US3749059A - Apparatus for developing electrostatic latent image - Google Patents

Apparatus for developing electrostatic latent image Download PDF

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Publication number
US3749059A
US3749059A US00067473A US3749059DA US3749059A US 3749059 A US3749059 A US 3749059A US 00067473 A US00067473 A US 00067473A US 3749059D A US3749059D A US 3749059DA US 3749059 A US3749059 A US 3749059A
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Prior art keywords
developing
liquid
developing electrode
electrophotographic
disposed
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US00067473A
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English (en)
Inventor
M Sato
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Fujifilm Holdings Corp
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Fuji Photo Film Co Ltd
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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
    • 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

Definitions

  • FIG. 3 Z ll/lj/ll/ INVENTOR J mo APPARATUS FOR DEVELOPING ELECTROSTATIC LATENT IMAGE BRIEF EXPLANATION OF THE DRAWING tribution of electriccharge onthe surfaceof theelectrophotographic material illustrated in FIG. 1.; FIG. 3
  • FIG. 4 is a-diagram showingthedistribution of electric field as derived' when a. developing electrode is grounded directly. and-.- when itis. grounded via agroundingresistance;
  • FIG. 5 is a side elevation in longitudinal section offthe developing. electrode and the sheet-shaped" electrophotographic material grounded via the grounding resistance;
  • FIG& 6 is adiagram showing thedistribution of electric field in the; direction perpendicularto the surfaceofsheetzas derived from:theqdistribution ofel'ectric charge illustrated in FIG. 2 in the; absence. of a developing electrode;
  • FIG. 4 isa-diagram showingthedistribution of electric field as derived' when a. developing electrode is grounded directly. and-.- when itis. grounded via agroundingresistance;
  • FIG. 5 is a side elevation in longitudinal section offthe developing. electrode and the sheet-shaped" electrophotographic material grounded via the grounding resistance;
  • FIG& 6 is adiagram showing thedistribu
  • FIG. 11' is adiagram' showing the, distribution of 1 electric: charge derived where there is residual electriccharge on the: sheetsurface;
  • FIGS; 7'and8- arediagramsshowing the distribution of electric field" as derived where the developing electrode. is grounded: directly and it is grounded -via'thegrounding resistancerespectively in the case 'ofthe 'diagram'of FIG. 6;,FIG. 9,.throughFIG; ll and FlG. l4-are side elevations in longitudinal-section of devices employed for: puttingthis invention to working; and
  • FIG. 12 and FIG. 1-3 are side elevations-in longitudinal section of the structure of bearingof theroller illustrated. in FIG. 11'.
  • This invention relatesto an apparatus for developing electrostatic latent image; More specifically, this invention relates. to. a liquid developingyapparatus so improved as to prevent theoccurrence. of'fogging (a phenornenonv which obscures the. background to uniform density) due to residual electric charge andfiof streaks in the image.
  • a liquid developingyapparatus so improved as to prevent theoccurrence. of'fogging (a phenornenonv which obscures the. background to uniform density) due to residual electric charge andfiof streaks in the image.
  • Photoconductive insulating layers used'in the fieldof electrophotography commonlyprocess more or less residual electric potential.
  • aphotoconductive insulating layer-is electrically chargeduniformly and subsequently exposed to. light throughan image theelectric chargeis neutralized in thearea where the layer has been exposed to light but the charge is retainedintact on the photoconductive insulating: layer in the area where the layer has escaped exposure to' light.
  • the electriccharge-to be neutralized increases with the in-- tensity of light to which the layer is exposeda'lhus, an electrostatic latent image conformingv to the. image which is represented in terms of light intensity is producedonthephotoconductiveinsulating layer.
  • the conventional method and apparatus has been found defective in that toner particles are accumulated on'thedevelopingelectrode and tend to comeinto con,- tact withthe electrostatic latent image and, as a result, smear the image.
  • the loss of toner particles because 0 such accumulation has been heavy.
  • This invention relates to an apparatusfor developing an image free from fogging due to residualcharge and faithful-to the original without requiring any external power source for the neutralization of residual poten tial.
  • One moredefect in liquid development is occurrence of streaks in developed image.
  • Next steps are usually involved in makingaprint by electrophotography; neg.- atively charging an electrophotographic material, c.g., a paper bonded a photoconductive layer consistingof zinc-oxide pigment in a resin binder, exposing it to form a latent electrostatic image, and developingithe latent image with positively charged fine particles dispersed in insulating liquid.
  • an electrophotographic material c.g., a paper bonded a photoconductive layer consistingof zinc-oxide pigment in a resin binder
