Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording-members for original recording by exposure, e.g. to light, to heat or to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/005—Materials for treating the recording members, e.g. for cleaning, reactivating, polishing
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G21/00—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge
  • G03G21/0005—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge for removing solid developer or debris from the electrographic recording medium

Definitions

• the present invention relates to electrophotography and more particularly to improvements in the formation of images by electrophotographic processes.
• electrophotographic processes for producing visible images comprise the steps of electrostatically charging in the dark a photoconductive surface of an inorganic photoconductor, e.g. zinc oxide and selenium,or of an organic photoconductor, image-wise'exposing the said surface to form a latent electrostatic image and developing thematerial to form a visible image by depositing on the image a finely divided electroscopic material usually.
• the toner particles are attracted and deposited on the charged areas of the latent image or are repelled by the charged areas and deposited on the discharged areas.
• the toner image is then fixed by heating, by an overcoating treatment or by the action of solvents. Before fixing, the toner image may be transferred to a support surface such as paper and then permanently affixed thereto.
• a support surface such as paper and then permanently affixed thereto.
• the toner is used in combination with solid carrier particlesor the toner particles can be dispersed in an insulating liquid.
• a dry developer is composed of two components, a finely ground pigmented or coloured resinous toner and a relatively coarse-grained carrier material.
• the developing mixture may be cascaded merely over the exposed plate.
• the carriermaterial e.g.,glass or steel beads, which may be enveloped by a resinous filmforming product, carries the toner as it cascades over the plate and also triboelectrically charges the toner particles to the desired polarity.
• the toner carrier mixture flows over the surface bearing the latent electrostatic image thetoner particles are'attracted by the charged areas of the image and not by the discharged areas or background areas of the image.
• the powder image formed is then fixed as described above on the photoconductive plate or can be transferred to a receptor surface, e.g. a paper sheet.
• the transfer can be accomplished by bringing the powder image in contact with the receptor surface, if necessary, in the presence of an electrostatic field. If the receptor surface, e.g. the paper sheet, is then stripped from the image-carrying surface, it carries with it a substantial amount of toner particles in-the form 'ofthe desiredim age. Subsequently, this image can be made permanent, i.e. fixed, according to any desired method such as heating or solvent fixing.
• Removal of the residual powder on the plate by means of a brush type cleaning means is usually effected by brushing the powder by means of one or more rotating brushes into a stream of air, which is exhausted through a filtering sys tem.
• the web type cleaning means comprises a web of fibrous material, which is advanced into pressure and rubbing contact with the plate surface.
• Cleaning of reusable photoconductive plates or V drums is not always satisfactory, which may depend on a whole series of factors, e.g. the nature of the tonercarrier mixture employed and the relative humidity of the atmosphere.
• When'relative humidity is high the electrical and transfer characteristics of the photoconductive imaging surfaces are generally adversely effected and proper cleaning is impaired.
• Some toners and carriers are abrasive in nature so that on contact thereof with the imaging surfaces mutual deterioration of these components is accelerated.
• the cleaning devices also have an abrasive influence on the imaging surfaces when contacted therewith. Through the erosion of the imaging surfaces, cleaning becomes more difficult to effect.
• an electrophotographic imaging process which comprises the steps of: forming a latent electrostatic image on an imaging surface; forming a powder image corresponding to said electrostatic image by applying a developing material to said surface, transferring said powder image from said imaging surface to a receptor surface, and. cleaning the said imaging surface, wherein at least one hydrophobic bivalent or trivalent metal salt of a halfester of a branched-chain or straight-chain aliphatic dicarboxylic acid and/or at least one bivalent or trivalent metal salt of a monoester or diester of a phosphorous oxyacid is-or are applied to said imaging surface before and/or during said cleaning thereof.
• the application to the electrostatographic imaging surface of one or more metal salts as defined above not only facilitates the usual cleaning carried out between use and reuse of the imaging surface in that removal of residual toner particles from the imaging surface is promoted but also reduces abrasion of the photoconductive imaging surfaces, reduces staining of the elec- 3 trophotographic images obtained on the receptor materials and yields images with improved contrast.
• the invention includes any electrophotographic imaging process involving the formation on a surface of an electrostatic image, its development by means of a powder, andsubsequent image-wise transfer of powder from said surface to a receptor material, wherein the surface on which said electrostatic image is formed is a surface on which there is a deposit of one or more metal salts as above defined.
