JPH10221881A - Magnetic developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the magnetic developer stabilized in the charged amount of the magnetic toner for a long period, even when the environments vary, and as a result, stabilized in a development to transfer efficiency and a consumption of the toner and prevented from lowering of image density and rise of fog by restraining overcharge of the toner, especially, under low temperature and low humidity. SOLUTION: This magnetic developer comprises the magnetic toner of a mixture of magnetic resin particles containing a magnetic powder and a binder resin, and at least fine resin particles, and a carrier, and when the above fine resin particles have an average particle diameter of 0.05-2μm and a dielectric loss tangent of A in a frequency of 1MHz and the fine magnetic resin particles has a dielectric loss tangent of B in a frequency of 1MHz, and the carrier has a dielectric loss tangent of C in a frequency of 1MHz, the following expressions are satisfied: 0.015<=A<=0.065, and B<A<C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic developer.

[0002]

2. Description of the Related Art As one of developing methods applied to an electrophotographic method or an electrostatic recording method, a two-component developer (hereinafter abbreviated as developer) composed of a toner and a carrier is used, and friction between the toner and the carrier is used. There is known a method in which a charge is applied to a toner by charging to visualize an electrostatic latent image with the toner. Such a method is a method in which a toner is attached to an electrostatic latent image on a photoreceptor or an electrostatic recording medium to form a toner image, 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 photoconductor or the electrostatic recording medium is cleaned in preparation for the next copying process. Therefore, in the case of the two-component developing system, it is necessary that the toner has good triboelectric charging properties mainly determined by the relationship with the carrier.

As a method for improving the triboelectric charging property of toner, for example, Japanese Patent Publication No. 52-32256,
JP-A-6-64352 discloses a method of adding a resin fine powder having a polarity opposite to that of a base toner as a charging auxiliary.
Japanese Patent Application Laid-Open No. -160760 proposes a method of adding a fluorine-containing compound as a charging auxiliary to a base toner. However, it is not easy to uniformly disperse an additive such as a charge adjuvant on the surface of the base toner, and additives that cannot be completely adhered to the base toner particles tend to aggregate, and this tendency is caused by friction of the charge adjuvant. The larger the charging ability,
That is, the smaller the dielectric loss and the finer the particle size, the more noticeable. In such a case, the amount of frictional charge of the toner becomes unstable, the image density is not constant, the image becomes fogged, or the content of the charging auxiliary agent changes when a large number of copies are made, 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 propose a method of mixing resin fine particles having an average particle size of 0.05 to 5 μm into a toner. However, these resin fine powders have a high triboelectric charging ability and a small dielectric loss, but have poor hydrophilicity on the surface, so that when a large number of copies are made at low temperature and low humidity, the toner obtained by mixing the resin fine particles is charged. The amount is too large, and the image density is reduced. In addition, under low temperature and low humidity, the charge amount of the resin fine particles becomes too large, so that the resin fine powder is easily aggregated, the mixing property is reduced, or the resin fine particles themselves are charged up, and the non-image portion is charged together with the toner. There is a problem of flying (so-called fogging). On the other hand, under high temperature and high humidity, there is a problem that the dielectric properties are apt to change and the developability deteriorates, and the toner consumption and the amount of collected toner increase, that is, the development / transfer efficiency decreases.

[0005] Among the two-component developers, a magnetic developer comprising a magnetic toner and a carrier can provide an image having no edge effect and less unevenness as compared with a two-component developer using a non-magnetic toner. Although it is preferable in terms of space and energy saving, it has the various problems described above, and its solution has been awaited.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the charge amount of a magnetic toner is stabilized for a long time even if the environment changes. As a result, the development / transfer efficiency and the toner It is an object of the present invention to provide a magnetic developer in which the consumption amount is stable, and in particular, by suppressing the charge-up of the toner under a low temperature and a low humidity, a decrease in image density and an increase in fog are prevented.

[0007]

That is, a first invention is a magnetic toner having magnetic resin particles containing magnetic powder and a binder resin and at least resin fine particles, and a magnetic toner having a magnetic powder-dispersed resin carrier. A developer, wherein the average particle diameter of the resin fine particles is 0.05 to 2 μm, the value of the dielectric tangent at a frequency of 1 MHz of the resin fine particles is A, and the value of the dielectric tangent of the magnetic resin particles at a frequency of 1 MHz is B;
When the value of the dielectric loss tangent at a carrier frequency of 1 MHz is C, 0.015 ≦ A ≦ 0.065 and B <A <
C is a magnetic developer that satisfies the following relationship:

In a second aspect, the resin fine particles are obtained by multi-stage polymerization, and have a plurality of layers of a coating layer and a layer inside the coating layer.
The magnetic developer according to the first invention, wherein the coating layer has a hydrophilic group.

