JPH09197721A - Electrostatic charge developing carrier and its production, developer and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obviate the occurrence of the image defects by carrier adhesion even in a high-speed development. SOLUTION: The carriers consist of a baked powder of raw material powder which is 0.1 to 10μm in number average primary particle diameter Dn and is 1.0 to 2.0 in the value of the ratio (Dv/Dn) of a volumetric average primary particle diameter Dv to Dn. The value of the saturation magnetization of the powder is 10 to 100emu/g. The image forming method has a stage for developing electrostatic latent image to sensitive image by a magnetic brush formed on a developing sleeve by a developer consisting of toners and the carriers. The value of the saturation magnetization of the carriers is 10 to 100emu/g and the magnetic force X (gauss) on the surface of the developing sleeve and the saturation magnetization Y (emu/g) of the carriers satisfy the condition (1) 300<=X<=1100 and condition (2) 0.1X-50<Y<0.1X+20.

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 for developing an electrostatic image in an electrophotographic method, an electrostatic recording method, an electrostatic printing method and the like, and a method for producing the carrier.
The present invention relates to a developer and an image forming method.

[0002]

2. Description of the Related Art At present, as an image forming method using an electrostatic image, a magnetic brush is formed by using a so-called two-component developer composed of toner and carrier.
A method of developing an electrostatic latent image formed on an electrostatic latent image carrier to make it visible is widely used. As a carrier that constitutes such a two-component developer, those composed of magnetic particles such as iron powder and ferrite are used, and a coating resin layer of an appropriate resin on the surface of such magnetic particles is further used. The resin-coated carrier formed is also used. According to such a resin-coated carrier, the coating resin layer can exert a suitable charging property and effectively prevent the generation of so-called spent toner in which a part of the toner is fused to the surface of the carrier particles. It is possible to obtain great durability for the developer.

Recently, it has been demanded to perform desired image formation at high speed, but in order to develop the electrostatic latent image formed on the electrostatic latent image carrier at high speed. In a so-called magnetic brush type developing device equipped with a developing sleeve having a magnet inside, it is necessary to rotate the developing sleeve at a high speed to increase the transport speed of the electrostatic image developer.

However, when the developing sleeve is rotated at a high speed in this manner, the rate of scattering of the developer is increased, and as a result, the scattered carrier adheres to the image on the electrostatic latent image bearing member. There is a possibility that a good visible image cannot be formed due to image loss caused by the carrier itself. In order to prevent the developer from scattering even when the developing sleeve is rotated at a high speed, it is effective to increase the magnetization of the carrier constituting the developer to improve the holding property by the developing sleeve. It has been found that the above carrier adhesion occurs when a developer containing a carrier having a low magnetization is used even in a ratio.

[0005]

As described above, in the conventional carrier, since the uniformity of the magnetization is not taken into consideration, there is a problem that image defects due to carrier adhesion easily occur in high speed development. is there. The present invention
The object of the present invention is to provide an electrostatic image developing carrier capable of obtaining an electrostatic image developer that does not cause image defects due to carrier adhesion even in high-speed development. To do.

Another object of the present invention is to provide a method for manufacturing a carrier which can surely and advantageously manufacture the carrier. Still another object of the present invention is to provide an electrostatic image developer using the carrier and an image forming method using the electrostatic image developer to obtain a good visible image. .

[0007]

The carrier for electrostatic image development according to the present invention has a number average primary particle diameter Dn of 0.1 to 10 .mu.m.
m, the ratio of the volume average primary particle diameter Dv to the number average primary particle diameter Dn (Dv / Dn) is 1.0 to 2.0, which is a sintered powder of the raw material powder, and the saturation magnetization is 10 to 100.
It is characterized by being emu / g. The electrostatic image developer of the present invention comprises the above carrier and toner.

In the method for producing a carrier for electrostatic image development of the present invention, the number average primary particle diameter Dn is 0.1 to 10 μm, and the ratio of the volume average primary particle diameter Dv to the number average primary particle diameter Dn (Dv / Dn). Of the raw material powder having a value of 1.0 to 2.0.

