US3820891A - Electrophotographic copying method using a liquid developing agent capable of effecting both regular copying and inverse copying - Google Patents

Electrophotographic copying method using a liquid developing agent capable of effecting both regular copying and inverse copying Download PDF

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Publication number
US3820891A
US3820891A US00361645A US36164573A US3820891A US 3820891 A US3820891 A US 3820891A US 00361645 A US00361645 A US 00361645A US 36164573 A US36164573 A US 36164573A US 3820891 A US3820891 A US 3820891A
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United States
Prior art keywords
photoreceptor
developing agent
copying
squeeze
electrostatic latent
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Expired - Lifetime
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US00361645A
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English (en)
Inventor
J Kurakawa
S Soga
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Ricoh Co Ltd
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Ricoh Co Ltd
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Publication date
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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

Definitions

  • ABSTRACT v A method of electrophotography using a liquid developing agent permitting regular copying (positive-topositive and negative-to-negative) or inverse copying (positive-to-negative and negative-to-positive) to be effected by selectively charging a photoreceptor either positively or negatively without the need to bother to use a developing agent of a suitable polarity.
  • the method comprises the steps of charging the photore ceptor so that it may carry a charge of a selected polarity,'exposing the charged photoreceptor to an optical image of an original to be copied, developing an electrostatic latent image formed by exposure on the photoreceptor or an electrostatic latent image transferred from the photoreceptor to a copy sheet with a liquid developing agent, and squeezing out excess liquid developing agent from the photoreceptor or copy sheet after developing by means of a squeeze roller.
  • a bias voltage of the same polarity as the electrostatic latent image is impressed on the squeeze roller when brought into contact with the image-bearing surface of the photoreceptor or copy sheet, or such squeeze roller is electrically insulated from other' members in the squeezing step.
  • the squeeze roller when brought into contact with the image-bearing surface of the photoreceptor or copy sheet is grounded.
  • This invention relates to an electrophotographic copying method using a liquid developing agent capable of effecting both regular copying and inverse copymg I
  • production of a positive duplicate from a positive original or a negative duplicate from a negative original is referred to as regular copying
  • production of a positive duplicate from a negative original or a negative duplicate from a positive original is referred to as inverse copying.
  • This invention has as its object the provision of an electrophotographic copying method, using a liquid developing agent of the type capable of effecting both regular copying and inverse copying, which permits a duplicate of high quality to be produced in positive-topositive and negativeto-negative copying or positiveto-negative and negative-to-positive copying by switching the squeeze roller between a positive potential and a ground potential or placing the squeeze roller in a position in which it is electrically insulated from other members when the photoreceptor is switched between a positive charge and a negative charge when it is charged according to the type of copying to be performed.
  • a method of electrophotographic copying which is free from the fear of toner particles being transferred from the photoreceptor to the squeeze roller and causing an offset phenomenon to occur, and which permits a du plicate of high quality to be produced at all times, because a duplicate made from an original consisting of surfaces and lines has a suitable degree of darkness, tone and-contrast.
  • FIG. ]l is a view of the charging device of an electrophotographic copying apparatus adapted to carry out the electrophotographic copying method according to the invention.
  • FIG. 2 is a view of the exposing device of an electrophotographic copying apparatus adapted to carry out the electrophotographic copying method according to the invention
  • FIG. 3 is a view of the developing device of an electrophotographic copying apparatus adapted to carry out the electrophotographic copying method according to the invention.