• the imaging surface used in such a process can be very readily cleaned without abrading the surface.
• a said metal salt or salts may be applied to the imaging surface in any convenient manner prior to forming the latent electrostatic image or subsequent to transferring the powder image from the imaged surface to the receptor surface.
• Such salt(s) may be applied to ,the imaging surface as loose powder, a melt, a solution, an emulsion or dispersion, etc.
• Loose powder can be sprinkled on the imaging surface and liquids containing the metal salts in dissolved or dispersed form may be applied to the imaging surface according to any conventional coating method, e.g., spraying, dip-coating etc.
• the metal salts are preferably dissolved or dispersed in a suitable solvent and the solution is then applied to the imaging surface whereupon'the solvent is removed by evaporation.
• the metal salts may also be cascaded in the form of powder over the imaging surface.
• said metal salt(s) is or are applied to the imaging surface after transfer of the powder image to the recep-- tor surface to promote cleaning of the surface at that stage.
• the salt(s) may be applied by rubhing or wiping said surface for a certain period of time with an applicator device or member carrying such salt(s) on at least the side thereof which contacts such surface.
• the said applicator device or member may be used solely for treating the photoconductive plate,
• drum or other member providing the imaging surface with the metal salt(s) but it is preferably also used for cleaning the re-usable photoconductive surface as referred to above.
• application of the metal salt(s) to the imaging surface and cleaning of the surface between use and re-use may be combined in a single operation.
• the salt(s) applied to the imaging surface may be completely wiped away but a feature which is at present considered likely to be of importance comprises the cleaning of the imaging surface so that a deposit of the salt(s), which may be a very slight deposit, remains on the surface. This is of course proposed primarily with a view-to re-use of the surface in the formation of a further electrophotographic image.
• cleaning by means of or with the aid of a said salt or salts may take place periodically, e.g., in every cycle or at intervals of two or more cycles.
• the metal salt(s) for use according to the present invention should be hydrophobic i.e., substantially insoluble in water, otherwise they would be adversely afgeneral comprise a straight-chain or branched-chain aliphatic hydrocarbon group of at least five carbon atoms, preferably at least 10 carbon atoms, which group may be substituted with hydrophobic groups, e.g. halogen, preferably fluorine and/or may be interrupted by hetero atoms, e.g.' oxygen, sulphur and nitrogen. This group may be an ester group of the said metal salts or a substituent on the chain linking the two carboxylic acid groups of the dicarboxylic acid. In the phosphorus oxyacids preferably all the hydrogen atoms that wereplaceable by a metal atom are replaced by a metal atom.
• hydrophobic groups e.g. halogen, preferably fluorine and/or may be interrupted by hetero atoms, e.g.' oxygen, sulphur and nitrogen.
• Typical dicarboxylic acids from which the hydrophobic metal salts may be derived include: succinic acid, glutaric acid, maleic acid and glutaconic acid and mixtures thereof.
• the phosphorus oxyacids include ortho-, pyroand hypophosphoric acid, phosphonic acids and phosphinic acids. Excellent results are obtained where the metal salts are zinc salts.
• other salts may also be used, for example magnesium salts, calcium salts, strontium. salts, barium salts, iron salts, cobalt salts, nickel salts, copper salts, cadmium salts, aluminium salts and lead salts.
• the preparationof the metal salts of the esters of phosphorus oxyacids. as defined is quite simple. According to a particularly suitable method a stoichiometric amount of oxyacid ester is dissolved in an aliphatic alcohol and added to a solution or suspension of a metal acetate inan aliphatic-alcohol. The metal salt of the phosphorus oxyacid ester normally separates by precipitation in the alcohol or is obtained therefrom by evaporation of the solvent.
• thermometer and droppingfunnel were placed: 2.8.litresof water, 300 ml of hydrochloric: acid and; 1,260rmlof dioxan.
• the mixture was heated on: a boilingwater-bath to 80 C whereupon a solution of l,0l0gzot thie,productformed in step (a) in 1,250 ml of dioxan was added dropwise over 90; minutes. The temperature rose to 9 2- C and the mixture was stirred for 5 hours. at thisteme perature.
• the mixture was cooled and the. oil separated and agitated with benzene. After concentration: on awater-bath of 75 C, 890 g (9 8? of isohexadecyl phosphate was. formed.
• the metal salt of the half-ester separates byprecipitation in the medium.
• the half-esters used can be prepared,'e.g., by refluxing the cyclic dicarboxylic anhydride and the alco- PREPARATION 4 ZINC DODECYL SUCCINATE 0.05 mole of succinic anhydride and 0.05 mole of dodecyl alcohol were refluxed for 5 hours-in 100 mlof toluene. The solution was concentrated by evaporation and the residue solidified at room temperature. The monolaurylsuccinic acid'was recrystallized from ml of hexane. s