  • exposing it to form a latent electrostatic image exposing it to form a latent electrostatic image
  • developingithe latent image with positively charged fine particles dispersed in insulating liquid.
  • the flow of liquid developer produces streaks.
  • the streaks are conspicuous inthe'case the flow of liquid developer is fast or the potential of the latent image is high. This phenomenon easily occurs when the liquiddeveloper-is' poured into the space
  • this invention is characterized by conferringupon either or both of the developing electrode and the electroconductive layer of electrophotographic material such magnitude of grounding resistance'as to permit prevention of excessive deposition of the aforementioned charged particles-in the highlight zone of electrostatic latent image (the zone where the surface potential is smallest).
  • the spirit of this invention resides 'in' conferring an adequate magnitude-off grounding resistance upon either or both of the devel- 3 oping electrode and electroconductive layers of electrophotographic material, whereby toners are prevented from depositing in the zone of the least charge density within the electrostatic latent image (namely,
  • FIGQl shows a condition under which electric charge exists uniformly only in the right half portion of surface on the electrophotographic sheet 10.
  • Numeral 11 denotes a'photoconductive insulating layer which may be made of any known substance. Examples are amorphous selenium and photoconductive zinc oxide powder blended respectively with an insulating resin.
  • Numeral l2 denotes an electroconductive base. The materials usable therefore include metal plate, plastic film treated so as to acquire electroconductivity, and paper. In the course of development, the base 12 is usually grounded.
  • the latent image of FIG. 1 represents a case wherein positive charge is distributed uniformly in the right half portion of the upper side of the photoconductive insulating layer 11 while negative charge of an equal magnitude exists in the half portion of the lower boundary.
  • FIG. 2 is a graph illustrating the distribution of positive charge on the layer 11 as shown in FIG. 1.
  • the origin represents the boundary between the zone containing electric charge and the zone devoid of electric charge as shown in FIG. I. It is assumed that the electric charge is uniformly distributed at a density of 0'0.
  • FIG. 3 is a graph illustrating the composition of electric fields distributed perpendicularly to the plane of latent image as formed, in the absence of a developing electrode, within the electric field close to the latent image which is produced by distribution of electric charge as shown in FIG. 2.
  • the distribution of electric charge shown in FIG. 2 has an entirely different shape from the distribution of electric field shown in FIG. 3. It is universally known that the phenomenon of edge effect results consequently. What should be noted at this point is the fact that even at the position satisfying 0' 0 in the diagram of FIG. 2, a negative electric field (with the electric field lying outward from the plane of latent image taken as a positive field) occurs in FIG. 3. This shall be referred to hereinafter as opposite electric field.
  • FIG. 4 is a diagram illustrating the distribution of electric fields corresponding to those of FIG. 3 where a developing electrode is disposed to confront the surface containing the latent image at a fixed distance.
  • the curve A represents a case wherein the grounding resistance of developing electrode (hereina after expressed as R") is very small (R 0), while the curve B represents a case wherein the grounding resistance is very large (R 0, for example).
  • the opposite electric field becomes muchnitude of grounding resistance R fixed at an extremely high level. Negative charge is induced through electrostatic induction in the areaof the developing electrode confronting the positive charge of latent image. In the other portion of the developing electrode, positive charge substantially equivalent to the induced negative charge is induced. Because of a large value of R, the positive charge is not immediately discharged to the ground. This positive charge can move about with considerable freedom within the developing electrode. Of the negative charge distributed as opposite charge of latent image in the boundary of the electroconductive layer 12, the magnitude of negative charge equivalent to the negative charge induced on the developing electrode acquires freedom of mobility and eventually confronts the positive charge induced on the developing electrode where there exists no electric charge of latent image, as shown in FIG. 5. Consequently, an opposite electric field is formed at this portion and properties as represented by the curve B of FIG. 4 are believed to be acquired.
  • FIG. 6 illustrates the distribution of electric charge as obtained where there exists a residual charge 0- This means that the electric charge a 0 remains where the magnitude of electric charge should desirably become 0-,, 0.
  • the distribution of electric charge shown in FIG. 2 represents an ideal case, while the distribution of electric charge which is actually obtained by charging and exposure to light is as shown in FIG. 6.
