US3341326A - Dark decay controlled xerography - Google Patents

Dark decay controlled xerography Download PDF

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Publication number
US3341326A
US3341326A US227487A US22748762A US3341326A US 3341326 A US3341326 A US 3341326A US 227487 A US227487 A US 227487A US 22748762 A US22748762 A US 22748762A US 3341326 A US3341326 A US 3341326A
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United States
Prior art keywords
plate
xerographic
pattern
charge
layer
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Expired - Lifetime
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US227487A
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English (en)
Inventor
Snelling Christopher
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Xerox Corp
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Xerox Corp
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Priority to NL298605D priority Critical patent/NL298605A/xx
Application filed by Xerox Corp filed Critical Xerox Corp
Priority to US227487A priority patent/US3341326A/en
Priority to GB37065/63A priority patent/GB1029199A/en
Priority to FR949258A priority patent/FR1377592A/fr
Priority to DE19631497069 priority patent/DE1497069A1/de
Application granted granted Critical
Publication of US3341326A publication Critical patent/US3341326A/en
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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
    • G03G5/14—Inert intermediate or cover layers for charge-receiving layers
    • 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
    • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
    • G03G5/08—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic
    • G03G5/082—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and not being incorporated in a bonding material, e.g. vacuum deposited
    • G03G5/08207—Selenium-based
    • 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
    • G03G5/10—Bases for charge-receiving or other layers
    • 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
    • G03G5/10—Bases for charge-receiving or other layers
    • G03G5/102—Bases for charge-receiving or other layers consisting of or comprising metals