  • FIG. ll. shows a charging device comprising a corona discharge electrode 12 disposed in a shield frame Ill and an opposite electrode plate I3 disposed in spaced juxtaposed relationship. Disposed on the opposite electrode plate 13 is a photoreceptor M for electrophotography comprising a conducting supporter l5 and a photoconductive material layer 16. i
  • the opposite electrode plate 13 is grounded while the corona discharge electrode 112 is connected to a movable contact 1% of a switch 117 which also has fixed contacts I9 and 20 connected to a positive output terminal and a negative output terminal of a DC power source 21 respectively.
  • the DC power source 21 also has a ground terminal which is grounded.
  • the movable contact 11% of the switch 117 When it is desired to perform regular copying, that is, to produce a positive duplicate from a positive original or a negative duplicate from a negative original with the toner particles in the liquid developing agent being positively charged, the movable contact 11% of the switch 117 is brought into engagement with the fixed terminal 20.
  • a negative voltage of a predetermined value is impressed on the corona discharge electrode 12, and a corona discharge takes place between the corona discharge electrode 12 and the opposite electrode plate 13 through the photoreceptor 14, so that the surface of the photoreceptor 14 is negatively charged throughout the entire extent.
  • the movable contact 18 of the switch 17 When it is desired to perform inverse copying, that is, to produce a positive duplicate from a negative original or a negative duplicate from a positive original with the toner particles in the liquid developing agent being positively charged, the movable contact 18 of the switch 17 is brought into engagement with the fixed terminal 19.
  • a positive voltage of a predetermined value is impressed on the corona discharge electrode 12, and a corona discharge takes place between the corona discharge electrode 12 and the opposite electrode plate 13 through the photoreceptor 14, so that the surface of the photoreceptor 14 is positively charged throughout the entire extent.
  • FIG. 2 shows an exposing device comprising an opposite electrode plate 22 which is grounded and on which the photoreceptor 14 charged by the charging device shown in FIG. 1 is placed.
  • the photoreceptor 14 on the opposite electrode plate 22 is exposed to an optical image of an original 23 through an optical system 24, so that an electrostatic latent image of the original is formed on the charged surface of the photoreceptor 14.
  • FIG. 3 shows a developing device comprising a liquid developing agent 26 contained in a developing tank 25.
  • the liquid developing agent 26 contains therein toner particles which are positively charged as aforementioned.
  • a guide 27 made of metal is disposed in the developing tank and an opposite electrode 28 made of metal in screen or plate form is also disposed in the developing tank 25 to form a photoreceptor passageway between the guide 27 and the opposite electrode 28.
  • the photoreceptor 14 on which an electrostatic latent image of the original 23 is formed by the exposing device shown in FIG. 2 is introduced into the developing tank 25 by a pair of guide rollers 29 and 30, moves through the photoreceptor passageway between the guide 27 and the opposite electrode 28 and is discharged from the developing device by a squeeze roller 31 and a roller 32.
  • the squeeze roller 31 which is adapted to come into engagement with the image-bearing surface of the photoreceptor 14 is made of metal and has a smooth surface which is adapted to be cleaned by a cleaner 33.
  • the periphery of the squeeze roller 31 may have a thin and smooth coat of a synthetic resinous material in order to increase the cleaning effect.
  • the roller 32 which is disposed against the squeeze roller 31 is made of metal and has a layer of rubber or sponge on its periphery.
  • the guide 27 and roller 32 are grounded, and the opposite electrode 28- and squeeze roller 31 are connected to a movable contact 35 of a switch 34 having one fixed terminal 36 which is grounded and the other fixed terminal 37 which is connected to a positive terminal of a DC power source 38 whose negative terminal is grounded.
  • the movable contact 35 of the switch 34 When it is desired to perform regular copying, the movable contact 35 of the switch 34 is brought into engagement with the fixed terminal 36; and when it is desired to perform inverse copying, the movable contact 35 is brought into engagement with the fixed terminal 37 or brought to a neutral position as indicated by dotted line 35a.
  • the switch 34 may be coupled to the switch 17 so as to close contacts 20 and 36, and 19 and 37, respectively, in unison.
  • the photoreceptor 14 formed thereon with a negatively charged positive electrostatic latent image by the charging device and exposing device is introduced into the developing tank 25 by the guide rollers 29 and 30 and moves through the photoreceptor passageway between the guide 27 and the opposite electrode 28 in the liquid developing agent 26.
