JP2015212777A - Carrier for electrostatic charge image development, electrostatic charge image developer, developer cartridge, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development that suppresses a reduction in image density in the early stage of image formation.SOLUTION: There is provided a carrier for electrostatic charge image development that includes core material particles and a coating layer that coats each of the core material particles and includes at least one selected from the group consisting of salicylic acid aluminum salt and salicylic acid derivative aluminum salt.

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 image formed on the surface of an image carrier (photoreceptor) is developed with a developer containing toner, and the resulting toner image is transferred to a recording medium, which is then heated with a hot roll or the like. An image can be obtained by fixing. The residual toner is removed from the image carrier to form an electrostatic charge image again. Note that the cleaning process may be omitted when there is almost no residual toner as in the case of using spherical toner.
As described above, dry developers used in electrophotography and the like are roughly classified into a one-component developer using a toner alone and a two-component developer obtained by mixing the toner with a carrier.

As a carrier for a two-component developer, for example, Patent Document 1 discloses “a carrier containing a salicylic acid metal salt or a salicylic acid derivative metal salt (metal is Cr, Zn, Zr, etc.) in the coating layer”. .
Patent Document 2 discloses “a carrier containing a salicylic acid metal salt or a salicylic acid derivative metal salt (metal is Zn, Ni, Co, Pb, Cr, etc.) in the coating layer”.
Patent Document 3 discloses “a carrier containing a holobis potassium salt, a salicylic acid zinc salt, a salicylic acid chromium salt, or a salicylic acid chromium salt in a coating layer”.

JP 2009-175349 A JP-A-2-68 JP 2009-276532 A

  An object of the present invention is to provide a carrier for developing an electrostatic image that suppresses a decrease in image density at the initial stage of image formation.

  The above problem is solved by the following means.

The invention according to claim 1
Core particles,
A coating layer that covers the core particles and includes at least one selected from the group consisting of an aluminum salicylic acid salt and a salicylic acid derivative aluminum salt; and a resin;
A carrier for developing an electrostatic charge image.

The invention according to claim 2
2. The electrostatic image developing carrier according to claim 1, wherein the coating layer includes a substituted salicylic acid aluminum salt in which an alkyl group is substituted on a phenyl group of at least one salicylic acid skeleton as the salicylic acid derivative aluminum salt.

The invention according to claim 3
The electrostatic charge image developing carrier according to claim 2, wherein the alkyl group is a branched alkyl group.

The invention according to claim 4
An electrostatic charge image developer comprising: an electrostatic charge image developing toner; and the electrostatic charge image developing carrier according to claim 1.

The invention according to claim 5
Containing the electrostatic charge image developer according to claim 4;
A developer cartridge attached to and detached from the image forming apparatus.

The invention according to claim 6
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.

The invention according to claim 7 provides:
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:

According to the first aspect of the present invention, there is provided an electrostatic charge image developing carrier that suppresses a decrease in image density at the initial stage of image formation as compared with a case where zinc salicylate is included in the coating layer.
According to the second aspect of the present invention, there is provided a carrier for developing an electrostatic charge image that suppresses a difference in image density between the initial stage of image formation and the diameter compared to the case where an aluminum salicylate salt is included in the coating layer.
According to the invention of claim 3, compared to the case where the coating layer contains an aluminum salicylic acid salt in which a linear alkyl group is substituted on at least one phenyl group of the salicylic acid skeleton, the image density at the initial stage of image formation and at the time of diameter A carrier for developing an electrostatic image that further suppresses the difference is provided.

  According to the invention of claim 4, 5, 6, or 7, the electrostatic charge that suppresses the decrease in image density at the initial stage of image formation, compared to the case where the electrostatic charge image developing carrier containing zinc salicylate in the coating layer is applied. An image developer, developer cartridge, process cartridge, or image forming apparatus is provided.

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 image forming apparatus of other this embodiment.

