JP4072474B2 - Magnetic toner - Google Patents

Description

  The present invention relates to a toner used in an image forming method such as an electrophotographic method, an electrostatic recording method, a magnetic recording method, or a toner jet method.

  Conventionally, magnetic external additive particles have been added to toners to improve fluidity and other properties.

For example, the toner used in the two-component development method has a particle size of 0.05 to 0.05 as an effect of preventing abrasion of the photosensitive member and preventing peeling of the carrier coating resin and improving toner transfer efficiency. There is a disclosure of a toner externally added with 1 μm magnetic powder and spherical resin particles. As a preferable magnetic property, the saturation magnetization is 50 to 150 emu / g. (For example, see Patent Document 1)
In addition, the major axis diameter is in the range of 0.1 to 0.5 μm, and the major axis with respect to the minor axis diameter is effective for suppressing image density unevenness and development ghost, as well as suppressing image flow and photoconductor wear. There is a disclosure of using magnetic powder whose diameter ratio is in the range of 3-5. As a preferable magnetic characteristic, the saturation magnetization is 5 Am ² / kg or less (see, for example, Patent Document 2).

The magnetic powder for external addition has an average particle size of 0.3 to 0.5 μm, a standard deviation of the particle size of 1.5 or less, and FeO / Fe ₃ O ₄ (weight ratio) of 3/97 to 15 There is a disclosure of magnetite that is / 85, and there is a disclosure that the filming phenomenon and the cleaning effect are excellent (for example, see Patent Document 3).
JP-A-7-152197 ([0009], [0010] and [0017]) JP-A-11-143121 ([0008] to [0012]) JP-A-9-73186 ([Claim 1] and [Effects of the Invention])

  In conventional magnetic toners with magnetic additive particles added, if the magnetic properties are kept low to adjust the polishing effect of the magnetic powder, the magnetic powder will be consumed excessively over a long period of time, and the effect will not last long. If the magnetic characteristics are kept high in order to suppress the problem, there is a problem that the image quality is inferior because the toner remains on the magnetic toner carrier or the magnetic toners are aggregated.

In order to solve the above problems, the present invention provides a magnetic toner comprising magnetic toner particles having magnetic powder and a binder resin, and magnetic external additive particles, wherein the weight average diameter of the magnetic toner is 5 to 11 μm, The magnetization amount Tm at a magnetic field strength of 79.6 kA / m is 15 to 50 Am ² / kg, and the magnetic external additive particles have a magnetization amount Te of 6 to 50 Am at a magnetic field strength of 79.6 kA / m. ² / kg, 0.1 to 3.5% by mass with respect to the mass of the magnetic toner, and a number average particle diameter of 0.3 to 3.0 μm on the toner particles, The following conditions are satisfied: 0.3 ≦ Te / Tm ≦ 1.7 for the magnetization amount Tm at a magnetic field strength of 79.6 kA / m and the magnetization amount Te at a magnetic field strength of 79.6 kA / m of the magnetic external additive particles.
It is characterized by satisfying.

  As described above, by using the magnetic toner of the present invention, an image having excellent image quality and no image defects can be obtained over a long period of time.

  As a result of intensive studies, the present inventors have significantly improved the uniformity of the triboelectric charging characteristics of the magnetic toner when the magnetization of the magnetic toner and the magnetization of the magnetic external additive particles are within a specific range. In addition, the present invention has been found to have an extremely favorable action when cleaning the surface of an image bearing member, and to have extremely good developability and cleaning characteristics.

In the magnetic quantity Tm of the magnetic toner at a magnetic field strength of 79.6 kA / m and the magnetic quantity Te of the magnetic external additive particles at a magnetic field strength of 79.6 kA / m, the following conditional expression 1;
0.3 ≦ Te / Tm ≦ 1.7 (conditional expression 1)
If the above condition is satisfied, the magnetic toner particles existing on the magnetic toner carrier and the magnetic external additive particles behave substantially in the same manner in the magnetic field, and as a result, the uniform chargeability of the magnetic toner is remarkably improved. A method for developing a thin layer of magnetic toner on the surface of the magnetic toner carrying carrier by using a regulating member, in particular, by reducing the amount of the magnetic toner carrying member that is free and adhering to the surface of the magnetic toner carrying member. When it is used, the non-uniform wear of the regulating member is effectively prevented, and it becomes possible to maintain a stable developability over a long period of time. Therefore, the inventors have found that good cleaning characteristics can be maintained, and have led to the invention.

  If Te / Tm is less than 0.3, the binding force of the magnetic external additive particles becomes small in the magnetic field, so that it is easily separated from the surface of the magnetic toner particles, so that the amount present in the magnetic toner tends to fluctuate. When Te / Tm exceeds 1.7, the binding force of the magnetic external additive particles increases, and the magnetic toner agglomerates or adheres firmly on the magnetic toner developing carrier and its surface. Is more preferably 0.4 or more and 1.5 or less.

Even if the amount of magnetization Tm at the magnetic field strength of 79.6 kA / m of the magnetic external additive particles exceeds 50 Am ² / kg, the amount remaining on the surface of the magnetic toner carrier even if the relationship (Condition 1) is satisfied. However, due to the polishing action, scraping of the surface of the magnetic toner carrier is promoted, and there is a tendency that sufficient durability cannot be obtained due to image defects such as a decrease in image density, an increase in fog, and the appearance of image streaks. is there. If it is less than 6 Am ² / kg, the magnetic binding force becomes weak and the amount present in the magnetic toner tends to fluctuate, and if the magnetic external additive particles are consumed rapidly, cleaning failure may occur. is there. Preferably it is 10-45 Am < ² > / kg.

