EP0552785A2 - Procédé de formation d'images fixeés - Google Patents

Procédé de formation d'images fixeés Download PDF

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Publication number
EP0552785A2
EP0552785A2 EP93100934A EP93100934A EP0552785A2 EP 0552785 A2 EP0552785 A2 EP 0552785A2 EP 93100934 A EP93100934 A EP 93100934A EP 93100934 A EP93100934 A EP 93100934A EP 0552785 A2 EP0552785 A2 EP 0552785A2
Authority
EP
European Patent Office
Prior art keywords
fixing
roller
elastomer layer
toner
conductive elastomer
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.)
Withdrawn
Application number
EP93100934A
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German (de)
English (en)
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EP0552785A3 (en
Inventor
Shin-Ichiro Yasuda
Kuniyasu Kawabe
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Kao Corp
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Kao Corp
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Filing date
Publication date
Application filed by Kao Corp filed Critical Kao Corp
Publication of EP0552785A2 publication Critical patent/EP0552785A2/fr
Publication of EP0552785A3 publication Critical patent/EP0552785A3/en
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/20—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat
    • G03G15/2003—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat
    • G03G15/2014—Apparatus for electrographic processes using a charge pattern for fixing, e.g. by using heat using heat using contact heat
    • G03G15/2053—Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating
    • 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
    • G03G13/20—Fixing, e.g. by using heat
    • 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
    • G03G9/093—Encapsulated toner particles
    • G03G9/09307—Encapsulated toner particles specified by the shell material
    • G03G9/09314—Macromolecular compounds
    • G03G9/09328—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds

Definitions

  • the present invention relates to a method for forming fixed images used for plain paper copying machines, laser printers, plain paper facsimiles, etc.
  • a cleaning device is provided for cleaning the residual toner after the transfer process with its rotation.
  • the temperature of the heating element of the fixing apparatus has to remain at a very high level (usually around 200°C) and further a high pressure is required (usually between 2.0 and 6.0 kg/cm).
  • Japanese Patent Laid-Open No. 159174/1984 Japanese Patent Laid-Open No. 159174/1984.
  • the fixing temperature is low, the nip pressure has to be elevated normally to not less than 4 kg/cm in this method, making the machine heavier.
  • it poses problems in the gloss of the images, deformation of the paper copy sheets and an insufficient fixing strength.
  • some attempts for enabling quick printings and fixing with conserved energy by using heating sheets in place of the conventionally used quartz heaters, nichrome wires, etc. as heat sources for the heat rollers in thermally fixing apparatuses have been known (Japanese Patent Laid-Open Nos. 196562/1983, 150183/1989 and 260475/1989).
  • the fixing temperature is set at such a high temperature of about 200°C
  • the heating element is inserted in a cylinder in order to avoid temperature unevenness, thereby delaying the rate of the temperature rise and making the energy efficiency of the fixing apparatus poor.
  • the relation between a radius of the elastic material roller and a nip width are such that the radius of the roller is from about 15 mm to at most 50 mm, and that the nip width thereof is from about 3 mm to at most 10 mm. Therefore, since the ratio of the nip width to the radius of the elastic material roller is usually from 0.05 to at most 0.20, those expensive elastic materials whose compression set at a temperature of 180°C to 200°C are extremely small have been used.
  • the reasons for using elastic materials having such properties are as follows:
  • the toner is usually fixed at a surface temperature of the heat roller of close to 200°C, and a high nip pressure is applied thereto, so that the toner can be melted and adhered onto a recording paper, etc.
  • the nip width is kept wide so that the time for heat conduction from the heat roller to the toner can be kept long.
  • An object of the present invention is to provide a method for forming fixed images using a thermally dissociating encapsulated toner.
  • Another object of the present invention is to provide a method for forming fixed images using an encapsulated toner whose shell is made of amorphous polyester.
  • a heat roller-type fixing apparatus for forming fixed images is used at a temperature of not more than 130°C, the apparatus comprising a heat roller, a pressure roller and a current supplying means, the rollers rotating in contact with each other to thermally fix a visible image onto the recording medium at the contacted surfaces, wherein a conductive elastomer layer is formed in a uniform thickness on a cylinder of the heat roller, and the electric current is passed into the layer by the current supplying means.
  • the present invention essentially relates to a method for forming fixed images using the above fixing apparatus.
  • a method for forming fixed images formed by the encapsulated toner in the present invention using a heat roller-type fixing apparatus comprises the steps of passing a current into a conductive elastomer layer formed in a uniform thickness on a cylinder of the heat roller; and thermally fixing the toner by heat generated thereby at a temperature of not more than 130°C.
  • Element 1 is a photoconductive drum, element 2 a charger, element 3 an exposure device, element 4 a developer device, element 5 a transfer device, element 6 a toner, element 7 a recording medium (a recording paper), element 8 a heat roller, element 9 a pressure roller, element 10 a radiator device, element 11 a cleaner device, element 12 an insulating layer, element 13 a heating layer, element 14 a developer sleeve, element 21 an elastic heating element, element 22 a conductive layer, element 23 a releasing layer, element 31 an elastic heating element, element 32 a releasing layer, element 41 an elastic heating element, element A a rotating shaft and element B a rotating shaft.
  • FIG. 1 is a schematic view showing an electrophotographic process used in the present invention
  • Element 1 is a photoconductive drum such as of amorphous selenium, amorphous silicon or organic photoconductor, etc., in which a photoconductive layer is provided on a conductive supporter.
  • Element 2 is a charger arranged opposite to the photoconductive drum 1.
  • the charging means is not particularly restricted, and any of the ordinarily used chargers, for example, a charger by corotron, a roller charger using a conductive roller, a brush charger using a conductive brush, etc. can be used.
  • Element 3 is an exposure device arranged opposite to the photoconductive drum 1 for forming electrostatic latent images on the surface of the photoconductor.
  • light sources such as semiconductor laser beams, LED or EL arrays, etc. are used in combination with an image-forming optical system.
  • a device based on optical systems projecting a reflected light of a document usually provided in the copying machine can be used.
  • Element 4 is a developer device for making visible the electrostatic latent image formed on the surface of the photoconductor with the toner.
  • a developer device any of the commonly used two-component magnetic brush developer devices, the one-component magnetic brush developer devices, and the one-component non-magnetic developer devices, etc. can be used.
  • the toner 6 charged inside the developer device passes through the developer sleeve 14 to visualize the electrostatic latent images formed on the surface of the photoconductor.
  • Element 5 is a transfer device which has the same function as that of the charger 2 with essentially the same mechanism. In the transfer process, the visualized images formed on the surface of the photoconductive drum 1 by using a developer is transferred onto the surface of the recording medium 7.
  • Element 11 is a cleaner device, by which about 5% to 20% of the toners which remain untransferred in the transfer process are removed.
