US3060020A - Method of electrophotographically producing a multicolor image - Google Patents

Method of electrophotographically producing a multicolor image Download PDF

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US3060020A
US3060020A US850392A US85039259A US3060020A US 3060020 A US3060020 A US 3060020A US 850392 A US850392 A US 850392A US 85039259 A US85039259 A US 85039259A US 3060020 A US3060020 A US 3060020A
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zinc oxide
coating
photoconductive
image
particles
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US850392A
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English (en)
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Harold G Greig
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RCA Corp
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RCA Corp
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Publication date
Priority to BE576841D priority Critical patent/BE576841A/xx
Priority to DER25126A priority patent/DE1168250B/de
Priority to GB8877/59A priority patent/GB914702A/en
Priority to FR789850A priority patent/FR1228380A/fr
Priority to CH7097859A priority patent/CH388772A/de
Priority to SE2723/59A priority patent/SE300928B/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US850392A priority patent/US3060020A/en
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Publication of US3060020A publication Critical patent/US3060020A/en
Anticipated expiration legal-status Critical
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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
    • G03G9/09—Colouring agents for toner particles
    • G03G9/0926—Colouring agents for toner particles characterised by physical or chemical properties
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/01—Electrographic processes using a charge pattern for multicoloured copies
    • G03G13/013—Electrographic processes using a charge pattern for multicoloured copies characterised by the developing step, e.g. the properties of the colour developers
    • G03G13/0133—Electrographic processes using a charge pattern for multicoloured copies characterised by the developing step, e.g. the properties of the colour developers developing using a step for deposition of subtractive colorant developing compositions, e.g. cyan, magenta and yellow
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/06—Developing
    • G03G13/08—Developing using a solid developer, e.g. powder developer
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/20—Fixing, e.g. by using heat
    • 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
    • G03G9/0825—Developers with toner particles characterised by their structure; characterised by non-homogenuous distribution of components
    • 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 electrostatic printing and particularly, but not exclusively, to improved electroscopic developer powders for electrostatic printing and to improved methods of electrostatic printing utilizing the improved developer powders.
  • An electrostatic printing process is that type of process for producing a visible record, reproduction or copy which includes as an intermediate step, converting a light image or electrical signal into an electrostatic charge pattern on an electrically-insulating layer.
  • the process usually includes the conversion of the charge pattern into a visible image which may be a substantially faithful reproduction of an original, except that it may be a different size.
  • a typical electrostatic printing process may include producing an over-all electrostatic charge on the surface of a photoconductive material such as selenium, anthracene or zinc oxide dispersed in an insulating binder.
  • a light image is focused on the charged surface, discharging the portions irradiated by the light rays, while leaving the remainder of the surface in a charged condition, to thus form an electrostatic image.
  • the electrostatic image is rendered visible by applying a developer powder which is held electrostatically to the charged areas of the surface.
  • the powder image thus formed may be fixed directly to the photoconductive material or it may be transferred to another surface upon which the reproduced image may be desired and then fixed thereon.
  • the fixing step commonly comprises fusing the developer powder to the photoconductive material by the application thereto of heat.
  • reproduction of images in a plurality of colors could be accomplished by successively transferring powder images of different colored powders from the photoconductive surface to another surface.
  • this type of process comprises exposing a photoconductive plate, first, to an original through light filters which enable one color to 'be recorded, and then developing with colored powder to produce a copy of that color, then repeating for each other color and superimposing the powder images on the same copy sheet.
  • One object of this invention is to provide improved developer powders which facilitate electrostatic printing in a plurality of colors.
  • Another object of the invention is to provide improved developer powders for electrostatic printing and improved methods of electrostatic printing utilizing such developer powders.
  • Another object is to provide improved developer pow ders which make possible the electrostatic printing of plural color images in situ such that one color is caused to overlap another in desired areas.
  • a further object is to provide improved electroscopic developer powders and methods of electrostatic printing which obviate the need for any transfer steps in electrostatically producing plural color images.
  • a still further object is to provide an improved electrostatic printing process in which plural color images are printed in situ in a manner such that undesired overlapping of one color image by a subsequently produced color image is prevented.
  • the foregoing objects and other advtntages may be accomplished in accordance with the instant invention which provides an improved electroscopic developer powder consisting essentially of finely divided particles of photoconductive zinc oxide coated with a film-forming material.
  • the film-forming material is electroscopic, has a melting point substantially within the range of from 90 C. to 250 C. and a viscosity substantially within a range of from 45 to 10,000 centipoises at a temperature just above its melting point.
