JP2000231225A - Electrostatic charge image developing carrier, its production, electrostatic charge image developer, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic charge image developing carrier capable of imparting temporally stable electrostatic chargeability to a developer including its early stages and giving an image having good image quality even after repeated copying, to provide an electrostatic charge image developer, and to provide an image forming method. SOLUTION: A resin coating is formed on the surfaces of iron-containing core material particles and agitation energy is applied to the coated particles under prescribed conditions to produce the objective electrostatic charge image developing carrier in which iron occupies 0.25-1.0 at.% of all elements whose atomic number is >=3 within the range from the surface of the carrier to 5 nm depth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image developing carrier used in electrophotography, electrostatic recording and the like, a method for producing the same, and an electrostatic image developer using the electrostatic image developing carrier. And an image forming method.

[0002]

2. Description of the Related Art Electrophotography for visualizing image information via an electrostatic latent image is currently used in various fields, and is described in U.S. Pat. Nos. 2,297,691 and 2,357,809. As is well known. In the electrophotographic method, generally, an electrostatic latent image is formed on a photoconductor (latent image carrier) through a charging step and an exposure step, and an electrostatic image developer containing toner (hereinafter simply referred to as “ The toner image is formed by developing the electrostatic latent image using a developer, and the toner image is transferred onto a transfer material such as paper or a plastic sheet in a transfer step. In this method, a permanent image is obtained by fixing the toner image on a transfer material using heat, a solvent, pressure, or the like.

[0003] There are many known methods for developing a developer. In addition to the cascade developing method described in US Pat. No. 2,618,552, the magnetic brush method described in US Pat. No. 2,870,463, and the touch-down method described in US Pat. There is a jumping brush development method for performing development.

Among them, a magnetic brush method is a typical method of a so-called two-component developer obtained by mixing a carrier for developing an electrostatic image (hereinafter sometimes simply referred to as "carrier") and a toner. No. This method uses a magnetic particle such as steel or ferrite as a carrier, carries a developer comprising a toner and a magnetic carrier on a magnet, forms the developer in a brush shape by the magnetic field of the magnet, and then forms the brush. When the magnetic brush comes into contact with the electrostatic latent image on the photoreceptor, the toner in the brush is attracted and developed according to the amount of charge of the latent image. The carrier is roughly classified into a coated carrier having a coating on the surface and an uncoated carrier having no coating on the surface, but considering the life of the developer, the coated carrier is superior. Therefore, various coated carriers have been developed and put into practical use. As the characteristics of the coated carrier, it is required at least that the toner can be provided with an appropriate chargeability (charge amount and charge distribution) and that the appropriate chargeability can be maintained for a long period of time. Therefore, various coated carriers that do not change the chargeability of the toner, have excellent impact resistance and friction resistance, and are stable against environmental changes such as humidity and temperature have been proposed.

[0005] For example, Japanese Patent Application Laid-Open No. 61-80161,
JP-A-61-80162 and JP-A-61-80163 disclose a copolymer of a nitrogen-containing fluorinated alkyl (meth) acrylate and a vinyl monomer, and a copolymer of a fluorinated alkyl (meth) acrylate and a nitrogen-containing vinyl monomer. It is described that a coated carrier having a relatively long life can be obtained by coating the surface of a carrier core material with a copolymer. Japanese Patent Application Laid-Open No. 1-118150 and the like disclose a polyamide resin, and Japanese Patent Application Laid-Open No. 2-79862 a melamine resin coated on the surface of a carrier core material and cured to form a coated carrier having a relatively hard coating. Is described. However, in the case of these carriers, contamination of the carrier surface by the toner component (impact).
There is a problem that can not be completely prevented.

In order to prevent such impaction, for example, a silicone resin as described in JP-A-60-186844 or the like,
It has also been considered to form a carrier film using a resin having a small surface energy such as a fluororesin described in JP-A-560-560. However, in such a carrier, the silicone resin and the fluorine-based resin are present in a relatively large amount near the surface of the carrier, but are slightly present in a deep portion in the thickness direction of the coating layer. However, when used for a long period of time, the effect of these resins is gradually lost due to abrasion of the coating, and conversely, there is a problem that the impact is gradually generated. In addition, when continuous copying is performed using such a developer, an image with excellent density reproducibility and image quality can be obtained initially, but after tens of thousands of copies, the image density is reduced, and Poor tonality and graininess.

[0007] Recently, full-color copying machines have attracted attention, and along with that, there has also been a need to satisfy the unique requirements of color different from conventional black-and-white copying. That is, a black-and-white copy original is generally a line image such as a chart or a document, and the image area occupying about 10% or less on a transfer material such as paper. Since the manuscript has a remarkably large image area such as a map, a photograph, a painting, and a portion having a gradation property, a technique for faithfully reproducing the portion is required.

Further, in a digital type full-color copying machine for electrophotography, the toner is required to have a high image quality such as obtaining halftone gradation and granularity of a digital image, and the particle size of the toner is being reduced. It is known that the particle size is 9 μm or less. Therefore, some developers have been proposed for the purpose of improving image quality. JP 5
In Japanese Patent Application Laid-Open No. 8-129439, the average particle size is 6 to 10 μm.
Non-magnetic toners having the largest number of particles of 5 to 8 μm have been proposed. However, since the fine dots of the latent image are clearly reproduced, the number of particles of 5 μm or less densely placed on the latent image is as small as 15% by number or less. However, there is a problem that graininess and gradation are poor. On the other hand, if the number of particles having a particle size of 5 μm or less is excessively large, there is a problem that the fluidity of the toner is deteriorated.

Further, the average particle size of the toner and 5
Even if the particle size distribution such as the number% of particles of μm or less is appropriate,
When a conventional carrier is used, good image quality can be obtained initially, but as the copying is repeated,
Deterioration of image quality such as fogging and non-uniform density in non-image areas occurs, and it is difficult to obtain an image having required gradation and graininess. This is considered to be a phenomenon that occurs because only toner that is easily developed is selectively consumed during repeated copying (referred to as selective development), and particularly, toner having poor developability stays in the developing machine. Further, in an image pattern having a large density difference, an edge effect in which only the peripheral portion of the image is emphasized occurs, or toner is not partially applied to the boundary of the image, and image quality defects such as formation of a false contour are small. The improvement cannot be achieved only by increasing the particle size.