  • Element 8 is a heat roller
  • element 9 is a pressure roller.
  • the visible image is formed by transferring the toner onto the recording medium 7 and fixing thereonto by passing through a fixing apparatus comprising a pair of these rollers.
  • Element 10 is a radiator device. Conventionally, driving systems or fans have been necessary in order to discharge forcefully high heat generated from the fixing apparatus from the printing machine. By contrast, when the fixing apparatus has a low heating temperature with low heat radiation as in the case of the present invention, a simple radiator device of a slit type or honeycomb type as shown in the figures serves its purposes.
  • a specified charge is uniformly supplied, e.g. by the corona charger to the photoconductor surface.
  • a photoconductor sensitive to a positive charge is taken here for an example, and the surface of the conductive supporter is coated with the photoconductive layer to form the photoconductor.
  • a uniform charge is applied by the corona charger to the photoconductive layer, thereby positively charging the surface of the photoconductive layer.
  • a light from the exposure device is irradiated to the surface of the related photoconductor, so that a leakage of charges occurs only in the exposed parts to form an electrostatic latent image on the photoconductive layer.
  • the toner triboelectrically charged inside the developer device is transported by the developer sleeve, and developed onto the photoconductor surface in proportion to the charge on the photoconductor surface.
  • the developing process is an assortment of normal development in which a reversely polarized toner adheres to the charges by the Coulomb's force and of reverse development in which the toner adheres to the charges lost due to exposure to the light.
  • the development process in the present invention applies to either method.
  • the toner image on the photoconductor body surface accepts the charges from the reverse side of the recording medium 7 such as a recording paper through a transfer-corotron or a transfer-roller, and it is then transferred to the recording medium 7.
  • the cleaning device 11 such as a cleaning web, which is arranged opposite to the photoconductor as shown in Figure 1.
  • the fixing apparatus in the present invention is constituted by a heat roller 8, which has a conductive elastomer layer, and a pressure roller 9 made of an elastic material or a rigid material.
  • the fixing apparatus of the present invention is constituted by a heat roller 8 comprising an insulating layer 12 formed in the periphery of the rotating shaft A and a conductive elastomer layer, which is a heating layer 13, formed thereon; and a pressure roller 9 made of an elastic material.
  • the fixing apparatus of the present invention is constituted by a heat roller 8 comprising a conductive elastomer layer, which is an elastic heating element 21, formed in the periphery of the rotating shaft A, a conductive layer 22 formed thereon and a releasing layer 23; and a pressure roller 9 made of an elastic material.
  • the fixing apparatus of the present invention is constituted by a heat roller 8 comprising a conductive elastomer layer, which is an elastic heating element 31, formed in the periphery of the rotating shaft A and a releasing layer 32 formed thereon; and a pressure roller 9 made of an elastic material.
  • the fixing apparatus of the present invention is constituted by a heat roller 8 comprising a conductive elastomer layer, which is an elastic heating element 41 formed in the periphery of the rotating shaft A; and a pressure roller 9 made of a rigid material.
  • a heat roller 8 comprising a conductive elastomer layer, which is an elastic heating element 41 formed in the periphery of the rotating shaft A; and a pressure roller 9 made of a rigid material.
  • the heat roller is provided with a conductive elastomer layer having a thickness without being subject to limitation as long as it has a uniform thickness, the thickness is preferably about 0.5 to 3.0 mm.
  • insulating materials such as heat-resistant resins and insulating ceramics can be used as a roller base material for the heat roller 8.
  • heat-resistant resins examples include polyamides, polyamide-imides, polyacetals, polycarbonates, denatured PPOs, polyethylene terephthalates, polybutylene terephthalates, polyarylates, polysulfones, polyether sulfones, polyether ether ketones, polyetherimides, aromatic polyesters, polyphenylene sulfides, fluorine polymers, ABS resins, AS resins, AAS resins, AES resins, ACS resins, methylpentene polymers, ultrahigh molecular polyethylenes, polypropylene resins, phenol resins, diallyl phthalate resins, unsaturated polyester resins, epoxy resins, polyimides, polyurethanes, cyclic polyolefins and liquid crystal polymers.
  • These resins may be used singly or in combination of two or more kinds. In addition, they may be supplemented with fillers such as glass fibers.
  • the insulating ceramic materials include metallic oxides such as alumina, magnesia, beryllia, zirconia, silica, forsterite, wollastonite, zircon, mullite, cordierite, spodumene, aluminum titanate, spinel and barium titanate, and non-oxide metallic compounds such as silicon nitride, sialon, aluminum nitride, titanium nitride, silicon carbide, boron carbide, titanium carbide, tungsten carbide, lanthanum borate, titanium borate and zirconium borate.
  • metallic oxides such as alumina, magnesia, beryllia, zirconia, silica, forsterite, wollastonite, zircon, mullite, cordierite, spodumene, aluminum titanate, spinel and barium titanate
  • non-oxide metallic compounds such as silicon nitride, sialon, aluminum nitride, titanium nitride
  • these insulating ceramic materials are used as roller base materials, one or more kinds thereof are used in any structural form selected from the group consisting of sintered bodies, glass and crystallized glass.
  • the insulating layer 12 becomes unnecessary.
  • the specific resistivity of the conductive elastomer layer is not more than 100 ⁇ cm, preferably 1 to 100 ⁇ cm, and more preferably 2 to 50 ⁇ cm.
  • the heat roller may fail to reach the set fixing temperature because the elastomer layer is not sufficiently heated unless a high charge is applied, and, in many cases, it takes too much time to reach the set temperature.
  • the resistivity is less than 1 ⁇ cm, the temperature control of the heat roller is difficult due to excess heating speed, and the resulting high temperature may undesirably damage the fixing apparatus including the fixing roller.
  • the maximum heating temperature of the conductive elastomer layer used in the present invention is not more than 150°C.
  • Examples of the conductive elastomers for the fixing apparatus of the present invention include tetrafluoroethylenepropylene, vinylidene fluoride, silicone, fluorosilicone and other fluorine-based or silicone-based heat-resistant elastomers; and acrylic elastomers, nitrile elastomers, epichlorohydrin elastomers, ethylene-propylene-non-conjugated diene terpolymer (EPDM) elastomers, and other general-purpose elastomers. Under certain conditions, neoprene, butadiene and isoprene elastomers are also usable. In the present invention, a preference is given to the fluorine-based and silicone-based heat-resistant elastomers and the acrylic elastomer.
  • the conductive elastomer used for the fixing apparatus of the present invention is prepared by dispersing a conductive material such as conductive carbon, conductive inorganic powder or conductive potassium titanate whisker in the above elastic material and shaping the dispersed mixture.
  • a conductive layer may be provided which comprises a dispersion of an organic polymer such as polypyrrole, polythiophene, polyparaphenylene or polyaniline or a charge transfer complex such as that of anthracene and tetracyanoquinoline or that of pyrene and tetracyanoethylene in the above elastic material.