  • the zinc oxide has a surface photoconductivity of at least about 10- ohm"- /square/watt/cm. and constitutes substantially from 50% to by weight of the developer powder.
  • a suitable coloring agent may be incorporated in the coating.
  • the photoconductive zinc oxides herein described have the property of being able to hold an electrostatic charge in the dark or under safe-light conditions for a period at least long enough to complete an electrostatic printing process.
  • a developer powder made in accordance with this embodiment is fixed by fusing, the powder image so produced is capable of being electrostatically overprinted.
  • a first powder image can be laid down on an insulating surface, such, for example, as photoconductive zinc oxide, and a second image of different color superimposed on top of the first.
  • suitable coloring agents are incorporated, colored developer powders are provided which can be superimposed one on the other to produce color copies which are substantially faithful reproductions of color prints.
  • the developer powders of this invention possess another useful property. These powders are capable of being processed in accordance with a procedure, to be described hereinafter, which renders them incapable of receiving a superimposed powder image. Thus, the developer powders of this invention are also useful in electrostatic printing processes for producing plural color images in contiguous areas on an insulating surface.
  • improved electrostatic printing methods are provided utilizing the above described electroscopic developer powders.
  • One such method comprises the steps of 1) developing a latent electrostatic image on an insulating surface by applying thereto an electroscopic developer powder of the type described heretofore; (2) applying heat to said developer powder to cause the coating on the zinc oxide particles to melt and flow toward the insulating surface thereby causing portions of the particles of zinc oxide to protrude above the molten coating material and leaving on those portions only a very thin film of coating material; (3) producing a second electrostatic image on the insulating surface having thereon the first developed image; (4) applying a different electroscopic developer powder to the second electrostatic image to produce a second powder image; and (5) fixing the second powder image.
  • the steps of the above method may be '2 repeated to produce, in as many colors as desired, a composite color image.
  • FIG. 1 is a partially-schematic sectional view of an apparatus for producing a blanket electrostatic charge upon an insulating surface.
  • FIG. 2 is a partially-sectional elevational view of an apparatus for projecting light to form by contact an electrostatic image upon the insulating surface of FIG. 1.
  • FIG. 3 is a sectional view of an apparatus for applying electroscopic developer powder, in accordance with this invention, to the image produced in FIG. 2..
  • FIG. 4 is a partially-schematic sectional view of an apparatus for fixing the developed image, produced in FIG. 3, to the insulating surface.
  • FIG. 5 is a partially-schematic sectional view illustrating the result obtained with the apparatus of FIG. 3 in accordance with the method of this invention.
  • FIG. 6 is similar to FIG. 5 but illustrates the result obtained in accordance with a modification of the method of this invention.
  • Zinc oxide which is a good photoconductor for electrostatic printing is an important feature of this invention. Several methods have been devised to distinguish between those which are suitable and those which function poorly or not at all in electrostatic printing.
  • Method 1 A mixture is prepared comprising about milligrams of dry zinc oxide powder and a few drops of an 80% solution of silicone resin in xylene (G.E.-SR 82, marketed by the General Electric Company, Silicone Products Division, Waterford, N.Y.) diluted with toluene in the ratio 60 grams solution to -105 grams toluene.
  • the mixture is coated on filter paper and dried to produce a dry coating over an area about 0.25 inch in diameter.
  • the dry coating is cooled to about 190 C. and examined in light from a mercury vapor lamp having a maximum output at about 3650* A.
  • the zinc oxides which produce printable coatings produce a lavender or orange luminescence. Other Zinc oxides exhibit a green or yellow luminescence.
  • Method 2.About 0.25 gram of dry zinc oxide powder is placed in a silica boat.
  • the boat is inserted into a silica tube and the system flushed with hydrogen gas.
  • the tube and boat are fired for about 5 minutes at about 1000 C. in a stagnant hydrogen atmosphere.
  • the boat is cooled in hydrogen to room temperature.
  • the fired zinc oxide is examined in light from a mercury vapor lamp having a maximum output at about 3650 A.
  • the zinc oxides which produce printable coatings luminesce brightly. Other zinc oxides luminesce weakly or not at all.
  • a preferred photoconductive zinc oxide is one which produces a lavender color in Method 1 and luminesces brightly in Method 2.
  • the useful Zinc oxides selected in accordance with the above procedures have a surface photoconductivity of at least about 10 ohm /square/ watt/cm. when subjected to light of a wavelength of about 3900 A.
