JP2008304747A - Toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner excellent in development stability while keeping fixability, having a clear image characteristic free from fogging, and excellent in charge stability and durable stability. <P>SOLUTION: This toner is a magnetic toner containing a magnetic toner particle containing at least a bonding resin, a magnetic substance and wax, and at least two kinds of inorganic fine powder, (i) a weight-averaged particle size of the magnetic toner is 4-9 μm, (ii) an average circularity of the magnetic toner is 0.95 or more, (iii) a methanol concentration TA is within a range of 50-70 vol.% when a transmittance is 50%, in case of measuring wettability of the magnetic toner to a methanol/water mixture solvent by the transmittance of light having 780 nm of wavelength, and (iv) a uniaxial collapse stress of the magnetic toner after magnetic-attracted satisfies relations of 0.1≤S5≤2.0 and 1.0≤S20≤4.0, where S5 and S20 are respectively the uniaxial collapse stresses (kPa) when the maximum compression stresses are 5 kPa and 20 kPa. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner for developing an electrostatic latent image using electrophotography, electrostatic recording, toner jet recording, or the like.

  Conventionally, many methods are known as electrophotographic methods. In general electrophotography, a photoconductive material is used, and an electrostatic latent image is formed on an electrostatic charge image carrier (hereinafter also referred to as “photoreceptor”) by various means, and then the latent image is formed on the latent image. Supply toner to make a visible image, obtain a toner image, transfer the toner image to a recording medium such as paper if necessary, and fix the toner image on the recording medium by heat or pressure, etc. The method of obtaining is known.

  Among these, a jumping development method using magnetic toner (a thin coating of insulating magnetic toner is applied on a developer carrying member, this is triboelectrically charged, and then this is brought very close to an electrostatic latent image under the action of a magnetic field. In addition, the method of developing without facing and developing is widely used as a method for obtaining a high-definition image with less fog.

  However, the developing method using magnetic toner has unstable factors related to the magnetic toner to be used. That is, the fluidity of the magnetic toner is lowered and the image stability is lowered due to the separation of the magnetic material by the friction between the toners or the regulating member, the separation or embedding of the toner external additive, and the like. For this reason, when used for a long period of time, the development stability is lowered such as a reduction in image density and occurrence of fog.

  In order to improve such problems and obtain good toner flow characteristics, charging characteristics, etc., a method of improving the surface properties of magnetic toner, a method of adding various inorganic fine powders as external additives to magnetic toner particles, etc. Has been proposed and widely used.

  For example, regarding the surface properties of magnetic toners, there are reports on special toners in which magnetic particles are contained only in specific portions inside the toner particles. Specifically, it is a pressure fixing toner manufactured by a 2-3 stage process in which a magnetic material is dry-attached after manufacturing core particles and then a shell layer is formed, and the magnetic material exists only in the toner intermediate layer. (See Patent Documents 1 and 2). There is also a report on a toner having a structure in which a resin layer having no magnetic particles is formed in the vicinity of the toner particle surface with a certain thickness or more (see Patent Document 3).

  However, it has been found that the toner in such a form has some problems in achieving high image quality, for example, when the average particle diameter of the toner is 10 μm or less and the toner is small. One is that charge-up is likely to occur in a low-temperature, low-humidity environment. According to the results of the study by the present inventors, the toner in which the magnetic particles are contained only in a specific portion inside the particles as described above is essentially free from the magnetic material on the surface. Since the surface of the toner is made of resin, it is considered that the toner surface directly reflects the charging characteristics of the resin with high resistance. For this reason, as the particle size of the toner decreases and the specific surface area of the toner increases, the charge-up becomes more significant. Furthermore, it has become clear that problems such as an increase in fixing temperature remain on the fixing surface due to the multilayer structure.

On the other hand, many methods for adjusting the chargeability as a toner by adding conductive fine particles to the magnetic toner particles as an external additive have been proposed. For example, carbon black as conductive fine particles is used to attach or adhere to the toner surface for the purpose of imparting conductivity to the toner, or for the purpose of suppressing excessive charging of the toner and making the tribo distribution uniform. It is widely known to be used as an external additive. Further, it is disclosed that conductive fine particles of tin oxide, zinc oxide, and titanium oxide are externally added to the high-resistance magnetic toner (Patent Documents 4 to 6). In addition, a toner that achieves both developability and transferability by adding conductive magnetic particles such as iron oxide, iron powder, and ferrite to a high-resistance magnetic toner, and accelerating charge induction to the magnetic toner. It has been proposed (Patent Document 7). Further, it is disclosed that graphite, magnetite, polypyrrole conductive particles, and polyaniline conductive particles are added to the toner, and it is known that various kinds of conductive fine particles are added to the toner (Patent Documents 8 to 8). 11).

However, even if such improvement means is used, it is not sufficient to sufficiently bring out the performance in terms of both the fluidity and the charging characteristics, and as a result, there is a sufficient improvement effect in image characteristics and durability. Is hard to say.
JP 60-3647 A JP 63-89867 A JP-A-7-209904 JP 57-151952 A JP 59-168458 A JP 60-69660 A JP-A-56-142540 JP-A 61-275864 JP-A-62-258472 Japanese Patent Laid-Open No. 61-141452 JP-A-2-120865

An object of the present invention is to provide a toner that solves the above problems. That is, the present invention is to provide a toner having excellent development stability while maintaining fixability.
A further object of the present invention is to provide a toner having clear image characteristics free from fogging and excellent in charging stability and durability stability.

  As a result of intensive studies on the physical properties and materials of a toner that is excellent in development stability while maintaining fixability and effective in having clear image characteristics without fogging, the present inventors have determined that a magnetic toner has a methanol / water mixture. It has been found that there is a close relationship between the wettability to a solvent and the uniaxial collapse stress of the magnetic toner after magnetization and the development stability, and the present invention has been completed.

That is, the present invention
(1) A magnetic toner including at least a binder toner, a magnetic toner particle including a magnetic material, and a wax, and at least two or more kinds of inorganic fine powders, and (i) a weight average particle diameter of the magnetic toner is 4 (Ii) The average circularity of particles having a circle equivalent diameter (number basis) of 2 μm or more of the magnetic toner is 0.95 or more, and (iii) methanol / water mixing of the magnetic toner. When the wettability with respect to the solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 50% is in the range of 50 to 70% by volume, and (iv) the maximum consolidation stress is 5 kPa and 20 kPa. The present invention relates to a magnetic toner characterized in that when the uniaxial collapse stress [kPa] is S5 and S20, the uniaxial collapse stress of the magnetic toner after magnetization satisfies the following formula.

(2) The present invention also relates to the magnetic toner according to (1), wherein the residual magnetization of the magnetic toner is 4.0 Am ² / kg or less at a magnetic field of 79.6 kA / m.

  (3) The present invention is also characterized in that one kind of the inorganic fine powder is an inorganic fine powder having an average particle size of primary particles of 30 to 300 nm and having a perovskite crystal structure (1) or ( The magnetic toner according to 2).

(4) Further, according to the present invention, one type of the inorganic fine powder has a primary particle average particle size of 30 to 300 nm, a cubic particle shape and / or a rectangular particle shape, and a perovskite crystal structure. In addition, the content of particles and aggregates having a particle diameter of 600 nm or more is 1% by number or less, and another kind of the inorganic fine powder has a BET specific surface area of 100 to 350 m ^2. The magnetic toner according to any one of (1) to (3), wherein the magnetic toner is an inorganic fine powder of / g.

  (5) Further, the present invention is characterized in that one kind of the inorganic fine powder is strontium titanate fine powder that has not passed through the sintering step, and the other kind of the inorganic fine powder is hydrophobic silica fine particles. The magnetic toner according to any one of (1) to (4).

  (6) Further, in the present invention, when the wettability of the magnetic toner particles with respect to the methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 50% is 35 to 50% by volume. The magnetic toner according to any one of (1) to (5), wherein

(7) In the invention, any one of (1) to (6) is characterized in that the residual magnetization of the magnetic material is 4.5 Am ² / kg or less at a magnetic field of 79.6 kA / m. It relates to the magnetic toner described.

  (8) The present invention also relates to the magnetic toner according to any one of (1) to (7), wherein the magnetic material is a hydrophobized magnetic material.

(9) The present invention is also characterized in that the magnetic toner has a liberation rate of iron and iron compounds of 0.05% to 3.00% with respect to the magnetic toner. The magnetic toner according to any one of the above.

  (10) The present invention also relates to the magnetic toner according to any one of (1) to (9), wherein the magnetic toner particles are magnetic toner particles produced in an aqueous medium.

  According to the present invention, it is possible to provide a toner that solves the above-described problems. Further, according to the present invention, it is possible to provide a toner having excellent development stability while maintaining fixability. Furthermore, according to the present invention, it is possible to provide a toner having clear image characteristics without fogging and excellent in charging stability and durability stability.

  The toner of the present invention is a magnetic toner containing magnetic toner particles containing at least a binder resin, a magnetic material, and wax, and at least two kinds of inorganic fine powders. The magnetic toner can be produced by any known method, and can be produced by a pulverization method, a dispersion polymerization method, an association aggregation method, a suspension polymerization method, or the like.

  Examples of the magnetic substance contained in the magnetic toner of the present invention include iron oxides such as magnetite, hematite, and ferrite; metals such as iron, cobalt, and nickel, or aluminum, cobalt, copper, lead, magnesium, tin, and zinc of these metals. And alloys of metals such as antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium, and mixtures thereof.

The magnetic material used in the present invention is more preferably a surface-modified magnetic material. The reason is as follows.
Even if a normal magnetic substance is contained in the polymerized toner, there are a large number of magnetic substances released from the toner particles, and the charging characteristics of the toner particles are significantly lowered by the free magnetic substances. Further, the dispersion of the magnetic material also tends to deteriorate, and it is difficult to satisfy the dispersibility of the magnetic material, which is an essential requirement of the present invention. Furthermore, during the production of the suspension polymerization toner, it is difficult to obtain a toner with a high degree of circularity due to the strong interaction between the magnetic substance and water, and the particle size distribution of the toner becomes wide.
This is because (1) the magnetic substance is generally hydrophilic, and thus tends to be present on the toner surface. (2) The magnetic substance moves randomly when the aqueous solvent is stirred, and the surface of the suspended particles composed of the monomer. This is thought to be caused by the fact that the shape is distorted and the shape is distorted to make it difficult to form a circle. In order to solve these problems, as described above, it is important to improve the surface characteristics of the magnetic material.

  The magnetic material used in the magnetic toner of the present invention is preferably hydrophobized with a coupling agent. As a method for hydrophobizing the surface of the magnetic material, it is more preferable to use a method in which the surface treatment is performed while hydrolyzing the coupling agent while dispersing the magnetic material to have a primary particle size in an aqueous medium. It is very preferable to use a method in which a magnetic material produced therein is washed and then subjected to a hydrophobic treatment without drying. In the hydrophobizing method in water, the magnetic bodies are less likely to coalesce than in the gas phase, and a more uniform treatment can be performed. In addition, in the method of hydrophobizing without passing through the drying step, the aggregation of the magnetic material does not occur at the time of drying, so that the primary particle size is dispersed almost at the time of hydrophobizing, and a very uniform surface treatment can be applied. I can do it.

  The method of treating the surface of the magnetic material while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates gas, such as chlorosilanes and silazanes. Furthermore, in the above-described treatment method, it is possible to use a high-viscosity coupling agent, which has been difficult to perform well in the gas phase so that magnetic materials can be easily combined with each other. The effect of hydrophobization is enormous.

  Examples of the coupling agent that can be used in the surface treatment of the magnetic material used in the present invention include a silane coupling agent and a titanium coupling agent. Since these substances are substances that do not inhibit polymerization even in the polymerization method, it is preferable to hydrophobize the surface of the magnetic material with such a surface modifier. More preferably used is a silane coupling agent, which is represented by the following general formula (I).

［式中、Ｒはアルコキシ基を示し、ｍは１〜３の整数を示し、Ｙはアルキル基、ビニル基、グリシドキシ基、メタクリル基の如き炭化水素基を示し、ｎは１〜３の整数を示す。た
だし、ｍ＋ｎ＝４である。］

[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, or a methacryl group, and n represents an integer of 1 to 3. Show. However, m + n = 4. ]

Examples of the silane coupling agent represented by the general formula (I) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, and β- (3,4 epoxycyclohexyl) ethyltrimethoxysilane. Γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane , Vinyltriacetoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyl Nyldiethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, trimethylmethoxysilane, n-hexyltrimethoxysilane, n-decyltrimethoxysilane, hydroxypropyltrimethoxysilane, n-hexadecyltrimethoxysilane, n -Octadecyltrimethoxysilane etc. can be mentioned.
Among these, in order to obtain sufficient hydrophobicity, an alkyltrialkoxysilane coupling agent represented by the following general formula (II) is preferably used.

［式中、ｐは２〜２０の整数を示し、ｑは１〜３の整数を示す。］

[In formula, p shows the integer of 2-20, q shows the integer of 1-3. ]

When p in the general formula (II) is smaller than 2, the hydrophobizing treatment is easy, but it is difficult to sufficiently impart hydrophobicity, and it is difficult to suppress the magnetic substance released from the toner particles. . On the other hand, when p is larger than 20, hydrophobicity is sufficient, but the coalescence of the magnetic materials increases, and it is difficult to sufficiently disperse the magnetic materials in the toner.
Moreover, when q in the said general formula (II) is larger than 3, the reactivity of a silane coupling agent will fall and it will become difficult to fully hydrophobize.
In particular, as a coupling agent, p in the general formula (II) represents an integer of 2 to 20 (more preferably, an integer of 3 to 15), and q is an integer of 1 to 3 (more preferably 1). Alternatively, an alkyltrialkoxysilane coupling agent having an integer of 2) is preferably used.

  The amount of the treatment is preferably such that the total amount of the silane coupling agent is 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the magnetic material, depending on the surface area of the magnetic material, the reactivity of the coupling agent, and the like. It is preferable to adjust the amount of the treatment agent.

  In order to perform a surface treatment using a coupling agent in an aqueous medium as a surface treatment of the magnetic substance, an appropriate amount of the magnetic substance and the coupling agent are stirred in the aqueous medium. This stirring is preferably performed sufficiently, for example, with a mixer having stirring blades so that the magnetic material becomes primary particles in the aqueous medium.

Here, the aqueous medium is a medium containing water as a main component. Specific examples of the aqueous medium include water itself, water added with a small amount of a surfactant, water added with a pH adjusting agent, and water added with an organic solvent.
As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid. Examples of the organic solvent include alcohols.

In addition, when using the said silane coupling agent, it is possible to process the surface of a magnetic body individually or in combination of several types. When the surface treatment is performed using a plurality of types in combination, the respective coupling agents are added simultaneously or with a time difference to treat the magnetic material.

In the magnetic material thus obtained, particle aggregation is not observed, and the surface of each particle is uniformly hydrophobized. For this reason, when the obtained magnetic material is used as a material for polymerized toner, the uniformity of toner particles is improved.
By using a magnetic material that has been subjected to a hydrophobic treatment, it is difficult for the magnetic material to be exposed on the surface of the toner particles, and control of wettability to a methanol / water mixed solvent, which will be described later, becomes easier.

  The volume average particle of these magnetic materials is preferably 2 μm or less, more preferably about 0.1 to 0.5 μm.

  The preferable content of the magnetic material used in the magnetic toner of the present invention is 10 to 200 parts by mass, and more preferably 20 to 180 parts by mass with respect to 100 parts by mass of the binder resin. If it is less than 10 parts by mass, the coloring power of the toner becomes poor, and the residual magnetization (σr1) of the magnetic toner, which will be described later, decreases, so it is difficult to suppress fogging. On the other hand, when the amount exceeds 200 parts by mass, the holding force by the magnetic force on the toner carrying member is increased and the developability is lowered. Further, not only is it difficult to uniformly disperse the magnetic material in individual toner particles, but magnetic aggregation easily occurs, which is not preferable in terms of controlling uniaxial collapse stress described later.

  The content of the magnetic substance in the magnetic toner of the present invention can be measured using, for example, a thermal analysis device manufactured by Perkin Elmer, TGA7. In the measurement method, the toner is heated from room temperature to 900 ° C. at a temperature rising rate of 25 ° C./min in a nitrogen atmosphere, and the weight loss% between 100 ° C. and 750 ° C. is defined as the binder resin amount, Approximate content of magnetic material.

  The shape of the magnetic body includes a polyhedron, an octahedron, a hexahedron, a sphere, a needle, a scaly shape, and the like, but a polyhedron, an octahedron, a hexahedron, a sphere, or the like having a small anisotropy is a magnetic body residual magnetization ( This is preferable in terms of reduction in σr2) and improvement in image density.

  The volume average particle diameter of the magnetic material can be measured using a transmission electron microscope. Specifically, after sufficiently dispersing the toner particles to be observed in the epoxy resin, a cured product obtained by curing for 2 days in an atmosphere at a temperature of 40 ° C. is obtained by a microtome. This sample is measured with a transmission electron microscope (TEM) for 100 magnetic particle diameters in the field of view at a magnification of 10,000 to 40,000 times. Then, the volume average particle diameter was calculated based on the equivalent diameter of a circle equal to the projected area of the magnetic material. It is also possible to measure the particle size with an image analyzer.

For example, in the case of magnetite, the magnetic material used in the magnetic toner of the present invention is produced by the following method.
An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide to the ferrous salt aqueous solution in an amount equivalent to or greater than the iron component. Air was blown in while maintaining the pH of the prepared aqueous solution at 7 or higher (preferably pH 8 to 14), and ferrous hydroxide was oxidized while heating the aqueous solution to 70 ° C. or higher. First, a seed crystal to be a core is generated.
Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals based on the amount of alkali added previously. While maintaining the pH of the solution at 6 to 14, the reaction of ferrous hydroxide is promoted while blowing air, and a magnetic iron oxide powder (magnetite) is grown with the seed crystal as a core. At this time, the shape of the magnetic material can be controlled by selecting an arbitrary pH. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but the pH of the liquid is preferably 7 or higher. After completion of the oxidation reaction, it is possible to adjust the pH and the like as it is for coupling treatment, but after completion of the oxidation reaction, the magnetic iron oxide powder obtained by washing and filtering is not dried, After re-dispersing in the medium, it is preferable to set the pH of the re-dispersed liquid to an acidic region, add a silane coupling agent with sufficient stirring, and raise the temperature after hydrolysis. Or it is preferable to perform a coupling process by making pH into an alkali range. In any case, it is important to perform the surface treatment after the oxidation reaction without passing through the drying step. If it is dried before the coupling treatment, it is difficult to uniformly disperse the magnetic material in the aqueous medium, and uniform treatment cannot be performed.
As the ferrous salt, iron sulfate generally produced as a by-product in the production of sulfuric acid titanium, iron sulfate produced as a by-product with the surface cleaning of the steel sheet can be used, and iron chloride or the like can be used.
In the method for producing magnetic iron oxide by the aqueous solution method, the iron concentration is preferably 0.5 to 2 mol / l in consideration of suppression of increase in viscosity during the reaction and solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the particle size of the product. Further, in the reaction, the larger the amount of air and the lower the reaction temperature, the more likely to atomize.
By using the magnetic toner containing the hydrophobic magnetic material produced in this way, stable toner chargeability can be obtained, transfer efficiency is high, and high image quality and high development stability are possible.

The magnetic toner of the present invention contains a wax (release agent) for improving the fixability.
The preferable content of the wax used in the present invention is 1 to 30% by mass, and more preferably 3 to 25% by mass with respect to the binder resin.
When the wax content is less than 1% by mass, the effect of suppressing low temperature offset is poor, and when it exceeds 30% by mass, the long-term storage stability is deteriorated and the toner charging uniformity is inferior due to oozing onto the toner surface. This leads to a decrease in transfer efficiency, which is not preferable. Furthermore, since a large amount of wax is included, the toner shape tends to become distorted.

  Examples of the wax used in the present invention include petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam and derivatives thereof; montan wax and derivatives thereof; hydrocarbon waxes and derivatives thereof according to the Fischer-Tropsch method; polyolefins represented by polyethylene These include waxes and derivatives thereof; natural waxes and derivatives thereof such as carnauba wax and candelilla wax; derivatives include oxides, block copolymers with vinyl monomers, graft modified products, and the like. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds of these fatty acids, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes and the like are also included. .

  Among these wax components, those having an endothermic peak by differential thermal analysis of 40 to 110 ° C., that is, a maximum endothermic peak in the region of 40 to 110 ° C. at the time of temperature rise in the DSC curve measured by a differential differential calorimeter. The wax which has in the area | region of 45-90 degreeC is further more preferable. By having the maximum endothermic peak in the above temperature range, it has good fixability and can suppress the exudation of the wax component. When the maximum endothermic peak is less than 40 ° C., the self-aggregation force of the wax component is weakened. As a result, the wax component tends to ooze out and the charging uniformity of the toner is lowered. On the other hand, when the maximum endothermic peak exceeds 110 ° C., in the suspension polymerization method, which is a preferred production method of the present invention, the solubility of the wax in the polymerizable monomer is extremely deteriorated. It deteriorates and is not preferable.

The melting point of the wax and the endothermic peak top of the wax can be measured by differential scanning calorimetry. More specifically, it is performed according to ASTM D 3417-99. For example, DSC-7 manufactured by PerkinElmer, DSC2920 manufactured by TA Instrument, and Q1000 manufactured by TA Instrument can be used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, and an empty pan is set for control and measured.
In the magnetic toner of the present invention, the modulated mode was used and measured under the following conditions, and the melting point of the release agent was determined from the DSC curve at the time of temperature increase.
<Modulated mode measurement conditions>
• Equilibrate at 20 ° C for 1 minute.
-Apply a modulation of 1.5 ° C / min and raise the temperature to 180 ° C at 2 ° C / min.
• Equilibrate at 180 ° C for 10 minutes.
-Apply a modulation of 1.5 ° C / min and lower the temperature to 20 ° C at 2 ° C / min.

  As the binder resin when the magnetic toner of the present invention is produced by a pulverization method, a homopolymer of styrene such as polystyrene and polyvinyltoluene and its substitute; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, Styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylamino acrylate Ethyl copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer Coalescence, styrene-vinyl ethyl ether Copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers, and other styrenic copolymers ; Polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic Alternatively, alicyclic hydrocarbon resin, aromatic petroleum resin, paraffin wax, carnauba wax and the like are included. These may be used alone or in combination. In particular, a styrene copolymer and a polyester resin are preferable in terms of development characteristics, fixing properties, and the like.

The magnetic toner of the present invention can also be produced by a polymerization method.
In the production of the magnetic toner of the present invention by the polymerization method, the polymerizable monomers constituting the polymerizable monomer system include the following.
Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, and p-ethylstyrene; methyl acrylate, ethyl acrylate, Acrylate esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate Types; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, Methacrylic acid dimethyl aminoethyl, methacrylic acid esters such as diethylaminoethyl methacrylate; and other acrylonitrile, methacrylonitrile, and the like monomers acrylamide. These monomers are used alone or in combination. Among the above-mentioned monomers, styrene or a styrene derivative is preferably used alone or mixed with other monomers from the viewpoint of the developing characteristics and durability of the toner.

In the production of a magnetic toner (polymerized magnetic toner) by polymerization, a resin may be added to the polymerizable monomer system for polymerization. For example, it contains hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups that cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the polymerizable monomer component into the toner, a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, and the like, Alternatively, it can be used in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. When a polymer containing such a polar functional group is allowed to coexist in the toner,
Since the above wax component is phase-separated and the encapsulation becomes stronger, a toner having good blocking resistance and developability can be obtained.

Among these resins, the effect is greatly increased by containing a polyester resin. This is presumed for the following reason.
Since the polyester resin contains many ester bonds which are functional groups having relatively high polarity, the polarity of the resin itself is increased. Due to the high polarity of the resin itself, there is a strong tendency for the polyester to be unevenly distributed on the surface of the droplets in the aqueous dispersion medium, polymerization proceeds while maintaining this state, and toner is formed. For this reason, the polyester resin is unevenly distributed on the toner surface, and the surface state and surface composition of the toner become uniform. As a result, the chargeability becomes uniform and the encapsulating property of the release agent becomes good. Due to these synergistic effects, the obtained magnetic toner has very good developability. Furthermore, it has also been clarified by the present invention that by using a polyester resin, the wettability of the magnetic toner of the present invention described later with respect to a methanol / water mixed solvent can be easily adjusted within a desired range.

  As the polyester resin used in the present invention, for example, a saturated polyester resin, an unsaturated polyester resin, or both of them may be appropriately selected and used for controlling physical properties such as chargeability, durability, and fixability of the toner. Is possible.

As the polyester resin used in the present invention, an ordinary resin composed of an alcohol component and an acid component can be used, and both components are exemplified below.
As alcohol components, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexane Diol, neopentyl glycol, 2-ethyl-1,3-hexanediol, cyclohexanedimethanol, butenediol, octenediol, cyclohexenedimethanol, hydrogenated bisphenol A, and bisphenol derivatives represented by formula (I);

［式中、Ｒはエチレンまたはプロピレン基であり、ｘ，ｙはそれぞれ１以上の整数であり、かつｘ＋ｙの平均値は２〜１０である。］、式（イ）の化合物の水添物、下記式（ロ）で示されるジオール、あるいは式（ロ）の化合物の水添物のジオールが挙げられる。

[Wherein, R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10. ], A hydrogenated product of the compound of the formula (I), a diol represented by the following formula (B), or a hydrogenated diol of the compound of the formula (B).

  As the divalent carboxylic acid, benzene dicarboxylic acid such as phthalic acid, terephthalic acid, isophthalic acid, phthalic anhydride or the anhydride; alkyl dicarboxylic acid such as succinic acid, adipic acid, sebacic acid, azelaic acid or the anhydride; Furthermore, succinic acid substituted with an alkyl or alkenyl group having 6 to 18 carbon atoms or an anhydride thereof; unsaturated dicarboxylic acid such as fumaric acid, maleic acid, citraconic acid, itaconic acid or the anhydride thereof may be used.

  In addition, polyhydric alcohols such as glycerin, pentaerythritol, sorbit, sorbitan, and oxyalkylene ethers of novolac type phenol resins can be cited as the alcohol component, and trimellitic acid, pyromellitic acid, 1,2,3,4- Examples thereof include polyvalent carboxylic acids such as butanetetracarboxylic acid, benzophenonetetracarboxylic acid and anhydrides thereof.

Among the above polyester resins, the alkylene oxide adduct of bisphenol A, which has excellent charging characteristics and environmental stability and is well balanced in other electrophotographic characteristics, is preferably used. In the case of this compound, the average number of added moles of alkylene oxide is preferably 2 to 10 in terms of fixability and toner durability.
It is preferable that 45-55 mol% of the polyester resin in this invention is an alcohol component, and 55-45 mol% is an acid component in all the components.

  In the polymerized magnetic toner of the present invention, the polyester resin has an acid value of 0.1 to 50 mg KOH / resin 1 g in order that the polyester resin is present on the surface of the toner particles and the resulting toner particles exhibit a stable chargeability. It is preferable. If it is less than 0.1 mg KOH / resin 1 g, the amount existing on the toner surface is absolutely insufficient, and if it exceeds 50 mg KOH / resin 1 g, the chargeability of the toner is adversely affected. Furthermore, in the present invention, the acid value range of 5 to 35 mg KOH / resin 1 g is more preferable. In the present invention, the wettability with respect to the methanol / water mixed solvent described later can also be achieved by controlling the acid value of the polyester resin. That is, a polyester resin having a low acid value is used to reduce the wettability with respect to the methanol / water mixed solvent, and conversely, a polyester resin with a high acid value is used to improve the wettability with respect to the methanol / water mixed solvent. Can be used.

  In the present invention, it is also preferable to prepare physical properties by using two or more polyester resins together, for example, by modifying with silicone or a fluoroalkyl group-containing compound, as long as the physical properties of the obtained toner particles are not adversely affected. To be done.

  Moreover, when using the high molecular polymer containing such a polar functional group, the average molecular weight is preferably 5,000 or more. If it is less than 5,000, especially 4,000 or less, the present polymer tends to concentrate in the vicinity of the surface, so that developability, blocking resistance, and durability tend to deteriorate, which is not preferable.

Further, a resin other than the above may be added to the monomer system for the purpose of improving the dispersibility and fixing properties of the material or the image characteristics. Examples of the resin used include homopolymers of styrene such as polystyrene and polyvinyltoluene and substituted products thereof; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic. Acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer Polymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, Styrene-vinyl methyl Styrene copolymers such as ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate , Polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, Aromatic petroleum resins are included. These may be used alone or in combination.

  As addition amount of these resin, 1-20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers. If it is less than 1 part by mass, the effect of addition is small, while if it exceeds 20 parts by mass, it becomes difficult to design various physical properties of the polymerized toner.

  Furthermore, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the polymerizable monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. I can do it.

As the polymerization initiator used in the production of the polymerized magnetic toner of the present invention, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1 Azo or diazo polymerization initiators such as' -azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile; Peroxide-based polymerization initiators such as oxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, t-butylperoxy 2-ethylhexanoate; Is mentioned.
A polymerization initiator having a half-life of 0.5 to 30 hours at the time of the polymerization reaction is subjected to a polymerization reaction at an addition amount of 0.5 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. A polymer having a maximum molecular weight peak between 100,000 can be obtained, and the toner can be provided with desirable strength and suitable melting characteristics.

  When producing the polymerized magnetic toner of the present invention, a crosslinking agent may be added. A preferable addition amount of the crosslinking agent is 0.001 to 15 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

  Here, as the crosslinking agent, a compound having two or more polymerizable double bonds is mainly used, for example, an aromatic divinyl compound such as divinylbenzene, divinylnaphthalene, etc .; for example, ethylene glycol diacrylate, ethylene glycol diester Carboxylic acid ester having two double bonds such as methacrylate, 1,3-butanediol dimethacrylate, etc .; Divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone, etc .; and having three or more vinyl groups A compound. These are used alone or as a mixture.

  In the production of the polymerized magnetic toner of the present invention, a known surfactant, organic dispersant, or inorganic dispersant can be used as a dispersion stabilizer.

  In particular, inorganic dispersants are less likely to produce harmful ultrafine powders, and because of their steric hindrance, dispersion stability is obtained, so even if the reaction temperature is changed, stability is not easily lost, and washing is easy and does not adversely affect the toner. Therefore, it can be preferably used. Examples of such inorganic dispersants include tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, phosphate polyvalent metal salts such as hydroxyapatite, carbonates such as calcium carbonate and magnesium carbonate, calcium metasuccinate, calcium sulfate, Examples thereof include inorganic salts such as barium sulfate and inorganic compounds such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide.

  A preferable content of these inorganic dispersants is 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. Moreover, the said dispersion stabilizer may be used independently and may be used together in multiple types. Furthermore, you may use together 0.001-0.1 mass part surfactant with respect to 100 mass parts of polymerizable monomers.

  When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated and used in an aqueous medium. For example, in the case of tricalcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate. The inorganic dispersant particles produced in the aqueous medium can disperse the toner component more uniformly and finely. At the same time, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine toner based on emulsion polymerization is produced. Since it becomes difficult to generate | occur | produce, it is more convenient.

  Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, potassium stearate and the like.

  The magnetic toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, a known one can be used, and a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable. Further, in the case of producing a polymerization toner, a charge control agent having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous dispersion medium is particularly preferable. Specific compounds of the charge control agent include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkyl salicylic acid, dialkyl salicylic acid, naphthoic acid, dicarboxylic acid, metal salts of azo dyes or azo pigments, or Examples thereof include a metal complex, a polymer compound having a sulfonic acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, and an imidazole compound.

  As a method of incorporating the charge control agent in the magnetic toner, there are a method of adding it inside the toner particles and a method of adding it externally. The amount of use of these charge control agents is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, and is not uniquely limited. When added internally, it is preferably used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin. Further, when externally added, the amount is preferably 0.005 to 1.0 part by mass, more preferably 0.01 to 0.3 part by mass with respect to 100 parts by mass of the toner particles.

  However, in the magnetic toner of the present invention, it is not essential to add a charge control agent, and the toner does not necessarily contain the charge control agent by actively utilizing frictional charging with the toner layer thickness regulating member or the toner carrier. There is no need.

  In the present invention, a colorant may be used in combination. Examples of the colorant that can be used in combination include magnetic or nonmagnetic inorganic compounds and known dyes and pigments. Specifically, for example, ferromagnetic metal particles such as cobalt and nickel, or alloys obtained by adding chromium, manganese, copper, zinc, aluminum and rare earth elements to these, particles such as hematite, titanium black, nigrosine dye / pigment , Carbon black, phthalocyanine and the like. These are also preferably used by treating the surface.

Next, two or more kinds of inorganic fine powders contained in the magnetic toner of the present invention will be described.
Here, one kind of the inorganic fine powder has a perovskite crystal structure. Among the inorganic fine powders of perovskite crystals, particularly preferred are, for example, strontium titanate fine powder, barium titanate fine powder, and calcium titanate fine powder, and among these, strontium titanate fine powder is more preferred.
In the present invention, it is also preferable in the present invention to perform surface treatment with a silicone oil, a silane coupling agent, a titanium coupling agent, and a fatty acid or a metal salt thereof generally used for improving the hydrophobicity of the external additive.

The average primary particle size of the inorganic fine powder having a perovskite crystal structure used in the present invention is preferably 30 to 300 nm, more preferably 40 to 300 nm, and further preferably 40 to 250 nm. An average particle size of less than 30 nm is not preferable because it tends to cause poor cleaning particularly when used for a long period of time. On the other hand, if it exceeds 300 nm, charging in the developing device tends to be insufficient, which is not suitable.
In the present invention, the reason why the inorganic fine powder having an average primary particle size of 30 to 300 nm and a perovskite crystal structure is preferably used is not clear, but uniform charging is obtained by the regular crystal lattice of the perovskite type. It is easy to be done. Further, even in a state where the magnetic toner having a high degree of circularity is densely packed, the average particle diameter of the primary particles is 30 to 300 nm. Consider that both sexes are compatible.

  As a method for obtaining a fine powder within a specific range, there is a crystal growth method in the case of producing it by a wet method. By controlling pH, temperature, concentration, reaction time, etc., a desired fine powder can be obtained. it can. In the case of dry production, the powder is heated at a temperature equal to or lower than the melting point to melt only the vicinity of the surface so that the particles have bonds having the same strength as the inside. The shape of the powder produced by this sintering method has a morphological feature that it has no corners and is rounded.

  About the average particle diameter of the inorganic fine powder of the perovskite type crystal | crystallization in this invention, 100 particle diameters were measured from the photograph image | photographed with the magnification of 50,000 times with the electron microscope, and the average was calculated | required. The particle size was determined as (a + b) / 2, where a is the longest side of the primary particles and b is the shortest side.

Further, the inorganic fine powder having the perovskite crystal structure does not necessarily exist as primary particles on the surface of the toner particles, and may exist as an aggregate. Even in such a case, it is preferable that the content of the particles having a particle diameter of 600 nm or more and the agglomerate is 1% by number or less because it is easily charged uniformly.
The content of particles and aggregates having a particle size of 600 nm or more is determined by measuring 100 particle sizes from a photograph taken at a magnification of 50,000 times with an electron microscope, and then particles having a particle size of 600 nm or more. And the content (rate) of the aggregates. Examples of a method for obtaining such an inorganic fine powder include a sintering method and a crystal growth method, and a crystal growth method is preferable.

  In addition, the particle shape of the inorganic fine powder is preferably spherical or nearly polyhedral, cubic or cuboid. Here, when the present invention was examined in detail, it was found that a cubic and / or rectangular parallelepiped particle shape was more preferable among them. The present inventors can efficiently regulate uniaxial collapse stress in a compacted state by using an inorganic fine powder having a perovskite type crystal structure whose particle shape is approximately cubic and / or rectangular parallelepiped as the inorganic fine powder. I found out. Although the specific reason for this is unclear, the present inventors indicate that the particle shape of the inorganic fine powder is approximately cubic and / or rectangular parallelepiped, and that the average particle size of primary particles is 30 to 300 nm. It is considered that the contact area between the inorganic fine powder and the magnetic toner particles is increased, excessive packing between the magnetic toner particles is suppressed, and the uniaxial collapse stress can be efficiently regulated in the compacted state. Furthermore, since the contact area between the inorganic fine powder and the magnetic toner particles is increased, the magnetic toner can be uniformly charged efficiently, leading to higher image quality. Among such inorganic fine powders in the form of cubes and / or cuboid particles, it was found that strontium titanate that does not go through the sintering step is more preferable because the shape of the inorganic fine powder is easily uniformized. .

An example of a method for producing strontium titanate that does not go through a sintering step is to wash a hydrous titanium oxide slurry obtained by hydrolysis from titanyl sulfate with an alkaline aqueous solution. Next, hydrochloric acid is added to the hydrous titanium oxide slurry to obtain a titania sol dispersion. NaOH is added to the titania sol dispersion to obtain hydrous titanium oxide. Sr (OH) ₂ .8H ₂ O is added to the hydrous titanium oxide to replace nitrogen gas, and distilled water is added. The slurry is heated to 80 ° C. in a nitrogen atmosphere and reacted at 80 ° C. for 6 hours. After the reaction, the reaction mixture is cooled to room temperature, washed repeatedly, and then filtered and dried to obtain strontium titanate fine particles not passing through the sintering step.

In the present invention, inorganic fine particles having a BET specific surface area of 100 to 350 m ² / g are preferably externally added to the toner particles as another kind of the inorganic fine powder. This is because, by adding an inorganic fine powder having a BET specific surface area of 100 to 350 m ² / g to the toner particles, appropriate fluidity and chargeability are imparted to the magnetic toner of the present invention.
The specific surface area BET can be determined by a low temperature gas adsorption method by a dynamic constant pressure method according to a BET method (preferably a BET multipoint method). For example, by using a specific surface area measuring device “Gemini 2375 Ver. 5.0” (manufactured by Shimadzu Corporation), nitrogen gas is adsorbed on the sample surface, and measurement is performed using the BET multipoint method. m ² / g) can be calculated.
Examples of the method for obtaining the inorganic fine particles having the BET specific surface area include a method for producing so-called dry silica or fumed silica.

  As another kind of inorganic fine powder, preferably, titanium oxide fine powder, silica fine powder, and alumina fine powder are used. In particular, silica fine powder is preferably used as another kind of inorganic fine powder. From the viewpoint of charging stability, hydrophobic silica fine particles are more preferably used.

When the above-mentioned inorganic fine powder is used together with another kind of the inorganic fine powder having a BET specific surface area of 100 to 350 m ² / g, it is generally excellent in fluidity and chargeability even in a harsh environment. It became clear to have. In particular, one kind of the inorganic fine powder is a strontium titanate fine powder that has not passed through the sintering step, and the other kind of the inorganic fine powder is a hydrophobic silica fine particle. From the point of view, it became clear that it was more preferable.

  Furthermore, in the present invention, in order to improve developability and durability, the following inorganic fine powder can be added to the toner. For example, oxides of metals such as silicon, magnesium, zinc, aluminum, titanium, cerium, cobalt, iron, zirconium, chromium, manganese, tin, antimony; metal salts such as barium sulfate, calcium carbonate, magnesium carbonate, aluminum carbonate; Examples thereof include clay minerals such as kaolin; phosphoric acid compounds such as apatite; silicon compounds such as silicon carbide and silicon nitride; and carbon powders such as carbon black and graphite.

  For the same purpose, the following organic particles and composite particles may be added to the toner. Resin particles such as polyamide resin particles, silicon resin particles, silicon rubber particles, urethane particles, melamine-formaldehyde particles, acrylic particles; rubbers, waxes, fatty acid compounds or resins, and inorganic particles of metals, metal oxides, and carbon black Composite particles comprising: Teflon (registered trademark), fluorine resin such as polyvinylidene fluoride; fluorine compound such as carbon fluoride; fatty acid metal salt such as zinc stearate; fatty acid derivative such as fatty acid ester; molybdenum sulfide, amino acid and amino acid Derivatives.

  Next, a method for producing the magnetic toner of the present invention will be described. As described above, the magnetic toner of the present invention can be produced by any known method.

  First, when magnetic toner is manufactured by a pulverization method, for example, the following method is used. Components necessary for magnetic toner such as binder resin, magnetic material, release agent, charge control agent, and colorant, and other additives, as well as other additives, etc. are thoroughly mixed by a mixer such as a Henschel mixer or a ball mill, and then heated. In addition, other magnetic toner materials such as a magnetic material are dispersed or dissolved in a kneader or extruder using a melt-kneading machine so that the resins are compatible with each other. Thereafter, after cooling and solidification, pulverization, classification, and surface treatment as necessary, toner particles can be obtained. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier in terms of production efficiency.

  The pulverization step can be performed by a method using a known pulverizer such as a mechanical impact type or a jet type. In order to obtain a toner having a specific circularity according to the present invention, it is preferable to further apply heat to spheroidize. Or it is preferable to perform the process which adds a mechanical impact auxiliary. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.

  Examples of means for applying mechanical impact force include a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. and a turbo mill manufactured by Turbo Industry Co. There is a method of applying a mechanical impact force to the toner by a force such as a compressive force or a frictional force by pressing the toner against the inside of the casing by a centrifugal force with a blade rotating at high speed, as in a device such as a hybridization system manufactured by the manufacturer.

  In the case of using the mechanical impact method, a thermomechanical impact in which the processing temperature is a temperature in the vicinity of the glass transition point Tg (Tg ± 10 ° C.) of the toner is preferable from the viewpoint of preventing aggregation and productivity. More preferably, it is particularly effective to improve the transfer efficiency to carry out at a temperature in the range of the glass transition point Tg ± 5 ° C. of the toner.

  The magnetic toner of the present invention can be produced by a pulverization method as described above, but the toner particles obtained by this pulverization method are generally indefinite. Therefore, in order to obtain the physical property that the average circularity, which is an essential condition of the toner according to the present invention, is 0.950 or more, as described above, it is necessary to perform mechanical, thermal, or some special treatment. It becomes inferior.

  Therefore, the magnetic toner of the present invention is preferably produced in an aqueous medium such as a dispersion polymerization method, an association aggregation method, or a suspension polymerization method. In particular, the polymerizable monomer composition is polymerized in an aqueous medium. The suspension polymerization method produced by the method is easy to satisfy the preferred conditions of the present invention and is a very preferred production method.

Next, a suspension polymerization method capable of suitably producing the magnetic toner of the present invention will be described. The polymerized magnetic toner of the present invention is generally a toner composition, that is, a polymerizable monomer serving as a binder resin, a magnetic substance, a release agent, and in some cases, a plasticizer, a charge control agent, a crosslinking agent, a colorant, etc. Components necessary for toner and other additives (for example, polymer, dispersing agent, etc.) are added as appropriate, and uniformly dissolved or dispersed by a disperser such as a homogenizer, ball mill, colloid mill, or ultrasonic disperser. A polymerizable monomer system. Thereafter, the polymerizable monomer system is dispersed in a continuous layer (for example, an aqueous phase) containing a dispersion stabilizer by using a suitable stirrer, and at the same time, a polymerization reaction is performed, so that a magnetic toner having a desired particle size is obtained. Get. At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size at a stretch. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Also, a polymerization initiator dissolved in a polymerizable monomer or solvent can be added immediately after granulation and before starting the polymerization reaction. After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented.
Then, the two inorganic fine powders described above are added. Furthermore, both organic fine powders and inorganic fine powders can be added, and all known ones can be used.
The amount of the inorganic fine powder added to the magnetic toner particles is preferably 0.1 to 5.0% by weight.
The magnetic toner particles and the inorganic fine powder can be sufficiently mixed by a mixer such as a Henschel mixer to produce the magnetic toner according to the present invention.

  The magnetic toner (polymerized magnetic toner) obtained by this suspension polymerization method has an average circularity of 0.960 or more and a mode circularity of 0.980 or more because the individual toner particle shapes are almost spherical. It is easy to obtain a magnetic toner satisfying the physical property requirements suitable for the invention, and such a magnetic toner has a high transferability because the charge amount distribution is relatively uniform.

  In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, waxes (release agents) to be sealed inside are precipitated by phase separation, and the encapsulation becomes more complete. In order to consume the remaining polymerizable monomer, the reaction temperature can be increased to 90 to 150 ° C. at the end of the polymerization reaction.

  The polymerized toner particles can be filtered, washed and dried by a known method after the polymerization is completed to obtain the magnetic toner particles of the present invention. It is also possible to put a classification step into the manufacturing process and cut coarse powder and fine powder.

The feature of the present invention is that the magnetic toner has a relatively small particle diameter and a high average circularity, but the uniaxial collapse stress after magnetization is low, and the wettability to a methanol / water mixed solvent. By making it within the desired range, good fixability is exhibited.
That is, the magnetic toner of the present invention is
(I) The weight average particle diameter of the magnetic toner is 4.0 to 9.0 μm,
(Ii) The average circularity of particles having an equivalent circle diameter (number basis) of 2 μm or more of the magnetic toner is 0.950 or more,
(Iii) When the wettability of the magnetic toner to the methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 50% is in the range of 50 to 70% by volume.
(Iv) When the uniaxial collapse stress [kPa] at the maximum consolidation stress of 5 kPa and 20 kPa is S5 and S20, respectively, the uniaxial collapse stress of the magnetic toner after magnetization satisfies the following formula.

  By having such characteristics of magnetic toner, the fixability and development stability are remarkably improved.

(I) The weight average particle diameter of the magnetic toner of the present invention is 4.0 to 9.0 μm. When the weight average particle diameter of the toner exceeds 9.0 μm, the reproducibility of the fine dot image is lowered. In addition, since the toner configuration of the present invention is more susceptible to the influence of particle size fluctuation in durability, the charging stability of the toner under the harsh environment obtained by the present invention cannot be sufficiently exhibited. On the other hand, when the weight average particle size of the toner is smaller than 4.0 μm, the deterioration of the external additive is likely to occur due to the decrease in fluidity, and problems such as fogging due to poor charging and low density are likely to occur. .
That is, in the toner of the present invention, remarkable effects appear on the image as compared with the conventional examples, such as improvement of charging stability and fluidity, in the weight average particle diameter of 4.0 to 9.0 μm, and more From the viewpoint of higher image quality, 5.0 to 8.5 μm is preferable.
Such a magnetic toner can be obtained by a pulverization method or a suspension polymerization method.

  The weight average particle size of the toner in the present invention can be measured using an apparatus capable of measuring the particle size distribution of particles mainly having a particle size distribution of about 2 to 10 μm. As a specific example, how to determine the weight average particle diameter of the toner in this embodiment is shown below.

  The measuring device uses a particle size measuring device Coulter Multisizer (manufactured by Coulter), and connects an interface (manufactured by Nikka) and a PC 9801 personal computer (manufactured by NEC) that outputs the number distribution and volume distribution. A 1% NaCl aqueous solution prepared using primary sodium chloride is used.

As a measuring method, 1 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic solution, and 10 mg of a measurement sample is further added. The electrolyte in which the sample is suspended is dispersed for 5 minutes with an ultrasonic disperser, and the volume and number distribution of toner particles of 2 μm or more are measured using the 100 μm aperture as the aperture with the Coulter Multisizer. And calculate.
Then, the volume-based weight average particle diameter obtained from the volume distribution related to the present invention is obtained.

(Ii) The average circularity of particles having a circle equivalent diameter (number basis) of 2 μm or more of the magnetic toner of the present invention is 0.95 or more. In order to reduce toner adhesion to the non-image area on the electrostatic image bearing member and the amount of residual toner, it is necessary that the chargeability of the toner particles be sufficient and uniform. Furthermore, when using a toner having a small particle diameter from the viewpoint of improving the image quality, the adhesion force of the toner particles increases, so that the shape of the toner particles has a great influence on the toner adhesion to the non-image area on the electrostatic charge image carrier. Effect. In other words, the closer the toner particles are to a spherical shape and the more uniform the shape, the smaller the adhesion area of the particles, the less toner adhesion to the non-image area on the electrostatic image bearing member and the remaining amount of transfer residual toner, and high image quality achieved. Is done.
Since the adhesion of the toner particles according to the present invention is reduced, the transfer efficiency of the toner from the electrostatic charge image carrier to the transfer material such as paper is greatly improved. This can be said to be an important toner performance for achieving high resolution as well as reproducibility of minute dot images.
Therefore, in the toner of the present invention, the average circularity of the toner is 0.950 or more, thereby achieving high image quality.
A magnetic toner having an average circularity of 0.950 or more can be obtained by a suspension polymerization method using a magnetic material subjected to coupling treatment, a mechanical treatment or a thermal treatment after a conventional pulverization method, or the like. it can.

  The average circularity C of the toner is calculated from the following equation, where the circularity (center value) at the dividing point i of the particle size distribution is ci and the number of measured particles is m. The average circularity means an average value of the circularity frequency distribution.

  The circularity in the present invention is an index indicating the degree of unevenness of toner particles, and is calculated from the following equation. The circularity is 1.000 when the toner particles are completely spherical, and the more complicated the surface shape, the smaller the circularity.

  The equivalent circle diameter is calculated from the following equation.

  Here, the “particle projected area” is the area of the binarized toner particle image, and the “peripheral length of the particle projected image” is the length of the contour line obtained by connecting the edge points of the toner particle image. Define. The measurement uses the perimeter of the particle image when image processing is performed at an image processing resolution of 512 × 512 (pixels of 0.3 μm × 0.3 μm).

The average circularity of the toner can be obtained from the toner particle image by the above formula. For example, the average circularity of the toner can be obtained by measuring using a flow type particle image measuring device “FPIA-2100 type” (manufactured by Sysmex Corporation). Can do.
In addition, “FPIA-2100” calculates the circularity of each particle, and then calculates the average circularity and the standard deviation of circularity. .01 is divided into equally divided classes, and the average circularity and circularity standard deviation are calculated using the center value of the division points and the number of measured particles.

As a specific measuring method, 10 ml of ion-exchanged water from which impure solids and the like are previously removed is prepared in a container, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant therein, and then further measurement is performed. Add 0.02 g of sample and disperse uniformly. As a means for dispersion, an ultrasonic disperser “Tetora 150 type” (manufactured by Nikka Ki Bios Co., Ltd.) is used, and dispersion treatment is performed for 2 minutes to obtain a dispersion for measurement. In that case, it cools suitably so that the temperature of the said dispersion liquid may not become 40 degreeC or more.
In order to suppress variation in circularity, the installation environment of the apparatus is controlled at 23 ° C. ± 0.5 ° C. so that the temperature inside the flow type particle image analyzer FPIA-2100 is 26 to 27 ° C. In addition, the autofocusing is preferably performed using 2 μm latex particles every two hours.

  To measure the circularity of the toner particles, the flow particle image measuring device is used, and the dispersion concentration is readjusted so that the toner particle concentration at the time of measurement is 3,000 to 10,000 particles / μl. 1,000 or more are measured. After the measurement, using this data, data having an equivalent circle diameter of less than 2 μm is cut to determine the average circularity of the toner particles.

(Iii) The wettability of the magnetic toner of the present invention with respect to a methanol / water mixed solvent is determined by measuring the transmittance of light having a wavelength of 780 nm, and the methanol concentration (TA) at a transmittance of 50% is 50 to 70% by volume. Is within the range. If TA is less than 50% by volume, it indicates that the affinity with water is high, and the chargeability in a high humidity environment tends to be lowered.
On the contrary, when TA exceeds 70% by volume due to the improvement in hydrophobicity and addition of a large amount of inorganic fine powder, the water repellency is too high. Detrimental effects such as deterioration, a decrease in image density, and adhesion of toner to the charge imparting member and the photoreceptor are brought about. Addition of a large amount of inorganic fine powder is not preferable because it deteriorates the fixing performance and contaminates the photosensitive member, the charging member of the photosensitive member, the toner charging member in the developing process, and the like.
Therefore, in the toner of the present invention, TA is preferably 50 to 70% by volume, and improvement in development stability and fixability is achieved. More preferably, TA is 55 to 65% by volume. The development stability and fixability are significantly improved.
Magnetic toners that have a wettability of 50 to 70% by volume with a methanol / water mixed solvent are magnetically produced by suspension polymerization or pulverization (mechanical or thermal) using a coupled magnetic material. It can be obtained by producing toner particles and externally adding 0.1 to 5.0 parts by mass of inorganic fine powder.

  In the present invention, when the wettability of the magnetic toner particles to the methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration (TB) at a transmittance of 50% is 35 to 50 volumes. % Is preferable. When TB is less than 35% by volume, the amount of the low softening point substance on the toner surface is small, which is not satisfactory in terms of low-temperature fixability. When the volume exceeds 50% by volume, the amount of low softening point substance on the toner surface is large and the low temperature fixability is good. However, when the fixing temperature is high, the resin and the low softening point substance are separated. However, sufficient hot offset resistance cannot be exhibited. Further, when used over a long period of time, embedding of external additives and the like is likely to occur, and the fluidity of the magnetic toner is lowered, and problems such as fogging and low density due to poor charging are likely to occur.

  The wettability with respect to a methanol / water mixed solvent refers to the point at which the transmittance is measured by methanol titration used in measuring the degree of methanol hydrophobization, and the point at which the sample is completely sunk, that is, the point at which the transmittance is minimized (the degree of methanol hydrophobization is This point is defined as the end point, and is defined as the methanol usage volume% at the time when the transmittance (50%) intermediate between the transmittance of the methanol before the sample addition and the transmittance before the sample addition is reached.

In the present invention, the wettability with respect to the methanol / water mixed solvent is determined as follows.
In the present invention, the wettability of a magnetic toner to a methanol / water mixed solvent, that is, the hydrophobic characteristics of the magnetic toner and toner particles are measured using a methanol dropping transmittance curve. Specifically, as the measuring device, for example, a powder wettability tester WET-100P manufactured by Reska Co., Ltd. may be mentioned, and specific measuring operations may include the methods exemplified below.
First, 70 ml of a hydrated methanol solution composed of 40% by volume of methanol and 60% by volume of water is placed in a flask and dispersed for 5 minutes with an ultrasonic disperser in order to remove bubbles and the like in the measurement sample. In this, 0.50 g of a magnetic toner as a specimen is precisely weighed and added to prepare a sample solution for measuring the hydrophobic characteristics of the magnetic toner.
Next, while stirring the sample solution for measurement at a speed of 6.67 m / s, methanol was added at 1.3 ml / min. Are continuously added at a dropping rate of 780 nm, the transmittance is measured with light having a wavelength of 780 nm, a methanol dropping transmittance curve is prepared, and the methanol concentration at which the transmittance is 50% is measured.
In this measurement, the flask used was a circle having a diameter of 5 cm and a glass made of 1.75 mm, and the magnetic stirrer was a spindle having a length of 25 mm and a maximum diameter of 8 mm, and was coated with a fluororesin. Use things.
Further, the magnetic toner particles can be measured by performing the same operation as in the case of the magnetic toner except that 70 ml of an aqueous solution of 100% by volume of water is put in a flask.

  (Iv) In the magnetic toner of the present invention, when the uniaxial collapse stress [kPa] at the maximum compaction stress of 5 kPa and 20 kPa is S5 and S20, respectively, the uniaxial collapse stress of the magnetic toner after magnetization satisfies the following formula: It is characterized by that.

A magnetic toner having a uniaxial collapse stress within the above range is obtained by subjecting the average circularity to 0.950 by a suspension polymerization method or a pulverization method (mechanical treatment or thermal treatment) using a coupled magnetic material.
The above magnetic toner particles can be produced and 0.1 to 5.0 parts by mass of inorganic fine powder can be externally added to obtain a methanol concentration in the range of 50 to 70% by volume.

Due to the relationship between the maximum compaction stress (X) and the uniaxial collapse stress (U), which is a feature of the present invention, the ease of loosening of the powder layer compacted with an arbitrary load, that is, the powder of the magnetic toner layer densely packed Body characteristics (cohesive force between developer particles) can be evaluated.
The uniaxial disintegration stress (U) of the magnetic toner after magnetization of the present invention is a shear stress necessary for starting the flow when the filler forming the powder layer is broken. That is, the uniaxial disintegration stress (U) is formed on the developer carrying member by the shear applied when passing through the regulating member in the process of forming a thin layer of the developer on the developer carrying member in the image forming process. This shows the stress that greatly affects the rising of the developer, the triboelectric chargeability, and the jumping process to the electrostatic latent image.
Further, the maximum consolidation stress (X) in the present invention is a vertical load required to make a powder aggregate into a powder layer. That is, it represents the stress applied to the densely packed developer layer formed by the shear that the developer receives in the developer container.
This is represented by the torque applied to the developer carrier. In other words, the maximum consolidation stresses of 5 kPa and 20 kPa, which are the characteristics of the present invention, are actually measured when the torque applied to the developer carrier is 0.1 N · m and 50 N · m. Accordingly, the powder characteristics in a state where the share of the developer is relatively small are discussed based on the uniaxial collapse stress when the maximum consolidation stress is 5.0 kPa, and the developer is analyzed based on the uniaxial collapse stress when the maximum consolidation stress is 20.0 kPa. It is possible to discuss the powder characteristics in a state where the market share is large. Then, by evaluating the transition of the uniaxial collapse stress between these maximum consolidation stresses, the powder characteristics of the developer layer under the consolidation state in the image forming process were expressed.

  In the magnetic toner of the present invention, when the uniaxial collapse stress [kPa] at the maximum consolidation stress of 5 kPa and 20 kPa is S5 and S20, respectively, the uniaxial collapse stress of the magnetic toner after magnetization preferably satisfies the following formula. .

That is, the uniaxial collapse stress at the maximum compaction stress of 5 kPa of the magnetic toner after magnetization is 0.1 to 2.0 kPa, and the uniaxial collapse stress at the maximum compaction stress of 20 kPa is 1.0 to 4.0 kPa. In some cases, since the difference in uniaxial collapse stress due to the change in maximum consolidation stress is small and the uniaxial collapse stress is relatively low, the magnetic toner exhibits fluidity in the developer. It can be maintained and a stable image density can be obtained over a long period of time. Further, since the shearing stress applied when the compacted developer layer passes through the regulating member to form magnetic ears is reduced, uniform ears can be stably formed. As a result, it is possible to fly the minimum amount of developer on the electrostatic latent image, so that not only high image quality can be achieved from the initial printing to the second half of the durability, but also the consumption of the developer is reduced. It is also possible. In addition, since the shear stress applied to the magnetic toner can be reduced, the magnetic toner of the present invention can introduce a low softening point substance that is advantageous for fixability and can reduce the softening point of the resin. Both sexes can be achieved.

Next, the uniaxial collapse stress (S5) at the maximum consolidation stress of 5 kPa of the magnetic toner is 2.0.
If the uniaxial collapse stress (S20) at the maximum compaction stress of 20 kPa of the magnetic toner is greater than 4.0 kPa, the developer is not easily loosened in the compacted state, that is, the interparticle cohesive force is increased. Indicates a large developer. Furthermore, when a developer having a resin structure that is advantageous for low-temperature fixability or a developer having a low softening point substance is introduced, the developer is likely to be packed particularly under high temperature and high humidity. When such a developer is used, the above-described problems occur in the image forming process.

Further, the uniaxial collapse stress (S5) at the maximum compaction stress of 5 kPa of the magnetic toner is smaller than 0.1 kPa, and the uniaxial collapse stress (S20) of the developer at the maximum compaction stress of 20 kPa is from 1.0 kPa. Is also small, it indicates that the developer has very low cohesion between particles and has very high fluidity in the developing unit. When such a developer is used, the shear stress in the developing device is not applied, but the frictional force between the surface of the developer carrying member and the developer becomes too small, so that it is necessary for development caused thereby. The amount of charge due to friction cannot be obtained. Accordingly, the developability is deteriorated and the image quality is further deteriorated.

  As described above, by controlling the index of interparticle cohesiveness under the compacted state of the developer within the range of the above relational expression, high durability, high reliability, and high performance without deterioration of the developer even during long-term use. It is possible to provide a developer satisfying image quality. Furthermore, both fixing ability and development stability can be achieved.

Here, the magnetized magnetic toner is a magnetic toner obtained by magnetizing under a magnetic field of 1000 × (10 ³ / 4π) · A / m (1000 oersted).

