CA1151932A - Developing apparatus including a toner particle with magnetic and non-magnetic portions - Google Patents
Developing apparatus including a toner particle with magnetic and non-magnetic portionsInfo
- Publication number
- CA1151932A CA1151932A CA000391760A CA391760A CA1151932A CA 1151932 A CA1151932 A CA 1151932A CA 000391760 A CA000391760 A CA 000391760A CA 391760 A CA391760 A CA 391760A CA 1151932 A CA1151932 A CA 1151932A
- Authority
- CA
- Canada
- Prior art keywords
- toner particle
- magnetic
- magnetic portion
- developer mixture
- latent image
- 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
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/0821—Developers with toner particles characterised by physical parameters
- G03G9/0823—Electric parameters
-
- 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
- G03G13/06—Developing
- G03G13/08—Developing using a solid developer, e.g. powder developer
- G03G13/09—Developing using a solid developer, e.g. powder developer using magnetic brush
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G9/00—Developers
- G03G9/08—Developers with toner particles
- G03G9/083—Magnetic toner particles
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Developing Agents For Electrophotography (AREA)
- Magnetic Brush Developing In Electrophotography (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A mixture of magnetic carrier granules having toner particles adhering triboelectrically thereto. The toner particles comprise a non-magnetic portion with a magnetic portion intregal therewith.
A mixture of magnetic carrier granules having toner particles adhering triboelectrically thereto. The toner particles comprise a non-magnetic portion with a magnetic portion intregal therewith.
Description
~515~32 A DEVELOPER MATEl~IA
This invention relates generally to an electrophotographic printing machine, and more particularly concerns a developer material employed therein to render the electrostatic latent image recorded on the photoconduc-tive surface thereof visible.
In electrophotographic printing, a light image of an original docu-ment is projected onto a charged photoconductive surface. This selectively dissipates the charge to record an electrostatic latent image of the original document on the photoconductive surface. The latent image is subsequently developed with toner particles. These toner particles are transferred to the copy sheet and permanently affixed thereto by the application of heat and/or pressure.
Generally, the developer material comprises toner particles ad-hering triboelectrically to carrier gramlles. This two-component developer mixture contacts the electrostatic latent image. The toner particles are attracted from the carrier granules to the latent image rendering it visible.
Generally, the carrier granules are made from a ferromagnetic material the toner particles being made from a thermoplastic material.
Various methods have been devised for transporting the developer material to the latent image. For example, the developer material may be cascaded over the latent image and the toner particles attracted from the carrier granules thereto. Other structures employed to develop the latent image include the use of magnetic field producing devices which form brush-like tufts of developer material extending outwardly therefrom in contact with the photoconductive surface.
In developing an electrostatic latent image, the toner particles are deposited thereon. However, frequently the toner particles are not only deposited on the electrostatic latent image but on the background areas.
When the toner particles are transferred from the photoconductive surface to the copy sheet, both the areas containing the electrostatic latent image and the backgound are transferred to the copy sheet. This produces a gray background significantly deteriorating the resultant copy. ~urthermore, the toner particles freguently escape from the developer housing contaminating the other systems of the printing machine. Various techniques have been devised to overcome the foregoing problem. The following art appears to be relevant:
,.~
U.S. Patent No. 3,239,465 Patentee: Rheinfrank Issued: March 8, 1966 U.S. Patent No. 3,345,294 Patentee: Cooper Issued: October 3, 1967 U.S. Patent No. 3,639,245 Patentee: Nelson Issued: February 1, 1972 The relevant portions of the foregoing patents may be briefly summarized as follows:
Rheinfrank discloses a toner particle having magnetic particles held in a binder. The magnetic material may be magnetite or hemitite with the binder being an organic resin. The ratio of binder to magnetic particle can vary from 19 to 1 to 2 to 3 by weight. For best results, there should be at least 20% of the magnetic powder but not over 70%.
Cooper describes developer powder which reduces the tendency of the toner to adhere to the background of the print. The toner comprises a polyamide resin mixed with a coloring agent and a magnetic substance. The magnetic substance may be present in an amount as small as 1% by weight and preferably between about 5% and about 25% by weight of the developer powder.
Nelson describes a dry ink made from magnetite blended with a resin and having carbon particles embedded therein.
In accordance with one aspect of the present invention, there is provided a mixture for developing an electrostatic latent image. The mixture includes a magnetic carrier granule having a toner particle adhering thereto. The toner particle comprises a non-magnetic portion with a magnetic portion integral therewith. Preferably, the magnetic portion is about 10~ of the volume of the toner particle.
