US3655419A - Electrophotographic reversal developing process - Google Patents

Electrophotographic reversal developing process Download PDF

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Publication number
US3655419A
US3655419A US875641A US3655419DA US3655419A US 3655419 A US3655419 A US 3655419A US 875641 A US875641 A US 875641A US 3655419D A US3655419D A US 3655419DA US 3655419 A US3655419 A US 3655419A
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United States
Prior art keywords
electrophotographic
developing
image
electrode
layer
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Expired - Lifetime
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US875641A
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English (en)
Inventor
Yasuo Tamai
Seiji Matsumoto
Satoru Honjo
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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
    • G03G13/00—Electrographic processes using a charge pattern
    • G03G13/06—Developing
    • 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
    • G03G13/22—Processes involving a combination of more than one step according to groups G03G13/02 - G03G13/20
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles

Definitions

  • ABSTRACT An electrophotographic reversal developing process where a charged electrophotographic element exposed to an optically negative image on an image bearing member where the area of the negative image is not over 10 percent of the area of the image bearing member.
  • the electrophotographic element is next disposed with respect to a developing electrode which is completely electrically insulated from its surroundings to thereby induce on said electrode a potential which causes an electric field to occur at the image portions of the whole electrostatic latent image which is oppositely directed from that occurring at the background portion which corresponds to the area of maximum charge density.
  • toner particles having a charge of the same polarity as that of the background portion are introduced between the developing electrode and the electrophotographic element to develop the image portions;
  • the present invention relates to electrophotography and more particularly to a so-called electrophotographic reversal developing process wherein a large amount of developpowder (toner particles) is deposited preferentially on areas having less electrostatic charge in an electrostatic latent image formed on an insulating layer and toner particles are not deposited on the areas thereof having the maximum electrostatic charge.
  • toner particles having an electrostatic charge of the same polarity as that of an electrostatic image formed on an insulator such as a photoconductive insulating layer are applied at the electrostatic latent image, the toner particles are repulsed by an electrostatic repulsive force at highly charged areas, while they deposit on discharged area.
  • the toner particles do not deposit on the insulating layer by an electrostatic attractive force, the deposited amount of the toner on the insulating layer corresponds not to the density of the electrostatic charges forming said electrostatic latent image but to the electrostatic field strength at the insulating layer surface. Accordingly, the toner particles deposit in a larger amount on the areas where the charge density charges discontinuously and hardly deposit on areas of uniform low charge density.
  • the potential applied to the developing electrode is preferably decreased synchronized to the dark decay of the surface potential.
  • the characteristics of the dark decay markedly depend upon the composition of insulating layer to be employed and surrounding conditions and hence are not so simple and it is quite difficult to vary the potential in accordance with the variation of the surface potential by the dark decay.
  • an object of the present invention is to provide an electrophotographic reversal developing process overcoming the aforesaid difficulties.
  • the practical object of this invention is to provide a quite simple electrophotographic reversal developing process employing a developing electrode to which an outer potential source need not be connected, utilizing the electrostatic energy of the electrostatic latent image to be developed itself.
  • object of the present invention is to provide an electrophotographic reversal developing process by which a high density reproduction is easily obtained from an optically negative original such as micro film comprising light transmitting line image areas and dark background.
  • Still other object of the present invention is to provide an electrophotographic reversal developing process having a high developing speed.
  • a reversal developing process of an electrostatic latent image formed on a photoconductive insulating layer on a conductive support using toner particles having an electrostatic charge of the same polarity as that of the electrostatic latent image to be developed wherein the photoconductive insulating layer is exposed to an optically negative image having an average transmittance of not over percent to the light of the spectral response range of said photoconductive layer to form an electrostatic latent image and then developing said latent image by placing an electrode adjacent the electrostatic latent image covering at least a part of the latent image-bearing area in such a manner that the electrode is electrically insulated from said conductive support and that the electrode is not connected with an outer power supply, thus the electric field at the space on the highlight portion in said latent image being substantially nullified, and supplying toner particles having the same polarity as that of the latent image to the space between said electrode and the latent image.
  • FIG. 6 is a cross-sectional view showing another embodiment of an electrophotographic element used in this invention.
  • FIG. 7 is a cross-sectional view showing an embodiment of the reversal developing process of this invention.