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

<Carrier for developing electrostatic image>
A carrier for developing an electrostatic charge image (hereinafter referred to as a carrier) according to the present embodiment includes core material particles and a coating layer that covers the core material particles.
And the coating layer is at least one selected from the group consisting of an aluminum salt of salicylic acid and an aluminum salt of a salicylic acid derivative (hereinafter, these aluminum salts may be referred to as “Al salt of salicylic acid or a derivative thereof”), Resin.

Here, in the electrophotographic system, the charge amount of the toner differs between the initial stage and the late stage of image formation because of the property of charging the developer toner including toner and carrier to form an image. Specifically, at the initial stage of image formation, the developer is not sufficiently stirred and the toner charge amount is low. On the other hand, at the later stage of image formation, the developer is sufficiently stirred and the toner is charged. The amount is high.
For this reason, if the toner is not charged quickly due to the stirring of the developer, the image density decreases from the initial stage of image formation over time. In particular, this phenomenon occurs remarkably in a high temperature and high humidity environment (temperature 30 ° C., humidity 80% RH).

  On the other hand, the carrier according to the present embodiment suppresses a decrease in image density from the initial stage of image formation to the passage of time by including an Al salt of salicylic acid or a derivative thereof in the coating layer. The reason for this is not clear, but is presumed to be as follows.

  First, salicylic acid or a derivative thereof has a property that a π electron of its phenyl group (aromatic ring) is free to move in the molecule and easily causes a bias of charge. If salicylic acid or a derivative thereof having such properties has a highly conductive aluminum salt structure, π electrons move freely in the molecule, and charge bias is likely to occur. Then, when friction between the carrier and the toner occurs due to stirring, in the Al salt of salicylic acid or a derivative thereof in the coating layer of the carrier, the charge is quickly biased and the polarization of the whole molecule is promoted. For this reason, the toner is quickly triboelectrically charged by the carrier. As a result, even when the developer is not sufficiently stirred at the initial stage of image formation, the charge amount of the toner increases rapidly.

  From the above, it is presumed that the carrier according to the present embodiment suppresses a decrease in image density at the initial stage of image formation. In addition, since the toner charge amount is quickly increased at the initial stage of image formation, fogging is easily suppressed.

  Hereinafter, the details of the carrier according to the present embodiment will be described.

-Core particles-
Examples of the core particles include magnetic metal particles (for example, particles of iron, steel, nickel, cobalt, etc.), magnetic oxide particles (for example, particles of ferrite, magnetite, etc.), and dispersed resin particles in which these particles are dispersed in a resin. Etc. Examples of the core material particles include particles obtained by impregnating a porous magnetic powder with a resin.

As a core material particle, it is good that it is a ferrite particle represented by a following formula, for example.
Formula: (MO) _X (Fe ₂ O ₃ ) _Y
In the formula, Y represents 2.1 or more and 2.4 or less, and X represents 3-Y. M represents a metal element, and preferably contains at least Mn as the metal element.
M is mainly composed of Mn, but is composed of Li, Ca, Sr, Sn, Cu, Zn, Ba, Mg, and Ti (preferably from an environmental point of view, from Li, Ca, Sr, Mg, and Ti). You may combine at least 1 type selected from the group which consists of.

  The core particles are obtained by magnetic granulation and sintering, but as a pretreatment, the magnetic material may be pulverized. The pulverization method is not particularly limited, and known pulverization methods may be mentioned, and specific examples include mortar, ball mill, jet mill and the like.

  Here, the resin contained in the dispersed resin particles as the core particles is not particularly limited. For example, styrene resin, acrylic resin, phenol resin, melamine resin, epoxy resin, urethane resin , Polyester resins, silicone resins and the like. In addition, the dispersed resin particles as the core material particles may further contain other components such as a charge control agent and fluorine-containing particles according to the purpose.

  The volume average particle size of the core particles is, for example, preferably from 10 μm to 500 μm, preferably from 15 μm to 80 μm, and more preferably from 20 μm to 60 μm.

