EP0296169B1 - Verfahren und gerät mit coronaentladung zum verbessern eines elektrophotographischen mehrfarbigen bildes - Google Patents
Verfahren und gerät mit coronaentladung zum verbessern eines elektrophotographischen mehrfarbigen bildes Download PDFInfo
- Publication number
- EP0296169B1 EP0296169B1 EP87901930A EP87901930A EP0296169B1 EP 0296169 B1 EP0296169 B1 EP 0296169B1 EP 87901930 A EP87901930 A EP 87901930A EP 87901930 A EP87901930 A EP 87901930A EP 0296169 B1 EP0296169 B1 EP 0296169B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- medium
- image
- voltage
- exposing
- toning
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- 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
- G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
- G03G15/0142—Structure of complete machines
- G03G15/0147—Structure of complete machines using a single reusable electrographic recording member
- G03G15/0152—Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member
- G03G15/0157—Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member with special treatment between monocolour image formation
-
- 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
- G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
- G03G15/0142—Structure of complete machines
- G03G15/0147—Structure of complete machines using a single reusable electrographic recording member
- G03G15/0152—Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member
- G03G15/0163—Structure of complete machines using a single reusable electrographic recording member onto which the monocolour toner images are superposed before common transfer from the recording member primary transfer to the final recording medium
Definitions
- This invention relates to electrographic development and more particularly to an improved method of plural stage development. While the following disclosure refers to a preferred embodiment employing liquid development, it will be understood that the invention is equally applicable to systems using dry developers.
- liquid development of electrostatic charge latent images as in electrophotography and in other processes that form and develop electrostatic charge patterns, a substrate having a charge pattern on its surface is contacted with a liquid developer which is essentially a suspension of colloidal toner particles in an insulating liquid.
- Liquid developers normally contain also a stabilizer or charge control agent. Liquid developers can be used in single stage or plural stage development processes. Examples of the latter may include the sequential development on a photoconductor of two or more color-separation images, the annotation of a previously developed image, or the repeated re-exposure and development of images on a reusable photoconductor, with transfer of images after each development.
- nonconductive overcoats are necessary when half-tone images are generated, as is required in the graphic imaging field.
- a conductive overcoat has been found to be unsatisfactory for generating half-tone images because the half-tone dots on a conductive surface tend to undergo image spread and will effectively disappear under adverse humidity conditions. Even continuous tone images have been found to severely degrade under such conditions using conductive overcoats.
- toe rise is unpredictably variable so that it is difficult, if not impossible, to control the entire process to provide satisfactory film performance. If provisions are not made to maintain the useable voltage range in systems utilizing a photoconductor having the foregoing phenomena of toe voltage rise with successive charge-expose cycles, the resulting images will have an undesirable susceptibility to image variation with variations in work place humidity. A variation in image quality across the area of the image can also occur under such operating conditions. More importantly, it has been found that with increases in the toe voltage noted above, it is impossible to achieve high image density with succeeding stages or colors. All of these factors are detrimental to obtaining graphic arts quality images.
- the electrophotographic method in which the present invention operates generally comprises uniformly charging a photoconductive element, exposing the photoconductive element to a pattern of actinic radiation to form a latent electrostatic image, developing the latent image with, for example, a liquid developer composition comprising a carrier liquid, a toner and charge control agent, rinsing the developed surface of the photoconductive element with a rinse solution, and drying the image. Thereafter, the surface of the photoconductive element is recharged and exposed to a pattern of actinic radiation to form a second latent electrostatic image which is developed with a liquid developer.
- the method of the present invention is useful in any electrostatic imaging process wherein a charge pattern is formed and developed with a developer on a surface which has previously been developed. It is particularly useful, however, in combination with a recently developed electrophotograhic method of making lithographic color proofs.
- This new method is described in the copending U.S. patent application of Ng et al., Serial No. 773,528 filed September 6, 1985.
- a photoconductor which has a uniformly charged thin transparent dielectric overcoat is subjected to a series of exposures through registered color separation transparencies. After each exposure the dielectric layer is developed with a liquid developer, the surface is again uniformly charged and exposed. The sequence is repeated for each of the color transparencies, usually four, with all of the developed images being superposed to form a multi-color image on the overcoat.
- the present invention provides a method and apparatus for producing a multi-color electrophotographic image that enhances the final image by the reduction or elimination of toe rise with successive charge-expose cycles of the photoconductor.
- the improvement provided by the present invention is simple and relatively easy to implement at a nominal cost, it does not have any significant negative effects on the resulting image.
