JP2002318462A - Electrophotographic toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic toner in which the charge amount of the toner is stable for a long time even when the environment changes and in particular, charge-up of the toner at a low temperature and in low humidity environment is suppressed so that decrease in the image density or increase in the fog is prevented and that cleaning failure or toner filming on an photoreceptor or an electrostatic recording body is prevented. SOLUTION: The toner is a two-component electrophotographic toner prepared by mixing color resin particles containing a coloring agent and a binder resin with fine powder having the average particle size smaller than the average particle size of the color resin particles. The fine powder is prepared by multistage polymerization by suspension polymerization. The fine powder is prepared by polymerizing or copolymerizing alkylacrylates and/or alkylmethacrylates in the polymerization stage prior to the final stage of the process and then polymerizing polymerizable carboxylic acids or polymerizable carboxylates in the final polymerization stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner and an electrophotographic developer, and more particularly, to an electrophotographic toner and an electrophotographic developer which prevent deterioration in characteristics under a low-temperature and low-humidity environment.

[0002]

2. Description of the Related Art As a developing method applied to an electrophotographic method or an electrostatic recording method, a two-component type electrophotographic developer comprising a toner and a carrier (hereinafter, also referred to as a two-component type developer) is used. A method is known in which a toner is charged by frictional charging between a toner and a carrier, and an electrostatic latent image is visualized with the toner. The electrostatic latent image formed on the photoreceptor or the electrostatic recording medium is visualized by toner, and the toner image is transferred to transfer paper and then fixed to form a copy. On the other hand, the toner remaining on the photoreceptor or the electrostatic recording medium after the transfer without being transferred is cleaned to prepare for the next copying process. In general, a two-component developer in the case of a two-component developing method including a toner and a carrier is:
The toner is charged to the required charge amount and charge polarity by friction with the carrier, and the electrostatic latent image on the photoreceptor or the electrostatic recording material is developed using electrostatic attraction. It is important that the toner has good triboelectricity as determined by the following formula.

Various studies have been made to ensure good charging characteristics of the toner. For example, Japanese Patent Publication No. 52-32
Japanese Patent Application Laid-Open No. 256-64352 discloses a method in which chargeable fine particles are added to a toner as a charging auxiliary, a method in which fine resin powder having the opposite polarity to the toner is added, and Japanese Patent Application Laid-Open No. 61-64352. JP 160760 proposes a method of adding a fluorine-containing compound to a toner. However, in the case of the above-described method, it is not easy to uniformly disperse the additive on the toner surface, and it is difficult to avoid that the additives that cannot completely adhere to the toner particles form aggregates.
This tendency becomes more remarkable as the triboelectric charging ability of the charging aid increases and as the particle size decreases. In such a case, the triboelectric charge amount of the toner becomes unstable, the image density is not constant, the image has a lot of fog, or the content of the charging auxiliary agent changes when copying many sheets, There are various problems such as that the image quality at the initial stage cannot be maintained.

[0004] Japanese Patent Publication No. 2-3173, 317
Nos. 4 and 3175 disclose a method in which fine particles of resin having an average particle size of 0.05 to 5 μm are mixed with a toner. However, these resin fine powders have high triboelectric charging ability, but have poor hydrophilicity on the surface, so that when a large number of copies are made under low temperature and low humidity, the charge amount of the toner obtained by mixing the resin fine powders increases. And there is a problem that the image density is reduced. Further, under low temperature and low humidity, the charge amount of the resin fine powder is too large, the resin fine powder is likely to aggregate, the mixing property is reduced,
Alternatively, the resin fine powder is likely to adhere to the carrier, which is one of the causes of poor friction between the carrier and the toner. As a result, the charging state becomes unstable, and fog (the toner flies and adheres to the non-image portion) Phenomenon) increases, and the quality of the copied image deteriorates.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and the charge amount of the toner is stable for a long period of time due to environmental changes. An electrophotographic toner and an electrophotographic developer using the toner that prevent a reduction in image density and an increase in fog by preventing the toner from being poorly cleaned on a photoconductor or an electrostatic recording medium or toner filming. The purpose is to provide.

[0006]

According to a first aspect of the present invention, a colored resin particle containing a colorant and a binder resin and a fine powder having an average particle size smaller than the average particle size of the colored resin particle are provided. A two-component electrophotographic toner obtained by mixing, wherein the fine powder is a fine powder obtained by multi-stage polymerization by suspension polymerization, and the alkyl acrylate and / or An electrophotographic toner, which is a fine powder obtained by polymerizing or copolymerizing an alkyl methacrylate and polymerizing a polymerizable carboxylic acid or a polymerizable carboxylate in the final stage of polymerization.

According to a second aspect of the present invention, the fine powder is a fine powder obtained by converting a carboxylic acid derived from a polymerizable carboxylic acid into a salt after polymerization in the final stage. Toner.

A third invention is the electrophotographic toner according to the first invention, wherein the polymerizable carboxylic acid salt is a divalent metal salt of a polymerizable carboxylic acid.

A fourth invention is characterized in that the fine powder is a fine powder comprising a carboxylic acid derived from a polymerizable carboxylic acid as a divalent metal salt after the final stage of polymerization. Is an electrophotographic toner.

A fifth invention is the electrophotographic toner according to any one of the first to fourth inventions, wherein the polymerization initiator used for the polymerization is a peroxide initiator. .

A sixth invention is characterized in that the polymerization initiator used for the polymerization is an azobis-based initiator.
An electrophotographic toner according to any one of the inventions to the fourth invention.

In a seventh aspect, the fine powder has an average particle size of 0.0
The electrophotographic toner according to any one of the first to sixth inventions, wherein the toner has a thickness of 5 to 5 μm.

According to an eighth aspect of the present invention, there is provided the electronic device according to any one of the first to seventh aspects, wherein 0.01 to 10 parts by weight of a fine powder is mixed with 100 parts by weight of the colored resin particles. It is a photographic toner.

A ninth invention is a two-component electrophotographic developer containing the electrophotographic toner according to any one of the first to eighth inventions, and a carrier.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the fine powder used as an external additive is a fine powder obtained by multi-stage polymerization by suspension polymerization. In the final stage of polymerization, a polymerizable carboxylic acid or a polymerizable carboxylic acid is used. It is important that the fine powder is obtained by polymerizing an acid salt. That is, if the surface of the fine powder is coated with a layer containing a carboxylic acid or a carboxylate having a relatively high hydrophilicity, the carboxylic acid or the carboxylate adsorbs moisture, so that the fine powder can be obtained under low temperature and low humidity.
Further, it is considered that excessive charge-up of the toner can be prevented, and reduction of image density and generation of fog under low temperature and low humidity can be suppressed or prevented.

The fine powder used in the present invention is a fine powder obtained by multi-stage polymerization by so-called suspension polymerization. For example, in the case of two-stage polymerization, a suspension containing the fine powder is prepared by the following method. can get. (1) A dispersion of fine particles of a polymer of alkyl acrylate and / or alkyl methacrylate or a dispersion of fine particles of a copolymer (hereinafter abbreviated as a first-stage dispersion) ), And then, as a second stage suspension polymerization, a polymerizable carboxylic acid monomer is added or dropped into the first stage suspension to carry out suspension polymerization. (2) In the method of (1), after completion of the second-stage suspension polymerization, a carboxyl group derived from a polymerizable carboxylic acid present near the surface of the dispersed particles is converted into a salt. (3) In the method of (1), in the suspension polymerization of the second step, a salt of a polymerizable carboxylic acid is added to the suspension of the first step instead of the polymerizable carboxylic acid monomer or added dropwise. , Suspension polymerization. Although the above (1) to (3) have been described for the case of two-stage polymerization, similarly, in the case of multi-stage polymerization exceeding two stages, the polymerizable carboxylic acid or polymerizable The carboxylate may be polymerized, and the polymerization or copolymerization of the alkyl acrylate and / or the alkyl methacrylate may be any one of the stages prior to the final stage. It is not limited to the stage immediately before.

In the present invention, the polymer or copolymer produced in the step before the final step includes a polymer of an alkyl acrylate monomer, a polymer of an alkyl methacrylate monomer, an alkyl acrylate monomer and A copolymer of an alkyl methacrylate monomer or a copolymer containing at least 50% by weight of an alkyl acrylate monomer or an alkyl methacrylate monomer and containing one or more other copolymerizable monomers is provided. No.

