JP6237382B2 - Electrostatic image developing carrier, electrostatic image developer, developer cartridge, process cartridge, and image forming apparatus - Google Patents

Description

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

  In electrophotography, an electrostatic latent image formed on the surface of an electrostatic latent image holding member (photoreceptor) is developed with toner containing a colorant, and the obtained toner image is transferred to the surface of a recording medium. An image can be obtained by fixing with a heat roll or the like. Further, the latent image holding member is cleaned with the transfer residual toner to form an electrostatic latent image again, and the cleaning process is omitted when there is almost no transfer residual toner as in the case of using spherical toner. In some cases. As described above, dry developers used for electrophotography and the like are divided into a one-component developer using a toner in which a binder is mixed with a colorant and the like, and a two-component developer in which the toner is mixed with a carrier. Broadly divided.

Patent Document 1 states that “in a ferrite carrier made of a ferrite material exhibiting soft magnetism, a formula: (MO) _100-x (Fe ₂ O ₃ ) _x (where M is a divalent element containing Cu and Zn as essential components). Ferrite characterized in that 0.05 to 5.0 parts by weight of BaO and / or CaO is added to 100 parts by weight of a ferrite component represented by a combination of metal elements, x = 55 to 95 mol%) Carrier "is disclosed.

Patent Document 2 states that "in the carrier for an electrostatic charge image developer having a resin coated on the surface of the magnetic material, the surface of the magnetic material is coated with 0.5 to 3.0% by weight of resin; and 1 ≦ R ₂ / R ₁ ≦ 10 R ₁ : satisfying volume resistivity when 1000 V is applied for 10 seconds at 1400 g load, and volume resistivity when R _{2 is} applied for 1000 V at 1400 g load for 30 seconds. A carrier for an electrostatic charge image developer, characterized in that:

  Patent Document 3 states that “Mn is contained in 10 to 30% by weight, Mg is contained in 1.0 to 3.0% by weight, Ti is contained in 0.3 to 1.5% by weight, and Fe is contained in 40 to 60% by weight. A ferrite carrier core material for an electrophotographic developer characterized by the above. "

JP-A-4-16862 JP-A-9-160307 JP 2012-13865 A

  An object of the present invention is to provide a carrier for developing an electrostatic charge image in which a change in image density is suppressed when image formation is repeated under high temperature and high humidity.

  In order to achieve the above object, the following invention is provided.

The invention according to claim 1 has a common logarithm A (log Ωcm) of resistance under an electric field of 24000 V / cm and an ordinary logarithm B of resistance under an electric field of 4800 V / cm in an environment of 30 ° C. and 85% relative humidity. (Logomegacm) is seen containing ferrite particles satisfying the following relational expression (1) and (2), the ferrite particles, iron, manganese, strontium, and the electrostatic image developing carrier containing silica.
Formula (1): 1.04 ≦ B / A ≦ 1.11
Formula (2): 6 ≦ A ≦ 9

  The invention according to claim 2 is the electrostatic charge image developing carrier according to claim 1, wherein the common logarithm A (log Ωcm) of resistance of the ferrite particles under an electric field of 24000 V / cm is 7 or more and 9 or less.

  The invention according to claim 3 is the carrier for developing an electrostatic charge image according to claim 1 or 2, further comprising a coating layer that includes a resin having a cycloalkyl group and covers at least a part of the surface of the ferrite particle.

  According to a fourth aspect of the present invention, there is provided an electrostatic charge image developer comprising the electrostatic charge image developing toner and the electrostatic charge image developing carrier according to any one of the first to third aspects.

The invention according to claim 5 is a developer cartridge that contains the electrostatic charge image developer according to claim 4 and is detachable from the image forming apparatus.
The invention according to claim 6 contains the electrostatic charge image developer according to claim 4 and develops the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer. And a process cartridge that is detachably attached to the image forming apparatus.
According to a seventh aspect of the present invention, there is provided an image carrier, a charging unit for charging the surface of the image carrier, an electrostatic charge image forming unit for forming an electrostatic image on the charged surface of the image carrier, and 4. A developing unit that contains the electrostatic charge image developer according to claim 4 and develops the electrostatic charge image formed on the surface of the image carrier as a toner image with the electrostatic image developer, and the surface of the image carrier. An image forming apparatus comprising: transfer means for transferring the toner image formed on the surface of the recording medium; and fixing means for fixing the toner image transferred to the surface of the recording medium.

  According to the first aspect of the present invention, compared to the case where the resistance of the ferrite particles contained in the carrier for developing an electrostatic charge image does not satisfy both of the relational expressions (1) and (2), an image can be obtained at high temperature and high humidity. There is provided a carrier for developing an electrostatic image in which a change in image density is suppressed when formation is repeated.

  According to the second aspect of the present invention, when image formation is repeated under high temperature and high humidity as compared with the case where the common logarithm A (log Ωcm) of resistance under an electric field of 24000 V / cm of the ferrite particles is less than 7, There is provided a carrier for developing an electrostatic image in which omission is suppressed.

  According to the invention of claim 3, when the image formation is repeated under high temperature and high humidity, the resin contained in the coating layer covering at least a part of the surface of the ferrite particle is a methyl methacrylate resin. There is provided a carrier for developing an electrostatic image in which the density change of the toner is suppressed.

  According to the fourth aspect of the present invention, the resistance of the ferrite particles is higher than that of the electrostatic charge image developer including the electrostatic charge image developing carrier that does not satisfy both of the relational expressions (1) and (2). Thus, an electrostatic charge image developer is provided in which the change in image density is suppressed when image formation is repeated.

  According to the inventions according to claims 5, 6, and 7, the electrostatic charge image developing carrier in which the resistance of the ferrite particles contained in the electrostatic charge image developing carrier does not satisfy both of the relational expressions (1) and (2). A developer cartridge, a process cartridge, and an image forming apparatus are provided in which a change in image density is suppressed when image formation is repeated under high temperature and high humidity as compared with a case where a developer containing the same is applied.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows an example of the process cartridge which concerns on this embodiment.

  Hereinafter, an embodiment which is an example of the present invention will be described in detail.

<Carrier for developing electrostatic image>
The electrostatic image developing carrier (hereinafter sometimes referred to as “carrier”) according to the present embodiment is an electric field of 24000 V / cm under an environment of high temperature and high humidity (30 ° C., relative humidity 85%). The common logarithm of resistance A (log Ωcm) and the common logarithm B of resistance under an electric field of 4800 V / cm (log Ωcm) include ferrite particles satisfying the following relational expressions (1) and (2). .
Formula (1): 1.04 ≦ B / A ≦ 1.11
Formula (2): 6 ≦ A ≦ 9

  In general, image formation by electrophotography is performed in the following steps. The developer in the developing device is stirred and charged. The charged developer is conveyed to a developer holding member of the developing device, and the electrostatic latent image formed on the surface of the opposite electrophotographic photosensitive member is developed with toner. At this time, if the resistance of the carrier in the developer is high, the toner is difficult to be separated from the carrier, and the density is likely to be insufficient. On the other hand, when the resistance is low, charges are injected into the carrier when the toner leaves, and the carrier tends to shift to the photoconductor. As a result, image defects such as white spots and color streaks are likely to occur in the image. This is particularly noticeable under high temperature and high humidity. Therefore, the carrier needs to maintain a suitable range of resistance. As a method for controlling the resistance of the carrier, it is used to provide a coating layer (coat layer) with controlled resistance on the surface of the carrier.

