CA1037102A - Electrophotographic reproduction method and apparatus - Google Patents
Electrophotographic reproduction method and apparatusInfo
- Publication number
- CA1037102A CA1037102A CA223,994A CA223994A CA1037102A CA 1037102 A CA1037102 A CA 1037102A CA 223994 A CA223994 A CA 223994A CA 1037102 A CA1037102 A CA 1037102A
- Authority
- CA
- Canada
- Prior art keywords
- toner particles
- photoconductive layer
- electrophotographic
- predetermined portion
- area
- 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
Links
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
- G03G15/22—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20
- G03G15/26—Apparatus for electrographic processes using a charge pattern involving the combination of more than one step according to groups G03G13/02 - G03G13/20 in which the charge pattern is obtained by projection of the entire image, i.e. whole-frame projection
-
- 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
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Wet Developing In Electrophotography (AREA)
- Dry Development In Electrophotography (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Disclosed is an electrophotographic reproduction method and apparatus which eliminates undesirable edge toning occurring at image borders on electrophotographic members.
The process includes restricting application of electro-statically charged toner particles to an electrophotographic member to an area which is entirely within and smaller than the area on the member which was electrostatically charged prior to image exposure and development. The apparatus includes an improved developing chamber through which toner particles are passed to contact the charged and imaged area of the electrophotographic member. The opening of the chamber which permits the toner particles to contact the electrophotographic member is formed by a mask which, in conjunction with a vacuum drawing the toner particles through the chamber, prevents toner particles from contacting the border region of the electrophotographic member.
Disclosed is an electrophotographic reproduction method and apparatus which eliminates undesirable edge toning occurring at image borders on electrophotographic members.
The process includes restricting application of electro-statically charged toner particles to an electrophotographic member to an area which is entirely within and smaller than the area on the member which was electrostatically charged prior to image exposure and development. The apparatus includes an improved developing chamber through which toner particles are passed to contact the charged and imaged area of the electrophotographic member. The opening of the chamber which permits the toner particles to contact the electrophotographic member is formed by a mask which, in conjunction with a vacuum drawing the toner particles through the chamber, prevents toner particles from contacting the border region of the electrophotographic member.
Description
1037~0Z
This invention relates generally to electrophotography and more particularly to improvements in developing an image on an electrophotographic element by a method and apparatus which produces a higher quality and more attractive image.
s In electrophotography, it is common to apply a uniform electrostatic charge to the surface of a photoconductive layer. The charge is then selectively dissipated in a pattern by exposing the surface to a light image. The resulting pattern of charges produces an electrostatic latent image on the photo-conductive layer which is rendered visible by applying thereto electrostatically charged developer particles which adhere to the surface of the photoconductive layer by electrostatic forces. A permanent visible image can be obtained, for example, by using developer particles which can be heat fused to the photoconductive layer and subjecting it to a heat application step.
Charging is conventionally accomplished by exposing the surface of the photoconductive layer to a corona discharge, the polarity of which is chosen to produce the desired results upon the particular photoconductive layer being charged. Superior image reproductions are obtainable only when very uniform electrostatic charges are established on the photoconductive layer before imaging. In many electrophoto-graphic apparatus either the corona generating element or the electrophotographic recording medium is moved during charging, which to some extent improves uniformity of charge over the surface of the photoconductive layer. Although relative move-ment is helpful, it is often difficult tc avoid nonuniformity of charging along the borders which are parallel to the direc-tion of movement~ `
.
This invention relates generally to electrophotography and more particularly to improvements in developing an image on an electrophotographic element by a method and apparatus which produces a higher quality and more attractive image.
s In electrophotography, it is common to apply a uniform electrostatic charge to the surface of a photoconductive layer. The charge is then selectively dissipated in a pattern by exposing the surface to a light image. The resulting pattern of charges produces an electrostatic latent image on the photo-conductive layer which is rendered visible by applying thereto electrostatically charged developer particles which adhere to the surface of the photoconductive layer by electrostatic forces. A permanent visible image can be obtained, for example, by using developer particles which can be heat fused to the photoconductive layer and subjecting it to a heat application step.
Charging is conventionally accomplished by exposing the surface of the photoconductive layer to a corona discharge, the polarity of which is chosen to produce the desired results upon the particular photoconductive layer being charged. Superior image reproductions are obtainable only when very uniform electrostatic charges are established on the photoconductive layer before imaging. In many electrophoto-graphic apparatus either the corona generating element or the electrophotographic recording medium is moved during charging, which to some extent improves uniformity of charge over the surface of the photoconductive layer. Although relative move-ment is helpful, it is often difficult tc avoid nonuniformity of charging along the borders which are parallel to the direc-tion of movement~ `
.