  • the heat roller may be provided with a releasing layer by coating silicone oil or by forming a film such as that of polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon, Teflon or PFA.
  • the thickness of the releasing layer is preferably not more than 200 ⁇ m, since thicknesses exceeding 200 ⁇ m result in decreased thermal conductivity. More preferably, the thickness of the releasing layer is not more than 100 ⁇ m, but it needs to be not less than 10 ⁇ m, since thicknesses under this level can result in pinholes, which in turn lead to leakages of electricity.
  • the ratio of the nip width to the roller radius is normally from 0.05 to at most 0.20.
  • this ratio is remarkably larger than those of the conventional fixing apparatuses, and it is adjusted to not less than 0.2, preferably 0.25 to 0.8, relative to the radius of the roller made of the elastic material.
  • a roller made of an elastic material means a roller comprising a roller base material in the form of a rod or cylinder made of SUS steel, aluminum or another material having an outer diameter of not less than 8 mm, and an elastic material coated thereon having a hardness of not more than 90 degrees as determined by using a JIS A-type rubber hardness tester.
  • the rubber hardness of pressure roller is 40 to 90 degrees, as determined by a JIS A-type rubber hardness tester, for the pressure rollers having a slow peripheral speed and a small roller radius, and it is 40 to 90 degrees as determined by a JIS C-type rubber hardness tester, for the pressure rollers having a high peripheral speed and a large roller radius.
  • at least one of the pair of rollers has a rubber hardness of not more than 90 degrees, preferably 20 to 90 degrees as determined by the JIS A-type rubber hardness tester.
  • the nip pressure becomes too high in the case where the roller-to-roller nip width is set in a specified range, which in turn causes a nip pressure difference between the center and both ends of the roller due to rotating shaft torsion of the roller, resulting in uneven fixing in the case of a small roller radius.
  • the rubber hardness is not more than 20 degrees, a sufficiently high nip pressure cannot be achieved when the nip width is set at a specified range, thereby resulting in an unsatisfactory fixing of the toner onto the recording medium.
  • At least one of the pair of rollers is made of a material having a low rubber hardness.
  • both the heat roller and the pressure roller made of materials having a low rubber hardness may be used.
  • the heat roller may be made of an elastic material having a high rubber hardness from the aspect of deterioration due to thermal load, etc.
  • the heat roller in order to widen the nip width by using a heat roller made of a material having a low rubber hardness and to lower the cost by using a pressure roller made of an inexpensive tough material, the heat roller is made of a material having a low rubber hardness, and the pressure roller is made of SUS steel or another steel material insulated with a PET film or the like.
  • the surface of the heat roller is conductive, it is necessary to form a protective film with an insulating sheet on the surface of the heat roller.
  • the toner can be heated at a fixing temperature of not more than 130°C, a sufficiently wide nip width can be obtained even when the roller radius is smaller, and the fixing can be carried out at a remarkably low nip pressure so as not to cause permanent set even when the strain is large.
  • the nip pressure in the fixing apparatus of the present invention is 0.01 to 4.0 kg/cm, preferably 0.1 to 3.0 kg/cm.
  • the heat roller of the fixing apparatus of the present invention is heated by applying a voltage to a conductive brush in contact with both ends of the heat roller as current supplying means, when an insulating layer is provided in the periphery of the rotating shaft and a heating layer of conductive elastomer is formed thereon as illustrated in Figure 1.
  • the conductive brushes include those formed in the periphery of a metal shaft in a brush-like manner with conductive resin fibers, such as nylon or rayon having conductive carbon dispersed therein, or with fibers having conductive carbon, conductive paint or the like adhered thereto.
  • both end surfaces of the roller may be coated with a conductive paint or the like having conductive carbon, tin oxide or copper powder dispersed therein.
  • the voltage may be applied between the rotating shaft and the conductive elastomer layer.
  • the fixing apparatus of the present invention is thus capable of thermally fixing a visible image onto a recording medium conveyed, by the pair of the heat roller and the pressure roller as described above, which rotate in contact with each other.
  • the fixing is carried out at the contacted surfaces of the rollers at a fixing temperature of not more than 130°C by heat generated by passing the electric current into the conductive elastomer layer.
  • the heat roller and the pressure roller rotate in contact with each other by specified driving means not illustrated in the figures in the direction shown in the respective drawings at a constant peripheral speed.
  • the peripheral speed is not particularly limitative, and it may be properly chosen.
  • the fixing is usually carried out at a high temperature of about 200°C because the softening point of the resin contained as the main component in the toner for forming the visible image is high.
  • various references proposing toners which can be fixed at low temperatures have been known.
  • the toner used in the present invention is an encapsulated toner wherein the function separation for the storage stability and the fixing ability, and the offset resistance can be achieved.
  • these toners are not particularly limitative, but those comprising a shell having improved storage stability and chargeabiity and a core having improved coloring, fixing ability and offset resistance are suitably used (see Japanese Patent Laid-Open Nos. 176642/1983, 176643/1983, 56352/1986, 128357/1988, 128358/1988, 267660/1989, 51175/1990 and 212169/1992, and Japanese Patent Application No. 259088/1992).
  • styrene resins Japanese Patent Laid-Open No.205162/1983
  • polyamide resins Japanese Patent Laid-Open No.66948/1983
  • epoxy resins Japanese Patent Laid-Open No.148066/1984
  • polyurethane resins Japanese Patent Laid-Open No.179860/1982
  • polyurea resins Japanese Patent Laid-Open No.150262/1987) and many others have been proposed.
  • thermoplastic resins whose glass transition points (Tg) are not less than 10°C and not more than 50°C such as polyester resins, polyamide resins, polyester-polyamide resins and polyvinyl resins can be used.
  • Such encapsulated toners can be obtained usually by the following production method.
  • the particularly preferred encapsulated toners include a thermally dissociating encapsulate toner produced by the interfacial polymerization method or the spray-drying method, and an encapsulated toner whose shell is made of amorphous polyester produced by the in situ polymerization method.
  • the interfacial polymerization method and the in situ polymerization method not only have the merit of an easy function separation for the core material and shell material but also are capable of producing a uniform toner in an aqueous state.
  • substances of low softening points can be used for the core material in these polymerization methods, making it particularly suitable from the aspect of fixing ability of the toner.
  • the thermally dissociating encapsulated toner means a toner which comprises a shell whose structure is fragile to heat, and a thermoplastic core material containing at least a thermoplastic resin and a coloring agent which can be fixed at a low temperature by pressure.
  • the shell structure of this toner changes with heat, and at the point where pressure is applied, the core material is discharged to effect the fixing of the toner.