-2a-Other aspects of the invention are as follows:
An apparatus for developing a latent image including:
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule, and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1~ to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 microcoulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10 8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transporting the developer mixture closely adjacent to the latent image.
An electrophotographic printing machine of the type in which an electrostatic latent image is recorded on a photoconductive surface, wherein the improvement includes:
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1% to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 microcoulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10 8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transporting the developer mixture closely adjacent to the latent image.
33~
- 2b -Other aspects of the present invention will become apparent upon a reading of the following detailed description and upon reference to the drawings, in which:
~193~
Figure 1 is a schematic elevational view depicting an electrophoto-grflphic printing machine incorporating the features of the present invention tllerein;
Figure 2 is a fragmentary elevational view illustrating the developer unit employed in the Figure 1 printing machine;
Figure 3 is a fragmentflry elevational view showing the arrange-ment of the forces on the developer mixture of the Figure 2 developer unit;
Figure 4 is a graph showing the force variation as Q function of the percentage of magnetic material in the toner particles for toner particles having a low charge; and Figure 5 is a graph depicting the force variation as a function of the percentage of magnetic material in the toner particles for toner particles having a high charge.
While the present invention will hereinafter be described in con-nection with a preferred embodiment flnd method of use therefore, it will be understood that it is not intended to limit the invention to that embodiment and method of use. On the contrary, it is in*ended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
For a general understanding of an electrophotographic printing machine incorporating the features of the present invention therein, reference is made to Figure l which depicts schematically the various components thereof. Hereinafter, like reference numerals will be employed throughout to designate identical elements. Although the developer mixture of the present invention is particularly well adapted for use in the development system of an electrophotographic printing machine, it should become evident from the following discllssion that this mixture is equally well suited for use in a widevariety of printing machines and is not necessarily limited to the particular embodiment shown herein.
Inasmuch as the art of electrophotographic printing is well known, the various processing stations for producing a copy of an original document are represented schematically in Figure l. Each of these processing stations will be described briefly hereinafter.
With continued reference to Figure l, the electrophotographic printing machine employs a drum l0 having a photoconductive surface 12 secured to the exterior circumferential surface of ~ conductive substrate. By ~19~Z
way of example, photoconductive surface 12 may be made from a suitable selenium alloy with the conductive substrate being made from a]uminum.
Orum 10 rot~tes in the direction of arrow 1~ so that successive portions of photoconductive surface 12 pass through the various processing stations 5disposed about the periphery thereof.
Initially, drum 10 rotates a portion of photoconductive surface 12 through charging station A. Charging station A includes a corona generating device, indicated generally by the reference numeral 16. Corona generating device 16 is located closely adjacent to photoconductive surface 12. When 10energiæed, corona generating device 16 charges a portion of photoconductive surface 12 to a relatively high substantially uniform potential.
The charged portion of photoconductive surface 12 is rotated to imaging station B. Imaging station B includes an exposure system, indicated generally by the reference numeral 18, comprising a transparent platen upon 15which the original document is disposed. Lamps illuminate the original document. Scanning of the original document is achieved by an oscillating mirror in a timed relationship with the movement of drum 10, or, in lieu thereof by moving the lamps and lens system in synchronism to form a flowing light image thereof. The light image of the original document is focused onto 20the charged portion of photoconductive surface 12. In this manner, photocon-ductive surface 12 is selectively discharged to record an electrostatic latent image thereon corresponding the informational areas contained within the original document.
Next, drum 10 rotates the electrostatic latent image recorded on 25photoconductive surface 12 to development station C. At development station C, a developer unit having a housing with a supply of developer mixture therein renders the electrostatic latent image visible. The developer mixture of the present invention includes magnetic carrier granules having toner particles adhering triboelectrically thereto. The toner particles comprise a 30non-magnetic portion and a magnetic portion. The magnetic portion is preferably about 10% of the volume of the toner particle. The detailed structure of developer unit 20 and the developer mixture employed therein will be described hereinafter with reference to Figures 2 throu~h 5, inclusive. In general, the electrostatic latent image attracts the toner particles from the 35carrier granules to form a toner powder image thereon.
With continued reference to Figure 1, a sheet of support material is advanced by sheet feeding appflratus 22 to transfer station D. Sheet feeding flpparatus 22 includes a feed roll 24 contacting the uppermost sheet of stack 26. Feed roll 24 rotates in the direction of flrrow 28 to advance the uppermost sheet from stack 26. I~egistration rollers 30, rotating in the direction of arrow 32, advance and align the sheet of support mflterial into chute 34. ~hute 34 5 directs the advancing sheet of support material into contact with drum 10 in atimed sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station D. Transfer station D includes a corona generating device 36. Corona generating device 36 sprays ions onto the side of the sheet of support material opposed from lOphotoconductive surface 12. The toner powder image adhering to photocon-ductive surface 12 is then attracted therefrom to the surface of the sheet of support material in contact therewith. After transferring the toner powder image to the sheet of support material, endless belt conveyor 38 advances the sheet of support material to fusing station E.
