US3807998A - Method of colour electrophotography - Google Patents

Method of colour electrophotography Download PDF

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Publication number
US3807998A
US3807998A US00094794A US9479470A US3807998A US 3807998 A US3807998 A US 3807998A US 00094794 A US00094794 A US 00094794A US 9479470 A US9479470 A US 9479470A US 3807998 A US3807998 A US 3807998A
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United States
Prior art keywords
layer
highly insulative
photosensitive element
insulative layer
image
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Expired - Lifetime
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US00094794A
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English (en)
Inventor
K Kinoshita
M Watanabe
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Katsuragawa Electric Co Ltd
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Katsuragawa Electric 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
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/02—Charge-receiving layers
    • G03G5/024—Photoelectret layers
    • 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
    • G03G13/01—Electrographic processes using a charge pattern for multicoloured copies
    • 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
    • G03G13/056—Electrographic processes using a charge pattern using internal polarisation

Definitions

  • a plurality of electrophotographic machine units are arranged side by side and a photosensitive element is successively passed through these machine units to successively form powder images of different colors.
  • a photosensitive element is successively passed through these machine units to successively form powder images of different colors.
  • it is difficult to exactly register a plurality of powder images.
  • the apparatus required is bulky and expensive.
  • Another object of this invention is to form color prints without the risk of being out of register with a single electrophotographic .machi'ne unit.
  • a further object of this invention is to reproduce intermediate colors or tones at high fidelities without the necessity of utilizing a screen.
  • a still further object of this invention is to readily produce latent images or color printed copies of relatively high contrast although color filters are used.
  • a method of color electrophotography comprising a first step of applying a first electric field across a photosensitive element including a transparent electrode layer, a photosensitive photoconductive layer exhibiting persistent internal polarization and a highly insulative layer to deposit a charge of one polarity on the surface of the highly insulative layer; a second step of applying a second field across the photosensitive element to deposit a charge of the opposite polarity on the surface of the highly insulative layer concurrently with the projection of a light image of one color upon the photosensitive photoconductive layer through the transparent electrode layer to form a latent image corresponding to the light image on the surface of the highly insulative layer; a third step of developing the latent image with a toner of said one color to form a first powder image of said one color; and a fourth step of repeating successively said first, second and third steps with a light image of another color and a toner of said another color while the photosensitive element is held stationary whereby to form a second powder image of said another
  • first and second fields may be applied by means of a contact electrode removably placed on the highly insulative layer it is advantageous to use a well known corona discharge unit.
  • FIG. 1 is a diagrammatic representation, partly in section, of an electrophotographic apparatus suitable for carrying out the method of this invention.
  • FIGS. 2 and 3 are sectional views showing modified photosensitive elements.
  • the electrophotographic apparatus shown in FIG. I employs a photosensitive element 5 which comprises a transparent substrate 1 such as a glass plate, a transparent electrode 2 on one side of substrate 1, a photosensitive photoconductive layer 3 having a plurality of charge trapping levels to exhibit persistent internal polarization and a highly insulative layer 4.
  • the layers are superposed on each other in the order mentioned and are bonded together into an integral unit.
  • the photosensitive element 5 is supported at a definite position or to be movable in the lateral direction with its substrate I faced upwardly.
  • a corona discharge unit 6 is disposed beneath photosensitive element 5 to deposit a charge of any desired polarity on the entire surface of the highly insulative layer 4.
  • -Corona discharge unit 6 is adjustable in the vertical direction or toward and away from the photosensitive element.
  • a charging device including a source of uniform light 8 and a second corona discharge unit 7 constructed to freely transmit the light from source 8 is provided to be movable across the surface of the highly insulative layer 4 to scan the same when the first corona discharge unit 6 is lowered.
