EP0242712B1 - Matériau de support pour développeurs électrophotographiques - Google Patents

Matériau de support pour développeurs électrophotographiques Download PDF

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Publication number
EP0242712B1
EP0242712B1 EP87105199A EP87105199A EP0242712B1 EP 0242712 B1 EP0242712 B1 EP 0242712B1 EP 87105199 A EP87105199 A EP 87105199A EP 87105199 A EP87105199 A EP 87105199A EP 0242712 B1 EP0242712 B1 EP 0242712B1
Authority
EP
European Patent Office
Prior art keywords
carrier
particles
spherical
magnetite
hematite
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
Application number
EP87105199A
Other languages
German (de)
English (en)
Other versions
EP0242712A2 (fr
EP0242712A3 (en
Inventor
Toshihiko Kohno
Shigeo Yokoe
Kazuyoshi Oka
Ulf Engström
Svenn-Erik Larssen
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.)
Kanto Denka Kogyo Co Ltd
Hoganas AB
Original Assignee
Kanto Denka Kogyo Co Ltd
Hoganas AB
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Kanto Denka Kogyo Co Ltd, Hoganas AB filed Critical Kanto Denka Kogyo Co Ltd
Publication of EP0242712A2 publication Critical patent/EP0242712A2/fr
Publication of EP0242712A3 publication Critical patent/EP0242712A3/en
Application granted granted Critical
Publication of EP0242712B1 publication Critical patent/EP0242712B1/fr
Expired legal-status Critical Current