15Fusing station E includes a fuser assembly, indicated generally by the reference numeral 40. Fuser assembly 40 heats the transferred toner powder image to permanently affix the toner particles to the sheet of support material. Preferably, fuser assembly 40 includes a heated fuser roller 42 flnd abackup roll 44. A sheet of support material, with the powder image thereon, is 20 interposed between fuser roll 42 and backup roll 44. The powder image contacts fuser roll 42. Release material applicator 46 applies release material to fuser roll 42. Blade 48, positioned closely adjacent to fuser roll 42, regulates the thickness of release material coating fuser roll 42. After the toner powder image is permanently affixed to the sheet of support material, 25 stripper blade 50 separates the sheet from fuser roller 42. Thereafter, the sheet of support material is advflnced by a series of rollers 52 to catch tray 54 for subsequent removal from the printing machine by the operator.
Invariably, residual particles remain adhering to photoconductive surface 12 after the transfer of the toner powder image to the sheet of 30 support material. These residual particles are removed from photoconductive surface 12 at cleaning station F. Cleaning station F includes a cleaning mechanism, generally designated by the reference numeral 56, having a corona generating device and a brush contacting photoconductive surface 12. Ini-tially, the pflrticles are brought under the influence of the corona generating 35 device to neutralize the charge remaining on photoconductive surface 12 and that of the residual particles. Thereafter, the neutralized particles are L r31~t3Z
--fi--removed from photoconductive surface ]2 by the rotatably mounted fibrous brush in contact therewith. After cleaning, a discharge lamp floods photocon-ductive surface 12 to return it to the initial level prior to the recharging thereof for the next successive imaging cycle.
It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrophotographic printing machine embodying the features of the present invention therein. Referring now to the specific subject matter of the present invention, Figure 2 depicts developer unit 20 transporting the developer 10 mixture into contact with the electrostatic latent image recorded on photo-conductive surface 12 of drum 10.
As illustrated in Figure 2, developer unit 20 includes a housing 58 defining a chamber 60 for storing a supply of developer mixture 62 therein.
Developer roller 64, mounted in chamber 60 of housing 58, preferably includes a tubular member made from a non-magnetic material such as aluminum.
Tubular member 64 is interfit over an elongated magnetic nlember 66.
B Preferably, magnetic member 66 is a bar magnetic made from~ferrite.
Magnetic member 66 is disposed interiorly of tubular member 64 and spaced therefrom. ~;haft 58 made preferably from steel, is mounted concentrically 20 within tubular member 64 to support magnetic member 66. A motor (not shown), coupled to tubular member 64, rotates tubular mernber 64 in the direction of arrow 70. Magnetic member 66 remains substantially stationary.
As tubular member 64 rotates relative to magnetic member 66, developer mixture 62 is advanced from chamber 60 to development zone 72. A power 25 supply (not shown) applies an electrical bias to tubular member 64. Pre-ferably, the voltage applied to tubular member 64 is about S00 volts.
However, this voltage level is adjustable and depends upon the background voltage level of photoconductive surface ~2. In operation, developer mixture 62, in chamber fiO of hollsing 58, is attracted by the magnetic fields produced 30 by magnetic member 68 to tubular member 64. As tubular member 64 rotates, the developer mixture moves into development zone 72. In development zone 72, the toner particles are attracted from the carrier granules disposed on tubular member 64 to the latent image recorded on photoconductive surface 12. In this way, the toner particles are deposited on the electrostatic latent 35 image forming a toner powder image thereon. In order to minimize develop-ment of the background areas, the toner particles include a magnetic portion.
3~
The carrier granules are mflgnetic and are preferably made from ferro-magnetic materiHls such as magnetite or hemitite. The non-magnetic portion ~3 of the toner particle is made from fusable resin such as ~. Thus, the toner particles comprise a fusable resin with magnetic particles such as iron, S magnetic iron oxide or magnetite, various magnetic metals and alloys, and the like dispersed therein. The magnetic portion of the toner particle comprise preferably 10% of the volume of the toner particle with the resin or plastic material comprising 90% of the toner particle by volume. However, it has been found that ranges of from 1 to 10% of magnetic material by volume improve development. Development is improved when the toner particle charge ranges from about 1 to about 20 microcoulo,~mbs per gram. It is clear that the introduction of the magnetic portion in the toner particle suppresses background development and facilitates development of the electrostatic latent image. This produces sharper, darker copies. Furthermore, magnetic loading causes the toner particles to better adhere to the carrier granules reducing toner particle contamination and dirt throughout the printing machine.
