US3300410A - Conductive liquid developer for xerographic images - Google Patents

Conductive liquid developer for xerographic images Download PDF

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Publication number
US3300410A
US3300410A US174989A US17498962A US3300410A US 3300410 A US3300410 A US 3300410A US 174989 A US174989 A US 174989A US 17498962 A US17498962 A US 17498962A US 3300410 A US3300410 A US 3300410A
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United States
Prior art keywords
resin
developer
image
solvent
conductive
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Expired - Lifetime
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US174989A
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English (en)
Inventor
Oliphant Keith Meridith
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Research Laboratories of Australia Pty Ltd
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Research Laboratories of Australia Pty Ltd
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Filing date
Publication date
Priority claimed from AU2370/61A external-priority patent/AU259423B2/en
Application filed by Research Laboratories of Australia Pty Ltd filed Critical Research Laboratories of Australia Pty Ltd
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Publication of US3300410A publication Critical patent/US3300410A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • G03G9/12—Developers with toner particles in liquid developer mixtures
    • G03G9/13—Developers with toner particles in liquid developer mixtures characterised by polymer components
    • G03G9/132—Developers with toner particles in liquid developer mixtures characterised by polymer components obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds

Definitions

  • This invention relates to liquid developers for electrostatic images with particular reference to the development of electrostatic images on plates or papers and other backings of the kind used in electrophotographic processes wherein an image is produced on an electrostatically charged plate by purely electrical or by photographic means.
  • the invention also relates to those processes where a sensitive layer is charged electrostatically and then exposed to form a latent image which is developed by a developer to give a powder image which may then be transferred to a sheet of transfer material.
  • the invention has for its purpose to afford a developer composed of material which is conductive when deposited and acts as a shield to protect the underlying sheet against subsequent charging so that subsequent charging is constrained to occur in the unshielded areas.
  • Developers previously used for the purpose comprised metallic particles and the like deposited on the photoconductor surfaces in pattern form for the purpose of shielding the surface beneath the deposited particles ied States Patent against the effect of charging which would ordinarily be achieved for example by submitting the photoconductive sheet to a corona discharge from an array of needles or wires.
  • This shielding is effected by using a developer containing conductive particles which when deposited from the developer carrier liquid or fluid will act as the necessary conductive shielding medium.
  • particulate material or powder which is milled or otherwise'coated with a resin and to suspend this in a liquid of high electrical volume resistivity and low dielectric constant whereby the particles are free to deposit under the influence of and in the direction of the electric field associated with the image or electrostatic pattern.
  • developers of this type is in the production of reversed images in Xerography or electrophotography where it is necessary to first develop the xerographic image by depositing the developer which will thereafter act to mask the areas on which it is deposited and then to recharge the areas on which the developer particles are not present or present to a lesser degree and to redevelop the so-formed image with a colour which will produce the required appearance of reversal, said second developer having a darker hue than said conductive developer.
  • the image in the first development comprises particulate material which limits resolution because of limitations in particle size because large particles are necessary otherwise the development results only in partial shielding where full shielding is desired.
  • Another dis- "ice advantage is that the first development is carried out with a developer which is coloured or at least solid material of white colour and all of this material may require removal or removal in part in order to reveal the finished reversal picture.
  • a further disadvantage is the limitation that the developer particles must themselves comprise material which is intrinsically conductive of itself and this excludes material which is intrinsically insulating.
  • one object of this invention is to provide an improved developer containing conductive material which comprise colourless or transparent substances available to deposit from suspension to form an image of an invisible kind which subsequently controls the deposition of a second developer by electrically shielding the underlying surface.
  • Another object of the present invention is to provide a conductive developer having improved resolution.
  • a still further object of thi invention is to provide a conductive developer for reversal of images which is characterised in that it is not necessary to remove the developer material of the first step when the surface has been subjected to development in the second step.
  • the objects of the invention are achieved by utilizing a resin or similar film-forming material for the first development, said film forming material having been rendered at least temporarily conductive by the addition thereto of a material with a low volume resistivity, such as a polar solvent, in such a manner that sufiicient solvent is retained in or on the resin or the like to render the film produced therefrom relatively conductive when deposited.