  • the surface photoconductivity of a zinc oxide can be determined by applying thereto a third method, as follows:
  • Method 3 A small quantity of Zinc oxide is reduced to a powder and compressed under high pressure (about 15,000 lbs. per square inch) to form a pellet. Electrodes, as of silver paste, are applied on the surface of the pellet leaving a square area of surface uncoated. The pellet is then placed in a monochromator with the aforementioned uncoated surface area facing the light source and successive wavelengths of light throughout the spectrum are projected on this surface. The light beam projected onto the surface is chopped at about 23.5 c.p.s. by a constant speed rotating disc, pierced to produce equal intervals of light and darkness. A D.-C. potential is placed across the electrodes and the current flowing between the electrodes is measured as a function of wavelength with the intensity of radiation being held constant.
  • the zinc oxides which are suitable are those which are substantially electrically non-conductive in the dark. When exposed to light, they should exhibit a surface photoconductivity of a certain level in order to be of practical use for the purposes of this invention. In testing zinc oxides to determine their suitability and utilizing a pellet form, it is convenient to express the results of the measurements of the test as surface photoconductivity because substantially all of the light is absorbed in a thin layer at the surface of the pellet. It has been found that, to be useful in this invention, the zinc oxide selected should have a surface photoconductivity of at least 10- ohm /square/watt/crn. when exposed to a wavelength of about 3900 A.
  • ZINC OXIDE COATINGS Proper selection of a suitable coating material for the particles of zinc oxide is another important feature of this invention.
  • a material is normally selected having a melting point less than the temperature at which paper will char.
  • a preferred temperature range is between C. and 250 C.
  • the coating be one which, when applied to an insulating surface and fused thereon, will function as a binder holding the zinc oxide on the insulating surface. Once the developer powder is fixed or fused to the insulating surface it must itself have insulating properties.
  • a preferred coating material has a high dielectric strength.
  • the viscosity of the coating material comprises another important criterion.
  • the viscosity must be low enough so that when melted the coating will flow off the particles of zinc oxide leaving them partially exposed or protruding with only a very thin film remaining on the exposed or protruding portions of zinc oxide particles.
  • the protruding particles of zinc oxide shall present a matte surface i.e. the film of coating material remaining on the protruding portions of zinc oxide must not be thick enough to provide a gloss finish which would impair subsequent printing operations. It is extremely difficult to measure the thickness of such a film, however, if the physical apearance substantially like that described, is achieved the developer powder will have the characteristics contemplated in this invention.
  • the coating should not be so free flowing as to allow it to migrate into unwanted areas of the insulating surface when melted.
  • a preferred viscosity range is from 45 cps. to 10,000 cps. as measured with a direct reading Brookfield viscosimeter with a spindle speed of 60 rpm.
  • the coating on the particles of zinc oxide have electroscopic properties so that the coated particles may be electrostatically attracted to charged areas of the insulating surface.
  • Coating materials having the foregoing properties may comprise certain natural or synthetic resins, waxes or other low melting materials or mixtures thereof.
  • any of the following materials or combinations of materials may be used:
  • BE Square Wax White (a microcrystalline petroleum wax of the Bareco Oil Co.).
  • Piccolyte S135 (a thermoplastic hydrocarbon terpene resin of the Pennsylvania Industrial Chemical Corp., Clairton, Pennsylvania).
  • Coating materials such as those specified may also include modifying agents such as plasticizers, toughening agents, hardening agents, dispersing agents, etc., which are added to obtain desired physical and electrical properties.
  • modifying agents such as plasticizers, toughening agents, hardening agents, dispersing agents, etc., which are added to obtain desired physical and electrical properties.
  • a developer powder of this invention includes a ratio of zinc oxide to coating material within a range of from 1 to 7 parts by weight of zinc oxide to 1 part by weight of coating material.
  • a powder is generally prepared by first melting the coating material and then dispersing finely divided zinc oXide in the melt. The melt is allowed to cool and harden after which it is broken up and reduced to the desired powder form.
  • the ratio of zinc oxide to coating material specified above is important in a given developer powder formula. The exact ratio depends to a large extent on the particle size and the dispersion of the zinc oxide chosen.
  • Coloring agents such as dyes, stains or pigments can be added to the melt to produce developer powders of a desired color.
  • suitable coloring agents include:
  • Oil Yellow 2 G (Color Index No. 11020, American Cyanamid, New York, N.Y.).
  • various sensitizing agents may be employed to vary the spectral response of a photoconductive zinc oxide.
  • photoconductive white zinc oxide has a spectral sensitivity having a peak in the ultraviolet range.