- a method and apparatus according to claims 1 and 13 is provided for producing a multi-stage electrophotographic image.
- the medium is reverse charged with a voltage that has an absolute value equal to or greater than (v o - v w ) and having a polarity opposite to that of (v o - v w ).
- the neutralization of trapped charges includes the step of exposing the medium to actinic radiation to facilitate the recombination of trapped and mobile charges in the medium.
- means for exposing the medium to radiation to facilitate the recombination of trapped and mobile charges therein after reverse charging only when the medium contains a charge barrier layer.
- Yet another embodiment of the present invention provides means for preventing toe rise in both p-type and n-type photoconductors, with and without charge barriers and regardless of whether the tonal reproduction is positive or negative.
- a method and apparatus according to claims 12 and 22 is provided for producing a multi-color electrophotographic image.
- the present invention is applicable to various electrophotographic elements, methods and apparatus, the embodiment to be described is directed to a multi-color electrophotographic image producing apparatus employing p-type electrophotographic medium of the type disclosed in the above-identified copending application, having a charge barrier layer and a releasable non-conductive overcoat on which the toners are deposited.
- FIG. 2 A schematic illustration of a multi-color electrophotographic image processor is illustrated in FIG. 2 and consists of a carrier or platen 12 which is movable along the processing path, represented by dotted line 14, past the respective processing stations of the apparatus, to be described hereinafter.
- the path 14 may be determined by guide rails or other structure of the apparatus in a manner well-known in the art whereby the platen may move from a first position, illustrated, to the right-most position and then returned to the left to the starting position.
- the platen 12 is preferably transparent and is provided with means, not shown, for retaining an electrophotographic medium 16 on the lower surface thereof with an image-bearing transparency 18 disposed therebetween which is used to generate the image in the electrophotograpic medium 16, in a manner more thoroughly described hereinbelow.
- the electrophotographic medium comprises a photoconductive layer on an electrically conducting substrate which is capable of transmitting actinic radiation to which the photoconductive layer is responsive.
- a dielectric support is releasably adhered to the substrate and either comprises the photoconductive layer or an overcoat thereof which forms an outer surface of the element capable of holding an electrostatic charge.
- the surface of the dielectric support is charged and the photoconductive layer is image-wise exposed to the actinic radiation, thereby forming a developable electrostatic image on the dielectric surface.
- the electrostatic image in turn is developed with a toner to form a first color image.
- a composite color image can be formed on the element by repeating the sequence one or more times with successive image-wise exposure of the photoconductive layer to actinic radiation transmitted through the transparent support and an image-bearing transparency, and developing over each preceding image with a different color toner.
- the composite toned image is then transferred with the dielectric support to a receiving element to form a color copy which may be a color proof closely simulating the color print expected from a color print press.
- the electrophotographic medium 16 is mounted onto the platen 12 with the transparency original 18, which may be a color separation representing a color to be printed, sandwiched therebetween.
- the electrophotographic medium 16 and the transparency original 18 may be held to the platen 12 by any suitable means known in the art such as a vacuum clamp such that they are maintained in close proximity to assure satisfactory exposure, processing and registration.
- the electrophotographic medium must also be suitably grounded to the apparatus to enable the charging process to be satisfactorily carried out. A number of grounding means are known in the art and will not be described herein.
- the dielectric support of the electrophotographic medium is given an overall charge via a charging means 20, such as a corona charger, to form a uniform potential, v o , on the surface of the dielectric support.
- a charging means 20 such as a corona charger
- the electrophotographic medium is image-wise exposed by passing beneath an exposure lamp apparatus 22 which projects light through the transparent platen 12, the transparency original 18, and through the transparent conductive substrate of the electrophotographic medium.
- an exposure lamp apparatus 22 which projects light through the transparent platen 12, the transparency original 18, and through the transparent conductive substrate of the electrophotographic medium.
- mobile charge carriers in thin case positively charged holes, are formed in the photoconductive layer and migrate away from the conducting layer as described in the above-identified application (or toward the conducting layer to give a negative image).
- the platen continues its movement, to the right in FIG. 2, passing over a pre-rinse head 24 which is fixed in position whereby the fluid head provided thereat, when activated, contacts the lower surface of the electrophotographic medium as it passes in the processing direction, i.e., to the right, but does not contact the medium when the fluid head is inactivated, as when the platen is moved to the left in FIG. 2, to the original position.
- the pre-rinse head prewets the medium with a dispersant dielectric liquid prior to the liquid toning step.