- 2 -In some electrophotographic apparatus, charging takes place with no relative movement between the corona generat-ing element and the electrophotographic recording medium. In such cases, the recording medium may be a multi-frame microfiche 5 and charging is commonly restricted to a small area on the electrophotographic member by some form of shielding or masking means. This form of charging is accomplished without relative movement between the member and the charging means, and it results in a generally uniform potential of several hundred volts across most of the surface being charged and a potential of zero volts at the borders of the area being charged.
- Unfortunately, the portion of the surface having uniform charge does not extend up to the borders. Rather, the amount of charge tapers down to zero volts over some finite distance lS as the borders are approached. After imaging and developing the charged area, this border area haq undesirable edge toning because of the charge gradient occurring there. Where the imaging step dissipates the entire charge in the border region, edge toning is not such a problem, but in conventional apparatus the charge in the border region is seldom entirely dissipated.
The prior art has dealt with this and related problems in several ways. For example, U. S. Patent No.
- Unfortunately, the portion of the surface having uniform charge does not extend up to the borders. Rather, the amount of charge tapers down to zero volts over some finite distance lS as the borders are approached. After imaging and developing the charged area, this border area haq undesirable edge toning because of the charge gradient occurring there. Where the imaging step dissipates the entire charge in the border region, edge toning is not such a problem, but in conventional apparatus the charge in the border region is seldom entirely dissipated.
The prior art has dealt with this and related problems in several ways. For example, U. S. Patent No.
3,556,655 to Lux et al. discloses discharge of the border ; 25 regions with special exposure lamps to prevent any toning of those areas. U. S. Patent No. 3,512,965 to Matkan discloses elimination of toning in the non-imaged areas, which include both the border areas and areas between image lines, by subjecting the exposed electrophotographic member to a coating of a barrier chemical to reduce the tendency of the toner particles to adhere to the areas which are not highly charged.
:
'~
--- 103q102 U. S. Patent No. 3,617,121 to Albert is concerned with the un desirable black border created by making positive copies from negatives, and discloses elimination of the black border by imaging through an opaque border mask. U. S. Patent No.
3,687,538 to Matusmoto discloses elimination of undesirable black border by use of a discharging light source at the borders.
All of these prior art devices require complex apparatus, which obviously is undesirable if simpler alternatives can be found.
Therefore, it is the object of the invention to eliminate the undesirable edge toning on an electrophotographic member through use of a simple, but effective, apparatus and method.
The invention eliminates the undesirable edge toning on an electrophotographic member by developing on the electrophotographic member an area which is smaller and entirely within the borders of a larger area which was subjected to electrostatic charging. This unique step is accomplished through use of a special developing chamber through which toner particles are passed to contact the charged and imaged area of the electrophotographic member. The developing chamber has an opening formed by a mask which, in conjunction with a vacuum drawing the toner particles through the chamber, sealingly engages the imaged photoconductive layer of the electrophotographic member and covers the portion of the charged area about the border which was nonuniformly charged.
In accordance with the present invention, there is provided an electrophotographic reproduction method which comprises electrostatically charging a first predetermined portion of the photoconductive layer of an electrophotographic element; projecting an illuminated image onto the first portion to form an electrostatic latent image on the photo-conductive layer, the borders about the electrostatic latent 1037~02 image retaining a significant amount of electrostatic charge;
and applying electrostatically charged toner particles to only a second predetermined portion of the photoconductive layer within the first portion, the edges of the first portion extending beyond the edges of the second portion in all directions whereby a border region in the first predetermined portion is not developed.
Figure 1 is an illustration of an electrophoto-graphic recording member with the area charged and the area developed indicated thereon.
Figure 2 is a cut-away side view of the developing chamber of the invention positioned against an electrophoto-graphic recording element.
Figure 3 is a schematic view of corona generating means and imaging means in operative position against an electrophotographic recording element.
Referring to Figure 1, an electrophotographic recording element in the form of a microfiche 10 is illustrated with a first predetermined portion of the photoconductive layer indicated as a rectangle 11 and a second predetermined ; portion 12 indicated as a rectangle within the first pre-; determined portion 11. The first predetermined portlon 11 is electrostatically charged by corona generating element 16 housed within the charging and imaging module 13, illustrated in Figure 3. The charging and imaging module 13 includes mask flange 14, forming an opening 15. The mask flange 14 is placed against the photoconductive layer of the electro-photographic element 10 where it shields all of the electro-photographic element except the first predetermined portion 11 from corona charging and imaging.