  • the structure and the thermal properties of the shell material concern themselves remarkably with the fixing ability of the whole toner. Since a particular polyurethane resin among the above-mentioned resins for the shell materials is thermally dissociating, having excellent storage stability and fixing ability at a low temperature, it is an extremely favorable shell material for the thermally dissociating encapsulated toner of the present invention.
  • the principal components of such a shell material include resins having at least one linkage selected from the group consisting of thermally dissociating urethane linkage, thiol urethane linkage and s-thiourethane linkage.
  • resins having at least one linkage selected from the group consisting of thermally dissociating urethane linkage, thiol urethane linkage and s-thiourethane linkage Particularly, in the thermally dissociating urethane resin which is the principal components of the shell material, at least 30% of all of the linkages formed from the isocyanate and/or isothiocyanate groups are thermally dissociating linkages.
  • resins obtainable from the reaction between an isocyanate compound and/or isothiocyanate compound and compounds containing a phenolic hydroxyl group and/or a thiol group are preferably used (EP0453857A).
  • the encapsulated toner whose shell is made of amorphous polyester means a toner coated on the surface of the thermoplastic core material containing at least a thermoplastic resin and a coloring agent, with amorphous polyester.
  • Such an amorphous polyester can be preferably obtained by condensation polymerization between at least one alcohol monomer selected from the group consisting of dihydric alcohol monomers and trihydric or higher polyhydric alcohol monomers and at least one carboxylic acid monomer selected from the group consisting of dicarboxylic acid monomers and tricarboxylic or higher carboxylic acid monomers, in which at least one of the monomers is trihydric or higher alcohol or tricarboxylic or higher carboxylic acid (Japanese Patent Application No. 259088/1992).
  • the shell structure of these toners easily changes with heat, and at the point where pressure is applied, the core material is discharged to effect the fixing of the toner.
  • the encapsulated toner used in the present invention is not particularly limitative as described above, the thermally dissociating encapsulated toner and the encapsulated toner whose shell is made of amorphous polyester are described in detail below as the modes of preferred embodiments.
  • thermally dissociating encapsulated toner is described in detail below.
  • the encapsulated toner in the present invention is composed of a heat-fusible core material containing at least a coloring agent and a shell formed thereon so as to cover the surface of the core material, wherein the main components of the shell are a resin prepared by reacting:
  • the thermally dissociating linkage is preferably one formed by the reaction between a phenolic hydroxyl and/or thiol group and an isocyanate and/or isothiocyanate group.
  • Examples of the monovalent isocyanate compounds to be used as the component (1) in the present invention include ethyl isocyanate, octyl isocyanate, 2-chloroethyl isocyanate, chlorosulfonyl isocyanate, cyclohexyl isocyanate, n-dodecyl isocyanate, butyl isocyanate, n-hexyl isocyanate, lauryl isocyanate, phenyl isocyanate, m-chlorophenyl isocyanate, 4-chlorophenyl isocyanate, p-cyanophenyl isocyanate, 3,4-dichlorophenyl isocyanate, o-tolyl isocyanate, m-tolyl isocyanate, p-tolyl isocyanate, p-toluenesulfonyl isocyanate, 1-naphthyl isocyanate, o-
  • divalent or higher isocyanate compounds to be used as the component (2) in the present invention include aromatic isocyanate compounds such as 2,4-tolylene diisocyanate, 2,4-tolylene diisocyanate dimer, 2,6-tolylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 3,3'-dimethyldiphenyl-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, m-phenylene diisocyanate, triphenylmethane triisocyanate and polymethylenephenyl isocyanate; aliphatic isocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate,
  • isothiocyanate compounds examples include phenyl isothiocyanate, xylylene-1,4-diisothiocyanate and ethylidene diisothiocyanate.
  • isocyanate and isothiocyanate compounds compounds having an isocyanate group directly bonded to an aromatic ring are preferred, because they are effective in forming a urethane resin having a low thermal dissociation temperature.
  • the monovalent isocyanate and/or isothiocyanate compound (1) also serves as a molecular weight modifier for the shell-forming resin and can be used in an amount of at most 30 mol % based on the isocyanate component and/or the isothiocyanate component. When the amount exceeds 30 mol %, the storage stability of the obtained encapsulated toner is undesirably poor.
  • Examples of compounds having one active hydrogen atom reactive with isocyanate and/or isothiocyanate groups to be used as component (3) in the present invention include aliphatic alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, tert-butyl alcohol, pentyl alcohol, hexyl alcohol, cyclohexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, lauryl alcohol and stearyl alcohol; aromatic alcohols such as phenol, o-cresol, m-cresol, p-cresol, 4-butylphenol, 2-sec-butylphenol, 2-tert-butylphenol, 3-tert-butylphenol, 4-tert-butylphenol, nonylphenol, isononylphenol, 2-propenylphenol, 3-propenylphenol, 4-propenylphenol, 2-methoxyphenol, 3-
  • a phenol derivative represented by the following formula (I) is preferably used: wherein R1, R2, R3, R4 and R5 each independently represents a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, an alkenyl group, an alkoxy group, an alkanoyl group, a carboalkoxy group or an aryl group or a halogen.
  • Examples of the dihydric or higher alcohols among the compounds having at least two active hydrogen atoms reactive with isocyanate and/or isothiocyanate groups to be used as the component (4) in the present invention include catechol, resorcinol, hydroquinone, 4-methylcatechol, 4-tert-butylcatechol, 4-acetylcatechol, 3-methoxycatechol, 4-phenylcatechol, 4-methylresorcinol, 4-ethylresorcinol, 4-tert-butylresorcinol, 4-hexylresorcinol, 4-chlororesorcinol, 4-benzylresorcinol, 4-acetylresorcinol, 4-carbomethoxyresorcinol, 2-methylresorcinol, 5-methylresorcinol, tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, t
  • catechol derivatives represented by the following formula (II) and resorcinol derivatives represented by the following formula (III) are preferably used: wherein R6, R7, R8 and R9 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group, an alkoxy group, an alkanoyl group, a carboalkoxy group or an aryl group or a halogen.
  • R10, R11, R12 and R13 each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group, an alkoxy group, an alkanoyl group, a carboalkoxy group or an aryl group or a halogen.