  • FIG. 7 is a diagram which is contrasted to that of the distribution of electric charge in FIG. 6 and which corresponds to FIG. 4.
  • the diagram represents a distribution obtained when the distance between the developing electrode and the latent image surface is fixed to comparatively small and the value of R is very small.
  • the electric field at the portion where the residual charge 0', exists constitutes a positive field except in the neighborhood of the boundary of charge distribution. In the vicinity of boundary, the edge effect persists to induce negative electric field.
  • this edge effect becomes greatly decreased.
  • the toner particles having negative charge in this example, are attracted to the positively charged right half area.
  • the counter'electrical field which prevents the attachment of toner; particles appearson the no charged area.
  • Atspecifio means of o fer ing groundin esistan eon the electroconduc-v tive layer- 0f, electrophqtographic material consists in noorporstina .s res stanc :l yo v onesth mlh .elec-trrr onduct v yer f electrophotoattttih o "tutorial or forming the aforementioned electroconductive vvlayer ne base.
  • FIG. 9 is .a side elevation in cross section of one; .pret od mbodim nt for, putti g the method .of this invention ,t o .working Nurneralflo ⁇ irt FIG. ;9 denotesandlessbo f r onv y na thes eotfshape l o roph Aeeordingly, developingjelectrode;intensistashi l-mn e iali10; wi hei tent i ge face he eo facin -i PP-Wa fd yi s su belt.
  • Thedeveloping, liquid 96. is stored in the container. scooped up by means of. a pump' which' is n'otiIlus trated; and applied to the nozzle 94..At asubStantially uniform distance upward from the sheetconveyingsurfaceof the endless belt 90, there is disposedaidevelop ing v electrode 93 of metal plate; grounded. via thegrounding resistance R.
  • R-isflOflJhe length of d'eveloping electrode in the direction of travel is 20 cm,
  • the space between'the developingelectrode and.the; electrostatic latent image surface is 052mm; andthe conveying: speed of sheet is Zorn/sec.
  • FIG. 10 illustrates another preferredv embodiment of this invention, namely, a. device suitable for developing a. web-shaped electrophotographic material loofwhich;
  • FIG. 11 is a sideelevation in cross section'of still an present invention-proves other example for which the particularly effective.
  • Numerals 11 191 through' 1 11 5 denote rollers which are made to rotate at a fixed speed irronesamedirection, and. numerals 112-1 through ll2-15:*are developing electroderollerswhich'areadapted .to rotate at a fixedspeed in oneandsame direction while :confront ing theaforementioned rollers. .
  • the rollers -11 l and the rollers 112 may be held in intimate contact or may be" separated slightly,
  • Therollers 111 may. be .those made ofmetal or non-metal.
  • rollers 1 12 may serve as developing electrode, they are requiredrto beielectroconductive on the surface or, if they are insular-"- ingon thesurface, they are required to be electrocon ductive in the regionclose to the surface.
  • metallic rollers having the .surfacethereof ren--- dered insulating or semi-conductive, andinsulating rollers having the surface thereof covered with an electroconductive layer are also used.
  • Numerals l 13-1 through 113-6 arenozzles used for sprayingthe rollers 112 .with the developing liquid.
  • the developing liquid is supplied by a pump not illustrated and fed to the nozzles.
  • the pairs of rollers 11] and rollers 112 seize and: transfer the sheet 10 containing the electrostatic latentimage on the upper surface at a fixed, speed toward rollers, '112 in the example shown in FIG: 11..
  • numeral 121- denotes a side plate made' such as of metal so as to serve as the bearingof the roll ers. 0n the side plate; there is provided a notch-11$ for inserting the shaft 114 ,of rollers.
  • the resisting element 122 is disposed on the surface of the notch.
  • a convenient resisting element for this purpose may be prepared by mixing silver or carbon particles into a resin or by blending electroconductive particles of silver or carbon into ceramic material.
  • FIG. 13 shows the shaft of rollers having a resisting element 13] disposed on the surface thereof instead of working on the side plate.
  • the resisting element that which is similar to the resisting element 122 of FIG. 12 may be used.
  • FIG. 14 illustrates still another preferred embodiment for which the present invention proves effective.
  • Numeral 140 is an electroconductive liquid, which may be water, an aqueous solution, or mercury.
  • the liquid 140 is so selected that it will have a larger specific'gravity than the developing liquid 104 and it will not be miscible with the liquid developer.
  • Numeral 141 denotes the electrode inserted into the liquid 140 to serve the purpose of grounding the liquid 140 via the resistance R.
  • the electrode 141 is not required where the liquid 140 has a high electroconductivity, but is required when the electroconductivity of the liquid 140 is relatively small (of the order of 10 for example).
  • an electroconductive liquid is used as the developing electrode (as disclosed in Japanese Patent Publication No. 44-6388,