Therefore, Japanese Patent Application Laid-Open Nos. 58-144839 and 61-204646 propose to specify the average particle size and the particle size distribution of the carrier used together with the toner. However, even when such a carrier was used, the above problem was not sufficiently solved.

Japanese Patent Application Laid-Open No. Hei 10-2789246 specifically describes the particle size distribution and magnetic properties of the carrier and the particle size distribution of the toner. However, even when the developer described in the publication is used, an image quality excellent in color reproducibility, gradation and graininess can be obtained at the initial stage. The image quality is degraded due to the edge effect, and is insufficient to achieve the target image quality.

On the other hand, in a copying machine, the development potential and the toner concentration in the developer are controlled in order to adjust the change in the amount of charge of the developer, but such an apparatus alone is not sufficient. Particularly, at the beginning, the developer tends to be activated and the charge amount tends to increase, and such a phenomenon causes initial carrier adhesion, image quality defect and fog.

[0013]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a developer with a charging property that is stable over time, including the initial stage, so that fog and density can be maintained even after repeated copying. A carrier for developing an electrostatic charge image, in which a clear image having no half-tone effect and edge effect is obtained without causing deterioration, and which has a good halftone gradation and graininess, and in particular, an initial image quality change is suppressed. And an image forming method using the carrier for developing an electrostatic image.

Another object of the present invention is to provide an electrostatic charge image which is stable in density reproducibility and does not generate toner spent in a developing machine even when continuous copying of a document having a large image area such as a photograph or a picture is performed. An object of the present invention is to provide a developing carrier and a method of manufacturing the same, and an electrostatic image developer and an image forming method using the electrostatic image developing carrier.

[0015]

The present inventors have conducted intensive studies to solve the above-mentioned problems of the prior art, and as a result, the change in the charge amount due to repeated copying occurs due to the change in the surface structure of the carrier. I found that. Initially, the change in the structure reaches a peak due to an increase in the charge amount due to abrasion or activation of the carrier electrode surface due to stirring in the developing machine. Thereafter, the charge amount decreases due to contamination by the toner component.

Although the contamination by the toner component can be improved by using a low surface energy resin for the resin coating layer, another measure is required for the initial structural change. It is effective to homogenize or activate the carrier surface structure so as to prevent the initial carrier pole surface structure change from occurring in the developing machine, and to use a developer whose charge amount is already near the peak. The present inventors have further studied from such a viewpoint, and as a result, in the carrier in the two-component developer, as a state after forming the resin coating layer on the surface of the core material particles, the exposure of iron which is the core material particle component is performed. It has been found that by appropriately controlling the amount, the obtained developer already has a state where the charge amount is close to the peak, and the above object is achieved.

That is, the first present invention relates to a carrier for developing an electrostatic image formed by forming a resin coating layer on the surface of core material particles containing iron, wherein the carrier exists near the surface of the carrier for developing an electrostatic image. The carrier for developing an electrostatic image is characterized in that iron accounts for 0.25 to 1.0 atom% of all elements having an atomic number of 3 or more.

By appropriately controlling the amount of exposure of iron as described above, the surface structure of the carrier is in a stable equilibrium, the charging characteristics are close to the saturation region, and the carrier is stable over time including the initial stage. The developer can be imparted with excellent chargeability, and does not cause fogging or decrease in density even after repeated copying. In addition, even if continuous copying of originals with large image areas such as photographs and paintings is performed, the density reproducibility is stable,
In addition, no toner spent in the developing machine occurs. Furthermore, even after repeated copying, a halftone image having good halftone gradation and graininess without any edge effect can be obtained, and a change in image quality is particularly suppressed.

Such a surface state can be achieved by adjusting various conditions at the stage of forming the resin coating layer, but can also be controlled afterward by the method of the second present invention described later. It is.

In the first aspect of the present invention, the resin coating layer is preferably formed by dispersing resin particles in a resin, and the resin particles are resin particles formed of a nitrogen-containing resin. Is preferred. Further, the resin coating layer is preferably formed by dispersing conductive particles in a resin, and the conductive particles are preferably carbon black particles. In the resin coating layer, both resin particles and conductive particles may be dispersed in a resin.

In the carrier for developing an electrostatic image of the first aspect of the present invention, it is preferable that the resin coating layer is in the range of 0.5 to 3.5 wt% based on the total weight of the carrier for developing an electrostatic image. The volume average particle size is preferably in the range of 15 to 45 μm.

On the other hand, when the exposed amount of the iron is not within an appropriate range as a state after the resin coating layer is formed on the surface of the core material particles, the iron is controlled ex post facto by the following second method of the present invention. can do.

That is, according to the second aspect of the present invention, the aggregating of the coated particles obtained by forming the resin coating layer on the surface of the iron-containing core material particles is performed under the condition represented by the following formula (1). And a method for producing a carrier for developing an electrostatic charge image.

3.0 × 10 ⁹ ≦ 1/2 mv ² × t / M ≦ 3.8 × 10 ¹⁰ (Formula 1) In the above formula, t represents stirring time [sec], and M exists in the stirrer. It represents the total weight [g] of the aggregate of the coated particles. Also, v is the shear rate between the stirring blade clearances [se
c ^-1 ], and is represented by the following formula 2, and m is the weight [g] of the aggregate of the coated particles existing between the stirring blade clearances.
And is represented by the following equation 3. v = πDN / h (Equation 2) m = πD × h × ρ × 10 ⁻³ (Equation 3) In the above Equations 2 and 3, π represents a pi, and D represents a diameter [mm] of a stirring blade. , N is the rotation speed of the stirring blade [times / sec]
c], h represents the gap [mm] between the tip of the stirring blade and the wall surface, and ρ represents the bulk density [g / cm ³ ] of the coated particles.

According to the method for producing a carrier for developing an electrostatic charge image according to the second aspect of the present invention, the exposed amount of iron falls within an appropriate range after the resin coating layer is formed on the surface of the core material particles. Even in the case of uncoated particles, the carrier for developing an electrostatic image of the first aspect of the present invention can be easily obtained. Also,
Even if the carrier for developing an electrostatic image obtained by the method for producing a carrier for developing an electrostatic image according to the second aspect of the present invention is slightly outside the scope of the first aspect of the invention, It will be familiar.