Referring now to Figure 3, there is shown a schematic distrihution of the forces involved in development of the electrostatic latent image. As depicted thereat, during development, developer mixture 62 is brought into the vicinity of photoconductive surface 12. Carrier granule 74 acts as a transport for toner particle 76. Toner particle 76 acquires charge through triboelectri-fication. This charge and the countercharges on carrier granule 74 produces adhesion force FR between toner particle 76 and carrier granule 74. The internal magnetic field also induces a dipole in particle 76 which adds to FR.
As carrier granule 74 is transported into development zone 72 closely adjacent to and in contact with photoconductive surface 12, toner particle 76 is transported therewith. The electrostatic latent image recorded on photocon-ductive surface 12 produces an electrostatic field which exerts a stripping force FD on toner particle 76. When stripping force FD exceeds retaining force FR, the toner particles leave carrier granules 74 and move to photocon-ductive surface 12. In this way, the electrostatic latent image is developed.
It has been found that the magnetic portion of the toner particle causes the introduction of a magnetic dipole which adds to FR. In this way, FR is increased and the background forces on photoconductive surface 12 are insufficient to separate toner particles 76 from carrier granules 74. However, 1"3~32 the fields introducecl by the latent image produce a sufficient force to separate the toner particles from the carrier granules resulting in development of the electrostatic latent image with the background remaining substnntially devoid of toner particles. In this way, background development is suppressed and electrostatic latent image development enhanced.
Referring now to Figure 4, there is shown the force attracting the toner particles produced by the background electrostatic field on the photo-conductive surface as a solid line, i.e. the stripping force, and the force retaining the toner particle to the carrier granule as a dotted line for both 0%magnetic loading and 10% magnetic loading. Figure 4 depicts the foregoing B conditions for a low charge toner particle, i.e. one having a 1 microcoulo~mb per gram charge thereon. As shown, when the mflgnetic loading is 10% by volume of the toner particle, the electrostatic force produced by the back-ground area is never sufficient to strip the toner particle from the carrier granule.
Referring now to Figure 5, the holding force is once again shown as a dotted line for 096 and 10% magnetic loading with the stripping force being shown as a solid line. The graph depicted in Figure 5 is for a highly charged toner particle, i.e. one having a charge of 20 microcoulo,~mbs per gram. Under these latter circumstances, there is an increase in the required background force necessary to electrostatically strip the toner particles from the carrier granules so as to develop the background areas. Thus, it is cleQr that magnetic loading of the toner particles produces a significant improvement when there are present toner particles with low charge and a minor improvement when the toner particles are highly charged.
In recapitulation, the present invention is directed to a developer mixture which may be employed to develop an electrostatic latent image. The developer mixture includes a toner particle having a non-magnetic portion and a magnetic portion with the magnetic portion being preferably about 1096 by volume of the toner particle. A developer mixture of this type improves development by reducing background development while maintaining image development at a highly satisfactory level. In this way, contrast is improved.
Furthermore, machine contamination due to the escape of toner particles from the developer housing is minimized.
It is, therefore, evldent that there has been provided in accordance with the present invention, a developer mixture that fully satisfies the aims ~ ~1932 9~
and advantages hereinbefore set forth. While this invention has been described in conjunction with a specific embodiment and method of use therefore, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fnll within the spirit and broad scope of the appended claims.
This invention relates generally to an electrophotographic printing machine, and more particularly concerns a developer material employed therein to render the electrostatic latent image recorded on the photoconduc-tive surface thereof visible.
In electrophotographic printing, a light image of an original docu-ment is projected onto a charged photoconductive surface. This selectively dissipates the charge to record an electrostatic latent image of the original document on the photoconductive surface. The latent image is subsequently developed with toner particles. These toner particles are transferred to the copy sheet and permanently affixed thereto by the application of heat and/or pressure.
Generally, the developer material comprises toner particles ad-hering triboelectrically to carrier gramlles. This two-component developer mixture contacts the electrostatic latent image. The toner particles are attracted from the carrier granules to the latent image rendering it visible.
Generally, the carrier granules are made from a ferromagnetic material the toner particles being made from a thermoplastic material.
Various methods have been devised for transporting the developer material to the latent image. For example, the developer material may be cascaded over the latent image and the toner particles attracted from the carrier granules thereto. Other structures employed to develop the latent image include the use of magnetic field producing devices which form brush-like tufts of developer material extending outwardly therefrom in contact with the photoconductive surface.