  • an electrophotographic element composed of a conductive support 1 and a'photoconductive insulating layer 2 bearing thereon an electrostatic latent image is placed close to an electrode 3.
  • the latent image is assumed to be formed by negative charges for convenience. That is, the latent image consists of negatively charged portions 4 and portions 5 having substantially no charges.
  • an optically negative image having a comparatively low average light transistance is utilized as an original and hence the area of the portion 4 is as a matter of course considerably larger than the area of the portion 5.
  • a negative micro film having recorded thereon a line image with very low density against a background having a uniformly higher density is generally used in the present invention.
  • the area of the image in the negative micro film does not exceed 10 percent of the whole area of the film, the average image area being about 5 percent.
  • the difference in density between the image portion and the background portion is at least about 1.0, the ratio of the image area may be considered, generally speaking, to show directly the transmittance of the micro film.
  • the electrode 3 assumes a certain value of potential. That is, assume the ratio of the area of the latent image corresponding to the line image to the area of the whole latent image to be r, and the potential of said line image area to be 0, and the potential of the background portion to be v, then the electrode 3 will assume an average potential of (1-r)v induced by the charge on the background area.
  • an electric field the same as that formed when a potential of rv is applied to the electrode 3 from an outer electric source will be formed between the electrode and the latent image-bearing layer.
  • the direction of the electric field is opposite to that of the field by the latent image and the intensity of the field generally is multiplied by about l-r 1).
  • an electric field having a definite intensity capable of attracting toner particles of negative polarity to the electrophotographic element is formed at the line image portion in the latent image 4 while at the background portion remains an electric field equals to (l-r)v, which is very weak when r is near 1, having opposite direction to that of the electric field at the image portion.
  • r cannot exceed 1, there is no trouble that an electric field of attracting the toner particles to the background portion is formed.
  • the energy in the charged portion of a latent image is also utilized in a reproduction of line image by utilizing field inversion at image edges in a conventional reversal developing process but the process of the present invention wherein the energy in the charged portion is effectively utilized by the aid of a conductor or electrode has never been disclosed.
  • the developing process of the present invention has the following merits as compared with a conventional reversal developing process wherein a developing electrode applied with an outer electric potential is employed:
  • the developing apparatus is simplified and the process can be conducted by using a compact and inexpensive means.
  • Electrode 3 is electrically insulated.
  • the electrode is carefully insulated from the conductive support of an electrophotographic element or the conductive part in the support.
  • the paper support must be prevented from being directly brought into contact with the electrode when the paper support has a surface resistance of l0 l0Q/cm or less.
  • a conductive intermediate layer such as a metallic layer or a conductive resin layer is formed on a paper support having a comparatively high electric resistance and an electrophotographic light-sensitive layer is formed on the intermediate layer
  • the conductive intermediate layer appears as a thin layer at the paper cross section or edge and it frequently occurs that the developing electrode contacts the thin layer at the cross section or edge of the paper.
  • One effective attempt for overcoming this trouble is to apply an insulating resin compositionv or an insulating tape to the cross sections of the electrophotographic sheet or to provide an electrophotographic element as shown in FIG. 2 of the accompanying drawings wherein an intermediate layer having an area smaller than that of the element is inserted between the paper support and the electrophotographic light-sensitive layer so that the edges of the conductive intermediate layer do not appear at the cross sections.
  • FIG. 2 an embodiment of an electrophotographic element used in the present invention.
  • the element is composed of a support 7 having a high electric resistance, such as a plastic film or a paper which has not been subjected to a conductive treatment, an electrophotographic light-sensitive layer 2, and a conductive intermediate layer 10 inserted therebetween and having an area smaller than that of the support and the electrophotographic light-sensitive layer.
  • the conductive intermediate layer is, for instance, a metallic film or a resin layer having a high electric conductivity, such as, a polymer of monomers containing quaternary ammonium base or potassium polyvinyl-benzene sulfonate. Furthennore, a carbon black-containing layer may be employed as such an intermediate conductive layer.
  • the developing electrode can be prevented from being shorted with the electrophotographic element.
  • a liquid developing system or a powder cloud developing system is most profitably employed as developing method.
  • the viscosity .of the white dispersion thus obtained was adjusted by adding further butyl acetate thereto and the resulting dispersion was applied to an aluminum layer of Metalmy Film (trade name, made by Toyo Rayon Co., Ltd.).
  • Metalmy was an aluminized film prepared by vacuum depositing a thin aluminum layer on one surface of a polyethylene terephthalate film. The thickness of the photoconductive light-sensitive layer after drying was about 8 microns. After completely drying the layer, the electrophotographic element thus prepared was stored in the dark for 20 hours at 40 C. to be subjected to dark adaptation.
