JPH10307430A - Electrophotographic carrier, electrostatic latent image developer and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a resin coating film having uniform compsn. of a chemical structure, to prevent a decrease in the charge amt. at high temp. and high humidity or an increase in the charge amt. at low temp. and low humidity, and to improve impact resistance and contamination resistance by controlling the resistance of the carrier core to a specified value or lower and controlling the resistance of a resin coating layer to a specified range. SOLUTION: The core material has <=1 Ωcm dynamic electric resistance in 10<4> V/cm electric field in a magnetic brush state, and the resin coating layer has 10 to 1×10<8> Ωcm electric resistance. The resin in the resin coating layer consists of a random copolymer produced by copolymn. of monomers expressed by formula I, etc., and monomers expressed by formula II, etc., as the essential components. In formula I, R1 is a hydrogen atom, etc., A is -(CH2 )n1 -NR2 R3 , wherein R2 and R3 are independently alkyl groups, etc., n1 is an integer 0 to 10. In formula II, R7 is a hydrogen atom, etc., A is -(CH2 )n3 -(CF2 )m -CF3 , etc., (n) is an integer 0 to 12 and (m) is an integer 1 to 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic carrier used for developing an electrostatic image formed by an electrophotographic method, an electrostatic recording method, etc., and an electrostatic latent image using the electrophotographic carrier. The present invention relates to a developer and an image forming method using the electrostatic latent image developer.

[0002]

2. Description of the Related Art Methods of visualizing image information via an electrostatic image such as electrophotography are currently used in various fields.
In the electrophotographic method, an electrostatic latent image is formed on a photoreceptor in a charging and exposing step, the electrostatic latent image is developed with a developer containing a toner, and visualized through a transfer and fixing step. The developer used here includes a two-component developer composed of a toner and a carrier, and a one-component developer used alone such as a magnetic toner. In the two-component developer, the carrier is used to stir and transport the developer. ,
It is widely used at present because it shares functions such as electrification and is separated in function as a developer, so that it has good controllability.

As a developing method, a cascade method or the like has been used in the past. At present, however, a magnetic brush method using a magnetic roll as a developer carrier is mainly used. 2
As the component magnetic brush development, a conductive magnetic brush (CMB) development using a conductive carrier and an insulating magnetic brush (IMB) development using an insulating carrier are known. Among them, in CMB development, charges are injected from a development roll due to low carrier resistance, and carriers in the vicinity of a photoreceptor play a role of a development electrode to increase an effective development electric field.
The toner is characterized in that toner transfer is sufficiently performed and solid image reproducibility is excellent. On the other hand, there is a problem that image defects such as a white line called a brush mark and a transfer of a carrier to a photoreceptor called a carrier over which occur due to charge injection from a developing roll or the like easily occur.

In recent years, colorization has rapidly progressed, and the required level of image quality has been increasing more and more. Solid images are particularly important in this color image quality, and there is therefore a strong demand for further improvements in CMB carrier performance, including durability. In Japanese Patent Publication No. 7-12008, a core material having relatively low resistance (hereinafter referred to as a “carrier core”,
Or simply "core." ) Is coated with a high-resistance resin, whereby the resistance changes abruptly in a certain electric field, and the carrier has a high resistance in a low electric field and a low resistance in a high electric field. It is described that since a high electric field is applied to the latent image portion and a low electric field is applied to the non-latent image portion, good black solid printing is obtained and at the same time, no carrier over occurs in the non-latent image portion. However, according to the invention (Japanese Patent Publication No. Hei 7-120086), the resin coating layer is considerably thin and the low-resistance core is partially exposed, according to the embodiment and the description in the operation. It is presumed that such a structure is considered to reduce the resistance in a high electric field. In fact, as in the comparative example described later, in the case of a complete coating having a thick resin coating layer, the resistance was high even in a high electric field, and a good solid image could not be obtained. In such a partial coating in which a part of the core having a low resistance is exposed, the electric charge easily moves through the exposed surface, so that a brush mark is easily generated in the latent image portion.

Further, Japanese Patent Application Laid-Open Nos.
1-1130959 discloses ferrite having relatively low resistance and having irregularities based on primary particles on its surface.
It is described that the presence of such fine irregularities suppresses leakage between charges of different polarities and prevents brush marks. However, since the carrier has fine irregularities on its surface, the contact area with the toner increases, and as a result, the toner tends to adhere, and the charging ability as a carrier deteriorates with time. Also, Japanese Patent Application Laid-Open No. 6-161157 discloses a device defined by the ratio of the resistance of a carrier core to that of a carrier coated with a resin, whereby the resolution, solid image density and fine line reproducibility can be simultaneously satisfied. It is shown. However, no sufficient effect has been found particularly in preventing image defects in color images.

[0006] On the other hand, there are various characteristics required for the resin-coated carrier, but it is necessary to impart an appropriate chargeability (charge amount and charge distribution) to the toner and maintain proper chargeability of the toner for a long period of time. Characteristics required for this purpose include impact resistance, abrasion resistance, and it is particularly important that the chargeability of the toner is not changed even with environmental changes such as humidity and temperature. Has been proposed. Specifically, a copolymer of a nitrogen-containing alkyl (meth) acrylate and a vinyl monomer or a fluorinated alkyl (meth)
A method using a copolymer of an acrylate and a vinyl monomer has been proposed (see JP-A-64-35562 and JP-A-2-24670).

It has also been proposed to obtain a resin-coated carrier having a relatively long life by coating a carrier core surface with a copolymer of a nitrogen-containing monomer and a fluorinated monomer (Japanese Patent Publication No. 3-23909). ), It is difficult to obtain a uniform composition, for example, it is difficult for monomers to copolymerize with each other, or phase separation occurs. Further, since the composition has a broad distribution, the characteristics are biased by the coated portion, and as a result, satisfactory impact resistance and stain resistance to toner are not satisfactory. In particular, since the stability of the chargeability of the developer is low due to a decrease in the charge amount under high temperature and high humidity and an extreme increase in the charge amount under low temperature and low humidity, the image cannot be used for a long time. Fog and density unevenness.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve the above-mentioned problems and is capable of forming a resin film having a uniform composition in terms of chemical structure. Extremely long life carrier for electrostatic charge development, excellent in impact resistance and toner contamination resistance, with no extreme increase in charge amount under low humidity, especially for color images, such as brush mark and carrier over It is an object of the present invention to provide a durable electrophotographic carrier, an electrostatic latent image developer, and an image forming method capable of obtaining a good solid image without causing image defects and also having durability.

[0009]

The present inventors have conducted research on the above problems, and as a result, in order to prevent image defects such as brush marks and carrier over and to obtain a good solid image, the resistance of the carrier has to be improved. Is required to be within a desired range, and for that purpose, it is important that the resistance of the carrier core is lower than a certain value and that the resistance of the resin coating layer falls within a certain range. On the other hand, it has been found that the composition and structure of the resin of the coating layer are important for maintaining stable image quality over time. That is, the present invention relates to an electrophotographic carrier having a resin coating layer containing conductive powder on a core material, wherein the core material is a magnetic brush and has a dynamic electric resistance under an electric field of 10 ⁴ V / cm. Is 1 Ωcm or less, the electric resistance of the resin coating layer is in the range of 10 to 1 × 10 ⁸ Ωcm, and the resin of the resin coating layer is represented by the following general formulas (I) and / or (II). A random copolymer, a block copolymer, or a graft copolymer obtained by copolymerizing a monomer and a monomer represented by the following general formulas (III) and / or (IV) as essential components: An electrophotographic carrier, an electrostatic latent image developer, and an image forming method. -General formula (I)

[0010]

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In the general formula (I), R ₁ represents a hydrogen atom or a methyl group, A represents — (CH ₂ ) _n1 —NR ₂ R ₃ , and R ₂ and R ₃ each independently represent an alkyl group or an aryl group. And n1 represents an integer of 0 to 10.・ General formula (II)

[0012]

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In the general formula (II), R ₄ represents a hydrogen atom or a methyl group, B represents — (CH ₂ ) _n2 —NR ₅ R ₆ , and R ₅ and R ₆ each independently represent an alkyl group or an aryl group. And n2 represents an integer of 0 to 10.・ General formula (III)

[0014]

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In the general formula (III), R₇Is a hydrogen atom or
A 'represents-(CH₂) _n3-(CF₂)_m−
CF₃Or

[0016]

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Wherein n3 represents an integer of 0 to 12;
Represents an integer of 1 to 12.・ General formula (IV)

[0018]

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In the general formula (IV), R₈Is a hydrogen atom or
Represents a chill group, B'is-(CH_Two) _n4-(CF_Two)_m−
CF_ThreeOr

[0020]

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Wherein n4 represents an integer of 0 to 8, m represents an integer of 1 to 10, and Z represents an oxygen atom, carbonyl or acid amide.

[0022]

DETAILED DESCRIPTION OF THE INVENTION The electrophotographic carrier of the present invention (hereinafter, simply referred to as "carrier".), The dynamic resistance at an electric field of 10 ⁴ V / cm in a state of the magnetic brush, 1 [Omega ·
cm ¹ to 10 ⁸ Ω ·
cm with a medium resistance resin coating layer. The reason why such a configuration can achieve both the quality of a solid image and the prevention of image defects such as brush marks and carrier over is estimated as follows. Generally, when a conductor is placed in an electric field, electric charges rearrange along the electric field,
So-called polarization occurs. The speed of the polarization is related to the resistance of the conductor, and the lower the resistance, the faster the speed of the polarization. It is thought that such a phenomenon is occurring inside the carrier core placed between the developing roll and the photoconductor,
When the polarization of the core is completed within about 10 ^-3 seconds when the development is performed with the resistance of the core sufficiently low, the development electrode effect due to the polarization of the core itself is added in addition to the charge injection from the development roll. And a good solid image can be obtained as a result. However, no matter how low the core resistance, if the resistance of the resin coating layer is too high, the overall resistance will increase,
A good solid image cannot be obtained. On the other hand, since the charge injected from the developing roll mainly flows on the carrier surface, if the resistance of the resin coating layer is too low, brush marks and carrier over are likely to occur. Therefore, the range of the electrical resistance of the core and the resin coating layer satisfying these conditions is:
It is believed to be as described above.

Further, by making the resin of the resin coating layer have the above structure, the durability of the carrier is improved by the mechanical strength of the resin. Also, conductive powder is added into the resin coating to keep the dynamic electric resistance of the resin coating layer in the above-mentioned predetermined range. However, if the amount of the conductive powder is too large, the chargeability of the carrier is reduced. Therefore, it is necessary to suppress the addition amount to some extent. However, by using the above-mentioned fluorine-based resin as the resin of the resin coating layer, the dispersibility of the conductive powder is reduced due to the low surface energy of the resin. As a result, the resistance can be reduced even when the amount of the conductive powder added is small, so that the amount of the conductive powder added can be suppressed.

As the carrier core used in the present invention, any conventionally known carrier core can be used, but a core of a low-resistance ferrite or magnetic powder-dispersed resin carrier is particularly preferably selected. As other carrier cores, for example, iron powder and magnetite are known, but iron powder has a large specific gravity, so that toner and external additives tend to adhere thereto, and therefore have poorer stability than ferrite. In addition, magnetite has a problem in that resistance is difficult to control and the latitude of electric resistance is narrow, while ferrite can be reduced in resistance after firing, for example, by reducing it at a certain temperature in a stream of hydrogen, thereby reducing hydrogen flow. By controlling the amount, temperature, reduction time and the like, various electric resistances can be obtained, which is particularly preferable. The volume average particle diameter of the carrier core made of magnetic particles such as ferrite is preferably 10 to 100 μm, more preferably 2 to 100 μm.
0 to 80 μm. If the volume average particle diameter is smaller than 10 μm, the developer easily scatters from the developing device, and if it is larger than 100 μm, it is difficult to obtain a sufficient image density.

On the other hand, the core of the magnetic powder-dispersed resin carrier is obtained by dispersing powder of a magnetic material such as ferrite, iron powder, and magnetite in a thermoplastic resin or a thermosetting resin. Specific examples of such thermoplastic resins and thermosetting resins include polyolefin resins, polyester resins,
Examples thereof include a polyurethane resin, a polycarbonate resin, a melamine resin, and a phenol resin. The particle size of the magnetic powder used here is suitably in the range of 0.01 to 10 μm, preferably 0.05 to 5 μm. The volume average particle diameter of the core of the magnetic powder-dispersed resin carrier in which these are dispersed in a resin is the same as that of the above magnetic particles, that is, 10 to 100.
μm, preferably in the range of 20-80 μm.

The carrier core used in the present invention has a dynamic electric resistance of 10 ⁴ V when measured in the form of a magnetic brush.
/ Cm at an electric field of 1 Ω · cm or less. The reason is that if the electric resistance is 1 Ω · cm or more, a carrier having a desired electric resistance cannot be obtained unless the electric resistance of the resin coating layer is considerably reduced, and image defects occur if the electric resistance of the resin coating layer is too low. Because it will. 10 ⁴ V / cm near the developing electric field in the actual equipment and the electric field, the electric resistance is defined by the value under the electric field. The dynamic electrical resistance of the carrier core is determined as follows. Diameter 4cm, axial length 10
2.5 m plate electrode with 3 cm ² area
The magnetic brush is formed by placing the carrier core on a developing roll facing the flat plate electrode with an interval of m. At this time, the weight of the carrier core per unit area is about 40 mg /
The weight of the carrier core was adjusted to be cm ² . 1
A voltage is applied between the developing roll and the plate electrode while rotating the developing roll at a rotation speed of 20 rpm, and the current flowing at that time is measured. From the obtained current-voltage characteristics, the electrical resistance is obtained using the equation of Ohm's law. Note that log J こ の E is generally between the applied electric field E and the current density J at this time.
It is well known that there is a relationship of 1/2 (for example, Japanese Journal of Applier
d Physics 19, No. 12, P2413
~). When the electric resistance is extremely low as in the carrier core used in the present invention, a large electric current may flow in a high electric field of 10 ³ V / cm or more, and measurement may not be performed. In such a case, three or more points are measured in a low electric field and extrapolated to an electric field of 10 ⁴ V / cm by the least squares method using the above relational expression.

Further, the above-mentioned carrier core is provided with a resin coating layer on the surface thereof, and an intermediate layer made of a silane coupling agent, a titanate coupling agent or the like may be provided between the carrier core and the resin coating layer. . Specifically, vinyl trimethoxy silane, vinyl triethoxy silane,
Tris- (β-methoxyethoxy) vinylsilane, vinyltriacetoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ -Mercaptopropyltrimethoxysilane, β-mercaptoethyltrimethoxysilane, γ-chloropropyltrimethoxysilane,
Known compounds such as isopropyl tristearoyl titanate and isopropyl methacrylisostearoyl titanate can be exemplified.

The resin of the resin coating layer in the present invention comprises: (1) a monomer represented by the following general formulas (I) and / or (II) and a monomer represented by the following general formulas (III) and / or (IV) It is a random copolymer, a block copolymer, or a graft copolymer obtained by copolymerizing the monomer represented as an essential component. -General formula (I)

[0029]

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In the general formula (I), R ₁ represents a hydrogen atom or a methyl group, A represents — (CH ₂ ) _n1 —NR ₂ R ₃ , and R ₂ and R ₃ each independently represent an alkyl group or an aryl group. And n1 represents an integer of 0 to 10.・ General formula (II)

[0031]

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In the general formula (II), R ₄ represents a hydrogen atom or a methyl group, B represents — (CH ₂ ) _n2 —NR ₅ R ₆ , and R ₅ and R ₆ each independently represent an alkyl group or an aryl group. And n2 represents an integer of 0 to 10.・ General formula (III)

[0033]

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In the general formula (III), R₇Is a hydrogen atom or
A 'represents-(CH₂) _n3-(CF₂)_m−
CF₃Or

[0035]

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Wherein n3 represents an integer of 0 to 12;
Represents an integer of 1 to 12.・ General formula (IV)

[0037]

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In the general formula (IV), R₈Is a hydrogen atom or
B 'represents-(CH_Two) _n4− (CF_Two)_m−
CF_ThreeOr

[0039]

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In the formula, n4 represents an integer of 0 to 8, m represents an integer of 1 to 10, and Z represents an oxygen atom, carbonyl or acid amide.

Specific examples of the monomers represented by the above general formulas (I) to (IV) are as follows, but the present invention is not limited thereto. -General formula (I)

[0042]

[Table 1]

General formula (II)

[0044]

[Table 2]

General formula (III)

[0046]

[Table 3]

General formula (IV)

[0048]

[Table 4]

(2) In addition to the monomers described in the above (1), the following general formulas (V) and (V) are used for improving the handling properties such as adjusting the glass transition point and solubility in a solvent in solution polymerization. It is preferable to use a random copolymer, a block copolymer, or a graft copolymer obtained by copolymerizing the monomer represented by (VI) as an essential component.・ General formula (V)

[0050]

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In the general formula (V), R ₉ represents hydrogen or a methyl group, and A ″ represents hydrogen, an alkyl group, a cycloalkyl group, an aryl group, an allyl group, an alkoxyalkylsilyl group, or an epoxyalkyl group.・ General formula (VI)

[0052]

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In the general formula (VI), R ₁₀ represents hydrogen or a methyl group, and B ″ represents hydrogen, an alkyl group, a cycloalkyl group or an aryl group.

The monomer represented by the above general formula (V) or (VI) includes acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, stearyl acrylate, cyclohexyl acrylate, acrylic acid Acrylic acid derivatives such as phenyl, methacrylic acid such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, 4-tolyl methacrylate, phenyl methacrylate, and glycidyl methacrylate Derivatives, styrenes such as styrene and α-methylstyrene, monomers containing an epoxyalkyl group, methacryloxypropyltrimethoxysilane, and the like can be mentioned, but are not limited thereto.

(3) In addition to the monomers described in the above (1) or (2), a random copolymer, block copolymer or graft copolymer obtained by copolymerizing a crosslinking monomer. Preferably, it is a polymer. Crosslinkable monomers that can be used in the present invention include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 4-hydroxyethyl methacrylate.
Examples include acryloxysilanes such as divinylbenzene, methacrylisocyanate, and methacryloxypropyltrimethoxysilane, but are not limited thereto.

The above-mentioned monomers can be easily obtained from the market. As a method for synthesizing a random copolymer, a block copolymer or a graft copolymer using these monomers, for example, , Radical polymerization, anionic polymerization, cationic polymerization and the like can be carried out by a conventionally known polymerization method. With respect to the total amount of the monomers represented by the general formulas (I) and / or (II) and the monomers represented by the general formulas (III) and / or (IV), the general formula ( I) and / or (II)
The proportion of the monomer represented by is suitably in the range of 1 to 99 mol%, preferably 5 to 70 mol%. The proportion of the monomer represented by the general formula (V) and / or (VI) is 0 to 90 mol% of the whole resin of the resin coating layer,
Preferably, the range of 10 to 90 mol% is appropriate. Further, the mixing ratio of the above-mentioned crosslinkable monomer is suitably in the range of 2 to 50 mol%, preferably 5 to 30 mol% of the whole resin of the resin coating layer. If the amount exceeds 50 mol%, the uncrosslinked portion increases even if a cross-linking reaction is performed, and the environmental stability of charging may decrease. Easy to get low.

In the present invention, the conductive powder to be added to the resin coating layer preferably has an electric resistance of 10 ⁶ Ω · cm or less, and when the conductive powder is nearly spherical, the volume average particle diameter is 10 Ω · cm. Those having a thickness of about 500 nm are preferred.

In the present invention, the conductive powder added to the resin coating layer preferably has a needle-like or fibrous shape. The “needle-like or fiber-like” here means
The ratio of the major axis (fiber length) to the minor axis (fiber diameter) (major axis / minor axis; hereinafter, referred to as “aspect ratio”) is 3 or more, preferably 5 or more, and more preferably 10 or more. Needle-like or fibrous conductive powder easily forms a continuous conductive path in the resin coating layer, so that the amount of addition can be reduced as compared with spherical conductive powder. The conductive powder has a hydroxyl group on the surface,
In many cases, the carrier is porous. Therefore, when water is easily adsorbed and the amount of addition is large, the electric resistance and chargeability of the carrier greatly fluctuate due to a change in humidity, and various problems occur. Therefore, by reducing the amount of the conductive powder added, the stability against humidity fluctuation can be improved. When the conductive powder is dispersed and mixed into the resin coating, the conductive powder may be cut in the fiber length direction and the aspect ratio may be reduced. Therefore, it is necessary to use a conductive powder having an aspect ratio as high as possible. Preferably, even when the conductive powder is cut, it is desired that the aspect ratio of the main conductive powder is in the above range and that the resin coating layer has a desired electric resistance.

The major axis of the conductive powder is 0.02 to 10 μm.
m is preferred. Even if the aspect ratio is 3 or more, if the major axis is shorter than 0.02 μm, a large amount of the resin is required to be added to the resin coating layer, and the dispersion stability and the charge reduction may be insufficient. If the major axis is longer than 10 μm, the proportion of the conductive powder protruding from the surface of the resin coating layer increases, and the movement of the electric charges from there tends to cause image defects. The short axis of the conductive powder is preferably 0.005 to 1 μm. If the ratio is out of this range, the dispersibility becomes poor and the characteristics of the carrier become non-uniform.

The material of the conductive powder is not particularly limited as long as it can impart a desired electric resistance to the resin coating layer. Specifically, for example, carbon black, zinc oxide,
Simple substances such as titanium oxide, tin oxide, iron oxide, and titanium black, and composite substances in which the surfaces of fine particles such as titanium oxide, zinc oxide, aluminum borate, and potassium titanate are coated with a conductive metal oxide Is mentioned. Here, examples of the conductive metal oxide include a metal oxide doped with antimony (for example, antimony-doped tin oxide) and an oxygen-deficient metal oxide (for example, oxygen-deficient tin oxide). However, in the oxygen-deficient type, it is preferable to use an antimony-doped type because water is relatively easily adsorbed to the oxygen-deficient portion. The content of the conductive powder is preferably 2 to 40% by volume, more preferably 3 to 30% by volume, and still more preferably 5 to 20% by volume based on the resin coating layer. When the content of the conductive powder is less than 2% by volume, the resistance of the resin coating layer does not decrease to a desired value, and when it is more than 40% by volume, the resin coating layer becomes brittle.

The resistance of the resin coating layer is 10¹-10⁸Ω ・ c
m, preferably 10³-10⁷Ω · cm. Resin coating
The resistance of the covering layer depends on the type and amount of conductive powder and resin used.
So control. The resistance of the resin coating layer is 10¹Ω
・ If the diameter is smaller than cm, the charge easily moves on the carrier surface.
And image defects occur. The resistance of the resin coating layer is 10 ⁸
If it is larger than Ω · cm, use low resistance core
However, a good solid image cannot be obtained. Resistance of resin coating layer
Uses an applicator on an ITO conductive glass substrate
To form a resin coating film with a thickness of zero μm to several μm
Then, a gold electrode is formed by vapor deposition on this²V / cm
It is determined from current-voltage characteristics in an electric field.

The preferable range of the dynamic electric resistance when the carrier coated with the resin is measured in the form of a magnetic brush is 10 ^{1 to} 1 × 1 at an electric field of 10 ⁴ V / cm.
0 ⁹ Ω · cm, more preferably 1 × 10 ^{3 to} 1 ×
It is 10 ⁹ Ω · cm. The above electric resistance is 10 ¹ Ω · cm
Smaller than the image defect is liable to occur, 10 ⁹ Ω · cm
If it is larger, it is difficult to obtain a good solid image. The method for measuring the dynamic electric resistance is the same as that for the carrier core.

In the present invention, as a method of coating a resin comprising the above-mentioned copolymer in which conductive powder is dispersed on a carrier core, a method comprising dispersing the conductive powder and dissolving the resin comprising the copolymer in a solvent is used. (Hereinafter referred to as “resin coating layer forming solution”), a dipping method in which the carrier core is dipped, a spray method in which the resin coating layer forming solution is sprayed on the surface of the carrier core, and a resin in a state where the carrier core is suspended by flowing air. Examples thereof include a fluidized bed method of spraying a solution for forming a coating layer and a kneader coater method of mixing a carrier core and a solution for forming a resin coating layer in a kneader coater to remove the solvent. The solvent used for the solution for forming the resin coating layer is not particularly limited as long as it dissolves the above-mentioned coating resin, and examples thereof include aromatic hydrocarbons such as toluene and xylene, and ketones such as acetone and methyl ethyl ketone. And ethers such as tetrahydrofuran and dioxane. Further, as a method of dispersing the conductive powder, a sand mill,
Dyno mills, homomixers, and the like.

The thickness of the resin coating layer is from 0.3 to 5 μm, preferably from 0.5 to 3 μm. The thickness of the resin coating layer is 0.
If the diameter is smaller than 3 μm, it is difficult to form a uniform resin coating layer on the core surface. In particular, when a low-resistance core is used as in the present invention, charge transfer occurs through the exposed surface and image defects occur. Likely to happen. On the other hand, if it is larger than 5 μm, granulation of carriers occurs, and a carrier having a uniform film thickness cannot be obtained.

The carrier of the present invention is mixed with a toner and used as a two-component developer. The toner is obtained by melt-kneading a binder resin with a colorant and other additives, cooling, pulverizing, and, if necessary, classifying the binder resin according to a conventional method. As the binder resin of the toner, styrenes, styrenes such as chlorostyrene, ethylene, propylene, butylene, monoolefins such as isoprene,
Vinyl acetate, vinyl propionate, vinyl benzoate, vinyl esters such as vinyl acetate, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, Α-methylene aliphatic monocarboxylic acid esters such as butyl methacrylate and dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone; Homopolymers or copolymers can be exemplified. Particularly typical binder resins include polystyrene, styrene-acrylate copolymer, styrene-methacrylate copolymer, and styrene. - acrylonitrile copolymer, styrene - butadiene copolymer, styrene - maleic anhydride copolymer, polyethylene, polypropylene. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, and wax can be exemplified.

Examples of coloring agents include carbon black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, and rose bengal. , C.I. I. Pigment Red 48: 1, C.I. I. Pigment Red 1
22, C.I. I. Pigment Red 57: 1, C.I. I.
Pigment Yellow 97, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 180, C.I.
I. Pigment Yellow 185, C.I. I. Pigment Yellow 12, C.I. I. Pigment Blue 15:
1, C.I. I. Pigment Blue 15: 3 and the like can be exemplified.

A known charge control agent may be added to the toner, if desired.
An additive such as a fixing aid (eg, polyethylene wax) may be included. The volume average particle diameter of the toner is 30 μm or less, preferably 3 to 15 μm. As a method for producing the toner, a conventionally known method can be used. For example, a method in which a resin is heated and melted, kneaded with a colorant, cooled, and then pulverized and classified, or a suspension polymerization method and a dissolution suspension method produced by a wet method can be used. The ratio of the toner when the developer is prepared by mixing the toner and the carrier is preferably in the range of 0.3 to 30% by weight of the entire developer. In addition, silica, alumina, tin oxide, strontium oxide, various resin powders, and other conventionally known external additives can be blended to improve the fluidity of the toner.

The developer thus obtained is provided with a step of forming a latent image on a latent image carrier, a step of developing the latent image using the developer, and a step of transferring the developed toner image to a transfer body. It can be used in an image forming method including a step of transferring and a fixing step of heating and fixing the toner image on the transfer body.

[0069]

The present invention will be described below in detail with reference to examples and comparative examples. In addition, the electric resistance measurement in an Example and a comparative example was all performed on the environment of 22 degreeC of temperature, and 55% of humidity.

[Synthesis Example of Polymer ] Synthesis Example 1 of Polymer ( Synthesis of Random Copolymer 1) 7.85 g (50.0 mmol) of monomer 2 and the compound N
O. 27.0 g (50.0 mmol) of monomer No. 18 and 100.0 g (1.0 mol) of methyl methacrylate
l) was dissolved in 300 g of toluene, 1.8 g (0.01 mol) of azoisobutyronitrile was added, and the mixture was reacted at 60 ° C. for 20 hours under a nitrogen stream. When the molecular weight of the copolymer obtained after the reaction was measured by gel permeation chromatography, the weight average molecular weight (Mw) was measured.
It was 23,000.

Polymer Synthesis Example 2 ( Synthesis of Random Copolymer 2) No. 9 and 1.6 g (10.0 mmol) of the compound NO.
30 monomer 28.3 g (50.0 mmol) and styrene 100.0 g (0.96 mol)
g of azoisobutyronitrile (1.8 g).
01 mol) and reacted at 60 ° C. for 40 hours under a nitrogen stream. After the completion of the reaction, the molecular weight of the obtained copolymer was measured by gel permeation chromatography and found to be a weight average molecular weight (Mw) of 45.000.

Synthesis Example 3 of Polymer ( Synthesis of Block Copolymer 1) 100.0 g (0.59 mol) of cyclohexyl methacrylate was dissolved in 300 g of toluene, and 0.59 of azoisobutyronitrile was dissolved.
g (0.006 mol) and added at 60 ° C. under nitrogen flow.
The reaction was performed for a time to obtain a prepolymer. . Compound N
O. 1.75 g (10.0 mmol) of the monomer No. 10 were dissolved in 30 g of toluene, and azoisobutyronitrile 0.0
After adding 2 g and reacting at 60 ° C. for 4 hours under a nitrogen stream, the compound NO. 7.2 g of 33 monomers (10.0
mmol) and the above prepolymer were added, and the reaction was further performed at 60 ° C. for 48 hours under a nitrogen stream. After the completion of the reaction, the molecular weight of the obtained copolymer was measured by gel permeation chromatography and found to be a weight average molecular weight (Mw) of 55,000.

Polymer Synthesis Example 4 ( Synthesis of Graft Copolymer 1) 7.85 g (10.0 mmol) of monomer No. 2
5.6 g (10.0 mmol) of the monomer 19 was dissolved in 300 g of toluene, and 0.18 g of azoisobutyronitrile was dissolved.
(0.001 mol), and the mixture was reacted at 60 ° C. for 4 hours under a nitrogen stream, and then glycidyl methacrylate 1 was added.
00.0 g (0.70 mol) and 1.8 g (0.01 mol) of azoisobutyronitrile were added, and the mixture was further reacted at 60 ° C. for 48 hours under a nitrogen stream. After the completion of the reaction, the molecular weight of the obtained copolymer was measured by gel permeation chromatography, and the weight average molecular weight (M
w) 85,000.

Polymer Synthesis Example 5 ( Synthesis of Graft Copolymer 2) 1.75 g (10.0 mmol) of the monomer No. 11 and the compound N
O. 5.7 g (10.0 mmol) of 30 monomer was dissolved in 300 g of toluene, and 0.1 g of azoisobutyronitrile was dissolved in 300 g of toluene.
After adding 8 g (0.001 mol) and performing a reaction at 60 ° C. for 4 hours under a nitrogen stream, 100.0 g (0.70 mol) of glycidyl methacrylate and 1.8 g (0.01 mol) of azoisobutyronitrile were added. In addition, the reaction was further performed at 60 ° C. for 48 hours under a nitrogen stream. After the completion of the reaction, the molecular weight of the obtained copolymer was measured by gel permeation chromatography and found to be a weight average molecular weight (Mw) of 45,000.

Polymer Synthesis Example-6 ( Synthesis of Random Copolymer 3) 7.85 g (50.0 mmol) of monomer 2 and the compound N
O. 17 (26.6 g, 47.5 mmol) and methacrylic acid methyl ester 85.0 g (0.85 mol)
1) 12.42 g (50 mmol) of 3-methacryloxypropyltrimethoxysilane in 300 g of toluene
And dissolved in the polymerization initiator AIBN 1.64 g (10 mm
ol) and reacted at 60 ° C. for 48 hours under a nitrogen stream. After completion of the reaction, the precipitate was precipitated in methanol, collected by filtration, and dried in vacuo. When the molecular weight of the obtained copolymer was measured by gel permeation chromatography, the weight average molecular weight (Mw) was 30,000.

[Preparation of Carrier] Example 1 100 parts by weight of magnetite (MX030A, volume average particle diameter 50 μm, manufactured by Fuji Electric Chemical Co., Ltd.) 13.5 parts by weight of toluene 1.8 parts by weight of polymer of Polymer Synthesis Example-1 Part: carbon black (VXC72, 10 ^-1 Ωcm, particle size: 30 nm, manufactured by Cabot Corporation) 0.3 part by weight The above components except magnetite were dispersed in a sand mill for 1 hour to prepare a solution for forming a resin coating layer. . Next, the resin coating layer forming solution and magnetite were placed in a vacuum deaeration type kneader and stirred at a temperature of 60 ° C. for 30 minutes while reducing the pressure to form a resin coating layer. The thickness of the resin coating layer was 0.8 μm. In addition, carbon black (VX
The content of C72) in the resin coating layer was 8% by volume.
When this carrier was observed with a scanning electron microscope, it was confirmed that the carrier was uniformly coated with no exposed surface. Further, a solution for forming a resin coating layer was applied to a thickness of 0.8 μm on an ITO conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. The electric resistance of magnetite and carrier A was measured in the form of a magnetic brush, and the resistance values when extrapolated to an electric field of 10 ⁴ V / cm were 4 × 10 ⁻⁵ Ω · cm and 1.8 × 10 ^{8, respectively.}
Ω · cm. FIG. 1 shows a graph for obtaining the extrapolated resistance value at this time. The resistance value of the resin coating film is 100
It was 3 × 10 ⁵ Ω · cm at an electric field of V / cm.

[0077]Example 2 ・ Ferrite (MF-35, volume average particle diameter 35 µm, manufactured by Powdertech Co., Ltd.) 100 parts by weight ・ Toluene 22 parts by weight ・ Polymer Synthesis Example-2 polymer 3 parts by weight ・ Carbon black (Monarch 880, 10^-1Ω · cm, volume average particle diameter 16 nm, manufactured by Cabot Co., Ltd.) 0.8 parts by weight The above components except ferrite are dispersed in a sand mill for 1 hour.
Then, a solution for forming a resin coating layer was prepared. Next, this resin coating
Cover layer forming solution and magnetite in vacuum degassing type kneader
Put in the resin and stir for 30 minutes while depressurizing at 60 ℃
A coating layer was formed and a carrier B was obtained. Resin coating layer thickness
Was 0.8 μm. In addition, carbon black (moner
880) in the resin coating layer is 13% by volume.
Was. This carrier was observed with a scanning electron microscope.
B, it was confirmed that there was no exposed surface and the resin was uniformly coated.
Was done. Applicator on ITO conductive glass substrate
To a thickness of 0.8 μm using a resin coating layer forming solution
And apply the sample to measure the electrical resistance of the resin coating film.
Obtained. Electrode Magnetite and Carrier B in the form of a magnetic brush.
Air resistance was measured and 10^FourWhen extrapolated to an electric field of V / cm
Are 5 × 10^-2Ω · cm, 4 × 10⁷Ω
Cm. The resistance value of the resin coating film is 100V /
2 × 10 cm in electric field ³Ω · cm.

Example 3 13.0% by weight of phenol ・ 6% by weight of formaldehyde (about 37% of formaldehyde, about 10% of methanol, about 53% of water) ・ 81% by weight of magnetite (about 0.2 μm in volume average particle diameter) Using ammonia as a basic catalyst and calcium fluoride as a polymerization stabilizer, the components were gradually heated to a temperature of 80 ° C. while stirring in an aqueous phase, and polymerization was performed for 3 hours. It was sufficiently dried with a dryer. The obtained particles were classified by a centrifugal classifier (TC-15N: manufactured by Nisshin Flour Milling Co., Ltd.), and the volume average particle diameter was 50 μm and d90%.
Volume diameter / d10% Volume diameter ratio = 2.7 [Measurement device: Microtrack (trade name), manufactured by Nikkiso Co., Ltd.] was obtained.

-80 parts by weight of the above carrier core 1-14 parts by weight of toluene-2 parts by weight of the polymer of Polymer Synthesis Example 3-Tin oxide (Pastran TYPE-IV, 1Ωcm, volume average particle diameter 100 nm, manufactured by Mitsui Kinzoku Co., Ltd.) 2 parts by weight The above components except the carrier core 1 were dispersed in a sand mill for 1 hour to prepare a resin coating layer forming solution. Next, this solution for forming a resin coating layer and the carrier core 1 were placed in a vacuum degassing type kneader, and stirred at a temperature of 60 ° C. for 30 minutes while reducing the pressure to form a resin coating layer. The thickness of the resin coating layer was 0.8 μm. The content of tin oxide in the resin coating layer was 13% by volume. When this carrier was observed with a scanning electron microscope, it was confirmed that the carrier was uniformly coated with no exposed surface. Further, a solution for forming a resin coating layer was applied to a thickness of 0.8 μm on an ITO conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. Measure the resistance of the carrier core 1 and the carrier in the form of a magnetic brush, and measure 10 ⁴ V / c
The resistance value when extrapolated to an electric field of m is 1 × 10
^-1 Ω · cm and 2 × 10 ⁶ Ω · cm. The resistance value of the resin coating film is 6 × 10 ⁴ Ω · at an electric field of 100 V / cm.
cm.

[0080] Example 4, iron powder (TSV, volume average particle diameter of 60 [mu] m, Powder Tech Co.) 100 parts by weight Toluene 8 parts by weight Polymer Synthesis Example -5 Polymer 1 part by weight Carbon black (VXC72,10 ^{- 1} Ω · cm, volume average particle diameter 30 nm, manufactured by Cabot Corporation) 0.2 parts by weight The above components except for iron powder were dispersed in a sand mill for 1 hour to prepare a resin coating layer forming solution. Next, the solution for forming a resin coating layer and the iron powder were put into a vacuum degassing type kneader, and the temperature was set to 6 °
The mixture was stirred for 20 minutes while reducing the pressure at 0 ° C. to form a resin coating layer, and a carrier D was obtained. The thickness of the resin coating layer is 0.8 μm
Met. The content of carbon black (VXC72) in the resin coating layer was 10% by volume. When this carrier was observed with a scanning electron microscope, it was confirmed that the carrier was uniformly coated with no exposed surface. Further IT
A solution for forming a resin coating layer was applied to a thickness of 0.8 μm on an O-conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. The resistance of the iron powder and the carrier D is measured in the form of a magnetic brush, and the resistance value when extrapolated to an electric field of 10 ⁴ V / cm is 1 × 10 ⁻¹⁴ each.
Ω · cm and 2 × 10 ³ Ω · cm. The resistance value of the resin coating film is 8 × 10 ³ Ω · c at an electric field of 100 V / cm.
m.

Comparative Example 1 Ferrite (C28-FB, volume average particle size 50 μm, manufactured by Fuji Electric Chemical Co., Ltd.) 100 parts by weight Toluene 14.5 parts by weight Methyl methacrylate / diethylamino methacrylate copolymer (copolymerization ratio) 70:30, weight average molecular weight 52000) 2 parts by weight A solution for forming a resin coating layer obtained by dissolving the above polymer in toluene and ferrite are placed in a vacuum degassing kneader, and the mixture is stirred at 60 ° C. for 20 minutes while reducing pressure. A resin coating layer was formed to obtain a carrier E. The thickness of the resin coating layer is 0.8 μm
Met. When this carrier was observed with a scanning electron microscope, it was confirmed that the carrier was uniformly coated with no exposed surface. Further, a solution for forming a resin coating layer was applied to a thickness of 0.8 μm on an ITO conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. The resistance of the ferrite and the carrier E was measured in the form of a magnetic brush. The resistance values when extrapolated to an electric field of 10 ⁴ V / cm are 1 × 10 ⁻⁵ Ω · cm and 6.3 × 10 ⁵ respectively.
It was ¹⁰ Ω · cm. 400V / c of carrier E
The value in an electric field of m is 1.0 × 10 ¹¹ Ω · cm, 4000 V
The value at an electric field of / cm was 9.8 × 10 ¹⁰ Ω · cm. The resistance value of the resin coating film was 1 × 10 ¹³ Ω · cm at an electric field of 100 V / cm. As can be seen from this comparative example, when the low-resistance core was uniformly coated with the high-resistance resin, no rapid change in resistance due to the electric field was observed.

Example 5 Ferrite (C28-FB, volume average particle diameter 50 μm, manufactured by Fuji Electric Chemical Co., Ltd.) 100 parts by weight Toluene 12.3 parts by weight Polymer 0.41 part by weight in Polymer Synthesis Example-1 Carbon 0.07 parts by weight of black (VXC72, 10 ^-1 Ω · cm, volume average particle size 30 nm, manufactured by Cabot Corporation) 0.07 parts by weight The above components except ferrite were dispersed in a sand mill for 1 hour to prepare a resin coating layer forming solution. Next, the resin coating layer forming solution and ferrite were put into a vacuum deaeration type kneader, and stirred at a temperature of 60 ° C. for 20 minutes while reducing the pressure to form a resin coating layer. The thickness of the resin coating layer was 0.2 μm. The content of carbon black in the resin coating layer was the same as in Example 1. Observation of this carrier with a scanning electron microscope revealed that the carrier had an exposed surface and was partially covered with resin. More ITO
A solution for forming a resin coating layer was applied to a thickness of 0.8 μm on a conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. The resistance of the carrier F was measured in the form of a magnetic brush, and the resistance value when extrapolated to an electric field of 10 ⁴ V / cm was 4.2 × 10 ⁶ Ω · cm. Note that the dynamic electric resistance value of the ferrite is the same as in Comparative Example 1. The resistance value of the resin coating film was 3 × 10 ⁵ Ω · cm at an electric field of 100 V / cm.

Example 6 Magnetite (MX030A, volume average particle diameter 50 μm, manufactured by Fuji Electric Chemical Co., Ltd.) 80 parts by weight Toluene 14 parts by weight Polymer 2 of polymer synthesis example-6 2 parts by weight Tin oxide (Pastran TYPE-IV) , 1 Ω · cm, volume average particle diameter 100 nm, manufactured by Mitsui Kinzoku Co., Ltd.) 2 parts by weight The above components except magnetite were dispersed in a sand mill for 1 hour to prepare a solution for forming a resin coating layer. Next, this resin coating layer forming solution and magnetite are put into a vacuum degassing type kneader, and stirred for 30 minutes while reducing the pressure at a temperature of 60 ° C. to form a resin coating layer. The mixture was stirred and a crosslinking reaction was carried out for 20 minutes.
I got The thickness of the resin coating layer was 0.8 μm. or,
The content of tin oxide in the resin coating layer was 13% by volume. When this carrier was observed with a scanning electron microscope, it was confirmed that the carrier was uniformly coated with no exposed surface. Further, a solution for forming a resin coating layer was applied to a thickness of 0.8 μm on an ITO conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. The electric resistance of the magnetite and the carrier G was measured in the form of a magnetic brush, and the resistance values when extrapolated to an electric field of 10 ⁴ V / cm were 1 × 10 ⁻¹ Ω · cm and 3 × 10 ⁶ Ω, respectively.
Cm. The resistance value of the resin coating film is 100 V /
It was 6.5 × 10 ⁴ Ω · cm at an electric field of cm.

Comparative Example 2 100 parts by weight of ferrite (F-300, volume average particle diameter 50 μm, manufactured by Powder Tech Co.), 12.3 parts by weight of toluene, styrene-methyl methacrylate copolymer (copolymerization ratio: 20:80, Weight average molecular weight 36000) 1.7 parts by weight Carbon black (VXC72, 10 ^-1 Ω · cm, volume average particle diameter 30 nm, manufactured by Cabot Corporation) 0.6 parts by weight The above components except for ferrite are dispersed in a sand mill for 1 hour. Thus, a solution for forming a resin coating layer was prepared. Next, the resin coating layer forming solution and ferrite were put into a vacuum degassing type kneader and stirred at a temperature of 60 ° C. for 20 minutes while reducing the pressure to form a resin coating layer. The thickness of the resin coating layer was 0.8 μm. In addition, carbon black (VXC7
The content in the resin coating layer of 2) was 17% by volume. When this carrier was observed with a scanning electron microscope, it was confirmed that the carrier was uniformly coated with no exposed surface.
Further, a solution for forming a resin coating layer was applied to a thickness of 0.8 μm on an ITO conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. When the resistance of the ferrite and the carrier H was measured in the form of a magnetic brush, the value at an electric field of 10 ⁴ V / cm was 9.1 each.
× 10 ⁷ Ω · cm (actual measurement value) and 1 × 10 ² Ω · cm (extrapolated value). The resistance value of the resin coating film is 100 V /
It was 3 × 10 ⁰ Ω · cm at an electric field of 10 cm.

Comparative Example 3 100 parts by weight of ferrite (EFC-50B, volume average particle diameter 50 μm, manufactured by Powder Tech Co., Ltd.) 12.6 parts by weight of toluene styrene-methyl methacrylate copolymer (copolymerization ratio 20:80, 1.7 parts by weight ・ Carbon black (VXC72, 10 ⁻¹ Ω · cm, volume average particle diameter 30 nm, manufactured by Cabot Corporation) 0.55 parts by weight The above components except ferrite are dispersed in a sand mill for 1 hour. Thus, a solution for forming a resin coating layer was prepared. Next, the resin coating layer forming solution and the ferrite were placed in a vacuum degassing type kneader, and stirred at a temperature of 60 ° C. for 20 minutes while reducing the pressure to form a resin coating layer. The thickness of the resin coating layer was 0.8 μm. In addition, carbon black (VXC7
The content in the resin coating layer of 2) was 15% by volume. When this carrier was observed with a scanning electron microscope, it was confirmed that the carrier was uniformly coated with no exposed surface.
Further, a solution for forming a resin coating layer was applied to a thickness of 0.8 μm on an ITO conductive glass substrate using an applicator to obtain a sample for measuring the electrical resistance of the resin coating film. Measure the resistance of ferrite and carrier I in the form of a magnetic brush,
The resistance values when extrapolated to an electric field of 10 ⁴ V / cm were 1 × 10 ² Ω · cm and 8 × 10 ⁴ Ω · cm, respectively. The resistance value of the resin coating film was 8 × 10 ⁰ Ω · cm at an electric field of 100 V / cm.

[0086]Comparative Example 4 In Example 1, the composition of the polymer was set to the following ratio.
Except for this point, the carrier J is manufactured in the same manner as in the first embodiment. [Polymer composition] -Polystyrene (weight average molecular weight 55,500) 100 parts by weight-Poly N, N-dimethylaminoethyl methacrylate (weight average molecular weight 35,000) 5.0 parts by weight-Methyl methacrylate and perfluorooctyl ethyl methacrylate Copolymer (copolymerization ratio 80:10:10, weight average molecular weight 15000) 10.0 parts by weight The obtained carrier was observed with a scanning electron microscope.
B, it was confirmed that there was no exposed surface and the resin was uniformly coated.
Was done. Applicator on ITO conductive glass substrate
To a thickness of 0.8 μm using a resin coating layer forming solution
And apply the sample to measure the electrical resistance of the resin coating film.
Obtained. Magnetite and carrier J are fixed in the form of a magnetic brush.
Anti-measure, 10^FourThe resistance when extrapolating to an electric field of V / cm
4x10 each^-FiveΩ · cm, 1.8 × 10⁸Ω
Cm. The resistance value of the resin coating film is 100V /
3 × 10 in cm electric field ^FiveΩ · cm.

[Production Method of Toner] Linear polyester resin (linear polyester obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexanedimethanol; Tg = 62 ° C., Mn = 4,000, Mw = 12) 000, acid value = 12, hydroxyl value = 25) 100 parts by weight Magenta pigment (CI Pigment Red 57) 4 parts by weight The above mixture is kneaded with an extruder, pulverized by a jet mill, and then subjected to wind classification. Classification by a press gave a magenta toner having d ₅₀ = 7 μm.

[Evaluation Test] Examples 1 to 6 and Comparative Examples 1 to
100 parts by weight of the carrier obtained in
It was mixed with parts by weight to prepare developers corresponding to the carriers of Examples 1 to 6 and Comparative Examples 1 to 4. About these developers, an electrophotographic copying machine (A-Co, manufactured by Fuji Xerox Co., Ltd.)
lor630), the evaluation environment was adjusted to a temperature of 22 ° C. and a humidity of 55%, and the following copy test was performed.

(Image Density) A solid image (20 × 20 mm ² ) having a document density of 1.30 was copied, and the relative reflection density of the output image with respect to white paper was copied using a Macbeth densitometer.
The measurement was performed for the sheet and the 50,000th sheet. Regarding the result of the 50,000th sheet, if the image density difference is within 0.1 from the original density (1.30), it is judged that the stability of the image density is good. And

(In-plane density unevenness) A solid image (20 × 20 mm ² ) having an original density of 1.30 was copied, a limit sample was provided, and the sensory evaluation was performed by visual observation of the output image. The symbol “に は” indicates complete uniformity, “○” indicates uniformity that does not cause any practical problem, and “×” indicates non-uniformity. The evaluation was performed on the tenth and 50,000th copies.