.. ~ , .
, . .
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The corona genera~ing element 1~ can be provided by any conventional form of corona discharge element, such as a wire or needle, and receives its generating potential from a conventional high voltage power source (not shown). Lens 17 is mounted in the charging and imaging module 13 at the appropriate distance to focus an illuminated image onto the photoconductive layer of the electrophotographic element 10.
The illuminated image of a document desired to be copied is projected through the lens 17 by conventional means such as a lamp 20, mirror 21, and transparent platen 19 for holding the document 18. During imaging, the conductive layer of the electrophotographic member 10 is grounded by conventional means (not shown).
After charging the first predetermined portion 11 of the electrophotographic element 10 and imaging, the photo-conductive layer of the electrophotographic element 10 is placed against an opening 25 in the developing chamber of developing module 23, illustrated in Eigure 2. The develop-ing module 23 consists of a passageway 29 between an inlet port 26 and an outlet port 27. The walls of the toner module 23 include a mask 24, forming in the passageway 29 the rec-t~ngular opening 25 against which the portion of the electro-photographic member 10 to be developed is placed. Electro-statically charged toner particles are drawn from a suitable supply reservoir through inlet port 26, through the passageway 29 and across the face of the portion of the electrophotographic : element 10 being developed, and then out through outlet port 27. The toner is drawn through the developing module 23 preferably by a vacuum to preclude leakage of the toner fluid from the seal formed by the mask 24 against the electrophoto-graphic element 10, although the vacuum might not be necessary . ;,~ ~
.~: - 6 10371~2 if the mask 24 is made from a material which alone satisfactorily seals against the element 10.
The developing module 23 is preferably constructed entirely of a suitable electrically insulating material, with S the exception of a development electrode 28, which is positioned close to the electrophotographic member 10. The electrode 28 is constructed of a thin sheet of electrically conductive material and aids in controlling deposition of toner particles onto the imaged areas of the electrophotographic element, in a manner known in the art.
The opening 25 bordered by the mask 24 is sized and positioned with respect to the electrophotographic element 10 so that it coincides with the second predetermined portion 12 of the electrophotographic element 10 to be developed. The mask 24 covers a portion of the border area of the charged portion 11 and prevents deposition of the toner particles in the border area. It is this border area which has been nonuniformly charged, and masking of this area during develop-ment prevents unsightly edge toning.
Although the invention broadly includes the prevention of the toner particles from being applied to any portion of the border region of the charged area, the invention ir its preferred form will prevent toning in a border strip having a width of at least 1% of the corresponding dimension in the area charged. In other words, the width of second predetermined portion 12 will be at least 2% (1% on each side) smaller than the width of the first predetermined portion 11. The same is true with respect to the lengths.
Also in a preferred form of the invention, the imaging means are positioned to image only the second predetermined portion - of the photoconductive layer.
:' ~ .
~ 10;~7102 The invention is p~rticularly useful where charging is accomplished while the electrophotographic member is stationary with respect to the charging apparatus, as illustrated in Figure 3. With this arrangement, nonuniformity of charging along the borders of the charged area is often quite extreme.
However, it should be recognized that the invention has value in use where charging is accomplished while there is relative movement between the electrophotographic member and the charging apparatus. Additionally, it should be noted that the first predetermined portion of an electrophotographic element charged could be the entire surface of the element.
'~
:
'~' .~ .
' '
:
'~
--- 103q102 U. S. Patent No. 3,617,121 to Albert is concerned with the un desirable black border created by making positive copies from negatives, and discloses elimination of the black border by imaging through an opaque border mask. U. S. Patent No.
3,687,538 to Matusmoto discloses elimination of undesirable black border by use of a discharging light source at the borders.
All of these prior art devices require complex apparatus, which obviously is undesirable if simpler alternatives can be found.
Therefore, it is the object of the invention to eliminate the undesirable edge toning on an electrophotographic member through use of a simple, but effective, apparatus and method.
The invention eliminates the undesirable edge toning on an electrophotographic member by developing on the electrophotographic member an area which is smaller and entirely within the borders of a larger area which was subjected to electrostatic charging. This unique step is accomplished through use of a special developing chamber through which toner particles are passed to contact the charged and imaged area of the electrophotographic member. The developing chamber has an opening formed by a mask which, in conjunction with a vacuum drawing the toner particles through the chamber, sealingly engages the imaged photoconductive layer of the electrophotographic member and covers the portion of the charged area about the border which was nonuniformly charged.
In accordance with the present invention, there is provided an electrophotographic reproduction method which comprises electrostatically charging a first predetermined portion of the photoconductive layer of an electrophotographic element; projecting an illuminated image onto the first portion to form an electrostatic latent image on the photo-conductive layer, the borders about the electrostatic latent 1037~02 image retaining a significant amount of electrostatic charge;
and applying electrostatically charged toner particles to only a second predetermined portion of the photoconductive layer within the first portion, the edges of the first portion extending beyond the edges of the second portion in all directions whereby a border region in the first predetermined portion is not developed.
Figure 1 is an illustration of an electrophoto-graphic recording member with the area charged and the area developed indicated thereon.
Figure 2 is a cut-away side view of the developing chamber of the invention positioned against an electrophoto-graphic recording element.
Figure 3 is a schematic view of corona generating means and imaging means in operative position against an electrophotographic recording element.
Referring to Figure 1, an electrophotographic recording element in the form of a microfiche 10 is illustrated with a first predetermined portion of the photoconductive layer indicated as a rectangle 11 and a second predetermined ; portion 12 indicated as a rectangle within the first pre-; determined portion 11. The first predetermined portlon 11 is electrostatically charged by corona generating element 16 housed within the charging and imaging module 13, illustrated in Figure 3. The charging and imaging module 13 includes mask flange 14, forming an opening 15. The mask flange 14 is placed against the photoconductive layer of the electro-photographic element 10 where it shields all of the electro-photographic element except the first predetermined portion 11 from corona charging and imaging.
.. ~ , .
, . .
-` 10;~ Z
The corona genera~ing element 1~ can be provided by any conventional form of corona discharge element, such as a wire or needle, and receives its generating potential from a conventional high voltage power source (not shown). Lens 17 is mounted in the charging and imaging module 13 at the appropriate distance to focus an illuminated image onto the photoconductive layer of the electrophotographic element 10.
The illuminated image of a document desired to be copied is projected through the lens 17 by conventional means such as a lamp 20, mirror 21, and transparent platen 19 for holding the document 18. During imaging, the conductive layer of the electrophotographic member 10 is grounded by conventional means (not shown).
After charging the first predetermined portion 11 of the electrophotographic element 10 and imaging, the photo-conductive layer of the electrophotographic element 10 is placed against an opening 25 in the developing chamber of developing module 23, illustrated in Eigure 2. The develop-ing module 23 consists of a passageway 29 between an inlet port 26 and an outlet port 27. The walls of the toner module 23 include a mask 24, forming in the passageway 29 the rec-t~ngular opening 25 against which the portion of the electro-photographic member 10 to be developed is placed. Electro-statically charged toner particles are drawn from a suitable supply reservoir through inlet port 26, through the passageway 29 and across the face of the portion of the electrophotographic : element 10 being developed, and then out through outlet port 27. The toner is drawn through the developing module 23 preferably by a vacuum to preclude leakage of the toner fluid from the seal formed by the mask 24 against the electrophoto-graphic element 10, although the vacuum might not be necessary . ;,~ ~
.~: - 6 10371~2 if the mask 24 is made from a material which alone satisfactorily seals against the element 10.
The developing module 23 is preferably constructed entirely of a suitable electrically insulating material, with S the exception of a development electrode 28, which is positioned close to the electrophotographic member 10. The electrode 28 is constructed of a thin sheet of electrically conductive material and aids in controlling deposition of toner particles onto the imaged areas of the electrophotographic element, in a manner known in the art.
The opening 25 bordered by the mask 24 is sized and positioned with respect to the electrophotographic element 10 so that it coincides with the second predetermined portion 12 of the electrophotographic element 10 to be developed. The mask 24 covers a portion of the border area of the charged portion 11 and prevents deposition of the toner particles in the border area. It is this border area which has been nonuniformly charged, and masking of this area during develop-ment prevents unsightly edge toning.
Although the invention broadly includes the prevention of the toner particles from being applied to any portion of the border region of the charged area, the invention ir its preferred form will prevent toning in a border strip having a width of at least 1% of the corresponding dimension in the area charged. In other words, the width of second predetermined portion 12 will be at least 2% (1% on each side) smaller than the width of the first predetermined portion 11. The same is true with respect to the lengths.