  • a plurality of developing units 9a and 9b containing toners of different colors are positioned beneath and on the opposite sides of the photosensitive element.
  • One of them 9a is movable in the vertical direction toward the surface of highly insulative layer 4 and along the surface of the photosensitive element whereas the other 9b is positioned close to the surface of the highly insulative layer 4 to develop the latent image formed thereon when the photosensitive element 5 is moved to the right.
  • An optical lens 12 and sources of light 11 for illuminating an original 10 are disposed above the photosensitive element to project the light image of the original upon photosensitive layer 3 through transparent substrate 1 and transparent electrode 2.
  • a plurality of optical color filters 13a and 13b transmitting light rays of different colors are disposed beneath lens 12 such that any one of them is selectable to cooperate with lens 12.
  • a light shield 14 may be provided to enclose lens 12, filters 13a and 13b and the upper surface of the photosensitive element 5 to intercept external light at the time of image projection.
  • An AC corona discharge unit 15 and a cleaner 16 are disposed to remove residual charge and toner when the photosensitive element 5 is moved to the left to prepare it for the next cycle.
  • the second corona discharge unit 7 and light source 8 may be omitted when a transparent counter electrode 17 is provided for the first corona discharge unit 6 and light sources 18 are provided beneath it as shown by dotted lines.
  • a powder image is formed on the surface of the highly insulative layer 4 in the following manner.
  • the first corona discharge unit 6 is operated to deposit a charge on the surface of the highly insulative layer 4 of a polarity opposite to the polarity of the majority carriers of the photoconductive material comprising the photosensitive photoconductive layer 3 whereby the majority carriers are trapped in the trapping levels at or near the interface between photoconductive layer 3 and highly insulative layer 4 thus establishing presistent internal polarization.
  • corona discharge unit 6 is operated to deposit a charge of the opposite polarity; that is, a charge of the same polarity as the majority carriers of the photoconductive material on the surface of the highly insulative layer.
  • the light image of the selected color of the original is projected upon the photosensitive photoconductive layer 3 through lens 12, one of the filters, 13a for example, and transparent electrode 2 so as to preserve the charge trapped in the photoconductive layer 3 during the first step at portions corresponding to the dark portions of the light image and to promptly release such trapped charge at portions corresponding to the bright portions of the light image whereby an electrostatic latent image is formed on the surface of the highly insulative layer 4 corresponding to the light image of the particular color.
  • corona discharge unit 6 is lowered to a position indicated by dot and dash lines and developing unit 9a containing a toner of the same color as that of the color image projected in the second step is raised to a position close to the photosensitive element and is then moved to the right as shown by the arrow to develop the latent image formed on the surface of highly insulative layer 4.
  • Such development can be carried out either in the dark or under room light. Without.
  • the fourth step is carried out.
  • another latent image of different color is formed by the steps identical to the first and second steps except that another color filter 13b is used.
  • the latent image of the different color image which is precisely superposed on the previously formed latent image, is developed by using another developing unit 9b containing'a toner of different color.
  • a powder image of any desired color can be formed which is transfer printed onto a recording paper and is then fixed in a manner well known inv the art. Intermediate colors can be reproduced at high fidelities because toners of different colors are suitably admixed at the time of fixing.
  • the powder image formed by the first image forming procedure is not destroyed or degraded by the second image forming and developing procedure. It is presumed that this is because the first powder image is held on the highly insulative layer by the electrostatic attractive force.
  • the charge may be applied in the dark during the first step. However, dependent upon the characteristics of the photosensitive photoconductive layer 3 this charge may be applied while uniform light is irradiated over the entire surface of the photosensitive element.
  • the first corona discharge unit 6 is lowered to the position shown by dot and dash lines and then the light transmitting second corona discharge unit 7 and associated light source 8 and moved to the right along the lower surface of the photosensitive element to scan the same.