  • fogging tends to occur because the space between the latent image surface and the developing electrode is very small. Accordingly, the method of this invention is extremely effective.
  • the magnitude of the grounding resistance to be used for the present invention cannot be fixed indiscriminately because it varies with the properties of liquid developer, the properties of electrophotographic material, and the nature of latent image. Where letters are reproduced, for example, R may be fairly large. In reproducing an image of continuous toner, details in the highlight area cannot be reproduced when R is too large. The highlight area suffers from fogging if R is too small. It is, therefore, desirable to minimize the value of R within the range which is free from formation of fogging. Empirically, it has been found that R is desired to fall in the range of 10' 10 9.
  • Apparatus for developing an electrostatic latent image on an electrophotographic sheet of material optionally having an electroconductive backing layer comprising:
  • a developing electrode disposed adjacent to and spaced from said electrophotographic sheet of material
  • resistive means for connecting either or both of said developing electrode and said electroconductive backing layer to -a reference potential, the resistance of said resistance means being in the range of 10 to 10 ohms, to prevent excessive background fogging and image streaking during development of said latent image.
  • Apparatus as in claim 1 including means for effecting relative movement between said electrophotographic sheet of material. and said developing electrode.
  • Apparatus as in claim 3 including a container for storing said developing liquidand where said means for effecting relative movement between said electrophotographic sheet of material and said developing electrode includes an endless belt driven around a pair of rollers, said electrophotographic sheet being disposed on said belt for movement with respect to said developing electrode and said endless belt being inclined by an angle of about 5 to 20 with respect to thehorizontal plane and where said means for providing'said developing liquid between said electrophotographic sheet and said developing electrode is disposed adjacent the upper end of said endless belt to introduce said developing liquid between said electrophotographic sheet and said developing electrode so that it flows therebetween and then to said container for said developing liquid which is disposed beneath the lower end of said endless belt.
  • Apparatus as in claim 3 including a container for said developing liquid, said developing electrode being disposed in said developing liquid and where said means for effecting said relative movement between said electrophotographic sheet and said developing electrode includes a rotatably driven drum having disposed around a portion thereof said electrophotographic sheet, said portion being partially disposed in said developing liquid and adjacent said developing electrode.
  • Apparatus as in claim 3 including a first plurality of drive rollers disposed at one side of said electrophotographic sheet and where said developing electrode includes a second plurality of drive rollers respectively disposed adjacent said first plurality of drive rollers at the other side of said electrophotographic sheet, said first and second plurality of drive rollers moving said electrophotographic sheet therebetween.
  • Apparatus as in claim 6 including a shaft for each of said second plurality of rollers and a bearing for each of said shafts.
  • Apparatus as in claim 3 including a container for said developing liquid and for a second liquid having a larger specific gravity than and immiscible with said developing liquid and where said developing electrode is disposed in said second liquid and where said means for effecting relative movement between said electrophotographic sheet and said developing electrode comprises a rotatably driven drum having disposed around a portion thereof said electrophotographic sheet, said portion being disposed completely in'said developing liquid and partially in said second liquid whereby said developing liquid is dragged between said drum and said developing electrode due to the rotation of said drum to thereby effect said develp g a 1 g 11.
  • Apparatus as in claim 3 including a container for said developing liquid and an electrically conductive liquid having a larger specific gravity than and immiscible with said developing liquid, said electrically conductive. liquid acting as said developing electrode and where means for effecting said relative movement between said electrophotographic sheet and said developing electrode comprises a rotatably driven drum having development of said latent image and an inclined elec? trophotographic material'transferring mechanism, said developing electrode arranged with a small space to the surface of the electrophotographic material and a noz- I zle arranged about the top of the developing electrode for supplying a liquid developer between the developing electrode and the electrophotographic material.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Wet Developing In Electrophotography (AREA)
  • Liquid Developers In Electrophotography (AREA)
US00067473A 1969-08-27 1970-08-27 Apparatus for developing electrostatic latent image Expired - Lifetime US3749059A (en)