  • examples of the compounds having at least one isocyanate- or isothiocyanate-reactive functional group other than the hydroxyl group and at least one phenolic hydroxyl group include o-hydroxybenzoic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 5-bromo-2-hydroxybenzoic acid, 3-chloro-4-hydroxybenzoic acid, 4-chloro-2-hydroxybenzoic acid, 5-chloro-2-hydroxybenzoic acid, 3,5-dichloro-4-hydroxybenzoic acid, 3-methyl-2-hydroxybenzoic acid, 5-methoxy-2-hydroxybenzoic acid, 3,5-di-tert-butyl-4-hydroxybenzoic acid, 4-amino-2-hydroxybenzoic acid, 5-amino-2-hydroxybenzoic acid, 2,5-dinitrosalicylic acid, sulfosalicylic acid, 4-hydroxy-3-methoxyphenylacetic acid, catechol-4-carboxylic acid, 2,4-dihydroxybenzoic acid
  • examples of the polythiol compounds having at least one thiol group in each molecule include ethanethiol, 1-propanethiol, 2-propanethiol, thiophenol, bis(2-mercaptoethyl)ether, 1,2-ethanedithiol, 1,4-butanedithiol, bis(2-mercaptoethyl) sulfide, ethylene glycol bis(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), 2,2-dimethylpropanediol bis(2-mercaptoacetate), 2,2-dimethylpropanediol bis(3-mercaptopropionate), trimethylolpropane tris(2-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), trimethylolethane tris(2-mercaptoacetate), trimethylolethane tris(2-mercaptoacetate), trimethylolethane tris(3-mer
  • thermally dissociating shell-forming resin used in the present invention at least 30%, preferably at least 50% of all of the linkages formed from isocyanate or isothiocyanate groups are thermally dissociating linkages.
  • content of the thermally dissociating linkages is less than 30%, the strength of the shell in the heat-and-pressure fixing cannot be sufficiently lowered, making it less likely to exhibit any advantageous fixing performance of the core material.
  • other compounds having an isocyanate-reactive functional group other than phenolic hydroxyl and thiol groups which may be used as a shell-forming material in such an amount as not to lower the ratio of the linkages formed by the reaction of isocyanate and/or isothiocyanate groups with phenolic hydroxyl and/or thiol groups to the all of the linkages formed from isocyanate and/or isothiocyanate groups is less than 30%, include, for example, the following active methylene compounds such as malonate and acetoacetate, oximes such as methyl ethyl ketone oxime, carboxylic acid, polyol, polyamine, aminocarboxylic acid and aminoalcohol.
  • the compound having one active hydrogen atom reactive with isocyanate and/or isothiocyanate groups as the component (3) may be used in an amount of at most 30 mol % based on the active hydrogen component. When the amount exceeds 30 mol %, the storage stability of the resulting toner is undesirably poor.
  • the molar ratio of (A) the isocyanate compound and/or isothiocyanate compound comprising the components (1) and (2) to (B) the active hydrogen compounds comprising the components (3) and (4) preferably lies between 1:1 and 1:20 in order to obtain a resin free from unreacted isocyanate groups.
  • the shell is preferably formed by an interfacial polymerization or an in situ polymerization.
  • it may be formed by a dry method comprising stirring in an air stream at a high rate matrix particles used as a core material together with particles used as a shell-forming material having a number-average particle size of one-eighth or less of that of the matrix particles.
  • the shell-forming resins can be produced in the presence of no catalysts.
  • catalysts including tin catalysts such as dibutyltindilaurate, etc.; amine catalysts such as 1,4-diazabicyclo[2.2.2]octane, N,N,N-tris(dimethylaminopropyl)-hexahydro-S-triazine, etc.; and any known urethane catalysts can be used.
  • the resins used in the core materials of the thermally dissociating encapsulated toner of the present invention are thermoplastic resins having glass transition points (Tg) of 10 to 50°C, and examples thereof include polyester resins, polyester-polyamide resins, polyamide resins and vinyl resins, among which vinyl resins are particularly preferable.
  • Tg glass transition point
  • the glass transition point (Tg) is less than 10°C, the storage stability of the resulting encapsulated toner is undesirably poor, and when it exceeds 50°C, the fixing strength of the encapsulated toner is undesirably poor.
  • Examples of the monomers constituting the vinyl resins include styrene and its derivatives such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ⁇ -methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-chlorostyrene and vinylnaphthalene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl formate and vinyl caproate; ethylenic monocarboxylic acids and esters thereof such as acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobut
  • the core material-forming resin contains, in the main chain of the resin, styrene or its derivatives preferably in an amount of 50 to 90 parts by weight, and the ethylenic monocarboxylic acid or an ester thereof preferably in an amount of 10 to 50 parts by weight to control the thermal properties of the resin, such as the softening point.
  • the monomer composition constituting the core material-forming resin according to the present invention contains a crosslinking agent, which may be also used, if necessary, as a mixture of two or more of them, any known crosslinking agents may be properly used.
  • a crosslinking agent which may be also used, if necessary, as a mixture of two or more of them, any known crosslinking agents may be properly used.
  • the amount of the crosslinking agent added is too large, the resulting toner is less likely to be heat-fused, thereby resulting in poor heat fixing ability and heat-and-pressure fixing ability.
  • the amount of the crosslinking agent is preferably 0.001 to 15% by weight, more preferably 0.1 to 10% by weight, based on the polymerizable monomers used.
  • the core material of the thermally dissociating encapsulated toner according to the present invention may further contain, if necessary, one or more offset inhibitors of any known kind for the purpose of improving offset resistance in the heat-and-pressure fixing. These offset inhibitors are contained in an amount of 1 to 20% by weight based on the resin contained in the core material.
  • the core material of the thermally dissociating encapsulated toner according to the present invention contains a coloring agent, which may be any one of the dyes and pigments used in the conventional toners.
  • the coloring agent is generally contained in an amount of 1 to 15 parts by weight based on 100 parts by weight of the resin contained in the core material.
  • a metal-containing dye which has been used for toners for example, a metal complex of an organic compound having a carboxyl or nitrogenous group, such as nigrosine, may be added in an effective amount as a charge control agent.
  • a charge control agent may be mixed with the toner.
  • the thermally dissociating encapsulated toner according to the present invention may contain, if necessary, a fluidity improver and/or a cleanability improver. Further, for the purpose of controlling the developability of the encapsulated toner, an additive, for example, finely powdered polymethyl methacrylate, etc. may be added. Furthermore, for the purposes of toning or resistance control, a small amount of carbon black may be used.
  • the thermally dissociating encapsulated toner of the present invention preferably has a softening point of 80 to 150°C.
  • the softening point is lower than 80°C, the offset resistance of the resulting encapsulated toner is undesirably poor, and when it exceeds 150°C, the fixing strength of the encapsulated toner is undesirably poor.
  • the particle size of the thermally dissociating encapsulated toner according to the present invention is not particularly limited, the average particle size thereof is generally 3 to 30 ⁇ m.
  • the preferred thickness of the shell of the encapsulated toner is from 0.01 to 1 ⁇ m. When the thickness is less than 0.01 ⁇ m, the blocking resistance of the resulting encapsulated toner is poor, and when it exceeds 1 ⁇ m, the heat fusibility of the resulting encapsulated toner is undesirably poor.
  • the amorphous polyester can be preferably obtained by condensation polymerization between at least one alcohol monomer selected from the group consisting of dihydric alcohol monomers and trihydric or higher polyhydric alcohol monomers and at least one carboxylic acid monomer selected from the group consisting of dicarboxylic acid monomers and tricarboxylic or higher carboxylic acid monomers, in which at least one of the monomers is trivalent or higher (Japanese Patent Application No. 259088/1992).
  • dihydric alcohol components include bisphenol A alkylene oxide adducts such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(3.3)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, polyoxypropylene(2.0)-polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, and polyoxypropylene(6)-2,2-bis(4-hydroxyphenyl)propane; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol,
  • trihydric or higher polyhydric alcohol components examples include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, and other trihydric or higher polyhydric alcohols.
  • these dihydric alcohol monomers and trihydric or higher polyhydric alcohol monomers may be used singly or in combination.
  • examples of the dicarboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, n-dodecylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, and acid anhydrides thereof, lower alkyl esters thereof and other dicarboxylic acids.
  • Examples of the tricarboxylic or higher carboxylic acid components include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, Empol trimer acid and acid anhydrides thereof, lower alkyl esters thereof and other tricarboxylic or higher carboxylic acids.
  • these dicarboxylic acid monomers and tricarboxylic or higher carboxylic acid monomers may be used singly or in combination.
  • the encapsulated toner whose shell is made of amorphous polyester suitably used in the present invention can be produced by any known methods such as in situ polymerization, and this encapsulated toner is composed of a heat-fusible core material containing at least a thermoplastic resin and a coloring agent, and a shell formed thereon so as to cover the surface of the core material.
  • the resins to be used as core materials of the encapsulated toner according to the present invention are thermoplastic resins having glass transition points (Tg) of 10 to 50°C, and examples thereof include polyester resins, polyester-polyamide resins, polyamide resins and polyvinyl resins, among which polyvinyl resins are particularly preferable.
  • Tg glass transition point
  • the glass transition point (Tg) is less than 10°C, the storage stability of the resulting encapsulated toner is undesirably poor, and when it exceeds 50°C, the fixing strength of the encapsulated toner is undesirably poor.
  • a shell is formed based on the principle that the concentration of the shell material on the surface of the droplets takes place in a mixture solution containing a core material and a shell material comprising amorphous polyester, which mixture solution is dispersed in a dispersion medium. Specifically, the separation of the core material and the shell material takes place in the droplets of the mixture solution due to the differences in the indices of solubility. In this state, the polymerization progresses to form an encapsulated structure.
  • the chargeability of the toner becomes uniform.
  • a dispersion stabilizer is required to be contained in the dispersion medium in order to prevent agglomeration and incorporation of the dispersed substances.
  • dispersion stabilizers examples include polyvinyl alcohol, sodium dodecylbenzenesulfonate, tricalcium phosphate, etc.
  • dispersion media of the dispersion stabilizer examples include water, methanol, ethanol, propanol, butanol, ethylene glycol, glycerol, isopropyl ether, tetrahydrofuran, etc. These dispersion media can be used singly or in combination.
  • the addition amount of the amorphous polyester is normally 3 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of the core material.
  • the resulting shell becomes too thin, thereby making the storage stability of the toner poor, and when it exceeds 50 parts by weight, the resulting mixture becomes highly viscous, posing difficulty in making the powder fine, thereby leading to poor production stability of the toner.
  • the amorphous polyester suitably used in the present invention has a glass transition point of 50 to 80°C, and an acid value of 3 to 50 KOH mg/g.
  • the resins to be used as core materials of the encapsulated toner are thermoplastic resins having glass transition points of 10 to 50°C.
  • the toner adhered onto the recording medium while conveying is fixed at a fixing temperature of not more than 130°C in the fixing process, it is no longer necessary to use expensive heat-resistant materials for the fixing apparatus and the periphery thereof, and inexpensive materials can be used.
  • the durability of the parts used become long, the service life of the overall apparatus becomes long, thereby making it possible to be low-cost printing machines.
  • the fixing is carried out at a fixing temperature of not more than 130°C and the nip pressure is also kept low, paper sheets are not likely to curl or jam, thereby conserving in its maintenance.
  • the temperature of the heating element in the fixing device can be set low with only a small rise of the temperature in the printing machine. Accordingly, a forced radiation device such as an electric fan can be made smaller or is not required, thereby reducing the noise. Also, since the waiting time for the temperature rise in the fixing apparatus can be shortened, quick printing becomes possible, making it suitable in the field requiring quick printings such as facsimile. Further, since the fixing is carried out at a fixing temperature of not more than 130°C, the fixing apparatus can be simplified, thereby making it possible to miniaturize and lower its overall cost.
  • the obtained mixture is introduced into an attritor (manufactured by Mitsui Miike Kakoki) and dispersed at 10°C for 5 hours to give a polymerizable composition.
  • This composition is added to 800 g of a 4% by weight aqueous colloidal solution of tricalcium phosphate which had been preliminarily prepared in a 2-liter separable glass flask, so as to give a concentration of 30% by weight.
  • the obtained mixture is emulsified and dispersed with a TK homomixer (manufactured by Tokushu Kika Kogyo) at 5°C and a rotational speed of 10000 rpm for 2 minutes.
  • a four-necked glass cap is set on the flask, and a reflux condenser, a thermometer, a dropping funnel fitted with a nitrogen inlet tube and a stainless steel stirring rod are set thereon.
  • the resulting flask is placed on an electric mantle heater.
  • a solution of 22.0 g of resorcinol, 3.6 g of diethyl malonate and 0.5 g of 1,4-diazabicyclo [2.2.2] octane in 40 g of ion-exchanged water is prepared, and the resulting mixture is dropped into the flask in a period of 30 minutes through the dropping funnel while stirring. Thereafter, the contents are heated to 80°C and reacted for 10 hours in a nitrogen atmosphere while stirring.
  • the reaction mixture After cooling the reaction mixture, it is dissolved into 10%-aqueous hydrochloric acid.
  • the resulting mixture is filtered and the obtained solid is washed with water, dried under a reduced pressure of 20 mmHg at 45°C for 12 hours and classified with an air classifier to give the thermally dissociating encapsulated toner with an average particle size of 9 ⁇ m having a shell made of a resin having a thermally dissociating urethane linkage.
  • the glass transition point assignable to the resin contained in the core material is 30.2°C, and its softening point is 130.0°C.
  • This composition is added to 800 g of a 4% by weight aqueous colloidal solution of tricalcium phosphate which is preliminarily prepared in a two-liter separable glass flask, so as to give a concentration of 30% by weight.
  • the obtained mixture is emulsified and dispersed with a TK homomixer (manufactured by Tokushu Kika Kogyo) at 5°C and a rotational speed of 10000 rpm for 2 minutes.
  • a four-necked glass cap is set on the flask, and a reflux condenser, a thermometer, a dropping funnel fitted with a nitrogen inlet tube and a stainless steel stirring rod are attached thereto.
  • the resulting flask is placed on an electric mantle heater.
  • a solution of 27.4 g of 4-acetylcatechol, 4.0 g of dimethyl malonate, 0.8 g of 1,2-ethanedithiol and 0.5 g of 1,4-diazabicyclo[2.2.2]octane in 40 g of ion-exchanged water is prepared, and the resulting mixture is dropped into the flask in a period of 30 minutes through the dropping funnel while stirring.
  • the contents are heated to 80°C and reacted for 10 hours in a nitrogen atmosphere while stirring.
  • the dispersing agent is dissolved into 10%-aqueous hydrochloric acid.
  • the resulting mixture is filtered, and the obtained solid is washed with water, dried under a reduced pressure of 20 mmHg at 45°C for 12 hours and classified with an air classifier to give the thermally dissociating encapsulated toner with an average particle size of 9 ⁇ m whose shell is made of a resin having a thermally dissociating urethane linkage.
  • the glass transition temperature assignable to the resin contained in the core material is 35.4°C, and its softening point is 133.5°C.
  • the degree of polymerization is determined based on the softening point measured according to ASTM E28-67, and the reaction is terminated when the softening point reaches 110°C.
  • the glass transition point of the obtained resin is measured by a differential scanning calorimeter (manufactured by Seiko Instruments, Inc.), it is 65°C.
  • its softening point and acid value are measured, and they are, respectively, 110°C and 18 KOH mg/g.
  • the acid value is measured according to JIS K0070.
  • This composition is added to 800 g of a 4% by weight aqueous colloidal solution of tricalcium phosphate which had been preliminarily prepared in a 2-liter separable glass flask, so as to give a concentration of 30% by weight.
  • the obtained mixture is emulsified and dispersed with a TK homomixer (manufactured by Tokushu Kika Kogyo) at 5°C and a rotational speed of 12000 rpm for 5 minutes.
  • a four-necked glass cap is set on the flask, and a reflux condenser, a thermometer, a nitrogen inlet tube and a stainless steel stirring rod are attached thereto.
  • the resulting flask is placed on an electric mantle heater. Thereafter, the contents are heated to 85°C and reacted for 10 hours in a nitrogen atmosphere while stirring. After cooling the reaction mixture, the dispersion medium is dissolved into 10%-aqueous hydrochloric acid.
  • the resulting mixture is filtered and the obtained solid is washed with water, dried under a reduced pressure of 20 mmHg at 45°C for 12 hours and classified with an air classifier to give the encapsulated toner with an average particle size of 8 ⁇ m whose shell is made of an amorphous polyester resin.
  • the glass transition temperature assignable to the resin contained in the core material is 30.6°C, and its softening point is 125.5°C.
  • the thermally dissociating encapsulated toner obtained in Production Example 1 of Encapsulated Toner is surface-treated with 0.5% of silica "R972" (manufactured by Nippon Aerosil Co., Ltd.), and then 50 g of the toner is blended together with 1 kg of a commercially available ferrite carrier to obtain a developer.
  • a commercially available copying machine is modified to produce an apparatus according to Figure 1, in which a fixing portion comprising a heat roller and a pressure roller is produced according to Figure 2.
  • each of the heat roller and the pressure roller has a diameter of 20 mm
  • the rubber hardness measured according to an A-type hardness tester is 60 degrees for the heat roller and 40 degrees for the pressure roller.
  • the heat roller is obtained by coating the rotating shaft of the heat roller with a silicone resin as an insulating layer, and then forming a conductive elastomer layer thereon with a silicone resin dispersing a carbon black to provide the specific resistivity of 3 ⁇ cm.
  • the pressure roller is made of an elastic material using silicone foam rubber.
  • the nip pressure of the fixing apparatus is 0.3 kg/cm and the nip width is 3 mm, and voltage is supplied to both ends of conductive elastomer layer using a conductive brush.
  • the nip width is measured by a roll nip tester manufactured by Toshiba Silicone Co., Ltd.
  • the ratio of the nip width to the roller radius is 0.30.
  • the obtained developer is used to carry out copying by using the modified copying machine to develop images.
  • the fixing temperature is measured, and it has been found that a sufficient fixing strength is exhibited even at a temperature of 90°C (lowest fixing temperature) at a peripheral speed of 25 mm/sec, and that it does not show any hot offsetting to the heat roller at a temperature of 150°C. Further, a continuous copying test for 10,000 sheets is carried out at a fixing temperature of 90°C, and substantially no failures caused on the formed images by the fixing apparatus are observed.
  • the lowest fixing temperature for the toner is the temperature of the paper surface at which the fixing rate of the toner exceeds 70%.
  • This fixing rate of the toner is determined by placing a load of 500 g on a sand-containing rubber eraser having a bottom area of 15 mm x 7.5 mm which contacts the fixed toner image, placing the loaded eraser on a fixed toner image obtained in the fixing device, moving the loaded eraser on the image backward and forward five times, measuring the optical reflective density of the eraser-treated image with a reflective densitometer manufactured by Macbeth Co., and then calculating the fixing rate from this density value and a density value before the eraser treatment using the following equation.
  • the thermally dissociating encapsulated toner obtained in Production Example 2 of Encapsulated Toner is surface-treated with 0.5% of silica "R972" (manufactured by Nippon Aerosil Co., Ltd.), and then 50 g of the toner is blended together with 1 kg of a commercially available ferrite carrier to obtain a developer.
  • the obtained developer is used to carry out copying by using the same apparatus and the same method as in Test Example 1 above, and the fixing temperature is measured.
  • a sufficient fixing strength is exhibited even at a temperature of 90°C (lowest fixing temperature) at a peripheral speed of 25 mm/sec, and that it does not show any hot offsetting to the heat roller at a temperature of 150°C.
  • a continuous copying test for 10,000 sheets is carried out at a fixing temperature of 90°C, and substantially no failures caused on the formed images by the fixing apparatus are observed.
  • the encapsulated toner whose shell is made of amorphous polyester obtained in Production Example 3 of Encapsulated Toner is surface-treated with 0.5% of silica "R972" (manufactured by Nippon Aerosil Co., Ltd.), and then 50 g of the toner is blended together with 1 kg of a commercially available ferrite carrier to obtain a developer.
  • the obtained developer is used to carry out copying by using the same apparatus and the same method as in Test Example 1 above, and the fixing temperature is measured. As a result, it has been found that a sufficient fixing strength is exhibited even at a temperature of 80°C (lowest fixing temperature) at a peripheral speed of 25 mm/sec, and that it does not show any hot offsetting to the heat roller at a temperature of 150°C. Further, a continuous copying test for 10,000 sheets is carried out at a fixing temperature of 90°C, and substantially no failures caused on the formed images by the fixing apparatus are observed.