  • the light-sensitive layer was developed in a liquid developer containing negatively charged toner particles.
  • the liquid developer was prepared by stirring a mixture of the following composition at a high speed.
  • Microlith Blue-M340 (trade name, made by CIBA, LTD.) 200 mg.
  • a Varnish (made by Toyo Ink Mfg. Co.) 400 mg.
  • Ethyl acetate 10 ml.
  • the blue and stable dispersion thus obtained was dispersed in a liquid having the following composition by means of an ultrasonic dispersing device;
  • the copolymer was insolubilized and deposited together with or including the blue pigment to provide toner particles.
  • the varnish dissolved in the liquid and contributed to disperse the toner particles thus deposited.
  • the toner particles dispersed in the liquid were quite fine, almost no turbidity was perceived in the blue liquid developer. That is, the particle size of the toner dispersed in the dispersion was less than 1 micron.
  • the liquid developer was placed in a stainless steel vat and the development of the aforesaid light-sensitive layer after exposure was carried out by immersing the light-sensitive layer in the liquid developer so that the latent image-bearing layer faced the bottom of the stainless steel vat. After conducting the development for 1 minute, the light-sensitive layer was rinsed with clear isoparaffin (Isopar-E, made by Esso Research & Development Co.) to remove the excessive liquid developer from the developed surface.
  • Isopar-E clear isoparaffin
  • a number of light-sensitive layers as mentioned above were subjected to the aforesaid charging, exposing, and developing procedures and the results thereof were compared. If the development was satisfactory or correctly conducted wholeout the procedures, the portion of the light-sensitive layer corresponding to the portion 12 of the original should have been developed in a high density and the edge effect should have been scarcely observed at the portion.
  • EXAMPLE 1 After charging the light-sensitive layer of the electrophotographic element as described in the aforesaid experiment, the four sides thereof were covered by an adhesive Mylar tape as shown in FIG. 4.
  • the adhesive Mylar tape was composed of a polyethylene terephthalate film having coated on one surface an adhesive.
  • the electrophotographic element used in the present invention was composed of a polyethylene terephthalate film 13 as a support for Metalmy, an aluminum layer 14, a light-sensitive layer 12, and the adhesive tape 15 covering the sides and edges of the element.
  • the light-sensitive layer thus insulated completely was developed in a stainless steel vat after being image exposed in a similar manner as in the aforesaid experiment. During the procedure, the stainless steel vat was carefully prevented from being earthed.
  • EXAMPLE 2 The almost same procedure as in Example 1 was followed with the exception that the sides of the photoconductive element were insulated by the adhesive Mylar tape before the light-sensitive layer was charged. In this case, since the charging of the light-sensitive layer became insufficient by the pressure of the adhesive tape, it was necessary to remove a part of the light-sensitive layer near the end of the sheet to expose the aluminum layer and to earth the exposed aluminum layer at charging. Before development, the exposed aluminum layer was insulated by an other piece of adhesive tape.
  • EXAMPLE 3 The white zinc oxide dispersion described in the aforesaid a conductive treatment in a dry thickness of 8 microns.
  • the four sides of the light-sensitive paper were covered by an insulating resin as shown in FIG. 5, wherein a light-sensitive layer 2 was formed on a paper 1 subjected to conductive treatment and the sides of the element were covered by an insulating resin 16.
  • the sides of the lightsensitive layer were completely insulated.
  • the light-sensitive layer was subjected to the charging, image exposing, and developing procedures as in Example I.
  • the development was conducted in a stainless steel vat. During the development, the conductive support 1 was perfectly insulated from the stainless steel vat.
  • EXAMPLE 4 The edges of the photographic element as shown in FIG. 3 were bent upwardly as shown in FIG. 6, wherein the element was composed of a conductive support 1 and a light-sensitive layer 2 and the element was immersed in the liquid developer in a stainless steel vat so that the lower light-sensitive layer faced the bottom plate of the stainless steel vat.
  • EXAMPLE 5 The reversal development was conducted by using a vat shown in FIG. 7 of the accompanying drawing.
  • the vat 17 was composed of an insulating material and an electrode 18 embedded in the bottom of the vat.
  • the area of the electrode 18 was smaller than that of the electrophotographic element and hence the electrode was effectively prevented from being electrically brought into contact with a conductive layer 14, such as an aluminum layer, of the electrophotographic element.
  • the conductive layer 14 was placed between an insulating support 13 and a light-sensitive layer 2.
  • the element was immersed in a liquid developer 19 having dispersed therein toner particles charged in the same polarity as that of an electrostatic latent image formed on the light-sensitive layer so that the light-sensitive layer faced the electrode 18 with a suitable interval therefrom.
  • An electrophotographic reversal developing process which comprises:
  • an electrophotographic element comprising a uniformly charged photoconductive insulating layer on an electrically conductive support to an optically negative image on an image bearing member where the area of the negative image is not over percent of the area of said image bearing member to form on said photoconductive insulating layer an electrostatic latent image corresponding to said image;