  • lamps 18 are lighted concurrently with the operation of corona discharge unit 6. In this case, it is advantageous to reciprocate corona discharge unit 6 in the longitudinal direction (to the left and right) over a small distance in order to eliminate non-uniform charging caused by the shadow of the discharge wires.
  • the photosensitive element 5 After transfer printing of the color powder image it is necessary to remove residual charge and toners from the photosensitive element. To this end, the photosensitive element 5 is moved to the left as shown by dot and dash lines to erase the residual latent image with the AC corona discharge unit 15 and to remove remaining toners from the surface of the highly insulative layer 4 by means of the cleaner 16. Thereafter, the element 5 is ready for use in the next cycle of image formation.
  • the photosensitive element utilized in this invention may take various other forms.
  • another highly insulative and transparent layer 4' may be interposed between transparent electrode 2 and photosensitive photoconductive layer 3 and integrally bonded to both layer3 and electrode 2.
  • a charge trapping layer 3' having a large light absorption coefficient and which can produce many free charge carriers when irradiated with light may be provided between highly insulative layer 4 (or electrode 2 when layer 4' is not used) and photosensitive photoconductive layer 3.
  • the photoconductive layer 3 is composed of material that permits free charge carriers injected from charge trapping layer 3' to migrate over long distances and the material forms only a small number of free charge carriers when it is excited thermally, thus providing a photosensitive element of high resolution and high photosensitivety.
  • the charge trapping layer 3 may be formed by the concurrent vapour deposition of Se and a SeTe alloy containing a relatively large quantity of Te, whereas the photosensitive photoconductive layer 3 may be formed by the vapour deposition of a SeTe alloy containing a relatively small quantity of Te.
  • these two layers are formed by consecutive vapour deposition steps, a well defined interface will not be formed therebetween, but the composition will vary gradually from one layer to the other.
  • the thickness of both highly insulative layers 4 and 4 may be a few microns but the layer 4 may be about 1 micron thick. Further, in the embodiment shown in FIG. 3 the highly insulative layer 4' may be omitted.
  • Developing units 9a and 9b may be of the powder clouding type wherein the powdery toner is sprayed onto the surface of the highly insulative layer 4 or a cascade type wherein the powdery toner is sprinkled over the highly insulative layer.
  • a developing unit of the magnetic brush type it is necessary to take care not to mechanically scratch the surface of the highly insulative layer.
  • the projected light image is not intercepted by the powder image even though a number of latent image forming steps and a number of developing steps by toners are performed alternately. For this reason, it is possible to precisely overlap a plurality of images of different colors 'thus reproducing intermediate colors at high fidelities. Moreover, as it is not necessary to use a screen to decompose the image into a number of discrete elements it is possible to preserve a high degree of resolution.
  • the high contrast latent image is formed on the surface of the highly insulative layer by partially or selectively releasing the charge that has been trapped in the photoconductive layer during the first step by the projection of the light image and application of the electric field during the second step it is possible to readily produce latent images of relatively high contrast irrespective of the decrease in the light quantity caused by the use of color filters and transparent electro e.
  • the original sometimes contains black portions in addition to colored patterns.
  • an additional step is used wherein the light image is projected without utilizing an optical filter and the latent image is developed with a black toner.
  • a method of color electrophotography comprising a first step of applying a first electric field across a photosensitive element including a transparent electrode layer, a photoconductive layer exhibiting persistent internal polarization and a highly insulative layer to deposit a charge of one polarity on the surface of said highly insulative layer; said layers being superposed on each other in the order mentioned and being bonded together into an integral unit; a second step of applying a second electric field across said photosensitive element to deposit a charge of the opposite polarity on the surface of said highly insulative layer concurrently with the projection of a light image of one color upon said photoconductive layer from the side of said element opposite the highly insulative layer and through said transparent electrode layer to form a latent image corresponding to said light image on the surface of said highly insulative layer; a third step of developing said latent image with a toner of said one color to form a first powder image of said one color; and a fourth step of repeating said first, second and third steps with a light image of another color and a to