  However, generally, as printing continues, the carrier deteriorates in the developing device. Carrier degradation occurs mainly in two forms. One is peeling or abrasion of the coating layer caused by stress in the developing device. The other is that an external additive contained in the toner adheres to the surface of the carrier and changes the physical properties of the carrier.

As a method for solving these problems, for example, there is a method of reducing the surface energy of the coating layer and suppressing the external additive of the toner from adhering to the carrier. However, a resin having a low surface energy is difficult to use because it has low chargeability and frictional charge is less likely to occur. Further, there is a method of refreshing the surface by appropriately wearing the coating layer, but the carrier deterioration due to the wear of the coating layer becomes remarkable in long-term use. Further, when the coating layer is protected with a crosslinked resin or the like, the surface contamination is accelerated and long-term use becomes difficult.
For this reason, when a developer is used for a long period of time, it is common to use a trickle system in which a new carrier is appropriately replaced.

  In the carrier using ferrite particles as the core material, the present inventors have used the common logarithm A (log Ωcm) of the resistance of the ferrite particles under an electric field of 24000 V / cm under conditions of 30 ° C. and 85% RH (relative humidity). The ratio (B / A) of the resistance of the ferrite particles to the common logarithm B (log Ωcm) under an electric field of 4800 V / cm is controlled within a specific range, and the resistance within a specific range is controlled under an electric field of 24000 V / cm. It has been found that by using the ferrite particles possessed, fluctuations in image density and color loss are suppressed over a long period of time even under high temperature and high humidity (30 ° C., 85% RH).

  The reason why the change in the density of the image is suppressed when the image formation is repeated under high temperature and high humidity by using the developer containing the electrostatic image developing carrier according to the present embodiment is not clear, but is 30 ° C., 85 When the resistance of the ferrite particles at% RH satisfies the above formulas (1) and (2), the main cause of carrier deterioration, that is, peeling of the resin layer and adhesion of the toner external additive to the carrier surface are suppressed. Guessed.

The carrier according to the present embodiment may be composed of only ferrite particles, or may be a resin-coated carrier in which at least a part of the surface of the ferrite particles serving as the core material is coated with a coating layer containing a resin.
Hereinafter, as a typical example of the carrier according to the present embodiment, a resin-coated carrier in which the surface of ferrite particles is coated with a coating layer containing a resin will be specifically described.

(Ferrite particles)
The ferrite particles contained in the carrier according to the present embodiment have a common logarithm of resistance A (log Ωcm) under an electric field of 24000 V / cm and an electric field of 4800 V / cm under an environment of 30 ° C. and 85% relative humidity. The common logarithm B (log Ωcm) of the resistance satisfies the following relational expressions (1) and (2).
Formula (1): 1.04 ≦ B / A ≦ 1.11
Formula (2): 6 ≦ A ≦ 9

  Among image defects caused by carrier deterioration, an image density defect due to an increase in carrier resistance has a high correlation with a resistance of 4800 V / cm. The resistance of the ferrite particles under an electric field of 4800 V / cm represents the resistance of the relatively surface of the carrier particles. By making this resistance suitable, the charge when the toner leaves the carrier is slightly released to the surface of the carrier. It is considered that the transfer to the photoconductor is facilitated.

  In the ferrite particles in this embodiment, the resistance at an applied voltage of 4800 V / cm in an environment of 30 ° C. and 85% RH is preferably 6.01 log Ωcm or more and 10.1 log Ωcm or less, more preferably 7 log Ωcm or more. 9 log Ωcm or less.

  The transfer to the photoreceptor due to the charge injection into the carrier correlates with the resistance at 24000 V / cm. 24000 V / cm represents the resistance from the surface of the carrier to the inside, and it is considered that charge injection into the carrier is suppressed by controlling this resistance within a specific range.

  In the ferrite particles in this embodiment, the resistance at an applied voltage of 24000 V / cm in an environment of 30 ° C. and 85% RH is 6 logΩcm or more and 9 logΩcm or less, preferably 7 logΩcm or more and 9 logΩcm or less, more preferably 7Ωcm or more. 8 log Ωcm or less.

  By suppressing the resistance change under the two electric fields to be low, both the image density defect and the carrier transfer can be suppressed. Further, by controlling the resistance of the ferrite particles, a change in resistance with respect to deterioration with time of the carrier is suppressed.

  Even if the resistance values of the ferrite particles under the two electric fields are within the above ranges, if the ratio (B / A) is outside the range of 1.04 or more and 1.10 or less, the in-machine temperature during continuous printing. In some cases, a change in the charging of the developer occurs due to an increase in the image, resulting in an image abnormality. The ferrite particles according to the present embodiment have a common logarithm ratio (B / A) of each resistance under the two electric fields in an environment of 30 ° C. and a relative humidity of 85% of 1.04 to 1.10, Preferably they are 1.06 or more and 1.08 or less.

The two resistances of the ferrite particles according to this embodiment are measured as follows.
Two electrode plates are opposed in parallel with a width of 1 mm, 0.25 g of ferrite particles are put between them, held by a magnet having a cross-sectional area of 2.4 cm ² , an applied voltage of 200 V is applied, and a current value is measured. The electric field at this time is 4800 V / cm. The resistance value is calculated from the obtained current value.
Similarly, the resistance at an applied voltage of 1000 V is measured. The electric field at this time is 24000 V / cm, and the resistance value is calculated from the obtained current value.

Examples of the ferrite used as the carrier core material include those having a structure represented by the following formula.
Formula: (MO) _X (Fe ₂ O ₃ ) _Y
In the above formula, M represents at least one selected from the group consisting of Cu, Zn, Fe, Mg, Mn, Ca, Li, Ti, Ni, Sn, Sr, Al, Ba, Co, and Mo. X and Y represent molar ratios, and X + Y = 100.

  Among the structures represented by the above formula as ferrite, those in which M represents a plurality of metals are known, for example, manganese-zinc ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, copper-zinc ferrite, etc. Things.

  In the ferrite particles according to the present embodiment, the resistance may satisfy the above formulas (1) and (2), but manganese ferrite is suitable. Manganese ferrite contains at least Fe and Mn as metals and has a good balance between magnetization and resistance. Manganese ferrite may include metals other than Fe and Mn, and examples thereof include Mn—Mg ferrite and Mn—Zn ferrite.

Examples of the volume average particle diameter (D50v) of the ferrite particles used in the present embodiment include 30 μm or more and 50 μm or less.
The volume average particle size of the ferrite particles and pulverized particles in the present embodiment is a value measured with a laser diffraction particle size distribution measuring apparatus LA-700 (manufactured by Horiba, Ltd.). With respect to the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume average particle size (D50v) is defined as a particle size that becomes 50% cumulative by subtracting the volume cumulative distribution from the small particle size side.