A third invention is the magnetic developer according to the first or second invention, wherein the hydrophilic group in the coating layer of the resin fine particles is a carboxylic acid or a carboxylate.

[0010] A fourth invention is directed to a non-magnetic colored resin particle 100.
The magnetic developer according to any one of the first to third inventions, wherein 0.01 to 10 parts by weight of resin fine particles are mixed with respect to part by weight.

A fifth invention is the magnetic developer according to any one of the first to fourth inventions, wherein the magnetic resin particles contain 10 to 40% by weight of magnetic powder.

A sixth invention is the magnetic developer according to any one of the first to fifth inventions, wherein the magnetic powder-dispersed resin carrier contains 60 to 95% by weight of magnetic powder. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies on the charging stability of a magnetic developer with respect to the environment. As a result, when the conditions described in the first invention are satisfied, the environmental stability of development / transfer efficiency is reduced. Excellent, stable toner consumption, stable chargeability, no image density reduction under low temperature and low humidity, and good images without fog can be obtained.

The reason is not clear yet, but is presumed as follows. That is, the resin fine particles are charged integrally with the magnetic resin particles, and since various electric fields are present during development / transfer, each of them is microscopically dielectrically polarized, and the resin fine particles become a dielectrically polarized coupling factor. The magnetic resin particles are gathered together, and a certain amount of aggregated magnetic toner is sucked from the magnetic developer to the electrostatic latent image on the photoreceptor, and further transferred collectively from the photoreceptor onto plain paper. It is considered that the development / transfer efficiency is better and the fogging is less likely than the transfer / transfer.

In general, the dielectric constant 物質 of a substance having a dielectric loss is represented by Ε = ε1−i × ε2 (where ε1 is a real part of the dielectric constant,
ε2 is the imaginary part of the permittivity, i is the imaginary number), and the dielectric tangent tanδ =
There is a relationship of ε2 / ε1, and it is recognized that the dielectric constant and the dielectric loss tangent are closely related. Here, the dielectric loss tangent tanδ is
Called the dielectric loss tangent or dissipation factor, the physical meaning indicates the ratio of stored energy per cycle to dissipated energy per cycle.
The dielectric loss tangent varies in size depending on the frequency, and indicates the surface (interface), orientation, and atomic (ionic) polarization of the dielectric.

The dielectric loss tangent indicates the degree of dielectric loss. When the dielectric loss tangent is small, the amount of charge tends to be maintained, and when the dielectric loss tangent is large, the amount of charge tends to decrease. By using magnetic resin particles that have a relatively small dielectric loss tangent and tend to maintain a charge amount, a stable charge state that is not significantly affected by environmental changes, and development / transfer efficiency are ensured.
In addition, by using resin fine particles having a relatively large dielectric tangent and tending to decrease the charge amount as an external additive, the chargeability of magnetic resin particles having a relatively small dielectric tangent and tending to maintain the charge amount is impaired. It is considered that the charge-up due to friction between the magnetic resin particles and the carrier under low temperature and low humidity was alleviated, and the image density did not decrease even under low temperature and low humidity, and a good image without fog could be obtained. Further, it is considered that the charge amount of the magnetic toner is stabilized by using a carrier having a larger dielectric loss tangent than the above two, and a stable image without carrier jump due to charge-up can be obtained.

In the present invention, the frequency 1
When the value of the dielectric loss tangent at a frequency of 1 MHz is A, the value of the dielectric loss tangent at a frequency of 1 MHz of the magnetic resin particles is B, and the value of the dielectric loss tangent at a frequency of 1 MHz of the carrier is C, 0.
It is important to satisfy the relationship of 015 ≦ A ≦ 0.065 and B <A <C.

When A is larger than 0.065, the charge loss of the resin fine particles becomes large, and the role as a dielectric polarization coupling factor for linking the magnetic toners is lost, and as a result, the development / transfer efficiency is improved. No longer. Further, since the charge amount of the toner decreases, adverse effects such as fog and toner scattering occur. On the other hand, if A is less than 0.015, the resin fine particles tend to agglomerate, making it impossible to intervene electrostatically between the magnetic toners. As a result, it does not contribute to the improvement of the development / transfer efficiency. A is 0.015
When the temperature is lower than the above, it is difficult to leak the electric charge accumulated in the magnetic toner under a low temperature and a low humidity. Therefore, it is not possible to suppress and prevent a decrease in the image density under a low temperature and a low humidity.

When A is not in the range of B <A <C, the chargeability of the magnetic developer is impaired, and a good image cannot be obtained. In particular, the charge amount decreases under high temperature and high humidity. Therefore, there arises a problem that toner consumption increases, toner scattering occurs, and fog increases. In addition, there is a problem that the development / transfer efficiency lacks environmental stability, the charge-up mitigation effect becomes insufficient, and the image density decreases at low temperature and low humidity.

The dielectric loss tangent tan δ in the present invention is determined as follows. In advance, 2
A sample (resin fine particles or magnetic resin particles) left standing for 24 hours in a constant temperature / humidity bath at 3 ° C./50 RH% was placed, and 400 kg /
Pressurize at ² cm ² to produce cylindrical pellets about 2 mm thick and 20 mm in diameter. The pellet was measured at a frequency of 1 MHz using an impedance analyzer 4194A (manufactured by Yokogawa Hewlett-Packard Company), and the dielectric loss tangent tan was measured.
The value of δ was determined.

It is important that the particle size of the resin fine particles used in the present invention is 0.05 to 2 μm.
More preferably, it is μm. When the particle diameter is smaller than 0.05 μm, the resin fine particles are easily embedded in the magnetic resin particles, and the resin fine particles are easily aggregated, and it is difficult to suppress or prevent a decrease in image density under low temperature and low humidity. On the other hand, if it is larger than 2 μm, the dispersion becomes non-uniform and it is difficult to integrate with the magnetic resin particles. Therefore, it is difficult to suppress and prevent the charge-up of the toner under low temperature and low humidity, and to suppress the decrease in image density under low temperature and low humidity.・ It tends to be difficult to prevent. If the resin fine particles have a large number of sharp corners, the photoconductor may be damaged. Therefore, the shape of the resin fine particles is preferably as small as possible and as round as possible, for example, spherical.

The resin fine particles used in the present invention are:
It is sufficient that the composition satisfies the above conditions, and the composition, the production method, and the like are not limited. It preferably has a hydrophilic group. Obtained by multi-stage polymerization below, having a plurality of layers of a coating layer and a layer on the inside thereof,
A method for producing resin fine particles whose coating layer has a hydrophilic group (hereinafter abbreviated as multi-stage polymerized resin fine particles) will be described.

The multi-stage polymer resin fine particles are obtained by multi-stage polymerization such as emulsion polymerization, soap-free polymerization, suspension polymerization and the like. In the polymerization at a stage prior to the final stage, alkyl acrylate and / or alkyl methacrylate are used. Preferably, the ester is polymerized or copolymerized, and the polymerizable carboxylic acid or polymerizable carboxylate is polymerized in the final stage of polymerization. For example, in the case of two-stage polymerization by emulsion polymerization, a dispersion containing the resin fine particles is obtained by the following method. (1) By the first-stage emulsion polymerization, a dispersion of fine particles of a polymer of an acrylic acid ester and / or an alkyl methacrylate or a dispersion of fine particles of a copolymer (hereinafter abbreviated as a first-stage dispersion). Then, as a second stage emulsion polymerization, a polymerizable carboxylic acid monomer is added or dropped into the first stage dispersion to carry out emulsion polymerization. (2) In the method of (1), after completion of the second-stage emulsion 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 second stage emulsion polymerization in the method of (1), the first
Emulsion polymerization is carried out by adding or dropping a salt of a polymerizable carboxylic acid to the dispersion liquid in place of the polymerizable carboxylic acid monomer. 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 acrylate and / or the alkyl methacrylate may be any one of the stages prior to the final stage, and may be performed immediately before the final stage. Is not limited to this stage.

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 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. Specific 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 pyrrolide; aliphatic monoolefins such as ethylene, propylene, butene, isobutylene; vinyl chloride, vinyl bromide, 1,2-dichloroethylene 1,3-dibromoethylene, halogenated aliphatic olefins such as isopropenyl chloride, isopropenyl bromide, allyl chloride, allyl bromide, vinylidene chloride, vinyl fluoride and vinylidene fluoride; Ene, 1,3-pentadiene, 2
Conjugated diene-based aliphatic olefins such as -methyl-1,3-butadiene; and styrenes such as styrene and α-methylstyrene.

The multi-stage polymer resin fine particles suitably used in the present invention may be obtained by polymerizing a polymerizable carboxylic acid in the final polymerization stage as described above, or by polymerizing a polymerizable carboxylic acid salt in the final polymerization stage. It may be polymerized.

The polymerizable carboxylic acid used in the final polymerization step includes acrylic acid, methacrylic acid, α-
Ethyl acrylic acid, crotonic acid, α-methyl crotonic acid, α-ethyl crotonic acid, isocrotonic acid, tiglic acid, addition-polymerizable unsaturated aliphatic monocarboxylic acid such as ungeric acid, or maleic acid, fumaric acid, itaconic acid, Examples include addition-polymerizable unsaturated aliphatic dicarboxylic acids such as 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.

As the salt forming agent used for forming the salt of the carboxylic acid before or after the polymerization, Na, Mg, K, Li, N
H ₄ , Ca, Ba, Zn, Fe, Cu, Al, Ni, C
hydroxides such as o and 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. The amount of these salt-forming agents added is
It is preferable to add it so that it becomes equivalent to the carboxyl group of the used or used polymerizable carboxylic acid. Even if it is less than the equivalent, it is effective in improving the stability of the charge amount 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 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 produced fine powder is added to the magnetic resin particles to form a toner, and the effect of improving the image density under low temperature and low humidity is poor. The dielectric loss tangent becomes too large due to moisture absorption, and the amount of triboelectric charge is reduced, so that it hardly contributes to the improvement of development / transfer efficiency.

Among the multistage polymer resin fine particles suitably used in the present invention, the polymerization initiator used in the case of emulsion polymerization includes a persulfate initiator, a redox initiator comprising a persulfate and a sulfoxy compound. And water-soluble azo initiators. Examples of the persulfate initiator include potassium persulfate and sodium persulfate. Examples of the Redox initiator composed of a persulfate and a sulfoxy compound include the above-described persulfate and potassium thiosulfate or sodium thiosulfate. Examples of the water-soluble azo initiator include 2,2′-azobis (2-amidinopropane) hydrochloride, 2,2′-azobis (2-amidinopropane) acetate, and 2,2′-azobis (N, N ′). -Dimethyleneisobutylamidine) dihydrochloride.

Among the multi-stage polymer resin particles suitably used in the present invention, the emulsifier used in the case of emulsion polymerization includes sodium higher alcohol sulfate,
Sodium alkyl diphenyl ether disulfonate,
Sodium alkylbenzenesulfonate, sodium dialkyl sulfosuccinate, sodium fatty acid,
Or anionic emulsifier such as potassium, alkyl (or alkylphenyl) ether, sodium sulfate or ammonium sulfate: Nonionic emulsifier such as alkylphenol ethylene oxide adduct, higher alcohol ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, etc. A cationic emulsifier such as a quaternary ammonium salt; and a water-soluble polymer such as polyvinyl alcohol.

Among the multistage polymer resin fine particles suitably used in the present invention, the same polymerization initiator as that used in the emulsion polymerization can be used as the polymerization initiator used in the case of soap-free polymerization.

In the case of soap-free polymerization, among the multistage polymer resin fine particles suitably used in the present invention, a water-soluble polymer compound is used as a protective colloid. Examples of the water-soluble polymer compound include polyvinyl alcohol. , Polyacrylamide, polyacrylic acid and its salts, polymethacrylic acid and its salts, polyethylene glycol, polyvinyl pyrrolidone, polyvinyl methyl ether, carboxymethyl cellulose and the like. It is up to the above that the resin fine particles used in the present invention may be any as long as they satisfy the conditions regarding the dielectric loss tangent and the average particle diameter, but among the preferred multistage polymerization methods, the soap-free polymerization method is Since an emulsifier is not used at the time of polymerization, the resin fine particles after drying, which will be described later, also do not contain an emulsifier, which is particularly preferable because environmental fluctuation of dielectric loss tangent is small.

Among the multistage polymer resin fine particles suitably used in the present invention, examples of the polymerization initiator used in the case of suspension polymerization include a peroxide initiator and an azobis initiator. Peroxide initiators include benzoyl peroxide and the like, and azobis initiators include 2,2′-
Azobisisobutyronitrile, 2,2′-azobisvaleronitrile and the like can be exemplified.

