US3664833A - Method of transferring an electrostatic image to a dielectric sheet - Google Patents

Method of transferring an electrostatic image to a dielectric sheet Download PDF

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Publication number
US3664833A
US3664833A US45124A US3664833DA US3664833A US 3664833 A US3664833 A US 3664833A US 45124 A US45124 A US 45124A US 3664833D A US3664833D A US 3664833DA US 3664833 A US3664833 A US 3664833A
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United States
Prior art keywords
image
transfer sheet
potential
positive
electrostatic
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Expired - Lifetime
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US45124A
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English (en)
Inventor
Susumu Tanaka
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Minolta Co Ltd
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Minolta 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
    • G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
    • G03G15/226—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 where the image is formed on a dielectric layer covering the photoconductive layer
    • 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
    • G03G13/14—Transferring a pattern to a second base
    • G03G13/18—Transferring a pattern to a second base of a charge pattern

Definitions

  • FIG. 1 A first figure.
  • FIG. 1 A first figure.
  • FIG. 1 A first figure.
  • An electrostatic image is transferred from a photoconductive layer onto a dielectric sheet of 10 1. to 200 thickness by applying an AC corona discharge to the dielectric sheet and projecting a uniform light onto the dielectric sheet from an incandescent light source.
  • the image on the dielectric sheet is developed with toner and the dielectric sheet is stripped from the photosensitive material.
  • a transfer sheet is put upon a photosensitive plate on which an electrostatic image is formed and by applying thereto a bias electric field the electrostatic image is transferred from the photosensitive plate to the transfer sheet.
  • the transfer sheet is stripped to obtain the electrostatic image on the surface thereof which has been in contact with the photoconductive plate.
  • drawbacks in this process it is difiicult to set up the bias voltage for promoting the transfer of electrostatic image from the photosensitive plate to the transfer sheet; the electrostatic image transferred is deteriorated remarkably as compared with the electrostatic image on the photosensitive plate; and an electric discharge produced by stripping the transfer sheet results in unevenness on the electrostatic image on the transfer sheet.
  • the visible image thereof is transferred onto the transfer sheet, so that-it is necessary to remove the remaining visible image on the photosensitive plate and this fact lowers the efficiency of the visible image transferring process.
  • the present invention is directed to a transferring process for electrostatic copiers which does not have the drawbacks described above in both prior art transferring processes.
  • the present invention forms an improved electrostatic image in accordance with an electrostatic latent image on a photosensitive body on the surface (not facing the photosensitive body) of a transfer sheet put upon the photosensitive body and develops the electrostatic image by applying an AC corona discharge onto the transfer sheet in a dark place and by applying an overall exposure onto the electrostatic image.
  • the primary object of the present invention is to provide an improved transferring process for electrostatic copying for transferring the electrostatic image onto the face of a transfer sheet opposite to the face facing the photosensitive body.
  • the second object of the present invention is to provide a transferring process for electrostatic copying in which the stripping of a transfer sheet from the photosensitive body is not necessary to obtain latent images and the development thereof.
  • the third object of the present invention is to provide a transferring process for electrostatic copying in which the transferring of electrostatic images has high sensitivity and high contrast.
  • the fourth object of the present invention is to provide a transferring process for electrostatic copying in which both positive-positive and negative-positive transfers which are free of fog can be effected.
  • the fifth object of the present invention is to provide a transferring process for electrostatic copying in which a half-tone can be formed correctly.
  • FIG. 1A the uniform charging process of a photosensitive body which is a step in the process of electrostatic copying
  • FIG. 1B shows the electrostatic image forming process on a photosensitive body which is also a step in the process of electrostatic copying
  • FIG. 1C shows the transfer sheet in place upon the photosensitive body in accordance with the process of the present invention
  • FIG. 1D shows the application of an AC corona discharge onto the transfer sheet in a dark place in accordance with the present invention
  • FIG. 1B shows the overall exposure process in accordance with the present invention.
  • FIG. 2 is a plot ShOWing the time-voltage relationship of the surface potential between a photosensitive body and a transfer sheet.
  • FIG. 3A shows the relative arrangement of an AC corona discharge device and an electrode
  • FIG. 3B shows the characteristics of the output current in FIG. 3A.
  • FIG. 4A shows positive-positive development and FIG. 4B shows negative-positive development.
  • Reference numeral 1 denotes a photosensitive body composed of photoconductive layer 1b provided with condu'ctive layer 1a on the back thereof for use in the conventional xerography process.
  • a photosensitive substance for forming an electrostatic image at low potential such as a resin dispersoid mainly composed of, for example, ZnO or a CdS resin dispersoid which is a high potential substance, which fogs readily, may be used in the process of the invention.
  • the process for forming an electrostatic image on a photosensitive body is about the same as the prior xerography process.
  • a discharge is made onto the face of photoconductive layer 1b of photosensitive body 1 by means of DC corona discharge device 5 in a dark place, and by moving it relative to the photosensitive body it is possible to charge it uniformly negative
  • the surface potential of photoconductive layer 1b of photosensitive body 1 increases along curve V as shown by (a) in FIG. 2 and is saturated to a maximum value at time T,,.