Definitions

  • Xerography as originally described in US. Patent 2,297,691 to Carlson and later related patents, generally comprises charging a photoconductive insulating member to sensitize it and then subjecting it to a light image or other pattern of activating electromagnetic radiation which serves to dissipate charge in radiation struck area-s, thus leaving a charge pattern or latent electrostatic image conforming to the electromagnetic radiation pattern on the photoconductor.
  • the image is then developed by the deposition of electrostatically attractable finely divided colored material, referred to in the art as toner, on the exposed photoconductor which by virtue of its latent electrostatic image, forms a corresponding toner image on its surface.
  • the toner image may then optionally be viewed in situ or transferred to a copy sheet and fixed.
  • the photoconductive insulating member known in the art as a xerographic plate, has undergone continuous improvement and development since the time of the original Carlson patent noted above as is attested to by the following exemplary US. patents, 2,599,542 to Carlson, 2,803,541 to Paris, 2,863,768 to Schalfert, 2,901,348 to Dessauer, and 2,970,906 to Bixby.
  • very good quality xerographic plates have resulted from this development work.
  • the faithful rendition and good definition of line copy such as printing, line drawings, and the like, has been so good that copying machines employing these plates have enjoyed wide commercial success within a very short time after their introduction.
  • a further object of this invention is to provide an improved method of xerographic copying.
  • Another object of this invention is to provide an improved xerographic plate capable of reproducing any type of original in conjunction with a very simple type of xerographic copier.
  • An additional object of this invention is to provide an improved xerographic plate of simple construction.
  • FIG. 1 is a cross-sectional according to this invention.
  • FIG. 2 is a fragmentary face View of one embodiment of the plate of FIG. 1 with a portion of the photoconductive coating removed to expose the material beneath the photoconductor in the plate.
  • FIG. 3 is a view of the plate similar to the one in FIG. 2 except that it illustrates a different pattern on the plate interface between the photoconductor and its backing.
  • FIG. 4 is a voltage versus time graph for two different types of xerographic plate interface materials.
  • FIG. 5 is an end view of a xerographic plate according to this invention illustrating a charge pattern on the plate and the field lines it produces.
  • the new xerographic plate according to this invention is fabricated so that it has a fine pattern of areas having different rates of charge loss or decay.
  • FIG. 1 there is illustrated a xerographic plate generally designated 11 embodying the concept of this invention.
  • a substrate 12 having one type of xerographic plate base properties, overcoated with a thin pattern 13 of a material having a second type of xerographic plate base properties, both underlying a photoconductive insulating layer 14 which may consist of vitreous selenium, cadmium sulfide, or any other photoconductive insulator or layer of photoconductive pigment in an insulating binder known in the art.
  • a photoconductive insulating layer 14 which may consist of vitreous selenium, cadmium sulfide, or any other photoconductive insulator or layer of photoconductive pigment in an insulating binder known in the art.
  • layer 12 may be formed from any material which causes a high rate of charge decay from a charged xerographic plate using it as a base material while layer 13 is formed from a material which causes a relatively low rate of charge decay from a charged xerographic plate using it as a base material when the plate is held in darkness after charging.
  • This pattern of materials when used under a photoconductive insulator to form a xerographic plate provides many small areas (corresponding to the pattern) of potential contrast a short time after the plate is uniformly charged.
  • This potential contrast pattern provides the strong fringing fields necessary to good xerographic de velopment as described more fully hereinafter while plate discharging effects from image exposure are superimposed on this built-in potential contrast pattern. It might be said that the image exposure is used to modulate or vary the magnitude of the potential contrast pattern as a whole by discharging, partially or fully, the charge retaining areas.
  • the base layer 12 is made up of a material having suificient electrical conductivity for the charging or sensitization of the xerographic plate and to accommodate the release of electric charge upon exposure of the plate.
  • this base member is also sufliciently strong to provide mechanical support of the remainder of the plate so as to make the plate suitable for use in xerographic copying machines.
  • the base member may consist of a metallic plate, web, foil, or the like, or a conductive plastic, glass, paper, or similar member any of which may be in the form of a cylindrical surface, a plane, hexagon, or other shapes.
  • This conductive support member may be relatively rigid as in the case of a metallic plate or cylinder, or may be relatively flexible as with a metallic foil, plastic web, or the like.
  • the term conductive as applied to this backing member 12 is only relative and thus the conductive support must only have high conductivity as compared with the photoconductive insulating layer of the plate.
  • the backing member should have a resistivity lower than about 10 ohms-cm. and preferably lower than about 10 ohm-cm.
  • Some known xerographic plates suffer from a fairly high rate of potential leakage after charging even in the absence of activating radiation, requiring relatively rapid processing so that the plate is not substantially discharged prior to development. This type of leakage is known in the art as high decay. Plates which hold their charge for relatively long periods of time when not subjected to activating radiation are referred to as having low dark decay.”
  • This charging is generally accomplished in commercial xerographic machinery by corona discharge from a wire filament or wire filament array spaced slightly from the surface of the plate as described, for example, in US. Patents, 2,588,699" to Carlson, 2,836,725 to Vyverberg, 2,777,957 to Walkup, 2,- 778,946 to Mayo, and others.
