JP2007163728A - Magnetic carrier, two components series developer, supply developer, and developing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic carrier, a two components series developer, a supply developer and a developing method for preventing carrier deposition on the surface of a photoreceptor even when a magnetic carrier of a small particle size is used and for obtaining an image of high picture quality without an image defect. <P>SOLUTION: The carrier is a magnetic material-containing resin carrier containing a resin and a magnetic material, having the absolute specific gravity of 2.5 to 4.2 g/cm<SP>3</SP>, magnetization intensity of 40 to 70 Am<SP>2</SP>/kg in a magnetic field of 1,000/4π (kA/m) and a 50%-particle diameter (D50) on a volume distribution basis of 15 μm to 25 μm and satisfying a relation of 0≤log(R1)-log(R2)≤2.0, wherein R1 (Ω cm) represents a specific resistance when a voltage giving an electric field intensity of 1.0×10<SP>6</SP>V/m is applied and R2 (Ω cm) represents a specific resistance when a voltage giving an electric field intensity of 2.5×10<SP>6</SP>V/m is applied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic carrier, a two-component developer, a replenishment developer, and a developing device used in an electrophotographic system, an electrostatic recording system, and an electrostatic printing system.

  In the electrophotographic method, a uniformly charged image forming body is exposed to light to form a latent image, the latent image is developed into a toner image, and then the toner image is transferred to a transfer material such as recording paper. Is done. When the transfer material carrying the toner image passes through the fixing device, the toner is fixed on the transfer material. In developing a latent image, a one-component or two-component development method is used, and the development method is adopted in accordance with these characteristics. The two-component development method is said to be excellent in high image quality and high durability.

  As described above, a two-component developer is preferably used for high image quality, and for further image quality development, the toner has a small particle size and a sharp particle size distribution, and the carrier has a smaller particle size. There has been a proposal to develop the agent in a non-contact manner (see, for example, Patent Document 1).

  However, although the toner particle size and carrier particle size are effective for high image quality, in non-contact development, the uniformity in the solid portion may be inferior. Furthermore, when the carrier is reduced in particle size, the granulation properties of the carrier particles are likely to be difficult, and the carrier strength is weakened due to insufficient carrier coalescence, fine powder generation, and sintering, and the developer fluidity. In some cases, fogging due to poor charging or crushed carrier adheres to the photoconductor, causing scratches on the photoconductor and causing image defects.

  Therefore, a magnetic material dispersion type resin carrier in which magnetic fine particles are dispersed in a binder resin instead of the conventional iron powder carrier, ferrite carrier and the like has been proposed (for example, see Patent Document 2).

  The magnetic material-dispersed resin carrier tends to have a relatively small particle size compared to the ferrite carrier, and in particular, the carrier made by the polymerization method tends to be spherical and has excellent fluidity and is suitably used for high image quality. Further, since the true specific gravity is small, it is advantageous for toner spent and has the advantage of excellent durability.

  However, even in the case of a magnetic material-dispersed resin carrier, when the particle size is reduced, a carrier having a low resistance is easily attached to the carrier. Thus, unless the resistance value of the carrier is increased, image defects are likely to become more prominent.

  Therefore, a proposal has been made to satisfy the charging property, durability, carrier adhesion prevention, etc. by coating the carrier surface and controlling the amount of fine powder in the carrier particle size distribution and the strength of magnetization of the fine powder (for example, (See Patent Document 3).

  However, in further reduction of the carrier particle diameter, carrier adhesion cannot be sufficiently improved only by controlling the strength of magnetization of the carrier fine powder.

  In the normal two-component development method, the toner in the developing device is consumed and the replenishment of the shortage is performed with new toner. However, since the carrier is continuously used, the development of the carrier is caused by the deterioration of the carrier. There is a problem that the performance deteriorates and the work of periodically changing the developer in the developing device occurs, and replenishment toner and carrier are replenished at a constant ratio, and the carrier in the developing device whose developing performance is deteriorated gradually. A new carrier has been proposed (referred to as trickle development), and these maintenance operations are unnecessary (see, for example, Patent Document 4).

  However, in this trickle development method, since the replenishment developer containing the carrier is replenished, there is a problem in the mixing property with the developer in the developing device. For example, when the mixing property is deteriorated, the charge amount of the developer may be uneven, and the development characteristics may be deteriorated.

Japanese Examined Patent Publication No. 6-90543, page 1, FIG. 1, FIG. Japanese Patent Registration No. 3284488, page 1-3 JP-A-2002-91090, page 2-4 Japanese Patent Publication No. 2-21591

  An object of the present invention is to provide a magnetic carrier, a two-component developer, and a replenishing agent that can prevent the carrier from adhering to the surface of the photoreceptor even when a magnetic carrier having a small particle diameter is used and can obtain a high-quality image without image defects. The object is to provide a developer and a developing method.

  Another object of the present invention is to provide a magnetic carrier and a two-component developer that can prevent deterioration of a toner that is excellent in low-temperature fixability or excellent in high-speed output and can output a stable image over a long period of time.

  It is another object of the present invention to develop a replenishment developer containing at least toner and a magnetic carrier while replenishing the developer, and to discharge the excess carrier inside the developer from at least the developer. An object of the present invention is to provide a replenishing agent and a developing method that can be mixed efficiently in a developing device to obtain high durability and high image quality in a replenishing developer for use in the two-component developing method.

  As a result of intensive studies, the present inventors have used a specific magnetic carrier, a two-component developer containing a toner and a carrier, and a replenishment developer, so that no carrier adhesion occurs, and the inside of the developing device It was found that the developer can be mixed efficiently and high durability and high image quality can be obtained.

That is, the above object can be achieved by using the following magnetic carrier, two-component developer, replenishment developer, and development method.
(1) A magnetic substance-containing resin carrier containing a resin and a magnetic substance,
The true specific gravity is 2.5 to 4.2 g / cm ³ ;
The magnetization intensity under a magnetic field of 1000 / 4π (kA / m) is 40 to 70 Am2 / kg,
50% particle size (D50) based on volume distribution is 15 μm to 25 μm,
The specific resistance when applying a voltage with an electric field strength of 1.0 × 10 ⁶ V / m is R1 (Ω · cm),
The relationship of 0 ≦ log (R1) −log (R2) ≦ 2.0, where R2 (Ω · cm) is the specific resistance when a voltage with an electric field strength of 2.5 × 10 ⁶ V / m is applied. A magnetic carrier characterized by satisfying
(2) The magnetic carrier according to claim 1, wherein the specific resistance R2 of the magnetic carrier is 1.0 × 10 ¹³ (Ω · cm) or more.
(3) The average circularity C of the magnetic carrier is 0.850 to 0.950 and satisfies the relationship of 0 ≦ (C−C30) ≦ 0.20 with the 30% value C30 of the circularity. The magnetic carrier according to (1) or (2), wherein
(4) (1) to (3) formed by forming a second resin coating layer containing conductive particles on the first resin coating layer and the first resin coating layer on the surface of the magnetic carrier core particles. Any one of the magnetic carriers.
(5) The magnetic carrier according to any one of (1) to (4), wherein 0.5 to 3.0% by mass of the first resin is coated on the magnetic carrier core particles.
(6) The magnetic carrier according to any one of (1) to (5), wherein the conductive particles contained in the second resin coating layer are carbon black.
(7) The magnetic carrier core particles are magnetic material dispersed resin core particles obtained by polymerizing a monomer for forming a binder resin in the presence of a magnetic material. (1) to (6) ) Magnetic carrier according to any one of
(8) A toner including at least a binder resin and a colorant and the magnetic carrier according to any one of (1) to (7), wherein the weight average particle diameter (D4) of the toner is Rt, and the volume distribution of the magnetic carrier. A two-component developer, wherein Rt / Rc is 0.15 or more and 0.80 or less, where Rc is a reference average particle diameter (D50).
(9) A replenishing developer containing 2 to 50 parts by mass of toner with respect to 1 part by mass of the magnetic carrier.
(10) Two-component development in which at least developer and developer containing toner and carrier are developed while being replenished to the developing device, and excessive toner and carrier are discharged from the developing device as needed. A two-component development method, wherein the magnetic carrier is the magnetic carrier according to any one of (1) to (7).

  According to the present invention, by reducing the carrier particle size, having a certain degree of magnetization, and suppressing the carrier resistance fluctuation with respect to the electric field strength, the carrier adhesion is prevented and a high-quality image is obtained. Deterioration can be prevented and a stable image can be obtained over a long period of time.

  In addition, by using the magnetic carrier, the two-component developer, the replenishment developer, and the developing method of the present invention, the developer can be efficiently mixed in the developing device, and high durability and high image quality can be stably obtained. Can do. Specifically, an image with good dot reproducibility and little fogging can be obtained over a long period of time.

The magnetic carrier of the present invention (hereinafter also simply referred to as “carrier”) is a magnetic substance-containing resin carrier containing a resin and a magnetic substance, and has a true specific gravity of 2.5 to 4.2 g / cm ³ , the strength of magnetization under a magnetic field of 1000 / 4π (kA / m) is 40 to 70 Am ² / kg, the volume distribution standard 50% particle size (D50) is 15 μm to 25 μm, The specific resistance when a voltage with an electric field strength of 0.0 × 10 ⁶ V / m is applied is R1, and the specific resistance when a voltage with an electric field strength of 2.5 × 10 ⁶ V / m is applied is R2. In this case, the relation 0 ≦ log (R1) −log (R2) ≦ 2.0 is satisfied.

  As a result of intensive studies on the magnetic carrier by the present inventors, by satisfying the above requirements, it is possible to prevent the carrier from adhering to the photoreceptor and to obtain a high-quality image, and further to prevent toner deterioration for a long time. It has been found that a stable image can be obtained and that high durability and high image quality can be obtained by mixing efficiently in a developing device.

  Details of the magnetic carrier of the present invention will be described below.

<Carrier of the present invention>
The carrier of the present invention is a carrier containing a resin and a magnetic material, and includes a coat layer.

  The magnetic material-containing resin core of the present invention (hereinafter also simply referred to as “carrier core”) includes a resin and a magnetic material. The carrier of the present invention may be a so-called resin-impregnated carrier in which a porous magnetic material (including porous ferrite) is impregnated with a resin, or a magnetic material-dispersed resin carrier in which a magnetic material is dispersed in a resin. Although it may be, it is preferably a magnetic material-dispersed resin carrier. In particular, a core made by a polymerization method is preferable.

  Examples of the magnetic material include 1) iron powder with oxidized or non-oxidized surface, 2) metals such as iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium, rare earth elements Particles, alloy particles thereof, or oxide particles containing these elements, 3) magnetite, or ferrite are included. Preferred examples of the magnetic material include magnetite fine particles or magnetic ferrite fine particles containing at least one element selected from copper, zinc, manganese, calcium, lithium, and magnesium elements.

  In the resin-impregnated carrier, the 50% particle size (D50) based on the volume distribution of the magnetic material (porous magnetic material) contained in the carrier core may be a particle size substantially corresponding to the carrier particle size. It is preferable that it is 25 micrometers. This is because the resin can be appropriately impregnated, so that occurrence of coalescence between carriers due to an excessive amount of the resin can be suppressed, and an appropriate circularity can be imparted to the carrier.

  On the other hand, in the magnetic material dispersed resin carrier, the number average particle diameter of the magnetic material contained in the carrier core is preferably about 80 to 800 nm. By adjusting the number average particle diameter within the above range, desorption of the magnetic substance from the binder resin is suppressed. Furthermore, adjusting the particle size of the magnetic material to the above range can suppress the aggregation of the magnetic material when the carrier is granulated, so it does not have a united carrier or spherical shape, so-called irregular shape The abundance of particles can be reduced.

The strength of magnetization of the magnetic substance contained in the carrier core is preferably 40 to 70 Am ² / kg under a magnetic field of 1000 / 4π (kA / m). More preferably, it is 45 to 65 Am ² / kg depending on the carrier particle size. This is because a good magnetic conveying force or restraining force is applied to the carrier, and the density of the developing magnetic brush at the developing pole is increased to obtain a high image quality.

The content of the magnetic substance in the carrier core is preferably 70 to 95% by mass and more preferably 80 to 92% by mass with respect to the entire carrier. This is because the true specific gravity of the carrier is reduced to 2.5 to 4.2 g / cm ³ and the mechanical strength of the carrier is sufficiently secured.

  The carrier core can be produced by polymerizing a polymerizable monomer in the presence of fine powder that is a magnetic substance. At this time, the fine powder that is a magnetic substance serves as a dispersing agent to unite the particles. It is possible to suppress the formation of carriers that are not substantially spherical. In order to obtain such an effect, the content of the magnetic substance in the carrier core is preferably as described above.

  The carrier core can contain a nonmagnetic inorganic compound and the like together with a magnetic substance. By including a nonmagnetic inorganic compound or the like, the magnetic characteristics and specific resistance of the carrier can be adjusted.

  In order to increase the specific resistance value of the carrier, 1) the specific resistance value of the nonmagnetic inorganic compound contained in the carrier core is preferably higher than the specific resistance value of the magnetic substance, and 2) contained in the carrier core. The number average particle diameter of the nonmagnetic inorganic compound is preferably larger than the number average particle diameter of the magnetic substance. The number average particle size of the nonmagnetic inorganic compound contained in the carrier core is preferably 100 to 1000 nm.

  In order to increase the specific resistance value of the carrier, there is a method in which a resin layer is provided on the surface layer of the carrier core, a high resistance barrier layer is formed, and a conventional coating layer is provided thereon.

Preferable examples of the nonmagnetic inorganic compound that can be contained in the carrier core include hematite (α-Fe ₂ O ₃ ) fine particles. This is to appropriately adjust the magnetic characteristics and true specific gravity of the carrier.

  When the carrier core includes a nonmagnetic inorganic compound and a magnetic material, the ratio of the mass of the magnetic material to the “total mass of the magnetic material and the nonmagnetic inorganic compound” is preferably 50 to 95%. This is because the magnetization of the carrier is adjusted to prevent the carrier from adhering to the photoconductor and the specific resistance value of the carrier is adjusted.

  Examples of the resin contained in the carrier core include vinyl resin having a methylene unit in the polymer chain, polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, silicone resin, and polyether resin. Etc. are included. The resin may be a single type of these resins or a mixed resin of two or more types.

