JPH09304972A - Image forming method and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a stable image extending over a long period, especially form a stable image even under high temperature and high humidity environment by using magnetic particles having a specified specific gravity for carrier. SOLUTION: In an image forming method comprising the steps of forming an electrostatic latent image on an organic photoreceptor having a surface layer containing fine particles, and developing the image with a developer composed of toner and carrier, magnetic particles having a specific gravity of 3.5-6.0 are used for carrier. As the magnetic particles used here, iron, magnetite ferrite are used. As a manufacturing method for magnetic particles, a sintering process, an atomize method are cited, and fine powder of two or more kinds at need are mixed and sintered to obtain the particles. As a binder resin of carrier, no limitation is put thereon and various kinds of resin can be used. For example, as a binder resin, cited are polyester resin, styrene, phenol resin and polyolefins and so on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming method and an image forming apparatus used in copying machines, printers and the like.

[0002]

2. Description of the Related Art In recent years, electrophotographic photoconductors are shifting from inorganic photoconductors such as selenium to organic photoconductors in view of prevention of environmental pollution. As the organic photoreceptor, a so-called laminated organic photoreceptor comprising a charge generation layer and a charge transport layer on a conductive support via an adhesive layer as necessary is 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.

In order 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-1-205
No. 171 discloses a photoreceptor having a protective layer containing an inorganic filler. In each case, various fine particles are added to the surface layer of the photoreceptor to improve the wear resistance of the photoreceptor. The purpose is to improve the durability of the photoreceptor by reducing the abrasion resistance.

However, when such a highly durable photoreceptor is used, the photoreceptor itself hardly wears out, and although the durability is improved due to the problem of wear, the adhesion to the photoreceptor surface is reduced. When it occurs, it is difficult to remove it, so that it is not possible 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 during long-term use, and the adsorption of water causes a problem that the charge on the surface of the photoconductor leaks and image deletion occurs. This phenomenon often occurs particularly in a high-temperature and high-humidity environment.

As described above, a stable image cannot be formed for a long period of time by an image forming method using a photoreceptor having a highly durable surface and a protective layer having an abrasion resistance function. .

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method and an image forming apparatus capable of forming a stable image for a long period of time, particularly a stable image even in a high temperature and high humidity environment.

[0007]

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

(1) In an image forming method in which an electrostatic latent image is formed on an organic photoreceptor having a surface layer containing fine particles and is developed with a developer comprising a toner and a carrier, the carrier is An image forming method comprising magnetic particles having a specific gravity of 3.5 to 6.0.

(2) In an image forming apparatus in which an electrostatic latent image is formed on an organic photoreceptor having a surface layer containing fine particles and is developed with a developer consisting of toner and carrier, the carrier is An image forming apparatus comprising magnetic particles having a specific gravity of 3.5 to 6.0.

(3) The volume average particle diameter of the carrier is 3
The image forming method as described in (1), which is 0 to 200 μm.

That is, the inventors of the present invention have diligently studied a method for preventing the influence of water adsorbed on the surface of the photosensitive member.
It has been found that the above 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 contacts the photoconductor with the two-component developer. Although the polishing effect is exhibited by the contact of the carrier itself, it has been found that it is necessary to use a carrier having a specific gravity for this purpose. It is presumed that, by specifying this specific gravity, the carrier itself exerts the polishing effect, finely polishes the photoconductor, and as a result, exhibits the action of removing the water or the like attached or adsorbed to the photoconductor.

The present invention is particularly effective in an image forming method or apparatus in which a developer layer is brought into contact with a photoreceptor in a developing area.

Structure of Carrier of the Present Invention The carrier of the present invention may be used as it is as magnetic particles,
A magnetic substance-dispersed carrier in which magnetic particles are dispersed and contained in a binder resin may be used. In any case, the surface of these carrier particles may be coated with a resin.

(Magnetic Particle Carrier) The magnetic particles used in the present invention include iron, magnetite, ferrite and the like.

The ferrite referred to here is MO.Fe ₂ O ₃
(M is a divalent metal such as copper, zinc, iron, nickel, cobalt, magnesium, and manganese).

Examples of the method for producing the magnetic particles include a sintering method and an atomizing method, and they can be obtained by mixing and sintering two or more kinds of fine powders, if necessary.

(Magnetic Material Dispersed Carrier) The binder resin of the carrier is not particularly limited and various resins can be used.