In developing an electrostatic latent image, the toner particles are deposited thereon. However, frequently the toner particles are not only deposited on the electrostatic latent image but on the background areas.
When the toner particles are transferred from the photoconductive surface to the copy sheet, both the areas containing the electrostatic latent image and the backgound are transferred to the copy sheet. This produces a gray background significantly deteriorating the resultant copy. ~urthermore, the toner particles freguently escape from the developer housing contaminating the other systems of the printing machine. Various techniques have been devised to overcome the foregoing problem. The following art appears to be relevant:
,.~
U.S. Patent No. 3,239,465 Patentee: Rheinfrank Issued: March 8, 1966 U.S. Patent No. 3,345,294 Patentee: Cooper Issued: October 3, 1967 U.S. Patent No. 3,639,245 Patentee: Nelson Issued: February 1, 1972 The relevant portions of the foregoing patents may be briefly summarized as follows:
Rheinfrank discloses a toner particle having magnetic particles held in a binder. The magnetic material may be magnetite or hemitite with the binder being an organic resin. The ratio of binder to magnetic particle can vary from 19 to 1 to 2 to 3 by weight. For best results, there should be at least 20% of the magnetic powder but not over 70%.
Cooper describes developer powder which reduces the tendency of the toner to adhere to the background of the print. The toner comprises a polyamide resin mixed with a coloring agent and a magnetic substance. The magnetic substance may be present in an amount as small as 1% by weight and preferably between about 5% and about 25% by weight of the developer powder.
Nelson describes a dry ink made from magnetite blended with a resin and having carbon particles embedded therein.
In accordance with one aspect of the present invention, there is provided a mixture for developing an electrostatic latent image. The mixture includes a magnetic carrier granule having a toner particle adhering thereto. The toner particle comprises a non-magnetic portion with a magnetic portion integral therewith. Preferably, the magnetic portion is about 10~ of the volume of the toner particle.
-2a-Other aspects of the invention are as follows:
An apparatus for developing a latent image including:
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule, and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1~ to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 microcoulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10 8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transporting the developer mixture closely adjacent to the latent image.
An electrophotographic printing machine of the type in which an electrostatic latent image is recorded on a photoconductive surface, wherein the improvement includes:
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1% to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 microcoulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10 8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transporting the developer mixture closely adjacent to the latent image.
33~
- 2b -Other aspects of the present invention will become apparent upon a reading of the following detailed description and upon reference to the drawings, in which:
~193~
Figure 1 is a schematic elevational view depicting an electrophoto-grflphic printing machine incorporating the features of the present invention tllerein;
Figure 2 is a fragmentary elevational view illustrating the developer unit employed in the Figure 1 printing machine;
Figure 3 is a fragmentflry elevational view showing the arrange-ment of the forces on the developer mixture of the Figure 2 developer unit;
Figure 4 is a graph showing the force variation as Q function of the percentage of magnetic material in the toner particles for toner particles having a low charge; and Figure 5 is a graph depicting the force variation as a function of the percentage of magnetic material in the toner particles for toner particles having a high charge.
While the present invention will hereinafter be described in con-nection with a preferred embodiment flnd method of use therefore, it will be understood that it is not intended to limit the invention to that embodiment and method of use. On the contrary, it is in*ended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
For a general understanding of an electrophotographic printing machine incorporating the features of the present invention therein, reference is made to Figure l which depicts schematically the various components thereof. Hereinafter, like reference numerals will be employed throughout to designate identical elements. Although the developer mixture of the present invention is particularly well adapted for use in the development system of an electrophotographic printing machine, it should become evident from the following discllssion that this mixture is equally well suited for use in a widevariety of printing machines and is not necessarily limited to the particular embodiment shown herein.
Inasmuch as the art of electrophotographic printing is well known, the various processing stations for producing a copy of an original document are represented schematically in Figure l. Each of these processing stations will be described briefly hereinafter.
With continued reference to Figure l, the electrophotographic printing machine employs a drum l0 having a photoconductive surface 12 secured to the exterior circumferential surface of ~ conductive substrate. By ~19~Z
way of example, photoconductive surface 12 may be made from a suitable selenium alloy with the conductive substrate being made from a]uminum.
Orum 10 rot~tes in the direction of arrow 1~ so that successive portions of photoconductive surface 12 pass through the various processing stations 5disposed about the periphery thereof.
Initially, drum 10 rotates a portion of photoconductive surface 12 through charging station A. Charging station A includes a corona generating device, indicated generally by the reference numeral 16. Corona generating device 16 is located closely adjacent to photoconductive surface 12. When 10energiæed, corona generating device 16 charges a portion of photoconductive surface 12 to a relatively high substantially uniform potential.
