US3799791A - Field control development of electrostatic images - Google Patents

Field control development of electrostatic images Download PDF

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Publication number
US3799791A
US3799791A US00244590A US24459072A US3799791A US 3799791 A US3799791 A US 3799791A US 00244590 A US00244590 A US 00244590A US 24459072 A US24459072 A US 24459072A US 3799791 A US3799791 A US 3799791A
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US
United States
Prior art keywords
field control
sheet
developer
channel
control member
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00244590A
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English (en)
Inventor
J Kolibas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AB Dick Co
Original Assignee
Multigraphics Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL6702972A priority Critical patent/NL6702972A/xx
Priority to FR102643A priority patent/FR1519108A/fr
Application filed by Multigraphics Inc filed Critical Multigraphics Inc
Priority to US00244590A priority patent/US3799791A/en
Application granted granted Critical
Publication of US3799791A publication Critical patent/US3799791A/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
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
    • G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
    • G03G15/108—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer with which the recording material is brought in contact, e.g. immersion or surface immersion development

Definitions

  • a developing station which includes a tank for holding a bath of liquid developer inimage areas.
  • the field control member must be placed close to but out of contact with the imaged sheet surface Continuation of application Ser. No. 763,606, Sept. 30, r
  • the field control member In order to replace the liquid developer in this restricted channel rapidly enough to prevent its being stripped of pigment particles, the field control member is provided with openings through which fresh liquid developer can be rapidly introduced into the channel, and spray means and baflles are arranged to effect this developer replacement as efiiciently and rapidly-as possible. Moreover,'the arrangement is such that hydrodynamic forces are also generated in the liquid developer in the channel to maintain the sheet against a guiding surface and hence at an accurate spacing from the field control member.
  • This invention relates to the deposition of particles upon the surface of a moving sheet in accordance with -a latent electrostatic pattern previously formed thereon,
  • the treating of an electrostatically imaged sheet with a liquid developer having electrostatically attractable particles dispersed therein is a well-known procedure and is immersing the sheet in a bath
  • the present invention is based upon the principle that improved deposition can be obtained by means of a conductive field control member'placed very closeto, but accurately spaced from, the surface of the sheet to be developed, and embodies a means for maintaining an accurate minimum spacing relationship between such a field control member. and the sheet surface under the relatively unstable circumstances represented in progressive appli- 1 3,799,791 Patented Mar. 26, 1974 cation of developing liquid to the electrostatic image on a sheet moving through a developer bath.
  • the invention also involves the maintenance of accurate spacing between these surfaces in a kinetic electrostatic development situation whether or not the process relates to immersion development or to some other type.
  • a conductive field control member placed close to the photoconductive surface during development not only speeds deposit but also assists in providing a uniform deposit over large solid areas and avoids edge effects.
  • edge effects is meant the electrical field phenomenon which results in a low intensity deposit found in the centers of large charged areas, which are intended to show a solid, uniform density when developed, but instead display dark edges shading to grey to white centers.
  • This invention in the presently preferred form provides a guide channel for a sheet to be developed and through which the sheet is fed and from which it is withdrawn by feed rollers.
  • the channel is arranged to expose the sheet to a bath of liquid developer, and this is brought about in the form shown by positioning the channel to dip into a bath of developer which is maintained at a predetermined depth.
  • One member making up the channel is a guide member against which the sheet rests and the other member is a conductive member placed in fixed closely spaced relation to the guide member so as to provide a field control effect at the place where electrostatic deposit of particles is occurring.
  • the sheet is held against the guide member by hydrodynamic forces generated in the liquid itself so as to provide consistent accurate spacing between the surface of the sheet and the field control member.
  • these hydrodynamic forces are generated by pumping or flowing the developing liquid rapidly through orifices in the field control member so as to hold the sheet strongly away from the field control member and against its locating guide member as it passes ment with a liquid developer in accordance with the present invention
  • FIG. 2 is a detail section consisting of a portion of a FIG. 1 drawn to an enlarged scale.
  • a tank 10 containing a bath 12 of liquid developer of the type designed for use with electrostatic deposition procedures, and having dispersed therein minute electroscopic particles which will deposit upon electrostatically charged areas of a sheet surface.
  • a sheet 14 provided with a latent electrostatic image on its upper surface is led down into and then up out of the bath 12 by an assembly 16 which provides a channel 18 within which the sheet is confined.
  • the assembly 16 comprises lower or guide plate 20 and an upper or field control plate or member 22 which is made of metal or other electrically conductive material form the functions respectively of introducing the sheet 14 into'the channel 18 and withdrawing it therefrom.
  • a reservoir 32 which has a supply of liquid developer therein and which houses a pump 34 driven by a motor 36.
  • the pump moves the liquid developer through a discharge conduit 38 to a manifold 40 extending across the top of the bath 12 transversely of the direction of sheet movement.
  • the manifold has a plurality of openings along its length, one of which is indicated at 42. These openings are downwardly directed so that the liquid developer which'is under the pressurein the manifold 40 is sprayed or flowed forcibly downwardly against the upper surface of the field control member 22 as indicated at 43.
  • the field control member is' provided with apertures 44 some of which are arranged in the path of the spray 43 so as to admit the spray to the channel 18 and against the upper surface of the sheet 14 from whence it escapes to the bath 12 through the open sides of the channel.