Among the multi-stage polymer resin particles suitably used in the present invention, the same emulsifier as used in the above-mentioned emulsion polymerization can be used as the emulsifier used in the case of suspension polymerization.

The multi-stage polymer resin particles suitably used in the present invention may be prepared by the above-mentioned salt-forming method after polymerization (emulsion polymerization, soap-free polymerization, suspension polymerization) or after polymerization (emulsion polymerization, soap-free polymerization, suspension polymerization). After the carboxylic acid on the surface is converted into a salt using an agent, water may be removed from the aqueous dispersion. 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 multi-stage polymer resin fine particles suitably used in the present invention may be used after polymerization (emulsion polymerization, soap-free polymerization, suspension polymerization) or after polymerization (emulsion polymerization, soap-free polymerization, suspension polymerization). After the carboxylic acid on the surface is converted into a salt using a salt forming agent, the emulsifier and the like can be removed from the aqueous dispersion by a cross-flow filtration method. For example,
The aqueous dispersion is placed in a table-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.

The resin fine particles used in the present invention preferably have a weight average molecular weight Mw in the range of 20 to 2,000,000. When Mw is larger than 2,000,000, the fixing property of the toner tends to be adversely affected, and when Mw is smaller than 20,000, the blocking resistance tends to deteriorate.

The magnetic resin particles used in the present invention contain a binder resin and a magnetic powder. Examples of the binder resin used include styrenes such as styrene, chlorostyrene and vinyl styrene, ethylene and propylene. ,
Monoolefins such as butylene and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate and phenyl acrylate Alkyl acrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, alkyl methacrylates, vinyl ethers such as vinyl ethyl ether and vinyl butyl ether, vinyl methyl ketone, vinyl hexyl ketone, and vinyl Homopolymers or copolymers of vinyl ketones such as isopropenyl ketone can be exemplified. Particularly typical binder resins include polystyrene and styrene-alkyl acrylate. Coalescence, styrene - methacrylic acid alkyl ester copolymer, styrene - acrylonitrile copolymer, styrene - butadiene copolymer, styrene - it can be maleic anhydride copolymer, polyethylene, polypropylene or the like. Furthermore, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, waxes can be used.

Examples of the magnetic powder for obtaining the magnetic resin particles used in the present invention include ferromagnetic elements and alloys and compounds containing them, such as iron, cobalt, nickel, manganese, zinc and the like such as magnetite, magmemite and ferrite. Compounds containing are preferable, but if necessary, carbon black, aniline blue, calcoil blue,
Ultramarine blue, methylene blue chloride, phthalocyanine blue, malachite green oxalate,
Lamp black, Rose Bengal, etc. may be added in order to obtain practically sufficient blackness.

The amount of the magnetic powder in the magnetic resin particles used in the present invention is preferably from 10 to 40% by weight, more preferably from 15 to 35% by weight. When the amount of the magnetic powder is less than 10% by weight, the magnetic restraining force is weakened and toner scattering occurs. When the amount is more than 40% by weight, the triboelectric charge decreases, and the magnetic restraining force is too strong and the image density decreases.

Further, a charge control agent may be blended with the magnetic resin particles. Examples include nigrosine dyes, quaternary ammonium salts, metal-containing azo dyes, salicylic acid derivative metal complexes, and the like. The binder resin, magnetic powder, and charge control agent are not limited to those described above.

The magnetic resin particles used in the present invention are obtained by subjecting a binder resin, a magnetic powder, and the like to melt kneading, cooling, pulverization, classification, and the like according to a conventional method. The magnetic resin particles used preferably have an average particle size of less than about 30 μm, and more preferably an average particle size of 3 to 20 μm. In the toner of the present invention, the above resin fine particles are preferably added 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 magnetic resin particles. .

The magnetic toner of the present invention may be obtained by adding various external additives to the magnetic resin particles in addition to the resin particles having a specific dielectric loss tangent. For example, silica,
Titania, a fluidizing agent that has been subjected to a hydrophobic treatment on each fine particle surface of alumina, a lubricant typified by polyvinylidene fluoride, an abrasive typified by tungsten carbide, a conductive fine powder, etc. are used in combination with the above fine powder. However, the present invention is not limited to these.