The carrier for developing an electrostatic image according to the first aspect of the present invention or the carrier for developing an electrostatic image according to the second aspect of the present invention comprises at least a toner and a carrier for developing an electrostatic image. When applied to an electrostatic image developer consisting of, it is possible to impart a stable charging property to the developer over time including the initial stage, even after repeated copying,
It does not cause fogging or decrease in density, has stable density reproducibility, and does not generate toner spent in a developing machine.

An image forming process includes a latent image forming step of forming a latent image on the latent image carrier using the electrostatic image developer, and a developing step of developing the latent image with the developer on the developer carrier. If the method is applied, even if a document having a large image area such as a photograph or a picture is continuously copied, the density reproducibility is stable and no toner spent in the developing machine. Further, even after repeated copying, a clear image having good halftone gradation and graininess of the digital image and no edge effect can be obtained.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described with reference to the first and second embodiments of the present invention, an electrostatic image developer using the electrostatic image developing carrier of the first embodiment, and image formation. The method will be described separately.

[First Invention] The first invention relates to a carrier for developing an electrostatic image, comprising a resin coating layer formed on the surface of iron-containing core material particles. Of all elements having an atomic number of 3 or more existing in the vicinity of the surface of iron, the proportion of which is occupied by iron (hereinafter, may be simply referred to as “iron exposure”) is in the range of 0.25 to 1.0 atom%. This is a carrier for developing an electrostatic image.

A. Exposure of Iron As described above, in the first aspect of the present invention, the exposure of iron is set to 0.1.
It is essential that the content be in the range of 25 to 1.0 atom%. When the exposure amount of iron exceeds 1.0 atom%, the surface change of the carrier is excessive, the abrasion of the resin coating layer is remarkable, and the maintenance of the charge amount in the copying machine becomes short. As a result, fogging may occur due to long-term use. The exposure amount of iron is preferably 0.8 atom% or less. On the other hand, the iron exposure was 0.25
If the content is less than atom%, the surface structure of the carrier becomes unstable, and the charging characteristics may not be sufficiently reached to the saturation region. The additional amount of iron exposure is 0.3
It is preferably 0 atom% or more.

In the present invention, the amount of exposed iron can be easily measured, for example, by using the following measuring instrument and conditions. In the first aspect of the present invention, the term “near the surface” defining the exposure amount of iron means a range where the measurement intensity is measured at 10.0 kV and 20 mA. -Measuring instrument: JPS-9000MX, manufactured by JEOL Ltd.-Measurement intensity: 10.0 kV, 20 mA-Source: MgKa

Of course, as long as the ratio of iron occupied by all elements having an atomic number of 3 or more existing near the surface of the carrier can be measured, any measuring instrument can be adopted by using the above-mentioned measured intensity. Can be.

In order to adjust the exposure amount of iron to the above range, the coating amount of the coating resin,
It is possible by adjusting various conditions such as the type of solvent, degassing conditions, and temperature. It is also possible to control ex post facto by the method of the second present invention described later.

B. Core Material Particles In the present invention (including the second invention, hereinafter, when simply referred to as “the present invention”, it relates to both the first and second inventions), iron is used as the core material particles. It is contained as a constituent element. For example, iron itself, alloys of iron with manganese, chromium, rare earth elements, and the like, and magnetic oxides such as ferrite and magnetite can be used. In the present invention, 98% or more of Cu-Zn-
Ferrite particles having a ferrite composition are preferred because the surface can be easily made uniform and the charge stability is excellent.

The core particles have an electric resistance of 10 ⁶ to ^109.5 Ω.
When it is in the range of cm, the image quality is excellent in stability over time. If the electric resistance is smaller than 10 ⁶ Ωcm, charge may be injected into the carrier when the toner concentration in the developer is reduced by repeated copying, and the carrier itself may be developed. On the other hand, the electric resistance may be 10 ^9.5 Ωcm. If the size is larger, the image quality such as a remarkable edge effect or a false contour may be adversely affected, which is not preferable.

The method for measuring the electric resistance of the core particles will be described below using the developing device shown in FIG. In addition,
The electric resistance of the core particles can be measured using any developing device as long as the following method is used.

The developing device shown in FIG. 1 includes a photoconductor (latent image carrier) 10 which rotates in the direction of arrow B, a developing housing 12 having an opening facing the photoconductor 10 and containing a developer.
And a developing sleeve 14 arranged on the developing housing 12 so as to face the photoconductor 10 from the opening.

First, the photoreceptor 10 was removed from the developing device of FIG. 1, only the core material particles to be measured were mounted in the developing housing 12, and the magnetic brush composed of the core material particles was formed on the developing sleeve 14. . An aluminum pipe having the same size as the photoreceptor 10 is loaded in place of the photoreceptor 10 (since the photoreceptor 10 and the aluminum pipe can be represented by the same shape in the drawings, the following description will be made using the same drawings. Aluminum pipe is "Aluminum pipe 1
0 "). Next, between the aluminum pipe 10 and the developing sleeve 14, (applied voltage) /
A direct current is applied so that the value of (the facing distance between the aluminum pipe and the photoconductor) has a predetermined electrolytic strength, and the value of the current flowing at this time is measured. Next, a resistance value is obtained from the applied voltage and the measured current value, and a value obtained by dividing the obtained resistance value by the effective length of the developing sleeve is defined as an electric resistance (Ωcm) at a predetermined electrolytic strength.

Here, the effective length refers to the width of the opening formed in the wall 12A of the developing housing 12 in the longitudinal direction (axial direction) of the developing sleeve 14 in the developing device shown in FIG. If the width of the opening is shorter than the length of the developing sleeve 14, the width of the opening is longer than the length of the developing sleeve 14. Length. The predetermined electrolytic strength in the measurement of the electric resistance of the core material particles was 2.0 V / μm.

The particle size of the core material particles is such that the obtained carrier can have a preferable particle size. Since the thickness of the resin coating layer coated on the surface of the core material particles is extremely small, the preferable particle size of the obtained carrier corresponds almost directly to the preferable particle size of the core material particles. The preferred particle size of the carrier will be described later.