  • a white photoconductive zinc oxide can be provided having an additional sensitivity peak in other por- 6 tions of'the spectrum. Satisfactory sensitizing agents include the following:
  • Patent Blue (Color Index No. 672).
  • FIG. 1 illustrates a means for applying a uniform electrostatic charge to an insulating surface 11.
  • the insulating surface 11 will comprise a photoconductive coating on a substrate 12 which is illustrated herein as a sheet of paper.
  • the sheet 12 is positioned on a grounded metal plate 13 following which a corona charging unit 14 is passed one or more times over the insulating surface to provide thereon a uniform electrostatic charge.
  • the next step in the process, illustrated in FIG. 2, is to produce an electrostatic image on the photoconductive insulating surface 11.
  • This may be accomplished by placing a photographic transparency 21 upon the charged photoconductive insulating surface 11 and exposing to light derived, for example, from a lamp 22 in the manner of conventional contact printing. Wherever the light strikes the surface 11, the electrostatic charge thereon is reduced or removed. This leaves an electrostatic image or pattern of charges corresponding to the non-illuminated areas of the light image.
  • the electrostatic image may be stored for a while if desired. Ordinarily, the next step is to apply developer powder to the surface 11. Referring to FIG. 3 this may be accomplished by passing a developer brush 31 containing the developer powder across the surface 11 bearing the electrostatic image. Coated particles 32 of developer powder are deposited on those areas of the surface 11 retaining the electrostatic charge.
  • the developer brush comprises a mixture of magnetic carrier particles, for example powdered iron, and the developer powder. The mixture is secured in a magnetic field by a magnet 33 to form the developer brush 31.
  • charging may be accomplished by friction, exposure by projection, and development by dusting the developer powder onto the insulating surface, all as well known in the art.
  • the developed image is now fixed to the surface. This is easily accomplished, as shown in FIG. 4, by passing a resistance heating unit 41 over the image-bearing photoconductor insulating surface 11. When a temperature above the melting point of the coating on the zinc oxide particles is applied thereto, the coating melts and becomes bonded to the surface 11.
  • the heating element 41 may comprise an infrared lamp, or the sheet 12 may be placed in an oven.
  • the zinc oxide particles would tend to be covered with a layer of insulating material too thick to permit discharge by exposure to light.
  • the coating material to have too low a viscosity, for example less than cps., there would be a tendency for it to spread into non-image areas thereby causing a loss in definition of the image. Because of this unique characteristic of the coating material a novel electrostatic printing process is possible as will be described hereinafter.
  • this process involves the overprinting of a first powder image with a second. This is made possible by employing in the development step, described in connection with FIG. 3, coated particles of photoconductive zinc oxide. Upon completion of the fixing step of FIG. 4, these particles provide surfaces in the image areas of the photoconductive insulating surface 11 which are capable of retaining an electrostatic charge in the dark or under safe light conditions. Accordingly, subsequent to the fixing step of FIG. 4, this first proces comprises the steps of (1) recharging the image bearing surface 11 with an overall charge as shown in FIG. 1, (2) exposing the surface to another light image as shown in FIG. 2 to produce a second electrostatic image and (3) developing the second electrostatic image with a different developer powder. The results of this process are shown in FIG. 5.
  • the developer powder first deposited consists of zinc oxide particles 43' and the fused coating material 42.
  • Coated zinc oxide particles 32' are deposited in configuration with the second electrostatic image. Because the zinc oxide in the first developer powder was photoconductive, the second image overlaps the first in those areas upon which light does not impinge during the second exposure, i.e., overprinting of the first image occurs in all areas where the second electrostatic image is superimposed upon the first developed image. Of course, it is also evident that any portions of the areas of the insulating surface 11 not covered by the first developer powder may also become image areas during the second exposure. Developer powder will also be attracted to these areas to complete the second powder image.
  • Charging, exposure, developing and fixing can be carried out a third time to produce a third overprinted powder image.
  • the last development step does not require the use of a photoconductive zinc oxide but, instead, may be accomplished with any type of developed powder commonly employed in the art of electrostatic printing.
  • NON-OVERPRINTING A different result made possible by the unique characteristics of the coating material comprises producing a powder developed image which cannot be overprinted in subsequent electrostatic printing steps. This is accomplished by uniformly flooding the image bearing insulating surface with light after the fusing step of FIG. 4 but before repeating the charging step of FIG. 5. This is easily done by exposing the surface 11 to the lamp 22 of FIG. 2 with the photographic transparency 21 removed to uniformly flood the surface with light. When this step is employed, a fused powder image is rendered incapable of retaining an electrostatic charge when the charging step of FIG. 1 is repeated. Thus, when a two-stage procedure similar to that described with respect to overprinting is carried out, the results obtained are as shown in PEG. 6.