  • a material with a low volume resistivity such as a polar solvent
  • the invention is carried into effect by dissolving a suitable resin in a strong polar solvent or by subjecting the resin to vapour of said solvent or by permitting said resin to otherwise imbibe said solvent by contact between the resin and the solvent such as for example the solvent methyl iso-butyl ketone after which the solution so formed is subjected to the action of a weaker non-polar solvent which is soluble in the methyl iso-butyl ketone but has a lower solubility for the resin so as to cause precipitation of the resin from the mixture because of the lowered solubility of the resin in the mixture.
  • the resin precipitate so produced is then dispersed in a liquid vehicle characterised by high electrical resistivity and low dielectric constant and the dispersion is used thereafter as a developer for electrostatic images the dispersion being such that the resin is available in a mobile colloidal form in the carrier liquid so as to allow the resin to be deposited electrically from the body of the liquid according to the electrostatic field relating to the latent electrostatic image existing on the photoconductive or other surface.
  • the resin is dissolved in a polar solvent or in a solvent with relatively low volume resistivity and this solution. is reduced in solvent power thereafter by the addition of a poor solvent and this results in precipitation of the resin.
  • This process of precipitation may be repeated a number of times or other polar solvents may be used for causing precipitation so as to eliminate any excess of polar solvent or low volume resistivity solvent in the final vehicle because the presence of polar solvent in the final carrier liquid requires control so that it does not lower the volume resistivity of the total liquid beyond the limit allowable for liquid developers. It is known for instance that liquid developers must utilize a carrier liquid having a volume resistivity in excess of ohm-cm.
  • the improved process has particular refer ence to the use of resins which are themselves colourless or substantially colourless and which would not in themselves be electrically conductive to the extent of masking an area of photoconductor surface against recharging but when such resins are treated with a conductive polar solvent or imbibe said solvent they will provide a conductive medium which will blanket the photoconductor beneath the resin deposit and will prevent said photoconductor from taking a surface charge when subject to a corona discharge or the like when applied in the customary way for charging insulator surfaces.
  • the invention thus allows a photoconductor surface such as for example a zinc oxide dispersed in a resin to retain a normal colouration and when a reversed image is produced by the present method only one development will be apparent namely the second development this being however deposited in the opposite or reverse areas to the original optical or X-ray or electrostatic image by means of which the first conductive developer material was attracted to the photoconductive surface.
  • a photoconductor surface such as for example a zinc oxide dispersed in a resin to retain a normal colouration and when a reversed image is produced by the present method only one development will be apparent namely the second development this being however deposited in the opposite or reverse areas to the original optical or X-ray or electrostatic image by means of which the first conductive developer material was attracted to the photoconductive surface.
  • FIGURE 1 shows a schematic dia gram of a sheet covered with an insulator or photoinsulator or photoconductive coating.
  • FIGURE 2 shows this sheet after first development with a conductive developer present in the image areas.
  • FIGURE 3 shows this sheet after recharging by means of a corona discharge with charges deposited in the nonimage areas
  • FIGURE 4 shows the sheet after the second development in which a known xerographic type of developer is deposited in the charged areas of FIGURE 3, to produce a reversal of the original image.
  • FIGURE 1 a sheet or backing of metal or wood or paper or other material is coated with an insulator material such as a film of resin or a photoinsulator such as selenium applied for example by vacuum evaporation or a layer of a photoconductor such as zinc oxide embedded in an insulating film such as for example an alkyd resin or an epoxy resin.
  • an insulator material such as a film of resin or a photoinsulator such as selenium applied for example by vacuum evaporation or a layer of a photoconductor such as zinc oxide embedded in an insulating film such as for example an alkyd resin or an epoxy resin.
  • the sheet is designated 1 and the coating thereon is designated 2.
  • FIGURE 2 shows said sheet 1 coated with said photoconductive coating 2 which has been subjected to an over all electrostatic charge which has been bled away by exposure to light or may consist merely of an electrostatic image produced by differential charging, so as to produce in the areas 5 and 6 charged Zones which will attract the conductive developer material 3 and 4 in which 3 represents the resin and 4 the adsorbed or imbibed polar solvent which is pictured as a continuous film on the top of the resin layer but may actually consist of particles or globules of resin having a coating or outer layer of conductive or polar solvent thereon.
  • FIGURE 3 shows the sheet 1 and coating 2, surmounted in the image areas 5 and 6 by the developer material 3 and 4 said sheet 1 has then been recharged overall by a corona discharge device but has retained charge only in the non-image areas designated 7 and 8.
  • FIGURE 4 shows the sheet 1 and coating 2 carrying the first developed image 3, 4 and the second developed image 9 and It) in the areas which were recharged and developed thereafter designated 7 and S, the second developed image 9 and 19 comprising a reversal of the original optical image or electrostatic image.