For example, as the binder resin, polyester resin, styrene, phenol resin, methyl acrylate,
Examples thereof include styrene resins obtained from ethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and the like, and styrene-acrylic resins, epoxy resins, polyolefins such as polyethylene and polypropylene. Further, these resins may be crosslinked by using a polyfunctional monomer in combination.

As a manufacturing method, a mixture of a binder resin and magnetic particles is melt-kneaded, cooled, and pulverized to obtain a carrier having a desired particle size, which is then sprayed in hot air using a spray dryer or the like. The surface is melted instantaneously and the carrier is made spherical by the surface tension, or the binder resin is dissolved in a soluble solvent, and the magnetic particles are mixed with this to make a slurry, which is then formed using a spray dryer. Examples thereof include a method in which the particles are dried and a method in which the magnetic particles are dispersed in a monomer constituting the resin and then obtained by a suspension polymerization method.

(Coating Resin) As the resin for coating the surface, a known appropriate resin can be used.
For example, fluororesin (vinylidene fluoride, tetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, fluoroalkyl (meth) acrylate copolymer, etc.), silicone resin (methyl silicone, dimethyl silicone, phenyl silicone, etc.) ), Styrene resins (styrene, chlorostyrene, methylstyrene, etc.), acrylic resins (methyl methacrylate, methyl acrylate, propyl acrylate, lauryl acrylate,
Lauryl methacrylate, acrylic acid, methacrylic acid,
Butyl methacrylate, butyl acrylate, etc.), styrene-acrylic resin, polyester resin, ethylene resin, rosin-modified resin, polyamide resin and the like. Also, these may be used in combination. Particularly preferred are silicone resins and fluororesins, which are low surface energy resins.

Examples of the coating method include a dipping method, a spray drying method and the like as a wet method, and a method in which a mechanical impact force is applied to fix the coating resin fine particles on the surface of the magnetic particles to coat them, as a dry method. The resin coating amount is preferably 0.01 to 30 wt%, and particularly preferably 0.05 to 20 wt% with respect to the magnetic particles.

(Carrier Particle Size) The volume average particle size of the carrier is preferably 20 to 300 μm, more preferably 30 to 300 μm.
200 μm. If it is less than 20 μm, carrier adhesion to the photoconductor tends to occur. If it is larger than 300 μm, the developing brush on the developing sleeve becomes rough and a good image cannot be obtained. The average particle diameter of the carrier is a volume-based average particle diameter measured by a laser diffraction type particle size distribution measuring device “HELOS” (manufactured by Sympatech Co.) equipped with a wet disperser.

(Carrier Specific Gravity) The carrier specific gravity is 3.
Those in the range of 5 to 6.0 are used. If it is less than 3.5, the image polishing and image blurring occur under high temperature and high humidity because the force for polishing the photoconductor is weak. If it exceeds 6.0, the force for polishing the photoconductor is too strong, so that the surface of the photoconductor is scratched. By repeating the development, the toner adheres to the surface to cause image defects such as black spots. The specific gravity referred to here is the true specific gravity measured by a high precision automatic volume meter VM-100 (manufactured by STEC Co., Ltd.).

Structure of Photoreceptor In the photoreceptor of the present invention, a charge generating layer and a charge transporting layer are laminated on the surface of a conductive substrate with an undercoating layer if necessary, or a charge generating substance and a charge transporting substance are mixed. Forming a photosensitive layer,
A photoreceptor having a layer containing fine particles formed on the surface thereof. In this case, an independent layer containing fine particles may not be formed, and a method of forming fine particle layers on the surface by dispersing fine particles in the entire photoreceptor layer may be used.

As the conductive substrate, a metal plate of aluminum, stainless steel, iron or the like, a metal layer of aluminum, palladium, gold or the like is provided by laminating or vapor deposition on the surface of a flexible support such as paper or plastic film. It is possible to use a material having a layer containing a conductive compound such as a conductive polymer, indium oxide or tin oxide applied or vapor-deposited on the surface of a flexible support such as paper or plastic film.

As an undercoat layer used as necessary, casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, polyamides (nylon 6, nylon 66, alkoxymethylated) Nylon etc.), polyurethane, gelatin and aluminum oxide 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 generating layer is a layer containing a charge generating substance, and the charge generating substance is not particularly limited, and examples thereof include phthalocyanine pigments, polycyclic quinone pigments, azo pigments, perylene pigments and 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 the charge-transporting substance is not particularly limited, and examples thereof include oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives and triazole derivatives. , Imidazole derivative, imidazolone derivative, imidazoline derivative, bisimidazolidine derivative, styryl compound, hydrazone compound, benzidine compound, pyrazoline derivative, stilbene compound, amine derivative, oxazolone derivative, benzothiazole derivative, benzimidazole derivative, quinazoline derivative , Benzofuran derivative, acridine derivative, phenazine derivative, aminostilbene derivative, poly-N-vinylcarbazoles, poly-1-vinylpyrenes, poly-9-vinylant Mosses and the like. It is formed by dispersing or dissolving these in a resin alone or in combination.

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, silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin, etc. You can The thickness of the charge transport layer is 5 to 50 μm, preferably 10 to 4
0 μm.

In the case of a photoreceptor layer composed of a mixture of a charge transport substance and a charge generating substance, the above charge transport substance and the charge generating substance are appropriately mixed and dispersed in the resin shown 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.

The fine particles used in the layer containing the fine particles of the present invention 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.

The Mohs hardness of the inorganic fine particles means the Mohs hardness of the substance having the material. The Mohs hardness is a relative hardness that is evaluated based on the presence or absence of scratches using a standard material in which talc is 1 and diamond is 10 in sequence.

Crosslinked organic fine particles are particularly preferable as the organic fine particles. The crosslinked organic fine particles are organic fine particles in which an insoluble content in a solvent is 30% or more. Specifically, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, , 4-dimethylstyrene, pt-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene and pn-dodecylstyrene. Styrene or styrene derivative, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacryl Lauryl acid, phenyl methacrylate, Acrylic acid diethylaminoethyl, methacrylate derivatives such as dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n- butyl acrylate, t-
Butyl, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, acrylate derivatives such as phenyl acrylate, olefins such as ethylene, propylene and isobutylene, vinyl chloride, Vinylidene chloride, vinyl bromide, vinyl fluoride and other halogenated vinyls, vinyl propionate, vinyl acetate, vinyl benzoate and other vinyl esters, vinyl methyl ether, vinyl ethyl ether and other vinyl ethers, vinyl methyl ketone, vinyl Vinyl ketones such as ethyl ketone and vinyl hexyl ketone; N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; vinyl compounds such as vinyl naphthalene and vinyl pyridine; Lil, methacrylonitrile, divinylbenzene relative to such vinyl monomers of acrylic acid or methacrylic acid derivatives such as acrylamide, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate,
Vinyl-based organic fine particles obtained by adding a polyfunctional vinyl compound such as diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and the like, and Examples thereof include condensation type organic fine particles such as polyurethanes, polyureas, crosslinked polyesters and crosslinked silicone resins formed by condensation of polyvalent isocyanates and polyvalent amines.

These fine particles have a number average primary particle diameter of 0.
It is preferably from 1 to 5 μm. More preferably 0.0
5 to 2 μm. When the particle size is large, the surface layer itself becomes brittle, the desired improvement in durability cannot be achieved, and the presence of fine particles causes damage to the cleaning mechanism. Further, when the particle size is small, the hardness does not improve due to the presence of fine particles, and the durability does not improve.

Further, the volume resistance of these fine particles themselves is 10
⁸ Ωcm or more is preferable. If the resistance is lower than this range, the resistance of the surface is reduced, the charge retention function is reduced, and a problem of causing image defects is induced.

When the surface layer is formed, it can be formed by dispersing the fine particles in a resin and coating the resin. The constituent resin is not particularly limited, for example, 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, silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, polyvinyl butyral resin Etc. can be given.

The content of fine particles in these resins is 0.05 to 200 parts, preferably 0.1 to 100 parts, relative to 100 parts of the resin (parts by weight unless otherwise specified). 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, the surface layer of the present invention has a thickness of 0.2 to 10 μm,
It is preferably 0.4 to 5 μm. When this layer is thin, the effect of improving durability of the present invention is not exhibited, and when the film thickness is thick, the effect of improving durability is exhibited, but occurrence of image defects due to light scattering and , Causes a problem of reduced sensitivity.

The layer containing the fine particles of the present invention preferably contains a charge transporting substance. That is, since the specific surface layer is not formed by containing the charge transporting substance, 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.

Structure of Cleaning Mechanism The mechanism for cleaning the toner remaining on the photosensitive member used in the present invention is not particularly limited, and a blade cleaning system, a magnetic brush cleaning system,
A known cleaning mechanism such as a fur brush cleaning method can be used. A preferred cleaning mechanism is a blade cleaning method using a so-called blade.

As this structure, any of the structures shown in FIGS. 1 and 2 can be used. 1 and 2, the holder 3 holds the cleaning blade 1. The number of photosensitive members is 2. The angle holder and the photosensitive member is formed theta ₁ shown in FIG either FIGS 1
It is 0 to 90 °, preferably 15 to 75 °.

An elastic body such as silicone rubber or urethane rubber can be used as a material for the cleaning blade itself. In this case, the rubber hardness is 30 to
90 ° is better. The thickness is preferably 1.5 to 5 mm, and the length other than the holder portion is preferably 5 to 20 mm. The pressure contact force with respect to the photoconductor is preferably 5 to 50 gf / cm.

The constituent toner of the developer such as the toner comprises a binder resin, a colorant and other additives which are optionally used, and the average particle diameter thereof is usually 1 to 1 in terms of volume average particle diameter. It is 30 μm, preferably 5 to 20 μm.

The binder resin constituting the toner is not particularly limited, and various conventionally known resins can be used. For example, styrene resin, acrylic resin, styrene-acrylic resin, polyester resin, etc. may be mentioned. The colorant that constitutes the toner is not particularly limited, and various conventionally known materials are used. Examples include carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, rose bengal, and the like. Examples of other additives include charge control agents such as salicylic acid derivatives and azo-based metal complexes.

From the viewpoint of imparting fluidity, inorganic fine particles may be added. The inorganic fine particles are preferably inorganic oxide particles such as silica, titania, and alumina, and the inorganic fine particles are preferably hydrophobized with a silane coupling agent, a titanium coupling agent, or the like.

The two-component developer is prepared by mixing the toner and the carrier of the present invention. The toner concentration is 2 to 10% by weight.

The developing method of the present invention is not particularly limited. As a suitable method, it is suitable for contact-type development. In this case, the layer thickness of the developer is 0.1 to 8 mm, preferably 0.4 to 5 mm in the developing area. Further, the gap between the photoconductor and the developer bearing member is 0.15.
-7 mm, preferably 0.2-4 mm.

FIG. 3 is a conceptual diagram of the periphery of the developing device preferably used in the present invention.

In this developing device, a magnet roll having a large number of N and S poles is housed in a developer carrier 13 made of a non-magnetic material such as aluminum. It is provided so that the front photosensitive surface of the photoconductor 14 serving as an electrostatic charge image carrier is located with a minute gap (Dsd) from the developer carrier 13. The developer carrier 13 and the photoconductor 14 are rotatably supported by the machine frame, and rotate in the same direction or in the opposite direction. In the present invention, it is desirable to drive the developer carrying member 13 and the photoconductor 14 at the developing position so that the moving directions thereof are the same direction (rotational directions are opposite to each other).

A fixed main magnetic pole (N
1) and fixed magnetic pole (N2), fixed magnetic pole (S1, S2, S
3) is arranged, the tilt angle (θ) of the fixed main pole (N1)
Is determined by an angle formed by a fixed main magnetic pole and a line (L1) connecting the rotation centers of the developer carrying member 13 and the photoconductor 14, and the fixed main magnetic pole rotates more than the L1. If it is on the upstream side in the direction, it is a positive value and the fixed main pole is L
If it is located on the downstream side of the developer carrying member 13 in the rotation direction, it is represented by a negative value.

In the present invention, the inclination angle (θ) of the fixed main magnetic pole (N1) provided in the developer carrying member 13 is preferably in the range of +2 to + 15 °. When the inclination angle of the fixed main magnetic pole (N1) is less than + 2 °, carrier adhesion may be significant, or the surface of the photoconductor 14 may be scratched, resulting in defective images. Further, when the inclination angle of the fixed main magnetic pole is larger than + 15 °, the width (rubbing width) in which the developer on the developer carrying member 13 can rub the surface of the photoconductor 14 becomes excessively small, resulting in the present invention. Not only the surface of the photoreceptor cannot be cleaned by the polishing effect of the carrier, but also the electrostatic image on the surface of the photoreceptor 14 cannot be sufficiently developed, and the density of the solid portion may decrease.

Between the developer carrier 13 and its peripheral edge,
It is preferable to arrange the brush cutting mechanism plate 15 so that the magnetic developer layer thickness can be regulated and the length of the brush of the developer can be made constant. The distance between the developer carrier 13 and the spike cutting mechanism plate 15 (H
Cut) is preferably in the range of 0.2 to 5 mm. In this case, the layer thickness of the developer is 0.1 to 8 mm in the developing area,
It is preferably 0.4 to 5 mm.

The gap between the developing sleeve (developer carrying member) and the photosensitive member is preferably 0.1 to 5 mm, particularly 0.3 to 3 m.
m is preferred. If the gap is larger than 5 mm, it is difficult to obtain a high-density image, and if it is smaller than 0.1 mm, the photoconductor may be swept with a developing brush, and horizontal lines may disappear or solid areas may have sweeps. Further, normally, a bias voltage is applied between the developer carrying member 13 and the photosensitive member 14 by a developing bias power source (not shown). The bias may be only a DC bias or may be combined with an AC bias. DC bias is 50-300V anyway
Is preferred.

[0055]

The present invention will be described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto. In the description, “parts” means “parts by weight”.

Preparation Example of Photoreceptor An undercoat layer made of polyamide resin and having a thickness of 0.3 μm was provided on an aluminum drum having a diameter of 80 mm.

Then, a mixed solution comprising 10 parts of polyvinyl butyral and 1600 parts of methyl ethyl ketone with respect to 30 parts of a perylene compound as a charge generating substance was prepared,
After dispersing the charge generating substance, it was coated on the undercoat layer and dried to form a charge generating layer having a thickness of 0.3 μm.

Subsequently, a solution was prepared by mixing 500 parts of a styryl compound as a charge transport material, 600 parts of a bisphenol Z type polycarbonate resin, and 3000 parts of dichloromethane, and the solution was applied onto the charge generation layer and dried to have a film thickness of 25 μm. Was formed on the charge transport layer.

Further, a liquid having the fine particles shown in Table 1 below dispersed in 100 parts of a bisphenol Z-type polycarbonate resin containing 100 parts of a styryl compound was prepared, coated and dried to have a high hardness on the surface. A protective layer was prepared.

[0060]

[Table 1]

The crosslinked styrene-acrylic resin fine particles are prepared by using divinylbenzene as a crosslinking agent and adjusting the particle size and the degree of crosslinking by emulsion polymerization or seed polymerization. The degree of crosslinking of this product, that is, the insoluble matter in the solvent is a measurement of the insoluble matter in methyl ethyl ketone. When no crosslinking agent is used, the insoluble content is 0%.

( Developer Production Example ) Carrier Production Example (1) Carrier 1 900 parts of magnetite having a number average primary particle size of 0.3 μm was added to 100 parts of styrene-acrylic resin and dry mixed using a Henschel mixer, After melt-kneading with a three-roll mill, after cooling, it is roughly crushed with a hammer mill, further crushed and classified, and instantaneous heat is applied with a spray dryer with a hot air temperature of 300 ° C to make it spherical, and the volume average particle size is Of 60 μm and a specific gravity of 3.6 were obtained.

(2) Carrier 2 molar ratio of Fe ₂ O ₃ = 54 mol%, CuO = 24 mol%,
Raw materials of ZnO = 22 mol% were weighed and mixed by a ball mill. The obtained mixed powder was pulverized, a binder was added, and the mixture was granulated by a spray dryer.

Thereafter, it is sintered and the volume average particle diameter is 60 μm.
Magnetic particles were obtained. To 500 parts of the magnetic particles, 50 parts of a room temperature curable silicone resin solution was sprayed using a fluidized bed apparatus, and then dried at 180 ° C. to obtain a silicone resin-coated carrier having a specific gravity of 4.6. The resin coating amount is 1 wt%.

(3) Carrier 3 Fe ₃ O ₄ was pulverized, a binder was added, and the mixture was granulated by a spray dryer. Then, it is sintered and the volume average particle size is 60.
Magnetic particles of μm were obtained. The magnetic particles (500 parts) were sprayed with room temperature curable silicone resin solution (50 parts) using a fluidized bed apparatus and then dried at 180 ° C. to give a specific gravity of 5.
0 silicone resin coated carrier was obtained. The resin coating amount is 1 wt%.

