EP0693191B1 - Lithium ferrite carrier - Google Patents

Lithium ferrite carrier Download PDF

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Publication number
EP0693191B1
EP0693191B1 EP94913384A EP94913384A EP0693191B1 EP 0693191 B1 EP0693191 B1 EP 0693191B1 EP 94913384 A EP94913384 A EP 94913384A EP 94913384 A EP94913384 A EP 94913384A EP 0693191 B1 EP0693191 B1 EP 0693191B1
Authority
EP
European Patent Office
Prior art keywords
carrier
ferrite
lithium
powder
carriers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP94913384A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0693191A1 (en
Inventor
Alan Sukovich
William R. Hutcheson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Powdertech Corp
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Powdertech Corp
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Publication date
Application filed by Powdertech Corp filed Critical Powdertech Corp
Publication of EP0693191A1 publication Critical patent/EP0693191A1/en
Application granted granted Critical
Publication of EP0693191B1 publication Critical patent/EP0693191B1/en
Anticipated expiration legal-status Critical
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    • 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
    • G03G9/1085—Ferrite carrier, e.g. magnetite with non-ferrous metal oxide, e.g. MgO-Fe2O3
    • 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

Definitions

  • the present invention relates to a magnetic carrier for use with electrophotographic development equipment and, more particularly, to an environmentally benign lithium ferrite carrier having a non-stoichiometric composition.
  • Carriers in the form of powder are used to transfer toner particles in electrophotographic development equipment, for example, in photocopying machines and most recently in laser printers.
  • such carriers are ferrites or ferrite powders in combination with various metals, for example, nickel, zinc, or copper.
  • Numerous patents have issued directed to various ferrite carrier compositions including the following: limura et al., U.S. Patent No. 4,623,603; Honjo et al., U.S. Patent No. 4,598,034; Tachibana et al., U.S. Patent No. 4,898,801, Imamura et al., U.S. Patent No. 4,485,162; and Jones, U.S. Patent No. 3,929,657.
  • Patent Abstracts of Japan, vol 8, no. 257 (P-316) (1694) also describes an electrophotographic lithium type ferrite carrier having a spinel crystalline structure and being resin coated. This abstract teaches a stoichiometric composition.
  • the present invention comprises an electrophotographic ferrite powder carrier comprising a non-stoichiometric lithium ferrite powder having a spinel crystalline structure and a compositional range represented by the formula: [(Li 2 O) .25 (Fe 2 O 3 ) .25 ] x (Fe 2 O 3 ) 1.00-x where 0.35 ⁇ x ⁇ 0.50 mole fraction.
  • the carrier may be formed in a generally spherical shaped magnetic core configuration for use in pre-existing conventional electrophotographic equipment.
  • Yet another object of the invention is to provide an electrophotographic carrier which is a non-stoichiometric lithium ferrite compound.
  • a further object of the invention is to provide a lithium ferrite powder for use as a carrier having a form and being in a condition for use with electrophotographic equipment already in service.
  • Another object of the invention is to provide an electrophotographic development carrier comprised of lithium ferrites having a range of composition.
  • Yet a further object of the invention is to provide a method for manufacture of a lithium ferrite carrier having a spinel crystalline structure and which is useful in electro- photographic processes.
  • the present invention comprises a generally spherical shaped, magnetic carrier core powder which may be used for magnetic brush development in copy machines and laser printers.
  • magnetic carriers such as ferrites are used to transfer toner particles from a developer mix onto a photoreceptor. The particles are then transferred by the photoreceptor onto plain paper.
  • the ferrite carrier powders are typically in the form of spherical beads or powder which may or may not be coated with resin. Also typically the ferrites are combined with various metal oxides which enhance the utility of the carrier powder.
  • the present invention is a magnetic ferrite carrier powder which does not contain elements considered potentially hazardous such as nickel, copper, zinc and barium.
  • the present invention comprises a generally non-stoichiometric lithium ferrite.
  • Stoichiometric lithium ferrite composition may be represented by the following formulation: (Li 2 O) .25 (Fe 2 O 3 ) .25 Fe 2 O 3
  • Other ways of representing the stoichiometric formulation of the lithium ferrite composition include the following:
  • compositional range which is preferred or which is specified as comprising the present invention is represented by the following generally non-stoichiometric relationship: [(Li 2 O) .25 (Fe 2 O 3 ) .25 ] x (Fe 2 O 3 ) 1.00-x where .35 ⁇ x ⁇ .50 mole percent.
  • this composition range is represented by the cross-hatched portion of the ferrite/lithium ferrite phase diagram.
  • the desired formulation of such a lithium ferrite powder material which constitutes a carrier has a spinel structure, is environmentally safe, and has the necessary characteristics to serve as an excellent carrier.
  • the composition is prepared by the following sequential steps:
  • the present invention produces carriers with a variety of magnetic properties which may be used in different applications of magnetic brush development.
  • the following is a table which sets forth the range of magnetic saturation as it correlates with the composition.
  • Mole Composition Magnetic Saturation EMU/g (4000 Oe drive field) [(Li 2 O) .25 (Fe 2 O 3 ) .25 ] .50 (Fe 2 O 3 ) .50 or (Li 2 O) .167 (Fe 2 O 3 ) .833 61.4 [(Li 2 O) .25 (Fe 2 O 3 ) .25 ] .46 (Fe 2 O 3 ) .54 or (Li 2 O) .149 (Fe 2 O 3 ) .851 60.6 [(Li 2 O) .25 (Fe 2 O 3 ) .25 ] .42 (Fe 2 O 3 ) .58 or (Li 2 O) .133 (Fe 2 O 3 ) .867 44.4 [(
  • lithium oxide ferrite carrier of the present invention is set forth below, and a comparison thereof to typical commercially produced CuZn and NiZn ferrite materials.
  • the carrier compositions are within the mole percentage range set forth in Figure 1 for the lithium oxide ferrite mixtures.
  • the example carriers are thus of the nature and have a crystalline structure which is principally a spinel structure.