  • the final sheet is composed thereof of a first image 3, 4 which is conductive and transparent and colourless and a second reversed image 9, 10 which may be composed of any ordinary xerographic developer material.
  • the polar solvent 4 may be allowed to evaporate if desired following which the resin first image may be retained as an insulating film which is invisible to the eye.
  • any polar solvent or any solvent with relatively low volume resistivity can be used in association with any resin capable of dissolving and holding the polar solvent at least during the first and second developments so that the presence of the polar solvent renders the resin at least temporarily conductive or semi-conductive.
  • a dye or colouring medium may be incorporated with the resin or the polar solvent if it is desired to produce for any reason a coloured first development.
  • Example 1 In the first example of the invention the resin which was used was epichlorohydrin resin supplied under the trademark Epikote 850 by Shell Co. This resin is supplied in solution in solvents which include butyl Cellosolve (ethylene glycol monobutyl ether) which is a polar solvent.
  • the first step in formulation was to produce a solution of epichiorohydrin resin in the polar solvent by evaporating to 60 percent solids.
  • this solution was dispersed in a hydrocarbon solvent having a Kauri Butanol value of 40, an aniline point of 49, containing 8 percent aromatics as known under the trademark Shell Solvent X55 by vigorously shaking the resin in the solvent at room temperatures, e.g., 20 C.
  • Example 2 A conductive resin dispersion was prepared from a short oil type linseed oil modified alkyd resin known under the tradename, Rhodene L9/50 supplied by Polymer Corporation Ltd., in which the alkyd resin was dissolved as a 50 percent solids solution in non-volatile aromatic hydrocarbon solvents.
  • Rhodene L9/50 has an oil length of 40%, an acid value of 25-35 and specific gravity at 20 C. of 0.98-0.99. This solution was diluted with 2 parts by volume of acetone to 1 part of solution and was then shock precipitated at 20 C. or in the range C. to 50 C. by the addition of 10 parts by volume of an aliphatic hydrocarbon such as the solvent known under the trademark Shell Solvent X55.
  • Example 3 In the first step of this example an epoxyester resin was used.
  • the particular resin was one marketed under the trade name Beckosol P786, by Reichhold Chemical, which is an epoxyester resin containing 42 percent dehydrated castor oil having an acid value of 3 maximum in solution in xylol to the extent of 50 percent solids.
  • This was diluted with 4 parts of acetone in which the resin is soluble and then shock precipitated by the addition at 20 C. of 10 parts of an aliphatic hydrocarbon liquid such as that known under the trademark Shell Solvent X4.
  • the excess liquid was decanted and the precipitate re-dissolved with toluene in the proportions 10 parts by volume of toluene to 1 part of precipitate.
  • a conductive resin dispersion was obtained by adding the resultant solution to the above alpihatic hydrocarbon liquid in the proportion 1 part of solution to 30 parts of the liquid by volume.
  • the resultant suspension was used as a colourless first developer in the process of reversal of an electrostatic image giving a resolution of more than 50 lines/ mm. for the first developer.
  • the invention resides in the production of a liquid developer for electrostatic images characterized in that a resin is first dissolved in or has dissolved in itself a polar solvent or a solvent which dissociates and therefore is able to conduct or transport electricity or to cause the collapse of an electric field relating to an image charge, said solution of the resin in the polar solvent or of the polar solvent in the resin as the case may be being thereafter dispersed having regard to temperature in a non-polar or insulating liquid of the type which it is well known now to use in the art of liquid development so as to produce a liquid developer for electrostatic images wherein the particles available for development are resinous fine particles or colourless colloid film-forming particles characterised by having a high electrical conductivity or high dielectric constant or dissociating character which will not support a charge after deposition of these particles on the surface of the photoconductive sheet but characterized by being inert for the purposes of liquid development in that the property of conductivity of the surface of the particles does not impair the charge supporting properties of the carrier liquid
  • a developer consisting essentially of an electrically insulating carrier liquid having a volume resistivity in excess of 10 ohm cm. and a dielectric constant less than 3, film-forming resin particles suspended in said carrier liquid in the volumetric proportion of from about 0.1 to 1.5 parts of said resin to parts of said carrier liquid, and an electrically conductive at least partial solvent for said resin and having a lower volume resistivity than said film-forming resin, wherein the volume resistivity of said partial solvent is below 10 ohm cm.
  • said partial solvent being adsorbed onto the resin particles and being present in a quantity just sufficient to be fully adsorbed by said suspended resin particles but not sufiicient to dissolve or disperse in said carrier liquid so as to lower substantially the volume resistivity thereof.
  • a developer according to claim 1 wherein the resin is selected from the group consisting of linseed oil modified alkyd resin and epoxy ester resin containing dehydrated castor oil.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Liquid Developers In Electrophotography (AREA)
US174989A 1961-03-13 1962-02-23 Conductive liquid developer for xerographic images Expired - Lifetime US3300410A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AU2370/61A AU259423B2 (en) 1961-03-13 Conductive liquid developer for xerographic images