  • louvers or baffles 46 are struck up from the plate 22 adjacent the apertures 44 to assist in guiding the spray in'th'e desired direction.
  • An overflow pipe 48 determines the proper level for liquid in the bath 12 and returns any excess to the reservoir 32.
  • this spacing S must be quite small and must be maintained constant with a certain degree of accuracy.
  • a distance of about inch has been found about the optimum in practice with paper sheets of usual thickness and electrical properties, and a range of spacing of about inch to A, inch is found to be the range of effective field control values.
  • spacing-within the general ranges identified may be referred to aseifective field control spacing.
  • the use of the hydrodynamic action of the'developing liquid to maintain the surface of the electrostatically imaged sheet against aguide which insures accurate spac ing from the surface of the conductive field control plate 22, makes it possible to' employ a field control technique latterpair, i.e'. rollers 28, 30, also preferably perform a" on a practical basis with very close spacing of the field I control member, and thereby produce imaging of the highest quality. It is, moreover, possible to accomplish these results in such a way that the need for complex -meansfor assuring proper positioning and adequately close tolerances of spacing of the sheet across its whole surface is avoided.
  • the hydrodynamic eifect o he veloping liquid acts automatically and simultaneously at all points on the sheet which are in the developing zone by reason of being exposed to the liquid.
  • the field control aspect of the equipment assists development, while in other respects it has been found to inhibit it.
  • this deposit can be so rapid that the small amount of developer liquid available in the area between the closely spaced surfaces tends to become stripped of particles so that subsequent image areas are starved and do not receive appropriate deposits if the sheet moves through the bath at normal copier speeds.
  • This effect is aggravated to some extent by the fact that changing the liquid adjacent the sheet surface necessarily becomes more difficult the closer the sheet surface is brought to the field control conductor since there is a smaller cross sectional area available through which fresh liquid can be introduced.
  • the forceful spraying of the liquid developer is at suflicient velocity, and the liquid is introduced into the channel 18 at a number of points which are close enough together so that there is fairly rapid movement of the liquid between the plates 20 and 22. Accordingly, the developer liquid in the channel 18 is sufficiently energized as to move parallel to the sheet surface with a speed suflicient to insure that any stripped developer rapidly escapes from the channel18,
  • a sheet 14 may be moved through the channel at a speed acceptable for commercial copier use without exhibiting deficient development in the trailing portions of the image.
  • the field control plate 22 has been referred to as conductive, it is found beneficial in some instances toactually apply a voltage across the gap between the field control plate and the surface of the sheet, in which case the guide plate 20 is also made conductive and a .source of EMF.is connected both to the plate 22 and to ;the guide plate 20. a V
  • a method of developing electrostatic latent images on sheet surfaces which comprises:
  • a guide member anbapertured electrically conductive field control memmeans mounting said members in close relationship with a gap therebetween defining an effective field control spacing; means for feeding a sheet whose surface has been electrostatically imaged through said gap with the imaged surface towards the field control member; means for introducing into the portion of the gap between said field control member and a sheet being fed through the gap an electrostatic developer fluid containing particles electrically attractable to the image on the sheet; and means for generating dynamic forces in the fluid developer entering between said sheet and field control member in a direction and of a magnitude to hold a sheet consistently away from the field control member and against the guide member during its passage between said members, said last-named means comprising equipment for moving developer fiuid through an aperture in the field control member and against the imaged surface of the sheet.
  • a conductive field control member parallelling the path of the sheet through the developer at the side thereof bearing the electrostatic image and arranged sufficiently closely to the path as determined by said guide means to provide an eifective field control spacing with relation to the surface of a sheet traveling in said path;
  • apparatus for developing an electrostatic image on a sheet of material, apparatus comprising:
  • a perforate metallic member in the pool juxtaposed to the upper side of the path and arranged sufliciently closely to the path to provide an effective field control spacing with relation to the surface of a sheet travelling in said path;
  • apparatus for developing an electrostatic image on a sheet of material, apparatus comprising:
  • a guide member for guiding a sheet along a development path
  • a perforate conductive member arranged adjacent the guide member and having a generally matching configuration, said members being arranged with a gap between them defining an efiective field control spacing, and mutually forming a channel for the sheet;
  • a developing device as set forth in claim 6 which further includes means for forcibly projecting liquid developer through the openings in said perforate member with a force and direction sufiicient to hold the sheet spaced from said conductive member and against said other member during development.
  • apparatus for developing electrostatic images on a sheet of material, apparatus comprising a container for a pool of developer, means for guiding the sheet through the pool along a predetermined path which dips into the pool with the image side of the sheet facing upwardly, upper and lower metallic members in the pool juxtaposed to the upper and lower sides of the path respectively, the upper member being perforate, and means for flowing developer downwardly through the perforate member to the image side of the sheet.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Wet Developing In Electrophotography (AREA)
US00244590A 1966-06-30 1972-04-17 Field control development of electrostatic images Expired - Lifetime US3799791A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
NL6702972A NL6702972A (enrdf_load_stackoverflow) 1966-06-30 1967-02-24
FR102643A FR1519108A (fr) 1966-06-30 1967-04-13 Procédé et dispositif pour le développement d'images électrostatiques latentes sur des surfaces
US00244590A US3799791A (en) 1966-06-30 1972-04-17 Field control development of electrostatic images

