JPH10288871A - Electrostatic charge image developer and image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developer and an image forming method capable of obtaining a good image even in an environment of high temperature and high humidity or low temperature and low humudity. SOLUTION: This electrostatic charge image developer comprising a toner, which is composed of at least a binder resin and a colorant and a quaternary ammonium salt represented by the formula, and a carrier comprising carrier grains each composed of a core made of a compound of (MO)x (Fe2 O3 )y , M being one of L1 , Mg, or Ca and each of x and y being a molar ratio, and a coating resin, for coating the core, containing a silane coupling agent. In the formula each of R<1> -R<4> is an optionally substituted 1-18C alkyl group and at least one of them is 8-18C alkyl group or an optionally substituted benzyl group; and A<-> is an anion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrostatic image developer and an image forming method using the same.

[0002]

2. Description of the Related Art Conventionally, a two-component developer composed of a carrier and a toner has been frequently used as an electrostatic image developer used in electrophotography and the like.

[0003] In recent years, coating carriers in which magnetic particles such as iron, magnetite, and ferrite are coated with a resin have become mainstream from the viewpoint of improving the durability and image quality of the carrier, particularly the reproducibility of fine lines. However, when an image is repeatedly formed, the coating resin is worn and peeled off, and the magnetic particles as the core are exposed on the carrier surface.

As a result, the charging effect of the carrier on the toner is significantly reduced, causing the occurrence of ground fog and the scattering of the toner in the machine. Further, a so-called toner spent phenomenon in which a part of the toner component adheres to the carrier surface occurs. Especially in continuous copying, the resin is easily worn and peeled off because a large shear force is applied to the toner and carrier,
In addition, the toner spent phenomenon is accelerated. It is the durability of the carrier that determines the durability of the two-component developer.

Accordingly, silicone resins have attracted attention as highly durable coating resins. Since the silicone resin has a three-dimensional cross-linked structure, the abrasion resistance is greatly improved, and since it is a low surface energy resin, the toner spent phenomenon is less likely to occur, and high durability is achieved.

[0006] Since a silicone resin-coated carrier generally has a low charge-imparting ability, it must impart chargeability to the toner side when used as an electrostatic charge image developer. Therefore, a method of adding a charge control agent to toner is known.

JP-A-63-289560, JP-A-64
JP-A-59238 proposes a developer comprising a silicone resin-coated carrier and a toner containing a nigrosine dye as a charge control agent, and JP-A-3-27052 discloses a developer comprising a silicone resin-coated carrier and a toner containing a quaternary ammonium salt. Developer has been proposed. However, when these developers are used in a high-temperature and high-humidity environment, the chargeability of the developers is remarkably reduced, and ground fogging occurs and toner is scattered in the machine. On the other hand, when used in a low-temperature and low-humidity environment, a charge-up phenomenon occurs, causing a significant reduction in concentration. That is, the dependence on the charging environment is increased.

Meanwhile, in recent electrophotographic copying machines, attention has been paid to the improvement of the durability of the photosensitive member, particularly the organic photosensitive member, as well as the improvement of the durability of the developer as a reduction of the total waste from the viewpoint of environmental protection and no pollution. ing.

As the organic photoreceptor, a so-called laminated type organic photoreceptor comprising a charge generation layer and a charge transport layer on a conductive support through an adhesive layer as necessary is often used. Since the charge transport layer is made of a resin containing a charge transport substance, abrasion occurs during use over time due to a process such as cleaning for removing toner remaining in a developing unit and transfer. Have problems with long-term use.

To solve this problem, Japanese Patent Laid-Open No.
JP-A-18667 discloses an organic photoreceptor having a coating layer in which hydrophobic silica is dispersed, and JP-A-57-30846 discloses a protective layer containing fine particles of a metal or metal oxide having an average particle size of 0.3 μm or less. Configuration, JP-A-1-20
Japanese Patent No. 5171 discloses a photoreceptor having a protective layer or the like containing an inorganic filler. However, any of these methods is a method of adding various fine particles to the surface layer of the photoreceptor to improve the abrasion resistance of the photoreceptor, and is intended to improve the durability of the photoreceptor by reducing the abrasion.

However, when such a highly durable photoreceptor is used, although the photoreceptor itself is less likely to be worn down, although the durability is improved due to the problem of wear, the photoreceptor surface has When foreign matter is attached, it is difficult to remove the foreign matter, so that it is impossible to prevent the problem caused by the attached matter. In the case of a conventional abradable photoreceptor, the surface of the photoreceptor is gradually polished, and as a result, a new surface state can be constantly maintained.

In particular, the adsorption of water or the like is likely to occur over a long period of use, and the adsorption of water leaks electric charges on the surface of the photoreceptor, causing a problem of image deletion. This phenomenon often occurs particularly in a high-temperature and high-humidity environment.

As described above, it is difficult to form a stable image over a long period of time by using an image forming method using a photosensitive member having a protective layer having a high durability and having a wear-resistant function on the surface.

Further, from the viewpoint of resource reuse, it is desired to use a so-called toner recycling system for reusing toner. The toner recycling system collects toner remaining on the photoconductor without being transferred by a cleaning device, and returns the collected toner to a developing device or a toner replenishing device for reuse. At this time, the collected toner is subjected to a large mechanical stress in the recycling pipe when transported to the developing device or the toner replenishing device, so that external additives existing on the toner surface are greatly embedded and the toner fluidity is reduced. And the toner is not uniformly mixed with the carrier, or the rising chargeability (initial chargeability) of the toner is greatly reduced, and toner scattering and ground fogging occur.

As a countermeasure, in order to improve the mixing property with the carrier in the developing device, the stirring speed of the screw type stirring member is increased, the number of stirring blades is increased, and the stirring path is lengthened. Measures such as extending the stirring time have been taken. However, in any case, since the shearing force on the carrier is increased, the durability of the carrier is significantly reduced, and at present, high durability of the developer cannot be achieved.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and specifically, to provide the following solutions.

A good image free from toner scattering and ground fogging can be obtained over a long period of use by preventing abrasion, peeling and spent of a coating resin, and a good image can be obtained under high temperature, high humidity and low temperature and low humidity. It is to provide a developer which can be used.