If the magnetic quantity Tm at a magnetic field strength of 79.6 kA / m is less than 15 Am ² / kg, the transportability on the magnetic toner developing carrier tends to be inferior, and if it exceeds 50 Am ² / kg, the development efficiency is increased. Tends to decrease, or the developed image tends to be disturbed, and is preferably 20 to 35 Am ² / kg.

  Furthermore, in the present invention, the magnetic external additive particles have a number average particle diameter of 0.3 to 3.0 μm on the toner particles, but even if (Condition 1) is satisfied, the number average If the particle diameter is less than 0.3 μm, even if it exists on the magnetic toner particles, it is inferior in the effect of improving the uniformity of the triboelectric charge characteristics, and it is difficult to collect by the cleaning means, resulting in poor cleaning or It tends to adhere to the surface of the image carrier and cause a filming phenomenon. If it exceeds 3.0 μm, it tends to behave independently of the magnetic toner particles, promotes wear on the surface of the magnetic toner carrier, and is contained by long-term use. There is a tendency for the amount to fluctuate and cause problems in developability and cleanability. More preferably, it is 0.3-1.1 micrometers.

As a more preferable configuration, the following conditional expression 2 is satisfied for the magnetization amount Tm of the magnetic toner at a magnetic field strength of 79.6 kA / m and the magnetization amount Te of the magnetic external additive particles at a magnetic field strength of 79.6 kA / m:
500 ≦ Te × Tm ≦ 1400 (conditional expression 2)
By satisfying the above, a more stable magnetic toner layer can be formed on the magnetic toner carrier, and the stable density and fog can be reduced. If Te × Tm is less than 500, the magnetic toner or magnetic external additive particles are likely to be scattered and the inside of the machine may be contaminated. When Te × Tm exceeds 1400, magnetic toner or magnetic additive particles tend to remain on the magnetic toner carrier, and tend to cause image defects due to low density or scraping of the surface of the magnetic toner carrier. .

  In the present invention, the magnetization amount Te at a magnetic field strength of 79.6 kA / m of the magnetic external additive particles and the magnetization amount Tm of the magnetic toner at a magnetic field strength of 79.6 kA / m are determined by the vibrating sample magnetometer VSM. -3S-15 (manufactured by Toei Kogyo Co., Ltd.) and measured under an external magnetic field of 79.6 kA / m.

  The weight average diameter of the magnetic toner in the present invention is determined by the following method. As a measuring device, Coulter Counter TA-II or Coulter Multisizer II (manufactured by Coulter Inc.) is used. As the electrolyte, first grade sodium chloride is used to prepare an approximately 1% NaCl aqueous solution. For example, ISOTON-II (manufactured by Coulter Scientific Japan) can be used. As a measurement method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and the number of toner particles are measured for each channel using the measuring apparatus with a 100 μm aperture. Thus, the toner volume distribution and number distribution are calculated. Then, the weight-based toner weight average particle diameter (D4) obtained from the volume distribution of the toner particles (the median value of each channel is a representative value for each channel) is obtained.

  As channels, 2.00 to 2.52 μm; 2.52 to 3.17 μm; 3.17 to 4.00 μm; 4.00 to 5.04 μm; 5.04 to 6.35 μm; 6.35 to 8. 00 μm; 8.00 to 10.08 μm; 10.08 to 12.70 μm; 12.70 to 16.00 μm; 16.00 to 20.20 μm; 20.20 to 25.40 μm; 25.40 to 32.00 μm; 13 channels of 32.00-40.30 μm are used.

The magnetic external additive particles used in the present invention have a magnetization amount Te of 6 to 50 Am ² / kg at a magnetic field strength of 79.6 kA / m, and 0.1 to 0.1 mass relative to the magnetic toner mass. 3.5% by mass is contained. If the added amount is less than 0.1% by mass with respect to the mass of the magnetic toner, the effect is insufficient, and if it exceeds 3.5% by mass, the adverse effect due to the presence of a large amount becomes conspicuous. . Preferably, it is 0.2-2.5 mass%, More preferably, it is 0.3-2.0 mass%.

  The number average particle diameter of the magnetic external additive particles on the magnetic toner particles in the present invention is measured by the following method. Using arbitrarily selected magnetic toner particles having magnetic external additive particles and photographed at 50,000 times with an electron microscope, about 100 magnetic additive particles arbitrarily selected, 0.05 to 5 μm In this range, the diameters of the circles equal to the projected area are obtained, and the arithmetic average value thereof is used as the number average particle diameter. In this case, when the particles are present in an aggregated state on the magnetic toner particles, the aggregate is regarded as a magnetic external additive particle and measured. Further, it is preferable that the proportion of the magnetic external additive particles aggregated is 5% by number or more because it is difficult to cause image streaks, more preferably 10% by number or more and 30% by number. Particularly preferred results are obtained.

  At this time, the standard deviation in the number distribution is 1.2 μm or less, and the coefficient of variation is preferably 100% or less, and the effect of stabilizing the characteristics of the magnetic toner over a long period of time while causing less harmful effects such as image streaks. Have More preferably, it is 50% or less, and a state having a sharp distribution of 30% or less is particularly preferable.

  Here, the standard deviation is obtained by the following equation, and the variation coefficient is obtained by the following equation based on the obtained standard deviation.