  • the developer powder first deposited consists of zinc oxide particles 43" and the fused coating material 42.
  • the second developer powder consisting of coated zinc oxide particles 32 is deposited in configuration with the second electrostatic image.
  • deposition of the second developer powder will only occur in those areas on the surface 11 not covered by the first deposited developer powder. Therefore, in accordance with this modification, composite color images can be produced consisting of two, three or more colors deposited in contiguous areas on an insulating surface.
  • PHOTOCONDUCTIVE DEVELOPER POWDERS The following group of examples provide developer powders suitable for use in the process described above. These powders, when fused, present a surface which can be overprinted in subsequent electrostatic printing steps.
  • Example I ⁇ VI-HTE DEVELOPER POWDER Parts by weight Carnauba wax 1 Photoconductive French process Zinc oxide 2
  • the wax is melted and particles of the zinc oxide having a particle size of from .025 to .5 micron mean diameter are added to the melt. Particle size and shape of the zinc oxide determine to some extent the ratio of zinc oxide to coating material. Due to the bulking characteristic of zinc oxide finer particles usually require more coating material since there is more total surface to be covered. Continuous stirring from 15 to 30 minutes is sufficient to thoroughly disperse the zinc oxide in the wax when the batch weighs about grams.
  • the mixture is then allowed to cool and harden after which it is reduced to a fine powder. This is accomplished by ball milling the mixture for about 3 hours and then classifying it as to particle size. For most purposes, the fraction below 200 mesh (74 microns) is suitable for use as an electroscopic developer powder.
  • Example II WHITE DEVELOPER POWDER Parts by weight Acrawax C 20 Photoconductive French process zinc oxide 30 Preparation the same as in Example I.
  • Example IV BLUE DEVELOPER POWDER Parts by weight Acrawax C 36 Silicone resin (solid) (Dow Corning No. R5071) 4 Photoconductive French process zinc oxide 70 Cyan Blue Toner G.T 3
  • Example VI RED DEVELOPER POWDER Parts by weight Acrawax C 3o Silicone resin (solid) (Dow Corning No. R5071) 5 Photoconductive French process zinc oxide 80 Benzidine Yellow 3 Preparation as in Example IV.
  • Example VII GREEN DEVELGPER POWDER Parts by weight Piccolyte S-l35 20 Photoconductive French process zinc oxide 30 Benzidine Yellow 1 Brilliant Oil Blue B.M.A 0.23
  • Example VIII GREEN DEVELOPER PO'WDER Parts by weight Piccolyte S-135 20 Photoconductive French process zinc oxide 30 Cyan Blue Toner G.T 1 Benzidine Yellow 1 Preparation as in Example VII.
  • sensitizing agents may be employed with any of the foregoing examples of overprinting developer powders. These sensitizing agents are added to the melt after the zinc oxide and coloring agents have been added.
  • Example IX Add Patent Blue to Examples I to VIII in a ratio of about 0.05 part Patent Blue to 70 parts by weight of zinc oxide. This provides a photoconductive developer powder having a second sensitivity peak of about 6380 A. in the orange portion of the spectrum.
  • Example XI Add Thioflavin T.G. to Examples I to vVIII in a ratio of about 0.1 part of Thiofiavin to about 70 parts by weight of zinc oxide. This provides a photoconductive developer powder having a second sensitivity peak at about 4080 A. in the blue portion of the spectrum.
  • Example XII Add Rose Bengal to Examples I to VIII in a ratio of about 0.05 part of Rose Bengal to about 70 parts by Weight of zinc oxide. This provides a photoconductive developer powder having a second sensitivity peak at about 5500 A. in the green portion of the spectrum.
  • Example XIII Add Fluorescein Sodium to Examples I to VIII in a ratio of about 0.05 part of Florescein to about 70 parts by Weight of zinc oxide. This provides a photoconductive developer powder having a second sensitivity peak at about 4770 A. in the blue-green portion of the spectrum.
  • Example XIV Add Eosin Y to Examples I to VIII in a ratio of about 0.05 part of Eosin Y to 70 parts by weight of zinc oxide. This provides a photoconductive developer powder having a second sensitivity peak at about 5000 A. in the green portion of the spectrum.