The method for producing the ferrite particles according to the present embodiment is not particularly limited, but can be produced by, for example, combining and adjusting SiO ₂ addition and heat treatment after firing.
In general, in order to increase the resistance of a high electric field, it is necessary to increase the number of nonmagnetic ions in the ferrite crystal. However, many non-magnetic ions have a limit because they lower the magnetization and do not form ferrite.
In this embodiment, as a raw material for producing ferrite particles, in addition to Fe ₂ O ₃ and Mn (OH) ₂ , silica and strontium carbonate are added and fired, so that silica is present at the grain interface and strontium is present inside. To do. At this time, the firing temperature is rapidly raised to a high temperature by extending the low temperature time for a long time, and then the temperature is quickly lowered. This increases the resistance at high electric fields. Furthermore, the resistance in a low electric field increases by heating at a suitable temperature and oxygen to increase the oxygen ratio in the crystal near the surface.

  Hereinafter, an example of a method for producing a ferrite particle according to the present embodiment will be described by showing specific materials and conditions. However, the ferrite particle according to the present embodiment is not limited to the materials and numerical values described below. Absent.

Fe ₂ O ₃ and Mn (OH) ₂ were mixed so that Fe and Mn were in a molar ratio of 2: 1, SrCO ₃ was added by 1.5% by mass, and silica was added by 1.0% by mass, Mix further.
Next, polyvinyl alcohol and water are added as a dispersant, and mixed and ground with zirconia beads having a media diameter of 1 mm.

  Next, granulation and drying are performed with a spray dryer so that the particles have a volume average particle diameter of 38 μm.

  The dried particles are heated to 1200 ° C. over 4 hours in an electric furnace, and then heated to 1400 ° C. in 10 minutes. At this time, firing is performed while adjusting the oxygen concentration to 1% in a mixed gas of oxygen and nitrogen.

  After baking at 1400 ° C. for 1 hour, the temperature is lowered to 1000 ° C. in 10 minutes.

It is left as it is in the atmospheric state, and is left at a constant temperature for 2 hours at 950 ° C.
Thereafter, target ferrite particles are obtained through a crushing step and a classification step.

(Coating layer)
Examples of the resin (coating resin) contained in the coating layer that coats the ferrite particles include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, and vinyl chloride-vinyl acetate. Copolymers, styrene-acrylic acid copolymers, alkyl (meth) acrylate resins, straight silicone resins containing organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenol resins, epoxy resins, etc. Can be mentioned. Here, “(meth) acrylate” means acrylate or methacrylate.

  The coating layer preferably contains a resin having a cycloalkyl group. The resin having a cycloalkyl group includes (1) a homopolymer of a monomer containing a cycloalkyl group, (2) a copolymer obtained by polymerizing two or more monomers containing a cycloalkyl group, and (3) a cycloalkyl group. Examples thereof include a copolymer of a monomer and a monomer not containing a cycloalkyl group.

By using a resin containing a cycloalkyl group in the coating layer, moderate surface wear occurs during long-term use, and carrier deterioration can be further suppressed. At this time, since the resistance of the ferrite particles is controlled, it is possible to suppress the wear effect of the coating layer.
In the above (1) to (3), examples of the cycloalkyl group include a 3- to 10-membered cycloalkyl group, and a 3- to 8-membered cycloalkyl group (having 3 to 8 carbon atoms). Group is preferred, and a cycloalkyl group having 5 to 6 members (5 to 6 carbon atoms) is more preferred. If the cycloalkyl group has 8 or less carbon atoms, the steric hindrance is small and good fastness of the resin can be obtained. If the cycloalkyl group has 5 to 6 carbon atoms, it is stable as a cyclic structure.
The structure of the cycloalkyl group is specified by NMR of the resin.

  The resin having a cycloalkyl group is preferably a resin containing a polymer unit derived from at least one selected from the group consisting of cycloalkyl acrylate and cycloalkyl methacrylate. Alkyl methacrylate, copolymer of cycloalkyl methacrylate and methacrylate, copolymer of cycloalkyl acrylate and methacrylate, copolymer of cycloalkyl methacrylate and acrylate, and also cycloalkyl acrylate, cycloalkyl methacrylate, acrylate, methacrylate A copolymer of cycloalkyl methacrylate and styrene, a copolymer of cycloalkyl acrylate and styrene, and a cycloalkyl group in the side chain. Polyester resin having a group, urethane resin having a cycloalkyl group in a side chain, such as urea resin having a cycloalkyl group in a side chain.

  In particular, the resin having a cycloalkyl group is preferably a copolymer of the monomer (3) containing a cycloalkyl group and a monomer not containing a cycloalkyl group, and is selected from cycloalkyl acrylate and cycloalkyl methacrylate. More preferably, it is a copolymer of at least one selected from methyl methacrylate and methacrylate, and a copolymer of cycloalkyl acrylate and at least one selected from methyl methacrylate and methacrylate is further provided. preferable. When the cycloalkyl group is a copolymer of cycloalkyl acrylate and at least one selected from methyl methacrylate and methacrylate, suppression of change in charge amount is maintained. This effect is thought to be due to improved adhesion between the coating layer and the ferrite particles.

  Copolymerization ratio in copolymer of at least one of cycloalkyl acrylate and cycloalkyl methacrylate and at least one of methyl methacrylate and methacrylate (at least one of cycloalkyl acrylate and cycloalkyl methacrylate: at least one of methyl methacrylate and methacrylate, mol (Ratio) includes 85:15 to 99: 1.

Furthermore, as a weight average molecular weight (Mw) of resin which has a cycloalkyl group, 3000-200000 is mentioned.
The weight average molecular weight was measured using gel permeation chromatography (GPC). GPC uses HLC-8120GPC, SC-8020 (manufactured by Tosoh Corporation), and column uses two TSKgel and SuperHM-H (manufactured by Tosoh Corporation, 6.0 mm ID × 15 cm). THF (tetrahydrofuran) was used. As experimental conditions, the sample concentration is 0.5 mass%, the flow rate is 0.6 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and a RI (Refractive Index) detector (differential refractive index detector) is used. The experiment was conducted using this. The calibration curve is “polystylen standard sample TSK standard” manufactured by Tosoh Corporation: “A-500”, “F-1”, “F-10”, “F-80”, “F-380”, “A-2500”. ”,“ F-4 ”,“ F-40 ”,“ F-128 ”, and“ F-700 ”.

Further, in the carrier according to the present embodiment, conductive particles (volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less) may be dispersed in the coating layer. Examples of the conductive particles include metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate, and tin oxide, but are not limited thereto. is not.