-Coating layer-
The coating layer includes an aluminum salt of salicylic acid or a derivative thereof (at least one selected from the group consisting of an aluminum salt of salicylic acid and an aluminum salt of salicylic acid) and a resin (hereinafter referred to as “coating resin”).

Examples of the Al salt of salicylic acid or its derivative include a mononuclear complex of salicylic acid or its derivative Al.
Examples of the salicylic acid derivative aluminum salt include a substituted salicylic acid aluminum salt in which at least one phenyl group of the salicylic acid skeleton is substituted with a substituent such as an alkyl group or a hydroxy group (OH group).
Among these, a substituted salicylic acid aluminum salt in which at least one phenyl group of the salicylic acid skeleton is substituted with an alkyl group (hereinafter, also referred to as “alkyl group-substituted salicylic acid Al salt”) is preferable. In this alkyl group-substituted salicylic acid Al salt, since the alkyl group substituted with the phenyl group of the salicylic acid skeleton becomes an electron donor, polarization of the whole molecule is further promoted. For this reason, the difference in image density between the initial image formation and the diameter is more easily suppressed.

  In the alkyl group-substituted salicylic acid Al salt, examples of the alkyl group substituted on the phenyl group include linear, branched, or cyclic alkyl groups having 1 to 10 (preferably 1 to 4) carbon atoms. Examples of the alkyl group also include a substituted alkyl group in which a substituent such as a phenyl group or a hydroxy group is substituted.

  In particular, as the alkyl group, a branched alkyl group is preferable, and a tert-butyl group is particularly preferable. The branched alkyl group (especially tert-butyl group) substituted salicylic acid Al salt is easy to express a large electron donating property of the entire branched alkyl group (especially tert-butyl group) as compared with the linear alkyl group. Furthermore, the polarization of the whole molecule is promoted. For this reason, the difference in image density between the initial image formation and the diameter is more easily suppressed.

  Specific examples of the Al salt of salicylic acid or a derivative thereof include compounds represented by the following general formula (SA).

In general formula (SA), Rsa ¹¹ , Rsa ¹² , Rsa ²¹ , Rsa ²² , Rsa ³¹ , and Rsa ³² (hereinafter, these may be collectively referred to as “Rsa”) each independently represent an alkyl group. .
n11, n12, n21, n22, n31, and n32 (hereinafter, these may be collectively referred to as “n”) each independently represent an integer of 0 or 1.

In general formula (SA), examples of the alkyl group represented by Rsa include linear, branched, or cyclic alkyl groups having 1 to 10 carbon atoms (preferably 1 to 4 carbon atoms). Examples of the alkyl group also include a substituted alkyl group in which a phenyl group, a hydroxy group or the like is substituted.
In particular, as the alkyl group, a branched alkyl group is preferable, and a tert-butyl group is particularly preferable.

  That is, the compound represented by the general formula (SA) is preferably a compound in which Rsa represents a branched alkyl group (particularly a tert-butyl group) and n represents an integer of 1.

  Specific examples of the Al salt of salicylic acid or its derivatives include, for example, aluminum trissalicylate, tris (3,5-di-tert-butylsalicylic acid) aluminum salt, tris [3,5-bis (α-methylbenzyl) salicylic acid ] Aluminum salt, tris [3-cyclohexyl-5- (α, α-dimethylbenzyl) salicylic acid] aluminum salt, tris (1,3-dimethylsalicylic acid) aluminum, tris (3,5-dimethylsalicyl) aluminum, tris (3 , 5-dimethylphenyl) aluminum and the like. However, it is not necessarily limited to these compounds.

  Salicylic acid or its derivative Al salt may be used singly or in combination of two or more.

  The content of the Al salt of salicylic acid or a derivative thereof is preferably 1% by mass or more and 90% by mass or less, and preferably 1% by mass or more and 60% by mass with respect to the entire coating layer, from the viewpoint of suppressing a decrease in image density at the initial stage of image formation. Hereinafter, it is more preferably 1% by mass or more and 30% by mass or less.