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JP44067795A JPS4825936B1 (fr) 1969-08-27 1969-08-27

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JP (1) JPS4825936B1 (fr)
BE (1) BE755061A (fr)
DE (1) DE2041895A1 (fr)
FR (1) FR2056881A5 (fr)
GB (1) GB1267888A (fr)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3791345A (en) * 1972-05-09 1974-02-12 Itek Corp Liquid toner applicator
US3878816A (en) * 1973-07-26 1975-04-22 Xerox Corp Imaging system
US3913524A (en) * 1972-03-13 1975-10-21 Rank Xerox Ltd Liquid developing apparatus for electrophotography
US3916827A (en) * 1973-03-07 1975-11-04 Scott Paper Co Perforate development electrode
US3957016A (en) * 1972-09-29 1976-05-18 Canon Kabushiki Kaisha Developer wringing and removing apparatus
US3990793A (en) * 1973-08-27 1976-11-09 Hitachi, Ltd. Developing station for electronic color photographing apparatus
US4052127A (en) * 1973-01-24 1977-10-04 Ricoh Co., Ltd. Developing system
US4128328A (en) * 1975-05-28 1978-12-05 Minolta Camera Kabushiki Kaisha Developing electrode type electrostatic copying machines
USRE31371E (en) * 1973-01-24 1983-09-06 Ricoh Co., Ltd. Developing system
US4586809A (en) * 1983-05-26 1986-05-06 Dainippon Screen Mfg. Co., Ltd. Liquid developing equipment for electrophotographic copying machine
US5036365A (en) * 1988-11-21 1991-07-30 Benzion Landa Field assisted filter and electrophotographic copying machine using the same

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2651646C3 (de) * 1976-11-12 1984-01-05 Hoechst Ag, 6230 Frankfurt Vorrichtung zum Entwickeln von latenten elektrostatischen Ladungsbildern
US4521101A (en) * 1982-06-18 1985-06-04 Mitsubishi Paper Mills, Ltd. Liquid developing apparatus for electrophotography
JPS6111717U (ja) * 1984-06-21 1986-01-23 京一 岡本 ズリ留め付きポケツト前掛け
JP3011222U (ja) * 1994-11-16 1995-05-23 株式会社ビブサカモト エプロン

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3913524A (en) * 1972-03-13 1975-10-21 Rank Xerox Ltd Liquid developing apparatus for electrophotography
US3791345A (en) * 1972-05-09 1974-02-12 Itek Corp Liquid toner applicator
US3957016A (en) * 1972-09-29 1976-05-18 Canon Kabushiki Kaisha Developer wringing and removing apparatus
US4052127A (en) * 1973-01-24 1977-10-04 Ricoh Co., Ltd. Developing system
USRE31371E (en) * 1973-01-24 1983-09-06 Ricoh Co., Ltd. Developing system
US3916827A (en) * 1973-03-07 1975-11-04 Scott Paper Co Perforate development electrode
US3878816A (en) * 1973-07-26 1975-04-22 Xerox Corp Imaging system
US3990793A (en) * 1973-08-27 1976-11-09 Hitachi, Ltd. Developing station for electronic color photographing apparatus
US4128328A (en) * 1975-05-28 1978-12-05 Minolta Camera Kabushiki Kaisha Developing electrode type electrostatic copying machines
US4586809A (en) * 1983-05-26 1986-05-06 Dainippon Screen Mfg. Co., Ltd. Liquid developing equipment for electrophotographic copying machine
US5036365A (en) * 1988-11-21 1991-07-30 Benzion Landa Field assisted filter and electrophotographic copying machine using the same

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BE755061A (fr) 1971-02-01
GB1267888A (en) 1972-03-22
DE2041895A1 (de) 1971-03-18
FR2056881A5 (fr) 1971-05-14
JPS4825936B1 (fr) 1973-08-02

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