The coverage of the ferrite particles by the coating layer is preferably 80% or more and 98% or less, and more preferably 90% or more and 98% or less.
Here, the coverage is measured by the following method.
As the X-ray electron spectroscopic analyzer, ESCA-9000MX manufactured by JEOL Ltd. is used, and the carrier is fixed to the sample holder and inserted into the ESCA chamber. The degree of vacuum of the chamber is set to 1 × 10 ⁻⁶ Pa or less, Mg—Kα is used as an excitation source, and the output is set to 200 W. Under the above conditions, the XPS spectra of the magnetic particles (ferrite particles) and the carrier are measured, and the coverage is calculated from the ratio of the area intensity of the detected Fe peak (2p3 / 2).
Coverage = F2 / F1 × 100
(F1: Fe area strength of magnetic particles, F2: Fe area strength of carriers)

Examples of the method of coating the surface of the ferrite particles with a resin include a method of coating a resin having a cycloalkyl group and, if necessary, various additives with a coating layer forming solution dissolved in an appropriate solvent. The solvent is not particularly limited, and may be selected in consideration of the coating resin to be used, coating suitability, and the like.
More specifically, a dipping method in which ferrite particles are immersed in a coating layer forming solution, a spray method in which a coating layer forming solution is sprayed on the surface of the ferrite particles, and a coating layer is formed in a state where the ferrite particles are suspended by flowing air. And a kneader coater method in which ferrite particles and a coating layer forming solution are mixed in a kneader coater to remove the solvent.

<Electrostatic image developer>
An electrostatic charge image developer according to the exemplary embodiment (hereinafter, appropriately referred to as a developer) includes an electrostatic charge image developing toner and the above-described electrostatic charge image development carrier.
The toner contained in the developer according to the exemplary embodiment includes toner particles and, if necessary, an external additive.

(Toner particles)
The toner particles include, for example, a binder resin and, if necessary, a colorant, a release agent, and other additives.

-Binder resin-
Examples of the binder resin include styrenes (eg, styrene, parachlorostyrene, α-methylstyrene, etc.), (meth) acrylic acid esters (eg, methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylic acid). n-butyl, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (for example, acrylonitrile, Methacrylonitrile, etc.), vinyl ethers (eg, vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (eg, ethylene, propylene, etc.) Emissions, a homopolymer of a monomer such as butadiene) and the like, or a vinyl-based resin composed of these monomers with two or more combinations copolymer.
As the binder resin, for example, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, non-vinyl resin such as modified rosin, a mixture of these with the vinyl resin, or these Examples also include a graft polymer obtained by polymerizing a vinyl monomer in the coexistence.
These binder resins may be used alone or in combination of two or more.

  The content of the binder resin is, for example, preferably 40% by weight to 95% by weight, more preferably 50% by weight to 90% by weight, and more preferably 60% by weight to 85% by weight with respect to the entire toner particles. Further preferred.

-Colorant-
Examples of the colorant include carbon black, chrome yellow, hansa yellow, benzidine yellow, selenium yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brilliantamine 3B, brilliant. Carmine 6B, Dupont Oil Red, Pyrazolone Red, Resol Red, Rhodamine B Lake, Lake Red C, Pigment Red, Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Pigment Blue, Phthalocyanine Green, Various pigments such as malachite green oxalate, or acridine series, xanthene series, azo series Various dyes such as benzoquinone, azine, anthraquinone, thioindico, dioxazine, thiazine, azomethine, indico, phthalocyanine, aniline black, polymethine, triphenylmethane, diphenylmethane, and thiazole Can be mentioned.
A colorant may be used individually by 1 type and may use 2 or more types together.

  As the colorant, a surface-treated colorant may be used as necessary, or it may be used in combination with a dispersant. A plurality of colorants may be used in combination.

  The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less with respect to the entire toner particles.

-Release agent-
Examples of mold release agents include hydrocarbon waxes; natural waxes such as carnauba wax, rice wax, and candelilla wax; synthetic or mineral / petroleum waxes such as montan wax; and ester waxes such as fatty acid esters and montanic acid esters. And so on. The release agent is not limited to this.

The melting temperature of the release agent is preferably 50 ° C. or higher and 110 ° C. or lower, and more preferably 60 ° C. or higher and 100 ° C. or lower.
The melting temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC) according to the “melting peak temperature” described in JIS K-1987 “Method for measuring the transition temperature of plastics”.

  The content of the release agent is, for example, preferably 1% by mass to 20% by mass and more preferably 5% by mass to 15% by mass with respect to the entire toner particles.

-Other additives-
Examples of other additives include known additives such as a magnetic material, a charge control agent, and inorganic powder. These additives are contained in the toner particles as internal additives.

-Toner particle characteristics-
The toner particles may be toner particles having a single layer structure, or toner particles having a so-called core / shell structure composed of a core (core particle) and a coating layer (shell layer) covering the core. May be.
Here, the core / shell structure toner particles include, for example, a core portion including a binder resin and, if necessary, other additives such as a colorant and a release agent, and a binder resin. It is good to be comprised with the comprised coating layer.

  The volume average particle diameter (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

The various average particle diameters and various particle size distribution indexes of the toner particles are measured using Coulter Multisizer II (manufactured by Beckman-Coulter), and the electrolyte is measured using ISOTON-II (manufactured by Beckman-Coulter). The
In the measurement, 0.5 mg to 50 mg of a measurement sample is added as a dispersant to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate). This is added to 100 ml or more and 150 ml or less of the electrolytic solution.
The electrolyte in which the sample is suspended is dispersed for 1 minute with an ultrasonic disperser, and the particle size distribution of particles having a particle size in the range of 2 μm to 60 μm is measured using a 100 μm aperture with a Coulter Multisizer II. taking measurement. The number of particles to be sampled is 50,000.
A cumulative distribution is drawn from the smaller diameter side to the particle size range (channel) divided based on the measured particle size distribution, and the cumulative particle size of 16% is the volume particle size D16v. D16p, a particle size that is 50% cumulative is defined as a volume average particle size D50v, a cumulative number average particle size D50p, and a particle size that is 84% cumulative is defined as a volume particle size D84v and a number particle size D84p.
Using these, the volume average particle size distribution index (GSDv) is calculated as (D84v / D16v) ^1/2 and the number average particle size distribution index (GSDp) is calculated as (D84p / D16p) ^1/2 .

  The shape factor SF1 of the toner particles is preferably 110 or more and 150 or less, and more preferably 120 or more and 140 or less.

The shape factor SF1 is obtained by the following formula.
Formula: SF1 = (ML ² / A) × (π / 4) × 100
In the above formula, ML represents the absolute maximum length of the toner, and A represents the projected area of the toner.
Specifically, the shape factor SF1 is quantified mainly by analyzing a microscope image or a scanning electron microscope (SEM) image using an image analyzer, and is calculated as follows. That is, by capturing an optical microscope image of particles dispersed on the surface of a slide glass into a Luzex image analyzer using a video camera, obtaining the maximum length and projected area of 100 particles, calculating by the above formula, and obtaining the average value can get.

(External additive)
Examples of the external additive include inorganic particles. As the inorganic particles, SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, CaO, K ₂ O, Na ₂ O, ZrO ₂ , CaO. _{SiO 2, K 2 O · (} TiO 2) n, Al 2 O 3 · 2SiO 2, CaCO 3, MgCO 3, BaSO 4, MgSO 4 , and the like.