According to the image forming method of the present invention, the electrostatic image developer composed of toner and carrier is supplied to a developing device having a developing sleeve having a magnet inside, and the magnetic image formed on the developing sleeve is supplied. There is a step of visualizing the electrostatic latent image carried on the electrostatic latent image carrier by a brush, and the carrier has a saturation magnetization value of 10 to 100 emu / g,
The magnetic force on the surface of the developing sleeve by the magnet is X
(Gauss), and the saturation magnetization of the carrier is Y (emu / g), the following condition is satisfied. Condition (1) 300 ≦ X ≦ 1100 Condition (2) 0.1X−50 <Y <0.1X + 20

[0010]

In the carrier for electrostatic image development of the present invention, the magnetic particles constituting the carrier have a saturation magnetization within a specific range, which is obtained by firing a ferrite raw material powder satisfying a condition regarding a specific particle size. Since it is composed of certain magnetic particles, the proportion of carrier particles whose degree of magnetization is insufficient is extremely small, and the uniformity of magnetic properties is sufficiently high. As a result, by using the electrostatic image developer with such carrier and toner, the magnitude of the magnetic force is within a certain range, and the magnitude of the magnitude that satisfies the specific condition with the saturation magnetization of the carrier is obtained. The developing device equipped with a developing sleeve having a magnetic force surely prevents carrier scattering even in the case of high-speed development, and as a result, carrier particles adhere to the electrostatic latent image carrier. Image defects that occur can be sufficiently effectively prevented, and a good visible image can always be formed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

[Magnetic Particles of Carrier] In the present invention, the material of the carrier is preferably ferrite because a carrier having a high magnetic distribution uniformity can be obtained. The composition of ferrite is represented by the formula (X ₂ O) _a (Fe ₂ O ₃ ) _1-a or the formula (ZO) _a (Fe ₂ O ₃ ) _1-a , where the value of a is 0. 05 to 0.50, X is a monovalent metal element, Z is a divalent metal element, and Cu, Zn, C
It is selected from o, Ni, Li, Be, Mg and the like.

Specifically preferred is a metal element selected from the group of iron oxides represented by Fe ₂ O ₃ and the light metal group consisting of alkali metal or alkaline earth metal of Group IA or IIA of the periodic table. Is a light metal ferrite containing at least one component of the oxide (hereinafter referred to as "light metal oxide"). Therefore, it is preferable that X in the formula is at least one selected from lithium, potassium and rubidium, and Z is at least one selected from beryllium, magnesium and calcium.
In particular, a light metal ferrite containing LiO ₂ and / or MgO as a component is preferable.

The carrier made of such a light metal ferrite is light in weight because of its small specific gravity, and has a large durability and a long service life when used as a carrier.

In the ferrite constituting the carrier,
The ratio of the metal oxide component other than the above iron oxide is preferably 5 to 50 mol%, and particularly preferably 10 to 45 mol% with respect to the total metal oxides. When the proportion of the other metal oxide component exceeds 50 mol%, the relative proportion of the iron oxide component becomes small, so that it becomes difficult to obtain the magnetic characteristics required as a carrier,
It is difficult to form an excellent image because a good magnetic brush cannot be formed.

It is preferable that the ferrite constituting the carrier contains a phosphorus component, whereby the carrier has high mechanical strength. Specific examples of the substance that gives such a phosphorus component include, for example, yellow phosphorus,
Examples thereof include red phosphorus, white phosphorus, black phosphorus, purple phosphorus, metallic phosphorus and phosphorus oxide. The phosphorus component is preferably contained in a proportion of 2% by weight or less, and more preferably 0.01 to 1% by weight, based on the whole substance constituting the carrier. If this proportion exceeds 2% by weight, the carrier obtained may have poor magnetic properties.

The carrier of the present invention is a compound of an iron element such as an oxide of iron serving as a ferrite component and a compound of another metal element such as an oxide of another metal, which is oxidized by firing treatment. It can be produced by a method in which a material that produces a product is used as a raw material, a material having a specific particle size and a particle size distribution is used as a raw material powder, and this is calcined at an appropriate temperature.

As a raw material for producing a light metal oxide component, for example, a mineral containing a light metal element such as oxyacid salt such as calcium carbonate, magnesium carbonate, lithium carbonate and lithium sulfide, a halide and lithiacite, Others can be used. It is also possible to use two or more of these in combination.

To the raw material powder, a substance that serves as a component for adjusting the electrical characteristics or charging characteristics of the magnetic particles to be obtained, or a firing accelerator can be added. Specific examples of such additives include V ₂ O ₅ and As.
₂ O ₃ , Bi ₂ O ₃ , Sb ₂ O ₃ , PbO ₂ , CuO,
There are compounds of B ₂ O ₃ , SiO ₂ , and rare earth elements such as Cs and Nb, and compounds such as CuSO ₄ and CuCl ₂ . The addition amount of these is preferably 1% by weight or less.