  In order to realize further high image quality, the present inventors have examined a carrier having a relatively small particle diameter of 25 μm or less. However, when a durable carrier is used with a small particle size carrier, the photoconductor and the intermediate transfer member are often damaged. As a result of various studies by the present inventors, it has been found that countless magnetic particles are present on the photoreceptor, and when they are traced, the main cause is the presence of carriers lower than a certain level of volume resistance from the beginning. .

-Specific resistance Here, carrier volume resistance is demonstrated using figures. FIG. 1 shows the relationship between the electric field strength of the carrier particles and the volume resistance value obtained in the present invention. The specific resistance when a voltage with an electric field strength of 1.0 × 10 ⁶ V / m is applied is R1, and the specific resistance when a voltage with an electric field strength of 2.5 × 10 ⁶ V / m is applied is R2. When the relationship of 0 ≦ log (R1) −log (R2) ≦ 2.0 is satisfied, even when a carrier having a relatively small particle diameter is used, the above-mentioned photosensitivity is mentioned. Innumerable magnetic particles existing on the body can be solved. By maintaining a high volume resistance value in a wide range of electric field strengths, the same physical state as the material is always maintained under all development conditions, and the phenomenon of developing toner on the photoreceptor can be stably performed. it can. In addition, even in a high electric field strength where the volume resistance is generally low, the resistance value of R2 in FIG. 1 is high, that is, the dependence of the carrier resistance on the electric field strength is small. The carrier in the developer can surely be prevented from flying to the surface of the photoreceptor. More preferably, 0 ≦ log (R1) −log (R2) ≦ 1.5 and R2 is 5.0 × 10 ¹³ or more and 5.0 × 10 ¹⁶ or less. When the specific resistance of the carrier is within this range, the toner can be developed faithfully with respect to the latent image on the photoreceptor, and an image with excellent dot reproducibility can be obtained.

When R2 is less than 1.0 × 10 ¹³ , there is a possibility that carrier particles that adhere to the carrier from the developing sleeve to the photoreceptor when a developing bias having a high electric field strength is applied, that is, Image defects are likely to occur. In addition, a carrier exceeding 5.0 × 10 ¹⁶ Ω · cm is likely to form a sharp edge-enhanced image, and further, the charge on the surface of the carrier is difficult to leak, so that the newly replenished carrier and toner are charged. This may cause fogging and scattering due to non-uniformity. Further, the toner may be charged with a substance such as the inner wall of the replenishing container, and the amount of charge of the toner to be originally applied may become non-uniform. In addition, it tends to cause image defects such as electrostatic external additives.

-Volume distribution based 50% particle size (D50) The carrier of the present invention needs to have a volume distribution based 50% particle size (D50) of 15 μm or more and less than 25 μm. This is because use of a smaller particle size than that of a conventionally used carrier can increase the toner density and supply a large amount of toner to the latent image, so that the image quality can be improved and the stress on the toner can be increased. This is because it can be reduced. In addition, the density of the magnetic brush at the developing pole is increased, and high image quality can be achieved.

  When trying to manufacture a carrier having a volume distribution standard 50% particle size (D50) of less than 15 μm, it is necessary to increase the stirring speed at the time of granulation. Difficult to control. In addition, since the particle size is excessively small, it tends to adhere to the photoreceptor, and a good image may not be obtained. Furthermore, the fluidity of the carrier is reduced, and fine powder is likely to accumulate, and uniform carrier recovery may not be performed satisfactorily.

  In the case of a particle size of 25 μm or less, the halftone homogeneity and the solid image denseness / homogeneity are very excellent as compared with those having higher particle size.

  The volume average particle diameter of the carrier is more preferably 17 μm or more and 23 μm or less for further improvement in image quality and durability stability.

-Magnetization strength The carrier of the present invention has a magnetization strength (σ1000) measured in a magnetic field of 1000 / 4π (kA / m) (1000 oersted) of 40 to 70 Am ² / kg. Preferably, it is 45 to 65 Am ² / kg, more preferably 45 to 60 Am ² / kg. Since the adhesion of the carrier having the magnetization strength (σ1000) in the above range to the photoreceptor is suppressed, the durability of the two-component developer containing the carrier is enhanced.

A carrier having a magnetization intensity (σ1000) exceeding 70 Am ² / kg is likely to deteriorate the toner due to a large stress applied to the toner in the replenishing developer or in the developer magnetic brush. The carrier may be susceptible to toner spent. Further, a carrier having a magnetization strength (σ1000) of less than 40 Am ² / kg is effective in preventing toner deterioration, but it adheres to the photoreceptor because the magnetic binding force to the developing sleeve is weak. May be easier.

  The strength of magnetization of the carrier of the present invention can be adjusted by appropriately selecting the type and amount of the magnetic substance contained.

- true specific gravity of the carrier of the present invention the true specific gravity is preferably 2.5~4.2g / cm ^3, more preferably 3.0~3.8g / cm ^3. A two-component developer containing a carrier having a true specific gravity in this range has a small load on the toner even when stirred and mixed, and toner spent on the carrier is suppressed. When the true specific gravity exceeds 4.2 g / cm ³ , the deterioration of the developer is promoted due to the magnetic restraining force in the developing machine, and the durability is likely to deteriorate. On the other hand, when the true specific gravity is less than 2.5 g / cm ³ , carrier adhesion is likely to occur although it is related to the magnetic properties of the carrier.

-About average circularity Average circularity is a coefficient showing the shape of the roundness of a particle | grain, and is calculated | required from the largest diameter of a particle | grain and the measured particle projected area. If the average circularity is 1.000, it indicates a perfect sphere (perfect circle), and the smaller the value, the longer the shape or the more irregular the shape.

  The average circularity of the carrier of the present invention is 0.850 to 0.950, more preferably 0.870 to 0.950, and still more preferably 0.880 to 0.950.

  In the present invention, a carrier having a spherical shape or an elliptical shape (0.850 or more) to a certain degree is circular so that 0 ≦ (C−C30) ≦ 0.20 between 30% value C30 of circularity. It is necessary to control the degree distribution narrowly in order to suppress the occurrence of scratches on the surface of the photoreceptor even if the carrier is excellent because it has excellent chargeability to the toner and is difficult to adhere to the carrier. More preferably, 0 ≦ (C−C30) ≦ 0.15 is necessary to make the toner more uniform when imparting high charge to the toner.

  Since the carrier of the present invention has a substantially spherical shape (that is, an average circularity of 0.850 or more), it has sufficient carrier strength, and is excellent in charge imparting property to the toner in the replenishment developer, In addition, the toner is less likely to be damaged, toner spent hardly occurs, and the durability is excellent.

  FIG. 2 shows an example of a graph of measurement results. The “arithmetic average value” in the “circularity arithmetic statistical value” section in the figure indicates the average circularity. Furthermore, “30% value” in the “circularity arithmetic statistical value” section indicates “30% value of circularity” and “C30”. These series of measurements and calculations are processed in the software attached to the multi-image analyzer.

Magnetic carrier core and first and second resin coating layers In order to achieve the above volume resistance condition, the carrier of the present invention forms a first coating layer containing at least a resin on the surface of the carrier core particles, It consists of a 2nd coating layer on one coating layer. FIG. 4 shows a configuration image of the carrier.

  The first coating layer may contain only resin components or filler particles, and it is a major object to provide higher resistance than the core by providing the first coating layer. By providing the first coating layer, it is preferable that the specific resistance becomes three orders of magnitude higher than the specific resistance of the core. Thereby, the resistance of the carrier described above can be increased, and high image quality without carrier adhesion can be realized.

  The coating amount is 0.5 to 3.0% by mass, preferably 1.0 to 2.5% by mass with respect to the core particles. By covering the carrier core in this range, a coating layer can be uniformly formed on the carrier core, and a stable image without carrier adhesion can be provided. When the amount of resin to be coated is less than 0.5% by mass, a uniform coating layer cannot be provided on the carrier core, and there is a possibility that carrier adhesion or the like may occur. If it exceeds 3.0% by mass, the particles are likely to be coalesced, and the uniformity of the particles is lacking, which is considered to cause image defects.

  On the other hand, when the carrier core that is porous ferrite is coated, it may be the same resin as the resin filled in the carrier core, a different resin, or a coating layer containing fine particles.

  The coating method will be described together with the carrier manufacturing method described later.

  Examples of the first coating layer include a crosslinked polymethyl methacrylate resin, a crosslinked polystyrene resin, a melamine resin, a phenol resin, and a nylon resin as examples of the crosslinked resin that forms resin fine particles as a resin component.

  Further, at the same time as increasing the resistance, filler particles can be contained in order to prevent the particles from aggregating, and any particles such as crosslinkable organic fine particles and inorganic fine particles can be contained.

  For example, a fine particle selected from one or more of magnetite, hematite, silica, alumina, and titanium-containing metal oxide is preferable.

  As the nitrogen-containing compound relating to the nitrogen-containing resin, at least one nitrogen-containing resin selected from the group consisting of an aromatic amine compound having at least one active hydrogen bonded to a nitrogen atom, an amide compound, and a thioamide compound, urea Thiourea, melamine, guanidine, guanamine, dicyandiamide and cyanuric acid, aromatic isocyanate, aliphatic isocyanate, such as diphenylmethane-4,4'-diisocyanate, polyphenylene polyphenyl polyisocyanate, hexamethylene diisocyanate Examples thereof include isocyanates such as imidazoles, quaternary ammonium salts, acrylonitrile and the like, and one or more can be used.

  As a result of this study, it is preferable to use a thermosetting resin for the first coating layer in order to provide the second coating layer, and more uniform by forming the first coating layer with a single resin component. Coating is possible. More preferably, a curable coating layer is provided by a polymerization method using a melamine resin.

  Regarding the second coating layer, it is preferable to use an insulating resin as the resin used in the second resin coating layer of the present invention. The insulating resin that can be used in this case may be a thermoplastic resin or a thermosetting resin. Specific examples of the resin forming the coating material include thermoplastic resins such as polystyrene, polymethyl methacrylate, acrylic resins such as styrene-acrylic acid copolymer, styrene-butadiene copolymer, and ethylene. -Vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinyl alcohol, polyvinyl acetal, polyvinyl pyrrolidone, petroleum resin, cellulose, cellulose acetate, Cellulose derivatives such as cellulose nitrate, methylcellulose, hydroxymethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, novolac resin, low molecular weight polyethylene, saturated alkyl polyester Resin, polyethylene terephthalate, polybutylene terephthalate, polyarylate such aromatic polyester resins, polyamide resins, polyacetal resins, polycarbonate resins, polyethersulfone resins, polysulfone resins, polyphenylene sulfide resins, polyether ketone resins.

  As the thermosetting resin, specifically, for example, phenol resin, modified phenol resin, malee resin, alkyd resin, epoxy resin, acrylic resin, or a combination of maleic anhydride, terephthalic acid and polyhydric alcohol. Unsaturated polyester obtained by condensation, urea resin, melamine resin, urea-melamine resin, xylene resin, toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, polyimide, polyamideimide Examples thereof include a resin, a polyetherimide resin, and a polyurethane resin.

  The above-mentioned resins can be used alone or in combination. In addition, a curing agent or the like can be mixed with a thermoplastic resin and cured for use. In a particularly preferred form, it is preferable to use a resin coating material that has a high charge imparting ability with respect to the toner and that has a higher releasability.

  Accordingly, the coat resin suitably used in the present invention is to contain at least one or more types of silicone resins, fluorine resins, and olefin resins having 4 to 10 carbon atoms.

  The silicone resin is preferably used from the viewpoint of adhesion to the core and prevention of spent.

  The silicone resin can be used alone, but is preferably used in combination with a coupling agent in order to increase the strength of the coating layer and control the charge to a preferable level. Furthermore, the coupling agent described above is preferably used as a so-called primer agent in which a part of the coupling agent is treated on the surface of the carrier core before coating the resin, and the subsequent coating layer is accompanied by a covalent bond. , It can be formed in a more adhesive state.

  Aminosilane is preferably used as the coupling agent. As a result, an amino group having positive chargeability can be introduced on the surface of the carrier, and high negative charge characteristics can be imparted to the toner.

During the coating treatment of the coating layer, it is preferable to coat in a reduced pressure state at a temperature of 30 to 80 ° C. The reason is not clear, but is expected to be described below.
(1) A moderate reaction proceeds at the coating stage, and the coating material is uniformly and smoothly coated on the surface of the carrier core.
(2) In the baking step, a low temperature treatment at at least 160 ° C. is possible, and excessive crosslinking of the resin can be prevented, and the durability of the coating layer can be enhanced.

  The resin used more preferably in the present invention is a copolymer having, as essential components, a methyl methacrylate monomer and a vinyl monomer having an alkyl chain having 4 or more carbon atoms via an ester bond. The mixing ratio of the methyl methacrylate monomer and the vinyl monomer having an alkyl chain having 4 or more carbon atoms via an ester bond is 1: 9 to 9: 1, more preferably 3: 7 to 7 on a mass basis. : A copolymer having a copolymer copolymerized at a ratio of 3 as an essential component has good charge imparting to the toner, and after the toner has reached the desired charge amount in the developing unit. Necessary for suppressing charge-up or charge-down. This is due to the high chargeability of methyl methacrylate, the stability of chargeability in various environments, and the use of a monomer that lengthens the alkyl chain to increase the crystallinity of the resin, thereby causing slippage of the carrier surface. This is considered to be because the property and the releasability are improved, and quick charging and toner contamination on the carrier can be prevented.

The second coating layer of the carrier of the present invention may contain conductive fine particles. The specific resistance of the conductive fine particles contained in the resin covering the carrier core is preferably 1 × 10 ⁸ Ω · cm or less, and more preferably 1 × 10 ⁶ Ω · cm or less. The specific resistance of the conductive fine particles can be obtained in the same manner as the measurement of the specific resistance of the carrier.

  The conductive fine particles include at least one fine particle selected from carbon black, graphite, zinc oxide, and tin oxide. Preferred examples of the conductive fine particles include carbon black fine particles. Since the carbon black fine particles can be made smaller in size, they are preferably used without inhibiting the formation of fine protrusions on the carrier surface by the fine particles.