  Examples of magnetic materials that can be used as the magnetic external additive particles of the present invention include metal oxides containing elements such as iron, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon. One means for obtaining magnetic characteristics preferably used in the present invention is to have a specific composition in the magnetic material, or to set a low content of FeO in the magnetite, or a trivalent metal such as aluminum. And the like may be included in the magnetic material.

  The magnetic toner particles of the present invention contain a binder resin and magnetic powder, and preferably contain a fixing aid or offset preventive agent, a charge control agent and the like.

  As an example of the binder resin preferably used for the magnetic toner particles of the present invention, examples of the binder resin used in the present invention include polystyrene, styrene-acrylate copolymer, and styrene-methacrylate copolymer. Styrene copolymers such as styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic resin, Acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin and the like can be used. A cross-linked styrene resin or polyester resin is a preferable binder resin.

The toner of the present invention is preferably used as a magnetic toner containing magnetic powder. Examples of magnetic materials that can be used include metal oxides containing elements such as iron, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon. These magnetic materials preferably have a BET specific surface area by nitrogen adsorption method of 1 to ²⁰ m ² / g, particularly 2.5 to 12 m ² / g, and a Mohs hardness of 5 to 7. Examples of the shape of the magnetic material include octahedron, hexahedron, spherical shape, needle shape, and flake shape, but those having low anisotropy such as octahedron, hexahedron, and spherical shape are preferable. This is because those having an isotropic shape can achieve good dispersion even with respect to the binder resin and the wax suitably used for the toner of the present invention. The number average particle size of the magnetic particles is preferably 0.05 to 0.5 μm, and more preferably 0.1 to 0.4 μm. Randomly select 100 particles on the photograph from a transmission electron micrograph (magnification 30000 times), measure the particle diameter, and use the average value as the number average particle diameter.

  The magnetic material is preferably added in an amount of 60 to 200 parts by weight, particularly preferably 70 to 150 parts by weight, based on 100 parts by weight of the binder resin. If the amount is less than 60 parts by mass, the toner transportability is insufficient, the toner layer on the magnetic toner carrier is uneven, and the image tends to be uneven. Further, the image density is lowered due to excessive increase in the charge of the toner. It tends to occur. On the other hand, when the amount exceeds 200 parts by mass, the toner cannot be sufficiently charged, and the image density is likely to be lowered.

  Examples of the wax used in the present invention are as follows. For example, aliphatic hydrocarbon wax such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, paraffin wax, microcrystalline wax, Fischer-Tropsch wax; oxide of aliphatic hydrocarbon wax such as oxidized polyethylene wax Or block copolymers thereof; plant waxes such as candelilla wax, carnauba wax, wax wax, rice wax, jojoba wax; animal waxes such as beeswax, lanolin, whale wax; ozokerite, ceresin, petrolactam, etc. Mineral waxes; waxes containing fatty acid esters such as montanic acid esters and castor waxes as main components; fatty acid esters such as deoxidized carnauba wax, which have been partially or fully deoxidized; and the like That.

  In a more preferable state of the toner of the present invention, the DSC curve at the time of temperature rise measured by a differential scanning calorimeter has a plurality of endothermic peaks at 60 to 170 ° C. More preferably, it is a preferable embodiment from the viewpoint of obtaining good fixability that has at least one endothermic peak in a temperature range of 60 to 110 ° C. As an achievement means for obtaining such a toner, it is preferable to include a wax having an endothermic peak in a temperature range of 60 to 110 ° C. in a DSC curve at the time of temperature rise measured by a differential scanning calorimeter.

  In the toner of the present invention, an organic metal compound is preferably used as the charge control agent, and in particular, a toner containing an organic compound rich in vaporization and sublimation as a ligand or counter ion is useful. As such a metal complex, a metal complex type monoazo compound is preferably used from the viewpoint of chargeability. Specific examples of the metal complex type monoazo compound include monoazo dyes described in JP-B No. 41-20153, JP-B No. 42-27596, JP-B No. 44-6397, JP-B No. 45-26478, and the like. There are metal complexes of In particular, from the viewpoint of dispersibility and chargeability, a metal complex type monoazo compound represented by the following general formula (I) is preferable, and among them, a metal complex type monoazo iron complex whose central metal is iron is preferably used. . More preferably, good results can be obtained by using a monoazo iron complex represented by the following general formula (II).

  The content of the metal complex monoazo compound is preferably 0.05 to 5 parts by mass, particularly preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the binder resin. If the content of the metal complex type monoazo compound is too large, the fluidity of the toner is deteriorated and fogging easily occurs. On the other hand, if the content is too small, it is difficult to obtain a sufficient charge amount.

  In the toner of the present invention, in addition to magnetic external additive particles, inorganic fine powder or hydrophobic inorganic fine powder is mixed with toner particles in order to improve environmental stability, charging stability, developability, fluidity, and storage stability. It is preferable. Examples of the inorganic fine powder include silica fine powder, titanium oxide fine powder, and hydrophobized products thereof. Silica fine powder is particularly preferable, and hydrophobized one is used.

  The hydrophobizing treatment is performed by chemically treating with an organosilicon compound that reacts or physically adsorbs with the silica fine powder. Preferable methods include a method in which a dry silica fine powder produced by vapor phase oxidation of a silicon halogen compound is treated with a silane compound or with a silane compound and simultaneously with an organosilicon compound such as silicone oil.