C. Resin coating layer The carrier in the present invention is obtained by coating the surface of core material particles with a resin to form a resin coating layer. The resin capable of forming the resin coating layer is not particularly limited as long as it can be used as a matrix resin, and can be appropriately selected depending on the purpose.

Specifically, for example, polyolefin resins such as polyethylene and polypropylene; polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral,
Polyvinyl resin such as polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone and polyvinylidene resin; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer: straight silicone resin comprising an organosiloxane bond or the same Modified products; fluorine resins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; silicone resins; polyesters; polyurethanes; polycarbonates; phenolic resins; urea-formaldehyde resins, melamine resins, benzoguanamine resins, Known resins such as amino resins such as urea resins and polyamide resins; epoxy resins; These may be used alone or in combination of two or more.

In the present invention, among these resins, it is preferable to use at least a fluorine resin and / or a silicone resin. The use of at least a fluorine-based resin and / or a silicone resin as the resin is advantageous in that the effect of preventing carrier contamination (impaction) due to toner and external additives is high.

The resin coating layer in the present invention is preferably formed by dispersing resin particles in a resin. When the resin particles are dispersed in the resin coating layer, the resin as the resin particles and the matrix resin is uniformly dispersed in the thickness direction and the tangential direction of the carrier surface. Even if the resin coating layer wears, it can always maintain the same surface configuration as when not in use,
Good charging ability to the toner can be maintained for a long period of time.

The resin particles include, for example, thermoplastic resin particles, thermosetting resin particles, and the like. Among these, a thermosetting resin is preferable from the viewpoint of relatively easily increasing the hardness, and a so-called charge-imparting agent is preferable. From the viewpoint of imparting a good negative charge to the toner, an N atom is preferred. A resin particle containing a so-called nitrogen-containing resin is preferable. These resin particles may be used alone or in combination of two or more.

The average particle size of the resin particles is, for example, preferably about 0.1 to 2 μm, and more preferably 0.2 to 1 μm. The resin particles have an average particle size of 0.
If it is less than 1 μm, the dispersibility of the resin particles in the resin coating layer becomes poor, while if it exceeds 2 μm, the resin particles easily fall off from the resin coating layer, and the original effect may not be exhibited, Each is not preferred.

The resin coating layer of the present invention, in which conductive particles are dispersed in a resin, can easily control the resistance of the carrier and can be used as a so-called S-CMB developer. Is preferred. In the case where the conductive particles are dispersed in the resin coating layer, in the thickness direction thereof, and in the tangential direction of the carrier surface, the resin as the conductive particles and the matrix resin is uniformly dispersed, Even if the resin coating layer is worn by using the carrier for a long period of time, the same surface configuration as that when the carrier is not used can be always maintained, and deterioration of the carrier can be prevented for a long period of time.

The conductive particles include metal particles such as gold, silver and copper, carbon black particles, semiconductive oxide particles such as titanium oxide and zinc oxide, titanium oxide, zinc oxide, barium sulfate and aluminum borate. And particles in which the surface of potassium titanate powder or the like is covered with tin oxide, carbon black, metal, or the like.

These may be used alone, or
Two or more kinds may be used in combination. Among these, carbon black particles are preferred from the viewpoints of production stability, cost, and good conductivity. The type of carbon black particles that can be used is not particularly limited, but the DBP oil absorption is 50 to 50%.
Carbon black particles of about 250 ml / 100 g are excellent in production stability and are preferred.

When both the resin particles and the conductive particles are dispersed in the resin coating layer, the above-described effects obtained by dispersing both particles can be simultaneously exhibited.

The method for forming the resin coating layer is not particularly limited. For example, a matrix resin such as a styrene acrylic resin, a fluorine-based resin, or a silicone resin, and the above-mentioned resin particles, conductive particles, etc. And a method in which core material particles are coated with a coating liquid for forming a resin coating layer obtained by dissolving and dispersing the above in a suitable solvent.

The solvent used in the coating solution for forming the resin film layer is not particularly limited as long as it can dissolve only the resin as the matrix resin, and is selected from known solvents per se. For example, toluene, aromatic hydrocarbons such as xylene, acetone, ketones such as methyl ethyl ketone, tetrahydrofuran,
Ethers such as dioxane;

The method for applying the core material particles with the coating liquid for forming a resin coating layer is, for example, a dipping method in which the coating liquid for forming a resin coating layer is dipped in the coating liquid for forming a resin coating layer. Examples of the method include a spray method of spraying the surface of the core material particles, a kneader coater method of mixing the coating material for forming the resin coating layer in a state where the core material particles are suspended with flowing air, and removing the solvent. In the present invention, among these, the kneader coater method is preferable.

The coating resin layer of the carrier (when resin particles, conductive particles, and the like are contained, the sum total thereof) is as follows:
0.5 to 3 based on the total weight of the electrostatic image developing carrier.
It is preferably in the range of 5 wt%, more preferably 1.5 to 2.5 wt%. If the amount is less than 0.5 wt%, it is difficult to control the toner to a desired charge amount, the resistance of the carrier itself tends to be low, and the carrier is likely to adhere to the background due to the injection of charge. on the other hand,
If the content exceeds 3.5% by weight, aggregation of carrier particles occurs, and toner adhesion due to a decrease in agitation with additional toner when used as a developer is likely to occur.

The volume average particle diameter of the carrier is as follows:
It is preferably in the range of 15 to 45 μm, more preferably 20 to 40 μm. If it is less than 15 μm, carrier adhesion to the background tends to occur. If it exceeds 45 μm, the resistance as a developer increases, and the density reproducibility of a document having a large image area deteriorates.

[Second Invention] The second invention is represented by the following formula 1 with respect to a set of coated particles obtained by forming a resin coating layer on the surface of core particles containing iron. A method for producing a carrier for developing an electrostatic image, characterized by applying stirring energy under the following conditions:

3.0 × 10 ⁹ ≦ 1/2 mv ² × t / M ≦ 3.8 × 10 ¹⁰ (Formula 1) In the above formula, t represents stirring time [sec], and M exists in the stirrer. It represents the total weight [g] of the aggregate of the coated particles. Also, v is the shear rate between the stirring blade clearances [se
c ^-1 ], and is represented by the following formula 2, and m is the weight [g] of the aggregate of the coated particles existing between the stirring blade clearances.
And is represented by the following equation 3. v = πDN / h (Equation 2) m = πD × h × ρ × 10 ⁻³ (Equation 3) In the above Equations 2 and 3, π represents a pi, and D represents a diameter [mm] of a stirring blade. , N is the rotation speed of the stirring blade [times / sec]
c], h represents the gap [mm] between the tip of the stirring blade and the wall surface, and ρ represents the bulk density [g / cm ³ ] of the coated particles.