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Wet Developing In Electrophotography (AREA)
  • Liquid Developers In Electrophotography (AREA)
US875641A 1968-11-12 1969-11-12 Electrophotographic reversal developing process Expired - Lifetime US3655419A (en)

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JP8269668 1968-11-12

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US (1) US3655419A (fr)
BE (1) BE741440A (fr)
DE (1) DE1956492A1 (fr)
FR (1) FR2023082A1 (fr)
GB (1) GB1287903A (fr)
NL (1) NL6916641A (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3804659A (en) * 1970-12-10 1974-04-16 Fuji Photo Film Co Ltd Electrophotographic reversal development process for enhancing the quality of the developed image
US3888666A (en) * 1971-12-22 1975-06-10 Rank Xerox Ltd Reversal developing method using photoconductive developing electrode
US3964436A (en) * 1974-04-08 1976-06-22 Scott Paper Company Electrophotographic development apparatus
US4278343A (en) * 1976-04-22 1981-07-14 Ricoh Co., Ltd. Inversion developing method for electrophotography and relevant apparatuses
US5051329A (en) * 1989-12-19 1991-09-24 Dximaging Reversal development of latent electrostatic images on xeroprinting masters

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2817598A (en) * 1955-02-01 1957-12-24 Haloid Co Continuous tone reversal development process
US2986521A (en) * 1958-03-28 1961-05-30 Rca Corp Reversal type electroscopic developer powder
US3211686A (en) * 1959-06-18 1965-10-12 Plastic Coating Corp Aqueous composition for prewetting a master carrying an image prepared by electrophotographic reproduction containing polyacrylic acid
US3249088A (en) * 1963-04-03 1966-05-03 Scm Corp Developing tank unit for electrostatic printing
US3336906A (en) * 1965-06-09 1967-08-22 Fairchild Camera Instr Co Apparatus for immersion development
US3367791A (en) * 1966-07-11 1968-02-06 Addressograph Multigraph Liquid development of electrostatic images
US3391082A (en) * 1965-04-06 1968-07-02 Koppers Co Inc Method of making xergographic toner compositions by emulsion polymerization

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2817598A (en) * 1955-02-01 1957-12-24 Haloid Co Continuous tone reversal development process
US2986521A (en) * 1958-03-28 1961-05-30 Rca Corp Reversal type electroscopic developer powder
US3211686A (en) * 1959-06-18 1965-10-12 Plastic Coating Corp Aqueous composition for prewetting a master carrying an image prepared by electrophotographic reproduction containing polyacrylic acid
US3249088A (en) * 1963-04-03 1966-05-03 Scm Corp Developing tank unit for electrostatic printing
US3391082A (en) * 1965-04-06 1968-07-02 Koppers Co Inc Method of making xergographic toner compositions by emulsion polymerization
US3336906A (en) * 1965-06-09 1967-08-22 Fairchild Camera Instr Co Apparatus for immersion development
US3367791A (en) * 1966-07-11 1968-02-06 Addressograph Multigraph Liquid development of electrostatic images

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3804659A (en) * 1970-12-10 1974-04-16 Fuji Photo Film Co Ltd Electrophotographic reversal development process for enhancing the quality of the developed image
US3888666A (en) * 1971-12-22 1975-06-10 Rank Xerox Ltd Reversal developing method using photoconductive developing electrode
US3964436A (en) * 1974-04-08 1976-06-22 Scott Paper Company Electrophotographic development apparatus
US4278343A (en) * 1976-04-22 1981-07-14 Ricoh Co., Ltd. Inversion developing method for electrophotography and relevant apparatuses
US5051329A (en) * 1989-12-19 1991-09-24 Dximaging Reversal development of latent electrostatic images on xeroprinting masters

Also Published As

Publication number Publication date
GB1287903A (fr) 1972-09-06
NL6916641A (fr) 1970-05-14
DE1956492A1 (de) 1970-10-29
BE741440A (fr) 1970-04-16
FR2023082A1 (fr) 1970-08-07

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