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US56178466A 1966-06-30 1966-06-30
US00244590A US3799791A (en) 1966-06-30 1972-04-17 Field control development of electrostatic images

Publications (1)

Publication Number Publication Date
US3799791A true US3799791A (en) 1974-03-26

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Family Applications (1)

Application Number Title Priority Date Filing Date
US00244590A Expired - Lifetime US3799791A (en) 1966-06-30 1972-04-17 Field control development of electrostatic images

Country Status (3)

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US (1) US3799791A (enrdf_load_stackoverflow)
FR (1) FR1519108A (enrdf_load_stackoverflow)
NL (1) NL6702972A (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3871329A (en) * 1972-10-16 1975-03-18 Dennison Mfg Co Development electrode
US3905331A (en) * 1970-11-05 1975-09-16 Ricoh Kk Means for precluding trailing of toner images in electrophotography of the wet type
US3916827A (en) * 1973-03-07 1975-11-04 Scott Paper Co Perforate development electrode
US3972306A (en) * 1973-10-05 1976-08-03 Sharp Kabushiki Kaisha Coil shaped developing electrode for a copying machine
US4014608A (en) * 1974-06-26 1977-03-29 Hitachi, Ltd. Developing apparatus for electrophotographic color copying apparatus
US4111156A (en) * 1974-12-09 1978-09-05 Olympus Optical Co., Ltd. Devices for developing an electrostatic charge image on a record sheet by a developer solution
US4233385A (en) * 1976-09-11 1980-11-11 U.S. Philips Corporation Method and apparatus for liquid electrostatic development of charge images on a tape-like record carrier
US5216201A (en) * 1989-09-05 1993-06-01 Fuji Photo Film Co., Ltd. Liquid electrophotographic developing device
US5319422A (en) * 1989-09-05 1994-06-07 Fuji Photo Film Co., Ltd. Liquid electrophotographic developing device and method thereof

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3905331A (en) * 1970-11-05 1975-09-16 Ricoh Kk Means for precluding trailing of toner images in electrophotography of the wet type
US3871329A (en) * 1972-10-16 1975-03-18 Dennison Mfg Co Development electrode
US3916827A (en) * 1973-03-07 1975-11-04 Scott Paper Co Perforate development electrode
US3972306A (en) * 1973-10-05 1976-08-03 Sharp Kabushiki Kaisha Coil shaped developing electrode for a copying machine
US4014608A (en) * 1974-06-26 1977-03-29 Hitachi, Ltd. Developing apparatus for electrophotographic color copying apparatus
US4111156A (en) * 1974-12-09 1978-09-05 Olympus Optical Co., Ltd. Devices for developing an electrostatic charge image on a record sheet by a developer solution
US4233385A (en) * 1976-09-11 1980-11-11 U.S. Philips Corporation Method and apparatus for liquid electrostatic development of charge images on a tape-like record carrier
US5216201A (en) * 1989-09-05 1993-06-01 Fuji Photo Film Co., Ltd. Liquid electrophotographic developing device
US5319422A (en) * 1989-09-05 1994-06-07 Fuji Photo Film Co., Ltd. Liquid electrophotographic developing device and method thereof

Also Published As

Publication number Publication date
NL6702972A (enrdf_load_stackoverflow) 1968-01-02
FR1519108A (fr) 1968-03-29

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