  • Example No. 1 - Lithium ferrite according to the formulation (Li 2 O) .1521 (Fe 2 O 3 ) .8479 was prepared. Specifically, batch mixtures of 45.4 kg (100 pounds) including 7.67% by weight lithium carbonate and 92.33% by weight iron oxide were mixed.
  • the batches were intensively dry mixed in an Eirich R-7 mixer/pelletizer. After pelletization, 7.6 l (two (2) gallons) of water was added to minimize dusting and promote pelletization of the raw oxides and carbonates. The pellets were oven dried and calcined in a batch electric kiln for four (4) hours at 1010°C.
  • Calcined pellets were charged to a batch type steel ball grinding mill and milled six (6) hours, with the following additives: 181.4 kg (400 lbs.) Calcinate 68.1 l (18 gallons) Water 0.91 kg (2 lbs.) Wetting Agent (Dispex A-40 by Allied Colloids) 0.91 kg (2 lbs.) SiO 2 (Syloid 244 by WR Grace)
  • Spray dried powder or beads resulting therefrom was classified using a 48" diameter Sweco brand vibratory separator with the acceptable mesh fraction being - 120 TBC Mesh, + 200 TBC Mesh (-149 ⁇ + 88 ⁇ ).
  • the resulting product was sintered at about 1165°C for seven (7) hours in an air atmosphere in an electric fired batch kiln. Refractory boots were used to contain the powder during sintering.
  • Example No. 2 - Lithium ferrite according to the formulation (Li 2 O) .145 (Fe 2 O 3 ) 0.855 was produced using processing similar to that in Example No. 1.
  • the resulting test properties are listed in Table 3.
  • Figures 4 and 5 depict the physical appearance of the carrier in SEM photomicrographs at 50 and 200 magnifications. These core elements are generally spherical and uniform in shape.
  • Example No. 3 Copper zinc ferrite of the formulation (CuO) 0.20 (ZnO) 0.11 (Fe 2 O 3 ) 0.69 was produced using processing like that of Example No. 1 with the exception that the calcine temperature was 790°C and final sintering temperature was 1300°C. Measured test properties are listed in Table 3. Figures 6 and 7 are SEM photomicrographs of the described prior art carrier and is offered for purposes of comparison to the carrier of Example No. 1 and No. 2. The size, shape and appearance is very similar to to the lithium ferrite carriers.
  • Example No. 4 Copper zinc ferrite of the formulation (CuO) 0.20 (ZnO) 0.25 (Fe 2 O 3 ) 0.55 was prepared using similar processing as in Example No. 1 with the exception that the calcining temperature was 790°C and the final sintering temperature was 1160°C. Measured test properties are also listed in Table 3. Figures 8 and 9 are SEM photomicrographs of another prior art formulation for a carrier and for purposes of comparison should be evaluated in relation to Figures 2, 3, 4 and 5. Again the comparison is one of high similarity.
  • Example No. 5 Nickel zinc ferrite of the formulation (NiO) .1563 (ZnO) .3220 (MnO) .0263 (CUO) .0160 (Fe 2 O 3 ) .4793 was prepared using similar processing as set forth in Example No. 1 with the exception that the atomization occurred in a rotary atomization dryer and firing occurring at 1290°C.
  • Figures 10 and 11 are SEM photomicrographs of this formulation and may be compared with the carriers of Figures 2, 3, 4 and 5. Measured test properties are listed in Table 3.
  • a ferrite carrier core material composition preferably has several attributes to permit its use as a reprographic or electrographic carrier core material. For example, it should have the ability to adjust magnetic moment, Ms, similar to the carriers of Examples No. 3 and No. 4. This permits utilization in various copy machine designs.
  • the described nonstoichiometric lithium ferrite carrier permits similar variations as set forth in Table 1 and for Examples No. 1 and No. 2.
  • Bulk densities should be similar to the existing ferrite core materials.
  • the lithium ferrite carriers of the invention have a bulk density very similar to that of existing ferrite core materials. Also, by changing sintering temperatures and soak time at temperature, bulk density may be varied higher or lower depending on the desired value.
  • Flow rate determines the flow characteristics of a material in a copy machine magnetic brush developer station.
  • the lithium ferrite composition of the invention has very similar flow characteristics to that of pre-existing ferrite carriers.
  • carrier core materials it is common for most carrier core materials to have either an acrylic, silicone, or fluoropolymer coating deposited on the carrier core surface to modify or enhance triboelectric or resistive properties for use with specific toners.
  • a new ferrite composition to comprise an acceptable substitute for existing coating technologies, it is important for surface texture, as measured by BET surface area and visual observation by scanning electron microscopy, to show similar properties. Scanning electron microscopy analysis of Examples No. 1 through No. 5 demonstrates that the lithium ferrite carrier core of the invention is virtually indistinguishable from CuZn ferrite carrier core material and is similar to NiZn carrier core material. Comparison of BET surface area also shows very similar values. Also, BET surface texture may be modified by adjustment of soak time, temperature, and processing conditions used to formulate the carrier core.
  • Section 66699 of the State of California Administrative Code, Title 22, Division 4 lists offending elements that are (per soluble threshold limit concentration (STLC) and total threshold limit concentration (TTLC) limits) classified as a hazardous waste.
  • STLC per soluble threshold limit concentration
  • TTLC total threshold limit concentration
  • lithium ferrite materials which have a range of non-stoichiometric compositions and a spinel structure are deemed to be materials which are environmentally safe. That is, such materials can be utilized safely to provide a magnetic brush for the carrying of toner particles, and when the material is expended or no longer useful, it can be easily disposed without constituting an environmental hazard.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Developing Agents For Electrophotography (AREA)
  • Compounds Of Iron (AREA)
  • Soft Magnetic Materials (AREA)
EP94913384A 1993-04-09 1994-04-07 Lithium ferrite carrier Expired - Lifetime EP0693191B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US4537993A 1993-04-09 1993-04-09
PCT/US1994/003843 WO1994024613A1 (en) 1993-04-09 1994-04-07 Lithium ferrite carrier
US45379 1998-03-19