Also in a preferred form of the invention, the imaging means are positioned to image only the second predetermined portion - of the photoconductive layer.
:' ~ .
~ 10;~7102 The invention is p~rticularly useful where charging is accomplished while the electrophotographic member is stationary with respect to the charging apparatus, as illustrated in Figure 3. With this arrangement, nonuniformity of charging along the borders of the charged area is often quite extreme.
However, it should be recognized that the invention has value in use where charging is accomplished while there is relative movement between the electrophotographic member and the charging apparatus. Additionally, it should be noted that the first predetermined portion of an electrophotographic element charged could be the entire surface of the element.
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:
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Claims (8)
1. An electrophotographic reproduction method which comprises:
(a) electrostatically charging a first predetermined portion of the photoconductive layer of an electrophotographic element;
(b) projecting an illuminated image onto the first portion to form an electrostatic latent image on the photo-conductive layer, the borders about the electrostatic latent image retaining a significant amount of electrostatic charge;
and (c) applying electrostatically charged toner particles to only a second predetermined portion of the photoconductive layer within the first portion, the edges of the first portion extending beyond the edges of the second portion in all directions whereby a border region in the first predetermined portion is not developed.
(a) electrostatically charging a first predetermined portion of the photoconductive layer of an electrophotographic element;
(b) projecting an illuminated image onto the first portion to form an electrostatic latent image on the photo-conductive layer, the borders about the electrostatic latent image retaining a significant amount of electrostatic charge;
and (c) applying electrostatically charged toner particles to only a second predetermined portion of the photoconductive layer within the first portion, the edges of the first portion extending beyond the edges of the second portion in all directions whereby a border region in the first predetermined portion is not developed.
2. Method according to claim 1, wherein the border region not developed has a width about its perimeter which is at least about 1% of the corresponding dimension of the first predetermined portion.
3. Method according to claim 1, wherein the illuminated image is projected entirely within the borders of the second predetermined portion of the photoconductive layer.
4. Method according to claim 1, wherein the photo-conductive layer is electrostatically charged while stationary with respect to the charging means.
5. Method according to claim 4, wherein the electro-photographic element is a multi-frame microfiche, and the second predetermined portion is a single frame.
6. Method according to claim 4, wherein the toner particles are applied to the photoconductive layer through means which are stationary with respect to the photoconductive layer.
7. In an apparatus for producing an image on an electrophotographic element which comprises:
(a) charging means for electrostatically charging a first predetermined portion of the photoconductive layer of an electrophotographic element;
(b) imaging means for projecting an illuminated image onto the first portion to form an electrostatic latent image on the photoconductive layer; and (c) developing means for applying electrostatically charged toner particles to the latent image on the photocon-ductive layer, the improvement wherein the developing means comprises a chamber through which the toner particles are passed to contact the charged and imaged area of the photo-conductive layer, the chamber having an opening formed by a mask which sealingly engages the photoconductive layer and blocks toner particles from an area of the first portion adjacent its border.
(a) charging means for electrostatically charging a first predetermined portion of the photoconductive layer of an electrophotographic element;
(b) imaging means for projecting an illuminated image onto the first portion to form an electrostatic latent image on the photoconductive layer; and (c) developing means for applying electrostatically charged toner particles to the latent image on the photocon-ductive layer, the improvement wherein the developing means comprises a chamber through which the toner particles are passed to contact the charged and imaged area of the photo-conductive layer, the chamber having an opening formed by a mask which sealingly engages the photoconductive layer and blocks toner particles from an area of the first portion adjacent its border.
8. Apparatus according to claim 7, wherein the mask blocks toner particles from an area having a width about the first portion which is at least 1% of the corresponding dimen-sion of the first portion.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US45819274A | 1974-04-05 | 1974-04-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1037102A true CA1037102A (en) | 1978-08-22 |
Family
ID=23819747
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA223,994A Expired CA1037102A (en) | 1974-04-05 | 1975-04-07 | Electrophotographic reproduction method and apparatus |
Country Status (3)
| Country | Link |
|---|---|
| BE (1) | BE827601A (en) |
| CA (1) | CA1037102A (en) |
| GB (1) | GB1483704A (en) |
-
1975
- 1975-04-04 BE BE1006574A patent/BE827601A/en unknown
- 1975-04-07 CA CA223,994A patent/CA1037102A/en not_active Expired
- 1975-04-07 GB GB4906175A patent/GB1483704A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| BE827601A (en) | 1975-10-06 |
| GB1483704A (en) | 1977-08-24 |
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