The charged portion of photoconductive surface 12 is rotated to imaging station B. Imaging station B includes an exposure system, indicated generally by the reference numeral 18, comprising a transparent platen upon 15which the original document is disposed. Lamps illuminate the original document. Scanning of the original document is achieved by an oscillating mirror in a timed relationship with the movement of drum 10, or, in lieu thereof by moving the lamps and lens system in synchronism to form a flowing light image thereof. The light image of the original document is focused onto 20the charged portion of photoconductive surface 12. In this manner, photocon-ductive surface 12 is selectively discharged to record an electrostatic latent image thereon corresponding the informational areas contained within the original document.
Next, drum 10 rotates the electrostatic latent image recorded on 25photoconductive surface 12 to development station C. At development station C, a developer unit having a housing with a supply of developer mixture therein renders the electrostatic latent image visible. The developer mixture of the present invention includes magnetic carrier granules having toner particles adhering triboelectrically thereto. The toner particles comprise a 30non-magnetic portion and a magnetic portion. The magnetic portion is preferably about 10% of the volume of the toner particle. The detailed structure of developer unit 20 and the developer mixture employed therein will be described hereinafter with reference to Figures 2 throu~h 5, inclusive. In general, the electrostatic latent image attracts the toner particles from the 35carrier granules to form a toner powder image thereon.
With continued reference to Figure 1, a sheet of support material is advanced by sheet feeding appflratus 22 to transfer station D. Sheet feeding flpparatus 22 includes a feed roll 24 contacting the uppermost sheet of stack 26. Feed roll 24 rotates in the direction of flrrow 28 to advance the uppermost sheet from stack 26. I~egistration rollers 30, rotating in the direction of arrow 32, advance and align the sheet of support mflterial into chute 34. ~hute 34 5 directs the advancing sheet of support material into contact with drum 10 in atimed sequence so that the toner powder image developed thereon contacts the advancing sheet of support material at transfer station D. Transfer station D includes a corona generating device 36. Corona generating device 36 sprays ions onto the side of the sheet of support material opposed from lOphotoconductive surface 12. The toner powder image adhering to photocon-ductive surface 12 is then attracted therefrom to the surface of the sheet of support material in contact therewith. After transferring the toner powder image to the sheet of support material, endless belt conveyor 38 advances the sheet of support material to fusing station E.
15Fusing station E includes a fuser assembly, indicated generally by the reference numeral 40. Fuser assembly 40 heats the transferred toner powder image to permanently affix the toner particles to the sheet of support material. Preferably, fuser assembly 40 includes a heated fuser roller 42 flnd abackup roll 44. A sheet of support material, with the powder image thereon, is 20 interposed between fuser roll 42 and backup roll 44. The powder image contacts fuser roll 42. Release material applicator 46 applies release material to fuser roll 42. Blade 48, positioned closely adjacent to fuser roll 42, regulates the thickness of release material coating fuser roll 42. After the toner powder image is permanently affixed to the sheet of support material, 25 stripper blade 50 separates the sheet from fuser roller 42. Thereafter, the sheet of support material is advflnced by a series of rollers 52 to catch tray 54 for subsequent removal from the printing machine by the operator.
Invariably, residual particles remain adhering to photoconductive surface 12 after the transfer of the toner powder image to the sheet of 30 support material. These residual particles are removed from photoconductive surface 12 at cleaning station F. Cleaning station F includes a cleaning mechanism, generally designated by the reference numeral 56, having a corona generating device and a brush contacting photoconductive surface 12. Ini-tially, the pflrticles are brought under the influence of the corona generating 35 device to neutralize the charge remaining on photoconductive surface 12 and that of the residual particles. Thereafter, the neutralized particles are L r31~t3Z
--fi--removed from photoconductive surface ]2 by the rotatably mounted fibrous brush in contact therewith. After cleaning, a discharge lamp floods photocon-ductive surface 12 to return it to the initial level prior to the recharging thereof for the next successive imaging cycle.
It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an electrophotographic printing machine embodying the features of the present invention therein. Referring now to the specific subject matter of the present invention, Figure 2 depicts developer unit 20 transporting the developer 10 mixture into contact with the electrostatic latent image recorded on photo-conductive surface 12 of drum 10.
As illustrated in Figure 2, developer unit 20 includes a housing 58 defining a chamber 60 for storing a supply of developer mixture 62 therein.
Developer roller 64, mounted in chamber 60 of housing 58, preferably includes a tubular member made from a non-magnetic material such as aluminum.
Tubular member 64 is interfit over an elongated magnetic nlember 66.
B Preferably, magnetic member 66 is a bar magnetic made from~ferrite.