  • the positively charged toner particles in the liquid developing agent 26 adhere to the image regions of the photoreceptor 14 and the electrostatic latent image is developed into a visible image.
  • the opposite electrode 28 is grounded through the switch 34 and shortcircuited to the non-image-bearing surface of the photoreceptor 14 to be disposed in close proximity to the photoconductive material of the photoreceptor 14, it is possible to produce a good developed image having no edge effect, even if the original 23 consists of surfaces and lines.
  • the photoreceptor 14 formed thereon with a positively charged negative electrostatic latent image by the charging device and exposing device is introduced into the developing tank by the guide rollers 29 and 30 to move through the developing agent 26 as aforementioned.
  • a positive DC voltage is impressed on the opposite electrode 28 from the DC power source 38 through the switch 34, or the opposite electrode 28 is electrically insulated from other parts.
  • the developed photoreceptor 14 is passed between the squeeze roller 31 and roller 32 to have excess developing agent thereon removed therefrom.
  • a positive DC voltage is impressed on the squeeze roller 31 from the DC power source 38 through the switch 34 or the squeeze roller 31 is electrically insulated from other members and switch 34 placed in the neutral position 350, so that the positively charged toner particles in the developing agent adhere to noncharged or slightly positively charged image regions of the photoreceptor l4 and do not adhere to positively charged non-image regions of the photoreceptor 14. Thus no offset phenomenon occurs.
  • the squeeze roller 31 is grounded at this time, the positively charged toner particles adhering to the noncharged or slightly positively charged image regions of 5 the photoreceptor 14 would be attracted in part to the grounded squeeze roller 31 and adhere thereto when excess developing agent is removed from the surface of the photoreceptor by the squeeze roller 31. This would result in reduced darkness of the image, and an offset phenomenon would tend to occur.
  • the method according to the invention is devoid of these disadvantages of the prior art.
  • the photoreceptor 114 having the electrostatic latent image thereon developed as'aforementioned is delivered to a fixing device (not shown) where the developed image is fixed and a desired duplicate is produced.
  • the method according to this invention can also be carried into practice by an electrophotographic copying apparatus in which the electrostatic latent image formed on the photoreceptor 114 by the charging device and exposing device shown in FIG. 1 and FIG. 2 respectively is transferred to a copy sheet and then developed into a toner image by the developing device shown in FIG. 3.
  • the aforementioned description refers to an embodiment in which the toner particles in the developing agent are positively charged.
  • the photoreceptor is positively charged in the charging step, and the squeezing roller is grounded in the squeezing step when regular copying is performed.
  • the photoreceptor is negatively charged in the charging step, and a negative bias voltage is impressed on the squeeze roller or the squeeze roller is electrically insulated from other members in the squeezing step.
  • An electrophotographic copying machine of the liquid development type having:
  • a pressingroller disposed opposite said squeeze roller and cooperating therewith to squeeze excess liquid from said member while passing therebetween;
  • a machine as in claim 2 further comprising an opdeveloping agent are of the same polarity as the electrostatic latent image on the photoreceptor,
  • posite electrode means disposed in said developing tank opposite said guide means and electrically connected to said squeeze roller.
  • a machine as in claim 2 further comprising:
  • discharge means for producing electrostatic charge for forming said electrostatic latent image
  • polarity means for connecting said discharge means alternatively to produce positive charge and negative charge, which polarity means is switched in unison with said switching means.
  • a machine as in claim 2 wherein said source of bias voltage is a DC power source.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Wet Developing In Electrophotography (AREA)
US00361645A 1972-05-25 1973-05-18 Electrophotographic copying method using a liquid developing agent capable of effecting both regular copying and inverse copying Expired - Lifetime US3820891A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP47052329A JPS4910740A (de) 1972-05-25 1972-05-25