  • FIG. 1B the exposure of a picture image is applied onto photoconductive layer 1b charged uniformly to a negative potential as described above. That is, the image of original copy 3 is projected onto the charged face of photoconductive layer 1b by means of lens 4.
  • the transferring process in accordance with the present invention is carried out in the processes shown in FIGS. 1C, D and E, however, in order to clarify the charging, the development of the surface potential, and the transfer thereof on the transfer sheet in FIGS. 1A and B in the processes shown in FIG. 1C, D and E, the explanation has been made in accordance with FIGS. 1A and B. i
  • FIG. 1C shows the process in which transfer sheet 2 is placed, in a dark place, upon the face of photoconductive layer 1b of photosensitive body 1 on which the electrostatic latent image is formed, and transfer sheet 2 is made of an insulating material, for example, a film of polyester, polyethylene, vinyl chloride, or the like can be used.
  • transfer sheet 2 is made of an insulating material, for example, a film of polyester, polyethylene, vinyl chloride, or the like can be used.
  • transfer sheet 2 is put upon the face of photoconductive layer 1b at time T,, the production of straight line V- of the light image shadow on photoconductive layer 1b of photosensitive body 1 decreases suddenly as shown by straight line V and the surface potential on the shadow on transfer sheet 2 assumes the value V In this state, if transfer sheet 2 is developed with toner having a positive electric charge it is developed only temporarily, however, this is realized only if transfer sheet 2 is thin-in the order of several microns-and the potential ditference corresponding to the light and darkness of the electrostatic image on photosensitive plate 1 is large. But such a thin transfer sheet is of no practical use.
  • the positive ions from AC corona discharge device 6 increase by being attracted by a negative electric field when electrode 7 is at a negative potential and conversely decreases by repulsion when electrode 7 is at a positive potential and curve i undergoes a charge as shown in FIG. 3B.
  • negative ions from AC corona discharge device 6 decrease by repulsion when electrode 7 is at a negative potential and increase by being attracted by a positive electric field when electrode 7 is at a positive potential and curve i undergoes a change as shown in FIG. 3B.
  • the overall exposure is applied from the side of transfer sheet 2 when sheet 2 is transparent, and when photosensitive body '1 is transparent (especially when photoconductive layer 1a thereof is transparent) the overall exposure can be applied from the photoconductive layer side and in this case transfer sheet 2 may be opaque.
  • photoconductive layer 111 Upon applying the overall exposure photoconductive layer 111 has increased conductivity, and on the shadow thereof, except the negative electric charge seized by the internal field of positive electric charge on transfer sheet 2, negative electric charge is discharged to photoconductive layer 1a, and the positive electric charge acts as the external field. And the surface potential on transfer sheet 2 increases suddenly from negative potential to positive potential to obtain a maximum value at time '1", and then is constant as shown by curve V in FIG. 2E.
  • the electrostatic image on transfer sheet 2 has different characteristics in accordance with its thickness, and if it is thick the surface potential on the shadow image portion becomes higher than if it is thin and the contrast thereof has a tendency to be lighter, and a transfer sheet having a thickness of as much as several hundred microns can be put to use.
  • FIG. 4A shows positive-positive development carried out with toner charged to a negative electric charge
  • FIG. 4B shows negative-positive development carried out with toner charged to a positive electric charge, however, in either case, the surface electric charge and the surface potential on the portion to be white are of the same polarity as the electric charge of the toner, so that there is no ground contamination.
  • the present invention has been explained for the case wherein the potential on the electrostatic image on photosensitive plate 1 is zero on the light image and negative potential on the shadow image portion, however, even if the remaining potential V is the light image of an electrostatic image on photosensitive body 1, in the case where V,, V and the value is small point P is between both potentials and as seen clearly in FIG. 3B the light image is not charged to a positive electric charge by the AC corona discharge process (FIG. 1D) so that no fog results.
  • an electrostatic image charged to a positive electric charge is formed as S by setting a point of intersection for the output current of the AC corona discharge device to be on the positive potential side, for example, as point P in FIG. 3, it is possible to carry out the process in the same way as in for the negative electric charge.
  • the setting of point P can be attained by applying positive voltage to the secondry coil side of the AC corona discharge device. That is, for example, by applying a positive voltage to AC corona discharge device 6 of 6000 v., the positive discharge becomes 6500 v. and the negative discharge becomes 5500 v.
  • the present invention by setting properly the characteristics of the output current of the AC corona discharge device, for example, by increasing or decreasing the corona discharge voltage or by changing the value of positive discharge voltage and negative discharge voltage, it is possible to move point P to increase the quantity of electric charge on transfer sheet 2 and also increase the sensitivity easily.
  • a ZnO-resin dispersed photosensitive plate is put to use, and after a polyester film having a thickness of 50 is put upon an electrostatic image composed of a light image of 0 v. and a shadow image of ()500 v., an AC corona discharge of 6000 v. is applied onto the film surface, and an electrostatic image of (-)250 v. on the light image and (+)250 v. on the shadow image can be obtained on the film surface.
  • a CdS-resin dispersed photosensitive plate is put to use, and after an electrostatic image composed of a light image of 100 v. and a shadow image of ()1000 v. is formed and the same transfer film as in the first embodiment is put upon the electrostatic image, an AC corona discharge of 6000 v. is applied, and an electrostatic image of ()400 v. on the light image and (+)450 v. on the shadow image can be obtained on the film surface.
  • a transferring process for electrostatic image copying comprising the steps of:

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Electrostatic Charge, Transfer And Separation In Electrography (AREA)
  • Control Or Security For Electrophotography (AREA)
US45124A 1969-06-16 1970-06-10 Method of transferring an electrostatic image to a dielectric sheet Expired - Lifetime US3664833A (en)

Applications Claiming Priority (1)

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JP4749169 1969-06-16

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US3664833A true US3664833A (en) 1972-05-23

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US (1) US3664833A (de)
CH (1) CH520959A (de)
DE (1) DE2029505C3 (de)
FR (1) FR2046812B1 (de)
NL (1) NL7008516A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830645A (en) * 1971-01-11 1974-08-20 Pitney Bowes Inc Method and apparatus for creating an electrostatic latent image by charge modulation
US3980475A (en) * 1972-07-27 1976-09-14 La Cellophane Process of transferring an electrostatic latent image to a dielectric support
US5241276A (en) * 1989-04-28 1993-08-31 Kabushiki Kaisha Toshiba Surface potential measuring system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3830645A (en) * 1971-01-11 1974-08-20 Pitney Bowes Inc Method and apparatus for creating an electrostatic latent image by charge modulation
US3980475A (en) * 1972-07-27 1976-09-14 La Cellophane Process of transferring an electrostatic latent image to a dielectric support
US5241276A (en) * 1989-04-28 1993-08-31 Kabushiki Kaisha Toshiba Surface potential measuring system

Also Published As

Publication number Publication date
DE2029505B2 (de) 1979-09-06
NL7008516A (de) 1970-12-18
DE2029505C3 (de) 1980-05-14
FR2046812A1 (de) 1971-03-12
DE2029505A1 (de) 1970-12-23
FR2046812B1 (de) 1973-01-12
CH520959A (de) 1972-03-31

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