Magnetic member 66 is disposed interiorly of tubular member 64 and spaced therefrom. ~;haft 58 made preferably from steel, is mounted concentrically 20 within tubular member 64 to support magnetic member 66. A motor (not shown), coupled to tubular member 64, rotates tubular mernber 64 in the direction of arrow 70. Magnetic member 66 remains substantially stationary.
As tubular member 64 rotates relative to magnetic member 66, developer mixture 62 is advanced from chamber 60 to development zone 72. A power 25 supply (not shown) applies an electrical bias to tubular member 64. Pre-ferably, the voltage applied to tubular member 64 is about S00 volts.
However, this voltage level is adjustable and depends upon the background voltage level of photoconductive surface ~2. In operation, developer mixture 62, in chamber fiO of hollsing 58, is attracted by the magnetic fields produced 30 by magnetic member 68 to tubular member 64. As tubular member 64 rotates, the developer mixture moves into development zone 72. In development zone 72, the toner particles are attracted from the carrier granules disposed on tubular member 64 to the latent image recorded on photoconductive surface 12. In this way, the toner particles are deposited on the electrostatic latent 35 image forming a toner powder image thereon. In order to minimize develop-ment of the background areas, the toner particles include a magnetic portion.
3~
The carrier granules are mflgnetic and are preferably made from ferro-magnetic materiHls such as magnetite or hemitite. The non-magnetic portion ~3 of the toner particle is made from fusable resin such as ~. Thus, the toner particles comprise a fusable resin with magnetic particles such as iron, S magnetic iron oxide or magnetite, various magnetic metals and alloys, and the like dispersed therein. The magnetic portion of the toner particle comprise preferably 10% of the volume of the toner particle with the resin or plastic material comprising 90% of the toner particle by volume. However, it has been found that ranges of from 1 to 10% of magnetic material by volume improve development. Development is improved when the toner particle charge ranges from about 1 to about 20 microcoulo,~mbs per gram. It is clear that the introduction of the magnetic portion in the toner particle suppresses background development and facilitates development of the electrostatic latent image. This produces sharper, darker copies. Furthermore, magnetic loading causes the toner particles to better adhere to the carrier granules reducing toner particle contamination and dirt throughout the printing machine.
Referring now to Figure 3, there is shown a schematic distrihution of the forces involved in development of the electrostatic latent image. As depicted thereat, during development, developer mixture 62 is brought into the vicinity of photoconductive surface 12. Carrier granule 74 acts as a transport for toner particle 76. Toner particle 76 acquires charge through triboelectri-fication. This charge and the countercharges on carrier granule 74 produces adhesion force FR between toner particle 76 and carrier granule 74. The internal magnetic field also induces a dipole in particle 76 which adds to FR.
As carrier granule 74 is transported into development zone 72 closely adjacent to and in contact with photoconductive surface 12, toner particle 76 is transported therewith. The electrostatic latent image recorded on photocon-ductive surface 12 produces an electrostatic field which exerts a stripping force FD on toner particle 76. When stripping force FD exceeds retaining force FR, the toner particles leave carrier granules 74 and move to photocon-ductive surface 12. In this way, the electrostatic latent image is developed.
It has been found that the magnetic portion of the toner particle causes the introduction of a magnetic dipole which adds to FR. In this way, FR is increased and the background forces on photoconductive surface 12 are insufficient to separate toner particles 76 from carrier granules 74. However, 1"3~32 the fields introducecl by the latent image produce a sufficient force to separate the toner particles from the carrier granules resulting in development of the electrostatic latent image with the background remaining substnntially devoid of toner particles. In this way, background development is suppressed and electrostatic latent image development enhanced.
Referring now to Figure 4, there is shown the force attracting the toner particles produced by the background electrostatic field on the photo-conductive surface as a solid line, i.e. the stripping force, and the force retaining the toner particle to the carrier granule as a dotted line for both 0%magnetic loading and 10% magnetic loading. Figure 4 depicts the foregoing B conditions for a low charge toner particle, i.e. one having a 1 microcoulo~mb per gram charge thereon. As shown, when the mflgnetic loading is 10% by volume of the toner particle, the electrostatic force produced by the back-ground area is never sufficient to strip the toner particle from the carrier granule.
Referring now to Figure 5, the holding force is once again shown as a dotted line for 096 and 10% magnetic loading with the stripping force being shown as a solid line. The graph depicted in Figure 5 is for a highly charged toner particle, i.e. one having a charge of 20 microcoulo,~mbs per gram. Under these latter circumstances, there is an increase in the required background force necessary to electrostatically strip the toner particles from the carrier granules so as to develop the background areas. Thus, it is cleQr that magnetic loading of the toner particles produces a significant improvement when there are present toner particles with low charge and a minor improvement when the toner particles are highly charged.