An object of the present invention is to provide an image forming method capable of forming a stable image over a long period of time, particularly, a stable image even under a high temperature and high humidity environment.

In a copying apparatus having a toner recycling system, there is provided an image forming method capable of preventing abrasion, peeling and spent of a coating resin and obtaining a good image free of toner scattering and fogging over a long period of use. I do.

[0020]

The object of the present invention is attained by adopting one of the following constitutions.

(1) In an electrostatic image developer comprising a toner and a carrier, the toner contains at least a binder resin, a colorant and a quaternary ammonium salt represented by the following general formula (1), and the carrier comprises a core. And a coating resin covering the core, and the core is (MO) _x (Fe
₂ O ₃ ) _{y wherein} M is any one of Li, Mg and Ca, x and y are molar ratios, and the coating resin is a silicone resin containing an aminosilane coupling agent. Electrostatic image developer.

[0022]

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[0023] (wherein, R ¹ to R ⁴ represents an alkyl group or a substituted or unsubstituted benzyl group having 1 to 18 carbon atoms substituted or unsubstituted, A ^-. Represents an anion provided that R ¹ ~
At least one of R ⁴ represents an alkyl group having 8 to 18 carbon atoms. (2) The electrostatic latent image on the photoreceptor is converted into a toner image using an electrostatic image developer composed of a toner and a carrier, and the toner image is transferred onto the supplied transfer material. In the image forming method for cleaning the remaining toner image, the toner constituting the toner image contains at least a binder resin, a colorant, and a quaternary ammonium salt represented by the general formula (1), and the carrier is The core comprises a core and a coating resin covering the core, and the core is (MO) _x (F
e ₂ O ₃ ) _{y wherein} M is any of Li, Mg and Ca, x and y are molar ratios, and the coating resin is a silicone resin containing an aminosilane coupling agent. An image forming method, wherein the body is obtained by sequentially coating a charge generation layer and a charge transport layer on a substrate, and further coating a charge transport layer thereon.

(3) The electrostatic latent image on the photoreceptor is converted into a toner image using an electrostatic image developer composed of a toner and a carrier, and the toner image is transferred to a supplied transfer material. In the image forming method for cleaning the toner image remaining on the toner image, the toner constituting the toner image contains at least a binder resin, a colorant, and a quaternary ammonium salt represented by the general formula (1). The carrier is composed of a core and a coating resin covering the core, and the core is (MO) _x (Fe ₂ O ₃ ) _y <where M is Li, Mg, Ca
Wherein x and y are molar ratios>, the coating resin is a silicone resin containing an aminosilane coupling agent, and the toner recovered in the cleaning step is returned to the developing step and used again for development. An image forming method.

One of the causes that the charge amount of the developer fluctuates depending on the environment is the influence of moisture. It is presumed that moisture is adsorbed or desorbed on the toner or carrier surface, thereby changing the charging sequence. Silicone resins are generally hydrophobic and hardly adsorb moisture. However, in the toner, inorganic fine particles such as silica fine particles which are externally added in order to obtain fluidity easily adsorb water, and the toner containing a charge controlling agent is easily affected by the water and the charging sequence is easily changed. Therefore, it is considered that the developer composed of the carrier and the toner greatly changes the positional relationship in the charging sequence between the two depending on the environment, and the environmental change of the charging property is increased.

The inventor of the present invention has made intensive studies and, as a result, has arrived at the invention as described above.

Although the reason why the constitution of the present invention is effective is not necessarily clear, the positively chargeable and relatively hydrophilic silicone resin is negatively charged and hydrophobic in the silicone resin. By containing an aminosilane coupling agent having a functional group, it became possible to adsorb moisture and change the charging sequence. The mechanism has not been sufficiently analyzed, but is estimated as follows.

In a high-temperature, high-humidity environment, moisture is adsorbed on the positively-chargeable amino compound, and the positively-chargeable property is reduced.
From the viewpoint of the entire carrier, the negative chargeability is improved. on the other hand,
Under a low-temperature and low-humidity environment, the positively chargeable aminosilane coupling agent is not affected by moisture, so that the positively chargeable aminosilane coupling agent is improved. When viewed from the whole carrier, the negative chargeability is reduced.
Therefore, the difference in charge amount between the high-temperature and high-humidity environment and the low-temperature and low-humidity environment is reduced. That is, the fluctuation of the charge amount due to the environment is reduced.

On the other hand, the size can be reduced by using the quaternary ammonium salt of the present invention as a charge control agent which does not easily change the charging sequence on the toner side.

Since the charge control agent of the present invention has a long-chain hydrocarbon component, it has good compatibility with the binder resin and is finely and uniformly dispersed in the binder resin. Therefore, the charge control agent is uniformly distributed to the toner particles. Further, the charge control agent on the surface of the toner particles is also finely and uniformly present. Therefore, the influence of the adsorbed moisture is reduced, and the change of the charging sequence can be suppressed.

By combining the carrier and the toner of the present invention, the positional relationship of the charging sequence depending on the environment can be kept constant, and the environmental fluctuation of the charging amount can be reduced.

Further, the present inventor has proposed an electrostatic latent image on a photoreceptor in which a charge generating layer and a charge transporting layer are sequentially coated on a substrate and further provided with a charge transporting layer, comprising a toner and a carrier. In an image forming method of forming a toner image using a developer, transferring the toner image to a supplied transfer material, and then cleaning the toner image remaining on the photoreceptor, an image that is stable for a long time, particularly It has made it possible to form a stable image even under a high temperature and high humidity environment.

That is, the present inventors have conducted intensive studies on a method for preventing the influence of water adsorbed on the surface of the photoreceptor, and as a result, they have found that this configuration can solve these problems. Although the reason for this is not clear, when developing the photoconductor, not only the toner but also the carrier of the two-component developer contacts the photoconductor. It is presumed that by controlling the hardness of the carrier, the carrier itself exerts a polishing effect, finely polishes the photoreceptor, and as a result, has an effect of removing water adhering or adsorbed to the photoreceptor. The present invention is particularly effective in an image forming method in which a developer contacts a photosensitive member.