• the amount of metal salt may also vary within wide limits and depends on the manner in which it is applied to the device, on the nature of the particular device employed, on the length of contact between the treating device'and thephotoconductive surface etc. Generally, satisfactory results are obtained when from 0.005 g to 5 g, preferably from 0.05 to 2 g, of metal salt is present persq.m.'
• the said member or device When applying the salt(s') to an applicator member or device which can be .used for simultaneously cleaning the imaging surface the said member or device preferably comprises a fibrous woven or non-woven material as this promotes uniformity of treatment a said fibrous treatment device or member may be of any suitable shape such as in the form of a continuous web, cylinder or belt. Suitable fibrous materials include paper tissue, furs, natural fibres such as cotton, flannel, wool derivatives.
• EXAMPLE 1 An electrophotographic dry developing mixture comprising about 99 parts by-weight of glass carrier particles with a particle size between 0.6 and 0.8 mm and about 1 part by weight of toner particles, which have a grain size comprised between 2 and 30 microns and have been prepared from 8 parts by weight of polystyrene having a molecular weight of 30,000, 1 part by weight of polyvinylbutyral comprising in addition to vinylbutyral groups 20 by weight of vinyl alcohol groups and 2.5 by weight of vinyl acetate groups, and 1 part by weight of carbon black, was cascaded across a selenium surface bearing an electrostatic image. The developed image was transferred by electrostatic means to a sheetof paper whereon it was fused by heat.
• a conventional continuous cleaning web as used in xerographic copying apparatus was impregnated with a l solution of zinc octadecylsuccinate in dimethyl formamide and dried.
• the cleaning web thus treated was used to remove the residual powder on the photoconductive selenium surface after transfer of the developed image.
• Example 1 was repeated with the difference that the cleaning web was not treated with a zinc salt as described in example 1.
• zinc dodecyl succinate was compressed to form a rod which was positioned in the xerographic copying apparatus so that the cleaning web came into contact with the rold of zinc salt before rubbing against the selenium drum for cleaning purposes.
• EXAMPLE 4 Zinc docosyl succinate was compressed to form a rod.
• the rod was rubbed against a selenium drum of a xerographic copying apparatus, so as to leave thereon a deposit of the zinc dococyl succinate, each time bcfore electrostatically charging the selenium drum.
• an electrophotograp'hic imaging process comprising the steps of forming a latent electrostatic image on an imaging surface, forming a powder image corresponding to said electrostatic image by applying a developing material to said surface, transferring said powder image from said imaging surface to a receptor surface, and cleaning said imaging surface, the improvement of applying to said surface not later than during said cleaning at least one member of the group consisting of a hydrophobic bivalent or trivalent metal salt of a half ester of a branched-chain or straight-chain aliphatic dicarboxylic acid containing an aliphatic hydrocarbon group of at least five carbon atoms and a hydrophobic bivalent or trivalent metal salt of a monoester or diester of a phosphorus oxyacid containing an aliphatic hydrocarbon group of at least five carbon atoms.
• a process according to claim 1 comprising applying said metal salt to said imaging surface subsequent to the transfer of the powder image to a receptor surface.
• a process according to claim 3 comprising applying said metal salt to said. imaging surface and cleaning such surface simultaneously.
• said applicator member comprises a fibrous web which makes contact with said imaging surface.
• a process according salt is a zinc salt.
• a process according to claim 1 wherein said aliphatic chain is a hydrocarbon group containing at least 10 carbon-atoms.
• a process according to claim 1 wherein said salt is a salt of a half ester of succinic acid.
• an electrophotographic imaging process comprising forming an electrostatic image on a surface, developing said image by means of powder, and subsequently transferring said powder image from said surface to a receptor material, the improvement wherein v the surface on which said electrostatic image is formed carries a deposit thereon of at least one compound of the group consisting of a bivalent or trivalent metal salt of a half ester of a branched-chainor straight-chain aliphatic'dicarboxylic acid containing an aliphatic hydrocarbon group of at least five carbon atoms and a bivalent or trivalent metal salt of a mono-ester or di-ester of a phosphorus oxyacid containing an aliphatic hydrocarbon group of at least five carbon atoms.
• An electrophotographic imaging process according to claim 12 wherein said aliphatic chain is a hydrocarbon group of at least 10 carbon atoms.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Developing Agents For Electrophotography (AREA)

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Citations (5)

• 1971
  • 1971-05-21 GB GB1634671A patent/GB1379252A/en not_active Expired
• 1972
  • 1972-05-10 CA CA141,829A patent/CA967817A/en not_active Expired
  • 1972-05-18 FR FR727218390A patent/FR2138936B1/fr not_active Expired
  • 1972-05-19 DE DE19722224504 patent/DE2224504A1/de active Pending
  • 1972-05-19 BE BE783767A patent/BE783767A/xx unknown
  • 1972-05-19 US US00254903A patent/US3793018A/en not_active Expired - Lifetime

Patent Citations (5)

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