  • Other charging techniques such as described in US. Patent 2,833,930 to Walkup known in the 'art and described in the patent literature have also been shown to be feasible and may be employed where desirable. (It should be noted that any one of these charging techniques may be used in charging the novel plate of this invention.) When portions of this charged layer are exposed to a pattern of electromagnetic radiation ofa frequency to which the photoconductive insulating material is sensitive, they are discharged.
  • the plate described in FIGURES 1-3 is made up of a base 12 selected so that it will cause a high rate of dark decay" from an ordinary charged xerographic plate using it as a base.
  • Some illustrative materials which may be used for this purpose include stainless steel, abraded aluminum, chemically cleaned aluminum, or aluminum subjected to a chromate conversion process including a bath with chromic and phosphoric acids.
  • Layer 13 is made up of a pattern or screen of thin insulating material. This pattern may be in the form of a dot pattern with round, elliptical, square, triangular, or any other regular or irregular dot shape or it may be in the form of a line pattern, or any other broken pattern whether regular, irregular, or random in shape and/or spacing.
  • layer 13 may comprise an integral layer of insulating materials with a pattern of holes or voids through it.
  • the percentage coverage of the screen or pattern over the base layer 12 may vary very widely without very wide variation in results and even then results vary only in degree. For example, it has been found that plates using screens covering from about 6- to 40% of the total area of the plate base results in fairly low density prints while plates with screen coverage of from about 40 to about 75% coverage of the base plate results in good density prints with very good gray scale reproduction and screens covering from about 75% to about 92% of the plate base result in very high density prints with relatively high contrast.
  • the fineness of the screen or number of dots per linear inch is also an optional plate parameter depending upon the quality of reproduction desired.
  • the number of dots per linear inch on the dot pattern may vary anywhere from 30 to 500 depending upon considerations of quality desired, cost, etc.
  • newspaper printing utilizes halftone patterns ranging from about 60 to about 100 lines per linear inch. It has been found that a pattern of approximately 150 dots per linear inch produces an image in which no dots are discernible to the naked eye.
  • the screen material is made of a good" xerographic plate interface material of the type described above and is insulating in nature and may include such diverse materials as aluminum oxide, copper oxide,
  • oxidized brass, polystyrene, and various organic materials including many of the well known photoresists such as Kodak Photoresist, available from Eastman Kodak Company of Rochester, NY. (believed to be formulated mainly from cinnamic acid esters), and Le Pages printed circuit resist.
  • photoresists such as Kodak Photoresist, available from Eastman Kodak Company of Rochester, NY. (believed to be formulated mainly from cinnamic acid esters), and Le Pages printed circuit resist.
  • An aluminum oxide pattern may be formed on an aluminum base plate by first forming a uniform layer of aluminum oxide on the surface of the plate by heating or chemical treatment and then scribing or engraving portions of the aluminum oxide off the plate.
  • Materials such as polystyrene may be laid down on plate bases such as clean copper aluminum or stainless steel by mixing them with solvents and printing them on the plate while the photoresist materials referred to may be placed on the plate surface in screen configuration by first laying down a uniform layer of the material and then exposing the layer to a light source through a screen pattern corresponding to the pattern to be provided on the plate. The photoresist is then developed and washed. This removes the unexposed sections of photoresist.
  • the photoconductive insulating layer may then be laid down on the plate surface by vacuum evaporation, casting, or other techniques well known in the art.
  • the screen pattern may either be very thin in which case it acts according to the tunneling theory described above, or it may be somewhat thicker in which case it acts as an insulator after plate charging both before and after plate exposure.
  • the insulator acts as a tunneling layer at thicknesses below about 2 microns and as an ordinary insulator above about 2 microns. Between charging and exposure a thin or a thick interface layer of insulating screen will have substantially the same elfect on the charge level across a xerographic plate because, as explained above, even a thin layer acts as an insulator and does not allow tunneling until after exposure.
  • either type of insulating layer sets up very many small areas of potential contrast with the charge level on the plate being relatively high over portions of the plate which are directly above the insulating screen material and the charge level on the plate directly above plate backing material which is not covered by portions of the insulating screen being relatively low because of the high dark decay in those areas resulting from charge injection from the conductive plate backing.
  • an insulating pattern too thick to allow tunneling is used as an interface material, it has the same effect on dark decay as the thinner type insulating layers; however upon exposure it continues to prevent charge injection from the plate backing and thus does not allow charge dissipation through it upon exposure.
  • Charging may be carried out with the conventional xerographic charging techniques described above.
  • Development may also utilize any of the known xerographic developing techniques such as cascade as described in US. Patents 2,618,551 and 2,638,416 to Walkup, and powder cloud as described in US. Patent 2,725,304 to Landrigan, among others.
  • FIGURE 5 where there is illustrated a conventional xerographic plate 18 having a grounded conductive backing layer 19 underlying three arbitrarily divided sections of photoconductive insulator 20, 21, and 22. As shown in FIGURE 5 the center area 21 carries a layer of uniform positive charge across its top surface.