(4) Carrier 4 In the same manner as in Carrier 1, except that 230 parts of iron powder having a number average primary particle size of 0.3 μm was added in place of magnetite, the volume average particle size was 60 μm and the specific gravity was 5.7. A magnetic material dispersed carrier was obtained.

(5) Carrier 5 (for comparison) In the same manner as carrier 1, except that 500 parts of magnetite having a number average primary particle diameter of 0.3 μm was added, the volume average particle diameter was 60 μm and the specific gravity was 3.0. A body-dispersed carrier was obtained.

(6) Carrier 6 (for comparison) Commercially available iron powder carrier (Dowa Iron Powder Co., Ltd .: DSP-138)
500 parts of 10 parts of the room temperature curable silicone resin solution was sprayed using a fluidized bed apparatus and then dried at 180 ° C. to obtain a silicone resin coated carrier having a volume average particle diameter of 120 μm and a specific gravity of 7.2. The resin coating amount is 1
wt%.

Toner Production Example 100 parts of polyester resin (PEs), 5 parts of carbon black and 3 parts of low molecular weight polypropylene were added, melted and kneaded, pulverized and classified, and then the volume average particle diameter was 8.3 μm.
To obtain colored particles of. Then, 0.8 wt% of hydrophobic silica was added to the resultant to obtain a toner.

Preparation of Developer The above toner was added to and mixed with the carrier of the present invention to prepare Developers 1 to 4 of the present invention and Comparative Developers 1 and 2 having a toner concentration of 6 wt%.

(Evaluation) Copy machine U-BIX3 manufactured by Konica
Evaluation was performed using 135. The developer layer is 1.
5 mm, and the gap between the photoconductor and the developer carrier is 0.5 mm.

By combining the above-mentioned photoconductor and the above-mentioned developer, copying was carried out at high temperature and high humidity (33 ° C., 80% RH) at a 5% pixel ratio for a total of 50,000 sheets for 10 days (5 Thousands / day), and the presence or absence of black spots due to drum scratches and defects on the image due to image deletion were evaluated in units of 1,000 sheets. The table below shows the number of image defects caused by image deletion and the number at the time when black spots started to occur.

As the cleaning condition, the angle θ formed by the holder and the photosensitive member is set in the configuration shown in FIG.
₁ is 22 °, and urethane rubber was used as a material constituting the cleaning blade itself. The rubber hardness was 65 °, the thickness was 2 mm, and the length outside the holder was 8 mm. Further, the pressure contact force with respect to the photoconductor is 15 gf / cm.

The evaluation paper used was A4.

[0075]

[Table 2]

When the developers 1 to 4 in the present invention are used,
Image deletion and black spots did not occur even in repeated 50,000 times repeated copy evaluation under high temperature and high humidity.

On the other hand, when the comparative developer 1 other than the present invention was used, black spots did not occur, but especially the image deletion occurred in the copied image at the beginning of the day. When the comparative developer 2 was used, black spots were generated from 6000 copies, although the image deletion did not occur.

[0078]

According to the present invention, it is possible to provide an image forming method and an image forming apparatus capable of forming a stable image for a long period of time, particularly a stable image even in a high temperature and high humidity environment.

[Brief description of drawings]

FIG. 1 is a sectional view showing a cleaning mechanism of an image forming apparatus used in the present invention.

FIG. 2 is a cross-sectional view showing a cleaning mechanism of the image forming apparatus used in the present invention.

FIG. 3 is a cross-sectional view showing the periphery of a developing device used in the present invention.

[Explanation of symbols]

 1 Cleaning Blade 2 Photoconductor 3 Holder 13 Developer Carrier 14 Photoconductor 15 Ear Cutting Mechanism Plate N1 Fixed Main Pole N2 Fixed Magnetic Pole S1, S2, S3 Fixed Magnetic Pole

Claims (3)

[Claims] 1. An image forming method in which an electrostatic latent image is formed on an organic photoreceptor having a surface layer containing fine particles and is developed with a developer comprising a toner and a carrier, wherein the carrier is 3 An image forming method comprising magnetic particles having a specific gravity of 0.5 to 6.0. 2. An image forming apparatus for forming an electrostatic latent image on an organic photoconductor having a surface layer containing fine particles and developing the latent image with a developer comprising a toner and a carrier. An image forming apparatus comprising magnetic particles having a specific gravity of 0.5 to 6.0. 3. The volume average particle diameter of the carrier is 30 to 2
The image forming method according to claim 1, wherein the image forming method is 00 μm.