JP2008015231A - Magnetic toner - Google Patents

Abstract

Provided is a toner having excellent cleaning properties and capable of obtaining a high-resolution and high-definition image even after a durability test of a large number of prints in a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment.
In a magnetic toner containing at least a binder resin and a magnetic material, the average circularity of the magnetic toner is 0.950 or more, 1 g of the magnetic toner is dispersed in 50 ml of an electrolytic solution, and the magnetic toner is captured at the bottom of the container. The weight average particle diameter (D4e) of the particles present in the supernatant when collected and the weight average particle diameter (D4t) of the magnetic toner are expressed by the following formula (1): 0.80 ≦ (D4t / D4e) ≦ 1.20 (1 ), And the ratio of the particles having a number average particle diameter of 4 μm or less in the supernatant is 10.0% by number or more and 50.0% by number or less.
[Selection figure] None

Description

  The present invention relates to a toner used in a recording method using an electrophotographic method, an electrostatic recording method, a magnetic recording method, a toner jet method, or the like.

  Many methods are known as electrophotographic methods. Generally, an electrostatic latent image is formed on an electrostatic charge image carrier (hereinafter also referred to as a “photosensitive member”) by using a photoconductive substance by various means. Then, the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a recording medium such as paper, and then the toner image is fixed on the recording medium by heat or pressure. To obtain a copy. Examples of such an image forming apparatus include a copying machine and a printer.

  As a method for visualizing an electrostatic latent image with a toner, a cascade developing method, a magnetic brush developing method, a pressure developing method, a magnetic brush developing method using a two-component developer composed of a carrier and a toner, a toner carrier is a photoreceptor. A non-contact one-component development method in which toner is allowed to fly from the toner carrier to the photoreceptor without contact, a contact one-component development method in which the toner carrier is pressed against the photoreceptor and the toner is transferred by an electric field, and further, a magnetic toner A so-called jumping method is also used in which a rotating sleeve having a magnetic pole at the center is used to fly between the photosensitive member and the sleeve by an electric field.

  Printers and copiers are progressing in the direction of high resolution of 300, 600 dpi, 1200, and 2400 dpi, and the development method is required to have higher definition. In addition, copiers are also becoming more sophisticated, and therefore are moving toward digitalization. In this direction, the method of forming an electrostatic charge image with a laser is the main method, so it is also proceeding in the direction of high resolution. Here, as with printers, high-resolution and high-definition developers are required. .

  In order to obtain a high-resolution and high-definition image quality, it is known that reducing the particle size and spherical shape of toner are effective means (for example, Patent Documents 1 and 2). As a means for obtaining a good image over a long period of time, there is a means for mixing polymer toner particles having an average particle diameter of 3 μm or more and 8 μm or less with a pulverized toner having an average particle diameter of 10 μm or more and 20 μm or less (Patent Document 3). There has been proposed a toner in which two types of particles, a particle A containing a resin, a colorant and a charge control agent, and a particle B consisting of a binder resin are mixed and the particle B is larger in particle size than the particle A. (Patent Document 4), a high-quality image with no void is obtained. However, toners that achieve such high resolution and high definition often have poor cleaning properties such as slipping through the blades. Also, environmental stability and higher resolution and high image quality in endurance tests for multiple printing in harsh environments. There was still room for improvement in terms of compatibility.

Japanese Patent Laid-Open No. 9-62029 EP1058157 JP-A-4-232965 Japanese Patent Laid-Open No. 9-204064

  An object of the present invention is to provide a toner that has excellent cleaning properties, and can obtain a high-resolution and high-definition image even after a durability test of a large number of prints in a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment. Is to provide.

The present invention can solve the aforementioned problems by using the following magnetic toner.
(1) In a magnetic toner containing at least a binder resin and a magnetic material, the average circularity of the magnetic toner is 0.950 or more, 1 g of the magnetic toner is dispersed in 50 ml of an electrolytic solution, and the magnetic toner is collected at the bottom of the container. The weight average particle diameter (D4e) of the particles present in the supernatant liquid and the weight average particle diameter (D4t) of the magnetic toner are expressed by the following formula (1):
0.80 ≦ (D4t / D4e) ≦ 1.20 (1)
And a ratio of particles having a number average particle diameter of 4 μm or less in the supernatant liquid is 10.0% by number or more and 50.0% by number or less.
(2) The magnetic toner according to (1), wherein the ratio of particles having a number average particle diameter of 4 μm or less in the supernatant liquid is 10.0% or more and 35.0% or less.
(3) The magnetic toner according to (1) or (2), wherein the liberation rate of iron and iron compound of the magnetic toner is 0.05% or more and 3.00% or less.
(4) The magnetic toner according to any one of (1) to (3), wherein an average circularity of the magnetic toner is 0.960 or more.
(5) The magnetic toner according to (1) to (4), wherein the magnetic toner has a mode circularity of 0.98 or more.
(6) The magnetic toner according to (1) to (5), wherein the magnetic toner contains 50 to 120 parts by mass of a magnetic material with respect to 100 parts by mass of the binder resin.
(7) The magnetic toner according to any one of (1) to (6), wherein the weight of the particles present in the supernatant is 0.001 part by mass or more and 0.5 part by mass or less with respect to 100 parts by mass of the magnetic toner. .