  Examples of the silane compound used for the hydrophobization treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and benzyl. Dimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethyldi Ethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetra Methyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and dimethylpolysiloxane containing 2 to 12 siloxane units per molecule and containing hydroxyl groups bonded to one silicon atom at each terminal unit Etc.

Examples of the organosilicon compound include silicone oil. Preferred silicone oils include those having a viscosity at 25 ° C. of 30 to 1000 mm ² / s. For example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified Particularly preferred is silicone oil.

  As a method for treating silicone oil, for example, silica fine powder treated with a silane compound and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or a method of spraying silicone oil on silica fine powder. May be used. Alternatively, after dissolving or dispersing silicone oil in an appropriate solvent, silica fine powder may be added and mixed to remove the solvent.

  The silica fine powder or titanium oxide fine powder is preferably added in an amount of 0.1 to 3 parts by weight, more preferably 0.2 to 2 parts by weight, based on 100 parts by weight of the toner.

  The magnetic toner of the present invention, after sufficiently mixing the above toner constituent materials with a mixer such as a ball mill, is melted, kneaded and kneaded using a heat kneader such as a heating roll, a kneader, an extruder, etc. It is pulverized using a pulverizer, and magnetic toner particles are obtained by strict classification using a classifier, and obtained by mixing external additives with a mixer such as a Henschel mixer. It can be obtained by removing coarse particles.

Examples of the mixer include Henschel mixer (manufactured by Mitsui Mining); Super mixer (manufactured by Kawata); Ribocorn (manufactured by Okawara Seisakusho); Nauter mixer, turbulizer, cyclomix (manufactured by Hosokawa Micron); Spiral pin mixer (Manufactured by Taiheiyo Kiko Co., Ltd.); Laedige mixer (manufactured by Matsubo);
As a kneading machine, KRC kneader (manufactured by Kurimoto Iron Works); Bus co-kneader (manufactured by Buss); TEM type extruder (manufactured by Toshiba Machine); TEX twin-screw kneader (manufactured by Nippon Steel Works); PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.); three roll mill, mixing roll mill, kneader (manufactured by Inoue Seisakusho); kneedex (manufactured by Mitsui Mining Co., Ltd.); MS pressure kneader, nider ruder (manufactured by Moriyama Seisakusho); Banbury mixer (manufactured by Kobe Steel);

  As a pulverizer, a counter jet mill, a micron jet, an inomizer (manufactured by Hosokawa Micron); an IDS type mill, a PJM jet pulverizer (manufactured by Nippon Pneumatic Industry Co., Ltd.); a cross jet mill (manufactured by Kurimoto Iron Works Co., Ltd.); SK Jet Oh Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Turbo Mill (manufactured by Turbo Industry Co., Ltd.);

  Classifiers include: Classy, Micron Classifier, Spedic Classifier (manufactured by Seishin Enterprise); Turbo Classifier (manufactured by Nissin Engineering); Micron Separator, Turboplex (ATP), TSP Separator (manufactured by Hosokawa Micron) Elbow Jet (manufactured by Nippon Steel & Mining Co., Ltd.), Dispersion Separator (manufactured by Nippon Pneumatic Industrial Co., Ltd.); YM Microcut (manufactured by Yaskawa Shoji Co., Ltd.).

  Furthermore, it is also preferable to use a sieving device used for sieving coarse particles, etc., as the sieving device, Ultrasonic (manufactured by Sakae Sangyo Co., Ltd.); Resona Sheave, Gyroshifter (Tokuju Kogakusha Co., Ltd.); Vibrasonic System ( Dalton Co.); Soniclean (Shinto Kogyo Co., Ltd.); Turbo Screener (Turbo Kogyo Co., Ltd.); Micro Shifter (Ogino Sangyo Co., Ltd.);

  The magnetic toner of the present invention is used in the following image forming method.

  Using a charging means such as a corona charger such as corotron or scorotron, a conductive roller, a fur brush, or a magnetic brush, a voltage is applied to charge the photoconductor in a contact or non-contact state. An electrostatic latent image is formed on the charged photoreceptor by exposure means such as a laser or LED, and developed with magnetic toner.

  The photoreceptor is an electrophotographic inorganic photoreceptor such as amorphous silicon, a single layer structure containing a charge generation material and a charge transport material as a photosensitive layer, and a charge transport containing a charge transport material on the charge generation layer containing the charge generation material. An electrophotographic organic photoreceptor having a function-separated laminated structure in which a layer is provided or a charge generation layer is provided on a charge transport layer can be used. Further, a protective layer can be provided on the photosensitive layer.

  As the developing means, a magnetic one-component developing means including a configuration in which a conductive sleeve containing a magnet is used as a toner carrier and a toner layer is regulated by a magnetic blade or an elastic blade is preferably used as a one-component magnetic toner.

  The magnetic toner image thus obtained can be transferred to a transfer material in a state of contact or non-contact with the photoreceptor using a corona charger or a conductive member such as a roller, a blade, or a brush as a voltage application unit, or a belt Then, after a toner transfer image is formed using the drum or the like as an intermediate transfer member, the image is transferred to a transfer material.

  The toner remaining on the photoreceptor or the intermediate transfer member is removed by the cleaning unit. Examples of the cleaning means include cleaning means using an elastic blade, an elastic roller, a fur brush, and a magnetic brush, and an elastic blade is a preferable configuration.

As one of preferred embodiments, a process cartridge that is detachable from the image forming apparatus and includes a developing device and at least one of a photosensitive member, a cleaning device, and a charging device can be exemplified.
In this case, the developing device has a toner container for storing the magnetic toner of the present invention, and preferably has the configuration shown in FIG. 1, FIG. 2, or FIG.