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

Definitions

  • the invention relates to a carrier material for electrophotographic developers which comprises a substantially spherical core material having a resinous layer coated thereon.
  • the electrostatic image formed on the photoconductor is developed by the magnetic brush method using either a so called “one-component” developer or a “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 should fullfil the following criteria:
  • the carrier should 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 should have a sufficient mechanical strength to protect the carrier particles from breaking or cracking.
  • the carrier particles should exhibit a good fluidity to facilitate their transfer on the sleeve of the magnetic roll in the printing machine and also to facilitate their mixing with the toner.
  • the carrier particles should be uniform in their electric and magnetic properties.
  • the carrier should be stable with respect to changes in the environmental conditions such as temperature and, in particular, humidity.
  • the carrier particles should have a sufficient durability to ensure an acceptable lifetime.
  • carriers have been selected from a variety of materials.
  • An example which has been most widely used is an iron (metallic) powder of irregular particulate form or shape.
  • the magnetic brush i.e. a tuft of filaments comprising the carrier particles having the toner particles theron, each of the filaments being generally formed with the carrier particles chained together in one length by the magnetic forces generated by and transferred from the magnetoroll, and each filament standing on end from the surface of the sleeve of the magnetoroll
  • This phenomenon may be often observed where the iron powder carrier is of a flat and irregular particulate shape.
  • a carrier comprising an iron powder of a spherical particulate shape. Since the iron particles are spherical and, thus, isotropic, the disadvantages which are caused by the anisotropy of the carrier comprising the irregularly shaped iron powder are significantly reduced by use of the spherical iron carrier.
  • the magnetic brushes formed therefrom are remarkedly short and dense. Accordingly, the developing torque required is also reduced.
  • this spherical iron powder is not completely satisfactory; since the carrier again comprises metallic iron and has a relatively high specific gravity and hence a relatively large apparent density (usually greater than 4.0 g/cm3), the particles tend to jump or fly away and to cause difficulties in the process and machine. To prevent the escape of the particles, it is necessary to adopt a special and complicated design for the magnetoroll and related parts of the copying machine. Further, the heavy iron carrier may give rise to a high stress on the toner particles when admixed together and may adversely affect the working life of the developer. With this type of carrier, although it is possible to develop a relatively high quality of copies having an improved gradient, the copies generally tend to have a relatively low degree of chromic density. This undesirable tendency has been reduced or removed by appropriate modifications of the machine or by regulation thereof, for example, by increasing the electrostatic potential charged on the surface of the photoconductor.
  • ferrite an oxidic ferromagnetic material
  • the ferrite carrier has a saturation magnetization (about 40-70 emu/g) lower than that of iron powder (about 200 emu/g)
  • the magnetic brush formed from the former is soft and thus fine copies of an improved gradient may be developed therewith.
  • the ferrite carrier is advantageous in that the stress exerted on the toner particles is significantly reduced and consequently the durability of developer is prolonged, since the ferrite carrier has a specific gravity lower than that of metallic iron. The developing torque required is also reduced.
  • the ferrite carrier is used only within a limited range of application, because the electrical resistivity of ferrite is rather high. Further the ferrite material is relatively sensitive to environmental conditions so that the performance of the ferrite carrier tends to be significantly influenced by such changes in the environmetal conditions as humidity variations and the resulting copy quality tends th change over the period of operation in which the ferrite carrier is used.
  • the ferrite carrier particles be provided with a resinous coating layer, although this further increases the undesirably high electrical resistivity of the material, resulting in a further limitation of the application range and additional production costs.
  • a carrier material for electrophotographic developers which comprises a substantially spherical core particle consisting of hematite - containing magnetite.
  • This carrier is manufactured by a specific process, namely by suspending iron powder in flames in the air, rapidly oxidizing it, melting it into grains, and further oxidizing the iron oxide grains at ⁇ 700°C.
  • a carrier small in density and mechanical load to be exerted on other materials and restraining a toner from attaching to it namely a hollow or porous fine spherical carrier composed essentially of magnetite and partially containing ⁇ -hematite and having a specified apparent density of 0,5 ⁇ 3,5 g/cc.
  • US-A- 4 076 640 discloses a method of manufacturing spheroidized beads used as electrostatographic carrier particles.
  • the carrier is manufactured by introducing magnetic ore particles to a plasma flame heating device in the presence of at least one gas, melting and spheroidizing the ore particles in a closed chamber having a controlled atmosphere wherein the ore droplets are allowed to fall by gravity and cool, and collecting the droplets.
