WO2003027771A1 - Electrophotographic carrier core magnetite powder - Google Patents
Electrophotographic carrier core magnetite powder Download PDFInfo
- Publication number
- WO2003027771A1 WO2003027771A1 PCT/SE2002/001757 SE0201757W WO03027771A1 WO 2003027771 A1 WO2003027771 A1 WO 2003027771A1 SE 0201757 W SE0201757 W SE 0201757W WO 03027771 A1 WO03027771 A1 WO 03027771A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- carrier core
- core material
- material according
- particles
- magnetite
- Prior art date
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
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
-
- 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
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/107—Developers with toner particles characterised by carrier particles having magnetic components
- G03G9/1075—Structural characteristics of the carrier particles, e.g. shape or crystallographic structure
-
- 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
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/107—Developers with toner particles characterised by carrier particles having magnetic components
- G03G9/108—Ferrite carrier, e.g. magnetite
-
- 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
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
- G03G9/1131—Coating methods; Structure of coatings
-
- 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
- G03G9/10—Developers with toner particles characterised by carrier particles
- G03G9/113—Developers with toner particles characterised by carrier particles having coatings applied thereto
- G03G9/1139—Inorganic components of coatings
Definitions
- This invention relates to particulate magnetite materials useful as a carrier component in electrophotographic developers, in particular two-component developers comprising the carrier component together with a toner component .
- the electrostatic image formed on the photoconductor is developed by the magnetic brush method using either the so called “one-component” developer or "two-component” developer.
- the two- component developer system comprises a mixture of relatively fine particles of a toner and relatively coarse particles of a carrier.
- the toner particles are held on the carrier particles by the electrostatic forces of opposite polarities which are generated by friction of the particles.
- the developer comes into contact with an electrostatic latent image formed on the photosensitive plate, the toner particles are attracted by the image and thus make the latter visible.
- the thus developed image is then transferred onto a recording medium, such as a paper sheet.
- the toner particles should be charged with an accurately controlled amount of static electricity so that they are preferentially attracted to the electrostatically imaged area of the photosensitive plate.
- the carrier which is used in combination with the toner must have an appropriate triboelectric property which enables it to electrostatically hold the toner particles and to transfer the held toner particles to the electrostatic latent image on the photosensitive plate when contacted.
- the carrier particles should have a sufficient mechanical strength to protect the carrier particles from breaking or cracking. These particles should also exhibit a good fluidity, be uniform in their electric and magnetic properties and be stable with respect to changes in the environmental conditions, such as humidity.
- the carrier particles should have a sufficient durability to ensure an acceptable lifetime.
- the distance between magnetic brush and photoreceptor is smaller and currents during printing are higher, a consequence of which is that the carrier core itself must be able to carry some of the amount of current in the copying process. More specifically higher voltage breakdown of the carrier core itself is needed. Preferably this higher voltage break- down should not be accompanied by a higher resistivity, but rather with a medium high resistivity.
- the carrier core materials normally used when high voltage breakdown values are required are selected from ferrites. These compounds have the chemical formula Fe 2 M0 4 wherein M can be Mn, Fe, Co, Ni , Cu, Zn, Cd, Mg.
- M can be Mn, Fe, Co, Ni , Cu, Zn, Cd, Mg.
- a problem is thus that, in order to obtain ferrite powders having optimal properties, it is often necessary to manipulate the chemistry of these ferrite base powders so as to include different types of oxides of heavy metals. Such metals should however to the outmost possible extent be avoided as they are detrimental to the environment .
- the most simple of the ferrites is the compound wherein M is Fe, i.e. the compound having the formula
- Magnetite Fe 3 0 4 , commonly called magnetite. Magnetite is not environmentally detrimental, but the voltage breakdown is low, normally between 30 -50 V. This is an indication that it would not be possible to use magnetite in the most recent printing technology.
- magnetite as a base material for the preparation of new carrier core materials having not only high voltage breakdown but which also in other respects can be tailored in order to meet different needs.