Examples of the alkyl acrylate monomer and the alkyl methacrylate monomer used in the present invention include esterified products of acrylic acid or methacrylic acid with alcohols such as alkyl alcohol, alkoxy alcohol, aralkyl alcohol and alkenyl alcohol. Examples of the alcohol include methyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, dodecyl alcohol, tetradecyl alcohol, alkyl alcohols such as hexadecyl alcohol; methoxyethyl alcohol, Alkoxy such as ethoxyethyl alcohol, methoxypropyl alcohol, ethoxypropyl alcohol Alcohol; benzyl alcohol, phenylethyl alcohol, such aralkyl alcohols phenylpropyl alcohol; allyl alcohol, include such alkenyl alcohols crotonyl alcohol, methyl acrylate, methyl methacrylate is preferable.

Other monomers which can be copolymerized with the above-mentioned alkyl acrylate monomer and alkyl methacrylate monomer include amides such as acrylonitrile, acrylamide, methacrylamide, N-dimethylacrylamide, N-dimethylmethacrylamide and nitriles. , Vinyl acetates, vinyl ethers; nitrogen-containing vinyl compounds such as vinyl carbazole, vinyl pyridine, vinyl pyrrolidone; ethylene, propylene, butene,
Aliphatic monoolefins such as isobutylene; vinyl chloride,
Halogenation of vinyl bromide, 1,2-dichloroethylene, 1,2-dibromoethylene, isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride, vinyl fluoride, vinylidene fluoride, etc. Aliphatic olefins; 1,3-butadiene, 1,3-pentadiene, 2
Conjugated diene-based aliphatic olefins such as -methyl-1,3-butadiene; and styrenes such as styrene and α-methylstyrene.

The fine powder used in the present invention may be obtained by polymerizing a polymerizable carboxylic acid in the final polymerization step as described above, or by polymerizing a polymerizable carboxylic acid salt in the final polymerization step. good. Fine powders having a carboxylic acid on the surface tend to be negatively charged, so it is preferable to add and blend them with colored resin particles that are positively charged, and fine powders having a carboxylate on the surface tend to be positively charged. Therefore, it is preferable to add and blend the colored resin particles with negative charge.

The polymerizable carboxylic acid used in the final polymerization step includes acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, α-methylcrotonic acid,
α-ethylcrotonic acid, isocrotonic acid, tiglic acid,
Addition-polymerizable unsaturated aliphatic monocarboxylic acids such as ungeric acid, and addition-polymerizable unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, and dihydromuconic acid. ,
One or more of these can be used, and acrylic acid and methacrylic acid are preferred. As the polymerizable carboxylic acid salt used in the final polymerization step, various salts of the above-mentioned polymerizable carboxylic acid are used.

The salt forming agents used for forming the carboxylic acid salt before or after the polymerization include Na, Mg, K, Li, N
H ₄ , Ca, Ba, Zn, Fe, Cu, Al, Ni, C
o, hydroxides such as Cr, oxides, inorganic acid salts, organic acid salts and organic amines, among which Mg, Ca, Ba,
Hydroxides, oxides, inorganic acid salts, organic acid salts, and organic amines of divalent metals such as Zn, Fe, Ni, and Co are preferable, and hydroxides of Mg, Ca, Ba, and Zn are preferable. Substances, inorganic acid salts, organic acid salts and organic amines are preferred,
Most preferred are hydroxides, oxides, inorganic acid salts, organic acid salts and organic amines of Zn. Organic acids include formic acid, acetic acid,
And propionic acid. It is preferable to add these salt-forming agents in an amount equivalent to the carboxyl group of the used or used polymerizable carboxylic acid. Even if it is less than the equivalent, it is effective for improving the stability to the charging ability under low temperature and low humidity. Even if it is added in an equivalent amount or more, there is no problem because the excess portion can be removed by performing a water washing step later.

The amount of the polymerizable carboxylic acid or the polymerizable carboxylic acid salt used is preferably 0.05 to 20% by weight based on 100 parts by weight of the total amount of the monomers used up to the polymerization step before the final step. If the amount is less than 0.05 part by weight, the effect of improving the image density under low temperature and low humidity is poor even when the produced fine powder is added to the colored resin to form a toner. As the effect of adsorbing moisture becomes too large, the triboelectrification ability tends to decrease.

The polymerization initiator used in the suspension polymerization of the fine powder used in the present invention includes a peroxide initiator, an azobis initiator and the like. When polymerized using a peroxide initiator, the polymer tends to be negatively charged, and azobis-based compounds such as 2,2′-azobisisobutyronitrile and 2,2′-azobisvaleronitrile are used. When the polymerization is carried out using an initiator, the polymer tends to be positively charged.Therefore, an appropriate polymerization initiator should be selected in accordance with the charging polarity of the colored resin particles to be added and blended with the fine powder as the polymer. I just need.

The emulsifier used in the suspension polymerization of the fine powder used in the present invention includes sodium higher alcohol sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkylbenzene sulfonate, sodium dialkyl sulfosuccinate, sodium fatty acid, and the like. Or an anionic emulsifier such as potassium, alkyl (or alkylphenyl) ether, sodium sulfate or ammonium ester; a nonionic emulsifier such as an alkylphenol ethylene oxide adduct, a higher alcohol ethylene oxide adduct, or a polypropylene glycol ethylene oxide adduct; Examples include cationic emulsifiers such as quaternary ammonium salts, and also use of water-soluble polymers such as polyvinyl alcohol. It can be.

The fine powder used in the present invention is prepared by subjecting the carboxylic acid on the surface to a salt after suspension polymerization or after the suspension polymerization using the above-mentioned salt-forming agent, and then removing water from the aqueous dispersion. You just have to be your body. As a means for removing water, various drying methods and pulverization methods / pulverization methods usually used for powder production can be applied. After spray-drying the aqueous dispersion, the dried product is pulverized / pulverized. Is preferred.

The fine powder used in the present invention is prepared by subjecting the surface carboxylic acid to a salt after suspension polymerization or after the suspension polymerization using the above-mentioned salt-forming agent, and then subjecting the aqueous dispersion to cross-flow filtration. Emulsifier and the like can be removed from the mixture. For example, an aqueous dispersion is placed in a tabletop type emulsion filter (manufactured by Soken Chemical Co., Ltd.), and the aqueous dispersion is washed by flowing water to remove an emulsifier and unreacted substances. After washing, water may be removed by the above method to obtain fine powder.

The fine powder used in the present invention can be obtained by various methods as described above.
To 5 μm, more preferably 0.1 to 2 μm. Suspension polymerization generally has a tendency for polymer particles to be larger than emulsion polymerization.However, by appropriately selecting stirring conditions, emulsifier concentration, and the like, a suspension of polymer particles having an average particle size of 0.05 to 5 μm can be obtained. Obtainable. When the thickness is less than 0.05 μm, agglomeration is likely to occur under low temperature and low humidity, and the aggregates are liberated, and it is difficult to suppress and prevent a decrease in image density under low temperature and low humidity. 5
If it exceeds μm, dispersion becomes uneven or it is difficult to integrate with the colored resin particles, so it is difficult to suppress / prevent toner charge-up under low temperature and low humidity, and suppress / prevent decrease in image density under low temperature and low humidity. It tends to be difficult. If the fine powder has a large number of sharp corners, the photoreceptor may be damaged. Therefore, the shape of the fine powder is preferably as small as possible with sharp edges and as round as possible, for example, spherical.

The toner for electrophotography (hereinafter abbreviated as toner) of the present invention is obtained by adding and mixing the above-mentioned fine powder with colored resin particles. The colored resin particles used in the present invention are those containing a binder resin and a colorant, and as the binder resin used, styrene, chlorostyrene,
Styrenes such as vinylstyrene, ethylene, propylene, butylene, monobutylene such as isobutylene, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl esters such as vinyl butyrate, methyl acrylate, ethyl acrylate, butyl acrylate, Dodecyl acrylate,
Octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate,
Alkyl acrylates such as dodecyl methacrylate and the like; alkyl methacrylates; vinyl ethers such as vinyl ethyl ether and vinyl butyl ether;
Examples thereof include homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone. Particularly typical binder resins include polystyrene and styrene-alkyl acrylate. Copolymers, styrene-alkyl methacrylate copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, styrene-maleic anhydride copolymers, polyethylene, polypropylene and the like can be mentioned. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide,
Modified rosin, paraffin and waxes can be mentioned.