The surface of the inorganic particles as an external additive is preferably subjected to a hydrophobic treatment. The hydrophobic treatment is performed, for example, by immersing inorganic particles in a hydrophobic treatment agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used individually by 1 type and may use 2 or more types together.
The amount of the hydrophobizing agent is usually, for example, 1 part by mass or more and 10 parts by mass with respect to 100 parts by mass of the inorganic particles.

  Examples of external additives include resin particles (resin particles such as polystyrene, PMMA, and melamine resin), cleaning activators (for example, metal salts of higher fatty acids typified by zinc stearate, particles of a fluorine-based high molecular weight substance), and the like. Can be mentioned.

  The external addition amount of the external additive is, for example, preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.01% by mass or more and 2.0% by mass or less with respect to the toner particles.

(Toner production method)
Next, a toner manufacturing method according to this embodiment will be described.
The toner according to the exemplary embodiment can be obtained by externally adding an external additive to the toner particles after the toner particles are manufactured.

The toner particles may be produced by any of a dry production method (for example, a kneading and pulverizing method) and a wet production method (for example, an aggregation coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). The production method of the toner particles is not particularly limited, and a known production method is adopted.
Among these, it is preferable to obtain toner particles by an aggregation and coalescence method.

  The toner according to the exemplary embodiment is manufactured, for example, by adding an external additive to the obtained dry toner particles and mixing them. Mixing may be performed, for example, with a V blender, a Henschel mixer, a Ladyge mixer, or the like. Furthermore, if necessary, coarse toner particles may be removed using a vibration classifier, a wind classifier, or the like.

  In the developer according to the exemplary embodiment, the mixing ratio (mass ratio) of the toner and the carrier is preferably toner: carrier = 1: 100 to 30: 100, and more preferably 3: 100 to 20: 100.

<Image Forming Apparatus / Image Forming Method>
The image forming apparatus / image forming method according to the present embodiment will be described.
The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic image forming unit that forms an electrostatic image on the surface of the charged image carrier, and an electrostatic charge. Development means for containing an image developer and developing the electrostatic image formed on the surface of the image carrier as a toner image with the electrostatic image developer, and the toner image formed on the surface of the image carrier as a recording medium Transfer means for transferring to the surface of the recording medium, and fixing means for fixing the toner image transferred to the surface of the recording medium. The electrostatic charge image developer according to this embodiment is applied as the electrostatic charge image developer.

  In the image forming apparatus according to this embodiment, a charging process for charging the surface of the image carrier, an electrostatic charge image forming process for forming an electrostatic image on the surface of the charged image carrier, and an electrostatic charge according to this embodiment. A developing step of developing an electrostatic charge image formed on the surface of the image carrier as a toner image with an image developer; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of the recording medium; An image forming method (an image forming method according to the present embodiment) including a fixing step of fixing the toner image transferred onto the surface of the recording medium is performed.

The image forming apparatus according to the present embodiment is a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; the toner image formed on the surface of the image carrier is transferred to an intermediate transfer member An intermediate transfer type apparatus that primarily transfers the toner image transferred to the surface of the intermediate transfer body and then secondary transfer the toner image to the surface of the recording medium; after the toner image is transferred, the surface of the image carrier before charging is cleaned. An apparatus provided with a cleaning unit; a known image forming apparatus such as an apparatus provided with a charge removing unit that discharges the surface of an image holding member by irradiating a discharge light after charging a toner image and before charging is applied.
In the case of an intermediate transfer type apparatus, the transfer means includes, for example, an intermediate transfer body on which a toner image is transferred to the surface, and a primary transfer that primarily transfers the toner image formed on the surface of the image holding body to the surface of the intermediate transfer body. And a secondary transfer unit that secondarily transfers the toner image transferred onto the surface of the intermediate transfer member onto the surface of the recording medium.

  In the image forming apparatus according to the present embodiment, for example, the part including the developing unit may have a cartridge structure (process cartridge) that is detachable from the image forming apparatus. As the process cartridge, for example, a process cartridge that accommodates the electrostatic charge image developer according to this embodiment and includes a developing unit is preferably used.

  Hereinafter, an example of the image forming apparatus according to the present embodiment will be described, but the present invention is not limited thereto. In addition, the main part shown to a figure is demonstrated and the description is abbreviate | omitted about others.

FIG. 1 is a schematic configuration diagram illustrating an image forming apparatus according to the present embodiment.
The image forming apparatus shown in FIG. 1 is a first to first electrophotographic method that outputs yellow (Y), magenta (M), cyan (C), and black (K) images based on color-separated image data. Fourth image forming units 10Y, 10M, 10C, and 10K (image forming means) are provided. These image forming units (hereinafter sometimes simply referred to as “units”) 10Y, 10M, 10C, and 10K are arranged in parallel at a predetermined distance from each other in the horizontal direction. The units 10Y, 10M, 10C, and 10K may be process cartridges that are detachable from the image forming apparatus.

Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt 20 as an intermediate transfer member is extended through each unit. The intermediate transfer belt 20 is provided by being wound around a drive roll 22 and a support roll 24 that are in contact with the inner surface of the intermediate transfer belt 20 that are spaced apart from each other in the left to right direction in the drawing. The vehicle travels in the direction toward the unit 10K. The support roll 24 is applied with a force in a direction away from the drive roll 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around the support roll 24. An intermediate transfer member cleaning device 30 is provided on the side of the image carrier of the intermediate transfer belt 20 so as to face the drive roll 22.
Further, each of the developing devices (developing means) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K has yellow, magenta, cyan, and black contained in the toner cartridges 8Y, 8M, 8C, and 8K. The toner including the four color toners is supplied.

  Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration, here, the first unit that forms a yellow image disposed on the upstream side in the intermediate transfer belt traveling direction. 10Y will be described as a representative. It should be noted that reference numerals with magenta (M), cyan (C), and black (K) are attached to the same parts as those of the first unit 10Y instead of yellow (Y). Description of the units 10M, 10C, and 10K will be omitted.