The developer of the present invention is a magnetic developer (hereinafter abbreviated as a developer) having a magnetic powder-dispersed resin carrier and a magnetic toner. The magnetic powder-dispersed resin carrier (hereinafter abbreviated as “resin carrier”) used in the developer of the present invention contains a magnetic powder such as iron, nickel, cobalt, iron oxide, or ferrite in the binder resin in the same manner as the aforementioned magnetic resin particles. It is preferable that the average particle diameter is about the same as the above-mentioned magnetic resin particles, that is, from about 3 to 30 μm to 200 μm. The resin carrier used in the developer of the present invention includes:
The magnetic powder preferably contains 60 to 95% by weight, more preferably 70 to 85% by weight. 60 magnetic powder
If it is less than the weight percentage, the magnetic binding force on the sleeve is weak,
Carrier spillage occurs, and if it exceeds 95% by weight, the resin is too small to solidify and cannot be used as a carrier. As the binder for the resin carrier, a styrene-acrylic resin, a polyester resin or the like is preferable among the above-mentioned ones. Further, the surface of these various carriers may be coated with a coating material such as a fluorine resin, an acrylic resin, or a silicone resin.

The developer of the present invention is most preferably formed by first mixing resin fine particles and magnetic 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 photosensitive member or an electrostatic recording member. That is, selenium, zinc oxide, cadmium sulfide, an inorganic photoconductive material such as amorphous silicon, phthalocyanine pigment, an electrophotographic electrostatic latent image formed on a photoreceptor made of an 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 using a needle 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, or a touch-down method. A toner image is formed by the developer of the present invention. 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.

[0049]

EXAMPLES In the following production examples, examples and comparative examples,
% Means weight%, and parts means part by weight.

Production Example 1 100 parts of methyl methacrylate, 200 parts of distilled water, 0.4 part of potassium persulfate were placed in a 1 L four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, and reflux condenser.
Parts, 4 parts of polyoxyethylene nonylphenol and 1 part of sodium lauryl sulfate.
Emulsion polymerization was performed at 0 ° C. for 4 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 4 parts of zinc acetate was added to form a salt. The obtained emulsion was filtered, washed, dried using a spray dryer, and crushed by a jet mill. Thus, resin fine particles having an average particle diameter of 0.3 μm were obtained. The dielectric loss tangent A of the resin fine particles thus obtained is A (1 MHz) = 2
2.3 * 10 ^-3 . Further, when the resin fine particles thus obtained were observed with a scanning electron microscope (SEM), they were almost spherical.

[0050]

[Production Example 2] Production Example 1 except that salt was not formed with zinc acetate.
In the same manner as in the above, substantially spherical resin fine particles having an average particle diameter of 0.3 μm were obtained. The dielectric loss tangent A of the resin fine particles thus obtained was A (1 MHz) = 35.0 * 10 ^-3 .

[0051]

Production Example 3 A resin having an average particle diameter of 0.4 μm was prepared in the same manner as in Production Example 1, except that 0.2 parts of polyvinyl alcohol was used instead of 4 parts of polyoxyethylene nonylphenyl ether and 1 part of sodium lauryl sulfate. Fine particles were obtained. The dielectric loss tangent A of the obtained resin fine particles is A (1 MH
z) = 23.0 * 10 ^-3

[0052]

Production Example 4 After completion of the two-stage polymerization in Production Example 3, the reaction solution was
In the same manner as in Production Example 3, except that zinc acetate was not added, substantially spherical resin fine particles having an average particle diameter of 0.4 μm were obtained. The dielectric loss tangent A of the resin fine particles thus obtained was A (1 MHz) = 36.3 * 10 ^-3 .

[0053]

Production Example 5 Resin fine particles having an average particle diameter of 0.3 μm were obtained in the same manner as in Production Example 2 except that 3 parts of dimethylaminoethanol was used instead of 4 parts of zinc acetate. The dielectric loss tangent A of the resin fine particles thus obtained is A (1 MHz) = 6.
8.2 * 10 ^-3 .