In order to manufacture the carrier of the present invention, it is preferable to use the following method. (1) Separately or by mixing the raw materials used,
For example, the number average primary particle diameter Dn is crushed by a ball mill or the like so that the number average primary particle diameter Dn is 0.1 to 10 μm, preferably 0.5 to 5 μm, and the ratio (Dv) of the volume average primary particle diameter Dv to the number average primary particle diameter Dn. / Dn) value is 1.0 to
Prepare a raw material powder that is 2.0. The number average primary particle diameter can be determined by, for example, a particle diameter measuring device using a laser light scattering method. (2) A water-soluble polymer is added to the above-mentioned raw material powder to prepare a slurry by dispersing the raw material powder, and the slurry is spray-dried to disperse the raw material powder in the water-soluble polymer. The particles are bound by a substance to form particles. (3) The raw material powder for firing thus obtained is fired. The firing temperature for obtaining general ferrite is about 1150 to 1600 ° C.

In the present invention, the calcination treatment is carried out under the condition that an oxidizing factor is excluded, that is, in a reducing atmosphere.
It is preferable to carry out in a closed state. In order to realize a reducing atmosphere, a means for allowing a reducing agent to coexist in the firing system can be used. Here, as the reducing agent, for example, a dedicated reducing agent such as carbon black can be used. However, when the water-soluble polymer substance is used to prepare the raw material for firing as in the above-mentioned example, the water-soluble polymer substance burns in the firing treatment step to reduce the reducing action. Is demonstrated,
When the necessary reducing conditions are not realized even by the reducing action of the water-soluble polymer substance, another reducing agent may be added. When a reducing agent such as carbon black is used, it is preferable to add the reducing agent at the stage of preparing the slurry.

The carrier of the present invention has a saturation magnetization value (value at a temperature of 25 ° C.) of 10 to 100 emu / g.
It is necessary to be. The value of saturation magnetization is 10 emu /
If it is less than g, the coercive force of the carrier in the developing device will be small, and it will be difficult to effectively prevent the carrier from scattering. On the other hand, if it exceeds 100 emu / g, the developing device The ears of the magnetic brush formed on the sleeve may become hard, and a sweeping phenomenon may occur in which the toner once attached to the electrostatic latent image carrier is scavenged by the succeeding ears. The above-mentioned measurement of magnetic properties can be carried out, for example, by “Direct Current Magnetization Property Automatic Recording Device Model 3257-35” manufactured by Yokogawa Electric Corporation.

The magnetic particles forming the carrier preferably have an electric resistance value of 1 × 10 ⁷ to 1 × 10 ¹³ Ω · cm. When the electric resistance value is smaller than 1 × 10 ⁷ Ω · cm, charges are easily injected from the surface of the electrostatic latent image carrier to the carrier particles to cause carrier adhesion.
If it is greater than × 10 ¹³ Ω · cm, it becomes difficult to obtain a high-density image. The electrical resistance is measured by inserting a sample powder whose humidity has been adjusted under the normal temperature and normal humidity environment into a thickness of about 3 mm between two electrode plates under the normal temperature and normal humidity environment, and applying 100V.
It is possible to measure and calculate the current value after 30 seconds have passed after applying the DC voltage.

The magnetic particles forming the carrier preferably have an average particle size of 20 to 300 μm, and particularly 30.
It is preferably from 200 to 200 μm. Average particle size is 30μ
When it is smaller than m, the phenomenon of carrier adhesion to the electrostatic latent image bearing member is likely to occur, while when it is larger than 300 μm, the density of the magnetic brush formed on the developing sleeve becomes small, so that a good visible image is formed. Difficult to form. Here, the average particle diameter means a volume-based average particle diameter measured by a laser diffraction type particle size distribution measuring device “HELOS” (manufactured by Sympatech Co.) equipped with a wet disperser.

The above magnetic particles can be used as a carrier as they are, but those having a coating resin layer formed on the surface of the magnetic particles as core particles are preferably used as a carrier.