  • this exposure-modified contrast pattern on the plate of this invention works very well in conjunction with conventional xerographic developing techniques because the contrast pattern sets up small fringing fields which are well adapted to attract xerographic developers. Since each of these fringing fields emanating from a small discrete portion of the plate produces its own field lines above the plate surface and since each of these small fields is dependent upon the amount of exposure to which it has been subjected, each portion of the plate tends to develop more nearly in conformance with the amount of exposure to which it has been subjected than do conventional xerographic plates whose field lines tend to go down into the plate except when they are used to copy originals which produce high potential gradients on them, thus producing a greatly improved result in the copying of continuous tone and large solid dark areas subjects.
  • a xerographic plate comprising a continuous photoconductive insulating layer on an electrically conductive base layer and further including a pattern of small, separate, discrete portions of an insulating material on said conductive substrate between portions of said conductive substrate, and portions of said continuous photoconductive insulating layer, said portions of an insulating material being thin relative to said continuous photoconductive insulating layer and having a thickness greater than 2 microns.
  • a xerographic plate comprising a continuous photd conductive insulating layer on an electrically conductive base layer and further including a pattern of small, separate, discrete portions of an insulating material on said Conductive substrate between portions of said conductive substrate, and portions of said photoconductive insulating layer, said portions of an insulating material being thin relative to said continuous photoconductive insulating layer and occurring in the range of from about 40 to about 500 per inch of plate surface.
  • a method of copying with a xerographic plate having a continuous surface of a photoconductive insulating material and including a fine pattern of small alternating first and second areas said first areas being characterized by their ability to hold charge for long periods of time in the absence of electromagnetic radiation said second areas being characterized by their relatively rapid rate of charge dissipation with respect to said first areas in the absence of electromagnetic radiation including the steps of applying charge to said xerographic plate, exposing said plate to an original to be copied with electromagnetic radiation actinic to said xerographic plate and developing said xerographic plate with finely divided electroscopic marking particles said charging and developing steps being temporally separated so as to allow for the formation of a fine potential contrast pattern across the surface of said plate prior to development.
  • a method of xerographic copying comprising charging a xerographic plate made up of a continuous photoconductive insulating layer on a substrate composed of a pattern of alternating small areas of first and second materials, said first material being characterized by its ability to inject charge carriers into said photoconductive insulating layer when itis charged prior to its illumination with activating electromagnetic radiation, said second material being characterized byits ability to prevent the injection of charge carriers into said photoconductive insulating layer after its charging and prior to its illumination with activating electromagnetic radiation, exposing said xerographic plate to an original to be copied with activating electromagnetic radiation and developing said xerographic plate with finely divided, electroscopic, mark ing particles, said charging and developing steps being temporally separated to allow for the formation of a fine potential contrast pattern in unexposed areas of said plate prior to its development.
  • a method according to claim 6 including carrying out said charging and exposing steps simultaneously with both being separated in time from said development step.
  • a method of xerographic reproduction comprising charging a xerographic plate made up of an electrically conductive substrate with a thin insulating barrier layer covering alternate, small, adjacent areas of said substrate and a continuous photoconductive insulating layer on the top surface of said xerographic plate, exposing said xerographic plate to an original to be copied with activating electromagnetic radiation and developing said xerographic plate with finely divided, electroscopic, marking particles, said charging and developing steps being separated in time so as to allow for the formation of a fine potential contrast pattern across the surface of said plate in unexposed areas prior to development.
  • a method of xerographic reproduction comprising charging a xerographic plate made up of an electrically conductive substrate with a thin insulating barrier layer covering alternate, small, adjacent areas of said substrate and a continuous amorphous selenium layer on the top surface of said xerographic plate, exposing said xerographic plate to an original to be copied with activating electromagnetic radiation and developing said xerographic plate with finely divided, electroscopic, marking particles, said charging and developing steps being separated in time so as to allow for the formation of a fine potential contrast pattern across the surface of said plate in unexposed areas prior to development.
  • a method of xerographic copying comprising charging a xerographic plate having a continuous surface of a photoconductive insulating material overlying a substrate made upof an electrically conductive material with a pattern of small, separated, discrete areas coated with a thin layer of an electrical insulator occurring on said electrically conductive layer in a range of from about 40 to about 500 per inch of plate surface, exposing said plate to an original to be copied with activating electromagnetic radiation and developing said plate with finely divided, electroscopic, marking particles, said charging and developing steps being separated in time so as to allow for the formation of a fine potential contrast pattern across the surface of said plate in unexposed areas prior to the development.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Photoreceptors In Electrophotography (AREA)
US227487A 1962-10-01 1962-10-01 Dark decay controlled xerography Expired - Lifetime US3341326A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
NL298605D NL298605A (en, 2012) 1962-10-01
US227487A US3341326A (en) 1962-10-01 1962-10-01 Dark decay controlled xerography
GB37065/63A GB1029199A (en) 1962-10-01 1963-09-20 Dark decay controlled xerography
FR949258A FR1377592A (fr) 1962-10-01 1963-10-01 Cliché xérographique et procédé de reproduction xérographique
DE19631497069 DE1497069A1 (de) 1962-10-01 1963-10-01 Xerographische Platte