- the new carrier core material essentially consists of a magnetite base powder, the particles of which are surrounded by an electrically insulating coating consisting of an inorganic material. More specifically the inorganic material should be such that the resitivity of the coated particles is higher than that of the magnetite base particles.
- the invention also concerns a method for the preparation of such a new carrier core material.
- the spherical magnetite base powder may be produced as described in the US patent 4 663 262 which is hereby incorporated by reference. According to this patent the magnetite base is produced from natural magnetite by the following general procedure:
- a magnetite powder is formed into agglomerates which are then calcined at a predetermined temperature under a specific atmosphere.
- the calcined granules are suitably cracked or dispersed and then classified into a desired size distribution.
- the agglomerates are formed with a binder material which is effective for reducing the raw magnetite (Fe 3 0 ) to wustite (FeO) , the magnetite is partially converted to wustite during the calcination to give a product magnetite usually containing 15-20% of wustite.
- magnetite powders containing less than 10%, preferably less than 3%, by weight of wustite may be obtained.
- the magnetite base material could of course be obtained from other sources such as synthetic sources.
- the magnetite base preferably consists of at least 70 % of magnetite. Minor amounts i.e. up to 30 % by weight of other compounds, such as hematite, wustite, silicon, metallic iron, phosphorus, aluminia, titanium oxide, or inert inorganic or organic materials may be included in the particulate magnetite base material.
- powders having particles with essentially spherical shape are preferred as such powders have isotropic magnetic properties which are advantageous in many xerographic applications.
- the particle size of the base material used according to the present invention is normally between 15 and 200 ⁇ m. Typical examples of such substantially spherical magnetite base powders which may be used are magnetite powders of the CM series from
- the coating on the particles of the ferromagnetic powder of the present invention should preferably exhibit a number of properties.
- the coating should be insoluble in water and organic solvents.
- the coating should not have a negative influence on powder properties, such as apparent density and flow. This means that the apparent density of the new carrier core powder should preferably vary between about 1 and 4 g/cm 3 and the flow between 20 and 25 s/50g.
- the inorganic insulating coating should completely cover the individual ferrite base particles.
- the coating should be coherent, homogenous and uniform and not contain organic material. An important feature of the coating is that it does not affect the magnetic properties of base powder, from which follows that the magnetic properties of the insulated powder particles are essentially the same as those of the base powder.
- Typical values for magnetic properties of suitable base powders are for saturation ⁇ s, 90-96 emu/g, for remenence, ⁇ r, ⁇ 3 emu/g and for coercivity, H c ⁇ 30 Oe .
- the coating should impart high voltage breakdown as well as other properties to the carrier core materials required for modern xerographic applications.
- the coating might be based on an inorganic compound such as an inorganic oxide, nitride or carbide, acetate.
- an inorganic compound such as an inorganic oxide, nitride or carbide, acetate.
- inorganic compounds manganese dioxide, boron trioxide, tin oxide, silicon dioxide, vanadium oxide, titanium oxide, zirconium dioxide, molybdenum oxide, magnesium oxide, aluminium oxide and yttrium oxide. Any one of these materials or a mixture of two or more of them can be used.
- the inorganic coating is obtained by mixing the magnetite base powder with an aqueous solution of phosphoric acid.
- the amount and concentration of the phosphorus acid is decided by the desired final properties of the insulated powder.
- the amount of coating solution may range between 20 and 80 ml per kg magnetite powder and the thickness may preferably vary within about 0.1 to about 5 ⁇ m.
- the coating solution may include other elements in order to obtain a coating layer which in addition to phosphorus also includes elements such as Ti , Al, Zr, Mg which may be advantageous for certain applications.
- Another preferred coating is obtained when the magnetite powder is treated with magnesium acetate and subsequently heat treated (300-700°C) .
- insulated particles having very high voltage breakdown values such as up to 1000 V or even higher may be obtained whereas values below about 500 V are less important for modern printing technology. For some applications, however, voltage breakdown values as low as 300 V are of interest.
- the resistivity of the insulated particles preferably varies between about 10 8 and 10 10 .