  The particle diameter of the conductive fine particles preferably has a peak value of 10 to 500 nm (more preferably 20 to 200 nm) on a number basis. This is preferable in order to satisfactorily remove residual charges on the carrier surface, prevent charge-up, and prevent desorption from the carrier. The particle diameter of the conductive fine particles is measured in the same manner as the above-described measurement of the particle diameter of the magnetic substance.

  It is preferable that the 2nd coating layer of the carrier of this invention contains 1-15 mass parts electroconductive fine particles with respect to 100 mass parts of resin. This is for the purpose of removing residual charges on the surface of the carrier without reducing the specific resistance of the carrier excessively.

<The manufacturing method of the magnetic body containing resin carrier of this invention>
The carrier of the present invention can be produced by producing a carrier core and then coating the carrier core with first and second coating layers.

  The carrier core of the magnetic substance-containing resin carrier of the present invention is produced, for example, as described below.

  The carrier core of the resin-impregnated carrier is manufactured using a porous magnetic material. Examples of porous magnetic materials include Ca—Mg—Fe ferrite, Li—Fe ferrite, Mn—Mg—Fe ferrite, Ca—Be—Fe ferrite, Mn—Mg—Sr—Fe ferrite, Li -Ferrite magnetic bodies of iron-based oxides such as -Mg-Fe-based ferrite and Li-Rb-Fe-based ferrite are included. Ferrites of iron-based oxides can be obtained by mixing metal oxides, carbonates, nitrates, and the like in a wet or dry manner and calcining to obtain a desired ferrite composition. The obtained iron oxide ferrite is pulverized to submicron. 20-50 mass% of water for adjusting the particle size is added to the pulverized ferrite, 0.1-10 mass% of polyvinyl alcohol (molecular weight: 500-10,000) is added as a binder, and the pore density is further controlled. A metal carbonate such as calcium carbonate is added in an amount of 0.5 to 15% by mass to prepare a slurry.

  The slurry can be granulated using a spray dryer or the like to obtain a porous magnetic material. Here, the particle size of the porous magnetic material can be controlled by appropriately adjusting the viscosity of the slurry and the size of the nozzle of the spray dryer.

  In order to produce a magnetic material-dispersed core, a vinyl-based or non-vinyl-based thermoplastic resin, a magnetic material, and other additives are sufficiently mixed by a mixer. The obtained mixture is melted and kneaded using a kneader such as a heating roll, a kneader, or an extruder. A carrier core can be obtained by pulverizing and further classifying the cooled melt-kneaded material. The obtained carrier core is thermally or mechanically spheroidized and can be used as the carrier core of the carrier of the present invention.

  Further, the carrier core of the carrier of the present invention is particularly preferably produced by polymerizing a resin monomer mixed with a magnetic substance. Examples of monomers to be polymerized include bisphenols and epichlorohydrin for forming epoxy resins, phenols and aldehydes for forming phenol resins, and urea resins in addition to the vinyl monomers described above. For urea and aldehydes, melamine and aldehydes.

  For example, when phenols and aldehydes are used as the monomers, a magnetic substance, phenols and aldehydes are added to an aqueous medium, and the phenols and aldehydes in the aqueous medium are polymerized in the presence of a basic catalyst. Thus, a carrier core can be manufactured.

  The phenols for producing the phenol resin may be compounds having a phenolic hydroxyl group in addition to phenol (hydroxybenzene). Examples of the compound having a phenolic hydroxyl group include alkylphenols such as m-cresol, p-tert-butylphenol, o-propylphenol, resorcinol, bisphenol A; hydrogen of an aromatic ring (for example, benzene ring) or hydrogen of an alkyl group Halogenated phenols partially or wholly substituted with chlorine or bromine atoms are included. More preferred examples of the phenols include phenol.

  Examples of aldehydes for producing a phenol resin include formaldehyde in the form of either formalin or paraaldehyde, furfural and the like, and more preferred examples include formaldehyde.

  The molar ratio of aldehydes to phenols is preferably 1 to 4, and more preferably 1.2 to 3. If the molar ratio of aldehydes to phenols is less than 1, particles are difficult to produce, and even if they are produced, the resin does not easily cure, and the strength of the particles produced tends to be weak. On the other hand, when the molar ratio of aldehydes to phenols is larger than 4, unreacted aldehydes remaining in the aqueous medium after the reaction tend to increase.

  The condensation of phenols with aldehydes can be performed using a basic catalyst. The basic catalyst may be any catalyst that is used in the production of ordinary resol type resins. Examples of the basic catalyst include alkylamines such as aqueous ammonia, hexamethylenetetramine, dimethylamine, diethyltriamine, and polyethyleneimine. Etc. are included. The molar ratio of these basic catalysts to phenols is preferably 0.02 to 0.3.

  As described above, the average circularity of the carrier of the present invention is 0.850 to 0.950 for more preferable use. In order to obtain such a carrier, it is preferable to appropriately control the amount of dissolved oxygen in the reaction medium at the start of the polymerization reaction in the polymerization reaction in the production of the carrier core.

That is, the amount of dissolved oxygen in the reaction medium at the start of the polymerization reaction is preferably 10.0 g / m ³ or less. Examples of methods for reducing the amount of dissolved oxygen in the reaction medium include 1) preheating the reaction system containing the solvent, monomer, magnetic substance, etc. 2) introducing an inert gas into the reaction medium during the polymerization reaction There are methods. The inert gas introduced into the reaction medium to reduce the amount of dissolved oxygen is preferably at least one selected from nitrogen gas, argon gas, and helium gas from an industrial viewpoint.

  The amount of the inert gas introduced into the reaction medium is 5 to 100% by volume / minute of the reaction vessel volume before the start of the polymerization reaction, and 1 to 20% by volume / minute after the start of the polymerization reaction. Is preferred. If the introduction amount of the inert gas before the start of the polymerization reaction is less than 5% by volume / min, the replacement efficiency of the dissolved oxygen with the inert gas is poor. On the other hand, if it exceeds 100% by volume / min, monomers and the like may be volatilized. is there.

  The flow rate of the inert gas after the start of the polymerization reaction is preferably smaller than the flow rate before the start of the polymerization reaction. By reducing the amount of inert gas introduced during the polymerization reaction to less than the amount introduced before the polymerization reaction, the production of fine particles having a particle size smaller than the desired particle size is suppressed. It is possible to prevent the particles from taking in the fine particles and deforming.

  When the introduction amount of the inert gas after the start of the polymerization reaction exceeds 20% by volume / min with respect to the reaction vessel volume, the aforementioned fine particles are likely to be generated. This is considered to be due to the fact that the reaction medium during the polymerization reaction is vigorously stirred by the introduced inert gas. On the other hand, when the flow rate of the inert gas introduced during the polymerization reaction is less than 1% by volume / min, the amount of oxygen present at the interface between the reaction medium and the outside air increases, and fine particles are easily generated.

  In the polymerization reaction in the production of the carrier core, the reaction medium containing the monomer is stirred. The stirring can be performed with a stirring blade, but the peripheral speed of the stirring blade during stirring is preferably controlled to 1.0 to 3.5 m / sec.

  If the peripheral speed of the stirring blade is less than 1.0 m / second, it becomes difficult to obtain particles having a desired particle size, and at the same time, the magnetic body is liable to settle due to poor stirring, and no spindle-shaped particles or magnetic bodies are contained. Balls tend to be formed easily. On the other hand, when the peripheral speed of the stirring blade exceeds 3.5 m / second, it becomes easy to form fine particles having a desired particle size distribution or less. The particles tend to be easily obtained.

  As described above, in the production of the carrier of the present invention, the carrier core is then coated with the first and second coating layers. As the resin for coating, at least the resin described in the above description of the carrier may be used.

  The coating with the first coating layer can be performed by an ordinary resin coating method, but it is also possible to polymerize and coat the carrier core surface like a melamine resin. An example of the latter is shown below.

  Phenols containing melamine, formalins, water and core particles are charged into a reaction kettle and stirred thoroughly. After adding ammonia, the temperature is raised while stirring, the reaction temperature is adjusted to 70-90 ° C, and the phenol resin is added. Harden. The cured reaction product is cooled to 40 ° C. or lower, and the resulting aqueous dispersion is separated into solid and liquid according to conventional methods such as filtration and centrifugation. Magnetic carrier particles having a layer made of polymerized phenol resin are obtained. At that time, in order to sufficiently cure the resin, for example, it is necessary to sufficiently cure the resin at a temperature of about 100 to 350 ° C., and to prevent oxidation of the core particles, for example, in an inert atmosphere, for example, It is desirable to perform the treatment while flowing an inert gas such as helium, argon, or nitrogen. The heat treatment lamp may be either a fixed type or a rotary type, but a rotary type is desirable in order to prevent aggregation of particles.

  By using the above method, the resin is uniformly and smoothly coated on the surface of the carrier core.

  The coating with the second coating layer can be performed by an ordinary method, and is not particularly limited. However, by performing it in a reduced pressure state at a temperature of preferably 60 to 80 ° C., moderate solvent volatilization proceeds at the coating stage. The resin is uniformly and smoothly coated on the surface of the carrier core.

  In addition, when the carrier core is coated with a resin, the optional component can be included in the resin coat layer covering the carrier core by allowing other optional components (such as conductive particles) to coexist. The dispersing step is preferably performed wet using a media disperser.

<Toner used in the present invention>
The replenishment developer of the present invention is characterized in that the above-mentioned carrier and the toner described later are contained in a mixing ratio of 2 to 50 parts by mass of the toner with respect to 1 part by mass of the carrier. If the toner is less than 2 parts by mass, charging to the toner will be good and the life of the developer will be improved, but the amount of replenishment developer will become heavy due to the large amount of carrier, and the toner will be discharged from the replenishment developer container. This is not preferable because the replenishability to the developing device is deteriorated, the substantial toner amount in the replenishment developer container is decreased, the frequency of replacement of the toner container is increased, and the load on the user is increased. On the other hand, if the amount exceeds 50 parts by mass, there is a possibility that charge imparting to the toner in the replenishment developer cannot be promoted much or the degree of carrier deterioration becomes worse when the toner consumption is low under low humidity. In some cases, it may be difficult to obtain a stable image over a long period of time.

  The toner for constituting the two-component developer in combination with the carrier described above contains at least a binder resin for toner and a colorant, and the weight average particle diameter of the toner is 4.0 to 8.0 μm. It is preferable that it is 4.0-7.0 micrometers, and it is still more preferable that it is 4.5-6.5 micrometers. This is to sufficiently increase dot reproducibility and transfer efficiency. A toner having a weight average particle diameter of less than 4.0 μm has an excessively large specific surface area, so that the amount of charge is difficult to control, and developability is deteriorated, and the toner may be deteriorated when used for a long time. Contamination to the carrier is also likely to occur. A toner having a weight average particle diameter exceeding 8.0 μm is inferior in dot reproducibility and causes a problem in improving image quality.

  The weight average particle diameter of the toner can be adjusted by classification of toner particles at the time of production, mixing of classified products, or the like.

  The toner and carrier used in the replenishment developer of the present invention may be the same as or different from the toner and carrier previously present in the developing device, but preferably the toner is the same type, Further, it is preferable that the toner and the carrier are of the same type in consideration of the stability of charge up or charge down.

  In the present invention, the carrier and the toner included in the two-component developer in the developing device in advance are preferably mixed so that the total specific surface area of the included carrier and the total specific surface area of the toner are close to each other. However, it is not particularly limited. The toner concentration in the two-component developer is preferably about 6 to 20% by mass with respect to the entire two-component developer. This is to improve the charging amount, fogging, image density, and the like.

Regarding the relationship between the toner weight average particle size (D4) and the average particle size (D50) based on the volume distribution of the carrier In the two-component developer of the present invention, the average particle size of the toner and the carrier has the following relationship.
When the volume average particle diameter (D4) of the toner is Rt and the average particle diameter (D50) based on the volume distribution of the magnetic carrier is Rc, Rt / Rc is 0.15 or more and 0.80 or less. In the present invention, since the carrier particle size is small, it has been found that there is a suitable balance between the average particle size of the toner and the carrier in order to more suitably charge the toner and efficiently develop the toner into a latent image. When it is from 0.15 to 0.80, it is possible to output an image having a uniform halftone image and excellent solid image reproducibility. If it exceeds 0.80, the fogging level is deteriorated because the charging ability is lowered.

  The replenishment developer of the present invention is characterized by containing at least a toner and a magnetic carrier. This makes it possible to maintain the performance of the developer in the developer unit by supplying toner and new carrier to the developer unit and discharging at least the excess carrier from the developer unit as necessary. became.

  The replenishment developer contains 2 to 50 parts by mass of toner with respect to 1 part by mass of the magnetic carrier. By using in this range, it is possible to maintain stable developer performance over a long period of time, and there is little fluctuation in toner chargeability, good dot reproducibility, and an image with little fogging.

  When the blending ratio of the toner is less than 2 parts by mass, the amount of toner to be replenished becomes relatively small, the charge amount of the toner becomes uneven, and image defects such as white streaks occur. When the amount exceeds 50 parts by mass, the carrier replenishment effect is difficult to be obtained, the performance of the developer is lowered, the durability is deteriorated, the dot reproducibility is also deteriorated, and the fog is increased.

  Preferred embodiments of the toner in the replenishment developer of the present invention are roughly classified into the following first and second embodiments.

  The toner of the first aspect of the replenishment developer of the present invention includes a toner containing a resin mainly composed of a polyester unit and a colorant (hereinafter also referred to as “the toner of the first aspect”). “Polyester unit” refers to a part derived from polyester, and “resin mainly composed of polyester unit” means a resin in which many of the repeating units constituting the resin are repeating units having an ester bond. However, these will be described in detail later.

  The toner of the first aspect preferably has a weight average diameter of 4.0 to 8.0 μm. The two-component developer containing the toner according to the first aspect is applied to an image forming apparatus using a low-temperature fixing method or an image forming apparatus with a high-speed output, so that transferability is maintained even when used for a long time. Both developability can be maintained satisfactorily.

  This is because a toner containing a resin having a polyester unit as a main component is a soft toner having a degree of circularity of an irregular shape or more to some extent, so that good chargeability is imparted to a two-component developer, and This is because the fluidity can be increased.