- the platen moves past a raised first liquid toning station 26 which is raised into operating position whereby the lower surface of the electrophotographic medium is contacted and a toner image is imparted thereto, in a manner well-known in the art.
- the liquid toner is deposited in the unexposed, still charged area of the electrophotographic medium thereby forming an image which is a duplicate of the image carried by the transparency 18.
- negative images can also be produced with similar electrophotographic processes wherein the charges imparted to the electrophotographic medium and the toners are appropriately adjusted to give a negative image.
- the platen continues movement to the right in the illustration, past appropriate rinse heads and dryers, not shown.
- the last station 28 at the right end of the apparatus is an erase lamp that exposes the electrophotographic medium after the toning operation to expose those parts of the photoconductor layer that were not exposed by the original image exposure so that the entire electrophotographic medium has substantially the same exposure history.
- Platen 12 is then reversed and is returned to the left towards the first position illustrated in FIG. 2.
- the charging means 20 As the platen reaches the charging means 20, it is activated as a corona erase apparatus in accordance with the present invention.
- the charge imparted by the corona erase mode of the charging means 20 is opposite in polarity to the charge initially given the photoconductor medium and of a magnitude substantially equal to the absolute value of (v o - v w ). It has been found that, while a potential as much as 50% less or 50% greater than the initial charge differential provides a satisfactory neutralization of trapped charges in the photoconductor medium, the preferred value is equal to or greater than the absolute value of (v o - v w ).
- the platen, transparency and medium have then reached the first position and the first original transparency or color separation 18 is removed and replaced by a second transparency or color separation and registered with the electrophotographic medium 16 preparatory for the next pass through the apparatus to generate the second color image.
- the electrophotographic medium 16 and the next original sheet 18 are re-registered on the platen 12
- the platen is again moved to the right to the charging station 20 where the electrophotographic medium is again charged and then to the exposure position 22 where light again is projected through the platen and the second color separation 18 to selectively charge the photoconductive layer in accordance with the transparency or color separation then in contact with the electrophotographic medium.
- the platen moves the electrophotographic medium to the pre-rinse station 24 and then to a second toning station 34 which is in operative position to tone the surface of the electrophotographic medium with a second color toner to produce a second color visible image overlying the first image.
- the platen subsequently moves past the aforementioned rinse and drying stations and again past the erase exposure station 28 before being returned to the first position at the left end of the apparatus.
- the charging, exposing, and toning steps will be repeated for two more color separation originals with the platen and electrophotographic medium being moved into operative contact with an additional two toning stations 36 and 38, one for each of the additional colors.
- the toning order may not necessarily be represented by the physical order of the toning stations in the apparatus, and the order given above is by way of example only.
- the corona erase cycle will be used after each exposure which is to be followed by a toning cycle after the corona erase. Thus, corona erase will not be necessary after the final charge-expose-tone cycle, but will be after an initial charge and expose only calibration cycle.
- the present invention provides a method and apparatus for regenerating a photoconductor to substantially revitalize the medium to a condition closely resembling its unused condition, substantially eliminating the rise in toe voltage associated with prior systems.
- the method and apparatus are simply and economically achieved and produce a high quality image suitable for use in graphic arts quality reproduction.
- the re-erase lamp must be arranged to expose both sides of the medium, as in a negative/positive mode wherein the medium is exposed through a negative, with a positive being formed by the toned image. In other situations it is possible to satisfactorily employ the present invention by only exposing one side of the medium to the re-erase lamp.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Color Electrophotography (AREA)
Claims (22)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US83900986A | 1986-03-12 | 1986-03-12 | |
US839009 | 1986-03-12 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0296169A1 EP0296169A1 (de) | 1988-12-28 |
EP0296169B1 true EP0296169B1 (de) | 1992-03-04 |
Family
ID=25278630
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP87901930A Expired - Lifetime EP0296169B1 (de) | 1986-03-12 | 1987-02-26 | Verfahren und gerät mit coronaentladung zum verbessern eines elektrophotographischen mehrfarbigen bildes |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0296169B1 (de) |