  In addition, the detection of the Al salt of salicylic acid or its derivative in the carrier is performed by the following method. The developer is rinsed out (washed) to isolate only the carrier. The carrier coating layer and core particles are separated, the separated coating layer components are dried, and the amount of Al salt of salicylic acid or its derivative is determined by quantifying Al with fluorescent X-rays. To do. In addition, in order to specify the structure of the Al salt of salicylic acid or its derivative, measurement is performed by gas chromatography mass spectrometry (GC-mass), Fourier transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (NMR). Do and detect.

  Examples of the coating resin for the coating layer include acrylic resin, polyethylene resin, polypropylene resin, polystyrene resin, polyacrylonitrile resin, polyvinyl acetate resin, polyvinyl alcohol resin, polyvinyl butyral resin, polyvinyl chloride resin, polyvinyl carbazole resin, and polyvinyl ether resin. , Polyvinyl ketone resin, vinyl chloride-vinyl acetate copolymer, styrene-acrylic acid copolymer, straight silicone resin having an organosiloxane bond or a modified product thereof, fluorine resin, polyester resin, polyurethane resin, polycarbonate resin, phenol resin, amino acid Examples thereof include resins, melamine resins, benzoguanamine resins, urea resins, amide resins, and epoxy resins.

The coating layer may contain resin particles for the purpose of controlling charging and conductive particles for the purpose of controlling resistance. The coating layer may contain other additives.
Although it does not specifically limit as a resin particle, The thing with charge control provision property is preferable, for example, a melamine resin particle, a urea resin particle, a urethane resin particle, a polyester resin particle, an acrylic resin particle etc. are mentioned.
Examples of the conductive particles include carbon black, various metal powders, and metal oxides (for example, titanium oxide, tin oxide, magnetite, ferrite, and the like). These may be used individually by 1 type and may use 2 or more types together. Among these, carbon black particles are preferable from the viewpoints of production stability, cost, conductivity, and the like. The type of carbon black is not particularly limited, but carbon black having a DBP oil absorption of about 50 ml / 100 g or more and 250 ml / 100 g or less is preferable because of excellent production stability.

  Examples of the method for forming the coating layer on the surface of the core material particles include a wet manufacturing method and a dry manufacturing method. The wet manufacturing method is a manufacturing method using a solvent that dissolves or disperses the coating resin of the coating layer. On the other hand, the dry process is a process that does not use the solvent.

  Examples of the wet manufacturing method include an immersion method in which core material particles are immersed in a coating layer forming resin liquid; a spray method in which the coating layer forming resin liquid is sprayed on the surface of the core material particles; Fluidized bed method in which the coating layer forming resin liquid is sprayed in a fluidized state; the kneader coater method in which the core material particles and the coating layer forming resin solution are mixed in the kneader coater and the solvent is removed; Can be mentioned.

  Examples of the dry production method include a method of forming a coating layer by heating a mixture of core material particles and a coating layer forming material in a dry state. Specifically, for example, the core material particles and the coating layer forming material are mixed and heated and melted in a gas phase to form a coating layer.

  The coating amount of the coating layer to the core particles is, for example, 0.5% by mass or more (preferably 0.7% by mass or more and 6% by mass or less, more preferably 1.0% by mass or more and 5% by mass) with respect to the mass of the entire carrier. 0.0 mass% or less).

