JPH09146308A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a stable image over a long term, especially, even under environment such as high temperature and high humidity by using magnetic grains with carrier having a specified grain diameter. SOLUTION: The surface shape of the carrier grain is fixed according to the size of the grain diameter. Namely, in the case the grain diameter is small, a rugged part on the carrier surface becomes large; on the contrary, in the case the grain diameter is large, the rugged part becomes small and the surface shape becomes smooth. The grain diameter is controlled to be 0.2-10μm. When a latent image on a photoreceptor is developed, not only toner but also carrier are brought into contact with the photoreceptor in the case of two-component developer. By controlling the shape of the carrier, the grinding effect of the carrier itself is achieved, so that the photoreceptor is finely ground, consequently, water adhering or absorbed in the photoreceptor is removed. As for a cleaning mechanism for removing the toner remaining on the photoreceptor 2; it is desirable that a cleaning blade 1 is held by a holder 3 and an angle θ1 formed by the photoreceptor 2 with the holder 3 is 10-90 deg..

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 used in copying machines, printers and the like.

[0002]

2. Description of the Related Art In recent years, electrophotographic photoconductors have been shifting from inorganic photoconductors such as selenium to organic photoconductors for the purpose of preventing environmental pollution and facilitating mass production.

There are various types of organic photoconductors, and a typical one is a structure in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support. It is a thing. In many cases, an intermediate layer is provided between the conductive support and the charge generation layer, or a surface protective layer is provided on the charge transport layer, if necessary.

In these so-called laminated organic photoreceptors, the charge transport layer is usually composed of a resin layer containing a charge transport substance (the same applies to the surface protective layer). However, the resin layer is generally soft, and when it is used over time, abrasion due to surface abrasion occurs in the process such as a magnetic brush in the developing section and a cleaning step for removing the toner remaining in the transfer, and therefore, it cannot be used for a long time. Has the problem of being intolerable.

In order to solve this problem, Japanese Patent Laid-Open No. 2-1
No. 18667 discloses an organic photoconductor having a coating layer in which hydrophobic silica is dispersed, and Japanese Patent Laid-Open No. 57-30846 discloses a protective layer containing fine particles of metal or metal oxide having an average particle size of 0.3 μm or less. Configuration, JP-A 1-2
Japanese Patent No. 05171 discloses a photoconductor having a protective layer containing an inorganic filler and the like. Each of these methods is a method of adding various fine particles to the surface layer of the photoconductor to improve the wear resistance of the photoconductor, and the purpose is to increase the wear resistance and improve the durability of the photoconductor.

However, when such a highly durable photoconductor is used, the photoconductor itself is less likely to wear, so that the wear is prevented but the durability is improved, but the adhesion to the surface of the photoconductor is prevented. If it occurs, it is difficult to remove it, so that it is not possible to prevent the occurrence of problems due to the deposits.

[0007] In the conventional photoconductor having wear resistance, the surface of the photoconductor is gradually polished, and as a result, a new surface state can be maintained at all times, so that such a problem is less likely to occur. 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, even in the image forming method using the highly durable photoreceptor having the layer having the abrasion resistance function on the surface, it is possible to form a stable image over a long period of time. The current situation is not.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to propose an image forming method 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.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method in which an organic photoreceptor having a surface layer containing fine particles is developed with a developer comprising a toner and a carrier. Can be achieved by an image forming method characterized by using magnetic particles having a grain diameter of 0.2 to 10.0 μm.

That is, as a result of intensive investigations by the present inventors regarding a method for preventing the influence of water adsorbed on the surface of the photosensitive member, it was found that the problems of the present invention can solve these problems.

Although the reason for this is not clear, when developing the latent image on the photoconductor, not only the toner but also the carrier contacts the photoconductor with the two-component developer. It is presumed that by controlling the shape of the carrier, the carrier itself exerts a polishing effect, minutely polishes the photoconductor, and as a result, exerts an action of removing water adhering to or adsorbing to the photoconductor. Therefore, the present invention is particularly effective in the image forming method in which the developer contacts the photoconductor. The carrier of the present invention is composed of a core composed of magnetic particles. The present invention can be achieved by controlling the grain diameter by controlling the grain diameter on the surface of the core according to the manufacturing method.

The structure of the present invention will be further described below.

Structure of Carrier of the Present Invention (Grain Diameter) The surface shape of carrier particles is determined by the size of the grain diameter. That is, if the grain diameter is small, the irregularities on the surface of the carrier will increase, and conversely, if the grain diameter is large, the irregularities will decrease, resulting in a smooth shape. It is presumed that by controlling the grain diameter to 0.2 to 10 μm, the photoconductor can be finely ground, and as a result, the water attached or adsorbed to the photoconductor can be removed.

When the grain diameter is smaller than 0.2 μm, the convex portion is broken by mechanical stress in the developing device, and carrier fine powder, so-called brown powder is generated, which adversely affects the charging property of the developer. On the other hand, when the grain diameter is larger than 10 μm, it is considered that the photoreceptor cannot be polished.

The carrier particles having the grain size of the present invention may occupy 50 wt% or more of the total weight of the carrier.
The grain diameter refers to a Feret diameter in which two ends of the grain are sandwiched by two lines parallel to a predetermined direction which is arbitrarily set and the distance between them is the particle diameter.

The carrier grain diameter is measured by randomly extracting 100 carriers, observing the surface of each carrier particle with a scanning electron microscope, and calculating the number average grain diameter by image analysis.

(Core composition) A substance that is strongly magnetized in that direction by a magnetic field, such as ferrite or magnetite composed of elements such as iron, nickel, copper, zinc, magnesium and barium, is preferable.

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

Here, the grain size of the core is controlled by the pulverized particle size of the raw material, the temperature at the time of sintering, the time, and the addition of additives.

(Coating Resin) The carrier of the present invention may be used as it is as a core, or may be used after being coated with a resin.

As the resin for coating the core surface, a known 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 resin (styrene, chlorostyrene, methylstyrene, etc.), acrylic resin (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 or the like or a combination thereof may be used. Especially preferred are silicone resins or fluororesins, which are low surface energy resins.

Examples of the coating method include a dipping method and a spray drying method as a wet method, and a method of applying a mechanical impact force to fix the coating resin fine particles on the surface of the magnetic particles to coat them as a dry method. The coating resin amount is preferably 0.01 to 30% by weight, and particularly preferably 0.05 to 20% by weight, based on the magnetic particles.

(Carrier Particle Size) The average particle size of the carrier particles is preferably 20 to 300 μm, more preferably 30 to 300 μm.
200 μm. If it is less than 30 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 size of the carrier is measured by a laser diffraction particle size distribution measuring device "HELOS" equipped with a wet dispersion device.
It is an average particle diameter on a volume basis measured by (Sympatech).

Structure of Photoreceptor A typical photoreceptor of the present invention has a charge generating layer and a charge transporting layer laminated on the surface of a conductive substrate, if necessary, with an intermediate layer interposed therebetween, or a charge generating substance and a charge transporting substance. Is a photoconductor in which a layer containing fine particles is formed on its surface. In this case, a layer independent of the layer containing the fine particles may not be formed, and a method of forming the fine particle layer on the surface by dispersing the 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 on the surface of a flexible support such as paper or plastic film by laminating or vapor deposition. 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 the intermediate 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, aluminum oxide and the like are used.
The thickness of the intermediate layer is preferably 0.1 to 10 μm, particularly preferably 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. 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.

As the binder resin used in the present invention, 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,
Examples thereof include polyvinyl butyral resin.

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 an oxazole derivative, an oxadiazole derivative, a thiazole derivative, a thiadiazole derivative and a triazole derivative. , 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. These are formed singly or in combination and dispersed or dissolved in a resin.

As the resin used in the present invention,
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,
Examples thereof include vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone alkyd resin, phenol formaldehyde resin, polyvinyl acetal resin, and polyvinyl butyral resin. The thickness of the charge transport layer is 5 to 50 μm, preferably 10
Is about 40 μm.

In the case of a photoreceptor layer composed of a mixture of a charge transporting substance and a charge generating substance, the above charge transporting 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 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, titanium oxide, silica, zirconium oxide,
Examples thereof include oxides such as alumina, carbon nitride, aluminum nitride, nitrides such as silicon nitride, carbides such as silicon carbide, and titanate compounds such as strontium titanate and barium titanate.

The Mohs hardness of the inorganic fine particles means the Mohs hardness of the substance used as the raw material. The Mohs hardness is a relative hardness which is evaluated by rubbing with a sample by using a standard substance in which talc is 1 and diamond is 10 in sequence, and whether scratches occur.

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, 2 , 4-dimethylstyrene, pt-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene. Styrene or styrene derivative, methyl methacrylate / ethyl methacrylate / methacrylic acid n-
Butyl, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate Methacrylic acid ester derivatives such as methyl acrylate / ethyl acrylate / isopropyl acrylate / n-butyl acrylate / acrylic acid t
-Acrylic ester derivatives such as butyl, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, etc., ethylene, propylene,
Olefin such as isobutylene, halogen vinyl such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinyl ester such as vinyl propionate, vinyl acetate, vinyl benzoate, vinyl methyl ether, vinyl ethyl ether, etc. Vinyl ethers, vinyl ketones such as vinyl methyl ketone / vinyl ethyl ketone / vinyl hexyl ketone, N-vinyl compounds such as N-vinylcarbazole / N-vinylindole / N-vinylpyrrolidone, vinyl compounds such as vinylnaphthalene / vinylpyridine Divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate against vinyl monomers such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, etc. Vinyl obtained by adding and polymerizing a polyfunctional vinyl compound such as ethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and trimethylolpropane triacrylate. Organic fine particles, and condensed 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.
05 to 2 μm. If the particle size is large, the surface layer itself becomes brittle, so that the intended improvement in durability cannot be achieved, and the presence of the fine particles may damage the cleaning mechanism. When the particle size is small,
There is no improvement in hardness due to the presence of the fine particles, and the durability does not improve.

Furthermore, the volume resistance of these fine particles themselves is 1.
0 ⁸ or more Ωcm 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, the fine particles can be dispersed in a resin and applied. 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 was 100 parts by weight of the resin (all parts by weight including the following).
05-200 parts, preferably 0.1-100 parts.
When the amount is less than 0.05 part, the amount of the fine particles is too small, and the effect of improving the hardness is not exhibited. When the amount exceeds 200 parts, the hardness is improved, but the amount of the fine particles is too large in the exposure. Light scattering occurs and causes image defects.

Further, the surface layer of the present invention has a thickness of 0.2 to 10 μm.
m, preferably 0.4 to 5 μm. When this layer is thin, the effect of improving durability of the present invention is not exerted, and
When the film thickness is large, the effect of improving durability is exhibited, but image defects due to light scattering and a problem of sensitivity decrease occur.

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

The developing method of the present invention is not particularly limited. As a suitable method, it is suitable for contact-type development.

Next, FIG. 1 is a conceptual diagram of the periphery of the developing device used in the present invention.

The developing device used in the present invention comprises a large number of N, S
A magnet roll having a pole 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
Each rotates in the same or opposite directions. 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
When 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 spike-cutting mechanism plate so that the thickness of the magnetic developer layer can be regulated and the length of the spikes of the developer can be made constant. The space between the developer carrying member 13 and the spike cutting mechanism plate 15 (Hcu
t) is preferably in the range of 0.2 to 5 mm. In this case, the layer thickness of the developer in the developing area is 0.1 to 8 mm, preferably 0.4 to 5 mm.

The gap (Dsd) between the developing sleeve (developer carrying member) and the photosensitive member is preferably 0.1 to 5 mm, particularly preferably 0.3 to 3 mm. 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. A bias voltage is normally applied between the developing sleeve 13 and the photoconductor 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. In any case, the DC bias is preferably 50 to 300V.

Examples of the photoconductor that can be used include selenium photoconductors, selenium-tellurium photoconductors, amorphous silicon photoconductors, and organic photoconductors that are commonly used.

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. 2 and 3 can be used. 2 and 3, the holder 3 holds the cleaning blade 1. The number of photosensitive members is 2. The angle formed by the holder and the photoconductor is θ shown in both figures.
₁ is 10 to 90 °, preferably 15 to 75 °.

As a material for the cleaning blade itself, it is desirable to use an elastic material such as silicone rubber or urethane rubber. In this case, the rubber hardness is 30
It is preferable that the angle is 90 °. The thickness is preferably 1.5 to 5 mm, and the length outside the holder is preferably 5 to 20 mm. The pressure contact force with respect to the photoconductor is preferably 5 to 50 gf / cm.

The toner constituting the developer, such as toner, contains a binder resin, a colorant, and other additives which are used if necessary, 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 that constitutes 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 constituting the toner is not particularly limited, and various conventionally known materials can be 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.

Other additives include, for example, a salicylic acid derivative, a charge control agent such as an azo metal complex, and the like.

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

To prepare the two-component developer, the toner is mixed with the carrier of the present invention. The toner concentration is 2 to 10% by weight.

[0059]

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 addition,
“Parts” means “parts by weight”.

Preparation Example of Photoreceptor An aluminum drum having a diameter of 80 mm was provided with an undercoating layer made of polyamide resin and having a thickness of 0.3 μm. Then, a mixed solution of 10 parts of polyvinyl butyral and 1600 parts of methyl ethyl ketone to 30 parts of perylene-based compound as a charge generating substance was prepared, and the charge generating substance was dispersed and then applied on the undercoat layer and dried. Then, a charge generation layer having a thickness of 0.3 μm was formed.

Then, a solution prepared by mixing 500 parts of a styryl compound, 600 parts of a bisphenol Z-type polycarbonate resin and 3000 parts of dichloromethane as a charge transporting substance was prepared, coated on the charge generating layer and dried to have a film thickness of 25 μm. A charge transport layer was formed. Further, the fine particles shown in the following table were added at the addition amounts shown in the table below to obtain styryl compound 100.
Of the bisphenol Z-type polycarbonate resin containing 100 parts of the solution was prepared, applied and dried to prepare a protective layer having high hardness on the surface.

[0062]

[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 content in the solvent, was obtained by measuring the insoluble content in methyl ethyl ketone. When no crosslinking agent is used, the insoluble content is 0%.

Carrier Production Example Fe ₂ O ₃ = 54 mol%, CuO = 24 mol% in molar ratio,
ZnO = 22 mol% raw materials were weighed and mixed by a ball mill. The obtained mixed powder was calcined and pulverized, a binder was added, and the mixture was granulated by a spray drier. afterwards,
Desired carrier core C sintered and having a volume average particle size of 70 μm
1 to C5 were obtained. The grain particle size as shown in Table 2 was obtained by changing the temperature and time during sintering.

Then, the following coating treatment was performed to obtain a carrier as shown in Table 2.

(1) Carriers CC1 and CC5 100 parts of the carrier core C1 was immersed in a coating resin solution prepared by dissolving 1 part of methyl silicone resin in 50 parts of xylene, and then heated to remove xylene, and further 180
Heat treatment was carried out at 0 ° C. for 3 hours, and then the agglomerates were sieved to obtain a coating carrier CC1. CC5 was obtained by replacing the carrier core with C5.

(2) Carriers CC2, CC4 Vinylidene fluoride-tetrafluoroethylene copolymer 1
A solution prepared by dissolving 0 part in 160 parts of acetone was spray-coated on 1000 parts of the carrier core C2, and then the agglomerates were sieved to obtain a coating carrier CC2. CC4 was obtained by replacing the carrier core with C4.

[0068]

[Table 2]

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% of hydrophobic silica was added to this product to obtain a toner.

Preparation of Developer The above toner was added to the carrier of the present invention to prepare the present developers 1 to 3 and the comparative developers 1 and 2 having a toner concentration of 6 wt%.

(Evaluation) Konica U- manufactured by Konica
The evaluation was performed using a modified IX3135 machine. In addition,
The gap (Dsd) between the developing sleeve (5-pole arrangement, θ = 7 °) and the photoreceptor is 0.6 mm, and the developer layer thickness in the developing area is 1.
5 mm.

By combining the above-mentioned photoconductor and the above-mentioned developer, 50,000 sheets of A4 paper were continuously copied at high temperature and high humidity (33 ° C./80% RH) at a pixel ratio of 5% for 10 days (5 (1,000 sheets / day), and the presence or absence of defects on the image due to image deletion was evaluated in units of 1,000 sheets. The following table shows these results as the number of image defects caused by image deletion.

As the cleaning condition, the angle θ formed by the holder and the photoconductor 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 pressing force against the photoconductor is 15 gf / cm.

[0074]

[Table 3]

When the developers 1 to 3 of the present invention were used, image deletion did not occur even after repeated copying evaluation of 50,000 times under high temperature and high humidity.

On the other hand, when the comparative developers 1 and 2 were used, the image deletion remarkably occurred in the copied image under high temperature and high humidity. In Table 3, the number in the column corresponding to the photoconductor number is the number of copies at which image deletion has started.

[0077]

According to the present invention, it is possible to propose an image forming method 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 the drawings]

FIG. 1 is a developing device used in the present invention.

FIG. 2 is a cleaning device according to the present invention.

FIG. 3 is a cleaning device according to the present invention.

[Explanation of symbols]

 1 Cleaning Blade 2 Photoconductor 3 Holder 13 Developer Carrier (Developing Sleeve) 14 Photoconductor 15 Ear Cutting Mechanism Plate N1 Fixed Main Magnetic Pole θ Fixed Main Magnetic Pole Angle

Claims (2)

[Claims] 1. An image forming method in which an organic photoreceptor having a surface layer containing fine particles is developed with a developer comprising a toner and a carrier, wherein the carrier is 0.2 to 1
An image forming method using magnetic particles having a grain diameter of 0.0 μm. 2. The image forming method according to claim 1, wherein the layer structure of the organic photoconductor is a structure in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support.