In the stirrer and the kneader, the portion where the shear is most applied is between the clearance between the tip of the stirring blade and the wall surface (in the present invention, simply referred to as "stirring blade clearance"). Therefore, the weight of the aggregate of the coated particles existing between the stirring blade clearances m [g] and the shear rate v [sec ^-1 ] between the stirring blade clearances are added to the aggregate of the coated particles existing between the stirring blade clearances. Energy was determined (1/2 mv ² ). The stirring time t
The above formula 1 expresses the stirring share per unit coated particle by multiplying the ratio of [sec] by the total weight M [g] of the set of coated particles present in the stirrer.

Here, the coated particles refer to particles after a resin coating layer has been formed on the core material particles, and generally, a carrier is formed in the state of the coated particles and is used for image formation. It is. In the second aspect of the present invention, the above-mentioned predetermined agitation energy is further applied to the aggregate of the coated particles in such a state, so as to impart appropriate charging characteristics to the carrier.

When the stirring energy is applied to the aggregate of the coated particles under the condition represented by the above formula 1, the exposed amount of iron is appropriate after the resin coating layer is formed on the surface of the core material particles. Even in the case of coated particles not in the range, the particles can be easily included in the range of the exposed amount of iron defined in the first invention. Further, it is assumed that the carrier for developing an electrostatic image obtained by adding stirring energy to the aggregate of the coated particles under the condition represented by the above formula 1 is not slightly included in the scope of the first invention. Will also be familiar at the beginning.

More preferably, the condition of the stirring energy to be added is a condition represented by the following formula 1 ′. 4.0 × 10 ⁹ ≦ 1 / 2mv ² × t / M ≦ 1.0 × 10 ¹⁰ (Equation 1 ′)

In the second aspect of the present invention, the device for applying the stirring energy is not particularly limited as long as it has a stirring blade. For example, a planetary mixer, a kneader coater, a Henschel mixer, a continuous mixer, an extruder, a crypton, a Fitzmill, a Loedige mixer, and the like can be mentioned. Further, when the resin coating device for forming the resin coating layer on the core material particles has a stirring blade, it is possible to continue stirring and to apply the above stirring energy after removing the solvent.

Hereinafter, representative kneader coaters and planetary mixers as devices for imparting stirring energy according to the second invention will be described. FIG. 2 is a sectional view from the front of the kneader coater (AA in FIG. 3).
FIG. 3 is a cross-sectional view, in which the stirring blade 20 is schematically shown. FIG. 3 is a cross-sectional view as viewed from above the kneader coater (FIG. 2).
(But, the stirring blade 20 is realistically represented by a twisted shape imitating the actual shape.)
4 is a cross-sectional view of the kneader coater from the right side (a cross-sectional view taken along line CC in FIG.
0 is schematically represented).

In FIGS. 2 to 4, reference numeral 21 denotes a rotational power generating means, 22 denotes a power transmitting means, and the rotational power transmitted by the power transmitting means 22 is transmitted through a transmission 23 and, if necessary, a gear 24. Then, the stirring blade 20 located in the stirring vessel 25 is rotated in the arrow X direction and the arrow Y direction. The stirring vessel 25 has a lid 26 for maintaining temperature and humidity at the top.
Is covered.

In order to keep the temperature conditions during stirring constant, the wall surface of the stirring vessel 25 is hollow, and a heat medium of a predetermined temperature is circulated in the hollow portion. Of course, if the configuration is such that the temperature inside the stirring vessel 25 can be kept constant, the configuration is not limited to the above-mentioned composition. For example, there is no problem even if the entire stirring vessel 25 is immersed in a predetermined heat medium bath. . The temperature at the time of stirring is not particularly limited, and there is no problem even if it does not have the above configuration. In addition, the temperature does not need to be particularly constant.

The (collected) coated particles are placed in a stirring vessel 25.
The energy is supplied by the stirring blade 20.
At this time, in FIGS. 2 to 4, h is the distance between the tip of the stirring blade 20 and the wall surface.
Is the gap [mm], and D is the diameter [mm] of the stirring blade 20.
And correspond to the same symbols in the above formulas 2 and 3, respectively.
You. And the number of rotations of the stirring blade N [times / sec]
By substituting into Equation 2, the clearance between the stirring blades
Shear speed v [sec ^-1] Can be obtained. Ma
ΠD × h corresponds to the volume between the stirring blade clearances,
This is applied to the bulk density ρ [g / cm^Three] With
By substituting into Equation 3, the clearance between the stirring blades
The weight [g] of the set of existing coated particles can be determined.
Wear.

The values of Equations 2 and 3 obtained in this manner, the total weight M [g] of the coated particles (aggregate) to be charged into the stirring vessel 25 (stirrer), and the stirring time t [s
ec] into Equation 1, the appropriate stirring conditions in FIGS. The stirring energy conditions when the second invention is applied to a kneader coater can be determined as described above.

The kneader coater shown in FIGS. 2 to 4 has two stirring blades. However, since there is no wall at the upper part, the actual clearance is reduced by half for each stirring blade. Becomes Therefore, 2 × 1/2, and eventually 1
It can be calculated as equivalent to the main clearance.

FIG. 5 is a schematic sectional view of a planetary mixer. In FIG. 5, reference numeral 51 denotes a rotating power generating means, and the generated rotating power rotates the stirring blade 50 located in the stirring vessel 55 in the arrow Z direction via the gear 54. The stirring vessel (stirring machine) 55 is covered with a lid 56 for keeping the temperature and humidity at the upper part.

In order to keep the stirring temperature condition constant, the wall surface of the stirring vessel 55 is hollow, and a heat medium of a predetermined temperature is circulated in the hollow portion. Of course, as long as the temperature inside the stirring vessel 55 can be kept constant, the configuration is not limited to the above-described one. For example, there is no problem even if the whole stirring vessel 55 is immersed in a predetermined heat medium bath. . The temperature at the time of stirring is not particularly limited, and there is no problem even if it does not have the above configuration. In addition, the temperature does not need to be particularly constant.

The (collected) coated particles are put into a stirring vessel 55, and energy is applied by a stirring blade 50.
At this time, in FIG. 5, h is the gap [mm] between the tip of the stirring blade 50 and the wall surface, D is the diameter [mm] of the stirring blade 50, and the numerical value is the same as in the above kneader coater. , Equations 3 and 1, it is possible to obtain an appropriate stirring energy condition in the apparatus of FIG. The number of stirring blades of the planetary mixer shown in FIG. 5 is calculated in the same manner as in the case of the kneader coater.

As described above, the typical kneader coater and the planetary mixer have been described as the devices for applying the stirring energy in the second invention, but the second invention is not limited to these, and the second invention is not limited thereto. As long as the apparatus has a stirring blade, any apparatus can be applied, and the conditions of the stirring energy can be calculated in the same manner as described above.

[Electrostatic Image Developer] The electrostatic image developing carrier of the first aspect of the present invention and the electrostatic image developing carrier obtained by the production method of the second aspect of the present invention are composed of a toner and an electrostatic charge. In an electrostatic image developer comprising an image developing carrier, that is, a so-called two-component developer, it can be used as an electrostatic image developing carrier. The toner applicable to the present invention contains a binder resin and a colorant as main components.

Examples of the binder resin contained in the toner include monoolefins such as ethylene, propylene, butylene and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate and acrylic acid Α-methylene aliphatic monocarboxylic acid esters such as phenyl, octyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl Homopolymers or copolymers of vinyl ketones such as methyl ketone, vinylhexyl ketone and vinyl isopropenyl ketone; and the like. Among these, particularly typical binder resins include, for example, polystyrene, styrene-alkyl acrylate copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polystyrene, polypropylene and the like. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin and the like can be mentioned.

The colorant contained in the toner is not particularly limited. For example, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow,
Methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment Red 48: 1, C.I.
I. Pigment Red 122, C.I. I. Pigment
Red 57: 1, C.I. I. Pigment Yellow 97,
C. I. Pigment Yellow 12, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 1
5: 3 and the like.

The toner applicable to the present invention can contain a charge controlling agent as required. In that case, especially when used for a color toner or the like, it is preferable to use a colorless or light-colored charge control agent that does not affect the color tone. As the charge control agent, known ones can be used, but it is preferable to use an azo-based metal complex, a metal complex or a metal salt of salicylic acid or alkylsalicylic acid.

Further, the toner applicable to the present invention may contain other known components such as low molecular weight propylene, low molecular weight polyethylene, and an offset inhibitor such as wax.

The inorganic oxide particles added to the toner include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, Z
nO, 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 , a reaction composition of metatitanic acid and a silicon compound, and the like. Among these, silica fine particles and titania fine particles are particularly preferable. It is desirable that the surface of the oxide fine particles is previously subjected to a hydrophobic treatment. This hydrophobic treatment is effective not only for improving the powder fluidity of the toner, but also for the environment dependency of charging and the resistance to carrier contamination.

The hydrophobizing treatment can be performed by immersing the inorganic oxide in a hydrophobizing agent. The hydrophobizing agent is not particularly limited, and examples thereof include a silane coupling agent, a silicone oil, a titanate coupling agent, and an aluminum coupling agent. These may be used alone or in combination of two or more. Among them, silane coupling agents are preferred.

As the silane coupling agent, for example, any one of chlorosilane, alkoxysilane, silazane and a special silylating agent can be used. Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyl Triethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltriethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N- (trimethylsilyl) ) Urea, tert-butyldimethylchlorosilane,
Vinyltrichlorosilane, vinyltrimethoxysilane,
Vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, and the like.

The amount of the hydrating agent varies depending on the type of the inorganic oxide fine particles and the like, and cannot be specified unconditionally, but is usually 5 to 50 parts by weight based on 100 parts by weight of the inorganic oxide fine particles. It is about.

In the present invention, the particle size distribution of the toner is not particularly limited, but is preferably as follows. The number of toner particles having a particle size of 4 μm or less is preferably 6 to 25% by number of the total number of toner particles, and more preferably 6 to 16% by number. When toner particles having a particle size of 4 μm or less are less than 6% by number, few particles contribute to minute dot reproducibility and granularity.
Because of the particle size effective for these characteristics, the toner is selectively consumed (so-called selective development), and toner having a particle size that does not contribute to development due to repeated copying stagnates in the developing machine. Getting worse. On the other hand, when the number of toner particles having a particle diameter of 4 μm or less exceeds 25% by number, the fluidity of the toner is deteriorated, so that the transportability of the developer is reduced, which may adversely affect the developability.

Further, the content of toner particles having a particle diameter of 16 μm or more is preferably 1.0% by volume or less. When the amount of toner particles having a particle diameter of 16 μm or more is more than 1.0% by volume, not only does fine line reproducibility and gradation be adversely affected, but also 16 μm during transfer.
When the coarse toner particles having a particle size of m or more intervene in the toner layer, they function to prevent the electrostatic adhesion state between the photosensitive member and the transfer member, so that the transfer efficiency may be reduced and the image quality may be reduced. .

The volume average diameter of the toner is 5 to 5.
It is preferably in the range of 9 μm, which is an important characteristic in combination with the above-mentioned particle size distribution in order to reproduce high image quality.
When the volume average diameter is less than 5 μm, not only does the flowability of the toner deteriorate, but also it becomes difficult to provide sufficient chargeability from the carrier, so that fog on the background portion occurs and the density reproducibility tends to decrease. When the volume average diameter exceeds 9 μm, the above-mentioned characteristics of the carrier cannot be sufficiently exhibited, and the effect of improving the reproducibility, gradation, and granularity of fine dots becomes poor. Therefore, by having the above-mentioned toner particle size distribution, even in repeated copying of a document having a large image area such as a photograph, a picture, a pamphlet, or the like having a density gradation, it can faithfully reproduce fine latent image dots. Can be expected.