The coating amount of the coating layer is determined as follows.
In the case of a solvent-soluble coating layer, a precise amount of carrier is dissolved in a soluble solvent (for example, toluene), the core particles are held with a magnet, and the solution in which the coating layer is dissolved is washed away. By repeating this several times, the core particles from which the coating layer has been removed remain. The coating amount is calculated by drying, measuring the mass of the core particles, and dividing the difference by the carrier amount.
Specifically, 20.0 g of the carrier is measured, put into a beaker, 100 g of toluene is added, and the mixture is stirred with a stirring blade for 10 minutes. A magnet is applied to the bottom of the beaker, and toluene is allowed to flow so that the core particles do not flow out. This is repeated 4 times, and the beaker after washing is dried. The amount of magnetic powder after drying is measured, and the coating amount is calculated by the formula [(carrier amount−core material particle amount after washing) / carrier amount].
On the other hand, in the case of a solvent-insoluble coating layer, Rigaku's Thermo plus EVOII differential type differential thermobalance TG8120 is heated in a nitrogen atmosphere at room temperature (25 ° C.) or more and 1000 ° C. or less to reduce its mass. From this, the coating amount is calculated.

-Carrier characteristics-
The volume average particle diameter of the carrier is, for example, 10 μm or more and 500 μm, preferably 15 μm or more and 80 μm or less, more preferably 20 μm or more and 60 μm or less.
Here, the volume average particle diameter of the carrier is measured as follows. The measurement of the volume average particle diameter of the core particles is the same.
Laser diffraction / scattering particle size distribution analyzer (LS Particle Size Analyzer (manufactured by Beckman-Coulter)) is used to measure particle size distribution, and ISOTON-II (manufactured by Beckman-Coulter) is used as the electrolyte. The number of particles to be measured is 50,000.
Then, the measured particle size distribution is drawn from the smaller diameter side with respect to the divided particle size range (channel), and the particle size (which may be expressed as “D50v” in some cases) is 50% cumulative. It is defined as “volume average particle diameter”.

As for the magnetic force of the carrier, the saturation magnetization in a magnetic field of 1000 Oersted may be, for example, 40 emu / g or more, or 50 emu / g or more.
Here, the saturation magnetization of the carrier is measured using a vibration sample type magnetometer VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.). 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 3000 oersted. Next, the applied magnetic field is reduced to create a hysteresis curve on the recording paper. The saturation magnetization is obtained from the curve data.

The volume electric resistance (25 ° C.) of the carrier may be, for example, from 1 × 10 ⁷ Ω · cm to 1 × 10 ¹⁵ Ω · cm, and from 1 × 10 ⁸ Ω · cm to 1 × 10 ¹⁴ Ω · cm. It may be 1 × 10 ⁸ Ω · cm or more and 1 × 10 ¹³ Ω · cm or less.
The volume electrical resistance of the carrier is measured as follows. On the surface of a circular jig provided with a 20 cm ² electrode plate, the measurement object is placed flat so as to have a thickness of 1 mm or more and 3 mm or less to form a layer. The 20 cm ² electrode plate is placed on this and the layer is sandwiched. In order to eliminate gaps between objects to be measured, the thickness (cm) of the layer is measured after applying a load of 4 kg on the electrode plate arranged 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. The measurement environment is a temperature of 20 ° C. and a humidity of 50% RH. 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. The coefficient 20 represents the area (cm ² ) of the electrode plate.

<Electrostatic image developer>
The electrostatic image developer (hereinafter referred to as developer) according to the present embodiment includes an electrostatic image developing toner (hereinafter referred to as “toner”) and the carrier according to the present embodiment.

Hereinafter, the toner will be described.
The toner has toner particles. The toner may contain an external additive as necessary.

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

-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 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.

In addition, 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 obtained 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, aluminum coupling agents and the like. 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 is produced, 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.

  The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer 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. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

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 containing at least yellow toner and a carrier 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, 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 with each other 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 image developer according to the present embodiment, and develops the electrostatic image formed on the surface of the image carrier as a toner image by the electrostatic 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. The main parts shown in the figure will be described, and the description of the other parts will be omitted.

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, “parts” means “parts by mass” and “%” means “% by mass”.

<Example 1>
Ferrite particles (Powder Tech, volume average particle size 35 μm): 100 parts Toluene: 15 parts Styrene / methyl methacrylate copolymer: 2.5 parts (glass transition temperature 71 ° C., weight average molecular weight 9.2) Million)
Tris (3,5-di-tert-butylsalicylic acid) aluminum salt: 0.2 parts Resin particles (melamine resin particles, volume average particle diameter 100 nm): 0.7 parts The above components excluding the ferrite particles for 60 minutes Stir and disperse with a stirrer to prepare a coating layer forming solution. The solution and ferrite particles are depressurized to -200 mmHg at 60 ° C. and mixed for 15 minutes, and then heated / depressurized and heated at 94 ° C./−720 mmHg for 30 minutes. The mixture was stirred and dried to obtain resin-coated particles. Next, the obtained resin-coated particles were sieved with a 75 μm mesh sieve to obtain a carrier.

<Examples 2-6, Comparative Examples 1-3>
Each carrier was obtained in the same manner as in Example 1 except that the material and the amount thereof were used according to Table 1 instead of the lithium (3,5-di-tert-butylsalicylic acid) aluminum salt.

<Evaluation>
[Production of toner]
(Colorant particle dispersion 1)
Cyan pigment: Copper phthalocyanine B15: 3 (manufactured by Dainichi Seika Co., Ltd.): 50 parts Anionic surfactant: Neogen SC (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 5 parts Ion-exchanged water: 200 parts The mixture was mixed and dispersed for 5 minutes with an Ultra-Turrax manufactured by IKA and for 10 minutes with an ultrasonic bath to obtain a colorant particle dispersion 1 having a solid content of 21%.
It was 160 nm when the volume average particle diameter was measured with a Horiba Seisakusho particle size measuring instrument LA-700.

(Releasing agent particle dispersion 1)
-Paraffin wax: HNP-9 (Nippon Seiki Co., Ltd.): 19 parts-Anionic surfactant: Neogen SC (Daiichi Kogyo Seiyaku Co., Ltd.): 1 part-Ion-exchanged water: 80 parts Then, the mixture was heated to 90 ° C. and stirred for 30 minutes. Next, the melt was circulated from the bottom of the container to the gorin homogenizer, and a circulation operation corresponding to 3 passes was performed under a pressure condition of 5 MPa. Thereafter, the pressure was increased to 35 MPa, and a circulation operation corresponding to three passes was performed. The emulsion thus prepared was cooled in the heat-resistant solution to 40 ° C. or lower to obtain a release agent particle 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 (Wako Pure Chemical Industries, Ltd.): 30 parts-N-butyl acrylate (Wako Pure Chemical Industries, Ltd.): 10 parts-β-carboxyethyl acrylate (manufactured by Rhodia Nikka Co., Ltd.): 1.3 parts · Dodecanethiol (Wako Pure Chemical Industries, Ltd.): 0.4 parts

-Water layer 1-
・ Ion-exchanged water: 17 parts ・ Anionic surfactant (Dowfax, manufactured by Dow Chemical Co.): 0.4 parts

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

The components of the oil layer and the component of the aqueous layer 1 were put into a flask and mixed with stirring to obtain a monomer emulsified 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.
Further, the above-mentioned 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.).
It was 52 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 Corporation make).
When the number average molecular weight (polystyrene conversion) was measured using THF (tetrahydrofuran) as a solvent using a molecular weight measuring instrument (HLC-8020 manufactured by Tosoh Corporation), it was 13,000.
As a result, a resin particle dispersion 1 having a volume average particle size of 250 nm, a solid content of 42%, a glass transition point of 52 ° C., and a number average molecular weight Mn of 13,000 was obtained.