As the resin constituting the coating resin layer,
A known appropriate resin can be used. Specific examples thereof include olefin resins such as polyethylene, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymers, fluororesins such as fluorinated alkyl (meth) acrylate copolymers, and polyresins. Silicone resin such as methyl silicone, polydimethyl silicone, polyphenyl silicone,
Styrene resins such as polystyrene, polychlorostyrene, polymethylstyrene, polymethylmethacrylate,
Polymethyl acrylate, polypropyl acrylate,
Acrylic resin such as polylauryl acrylate, polylauryl methacrylate, polyacrylic acid, polymethacrylic acid, polybutyl methacrylate, polybutyl acrylate, styrene-acrylic copolymer resin, polyester resin, ethylene resin, rosin modified resin, polyamide Resin and others can be used. These may be used in combination. Of these, particularly preferred are olefin resins, silicone resins, and fluororesins.

The coating amount of the coating resin layer is preferably in the range of 0.01 to 15% by weight, more preferably 0.05 to 10% by weight, based on the magnetic particles.
If this ratio is too small, the film thickness of the coating resin layer becomes too small, so that part of the surface of the magnetic particles is exposed, and as a result, stable charging performance by the coating resin layer can be obtained. On the other hand, if it is too large, on the other hand, the film thickness of the coating resin layer becomes too large, so that the phenomenon that the coating resin layer peels off easily occurs.

As the method for forming the coating resin layer on the magnetic particles, the wet method is the dipping method, the spray drying method,
A fluidized bed coating method can be used. In the dry method, resin fine particles are used as a material for forming the resin phase for the coating resin layer, and the fine particles are attached to the magnetic particles by mechanical impact force to form a film. The dry mechanical impact method and the like can be mentioned.

A particularly preferred method for forming the coating resin layer is to carry a polymerization catalyst on the surface of the magnetic particles in advance and use this to polymerize a monomer such as ethylene on the surface of the magnetic particles. The method is a surface polymerization coating method for forming a polymer layer by the method described in JP-A-60-106808. According to this surface polymerization coating method,
Since the coating resin layer having extremely high adhesion to the surface of the magnetic particles is formed, the obtained carrier has stable charging characteristics and excellent durability.

Monomers used in this surface polymerization coating method include ethylene, propylene, butene, butadiene,
Aliphatic hydrocarbon-based monomers such as octene, cyclopentene, and cyclopentadiene are used. It is also possible to use other vinyl monomers. In particular, it is preferable to use ethylene as the monomer and form the coating resin layer made of polyethylene.

[Toner] The carrier composed of the magnetic particles is mixed with an appropriate toner to form a two-component developer. Here, the toner is not particularly limited, but a toner composed of colored particles containing at least a binder resin and a coloring material is used, and in particular, an inorganic fine powder is added to and mixed with the toner powder. Those that are preferred are.

The binder resin for the toner is not particularly limited, but known resins such as styrene-acrylic polymer and polyester resin can be preferably used. In addition to the binder resin, the toner particles may contain a fixing improving agent such as polypropylene, various known charge control agents, and other additives.

As the colorant used in the toner, for example, carbon black or nigrosine dye is used for the black toner, and the pigments required for the yellow, magenta and cyan toners are C.I. I. Pigment Blue 1
5: 3, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 6, C.I. I. Pigment Blue 6
8, C.I. I. Pigment Red 48-3, C.I. I. Pigment Red 122, C.I. I. Pigment Red 21
2, C.I. I. Pigment Red 57-1, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 8
1, C.I. I. Pigment Yellow 154 and the like can be preferably used.

Appropriate inorganic fine particles and / or organic fine particles can be added to and mixed with the toner powder. As the inorganic fine powder, silica fine powder whose surface is hydrophobized with a silane coupling agent, a titanium coupling agent, or the like, from the viewpoint of chargeability and fluidity.
Titania fine powder and the like are preferably used. The inorganic fine powder preferably has a number average primary particle diameter of 5 to 100 nm. As the organic fine particles, for example, polymethylmethacrylate having a number average primary particle diameter of 5 to 10 is used.
Those having a thickness of 0 nm are preferably used.

The electrostatic latent image provided with the above two-component developer for development may be one formed on any electrostatic latent image carrier, for example, a selenium photoconductor, an amorphous silicon photoconductor, A laminated organic photoconductor or the like is preferably used.