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US3300410A true US3300410A (en) 1967-01-24

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US (1) US3300410A (fr)
BE (1) BE615061A (fr)
CH (1) CH424480A (fr)
DE (1) DE1250738B (fr)
FR (1) FR1317622A (fr)
GB (1) GB1001554A (fr)
NL (1) NL275581A (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3498917A (en) * 1965-10-23 1970-03-03 Philips Corp Liquid developer for electrostatic images
US3793205A (en) * 1963-07-11 1974-02-19 Commw Chargeless developer
US3804658A (en) * 1964-07-09 1974-04-16 K Metcalfe Method of improving development of xerographic images
US3808026A (en) * 1972-03-13 1974-04-30 Xerox Corp Liquid development of electrostatic latent image
US3836361A (en) * 1971-09-30 1974-09-17 Commw Of Au Care Of The Secret Method of developing an electrophotographic image with a bias field
US3901698A (en) * 1971-12-10 1975-08-26 Rank Xerox Ltd Method of reversal development using two electrostatic developers
US3907694A (en) * 1973-05-25 1975-09-23 Xerox Corp Non-volatile conductive inks
US3972611A (en) * 1970-03-18 1976-08-03 Canon Kabushiki Kaisha Apparatus for transferring images produced by liquid developer

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2907674A (en) * 1955-12-29 1959-10-06 Commw Of Australia Process for developing electrostatic image with liquid developer
US2939804A (en) * 1958-01-23 1960-06-07 Uarco Inc Resin particle coated with metal
US2945825A (en) * 1957-10-21 1960-07-19 Myron A Coler Conductive plastic structure
US3005726A (en) * 1958-05-01 1961-10-24 Xerox Corp Process of developing electrostatic images
US3135695A (en) * 1961-02-20 1964-06-02 Eastman Kodak Co Liquid developers for electrostatic photography

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2907674A (en) * 1955-12-29 1959-10-06 Commw Of Australia Process for developing electrostatic image with liquid developer
US2945825A (en) * 1957-10-21 1960-07-19 Myron A Coler Conductive plastic structure
US2939804A (en) * 1958-01-23 1960-06-07 Uarco Inc Resin particle coated with metal
US3005726A (en) * 1958-05-01 1961-10-24 Xerox Corp Process of developing electrostatic images
US3135695A (en) * 1961-02-20 1964-06-02 Eastman Kodak Co Liquid developers for electrostatic photography

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793205A (en) * 1963-07-11 1974-02-19 Commw Chargeless developer
US3804658A (en) * 1964-07-09 1974-04-16 K Metcalfe Method of improving development of xerographic images
US3498917A (en) * 1965-10-23 1970-03-03 Philips Corp Liquid developer for electrostatic images
US3972611A (en) * 1970-03-18 1976-08-03 Canon Kabushiki Kaisha Apparatus for transferring images produced by liquid developer
US3836361A (en) * 1971-09-30 1974-09-17 Commw Of Au Care Of The Secret Method of developing an electrophotographic image with a bias field
US3901698A (en) * 1971-12-10 1975-08-26 Rank Xerox Ltd Method of reversal development using two electrostatic developers
US3808026A (en) * 1972-03-13 1974-04-30 Xerox Corp Liquid development of electrostatic latent image
US3907694A (en) * 1973-05-25 1975-09-23 Xerox Corp Non-volatile conductive inks

Also Published As

Publication number Publication date
GB1001554A (en) 1965-08-18
DE1250738B (fr)
BE615061A (fr)
NL275581A (fr)
CH424480A (fr) 1966-11-15
FR1317622A (fr) 1963-05-08

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