  According to the present invention, a high-resolution and high-definition image can be obtained even after a durability test of a large number of prints under a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment.

  As a result of intensive studies by the present inventors, at least a binder resin and a magnetic toner composed of a magnetic material, the average circularity of the magnetic toner is 0.950 or more, and 1 g of the magnetic toner is dispersed in 50 ml of an electrolytic solution. The weight average particle diameter (D4e) of the particles present in the supernatant liquid when the magnetic toner is collected at the bottom of the container and the weight average particle diameter (D4t) of the magnetic toner satisfy 0.80 ≦ (D4t / D4e) ≦ 1.20. The ratio of the particles with a number average particle size of 4μm or less in the supernatant liquid is 10.0% or more and 50.0% or less, providing excellent cleaning properties. The inventors have found that high-resolution and high-definition images can be obtained even in a durability test for printing a large number of sheets in a low-humidity environment. This is considered to be the following reason.

  Particles (hereinafter referred to as low specific gravity particles) present in the supernatant liquid when 1 g of magnetic toner is dispersed in 50 ml of electrolyte and collected at the bottom of the container have a low specific gravity, and in the case of the same particle size, the toner Small compared to the mass of one particle. On the other hand, since toners having the same particle diameter have the same surface area, the chances of charging due to friction with a sleeve or a blade during development are substantially equal, and as a result, the amount of charge given is usually substantially equal. In that case, the value of the charge amount per unit mass, that is, the value of the charge amount is higher in the low specific gravity particles present in the supernatant. Due to the presence of the low specific gravity particles, the magnetic toner is triboelectrically charged when it comes into contact with the low specific gravity particles, so that a high charge amount can be stably obtained even in a high temperature and high humidity environment. It is considered that density uniformity is obtained even when an image with a high ratio is output, and a high-resolution and high-definition image can be obtained.

  However, when using toner with reduced particle size or spheroidization to obtain a high-resolution, high-definition image, if the blade cleaning method is used in the image carrier surface cleaning process after toner transfer, A phenomenon that the toner slips through occurs, resulting in poor cleaning. However, the present inventors have found that such defective cleaning does not occur when the ratio of the low specific gravity particles having a number average particle diameter of 4 μm or less is 10.0% by number or more and 50.0% by number or less. The reason is not clear, but I think it is as follows.

  First, a developing bias is applied to the magnetic toner and low specific gravity particles during development. As a result, the development is performed. For the above reason, the low specific gravity particles have a relatively high charge compared to the magnetic toner, and the development is held on the image carrier stronger than the magnetic toner. The Rukoto. Since such low specific gravity particles have high chargeability on the image carrier, they become nuclei to form electrostatic aggregates and are held on the image carrier without being transferred onto the transfer medium during transfer. It is expected that the aggregate plays a role of spacer particles between the blade and the image carrier during cleaning, prevents the toner that has not been transferred from slipping through the blade, and improves the cleaning performance.

  At this time, it is essential that the ratio of the low specific gravity particles having a number average particle diameter of 4 μm or less is 10.0% by number or more and 50.0% by number or less. If the ratio of the number average particle diameter of the low specific gravity particles is 4 μm or less is less than 10.0%, the charge distribution of the low specific gravity particles becomes sharp, but the charge imparting ability to the toner is increased due to the above-mentioned effect. Therefore, it is difficult to suppress fog due to charge up in a low temperature and low humidity environment. On the other hand, when the ratio of the low specific gravity particles having a number average particle size of 4 μm or less is larger than 50.0%, the charge distribution effect of the low specific gravity particles becomes broad and the charge imparting effect as described above is difficult to obtain. In addition to impairing the uniformity of a solid image in a high humidity environment, the charge distribution is broad, so the formation of electrostatic aggregates as described above is suppressed, resulting in toner slipping. Impairs cleaning performance. Therefore, it is essential that the ratio of the low specific gravity particles having a number average particle diameter of 4 μm or less is 10.0% by number or more and 50.0% by number or less. High-resolution and high-definition images can also be obtained in a durability test for printing a large number of sheets under a high-temperature and high-humidity environment and a low-temperature and low-humidity environment. The ratio of particles having a specific gravity of 4 μm or less in the low specific gravity particles is more preferably 10.0% by number or more and 35.0% by number or less.