- EP 955567 discloses surface modified magnetite particles. According to this patent publication the particles having an average particle diameter of about 0.02-0.5 ⁇ m are covered with a first layer of hydrated aluminna or alumina sol and the surface of the first layer is coverd with a second layer of silica particles. The particles are useful as toners.
- the US patent 4 925 762 discloses carriers for a two-component dry developer are based on a ferrite or iron-containing core which carries a metal oxide layer consisting of reaction products deposited in the gas phase. Specifically disclosed are layers of iron oxide and titanium dioxide on particles of ferrite or iron.
- carriers for electrophotography are based on magnetic cores coated with a first layer A) of different metal oxides, which essentially consists of electrically insulating metal oxide and a second layer B) which essentially consists of metal oxide controlling the electrostatic charging of the toner and which does not substantially decrease the electroresistance of the carriers, which resistance is provided by the layer (A) .
- the cores may consist of e.g. iron, steel, magnetite, ferrite, cobalt or nickel. Titanium dioxide, alumina, iron oxide and especially silica, as well as mixtures thereof, are particularly suitable for the first, electrically insulating metal oxide layer (A) .
- the insulated carrier core particles according to the present invention are subsequently coated with a thin resinous layer in order to produce a carrier material.
- This layer is needed e.g. in order to adjust the tribo and increase life.
- the amount of this organic or resinous layer is normally between about 1.5 to 6% by weight of the carrier core.
- the base material in the following examples is CM 70, a spherical magnetite with a mean particle size of 70 ⁇ m available from H ⁇ ganas AB Sweden.
- a coating solution was obtained by dissolving various amounts of ortophosphorous acid in water.
- the coating solutions were thoroughly mixed just before they were added to the magnetite powders in order to avoid segregation.
- the coating solutions were added to the powder with a rate of 25 mg per kg powder for a period of 90 s.
- the obtained mixture was thoroughly mixed while the temperature was maintained between 80 and 90°C.
- the solution was then evaporated leaving the insulated particles as a residue.
- the dried powder was sieved in order to eliminated oversized particles and agglomerates .
- the inorganic coating increases the resistivity of the carrier core material .
- CM 40 base magnetite powder
- This powder was subjected to an oxidation treatment as suggested in the US patent 4663262.
- Sample CM40A Part of the obtained oxidised powder
- Sample CM40B an inorganic coating according to the present invention.
- the resistivity is increased by the oxidation treatment.
- the voltage breakdown is considerably lower than that of the coated powder according to the present invention.
- the electrical properties are considerably improved by using an inorganic coating according to the present invention.
- the voltage breakdown can reach high values which are comparable to those of ferrites .
- An unexpected effect is that the high voltage breakdown properties do not necessary involve high resitivity of the carrier cores.
- High resistivity of the carrier cores is not desired as the amount of toner per carrier is decreased when the resistivity is increased. Additionally the improvements in the electrical properties do not affect other properties such as magnetic properties of the carrier cores.
- the base material used in this example was CM 70. 50 ml of a solution prepared by dissolving 350 mg Mg acetate in 1000 g water were added to 1 kg CM 70 according to a procedure similar to that of advantage 1. The obtained powders, designated Sample A, B and C were heat treated for 30 minutes as follows:
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Developing Agents For Electrophotography (AREA)
Abstract
Description
Claims
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP02773101A EP1430363A1 (en) | 2001-09-28 | 2002-09-26 | Electrophotographic carrier core magnetite powder |
US10/432,242 US20040038144A1 (en) | 2001-09-28 | 2002-09-26 | Electrophotographic carrier core magnetite powder |
JP2003531254A JP2005504345A (en) | 2001-09-28 | 2002-09-26 | Electrophotographic carrier core magnetite powder |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SE0103263-0 | 2001-09-28 | ||
