin coating permanently bonded on said core, said coating and powder particles having a tribeelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
9. In an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically attractable material, the improvement comprising developing the image by cascading thereacross a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a glass bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
10. In an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically-attractable material, the improvement comprising developing the image by cascading ther across a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a steel bead core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
11. In an electrographic process wherein an electrostatic latent image is developed to yield an electrostatically adhering image of electrostatically-attractable material, the improvement comprising developing the image by cascading thereacross a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a carborundum core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectri'c relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mixing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
12. In an electrophotographic process, the steps of which comprise imposing an electrostatic charge 011 the photoconductive insulating surface of an electrophotographic plate havin a photoconductive insulating layer on a conductive backing, exposing the charged surface to a light image to yield an electrostatic latent image and developing the electrostatic latent image, the improvement comprising developing the image by cascading thereacross a dry mixture of loose movable particles of electrostatically-attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity higher than the specific gravity of the powder particles, whereby it does not adhere to electrostatic latent image surfaces, and a resin coating permanently bonded on said core, said coating and powder particles having a triboelectric relationship of opposite polarity, the powder particles thereby being electrostatically charged through triboelectric action by mix ing with the granular carrier material to movably adhere electrostatically to the surface of the carrier granules and being attractable by an electrostatically-charged insulating layer, and the coating of the granular material being correspondingly electrostatically charged to opposite polarity and thus adapted to attract said charged powder particles and to remove them from uncharged areas of the electrostatic latent image surface when cascaded thereacross.
13. A developer for electrostatic latent images comprising a mixture of loose movable particles of electrostatically attractable powder and separate granular carrier material, the granular material being composed of loose, freely movable particles each of which includes a core having a specific gravity and particle size grossly higher than the specific gravity and particle size of the powder particles and a coating permanently bonded on said core and having a triboelectric relationship of opposite polarity to the powder, the powder material being mcvably and electro statically secured on the surface of said coated granular particles,
LEWIS E. WALKUP.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 389,552 Dean Sept. 18, 1888 1,901,325 Novotny Mar. 14, 1933 2,192,241 Robijns Mar. 5, 1940 2,216,728 Benner et al Oct. 8, 1940 2,297,691 Carlson 1 Oct. 6, 1942 2,345,941 Lehman Apr, 4, 1944 2,440,584 Heltzer et a1. Apr. 27, 1948 2,484,782 Copley Oct. 11, 1949

Claims (1)

1. A DEVELOPER FOR ELECTROSTATIC LATENT IMAGES COMPRISING A DRY MIXTURE OF LOOSE MOVEABLE PARTICLES OF ELECTROSTATICALLY-ATTRACTABLE POWDER AND SEPARATE GRANULAR CARRIER MATERIAL, THE GRANULAR MATERIAL BEING COMPOSED OF LOOSE, FREELY MOVABLE PARTICLES EACH OF WHICH INCLUDES A CORE HAVING A SPECIFIC GRAVITY HIGHER THAN THE SPECIFIC GRAVITY OF THE POWDER PARTICLES, WHEREBY IT DOES NOT ADHERE TO ELECTROSTATIC LATENT IMAGE SURFACES, AND A COATING PERMANENTLY BONDED ON SAID CORE, SAID COATING AND POWDER PARTICLES HAVING A TRIBOELECTRIC RELATIONSHIP OF OPPOSITE POLARITY, THE POWDER PARTICLES THEREBY BEING ELECTROSTATICALLY CHARGED THROUGH TRIBOELECTRIC ACTION BY MIXING WITH THE GRANULAR CARRIER MATERIAL TO MOVABLY ADHERE ELECTROSTATICALLY TO THE SURFACE OF THE CARRIER GRANULES AND BEING ATTRACTABLE BY AN ELECTROSTATICALLYCHARGED INSULATING LAYER, AND THE COATING OF THE GRANULAR MATERIAL BEING CORRESPONDINGLY ELECTROSTATICALLY CHARGED TO OPPOSITE POLARITY AND THUS ADAPTED TO ATTRACT SAID CHARGED POWDER PARTICLES AND TO REMOVE THEM FROM UNCHARGED AREAS OF THE ELECTROSTATIC LATENT IMAGE SURFACE WHEN CASCADED THEREACROSS.
US55645A 1948-10-20 1948-10-20 Developer for electrostatic images Expired - Lifetime US2618551A (en)

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CH292431D CH292431A (en) 1948-10-20 1950-03-17 Developer of electrostatic images.
DEB2977A DE926587C (en) 1948-10-20 1950-04-09 Developer for photographically generated electrostatic latent images

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GB686466A (en) 1953-01-28
DE926587C (en) 1955-04-21
CH292431A (en) 1953-08-15
FR1018653A (en) 1953-01-12

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