[0054]

Production Example 6 55 parts of methyl methacrylate, 45 parts of styrene, 200 parts of distilled water, 200 parts of distilled water, benzoyl peroxide and 4 parts of polyvinyl alcohol were placed in a 1 L four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a reflux condenser. The emulsion polymerization was carried out at 80 ° C. in a nitrogen stream. After completion of the polymerization, the reaction solution was cooled to 20 ° C., the obtained suspension was filtered, washed, dried using a spray drier, and crushed by a jet mill to obtain resin fine particles having an average particle size of 0.5 μm. Was. The dielectric loss tangent A of the resin fine particles thus obtained is A (1 MH
z) = 13.3 * 10 ^-3

[0055]

Example 1 Copolymer of styrene and n-butyl methacrylate (binder resin) 76 parts Charge control agent (Spiron Black TRH: Hodogaya Chemical) 2 parts Wax 4 parts Colorant (carbon black) 2 parts Premixed 16 parts of magnetic powder (magnetite) with a Henschel mixer, melt-kneaded with an extruder, cooled and crushed with a hammer mill,
Next, the mixture was finely pulverized with an air jet mill and classified to obtain magnetic resin particles having an average particle diameter of 10 μm. The dielectric loss tangent B of the obtained magnetic resin particles is B (1 MHz) = 6.7 * 1.
It was 0 ^-3 . To 100 parts of the obtained magnetic resin particles, 0.5 part of the resin fine particles obtained in Production Example 1 as an external additive and 0.5 parts of silica fine powder R972 (Nippon Aerosil) as a fluidizing agent were added.
Were mixed to obtain a magnetic toner.

75 parts of magnetic powder (magnetite) is a styrene resin: polyether resin = 1: 1 insulating resin 25
After dispersing and mixing in the part, melt-knead with an extruder,
After cooling, it was crushed to obtain a resin carrier having an average particle size of 50 μm. The dielectric loss tangent C of the obtained resin carrier is C (1 MH
z) = 219.0 * 10 ^-3

11 parts of the magnetic toner and 89 parts of the resin carrier were mixed to obtain a magnetic developer. Using this magnetic developer, 30,000 sheets were printed at 23 ° C./50% RH on a commercial plain paper copier. The average development / transfer efficiency was 84%, the image density was 1.33, and the fog Good image without edge effect is obtained, and toner consumption is 1K (1,000 sheets)
The average weight was as low as 37 g. In addition, under high temperature and high humidity (3
(0 ° C./85% RH), the same image was formed as described above. The average development / transfer efficiency was 81%, and the image density was 1.
34, a good image without fog was obtained, and the toner consumption was as small as 41 g per 1K on average. Further, when the same image was formed at a low temperature and a low humidity (10 ° C./20% RH), the average development / transfer efficiency was as high as 85%, and an image density of 1.30 and a stable good image were obtained. The toner consumption was also as small as 35 g on average per 1 K.

The development / transfer efficiency is ((toner consumption-recovered toner amount) / toner consumption) × 100%, and indicates the ratio of toner effectively consumed for image formation. A developer with low toner consumption, high development / transfer efficiency and high image density has a long life and is desirable.

[0059]

Example 2 Copolymer of styrene and n-butyl methacrylate (binder resin) 73 parts Charge control agent (Nigrosine dye: Orient Chemical) 2 parts Wax 5 parts Magnetic powder (iron powder) 20 parts Henschel mixer Pre-mixing, melt-kneading with an extruder, crushing with a hammer mill after cooling,
Then, the mixture was finely pulverized with an air jet mill and classified to obtain magnetic resin particles having an average particle size of 8.5 μm. The dielectric loss tangent B of the obtained magnetic resin particles is B (1 MHz) = 7.4 *
It was 10 ^-3 . To 100 parts of the obtained magnetic resin particles, 2.0 parts of the resin fine particles obtained in Production Example 2 as an external additive and 0.5 parts of silica fine powder R972 (Nippon Aerosil) as a fluidizing agent were added.
Were mixed to obtain a magnetic toner. Then, 75 parts of magnetic powder (magnetite) is dispersed and mixed in 25 parts of styrene resin, melt-kneaded with an extruder, and crushed to obtain an average particle size of 5 parts.
A resin carrier of 0 μm was obtained. The dielectric loss tangent C of the obtained resin carrier was C (1 MHz) = 158.4 * 10 ^-3 .

A magnetic developer was prepared by mixing 11 parts of magnetic toner and 89 parts of a resin carrier. When 30,000 sheets were printed at 23 ° C./50% RH with a commercially available printer using this magnetic developer, the development / transfer efficiency was high at an average of 85%, the image density was 1.33, and a good image without fogging was obtained. An image was obtained, and the toner consumption was as low as 36 g on average per 1K (1,000 sheets). Under high temperature and high humidity (30 ° C / 85% RH)
When the same image was formed as described above, the development / transfer efficiency was as high as 81% on average, a good image with an image density of 1.36 and no fog was obtained, and the toner consumption was 3 on average per 1K.
The amount was as small as 9 g. Furthermore, under low temperature and low humidity (10 ° C / 20%
RH), the same development as described above was carried out. As a result, the development / transfer efficiency was as high as 84% on average, an image density of 1.31 and a stable good image was obtained, and the toner consumption was as small as 35 g per 1K on average. Met.

[0061]

Example 3 A magnetic toner was obtained in the same manner as in Example 1, except that the fine resin particles obtained in Production Example 3 were used. Using the obtained magnetic toner, a magnetic developer was obtained in the same manner as in Example 1, and image formation was performed in the same manner as in Example 1 using the magnetic developer. The image density was 1.32 at low temperature and low humidity. The development / transfer efficiency was stable in each environment, and a good image was obtained.

[0062]

Example 4 A magnetic toner was obtained in the same manner as in Example 2 except that the fine resin particles obtained in Production Example 4 were used. A magnetic developer was obtained using the obtained magnetic toner in the same manner as in Example 2, and image formation was performed in the same manner as in Example 2 using the magnetic developer. The image density was 1.31 at low temperature and low humidity. The development / transfer efficiency was stable in each environment, and a good image was obtained.

[0063]

Comparative Example 1 A magnetic toner and a magnetic developer were obtained in the same manner as in Example 1 except that no resin fine particles were used, and an image was formed in the same manner as in Example 1 using the magnetic developer.
In each environment, the development / transfer efficiency was not stable. Particularly, under high temperature and high humidity, it was remarkably reduced to 58%, and under low temperature and low humidity, the image density was remarkably reduced to 1.15, and fogging occurred.

[0064]

Comparative Example 2 A magnetic toner was obtained in the same manner as in Example 1 except that the resin fine particles obtained in Production Example 5 were used. When an image was formed using the obtained magnetic toner in the same manner as in Example 1, toner scattering occurred under high temperature and high humidity. Further, the toner consumption increased to 58 g per K, and the development / transfer efficiency was remarkably reduced to 67%.

[0065]

Comparative Example 3 A magnetic toner was obtained in the same manner as in Example 1 except that the resin fine particles obtained in Production Example 6 were used. When an image was formed using the obtained magnetic toner in the same manner as in Example 1, significant fog occurred at low temperature and low humidity.

[0066]

The effects obtained by the developer of the present invention are as follows. 1. The development / transfer efficiency under each environment can be improved, and the amount of toner consumption can be optimized. Even if a large number of copies are made, if the resin fine particles have a dielectric loss tangent in a suitable range and satisfy a specific relationship in the dielectric loss tangent between the magnetic resin particles and the carrier, the development / transfer efficiency is improved. As a result, good development can be performed with less toner consumption, and a stable image can be obtained even in various environments. 2. The image density can be improved under a low temperature and a low humidity where the image density is easily reduced, which can prevent the image density from decreasing and the fog from increasing under each environment, and the fog can be prevented from increasing.

Claims (6)

[Claims] 1. A magnetic toner having magnetic resin particles containing magnetic powder and a binder resin and at least resin fine particles, and a magnetic developer having a magnetic powder-dispersed resin carrier, wherein the average particle size of the resin fine particles is The diameter is 0.05 to 2 μm, the value of the dielectric loss tangent at a frequency of 1 MHz of the resin fine particles is A, the value of the dielectric loss tangent at a frequency of 1 MHz of the magnetic resin particles is B, and the value of the dielectric loss tangent at a frequency of 1 MHz of the carrier is C. A magnetic developer characterized by satisfying the following relationship: 0.015 ≦ A ≦ 0.065 and B <A <C. 2. The magnetic material according to claim 1, wherein the fine resin particles are obtained by multi-stage polymerization, the resin fine particles have a plurality of layers including a coating layer and a layer inside the coating layer, and the coating layer has a hydrophilic group. Developer. 3. The magnetic developer according to claim 1, wherein the hydrophilic group in the coating layer of the resin fine particles is a carboxylic acid or a carboxylate. 4. The magnetic developer according to claim 1, wherein 0.01 to 10 parts by weight of resin fine particles are mixed with 100 parts by weight of magnetic resin particles. 5. The magnetic developer according to claim 1, wherein the magnetic resin particles contain 10 to 40% by weight of a magnetic powder. 6. The magnetic developer according to claim 1, wherein the magnetic powder-dispersed resin carrier contains 60 to 95% by weight of magnetic powder.