In recapitulation, the present invention is directed to a developer mixture which may be employed to develop an electrostatic latent image. The developer mixture includes a toner particle having a non-magnetic portion and a magnetic portion with the magnetic portion being preferably about 1096 by volume of the toner particle. A developer mixture of this type improves development by reducing background development while maintaining image development at a highly satisfactory level. In this way, contrast is improved.
Furthermore, machine contamination due to the escape of toner particles from the developer housing is minimized.
It is, therefore, evldent that there has been provided in accordance with the present invention, a developer mixture that fully satisfies the aims ~ ~1932 9~
and advantages hereinbefore set forth. While this invention has been described in conjunction with a specific embodiment and method of use therefore, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fnll within the spirit and broad scope of the appended claims.
Claims (8)
1. An apparatus for developing a latent image including:
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule, and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1% to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 micro-coulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10-8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transport-ing the developer mixture closely adjacent to the latent image.
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule, and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1% to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 micro-coulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10-8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transport-ing the developer mixture closely adjacent to the latent image.
2. An apparatus according to claim 1, wherein the non-magnetic portion of the toner particle is made preferably from a plastic material.
3. An apparatus according to claim 2, wherein the magnetic portion of the toner particle is made preferably from a ferromagnetic material.
4. An apparatus according to claim 3, wherein said transporting means includes:
a rotatably mounted tubular member; and a magnetic member disposed interiorly of said tubular member for attracting the developer mixture to the exterior circumferential of said tubular member.
a rotatably mounted tubular member; and a magnetic member disposed interiorly of said tubular member for attracting the developer mixture to the exterior circumferential of said tubular member.
5. An electrophotographic printing machine of the type in which an electrostatic latent image is recorded on a photoconductive surface, wherein the improvement includes:
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1% to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 micro-coulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10-8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transporting the developer mixture closely adjacent to the latent image.
a housing defining a chamber for storing a supply of developer mixture comprising a magnetic carrier granule and a toner particle adhering to the carrier granule, the toner particle comprising a non-magnetic portion and a magnetic portion integral therewith, the volume of the magnetic portion of the toner particle being from about 1% to about 10% of the volume of the toner particle, the toner particle having a charge ranging from about 1 micro-coulomb per gram to about 20 microcoulombs per gram, the toner particle being attracted to the carrier granule with a force of at least 10-8 newtons; and means, operatively associated with the developer mixture stored in the chamber of said housing, for transporting the developer mixture closely adjacent to the latent image.
6. A printing machine according to claim 5, wherein the non-magnetic portion of the toner particle is made preferably from a plastic material.
7. A printing machine according to claim 6, wherein the magnetic portion of the toner particle is made preferably from a ferromagnetic material.
8. A printing machine according to claim 7, wherein the transporting means includes:
a rotatably mounted tubular member; and a magnetic member disposed interiorly of said tubular member for attracting the developer mixture to the exterior circumferential surface of said tubular member.
a rotatably mounted tubular member; and a magnetic member disposed interiorly of said tubular member for attracting the developer mixture to the exterior circumferential surface of said tubular member.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US22969281A | 1981-01-29 | 1981-01-29 | |
| US229,692 | 1981-01-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1151932A true CA1151932A (en) | 1983-08-16 |
Family
ID=22862315
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000391760A Expired CA1151932A (en) | 1981-01-29 | 1981-12-08 | Developing apparatus including a toner particle with magnetic and non-magnetic portions |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0057585A3 (en) |
| JP (1) | JPS57147647A (en) |
| CA (1) | CA1151932A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL9000912A (en) * | 1990-04-18 | 1991-11-18 | Oce Nederland Bv | METHOD FOR FORMING VISIBLE IMAGES, AND TONER POWDER FOR USE IN THE METHOD |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3345294A (en) * | 1964-04-28 | 1967-10-03 | American Photocopy Equip Co | Developer mix for electrostatic printing |
| US4185916A (en) * | 1977-04-08 | 1980-01-29 | Xerox Corporation | Composite developer particles and apparatus for using same |
-
1981
- 1981-12-08 CA CA000391760A patent/CA1151932A/en not_active Expired
-
1982
- 1982-01-27 JP JP57011469A patent/JPS57147647A/en active Pending
- 1982-01-29 EP EP82300462A patent/EP0057585A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57147647A (en) | 1982-09-11 |
| EP0057585A2 (en) | 1982-08-11 |
| EP0057585A3 (en) | 1982-10-06 |
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| MKEX | Expiry |