  The toner image formed on the transfer material is fixed by heat or pressure.

  FIG. 1 is a schematic view showing one preferred embodiment of a developing device using the magnetic toner of the present invention. In FIG. 1, an electrophotographic photosensitive member (drum) 1 which is an image carrier that holds the formed electrostatic latent image is rotated in the direction of arrow B. The conductive sleeve 8 as a toner carrier carries the magnetic toner 4 supplied by the hopper 3 as a toner container and rotates in the direction of arrow A, whereby the conductive sleeve 8 and the electrophotographic photosensitive member (drum). The magnetic toner 4 is transported to the developing area D that is opposite to the developing area D. In the conductive sleeve 8, in order to magnetically attract and hold the magnetic toner 4 on the conductive sleeve 8, a magnet roller 5 as a magnet included is disposed.

  The conductive sleeve 8 preferably used in the present invention can use the metal cylindrical tube 6 as a base as it is, but preferably has a conductive resin coating layer 7 coated on the metal cylindrical tube 6. It is also one of preferable configurations to have a thin metal layer (preferably 1 to 300 μm) formed by plating a metal such as nickel, chromium or molybdenum on a metal cylindrical tube 6 as a substrate. One. In the hopper 3, a stirring blade 10 for stirring the magnetic toner 4 is provided. A gap 12 indicates that the conductive sleeve 8 and the magnet roller 5 are not in contact with each other.

  In the example of FIG. 1, in order to regulate the layer thickness of the magnetic toner 4 conveyed to the development region D, the magnetic regulation member 2 made of ferromagnetic metal as the magnetic toner layer thickness regulation member is provided on the surface of the conductive sleeve 8. Is suspended from the hopper 3 so as to have a gap width of about 50 to 500 μm. A magnetic force line from the magnetic pole N 1 of the magnet roller 5 concentrates on the magnetic restriction member 2, whereby a thin layer of the magnetic toner 4 is formed on the conductive sleeve 8. In the present invention, a nonmagnetic member can be used instead of the magnetic regulating member 2. The thickness of the thin layer of the magnetic toner 4 formed on the conductive sleeve 8 by the magnetic toner layer thickness regulating member is smaller than the minimum gap between the conductive sleeve 8 and the electrophotographic photosensitive member (drum) 1 in the region D. Also make it thinner.

  The magnetic toner carrier of the present invention is particularly effective when incorporated in a developing device that develops an electrostatic latent image with a thin layer of magnetic toner as described above, that is, a non-contact developing device.

  In order to cause the magnetic toner 4 carried on the conductive sleeve 8 to fly, a developing bias voltage is applied to the conductive sleeve 8 by a developing bias power source 9 as a bias applying means. When a DC voltage is used as the developing bias voltage, a voltage having a value between the potential of the image portion of the electrostatic latent image (the region visualized by adhesion of the magnetic toner 4) and the potential of the background portion is electrically conductive. Although applied to the sleeve 8, in order to increase the density of the developed image or improve the gradation, an alternating bias voltage is applied to the conductive sleeve 8, and the direction is alternately reversed in the development region D. It is more preferable to form an oscillating electric field.

  2 and 3 are schematic configuration diagrams showing another preferred embodiment of the developing device using the magnetic toner of the present invention, and FIG. 2 is a schematic configuration diagram showing still another preferred embodiment.

  2 and 3, the magnetic toner layer thickness regulating member 11 for regulating the layer thickness of the magnetic toner 4 on the conductive sleeve 8 is a material having rubber elasticity such as urethane rubber or silicone rubber, or A magnetic toner layer thickness regulating member made of an elastic plate made of a material having metal elasticity such as phosphor bronze or stainless steel is used. In the developing device shown in FIG. 2, the magnetic toner layer thickness regulating member 11 is pressed in the direction opposite to the rotation direction of the conductive sleeve 8, and in the developing device shown in FIG. A characteristic is that the contact sleeve 8 is in pressure contact with the direction of rotation and the forward direction.

  In these developing devices, the magnetic toner layer thickness regulating member 11 is elastically pressed against the conductive sleeve 8 via the magnetic toner layer. When there is no magnetic toner layer, the conductive sleeve 8 and the magnetic toner layer thickness regulating member 11 are in contact with each other. Since the magnetic toner thin layer is formed on the conductive sleeve, the magnetic toner layer can be formed on the conductive sleeve 8 more stably than in the case of FIG. It is. The contact pressure of the magnetic toner layer thickness regulating member 11 with respect to the conductive sleeve 8 is a linear pressure of 5 to 50 g / cm, so that the regulation of the magnetic toner can be stabilized and the magnetic toner layer thickness can be made suitable. This is preferable. When the contact pressure of the magnetic toner layer thickness regulating member is less than the linear pressure of 5 g / cm, the regulation of the magnetic toner becomes weak, which may cause fogging or leakage of the magnetic toner. If it exceeds, damage to the magnetic toner is increased, which tends to cause deterioration of the magnetic toner and fusion to the conductive sleeve 8 and the magnetic toner layer thickness regulating member 11.

  2 and 3 is the same as that of the developing device shown in FIG. FIGS. 1 to 3 schematically illustrate a developing device in which the magnetic toner of the present invention is preferably used. Various forms of the shape of the magnetic toner container (hopper 3), the presence / absence of the stirring blade 10 and the arrangement of the magnetic poles are illustrated. It goes without saying that there is.