Colorants for obtaining the colored resin particles used in the present invention include carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, quinoline yellow, methylene blue chloride, phthalocyanine blue, and malachite green oxalate. , Lamp black, rose bengal, and the like. Further, a charge control agent may be blended with the colored resin particles. For example, nigrosine dyes, quaternary ammonium salts, salicylic acid derivative metal complexes and the like can be mentioned.

The colored resin particles used in the present invention are used after melt-kneading, cooling, pulverizing, classifying, etc., a binder resin, a colorant and the like according to a conventional method. The colored resin particles used preferably have an average particle size of less than about 30 μm, more preferably an average particle size of 3 to 20 μm. The toner of the present invention is preferably added with the fine powder in an amount of 0.01 to 10 parts by weight, more preferably 0.05 to 3.0 parts by weight, based on 100 parts by weight of the colored resin particles. .

As described above, the fine powder having a carboxylic acid or a salt thereof on its surface is less susceptible to environmental changes as described above, The toner of the present invention in which the fine powder is added to the colored resin particles has a good triboelectric charging ability against environmental changes because the adhesion between the particles is small and the mixing property with the colored resin particles is small. This makes it possible to have an excellent cleaning property. That is, since the carboxylic acid or its salt on the surface of the fine powder adsorbs moisture, the fine powder and the toner obtained by adding the fine powder can maintain stable chargeability without charging up even under low humidity. As described above, the fine particles have a smaller adhesion between the particles, and the fine particles can move freely on the surface of the colored resin particles. It is considered that a good cleaning property can be obtained because of the action of the lubricant particles at the interface between the body and the cleaning blade.

The toner of the present invention may be obtained by adding various additives to the colored resin particles in addition to the fine powder having a carboxylic acid or a salt thereof on the surface. For example, fine particles of silica, titania, and alumina each having been subjected to a hydrophobic treatment, conductive fine powder, or the like can be used in combination with the fine powder.

The developer of the present invention is a so-called two-component developer having a carrier and a toner (hereinafter abbreviated as a developer). As the carrier that can be used in the developer of the present invention, the average particle diameter is substantially the same as the toner particle diameter, or 5 to 5.
Particles up to 00 μm, iron, nickel, cobalt,
Various known materials such as iron oxide, ferrite, glass beads, granular silicon, and magnetic powder-dispersed resin particles are used. Further, the surface of these particles may be covered with a coating agent such as a fluorine resin, an acrylic resin, and a silicone resin.

The developer of the present invention is most preferably obtained by first mixing a fine powder and colored resin particles to obtain a toner, and then mixing the toner with a carrier. In advance, fine powder may be added and mixed.

The developer of the present invention can develop an electrostatic latent image formed on a photoreceptor or an electrostatic recording medium. That is, selenium, zinc oxide, cadmium sulfide, inorganic photoconductive material such as amorphous silicon, phthalocyanine pigment, an electrophotographic electrostatic latent image formed on a photoreceptor made of organic photoconductive material such as bisazo face, or An electrostatic latent image is formed on an electrostatic recording medium having a dielectric material such as polyethylene terephthalate by a needle-shaped electrode or the like, and the electrostatic latent image is formed on the electrostatic latent image by a developing method such as a magnetic brush method, a cascade method, and a touch-down method. A toner image is formed by the developer. This toner image is transferred to a transfer material such as paper and then fixed to form a copy,
The toner remaining on the surface of the photoreceptor or the like is cleaned. Various methods such as a blade method, a brush method, a web method, and a roll method can be used as the cleaning method.