SE0103264A SE0103264D0 (en) | 2001-09-28 | 2001-09-28 | Electrophotographic carrier core ferrite powder |
SE0103263A SE0103263D0 (en) | 2001-09-28 | 2001-09-28 | Electrophotografic carrier core magnetite powder |
SE0103264-8 | 2001-09-28 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2003027771A1 true WO2003027771A1 (en) | 2003-04-03 |
Family
ID=26655559
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/SE2002/001757 WO2003027771A1 (en) | 2001-09-28 | 2002-09-26 | Electrophotographic carrier core magnetite powder |
Country Status (4)
Country | Link |
---|---|
US (1) | US20040038144A1 (en) |
EP (1) | EP1430363A1 (en) |
JP (1) | JP2005504345A (en) |
WO (1) | WO2003027771A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1522902A2 (en) * | 2003-10-10 | 2005-04-13 | Ricoh Company, Ltd. | Carrier for use in devloper for developing latent electrostatic images, developer for use in developing latent electrostatic images, devloper container, image forming apparatus, developing method and process cartridge |
JP2005181944A (en) * | 2003-03-13 | 2005-07-07 | Ricoh Co Ltd | Electrostatic latent image developing carrier, developer, developer container, image forming method, and processing cartridge |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102006023245A1 (en) * | 2006-05-18 | 2007-11-22 | Lanxess Deutschland Gmbh | Oxidation-stable iron oxide pigments, process for their preparation and their use |
JP5517471B2 (en) * | 2008-03-11 | 2014-06-11 | キヤノン株式会社 | Two-component developer |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4925762A (en) * | 1987-08-17 | 1990-05-15 | Basf Aktiengesellschaft | Carrier for reprography and production of this carrier |
US5534378A (en) * | 1994-03-23 | 1996-07-09 | Basf Aktiengesellschaft | Carriers doubly coated with metal oxide and intended for electro-photography |
EP0955567A2 (en) * | 1998-05-07 | 1999-11-10 | Titan Kogyo Kabushiki Kaisha | Surface-modified magnetite particles as well as preparation processes and uses thereof |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6333072B1 (en) * | 1999-12-23 | 2001-12-25 | The United States Of America As Represented By The Department Of Energy | Method of producing adherent metal oxide coatings on metallic surfaces |
US6723481B2 (en) * | 2000-05-17 | 2004-04-20 | Heidelberger Druckmaschinen Ag | Method for using hard magnetic carriers in an electrographic process |
-
2002
- 2002-09-26 JP JP2003531254A patent/JP2005504345A/en not_active Abandoned
- 2002-09-26 WO PCT/SE2002/001757 patent/WO2003027771A1/en not_active Application Discontinuation
- 2002-09-26 US US10/432,242 patent/US20040038144A1/en not_active Abandoned
- 2002-09-26 EP EP02773101A patent/EP1430363A1/en not_active Withdrawn
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4925762A (en) * | 1987-08-17 | 1990-05-15 | Basf Aktiengesellschaft | Carrier for reprography and production of this carrier |
US5534378A (en) * | 1994-03-23 | 1996-07-09 | Basf Aktiengesellschaft | Carriers doubly coated with metal oxide and intended for electro-photography |
EP0955567A2 (en) * | 1998-05-07 | 1999-11-10 | Titan Kogyo Kabushiki Kaisha | Surface-modified magnetite particles as well as preparation processes and uses thereof |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2005181944A (en) * | 2003-03-13 | 2005-07-07 | Ricoh Co Ltd | Electrostatic latent image developing carrier, developer, developer container, image forming method, and processing cartridge |
EP1522902A2 (en) * | 2003-10-10 | 2005-04-13 | Ricoh Company, Ltd. | Carrier for use in devloper for developing latent electrostatic images, developer for use in developing latent electrostatic images, devloper container, image forming apparatus, developing method and process cartridge |
EP1522902A3 (en) * | 2003-10-10 | 2006-04-05 | Ricoh Company, Ltd. | Carrier for use in developer for developing latent electrostatic images, developer for use in developing latent electrostatic images, devloper container, image forming apparatus, developing method and process cartridge |
CN100437363C (en) * | 2003-10-10 | 2008-11-26 | 株式会社理光 | Developer, carrier and container, imaging device, developing method and process cartridge |
Also Published As
Publication number | Publication date |
---|---|
US20040038144A1 (en) | 2004-02-26 |
JP2005504345A (en) | 2005-02-10 |
EP1430363A1 (en) | 2004-06-23 |
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