(Evaluation method and image forming apparatus used for evaluation)
In Examples described later, the magnetic toner was evaluated using the image forming apparatus shown in FIG.

  First, the surface of an electrophotographic photosensitive member (drum) 1 as an image carrier is negatively charged by contact (roller) charging means 17 as primary charging means, and a digital latent image is obtained by image scanning by laser light exposure 18. Is formed on the electrophotographic photosensitive member (drum) 1. Next, the above-mentioned digital latent image is transferred into the hopper 3 as a magnetic toner container by a developing device having a magnetic toner layer thickness regulating member 12 'and having a conductive sleeve 8 as a magnetic toner carrier. Reversal development is performed by magnetic toner 4 (in this case, negative chargeability). As shown in FIG. 4, the electroconductive substrate of the electrophotographic photosensitive member (drum) 1 is grounded. An alternating bias voltage, an oscillating electric field and / or a DC voltage is applied to the conductive sleeve 8 by a bias applying means 9.

  In this embodiment, the process speed was 94 mm / s, and a charging roller having a diameter of 12 mm was used as the charging means. The charging bias to be applied superimposes -700 V as a direct current component, a frequency of 1 kHz and a sine wave of 1500 Vpp as an oscillating electric field, and charges the electrophotographic photosensitive member (drum) 1. The bright portion potential of the electrophotographic photosensitive member (drum) 1 by the exposure 18 of the laser beam is -120V.

  The electrophotographic photosensitive member (drum) 1 is formed by forming a charge generation layer containing a phthalocyanine pigment on a 30 mm diameter aluminum cylinder and then a charge transport layer containing a polycarbonate resin and a charge transport agent to a thickness of 26 μm. Is.

  The magnetic toner layer thickness regulating member 12 'is obtained by abutting a silicone rubber blade having a thickness of 1 mm as shown in the figure. The contact pressure was a linear pressure of 30 g / cm.

  Next, when the recording material P is conveyed and arrives at the transfer portion, the contact (roller) transfer means 19 as the transfer means causes the recording material P from the back surface (the surface opposite to the electrophotographic photosensitive member (drum) 1 side). By being charged by the voltage application means 20, the developed image formed on the surface of the electrophotographic photosensitive member (drum) 1 is transferred onto the recording material P by the contact transfer means 19. Next, the recording material P separated from the electrophotographic photosensitive member (drum) 1 is conveyed to a heat and pressure roller fixing device 21 as a fixing unit, and the developed image on the recording material P is fixed by the fixing device. Processing is done.

  The magnetic toner 4 remaining on the electrophotographic photosensitive member (drum) 1 after the transfer process is removed by a cleaning unit 23 having a cleaning blade 22. When the remaining magnetic toner 4 is small, the cleaning step can be omitted. The electrophotographic photosensitive member (drum) 1 after cleaning is neutralized by erase exposure 24 if necessary, and the above process starting from the charging process by the contact (roller) charging means 17 as the primary charging means is repeated again.

  The electrophotographic photosensitive member (drum) 1 has a photosensitive layer and a conductive substrate, and moves in the direction of arrow B. The conductive sleeve 8 rotates so as to proceed in the same direction (arrow A direction) as the surface of the electrophotographic photosensitive member (drum) 1 in the development region D. The magnetic toner 4 in the hopper 3 is carried on the conductive sleeve 8 and, for example, negative triboelectric charge is given by friction with the surface of the conductive sleeve 8 and / or friction between the developers. Further, the thickness of the magnetic toner layer is controlled to be thin (30 μm to 300 μm) and uniformly by the magnetic toner regulating member 12 ′, and the gap between the electrophotographic photosensitive member (drum) 1 and the conductive sleeve 8 in the development region D is determined. A thinner magnetic toner layer is formed. In this embodiment, the gap between the electrophotographic photosensitive member (drum) 1 and the conductive sleeve 8 in the developing region D is set to 300 μm, the rotation speed of the developing sleeve 8 is set to the surface speed of the conductive sleeve 8. The speed is set to 1.1 times the speed of the surface of the body (drum) 1.

  In the developing region D, an alternating bias voltage or an oscillating electric field is applied to the conductive sleeve 8 as a developing bias voltage by the bias applying means 9. The alternating bias voltage only needs to be a frequency f of 200 to 4,000 Hz and a Vpp of 500 to 3,000 V. In this embodiment, a rectangular wave of 2 kHz and 1600 Vpp was used. When the magnetic toner is transferred in the development region D, the magnetic toner is transferred to the electrostatic latent image side by the electrostatic force on the surface of the electrophotographic photosensitive member (drum) 1 and the development bias voltage such as an alternating bias voltage or an oscillating electric field. To do.

  The evaluation was performed in three environments of a temperature 23 ° C. relative humidity 5% (N / L), a temperature 23 ° C. relative humidity 55% (N / N), and a temperature 30 ° C. relative humidity 85% (H / H). After 100 sheets of A4 landscape feed were passed through one sheet of paper and a character image having a printing ratio of 3% was printed out, 4000 sheets of A4 paper was fed through 3 sheets of paper at a rate of 3%, and the printing ratio was 3%. Printed out a character image with. In the examples described later, Table 4 shows the evaluation results after 100-sheet printout performed with one sheet spacing, and Table 5 shows the evaluation results after 4000-sheet printout performed with three sheet spacing.