  In the present invention, the weight average particle diameter (D4e) of the particles present in the supernatant when the magnetic toner is collected at the bottom of the container and the weight average particle diameter (D4t) of the magnetic toner are 0.80 ≦ (D4t / D4e). It is essential to satisfy ≦ 1.20. If (D4t / D4e) is less than 0.80, the specific surface area of the low specific gravity particles will be relatively small, so the triboelectric charge obtained during development will be high, and will tend to charge up in a low temperature and low humidity environment. Therefore, fog is likely to occur and the image density is liable to decrease. On the other hand, when (D4t / D4e) is greater than 1.20, the specific surface area of the low specific gravity particles is relatively high when viewed relatively, so that the triboelectric charge during development tends to be small. As a result, it tends to cause uneven density of the image. Therefore, in the present invention, it is essential to satisfy 0.80 ≦ (D4t / D4e) ≦ 1.20, whereby there is no decrease in image density even in a normal temperature and normal humidity environment, a low temperature and low humidity environment, and a high temperature and high humidity environment, A high-definition image can be obtained.

  By adding a metal oxide such as strontium titanate to the toner, it is possible to improve the cleaning property and the charging property. In general, however, such metal oxides tend to damage the surface of the image bearing member in the latter half of the endurance when used for a long period of time, which may inhibit charging stability and may cause contamination of the charging member. . However, the low specific gravity particles of the present invention, for example, when resin particles are used in the above range, have a large particle size compared to such metal oxides and are soft compared to metal oxides. The particles do not damage the drum and do not contaminate the charging member, and can provide a stable charging property to the magnetic toner. Thereby, a high-resolution and high-definition image can be obtained even in long-term use. In addition, low specific gravity particles and magnetic toner are almost equivalent resin particles against stress caused by agitation in the developing unit, so they have high stress resistance and can be used without problems in long-term durability tests. It is. However, a metal oxide such as strontium titanate can be used at the same time if it is used in combination with low specific gravity particles.

  In the present invention, it is essential that the average circularity of the magnetic toner is 0.950 or more, more preferably 0.960 or more. When the toner is nearly spherical or spherical, the toner is excellent in fluidity, and uniform triboelectric chargeability is easily obtained. In addition, the contact area between the toner particles and the image carrier is reduced, and the adhesion force of the toner particles to the image carrier due to the mirror force or van der Waals force is reduced. Since the contact opportunities also increase, the above-described cleaning effect can be obtained more remarkably. The magnetic toner of the present invention preferably has a mode circularity of 0.98 or more in the circularity distribution of the toner. A mode circularity of 0.98 or more means that most of the toner particles have a shape close to a true sphere, and the above action becomes more remarkable, which is preferable. When the average circularity is less than 0.950, it becomes difficult to obtain the action with the low specific gravity particles, and the image quality is also inferior, and it is difficult to achieve both high image quality and cleaning.

  As described above, the average circularity of the magnetic toner is 0.950 or more, the weight average particle diameter (D4e) of the low specific gravity particles and the weight average particle diameter (D4t) of the magnetic toner are 0.80 ≦ (D4t / D4e) ≦ 1.20, and the ratio of particles with a particle size of 4 μm or less in the supernatant liquid is 10.0% or more and 50.0% or less, providing excellent cleaning performance. High-resolution and high-definition images can be obtained even in endurance tests for printing multiple sheets.

  In the present invention, the liberation rate of iron and iron compound in the magnetic toner is preferably 0.05% or more and 3.00% or less, more preferably 0.05% or more and 1.50% or less. In this case, since the toner charge amount distribution becomes sharp and the uniform chargeability is improved, the toner charge reversal component is reduced, which is preferable.

  The liberation rate of iron and iron compound of the magnetic toner in the present invention is measured by 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 can introduce fine particles such as toner into the plasma one by one, and can know 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 (5) from the simultaneous emission of carbon atoms, which are constituent elements of the binder resin, and emission of iron atoms.
Formula (5)
Free rate of iron and iron compounds (%) = 100 × number of light emission of iron atom only / (number of light emission of iron atom emitted simultaneously with carbon atom + number of light emission of iron atom only)

  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. . The simultaneous light emission of carbon atoms and iron atoms is considered to be light emission from the magnetic powder dispersed in the toner, and the light emission of only iron atoms is considered to be light emission from the magnetic powder in a state free from the toner.

  The specific measurement method is as follows. Measurement is performed using a 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 used 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 3.3964). In this scan, sampling is performed so that the number of light emission of carbon atoms is 1000 or more and 1400 or less, and the scan is repeated until the total number of light emission of carbon atoms is 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 that the distribution has one 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.

  Toners with an iron and iron compound release rate exceeding 3.0% have a low toner charge amount, and free magnetic powder accumulates irregularly on the toner carrier, resulting in poor cleaning properties. In addition, the uniform chargeability of the toner is hindered, and the charge amount distribution tends to be broad, which is not preferable. On the other hand, if the liberation rate of iron and iron compound is less than 0.05%, it means that the magnetic powder is not substantially liberated from the toner. As described above, a toner having a low liberation rate of iron and iron compound has a high charge amount. However, since there is no leakage site of charge, it becomes easy to charge up and uniform charging becomes difficult. Therefore, the reverse fog tends to increase, which is not preferable.