Further, the obtained maximum consolidation stress (X) and uniaxial collapse stress (U) were measured by shear scan TS-12 (manufactured by Sci-Tec). Virendra M.M. 'Characterizing Powder' written by Puri
Measurement is performed according to the principle of the Morcoulomb model described in Flowability (2002.1.24) '. Specifically, the measurement is performed in a room temperature environment (23 to 28 ° C., 40 to 70%) using a linear shear cell (columnar shape, diameter 80 mm, capacity 140 cm ³ ). A developer is put in this cell, and a vertical load is applied so as to be 2.5, 5, 10 kPa, and a compacted powder layer is formed. Since the shear scan automatically detects pressure, this compacted powder layer (consolidated state) can be produced without individual differences. Therefore, in the present invention, it is preferable to perform measurement by share scanning. Specifically, a shear stress is gradually applied to the sample formed at each vertical load, a shear stress measurement test is performed, and a steady point is set. In the above test, it is judged that the steady point has been reached. The inclination between 10 measurement points for 0.5 seconds continuously “change width of shear stress (kPa) / sensor moving vertically to apply a vertical load” It is assumed that the stationary point has been reached when the moving distance (mm) of “0.1” is 0.1. Next, the vertical load is gradually unloaded from the compacted powder layer that has reached the steady point, a fracture envelope (vertical load stress vs. shear stress plot) at each load is created, and the Y intercept and inclination are obtained. In the analysis by the Moul-Coulomb model, the uniaxial collapse stress and the maximum consolidation stress are expressed by the following equations, and the Y intercept becomes “cohesive force” and the inclination becomes “internal friction angle”.
Uniaxial collapse stress = 2c (1 + sinφ) / cosφ
Maximum consolidation stress = ((A- (A ² sin ² φ-τ _ssp ² cos ² φ) ^0.5 ) / cos ² φ) × (1 + sinφ)-(c / tanφ)
(A = σ _ssp + (c / tanφ), c = cohesive force, φ = internal friction angle, τ _ssp = c + tan (φ) σ _ssp normal point vertical load, σ _ssp = required to obtain a steady state Vertical load)
The uniaxial collapse stress and the maximum consolidation stress calculated for each load are plotted (Flow Function Plot), and a straight line is drawn based on the plot. From this straight line, the maximum consolidation stress at uniaxial collapse stress of 5.0 kPa and 20.0 kPa is obtained.
In the present invention, in order to evaluate the degree of ease of loosening accompanying the dependence of the pressure from the compacted state at the light pressure, the light pressure state is set at a maximum compaction stress of 5 kPa, and represents the highest compacted state of the developer. The state was assumed to be a maximum consolidation stress of 20 kPa, and the value of the uniaxial collapse stress in the range of the maximum consolidation stress was evaluated as an index for evaluating the interparticle cohesiveness in the consolidation state.

  In order to develop the effects of the present invention as a result of the study of the present inventors, the powder characteristics of the magnetic toner after being magnetized under the compacted state are the shape of the magnetic toner particles, the surface property, the magnetic substance, and It became clear that it can be easily controlled by controlling the relationship of the inorganic fine powder added externally.

  First, with respect to the shape and surface property of the magnetic toner particles, the weight average particle diameter, the average circularity of the magnetic toner and the wettability of the magnetic toner with respect to the methanol / water mixed solvent are controlled within the ranges described above. It became clear that an effect can be expressed by this.

The magnetic toner preferably has a magnetic property under application of 79.6 kA / m (1 kilo Oersted) and a residual magnetization (σr1) of 4.0 Am ² / kg or less.
When the residual magnetization (σr1) of the magnetic toner is larger than 4.0 Am ² / kg, the toner discharged from the N2 pole in the developing device 140 shown in FIG. 1 has poor fluidity due to magnetic aggregation. Further, since the toner is fed from a feeding member (not shown) of the developing device over N2 to S2, the toner is physically easy to be packed, and the packing pressure is applied in addition to the above magnetic aggregation. Therefore, the uniaxial collapse stress tends to be large, and the fluidity is lowered and the toner is easily deteriorated. Therefore, the residual magnetization (σr1) of the magnetic toner is 4.0 Am ² / kg.
The following is preferable.
A magnetic toner having a residual magnetization in the above range is made into a toner by using a magnetic substance having a residual magnetization of 4.5 Am ² / kg and containing 10 to 200 parts of the magnetic substance with respect to 100 parts by mass of the binder resin. Is obtained.

Further, the magnetic toner preferably has a magnetic property when applied to 79.6 kA / m (1 kilo Oersted) and a saturation magnetization (σs) of 20 Am ² / kg or more. If the saturation magnetization (σs) of the magnetic toner is 20 Am ² / kg or less, the restriction on the magnet roller is difficult to be sufficiently controlled. It is not preferable.

The residual magnetization (σr2) of the magnetic material used in the magnetic toner of the present invention is preferably 4.5 Am ² / kg or less in a magnetic field of 79.6 kA / m (1 kiloOersted). When the remanent magnetization (σr2) of the magnetic material is greater than 4.5 Am ² / kg, the remanent magnetization (σr1) of the magnetic toner containing the magnetic material tends to increase, and the remanent magnetization (σr1) of the magnetic toner is 4. It becomes difficult to control to 0 Am ² / kg or less. For this reason, in order to control σr1 and not cause magnetic aggregation, the preferable remanent magnetization (σr2) of the magnetic material is 4.5 Am ² / kg or less, more preferably 4.0 Am ² / kg or less.

However, it is known that when the remanent magnetization (σr2) of the magnetic material is lowered, the saturation magnetization is also lowered, and the fog is deteriorated simply by reducing σr2. In particular, when a small-diameter toner carrier is used, the tendency becomes strong, and fogging in a low-temperature and low-humidity environment tends to deteriorate.
For this reason, it is necessary to increase the saturation magnetization of the toner and suppress fogging by the magnetic binding force, and the saturation magnetization of the magnetic substance in the external magnetic field of 79.6 kA / m is 67.0 to 75.0 Am ² / kg. preferable.

Any magnetic material may be used as long as it can lower the residual magnetization of the magnetic material and increase the saturation magnetization. As a result of various studies in the present invention, it is preferable that the phosphorus element is 0.05 to 0.25% by mass with respect to the total amount of the magnetic material, and the silicon element is 0.5% with respect to the total amount of the magnetic material.
A magnetic material containing 3 to 1.0% by mass and having a phosphorus element to silicon element ratio (P / Si) of 0.15 to 0.50 satisfies these magnetic characteristics and is effective in reducing fog. I understood that.
The reason for this is not clear, but by using a specific amount of phosphorus and silicon elements in a specific ratio, phosphorus and silicon elements exist in a special state in the crystal lattice of the magnetic material (Fe ₂ O ₃ ). However, it is considered that such magnetic characteristics can be achieved.

The magnetic properties of the magnetic toner and the magnetic material are measured using a vibration type magnetometer, for example, VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.) under conditions of 25 ° C. and an external magnetic field of 79.6 kA / m. be able to. The magnetic characteristic value of the magnetic material is an external magnetic field of 79.6 kA / m (1 kiloOersted), and the strength of magnetization at that time is obtained. Pack the magnetic material in a cylindrical plastic container so that the magnetic particles do not move sufficiently, measure the magnetization moment in this state, measure the actual weight when the sample is put, The strength of magnetization (Am ² / kg) is obtained. Next, the true specific gravity of the magnetic particles is obtained by a dry automatic densitometer AccuPick 1330 (manufactured by Shimadzu Corporation), and the magnetization intensity (Am ² / kg) is multiplied by the true specific gravity to determine the magnetization per unit volume. The strength (kA / m) can be determined. The magnetic properties of the magnetic material can be adjusted by, for example, the type of the magnetic material to be used and the mixture of the magnetic or nonmagnetic metal oxide and the magnetic material.

  The liberation rate of iron and iron compound of the magnetic toner of the present invention is preferably 0.05% to 3.00% with respect to the magnetic toner, more preferably 0.05 to 1.50%. Preferably it is 0.05 to 1.00%.

  In the present invention, the liberation rate of iron and iron compound of the magnetic toner is measured by, for example, a particle analyzer (PT1000: manufactured by Yokogawa Electric Corporation). The particle analyzer performs the measurement according to the principle described on pages 65-68 of the Japan Hardcopy 97 papers. The apparatus introduces fine particles such as toner one by one into the plasma, and can determine the element of the luminescent material, the number of particles, and the particle size of the particles from the emission spectrum of the fine particles.

  Among these, the liberation rate is defined as a value obtained by the following equation from the simultaneous emission of light emission of carbon atoms, which are constituent elements of the binder resin, and light emission of iron atoms.

  Here, the simultaneous light emission of the carbon atom and the iron atom means that the light emission of the iron atom emitted within 2.6 msec from the light emission of the carbon atom is the simultaneous light emission, and the light emission of the iron atom thereafter is the light emission of only the iron atom. .

  Since the present invention contains a large amount of magnetic substance, simultaneous emission of carbon and iron atoms means that the magnetic substance is dispersed in the toner particles, and the emission of only iron atoms is magnetic. It can be paraphrased to mean that the body is free from the toner particles.

Specifically, the liberation rate of iron and iron compound in the magnetic toner is measured by the following method.
Measurement is performed using helium gas containing 0.1% oxygen at 23 ° C. in an environment of 60% humidity, and the toner sample is left to stand overnight in the same environment, and the humidity is adjusted for measurement. Also, channel 1 measures carbon atoms (measurement wavelength 247.860 nm, K factor uses recommended value), and channel 2 measures iron atoms (measurement wavelength 239.56 nm, K factor uses 3.3764). In this scan, sampling is performed so that the number of light emission of carbon atoms is 1000 to 1400, and the scan is repeated until the total number of light emission of carbon atoms reaches 10,000 or more, and the number of light emission is integrated. At this time, in the distribution in which the number of light emission of the carbon element is taken on the vertical axis and the cube root voltage of the element is taken on the horizontal axis, the distribution is sampled so as to have a maximum and no valley exists. And measure. Based on this data, the noise cut level of all elements is set to 1.50 V, and the liberation rate of iron and iron compounds is calculated using the above formula. The same measurement was performed in the examples described later.

  In addition, toners may contain materials other than inorganic compounds containing iron atoms, such as azo-based iron compounds that are charge control agents. These compounds are also present in organic compounds at the same time as iron atoms. This carbon also emits light at the same time, so it is not counted as a free iron atom.

  Here, the toner having a high liberation rate of iron and iron compounds has a low toner charge amount, and the free magnetic material accumulates irregularly on the developer carrier, resulting in a uniform chargeability of the toner. This hinders transfer efficiency from decreasing, and as a result, residual toner increases, which is not preferable. Further, when such a toner is used, the free magnetic material contaminates the charging member, or the image bearing member is damaged when passing through the nip portion between the charging member and the image bearing member. .

Therefore, in the present invention, the liberation rate of iron and iron compound in the magnetic toner is 3.00% or less, preferably 1.50% or less, and more preferably 1.00% or less.
On the other hand, if the release rate of iron and iron compound in the magnetic toner is less than 0.05%, it means that the magnetic substance is not substantially released from the toner. As described above, although the toner having a low liberation rate of iron and iron compound has a high charge amount, since there is no leakage site of charge, it becomes easy to charge up, and uniform charging becomes difficult. Therefore, inversion fog tends to increase, which is not preferable.

The liberation rate of iron and iron compounds depends on the amount of the magnetic material contained in the toner, the particle size of the magnetic material, the particle size distribution, the toner production method, and the like. In the suspension polymerization method which is a preferred production method of the present invention, the liberation rate of iron and iron compound depends on the degree of hydrophobicity of the magnetic material, the uniformity of treatment, the granulation conditions, and the like. As an example of magnetic toner obtained by suspension polymerization method, when the surface treatment of the magnetic material is non-uniform, it has a part that is not sufficiently surface-treated (strongly hydrophilic) and is not sufficiently dispersed Polymerization may be incomplete or not polymerized, and as a result, a part or all of the magnetic material with non-uniform surface treatment is released from the magnetic toner particles.
Magnetic toners having a liberation rate of iron and iron compounds of 3.00% or less are used in the suspension polymerization method by using the hydrophobized magnetic material of the present invention, by the production method of the present invention, and by the pulverization method. As described later in <Magnetic toner production example 16>, it can be obtained by impact type surface treatment.

  The glass transition temperature (Tg) of the magnetic toner of the present invention is preferably 40 to 80 ° C., more preferably 45 to 70 ° C. When the Tg is lower than 40 ° C., the storage stability of the toner is lowered, and when the Tg is higher than 80 ° C., the fixing property is inferior. To measure the glass transition point of the toner, for example, a high-accuracy internal heat input compensation type differential scanning calorimeter such as DSC-7 manufactured by Perkin Elmer is used. The measurement method is performed according to ASTM D3418-8. In the present invention, a DSC curve is used that is measured when the sample is heated once and then history is taken, then rapidly cooled, and heated again at a temperature rising rate of 10 ° C./min and a temperature of 30 to 200 ° C.

  A sectional view of an example of a developing device suitable for the magnetic toner of the present invention is shown in FIG. The developing device 140 includes a developing container for containing the developer, a developer carrier 102 that is rotatably disposed in an opening of the developer container, and a magnet roller that is immovably disposed inside the developer carrier 102. 104, an elastic member that is disposed in contact with the developer carrier 102 and that regulates the thickness of the toner layer on the developer carrier 102 by regulating the toner carried on the developer carrier 102. The blade 103 and a stirring member 141 that stirs the toner in the developing container are configured. The developing device 140 is disposed at a position where the developer carrying member 102 and the photoconductor 100 are not in contact with the photoconductor 100. Further, the magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure. S1 influences development, N1 regulates the toner coat amount, S2 takes in / conveys toner, and N2 influences toner ejection.

  The developing device suitable for the magnetic toner of the present invention is restrained by a regulating member so that the torque applied to the developer carrying member in a state where the developer layer is formed in the developing device is 0.1 N · m to 50 N · m. It is preferable to control the force. When the torque applied to the developer carrying member is smaller than 0.1 N · m, it becomes impossible to obtain the charge amount necessary for development in the charging process due to the friction between the developer and the developer carrying member. When the torque applied to the developer carrying member is larger than 50 N · m, the developer deteriorates due to embedding of an external additive due to an increase in the share of the developer container. As a result, the density decreases during long-term use due to a decrease in the charge amount of the developer. Furthermore, in the process of forming a thin layer of developer on the developer carrier, the rise of the developer formed on the developer carrier becomes non-uniform due to the shear stress applied when passing through the regulating member. In addition, the image quality deteriorates and the fog also deteriorates. Further, since the developer is deteriorated by the shear stress applied when passing through the regulating member, the density is lowered during long-term use. Therefore, in order to evaluate the powder characteristics of the developer of the present invention, it is preferable to evaluate at a maximum consolidation stress of 20 kPa or less.

  Next, an image forming method using the magnetic toner of the present invention will be described.

First, a preferred embodiment of an image forming method using the magnetic toner of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these.
In FIG. 2, a charge amount adjusting member 116, a charging roller 117 as a contact charging member, a developing device 140, a transfer roller 114, a register roller 124, and the like are provided around a photosensitive member 100 as an image carrier. The photosensitive member 100 is charged by the charge amount adjusting member 116 and the charging roller 117 (the applied voltage of the charge amount adjusting member 116 is DC voltage: −1000 V, and the applied voltage of the charging roller 117 is AC voltage 1.8 kVpp (Vpp: Peak-to-peak potential), DC voltage -620 Vdc (power supply not shown). Then, exposure is performed by irradiating the photosensitive member 100 with a laser beam 123 by the laser beam scanner 121. The electrostatic latent image on the photoconductor 100 is developed with magnetic toner by the developing device 140 and transferred onto the recording medium by the transfer roller 114 in contact with the photoconductor via the recording medium. The recording medium P on which the toner image is placed is conveyed to the fixing device 126 by the conveying belt 125 or the like and fixed on the recording medium P. In addition, a part of the toner remaining on the photosensitive member is retained by the charge amount adjusting member 116 and injected, and then discharged, passes through the charging roller 117, and is collected by the developing device 140. As shown in FIG. 1 described above, the developing device 140 includes a developing container that stores a developer, a developer carrier 102 that is rotatably disposed in an opening of the developer container, and an interior of the developer carrier 102. And a toner roller layer on the developer carrier 102 that regulates the toner carried on the developer carrier 102 and is in contact with the developer carrier 102. The elastic blade 103 is a regulating member that regulates the thickness, and an agitating member 141 that agitates the toner in the developing container. The developing device 140 is disposed at a position where the developer carrying member 102 and the photoconductor 100 are not in contact with the photoconductor 100. Further, the magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure, where S1 influences development, N1 regulates the toner coat amount, S2 takes in / conveys toner, and N2 influences toner ejection.

  In the image forming method using the magnetic toner of the present invention, the photoconductor uses a photoconductive substance, and an organic photoconductor, a photoconductor such as amorphous silicon, and the like are preferably used.

  In the photoconductor, (i) when a protective film mainly composed of a resin is provided on an inorganic photoconductor such as selenium or amorphous silicon, or (ii) as a charge transport layer of a function-separated organic image carrier, In the case of having a surface layer made of a transport material and a resin, (iii) a protective layer as described in (i) above may be further provided on the surface layer.

In order to improve the transferability of the toner and the durability of the photoconductor, it is preferable to impart releasability to the photoconductor. As a means for imparting releasability to the surface layer or protective layer as described above,
1. Use a resin having a low surface energy as the resin constituting the film.
2. Add additives that impart water repellency and lipophilicity,
3. Disperse the material having high releasability in powder form.
Etc.

1. A resin having a low surface energy can be obtained by introducing a fluorine-containing group, a silicone-containing group or the like into the resin structure. A surfactant or the like may be used as the additive in 2.
3. Examples of the material having high releasability include compounds containing fluorine atoms, that is, polytetrafluoroethylene, polyvinylidene fluoride, carbon fluoride, and the like.

By these means, the contact angle with respect to water on the surface of the photoreceptor can be set to 85 degrees or more, and toner transferability and durability of the photoreceptor can be further improved. Preferably, the contact angle with water is 90 degrees or more.
Among these means, the method of dispersing the releasable powder such as 3. fluorine-containing resin in the outermost surface layer is preferable, and polytetrafluoroethylene is particularly preferable.

  In the image forming method using the magnetic toner according to the present invention, the charging step includes a photosensitive member which is a member to be charged and an image carrier, and a conductive type such as a roller type (charging roller), a fur brush type, a blade type (charging blade) and the like. A contact charging device is used in which a contact portion is formed and brought into contact with the charging member, and a predetermined charging bias is applied to the contact charging member to charge the surface of the photosensitive member to a predetermined polarity and potential. Further, by performing contact charging in this way, stable and uniform charging can be performed, and further, an effect that generation of ozone is reduced can be obtained.

  However, in general, when a fixed type charging member is used, it is difficult to maintain uniform contact between the charging member and the rotating image carrier (photoreceptor), so that uneven charging tends to occur. For this reason, a charging member (charging roller) that rotates in the same direction as the image bearing member (photosensitive member) is used in the charging process in order to maintain uniform contact with the image bearing member (photosensitive member) and perform uniform charging. It is more preferable.

  In the image forming method using the magnetic toner of the present invention, the magnetic toner carrier is thinner than the closest distance (between S and D) between the magnetic toner carrier and the photoconductor in order to obtain a high image quality without fogging. It is preferable to apply magnetic toner with a layer thickness and develop it in the development step.

  In general, the thickness of the toner layer on the magnetic toner carrier is regulated by a layer thickness regulating member (magnetic cut, regulating blade, etc.) that regulates the magnetic toner on the magnetic toner carrier. On the other hand, in the present invention, the layer thickness regulating member needs to be regulated by contacting the magnetic toner carrier via the magnetic toner. As the layer thickness regulating member that contacts the toner carrier, a regulating blade is generally used and can be suitably used in the present invention.

  By regulating the toner layer thickness by making the regulating blade head contact with the magnetic toner carrier, the transfer efficiency can be improved and the fog can be reduced. This is because the material of the regulation blade can be designed according to the chargeability of the toner, and since the regulation blade is in contact with the magnetic toner carrier with a specific contact pressure, sufficient frictional charging is performed, and the toner This is considered to be because the charge amount of the toner increases and uniform chargeability is obtained.

  As the regulating blade, a rubber elastic body such as silicone rubber, urethane rubber or NBR; a synthetic resin elastic body such as polyethylene terephthalate; or a composite of these may be used. A rubber elastic body is preferable.

  The material of the regulating blade is greatly involved in charging the toner on the toner carrier. Therefore, when an elastic body is used as the regulating blade, an organic or inorganic substance may be added to the elastic body, and it may be melt-mixed or dispersed. Examples of the organic or inorganic substance include metal oxides, metal powders, ceramics, carbon allotropes, whiskers, inorganic fibers, dyes, pigments, and surfactants. Further, a charge control substance such as resin, rubber, metal oxide, or metal is applied to the contact portion of the toner carrier for the purpose of controlling the chargeability of the toner against an elastic support such as rubber, synthetic resin, or metal elastic body. You may use what was attached to. Further, it is preferable that the metal elastic body is bonded with resin and rubber so as to contact the toner carrier contact portion.

  When the toner is negatively charged, the elastic support and the charge control substance are preferably those that are easily charged to positive polarity such as urethane rubber, urethane resin, polyamide resin, and nylon resin. When the toner is positively charged, the elastic blade and the charge control substance are easily charged to negative polarity such as urethane rubber, urethane resin, silicone rubber, silicone resin, polyester resin, fluorine resin, polyimide resin. Is preferred.

  When the toner carrier contact part is a molded body of resin or rubber, in order to adjust the chargeability of the toner, a metal oxide such as silica, alumina, titania, tin oxide, zirconia oxide, zinc oxide, It is also preferred to contain carbon black, a charge control agent generally used in toners.

  The base, which is the upper side of the regulating blade, is fixedly held on the toner container side, and the lower side is bent against the elastic force of the blade in the forward or reverse direction of the toner carrying member on the surface of the toner carrying member. Abut with moderate elastic pressure.

  In the present invention, the contact pressure between the regulation blade and the toner carrier is 0.98 N / m (1 g / cm) or more, preferably 1.27 to 245 N / m (linear pressure in the toner carrier bus direction). 3 to 250 g / cm), more preferably 4.9 to 118 N / m (5 to 120 g / cm). When the contact pressure is less than 0.98 N / m (1 g / cm), it is difficult to uniformly apply the toner, which causes fogging and scattering. When the contact pressure exceeds 245 N / m (250 g / cm), a large pressure is applied to the toner, and the toner is likely to be deteriorated.

As the toner layer on the toner carrier, a toner layer of 5 to 50 g / m ² is preferably formed. If the amount of toner on the magnetic toner carrier is less than 5 g / m ^2, it is difficult to obtain a sufficient image density, and unevenness of the toner layer due to excessive charging of the toner occurs. When the amount of toner on the magnetic toner carrier is more than 50 g / m ² , it is difficult to uniformly charge the toner, transferability is lowered, and fog is increased.

  As the magnetic toner carrier used in the image forming method using the magnetic toner of the present invention, a conductive cylinder (developing roller) formed of a metal or alloy such as aluminum or stainless steel is preferably used. The magnetic toner carrier may have a conductive cylinder formed of a resin composition having sufficient mechanical strength and conductivity, and a conductive rubber roller may be used as the magnetic toner carrier. Further, the magnetic toner carrier is not limited to the cylindrical shape as described above, and may be in the form of an endless belt that is rotationally driven.

  The surface roughness of the magnetic toner carrier used in the image forming method using the magnetic toner of the present invention is preferably in the range of 0.2 to 3.5 μm in terms of JIS centerline average roughness (Ra). More preferably, it is in the range of 0.5 to 3.0 μm. If Ra is less than 0.2 μm, the amount of charge on the magnetic toner bearing member tends to be high, and the developability tends to be insufficient. When Ra exceeds 3.5 μm, unevenness occurs in the toner coat layer on the magnetic toner carrier, and there is a tendency that the density is uneven on the image.

  In the present invention, the surface roughness Ra of the magnetic toner carrier is determined based on JIS surface roughness “JIS B 0601” using a surface roughness measuring device (for example, Surfcoder SE-30H, manufactured by Kosaka Laboratory Co., Ltd.). Corresponds to the centerline average roughness measured using. Specifically, a 2.5 mm portion as the measurement length a is extracted from the roughness curve in the direction of the center line, the center line of this extraction portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is When expressed by y = f (x), it means a value obtained by the following formula expressed in micrometers (μm).

  In order to adjust the surface roughness (Ra) of the magnetic toner carrier used in the image forming method using the magnetic toner of the present invention to the above range, for example, the polishing state of the surface layer of the toner carrier is changed, or spherical carbon This is achieved by adding particles, carbon fine particles, graphite and the like.

  Further, since the magnetic toner of the present invention has a high charging ability, it is desirable to control the total charge amount of the toner during development, and the magnetic toner carrier used in the image forming method using the magnetic toner of the present invention is desirable. The surface is preferably covered with a resin layer in which conductive fine particles and / or a lubricant are dispersed.

The conductive fine particles contained in the coating layer of the magnetic toner carrier preferably have a resistance value of 0.5 Ωcm or less after being pressed with 11.7 Mpa (120 kg / cm ² ). The conductive fine particles are preferably carbon fine particles, a mixture of carbon fine particles and crystalline graphite, or crystalline graphite. Moreover, the preferable particle size of the said electroconductive fine particles is 0.005-10 micrometers.

  Examples of the resin used for the coating layer include thermoplastic resins such as styrene resin, vinyl resin, polyethersulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, fluororesin, fiber resin, and acrylic resin. A thermosetting resin such as an epoxy resin, a polyester resin, an alkyd resin, a phenol resin, a melamine resin, a polyurethane resin, a urea resin, a silicone resin, or a polyimide resin, or a photocurable resin.

The surface of the magnetic toner carrying member carrying the magnetic toner of the present invention is preferably moved in the same direction as the moving direction of the photosensitive member surface at the contact surface. Further, the moving speed of the magnetic toner carrier is preferably 1.00 to 1.80 times the ratio of the moving speed of the photoconductor. If the moving speed ratio is less than 1.00 times, the image quality tends to deteriorate, and the larger the moving speed ratio, the more toner is supplied to the development site, and an image that is faithful to the latent image than the latent image. can get. However, if the moving speed ratio of the magnetic toner carrier is larger than 1.80 times, the toner is likely to be deteriorated, and the image quality is deteriorated by long-term use.

  The magnetic toner carrier for carrying the magnetic toner of the present invention preferably has a fixed magnet having multiple poles inside, and preferably has 3 to 10 magnetic poles. Further, the center of the development pole of the magnet is usually located on a line connecting the center of the photoreceptor and the magnetic toner carrier, but the magnetic toner carrier carrying the magnetic toner of the present invention has the center of the development pole of the magnet as the photoreceptor. It is preferable to shift it 3 ° to 10 ° upstream (regulation blade side) from the line connecting the center of the toner and the magnetic toner carrier. This is because the fog does not increase even when used for a long time if it is shifted from the line connecting the centers of the photosensitive member and the magnetic toner carrier. This is because when the center of the development pole is on a line connecting the center of the photoreceptor and the toner carrier, the remaining toner existing on the image carrier is considered to be collected only in the development area, whereas By shifting the center of the pole to the upstream side, recovery of the residual toner by the magnetic field is started on the upstream side of the normal development region, and it is considered that fogging can be suppressed even in long-term use by improving the recovery performance. However, since the development area due to the electric field is almost constant regardless of the position of the magnetic field, shifting the center of the development pole more than 10 ° upstream is not preferable because it causes deterioration in developability and causes image loss. .

  In the development process in the image forming method using the magnetic toner of the present invention, an alternating electric field is applied as a developing bias to the magnetic toner carrier, and the toner is transferred to the electrostatic latent image on the photoreceptor to form a toner image. The applied developing bias may be a voltage in which an alternating electric field is superimposed on a DC voltage.

  The development bias applied between the magnetic toner carrier carrying the toner and the image carrier is preferably 3.8 to 4.8 V / μm in terms of the maximum electric field strength during development, and the frequency is 1600 to 4500 Hz. It is preferable that

  The maximum electric field strength during development is expressed by the following equation.

  Here, Vpp is the peak-to-peak voltage of the AC voltage, VL is the bright potential of the image carrier, and Vdc is the potential of the DC voltage. In the case where the ratio of the time of the electric field applied during development and the time of the electric field of withdrawal is different (described later), the potential at the time of developing the AC component is used instead of 1/2 Vpp.

  By increasing the maximum electric field strength, a high tribotoner having strong adhesion to the image carrier is developed, so that a high-definition image can be obtained. In addition, the maximum electric field strength can be increased by increasing the AC voltage Vpp. In this case, the electric field strength returned from the image carrier is also increased, so that the recoverability is improved. For these reasons, the maximum electric field during development is preferably 3.8 V / μm or more. However, if the maximum electric field strength is excessively increased, fog tends to increase. If the maximum electric field strength is greater than 4.8 V / μm, fog increases and dielectric breakdown is likely to occur.

  Further, as a result of examining the frequency of the AC bias, when the frequency is less than 1600 Hz, the fog toner increases and the number of developments and pullbacks decreases, so that the image quality deteriorates. On the other hand, when the frequency is higher than 4500 Hz, the toner cannot follow the bias, and the density and the recoverability are lowered.

Further, among the alternating current components of the alternating electric field applied to the magnetic toner carrier, when the voltage application time in the direction of ejecting the toner is t1, and the voltage application time in the direction of returning the toner from the image carrier is t2, A ratio of t1 / t2 of 1.10 to 2.30 is preferable because good developability is maintained and fogging is reduced.
This is considered to be the following reason.
Increasing the ratio of t1 / t2 increases the voltage application time in the developing direction, but lowers the voltage. On the other hand, the application time of the return voltage is shortened, but the return voltage is increased, and the pullback strength of the toner on the image carrier is increased, which is preferable because fog is reduced. However, if the ratio of t1 / t2 is too large, the image density is lowered, and selective development is likely to occur. For this reason, the preferable ratio of t1 / t2 is 1.10 to 2.30, more preferably 1.15 to 1.80.

  In the image forming method using the magnetic toner of the present invention, it is preferable that the electrostatic latent image forming step of forming an electrostatic latent image on the charging surface of the image carrier is performed by an image exposure unit. The image exposure means for forming the electrostatic latent image is not limited to the laser scanning exposure means for forming a digital latent image, and other light emitting elements such as normal analog image exposure and LEDs may be used. It does not matter as long as it can form an electrostatic latent image corresponding to image information, such as a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter.

Next, a process cartridge using the magnetic toner of the present invention will be described.
The process cartridge transfers toner to an electrostatic latent image formed on a photoreceptor to be visualized to form a toner image, and forms the image by transferring the toner image to a transfer material. A process cartridge configured to be detachable from an image forming apparatus used in an image forming method using magnetic toner, and at least two or more selected from a photosensitive member, a charging unit, and a developing unit are integrally supported. The toner is a process cartridge characterized by being the magnetic toner of the present invention. As the photosensitive member, the charging unit, and the developing unit, those used in the image forming method using the magnetic toner of the present invention can be used.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. “Part” and “%” are based on mass unless otherwise specified.

<1> Production Example of Magnetic Material <Manufacture of Magnetic Material 1>
In ferrous sulfate aqueous solution, l. 0 to 1.1 equivalents of caustic soda solution, P ₂ O _{5 in} an amount of 0.15% by mass in terms of phosphorus with respect to iron element, and 0.55% by mass in terms of silicon element with respect to iron element SiO ₂ was mixed to prepare an aqueous solution containing ferrous hydroxide.
The pH of the aqueous solution was 8.0, and an oxidation reaction was performed at 85 ° C. while blowing air to prepare a slurry liquid having seed crystals.
Then, after adding ferrous sulfate aqueous solution so that it becomes 0.9 to 1.2 equivalent to the initial alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH 7.6, The oxidation reaction was promoted while blowing air to obtain a slurry liquid containing magnetic iron oxide. After filtration and washing, the water-containing slurry was once taken out. At this time, a small amount of water-containing sample was collected and the water content was measured. Next, the water-containing sample is put into another aqueous medium without being dried, and sufficiently redispersed with a pin mill while stirring and circulating the slurry, and the pH of the redispersed liquid is adjusted to about 4.8. Then, add 1.5 parts by mass of n-hexyltrimethoxysilane coupling agent with respect to 100 parts by mass of magnetic iron oxide (the amount of magnetic iron oxide was calculated by subtracting the water content from the water-containing sample) with sufficient stirring. Hydrolysis was performed. Thereafter, the mixture was sufficiently stirred and dispersed with a pin mill while circulating the slurry, and the pH of the dispersion was adjusted to 8.9 to perform a coupling treatment. The produced hydrophobic magnetic material was filtered with a filter press, washed sufficiently, dried at 100 ° C. for 15 minutes, and then at 90 ° C. for 30 minutes, and the resulting particles were crushed to give a volume average particle size of 0.00. A 24 μm magnetic body 1 was obtained. The physical properties of the obtained magnetic body 1 are shown in Table 1.

<Manufacture of magnetic body 2>
In the production of the magnetic substance 1, added to P ₂ O ₅ and the amount of P ₂ O ₅ to the SiO ₂ 0.04 wt% in terms of phosphorus, the amount of SiO ₂ comprised 0.25 wt% of silicon in terms of element A magnetic body 2 was obtained in the same manner as in the manufacture of the magnetic body 1 except that The physical properties of the obtained magnetic body 2 are shown in Table 1.

<Manufacture of magnetic body 3>
As in the production of magnetic body 1, the oxidation reaction was advanced, the magnetic iron oxide powder produced after the end of the oxidation reaction was washed, filtered and dried, and the aggregated particles were crushed to obtain a magnetic body. This magnetic material was dispersed again in an aqueous medium, and then the pH of the redispersed liquid was adjusted to about 4.5, and the n-hexyltrimethoxysilane coupling agent was added to 0.1 part of 100 parts of magnetic iron oxide while stirring. 6 parts were added and hydrolyzed. Thereafter, the pH of the dispersion was adjusted to about 10, a condensation reaction was performed, and a coupling treatment was performed. The produced hydrophobic magnetic material was washed, filtered, and dried by a conventional method, and the resulting particles were sufficiently pulverized to obtain a surface-treated magnetic material 3. Table 1 shows the physical properties of the magnetic body 3 obtained.

<2> Production Example of Perovskite Crystalline Inorganic Fine Powder <Production Example 1 of Perovskite Crystalline Inorganic Fine Powder>
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, hydrochloric acid was added to the hydrous titanium oxide slurry to adjust the pH to 0.7 to obtain a titania sol dispersion. NaOH was added to the titania sol dispersion, the pH of the dispersion was adjusted to 5.0, and washing was repeated until the electrical conductivity of the supernatant reached 70 μS / cm.
A 0.98-fold molar amount of Sr (OH) ₂ .8H ₂ O was added to the hydrous titanium oxide, placed in a SUS reaction vessel, and purged with nitrogen gas. Furthermore, distilled water was added so as to be 0.5 mol / liter in terms of SrTiO ₃ . The slurry was heated to 80 ° C. at a rate of 7 ° C./hour in a nitrogen atmosphere, and reacted for 6 hours after reaching 80 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles not passing through the sintering step. The strontium titanate fine particles were used as inorganic fine powder 1. The physical properties of the inorganic fine powder 1 are shown in Table 2.

<Production Example 2 of Perovskite Crystalline Inorganic Fine Powder>
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, hydrochloric acid was added to the hydrous titanium oxide slurry to adjust the pH to 4.0 to obtain a titania sol dispersion. NaOH was added to the titania sol dispersion, the pH of the dispersion was adjusted to 8.0, and washing was repeated until the electrical conductivity of the supernatant reached 100 μS / cm.
To this hydrous titanium oxide, 1.02 times the molar amount of Sr (OH) ₂ .8H ₂ O was added and placed in a SUS reaction vessel, and the nitrogen gas was replaced. Furthermore, distilled water was added so as to be 0.3 mol / liter in terms of SrTiO ₃ . The slurry was heated to 90 ° C. at 30 ° C./hour in a nitrogen atmosphere, and reacted for 5 hours after reaching 90 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles having an average primary particle diameter of 30 nm that did not go through the sintering step. The strontium titanate fine particles were used as inorganic fine powder 2. Table 2 shows the physical properties of the inorganic fine powder 2.

<Production Example 3 of Perovskite Crystalline Inorganic Fine Powder>
The hydrous titanium oxide slurry obtained by hydrolyzing the aqueous titanyl sulfate solution was washed with an alkaline aqueous solution. Next, hydrochloric acid was added to the hydrous titanium oxide slurry to adjust the pH to 1.0 to obtain a titania sol dispersion. NaOH was added to the titania sol dispersion, the pH of the dispersion was adjusted to 5.0, and washing was repeated until the electrical conductivity of the supernatant reached 100 μS / cm.
To this hydrous titanium oxide, 1.02 times the molar amount of Sr (OH) ₂ .8H ₂ O was added and placed in a SUS reaction vessel, and the nitrogen gas was replaced. Furthermore, distilled water was added so as to be 0.3 mol / liter in terms of SrTiO ₃ . The slurry was heated to 90 ° C. at 70 ° C./hour in a nitrogen atmosphere, and reacted for 5 hours after reaching 90 ° C. After the reaction, the reaction solution was cooled to room temperature, and the supernatant was removed. Then, the washing was repeated with pure water, and then filtered with Nutsche. The obtained cake was dried to obtain strontium titanate fine particles having an average primary particle diameter of 295 nm that did not pass through the sintering step. The strontium titanate fine particles were used as inorganic fine powder 3. The physical properties of the inorganic fine powder 3 are shown in Table 2.

<Production Example 4 of Perovskite Crystalline Inorganic Fine Powder>
600 g of strontium carbonate and 350 g of titanium oxide were wet mixed in a ball mill for 8 hours and then filtered and dried. The mixture was molded at a pressure of 10 kg / cm ² and sintered at 1200 ° C. for 7 hours. This was mechanically pulverized to obtain strontium titanate fine particles having an average primary particle diameter of 200 nm through a sintering process. The strontium titanate fine particles were used as inorganic fine powder 4. Table 2 shows the physical properties of the inorganic fine powder 4.

Next, toner production examples and comparative production examples will be described.
<3> Magnetic toner production example <Magnetic toner production example 1>
After adding 451 parts of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution to 709 parts of ion-exchanged water and heating to 60 ° C., 68 parts of 1.0 mol / liter-CaCl ₂ aqueous solution was gradually added and Ca ₃ ( An aqueous medium containing PO ₄ ) ₂ was obtained.

on the other hand,
Styrene 82 parts n-Butyl acrylate 18 parts Saturated polyester resin 5 parts Negative charge control agent (Fe compound of monoazo dye) 2 parts Magnetic material 1 80 parts Using the above-mentioned formulation with Attritor (Mitsui Miike Chemical Co., Ltd.) Uniformly dispersed and mixed. This monomer composition was heated to 60 ° C., 10 parts of ester wax (melting point: 72 ° C.) was mixed and dissolved therein, and polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was added thereto. [T1 / 2 = 140 minutes, 60 ° C.] 5 parts were dissolved.

The polymerizable monomer system was put into the aqueous medium, and the mixture was granulated by stirring at 10,000 rpm for 15 minutes with Claremix (manufactured by M Technique Co., Ltd.) at 60 ° C. in an N ₂ atmosphere. Thereafter, the mixture was reacted at 60 ° C. for 6 hours while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C. and stirring was continued for 4 hours. After completion of the reaction, the suspension was cooled and hydrochloric acid was added to dissolve the dispersant, followed by filtration, washing with water and drying to obtain toner particles.

100 parts of the toner particles, 1.0 part of a hydrophobic silica fine powder treated with hexamethyldisilazane and then treated with silicone oil (BET specific surface area after treatment is 120 m ^{2 /} g), and 0.5 part of inorganic fine powder The body 1 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare a magnetic toner A (weight average particle size 6.0 μm). Table 3 shows the physical properties of the magnetic toner A.

<Production Example 2 of Magnetic Toner>
519 parts of a 0.1 mol / liter-Na ₃ PO ₄ aqueous solution was added to 709 parts of ion-exchanged water and heated to 60 ° C., and then 78 parts of a 1.0 mol / liter-CaCl ₂ aqueous solution was gradually added to add Ca ₃ ( Except that an aqueous medium containing PO ₄ ) ₂ was obtained, toner particles were obtained in the same manner as in the magnetic toner 1 production example.
100 parts of the toner particles, 1.3 parts of hydrophobic silica fine powder treated with hexamethyldisilazane and then treated with silicone oil (BET specific surface area after treatment is 120 m ^{2 /} g), 0.8 parts of inorganic fine powder Body 1 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare magnetic toner B (weight average particle size 4.1 μm). Table 3 shows the physical properties of Magnetic Toner B.

<Production Example 3 of Magnetic Toner>
After adding 392 parts of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution to 709 parts of ion-exchanged water and heating to 60 ° C., 59 parts of 1.0 mol / liter-CaCl ₂ aqueous solution was gradually added and Ca ₃ ( Except for obtaining an aqueous medium containing PO ₄ ) ₂ , the same operation as in the production example of the magnetic toner 1 was performed to obtain toner particles.
100 parts of the toner particles, 0.6 part of a hydrophobic silica fine powder treated with hexamethyldisilazane and then treated with silicone oil (treated with a BET specific surface area of 120 m ^{2 /} g), 0.6 part,
. 3 parts of the inorganic fine powder 1 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare a magnetic toner C (weight average particle size 9.0 μm). Table 3 shows the physical properties of the magnetic toner C.

<Magnetic toner production example 4>
In the production example of magnetic toner 1, 7,0 by Claremix (M Technique Co., Ltd.)
Except that the mixture was stirred for 15 minutes at 00 rpm and granulated, the same operation as in the production example of the magnetic toner 1 was performed to obtain toner particles.
100 parts of the toner particles, 1.0 part of a hydrophobic silica fine powder treated with hexamethyldisilazane and then treated with silicone oil (BET specific surface area after treatment is 120 m ^{2 /} g), and 0.5 part of inorganic fine powder The toner 1 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare a magnetic toner D (average circularity 0.950). Table 3 shows the physical properties of the magnetic toner D.

<Magnetic toner production example 5>
In the production example of magnetic toner 1, 100 parts of toner particles and 0.3 part of hydrophobic silica fine powder (treated with a BET specific surface area of 120 m ^{2 /} g) treated with hexamethyldisilazane and then with silicone oil, Magnetic toner E (methanol / water mixture) was prepared in the same manner as in magnetic toner 1 except that 0.2 part of inorganic fine powder 1 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Wettability with respect to the liquid = methanol concentration 50%). Table 3 shows the physical properties of Magnetic Toner E.

<Magnetic Toner Production Example 6>
In the production example of magnetic toner 1, 100 parts of toner particles and 2.0 parts of hydrophobic silica fine powder (treated with a BET specific surface area of 120 m ^{2 /} g after treatment with hexamethyldisilazane and then with silicone oil), The magnetic toner F (methanol / water mixture) was prepared in the same manner as in the magnetic toner 1 except that 0.5 part of the inorganic fine powder 1 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Wettability with respect to the liquid = methanol concentration 69%). Table 3 shows the physical properties of the magnetic toner F.

<Magnetic Toner Production Example 7>
In the production example of magnetic toner 1, 100 parts of toner particles and 2.0 parts of hydrophobic silica fine powder (treated with a BET specific surface area of 120 m ^{2 /} g after treatment with hexamethyldisilazane and then with silicone oil), The magnetic toner G (S5 = 0.0.0) was prepared in the same manner as in the magnetic toner 1 except that 0.1 part of the inorganic fine powder 1 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). 10, S20 = 1.00). Table 3 shows the physical properties of the magnetic toner G.

<Magnetic toner production example 8>
In the production example of magnetic toner 1, 100 parts of toner particles and 0.3 part of hydrophobic silica fine powder (treated with a BET specific surface area of 120 m ^{2 /} g) treated with hexamethyldisilazane and then with silicone oil, Except for mixing 1.5 parts of inorganic fine powder 1 with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.), the same operation as in the production example of magnetic toner 1 was performed, and magnetic toner H (S5 = 1. 90, S20 = 4.00). Table 3 shows the physical properties of the magnetic toner H.

<Magnetic Toner Production Example 9>
In the magnetic toner 1 manufacturing example, the same operation as in the magnetic toner 1 manufacturing example was performed except that 150 parts of the magnetic body 2 was used instead of 80 parts of the magnetic body 1, and the magnetic toner I (σr1 of magnetic toner = 4.0) was prepared. Table 3 shows the physical properties of Magnetic Toner I.

<Manufacturing Example 10 of Magnetic Toner>
100 parts of toner particles, 1.0 part of hydrophobic silica fine powder treated with hexamethyldisilazane (BET specific surface area after treatment is 120 m ^{2 /} g) and 0.5 part of inorganic fine powder ^{2 are} mixed with a Henschel mixer ( A magnetic toner J (particle size of inorganic fine powder = 30 nm) was prepared by carrying out the same operations as in the production example of the magnetic toner 1 except for mixing by Mitsui Miike Chemical Co., Ltd.). Table 3 shows the physical properties of the magnetic toner J.

<Production Example 11 of Magnetic Toner>
100 parts of toner particles, 1.0 part of a hydrophobic silica fine powder treated with hexamethyldisilazane and then treated with silicone oil (BET specific surface area after treatment is 120 m ^{2 /} g), 0.5 part,
The magnetic toner K (particle diameter of the inorganic fine powder = the same as in the production example of the magnetic toner 1) except that the inorganic fine powder 3 in part is mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). 295 nm) was prepared. Table 3 shows the physical properties of the magnetic toner K.

<Example 12 of magnetic toner production>
100 parts of toner particles, 1.0 part of a hydrophobic silica fine powder treated with hexamethyldisilazane and then treated with silicone oil (BET specific surface area after treatment is 120 m ^{2 /} g), 0.5 part,
The magnetic toner L (inorganic fine powder = amorphous 200 nm) was prepared in the same manner as in the magnetic toner 1 except that the inorganic fine powder 4 was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). ) Was prepared. Table 3 shows the physical properties of the magnetic toner L.

<Manufacturing Example 13 of Magnetic Toner>
In the production example of the magnetic toner 1, the same operation as in the production example of the magnetic toner 1 is performed except that 15 parts of the saturated polyester resin is used instead of 5 parts of the saturated polyester resin. Wetability 35%) was prepared. Table 3 shows the physical properties of the magnetic toner M.

<Manufacturing Example 14 of Magnetic Toner>
In the magnetic toner 1 production example, the same operation as in the magnetic toner 1 production example was performed except that 20 parts of ester wax (melting point: 72 ° C.) was used instead of 10 parts of ester wax (melting point: 72 ° C.). The magnetic toner N (49% wettability of magnetic toner particles) was prepared. Table 3 shows the physical properties of the magnetic toner N.

<Manufacturing Example 15 of Magnetic Toner>
In the production example of the magnetic toner 1, the same operation as in the production example of the magnetic toner 1 was performed except that 80 parts of the magnetic body 3 was used instead of 80 parts of the magnetic body 1, and the magnetic toner O (free rate 3.00) was used. %) Was prepared. Table 3 shows the physical properties of the magnetic toner O.

<Manufacturing Example 16 of Magnetic Toner>
Styrene / n-butyl acrylate copolymer (mass ratio 78/22)
(Mn = 24300, Mw / Mn = 3.0) 100 parts saturated polyester resin (acid value: 8, Mp: 12000) 5 parts negative charge control agent (monoazo dye-based Fe compound) 2 parts magnetic body 1 20 parts 5 parts of ester wax used in the production of magnetic toner A The above materials were mixed in a blender, melt-kneaded with a biaxial extruder heated to 110 ° C., and the cooled kneaded product was coarsely pulverized with a hammer mill, and coarsely pulverized product Was pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and the resulting finely pulverized product was classified by air to obtain toner particles having a weight average particle diameter of 6.0 μm. Thereafter, 60 parts of the magnetic material 1 is externally added to 100 parts of the toner particles, and the magnetic material is fixed to the surface using an impact surface treatment apparatus (treatment temperature 55 ° C., rotary treatment blade peripheral speed 90 m / sec.). Thus, magnetically fixed toner particles were obtained.
Further, 8 parts of emulsified particles (styrene-methacrylic acid, particle size 0.05 μm) are externally added to 100 parts of magnetic substance-fixed toner particles, and then an impact surface treatment apparatus (treatment temperature 50 ° C., rotational treatment blade peripheral speed). 90 m / sec.) Was used for fixing and film formation to obtain coated toner particles. In the same manner as in the production of the magnetic toner A, 100 parts of the toner particles obtained were treated with hexamethyldisilazane and then with a hydrophobic silica fine powder treated with silicone oil (treated BET specific surface area). Is 120 m ^{2 /} g) and 0.5 part of the inorganic fine powder 1 is mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to obtain a magnetic toner P (weight average particle diameter 6.0 μm). ) Was prepared. The physical properties of the magnetic toner P are shown in Table 3 (release rate 0.05
%).

<Comparative Production Example 1 of Magnetic Toner>
In magnetic toner production example 13, instead of using 1.0 part of hydrophobic silica fine powder and 0.5 part of inorganic fine powder 1, 0.3 part of hydrophobic silica fine powder and 0.2 part of inorganic fine powder 1 were used. A magnetic toner a (methanol wettability 43%) was prepared in the same manner as in Magnetic Toner Production Example 12 except that it was used. Table 3 shows the physical properties of the magnetic toner a.

<Comparative Production Example 2 of Magnetic Toner>
In Production Example 14 of magnetic toner, 1.0 part of hydrophobic silica fine powder and 1.0 part of inorganic fine powder 1 were added.
Instead of using 5 parts, magnetic toner b (77% methanol wettability) was prepared in the same manner as in magnetic toner production example 13 except that 2.0 parts of hydrophobic silica fine powder and 0.5 part of inorganic fine powder 1 were used. ) Was prepared. Table 3 shows the physical properties of the magnetic toner b.

<Comparative Production Example 3 of Magnetic Toner>
In Comparative Example 1 of magnetic toner, instead of using 1.0 part of hydrophobic silica fine powder and 0.5 part of inorganic fine powder 1, 2.0 part of hydrophobic silica fine powder and 0.5 part of inorganic fine powder 1 were used. The magnetic toner c (S5 = 0.04, S2) was used in the same manner as in the comparative magnetic toner production example 1 except for using the same amount.
0 = 0.40) was prepared. Table 3 shows the physical properties of the magnetic toner c.

<Comparative Production Example 4 of Magnetic Toner>
In Comparative Example 2 of magnetic toner, instead of using 1.0 part of hydrophobic silica fine powder and 0.5 part of inorganic fine powder 1, 0.3 part of hydrophobic silica fine powder and 0.2 part of inorganic fine powder 1 were used. The magnetic toner d (S5 = 2.50, S2) was used in the same manner as in the magnetic toner comparative production example 2 except that the amount of
0 = 4.50) was prepared. Table 3 shows the physical properties of the magnetic toner d.

<Comparative Production Example 5 of Magnetic Toner>
Styrene / n-butyl acrylate copolymer (mass ratio 78/22)
(Mn = 24300, Mw / Mn = 3.0) 100 parts saturated polyester resin (acid value: 8, Mp: 12000) 5 parts negative charge control agent (monoazo dye-based Fe compound) 2 parts magnetic material 1 80 parts 5 parts of ester wax used in the production of magnetic toner A The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 110 ° C., and the cooled kneaded product is coarsely pulverized with a hammer mill, and then coarsely pulverized product Was pulverized with a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and the resulting finely pulverized product was subjected to air classification to obtain toner particles having a weight average particle diameter of 6.0 μm.
In the same manner as in the production of magnetic toner A, 100 parts of the toner particles obtained were treated with hexamethyldisilazane and then with silicone oil, and the treated BET specific surface area was 120 m ² / g. 1.0 part of the hydrophobic silica fine powder and 0.5 part of the inorganic fine powder 1 were mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.), and the magnetic toner e (weight average particle diameter 6.3 μm) was mixed. Prepared. Table 3 shows the physical properties of the magnetic toner e.

<Example 1>
As the image forming apparatus, LBP-3000 (manufactured by Canon) was used with modification as shown in FIG.
As shown in FIG. 2, the image forming apparatus includes a photoconductor 100, a conductive charging roller 117 that is arranged in contact with the photoconductor 100 and charges the photoconductor 100, and a laser beam corresponding to an image to be formed. A laser generator 121 which is an exposure device that irradiates the charged photosensitive member 100 with 123 to form an electrostatic latent image on the photosensitive member 100, and develops the formed electrostatic latent image with toner to produce a toner image A developing device 140 formed on 100, a transfer material P brought into contact with the photosensitive member 100, a conductive transfer roller 114 for transferring the formed toner image to the transfer material P, and a toner image on the transfer material P transferred. A fixing device 126 for fixing to the material P, a cleaner 116 having a cleaning blade for removing transfer residual toner remaining on the surface of the photoconductor 100 after transfer, a photoconductor 100 and a transfer roller 114, It has a register roller 124 for conveying the transfer material P between, and a conveying belt 125 for conveying the transfer material P to which the toner image is transferred to the fixing device 126.
As shown in FIG. 1, the developing device 140 is disposed in a developing container that contains a developer, a developing sleeve 102 that is rotatably disposed in an opening of the developing container, and a stationary inside the developing sleeve 102. A magnet roller 104 that is in contact with the developing sleeve 102, an elastic blade 103 that regulates the toner carried on the developing sleeve 102 and regulates the thickness of the toner layer on the developing sleeve 102, and the inside of the developing container. And an agitating member 141 for agitating the toner. The developing device 140 is disposed at a position where the developing sleeve 102 and the photoconductor 100 are not in contact with the photoconductor 100.
As shown in FIG. 3, the transfer roller 114 includes a cored bar 114a and a conductive elastic layer 114b that covers the peripheral surface of the cored bar 114a. A transfer bias power source 115 for applying a transfer bias applied from the back surface of the transfer material P when the toner image is transferred is connected to the metal core 114a. The charging roller 117 can also be configured in the same manner as the transfer roller 114.
It should be noted that the devices and members shown in FIGS. 1 to 3 can all be constituted by known members.
In this embodiment, the peripheral speed of the developing sleeve was modified to 105% (118 mm / sec) in the forward direction with respect to the peripheral speed (112 mm / sec) of the photosensitive member.

First, toner A was used as a toner, and an image printing test was performed in a normal temperature and normal humidity (23 ° C., 60% RH) environment. As a transfer material, A4 paper of 75 g / m ² was used. As a result, a high density and transferability were exhibited in the initial stage, and a good image without back stain due to fixing offset, no ghosting on the image, and no fogging on the non-image area was obtained.
Next, durability was evaluated by printing an image pattern consisting only of horizontal lines with a printing area ratio of 2% up to 2000 printed sheets in the intermittent mode. Image evaluation and toner durability evaluation were performed as follows.

a) Image density A solid image portion was formed and evaluated after the initial and 2000 printouts were completed. The image density was measured by using a “Macbeth reflection densitometer” (manufactured by Macbeth Co.), which is an image density measuring device, to measure a relative density with respect to a printout image of a white background portion having a document density of 0.00. If the image density is 1.40 or more, the image has no practical problem.

b) Fog The fog was measured using a reflection densitometer REFECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. The filter was calculated from the following formula using a green filter. If the fog (reflectance) is 2.0% or less, the image has no practical problem.

c) Halftone uniformity Judgment was made based on the uniformity of the halftone image output after 3 sheets of solid black.
A: A very clear image with very good image uniformity.
B: A clear image with excellent image uniformity.
C: A good image although the uniformity of the image is slightly inferior.
D: Image quality with no practical problem.
E: Image with poor uniformity of image and unpreferable for practical use.

d) Fixability As a fixing rubbing test, A4 plain paper for copying machines (105 g / m ² ) was adjusted so that the toner mass per unit area was 0.5 mg / cm ² and 10 mm × 10 mm for density measurement. An image having a large number of 3 dot 3 space (600 dpi) images was output, and the obtained fixed image was rubbed 5 times with sylbon paper applied with a weight of 50 g / cm ² , and the image density after the rub was lowered. The rate was evaluated based on the following. The image density was measured by using a Macbeth reflection densitometer (Macbeth Co., Ltd.), measuring the relative density with respect to the printout image of the white background portion where the document density was 0.00, and the reduction rate of the image density after rubbing. If the fixing property by the fixing rubbing test is A to C, there is no practical problem.
A: Less than 2% B: 2% or more, less than 5% C: 5% or more, less than 10% D: 10% or more

  The results obtained are shown in Table 4. As can be seen from Table 4, toner A has a good initial image evaluation under a normal temperature and normal humidity (23 ° C., 60% RH) environment, and shows a satisfactory value even after a durability of 2,000 sheets. The durability result was shown.

Next, an image formation test was conducted in the same manner under a high temperature and high humidity (32.5 ° C., 80% RH) environment, and also showed good image characteristics and durability.
Table 4 shows the obtained results.

<Examples 2 to 16>
Toners B to P were used as toners, and an image forming test and an endurance test were performed by the same image forming method as in Example 1. As a result, as shown in Table 4, good results were obtained with respect to image characteristics and durability.

<Comparative Example 1>
The toner a was used as the toner, and an image forming test was conducted by the same image forming method as in Example 1. As shown in Table 4, the toner a was deteriorated, the image characteristics after durability were poor, and it was not practically tolerable.

<Comparative Examples 2-4>
Toners b to d were used as toners, and an image output test was performed by the same image forming method as in Example 1. As shown in Table 4, the toners b to d were practically unbearable in terms of image density, fog, transfer efficiency, and fixability.

FIG. 3 is a schematic diagram illustrating a configuration of a developing device 140 in the image forming apparatus illustrated in FIG. 2. 1 is a schematic diagram illustrating a configuration of an image forming apparatus used in an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating a transfer roller 114 in the image forming apparatus illustrated in FIG. 1.

Explanation of symbols

21a to 21d Photosensitive drums 24a to 24d, 140 Developing device 27 Transport charger 29a to 29d Image forming unit 30a to 30d Transfer discharging unit 31 Charger 32 Discharge port 100 Photoconductor 102 Developing sleeve (magnetic toner carrier)
103 Elastic blade (regulator blade)
104 Magnet roller 114 Transfer roller 114a Core metal 114b Conductive elastic layer 115 Transfer bias power supply 116 Charge amount adjusting member (cleaner)
117 Charging roller 121 Laser generator (laser beam scanner)
123 Laser light 124 Register roller 125 Conveying belt 126 Fixing device 140 Developing device 141 Stirring member P Transfer material (recording medium)

Claims (10)

A magnetic toner comprising at least a binder toner, a magnetic toner particle containing a magnetic material, and a wax, and at least two or more inorganic fine powders,
(I) The magnetic toner has a weight average particle diameter of 4.0 to 9.0 μm,
(Ii) The average circularity of particles having an equivalent-circle diameter (number basis) of 2 μm or more of the magnetic toner is 0.950 or more,
(Iii) When the wettability of the magnetic toner to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration at a transmittance of 50% is in the range of 50 to 70% by volume;
(Iv) Magnetic properties characterized in that the uniaxial collapse stress of the magnetic toner after magnetization satisfies the following formula when the uniaxial collapse stress [kPa] at the maximum consolidation stress of 5 kPa and 20 kPa is S5 and S20, respectively. toner.

2. The magnetic toner according to claim 1, wherein the residual magnetization of the magnetic toner is 4.0 Am ² / kg or less at a magnetic field of 79.6 kA / m. 3. The magnetic toner according to claim 1, wherein one kind of the inorganic fine powder is an inorganic fine powder having an average primary particle diameter of 30 to 300 nm and a perovskite crystal structure. One kind of the inorganic fine powder is
The average particle size of the primary particles is 30-300 nm,
Having a cubic particle shape and / or a rectangular parallelepiped particle shape,
An inorganic fine powder having a perovskite type crystal structure and having a particle size of 600 nm or more and an aggregate content of 1% by number or less,
Furthermore, another kind of the inorganic fine powder is
The magnetic toner according to claim 1, wherein the magnetic toner is an inorganic fine powder having a BET specific surface area of 100 to 350 m ² / g. 5. One of the inorganic fine powders is a strontium titanate fine powder that does not go through a sintering step, and the other kind of the inorganic fine powder is hydrophobic silica fine particles. The magnetic toner according to claim 1. When the wettability of the magnetic toner particles to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 50% is in the range of 35 to 50% by volume. The magnetic toner according to any one of claims 1 to 5. The magnetic toner according to claim 1, wherein the magnetic material has a residual magnetization of 4.5 Am ² / kg or less at a magnetic field of 79.6 kA / m. The magnetic toner according to claim 1, wherein the magnetic material is a hydrophobized magnetic material. The magnetic toner according to any one of claims 1 to 8, wherein a liberation rate of iron and an iron compound of the magnetic toner is 0.05% to 3.00% with respect to the magnetic toner. The magnetic toner according to claim 1, wherein the magnetic toner particles are magnetic toner particles produced in an aqueous medium.

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