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electrophotography Using Other Than Carlson'S Method (AREA)
  • Color Electrophotography (AREA)
US00094794A 1969-12-17 1970-12-03 Method of colour electrophotography Expired - Lifetime US3807998A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP44101500A JPS4938170B1 (de) 1969-12-17 1969-12-17

Publications (1)

Publication Number Publication Date
US3807998A true US3807998A (en) 1974-04-30

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US00094794A Expired - Lifetime US3807998A (en) 1969-12-17 1970-12-03 Method of colour electrophotography

Country Status (7)

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US (1) US3807998A (de)
JP (1) JPS4938170B1 (de)
CA (1) CA921546A (de)
DE (1) DE2061333C3 (de)
FR (1) FR2073706A5 (de)
GB (1) GB1283808A (de)
NL (1) NL144741B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3910232A (en) * 1973-06-14 1975-10-07 Canon Kk Color reproduction device
US4007044A (en) * 1973-12-11 1977-02-08 Ricoh Co., Ltd. Color electrophotographic process
US4275134A (en) * 1974-07-30 1981-06-23 Canon Kabushiki Kaisha Electrophotographic method for reproducing a multicolor image
US5362586A (en) * 1990-12-27 1994-11-08 Xerox Corporation Process for two color imaging comprising a photoreceptor having a unipolar hole transporting layer

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5061583A (en) * 1990-01-19 1991-10-29 Minnesota Mining And Manufacturing Company Color electrophotography for high quality half-tone images

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3043686A (en) * 1958-07-08 1962-07-10 Xerox Corp Xerographic color masking
US3178281A (en) * 1956-07-16 1965-04-13 Eastman Kodak Co Electrostatic color printing
US3376133A (en) * 1964-11-25 1968-04-02 Interchem Corp Multicolor electrostatic printing
US3438706A (en) * 1966-10-07 1969-04-15 Canon Kk Electrophotographic device
US3457070A (en) * 1964-07-25 1969-07-22 Matsuragawa Electric Co Ltd Electrophotography
US3615383A (en) * 1966-05-26 1971-10-26 Canon Camera Co Chargeless electrophotographic printing process
US3655369A (en) * 1967-09-05 1972-04-11 Katsuragawa Denki Kk Persistent internal polarization process in electrophotography

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3178281A (en) * 1956-07-16 1965-04-13 Eastman Kodak Co Electrostatic color printing
US3043686A (en) * 1958-07-08 1962-07-10 Xerox Corp Xerographic color masking
US3457070A (en) * 1964-07-25 1969-07-22 Matsuragawa Electric Co Ltd Electrophotography
US3376133A (en) * 1964-11-25 1968-04-02 Interchem Corp Multicolor electrostatic printing
US3615383A (en) * 1966-05-26 1971-10-26 Canon Camera Co Chargeless electrophotographic printing process
US3438706A (en) * 1966-10-07 1969-04-15 Canon Kk Electrophotographic device
US3655369A (en) * 1967-09-05 1972-04-11 Katsuragawa Denki Kk Persistent internal polarization process in electrophotography

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3910232A (en) * 1973-06-14 1975-10-07 Canon Kk Color reproduction device
US4007044A (en) * 1973-12-11 1977-02-08 Ricoh Co., Ltd. Color electrophotographic process
US4275134A (en) * 1974-07-30 1981-06-23 Canon Kabushiki Kaisha Electrophotographic method for reproducing a multicolor image
US5362586A (en) * 1990-12-27 1994-11-08 Xerox Corporation Process for two color imaging comprising a photoreceptor having a unipolar hole transporting layer

Also Published As

Publication number Publication date
DE2061333A1 (de) 1971-06-24
DE2061333C3 (de) 1979-02-22
NL7018038A (de) 1971-06-21
FR2073706A5 (de) 1971-10-01
JPS4938170B1 (de) 1974-10-16
CA921546A (en) 1973-02-20
NL144741B (nl) 1975-01-15
DE2061333B2 (de) 1978-06-22
GB1283808A (en) 1972-08-02

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