  • the spheroidized carriers thus manufactured possess smooth outer surfaces which are highly resistant to cracking, chipping and flaking, and its spherical surface enhances the triboelectric action of the carrier particles across the electrostatographic surfaces and reduces the tendency of the carrier particles to adhere to electrostatographic imaging surfaces.
  • the magnetic ore particles typically can include magnetite, hematite, taconite, ilmenite, and the like.
  • the carrier particles may be coated with any suitable coating material which can be a resinous material. The coating increases the durability and toner impaction resistance and should preferably comprise from about 0,1 to 1,0 percent by weight based on the weight of the coated carrier particles.
  • An object of the present invention is to provide a novel carrier material with which the problems associated with the known carriers are obviated or substantially removed.
  • Another object of the invention is to provide methods for preparing this novel carrier.
  • a further object of the invention is to provide a novel carrier which is effective in producing electrophotographic copies of excellent quality, is stable irrespective of changes in environmental conditions, and has increased durability.
  • the present invention provides a carrier material for electrophotographic developers which has a saturation magnetization of 40-80 emu/g and which comprises a substantially spherical core particle consisting of hematite-containing magnetite and having a resinous layer coated thereon in an amount of 1,5 to 6 % by weight.
  • the hematite-containing magnetite has a lower electrical resistivity than ferrite. This low resistivity provides a wide room for increasing the resistivity over a wide range by coating the material with a resinous insulating material. Therefore, it is possible to accommodate the resistivity to various types of copying machines and processes requiring different optimal levels of resistivity with respect to the carrier material.
  • the spherical shape of the carrier particles provides the carrier with a desirable fluidity.
  • the present carrier material has a specific gravity lower than iron and an apparent density comparable with that of the ferrite carrier. Therefore, with the present carrier, a relatively low level of developing torque is required in the machine and a satisfactory developer working life is provided.
  • the present carrier material has a saturation magnetization ( ⁇ s ) within the range of 40 - 80 emu/g similar to that of ferrite and will form a soft and dense magnetic brush resulting in development of a high quality copy.
  • the relatively low saturation magnetization will reduce the torque required for cutting the top of the brush during conveyance of the developer on the magnetic roll and, thus, will contribute to extend the durability of the material.
  • hematite-containing magnetite particles which may be used in the present invention may be prepared, for example, in the following manners:
  • the saturation magnetization may be determined in a magnetometer, for example a sample-vibrating type Magnetometer VSMP-1 (ex. Toei Kogyo Co., Japan). It has been found that the present product exhibits maximum saturation magnetization in a magnetic field of about 14.5 KOe.
  • ⁇ s of the particles is less than 40 emu/g, it is difficult to prepare the particles in a homogeneous state. In other words, though it is possible to prepare carrier particles having a value of ⁇ s as low as about 30 emu/g, the respective particles are not equal to each other in their magnetic properties. On the other hand, if the particles have a ⁇ s exceeding 80 emu/g, they tend to form an undesirably hard brush on the magnetic roll. In the both cases, the particles are not suitable for the purpose of the invention.
  • the size of the spherical core particles is in the range of about 30 - 200 ⁇ m.
  • the spherical core particles having the preferred ranges of the physical properties may be coated by an appropriate resinous material.
  • the resinous material may be applied to the core particles as a solution in an organic solvent, such as methyl ethyl ketone, xylene, n-butanol, methyl cyclohexane or toluene.
  • the resinous solution may be applied to the core particles, for example, by dipping the particles in the solution or spraying the solution over a fluidized mass of the core particles.
  • a thermosetting resin is employed, the coated particles are subjected to a suitable heat treatment to give the resin-coated carrier material. Any resin may be used in the preparation of the carrier material of the present invention provided that it is effectively soluble in the common solvents.
  • the amount of the resinous material to be applied to the core material is governed by the nature of the resin employed and the type of copying machine (and hence the electrostatic and electrical resistivity properties suitable for the particle machine) far which the product carrier is to be supplied. For this reason, the amount of resin suitable for the purpose of the invention is in the range of 1,5 - 6 % by weight.
  • the resin-coated carrier material according to the present invention may be used in conjunction with conventional toners such as those, for example, made from a natural resin, a synthetic resin, a blend of natural and synthetic resins or such a material modified by incorporation of any appropriate additives.
  • hematite powder To 100 parts of magnetite powder, 30 parts of hematite powder was added (by weight). The mixture charged into a wet attrition mill and mixed thoroughly to give a homogeneous aqueous slurry. Then the slurry was dried in a spray-drier to form spherical granules of 30 - 150 ⁇ m in diameter. The granules were calcined at about 1200° C for about 2 hours in a nitrogen atmosphere and allowed to cool. The calcined mass was lightly ground and classified to give a fraction of 75 - 150 ⁇ m in diameter.