The above two-component developer is supplied to the electrostatic latent image on the electrostatic latent image carrier to a developing device of a magnetic brush system according to specific conditions to form a visible image. That characteristic is exhibited. Specifically, using a developing device equipped with a rotary developing sleeve having a fixed magnet inside,
The developer charged by stirring and mixing is supplied to the outer peripheral surface of the developing sleeve to form a thin layer, which is conveyed to the developing area where the developing sleeve faces the electrostatic latent image carrier through a gap, The magnetic brush of the developer formed by the action of the magnetic force of the magnet comes into contact with the surface of the electrostatic latent image carrier in the developing area, so that the electrostatic latent image carried on the electrostatic latent image carrier is brought into contact. According to the method, a developing method is used in which the toner adheres and the toner is visualized.

In this developing method, the magnetic force on the surface of the developing sleeve is X (Gauss) and the saturation magnetization of the carrier is Y.
When it is (emu / g), the following conditions (1) and (2) are both satisfied. Condition (1) 300 ≦ X ≦ 1100 Condition (2) 0.1X−50 <Y <0.1X + 20

When the value X of the magnetic force is less than 300 (Gauss), the holding force for the carrier on the developing sleeve becomes too small, so that carrier scattering cannot be effectively prevented, and 1100 (Gauss). If it exceeds, the holding power becomes too large and a good development result cannot be obtained. Further, when the value of Y is too small in relation to X, the holding property of the carrier is lowered, and the scattering of the carrier itself cannot be suppressed, while the value of Y is too large in relation to X. In some cases, the ears of the developing brush on the surface of the developing sleeve become hard, resulting in failure to obtain good developability.

In the above developing method, the thickness of the thin layer of the developer on the developing sleeve is preferably 0.1 to 8 mm, particularly 0.4 to 5 mm in the developing area. The distance between the developing sleeve and the electrostatic latent image carrier in the developing area is, for example, 0.15 to 7 mm, preferably 0.2.
４4 mm. In high-speed development, the linear velocity during development is 200 mm / sec or more, and the developing sleeve is
Usually, the peripheral speed is rotated at a speed of 200 to 3000 mm / sec.

[0039]

Hereinafter, embodiments of the present invention will be described.
The present invention is not limited to these examples. In addition, "part" shows a weight part.

[Production of Magnetic Particles] Fe ₂ O ₃ , LiO
₂ and MgO were used as raw materials, and each was pulverized by a wet pulverizer, and the pulverized product was classified in water using the difference in weight due to the difference in particle size, as shown in Table 1 below. In each of the four raw materials, the number average primary particle diameter Dn, the volume average primary particle diameter Dv, and the ratio of the volume average primary particle diameter Dv to the number average primary particle diameter Dn (Dv / Dn) are different. A powder was prepared. In the raw material powder for comparison, the ratio (Dv / Dn) of the volume average primary particle diameter Dv to the number average primary particle diameter Dn is out of the range of 1.0 to 2.0.

[0041]

[Table 1]

Each raw material powder was weighed according to the following Table 2 so that the ratio of Fe ₂ O ₃ was 64 mol%, LiO ₂ was 22 mol%, and MgO was 14 mol%.
0.5 wt% of red phosphorus was added to the total and mixed by a ball mill, and the resulting mixture was mixed with polyvinyl alcohol (PV
A slurry was prepared by adding and dispersing in water containing A). Then, this slurry was granulated and dried by a spray dryer to obtain a raw material powder for firing. The respective raw material powders for firing were put into a firing furnace filled with an inert gas, and subjected to firing treatment at a firing temperature shown in Table 2 in a closed atmosphere to obtain magnetic particles having a volume average particle diameter of 65 μm. . These are referred to as "magnetic particles 1" to "magnetic particles 6" and "comparative particles 1" and "comparative particles 2". When the saturation magnetization of these magnetic particles in a magnetic field of 1000 gauss was measured, they were all 64 emu / g.

[0043]

[Table 2]

[Production of Carrier] 500 ml of dehydrated hexane and 450 g of the dried magnetic particles described above were placed in an autoclave and stirred, and then 2.0 mmol of Ziegler-Natta catalyst was added and stirred. ,
A catalytic substance was supported on the surface of the magnetic particles. After that, the internal pressure of the autoclave was set to 6.0 kg / cm ² G, ethylene gas was continuously supplied at a temperature of 90 ° C., and the reaction was carried out for 45 minutes to polymerize ethylene on the surface of the magnetic particles, thereby producing a magnetic material. A carrier was produced in which a coating resin layer made of polyethylene was formed on the surface of the particles at a ratio of 5% by weight based on the magnetic particles.