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US3820891A true US3820891A (en) 1974-06-28

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US (1) US3820891A (de)
JP (1) JPS4910740A (de)
DE (1) DE2325962C3 (de)
GB (1) GB1376278A (de)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3990793A (en) * 1973-08-27 1976-11-09 Hitachi, Ltd. Developing station for electronic color photographing apparatus
US4095885A (en) * 1974-06-17 1978-06-20 Freeman Lawrence M Polarity switch circuit for 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
US4126101A (en) * 1976-07-09 1978-11-21 Minolta Camera Kabushiki Kaisha Excess developing solution removing apparatus
US4127082A (en) * 1975-09-26 1978-11-28 Sharp Kabushiki Kaisha Wiper roller for drying a wet sheet in a copying machine
US4139653A (en) * 1973-01-10 1979-02-13 Agfa-Gevaert N.V. Method for the development of electrostatic charge patterns
FR2405507A1 (fr) * 1977-10-05 1979-05-04 Honeywell Inf Systems Systeme d'impression electrographique permettant de rendre visibles des images sur les deux cotes d'un support d'enregistrement prepare
US4270856A (en) * 1978-05-23 1981-06-02 Applied Copy Technology, Inc. Conversion kit for photocopying machine
US4286039A (en) * 1979-05-15 1981-08-25 Savin Corporation Method and apparatus for removing excess developing liquid from photoconductive surfaces
US4541707A (en) * 1983-04-08 1985-09-17 Canon Kabushiki Kaisha Recording apparatus having parting agent removing means
US5060024A (en) * 1988-06-17 1991-10-22 Mitsubishi Paper Mills Limited Method and apparatus for cleaning squeeze rollers in liquid electrophotographic developing apparatus
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

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5543389Y2 (de) * 1974-11-06 1980-10-13
JPS5543390Y2 (de) * 1974-11-26 1980-10-13
GB2041790B (en) * 1979-02-23 1983-07-27 Savin Corp Liquid development of electrostatic images

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4139653A (en) * 1973-01-10 1979-02-13 Agfa-Gevaert N.V. Method for the development of electrostatic charge patterns
US3990793A (en) * 1973-08-27 1976-11-09 Hitachi, Ltd. Developing station for electronic color photographing apparatus
US4095885A (en) * 1974-06-17 1978-06-20 Freeman Lawrence M Polarity switch circuit for 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
US4127082A (en) * 1975-09-26 1978-11-28 Sharp Kabushiki Kaisha Wiper roller for drying a wet sheet in a copying machine
US4126101A (en) * 1976-07-09 1978-11-21 Minolta Camera Kabushiki Kaisha Excess developing solution removing apparatus
FR2405507A1 (fr) * 1977-10-05 1979-05-04 Honeywell Inf Systems Systeme d'impression electrographique permettant de rendre visibles des images sur les deux cotes d'un support d'enregistrement prepare
US4161141A (en) * 1977-10-05 1979-07-17 Lakhani Kishor M Two side multi roller toner station for electrographic non-impact printer
US4270856A (en) * 1978-05-23 1981-06-02 Applied Copy Technology, Inc. Conversion kit for photocopying machine
US4286039A (en) * 1979-05-15 1981-08-25 Savin Corporation Method and apparatus for removing excess developing liquid from photoconductive surfaces
US4541707A (en) * 1983-04-08 1985-09-17 Canon Kabushiki Kaisha Recording apparatus having parting agent removing means
US5060024A (en) * 1988-06-17 1991-10-22 Mitsubishi Paper Mills Limited Method and apparatus for cleaning squeeze rollers in liquid electrophotographic developing apparatus
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
DE2325962A1 (de) 1973-11-29
DE2325962B2 (de) 1979-02-08
DE2325962C3 (de) 1979-10-04
GB1376278A (en) 1974-12-04
JPS4910740A (de) 1974-01-30

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