  • the method of electrostatic printing comprising the steps of electrophotographically producing a first electrostatic image on a photo-conductive insulating surface, applying to said electrostatic image a first developer powder having a characteristic color and consisting essentially of particles of photoconductive zinc oxide having a surface photoconductivity of at least 10 ohm /square/watt/ cm. at a wavelength of about 3900 A., said particles having a coating thereon of a thermoplastic, electroscopic, insulating material having a melting point substantially within a range of from C. to 250 C.
  • the method of electrostatic printing comprising the steps of electrophotographically producing a first electrostatic image on an insulating surface, applying to said electrostatic image a first developer powder having a characteristic color and consisting essentially of particles of photoconductive zinc oxide having a surface photoconductivity of at least 10" hm /square/watt/cm. at a wavelength of about 3900 A., said particles having a coating thereon of a thermoplastic, electroscopic, insulating material having a melting point substantially within a range of from about 90 C. to 250 C.
  • the method of electrostatic printing comprising the steps of producing a substantially uniform electrostatic charge upon a photoconductive insulating surface, exposing said photoconductive surface to a light image to produce thereon a first electrostatic image, applying to said first electrostatic image a first developer powder having a first characteristic color and consisting essentially of particles of photoconductive Zinc oxide having a surface photoconductivity of at least ohm /square/watt/ cm. at a wavelength of about 3900 A., said particles having a coating thereon of a thermoplastic, electroscopic, insulating material having a melting point substantially within a range of from 90 C. to 250 C.
  • the method of electrostatic printing comprising the steps of producing a substantially uniform electrostatic charge on a photoconductive insulating surface, exposing said photoconductive surface to a first light image to produce thereon a first electrostatic image, applying to said electrostatic image a yellow developer powder consisting essentially of particles of photoconductive Zinc oxide having a surface photoconductivity at least 10- ohm- /square/watt/cm. at a wavelength of about 3900 A., said particles having a coating thereon of a thermoplastic, electroscopic, insulating material including a minor proportion of a yellow coloring agent, said material having a melting point substantially within a range of from C. to 250 C.
  • the method of electrostatic printing comprising the steps of: (l) producing a substantially uniform electrostatic charge upon a photoconductive insulating surface; (2) exposing said photoconductive surface to a first light image to produce therein a first electrostatic image; (3) developing said first electrostatic image by applying thereto a yellow developer powder consisting essentially of particles of photoconductive zinc oxide having a surface photoconductivity of at least l0 ohm /square/watt/ cm. at a wavelength of about 3900 A., said particles having a coating thereon of a thermoplastic, electroscopic, insulating material including a minor proportion of a yellow coloring agent, said material having a melting point substantially within a range of from 90 C. to 250 C.

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  • General Physics & Mathematics (AREA)
  • Developing Agents For Electrophotography (AREA)
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US850392A 1958-03-20 1959-11-02 Method of electrophotographically producing a multicolor image Expired - Lifetime US3060020A (en)

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Application Number Priority Date Filing Date Title
BE576841D BE576841A (zh) 1958-03-20
DER25126A DE1168250B (de) 1958-03-20 1959-03-11 Verfahren zur Herstellung mehrfarbiger Kopien nach einem elektrostatischen Verfahren
GB8877/59A GB914702A (en) 1958-03-20 1959-03-13 Improvements in electrostatic printing
FR789850A FR1228380A (fr) 1958-03-20 1959-03-19 Perfectionnements à l'impression électrostatique
CH7097859A CH388772A (de) 1958-03-20 1959-03-19 Entwicklerpulver für das elektrostatische Kopieren und Verwendung desselben
SE2723/59A SE300928B (zh) 1958-03-20 1959-03-20
US850392A US3060020A (en) 1958-03-20 1959-11-02 Method of electrophotographically producing a multicolor image