  The resin contained in the toner of the first embodiment has a polyester unit as a main component, and the polyester unit is formed by condensation polymerization of an ester monomer. The ester-based monomer includes a polyhydric alcohol component and a carboxylic acid component such as a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, or a polyvalent carboxylic acid ester having two or more carboxyl groups.

  Examples of the dihydric alcohol component among the polyhydric alcohol components include polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2 -Bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0)- Alkylene oxide adducts of bisphenol A such as 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-butane , Neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol , Bisphenol A, hydrogenated bisphenol A and the like.

  Examples of the trihydric or higher alcohol component among the polyhydric alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, , 2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3, 5-trihydroxymethylbenzene and the like are included.

  Examples of the carboxylic acid component constituting the polyester unit include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid or anhydrides; alkyl dicarboxylic acids such as oxalic acid, adipic acid, sebacic acid and azelaic acid, or Succinic acid substituted with an alkyl group having 6 to 12 carbon atoms or an anhydride thereof; unsaturated dicarboxylic acids such as fumaric acid, maleic acid and citraconic acid or the anhydride thereof;

  Preferred examples of the resin having a polyester unit contained in the toner of the first aspect include a bisphenol derivative represented by the structure represented by the following general formula (5) as an alcohol component, a divalent or higher carboxylic acid or Carboxylic acid component (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, dodecenyl succinic acid, trimellitic acid, pyromellitic acid, etc.) consisting of the acid anhydride or lower alkyl ester thereof As mentioned above, polyester resins obtained by condensation polymerization of these are included. This polyester resin has good charging characteristics. The charging characteristics of the polyester resin are more effectively exhibited when used as a resin contained in a color toner contained in a two-component developer.

〔式中、Ｒはエチレン基及びプロピレン基から選ばれる１種以上であり、ｘ及びｙはそれぞれ１以上の整数であり、且つｘ＋ｙの平均値は２〜１０である。〕

[In the formula, R is at least one selected from an ethylene group and a propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10. ]

  A preferable example of the resin having a polyester unit contained in the toner of the first aspect includes a polyester resin having a cross-linked site. The polyester resin having a crosslinking site can be obtained by subjecting a polyhydric alcohol and a carboxylic acid component containing a trivalent or higher polyvalent carboxylic acid to a condensation polymerization reaction. Examples of the trivalent or higher polyvalent carboxylic acid component include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 7-naphthalene tricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, and acid anhydrides and ester compounds thereof are included. The content of the trivalent or higher polyvalent carboxylic acid component contained in the ester-based monomer to be polycondensed is preferably 0.1 to 1.9 mol% based on the total monomers.

Furthermore, preferable examples of the resin having a polyester unit contained in the toner of the first aspect include (a) a hybrid resin having a polyester unit and a vinyl polymer unit, and (b) a hybrid resin and a vinyl type. Includes a mixture of a polymer, (c) a mixture of a polyester resin and a vinyl polymer, (d) a mixture of a hybrid resin and a polyester resin, and (e) a mixture of a polyester resin, a hybrid resin, and a vinyl polymer. It is.
The hybrid resin includes a polyester unit and a vinyl polymer unit (for example, a poly (meth) acrylic acid ester unit) obtained by polymerizing a monomer component having a carboxylic acid ester group such as (meth) acrylic acid ester. , Formed by transesterification and bonding. Preferable examples of the hybrid resin include a graft copolymer (or block copolymer) having a vinyl polymer as a trunk polymer and a polyester unit as a branch polymer.

  The “vinyl polymer unit” refers to a portion derived from a vinyl polymer. A vinyl polymer unit or a vinyl polymer is obtained by polymerizing a vinyl monomer described later.

  The toner of the second aspect of the replenishment developer of the present invention includes a toner obtained from a direct polymerization method or in an aqueous medium (hereinafter also referred to as “the toner of the second aspect”). The toner according to the second aspect may be produced by a direct polymerization method, or may be produced by previously forming emulsified fine particles and then aggregating together with a colorant, a release agent and the like. The toner produced by the latter is also referred to as “toner obtained from an aqueous medium” or “toner obtained by an emulsion polymerization method”.

  The toner of the second aspect includes toner particles mainly composed of a vinyl resin, has a weight average particle diameter of 4.0 to 8.0 μm, and has an average circularity of 0.960 to 1.000. It is preferable to have.

The toner according to the second aspect has a very high initial transfer efficiency, can maintain a high transfer efficiency even after durable use, and can be optimally used in a cleanerless system.
The toner having a nearly spherical shape, like the toner of the second aspect, generally has a problem that it easily deteriorates external additives and the like existing on the toner surface although the rise of charge is fast. That is, when the toner collides with the carrier or the toners collide with each other, the fluidity improver present on the toner surface is likely to be driven into the toner. However, the carrier contained in the replenishment developer according to the second aspect has a low specific gravity and a low magnetic force, uses a specific acrylic resin for the coating resin, and further contains fine particles in the coating resin. As a result, the deterioration of the toner external additive due to the collision between the carrier and the toner can be greatly reduced.

  When the average circularity of the toner contained in the two-component developer of the second aspect is less than 0.960, transfer efficiency may be slightly insufficient when applied to a cleanerless system. In general, a toner having a very high average circularity of 0.960 or more tends to deteriorate. Nevertheless, one of the reasons that the toner contained in the replenishment developer of the second embodiment can be used without deterioration is that the toner contained in the main component is a vinyl resin obtained by a direct polymerization method or the like. This is because the toner surface hardness can be maintained over a long period of time.

  The toner of the second aspect preferably contains particles mainly composed of a vinyl-based resin obtained by a direct polymerization method or an emulsion polymerization method. The vinyl resin that is the main component of the particles is produced by polymerization of a vinyl monomer. Examples of vinyl monomers include styrene monomers; (meth) acrylic monomers; monomers of ethylenically unsaturated monoolefins; monomers of vinyl esters; monomers of vinyl ethers; monomers of vinyl ketones; Monomer: Other vinyl monomers are included.

  Examples of styrenic monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, 3,4-dichloro styrene, p- Ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl Styrene, pn-dodecyl styrene and the like are included.

  Examples of (meth) acrylic monomers include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, acrylic Acrylic acid esters such as stearyl acid, dimethylaminoethyl acrylate, phenyl acrylate, acrylic acid and acrylic amides; and ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-methacrylate Methacrylic acid esters such as octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, Methacrylic acid and methacrylic acid amides and the like.

  Examples of monomers of ethylenically unsaturated monoolefins include ethylene, propylene, butylene, isobutylene, etc .; examples of monomers of vinyl esters include vinyl acetate, vinyl propionate, vinyl benzoate, etc. Examples of vinyl ether monomers include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc .; examples of vinyl ketone monomers include vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone, and the like. Examples of monomers of the N-vinyl compound include N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone and the like. Examples of other vinyl monomers include acrylic acid derivatives or methacrylic acid derivatives such as vinyl naphthalenes, acrylonitrile, methacrylonitrile and acrylamide.

  These vinyl monomers can be used alone or in combination of two or more.

  Examples of the polymerization initiator used in producing the vinyl resin include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1 Azo or diazo polymerization initiators such as' -azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; benzoyl peroxide Methyl ethyl ketone peroxide, diisopropyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis (4,4- t-butylperoxycyclohexyl) propane Potassium persulfate, such as ammonium persulfate persulfate; - tris initiator having a side chain a peroxide-based initiator or a peroxide such as (t-butylperoxy) triazine and the like hydrogen peroxide.

  Examples of radically polymerizable trifunctional or higher polymerization initiators include tris (t-butylperoxy) triazine, vinyltris (t-butylperoxy) silane, 2,2-bis (4,4-di-). t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane Radical-polymerizable polyfunctional polymerization initiators such as 2,2-bis (4,4-di-t-butylperoxycyclohexyl) butane.

  The replenishment developer of the present invention is preferably used in an electrophotographic process that employs oilless fixing. For this reason, the toner contained in the replenishment developer of the present invention preferably contains a release agent.

  Examples of mold release agents include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymers, polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; aliphatics such as oxidized polyethylene wax Oxides of hydrocarbon waxes or block copolymers thereof; waxes based on fatty acid esters such as carnauba wax, montanate ester wax, behenyl behenate; fatty acid esters such as deoxidized carnauba wax Some or all of them are deoxidized.

  Furthermore, examples of mold release agents include saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group; brassic acid, eleostearic acid, valinal acid Unsaturated fatty acids such as stearic alcohol, aralkyl alcohol, behenyl alcohol, carnauvyl alcohol, seryl alcohol, melyl alcohol, and saturated alcohols such as long chain alkyl alcohols having a long chain alkyl group; Monohydric alcohols; fatty acid amides such as linoleic acid amide, oleic acid amide, lauric acid amide; saturated fats such as methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene bisstearic acid amide Unsaturated fatty acid amides such as bisamides, ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; Aromatic bisamides such as acid amide and N, N′-distearylisophthalic acid amide; fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (generally referred to as metal soap); Waxes grafted onto aliphatic hydrocarbon waxes using vinyl monomers such as styrene and acrylic acid; Partially esterified products of fatty acids such as behenic acid monoglyceride and polyhydric alcohols; Obtained by hydrogenation of vegetable oils and fats Hydroxyl group And the like methyl ester compounds.

  A preferred example of the release agent contained in the toner of the first aspect of the present invention includes hydrocarbon wax. There is one or more endothermic peaks in the temperature range of 30 to 200 ° C. in the endothermic curve of the toner in the differential thermal analysis measurement of the toner of the first aspect, and the temperature of the maximum endothermic peak in the endothermic peak is 65 to 110 ° C. As a result, the toner can have good low-temperature fixability and durability.

  On the other hand, a suitable example of the release agent contained in the toner of the second aspect of the present invention includes paraffin wax.

  The content of the release agent in the toner contained in the two-component developer of the present invention is preferably 1 to 15 parts by mass, and preferably 3 to 10 parts by mass with respect to 100 parts by mass of the binder resin. More preferred. If the content of the release agent is less than 1 part by mass, the release property may not be exhibited well at the time of oilless fixing. When the amount exceeds 15 parts by mass, the release agent tends to ooze out to the toner surface, and the transferability may deteriorate.

  The toner used in the present invention may contain a charge control agent. Examples of the charge control agent include organometallic complexes, metal salts, chelate compounds and the like. Specific examples of the organometallic complex include a monoazo metal complex, an acetylacetone metal complex, a hydroxycarboxylic acid metal complex, a polycarboxylic acid metal complex, and a polyol metal complex. Other examples include carboxylic acid derivatives such as metal salts of carboxylic acids, carboxylic acid anhydrides, esters, and condensates of aromatic compounds. In addition, phenol derivatives such as bisphenols and calixarenes are also used as charge control agents. The charge control agent contained in the toner in the present invention is preferably a metal compound of an aromatic carboxylic acid. This is for improving the rising of charging of the toner.

  The content of the charge control agent in the toner used in the present invention is preferably 0.1 to 10.0 parts by mass, and 0.2 to 5.0 parts by mass with respect to 100 parts by mass of the binder resin. It is more preferable. If the amount is less than 0.1 parts by mass, the change in the charge amount of the toner may become large in a wide range of environments from high temperature and high humidity to low temperature and low humidity. When the amount is more than 10.0 parts by mass, the toner may be inferior in low-temperature fixability.

The triboelectric charge amount of the toner contained in the two-component developer of the present invention is not particularly limited, but the absolute value is preferably 25 to 45 mC / kg.
The triboelectric charge amount of the toner can be measured by the following procedure. The following procedure is performed in an environment controlled at 23 ° C. and 60% RH.

  First, the toner and the carrier are mixed so as to have a predetermined toner concentration, and then mixed for 120 seconds with a tumbler mixer. When measuring the triboelectric charge amount of the toner during durability, the developer (including toner) adhering to the developing sleeve can be collected by a magnet through a plastic bag or the like and used as a measurement sample.

  The toner included in the present invention may contain a colorant. Here, the colorant may be a pigment or dye, or a combination thereof.

  Examples of dyes include C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic green 6 etc. are included.

  Examples of pigments are Mineral Fast Yellow, Navel Yellow, Naphthol Yellow S, Hansa Yellow G, Permanent Yellow NCG, Tartrazine Lake, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Permanent Red 4R, Watching Red Calcium Salt, Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue BC, Chrome Green, Pigment Green B , Malachite Green Lake, Final Yellow Green G and the like.

  When the two-component developer of the present invention is used as a developer for forming a full color image, the toner can contain a magenta color pigment. Examples of color pigments for magenta include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, 238, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are included.

  The toner may contain only a magenta color pigment, but if it contains a combination of a dye and a pigment, the clarity of the developer can be improved and the image quality of a full-color image can be improved. Examples of magenta dyes include C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as Disperse Violet 1; I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, C.I. I. Basic dyes such as basic violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28 are included.

  Examples of the color pigment for cyan include C.I. I. Pigment Blue 2, 3, 15, 15: 1, 15: 2, 15: 3, 16, 17; I. Acid Blue 6; I. Acid Blue 45 or a copper phthalocyanine pigment having 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton is included.

  Examples of color pigments for yellow include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 93, 97, 155, 180, C. I. Bat yellow 1, 3, 20, etc. are included.

  Examples of the black pigment include carbon black such as furnace black, channel black, acetylene black, thermal black, lamp black, and magnetic powder such as magnetite and ferrite.

  Further, the color may be adjusted by combining a magenta dyed pigment, a yellow dyed pigment, a cyan dyed pigment, and the like, and the carbon black or the like may be used in combination.

  The colorant content in the toner contained in the replenishment developer of the present invention is preferably 1 to 15 parts by mass, more preferably 3 to 12 parts by mass with respect to 100 parts by mass of the binder resin. More preferably, it is 4-10 mass parts. When the content of the colorant is more than 15 parts by mass, the transparency is lowered, and in addition, the reproducibility of intermediate colors as typified by human skin color is likely to be lowered, and further, the chargeability of the toner is stabilized. And the low-temperature fixability becomes difficult to obtain. When the content of the colorant is less than 1 part by mass, the coloring power may not be sufficient. Further, since a large amount of toner must be used to obtain the density, dot reproducibility is likely to be impaired, and it may be difficult to obtain a high-quality image with a high image density.

  The toner contained in the replenishment developer of the present invention may be externally added with external additives which are fine particles. By externally adding fine particles, fluidity and transferability can be improved. The external additive externally added to the toner surface preferably contains any one of titanium oxide, alumina oxide, and silica fine particles. Since the externally added inorganic fine particles function as spacer particles for making it easy for the toner to be separated from the carrier, the average particle size (peak value of the number distribution) is preferably 80 to 200 nm.

  The external additive can contain fine particles having an average particle size (peak value of number distribution) of 50 nm or less together with the inorganic fine particles having an average particle size of 80 to 200 nm, thereby improving the fluidity of the toner. be able to.

  The surface of the inorganic fine particles contained in the external additive is preferably subjected to a hydrophobic treatment. The hydrophobizing treatment is preferably performed by so-called coupling agents such as various titanium coupling agents and silane coupling agents; fatty acids and metal salts thereof; silicone oils; or a combination thereof.

  Examples of titanium coupling agents for hydrophobizing inorganic fine particles contained in external additives include tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecyl benzene sulfonyl titanate, bis (dioctyl pyrone). Phosphate) oxyacetate titanate and the like.

  Examples of silane coupling agents include γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N- β- (N-vinylbenzylaminoethyl) γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, Examples include decyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, and the like.

  Examples of fatty acids for hydrophobizing inorganic fine particles include undecyl acid, lauric acid, tridecyl acid, dodecyl acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, olein Long-chain fatty acids such as acid, linoleic acid, and arachidonic acid are included, and metals of these fatty acid metal salts include zinc, iron, magnesium, aluminum, calcium, sodium, lithium, and the like.

  Examples of the silicone oil for performing the hydrophobizing treatment include dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil and the like.

  The hydrophobizing treatment may be performed by adding 1 to 30% by mass (more preferably 3 to 7% by mass) of a hydrophobizing agent to the inorganic fine particles and coating the inorganic fine particles with respect to the inorganic fine particles. preferable.

  The content of the external additive in the toner is preferably 0.1 to 5.0% by mass, and more preferably 0.5 to 4.0% by mass. The external additive may be a combination of a plurality of types of fine particles.

[Example of image forming method]
The replenishment developer of the present invention can be applied to any electronic image forming process, and its application range is not particularly limited. Hereinafter, an example of an image forming method in which the carrier and the two-component developer of the present invention are suitably employed (hereinafter also referred to as “image forming method in the present invention”) will be described with reference to FIGS. 5 and 6. .

  The image forming method used in the present invention is a method of forming a color image using two or more two-component developers of the present invention having different colors. The image forming method used in the present invention includes at least (I) a charging step for charging the surface of the photoreceptor, and (II) sequentially forming an electrostatic latent image corresponding to each color on the charged photoreceptor. A latent image forming step, (III) a developing step of visualizing the electrostatic latent image formed on the photosensitive member with a corresponding color toner to form a toner image, and (IV) the visualizing in the developing step. (V) a step of fixing the toner formed on the transfer material in the transfer step by heat, pressure, or the like.

  The developing step (I) uses a developing container (10a to 10d in FIG. 5) having a plurality of developing units each having a developing roller carrying a two-component developer corresponding to each color toner, and the developing roller of each developing container. A developer is carried on the developing roller, and a developing bias formed by superimposing an AC electric field on a DC electric field is applied to the developing roller, thereby sequentially forming toner images of respective colors on the photosensitive member.

  The replenishment developer of the present invention is placed in a replenishment container (not shown in the figure) provided on the upper part of the development container (10a to 10d in FIG. 5). The supply container will be described later. Further, the developing container is provided with a discharge port (not shown in the figure) for discharging the excess carrier and toner as necessary. This will also be described later.

  An example of a color image forming apparatus (a copying machine or a laser beam printer) that suitably realizes the image forming method will be described with reference to FIG. Reference numeral 7a denotes a drum-shaped photoconductor as a first image carrier, which is rotationally driven at a predetermined peripheral speed (process speed) in the direction of the arrow in the figure. In the rotation process, the photoreceptor 7a is uniformly charged to a predetermined potential by the charging device 8a (charging process), and then exposed by the image exposure apparatus 9a (latent image forming process). In this manner, an electrostatic latent image corresponding to the first color component image (for example, a yellow toner image) of the target color image is formed.

  Next, the electrostatic latent image is developed into a yellow toner image which is the first color by the first developing device (yellow toner developing device 10a). Sequentially, the same development is performed by the second to fourth developing units, that is, the magenta toner developing unit 10b, the cyan toner developing unit 10c, and the black toner developing unit 10d (developing step).

  The toner image formed on the photoconductor in the developing process is subjected to a transfer process. In the transfer process used in the image forming method of the present invention, the color toner images to be formed on the transfer material are formed by sequentially superimposing and transferring the toner images of the respective colors formed on the photosensitive member onto the intermediate transfer member. Can be composed of a primary transfer step for forming the toner image on the intermediate transfer member and a secondary transfer step for transferring the color toner image formed on the intermediate transfer member onto the transfer material.

  In FIG. 5, the intermediate transfer belt 14 as an intermediate transfer member is rotationally driven in the direction of the arrow at the same peripheral speed as the photosensitive member 7a (up to 7d). The yellow toner image of the first color formed on the photoconductor 7 a is applied to the intermediate transfer belt 14 via the primary transfer roller 13 in the process of passing through the contact portion between the photoconductor 7 a and the intermediate transfer belt 14. The image is sequentially transferred onto the outer peripheral surface of the intermediate transfer belt 14 by the electric field formed by the primary transfer bias. Note that a bias having a polarity opposite to that of the toner is applied as the primary transfer bias at this time. The applied voltage is, for example, in the range of +100 V to +2 kV. The surface of the photoreceptor 7a after the transfer of the first color yellow toner image to the intermediate transfer belt 14 is cleaned by the cleaning device 1a. Similarly, magenta, cyan, and black toner images are also transferred to the intermediate transfer belt 14 to form a full-color image on the intermediate transfer belt 14.

  Next, the color toner image is transferred to a transfer material, and this process is called a secondary transfer process. Reference numeral 4 denotes a secondary transfer roller, which is supported in parallel with the secondary transfer counter roller 3 and arranged in a state in which it can be separated from the lower surface of the intermediate transfer belt 14.

  The secondary transfer roller 4 is brought into contact with the intermediate transfer belt 14, and the transfer material P is fed from the paper feed roller 16 to the contact portion between the intermediate transfer belt 14 and the secondary transfer roller 4 at a predetermined timing. At this time, the secondary transfer bias is applied to the secondary transfer roller 4, whereby the full color image transferred onto the intermediate transfer belt 14 is secondarily transferred to the transfer material P. The transfer material P onto which the toner image has been transferred is introduced into the fixing device 15 and is heated and fixed. After the image transfer to the transfer material P is completed, the toner (transfer residual toner) remaining on the intermediate transfer belt is scraped off by the belt cleaning device 5 and carried to a waste toner box.

  Further, the replenishment developer of the present invention can be applied to a cleanerless system as shown in FIG. The image forming apparatus shown in FIG. 6 has substantially the same configuration as the image forming apparatus shown in FIG. 5 except that the cleaning apparatuses 1a to 1d are not provided. In order to improve the cleaner-less state, the developing roller rotates in the counter direction (clockwise in FIG. 6) with respect to the photosensitive member, and development is performed by applying a developing bias in which an AC electric field is superimposed on a DC electric field. It is preferable to improve the recoverability of the transfer residual toner. In this image forming apparatus, the developer remaining on the surface of the photoconductors 8a to 8d after the transfer onto the intermediate transfer belt 14 is not removed by the cleaning device, and the rotation of the photoconductor is performed. It reaches the developing section (contact section of the photosensitive member with the developing roller) via the charging section (the portion facing the charging device of the photosensitive member), and the developing roller attaches the developer to the image portion on the photosensitive member. At the same time, the developer adhering to the non-image area (that is, the developer remaining after transfer) is collected (this is called “development simultaneous cleaning”).

  When the T / C ratio (mixing ratio of toner and carrier, that is, the toner concentration in the developer) of the developer 119 in the developing device 104 is reduced by the above development, the replenishment developer 118 is developed from the replenishment developer storage chamber R3. The carrier that has been replenished to the agitating chamber R2 in an amount that is suitable for the amount consumed in step S2 and increased more than necessary is removed from the discharge screw 129 to the outside as a deteriorated developer mixed with the toner, and the inside of the developing device 104 The T / C and carrier amount of the developer 119 are maintained at a predetermined amount.

  The carrier increased by the carrier contained in the replenishment developer overflows the capacity UP and is taken into the developer collection auger and conveyed to the replenishment developer container or another collection container.

  A preferred method for measuring physical properties according to the present invention will be described below.

<Method for measuring particle size of magnetic material>
The volume distribution standard 50% particle size (D50) of the magnetic substance contained in the carrier core of the resin-impregnated carrier can be measured according to the measurement of the carrier particles.

  On the other hand, the number average particle diameter of the magnetic substance contained in the carrier core of the magnetic substance-dispersed resin carrier is measured by the following procedure.

  The cross section of the carrier cut by a microtome or the like is observed with a scanning electron microscope (50,000 times), and 300 or more particles having a particle size of 5 nm or more are randomly extracted. The length of the major axis and minor axis of each extracted particle is measured with a digitizer. The average value of the measured lengths of the major axis and the minor axis is defined as the particle size, and the particle size distribution of 300 or more particles (column width is 5-15, 15-25, 25-35, 35-45, 45- 55, 55-65, 65-75, 75-85, 85-95 (unit: nm), etc. (the column histogram divided every 10 nm is used). Let the diameter be the number average particle diameter.

  The number average particle diameter of the nonmagnetic inorganic compound contained in the carrier core, which will be described later, is also measured in the same manner as described above.

  In addition, the number average particle diameter of the magnetic substance or nonmagnetic inorganic compound is determined by measuring the raw material magnetic substance or nonmagnetic inorganic compound (in a state not contained in the resin) with a transmission electron microscope (TEM) (50,000 times). Observe and can be obtained in the same manner as described above.

<Measurement of carrier resistivity>
The specific resistance value of the carrier of the present invention is measured by using a measuring apparatus outlined in FIG. The cell E is filled with carrier particles 27, the lower electrode 21 and the upper electrode 22 are arranged so as to be in contact with the filled carrier particles, a voltage is applied between these electrodes, and the current flowing at that time is measured. Find the specific resistance.

The specific resistance is measured under the condition that the contact area S between the filled carrier particles and the electrode is about 2.3 cm ² , the thickness L of the filled carrier particles is about 0.5 mm, and the load of the upper electrode 22 is 180 g.

  The specific resistance of the nonmagnetic inorganic compound, the magnetic material and the conductive particles can be measured in the same manner.

<Measurement of carrier volume particle size>
The 50% particle diameter (D50) based on the volume distribution of the carrier of the present invention is a dry or wet laser diffraction type particle size distribution meter as long as the measurement range is from submicron to several hundred microns. Can be measured. Examples of the laser diffraction particle size distribution analyzer include a laser diffraction particle size distribution analyzer SALD-3000 (manufactured by Shimadzu Corporation).

<Measurement of carrier magnetization>
The magnetization strength of the carrier of the present invention can be determined by a vibrating magnetic field type magnetic property apparatus VSM (Vibrating sample magnetometer). Examples of the oscillating magnetic field type magnetic property device include an oscillating magnetic field type magnetic property automatic recording device BHV-30 manufactured by Riken Electronics Co., Ltd. Using this, it can be measured by the following procedure. The cylindrical plastic container is filled with the carrier sufficiently densely, while an external magnetic field of 1000 / 4π (kA / m) (1000 oersted) is created, and the magnetization moment of the carrier filled in the container is measured in this state. . Further, the actual mass of the carrier filled in the container is measured to determine the magnetization strength (Am ² / kg) of the carrier.

<Measurement of true specific gravity>
It can be measured using a dry automatic densimeter autopycnometer (manufactured by Yuasa Ionics).

<Measurement of circularity>
The average circularity of the carrier is preferably a number-based average circularity. The number-based average circularity is measured as follows using a multi-image analyzer (manufactured by Beckman Coulter).

  A solution obtained by mixing about 1% NaCl aqueous solution and glycerin at 50% by volume: 50% by volume is used as the electrolytic solution. Here, the NaCl aqueous solution may be prepared using primary sodium chloride, and may be, for example, ISOTON (registered trademark) -II (manufactured by Coulter Scientific Japan). Glycerin may be a special grade or first grade reagent.

  To the electrolytic solution (about 30 ml), 0.1 to 1.0 ml of a surfactant (preferably alkylbenzenesulfone hydrochloride) is added as a dispersant, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is dispersed for about 1 minute with an ultrasonic disperser to obtain a dispersion.

  Using a 200 μm aperture and a 20 × lens as the aperture, the equivalent circle diameter and circularity are calculated under the following measurement conditions.

  Average luminance within measurement frame: 220 to 230, measurement frame setting: 300, SH (threshold): 50, binary level: 180

  The electrolytic solution and the dispersion liquid are put into a glass measuring container, and the concentration of carrier particles in the measuring container is set to 5 to 10% by volume. Stir the contents of the glass measuring container at the maximum stirring speed. The sample suction pressure is 10 kPa. When the carrier specific gravity is large and the sedimentation is likely to occur, the measurement time is 15 to 30 minutes. Further, the measurement is interrupted every 5 to 10 minutes to replenish the sample solution and the electrolytic solution-glycerin mixed solution.

  The number of measurements is 2000. After the measurement is finished, the main body software removes a defocused image, aggregated particles (multiple simultaneous measurements), etc. on the particle image screen.

The circularity and equivalent circle diameter of the carrier are calculated by the following formula.
Circularity = (4 × Area) / (MaxLength ² × π)
Equivalent circle diameter = √4 · Area / π

  Here, “Area” is the projected area of the binarized carrier particle image, and “MaxLength” is defined as the maximum diameter of the carrier particle image. The equivalent circle diameter is represented by the diameter of a perfect circle when “Area” is the area of the perfect circle. The equivalent circle diameter is divided into 256 parts of 4 to 100 μm and is used logarithmically based on the number.

<Measurement of toner particle size>
The weight average particle diameter of the toner contained in the two-component developer of the present invention can be measured using a Coulter Counter TA-II or Coulter Multisizer II (manufactured by Beckman Coulter, Inc.) as a measuring device. The electrolytic solution is an approximately 1% NaCl aqueous solution and may be prepared using primary sodium chloride, or may be a commercial product such as ISOTON (registered trademark) -II (manufactured by Coulter Scientific Japan).

  The weight average particle diameter of the toner is measured as follows. To 100 to 150 ml of the electrolytic solution, 0.1 to 5 ml of a surfactant (preferably alkylbenzenesulfone hydrochloride) is added as a dispersant, and 2 to 20 mg of a measurement sample (toner) is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes to obtain a measurement sample.

  The aperture is a 100 μm aperture. The volume and number of samples are measured for each channel, and the volume distribution and number distribution of the samples are calculated. From the calculated distribution, the weight average particle diameter of the sample 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 32-40.30 μm are used.

<Measurement of endothermic peak>
The maximum thermal peak of the toner or release agent contained in the replenishment developer according to the present invention is measured by ASTM D3418-82 using a differential thermal analysis measurement device (DSC measurement device) and DSC2920 (TA Instruments Japan). Can be measured under the following conditions.

Temperature curve: Temperature increase I (30 ° C. to 200 ° C., temperature increase rate 10 ° C./min)
Temperature drop I (200 ° C-30 ° C, temperature drop rate 10 ° C / min)
Temperature increase II (30 ° C to 200 ° C, temperature increase rate 10 ° C / min)

  The specific measurement procedure may be as follows. A measurement sample of 5 to 20 mg (preferably 10 mg) is accurately weighed. This is put in an aluminum pan, and an empty aluminum pan is used as a reference, and measurement is performed at a temperature rise rate of 10 ° C./min and a normal temperature and humidity in a measurement temperature range of 30 to 200 ° C. The peak having the highest height from the baseline in the region of the Tg endothermic peak or higher in the process of temperature increase II is defined as the maximum endothermic peak. If the endothermic peak of Tg overlaps with another endothermic peak and is difficult to discriminate, the peak having the highest height from the plurality of overlapping maximum peaks is taken as the maximum endothermic peak.

<Measurement of triboelectric charge amount of toner>
The measurement of the triboelectric charge amount of the toner was measured using E-SPART Analyzer MODEL EST-III ver. This is performed using 9.03 (manufactured by Hosokawa Micron).

  The above-described developer is held in a two-component feeder (developer holding stand having a rotating plate with a built-in magnet) attached to E-SPART Analyzer (manufactured by Hosokawa Micron). Next, nitrogen gas is sprayed from the air nozzle to the developer held magnetically in the two-component feeder to blow off only the toner, and only the toner is sucked into the E-SPART Analyzer measuring section through the sample introduction tube at the bottom of the two-component feeder. Introduce. The toner sucked into the measuring unit is measured for a charge amount q / d (femto-C / μm) corresponding to the particle diameter d (μm). Based on this data, the average triboelectric charge quantity q / m of all particle diameters is obtained by the attached software. The measurement conditions for E-SPART Analyzer are as follows.

Nitrogen gas blow pressure: 20 kPa
Nitrogen gas blow time: 1 second Nitrogen gas blow interval: 4 seconds Applied voltage: 100V
Count number: 3000

<Measurement of average particle size of fine particles (external additive)>
The average particle diameter of the fine particles (external additive) externally added to the toner is measured by the following procedure.

  From the scanning electron microscope image (50,000 times), the major and minor axes of randomly extracted fine particles (500 or more) having a particle diameter of 5 nm or more are measured with a digitizer. The particle diameter distribution of 500 or more particles (column widths are 5-15, 15-25, 25-35, 35-45, 45-55, 55 with the average value of the measured major axis and minor axis as the particle diameter. -65, 65-75, 75-85, 85-95 (unit: nm), etc. (using the histogram of the column divided every 10 nm, such as...) The average particle diameter (number distribution peak value) is calculated.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely with reference to an Example, this invention is not limited only to these Examples.

[Manufacture of magnetic carrier 1]
Magnetite powder (number average particle diameter 250 nm, magnetization strength 65 Am ² / kg, specific resistance 3.3 × 10 ⁵ Ω · cm) is used as a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane. ) (Amount of 3.0% by mass with respect to the magnetite powder) was mixed and stirred at a high speed at 100 ° C. or higher in the container to surface-treat each fine particle.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 37% by weight aqueous solution) 16 parts by weight-Surface-treated magnetite 85 parts by weight The above materials, 28 parts by weight ammonia water 5 parts by weight, water 15 parts by weight are placed in a flask and stirred. While mixing, the temperature was raised to 85 ° C. over 30 minutes, and the polymerization reaction was carried out in a pressurized state for 3 hours to be cured. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a magnetic carrier core 1 a in which a magnetic material was dispersed.

Next, (i) melamine 2.5 parts by mass (ii) formalin solution 4.0 parts by mass (about 40% formaldehyde, about 10% methanol, the rest is water)
(Iii) 160 parts by mass of magnetic carrier core 1a (iv) 0.5 parts by mass of calcium fluoride Add the above materials and 200 parts by mass of water, adjust the solution pH to 8.5 with sodium hydroxide while stirring, and then for 40 minutes The temperature was raised to 85 ° C. for 15 minutes at this temperature.

After completion of the reaction, cool to 30 ° C,
(V) 30% by mass of 5% ammonium solution was added, the temperature was raised to 85 ° C. over 60 minutes, and the reaction and curing were performed at the temperature for 90 minutes.

  After completion of the reaction and curing, the contents in the flask are cooled to 30 ° C., washed several times with water, air-dried, and then dried under reduced pressure (5 mmHg or less) at 60 ° C. to coat the magnetic carrier core with melamine resin Particles 1b were obtained.

  2 parts by weight of methyl methacrylate macromer (weight average molecular weight 5,000) having an ethylenically unsaturated group at one end, 50 parts by weight of cyclohexyl methacrylate monomer having an ester moiety with cyclohexyl as a unit, and methyl methacrylate monomer 45 A part by mass was added to a four-necked flask having a reflux condenser, a thermometer, a nitrogen suction tube, and a friction stirrer. Further, 90 parts by mass of toluene, 110 parts by mass of methyl ethyl ketone, and 2.0 parts by mass of azobisisovaleronitrile were added. The obtained mixture was held at 70 ° C. for 10 hours under a nitrogen stream to obtain a graft copolymer solution (solid content: 33% by mass). The weight average molecular weight of this solution by gel permeation chromatography (GPC) was 97,000.

To 30 parts by mass of the obtained graft copolymer solution (solid content: 33% by mass), carbon black (maximum peak particle size based on number distribution is 30 nm, specific resistance is 1.0 × 10 ⁻⁴ Ω · cm) 5 parts by mass and 200 parts by mass of toluene were added and mixed well with a homogenizer to obtain a coating solution.

  Next, the above coating solution was gradually added while stirring 2000 parts by mass of the magnetic carrier core 1b while continuously applying shear stress. The solvent was evaporated while maintaining stirring at 70 ° C. under reduced pressure (5 hPa), and the magnetic carrier core surface was coated with a resin.

The resin-coated magnetic carrier was heat-treated with stirring at 100 ° C. for 2 hours. After cooling, the mixture was crushed and coarse particles were removed with a sieve having an opening of 76 μm to obtain a magnetic carrier 1 which is a magnetic material-dispersed resin carrier. The volume-based 50% particle size (D50) of the magnetic carrier 1 is 21 μm, the true specific gravity is 3.6 g / cm ³ , the magnetization strength is 64 Am ² / kg, and the specific resistance R1 is 1.0 × 10 ¹⁴ Ω · cm. The specific resistance R2 was 7.0 × 10 ¹³ Ω · cm, the average circularity C and C-C30 were 0.930 and 0.10, respectively. The physical properties of the obtained magnetic carrier 1 are shown in Table 1.

[Manufacture of magnetic carrier 2]
Magnetite powder (number average particle size 250 nm, magnetization strength 65 Am ² / kg, specific resistance 3.2 × 10 ⁵ Ω · cm) and hematite powder (number average particle size 600 nm, specific resistance 7.0 × 10 ⁷ Ω) Cm) and a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane) (amount of 3.0% by mass with respect to magnetite powder or hematite powder) in a container. Each fine particle was surface-treated by high-speed mixing and stirring at a temperature of 0 ° C. or higher.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 37% by mass aqueous solution) 16 parts by mass-Surface-treated magnetite 80 parts by mass-Surface-treated hematite 10 parts by mass The above materials, 5 parts by mass of 28% by mass ammonia water, 15 parts by mass of water The portion was placed in a flask, heated and maintained at 85 ° C. for 30 minutes with stirring and mixing, and cured by polymerization reaction under pressure for 3 hours. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a magnetic carrier core 2 a in which a magnetic material was dispersed.

Carbon black (number distribution standard maximum peak particle size is 30 nm, specific resistance is 1.0 × 10 ⁻⁴ Ω · cm) to 30 parts by mass of graft copolymer solution (solid content: 33% by mass) used in carrier 1 0.5 parts by mass and 200 parts by mass of toluene were added and mixed well with a homogenizer to obtain a coating solution.

  Subsequently, 2000 parts by mass of the magnetic carrier core (2a) was gradually added while stirring while continuously applying shear stress. The solvent was evaporated while maintaining stirring at 70 ° C. under reduced pressure (5 hPa), and the magnetic carrier core surface was coated with a resin.

The resin-coated magnetic carrier core was heat-treated with stirring at 100 ° C. for 2 hours. After cooling, the mixture was crushed and coarse particles were removed with a sieve having an opening of 76 μm to obtain carrier 1 which is a magnetic material-dispersed resin carrier. The volume-based 50% particle size (D50) of the magnetic carrier 1 is 22 μm, the true specific gravity is 3.7 g / cm ³ , the magnetization strength is 58 Am ² / kg, and the specific resistance R1 is 1.0 × 10 ¹⁵ Ω · cm. The specific resistance R2 was 2.0 × 10 ¹³ Ω · cm, the average circularity C and C-C30 were 0.900 and 0.18, respectively. The physical properties of the obtained magnetic carrier 2 are shown in Table 1.

[Manufacture of magnetic carrier 3]
Magnetite powder (number average particle diameter 250 nm, magnetization strength 65 Am ² / kg, specific resistance 3.3 × 10 ⁵ Ω · cm) is used as a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane. ) (Amount of 3.0% by mass with respect to the magnetite powder) was mixed and stirred at a high speed at 100 ° C. or higher in the container to surface-treat each fine particle.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 37% by mass aqueous solution) 16 parts by mass-Surface-treated magnetite 85 parts by mass The above materials, 3 parts by mass of 30% by mass ammonia water, and 20 parts by mass water are placed in a flask and stirred. While mixing, the temperature was raised to 85 ° C. over 30 minutes, and the polymerization reaction was carried out in a pressurized state for 3 hours to be cured. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a magnetic carrier core 3 a in which a magnetic material was dispersed. Thereafter, the same processing as that for the carrier 1 was performed to obtain the carrier 3. The volume-based 50% particle size (D50) of the magnetic carrier 3 is 24 μm, the true specific gravity is 3.6 g / cm ³ , the magnetization strength is 64 Am ² / kg, and the specific resistance R1 is 5.0 × 10 ¹³ Ω · cm. The specific resistance R2 was 2.0 × 10 ¹² Ω · cm, the average circularity C and C-C30 were 0.926 and 0.12, respectively. Table 1 shows the physical properties of the magnetic carrier 3 obtained.

[Manufacture of magnetic carrier 4]
Magnetite powder (number average particle diameter 250 nm, magnetization strength 65 Am ² / kg, specific resistance 3.3 × 10 ⁵ Ω · cm) is used as a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane. ) (Amount of 3.0% by mass with respect to the magnetite powder) was mixed and stirred at a high speed at 100 ° C. or higher in the container to surface-treat each fine particle.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 37% by mass aqueous solution) 16 parts by mass-Surface-treated magnetite 85 parts by mass The above materials, 40 parts by mass ammonia water 10 parts by mass, and water 20 parts by mass are placed in a flask and stirred. While mixing, the temperature was raised to 85 ° C. over 30 minutes, and the polymerization reaction was allowed to cure for 3 hours with increased pressure. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a magnetic carrier core 3 a in which a magnetic material was dispersed. Thereafter, the same processing as that for the carrier 1 was performed to obtain the carrier 3. The volume-based 50% particle size (D50) of the carrier 4 is 16 μm, the true specific gravity is 3.6 g / cm ³ , the magnetization strength is 64 Am ² / kg, the specific resistance R1 is 2.0 × 10 ¹⁵ Ω · cm, The specific resistance R2 was 8.0 × 10 ¹⁴ Ω · cm, the average circularity C and C-C30 were 0.927 and 0.11, respectively. Table 1 shows the physical properties of the magnetic carrier 4 obtained.

[Manufacture of magnetic carrier 5]
Magnetite powder (number average particle diameter 250 nm, magnetization strength 65 Am ² / kg, specific resistance 3.3 × 10 ⁵ Ω · cm) is used as a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane. ) (Amount of 3.0% by mass with respect to the magnetite powder) was mixed and stirred at a high speed at 100 ° C. or higher in the container to surface-treat each fine particle.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 37% by weight aqueous solution) 16 parts by weight-Surface-treated magnetite 85 parts by weight The above materials, 28 parts by weight ammonia water 5 parts by weight, water 15 parts by weight are placed in a flask and stirred. While mixing, the temperature was raised to 85 ° C. over 30 minutes, and the polymerization reaction was carried out in a pressurized state for 3 hours to be cured. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a magnetic carrier core 5 a in which a magnetic material was dispersed.

Next, (i) 0.40 part by mass of phenol (ii) 0.25 part by mass of formalin solution (about 40% formaldehyde, about 10% methanol, the rest is water) in a three-necked flask
(Iii) Lipophilicized hematite 4.0 parts by weight (iv) Magnetic carrier core particles 5a 160 parts by weight 28% Aqueous ammonia and water are used, and the temperature is raised to 85 ° C. over 40 minutes while stirring and mixing. Retained, reacted and cured for 3 hours. After cooling to 30 ° C. and further adding water, the supernatant was removed, the precipitate was washed with water and air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a carrier core 5 b in which a magnetic material was dispersed. Thereafter, the same treatment as that of the carrier 1 was performed to obtain a magnetic carrier 5. The volume-based 50% particle size (D50) of the magnetic carrier 5 is 22 μm, the true specific gravity is 3.6 g / cm ³ , the magnetization strength is 64 Am ² / kg, and the specific resistance R1 is 7.0 × 10 ¹⁴ Ω · cm. The specific resistance R2 was 5.0 × 10 ¹³ Ω · cm, the average circularity C and C-C30 were 0.926 and 0.21, respectively. Table 1 shows the physical properties of the magnetic carrier 4 obtained.

[Manufacture of magnetic carrier 6]
A magnetic carrier 6 was obtained in the same manner as in Magnetic Carrier Production Example 1 except that carbon black was not used in the coating solution. The volume-based 50% particle size (D50) of the magnetic carrier 6 is 22 μm, the true specific gravity is 3.6 g / cm ³ , the magnetization strength is 64 Am ² / kg, and the specific resistance R1 is 7.0 × 10 ¹⁴ Ω · cm. The specific resistance R2 was 5.0 × 10 ¹³ Ω · cm, the average circularity C and C-C30 were 0.926 and 0.21, respectively. Table 1 shows the physical properties of the magnetic carrier 6 obtained.

[Manufacture of magnetic carrier 7]
Magnetite powder (number average particle size 250 nm, magnetization strength 65 Am ² / kg, specific resistance 3.2 × 10 ⁵ Ω · cm) and hematite powder (number average particle size 250 nm, specific resistance 7.0 × 10 ⁷ Ω) Cm) and a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane) (amount of 3.0% by mass with respect to magnetite powder or hematite powder) in a container. Each fine particle was surface-treated by high-speed mixing and stirring at a temperature of 0 ° C. or higher.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 37% by mass aqueous solution) 16 parts by mass-Surface-treated magnetite 64 parts by mass-Surface-treated hematite 27 parts by mass The above materials, 5 parts by mass of 28% by mass ammonia water, 15 parts by mass of water The portion was placed in a flask, heated and maintained at 85 ° C. for 30 minutes with stirring and mixing, and cured by polymerization reaction under pressure for 3 hours. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Next, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain a magnetic carrier core 7 a in which a magnetic material was dispersed.

Next, (i) 1.0 part by weight of melamine (ii) 4.0 parts by weight of formalin solution (about 40% formaldehyde, about 10% methanol, the rest is water)
(Iii) 160 parts by mass of magnetic carrier core 7a (iv) 0.5 parts by mass of calcium fluoride The above materials and 200 parts by mass of water are added, and the solution pH is adjusted to 8.5 with sodium hydroxide while stirring, and then for 40 minutes. The temperature is raised to 85 ° C. for 15 minutes at this temperature.

After completion of the reaction, cool to 30 ° C,
(V) 30% by mass of 5% ammonium solution was added, the temperature was raised to 85 ° C. over 60 minutes, and the reaction and curing were performed at the temperature for 90 minutes.

After completion of the reaction and curing, the contents in the flask are cooled to 30 ° C., washed several times with water, air-dried, and dried under reduced pressure at 60 ° C. (5 mmHg or less) to coat with a melamine resin. Particles 1b were obtained. Thereafter, the same coating treatment as that of the carrier 1 was performed to obtain a magnetic carrier 7. The volume-based 50% particle size (D50) of the magnetic carrier 7 is 23 μm, the true specific gravity is 3.7 g / cm ³ , the magnetization strength is 42 Am ² / kg, and the specific resistance R1 is 3.0 × 10 ¹⁵ Ω · cm. The specific resistance R2 was 2.0 × 10 ¹⁴ Ω · cm, the average circularity C and C-C30 were 0.870 and 0.18, respectively. Table 1 shows the physical properties of the magnetic carrier 7 obtained.

[Manufacture of magnetic carrier 8]
A magnetic carrier 8 was obtained in the same manner as in Magnetic Carrier Production Example 1 except that the polymerization reaction was performed at normal pressure. The volume-based 50% particle size (D50) of the magnetic carrier 8 is 28 μm, the true specific gravity is 3.6 g / cm ³ , the magnetization strength is 64 Am ² / kg, and the specific resistance R1 is 7.0 × 10 ¹³ Ω · cm. The specific resistance R2 was 1.0 × 10 ¹² Ω · cm, the average circularity C and C-C30 were 0.929 and 0.12, respectively. Table 1 shows the physical properties of the magnetic carrier 8 obtained.

[Manufacture of magnetic carrier 9]
A magnetic carrier 9 was obtained in the same manner as in Magnetic Carrier Production Example 4 except that the production was changed to 10 parts by mass of 40% by mass ammonia water. The volume-based 50% particle size (D50) of the magnetic carrier 9 is 13 μm, the true specific gravity is 3.6 g / cm ³ , the magnetization strength is 63 Am ² / kg, and the specific resistance R1 is 5.0 × 10 ¹⁵ Ω · cm. The specific resistance R2 was 9.0 × 10 ¹⁴ Ω · cm, and the average circularity C and C-C30 were 0.910 and 0.13, respectively. Table 1 shows the physical properties of the magnetic carrier 9 obtained.

[Manufacture of magnetic carrier 10]
These metal oxide particles were weighed so that the molar ratio was Fe ₂ O ₃ = 78 mol%, MnO = 5 mol%, and MgO = 15 mol%, and mixed using a ball mill. After calcining this, it was pulverized with a ball mill and further granulated with a spray dryer. This was sintered and further classified to obtain a Mn—Mg ferrite carrier core. Thereafter, a magnetic carrier 10 was obtained in the same manner as in Magnetic Carrier Production Example 2. The volume-based 50% particle size (D50) of the magnetic carrier 10 is 37 μm, the true specific gravity is 4.5 g / cm ³ , the magnetization strength is 63 Am ² / kg, and the specific resistance R1 is 1.0 × 10 ⁸ Ω · cm. The specific resistance R2 was breakdown, and the average circularity C and C-C30 were 0.874 and 0.14, respectively. The physical properties of the obtained magnetic carrier 10 are shown in Table 1.

[Manufacture of magnetic carrier 11]
MnO = 25 mol%, MgO = 3 mol%, Fe ₂ O ₃ = 70 mol% and SrCO ₃ were pulverized in a 1 mol% wet ball mill for 5 hours, mixed, dried, and held at 950 ° C. for 3 hours. Pre-baking was performed. This was pulverized with a wet ball mill to 2 μm or less. A dispersant and a binder (polyvinyl alcohol) were added to the slurry by several mass%, and then granulated and dried by a spray dryer to obtain a granulated product. This granulated product was put in an electric furnace, and held at 1100 ° C. for 3 hours in a mixed gas in which the oxygen concentration in nitrogen gas was adjusted to 2.0 vol%, followed by firing. Thereafter, it was crushed and further sieved to obtain a magnetic carrier core 11a having a volume average particle size of 24 μm.

next,
Straight silicone (KR255 manufactured by Shin-Etsu Chemical Co., Ltd. (in terms of solid content)) 100 parts by mass Silane coupling agent (γ-aminopropylethoxysilane) 10 parts by mass Carbon black 10 parts by mass The above components are mixed with 300 parts by mass of xylene. A magnetic carrier resin coating solution was obtained. While stirring using a fluidized bed heated to 70 ° C. using this resin coating solution, the magnetic carrier core 11a was coated and solvent-removed so as to be 12% by mass based on the straight silicone resin. Furthermore, the magnetic carrier 11 was obtained by performing a treatment for 2.5 hours at 230 ° C. using an oven, crushing, and classifying with a sieve. The volume-based 50% particle diameter (D50) of the magnetic carrier 11 is 23 μm, the true specific gravity is 3.8 g / cm ³ , the magnetization strength is 45 Am ² / kg, and the specific resistance R1 is 3.0 × 10 ¹⁴ Ω · cm. The specific resistance R2 was 6.0 × 10 ¹³ Ω · cm, the average circularity C and C-C30 were 0.902 and 0.14, respectively. Table 1 shows the physical properties of the magnetic carrier 11 obtained.

[Manufacture of magnetic carrier 12]
120 parts by mass of resin (1) (see below) having an acid value of 0 KOHmg / g and Tg of 60 ° C. and 450 parts by mass of surface-treated magnetite were sufficiently mixed by a Henschel mixer, and then at 180 ° C. by a bent biaxial kneader. After melt-kneading and cooling this, coarsely pulverized by a feather mill, further finely pulverized by a jet pulverizer, and then classified by wind force, and further a sufusing system (manufactured by Nippon Pneumatic Industry Co., Ltd .; SFS-1) Type) to obtain a magnetic carrier core. Then, the magnetic carrier 12 was obtained by coating with melamine resin in the same manner as in Magnetic Carrier Production Example 1 and coating. The volume-based 50% particle size (D50) of the magnetic carrier 12 is 24 μm, the true specific gravity is 2.8 g / cm ³ , the magnetization strength is 55 Am ² / kg, and the specific resistance R1 is 1.0 × 10 ¹³ Ω · cm. The specific resistance R2 was 2.0 × 10 ¹¹ Ω · cm, the average circularity C and C-C30 were 0.875 and 0.27, respectively. Table 1 shows the physical properties of the magnetic carrier 12 obtained.

  In producing the resin (1), 118 g of styrene and 82 g of butyl methacrylate were charged into a flask purged with nitrogen, the internal temperature was raised to 130 ° C., and polymerization was performed at this temperature for 10 hours. 100 g of xylene was added, and a solution of 0.5 g of azobisisobutyronitrile dissolved in 100 g of xylene was continuously added over 9 hours while maintaining the temperature at 135 ° C., followed by further polymerization for 2 hours to obtain resin (1). Obtained. In addition, it was 0 KOHmg / g when the acid value of this resin (1) was measured by JIS K5400 method.

  Next, the toner used in the present invention will be described.

<Example of binder resin production>
(Example of hybrid resin production)
As a vinyl copolymer, a mixture of styrene 2.0 mol, 2-ethylhexyl acrylate 0.21 mol, fumaric acid 0.15 mol, α-methylstyrene dimer 0.03 mol, and dicumyl peroxide 0.05 mol was added dropwise. I put it in the funnel.

  On the other hand, polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 7.0 mol, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane 3. A mixture of 0 mol, terephthalic acid 3.0 mol, trimellitic anhydride 1.7 mol, fumaric acid 5.0 mol and dibutyltin oxide 0.2 g was placed in a glass 4-liter four-necked flask.

  The above-mentioned dropping funnel, thermometer, stirring rod, condenser and nitrogen introducing tube were attached to this four-necked flask, and the four-necked flask was placed in a mantle heater. Next, the temperature of the flask was gradually increased to 145 ° C. while stirring the contents of the flask while flowing nitrogen gas into the four-necked flask. After reaching 145 ° C., the contents of the above dropping funnel were added dropwise over 4 hours. After completion of the dropwise addition, the temperature was raised to 200 ° C. and reacted at the same temperature for 4 hours to obtain a hybrid resin.

<Example of toner production>
(Production example of pulverized toner)
-Resin obtained above 100 parts by mass-Fischer-Tropsch wax (maximum endothermic peak temperature 80 ° C) 4 parts by mass-Aluminum 3,5-di-t-butylsalicylate compound 0.5 parts by mass-C.I. I. Pigment Blue 15: 3 5 parts by mass The above-mentioned ingredients were mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), and then a twin-screw kneader (PCM-30 type, Ikegai) set at 130 ° C. Kneading was carried out by an ironworker. The obtained kneaded product was cooled and coarsely pulverized to about 1 mm with a hammer mill to obtain a coarsely pulverized product. The obtained coarsely crushed material was pulverized using a collision type airflow pulverizer using high-pressure gas. Furthermore, the pulverized product was classified by a multi-division classifier using the Coanda effect to obtain a classified product.

  Furthermore, surface modification of the classified product was performed by a hybridizer (manufactured by Nara Machinery Co., Ltd.) (rotation speed: 6400 rpm, treatment time: 3 minutes, treatment frequency: 2 times) to obtain cyan particles.

  To 100 parts by mass of the obtained cyan particles, 1.0 part by mass of silica particles (the maximum peak particle size based on the number distribution is 110 nm), 0.9 parts by mass of titanium oxide particles (the maximum peak particle size based on the number distribution is 40 nm) Was added and mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.) to obtain toner 1. The weight average particle diameter (D4) of Toner 1 was 5.7 μm.

(Production example of suspension polymerization toner)
710 parts by mass of ion-exchanged water was charged with 460 parts by mass of a 0.12M-Na ₃ PO ₄ aqueous solution, and the aqueous solution obtained by heating to 60 ° C. was obtained using a TK homomixer (manufactured by Special Machine Industries). And stirred at 15,000 rpm. To this, 67 parts by mass of 1.2M-CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

-Styrene 165 parts by mass-n-butyl acrylate 38 parts by mass-Ester wax (maximum endothermic peak temperature 72 ° C) 20 parts by mass-3,5-di-t-butylsalicylic acid aluminum compound 1 part by mass-Saturated polyester (terephthalic acid- Propylene oxide modified bisphenol A;
Acid value, peak molecular weight 6000) 10 parts by mass / C.I. I. Pigment Blue 15: 3 13 parts by mass The above-mentioned material was heated to 60 ° C., and uniformly dissolved and dispersed at 10,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.). In this, 10 parts of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The obtained polymerizable monomer composition was put into the aforementioned aqueous medium. The obtained mixture was stirred at 15,000 rpm for 10 minutes at 60 ° C. in a nitrogen atmosphere using a TK homomixer to granulate the polymerizable monomer composition. Then, it heated up at 80 degreeC, stirring with a paddle stirring blade, and was made to react for 10 hours. After completion of the polymerization reaction, the remaining monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) _{2 and the} like. The resulting solution was filtered, and the filtered product was washed with water and dried to obtain cyan particles.

  To 100 parts by mass of the obtained cyan particles, 1.0 part by mass of silica particles (maximum peak particle size 110 nm based on number distribution), 0.5 mass of anatase-type titanium oxide particles (maximum peak particle size 40 nm based on number distribution) Part and 0.8 part by mass of silica particles (the maximum peak particle size based on the number distribution is 30 nm) are added and mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.) to obtain toner 2. It was. The weight average particle diameter (D4) of Toner 2 was 5.7 μm.

(Example of production of emulsion aggregation toner)
-Styrene 86 mass parts-n-butyl acrylate 14 mass parts-Acrylic acid 2 mass parts-Dodecanethiol 5 mass parts-Carbon tetrabromide 1 mass part The material of the said prescription was mixed and melt | dissolved, and the organic solution was obtained.

  On the other hand, 1.5 parts by mass of a nonionic surfactant (Sanyo Kasei Co., Ltd .: Nonipol 400) and 2.5 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC) , And dissolved in 140 parts by mass of ion-exchanged water in a flask. The organic solution was added to the obtained aqueous solution, dispersed and emulsified, and slowly mixed for 10 minutes.

  To the obtained mixture, 10 parts by mass of ion-exchanged water in which 1 part by mass of ammonium persulfate was dissolved was added to perform nitrogen substitution. While stirring the inside of the flask, the contents were heated in an oil bath until the temperature reached 70 ° C., and emulsion polymerization was continued as it was for 5 hours to prepare a resin particle dispersion 1. The number average particle diameter of the particles contained in the resin particle dispersion 1 was 0.15 μm.

-Styrene 75 mass parts-n-butyl acrylate 25 mass parts-Acrylic acid 3 mass parts The material of the said prescription was mixed and the organic solution was obtained.

  On the other hand, 1.5 parts by mass of a nonionic surfactant (Sanyo Kasei Co., Ltd .: Nonipol 400) and 3 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC) An aqueous solution was obtained by dissolving in 150 parts by mass of exchange water in a flask. The organic solution was added to the obtained aqueous solution, dispersed and emulsified, and slowly mixed for 10 minutes.

  While mixing, 10 parts by mass of ion-exchanged water in which 0.8 part by mass of ammonium persulfate was further dissolved was added to perform nitrogen substitution. While stirring the inside of the flask, the content was heated in an oil bath until the temperature reached 70 ° C., and emulsion polymerization was continued for 5 hours to prepare a resin particle dispersion 2. The number average particle diameter of the particles contained in the resin particle dispersion 2 was 0.12 μm.

Paraffin wax (melting point 95 ° C.) 50 parts by mass Anionic surfactant 5 parts by mass (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC)
-Ion-exchanged water 200 parts by weight In addition, after heating the material of the above formulation to 97 ° C and using a homogenizer (IKA: Ultra Turrax T50), the material was further dispersed with a pressure discharge homogenizer. A release agent particle dispersion was prepared. The number average particle diameter of the release agent particles in the dispersion was 0.42 μm.

・ C. I. Pigment Blue 15: 3 11 parts by mass, anionic surfactant 2 parts by mass (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC)
-Ion exchange water 78 mass parts Furthermore, the coloring agent dispersion liquid was prepared by carrying out the dispersion | distribution process of the material of said prescription using the sand grinder mill.

-150 parts by mass of the resin particle dispersion 1-210 parts by mass of the resin particle dispersion 2-40 parts by mass of the colorant dispersion-70 parts by mass of the release agent dispersion 70 The reaction vessel was equipped with a thermometer and stirred. The mixture was adjusted to pH = 5.3 with 1N potassium hydroxide.

  150 parts by mass of a 10% sodium chloride aqueous solution as a flocculant was dropped into the obtained mixed liquid, and the flask was heated to 70 ° C. while stirring in the heating oil bath. While maintaining this temperature, 3 parts by mass of the resin particle dispersion 2 was further added. After maintaining the obtained solution at 60 ° C. for 1 hour, after adding 3 parts by mass of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd .: Neogen SC), the stainless steel reaction vessel was sealed, The mixture was heated to 90 ° C. while continuing stirring using a magnetic seal and held for 3 hours.

  After cooling, the reaction product was filtered, and the resulting filtered product was sufficiently washed with ion-exchanged water and then dried to obtain cyan particles.

  100 parts by mass of the obtained cyan particles, 2.0 parts by mass of silica particles (number distribution-based maximum peak particle size 110 nm), silica particles (number distribution-based maximum peak particle size 30 nm) 0.8 parts by mass, rutile type Toner 3 was obtained by adding 0.9 part by mass of titanium oxide particles (maximum peak particle size of 80 nm based on the number distribution) and mixing with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.). The weight average particle diameter (D4) of Toner 3 was 5.5 μm.

(Production Example of Dissolved Suspension Granulation Toner)
730 parts by mass of bisphenol A ethylene oxide 2-mole adduct, 280 parts by mass of isophthalic acid and 2 parts by mass of dibutyltin oxide were placed in a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, at 230 ° C. at normal pressure. After reacting for 8 hours and further reacting at a reduced pressure of 10 to 15 mmHg for 5 hours, the mixture was cooled to 160 ° C., 31 parts by mass of phthalic anhydride was added thereto, and reacted for 2 hours. Subsequently, it cooled to 80 degreeC and reacted with 190 mass parts of isophorone diisocyanate in ethyl acetate for 2 hours, and the polyester prepolymer (A) which has an isocyanate group was obtained.

  Next, 270 parts by mass of prepolymer (A) and 15 parts by mass of isophoronediamine were reacted at 50 ° C. for 2 hours to obtain a urea-modified polyester resin (i) having a weight average molecular weight of 65,000.

  In the same manner as above, 724 parts by mass of bisphenol A ethylene oxide 2-mole adduct and 278 parts by mass of terephthalic acid were subjected to polycondensation at 230 ° C. for 8 hours under normal pressure, and then reacted for 5 hours at a reduced pressure of 10 to 15 mmHg. A polyester (a) which was not modified was obtained.

  200 parts by mass of urea-modified polyester resin (i) and 800 parts by mass of unmodified polyester (a) are dissolved and mixed in 2000 parts of a mixed solvent of ethyl acetate / MEK (1/1), and acetic acid in the toner binder (1). An ethyl / MEK solution was obtained. Part of the mixture was dried under reduced pressure to isolate toner binder (1). Tg was 58 ° C.

  In a beaker, 240 parts by mass of the ethyl acetate / MEK solution of the toner binder (1), 20 parts by mass of pentaerythritol tetrabehenate (melting point: 81 ° C., melt viscosity: 25 cps), C.I. I. Pigment Blue 15: 3 raw pigment (6 parts by mass) was added, and the mixture was stirred at 12000 rpm with a TK homomixer at 60 ° C., and uniformly dissolved and dispersed. In another beaker, 706 parts by mass of ion-exchanged water, 294 parts by mass of hydroxyapatite 10% suspension (Superite 10 manufactured by Nippon Chemical Industry Co., Ltd.), and 0.2 parts by mass of sodium dodecylbenzenesulfonate were uniformly dissolved. . Next, the temperature was raised to 60 ° C., and the toner material solution was added and stirred for 10 minutes while stirring at 12000 rpm with a TK homomixer. The mixture was then transferred to a Kolben equipped with a stir bar and a thermometer, heated to 98 ° C. to remove the solvent, filtered, washed, dried, and then classified by air to obtain toner particles.

  100 parts by mass of the obtained cyan particles, 2.0 parts by mass of silica particles (number distribution-based maximum peak particle size 110 nm), silica particles (number distribution-based maximum peak particle size 30 nm) 0.8 parts by mass, rutile type Toner 4 was obtained by adding 0.9 parts by mass of titanium oxide particles (maximum peak particle size of 80 nm based on number distribution) and mixing with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.). The weight average particle diameter (D4) of Toner 4 was 5.8 μm.

[Example 1]
20.0 parts by mass of toner 1 was added to 80.0 parts by mass of magnetic carrier 1, and mixed by a tumbler mixer to obtain developer 1 for start. Similarly, 7.0 parts by mass of toner 1 was added to 1.0 part by mass of magnetic carrier 1 and mixed by a tumbler mixer to obtain replenishment developer 1. Table 3 shows the blending ratio of the toner with respect to 1 part by mass of the carrier of the obtained start developer 1 and replenishment developer 1.

  Using these developers, Canon's full-color copier CLC5000 remodeled machine (laser spot diameter is reduced, output is possible at 1200 dpi, the surface of the fixing roller of the fixing unit is changed to a PFA tube, and the oil application mechanism is removed) Durability image output evaluation (A4 horizontal, 10% printing ratio, 100,000 sheets) was performed under normal temperature and humidity (23 ° C., 60% RH). The items for image output evaluation after 100,000 sheets are passed and the evaluation criteria are shown below.

(1) Dot reproducibility (end of life and after 100,000 sheets)
A halftone image was formed using the developer and the modified machine, this image was visually observed, and the dot reproducibility of the image was evaluated based on the following criteria. The formed halftone image is a halftone image when the 48th density in the 256 gradation display in which 0 is solid white and 256 is solid black.
A: Smooth and smooth.
B: I don't feel a lot of rustling.
C: Although there is a slight feeling of roughness, it is at a level where there is no practical problem.
D: Strong feeling

(2) Fog (early endurance and after 100,000 sheets)
The average reflectance Dr (%) of plain paper before image printing was measured by a reflectometer (“REFLECTOMETER MODEL TC-6DS” manufactured by Tokyo Denshoku Co., Ltd.).

At the beginning of the endurance, a solid white image was printed on plain paper by changing Vd every 50V so that Vback was 0V to 300V. Further, after endurance output, a solid white image (Vback: 150 V) was drawn on plain paper. The reflectivity Ds (%) of the imaged solid white image was measured. The fog (%) was calculated from the obtained Dr and Ds (initial and subsequent durability) using the following formula. The obtained fog was evaluated according to the following evaluation criteria.
Fog (%) = Dr (%) − Ds (%)

(Evaluation criteria)
A: 0.5% or less B: 0.6-1.0% or less C: 1.1-2.0% or less D: 2.1% or more

(3) Carrier adhesion (initial durability and after 100,000 sheets)
A halftone image is formed on the paper using the developer and the modified machine, and the number of carriers present is counted with an optical microscope within an area of 1 cm ² on the halftone image.
A: 0 to 5 pieces: hardly noticeable and very good.
B: 6 to 10: Good.
C: 11-20 pieces: Black spots are visible, but at a level that is not problematic for practical use.
D: 21 or more: A poor cleaning occurs in the morning.

  Table 4 shows the evaluation results of (1) to (3) in the durability evaluation.

[Examples 2 to 12 and Comparative Examples 1 to 9]
The same evaluations (1) to (3) as in Example 1 were performed with the combinations and blending ratios of the magnetic carrier and the toner shown in Table 3.

  Table 4 shows the evaluation results of (1) to (3).

It is a graph for demonstrating the carrier specific resistance range of this invention. It is a schematic diagram which shows an example of the graph which measures the circularity of a carrier. It is typical sectional drawing of the apparatus which measures the specific resistance value of a carrier, a nonmagnetic inorganic compound, and a magnetic body. It is a carrier schematic diagram of the present invention. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus that can suitably implement the present invention. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus of a cleanerless system that can suitably implement the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a-1d Cleaning apparatus 2 Follower roller 3 Secondary transfer counter roller 4 Secondary transfer roller 5 Belt cleaning apparatus 6 Paper cassette 7a-7d Photosensitive drum 8a-8d Charging apparatus 9a-9d Image exposure apparatus 10a-10d Developer container 11 Drive roller 12a to 12d Process cartridge 13 Primary transfer roller 14 Intermediate transfer belt 15 Fixing device 16 Paper feed roller 21 Lower electrode 22 Upper electrode 23 Insulator 24 Ammeter 25 Voltmeter 26 Constant voltage device 27 Carrier 28 Guide ring E Resistance measurement cell L Sample Thickness P Transfer material

Claims (10)

A magnetic substance-containing resin carrier containing a resin and a magnetic substance,
The true specific gravity is 2.5 to 4.2 g / cm ³ ;
The magnetization intensity under a magnetic field of 1000 / 4π (kA / m) is 40 to 70 Am ² / kg;
50% particle size (D50) based on volume distribution is 15 μm to 25 μm,
The specific resistance when applying a voltage with an electric field strength of 1.0 × 10 ⁶ V / m is R1 (Ω · cm),
The relationship of 0 ≦ log (R1) −log (R2) ≦ 2.0, where R2 (Ω · cm) is the specific resistance when a voltage with an electric field strength of 2.5 × 10 ⁶ V / m is applied. A magnetic carrier characterized by satisfying 2. The magnetic carrier according to claim 1, wherein the specific resistance R2 of the magnetic carrier is 1.0 × 10 ¹³ (Ω · cm) or more.   The average circularity C of the magnetic carrier is 0.850 to 0.950, and satisfies the relationship of 0 ≦ (C−C30) ≦ 0.20 with the 30% value C30 of the circularity. The magnetic carrier according to claim 1 or 2.   The first resin coating layer and a second resin coating layer containing conductive particles on the first resin coating layer are formed on the surface of the magnetic carrier core particles. Magnetic carrier.   The magnetic carrier according to any one of claims 1 to 4, wherein 0.5 to 3.0 mass% of the first resin is coated on the magnetic carrier core particles.   6. The magnetic carrier according to claim 1, wherein the conductive particles contained in the second resin coating layer are carbon black.   The magnetic carrier core particle is a magnetic material-dispersed resin core particle obtained by polymerizing a monomer for forming a binder resin in the presence of a magnetic material. The magnetic carrier described.   A toner containing at least a binder resin and a colorant and the magnetic carrier according to any one of claims 1 to 7, wherein Rt is a weight average particle diameter (D4) of the toner, and an average particle diameter based on a volume distribution of the magnetic carrier. A two-component developer, wherein Rt / Rc is 0.15 or more and 0.80 or less when (D50) is Rc.   A replenishing developer containing 2 to 50 parts by mass of toner with respect to 1 part by mass of the magnetic carrier.   This is a two-component development method in which a developer for replenishment containing at least toner and a magnetic carrier is developed while being replenished to the developing device, and at least the excess carrier inside the developing device is discharged from the developing device as necessary. A two-component developing method, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 7.

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