[0037]

EXAMPLES Production Example 1 1 equipped with a stirrer, thermometer, nitrogen inlet tube and reflux condenser
L in a four-necked flask, 100 parts of methyl methacrylate,
0.4 parts of benzoyl peroxide, 4 parts of polyoxyethylene nonylphenol, sodium lauryl sulfate 1
Parts, 200 parts of distilled water, and 4 at 80 ° C. in a nitrogen stream.
Suspension polymerization was performed for hours. After 4 hours, 3 parts of acrylic acid were added, and the polymerization was further continued for 1 hour. After completion of the polymerization, the reaction solution was cooled to 20 ° C., and 1.2 parts of calcium oxide was added to form a salt. The obtained dispersion was dried using a spray drier and crushed by a jet mill to obtain a fine powder having an average particle diameter of 0.3 μm. When the fine powder thus obtained was observed with a scanning electron microscope (SEM), it was almost spherical. Table 1 shows the water content of the obtained fine powder under each environment.

Production Example 2 The dispersion obtained in the same manner as in Production Example 1 was filtered and washed using a table-top emulsion filter (manufactured by Soken Chemical Co., Ltd .: Cross-flow filtration device). Dry using a spray dryer, crush with a jet mill,
A fine powder having an average particle size of 0.3 μm was obtained. When the fine powder thus obtained was observed with a scanning electron microscope (SEM), it was almost spherical.

Production Example 3 A fine powder having an average particle diameter of 0.2 μm was obtained in the same manner as in Production Example 2 except that calcium oxide was not used.

Production Example 4 An average particle diameter of 0.4 μm was obtained in the same manner as in Production Example 2 except that 2 parts of zinc acetate was used instead of 1.2 parts of calcium oxide.
Was obtained.

Production Example 5 The procedure of Production Example 4 was repeated, except that 0.4 parts of azobisisobutyronitrile was used instead of 0.4 parts of benzoyl peroxide, and no zinc acetate was used. A fine powder of 0.4 μm was obtained.

Production Example 6 A fine powder having an average particle diameter of 0.4 μm was obtained in the same manner as in Production Example 4, except that 2 parts of magnesium acetate was used instead of 2 parts of zinc acetate.

Production Example 7 Fine powder having an average particle diameter of 0.1 μm was obtained in the same manner as in Production Example 1 except that 5 parts of sodium methacrylate was used instead of 3 parts of acrylic acid, and no calcium oxide was used after polymerization. Was.

Production Example 8 1 equipped with a stirrer, thermometer, nitrogen inlet tube and reflux condenser
L in a four-necked flask, 100 parts of methyl methacrylate,
0.4 parts of benzoyl peroxide, 2 parts of polyoxyethylene nonylphenol, sodium lauryl sulfate 0.
Five parts and 200 parts of distilled water were added and reacted at 80 ° C. for 4 hours in a nitrogen stream. After completion of the polymerization, the reaction solution was cooled to 20 ° C., and the reaction solution polymerized in the same manner as in Production Example 2 was filtered and washed with a cross-flow filtration device, dried, and pulverized to obtain an average particle size of 0.1
μm fine particles were obtained. As in Production Example 2, the particles were substantially spherical.

Production Example 9 1 equipped with a stirrer, thermometer, nitrogen inlet tube and reflux condenser
L in a four-necked flask, put 60 parts of methyl methacrylate, 40 parts of acrylic acid, 0.6 parts of benzoyl peroxide, 4 parts of polyoxyethylene nonylphenol, 0.5 parts of sodium lauryl sulfate, and 200 parts of distilled water. At 80 ° C. for 4 hours. After completion of the polymerization, the reaction solution was cooled to 20 ° C., and fine particles having an average particle size of 0.1 μm were obtained in the same manner as in Production Example 8. As in Production Example 1, the particles were substantially spherical.

Example 1 A copolymer of styrene and n-butyl methacrylate was used as a binder resin, and carbon black was used as a colorant. 100 parts of colored resin particles having an average particle size of 12 μm were obtained in Production Example 1. The fine powder (0.5 part) was mixed using a Henschel mixer to obtain a two-component electrophotographic toner of the present invention. Then, 3 parts of the above toner were mixed with 97 parts of a carrier obtained by coating a silicone-based resin on spherical ferrite powder having an average particle diameter of 100 μm to obtain a two-component type electrophotographic developer.
Using this two-component electrophotographic developer, a continuous copy test of 50,000 sheets was performed with a commercially available copying machine. As shown in Table 2, the charge amount and image density under low temperature and low humidity were low even in the early stage of copying. Even after the continuous copy test of 50,000 sheets, there was almost no change. Further, although the reason is not well understood, fog hardly occurred under low temperature, low humidity and high temperature, high humidity.