[Production of Toner] 100 parts of styrene-acrylic copolymer, 8 parts of low molecular weight polypropylene and 8 parts of carbon black are mixed, melted, kneaded, pulverized and classified to obtain a toner powder, to which hydrophobic silica is added. By mixing 0.8 parts of fine powder, a toner having a volume average particle diameter of 8.7 μm was manufactured.

[Preparation of Developer] Each of the above carriers,
By mixing with toner, toner concentration is 6% by weight
Was prepared.

[Actual Copy Test] This is a modified machine of an electronic copying machine "U-BIX 3035" (manufactured by Konica Corporation) in which a laminated organic photoreceptor is mounted, and the size of the gap in the developing area is set to 0.
8 mm, the thickness of the thin layer of developer in the development area is 1.2
Using a developing device having a developing sleeve having a magnetic force value of 800 gauss in a contact type developing method of 800 mm, the developing device is filled with each of the above-mentioned developing agents in an environment of normal temperature and normal humidity. A live-action test was performed by forming the. Here, the peripheral speed of the developing sleeve is 510 m.
m / sec. Then, an A3 size solid black image was used as an original to form a copy image 10 times, and the number of carriers attached to the surface of the obtained solid black image was examined. Furthermore, from the relationship with the amount of developer charged to the developing device, 100 g of developer
The number of adhered carriers was calculated. Furthermore, the state of image defects due to carrier adhesion was visually determined. The results are as shown in Table 3.

[0048]

[Table 3]

From the results shown in Table 3, it is clear that the carrier of the present invention hardly causes carrier adhesion, does not cause image defects, and always forms a good visible image. On the other hand, it is understood that the carrier for adhesion is remarkable and the image defect is caused in the comparative carrier made of the magnetic particles made of the raw material powder which does not satisfy the conditions of the present invention.

[0050]

Industrial Applicability The carrier for electrostatic image development of the present invention has a specific saturation magnetization, which is obtained by firing a ferrite raw material powder that composes the magnetic material particles satisfying the conditions relating to a specific particle size. Since it is composed of magnetic particles in the range, the proportion of the carrier particles whose degree of magnetization is insufficient is extremely small, and the uniformity of magnetic characteristics is sufficiently high. As a result, by using the electrostatic image developer with such carrier and toner, the magnitude of the magnetic force is within a certain range, and the magnitude of the magnitude that satisfies the specific condition with the saturation magnetization of the carrier is obtained. By the developing device having the developing sleeve having magnetic force, the scattering of the carrier is surely prevented even in the case of high speed development,
As a result, it is possible to sufficiently effectively prevent an image defect caused by the carrier particles adhering to the electrostatic latent image carrier, and always form a good visible image.

Claims (5)

[Claims] 1. The number average primary particle diameter Dn is 0.1 to 10 μm.
m, the ratio of the volume average primary particle diameter Dv to the number average primary particle diameter Dn (Dv / Dn) is 1.0 to 2.0, which is a sintered powder of the raw material powder, and the saturation magnetization is 10 to 100.
An electrostatic image developing carrier characterized by having an emu / g. 2. The number average primary particle diameter Dn is 0.1 to 10 μm.
m, a step of firing the raw material powder having a ratio (Dv / Dn) of the volume average primary particle diameter Dv to the number average primary particle diameter Dn of 1.0 to 2.0 is included.
A method for producing the carrier for developing an electrostatic image according to item 1. 3. An electrostatic image developer comprising the carrier according to claim 1 and a toner. 4. An electrostatic image developer composed of toner and carrier is supplied to a developing device having a developing sleeve having a magnet inside, and an electrostatic latent image is formed by a magnetic brush formed on the developing sleeve. There is a step of visualizing an electrostatic latent image carried on a carrier, wherein the carrier has a saturation magnetization value of 10 to 100 emu /
g, and the magnetic force on the surface of the developing sleeve by the magnet is X.
(Gauss) and the saturation magnetization of the carrier is Y (emu / g), the following condition is satisfied: Condition (1) 300 ≦ X ≦ 1100 Condition (2) 0.1X−50 <Y <0.1X + 20 5. The image forming method according to claim 4, wherein the electrostatic image developer used is that according to claim 1.