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Application Number Priority Date Filing Date Title
US227487A US3341326A (en) 1962-10-01 1962-10-01 Dark decay controlled xerography

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US3341326A true US3341326A (en) 1967-09-12

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DE (1) DE1497069A1 (en, 2012)
GB (1) GB1029199A (en, 2012)
NL (1) NL298605A (en, 2012)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3607258A (en) * 1966-01-06 1971-09-21 Xerox Corp Electrophotographic plate and process
EP0018742A1 (en) * 1979-04-16 1980-11-12 EASTMAN KODAK COMPANY (a New Jersey corporation) Method of improving maximum density and tonal range of electrographic images and an electrographic copying apparatus using the method
US4587193A (en) * 1984-03-23 1986-05-06 Oce-Nederland, B.V. Copying process with patterned charge injection into charge transport layer
US5324608A (en) * 1992-11-23 1994-06-28 Mitsubishi Kasei America, Inc. Photoconductor drum, having a non-conductive layer, with an area of electrical contact and method of manufacturing the same

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2543051A (en) * 1948-12-06 1951-02-27 Haloid Co Method of charging and exposing electrophotographic plates
US2599542A (en) * 1948-03-23 1952-06-10 Chester F Carlson Electrophotographic plate
US2844543A (en) * 1955-03-18 1958-07-22 Horizons Inc Transparent photoconductive composition
US2853383A (en) * 1953-10-02 1958-09-23 Paul H Keck Method and apparatus for amplifying photoelectric currents
US2881340A (en) * 1956-03-02 1959-04-07 Rca Corp Photoconductive television pickup tube
US2901348A (en) * 1953-03-17 1959-08-25 Haloid Xerox Inc Radiation sensitive photoconductive member
US2917385A (en) * 1955-08-26 1959-12-15 Haloid Xerox Inc Reflex xerography
US3005707A (en) * 1956-04-16 1961-10-24 Leonard E Ravich Devices exhibiting persistent internal polarization and methods of utilizing the same
US3031572A (en) * 1959-11-05 1962-04-24 Charles E Ryan Infrared xerography
US3234017A (en) * 1959-11-05 1966-02-08 Agfa Ag Process for the production of developed electrophotographic images including application of a breakdown potential to discrete small areas of a photoconductor
US3281240A (en) * 1960-10-12 1966-10-25 Gevaert Photo Prod Nv Electrophotographic material

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2599542A (en) * 1948-03-23 1952-06-10 Chester F Carlson Electrophotographic plate
US2543051A (en) * 1948-12-06 1951-02-27 Haloid Co Method of charging and exposing electrophotographic plates
US2901348A (en) * 1953-03-17 1959-08-25 Haloid Xerox Inc Radiation sensitive photoconductive member
US2853383A (en) * 1953-10-02 1958-09-23 Paul H Keck Method and apparatus for amplifying photoelectric currents
US2844543A (en) * 1955-03-18 1958-07-22 Horizons Inc Transparent photoconductive composition
US2917385A (en) * 1955-08-26 1959-12-15 Haloid Xerox Inc Reflex xerography
US2881340A (en) * 1956-03-02 1959-04-07 Rca Corp Photoconductive television pickup tube
US3005707A (en) * 1956-04-16 1961-10-24 Leonard E Ravich Devices exhibiting persistent internal polarization and methods of utilizing the same
US3031572A (en) * 1959-11-05 1962-04-24 Charles E Ryan Infrared xerography
US3234017A (en) * 1959-11-05 1966-02-08 Agfa Ag Process for the production of developed electrophotographic images including application of a breakdown potential to discrete small areas of a photoconductor
US3281240A (en) * 1960-10-12 1966-10-25 Gevaert Photo Prod Nv Electrophotographic material

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3607258A (en) * 1966-01-06 1971-09-21 Xerox Corp Electrophotographic plate and process
EP0018742A1 (en) * 1979-04-16 1980-11-12 EASTMAN KODAK COMPANY (a New Jersey corporation) Method of improving maximum density and tonal range of electrographic images and an electrographic copying apparatus using the method
FR2454646A1 (fr) * 1979-04-16 1980-11-14 Eastman Kodak Co Procede pour ameliorer la densite maximale et l'intervalle des tonalites des images electrographiques et appareil pour la mise en oeuvre de ce procede
US4587193A (en) * 1984-03-23 1986-05-06 Oce-Nederland, B.V. Copying process with patterned charge injection into charge transport layer
US5324608A (en) * 1992-11-23 1994-06-28 Mitsubishi Kasei America, Inc. Photoconductor drum, having a non-conductive layer, with an area of electrical contact and method of manufacturing the same

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NL298605A (en, 2012)
DE1497069A1 (de) 1969-05-08
GB1029199A (en) 1966-05-11

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