  The liberation rate of iron and iron compounds depends on the amount of magnetic powder contained in the toner, the particle size of the magnetic powder, the particle size distribution, the toner production method, and the like, and is the preferred production method of the present invention. The suspension polymerization method (described later) depends on the degree of hydrophobicity of the magnetic material, the uniformity of the treatment, the granulation conditions, etc., but as an example, the surface treatment of the magnetic powder is not uniform. In this case, a part or all of the magnetic powder that is not sufficiently surface-treated (strongly hydrophilic) is released.

  The magnetic toner of the present invention can be produced by any known method. First, in the case of producing by a pulverization method, for example, binder resin, magnetic material, and if necessary, components necessary for magnetic toner such as a release agent, charge control agent, colorant, and other additives and other additives are added to Henschel. Mix thoroughly with a mixer such as a mixer or ball mill, and then melt and knead using a heat kneader such as a heating roll, kneader or extruder to mix the resins with each other. The toner particles can be obtained by dispersing or dissolving the magnetic toner material, cooling and solidifying, pulverizing, classification, and surface treatment as necessary. 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 an average circularity of 0.950 or more, which is an essential feature of the present invention, it is preferable to further pulverize by applying heat or to add a mechanical impact as an 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.

  As a binder resin when the toner according to the present invention is produced by a pulverization method, styrene such as polystyrene and polyvinyltoluene and a homopolymer of a substituted product thereof; 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-vinylmethyl Ether copolymer, styrene-vinylethyl Styrene copolymer such as ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Combined; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, temper resin, phenol resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin wax, carnauba wax and the like can 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 the pulverization method as described above, but the toner particles obtained by this pulverization method are generally indefinite and are essential conditions for the toner according to the present invention. In order to obtain a physical property having an average circularity of 0.950 or more, it is necessary to perform mechanical / thermal or some special treatment, resulting in poor productivity. Therefore, the toner of the present invention is preferably produced in a wet medium such as a dispersion polymerization method, an association aggregation method, or a suspension polymerization method. In particular, the suspension polymerization method easily satisfies the preferable conditions of the present invention and is very Is preferable. In the suspension polymerization method, a polymerizable monomer and a colorant (in addition, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives as necessary) are uniformly dissolved or dispersed to form a polymerizable monomer. After preparing the composition, the polymerizable monomer composition is dispersed in a continuous layer containing a dispersion stabilizer (for example, an aqueous phase) using an appropriate stirrer, and simultaneously subjected to a polymerization reaction, thereby obtaining a desired particle size. A toner having the above is obtained. The toner obtained by this suspension polymerization method (hereinafter referred to as polymerized toner) has toner particles with an average circularity of 0.950 or more, since the individual toner particle shapes are almost spherical. It is easy to satisfy and is preferable.

  However, as described above, even when a normal magnetic powder is contained in the polymerized toner, a large number of free magnetic powders exist, and the charging characteristics of the toner particles may be remarkably deteriorated. In addition, the dispersion of the magnetic powder tends to deteriorate, and furthermore, the toner having the desired circularity can be obtained due to the strong interaction between the dispersion medium water and the magnetic powder during the production of the suspension polymerization toner. The toner particle size distribution tends to be wide.

  This is because i) the magnetic powder is generally hydrophilic and thus easily present on the toner surface, and ii) the magnetic powder 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, it is important to modify the surface characteristics of the magnetic powder.

  Therefore, the magnetic powder used in the magnetic toner of the present invention is preferably hydrophobized with a coupling agent. Furthermore, when hydrophobizing the surface of the magnetic powder, it is more preferable to use a method in which the surface treatment is performed while hydrolyzing the coupling agent while dispersing the magnetic powder to have a primary particle size in an aqueous medium. Furthermore, it is very preferable that the magnetic material produced in an aqueous solution is washed and then subjected to a hydrophobic treatment without drying. In the hydrophobization method in water, the magnetic powders are less likely to coalesce than in the gas phase, and more uniform treatment can be performed. Moreover, since the thing which hydrophobizes without passing through a drying process does not occur the aggregation which arises at the time of drying, since it is disperse | distributed to the primary particle diameter at the time of a process, a very uniform surface treatment can be performed.

  The method of treating the surface of the magnetic powder 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, a high-viscosity coupling agent that has been easy to combine with each other in the gas phase and has been difficult to perform well can be used, and the hydrophobizing effect is enormous.

Examples of the coupling agent that can be used in the surface treatment of the magnetic powder according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used are silane coupling agents, which are represented by the general formula.
RmSiYn
[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 include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4 epoxy cyclohexyl) ethyltrimethoxysilane, γ -Glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyl Triacetoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyl Ethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, trimethylmethoxysilane, n-hexyltrimethoxysilane, n-decyltrimethoxysilane, hydroxypropyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyl A trimethoxysilane etc. can be mentioned.