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US72270758A 1958-03-20 1958-03-20
US850392A US3060020A (en) 1958-03-20 1959-11-02 Method of electrophotographically producing a multicolor image

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BE (1) BE576841A (zh)
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Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3206601A (en) * 1963-05-21 1965-09-14 Keuffel & Esser Co Plastic film thermography
US3212887A (en) * 1961-04-07 1965-10-19 Minnesota Mining & Mfg Laterally disposed coterminously adjacent multicolor area containing graphic reproduction receptor and electrophotographic process of using same
US3241957A (en) * 1961-06-08 1966-03-22 Harris Intertype Corp Method of developing electrostatic images and liquid developer
US3298830A (en) * 1962-06-16 1967-01-17 Agfa Ag Imagewise sensitization of electro-photographic layers
US3334000A (en) * 1963-12-26 1967-08-01 Xerox Corp Method for simultaneous production of a plurality of microcircuit wafers
US3337340A (en) * 1961-12-28 1967-08-22 Australia Res Lab Method for the reproduction of color
US3342119A (en) * 1961-12-08 1967-09-19 Commw Of Australia Xerographic safe-light
DE1289430B (de) * 1963-07-25 1969-02-13 Hitachi Ltd Geraet fuer die Mehrfarbenreproduktion
US3431412A (en) * 1965-01-08 1969-03-04 Kenichi Nagai Infrared copying process and copying material which releases water of crystallization
US3472657A (en) * 1965-04-30 1969-10-14 Xerox Corp Xerographic development method and apparatus
US3502582A (en) * 1967-06-19 1970-03-24 Xerox Corp Imaging systems
US3511654A (en) * 1964-12-30 1970-05-12 Keuffel & Esser Co Reprographic process
US3609082A (en) * 1967-06-05 1971-09-28 Xerox Corp Electrostatic developer particles containing resin, colorant, metal salt and phthalate
US3620722A (en) * 1967-09-18 1971-11-16 Supply Australia Sensitized developers for electrophotography and electroradiography
US3702483A (en) * 1970-12-23 1972-11-07 Xerox Corp Color rendition method
US3725283A (en) * 1971-01-06 1973-04-03 Xerox Corp Electrostatographic developer containing uncoated glass-ceramic carrier particles
US3870644A (en) * 1969-02-10 1975-03-11 Ricoh Kk Liquid developer for plural-color electrophotography
US3982938A (en) * 1973-02-13 1976-09-28 Fuji Photo Film Co., Ltd. Photoconductive toners which include photoconductive pigment particles in a charge-transporting insulating binder
US4063946A (en) * 1973-01-22 1977-12-20 Rank Xerox Ltd. Electrophotographic color reproduction process employing photoconductive material with dual light fatigue properties
US4147645A (en) * 1977-12-23 1979-04-03 Xerox Corporation Electrographic flash fusing toners
US4206064A (en) * 1977-04-13 1980-06-03 Canon Kabushiki Kaisha Negatively charged toner for developing electrostatic images containing metal complex of salicyclic acid compound as charge control agent
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
US4299903A (en) * 1980-07-03 1981-11-10 Xerox Corporation Emulsion polymerization process for dry positive toner compositions employs charge control agent as wetting agent
EP0081887A1 (en) * 1981-12-16 1983-06-22 Coulter Stork Patents B.V. Method for the application of a protective light-transmitting coating on a toner image formed on a substrate
US4430402A (en) 1979-08-02 1984-02-07 Ricoh Co., Ltd. Dichromatic electrophotography using two developer compositions applied sequentially
US4510223A (en) * 1983-02-07 1985-04-09 Coulter Systems Corporation Multicolor electrophotographic imaging process
EP0270728A1 (en) * 1986-11-10 1988-06-15 EASTMAN KODAK COMPANY (a New Jersey corporation) Electrophotographic apparatus for forming a multi-color image

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US2297691A (en) * 1939-04-04 1942-10-06 Chester F Carlson Electrophotography
US2584695A (en) * 1947-08-14 1952-02-05 Bell & Howell Co Electrostatic reproduction process and apparatus
US2735785A (en) * 1953-07-30 1956-02-21 Process of electrostatic printing
US2758939A (en) * 1953-12-30 1956-08-14 Rca Corp Electrostatic printing
US2808328A (en) * 1950-07-15 1957-10-01 Carlyle W Jacob Method and apparatus for xerographic reproduction
US2868642A (en) * 1955-01-03 1959-01-13 Haloid Xerox Inc Electrophotographic method
US2894840A (en) * 1955-06-14 1959-07-14 Haloid Xerox Inc Method for fixing xerographic images
US2924519A (en) * 1957-12-27 1960-02-09 Ibm Machine and method for reproducing images with photoconductive ink
US2972304A (en) * 1959-06-02 1961-02-21 Eastman Kodak Co Electrostatic printing