[Image Forming Method] The electrostatic image developer as described above comprises a latent image forming step of forming a latent image on a latent image carrier,
A developing step of developing the latent image with a developer on a developer carrier, that is, a developer (two-component developer) in an electrophotographic method using a general two-component developer.
Can be used as With this configuration, even when a document having a large image area, such as a photograph or a painting, is continuously copied, the density reproducibility is stable and no toner spent in the developing machine.

[0086]

EXAMPLES Examples of the present invention will be described below.
The present invention is not limited to these examples. In the following description, unless otherwise specified.
All "parts" mean "parts by weight".

<Manufacture of Toner Particles> 95 parts of polyester resin 5 parts of Pigment Blue 15: 3

The above components were sufficiently premixed with a Henschel mixer, melt-kneaded with a twin-screw roll mill, cooled, pulverized finely with a jet mill, and classified twice with a wind-type classifier to obtain a volume average diameter. 4 μm at 6.5 μm
The toner particles (cyan toner) of 15% by number of toner particles having a particle diameter of m or less and 0.7% by volume of toner particles having a particle diameter of 16 μm or more were produced.

100 parts of the particles and BET as an external additive
Hydrophobic titanium oxide fine particles having a specific surface area of 100 m ² / g
5 parts with a Henschel mixer to form toner particles a
Was prepared.

<Manufacture of Carrier> -Manufacture of Carrier A- Perfluorooctylethyl acrylate / methacrylate copolymer, carbon black particles and crosslinked melamine resin particles are diluted with toluene and dispersed by a sand mill to form a resin coating layer. A coating solution was prepared, and the coating solution for forming a resin coating layer and ferrite particles were placed in a vacuum degassing type kneader, stirred at 120 ° C. for 30 minutes, and then depressurized to remove toluene. The carrier A was obtained by forming a resin coating layer on the substrate. The mixing ratio and details of each material are as follows.

100 parts of ferrite particles (specific surface area 1000 cm ² / g, core material electric resistance 10 ⁸ Ωcm) 10 parts of toluene Perfluorooctylethyl acrylate / methacrylate copolymer (copolymerization ratio 40/60, Mw = 50,000) 1.5 parts ・ Carbon black (VXC-72; manufactured by Cabot) 0.2 part ・ Crosslinked melamine resin (average particle size: 0.3 μm) 0.3 part

—Preparation of Carrier B— Perfluorooctylethyl acrylate / methacrylate copolymer, carbon black particles and crosslinked melamine resin particles were diluted with toluene and dispersed in a sand mill with the same material and composition ratio as carrier A. To prepare a coating solution for forming a resin coating layer, and put the coating solution for forming a resin coating layer and ferrite particles into a vacuum degassing kneader.
After stirring at 0 ° C. for 30 minutes, the toluene was removed under reduced pressure to form a resin coating layer on the ferrite particle surface,
Carrier B was obtained.

—Preparation of Carrier C— Perfluorooctylethyl acrylate / methacrylate copolymer, carbon black particles and crosslinked melamine resin particles were diluted with toluene and dispersed in a sand mill with the same material and composition ratio as carrier A. To prepare a coating solution for forming a resin coating layer, and put the coating solution for forming a resin coating layer and ferrite particles in a vacuum degassing kneader.
After stirring at 30 ° C. for 30 minutes, the toluene was removed under reduced pressure to form a resin coating layer on the ferrite particle surface,
Carrier C was obtained.

—Production of Carrier D— Perfluorooctylethyl acrylate / methacrylate copolymer, carbon black particles and crosslinked melamine resin particles were diluted with toluene and dispersed in a sand mill with the same material and composition ratio as carrier A. To prepare a coating solution for forming a resin coating layer, and put this coating solution for forming a resin coating layer and ferrite particles into a vacuum degassing type kneader.
After stirring at 30 ° C. for 30 minutes, the toluene was removed under reduced pressure to form a resin coating layer on the ferrite particle surface,
Carrier D was obtained.

—Production of Carrier E— Perfluorooctylethyl acrylate / methacrylate copolymer, carbon black particles and crosslinked melamine resin particles were diluted with toluene and dispersed in a sand mill with the same material and composition ratio as carrier A. To prepare a coating solution for forming a resin coating layer, and put the coating solution for forming a resin coating layer and ferrite particles into a vacuum degassing type kneader.
After stirring at 30 ° C. for 30 minutes, the toluene was removed under reduced pressure to form a resin coating layer on the ferrite particle surface,
Carrier E was obtained.

—Preparation of Carrier F— A perfluorooctylethyl acrylate / methacrylate copolymer and a styrene methacrylate copolymer were diluted with toluene and dispersed with a sand mill to prepare a coating solution for forming a resin coating layer. The coating solution for forming the resin coating layer and the ferrite particles are placed in a vacuum degassing kneader, stirred at 80 ° C. for 30 minutes, and then the toluene is removed under reduced pressure to form a resin coating layer on the surface of the ferrite particles. Thus, a carrier F was obtained. The mixing ratio and details of each material are as follows.

100 parts of ferrite particles (specific surface area: 1000 cm ² / g, core material electric resistance: 10 ⁸ Ωcm), 10 parts of toluene, perfluorooctylethyl acrylate / methacrylate copolymer (copolymerization ratio: 40/60 Mw = 5) 10,000 parts ・ Styrene methacrylate copolymer (copolymerization ratio 40/60 Mw = 70,000) 1.0 part

—Preparation of Carrier G— A perfluorooctylethyl acrylate / methacrylate copolymer and a styrene methacrylate copolymer were diluted with toluene and dispersed in a sand mill using the same material and composition ratio as the carrier F to obtain a resin. A coating solution for forming a coating layer was prepared, and the coating solution for forming a resin coating layer and ferrite particles were placed in a vacuum degassing type kneader, stirred at 60 ° C. for 30 minutes, and then depressurized to remove toluene. A film was formed on the surface of the ferrite particles to obtain a carrier G.