  • the thus prepared spherical particles containing magnetite and hematite exhibited a saturation magnetization ( ⁇ s ) of 60 emu/g.
  • the carrier was mingled with a commercially available toner for magnetic brush development (a negatively chargeable toner adapted for use in "Xerox 3870" machine).
  • the thus obtained developer was used for developing an electrostatic latent image formed on a selenium photoconductive surface to obtain a high quality copy showing an excellent reproducibility in the intermediate tone range. It was found that the initial copy quality was substantially maintained even after reproduction of 60,000 copies.
  • aqueous slurry of magnetite powder was spray-dried in a spray drier to give spherical particles of 30 - 150 ⁇ m in diameter. After about 2 hours of calcination at about 1200°C in a nitrogen atmosphere, the product was cooled, lightly ground and classified to give a fraction of 75 - 150 ⁇ m in diameter.
  • the spherical magnetite particles were heat treated at 300°C in a rotary kiln for 3 hours in air.
  • Spherical hematite-containing magnetite particles formed by partial oxidation of the magnetite.
  • the obtained spherical hematite-containing magnetite particles had a saturation magnetization of 45 emu/g.
  • Example 2 To 10 kg of the spherical powder, 1 kg of the same resin solution as in Example 1 was spray coated to give a carrier powder according to the invention.
  • Example 2 In the same manner as in Example 1, a developer was prepared. Using this developer, an electrostatic latent image on a selenium photoconductive surface was developed, with a high quality copy of a good intermediate tone. No substantial changes were seen in the copy quality after as many as 60,000 times of development.
  • An aqueous slurry of magnetite powder was spray-dried in a spray drier to give spherical particles of 30 - 150 ⁇ m in diameter. After about 2 hours of calcination at about 1200°C in an nitrogen atmosphere, the product was cooled, lightly ground and classified to give a powder of 75 - 150 ⁇ m in diameter.
  • the resulting spherical magnetite particles had a saturation magnetization of 86 emu/g.
  • the powder was coated in the similar manner to that in Example 1.
  • the resulting carrier powder was used to prepare a developer in the same manner as in Example 1.
  • the developer was subjected to the copying test as described in Example 1.
  • the resulting copy showed a high contrast with a poor intermediate tone.
  • the results were poor than those of Examples 1 and 2.
  • An aqueous slurry of magnetite powder was spray-dried in a spray drier to give spherical particles of 30 - 150 ⁇ m in diameter. After about 2 hours of calcination at about 1200°C in a nitrogen atmosphere, the product was cooled, lightly ground and classified to give a powder of 40 - 75 ⁇ m in diameter.
  • the spherical magnetite particles were heat treated at 800°C in a rotary kiln for 2.5 hours in air to give spherical particles of hematite-containing magnetite.
  • the obtained spherical particles of hematite-containing magnetite had a saturation magnetization of 35 emu/g.
  • the spherical particle powder of hematite-containing magnetite (10 kg) was coated with 1.5 kg of a solution of acryl resin ("BR83" produced by Mitsubishi Rayon Co., Ltd.) in toluene (resin content: 6%) by spraying technique.
  • a solution of acryl resin ("BR83" produced by Mitsubishi Rayon Co., Ltd.) in toluene (resin content: 6%)
  • the thus-obtained carrier powder was mixed with a toner for magnetic brush development (negatively-chargeable toner, "BD8811” produced by Toshiba Electric Co., Ltd.) to prepare a developer, with which an electric latent image on a selenium photosensitive member was developed. An accidental carrier deposition on the photoconductive surface occurred. With such an accident, the carrier could not be put into practical use.
  • a toner for magnetic brush development negatively-chargeable toner, "BD8811” produced by Toshiba Electric Co., Ltd.
  • the carrier material produced in this comparative example exhibited a saturation magnetization in the range of as low as 15 - 25 emu/g.
  • An aqueous slurry of magnetite powder was spray-dried in a spray drier to give spherical particles of 30 - 150 ⁇ m in diameter. After about 2 hours of calcination at about 1200°C in a nitrogen atmosphere, the product was cooled, lightly ground and classified to give a powder of 40 - 75 ⁇ m in diameter.
  • the spherical magnetite particles were heat treated at 400°C for 30 minutes to give spherical particles of hematite-containing magnetite.
  • the obtained spherical particles of hematite-containing magnetite had a saturation magnetization of 73 emu/g.
  • the spherical particle powder magnetite (10 kg) was coated with 2.5 kg of a solution of acryl resin ("BR83" produced by Mitsubishi Rayon Co., Ltd.) in toluene (resin content: 6%) by spraying technique.
  • a solution of acryl resin ("BR83" produced by Mitsubishi Rayon Co., Ltd.) in toluene (resin content: 6%)
  • the thus-obtained carrier powder was mixed with a toner for magnetic brush development (negatively-chargeable toner, "BD8811” produced by Toshiba Electric Co., Ltd.) to prepare a developer, with which an electric latent image on a selenium photosensitive member was developed. An high quality copy with a relatively good intermediate tone was reproduced.
  • a toner for magnetic brush development negatively-chargeable toner, "BD8811” produced by Toshiba Electric Co., Ltd.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Developing Agents For Electrophotography (AREA)