Examples 2 to 7 Production Example 2 was applied to 100 parts of the same colored resin particles as in Example 1.
0.5 parts of the fine powders obtained in Steps 7 to 7 were mixed using a Henschel mixer to produce a two-component electrophotographic toner of the present invention. 3 parts of this toner was used in the same carrier 97 as in Example 1.
Of the two-component electrophotographic developer, and the same evaluation as in Example 1 was performed. Table 2 shows the results. FIG. 1 shows the relationship between the image density and the number of copies under low temperature and low humidity in Example 4 and Comparative Example 1 described later.

Comparative Examples 1 and 2 To 100 parts of the same colored resin particles as in Example 1, 0.5 part of the fine powder obtained in Production Examples 8 and 9 was mixed using a Henschel mixer to obtain a two-component electrophotograph. Was manufactured. Three parts of this toner were mixed with 97 parts of the same carrier as in Example 1 to obtain a two-component electrophotographic developer.
The same evaluation was made. Table 2 shows the results.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

The effects obtained by the present invention are as follows. 1. Prevents decrease in image density at low temperature and low humidity.Even when copying many sheets in a low temperature and low humidity environment, the fine powder coated with the carboxylic acid or its salt added to the colored resin particles adsorbs moisture and becomes excessively large. Charge-up is suppressed, so that a suitable charge amount can be maintained,
Even when a large number of copies are made in a low-temperature and low-humidity environment, a decrease in image density can be prevented. 2. An increase in fog at high temperature and high humidity can be prevented. 3. Cleaning failure can be prevented. When cleaning the toner remaining on the photoreceptor or the like, according to the developer to which the fine powder of the present invention is added, even if a large number of copies are made, cleaning failure does not occur. Also, generally negatively charged ozone deposits that have fallen on the photoreceptor due to corona discharge are accumulated and cause image defects,
Since the fine powder has a polar group on its surface, it has an effect of adsorbing ozone deposits and the like and cleaning the surface of the photoreceptor.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between image density and the number of copies under low temperature and low humidity in Example 4 and Comparative Example 1.

Claims (8)

[Claims] 1. A two-component electrophotographic apparatus comprising a mixture of colored resin particles containing a colorant and a binder resin and fine powder having an average particle size smaller than the average particle size of the colored resin particles. A toner, wherein the fine powder is a fine powder obtained by multi-stage polymerization by suspension polymerization, wherein the alkyl acrylate and / or alkyl methacrylate are polymerized or copolymerized in the polymerization at a stage prior to the final stage. ,
An electrophotographic toner, which is a fine powder obtained by polymerizing a polymerizable carboxylic acid or a polymerizable carboxylate in the final stage of polymerization. 2. The electrophotographic toner according to claim 1, wherein the fine powder is a fine powder obtained by converting a carboxylic acid derived from a polymerizable carboxylic acid into a salt after polymerization in the final step. 3. The electrophotographic toner according to claim 1, wherein the polymerizable carboxylic acid salt is a divalent metal salt of a polymerizable carboxylic acid. 4. The electrophotographic toner according to claim 2, wherein the fine powder is a fine powder obtained by converting a carboxylic acid derived from a polymerizable carboxylic acid into a divalent metal salt after polymerization in the final stage. . 5. The electrophotographic toner according to claim 1, wherein the polymerization initiator used for the polymerization is a peroxide-based initiator. 6. The electrophotographic toner according to claim 1, wherein the polymerization initiator used for the polymerization is an azobis-based initiator. 7. The electrophotographic toner according to claim 1, wherein the fine powder has an average particle size of 0.05 to 5 μm. 8. The electrophotographic toner according to claim 1, wherein 0.01 to 10 parts by weight of a fine powder is mixed with 100 parts by weight of the colored resin particles.