An appropriate carrier hardness can be obtained by including an aminosilane coupling agent in a silicone resin.
The adhesiveness between the silicone resin and the core is improved, and even during long-term use, a suitable polishing effect can be maintained without abrasion and peeling of the resin.

Further, the present inventor has made the electrostatic latent image on the photoreceptor into a toner image using a developer comprising a toner and a carrier, transfers the toner image to a supplied transfer material, and thereafter, exposes the photosensitive image to a photosensitive material. The toner image remaining on the body is cleaned, and the toner recovered in the cleaning process is returned to the developing process, and in the image forming method used for development again, wear, peeling and spent of the coating resin of the carrier used are prevented. As a result, an image forming method capable of repeatedly obtaining a good image without toner scattering and background fogging over the copying operation has been made possible.

The carrier particles are subjected to mechanical shearing force by a stirring member such as a screw type in a developing device and mixed in order to impart a predetermined charge amount to the toner. that time,
Stress is applied between the stirring member and the carrier, and the repetition causes peeling of the coating resin, abrasion, and spent phenomenon from the toner. Therefore, in order to prevent these phenomena, coating a resin containing an aminosilane coupling agent in a silicone resin and lowering the specific gravity of the magnetic particles, which are the cores of the carrier, reduce stress on the coating resin. It has become clear that this can be achieved.

The specific gravity of the core is reduced by (MO) _x (Fe
₂ O ₃ ) _y . Here, M is any of Li, Mg, and Ca, and two or more kinds may be mixed. X and y are molar ratios.

Containing at least one oxide of Fe ₂ O ₃ and an element selected from the group consisting of low-density elements belonging to groups IA and IIA of the periodic table, that is, elements having a density of 2.0 g / cm ³ or less; When these components are mutually dissolved, appropriate magnetic properties and low specific gravity can be obtained.

Further, when the external additive is embedded, the fluidity is remarkably reduced, and the charge control agent is represented by the following general formula (1) in order to stabilize the toner in which the rising charge property becomes unstable. A quaternary ammonium salt is added to the toner.

[0040]

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[0041] (wherein, R ¹ to R ⁴ represents an alkyl group or a substituted or unsubstituted benzyl group having 1 to 18 carbon atoms substituted or unsubstituted, A ^-. Represents an anion provided that R ¹ ~
At least one of R ⁴ represents an alkyl group having 8 to 18 carbon atoms. Specific examples of the compound include the following.

[0042]

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[0043]

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The compounds, image forming techniques and the like according to the present invention will be further described.

1. Composition of carrier Fe ₂ O ₃ and periodic table IA, II
Group A low-density element, that is, an element having a density of 2.0 g / cm ³ or less, containing at least one oxide of an element selected from the light metal group consisting of Li, Mg, and Ca, and these components are mutually dissolved. By doing so, appropriate magnetic properties and low specific gravity can be obtained. Particularly preferred are Li ₂ O. The low specific gravity mentioned here is 4.9 or less,
Preferably it is 4.7 or less. The specific gravity was measured by a high-precision automatic volume meter (VM-100, manufactured by S-Tech Co., Ltd.) based on a gas phase displacement method.

The light metal oxide is preferably present in a molar ratio of 5 to 50 mol%, more preferably 10 to 45 mol%, based on the total amount of the carrier composition.
Molar% is preferred. When the content of the light metal oxide is 5 mol% or more, the specific gravity is reduced. On the other hand, when the content of the light metal oxide is 50 mol% or less, magnetic characteristics necessary for accurately developing the electrostatic latent image formed on the photoconductor are obtained. Can be

The light metal oxide constituting the composition of the carrier does not necessarily have to be an oxide at the time of the raw material, but may be an oxide after sintering. For example, there are oxyacid salts such as calcium carbonate, magnesium carbonate, lithium carbonate and lithium sulfate, halides, and minerals mainly composed of light metal (lithium) such as lithiachite.

It is preferable to add a P compound. The addition improves the strength of the carrier. There are many unclear points about this phenomenon, but it is considered as follows. By adding the P compound, the crystallization of the carrier grains is promoted, and the strength of the carrier is improved in order to realize uniform growth.

Further, the content of Fe ₂ O ₃ and other components other than the oxide component of the light metal group and the P compound, for example, components such as a sintering accelerator and a grain size controlling agent should be 3% by weight or less. Thereby, the effect can be exhibited without adversely affecting the magnetic characteristics and the reduction in specific gravity.

The P compound added to improve the strength of the carrier includes, for example, yellow phosphorus, red phosphorus, white phosphorus, black phosphorus, purple phosphorus, metal phosphorus, and phosphorus oxide. The P compound is preferably at most 2% by weight, particularly preferably at most 1% by weight, based on the total amount of the carrier composition.

Other components excluding Fe ₂ O ₃ and the components of the group include components for controlling the electric resistance and charge amount of the carrier, or V ₂ O ₅ , As as a sintering accelerator.
₂ O ₃ , Bi ₂ O ₃ , Sb ₂ O ₃ , PbO ₂ , CuO, B
_{2 0 3, SiO 2, Cs} , rare earth compound such as Nb, CuS
O ₄ , CuCl ₂ and the like.

The core of the carrier can be manufactured by a manufacturing method such as a sintering method or an atomizing method, and can be obtained by mixing and sintering two or more kinds of fine powders as necessary.

In order to accurately develop an electrostatic latent image formed on a photoreceptor by taking such a composition form, 1000
(Oe) (Oersted) magnetization intensity (σ1
k) is preferably from 35 to 100 (emu / g), and more preferably from 45 to 80 (emu / g).

The holding power is preferably 100 (Oe) or less, more preferably 50 (Oe) or less.

The magnetic characteristics are measured by a DC magnetization characteristics automatic recording device (3257-35, manufactured by Yokogawa Electric Corporation).

The electric resistance of the magnetic particles as the core is 10
^It is preferably from ⁷ to 10 ¹³ (Ω · cm). 10 ⁷ (Ωcm)
If the particle diameter is smaller than the above range, carrier adhesion due to charge injection from the photoreceptor surface to carrier particles is likely to occur, and
^When it is larger than ¹³ (Ω · cm), it is difficult to obtain a high-density image. The electric resistance is measured in a room temperature and normal humidity environment, and a carrier conditioned at room temperature and normal humidity is applied to two electrodes by a thickness of about 3 (m).
m), a DC voltage of 100 (V) is applied, and the current value is measured and calculated.

The average particle size of the carrier particles is from 20 to 300.
(Μm) is preferable, and more preferably 30 to 200 μm.
(Μm). If it is less than 30 (μm), carrier adhesion to the photoconductor is likely to occur. If it is larger than 300 (μm), the developing brush on the developing sleeve becomes coarse and a good image cannot be obtained. The average particle size of the carrier is a volume-based average particle size measured by a laser diffraction type particle size distribution analyzer “HELOS” (manufactured by Sympatech) equipped with a wet disperser.

The silicone resin that can be used in the present invention is an aggregate of segments represented by the following general formulas (I) and (II).

[0059]

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R ^{5 to} R ⁸ each represent a methyl group, an ethyl group,
Represents a hydrocarbon group selected from a phenyl group and a vinyl group.
A methyl group is particularly preferable from the viewpoint of adhesiveness and hardness. Further, modified types such as alkyd-modified, acrylic-modified, polyester-modified, phenol-modified, melamine-modified, and urethane-modified may be used.

The ratio of the general formulas (I) and (II) of the segment is preferably (I) / (II) = 0/100 to 70/30,
More preferred is 0/100 to 50/50.

When (I) / (II)> 70/30, the hardness is reduced due to the large amount of linear components.

The aminosilane coupling agent used in the present invention is not particularly limited, but the following can be used.

Γ-aminopropyltrimethoxysilane,
γ-aminopropyltriethoxysilane, γ-aminoethyl-aminopropyltrimethoxysilane, methyl-γ
-Aminopropyldimethoxysilane, methyl-γ-aminoethylaminopropyldimethoxysilane, γ-dimethylamino-propyltrimethoxysilane, γ-anilinopropyltrimethoxysilane, γ-morpholinopropyltrimethoxysilane, N, N′-bis (3-Trimethoxysilyl) ethylenediamine and partial condensates thereof can be used. Further, two or more aminosilane coupling agents may be used in combination.

The amount of the aminosilane coupling agent added is 0.01 to 100 parts by weight of the solid content of the silicone resin.
To 8 parts by weight, preferably 0.1 to 5 parts by weight.

Other additives may be added to the silicone resin of the present invention. For example, as the cross-linking agent, generally known low-molecular-weight silane compounds such as dealcohol-type, deacetic acid-type, deoxime-type, deamide-type, deaminoxy-type, and deacetone-type can be used.

As curing catalysts, Zn, Sn, Fe, P
Metal soaps such as b, Co, Ni, Al and Zr, chelate compounds, organic acids such as oxalic acid and acetic acid, and bases such as amines can be used. The addition amount of these additives is preferably 0.01 to 5 parts by weight based on 100 parts by weight of the solid content of the silicone resin.

Solvents used for coating include toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone and the like.

The silicone resin coating amount in the resin-coated carrier is 0.01 to 10% by weight based on the carrier core.
And more preferably 0.1 to 5% by weight. If the silicone resin coating amount is less than 0.01% by weight, a uniform coating layer cannot be formed on the core surface. On the other hand, if it exceeds 10% by weight, granulation of the carrier particles occurs, the fluidity decreases, and the mixing property with the toner decreases.

As a method of forming a coating layer on the carrier core, a silicone resin is dissolved in a solvent,
Apply to the core surface by immersion method, spray dry method, etc.
The solvent is removed by drying. Thereafter, baking is performed. The baking temperature is 150 to 300 ° C, preferably 170 to 280 ° C.

2. Structure of Photoconductor In the present invention, the photoconductor is a photosensitive layer in which a charge generation layer and a charge transport layer are laminated on a conductive substrate surface via an undercoat layer as necessary, or a charge generation material and a charge transport material are mixed. Is formed, and a charge transport layer is further formed on the surface thereof. In this case, a separate layer may not be formed, and a method of forming a fine particle layer on the surface by dispersing fine particles throughout the photoconductor layer may be used.

As a conductive substrate, a metal plate such as aluminum, stainless steel, iron, or the like, or a flexible support such as paper or plastic film, is provided with a metal layer such as aluminum, palladium, or gold by lamination or vapor deposition. Examples thereof include those obtained by applying or depositing a layer containing a conductive compound such as a conductive polymer, indium oxide, or tin oxide on the surface of a flexible support such as paper or a plastic film.

The undercoat layer used if necessary includes casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, polyamides (nylon 6, nylon 66, alkoxymethylated Nylon, etc.), polyurethane, gelatin, aluminum oxide and the like are used. The thickness of the undercoat layer is preferably from 0.1 to 10 μm, particularly preferably from 0.1 to 5 μm.

The charge generation layer is a layer containing a charge generation material, and is not particularly limited. Examples of the charge generation material include phthalocyanine pigments, polycyclic quinone pigments, azo pigments, perylene pigments, indigo Pigments, quinacridone pigments, azurenium pigments, squarylium dyes, cyanine dyes, pyrylium dyes, thiopyrylium dyes, triphenylmethane dyes, styryl dyes, and the like can be used, and these are formed alone or dispersed in a resin. The resin used here is styrene-
Acrylic resin, bisphenol A type polycarbonate,
Bisphenol Z-type polycarbonate, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, styrene resin, polyvinyl acetate, styrene-butadiene resin, vinylidene chloride-acrylonitrile resin, vinyl chloride-vinyl acetate resin, vinyl chloride-vinyl acetate -Maleic anhydride resin, silicone resin,
Examples include silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin, and the like.

The charge transporting layer is a layer containing a charge transporting substance and is not particularly limited as a charge transporting substance. Examples thereof include oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, and triazole derivatives. , Imidazole derivatives, imidazolone derivatives, imidazoline derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, benzidine compounds, pyrazoline derivatives, stilbene compounds, amine derivatives, oxazolone derivatives, benzothiazole derivatives, benzimidazole derivatives, quinazoline derivatives Benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, poly-N-vinylcarbazoles, poly-1-vinylpyrenes, poly-9-vinylant Mosses and the like. These are formed singly or in combination and dispersed or dissolved in a resin. The resin used here is styrene-
Acrylic resin, bisphenol A type polycarbonate,
Bisphenol Z-type polycarbonate, polyester resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, styrene resin, polyvinyl acetate, styrene-butadiene resin, vinylidene chloride-acrylonitrile resin, vinyl chloride-vinyl acetate resin, vinyl chloride-vinyl acetate -Maleic anhydride resin, silicone resin,
Examples include silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin, and the like. The thickness of the charge transport layer is 5 to 50 μm, preferably 10 to 40 μm.
It is.

In the case of a photosensitive layer composed of a mixture of a charge transport material and a charge generation material, the charge transport material and the charge generation material are appropriately mixed and dispersed in the resin described above. It is obtained by forming a layer later. in this case,
The thickness of the layer is 5 to 50 μm, preferably 10 to 40 μm.

When the surface layer is formed, the constituent resin is not particularly limited. For example, styrene-acrylic resin, bisphenol A type polycarbonate, bisphenol Z type polycarbonate, polyester resin, acrylic resin, poly Vinyl chloride resin, polyvinylidene chloride resin, styrene resin, polyvinyl acetate, styrene-butadiene resin, vinylidene chloride-acrylonitrile resin, vinyl chloride-vinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone alkyd resin And phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin and the like. Fine particles may be contained in these resins. The fine particles may be either inorganic fine particles or organic fine particles. The inorganic fine particles are not particularly limited, but those having a Mohs hardness of 5 or more are preferable. Specifically, oxides such as titanium oxide, silica, zirconium oxide and alumina; nitrides such as carbon nitride, aluminum nitride and silicon nitride; carbides such as silicon carbide; titanate compounds such as strontium titanate and barium titanate And so on.

As the organic fine particles, crosslinked organic fine particles are particularly preferable. The crosslinked organic fine particles are organic fine particles in which an insoluble content in a solvent is 30% or more. Specifically, styrene, methylstyrene, α-methylstyrene,
Condensed organic fine particles such as olefins such as ethyl methacrylate, n-butyl methacrylate, methyl acrylate, ethyl acrylate, ethylene, propylene and isobutylene, vinyl chloride, vinylidene chloride, crosslinked polyesters and crosslinked silicone resins. I can give it.

These fine particles have a number average primary particle size of 0.1.
It is preferably from 1 to 5 μm. More preferably, 0.
05 to 2 μm. The content of the fine particles in these resins is 100 parts of the resin (unless otherwise specified,
“Parts” means “parts by weight”).
0 parts, preferably 0.1 to 100 parts. When the amount is less than 0.05 part, the amount of the fine particles is too small, and the effect of improving the hardness is not exhibited. When the amount exceeds 200 parts, the hardness is improved, but the amount of the fine particles is too large in the exposure. Light scattering occurs and causes image defects.

Further, in the present invention, the surface layer is 0.2
10 to 10 μm, preferably 0.4 to 5 μm.

In the present invention, the surface layer preferably contains a charge transporting substance. That is, since a specific surface layer is not formed by containing the charge transport material, the charge is uniformly transported, and the charge distribution according to the image can be stably formed. The content ratio of the charge transport material in the surface layer is 30 to 300 parts, preferably 50 to 200 parts, per 100 parts of the resin constituting the protective layer.

In the present invention, in the structure having a plurality of charge transporting layers, the weight average molecular weight of the resin for forming the outermost charge transporting layer is less than the weight of the resin forming the other charge transporting layers. It is preferably larger than the average molecular weight. In this case, the aforementioned fine particles may be contained,
Further, it may not contain fine particles.

The weight average molecular weight of this resin is usually 1 × 1
0 ⁴ are of to 1 × 10 ^6, the ratio of the molecular weight of the resin (Mw2) that constitute the molecular weight of the resin contained in the charge transport layer constituting the surface and (Mw1) Other charge transport layer (Mw
(1 / Mw2) is preferably 1.5 or more. The resin contained in the charge transport layer constituting the outermost layer preferably has a weight average molecular weight of 5 × 10 ⁴ to 1 × 10 ⁶ .

The weight average molecular weight is measured by a molecular weight distribution of a chromatogram obtained by gel permeation chromatography (GPC) using a tetrahydrofuran (THF) -soluble component of the resin in THF as a solvent.

In the measurement, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the count number.

3. Image Forming Method When forming a toner image using a two-component developer composed of a toner and a carrier, in developing the toner after forming the latent image, in order to obtain a sufficient image density and a faithful and clear image without disturbance to the document This depends on the temporal and spatial uniform supply of the developer to the developing site, the latent image charge holding stability of the latent image carrier (photoconductor), and the properties of the developer.

The supply of the developer to the developing site is generally performed by using a developing sleeve containing a group of magnets for forming a magnetic field.
When only the sleeve rotates, the rotation is performed by, for example, rotating the magnet group and the sleeve in the same or opposite directions. In order to further exert the effect in the present invention, it is preferable that the surface of the photoconductor is in contact with the developer conveyed to the developing nip (contact development). And uniform blade cleaning becomes possible.

For example, as a specific configuration when the magnet group is fixed and the sleeve rotates, the gap between the photosensitive member and the developing sleeve is 0.1 to 2.0 mm, preferably 0.3 to 1.5 mm.
mm. Also, the gap between the spike regulating member and the sleeve is 0.05 to 1.8 mm, preferably 0.2 to 1.4 m.
m.

FIG. 1 is a schematic sectional view of an image forming apparatus which can be used for explaining the image forming method of the present invention. Around a photoconductor 20 having a photoconductive photosensitive layer, a band electrode 21,
Developing mechanism 22, transfer separation pole 23, cleaning mechanism 2
4. The static elimination lamp 25 is provided. The recording material from the paper feeding mechanism 26 is conveyed by a conveying mechanism 27, and after the toner image is transferred by the transfer / separation pole 23, the fixing mechanism 28
To form an image. Photoreceptor 2 after transfer
The toner remaining on the surface 0 is scraped and removed by the cleaning mechanism 24. The collected toner is preferably returned to the developing mechanism 22 again by a recycling mechanism such as 29 and reused.

The developer of the present invention is transported to a development area by a developer transport carrier, and the electrostatic latent image on the image carrier is developed by the developer to form an unfixed toner image. As a developing method, a contact magnetic brush developing method is desirable.

In this method, as shown in a schematic sectional view in FIG. 2, a magnetic brush of a developer having a higher height than a gap in a developing area is formed on a developer carrying carrier (developing sleeve) 31. While the brush is being conveyed to the developing area and the electrostatic latent image on the photoconductor 20 is rubbed, the toner in the magnetic brush is adhered to the electrostatic latent image to perform development. In addition, 32 is a main stirring roller, 33 is an auxiliary stirring roller, 34 is a toner conveying screw, 35 is a spike regulating plate, and 36 is a doctor blade.

[0092] 4. Toner recycling system The toner collected by cleaning is returned to the developing mechanism by an appropriate recycling system and reused. FIG. 3 is a schematic sectional view illustrating an example of the recycling system. 20 is a photoreceptor, 22 is a developing mechanism, 24 is a cleaning mechanism, 29 is a recycle mechanism, 41 is a magnetic brush mechanism, 42 is a toner receiving and distributing mechanism, 43 is a screw conveyor, 44 is a first screw, and 45 is a second screw. is there. In this example, the first screw 44 and the second screw 45 supply toner from the screw conveyor 43 to the toner receiving and distributing mechanism 42.

That is, the first screw 44 and the second
Each of the screws 45 has a rotating shaft inside and a blade provided in a spiral shape along the rotating shaft. In the first screw 44, the toner sent by the screw conveyor 43 is rotated by the rotation of the rotating shaft. The blades are sequentially pushed up and sent to the second screw 45,
In the screw 45, the toner is supplied to the toner receiving and distributing mechanism 42 to which the toner is sequentially fed in the horizontal direction according to the same principle as the first screw 44, and the collected toner is again developed into the electrostatic latent image on the photoconductor 20. To be served.

5. Toner used in the present invention In the present invention, the amount of the colorant added to the toner is preferably 2 to 20 parts by weight, more preferably 4 to 15 parts by weight based on 100 parts by weight of the binder resin.

The binder resin used in the toner of the present invention is not particularly limited, and various conventionally known resins can be used. For example, a styrene resin, an acrylic resin, a styrene-acryl resin, a polyester resin, and the like can be given.

Colorants used in the toner of the present invention include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, Dupont oil red, orient oil red, quinoline yellow, methylene blue chloride, and phthalocyanine. Blue, malachite green oxalate, lamp black, rose bengal and the like.

The toner of the present invention may contain a release agent, if necessary. As the release agent, any of the conventionally used release agents can be used. Specifically, low molecular weight polypropylene, low molecular weight polyethylene, ethylene-
Examples include olefins such as propylene copolymer, microcrystalline wax, carnauba wax, sasol wax, and paraffin wax. The release agent is preferably added in an amount of 1 to 10 parts by weight, more preferably 1 to 6 parts by weight, based on 100 parts by weight of the binder resin.

The method for producing the toner is not particularly limited, but a typical toner of the present invention is obtained by dry-mixing raw materials in advance, and then melt-kneading, pulverizing, and classifying. Examples of the method of dry-mixing the raw materials include a method using a Henschel mixer, a V-type mixer, a Loedige mixer, a Nauter mixer, a W cone mixer, a vibratory mill, a turbuler, and the like.

Further, inorganic fine particles may be added to the toner of the present invention from the viewpoint of imparting fluidity. As the inorganic fine particles, inorganic oxide particles such as silica, titania, and alumina are preferable, and these inorganic fine particles may be subjected to a hydrophobic treatment with a silane coupling agent, a titanium coupling agent, or the like. Above all, the addition of hydrophobic silica is particularly preferred, and the number average particle diameter of the primary particles of the hydrophobic silica fine particles is preferably in the range of 5 to 300 nm. Further, the addition ratio of the hydrophobic silica fine particles is preferably in the range of 0.1 to 2 parts by weight based on the toner.

[0100]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

[0102] <Example> 22 mol% of Li ₂ O ₃ <Preparation 1 of core>, Fe ₂ 0 ₃ 2 hours pulverized with a wet ball mill to 78 mol%, and after mixed dry and held for 2 hours at 900 ° C. Thus, it is calcined. This was ground by a ball mill for 3 hours to form a slurry. A dispersant and a binder were added, and the mixture was granulated and dried by a spray drier, and then main-baked at 1200 ° C. for 3 hours to obtain ferrite core particles 1 having a volume average particle diameter of 60 μm.

<Production of core 2> 25 mol of Li ₂ CO ₃
%, Mg (OH) 5 mol%, Fe ₂ O ₃ 70 mol
%, Ferrite core particles 2 having a volume average particle diameter of 70 μm were obtained in the same manner as in Carrier Production 1.

<Core Production 3> 15 mol% of CuO
Except that ZnO was 16 mol% and Fe ₂ O ₃ was 69 mol%, the volume average particle diameter was 70
μm ferrite core particles 3 were obtained.

<Production 1 of Carrier> A silicone resin 1 containing a segment (R / R = 2/98) in which R ^{5 to} R ⁸ are CH ₃ in the general formulas (I) and (II) 100 parts by weight (solid content: 50%) and 2 parts by weight of γ-aminopropyltrimethoxysilane were added to a toluene solvent, and then 0.5% by weight was coated on the ferrite core particles 1 using a fluidized bed. Baking was performed at 3 ° C. for 3 hours to obtain Carrier 1.

<Manufacture of Carrier 2> 100 parts by weight of the silicone resin 1 (50% solid content) shown in Preparation of Carrier 1 and 3 parts by weight of methyl-γ-aminopropyldimethoxysilane were added to a toluene solvent, and then, The ferrite core particles 1 were coated with 0.8% by weight using a floor, and baked at 200 ° C. for 3 hours to obtain Carrier 2.

<Preparation of Carrier 3> 100 parts by weight of the silicone resin 1 (50% solid content) and 1 part by weight of γ-aminopropyltriethoxysilane shown in Preparation of Carrier 1 were added to a toluene solvent, and then added to a fluidized bed. Was coated on the ferrite core particles 2 using 0.8% by weight, and baked at 200 ° C. for 3 hours to obtain Carrier 3.

<Preparation of Carrier 4> 100 parts by weight of the silicone resin 1 (50% solid content) and 2 parts by weight of γ-aminopropyltrimethoxysilane shown in Preparation 1 of Carrier were added to a toluene solvent, and then added to a fluidized bed. Was applied to the ferrite core particles 3 by 1.0% by weight, and baked at 190 ° C. for 3 hours to obtain a carrier 4.

<Preparation of Carrier 5> After 100 parts by weight of the silicone resin 1 (solid content 50%) shown in Preparation 1 of Carrier was added to a toluene solvent, no aminosilane coupling agent was used, and a fluidized bed was used. 0.8% by weight to ferrite core particles 1
Baking was performed at 0 ° C. for 3 hours to obtain Carrier 5.

(Production of Toner) A mixture having the composition shown in Table 1 was mixed, melt-kneaded, pulverized and classified to obtain a volume average particle size of 8.5 μm
Of colored particles 1 to 5 were prepared.

[0110]

Embedded image

[0111]

[Table 1]

To the above-mentioned colored particles 1 to 5, 0.8 (% by weight) of hydrophobic silica fine particles was added to 100 parts by weight, and mixed with a high-speed stirrer to obtain toners 1 to 5.

(Preparation of Developer) The toner and carrier were combined as shown in Table 2 to prepare a toner having a toner content of 4.0% by weight, and Examples 1 to 6 and Comparative Examples 1 to 4 were prepared. Obtained.

[0114]

[Table 2]

(Preparation of Photoreceptor) A 0.3 μm thick undercoat layer made of a polyamide resin was provided on an aluminum drum having a diameter of 80 mm. Then, a liquid mixture consisting of 10 parts by weight of polyvinyl butyral and 1600 parts by weight of methyl ethyl ketone with respect to 30 parts by weight of the perylene compound as a charge generating substance is prepared, and the charge generating substance is dispersed, and then coated on the undercoat layer. And dried to a thickness of 0.3 μm
Was formed. Next, a solution was prepared by mixing 500 parts by weight of a styryl compound as a charge transport material, 600 parts by weight of a bisphenol Z-type polycarbonate resin (Mw = 8 × 10 ⁴ ), and 3000 parts by weight of dichloromethane, and coated on the charge generation layer. Dried, film thickness 2
A 5 μm charge transport layer was formed. Further, a liquid dispersed in 100 parts by weight of a bisphenol Z-type polycarbonate resin (Mw = 2 × 10 ⁵ ) containing 100 parts by weight of a styryl compound was prepared, applied and dried to prepare a protective layer having high hardness on the surface.

(Evaluation of Developer) Environmental Variation of Charge Amount 1 g of the developer to be measured was placed in a stainless steel mesh-filled cell, and charged at a nitrogen gas pressure of 0.2 (kg / cm ² ).
The charge amount of the developer was obtained by blowing for (sec) and measuring the charge of the remaining carrier.

In actual shooting evaluation of low-temperature and low-humidity (10 ° C. 20% RH, LL) and high-temperature and high-humidity (30 ° C. 80% RH, HH) environments, the charge amount after 10,000 copies in each environment was measured, and the difference (Q /
M) was determined and environmental changes were evaluated.

：: Q / M = less than 3 μC / g Δ: Q / M = 3 μC / g or more and less than 10 μC / g ×: Q / M = 10 μC / g or more Variation in copy number of charge amount After 10,000 copies and 200,000 The charge amount after copying was measured, the difference (Q / M) was obtained, and the variation in copy number was evaluated.

：: Q / M = less than 3 μC / g Δ: Q / M = 3 μC / g or more and less than 7 μC / g ×: Q / M = 7 μC / g or more Image density Macbeth densitometer (RD-918, manufactured by Macbeth Co.) ), The relative density of the solid black portion of the copy image corresponding to the white background portion (reflection density 0.00) of the transfer paper was measured.
The above is "O", 1.10 or more and less than 1.25 is "△"
Less than 1.10 was marked as "x".

Fog Using a Sakura Densitometer (manufactured by Konica Corporation), the relative density of the white background portion of the copy image corresponding to the white background portion (reflection density of 0.00) of the transfer paper was measured. Less than 0.005 is a level that is not a problem, and is "○", 0.005 or more, 0.01
Less than "△" is less than 0.01 and more than 0.01 is a practically problematic level.

Toner Scattering A blank sheet is placed under the development area, scattering toner is adhered, the blank sheet is fixed under the same fixing conditions as in the same evaluation machine, and the density is measured by a Sakura densitometer with a white area of the paper. The relative density corresponding to (reflection density 0.0) was measured, and when the relative density was less than 0.1, “○”; when the relative density was 0.1 or more and less than 0.2, “△”; "X" for case
And

A carrier alone is separated from the spent developer using a surfactant,
3.0 g of the carrier was placed in 100 ml of methyl ethyl ketone, and the spent material was dissolved.
The transmittance at m was measured by a spectrophotometer (330 type self-recording spectrophotometer, manufactured by Hitachi, Ltd.), and the value was used as a spent amount (carrier contamination degree).

When there is no spent material, it is 100%.
The value decreases as the spent increases. "○" for 90% or more, "△" for 70% or more and less than 90%
When it is less than 70%, the charge amount of the developer is remarkably reduced and toner scattering and fogging occur.

Carrier core exposure The carrier after the spent amount measurement was dried to obtain a sample.

Shimadzu X-ray photoelectron analyzer (ESCA-10)
00, manufactured by Shimadzu Corporation), the X-ray output was 10 kV,
30 mA, silicon = Si (2p), carbon = C (1
s), oxygen = O (1s), iron = Fe (2p3 / 2) (assuming that the composition on the core surface is uniform, and selecting an element that is a main element), calculating an element ratio from an element peak area intensity, On the other hand, the same measurement was performed for the core, and (Fe ratio of coated carrier / Fe ratio of core) × 100 was defined as the core exposure amount.

When the amount of exposure of the core is less than 10%, "○"; when it is 10% or more and less than 20%, "％", 20
%, The charge amount of the developer is remarkably reduced, and toner scattering and fogging occur.

Image blur In a high-temperature, high-humidity (33 ° C., 80% RH) environment, 200,000 copies were actually photographed, and after standing overnight, image evaluation was performed the next morning to confirm the presence or absence of image blur.

The case where no image blur was recognized was marked with “○”, the case where image blur occurred on the entire surface was marked as “XX”, and the case where image blur was partially occurred was marked as “×”.

(Evaluation of Developer) An electronic copier (Konica) equipped with the above-mentioned negatively chargeable organic photoreceptor 1, a magnetic permeability type toner density sensor and a toner recycling system.
U-Bix 4155 (manufactured by Konica) was used to modify the LL environment (15 ° C., 20% RH) and the HH environment (33
(80.degree. C., 80% RH), and 200,000 copies of each image were evaluated.

The evaluation results are shown in Tables 3, 4 and 5.

[0131]

[Table 3]

[0132]

[Table 4]

[0133]

[Table 5]

As is clear from Tables 3 to 5, in Examples 1 to 6, there was no change in the amount of charge due to environmental fluctuation.
The image density was high and stable up to 10,000 copies, and a high quality image was obtained without fogging or toner scattering. Further, there was almost no occurrence of spent, peeling and abrasion of the coating resin, the charge amount of the developer was stabilized, and sufficient durability was obtained. Also, there was no occurrence of image blur in the HH environment.

On the other hand, Comparative Example 1 was liable to be subjected to mechanical stress in the developing device, which caused peeling, abrasion, and increase in the amount of spent resin, markedly reduced the charge amount of the developer, and caused fogging and toner scattering. Caused the outbreak. Further, the stress on the photoreceptor was large, and the surface of the photoreceptor was damaged.

In Comparative Examples 2 to 4, fluctuating fog and toner scattering occurred in the HH environment at 10,000 copies, and the density became low in the LL environment at 10,000 copies when the environmental fluctuation of the charge amount was large. When the copy number increases, peeling of spent and coating resin,
Abrasion occurred, causing toner scattering and fogging. Image blur also occurred in the HH environment.

[0137]

According to the present invention, the following effects can be obtained.

By preventing abrasion, peeling and spent of the coating resin, it is possible to obtain a good image without toner scattering and fogging over a long period of time, and to obtain a good image even under high temperature, high humidity and low temperature and low humidity. It is possible to provide a developer that can be used.

It is possible to provide an image forming method capable of forming a stable image over a long period of time, especially a stable image even under a high temperature and high humidity environment.

In an image forming method using a copying apparatus equipped with a toner recycling system, an image forming method capable of preventing abrasion, peeling and spent of a coating resin and obtaining a good image without toner scattering and background fogging over repeated copying. A method can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view illustrating an image forming method of the present invention.

FIG. 2 is a schematic sectional view illustrating a contact magnetic brush developing method according to the present invention.

FIG. 3 is a schematic sectional view illustrating an example of a recycling system.

[Explanation of symbols]

 Reference Signs List 20 photoconductor 21 band electrode 23 transfer separation electrode 24 cleaning mechanism 25 static elimination lamp 26 paper feed mechanism 28 fixing mechanism 43 screw conveyor 45 second screw

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 9/10 352 (72) Inventor Yuji Marukawa 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation

Claims (3)

[Claims] 1. An electrostatic image developer comprising a toner and a carrier, wherein the toner contains at least a binder resin, a colorant, and a quaternary ammonium salt represented by the following general formula (1). The core comprises (MO) _x (Fe ₂ O ₃ ) _y <where M is any of Li, Mg and Ca, and x and y are molar ratios> An electrostatic image developer, wherein the coating resin comprises a silicone resin containing an aminosilane coupling agent. Embedded image (Wherein, R ^{1 to} R ⁴ are substituted or unsubstituted C ^{1 to} C 1)
8 represents an alkyl group or a substituted or unsubstituted benzyl group, and A ⁻ represents an anion. However, at least one of R ^{1 to} R ⁴ represents an alkyl group having 8 to 18 carbon atoms. ) 2. An electrostatic latent image on a photoreceptor is formed into a toner image using an electrostatic image developer comprising a toner and a carrier, and the toner image is transferred to a supplied transfer material. In the image forming method for cleaning the toner image remaining in the toner, the toner constituting the toner image contains at least a binder resin, a colorant, and a quaternary ammonium salt represented by the following general formula (1), Is composed of a core and a coating resin covering the core, and the core is (MO)
_x (Fe ₂ O ₃ ) _y <where M is any of Li, Mg and Ca, x and y are molar ratios>, and the coating resin is a silicone resin containing an aminosilane coupling agent; An image forming method, wherein the photoreceptor is obtained by coating a charge generation layer and a charge transport layer on a substrate in that order, and further coating a charge transport layer thereon. Embedded image (Wherein, R ^{1 to} R ⁴ are substituted or unsubstituted C ^{1 to} C 1)
8 represents an alkyl group or a substituted or unsubstituted benzyl group, and A ⁻ represents an anion. However, at least one of R ^{1 to} R ⁴ represents an alkyl group having 8 to 18 carbon atoms. ) 3. An electrostatic latent image on a photoreceptor is formed into a toner image using an electrostatic image developer comprising a toner and a carrier, and the toner image is transferred to a supplied transfer material. In the image forming method for cleaning the toner image remaining in the toner, the toner constituting the toner image contains at least a binder resin, a colorant, and a quaternary ammonium salt represented by the following general formula (1), Is composed of a core and a coating resin covering the core, and the core is (MO)
_x (Fe ₂ O ₃ ) _y <where M is any of Li, Mg and Ca, x and y are molar ratios>, and the coating resin is a silicone resin containing an aminosilane coupling agent; An image forming method, wherein the toner collected in the cleaning step is returned to the developing step and is used again for development. Embedded image (Wherein, R ^{1 to} R ⁴ are substituted or unsubstituted C ^{1 to} C 1)
8 represents an alkyl group or a substituted or unsubstituted benzyl group, and A ⁻ represents an anion. However, at least one of R ^{1 to} R ⁴ represents an alkyl group having 8 to 18 carbon atoms. )