In particular, in order to obtain sufficient hydrophobicity, it is preferable to use an alkyltrialkoxysilane coupling agent represented by the following formula.
_{C p H 2p + 1 -Si- (} OC q H 2q + 1) 3
[In formula, p shows the integer of 2-20, q shows the integer of 1-3. ]

  When p in the above formula is smaller than 2, the hydrophobization treatment is easy, but it is difficult to sufficiently impart hydrophobicity and it is difficult to suppress free magnetic powder. On the other hand, if p is larger than 20, the hydrophobicity is sufficient, but the coalescence between the magnetic powders increases, making it difficult to sufficiently disperse the magnetic powders in the toner.

  On the other hand, when q is larger than 3, the reactivity of the silane coupling agent is lowered and the hydrophobicity is not sufficiently performed. In particular, p in the formula represents an integer of 2 to 20 (more preferably an integer of 3 to 15), and q represents an integer of 1 to 3 (more preferably an integer of 1 or 2). A coupling agent should be used.

  The amount of the treatment is such that the total amount of the silane coupling agent is 0.05 parts by mass or more and 20 parts by mass or less, preferably 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the magnetic powder. It is preferable to adjust the amount of the treatment agent according to the surface area of the resin, the reactivity of the coupling agent, and the like.

  In order to treat the surface of the magnetic powder with a coupling agent in an aqueous medium, a method of stirring an appropriate amount of the magnetic powder and the coupling agent in the aqueous medium can be mentioned. Stirring is preferably performed sufficiently, for example, with a mixer having stirring blades so that the magnetic powder becomes primary particles in the aqueous medium.

  Here, the aqueous medium is a medium containing water as a main component. Specifically, water or water added with a small amount of a surfactant, water added with a pH adjusting agent, water added with an organic solvent may be mentioned as an aqueous medium. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1% by mass 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 above silane coupling agent, it is possible to treat alone or in combination with a plurality of types, and when used together, each coupling agent is charged simultaneously or with a time difference, The magnetic powder is processed. In the magnetic powder thus obtained, no particle aggregation is observed, and the surface of each particle is uniformly hydrophobized, so that when used as a material for polymerized toner, the uniformity of the toner particles is good. Become.

The magnetic powder used in the magnetic toner of the present invention is mainly composed of iron oxide such as triiron tetroxide and γ-iron oxide, and includes phosphorus, cobalt, nickel, copper, magnesium, manganese and aluminum. Further, it may contain an element such as silicon. These magnetic powders preferably have a BET specific surface area of 2 m ² / g or more and 30 m ² / g or less, more preferably 3 m ² / g or more and 28 m ² / g or less by a nitrogen adsorption method. Further, those having a Mohs hardness of 5 or more and 7 or less are preferable. The shape of the magnetic powder includes polyhedron, octahedron, hexahedron, spherical shape, needle shape, flake shape, etc., but those having less anisotropy such as polyhedron, octahedron, hexahedron, spherical shape and the like have an image density. It is preferable in terms of enhancement.

  In addition, the magnetic powder of the present invention preferably has a small residual magnetization (σr) at a magnetic field of 79.6 kA / m (1000 oersted) as described above, and a spherical shape, a polyhedron, a hexahedron, etc. are preferable because the residual magnetization is small. It is. Furthermore, it is effective to make the magnetic powder have an element such as phosphorus or silicon in order to reduce the residual magnetization of the magnetic powder. The shape of the magnetic powder can be confirmed by a scanning electron microscope (SEM) or a transmission electron microscope (TEM). If there is a distribution in the shape, the magnetic powder has the largest number of existing shapes. The shape of the powder.

  The volume average particle size of the magnetic powder is preferably 0.05 μm or more and 0.40 μm or less. When the volume average particle size is less than 0.05 μm, the decrease in blackness becomes remarkable, and the coloring power is insufficient as the colorant for the black and white toner, and the aggregation of the composite oxide particles becomes strong. Dispersibility tends to decrease. Further, the increase in the surface area of the magnetic powder increases the residual magnetization of the magnetic powder, and as a result, the residual magnetization of the toner also increases. On the other hand, when the volume average particle size exceeds 0.40 μm, the residual magnetization becomes small, but the coloring power becomes insufficient. In addition, when used as a colorant for a toner having a small particle diameter, it is not preferable because it is difficult to disperse the magnetic powder uniformly in individual toner particles, and the dispersibility tends to be lowered.

  The volume average particle size of the magnetic powder can be measured using a transmission electron microscope. Specifically, the toner particles to be observed are sufficiently dispersed in the epoxy resin, and then cured in an atmosphere at a temperature of 40 ° C. for 2 days to obtain a cured product. The obtained cured product is used as a sample on a thin piece with a microtome, and the diameter of 100 magnetic powder particles in the field of view is measured with a transmission electron microscope 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 powder. It is also possible to measure the particle size with an image analyzer.

  In the present invention, the magnetic material also has the effect of a colorant, but other colorants may be used in combination as long as the main colorant is a magnetic powder. 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.

  The degree of hydrophobicity of the magnetic powder used in the present invention is preferably 35% or more and 95% or less, more preferably 45% or more and 95% or less. The degree of hydrophobicity can be arbitrarily changed depending on the type and amount of the treatment agent on the surface of the magnetic powder and the treatment method. The degree of hydrophobicity indicates the hydrophobicity of the magnetic powder, and those having a low degree of hydrophobicity mean that the hydrophilicity is high. Therefore, when magnetic powder having a low degree of hydrophobicity is used, the suspension polymerization method suitably used for producing the toner of the present invention causes the magnetic powder to move to an aqueous system during granulation, and the particle size As the distribution becomes broad, it exists as a free magnetic powder, which is not preferable. Furthermore, the dispersibility of the magnetic powder tends to decrease. Further, in order to make the degree of hydrophobicity higher than 95%, it is necessary to use a large amount of the treatment material on the surface of the magnetic powder. In such a state, the magnetic powder is likely to coalesce, and the processing uniformity. Will be damaged.

The degree of hydrophobicity in the present invention is measured by the following method.
The degree of hydrophobicity of the magnetic powder is measured by a methanol titration test. The methanol titration test is an experimental test for confirming the degree of hydrophobicity of a magnetic powder having a hydrophobic surface.

  Hydrophobization degree measurement using methanol is performed as follows. Add 0.1 g of magnetic powder to 50 ml of water in a 500 ml beaker. Thereafter, methanol is gradually added to the liquid and titration is performed. At this time, methanol is supplied from the bottom of the liquid and is gently stirred. The end of sedimentation of the magnetic powder is when the suspended matter of the magnetic powder is no longer confirmed on the liquid surface, and the degree of hydrophobicity is the volume percentage of methanol in the methanol and water mixture when the end of sedimentation is reached. Appears. The same measurement was performed in the examples described later.

  The magnetic powder used in the magnetic toner of the present invention is preferably used in an amount of 50 to 120 parts by mass with respect to 100 parts by mass of the binder resin. If the magnetic powder is less than 50 parts by mass, the coloring power of the toner is poor and it is difficult to suppress fogging. On the other hand, when the magnetic powder exceeds 120 parts by mass, not only the retention force by the magnetic force on the toner carrier is increased and the developability is lowered, but it becomes difficult to uniformly disperse the magnetic powder into individual toner particles, This is not preferable because the residual magnetization per toner particle increases.

  The content of the magnetic powder in the toner can be measured using a Perkin Elmer thermal analyzer: 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 from 100 ° C. to 750 ° C. is defined as the binder resin amount, and the remaining weight is approximated. The amount of magnetic powder.

  For example, in the case of magnetite, the magnetic powder 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 is blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 or higher and 14 or lower), and ferrous hydroxide is oxidized while heating the aqueous solution to 70 ° C. or higher. First, a seed crystal to be the core of 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 the magnetic iron oxide powder is grown around the seed crystal. At this time, it is possible to control the shape of the magnetic powder 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 not less than 6. After completion of the oxidation reaction, it is possible to adjust the pH and the like as it is, but it is possible to carry out a coupling treatment. After re-dispersing in, the pH of the re-dispersed liquid is set to the acidic range, and the silane coupling agent is added with sufficient stirring. After hydrolysis, the temperature is increased, or the pH is adjusted to the alkaline range. It is preferable to perform a ring process. In any case, it is important to perform a surface treatment after the oxidation reaction without passing through a drying step, and if it is dried before the coupling treatment, it is difficult to uniformly disperse the magnetic powder in the aqueous medium. Uniform processing becomes difficult.

  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 general, a method for producing magnetic iron oxide by an aqueous solution method uses an iron concentration of 0.5 mol / l or more and 2 mol / l or less from the viewpoint of preventing an increase in viscosity during the reaction and the 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 easier the atomization.

  By using the magnetic toner made of the hydrophobic magnetic powder produced as described above, a stable chargeability of the toner can be obtained, and high image quality and high stability become possible.

  In the present invention, it is preferable to contain 0.001 part by mass or more and 0.5 part by mass or less of low specific gravity particles with respect to 100 parts by mass of the magnetic toner. More preferably, it is 0.001 mass part or more and 0.2 mass part or less. If the low specific gravity particles are less than 0.001 part by mass, it is difficult to obtain the above cleaning effect. On the other hand, if the low specific gravity particles exceed 0.5 parts by mass, the toner is highly charged and the tendency to charge up in a low-temperature, low-humidity environment increases, which is undesirable.

  A production method by suspension polymerization which can suitably produce the magnetic toner of the present invention will be described. The polymerized toner according to the present invention is generally a toner composition, that is, a polymerizable monomer composed of a binder resin, a magnetic powder, a release agent, a plasticizer, a charge control agent, a crosslinking agent, and optionally a colorant. Components and other additives necessary as a toner are added appropriately, for example, a polymer, a dispersant, etc., and a polymerizable monomer composition that is uniformly dissolved or dispersed by a disperser or the like is dispersed and stabilized. It can be produced by suspending in an aqueous medium containing an agent.

  In the production of the polymerized toner according to the present invention, examples of the polymerizable monomer constituting the polymerizable monomer composition include the following. Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, 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 , 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 other acrylonitrile such as diethylaminoethyl methacrylate, methacrylonitrile, and the like monomers acrylamide. These monomers can be 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 the polymerized toner according to the present invention, the polymerization may be performed by adding a resin to the polymerizable monomer composition. 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 such a polymer containing a polar functional group is allowed to coexist in the toner, the above-described wax component is phase-separated, the encapsulation becomes stronger, and a toner having good blocking resistance and developability can be obtained.

  Among these resins, the effect is particularly increased by containing a polyester resin. I think this is because of the following reasons. 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 its polarity, the tendency of the polyester to be unevenly distributed on the surface of the droplets in the aqueous dispersion medium becomes strong, and the polymerization proceeds while maintaining this state, resulting in a toner. For this reason, the polyester resin is unevenly distributed on the toner surface, resulting in a uniform surface state and surface composition. As a result, a very good development can be achieved due to a synergistic effect of uniform chargeability and good release agent encapsulation. You can get sex.

  The polyester resin used in the present invention is, for example, a saturated polyester resin, an unsaturated polyester resin, or both are appropriately selected and used for controlling physical properties such as charging property, durability, and fixing property of the toner. Is possible.

  As the polyester resin used in the present invention, a normal resin composed of an alcohol component and an acid component can be used, and both components are exemplified below.

［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。］、或いは上記化合物の水添物、
または、下記式で示されるジオール；

［式中Ｒ’は

，

または

を表す。］、或いは、上記化合物の水添物のジオールが挙げられる。 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 the following formula:

[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. Or a hydrogenated product of the above compound,
Or a diol represented by the following formula;

[Wherein R ′ is

,

Or

Represents. Or a hydrogenated diol of the above compound.

  Divalent carboxylic acids include benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, or anhydrides thereof; 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 polyester resins, the alkylene oxide adduct of bisphenol A, which is excellent in charging characteristics and environmental stability and 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 or more and 10 or less in terms of fixability and toner durability.

  It is preferable that 45 mol% or more and 55 mol% or less of the polyester resin in the present invention is an alcohol component, and 55 mol% or more and 45 mol% or less is an acid component.

  In the magnetic toner of the present invention, the polyester resin has an acid value of 0.1 mgKOH / resin 1 g or more and 50 mgKOH / resin 1 g or less in order to improve the charging stability of the toner particles obtained on the toner particle surface. Is preferred. If the oxidation of the polyester resin is less than 0.1 mgKOH / resin 1 g, the amount existing on the toner surface is absolutely insufficient, and it is difficult to provide uniform charging. If it exceeds 50 gKOH / resin 1 g, the hydrophilic part of the polyester increases, and the toner charge is increased. Adversely affects sex. Furthermore, in the present invention, the oxidation of the polyester resin is more preferably in the range of 5 mg KOH / resin 1 g or more and 35 mg KOH / resin 1 g or less.

  In the present invention, the physical properties can be adjusted by using two or more kinds of polyester resins in combination as long as the physical properties of the resulting toner particles are not adversely affected, or by modifying with, for example, a silicone or a fluoroalkyl group-containing compound. It is.

  Moreover, when using the high molecular polymer containing such a polar functional group, the average molecular weight is preferably 3000 or more. Since such a resin containing a polar functional group concentrates in the vicinity of the toner surface, if the number average molecular weight is less than 3000, the developing property, blocking resistance, and durability tend to decrease, which is not preferable.

  In addition, a resin other than the above may be added to the monomer composition 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, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer Polymer, styrene-vinyl Styrene copolymers such as methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate , Polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, temper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, Aromatic petroleum resins can be used alone or in combination. As addition amount of these resin, 1 to 20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers. When the addition amount of the resin is less than 1 part by mass, the effect of addition is small. On the other hand, addition of 20 parts by mass or more makes it 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.

  In the present invention, a known charge control agent can be used without any particular limitation, and a resin having an organometallic compound or a charge control substance (hereinafter referred to as “charge control resin”) is used. It is preferable. Further, from the viewpoint of uniform charging, it is more preferable to use a charge control resin than to use an organometallic compound. In particular, when suspension polymerization, which is a preferred method for producing the toner of the present invention (described later), is performed, it is very advantageous to use a charge control resin from the viewpoint of reducing toner consumption. This is because when suspension polymerization is performed using a charge control resin, the charge control resin is likely to be localized on the surface of the oil liquid due to the hydrophilic groups contained in the charge control resin, so that the charge control resin makes the toner surface layer uniform. This is because the toner is quickly charged for covering, and regular charging is easily performed, so that the reversal component is reduced. Even when the toner is manufactured by a pulverization method, the binder resin and the charge control resin are well mixed in the kneading process, so that it is easy to have a uniform charge, which is effective in reducing consumption. .