—Preparation of Carrier H— A resin prepared by diluting a perfluorooctylethyl acrylate / methacrylate copolymer and a styrene methacrylate copolymer with toluene with the same material and composition ratio as the carrier F and dispersing the diluted mixture in a sand mill. A coating solution for forming a coating layer was prepared, and the coating solution for forming a resin coating layer and ferrite particles were placed in a vacuum degassing type kneader, stirred at 40 ° C. for 30 minutes, and then depressurized to remove toluene. A resin coating layer was formed on the surface of the ferrite particles to obtain a carrier H.

-Carriers A-1 to A-12 and F-1
-Production of F-2-Carriers A and F were stirred under the conditions shown in Table 1 to obtain Carriers A-1 to A-12 and F-1 to F-2.

[0101]

[Table 1]

Each of the obtained carriers A, A-1 to A-1
2, the exposure amount of iron of B, C, D, E, F, F-1 to F-2, G, and H (the ratio of iron among all elements having an atomic number of 3 or more existing near the surface) It measured by the method and conditions of the specific example of the above-mentioned measuring method (made by JEOL Ltd., by JP-9000MX). The results are summarized in Table 2 below.

<Production of an electrostatic image developer> 10 parts of the toner particles a and 10 parts of each of the carriers A, A-1 to A-12,
B, C, D, E, F, F-1 to F-2, G, and H; 90 parts each were mixed, and this was mixed with Examples 1 to 14 and Comparative Examples 1 to 8 as shown in Table 2 below. Of the electrostatic image developer.

[0104]

[Table 2]

<Evaluation Test> The obtained electrostatic image developer was used in an electrophotographic copying machine (A-color 935, manufactured by Fuji Xerox Co., Ltd.) under a high temperature and high humidity environment (30 ° C., 90 ° C.).
RH%) and a low-temperature, low-humidity environment (10 ° C,
(15 RH%). Initial period under each environment (1st to 20th sheets, check for total number)
The image quality was evaluated at the time when the charge amount peaked (checked on the 3000th sheet) and the time when the durability was checked (checked on the 1,000,000th sheet). The evaluation criteria were as follows.

OK: Image quality is good and there is no problem. A: White spots occurred in the solid portion which are considered to be caused by carrier scattering. B: Fogging to the background occurred. Table 2 shows the evaluation results together with the iron exposure.

[0107]

[Table 3]

As is apparent from Table 3, it is understood that excellent image quality can be formed over a long period of time by using the developer comprising the carrier of the present invention. On the other hand, Comparative Examples 1 and 2, in which the exposure amount of iron on the carrier surface was small,
In Nos. 4, 5, and 7, the carrier surface structure was not sufficiently equilibrated, and whitening occurred on the copy due to carrier adhesion. Conversely, in Comparative Examples 3, 6, and 8, in which the amount of iron exposed on the carrier surface is too large, the charge amount is not sufficiently maintained.

[0109]

According to the present invention, it is possible to impart a stable charging property to the developer over time including the initial stage, and it is possible to prevent fogging and density reduction even after repeated copying.
Good halftone gradation and graininess of digital images,
A carrier for developing an electrostatic image capable of obtaining a clear image without an edge effect, particularly suppressing an initial change in image quality, a method of manufacturing the same, an electrostatic image developer using the carrier for developing an electrostatic image, and image formation A method can be provided.

Further, according to the present invention, even when a continuous copy of an original having a large image area such as a photograph or a picture is performed, the density reproducibility is stable and the toner image does not generate toner spent in the developing machine. It is possible to provide a developing carrier and a method for producing the same, and an electrostatic image developer and an image forming method using the electrostatic image developing carrier.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a developing device used for measuring electric resistance of core material particles.

FIG. 2 is a sectional view from the front of a kneader coater as a device for applying stirring energy.

FIG. 3 is a sectional view taken along line BB of the kneader coater of FIG.

FIG. 4 is a sectional view of the kneader coater of FIG. 2 taken along line CC.

FIG. 5 is a schematic sectional view of a planetary mixer as a device for applying stirring energy.

[Explanation of symbols]

 Reference Signs List 10 photoconductor (aluminum pipe) 12 developing housing 12A wall 14 developing sleeve 20, 50 stirring blade 22 power transmission means 23 transmission 24, 54 gear 25, 55 stirring container (stirring machine) 26, 56 lid

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuka Ishihara 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Kaori 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. (72 ) Inventor Yoshito Nakajima 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Hiroshi Nakazawa 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. 1600 Takematsu Fuji Xerox Co., Ltd. F-term (reference) 2H005 BA02 BA06 BA11 CB02 EA07 FA01

Claims (4)

[Claims] 1. An electrostatic image developing carrier comprising a resin coating layer formed on the surface of iron-containing core material particles, wherein all of the atomic number 3 or more existing near the surface of the electrostatic image developing carrier are present. Iron accounts for 0.25% of the elements
A carrier for developing an electrostatic image, wherein the carrier content is 1.0 atom%. 2. An aggregate of coated particles obtained by forming a resin coating layer on the surface of iron-containing core material particles is expressed by the following formula 1
A method for producing a carrier for developing an electrostatic image, characterized by adding stirring energy under the conditions represented by: 3.0 × 10 ⁹ ≦ 1/2 mv ² × t / M ≦ 3.8 × 10 ¹⁰ (Formula 1) In the above formula, t represents a stirring time [sec], and M represents a value of the coated particles existing in the stirrer. Represents the total weight of the aggregate [g]. Also, v is the shear rate between the stirring blade clearances [se
c ^-1 ], and is represented by the following formula 2, and m is the weight [g] of the aggregate of the coated particles existing between the stirring blade clearances.
And is represented by the following equation 3. v = πDN / h (Equation 2) m = πD × h × ρ × 10 ⁻³ (Equation 3) In the above Equations 2 and 3, π represents a pi, and D represents a diameter [mm] of a stirring blade. , N is the rotation speed of the stirring blade [times / sec]
c], h represents the gap [mm] between the tip of the stirring blade and the wall surface, and ρ represents the bulk density [g / cm ³ ] of the coated particles. 3. An electrostatic image developer comprising at least a toner and an electrostatic image developing carrier, wherein the electrostatic image developing carrier is the electrostatic image developing carrier according to claim 1. Electrostatic image developer. 4. An image forming method comprising: a latent image forming step of forming a latent image on a latent image carrier; and a developing step of developing the latent image with a developer on the developer carrier. An image forming method using the electrostatic image developer according to claim 3.