The first unit 10Y includes a photoreceptor 1Y that functions as an image holding member. Around the photoreceptor 1Y, a charging roll (an example of a charging unit) 2Y for charging the surface of the photoreceptor 1Y to a predetermined potential, and the charged surface is exposed by a laser beam 3Y based on a color-separated image signal. Then, an exposure device (an example of an electrostatic image forming unit) 3 that forms an electrostatic image, and a developing device (an example of a developing unit) 4Y that develops the electrostatic image by supplying toner charged to the electrostatic image, developed A primary transfer roll 5Y (an example of a primary transfer unit) that transfers a toner image onto the intermediate transfer belt 20, and a photoconductor cleaning device (an example of a cleaning unit) 6Y that removes toner remaining on the surface of the photoconductor 1Y after the primary transfer. Are arranged in order.
The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20, and is provided at a position facing the photoreceptor 1Y. Further, a bias power source (not shown) for applying a primary transfer bias is connected to each of the primary transfer rolls 5Y, 5M, 5C, and 5K. Each bias power source varies the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

Hereinafter, an operation of forming a yellow image in the first unit 10Y will be described.
First, prior to operation, the surface of the photoreceptor 1Y is charged to a potential of −600V to −800V by the charging roll 2Y.
The photoreceptor 1Y is formed by laminating a photosensitive layer on a conductive substrate (for example, volume resistivity at 20 ° C .: 1 × 10 ⁻⁶ Ωcm or less). This photosensitive layer usually has a high resistance (general resin resistance), but has a property that the specific resistance of the portion irradiated with the laser beam changes when irradiated with the laser beam 3Y. Therefore, a laser beam 3Y is output to the surface of the charged photoreceptor 1Y via the exposure device 3 in accordance with yellow image data sent from a control unit (not shown). The laser beam 3Y is applied to the photosensitive layer on the surface of the photoreceptor 1Y, whereby an electrostatic charge image having a yellow image pattern is formed on the surface of the photoreceptor 1Y.

The electrostatic charge image is an image formed on the surface of the photoreceptor 1Y by charging, and the specific resistance of the irradiated portion of the photosensitive layer is lowered by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flows. On the other hand, this is a so-called negative latent image formed by the charge remaining in the portion not irradiated with the laser beam 3Y.
The electrostatic charge image formed on the photoreceptor 1Y is rotated to a predetermined development position as the photoreceptor 1Y travels. At this development position, the electrostatic charge image on the photoreceptor 1Y is visualized (developed image) as a toner image by the developing device 4Y.

  In the developing device 4Y, for example, an electrostatic charge image developer including at least yellow toner and the carrier according to the present embodiment is accommodated. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y, and has a charge of the same polarity (negative polarity) as the charged electric charge on the photoreceptor 1Y, and has a developer roll (a developer holding member). Example) is held on. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner is electrostatically attached to the latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. . The photoreceptor 1Y on which the yellow toner image is formed continues to run at a predetermined speed, and the toner image developed on the photoreceptor 1Y is conveyed to a predetermined primary transfer position.

When the yellow toner image on the photoreceptor 1Y is conveyed to the primary transfer, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y toward the primary transfer roll 5Y is applied to the toner image, so that the photoreceptor is exposed. The toner image on 1Y is transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the polarity (−) of the toner, and is controlled to +10 μA by the control unit (not shown) in the first unit 10Y, for example.
On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the photoreceptor cleaning device 6Y.

Further, the primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K after the second unit 10M is also controlled in accordance with the first unit.
Thus, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of the respective colors are superimposed and transferred in a multiple manner. The

  The intermediate transfer belt 20 on which the four color toner images are transferred in multiple ways through the first to fourth units is disposed on the image transfer surface side of the intermediate transfer belt 20, the support roll 24 in contact with the inner surface of the intermediate transfer belt 20. The secondary transfer roll (an example of a secondary transfer unit) 26 is formed to a secondary transfer portion configured. On the other hand, a recording paper (an example of a recording medium) P is fed at a predetermined timing into a gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact via a supply mechanism, and the secondary transfer bias is supplied to the support roll. 24. The transfer bias applied at this time is a (−) polarity that is the same polarity as the polarity (−) of the toner, and an electrostatic force from the intermediate transfer belt 20 toward the recording paper P is applied to the toner image, so The toner image is transferred onto the recording paper P. The secondary transfer bias at this time is determined according to the resistance detected by a resistance detection means (not shown) for detecting the resistance of the secondary transfer portion, and is voltage-controlled.

  Thereafter, the recording paper P is fed into the pressure contact portions (nip portions) of a pair of fixing rolls in a fixing device (an example of a fixing unit) 28, and the toner image is fixed on the recording paper P to form a fixed image.

Examples of the recording paper P to which the toner image is transferred include plain paper used in electrophotographic copying machines, printers, and the like. In addition to the recording paper P, the recording medium may be an OHP sheet.
In order to further improve the smoothness of the image surface after fixing, the surface of the recording paper P is also preferably smooth. For example, coated paper with the surface of plain paper coated with resin, art paper for printing, etc. are preferably used. Is done.

  The recording paper P on which the color image has been fixed is carried out toward the discharge unit, and a series of color image forming operations is completed.

<Process cartridge / Developer cartridge>
The process cartridge according to this embodiment will be described.
The process cartridge according to the present embodiment accommodates the electrostatic charge image developer according to the present embodiment, and develops the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer. And a process cartridge that can be attached to and detached from the image forming apparatus.

  Note that the process cartridge according to the present embodiment is not limited to the above-described configuration, and other means such as a developing device and other units such as an image carrier, a charging unit, an electrostatic charge image forming unit, and a transfer unit, if necessary. And at least one selected from the above.

  Hereinafter, an example of the process cartridge according to the present embodiment will be shown, but the present invention is not limited to this. In addition, the main part shown to a figure is demonstrated and the description is abbreviate | omitted about others.

FIG. 2 is a schematic configuration diagram showing a process cartridge according to the present embodiment.
The process cartridge 200 shown in FIG. 2 is provided around the photoconductor 107 and the photoconductor 107 by, for example, a housing 117 provided with an attachment rail 116 and an opening 118 for exposure. A charging roller 108 (an example of a charging unit), a developing device 111 (an example of a developing unit), and a photoconductor cleaning device 113 (an example of a cleaning unit) are integrally combined and held to form a cartridge. Yes.
In FIG. 2, 109 is an exposure device (an example of an electrostatic charge image forming unit), 112 is a transfer device (an example of a transfer unit), 115 is a fixing device (an example of a fixing unit), and 300 is a recording paper (a recording medium). An example).

Next, the developer cartridge according to this embodiment will be described.
The developer cartridge according to the present embodiment is a developer cartridge that houses the developer according to the present embodiment and is detachable from the image forming apparatus.
For example, in the image forming apparatus shown in FIG. 1, the toner cartridges 8Y, 8M, 8C, and 8K may be developer cartridges according to the present embodiment. When the developer stored in the cartridge becomes low, the cartridge is replaced.

EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.
Unless otherwise specified, “part” means “part by mass”.

[Production of Toner 1]

(Colorant dispersion 1)
Cyan pigment: Copper phthalocyanine B15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd.) 50 parts by mass Anionic surfactant: Neogen SC (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by mass Ion-exchanged water 200 parts by mass

  The above were mixed, and dispersed for 5 minutes with an Ultra-Turrax made by IKA and further for 10 minutes with an ultrasonic bath to obtain a colorant dispersion 1 having a solid content of 21% by mass. It was 160 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Releasing agent dispersion 1)
Paraffin wax: HNP-9 (Nippon Seiki Co., Ltd.) 19 parts by weight Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku Co., Ltd.) 1 part by weight Ion-exchanged water 80 parts by weight

  The above was mixed in a heat-resistant container, heated to 90 ° C., and stirred for 30 minutes. Next, the molten liquid is circulated from the bottom of the container to the gorin homogenizer, and under a pressure condition of 5 MPa, a circulation operation corresponding to 3 passes is performed. Then, the pressure is increased to 35 MPa, and further a circulation operation corresponding to 3 passes is performed. It was. The emulsion thus prepared was cooled in the heat-resistant solution to 40 ° C. or lower to obtain a release agent dispersion 1. It was 240 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Resin particle dispersion 1)
-Oil layer-
Styrene (manufactured by Wako Pure Chemical Industries, Ltd.) 30 parts by mass n-butyl acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 10 parts by mass β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.) 1.3 masses Part Dodecanethiol (Wako Pure Chemical Industries, Ltd.) 0.4 parts by mass

-Water layer 1-
17 parts by weight of ion-exchanged water Anionic surfactant (Dowfax, manufactured by Dow Chemical Company) 0.4 parts by weight

-Water layer 2-
Ion-exchanged water 40 parts by weight Anionic surfactant (Dowfax, manufactured by Dow Chemical Company) 0.05 parts by weight Ammonium peroxodisulfate (Wako Pure Chemical Industries, Ltd.) 0.4 parts by weight

  The above oil layer component and water layer 1 component were placed in a flask and mixed with stirring to obtain a monomer emulsion dispersion. The components of the aqueous layer 2 were charged into the reaction vessel, the inside of the vessel was sufficiently replaced with nitrogen, and the reaction system was heated to 75 ° C. with an oil bath while stirring. The above monomer emulsified dispersion was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. After completion of the dropping, the polymerization was further continued at 75 ° C., and the polymerization was terminated after 3 hours.

  The obtained resin particles were 250 nm when the volume average particle diameter D50v of the resin particles was measured with a laser diffraction particle size distribution analyzer LA-700 (manufactured by Horiba, Ltd.). Moreover, it was 53 degreeC when the glass transition point of resin was measured with the temperature increase rate of 10 degree-C / min using the differential scanning calorimeter (DSC-50 Shimadzu Corp. make). Moreover, it was 13,000 when the number average molecular weight (polystyrene conversion) was measured using THF as a solvent using the molecular weight measuring device (made by HLC-8020 Tosoh Corporation). As a result, a resin particle dispersion 1 having a volume average particle size of 250 nm, a solid content of 42% by mass, a glass transition point of 52 ° C., and a number average molecular weight Mn of 13,000 was obtained.

(Preparation of Toner 1)
Resin particle dispersion 1 150 parts by weight Colorant particle dispersion 1 30 parts by weight Release agent dispersion 1 40 parts by weight Polyaluminum chloride 0.4 part by weight

  The above components were thoroughly mixed and dispersed in a stainless steel flask using an IKE Ultra Turrax, and then heated to 48 ° C. while stirring the flask in a heating oil bath. After maintaining at 48 ° C. for 80 minutes, 70 parts by mass of the same resin particle dispersion 1 as above was gradually added thereto.

  Then, after adjusting the pH in the system to 6.0 using an aqueous sodium hydroxide solution having a concentration of 0.5 mol / L, the stainless steel flask is sealed, and the stirring shaft seal is magnetically sealed while stirring is continued. Heat to 97 ° C. and hold for 3 hours. After completion of the reaction, the temperature lowering rate was cooled at 1 ° C./min, filtered and thoroughly washed with ion-exchanged water, and then solid-liquid separation was performed by Nutsche suction filtration. This was further redispersed with 3 L of ion exchanged water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. This washing operation was further repeated 5 times. When the pH of the filtrate was 6.54 and the electric conductivity was 6.5 μS / cm, No. 2 was obtained by Nutsche suction filtration. Solid-liquid separation was performed using 5A filter paper. Next, vacuum drying was continued for 12 hours to obtain toner particles.

The volume average particle diameter D50v of the toner particles was measured with a Coulter counter and found to be 6.2 μm, and the volume average particle size distribution index GSDv was 1.20. When the shape was observed with a Luzex image analyzer manufactured by Luzex, the shape factor SF1 of the particles was 135, and it was observed that the particles had a potato shape.
The glass transition point of the toner particles was 52 ° C.

Further, silica particles (SiO ₂ ) having a primary particle average particle size of 40 nm, surface-hydrophobized with hexamethyldisilazane (hereinafter sometimes abbreviated as “HMDS”), metatitanic acid and isobutyltrimethoxy are added to the toner particles. A metatitanic acid compound particle having a primary particle average particle diameter of 20 nm, which is a reaction product of silane, was added so as to have a coverage of 40% with respect to the surface of the toner particles, and mixed with a Henschel mixer to prepare toner 1.

(Preparation of coating solution 1)
Cyclohexyl acrylate resin (weight average molecular weight Mw: 50,000) 36 parts by mass Carbon black VXC72 (manufactured by Cabot) 4 parts by mass Toluene 250 parts by mass Isopropyl alcohol 50 parts by mass

  The above components and the same amount of glass beads (particle size: 1 mm) as toluene were put into a sand mill manufactured by Kansai Paint Co., Ltd., and stirred for 30 minutes at a rotational speed of 1200 rpm to prepare a coating liquid 1 having a solid content of 11% by mass.

(Preparation of coating solutions 2 to 4)
Coating solutions 2 to 4 were prepared in the same manner as the coating solution 1 except that the cyclohexyl acrylate resin was changed to the following resin in the preparation of the coating solution 1.
・ Coating liquid 2: cyclooctyl acrylate resin (Mw: 80,000)
-Coating liquid 3: cyclopropyl acrylate resin (Mw: 40,000)
-Coating liquid 4: Methyl methacrylate (Mw: 50,000)

(Preparation of ferrite particles 1)
1597 parts by mass of Fe ₂ O ₃ , 890 parts by mass of Mn (OH) ₂ , 37 parts by mass of SrCO ₃ , 25 parts by mass of silica, 6.6 parts by mass of polyvinyl alcohol as a dispersant, and water, The mixture was pulverized and mixed with a zirconia bead having a media diameter of 1 mm in a sand mill.
Next, it was granulated and dried so as to have a dry particle size of 38 μm with a spray dryer.

-Initial firing-
Furthermore, the temperature was raised to 1300 ° C. over 4 hours in an electric furnace under an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1%.

-Mid-term firing-
Next, after raising the temperature to 1400 ° C. in 10 minutes, it was left as it was for 2 hours.

-cooling-
After 2 hours, the temperature was lowered to 1000 ° C. in 10 minutes, and then taken out.

-Terminal-
Next, it moved to the rotary kiln and heated, stirring at 950 degreeC for 2 hours.
After the obtained particles were subjected to a crushing step and a classification step, ferrite particles 1 were obtained.

(Preparation of ferrite particles 2 to 5)
Ferrite particles 2 to 5 were produced in the same manner as the production of the ferrite particles 1 except that the conditions were changed as shown in Table 1 in the production of the ferrite particles 1.

  Regarding the ferrite particles 1 to 5 produced as described above, the particle diameters of the ferrite particles and the pulverized particles and the resistance of the ferrite particles were measured by the following methods.

-Particle size The volume average particle size of ferrite particles and pulverized particles is measured with a laser explanation particle size distribution measuring apparatus LA-700 (Horiba Seisakusho). With respect to the particle size range (channel) obtained by dividing the obtained particle size distribution, the volume average particle size is determined by subtracting the volume cumulative distribution from the small particle size side to obtain a cumulative 50%.

・ Resistance measurement: Two electrode plates face each other in parallel with a width of 1 mm, and 0.25 g of ferrite particles are put between them, held by a magnet with a cross-sectional area of 2.4 cm ² , an applied voltage of 200 V is applied, and the current value is It was measured. The electric field at this time is 4800 V / cm. The resistance value is calculated from the obtained current value.
Similarly, the resistance at an applied voltage of 1000 V is measured. The electric field at this time is 24000 V / cm. The resistance value is calculated from the obtained current value.

The particle diameter of the ferrite particle 1 was 35 μm.
When the resistance of the ferrite particle 1 was measured under the conditions of 30 ° C. and 85% RH, the common logarithm A of the resistance under an electric field of 24000 V / cm was 7.60 logΩcm, and the resistance under an electric field of 4800 V / cm. The common logarithm B was 8.20 log Ωcm, and the ratio (B / A) was 1.08.

<Example 1>
(Preparation of carrier 1)
In a vacuum degassing type 5 L kneader, 2000 g of ferrite particles 1 and 560 g of coating liquid 1 are added, and while stirring, the pressure is reduced to −200 mmHg at 60 ° C. and mixed for 15 minutes. The mixture was stirred and dried at 720 mmHg for 30 minutes to obtain resin-coated particles. Next, sieving was performed with a 75 μm mesh sieving net to obtain Carrier 1.

<Examples 2 to 6 and Comparative Examples 1 to 2>
(Production of carriers 2 to 8)
Carriers 2 to 8 were produced in the same manner as the production of carrier 1 except that the ferrite particles and the coating liquid used in the production of carrier 1 were changed as shown in Table 2.

[Evaluation]
A Cyan toner cartridge excluding the trickle carrier was installed in DCC400 manufactured by Fuji Xerox Co., Ltd. modified so that printing by Cyan alone was performed, and the developer of Example 1 was installed.

  The sample was allowed to stand for 1 day in an environment of 30 ° C. and 85% RH, and thereafter, continuous printing of 5000 sheets of 20 cm square solid printing (image density 100%) was performed. Then, it left still under 30 degreeC and 85% RH until the next day. This was repeated 60 times to print a total of 300,000 sheets.

  The 10th printed material on the first day was printed material 1, and the final printed material on the last day was printed material 2.

<Image defect (white dot): Print 2>
The presence or absence of image observation image defects (white spots) on the printed material 2 was evaluated according to the following criteria.
A: No image loss visually (no white spots)
B: 1 or more and 4 or less white spots (images with white particles) C: 5 to 9 white spots visually D: 10 or more white spots visually

<Density change (ΔE): ΔE difference between printed material 1 and printed material 2>
For each image density of the printed matter 1 and the printed matter 2, a color density (ΔE) was measured using a reflection densitometer X-rite 938 (manufactured by X-rite). The color difference (ΔE) is obtained by taking the square root of the square sum of the distance difference in the L * a * b * space in the CIE 1976 (L * a * b *) color system. The CIE 1976 (L * a * b *) color system is a color space recommended by the CIE (International Lighting Commission) in 1976, and is defined in “JIS Z 8729” in the Japanese Industrial Standards.

  The change in density was evaluated according to the following criteria based on the color difference (ΔE) between the printed material 1 and the printed material 2.

A: ΔE difference is less than 1 B: ΔE difference is 1 or more and less than 2.5 C: ΔE difference is 2.5 or more and less than 3.0 D: ΔE difference is 3.0 or more

  Print 2 was good with no defects in the image. Further, the difference in ΔE between the printed material 1 and the printed material 2 was 0.5, which was good.

<Examples 2 to 6 and Comparative Examples 1 and 2>
The developers in Examples 2 to 6 and Comparative Examples 1 and 2 were also evaluated in the same manner as the developer in Example 1. The evaluation results are shown in Table 3.

1Y, 1M, 1C, 1K, photoconductor (an example of an image carrier)
2Y, 2M, 2C, 2K, charging roll (an example of charging means)
3. Exposure device (an example of electrostatic charge image forming means)
3Y, 3M, 3C, 3K Laser beams 4Y, 4M, 4C, 4K Developing device (an example of developing means)
5Y, 5M, 5C, 5K primary transfer roll (an example of primary transfer means)
6Y, 6M, 6C, 6K Photoconductor cleaning device (an example of cleaning means)
8Y, 8M, 8C, 8K Toner cartridge 10Y, 10M, 10C, 10K Image forming unit 20 Intermediate transfer belt (an example of an intermediate transfer member)
22 Drive roll 24 Support roll 26 Secondary transfer roll (an example of secondary transfer means)
30 Intermediate transfer member cleaning device 107 Photosensitive member (an example of an image holding member)
108 Charging roll (an example of charging means)
109 Exposure apparatus (an example of electrostatic charge image forming means)
111 Developing device (an example of developing means)
112 Transfer device (an example of transfer means)
113 photoconductor cleaning device (an example of cleaning means)
115 Fixing device (an example of fixing means)
116 Attachment rail 118 Opening 117 for exposure 117 Case 200 Process cartridge 300 Recording paper (an example of recording medium)
P Recording paper (an example of a recording medium)

Claims (7)

Under an environment of 30 ° C. and 85% relative humidity, the common logarithm A (log Ωcm) of resistance under an electric field of 24000 V / cm and the common logarithm B of resistance (log Ωcm) under an electric field of 4800 V / cm are expressed by the following relational expressions: (1) and (2) look-containing ferrite grains satisfying the ferrite particles, iron, manganese, strontium, and the electrostatic image developing carrier containing silica.
Formula (1): 1.04 ≦ B / A ≦ 1.11
Formula (2): 6 ≦ A ≦ 9   2. The electrostatic charge image developing carrier according to claim 1, wherein a common logarithm A (log Ωcm) of resistance of the ferrite particles under an electric field of 24,000 V / cm is 7 or more and 9 or less.   The electrostatic charge image developing carrier according to claim 1, further comprising a coating layer that includes a resin having a cycloalkyl group and covers at least a part of a surface of the ferrite particle.   An electrostatic image developer comprising: an electrostatic image developing toner; and the electrostatic image developing carrier according to claim 1. Containing the electrostatic charge image developer according to claim 4;
A developer cartridge attached to and detached from the image forming apparatus. A developing means for containing the electrostatic charge image developer according to claim 4 and developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer,
A process cartridge attached to and detached from the image forming apparatus. An image carrier,
Charging means for charging the surface of the image carrier;
An electrostatic charge image forming means for forming an electrostatic charge image on the surface of the charged image carrier;
Development means for containing the electrostatic charge image developer according to claim 4 and developing the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer;
Transfer means for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
Fixing means for fixing the toner image transferred to the surface of the recording medium;
An image forming apparatus comprising: