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, 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
  • G03G21/0088—Arrangements not provided for by groups G03G13/00 - G03G19/00, e.g. cleaning, elimination of residual charge removing liquid developer

Definitions

• This invention relates to imaging systems, and more particularly, to improved cleaning systems and techniques.
• the formation and development of images on the surface of photoconductive materials by electrostatic means is well known.
• the basic xerographic process as taught by C. F. Carlson in U.S. Pat. 2,297,691 involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light-and-shadow image to dissipate the charge on the areas of the layer exposed to the light and developing the resulting electrostatic latent image by depositing on the image a finelydivided electroscopic material referred to in the art as toner.
• the toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image.
• This powder image may then be transferred to a support surface such as paper.
• the transferred image may subsequently be permanently affixed to a support surface as by heat.
• latent image formation by uniformly charging the photoconductive layer and then exposing the layer to a light-and-shadow image
• the powder image may be fixed to the photoconductive layer if elimination of the powder image transfer step is desired.
• Other suitable fixing means such as solvent or overcoating treatment may be substituted for the foregoing heat fixing step.
• electrostatic latent image may also be achieved with liquid rather than dry developer materials.
• electrophoretic development an insulating liquid vehicle having finely divided solid material dispersed therein contacts the imaging surface in both charged and uncharged areas. Under the influence of the electric field associated with the charged image pattern, the suspended particles migrate toward the charged portions of the imaging surface separating out of the insulating liquid. This electrophoretic migration of charged particles results in the deposition of the charged particles on the imaging surface in image configuration.
• a further technique for developing electrostatic latent images is the liquid development process disclosed by R. W. Gundlach in U.S. Pat. 3,084,043 hereinafter referred to as polar liquid development.
• an electrostatic latent image is developed or made visible by presenting to the imaging surface a liquid developer on the surface of a developer dispensing member having a plurality of raised portions or lands defining a substantially regular patterned surface and a plurality of portions depressed below the raised portions or valleys.
• the depressed portions of the developer dispensing member contains a layer of conductive liquid developer which is maintained out of contact with the electrostatographic imaging surface. Development is achieved by moving the developer dispensing member loaded with liquid developer in the depressed portions into developing configuration with the imaging surface.
• the liquid developer is believed to be attracted from the depressed portions of the applicator surface in the charged field or image areas only.
• the developer liquid may be pigmented or dyed.
• the development system disclosed in U.S. Pat. 3,084,043 differs from electrophoretic development systems where substantial contact between the liquid developer and both the charged and uncharged area of an electrostatic latent image hearing surface occurs. Unlike electrophoretic development systems, substantial contact between the polar liquid and the areas of the electrostatic latent image bearing surface not to be developed is prevented in the polar liquid development technique. Reduced contact between a liquid developer and the non-image areas of the surface to be developed is desirable because the formation of background deposits is thereby inhibited.
• An additional liquid development technique is that referred to as wetting development or selective wetting as described in U.S. Pat. 3,285,741.
• wetting development or selective wetting as described in U.S. Pat. 3,285,741.
• an aqueous developer uniformly contacts the entire imaging surface and due to the selected wetting and electrical properties of the developer substantially only the charged areas of the imaging surface are wetted by the developer.
• the developer should be relatively conductive having a resistivity generally from about 10 to 10 ohm-cm. and having wetting properties such that the wetting angle measured when placed on the imaging surface is smaller than at the charged area and greater than 90 at the uncharged areas.
• liquid development systems While capable of producing satisfactory images, these liquid development systems in general, suffer deficiencies in certain areas and are in need of further development and improvement. Particularly troublesome difficulties are encountered in liquid development systems employing reusable or cycling electrostatographic imaging surfaces.
• a photoconductor such as a selenium or selenium alloy drum as the photoconductor surface is charged, exposed to a light and shadow image and developed by bringing the image bearing surface into developing configuration with an applicator containing developing quantities of liquid developer thereon.
• the liquid developer is transferred according to the appropriate technique from the developer applicator onto the image bearing surface in image configuration. Thereafter, the developer pattern on the electrostatographic imaging surface is transferred to copy paper and the liquid developer may be absorbed by the paper to form a permanent print.
• the celaning solvents employed may act as solvents for the resin binder in a binder plate or may induce crystallization of the thin layer of selenium.
• a cycling electrostatographic imaging system having a cleaning system which enables complete cyclic cleaning of residual liquid developer without imaging surface degradation. More specifically, in a liquid development system employing a cycling or reusable electrostatographic imaging surface the residual developer is cyclically substantially completely cleaned from the imaging surface by treating the surface with a small quantity of highly absorbent dry powder.
• the cleaning aids of this invention may generally be described as small sized highly absorbent dry powders that functionas tiny sponges.
• the powder be relatively non-abrasive with respect to the imaging surface.
• the dry powders preferably are softer than the surface which they are to clean.
• the powders are also preferably not soluble in the liquid developer, are abhesive after they have absorbed the developer liquid thereby enabling ready removal of the cleaning particles from the surface and do not introduce anything to contaminate or degrade the photoconductor.
• the absorbent powders typically have a surface area of from about 30 to about 950 m. gm. Particularly effective cyclic cleaning may be obtained with powders having a surface area of from about 100 to about 800 m. gm. These powders are quickly and easily dispersed in residual liquid developer and only a minimum of powder is required to efficiently absorb the developer liquid.
• the cleaning powders of this invention may be of any suitable size which provides the necessary surface area and sorptive ability.
• the particles range in size from about 0.1 to about 30 microns. As the size of the particles and their hardness increases, they become more abrasive. On the other hand, as the size decreases greater caution must be exercised in the handling and containment of the powders. For these reasons average particle sizes of from about 1 to about 20 microns are preferred with average particle sizes of from about 3 to about 15 microns providing optimum balance in handling and performance.
• the particular cleaning powders should, in general, be selected based on the absorptive capacity of the powder for the particular developer. If the developers are oil based material, the cleaning powder preferably has a high oil absorption. If the developer is a polar liquid, the cleaning powder preferably has high absorptive power for the polar developer and may have low oil absorption. Typically, the absorption capacity is from about 40' to about 500 mg. developer/100 mg. powder. Preferably the absorption capacity is from about to about 350 mg. developer per mg. powder to provide adequate cleaning while minimizing powder packing and caking.
• Typical absorbent microporous materials useful in the practice of this invention include the finely divided forms of carbon, such as furnace black, channel black, lamp black, bone black, graphite and charcoal; clays such as kaolin and China clay; diatomaceous earth, pumice, mica, fly ash, infusorial earth; pigments such as titanium dioxide, precipitated calcium carbonate, lithopone, iron oxide, silica, zinc oxide, calcium silicate and magnesium aluminum silicate. Other pigments having adequate sorptive capacity include qui-nacridones, phthalocyanines, benzidine yellow, and Hausa yellow. Additional materials functioning as micro-sponges include micro-reticulated plastics such as polyurethane and polyethylene.
• silica gels Especially satisfactory cleaning is obtained with silica gels, kaolin clays, carbon blacks and titanium dioxide.
• Particularly preferred materials in handling and cleaning ability are the silica gels having a particle size of from about 3 microns to about 11 microns, a surface area of from about 200 m. /gm. to about 350 mF/gm. and an oil absorption of from about 100 to about 315 mg. per 100 mg. powder.
• the absorbent cleaning powder may be applied to the surface to be cleaned in any suitable amount.
• the absorbing power of the powder is at least sufiicient to absorb all the residual liquid on the surface.
• the absorbing power of the powder is at least sufiicient to absorb all the residual liquid on the surface.
• the amount of cleaning powder applied provides an absorbing power greater than that necessary to absorb all the residual liquid.
• the residual developer is present on the imaging surface in an amount up to a maximum of about 2.3 mg./cm.
• About 80% by weight of the developer consists of various liquid components and for such amounts of liquid in the developer from about 1 to about by weight of the developer of the cleaning powders, are generally added.
• the cleaning powders of this invention may be applied to the surface to be cleaned in any suitable manner. Typi cally, the powders may be dusted, sprinkled, brushed, cascaded across the surface and applied as a powder cloud. The powders may also be applied by wiping with powder impregnated or coated sheets, webs, papers and cotton wadding. They may also be applied as an aerosol spray. In providing uniform cleaning and to minimize problems of dust, it is preferred to apply the absorbent microporous powders in the form of coated or impregnated webs, sheets or wadding. To minimize wear and abrasion of the surface to be cleaned, the powder is preferably applied with sufiicient mixing on the surface to be cleaned to absorb all the liquid and wiped 01f with sufficient pressure to provide a clean surface.
• the cleaning powders After mixing the cleaning powders contain substantially all the residual liquid developer and are present on the imaging surface substantially in the form of a liquid loaded powdery residue.
• This powdery residue of cleaning powder containing absorbed liquid may be removed from the imaging surface in any suitable manner.
• the powdery residue may, for example, be removed by wiping with a cloth, brush Web or by contact with a wiper blade since the substantially dry powdery residue does not readily adhere to the imaging surface.
• the cleaning powders and techniques of this invention provide a substantially complete cleaning of residual developer from the imaging surface on every cycle, no problem of charging and imaging through a residual liquid film exists and developers of both low and high conductivity may be employed.
• Any suitable developer may be used,
• the developers for which the cleaning aids of this invention are effective have a conductivity of from about 10- (ohm-cm.)* to about 10* (ohm-cm.)-
• Typical vehicles within this group providing these properties include water, methanol, ethanol, propanol, glycerol, ethylene glycol, polypropylene glycol, 2,5-hexanediol, mineral oil, the vegetable oils including castor oil, peanut oil, coconut oil, sunflower seed oil, corn oil, rape seed oil and sesame oil.
• silicone oil mineral oil, mineral spirits; fluorinated hydrocarbons such as Du Ponts 'Freon solvents and Krytox oils; silicone oils, esters such as fatty or acid esters, kerosene, and oleic acid.
• the developers may contain one or more secondary vehicles, dispersants, pigments or dyes, viscosity controlling additives or additives which contribute to fixing the pigment on the copy paper.
• Any suitable electrostatographic imaging surface may be cleaned with the technique of this invention. Basically, any surface upon which an electrostatic charge pattern may be cyclically formed or developed may be employed.
• Typical electrostatographic imaging surfaces include dielectrics such as plastic coated papers, xeroprinting masters and photoconductors and overcoated photoconductors.
• Typical photoconductors that may be employed include selenium and selenium alloys, cadmium sulfide, cadmium sulfo selenide, phthalocyanine binder coatings and polyvinyl carbazole sensitized with 2,4,7 trinitrofiuorenone.
• Typical overcoated photoconductors include those described in 'U.S. Pats.
• 3,251,686 and 3,234,019 may comprise a selenium layer on a conductive aluminum substrate overcoated with a thin film of insulating material such as polyethylene terephthalate.
• the electrostatographic imaging surface may be employed in any suitable structure including plates, belts or drums and may be employed in the form of a binder layer. For more elfective cleaning, it is preferred to provide a surface to be cleaned which has a very smooth surface since generally the smooth and more uniform the surface the better will be the cleaning.
• Example I A Type E selenium xerographic plate commercially available from Xerox Corporation, Rochester, N.Y., 11 by 16 inches and comprising a surface layer of selenium about 50 microns thick on a conductive aluminum plate is positively charged and exposed to a light and shadow image in conventional manner.
• the electrostatic latent image thus formed is developed by moving a patterned surface applicator roll having developing quantities of developer in the depressed portions thereof past the image bearing surface so that liquid developer is pulled out of the depressed portions to the image bearing surface in image configuration.
• the speed of development is about 10 inches per second.
• the developer employed is of the following composition:
• Drakeol 9 is a mineral oil manufactured by Pennsylvania Refining Company having a kinematic 'viscosity of about 15.718.1 centistokes at 25 C. and a specific gravity of about 0.85.
• Microlith CT is a resinated predispersed carbon black pigment composed of about 40% carbon black pigment and 60% ester gum resin, manufactured by CIBA.
• Parafiint RG is a hard synthetic wax available in flake form from Moore & Munger.
• Ganex V216 is an alkylated polyvinyl pyrrolidone compound, manufactured by GAP Corporation, which serves as additional pigment dispersant and may also be regarded as a secondary vehicle.
• the developer is prepared by combining the mineral oil and Ganex V216 in a suitable vessel while stirring, heating to about 100 C. and then adding the pigment and other ingredients while continuing the stirring.
• the developer on the photoconductor is transferred to Xerox 4024 copy paper in image configuration.
• About mg. of Syloid 308, a silica gel available from Davison Chemical Division W. R. Grace & Company is sprinkled from a salt shaker onto the selenium plate.
• the plate is then gently wiped with absorbent cotton to remove all the residual developer.
• the plate is observed to be clean, free of all removable developer and free of interference patterns.
• the first print is free of background and has a resolution of about 10 line pairs per millimeter.
• the clean photoconductor plate is again subjected to the same cycle of charging, exposing, developing, transferring and cleaning. In the course of making sequential prints according to this cycle no significant change in print quality is observed.
• Example I is repeated except that after each transfer the silica gel is not added. Instead the plate is wiped with absorbent cotton with equal or greater effort than in Example I. Residual developer in the form of interference patterns in streaks is observed to remain on the drum after each cycle.
• the first print is free of background and has a resolution of about 10 line pairs per millimeter. After 10 cycles the resolution is observed to gradually decrease to about 3 line pairs per millimeter and by the fifteenth cycle to be about 1 line pair per millimeter.
• EXAMPLE III An overcoated photoconductor about 9 inches by 14 inches in dimension comprising a one quarter mill film of polyethylene terephthalate (obtained from E. I. du Pont de Nemours & Company under the trade name Mylar) overcoated on a 20 micron thick layer of selenium on an aluminum substrate prepared according to the procedure of Example I in US. Pat. No. 3,251,686 is charged and exposed to a light and shadow image in conventional manner. Development of the electrostatic latent image is obtained with the developer and in the manner described in Example I. The developer on the overcoated photoconductor is transferred to bond paper in image configuration. The overcoated photoconductor has about 60 mg. of Syloid 30 8, silica gel sprinkled on to its surface.
• the surface overcoating is gently wiped with absorbing cotton and all the residual developer is removed.
• the first print is free of background and has a resolution of about 10 line pairs per millimeter.
• a xeroprinting master 9 x 14 is prepared by placing a thin insulating coating of epoxy resin about .0005 inch thick in image configuration on a conductive plate of aluminum by means of a silk screen stencil, and then hardening the resin in known manner. The plate is charged to +450 volts by passing it under a corona charging unit. The image is developed in the manner described in Example I with a liquid developer having the following composition:
• the developer is transferred to bond paper and the resulting print has image density of about 0.9, background density of less than 0.01 and a resolution of about 7 line pairs per millimeter.
• the plate is cleaned with about 100 milligrams of Mogul A carbon black pigment available from Cabot Corporation with the technique described in Example I. Thereafter, the xeroprinting master is repeatedly charged, developed With developer being transferred to bond paper and cleaned as described above for 25 cycles. The speed of development is about 12 inches per second and the 25th print obtained is of substantially the same quality as the first print.
• a xerographic plate comprising a phthalocyanine binder layer in which the binder is an epoxy phenolic resin prepared in the manner of Example XXIX in US. application Ser. No. 375,191, filed June 15, 1964, now abandoned, is charged positively and exposed to a light and shadow image in conventional manner.
• the resultant electrostatic latent image is developed in the manner described in Example I with the following composition:
• Paraflint RGW is a synthetic wax manufactured by Moore and Munger.
• the developer on the photoconductor is transferred to bond paper in image configuration. Thereafter the photoconductor is cleaned with a web held against the photoconductor. The web contains a layer of loosely bound diatomaceous earth.
• the plate is then repeatedly subjected to the charge, exposure, transfer and clean cycle for 55 cycles.
• the resulting prints have image density of about 0.8, background density of less than about 0.01 and a resolution of about 6 line pairs per millimeter.
• the xerographic plate shows no significant wear and no significant charge in print quality is observed.
• the method of cyclically developing electrostatic latent images on a reusable electrostatographic imaging surface comprising the steps of forming an electrostatic latent image on the imaging surface, developing the image with a liquid developer, transferring the developer from the imaging surface to a receiving surface in image configuration, contacting the imaging surface with a finely divided, liquid developer absorbent silica powder, having a surface area of from about 30 to about 950 mF/gm. to absorb substantially all the residual liquid developer on the imaging surface, removing the absorbent powder containing absorbed residual liquid to prepare the imaging surface for the next imaging cycle and repeating the method sequence at least one additional time, said powder being insoluble in said liquid developer and relatively nonabrasive with respect to said imaging member.
• silica gel has a particle size of from about 3 to about 11 microns and a surface area of from about 200 to about 350 mF/gm.
• photoconductor is selected from the group consisting of selenium and selenium alloys.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Cleaning In Electrography (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=25360978

Family Applications (1)

Country Status (10)

Cited By (3)

Families Citing this family (1)

• 0
  • BE BE758060D patent/BE758060A/xx unknown
• 1969
  • 1969-10-31 US US873103A patent/US3697263A/en not_active Expired - Lifetime
• 1970
  • 1970-08-15 JP JP45071673A patent/JPS4911580B1/ja active Pending
  • 1970-10-26 CH CH1581670A patent/CH519186A/de not_active IP Right Cessation
  • 1970-10-26 DE DE19702052535 patent/DE2052535A1/de active Pending
  • 1970-10-27 GB GB5101670A patent/GB1328406A/en not_active Expired
  • 1970-10-28 SE SE14549/70A patent/SE365624B/xx unknown
  • 1970-10-28 FR FR7041623A patent/FR2090454A5/fr not_active Expired
  • 1970-10-28 ES ES385000A patent/ES385000A1/es not_active Expired
  • 1970-10-30 NL NL7015964A patent/NL7015964A/xx unknown

Also Published As

Similar Documents