(Production of toner particles)
Resin particle dispersion 1: 150 parts Colorant particle dispersion 1: 30 parts Release agent particle dispersion 1: 40 parts Polyaluminum chloride: 0.4 parts

  Each of the above components was sufficiently 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 holding at 48 ° C. for 80 minutes, 70 parts of the same resin particle dispersion 1 as above was gently 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 size of the toner particles is 6.2 μm when measured with a 50 μm aperture diameter using a Coulter Multisizer-II type (manufactured by Beckman-Coulter), and the volume average particle size distribution index GSDv is 1.20. there were.
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 shape was distorted like a potato.
The glass transition point of the toner was 52 ° C.

(External additives)
Further, this toner was treated with hexamethyldisilazane (HMDS) and subjected to surface hydrophobization treatment. Silica (SiO ₂ ) particles having an average particle size of 40 nm and an average particle size of primary particles which are a reaction product of metatitanic acid and isobutyltrimethoxysilane. A metatitanic acid compound particle having a particle diameter of 20 nm was added so that the coverage with respect to the surface of the toner particle was 40%, and mixed with a Henschel mixer to prepare a toner.

[Production of developer]
100 parts of the carrier prepared in each example and 10 parts of the toner were stirred at 40 rpm for 20 minutes using a V-blender, and sieved with a sieve having a 125 μm mesh to obtain a developer.

[Evaluation of image density and image density unevenness]
Each obtained developer was stored in a developing machine of 700 Digital Color Press (Fuji Xerox Co., Ltd.). Using this image forming apparatus in a high temperature and high humidity environment (temperature 30 ° C., humidity 80% RH), a solid image of 10 cm × 5 cm (toner paste amount 0.6 mg / cm ³ ) on 1000 sheets of paper The output was evaluated, and the solid image density and fogging were evaluated for the initial (50th sheet) and late (1000th sheet) images. Evaluation was performed for the case where P paper A4 manufactured by Fuji Xerox Co. was used as the paper and the image area coverage was 1% as the image forming condition.

Specifically, the density of the solid image was determined by randomly measuring 10 points of the solid image portion with an image densitometer X-Rite 938 (manufactured by X-Rite) for the output 10 cm × 5 cm solid image, and averaging Values were obtained and evaluated according to the following criteria. The image density was 1.3 or more (A), and the initial / time density difference was 0.1 or less (A and B).
-Image density-
A: 1.30 or more B: less than 1.30 −initial / time-dependent concentration difference−
A: 0.02 or less B: more than 0.02 or less 0.05 or less C: more than 0.05 or less 0.1 or less D: more than 0.1

On the other hand, the evaluation of fogging was performed by measuring 10 non-image areas at random using an image densitometer X-Rite 938 (manufactured by X-Rite), obtaining an average value thereof, and evaluating it according to the following criteria. The allowable range of fogging is that the density of the non-image area is 0.01 or less (A, B, and C).
-Cover-
A: 0.004 or less B: More than 0.004 and 0.008 or less C: More than 0.008 and 0.01 or less D: More than 0.01

  The details of the carriers of each example and the evaluation results of each example are listed in Table 1 below.

From the above results, it can be seen that in this embodiment, the density reduction of the solid image at the initial stage of image formation is suppressed as compared with the comparative example.
In addition, it can be seen that Examples 1, 2, and 4 to 6 have less image density difference between the initial image formation and the diameter compared to Example 3. Further, it can be seen that in Examples 1 and 2, the difference in image density between the initial image formation and the diameter is more suppressed than in Examples 4 to 6.

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)

Core particles,
A coating layer that covers the core particles and includes at least one selected from the group consisting of an aluminum salicylic acid salt and a salicylic acid derivative aluminum salt; and a resin;
A carrier for developing an electrostatic charge image.   2. The electrostatic image developing carrier according to claim 1, wherein the coating layer includes a substituted salicylic acid aluminum salt in which an alkyl group is substituted on a phenyl group of at least one salicylic acid skeleton as the salicylic acid derivative aluminum salt.   The electrostatic charge image developing carrier according to claim 2, wherein the alkyl group is a branched alkyl group.   An electrostatic charge image developer comprising: an electrostatic charge image developing toner; and the electrostatic charge 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: