JPH0954453A - Electrophotographic image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic image forming method by which a stable image, especially an image having stability even in an environment at high temp. and humidity can be formed over a long period of time. SOLUTION: An image is formed on an org. photoreceptor with a surface layer contg. at least fine particles by development with a toner obtd. by adding inorg. fine particles to colored particles consisting essentially of a resin and a colorant. The inorg. fine particles added to the toner are hydrophobic inorg. fine particles having a pH change represented by pHA-pHB<=1.0 between the pH (pHA) before the particles are allowed to stand at 50 deg.C and 50% RH for 24hr and the pH (pHB) after the particles are allowed to stand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic method, and more particularly to an electrophotographic image forming method in which development is performed using a toner containing specific inorganic fine particles.

[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, an organic photoreceptor having a resin dispersion layer containing a charge generating substance and a charge transporting substance on an electrically conductive support through an adhesive layer, if necessary, is favored. Since the organic photoreceptor having this resin dispersion layer has a structure in which a resin layer is applied, abrasion due to steps such as the developing section, the transfer section, and the cleaning section for removing the residual toner when used over time. Therefore, it has a problem in long-term use.

In order to solve this problem, Japanese Patent Laid-Open No.
No. 18667, an organic photoreceptor having a coating layer in which hydrophobic silica is dispersed, and, in JP-A No. 57-30846, a protective layer containing metal or metal oxide fine particles having an average particle diameter of 0.3 μm or less, Japanese Patent Application Laid-Open No. 1-205171 proposes a photoreceptor having a protective layer containing an inorganic filler. In each case, various fine particles are added to the surface layer of the photoconductor to improve the wear resistance of the photoconductor.

However, when such a highly durable photoconductor is used, the photoconductor itself is less likely to wear, and therefore the durability is improved due to the problem of wear, but foreign matter remains on the photoconductor surface. If attached, it is difficult to remove, so that it is not possible to prevent the occurrence of problems due to 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 is likely to occur during long-term use, and the surface charge of the photoconductor leaks due to the adsorption of water, causing so-called image deletion. 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 Therefore, an object of the present invention is to provide an electrophotographic 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. It is in.

[0007]

The above object of the present invention is to provide a toner obtained by adding inorganic fine particles to colored particles comprising at least a resin and a colorant on an organic photoreceptor having a surface layer containing at least the fine particles. In the image forming method of developing using, the inorganic fine particles added to the toner are 50 ° C.
/ 50% RH pH for 24 hours before standing (pH _A )
And the change in pH (pH _B ) after standing is pH _A −pH _B ≦ 1.
It was achieved by an image forming method characterized by having 0 hydrophobic inorganic fine particles.

The present invention will be described in detail below.

In the image forming method of the present invention, since the wear of the photoconductor itself is small, it is important to reduce the adsorption of moisture to the photoconductor. As a result of intensive investigations focusing on this phenomenon, the object of the present invention can be achieved by developing using a toner containing the inorganic fine particles having a small pH fluctuation shown in the present invention.

Although the reason for this is not clear, the free acid or base generated by the coupling treatment used for so-called hydrophobicization promotes the adsorption of moisture to the inorganic fine particles. As a result, when the development is repeated by using the inorganic fine particles that adsorb water, the water is successively supplied to the photoreceptor. On the other hand, when a photoconductor with high hardness and extremely low abrading property is used, it is difficult to effectively remove the supplied water, so that the water accumulates and, as a result, the photoconductor due to the adsorbed water is absorbed. It is presumed that leakage of electric charges on the surface occurs and problems such as image deletion occur.

In the present invention, it has been found that these problems can be solved by removing the volatile components that cause the adsorption of water and using them.

To this end, it is necessary to prevent changes in volatile components due to an increase in the temperature inside the machine, which is 50 ° C./50.
Even if left in the environment of% RH for 24 hours, the fluctuation of pH is 1.
It must be 0 or less. This fluctuation range is such that in a high temperature environment, the temperature inside the machine, especially the temperature inside the developing device is 50
The temperature may rise to about 0 ° C., and the object of the present invention can be achieved by not changing under this condition.

2 under the conditions of 50 ° C./50% RH shown above.
PH before standing for 4 hours (pH _A ) and pH after standing (pH _B )
The hydrophobic inorganic fine particles having a change of pH _A −pH _B ≦ 1.0 are treated with a so-called coupling agent for hydrophobizing, and then dried under a temperature condition of 30 to 100 ° C. It can be obtained by removing the volatile components to make the pH stable. Also, 30
A method of removing volatile components using a depressurizing step under a temperature condition of -100 ° C may be used. In this case, the depressurizing condition is preferably 1-100 mmHg. In the above method, under high temperature conditions, unreacted coupling agent reacts, and further, the surface of the hydrophilic inorganic fine particles causes problems such as alteration, which is not preferable. Further, when the temperature condition is low, the volatile components cannot be removed, and the adsorption of water cannot be prevented.

<< Photoreceptor >> In the present invention, the photoreceptor is a laminate of a charge generating layer and a charge transporting layer, or a charge generating substance and a charge transporting substance are mixed on the surface of a conductive substrate with an undercoat layer as needed. And a layer containing fine particles is formed on the surface of the photosensitive layer. In this case, a separate layer may not be formed, and a method of forming a fine particle layer on the surface by dispersing fine particles throughout the photoconductor layer may be used.

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

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

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

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 indicates the Mohs hardness of a 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.

As the organic fine particles, crosslinked organic fine particles are particularly preferable. The crosslinked organic fine particles are organic fine particles in which an insoluble content in a solvent is 30% or more. Specifically, styrene, 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 size of 0.1.
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.

Further, 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, it can be formed by dispersing the fine particles in a resin and applying the dispersion. 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 the fine particles in these resins is 1 to 200 parts, preferably 5 to 10 parts per 100 parts of the resin.
0 parts. When the amount is less than 1 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 excessive due to the excessive amount of the fine particles. Scattering occurs and causes image defects.

Further, in the present invention, the surface layer is 0.2
When this layer is thin, the effect of improving the durability of the present invention is not exhibited, and when the layer is thick, the effect of improving the durability is not exhibited. However, image defects due to light scattering and a problem of a decrease in sensitivity occur.

In the present invention, it is preferable that the layer containing fine particles 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 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.

<< Inorganic Fine Particles >> As the inorganic fine particles of the present invention, inorganic fine particles having a number average primary particle diameter of 5 to 100 nm can be used. This particle size is obtained by observation with a transmission electron microscope.

Various inorganic oxides, nitrides, borides and the like are preferably used as the material for forming the inorganic fine particles.
For example, silica, alumina, titania, zirconia, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, cerium oxide, zinc oxide, chromium oxide, cerium oxide, antimony oxide,
Tungsten oxide, tin oxide, tellurium oxide, manganese oxide, boron oxide, silicon carbide, boron carbide, titanium carbide, silicon nitride, titanium nitride, boron nitride, and the like.

Particularly preferable inorganic fine particles include silica, alumina, titania and zirconia. Although the reason for this is not clear, it can be mentioned that these particles have a high effect of imparting fluidity to the toner and have a high hardness as particles.

The inorganic fine particles are added to the toner in an amount of 0.1 to 5% by weight, preferably 0.2 to 2.0% by weight. If the added amount of the inorganic fine particles is too small, the effect of imparting fluidity to the toner is reduced, and if the added amount of the inorganic fine particles is too large, the release of the inorganic fine particles causes a problem such as contamination of the band electrode.

Various titanium coupling agents and silane coupling agents can be used as materials for the hydrophobic treatment. Examples of the titanium coupling agent include tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, and bis (dioctyl pyrophosphate) oxyacetate titanate. Further, as the silane coupling agent, γ-
(2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) γ-amino Propyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxy Examples include silane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, and the like.

In particular, examples of coupling agents which generate volatile components include hexamethyldisilazane, dichlorodimethylsilane, 3-aminopropyltriethoxysilane,
Although there are silane coupling agents such as alkyl trialkoxysilanes, the fluctuation of pH is particularly remarkable in hexamethyldisilazane and dichlorodimethylsilane from which hydrochloric acid and ammonia are eliminated.

These compounds are preferably added by 1 to 10% by weight with respect to the inorganic fine particles, and are preferably coated.
It is 3 to 7% by weight. Further, these materials can be used in combination.

The volatile components may be removed by drying in a dryer set at 30 to 100 ° C., or the drying may be accelerated by simultaneously reducing the pressure. As described in the present invention, a portion of the sample was taken immediately after drying p
H is measured, and the sample is taken out after leaving it in a 50 ° C./50% RH environment for 24 hours, and the pH is measured. It is advisable to continue drying until the pH difference between the two falls within the range of the present invention. The pH is measured by pure water 50 cc and methanol 50
4 g of the above-mentioned inorganic fine particles are added to the solution mixed with cc, and the mixture is vigorously stirred for 5 minutes. Then, stop stirring and pH the glass electrode.
The pH is measured with a meter.

<Cleaning Mechanism> The mechanism for cleaning the toner remaining on the photosensitive member used in the present invention is not particularly limited, and a known blade cleaning method, magnetic brush cleaning method, fur brush cleaning method, or the like is used. A cleaning mechanism 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 cleaning blade 1 is attached to the holder 3.
Is held. The number of photosensitive members is 2. The angle formed by the holder and the photosensitive member is such that θ ₁ shown in each of FIGS. 1 and 2 is 10 to 90 °, preferably 15 to 75.
°. As a material constituting the cleaning blade itself, an elastic body such as silicon rubber or urethane rubber can be used. In this case, the rubber hardness is 30 to 90.
The one of ° is good. 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 photoreceptor is preferably 5 to 50 gf / mm.

<Developer> The toner used in the present invention is a toner obtained by adding and mixing the inorganic fine particles of the present invention to colored particles containing a binder resin, a colorant, and other additives used as necessary. is there. The average particle size is usually from 1 to 30 μm, preferably from 5 to 15 μm, as a volume average particle size. The binder resin that constitutes the colored particles is not particularly limited, and various conventionally known resins can be used. For example, a styrene resin, an acrylic resin, a styrene / acrylic resin, a polyester resin, and the like can be given. The colorant is not particularly limited, and is conventionally known for color toners, such as 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.

For example, carbon black and nigrosine dye are used as the black toner, and yellow, magenta,
Examples of pigments required for cyan toner include C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15,
C. I. Pigment Blue 15: 6, C.I. I. Pigment Blue 68, C.I. I. Pigment Red 48-3,
C. I. Pigment Red 122, C.I. I. Pigment Red 212, C.I. I. Pigment Red 57-1,
C. I. Pigment Yellow 17, C.I. I. Pigment Yellow 81, C.I. I. Pigment Yellow 154 and the like can be preferably used.

Examples of other additives include charge control agents such as salicylic acid derivatives and azo metal complexes, and fixability improving agents such as low molecular weight polyolefins and carnauba wax.

As the carrier constituting the two-component developer, an uncoated carrier composed only of magnetic material particles such as iron and ferrite, a resin coated carrier in which the surface of magnetic material particles is coated with resin, or a resin and magnetic powder are used. Any of the resin dispersion type carriers obtained by mixing the above may be used.
The average particle size of this carrier is 30 to 150 in terms of volume average particle size.
μm is preferred.

[0042]

EXAMPLES << Preparation of Photoreceptor >> An undercoating 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. Next, a mixed solution comprising 10 parts of polyvinyl butyral and 1600 parts of methyl ethyl ketone with respect to 30 parts of perylene pigment as a charge generating substance is prepared, and the charge generating substance is dispersed and then coated on the undercoat layer,
After drying, a charge generation layer having a thickness of 0.3 μm was formed. Then, a solution in which 500 parts of a styryl compound, 600 parts of a bisphenol Z-type polycarbonate resin, and 3000 parts of dichloromethane are mixed as a charge transport material is prepared, coated on the charge generation layer and dried to form a charge transport layer having a thickness of 25 μm. Was formed. Furthermore, a liquid in which 100 parts of a bisphenol Z-type polycarbonate resin containing 100 parts of a styryl compound was dispersed in the fine particles shown in Table 1 below was prepared, coated and dried to form a protective layer having high hardness on the surface. Was prepared.

[0043]

[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%.

<< Preparation of Inorganic Fine Particles >><< Preparation Example 1 >>: Hydrophilic silica having a number average primary particle diameter of 17 nm was treated with dimethyldichlorosilane to obtain hydrophobic silica. The pH of this product immediately after adjustment was 4.0. This was placed in a dryer at 50 ° C. and dried for 48 hours. The pH (pH _A ) after drying was 5.1. Then, it was put into a dryer adjusted to 50 ° C./50% RH and dried for 24 hours. The pH (pH _B ) after drying was 5.4. This is referred to as "hydrophobic silica 1". In addition, the silica which is not put into the dryer is referred to as “comparative silica 1”.