  • the thermally dissociating encapsulated toner obtained in Production Example 1 of Encapsulated Toner is surface-treated with 0.5% of silica "R972" (manufactured by Nippon Aerosil Co., Ltd.), and then 50 g of the toner is blended together with 1 kg of a commercially available ferrite carrier to obtain a developer.
  • the fixing apparatus used in the commercially available copying machine is modified so as to make it variable in fixing temperature and roller rotating speed.
  • the heat roller comprises an aluminum cylinder coated with a fluorine resin, which has a roller radius of 30 mm and a quartz heater disposed inside the cylinder.
  • the pressure roller has a rubber hardness measured by the A-type tester of 80 degrees, a roller radius of 20 mm, and a nip pressure is 0.5 kg/cm and a nip width is 3 mm. The ratio of the nip width to the roller radius is 0.15.
  • the obtained developer is used to carry out copying using the copying machine to develop images, and the fixing temperature is measured. As a result, it has been found that although a sufficient fixing strength is exhibited even at a temperature of 90°C (lowest fixing temperature) at a peripheral speed of 25 mm/sec, a hot offsetting to the heat roller takes place at a temperature of 120°C.
  • the encapsulated toner whose shell is made of amorphous polyester obtained in Production Example 3 of Encapsulated Toner is surface-treated with 0.5% of silica "R972" (manufactured by Nippon Aerosil Co., Ltd.), and then 50 g of the toner is blended together with 1 kg of a commercially available ferrite carrier to obtain a developer.
  • the obtained developer is used to carry out copying by using the same apparatus and the same method as in Comparative Test Example 1 above, and the fixing temperature is measured. As a result, it has been found that although a sufficient fixing strength is exhibited even at a temperature of 80°C (lowest fixing temperature) at a peripheral speed of 25 mm/sec, a hot offsetting to the heat roller takes place at a temperature of 120°C.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Fixing For Electrophotography (AREA)
  • Developing Agents For Electrophotography (AREA)
EP19930100934 1992-01-23 1993-01-21 Method for forming fixed images Withdrawn EP0552785A3 (en)

Applications Claiming Priority (2)

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JP34432/92 1992-01-23
JP4034432A JPH05204269A (ja) 1992-01-23 1992-01-23 定着方法

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EP0552785A3 EP0552785A3 (en) 1993-10-06

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0587036A2 (fr) * 1992-09-01 1994-03-16 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
EP0595347A1 (fr) * 1992-10-30 1994-05-04 Kao Corporation Méthode de développement et méthode de formation d'images fixées utilisant du toner encapsulé et magnétique
EP0615167A1 (fr) * 1993-03-10 1994-09-14 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
EP0642059A1 (fr) * 1993-09-01 1995-03-08 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
EP0656568A1 (fr) * 1993-11-05 1995-06-07 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
EP0672957A2 (fr) * 1994-03-09 1995-09-20 Kao Corporation Révélateur éncapsulé pour fixation à la chaleur et à la pression
CN100340931C (zh) * 2003-02-27 2007-10-03 佳能株式会社 图像加热装置

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JPS6486185A (en) * 1987-06-08 1989-03-30 Oki Electric Ind Co Ltd Fixing roller and its manufacture
DE3836857A1 (de) * 1987-10-30 1989-05-11 Sharp Kk Fixiervorrichtung fuer einen elektrophotographischen kopierer und verfahren zur herstellung einer dafuer bestimmten heizwalze
JPH0232368A (ja) * 1988-07-21 1990-02-02 Canon Inc 低温軽圧定着方法
EP0453857A1 (fr) * 1990-04-11 1991-10-30 Kao Corporation Toner encapsulé pour fixage par chaleur et pression
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DE2306440B2 (de) * 1972-02-09 1976-04-29 KJC. Ricoh, Tokio Waermefixierrolle
JPS59189381A (ja) * 1983-04-12 1984-10-26 Fuji Xerox Co Ltd 複写機の熱定着装置
JPS6230280A (ja) * 1985-07-31 1987-02-09 Tokai Rubber Ind Ltd 加熱ロ−ル装置
GB2197619A (en) * 1986-10-13 1988-05-25 Hitachi Metals Ltd Toner heat-fixing apparatus
JPS6486185A (en) * 1987-06-08 1989-03-30 Oki Electric Ind Co Ltd Fixing roller and its manufacture
DE3836857A1 (de) * 1987-10-30 1989-05-11 Sharp Kk Fixiervorrichtung fuer einen elektrophotographischen kopierer und verfahren zur herstellung einer dafuer bestimmten heizwalze
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Cited By (16)

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Publication number Priority date Publication date Assignee Title
US5763130A (en) * 1992-09-01 1998-06-09 Kao Corporation Encapsulated toner for heat-and-pressure fixing and method for production thereof
EP0587036A3 (en) * 1992-09-01 1995-08-16 Kao Corp Encapsulated toner for heat-and-pressure fixing and method for production thereof
EP0587036A2 (fr) * 1992-09-01 1994-03-16 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
US5529876A (en) * 1992-09-01 1996-06-25 Kao Corporation Encapsulated toner for heat - and pressure - fixing and method for production thereof
EP0595347A1 (fr) * 1992-10-30 1994-05-04 Kao Corporation Méthode de développement et méthode de formation d'images fixées utilisant du toner encapsulé et magnétique
US5443936A (en) * 1992-10-30 1995-08-22 Kao Corporation Developing method and method for forming fixed images using magnetic encapsulated toner
US5536612A (en) * 1993-03-10 1996-07-16 Kao Corporation Encapsulated toner for heat-and-pressure fixing and method for production thereof
EP0615167A1 (fr) * 1993-03-10 1994-09-14 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
EP0642059A1 (fr) * 1993-09-01 1995-03-08 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
US5571652A (en) * 1993-09-01 1996-11-05 Kao Corporation Encapsulated toner for heat-and-pressure fixing and method for producing the same
US5567567A (en) * 1993-11-05 1996-10-22 Kao Corporation Method for producing encapsulated toner for heat-and-pressure fixing and encapsulated toner obtained thereby
EP0656568A1 (fr) * 1993-11-05 1995-06-07 Kao Corporation Toner encapsulé pour fixation à la chaleur et à la pression et procédé pour sa fabrication
US5565293A (en) * 1994-03-09 1996-10-15 Kao Corporation Encapsulated toner for heat-and-pressure fixing
EP0672957A3 (fr) * 1994-03-09 1996-02-28 Kao Corp Révélateur éncapsulé pour fixation à la chaleur et à la pression.
EP0672957A2 (fr) * 1994-03-09 1995-09-20 Kao Corporation Révélateur éncapsulé pour fixation à la chaleur et à la pression
CN100340931C (zh) * 2003-02-27 2007-10-03 佳能株式会社 图像加热装置

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