Evaluation items are
1. Image density The density of a solid image printed on ordinary plain paper for copying machines (75 g / m ² ) is measured using a Macbeth reflection densitometer (manufactured by Macbeth).
A: 1.35 or more B: 1.30 to 1.34
C: 1.20-1.29
D: 1.19 or less Fog Fog is measured using a reflection densitometer (TOKYO DENSHOKU CO., LTD, REFECTOMETERMODEL TC-6DS) (Ds is the worst reflection density value of a solid white image after printing, Ds is the average reflection density value of the paper before printing. (Dr and Ds-Dr were used as fogging amounts). If the fogging amount exceeds 5%, the fogged image becomes conspicuous. If the fogging amount is less than 5%, the fogging is somewhat noticeable. If it is less than 2%, it is an image with little fog, and if it is less than 1%, it is an image without fog.
A: Fog is less than 1% B: Fog is less than 1 to 2% C: Fog is 2 to 5% or less D: Fog is more than 5% Image streaks Evaluate with solid black, solid white, or halftone images.
A: No image streaks B: Slightly recognized C: Slight but slight D: Clearly recognized 4. Cleanability A: No cleaning failure B: Cleaning is minor but minor C: Cleaning failure Image flow A: None B: Slight occurrence C: Occurrence Spatter A: No B: Slightly C: Yes

(Example)
Hereinafter, examples will be shown, but the present invention is not limited to the description of the examples.

(Magnetic external additive particles 1)
In a 4-liter three-necked flask, 1 liter of 0.35 mol / l aluminum sulfate aqueous solution was mixed with sodium hydroxide aqueous solution, and 1 liter of 0.8 mol / l ferrous sulfate aqueous solution was added thereto to adjust the pH to 11 Oxidation was performed at about 75 ° C. while blowing an oxygen-containing gas while maintaining the degree. Next, after adjusting the pH of the reaction solution to about 7, the magnetic particles were filtered, washed with water, classified by sedimentation, dried and crushed to obtain magnetic external additive particles 1. The properties are listed in Table 1.

(Magnetic external additive particles 2, 3 and 4)
In the magnetic external additive particles 1, the concentrations of the aqueous sodium hydroxide solution and the aqueous aluminum sulfate solution were changed to obtain magnetic external additive particles 2, 3 and 4. The properties are listed in Table 1.

(Magnetic external additive particles 5)
An acicular goethite core particle is generated by aeration of an oxygen-containing gas into a reaction solution containing an iron-containing precipitate obtained by reacting an aqueous ferrous salt solution with an aqueous solution of less than an equivalent amount, and then the needle-like goethite core particles are generated. By passing an oxygen-containing gas through the ferrous salt reaction aqueous solution containing goethite core particles while maintaining the pH value of this solution within the range of 3 to 6 while adding an alkaline aqueous solution, A growth reaction is performed to produce acicular goethite particles. Next, the acicular goethite particles are gently reduced, and the magnetic external additive particles 5 having a number average particle size of 0.37 μm, a magnetization amount Te at a magnetic field strength of 79.6 kA / m of 4.6 Am ² / kg, and so on. Got. The properties are listed in Table 1.

(Magnetic external additive particles 6)
In the magnetic external additive particles 5, the acicular goethite generation conditions are adjusted, and after obtaining the acicular goethite particles, they are reduced and the number average particle diameter 0.17 μm The magnetic field strength Te at a magnetic field strength of 79.6 kA / m However, magnetic external additive particles 6 of 15.7 Am ² / kg were obtained. The properties are listed in Table 1.

(Magnetic external additive particles 7)
Α-Fe ₂ O ₃ having an average particle size of 0.5 μm was heated in air at 1000 ° C. for 5 hours, then cooled and pulverized by an atomizer to obtain α-Fe ₂ O ₃ having an average particle size of about 4 μm. . This was reduced, crushed after cooling, and magnetic external additive particles 7 having a number average diameter of 3.5 μm were obtained. The properties are listed in Table 1.

(Magnetic external additive particles 8)
Α-Fe ₂ O ₃ having an average particle size of 0.5 μm was heated in air at 1000 ° C. for 5 hours, then cooled and pulverized by an atomizer to obtain α-Fe ₂ O ₃ having an average particle size of about 2 μm. . This was reduced, crushed after cooling, and 1.3 μm magnetic external additive particles 8 were obtained. The properties are listed in Table 1.

(Magnetic external additive particles 9)
The magnetic external additive particles 8 were classified by a sedimentation method to obtain 1.5 μm magnetic external additive particles 9. The properties are listed in Table 1.

(Example of magnetic toner particle production)
Styrene acrylic resin (styrene / n-butyl acrylate / n-butyl methacrylate copolymer resin, copolymerization ratio 80/14/6, weight average molecular weight 350,000), magnetite (number average diameter 0.25 μm, saturation magnetization at 796 kA / m) Amount σs 89 Am ² / kg), paraffin wax (melting point 105 ° C.) and metal-containing azo compound having the following structure (Chemical formula 3), molar ratio of NH ⁴⁺ , Na ⁺ and H ⁺ = 0.9: 0.05: 0 .05) was prepared.
Styrene acrylic resin 100 parts by weight Magnetite 100 parts by weight Paraffin wax 3.5 parts by weight Metal-containing azo compound 1.5 parts by weight The above was mixed with a Henschel mixer, kneaded with a biaxial extruder, and obtained with a hammer mill The coarsely pulverized material was pulverized and classified to adjust the particle size, whereby magnetic toner particles 1 were obtained.