(Brush mark) The number of white marks included in the output image is determined by the unit length (5 mm) perpendicular to the brush direction.
Was evaluated with a microscope. The evaluation was performed on the first copy.

The above results are shown in Table 5 below.

[0093]

[Table 5]

As can be understood from this table, when the carrier (A, B, C, D, F, G) of the present invention was used, a high solid image density was obtained, and there was no unevenness in density and no change with time. Or less. In addition, no brush marks at all
Or hardly ever. The stability of carrier D is slightly inferior to that of carriers A, B and C. Also,
As in the case of the carrier F, when a core having a low resistance was coated with a thin resin coating layer having a medium resistance as compared with the carrier A of the example 1, brush marks were slightly generated. This is probably because although the resistance of the carrier is within the desired range, the presence of the exposed surface causes the electric charge to leak therefrom and a slight brush mark is generated.

On the other hand, when the low-resistance core is uniformly coated with the high-resistance resin like the carrier E of the comparative example,
No brush mark was observed, but density unevenness was observed at the center and the periphery of the solid image, and the image density was low. This is presumably because the resistance of the resin coating layer was too high and the resistance of the carrier also exceeded a desired value, resulting in IMB-like characteristics. When a low-resistance resin coating layer was formed on a high-resistance core like the carrier H of the comparative example, a brush mark was generated, the image density was low, and density unevenness was observed.
Even when a low-resistance resin coating layer was formed on a medium-resistance core like the carrier I of the comparative example, brush marks were generated, and the image density was low and density unevenness was observed. It is considered that, although the resistance of the carrier is within a desired range, the resistance of the resin coating layer is too low and an image defect occurs. In the case of the carrier J of Comparative Example 4, the image quality stability over time is lacking. This is presumably because defects of the resin coating layer occur early because the incompatible resin is used in the resin coating layer.

As can be seen from the above results, a high-quality color image free from image defects can be obtained by uniformly forming a medium-resistance resin coating layer on a low-resistance core and controlling the carrier resistance to a desired range. Is obtained.

[0097]

According to the present invention, the charge amount under high temperature and high humidity conditions and the charge amount under low temperature and low humidity conditions are not significantly increased. A long-life carrier for electrostatic charge development, an electrostatic latent image developer, and an image forming method can be provided. Particularly for color images, good solid images without causing image defects such as brush marks and carrier over. And a durable electrophotographic carrier, an electrostatic latent image developer, and an image forming method.

[Brief description of the drawings]

FIG. 1 shows the results when resistance was measured using the carrier of Example 1 in the form of a magnetic brush, and the current density J and applied electric field E were measured.
Shows the relationship. The resistance value is a value when extrapolated to an electric field of 10 ⁴ V / cm.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaneishi 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (12)

[Claims] 1. A resin coating containing conductive powder on a core material.
In an electrophotographic carrier having a layer, the core material is magnetic.
10 with brush^FourDynamic electricity under electric field of V / cm
The air resistance is 1 Ωcm or less, and the electric resistance of the resin coating layer is
10 to 1 × 10⁸Is in the range of Ωcm and the resin coating
The resin of the covering layer is represented by the following general formula (I) and / or (II).
Represented by the following general formula (III) and / or (IV)
Of a monomer to be copolymerized as an essential component
Dam copolymer, block copolymer, or graft copolymer
An electrophotographic carrier characterized by being united. -General formula (I)In the general formula (I), R₁Represents a hydrogen atom or a methyl group
And A is-(CH₂)_n1-NR₂R₃And R₂And
And R₃Are each independently an alkyl group or an aryl group
And n1 represents an integer of 0 to 10.・ General formula (II)In the general formula (II), R_FourRepresents a hydrogen atom or a methyl group
And B is-(CH₂)_n2-NR_FiveR₆And R_FiveAnd
And R₆Are each independently an alkyl group or an aryl group
And n2 represents an integer of 0 to 10.・ General formula (III)In the general formula (III), R₇Represents a hydrogen atom or a methyl group
And A'is-(CH₂) _n3-(CF₂)_m-CF₃Also
IsAnd n3 represents an integer of 0 to 12, and m represents 1 to 12
Represents an integer. -General formula (IV)In the general formula (IV), R₈Represents a hydrogen atom or a methyl group
B'is-(CH₂) _n4-(CF₂)_m-CF₃Also
Is, N4 represents an integer of 0 to 8, and m is an integer of 1 to 10.
Z represents an oxygen atom, carbonyl or acid amide
Represent 2. The resin of the resin coating layer is obtained by copolymerizing a monomer represented by the following general formula (V) and / or (VI) as an essential component in addition to the monomer described in claim 1. An electrophotographic carrier, which is a random copolymer, a block copolymer, or a graft copolymer. -General formula (V) In the general formula (V), R ₉ represents hydrogen or a methyl group;
A "represents hydrogen, an alkyl group, a cycloalkyl group, an aryl group, an allyl group, an alkoxyalkylsilyl group, or an epoxyalkyl group.-General formula (VI) In the general formula (VI), R ₁₀ represents hydrogen or a methyl group,
B ″ represents hydrogen, an alkyl group, a cycloalkyl group, or an aryl group. 3. A random copolymer, a block copolymer, or a resin in which a resin of a resin coating layer is obtained by copolymerizing a crosslinkable monomer as an essential component in addition to the monomer according to claim 1 or 2. And an electrophotographic carrier, which is a graft copolymer. 4. The electrophotographic carrier according to claim 1, wherein the resin coating layer has a thickness of 0.3 to 5 μm. 5. The core material has a volume average particle diameter of 10 to 100.
The electrophotographic carrier according to any one of claims 1 to 4, wherein the thickness of the carrier is μm. 6. The carrier for electrophotography according to claim 1, wherein the core material is ferrite. 7. The carrier for electrophotography according to claim 1, wherein the core material comprises magnetic powder dispersed in a thermoplastic resin or a thermosetting resin. 8. The electrophotographic carrier according to claim 1, wherein the electric resistance of the conductive powder is 10 ⁶ Ωcm or less. 9. The method according to claim 9, wherein the conductive powder is contained in the resin coating layer in an amount of 2 to 40.
The electrophotographic carrier according to any one of claims 1 to 8, wherein the carrier is contained by volume%. 10. The electrophotographic carrier according to claim 1, wherein the dynamic electrical resistance in an electric field of 10 ⁴ V / cm in the state of a magnetic brush is in the range of 10 to 1 × 10 ⁹ Ωcm. 10. The carrier for electrophotography according to item 9. 11. An electrostatic latent image developer comprising toner particles comprising a binder resin and a colorant, and a carrier having a resin coating layer provided on a core material, wherein the carrier is used.
3. An electrostatic latent image developer, which is the carrier for electrophotography according to item 1. 12. A step of forming a latent image on a latent image carrier,
An image forming method comprising: developing the latent image using a developer; transferring the developed toner image to a transfer member; and fixing the toner image on the transfer member by heating. An image forming method using the electrostatic latent image developer according to claim 11.