Claims (6)

  1. Matériau de support pour développeur électrophotographiques qui a une magnétisation de saturation de 40-80 emu/g et qui comprend une particule formant noyau sensiblement sphérique consistant en magnétite contenant de l'hématite et ayant une couche résineuse qui y est enduite en une quantité de 1,5 à 6 % en poids.
  2. Matériau de support selon la revendication 1, qui a une taille de particule comprise entre 30 et 200 µm.
  3. Méthode de préparation du matériau de support selon l'une quelconque des revendications précédentes qui comprend les étapes de:
    produire les particules formant âme comprenant de la magnétite contenant de l'hématite et qui sont sensiblement sphériques; et
    enduire les particules sphériques formant âme d'un matériau résineux.
  4. Méthode selon la revendication 3, caractérisée en ce que les particules formant âme sont formées d'un mélange intime de magnétite et d'hématite en poudre.
  5. Méthode selon la revendication 3, caractérisée en ce que les particules formant âme sont préparées par l'oxydation partielle de particules sphériques de magnétite.
  6. Développeur électrophotographique comprenant une poudre d'un toner et d'un matériau de support selon l'une quelconque des revendications 1 et 2.
EP87105199A 1986-04-09 1987-04-08 Matériau de support pour développeurs électrophotographiques Expired EP0242712B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP81867/86 1986-04-09
JP61081867A JPS62238580A (ja) 1986-04-09 1986-04-09 電子写真現像剤用キヤリア

Publications (3)

Publication Number Publication Date
EP0242712A2 EP0242712A2 (fr) 1987-10-28
EP0242712A3 EP0242712A3 (en) 1988-02-10
EP0242712B1 true EP0242712B1 (fr) 1992-07-22

Family

ID=13758418

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87105199A Expired EP0242712B1 (fr) 1986-04-09 1987-04-08 Matériau de support pour développeurs électrophotographiques

Country Status (4)

Country Link
EP (1) EP0242712B1 (fr)
JP (1) JPS62238580A (fr)
CA (1) CA1340150C (fr)
DE (1) DE3780500T2 (fr)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2703917B2 (ja) * 1988-03-03 1998-01-26 キヤノン株式会社 二成分系現像剤及び画像形成方法
JP2667904B2 (ja) * 1989-05-19 1997-10-27 株式会社日立製作所 電子写真装置
TW251373B (fr) * 1993-05-20 1995-07-11 Fujidenki Kagaku Kk
US5538656A (en) * 1993-08-31 1996-07-23 Fuji Electrochemical Co., Ltd. Magnetic oxide and process for producing same
WO2004088680A2 (fr) * 2003-03-31 2004-10-14 Kanto Denka Kogyo Co. Ltd. Ferrite a base de mg, vehicule de developpement electrophotographique contenant cette ferrite et revelateur contenant ce vehicule

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4076640A (en) * 1975-02-24 1978-02-28 Xerox Corporation Preparation of spheroidized particles
JPS60458A (ja) * 1983-06-09 1985-01-05 Kanto Denka Kogyo Kk 電子写真用キヤリア−
JPS6045262A (ja) * 1983-08-22 1985-03-11 Shintou Bureetaa Kk 電子写真現像用キヤリア材およびその製造法
JPS60144758A (ja) * 1983-12-31 1985-07-31 Dowa Teppun Kogyo Kk 電子写真現像用キヤリヤおよびその製造法
JPS6120054A (ja) * 1984-07-06 1986-01-28 Shintou Bureetaa Kk 電子写真現像用キヤリア

Also Published As

Publication number Publication date
JPS62238580A (ja) 1987-10-19
DE3780500T2 (de) 1993-02-25
CA1340150C (fr) 1998-12-01
EP0242712A2 (fr) 1987-10-28
EP0242712A3 (en) 1988-02-10
DE3780500D1 (de) 1992-08-27

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