  Hereinafter, magnetic toner particles 2, 3 and 4 listed in Table 2 were produced according to the formulations listed in Table 2. Table 2 lists the characteristics of each magnetic toner particle.

Example 1
Further to 1.0 part by mass of magnetic external additive particles 1 and 100 parts by mass of magnetic toner particles 1 and silica treated with hexamethyldisilazane (original BET specific surface area 200 m ² / g) 1.2 parts by mass of hydrophobic silica treated with dimethyl silicone oil was added and mixed with a Henschel mixer to obtain a magnetic toner.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

(Example 2)
Furthermore, the silica particles (BET specific surface area 200 m ² / g of the original material) subjected to surface treatment with 0.8 parts by mass of the magnetic external additive particles 1 and hexamethyldisilazane with respect to 100 parts by mass of the magnetic toner particles 2 are further added. 1.0 part by mass of hydrophobic silica treated with dimethyl silicone oil was added and mixed with a Henschel mixer to obtain a magnetic toner.
Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

(Example 3)
Further, silica (surface BET specific surface area of 200 m ² / g of the original) was further applied to 1.3 parts by mass of magnetic external additive particles 1 and 100 parts by mass of magnetic toner particles 3 and hexamethyldisilazane. 1.5 parts by mass of hydrophobic silica treated with dimethyl silicone oil was added and mixed with a Henschel mixer to obtain a magnetic toner.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

(Example 4) to (Example 7)
A magnetic toner was produced in the same manner as in Example 1 except that the magnetic external additive particles shown in Table 3 were used.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

(Example 8)
Further, to 100 parts by mass of magnetic toner particles 4 and silica (surface BET specific surface area 200 m ² / g) obtained by subjecting the magnetic external additive particles 1 to surface treatment with 0.7 parts by mass and hexamethyldisilazane. 0.8 parts by mass of hydrophobic silica treated with dimethyl silicone oil was added and mixed with a Henschel mixer to obtain a magnetic toner.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

Example 9
In Example 3, a magnetic toner was produced in the same manner except that the magnetic external additive particles shown in Table 3 were used.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

(Comparative Example 1) to (Comparative Example 4)
A magnetic toner was prepared in the same manner as in Example 1 except that the magnetic external additive particles were changed as shown in Table 3.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

  In Comparative Example 1, the evaluation was aborted because defects caused by scraping of the electrophotographic photosensitive member (drum) occurred during 2000 durability tests.

  In Comparative Example 3, the evaluation was terminated because the filming due to the magnetic external additive particles occurred on the electrophotographic photosensitive member (drum) during 1000 durability tests and the image density decreased.

  Image streaks in Comparative Example 4 are largely caused by scratches on the photoreceptor.

(Comparative Example 5)
To the silica (the original BET specific surface area 200 m ² / g) subjected to surface treatment with 0.8 parts by mass of magnetic external additive particles 2 and hexamethyldisilazane with respect to 100 parts by mass of magnetic toner particles 2 1.0 part by mass of hydrophobic silica treated with dimethyl silicone oil was added and mixed with a Henschel mixer to obtain a magnetic toner.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

  Image streaks after the durability test are caused by wear of the conductive sleeve.

(Comparative Example 6)
Furthermore, the magnetic external additive particles 2 are added to 0.7 parts by mass of the magnetic toner particles 4 and 100 parts by mass of silica and the surface-treated silica (hexagonal BET specific surface area of 200 m ² / g) is further added to hexamethyldisilazane. 1.0 part by mass of hydrophobic silica treated with dimethyl silicone oil was added and mixed with a Henschel mixer to obtain a magnetic toner.

  Table 3 shows the characteristics, and Table 5 shows the evaluation results after printing out 100 sheets performed with one sheet, and Table 5 shows the evaluation results after printing 4000 sheets with three sheets.

  Image streaks after the durability test are caused by wear of the conductive sleeve.

1 shows an example of a developing device of the present invention. 1 shows an example of a developing device of the present invention. 1 shows an example of a developing device of the present invention. 1 shows an example of an image forming apparatus of the present invention.

Claims (3)

In a magnetic toner containing magnetic toner particles having magnetic powder and binder resin and magnetic additive particles,
The magnetic toner has a weight average diameter of 4 to 11 μm, a magnetization Tm at a magnetic field strength of 79.6 kA / m of 15 to 50 Am ² / kg,
The magnetic external additive particles have a magnetization amount Te of 6 to 50 Am ² / kg at a magnetic field strength of 79.6 kA / m, and are contained in an amount of 0.1 to 3.5% by mass with respect to the mass of the magnetic toner. A number average particle diameter of 0.3 to 3.0 μm on the toner particles,
With respect to the magnetization amount Tm of the magnetic toner at a magnetic field strength of 79.6 kA / m and the magnetization amount Te of the magnetic external additive particles at a magnetic field strength of 79.6 kA / m, the following conditions are satisfied: 0.3 ≦ Te / Tm ≦ 1 .7
A magnetic toner characterized by satisfying   2. The magnetic toner according to claim 1, wherein the magnetic toner has silica fine powder on the surface of the magnetic toner particles in addition to the magnetic external additive. In the magnetic toner, the magnetization amount Tm at a magnetic field strength of 79.6 kA / m and the magnetic amount of the magnetic external additive particles at a magnetic field strength Te of 79.6 kA / m under the following conditions:
500 ≦ Te × Tm ≦ 1400
The magnetic toner according to claim 1, wherein:

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