JP (1) | JPS63503329A (de) |
WO (1) | WO1987005720A1 (de) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5537198A (en) * | 1994-12-12 | 1996-07-16 | Xerox Corporation | Double split recharge method and apparatus for color image formation |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3687661A (en) * | 1969-12-01 | 1972-08-29 | Xerox Corp | Color electrophotographic process |
BE759846A (fr) * | 1969-12-08 | 1971-06-03 | Rank Xerox Ltd | Procede electrophotographique polychrome |
JPS5522789B2 (de) * | 1973-08-27 | 1980-06-19 | ||
JPS6024467B2 (ja) * | 1976-07-10 | 1985-06-13 | コニカ株式会社 | 液体現像装置 |
JPS5814854A (ja) * | 1981-07-20 | 1983-01-27 | Matsushita Graphic Commun Syst Inc | 多色静電記録装置 |
US4510223A (en) * | 1983-02-07 | 1985-04-09 | Coulter Systems Corporation | Multicolor electrophotographic imaging process |
-
1987
- 1987-02-26 WO PCT/US1987/000383 patent/WO1987005720A1/en active IP Right Grant
- 1987-02-26 JP JP50155387A patent/JPS63503329A/ja active Pending
- 1987-02-26 EP EP87901930A patent/EP0296169B1/de not_active Expired - Lifetime
Non-Patent Citations (1)
Title |
---|
Patent Abstacts of Japan, vol. 7, no. 176 (p-214)(1321), 04 August 1983, see the whole abstract & JPA5880653 * |
Also Published As
Publication number | Publication date |
---|---|
JPS63503329A (ja) | 1988-12-02 |
WO1987005720A1 (en) | 1987-09-24 |
EP0296169A1 (de) | 1988-12-28 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4771314A (en) | Developer apparatus for a highlight printing apparatus | |
GB1565232A (en) | Electrophotographic copying | |
JP3828171B2 (ja) | 画像形成装置 | |
US4804602A (en) | Method and apparatus utilizing corona erase for improving a multi-color electrophotographic image | |
US5025292A (en) | Method and apparatus for improving a multi-color electrophotographic image using heat fusing | |
US5061969A (en) | Hybrid development scheme for trilevel xerography | |
EP0465211B1 (de) | Druckgerät mit Hervorhebung der Farben | |
EP0290475B1 (de) | Verfahren und gerät zum verbessern eines elektrophotographischen mehrfarbigen bildes | |
JPS63311364A (ja) | 多色記録装置 | |
US4725867A (en) | Apparatus for forming a multi-color image on an electrophotographic element which is sensitive to light outside the visible spectrum | |
US4967236A (en) | Charge retention xeroprinting | |
US4226930A (en) | Electrophotographic method for producing photopolymer printing plate | |
US5014090A (en) | Method and apparatus for improving a multi-color electrophotographic image using vapor fusing | |
EP0296169B1 (de) | Verfahren und gerät mit coronaentladung zum verbessern eines elektrophotographischen mehrfarbigen bildes | |
JPH10282759A (ja) | イメージ・オン・イメージ・マルチカラー印刷装置及び方法 | |
US5480751A (en) | Tri-level background suppression scheme using an AC scorotron with front erase | |
EP0399478B1 (de) | Verfahren und Gerät zum Verbessern eines elektrophotographischen mehrfarbigen Bildes durch Polieren | |
US5260155A (en) | Xeroprinting method, master and method of making | |
US4913992A (en) | Method of improving a multi-color electrophotographic image by buffing an image toned with an improved toner | |
US4998142A (en) | Method of improving a multi-color electrophotographic image | |
US5016054A (en) | Apparatus for improving a multi-color electrophotographic image | |
US5110699A (en) | Method and apparatus for forming masters and images therefrom | |
JP3509281B2 (ja) | 画像形成装置 | |
JPS6358464A (ja) | 3色画像形成方法 | |
JPS60252369A (ja) | 2色電子写真装置の現像方法 |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 19880912 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): DE FR GB NL |
|
17Q | First examination report despatched |
Effective date: 19910514 |
|
GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): DE FR GB NL |
|
REF | Corresponds to: |
Ref document number: 3777173 Country of ref document: DE Date of ref document: 19920409 |
|
ET | Fr: translation filed | ||
PLBE | No opposition filed within time limit |
Free format text: ORIGINAL CODE: 0009261 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT |
|
26N | No opposition filed | ||
REG | Reference to a national code |
Ref country code: GB Ref legal event code: IF02 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: GB Payment date: 20030106 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: NL Payment date: 20030110 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 20030204 Year of fee payment: 17 |
|
PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 20030228 Year of fee payment: 17 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: GB Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20040226 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: NL Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20040901 Ref country code: DE Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20040901 |
|
GBPC | Gb: european patent ceased through non-payment of renewal fee |
Effective date: 20040226 |
|
PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: FR Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 20041029 |
|
NLV4 | Nl: lapsed or anulled due to non-payment of the annual fee |
Effective date: 20040901 |
|
REG | Reference to a national code |
Ref country code: FR Ref legal event code: ST |