Publications (2)

Publication Number Publication Date
EP0693191A1 EP0693191A1 (en) 1996-01-24
EP0693191B1 true EP0693191B1 (en) 1999-07-28

Family

ID=21937552

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94913384A Expired - Lifetime EP0693191B1 (en) 1993-04-09 1994-04-07 Lithium ferrite carrier

Country Status (7)

Country Link
EP (1) EP0693191B1 (ko)
JP (1) JP3429312B2 (ko)
KR (1) KR960702123A (ko)
CA (1) CA2160138A1 (ko)
DE (1) DE69419742T2 (ko)
TW (1) TW349187B (ko)
WO (1) WO1994024613A1 (ko)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5798198A (en) * 1993-04-09 1998-08-25 Powdertech Corporation Non-stoichiometric lithium ferrite carrier

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5948774A (ja) * 1982-09-13 1984-03-21 Nippon Teppun Kk 電子写真現像用キヤリヤ
JPS59127054A (ja) * 1983-01-11 1984-07-21 Hitachi Metals Ltd 電子写真用現像剤
JPH0648397B2 (ja) * 1985-03-01 1994-06-22 三井金属鉱業株式会社 電子写真現像用キヤリヤ
US5104761A (en) * 1990-09-14 1992-04-14 Eastman Kodak Company Interdispersed three-phase ferrite composite and electrographic magnetic carrier particles therefrom

Also Published As

Publication number Publication date
EP0693191A1 (en) 1996-01-24
JPH08511108A (ja) 1996-11-19
WO1994024613A1 (en) 1994-10-27
DE69419742T2 (de) 1999-12-02
CA2160138A1 (en) 1994-10-27
TW349187B (en) 1999-01-01
DE69419742D1 (de) 1999-09-02
JP3429312B2 (ja) 2003-07-22
KR960702123A (ko) 1996-03-28

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