JP2010072532A - Carrier for electrostatic charge image development, developer for electrostatic charge image development, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development, capable of suppressing image defects, such as white void, caused by damages or breakage of the carrier or carrier transfer from a developing device to a photoreceptor, and which is capable of giving stable images for a long period of time. <P>SOLUTION: The carrier for electrostatic charge image development contains core particles, resin and grease. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developing developer, and an image forming apparatus.

  A method for visualizing image information through an electrostatic latent image (electrostatic image) such as electrophotography is currently used in various fields. In electrophotography, an electrostatic latent image formed on a photoreceptor by charging and exposure processes contains an electrostatic charge image developing toner (hereinafter sometimes referred to simply as “toner”). It is developed with an agent (hereinafter sometimes simply referred to as “developer”), and visualized through a transfer and fixing process. As a developer used for development, a two-component developer including a toner and a carrier for developing an electrostatic image (hereinafter sometimes simply referred to as “carrier”) and a toner used alone such as a magnetic toner are used. There are component developers, but the two-component developer has characteristics such as good controllability because the carrier shares functions such as stirring, transport and charging of the developer and is separated as a developer. Is currently widely used.

  Carriers are generally classified into resin-coated carriers having a resin coating layer on the surface of magnetic particles (core particles) and uncoated carriers having no coating layer on the surface. Developers using resin-coated carriers are generally charged. It has excellent controllability and is relatively easy to improve environmental dependency and stability over time. As a developing method, the cascade method has been used in the past, but at present, the magnetic brush method using a magnetic roll as a developer conveying unit is the mainstream.

  In recent years, as the image quality of image forming apparatuses using electrophotography increases, the toner particle size has been reduced. A high-quality image can be obtained by obtaining a fine developed image using a small particle size toner, but the specific surface area of the toner increases as the particle size of the toner decreases. In order to sufficiently frictionally charge the toner surface, the carrier tends to be reduced in size in order to increase the specific surface area and to facilitate contact charging. As the particle size of the carrier decreases, the transfer of the carrier from the developing device to the photoconductor becomes significant, and image defects may occur.

  In Patent Document 1, attempts are made to regulate the carrier particle size, magnetic force, resistance, charge amount, magnetic force of the developer carrier, and the like, to suppress the transfer of the carrier to the photoconductor.

  Patent Document 2 describes that image defects are suppressed by defining a magnetic pole pattern of a developer carrier with respect to foreign matter mixed in the developing device.

JP 2003-167441 A JP-A-5-88555

  The present invention is for electrostatic charge image development that can suppress image defects such as white spots caused by carrier breakage, cracking, carrier transfer from the developing device to the photoreceptor side, etc., and can obtain a stable image over a long period of time. A carrier, a developer for developing an electrostatic image, and an image forming apparatus;

  The present invention is an electrostatic charge image developing carrier containing core particles, a resin, and grease.

  Further, in the electrostatic charge image developing carrier, the inclusion or decomposition product of the grease is an alkyl isocyanate having an alkyl group having 2 to 18 carbon atoms and an aryl isocyanate having an aryl group having 6 to 18 carbon atoms. It is preferable to include at least one.

  In the electrostatic image developing carrier, the core particles preferably include ferrite.

  The present invention also provides an electrostatic charge image developing developer comprising the electrostatic charge image developing carrier and the electrostatic charge image developing toner.

  The present invention also provides an image carrier, latent image forming means for forming an electrostatic latent image on the surface of the image carrier, and developing the electrostatic latent image using a developer to form a toner image. The image forming apparatus includes a developing unit and a transfer unit that transfers the developed toner image to a transfer target, and the developer is the developer for developing an electrostatic image.

  According to claim 1 of the present invention, image defects such as white spots caused by carrier breakage, cracking, carrier transfer from the developing device to the photoconductor side, and the like are suppressed as compared with the case where grease is not included. An electrostatic charge image developing carrier capable of obtaining a stable image over a long period of time can be provided.

  According to claim 2 of the present invention, the grease content or decomposition product is at least one of an alkyl isocyanate having an alkyl group having 2 to 18 carbon atoms and an aryl isocyanate having an aryl group having 6 to 18 carbon atoms. Compared to the case where no toner is included, it is possible to suppress image defects such as white breakage caused by breakage or cracking of the carrier or carrier transfer from the developing device to the photoconductor side, and a stable image can be obtained over a long period of time. A carrier for developing an electrostatic image can be provided.

  According to claim 3 of the present invention, image defects such as white spots caused by carrier breakage, cracking, or carrier transfer from the developing device to the photoconductor side, compared to the case where the core material particles do not contain ferrite. It is possible to provide a carrier for developing an electrostatic image capable of suppressing the above and capable of obtaining a stable image over a long period of time.

  According to claim 4 of the present invention, image defects such as white spots caused by carrier breakage, cracking, and carrier transfer from the developing device to the photoconductor side are suppressed as compared with the case where the grease is not included. It is possible to provide a developer for developing an electrostatic image capable of obtaining a stable image over a long period of time.

  According to claim 5 of the present invention, image defects such as carrier breakage and cracking and white spots due to carrier transfer from the developing device to the photoconductor side are suppressed as compared with the case where the grease is not included. An image forming apparatus capable of obtaining a stable image over a long period of time can be provided.

  Embodiments of the present invention will be described below. This embodiment is an example for carrying out the present invention, and the present invention is not limited to this embodiment.

<Carrier for developing electrostatic image>
In the developing device, in order to maintain a desired charge amount of the developer, the developer is stirred by rotating a stirring member such as a paddle, and a shearing force is applied between the toner and the carrier to frictionally charge the developer. ing. In order to sufficiently triboelectrically charge the developer, it is preferable to increase the stirring force in order to give a large shearing force. Specifically, the shape of the agitating member is devised, the gap between the agitating member and the inner wall of the developer accommodating portion is adjusted, and the rotational speed is improved. However, when the stirring force is increased, a very small amount of the carrier may be broken or cracked in the developer. Although this amount is very small, it is easy to shift to the photosensitive member side when transported to the developing area in the developing device, so that it is preferable that the carrier is not damaged as much as possible.

  The inventors of the present invention, such as carrier breakage, developer forms a layer in the gap between the sliding portion in the developing device and the stirring member and the inner wall of the developer accommodating portion, it is compressed, As a result of applying the stress, it was found that damage was caused from a weak part of the carrier. For this reason, it is considered that if the stress is relaxed by breaking or deforming the developer layer before the developer layer is compressed, the carrier can be prevented from being damaged. However, when a lubricant such as oil or grease is applied to the gap between the sliding part in the developing device or the stirring member and the inner wall of the developer accommodating part, the adhesive strength of those parts increases, and the developer Deposits or the like occurs, or the developer enters the bearings of the stirring member and the like, making it difficult for the developer to come out, resulting in damage to the carrier. Accordingly, the present inventors have found that by adding grease to the carrier, the developer is less likely to form an aggregate, and the developer moves slightly when stress is applied, and the stress can be relaxed. As a result, breakage and cracking of the carrier in the developer are remarkably reduced, carrier transfer from the developing device to the photoreceptor side is also suppressed, image defects such as white spots are suppressed, and a stable image can be obtained over a long period of time. It has become possible.

  The carrier for developing an electrostatic charge image according to the embodiment of the present invention contains core particles, a resin, and grease. The carrier according to the present embodiment can be used as a two-component developer, and is preferably a resin-coated carrier having a resin coating layer on the surface of the core particle. In the carrier according to the present embodiment, the grease is contained, for example, in the resin coating layer, at the interface between the core material particles and the resin coating layer, or the like.

  The “resin” contained in the carrier according to the present embodiment refers to a resin contained in the carrier. For example, in the case of having a resin coating layer, a resin constituting the resin coating layer, a resin-dispersed core material When it has particles, it means a resin that constitutes the resin-dispersed core particles.

[Grease]
Although there is no restriction | limiting in particular in the grease contained in a carrier, You may contain additives, such as lubricating oil and a thickener mainly giving viscosity, as needed.

  Lubricating oils include mineral oil such as spindle oil and cylinder oil, synthetic hydrocarbon oil, ester oil such as diester and polyol ester, polyalkylene glycol oil such as silicone oil and polyglycol, ether oil such as diphenyl ether, fluorine oil, etc. Synthetic oils, vegetable oils, animal oils and the like.

  Examples of the thickener include soaps such as Ca soap, Li soap, Li composite soap, Al composite soap, and Ca composite soap, urea compounds, organic soaps such as bentonite, and silica. From the viewpoint of sex. Examples of the urea compound include an alkyl isocyanate having an alkyl group having 2 to 18 carbon atoms, preferably 3 to 10 carbon atoms, and an aryl group having 6 to 18 carbon atoms, preferably 6 to 10 carbon atoms. Examples include urea compounds that contain isocyanate compounds such as aryl isocyanates or that are produced as thermal decomposition products. Examples of the alkyl isocyanate having an alkyl group having 2 to 18 carbon atoms include ethyl isocyanate, propyl isocyanate, hexyl isocyanate, octyl isocyanate, octadecyl isocyanate, cyclohexyl isocyanate, methoxypropyl isocyanate, etc., and 6 to 18 carbon atoms. Examples of the aryl isocyanate having an aryl group include phenyl isocyanate, tolyl isocyanate, and benzyl isocyanate. When the grease contains the urea compound as a thickener, the heat resistance is improved.

  Additives include antioxidants, corrosion inhibitors, rust inhibitors, thickeners, extreme pressure additives, molybdenum disulfide, graphite, polytetrafluoroethylene (PTFE), melamine cyanurate (MCA). Etc.

  Moreover, although there exist a grease for motor vehicles and an industrial use, industrial uses, such as vacuum grease, are preferable. Examples of main greases include Daphne Eponex Grease, Daphne Eponex EP, Daphne Eponex SR, Daphne Multilex WR, Daphne Grease M, Daphne Molybdenum Grease, Daphne Polylex Grease 2, Daphne Polylex HL, Daphne Grease LT, Daphne Grease XLA, Daphne Bios Grease HC (made by Idemitsu Kosan), Shell Sunlite Grease, Sunlite Grease MB, Retinax Grease CL, Albania Grease S, Albania Grease HDX, Albania EP Grease, Albania Grease RA, Albania Grease HVQ, Stamina Grease RL, Stamina EP Grease, Stamina Grease HDP, Cartridge Grease EP, Mareus OGP, Tactic EMV (above, Showa Shell), Cup Grease, Epi Knock Grease AP (N), Martinoch Grease, Martinock Deluxe, Martinock Wide 2, Martinock SDX, Martinock Urea, ENS Grease, Pyro Knock Niversal 0, Pyronock Universal 2, Pyronock Grease, Pyronock CC, Molinoc Grease AP, Epinoc Grease LT, Epinoc 203K2, Pyronock WH-1, Pyronock Grease WS, Gear Coupling Grease, CP Grease L, Seal Knock Grease , Pyronock Universal 00,000, Bionock Zinen, Chevron FM, Grease EP, Clanock Compound, OG Grease 500, Spray Compound (made by Nippon Oil Co., Ltd.), Cosmo Wide Grease WR, Cosmo Grease Dynamax, Cosmo Grease Dynamax Super, Cosmo Grease Super Galaxy, Cosmo Grease Galaxy, Cosmo Molybdenum Grease Special No. 2. Cosmo Molybdenum Grease, Cosmo Grease Dynamax EP, Cosmo Concentrated Grease, Cosmo Concentrated Grease Special, Cosmo Low Temperature Grease, Cosmo Urea Grease, Cosmo Heat Resistant Grease A, Cosmo Heat Resistant Grease B, Cosmo Cup Grease, Cosmo Graphite Grease, Cosmo High Chuck Grease, Cosmo Gear Compound, Cosmo Rope Grease, Cosmo Special Grease H1, Cosmo Terra Grease EP, Cosmo White P, Cosmo Pure Spin, Cosmo Pure Safety, Cosmo Neutral, Cosmo SP (above, Cosmo Oil), NIPPECO MP, NIPPECO GR, NIPPECO S, NIPPECO GB, NIPPECO A, NIPPECO LT-K, NIPPECO LTS, DAVELEX, Calforex EP, Attlebe, Attlebe KR, A Lub MS, Attorb HD, Permalb B, Dubrex, Carrea HB, Eulet AA, Eulet CC, Eulet DD, Eulet El-1, Eulet M, Dubrex, FG-13, Nipeco LLP, Dubrex BC SP, Dubrex Gear SP , Dubrex F-642, Dubrex VB, Dubrex EL, Super heat-resistant GP (manufactured by Nippon Steel Oil Co., Ltd.), Uniluve DL, Emulub L, Newmax EP, Palmmax RGB, Powerlight WR, Morirex M, GC Grease, Multemp ET-100K, Full Tribo MH, Biotemp VC, Full Tribo VAC, Multemp ET Series, Space Lube Series (made by Kyodo Yushi Co., Ltd.), etc., especially Daphne Polylex Grease No. A heat resistant grease such as 2 is preferred.

  The content of the grease is preferably in the range of 0.001% by weight to 0.15% by weight and preferably in the range of 0.002% by weight to 0.1% by weight with respect to the weight of the carrier. It is more preferable. When the grease content is less than 0.001% by weight, it becomes difficult to relieve stress at the sliding part in the developing machine, and the carrier is damaged. As a result, the carrier is damaged in the image where the toner is not developed. White spots may occur in the image due to scattering, and if it exceeds 0.15% by weight, the amount of grease exposed to the carrier surface becomes excessive and the adhesion between the toner and the carrier increases, resulting in the result. In some cases, fluidity as a developer deteriorates, charge exchange between toners deteriorates, and fluidity of the developer deteriorates.

  In the carrier according to the present embodiment, when the grease contains a urea compound as a thickener, the alkyl isocyanate or isocyanate having an alkyl group having 2 to 18 carbon atoms, preferably 3 to 10 carbon atoms, such as n-octyl isocyanate. It may contain isocyanate compounds such as adducts and isocyanurates, or may contain them as raw materials.

  The grease can be added, for example, when the resin coating layer is formed on the core material particles.

[Core particles]
The core particles used in the carrier according to the present embodiment are not particularly limited, but from the viewpoint of using the magnetic brush method, the carrier is preferably a magnetic carrier, and therefore the core particles are also preferably magnetic. . Examples of the material constituting the core particles include magnetic metals such as iron, steel, nickel and cobalt; alloys of these magnetic metals with manganese, chromium and rare earths; and magnetic oxides such as ferrite and magnetite. Can be mentioned.

  Alternatively, resin-dispersed core particles in which magnetic powder or the like is dispersed in a matrix resin may be used. In that case, the matrix resin used is polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid copolymer. Examples include polymers, straight silicone resins composed of organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenol resins, epoxy resins, urea resins, urethane resins, melamine resins, etc., but are not limited thereto. It is not something.

  The core particles used in the carrier according to the present embodiment are preferably ferrite particles containing ferrite from the viewpoint of easy surface uniformity and stable chargeability.

  Ferrite core particles are formed by granulation, sintering, etc., but are preferably pulverized as a pretreatment. The pulverization method is not particularly limited, and pulverization can be performed according to a known pulverization method. Specific examples include a mortar, ball mill, jet mill and the like. Although the final pulverized state in the pretreatment varies depending on the material and the like, the volume average particle diameter is preferably 2 μm or more and 10 μm or less. When the volume average particle size is less than 2 μm, a desired particle size may not be obtained. When the volume average particle size exceeds 10 μm, the particle size may be too large or the circularity may be decreased.

  In addition, the sintering temperature is preferably kept lower than in the conventional case, and specifically varies depending on the material used, but is preferably in the range of 500 ° C to 1400 ° C, more preferably in the range of 600 ° C to 1200 ° C. preferable. If the sintering temperature is less than 500 ° C., the magnetic force required for the carrier may not be obtained. If the sintering temperature exceeds 1400 ° C., the crystal growth is fast and the internal structure tends to become non-uniform, causing cracks and cracks. Easy to enter.

  In order to keep the sintering temperature low, in the sintering process, it is preferable to perform preliminary sintering stepwise. Therefore, it is preferable to increase the time required for the entire sintering.

  The volume average particle size of the core particles is preferably in the range of 10 μm to 150 μm, more preferably in the range of 20 μm to 75 μm, and still more preferably in the range of 20 μm to 50 μm. When the volume average particle size of the core material particles is less than 10 μm, when used as a developer for developing an electrostatic image, the adhesion force between the toner and the carrier is increased, and the toner development amount may be reduced. On the other hand, when the volume average particle size exceeds 150 μm, the magnetic brush becomes rough, and it may be difficult to form a fine image.

  As for the magnetic force of the core material particles, the saturation magnetization at 1,000 oersted is preferably 50 emu / g or more, and more preferably 60 emu / g or more. If the saturation magnetization is weaker than 50 emu / g, the carrier may be developed on the photoreceptor together with the toner.

  As an apparatus for measuring magnetic properties, a vibrating sample type magnetic measuring apparatus VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.) can be used. A measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm, and set in the apparatus. The measurement applies an applied magnetic field and sweeps up to 1,000 oersted. Next, the applied magnetic field is decreased to create a hysteresis curve on the recording paper. Saturation magnetization, residual magnetization, and coercive force are obtained from the hysteresis curve data. In the present embodiment, the saturation magnetization indicates the magnetization measured in a 1,000 oersted magnetic field.

The volume electrical resistance (volume resistivity) of the core particles is preferably in the range of 10 ⁵ Ω · cm to 10 ¹² Ω · cm, and preferably in the range of 10 ⁷ Ω · cm to 10 ⁹ Ω · cm. It is more preferable. If the volume electric resistance is less than 10 ⁵ Ω · cm, when the toner concentration in the developer decreases due to repeated copying, charges may be injected into the carrier and the carrier itself may be developed. On the other hand, if the volume electric resistance is greater than 10 ¹² Ω · cm, the image quality may be adversely affected, such as prominent edges and pseudo contours.

The volume electric resistance (Ω · cm) of the core particles can be measured as follows. The measurement environment is a temperature of 20 ° C. and a humidity of 50% RH. A measurement object is placed flat on the surface of a circular jig having a 20 cm ² electrode plate so as to have a thickness of about 1 mm or more and 3 mm or less to form a layer. A similar electrode plate of 20 cm ² is placed on this and the layers are sandwiched. In order to eliminate gaps between objects to be measured, a thickness (cm) of the layer is measured after a load of 4 kg is applied on the electrode plate placed on the layer. Both electrodes above and below the layer are connected to an electrometer and a high voltage power generator. A high voltage is applied to both electrodes so that the electric field is 103.8 V / cm, and the current value (A) flowing at this time is read to calculate the volume electric resistance (Ω · cm) of the measurement object. The calculation formula of the volume electrical resistance (Ω · cm) of the measurement object is as shown in the following formula.
R = E × 20 / (I−I ₀ ) / L
In the above formula, R is the volume electrical resistance (Ω · cm) of the measurement object, E is the applied voltage (V), I is the current value (A), I ₀ is the current value (A) at the applied voltage of 0 V, and L is Each layer thickness (cm) is expressed. A coefficient of 20 represents the area (cm ² ) of the electrode plate.

[Resin coating layer]
Examples of the coating resin used for the resin coating layer of the carrier include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene- Acrylic acid copolymers, resins with alicyclic groups such as cyclohexyl methacrylate resins, straight silicone resins composed of organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenol resins, epoxy resins, urea resins, urethane resins, Melamine resins and the like can be exemplified, but are not limited thereto.

  The resin coating layer may contain conductive powder as needed for the purpose of controlling resistance.

  Specific examples of the conductive powder include metal particles such as gold, silver and copper; carbon black; ketjen black; acetylene black; semiconductive oxide particles such as titanium oxide and zinc oxide; titanium oxide, zinc oxide and sulfuric acid. And particles having the surface of barium, aluminum borate, potassium titanate powder or the like covered with tin oxide, carbon black, metal, or the like. These may be used individually by 1 type and may use 2 or more types together.

  As the conductive powder, carbon black particles are preferable in terms of good production stability, cost, conductivity and the like.

  Although there is no restriction | limiting in particular as a kind of carbon black, The carbon black whose DBP oil absorption is 50 mL / 100g or more and about 250 mL / 100g or less is excellent in manufacturing stability, and is preferable.

  The volume average particle size of the conductive powder is preferably 0.5 μm or less, more preferably 0.05 μm or more and 0.5 μm or less, and even more preferably 0.05 μm or more and 0.35 μm or less. If the volume average particle size is less than 0.05 μm, the sensitivity to resistance control may be lost, and if the volume average particle size is greater than 0.5 μm, the conductive powder tends to fall off from the resin coating layer, resulting in stable chargeability. It may not be obtained.

  The volume average particle diameter of the conductive powder can be measured using a laser diffraction particle size distribution measuring apparatus (LA-700: manufactured by Horiba, Ltd.).

  As a measurement method, 2 g of a measurement sample is added to a surfactant, preferably 50 mL of a 5% aqueous solution of sodium alkylbenzenesulfonate, and dispersed for 2 minutes with an ultrasonic disperser (1,000 Hz) to prepare a sample. taking measurement. The obtained volume average particle diameter for each channel is accumulated from the smaller volume average particle diameter, and the place where the accumulation reaches 50% is defined as the volume average particle diameter.

The volume electrical resistance of the conductive powder is preferably in the range of 10 ¹ Ω · cm to 10 ¹¹ Ω · cm, and more preferably in the range of 10 ³ Ω · cm to 10 ⁹ Ω · cm.

  The volume electrical resistance of the conductive powder can be measured in the same manner as the volume electrical resistance of the core particles.

  The content of the conductive powder is preferably in the range of 0.05% by mass to 1.5% by mass with respect to the entire resin coating layer, and 0.10% by mass to 3% by mass to 1.0% by mass. % Or less is more preferable. When the content is larger than 1.5 mass 50% by volume, the carrier resistance is lowered, and the image may be lost due to carrier adhesion to the developed image. On the other hand, if the content is less than 0.05 mass 1% by volume, the carrier is insulated, and during development, the carrier becomes difficult to work as a developing electrode, and an edge effect is produced particularly when a black solid image is formed. The reproducibility of a solid image may be inferior.

  In addition, the resin coating layer may contain resin particles. Examples of the resin particles include thermoplastic resin particles and thermosetting resin particles. Among these, thermosetting resins are preferable from the viewpoint of relatively easily increasing the hardness, and resin particles made of nitrogen-containing resin containing N atoms are preferable from the viewpoint of imparting negative chargeability to the toner. In addition, these resin particles may be used individually by 1 type, and may use 2 or more types together.

  The volume average particle size of the resin particles is, for example, preferably in the range of 0.1 μm to 2.0 μm, and more preferably in the range of 0.2 μm to 1.0 μm. If the volume average particle diameter of the resin particles is less than 0.1 μm, the dispersibility of the resin particles in the resin coating layer may be deteriorated. On the other hand, if it exceeds 2.0 μm, the resin particles fall off from the resin coating layer. May occur and the original effect may not be exhibited.

  The volume average particle diameter of the resin particles can be determined by performing the same measurement as the volume average particle diameter of the conductive powder.

  The content of the resin particles is preferably in the range of 1% by mass to 50% by mass and more preferably in the range of 1% by mass to 30% by mass with respect to the entire resin coating layer. The range of volume% or more and 20 mass% or less is more preferable. If the content of the resin particles is less than 1% by mass, the effect of the resin particles may not be expressed. If the content exceeds 50% by mass, the resin coating layer is likely to fall off, and stable chargeability is obtained. It may not be possible.

  The method for forming the resin coating layer on the surface of the core particle is not particularly limited. For example, a film forming liquid containing conductive powder and an alicyclic group-containing acrylic resin or polycarbonate resin in a solvent is used. The method etc. are mentioned.

  For example, a dipping method in which core material particles are immersed in a film forming liquid, a spray method in which a film forming liquid is sprayed on the surface of the core material particles, and the core material particles are mixed with the film forming liquid in a state of being suspended by flowing air. And a kneader coater method for removing the solvent. Among these, the knea coater method is preferable, and the coating is formed in the recesses on the surface of the core material particles by mixing the coating film forming liquid and the core material particles at the initial stage of the coating and mixing the particles for a long time. When the working solution is soaked, the volatile substance is hardly supported between the core material particles and the coating film. Therefore, it is preferable to carry out this acclimatization step in as short a time as possible and to carry out the desolvation step at once.

  The solvent used for the film forming liquid is not particularly limited as long as it can dissolve the resin, and can be selected from known solvents. Specific examples include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane.

  When resin particles are dispersed in the resin coating layer, the resin particles are substantially uniformly dispersed in the thickness direction and the tangential direction of the carrier surface. Even when the toner is worn, it is possible to maintain the same surface formation as when it is not used, and to maintain a good charge imparting ability for the toner over a long period of time.

  When conductive powder is dispersed in the coating resin layer, the conductive powder is substantially uniformly dispersed in the thickness direction and the tangential direction of the carrier surface. Even if the resin layer is worn, the same surface formation as when not in use can be maintained, and carrier deterioration can be prevented for a long time.

  In the case where resin particles and conductive powder are dispersed in the coating resin layer, the above-described effects can be achieved at the same time.

  Further, the resin coating layer is not limited to a single layer, and may have a configuration of two or more layers.

  The content of the resin coating layer in the carrier according to the present embodiment is preferably in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the core particles, and preferably 1 to 5 parts by weight. The range is more preferable, and the range of 1 part by weight to 3 parts by weight is more preferable. When the content of the resin coating layer is less than 0.5 parts by weight, the surface exposure of the core particles is too much, so that a development electric field may be easily injected. Further, when the content of the resin coating layer is larger than 10 parts by weight, the resin powder released from the resin coating layer is increased, and there is a possibility that the carrier resin powder peeled off in the developer from the beginning is contained. is there.

  The coverage of the core particle surface by the resin coating layer is preferably 80% or more, more preferably 85% or more, and particularly preferably as close to 100% as possible. When the coverage is less than 80%, charge injection into the carrier occurs when used over a long period of time, the carrier in which charge injection has occurred migrates to the photoreceptor, and white spots occur on the image. There is a case.

[Characteristics of carrier]
The weight average particle size of the carrier is preferably in the range of 10 μm to 150 μm, more preferably in the range of 20 μm to 75 μm, and still more preferably in the range of 20 μm to 50 μm. When the weight average particle diameter of the carrier is smaller than 10 μm, the carrier contamination may be deteriorated. On the other hand, if the weight average particle diameter of the carrier is larger than 150 μm, toner deterioration due to stirring may become remarkable.

  The weight average particle diameter of the carrier can be measured using a laser diffraction / scattering particle size distribution analyzer (LS Particle Size Analyzer: LS13 320, manufactured by Beckman Coulter, Inc.). As the electrolytic solution, ISOTON-II (manufactured by Beckman Coulter, Inc.) is used.

  Further, the shape factor SF1 of the carrier is preferably 100 or more and 145 or less. This is because the agitation efficiency of the developer can be compatible.

The carrier shape factor SF1 is obtained by the following equation.
SF1 = (ML ² / A) × (π / 4) × 100
Here, ML is the maximum length (μm) of the carrier particles, and A is the projected area (μm ² ) of the carrier particles. The maximum length and projected area of the carrier particles are determined by observing the carrier particles sampled on the slide glass with an optical microscope and importing them into an image analyzer (LUZEX III, manufactured by NIRECO) through a video camera for image analysis. It can ask for. The number of samplings at this time is 100, and the shape factor shown in the above equation is obtained to obtain an average value.

  The saturation magnetization of the carrier is preferably 40 emu / g or more, and more preferably 50 emu / g or more.

  As a magnetic property measuring device, a vibrating sample type magnetic measuring device VSMP10-15 (manufactured by Toei Industry Co., Ltd.) is used. The measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm and set in the apparatus. The measurement applies an applied magnetic field and sweeps up to 1000 oersted. Next, the applied magnetic field is decreased to create a hysteresis curve on the recording paper. Saturation magnetization, residual magnetization, and coercive force are obtained from the curve data.

The volume electric resistance of the carrier is preferably in the range of 1 × 10 ⁷ Ω · cm to 1 × 10 ¹⁵ Ω · cm, and preferably in the range of 1 × 10 ⁸ Ω · cm to 1 × 10 ¹⁴ Ω · cm. More preferably, it is in the range of 1 × 10 ⁸ Ω · cm to 1 × 10 ¹³ Ω · cm.

When the volume electrical resistance of the carrier exceeds 1 × 10 ¹⁵ Ω · cm, the resistance becomes high, and it becomes difficult to work as a developing electrode during development. There is a case. On the other hand, if it is less than 1 × 10 ⁷ Ω · cm, the resistance becomes low, so that when the toner concentration in the developer is lowered, charges are injected from the developing roll into the carrier, and the carrier itself is developed. It may be easier.

  The volume electric resistance of the carrier can be measured in the same manner as the volume electric resistance of the core particles.

<Toner for electrostatic image development>
The toner for developing an electrostatic charge image used in the exemplary embodiment is not particularly limited, but it contains at least toner base particles including a binder resin and a colorant and an external additive, such as fluidity and charging characteristics. From the viewpoint of

[Toner mother particles]
The toner base particles of the toner contain a binder resin and a colorant, and if necessary, contain a release agent, silica, a charge control agent and the like.

  Binder resins include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate , Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl Homopolymers and copolymers of vinyl ethers such as methyl ether, vinyl ethyl ether, vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone; Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include coalescence, polyethylene, and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like. Among these, styrene-alkyl acrylate copolymers, styrene-alkyl methacrylate copolymers, and polyester resins are particularly preferable.

  In addition, toner colorants include magnetic powders such as magnetite and ferrite, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, and malachite green oxa. Rate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 can be exemplified as a representative one.

  In the toner according to the exemplary embodiment, the content of the colorant is preferably in the range of 1 part by weight to 30 parts by weight with respect to 100 parts by weight of the binder resin. It is also effective to use a processed colorant or a pigment dispersant. By appropriately selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.

  Typical examples of the release agent include low molecular polyethylene, low molecular polypropylene, Fischer-Tropsch wax, montan wax, carnauba wax, rice wax, and candelilla wax.

  Known charge control agents can be used, but azo metal complex compounds, metal complex compounds of salicylic acid, resin type charge control agents containing polar groups, and the like can be used. When the toner is manufactured by a wet manufacturing method, it is preferable to use a material that is difficult to dissolve in water in terms of controlling ionic strength and reducing wastewater contamination. The toner in this embodiment may be either a magnetic toner containing a magnetic material or a non-magnetic toner not containing a magnetic material.

  The toner base particles are produced by, for example, a kneading and pulverizing method in which a binder resin, a colorant, and a release agent, a charge control agent, and the like are kneaded, pulverized, and classified; particles obtained by a kneading and pulverizing method The shape is changed by mechanical impact force or thermal energy; the polymerizable monomer of the binder resin is emulsion-polymerized, the formed dispersion, the colorant, and if necessary, the release agent, electrification Emulsion polymerization agglomeration method to obtain toner particles by mixing with a dispersion of a control agent, etc., and agglomerating and heat-fusing; a polymerizable monomer for obtaining a binder resin, a colorant, and separation if necessary Suspension polymerization method in which a solution of a mold agent, a charge control agent, etc. is suspended in an aqueous solvent for polymerization; a binder resin, a colorant, and, if necessary, a solution of a release agent, a charge control agent, etc., in an aqueous system For example, a solution suspension method of suspending in a solvent and granulating can be used. Further, a manufacturing method may be performed in which the toner obtained by the above method is used as a core, and resin particles are further adhered and heat-fused to have a core-shell structure.

  The toner base particles produced as described above have a volume average particle diameter of preferably 2 μm or more and 12 μm or less, and more preferably 3 μm or more and 9 μm or less.

The toner base particles are preferably pseudo-spherical from the viewpoints of developability, improved transfer efficiency, and high image quality. The degree of spheroidization of the toner base particles can be expressed using a shape factor SF1 of the following formula. The average value of the coefficient coefficient SF1 of the toner base particles used in this embodiment is preferably 140 or less, more preferably in the range of 115 to 145, and in the range of 120 to 140. Further preferred.
SF1 = (ML ² / A) × (π / 4) × 100
In the above formula, ML represents the maximum length (μm) of each toner base particle, and A represents the projected area (μm ² ) of each toner base particle.

  When the average value of the shape factor SF1 is larger than 145, the transfer efficiency may be lowered, and the deterioration of the image quality of the print sample may be visually confirmed.

  The average value of the shape factor SF1 is obtained by taking 1,000 toner images magnified 250 times from an optical microscope into an image analyzer (LUZEX III, manufactured by Nireco), and calculating the individual values from the maximum length and the projected area. The value of SF1 is obtained for the particles and averaged.

  There are no particular restrictions on the external additive of the toner, but at least one kind is a small-diameter inorganic having a primary particle size responsible for functions such as powder flowability and charge control, and having a volume average particle size in the range of 7 nm to 40 nm. An oxide is preferable. Examples of the small-diameter inorganic oxide include silica, alumina, titanium oxide (such as titanium oxide), calcium carbonate, magnesium carbonate, calcium phosphate, and carbon black.

  In particular, the use of titanium oxide having a volume average particle size of 15 nm or more and 40 nm or less hardly affects the transparency even in a full-color image, and has good chargeability, environmental stability, fluidity, caking resistance, This is preferable in that stable negative chargeability, image quality maintenance, and the like can be obtained.

  Moreover, about an external additive, dispersibility becomes high and the effect which raises powder fluidity | liquidity becomes large by surface-treating. As the surface treatment, known ones can be used. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrichlorosilane. Methoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (Bistrimethylsilyl) acetamide, N, N-bis (trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyl Rutrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyl Representative examples include diethoxysilane, γ-mercaptopropyltrimethoxysilane, and γ-chloropropyltrimethoxysilane.

  The addition amount of the small-diameter inorganic oxide is preferably in the range of 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the toner base particles.

  Further, when toner base particles having a toner shape factor SF1 of 145 or less are used, it is preferable from the standpoint of transfer efficiency and cleaning process stability that a large-diameter external additive of 60 nm or more is used alone or in combination. The large-diameter external additive is preferably a large-diameter inorganic oxide having a volume average particle size in the range of 60 nm to 300 nm, and more preferably a large-diameter inorganic oxide in the range of 80 nm to 300 nm. .

  As large-diameter inorganic oxides, silica, titanium oxide, metatitanic acid, aluminum oxide, magnesium oxide, alumina, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, chromium oxide, antimony trioxide, Examples thereof include magnesium oxide and zirconium oxide. Among these, it is preferable to use one selected from silica, titanium oxide, and metatitanic acid from the viewpoint of precise charge control.

  Further, in an image that requires high transfer efficiency such as a full-color image, it is preferable to use silica as an external additive, the true specific gravity is in the range of 1.3 to 1.9, and the volume average particle diameter is 60 nm. It is more preferable to use monodispersed spherical silica having a range of 300 nm or less. The volume average particle diameter of the monodispersed spherical silica is more preferably in the range of 80 nm to 200 nm. By controlling the true specific gravity to 1.9 or less, peeling from the toner base particles can be suppressed. Further, by controlling the true specific gravity to 1.3 or more, aggregation and dispersion can be suppressed. The true specific gravity of monodispersed spherical silica is more preferably in the range of 1.4 to 1.8.

  When the volume average particle size of the monodispersed spherical silica is less than 60 nm, the monodispersed spherical silica tends not to effectively work to reduce the non-electrostatic adhesion between the toner and the photoreceptor. In particular, the monodispersed spherical silica is easily embedded in the toner base particles due to stress in the developing device, and the effect of improving developability and transferability is likely to be significantly reduced. On the other hand, if it exceeds 300 nm, it will be easy to detach from the toner base particles, and it will not work effectively to reduce non-electrostatic adhesion, and at the same time it will easily move to the contact member, causing secondary obstacles such as charging inhibition and image quality defects. It becomes easy to cause.

  Since the monodispersed spherical silica is monodispersed and spherical, it can be dispersed substantially uniformly on the surface of the toner base particles, and a stable spacer effect can be obtained. The definition of monodispersion can be discussed with the standard deviation with respect to the average particle diameter including aggregates, and the volume average particle diameter D50 × 0.22 or less is preferable as the standard deviation. Further, the definition of sphere can be discussed by Wadell's degree of sphericity, and the degree of sphericity is preferably 0.6 or more, and more preferably 0.8 or more.

The Wadell's degree of spheroidization can be obtained from the following equation.
Degree of sphericity = (surface area of sphere having the same volume as actual particle) / (surface area of actual particle)
In the above formula, the molecule = (surface area of a sphere having the same volume as the actual particle) can be calculated from the volume average particle diameter. Further, the denominator = (actual particle surface area) can be substituted by the BET specific surface area measured using Shimadzu powder specific surface area measuring apparatus SS-100 type.

  The reason why silica is preferable is that the refractive index is around 1.5, and even if the particle size is increased, the transparency decreases due to light scattering, especially the PE value (light transmission when capturing images on the surface such as OHP in color images). For example, it does not affect the sex index).

  The addition amount of the large-diameter inorganic oxide is preferably in the range of 1.0 to 5.0 parts by weight with respect to 100 parts by weight of the toner base particles.

  Furthermore, lubricant particles may be included as an external additive. Lubricant particles include solid lubricants such as graphite, molybdenum disulfide, talc, fatty acids, higher alcohols, aliphatic alcohols, fatty acid metal salts, and low molecular weight polyolefins such as polypropylene, polyethylene, polybutene, etc .; Silicones; aliphatic amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, stearic acid amide; plant waxes such as carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, etc .; Animal waxes such as beeswax; minerals such as montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, and petroleum waxes; and their modified materials may be used in combination. It is preferable shape factor SF1 of the particles are 140 or more in order to obtain the cleaning performance.

  Furthermore, you may use together a well-known inorganic oxide material as an abrasive | polishing agent. Examples of inorganic oxide materials include cerium oxide, strontium titanate, magnesium oxide, alumina, silicon carbide, zinc oxide, silica, titanium oxide, boron nitride, calcium pyrophosphate, zirconia, barium titanate, calcium titanate, calcium carbonate. Etc. Moreover, you may use these composite materials.

  Since the toner base particles used in the exemplary embodiment are preferably pseudo-spherical, the effect of adding an inorganic oxide is superior to that of an irregular toner base particle. That is, when the same amount of inorganic oxide is added to the toner base particles, the powder fluidity of the toner of the pseudo spherical toner base particles is higher than that of the amorphous toner base particles. Even if the amount is the same, the toner of the pseudo spherical toner base particles exhibits high developability and transferability.

  The mixing of the toner base particles and the external additive may be performed by any method. For example, it can be manufactured by mixing with a Henschel mixer or a V blender. In addition, external addition and mixing is performed in equipment having mechanical impact force such as hybridization systems, mechano-fusion systems such as nanocula, and crushers such as I-type mills and kryptrons, and the toner base particles are wet. When manufacturing, it is also possible to externally add in a wet process.

<Developer for developing electrostatic image>
The developer according to this embodiment is a two-component developer including a toner and a carrier, and is manufactured by mixing the toner and the carrier described above.

  The mixing ratio (weight ratio) between the toner and the carrier in the developer is preferably in the range of toner: carrier = 1: 99 to 20:80, preferably in the range of 3:97 to 12:88. Is more preferable.

<Image forming apparatus>
The image forming apparatus according to the present embodiment uses an image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, and a developer carried on the developer carrier. A developing unit that develops an electrostatic latent image formed on the surface of the body to form a toner image; and a transfer unit that transfers the developed toner image to a transfer target. An image developing developer is used. In addition, the image forming apparatus according to the present embodiment includes means other than those described above, for example, charging means for charging the image holding member, fixing means for fixing the toner image transferred to the surface of the transfer target, and the surface of the image holding member. Further, it may include a cleaning means for removing the remaining toner, carrier and the like.

  An example of the image forming apparatus according to the present embodiment is schematically shown in FIG. The image forming apparatus 1 includes a charging unit 10, an exposure unit 12, an electrophotographic photosensitive member 14 that is an image holding member, a developing unit 16, a transfer unit 18, a cleaning unit 20, and a fixing unit 22.

  In the image forming apparatus 1, the charging unit 10 that is a charging unit that charges the surface of the electrophotographic photosensitive member 14 and the charged electrophotographic photosensitive member 14 are exposed around the electrophotographic photosensitive member 14 according to image information. The exposure unit 12 is a latent image forming unit that forms an electrostatic latent image, the developing unit 16 is a developing unit that develops the electrostatic latent image with toner to form a toner image, and the surface of the electrophotographic photoreceptor 14. A transfer unit 18 that is a transfer unit that transfers the toner image formed on the surface of the transfer target 24, and a cleaning unit 20 that is a cleaning unit that removes toner remaining on the surface of the electrophotographic photosensitive member 14 after transfer. Are arranged in this order. A fixing unit 22 that is a fixing unit that fixes the toner image transferred to the transfer target 24 is arranged on the left side of the transfer unit 18.

  An operation of the image forming apparatus 1 according to the present embodiment will be described. First, the surface of the electrophotographic photosensitive member 14 is uniformly charged by the charging unit 10 (charging process). Next, light is applied to the surface of the electrophotographic photosensitive member 14 by the exposure unit 12, and the charged charges in the irradiated portion are removed, and an electrostatic charge image (electrostatic latent image) is formed according to the image information. (Latent image forming step). Thereafter, the electrostatic charge image is developed by the developing unit 16, and a toner image is formed on the surface of the electrophotographic photosensitive member 14 (developing step). For example, in the case of a digital electrophotographic copying machine using an organic photoconductor as the electrophotographic photoconductor 14 and using a laser beam as the exposure unit 12, the surface of the electrophotographic photoconductor 14 is negatively charged by the charging unit 10. Then, a digital latent image is formed in a dot shape by the laser beam light, and toner is applied to the portion irradiated with the laser beam light by the developing unit 16 to be visualized. In this case, a negative bias is applied to the developing unit 16. Next, a transfer member 24 such as paper is superposed on the toner image at the transfer unit 18, and a charge opposite in polarity to the toner is applied to the transfer member 24 from the back side of the transfer member 24, and the toner image is generated by electrostatic force. Is transferred to the transfer target 24 (transfer process). The transferred toner image is heated and pressed by a fixing member in the fixing unit 22 and is fused and fixed to the transfer target 24 (fixing step). On the other hand, toner remaining on the surface of the electrophotographic photoreceptor 14 without being transferred is removed by the cleaning unit 20 (cleaning step). One cycle is completed in a series of processes from charging to cleaning. In FIG. 1, the toner image is directly transferred to the transfer target 24 such as a sheet by the transfer unit 18, but may be transferred via a transfer member such as an intermediate transfer member.

  Hereinafter, the charging unit, the image carrier, the exposure unit, the developing unit, the transfer unit, the cleaning unit, and the fixing unit in the image forming apparatus 1 of FIG. 1 will be described.

(Charging means)
For example, a charging device such as a corotron as shown in FIG. 1 is used as the charging unit 10 serving as a charging unit, but a conductive or semiconductive charging roll may be used. A contact charger using a conductive or semiconductive charging roll may apply a direct current to the electrophotographic photosensitive member 14 or may superimpose an alternating current. For example, the charging unit 10 charges the surface of the electrophotographic photosensitive member 14 by generating a discharge in a minute space near the contact portion with the electrophotographic photosensitive member 14. Normally, it is charged to −300V or more and −1000V or less. The conductive or semiconductive charging roll may have a single layer structure or a multiple structure. Further, a mechanism for cleaning the surface of the charging roll may be provided.

(Image carrier)
The image carrier has a function of forming at least a latent image (electrostatic charge image). As the image carrier, an electrophotographic photosensitive member is preferably exemplified. The electrophotographic photoreceptor 14 has a coating film containing an organic photoreceptor or the like on the outer peripheral surface of a cylindrical conductive substrate. The coating film is formed by forming, in this order, a subbing layer, a charge generation layer containing a charge generation material, and a charge transport layer containing a charge transport material in this order on a substrate. is there. The order of stacking the charge generation layer and the charge transport layer may be reversed. These are laminated photoconductors in which a charge generation material and a charge transport material are contained in separate layers (charge generation layer, charge transport layer), but both the charge generation material and the charge transport material are the same. A single-layer type photoreceptor included in the above layer may be used, and a laminated photoreceptor is preferable. Further, an intermediate layer may be provided between the undercoat layer and the photosensitive layer. In addition, other types of photosensitive layers such as an amorphous silicon photosensitive film may be used in addition to the organic photoreceptor.

(Exposure means)
There are no particular limitations on the exposure unit 12 that is an exposure means. For example, an optical device that can expose a light source such as semiconductor laser light, LED light, or liquid crystal shutter light on the surface of the image carrier in a desired image-like manner. Can be mentioned.

(Development means)
The developing unit 16 serving as a developing unit has an electrostatic latent image formed on the image carrier by bringing a developer carrier having a developer layer containing toner on the surface thereof in contact with or in proximity to the image carrier. Has a function of forming toner images by adhering toner particles. A developing unit for storing the developer for developing an electrostatic charge image has a sliding portion of a stirring member for stirring the developer. Such a developing device is not particularly limited as long as it has the above-mentioned function, and can be appropriately selected according to the purpose. For example, toner for developing an electrostatic image is used using a brush, a roller, or the like. A known developing device having a function of adhering to the electrophotographic photosensitive member 14 may be used. The electrophotographic photoreceptor 14 normally uses a DC voltage, but may be used with an AC voltage superimposed thereon.

(Transfer means)
As the transfer unit 18 serving as a transfer unit, for example, a charge having a polarity opposite to that of the toner is applied to the transfer target 24 from the back side of the transfer target 24 as shown in FIG. A transfer roll and a transfer roll pressing device using a conductive or semiconductive roll that transfers directly to the surface of the transfer target 24 via the transfer target 24 can be used. . A direct current may be applied to the transfer roll as a transfer current applied to the image carrier, or an alternating current may be applied in a superimposed manner. The transfer roll can be arbitrarily set depending on the width of the image area to be charged, the shape of the transfer charger, the opening width, the process speed (circumferential speed), and the like. Further, a single layer foam roll or the like is suitably used as a transfer roll for cost reduction. As a transfer method, a method of transferring directly to the transfer target 24 such as paper or a method of transferring to the transfer target 24 via an intermediate transfer member may be used.

  A known intermediate transfer member can be used as the intermediate transfer member. Materials used for the intermediate transfer member include polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene phthalate, PC / polyalkylene terephthalate (PAT) blend material, ethylene tetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend materials, and the like can be mentioned. From the viewpoint of mechanical strength, an intermediate transfer belt using a thermosetting polyimide resin is preferable.

(Cleaning means)
The cleaning unit 20 serving as a cleaning unit may be appropriately selected such as one that employs a blade cleaning method, a brush cleaning method, or a roll cleaning method as long as the toner remaining on the image carrier is cleaned. Among these, it is preferable to use a cleaning blade having elasticity.

  The material of the cleaning blade is not particularly limited, and various elastic bodies can be used. Specific elastic bodies include elastic bodies such as polyurethane elastic bodies, silicone rubber, and chloroprene rubber. Among them, it is preferable to use a polyurethane elastic body because of its excellent wear resistance.

  As the polyurethane elastic body, generally used is a polyurethane synthesized through an addition reaction of an isocyanate with a polyol and various hydrogen-containing compounds. This uses a polyether polyol such as polypropylene glycol or polytetramethylene glycol as a polyol component, or a polyester polyol such as an adipate polyol, polycaprolactam polyol or polycarbonate polyol, and a tolylene diisocyanate as an isocyanate component. Aromatic polyisocyanates such as 4,4′-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, toluidine diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, dicyclohexylmethane diisocyanate, etc. Prepare a urethane prepolymer, add a curing agent to it, and inject into a predetermined mold , After crosslinking and curing, it is prepared by aging at room temperature. As the curing agent, a dihydric alcohol such as 1,4-butanediol and a trihydric or higher polyhydric alcohol such as trimethylolpropane or pentaerythritol are usually used in combination.

(Fixing means)
The fixing unit 22 serving as a fixing unit (image fixing device) fixes the toner image transferred to the transfer medium 24 by heating, pressing, or heating and pressing, and includes a fixing member.

(Transfer)
Examples of the transfer target (paper) 24 to which the toner image is transferred include plain paper, OHP sheet, and the like used in electrophotographic copying machines, printers, and the like. In order to further improve the smoothness of the image surface after fixing, it is preferable that the surface of the transfer target is as smooth as possible. For example, coated paper in which the surface of plain paper is coated with resin, art paper for printing, etc. Can be preferably used.

  In the case of producing a full-color image, each of the plurality of image carriers has a developer carrier for each color, and a latent image forming step and a development step by each of the plurality of image carriers and developer carriers. Then, through a series of processes including a transfer process and a cleaning process, toner images of the respective colors are sequentially stacked on the same transfer target surface, and the stacked full-color toner images are fixed in a fixing process. The method is preferably used. Then, by using the developer for developing an electrostatic image in the image forming method, stable development, transfer, and fixing performance can be obtained even in a tandem system suitable for, for example, small size and high-speed color.

  Hereinafter, although an example and a comparative example are given and the present invention is explained more concretely in detail, the present invention is not limited to the following examples.

[Production of Toner Particles a]
Polyester resin (weight average molecular weight Mw: 17,000) 87 parts by weight Plant wax (carnauba wax) 8 parts by weight Pigment Blue 15: 3 (manufactured by Clariant Japan) 5 parts by weight Sufficiently premixed the above components with a Henschel mixer The toner is melt kneaded with a twin-screw roll mill, cooled, finely pulverized with a jet mill, and further classified twice with a wind classifier, so that the toner has a volume average particle diameter of 6.0 μm and 4 μm or less. Toner mother particles (cyan toner) having 18% by number of particles and 0.3% by volume of toner particles having a particle diameter of 16 μm or more were produced.

100 parts by weight of the toner base particles, 0.5 parts by weight of hydrophobic titanium oxide particles (Nippon Aerosil, P25) having a BET specific surface area of 100 m ² / g as external additives, and hydrophobic silica particles having a volume average particle size of 40 nm Toner particles a were prepared by mixing 1.1 parts by weight (manufactured by Nippon Aerosil Co., Ltd., R812) with a Henschel mixer.

[Manufacture of carrier A]
Mn—Mg—Sr—ferrite particles (true specific gravity ρ = 4.7, volume average particle size 35.5 μm, core material electric resistance 10 ⁸ ) 100 parts by weight Toluene 25 parts by weight Styrene / methyl methacrylate copolymer resin (styrene monomer: (Methyl methacrylate monomer = 25% by weight: resin copolymerized at 75% by weight, Mw = 72,000)
2.2 parts by weight Grease (Daphney Polylex Grease No. 2, manufactured by Idemitsu Kosan Co., Ltd.) 0.02 parts by weight

  The styrene / methyl methacrylate resin was diluted with toluene and then stirred for 5 minutes with a homogenizer to prepare a resin solution. The Mn-Mg-Sr-ferrite particles were put in a vacuum degassing type kneader and stirred at 100 ° C. When the Mn-Mg-Sr-ferrite particles reached 50 ° C, grease was added and stirring was continued. When the mixture reached 75 ° C., the resin solution was added, and after stirring for 7 minutes, the solvent was removed with a vacuum pump. The solvent removal was completed in 20 minutes, and the taken-out carrier was sieved with a 106 μm mesh to obtain carrier A.

Regarding carrier A, the content and content of grease were confirmed by the following method using the n-octyl isocyanate contained in the grease content or decomposed product as a tracer.
(1) Weigh 2 g of carrier A into the glass bottle 1.
(2) Add 2 g of ethanol to the container, mix well, leave it for 60 minutes, attach a magnet to the bottom of the container to fix the carrier, and collect the supernatant in another glass bottle 2.
(3) The same operation as (2) is performed, and the glass bottle 2 is collected.
(4) The ethanol solution in the glass bottle 2 is vacuum-dried at 80 ° C. for 1 hour and dried.
(5) Add 0.3 g of acetone to the dried product and dissolve again.
(6) Using a micro syringe, 0.05 mL of an acetone solution is dropped into an inert treatment stainless cup for measurement.
(7) The measurement-treated inert treated stainless steel cup is vacuum-dried at 40 ° C. for 1 hour.
(8) 0.1 g of grease (Daphne Polylex Grease No. 2) is taken in an inert treatment stainless cup for measurement, and pyrolysis GCMS (py2020iD (pyrolysis unit), GC17A (gas chroma), QP5050A (MS), Shimadzu Corporation The product is measured under conditions where the peak of n-octyl isocyanate contained in the grease is observed. The peak area was 45,325.
(9) Using the pyrolytic GCMS (py2020iD (pyrolysis unit), GC17A (gas chromatograph), QP5050A (MS)), the inert treatment stainless cup for measurement of (8) is measured in the same manner as (8). The peak area of n-octyl isocyanate was 11,351,544.

[Manufacture of carrier B]
Mn-Mg-Sr-ferrite particles (ρ = 4.7, volume average particle size 35.5 μm, core material electric resistance 10 ⁸ ) 100 parts by weight Toluene 25 parts by weight Styrene / methyl methacrylate copolymer resin (styrene monomer: methyl methacrylate) Monomer = 25% by weight: resin copolymerized at 75% by weight, Mw = 72,000)
2.2 parts by weight

  The styrene / methyl methacrylate resin was diluted with toluene and then stirred for 5 minutes with a homogenizer to prepare a resin solution. Mn-Mg-Sr-ferrite particles are placed in a vacuum degassing kneader and stirred at 100 ° C. When the Mn-Mg-Sr-ferrite particles reach 75 ° C, a resin solution is added and stirred for 7 minutes. The solvent was removed with a vacuum pump. The solvent removal was completed in 20 minutes, and the taken-out carrier was sieved with a 106 μm mesh to obtain carrier B.

  For carrier B, the content and content of grease were confirmed by the same method as for carrier A. The peak of n-octyl isocyanate was not observed.

[Manufacture of Carrier C]
The grease of carrier A is Daphne Polylex Grease No. The carrier C was obtained in the same manner as in Example 1 except that Albania Grease S (made by Showa Shell) was changed to 0.02 parts by weight and 0.00002 parts by weight of decyl isocyanate (made by Showa Chemical) was added. It was.

  For carrier C, the grease content and content were confirmed by the same method as for carrier A. A peak of decyl isocyanate was observed.

[Manufacture of carrier D]
The grease of carrier A is Daphne Polylex Grease No. The carrier D was obtained in the same manner as in Example 1 except that Albania Grease S (made by Showa Shell) 2 was changed to 0.02 parts by weight and 0.00002 parts by weight of propyl isocyanate (reagent) was further added.

  For carrier D, the content and content of grease were confirmed by the same method as for carrier A. A peak of propyl isocyanate was observed.

[Manufacture of Carrier E]
The grease of carrier A is Daphne Polylex Grease No. The carrier E was changed in the same manner as in Example 1 except that 0.02 parts by weight of Albanya Grease S (made by Showa Shell) was changed from 2 to 0.00002 parts by weight of octadecyl isocyanate (a reagent manufactured by Wako Pure Chemical Industries). Obtained.

  For carrier E, the content and content of grease were confirmed by the same method as for carrier A. An octadecyl isocyanate peak was observed.

[Manufacture of Carrier F]
The grease of carrier A is Daphne Polylex Grease No. The carrier F was obtained in the same manner as in Example 1 except that Albania Grease S (manufactured by Showa Shell) was changed to 0.02 parts by weight and 0.00002 parts by weight of ethyl isocyanate (reagent) was further added.

  For carrier F, the content and content of grease were confirmed by the same method as for carrier A. An ethyl isocyanate peak was observed.

[Manufacture of carrier G]
The grease of carrier A is Daphne Polylex Grease No. The carrier G was replaced in the same manner as in Example 1 except that 0.02 parts by weight of Albania Grease S (made by Showa Shell) was changed from 2 to 0.00002 parts by weight of hexamethylene diisocyanate (reagent made by Showa Chemical). Obtained.

[Manufacture of Carrier H]
A carrier H was obtained in the same manner as in Example 1 except that Daphne Grease M (manufactured by Idemitsu Kosan Co., Ltd.) was used as the grease.

[Manufacture of Carrier I]
Carrier I was obtained in the same manner as in Example 1 except that the amount of grease (Daphne Polylex Grease No. 2) was 0.100 part by weight.

  For carrier I, the grease content and content were confirmed by the same method as for carrier A. A peak of n-octyl isocyanate was observed. The peak area was 222,386.

[Manufacture of Carrier J]
Carrier J was obtained in the same manner as in Example 1 except that the amount of grease (Daphne Polylex Grease No. 2) was 0.002 part by weight.

  For carrier J, the grease content and content were confirmed in the same manner as carrier A. A peak of n-octyl isocyanate was observed. Its peak area was 3,996.

[Manufacture of carrier K]
A carrier K was obtained in the same manner as in Example 1 except that the amount of grease (Daphne Polylex Grease No. 2) was 0.150 part by weight.

  For carrier K, the grease content and content were confirmed by the same method as for carrier A. A peak of n-octyl isocyanate was observed. The peak area was 332,590.

[Manufacture of carrier L]
Carrier L was obtained in the same manner as in Example 1 except that the amount of grease (Daphne Polylex Grease No. 2) was 0.001 part by weight.

  For carrier L, the content and content of grease were confirmed by the same method as for carrier A. A peak of n-octyl isocyanate was observed. The peak area was 2,235.

[Manufacture of Carrier M]
Carrier M was obtained in the same manner as in Example 1 except that the core material particles (Mn—Mg—Sr—ferrite particles) of carrier A were changed to MRC2932 manufactured by Toda Kogyo Co., Ltd., which is a resin-dispersed core material particle.

  For carrier M, the grease content and content were confirmed in the same manner as carrier A. A peak of n-octyl isocyanate was observed. The peak area was 44,285.

<Example 1>
The developer A was obtained by mixing 91 parts by weight of carrier A and 9 parts by weight of toner a. In addition, the toner a was put in a cartridge for an image forming apparatus (DocuCenter Color a450, manufactured by Fuji Xerox Co., Ltd.).

  Using these electrostatic image developer and toner cartridge, developability, fog, and white spots are obtained by the following methods in an electrophotographic copying machine / printer combination machine (DocuCenter Color a450, manufactured by Fuji Xerox Co., Ltd.). Image quality defect evaluation was performed in a high temperature and high humidity environment (30 ° C., 80% RH) and a low temperature and low humidity environment (10 ° C., 10% RH).

[Developability, fog, image quality evaluation]
Under each environment, develop a solid patch of 5 cm × 2 cm for each color, transfer the developed toner image on the surface of the photoreceptor using the adhesiveness of the tape surface, and measure its mass (W1). The developability was evaluated according to the following evaluation criteria. Similarly, the background part of the photoconductor surface is transferred using the adhesiveness of the tape surface and affixed to the surface of paper (J paper: manufactured by Fuji Xerox Office Supply Co., Ltd.). Evaluated by criteria.

[Development evaluation criteria]
○: W1 is 4.5 g / m ² or more Δ: W1 is 4.0 or more and less than 4.5 g / m ² ×: W1 is less than 4.0 g / m ²

[Fog evaluation criteria]
○: No fogging visually X: There is fogging

[Unclear image quality defect]
◯: No white spot is observed in a 5 cm × 2 cm solid patch evaluated for developability Δ: One white spot is observed in a 5 cm × 2 cm solid patch evaluated for developability X: Developability was evaluated Two or more white spots are observed in a solid patch of 5 cm x 2 cm

  After these evaluations are completed, in each environment, continuous printing is performed so that the image density is 0% (white paper): the image density is 1%: the image density is 5% = 10: 10: 7. I went. On the way, every 1,000 sheets, the above-mentioned developability, fogging, and white-out image quality defects were judged according to the following evaluation criteria, and the evaluation was made over time. The results are shown in Table 1.

[Development evaluation criteria]
○: W1 is 4.5 g / m ² or more for all 1,000 print samples (10 samples) Δ: W1 is 4.0 or more for all 1,000 print samples (10 samples) 4 Less than 5 g / m ² is 2 or less x: All 1,000 print samples (10 samples) have W1 of 4.0 or more and less than 4.5 g / m ² or more, or One or more W1 is less than 4.0 g / m ²

[Fog evaluation criteria]
○: All print samples per 1,000 sheets (10 specimens) are not fogged visually. X: All print samples per 1,000 sheets (10 specimens) are fogged, and even one sheet is observed.

[Unclear image quality defect]
○: No white spots are observed in every 1,000 print samples in a 5 cm × 2 cm solid patch evaluated for developability. Δ: All print samples for every 1,000 sheets evaluated for developability (10 The number of white spots observed in a solid patch of 5 cm × 2 cm is 2 or less ×: 5 cm of all 1,000 print samples (10 samples) evaluated for developability 3 cm or more of all printed samples (10 specimens) for every 1,000 sheets in which a single white spot was observed in a solid patch of 2 cm or more or 3 sheets were evaluated for developability. There is even one piece with two or more white spots observed inside

<Examples 2 to 12>
In the same manner as in Example 1, 91 parts by weight of carriers C to M and 1 part by weight of toner a were mixed to obtain developers C to M. In addition, the toner a was put in a cartridge for an image forming apparatus (DocuCenter Color a450, manufactured by Fuji Xerox Co., Ltd.). Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
In the same manner as in Example 1, 91 parts by weight of carrier B and 1 part by weight of toner a were mixed to obtain developer B. In addition, the toner a was put in a cartridge for an image forming apparatus (DocuCenter Color a450, manufactured by Fuji Xerox Co., Ltd.). Evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

  From the results shown in Table 1, since the developer of Examples 1 to 12 hardly causes breakage or cracking of the carrier even by agitation in the developing device for a long time, image defects such as white spots are suppressed and a stable image is obtained. Could be obtained for a long time.

1 is a schematic diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 10 charging part, 12 exposure part, 14 electrophotographic photosensitive member, 16 developing part, 18 transfer part, 20 cleaning part, 22 fixing part, 24 to-be-transferred body.

Claims (5)

  A carrier for developing an electrostatic charge image, comprising core particles, a resin, and grease. The electrostatic charge image developing carrier according to claim 1,
The grease content or decomposition product includes at least one of an alkyl isocyanate having an alkyl group having 2 to 18 carbon atoms and an aryl isocyanate having an aryl group having 6 to 18 carbon atoms. Carrier for developing charge image. The electrostatic charge image developing carrier according to claim 1 or 2,
The electrostatic charge image developing carrier, wherein the core material particles contain ferrite.   An electrostatic image developing developer comprising the electrostatic image developing carrier according to claim 1 and an electrostatic image developing toner. An image carrier, a latent image forming unit that forms an electrostatic latent image on the surface of the image carrier, a developing unit that develops the electrostatic latent image using a developer to form a toner image, and the development A transfer means for transferring the toner image thus transferred to a transfer medium,
The image forming apparatus according to claim 4, wherein the developer is a developer for developing an electrostatic image according to claim 4.

Images