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2297691A (en) * 1939-04-04 1942-10-06 Chester F Carlson Electrophotography
US2584695A (en) * 1947-08-14 1952-02-05 Bell & Howell Co Electrostatic reproduction process and apparatus
US2808328A (en) * 1950-07-15 1957-10-01 Carlyle W Jacob Method and apparatus for xerographic reproduction
US2735785A (en) * 1953-07-30 1956-02-21 Process of electrostatic printing
US2758939A (en) * 1953-12-30 1956-08-14 Rca Corp Electrostatic printing
US2868642A (en) * 1955-01-03 1959-01-13 Haloid Xerox Inc Electrophotographic method
US2894840A (en) * 1955-06-14 1959-07-14 Haloid Xerox Inc Method for fixing xerographic images
US2924519A (en) * 1957-12-27 1960-02-09 Ibm Machine and method for reproducing images with photoconductive ink
US2972304A (en) * 1959-06-02 1961-02-21 Eastman Kodak Co Electrostatic printing

Cited By (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3212887A (en) * 1961-04-07 1965-10-19 Minnesota Mining & Mfg Laterally disposed coterminously adjacent multicolor area containing graphic reproduction receptor and electrophotographic process of using same
US3241957A (en) * 1961-06-08 1966-03-22 Harris Intertype Corp Method of developing electrostatic images and liquid developer
US3342119A (en) * 1961-12-08 1967-09-19 Commw Of Australia Xerographic safe-light
US3337340A (en) * 1961-12-28 1967-08-22 Australia Res Lab Method for the reproduction of color
US3298830A (en) * 1962-06-16 1967-01-17 Agfa Ag Imagewise sensitization of electro-photographic layers
US3206601A (en) * 1963-05-21 1965-09-14 Keuffel & Esser Co Plastic film thermography
DE1289430B (de) * 1963-07-25 1969-02-13 Hitachi Ltd Geraet fuer die Mehrfarbenreproduktion
US3531195A (en) * 1963-07-25 1970-09-29 Hitachi Ltd Method and apparatus for multicolor printing
US3334000A (en) * 1963-12-26 1967-08-01 Xerox Corp Method for simultaneous production of a plurality of microcircuit wafers
US3511654A (en) * 1964-12-30 1970-05-12 Keuffel & Esser Co Reprographic process
US3431412A (en) * 1965-01-08 1969-03-04 Kenichi Nagai Infrared copying process and copying material which releases water of crystallization
US3472657A (en) * 1965-04-30 1969-10-14 Xerox Corp Xerographic development method and apparatus
US3609082A (en) * 1967-06-05 1971-09-28 Xerox Corp Electrostatic developer particles containing resin, colorant, metal salt and phthalate
US3502582A (en) * 1967-06-19 1970-03-24 Xerox Corp Imaging systems
US3620722A (en) * 1967-09-18 1971-11-16 Supply Australia Sensitized developers for electrophotography and electroradiography
US3870644A (en) * 1969-02-10 1975-03-11 Ricoh Kk Liquid developer for plural-color electrophotography
US3702483A (en) * 1970-12-23 1972-11-07 Xerox Corp Color rendition method
US3725283A (en) * 1971-01-06 1973-04-03 Xerox Corp Electrostatographic developer containing uncoated glass-ceramic carrier particles
US4063946A (en) * 1973-01-22 1977-12-20 Rank Xerox Ltd. Electrophotographic color reproduction process employing photoconductive material with dual light fatigue properties
US3982938A (en) * 1973-02-13 1976-09-28 Fuji Photo Film Co., Ltd. Photoconductive toners which include photoconductive pigment particles in a charge-transporting insulating binder
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
US4206064A (en) * 1977-04-13 1980-06-03 Canon Kabushiki Kaisha Negatively charged toner for developing electrostatic images containing metal complex of salicyclic acid compound as charge control agent
US4147645A (en) * 1977-12-23 1979-04-03 Xerox Corporation Electrographic flash fusing toners
US4430402A (en) 1979-08-02 1984-02-07 Ricoh Co., Ltd. Dichromatic electrophotography using two developer compositions applied sequentially
US4299903A (en) * 1980-07-03 1981-11-10 Xerox Corporation Emulsion polymerization process for dry positive toner compositions employs charge control agent as wetting agent
EP0081887A1 (en) * 1981-12-16 1983-06-22 Coulter Stork Patents B.V. Method for the application of a protective light-transmitting coating on a toner image formed on a substrate
US4510223A (en) * 1983-02-07 1985-04-09 Coulter Systems Corporation Multicolor electrophotographic imaging process
EP0270728A1 (en) * 1986-11-10 1988-06-15 EASTMAN KODAK COMPANY (a New Jersey corporation) Electrophotographic apparatus for forming a multi-color image

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BE576841A (zh)
DE1168250B (de) 1964-04-16
FR1228380A (fr) 1960-08-29

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