<< Preparation Example 2 >>: The number average primary particle diameter is 12 nm
Hexamethyldisilazane was treated to the hydrophilic silica of to obtain hydrophobic silica. The pH immediately after the adjustment was 7.6. This was placed in a dryer at 60 ° C. and dried for 100 hours. The pH (pH _A ) after drying was 6.0. Then, it was put into a dryer adjusted to 50 ° C./50% RH and dried for 24 hours. The pH (pH _B ) after drying was 5.9. This is designated as "hydrophobic silica 2". In addition, the silica which is not put into the dryer is referred to as “comparative silica 2”.

<< Preparation Example 3 >>: 10 m under the temperature condition of 60 ° C. instead of drying in the dryer at 60 ° C. in Preparation Example 2
It was dried under reduced pressure of mHg for 24 hours. PH after drying (p
H _A ) was 5.9. Next, 50 ° C / 50% RH
It was put into a dryer adjusted to the conditions of and dried for 24 hours. The pH (pH _B ) after drying was 5.8. This is referred to as “hydrophobic silica 3”.

<< Preparation of Colored Particles >><< Preparation of Colored Particles 1 >> 100 parts of polyester resin, 8 parts of carbon black and 3 parts of low molecular weight polypropylene were mixed, kneaded, pulverized and classified according to a conventional method to obtain a volume average particle size of Colored particles of 8.9 μm were obtained. This is "colored particle 1".
And

<< Preparation of Colored Particle 2 >> In the preparation of the colored particle 1, the volume average particle diameter is 8.2 in the same manner except that the styrene-acrylic resin is used in place of the polyester resin.
Colored particles of μm were obtained. This is designated as “colored particle 2”.

<< Preparation of Colored Particles 3 >> In the preparation of the colored particles 1, the volume average particle diameter is the same except that 55 parts of magnetite having a number average primary particle diameter of 0.3 μm is used in place of carbon black. Colored particles of 8.3 μm were obtained. This is designated as "colored particle 3".

<< Preparation of Colored Particle 4 >> In the preparation of the colored particle 3, the volume average particle diameter is 8.1 in the same manner except that a styrene-acrylic resin is used instead of the polyester resin.
Colored particles of μm were obtained. This is designated as "colored particle 4".

<< Preparation and Evaluation of Toner >> The fine particles described above were added to the colored particles as shown in Table 2 below,
A Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.) was mixed to obtain a toner of the present invention and a comparative toner.

[0053]

[Table 2]

Toner 1 to "toner 3", "comparative toner 1" and "comparative toner 2" are mixed with a ferrite carrier having a volume average particle diameter of 60 μm and coated with a styrene-acrylic resin. A developer having a density of 6% was prepared and used. On the other hand, "toner 4" to "toner 6",
"Comparative Toner 3" and "Comparative Toner 4" were used as they were as one-component developers.

<< Evaluation >>"Toner1" to "Toner 3",
Since “Comparative Toner 1” and “Comparative Toner 2” are two-component developers, the evaluation is 313 manufactured by Konica.
5, "Toner 4" to "Toner 6", "Comparative Toner 3" and "Comparative Toner 4" were evaluated using Konica laser beam printer LP-3110 and the above photoconductor. I went.

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 pressure contact force with respect to the photoconductor is 15 gf / mm.

5% at high temperature and high humidity (33 ° C / 80% RH)
Printing was performed at a speed of one sheet per minute at a pixel rate up to 50,000 sheets, and the presence or absence of image deletion was evaluated in units of 1,000 sheets. Table 3 below shows these results.

[0058]

[Table 3]

As is clear from Table 3, the toner of the present invention can form a stable image for a long period of time, but the comparative toner causes image defects due to the fluctuation of pH, and the toner of the present invention has the same pH. It can be seen that good results can be obtained by reducing the fluctuation.

[0060]

According to the present invention, it is possible to provide an electrophotographic 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 drawings]

FIG. 1 is a diagram showing an example of a blade cleaning method.

FIG. 2 is a diagram showing an example of a blade cleaning method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cleaning blade 2 Photoconductor 3 Holder

Claims (1)

[Claims] 1. An image forming method comprising: developing on a organic photoreceptor having a surface layer containing at least fine particles with a toner obtained by adding inorganic fine particles to colored particles comprising at least a resin and a colorant, The change of the pH (pH _A ) before standing and the pH (pH _B ) after standing for 24 hours under the condition that the inorganic fine particles added to the toner are 50 ° C./50% RH
An image forming method characterized by comprising hydrophobic inorganic fine particles having _A- pH _B ≤ 1.0.