  The charge control resin used in the present invention is, for example, a sulfur-containing polymer, and examples of the monomer having a sulfur element for producing the sulfur-containing polymer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfone. Examples include acid, 2-methacrylamideamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, and methacryl sulfonic acid.

  The sulfur-containing polymer that can be used in the present invention may be a homopolymer of the above monomer, or a copolymer of the above monomer and another monomer. Among these, a copolymer of a sulfonic acid group-containing (meth) acrylamide monomer and styrene is particularly preferable from the viewpoint of chargeability of the toner.

  As a monomer that forms a copolymer with a monomer having a sulfur element, there is a vinyl-based polymerizable monomer, and a monofunctional polymerizable monomer or a polyfunctional polymerizable monomer should be used. I can do it.

  Monofunctional polymerizable monomers include styrene; α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, pn-butyl. Styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p -Styrene derivatives such as phenylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2 -Ethylhexyl acrylate , N-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethyl phosphate ethyl acrylate, diethyl phosphate ethyl acrylate, dibutyl phosphate ethyl acrylate, 2-benzoyloxyethyl acrylate Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl Methacrylate, n-nonyl methacrylate, diethyl phosphate ethyl methacrylate Methacrylic polymerizable monomers such as dibutyl phosphate ethyl methacrylate; methylene aliphatic monocarboxylic acid esters; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl formate; vinyl methyl ether Vinyl ether such as vinyl ethyl ether and vinyl isobutyl ether; vinyl ketone such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropyl ketone.

  As polyfunctional polymerizable monomers, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol Diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4- (acryloxydiethoxy) phenyl) propane, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol Dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis (4- (methacryloxy-diethoxy) phenyl) propane, 2,2′-bis (4-methacryloxy / polyethoxy) phenyl) propane, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, divinylbenzene, divinylnaphthalene, divinyl ether, and the like.

  The method for producing the sulfur-containing polymer includes bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, ionic polymerization and the like, but solution polymerization is preferable from the viewpoint of operability.

The polymer having a sulfonic acid group is
X (SO ₃ ⁻ ) _n · mY ^{k +}
(X represents a polymer site derived from the polymerizable monomer, Y ⁺ represents a counter ion, k is a valence of the counter ion, m and n are integers, and n = k × m. It has a structure as shown in FIG. Counter ions are preferably hydrogen ions, sodium ions, potassium ions, calcium ions, ammonium ions, and more preferably hydrogen ions.

  On the other hand, as other charge control agents, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid, dicarboxylic acid, metal salts or metals of azo dyes or azo pigments Organometallic compounds such as complexes; boron compounds, urea compounds, silicon compounds, calixarenes and the like, and aluminum di-tert-butylsalicylate compounds are preferably used. Examples of positive charge control agents include quaternary ammonium salts, guanidine compounds, nigrosine compounds, and imidazole compounds.

  As a method of incorporating the charge control agent into the toner, a method of adding the toner inside the toner particles, and suspension polymerization, when forming the oil droplets in water or forming the oil droplets in water, It is also possible to perform seed polymerization during the polymerization or by adding a polymerizable monomer in which the charge control agent is dissolved and suspended after the polymerization. In the case where an organometallic compound is used as the charge control agent, it is also possible to introduce these compounds by adding them externally to the toner particles, mixing and stirring them with shear.

  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 parts by mass or more and 1.0 parts by mass or less, more preferably 0.01 parts by mass or more and 0.3 parts by mass or less with respect to 100 parts by mass of the toner.

  The magnetic toner of the present invention may contain a release agent for improving fixability, and preferably contains 1 part by mass or more and 30 parts by mass or less, more preferably 5 parts by mass with respect to 100 parts by mass of the binder resin. It is not less than 20 parts by mass. If the content of the release agent is less than 1 part by mass, the effect of suppressing the low temperature offset is poor, and if it exceeds 30 parts by mass, the long-term storage stability is deteriorated and the toner is charged uniformly due to oozing out onto the toner surface. Is inferior, and it tends to cause a decrease in concentration in a high-temperature and high-humidity environment. Furthermore, since a large amount of wax is included, the toner shape tends to become distorted.

  Examples of the release agent usable in the magnetic toner according to 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 by Fischer-Tropsch method. Polyolefin waxes and their derivatives typified by polyethylene, natural waxes and their derivatives such as carnauba wax and candelilla wax, and the derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes and the like can also be used.

  Among these release agent components, those having a maximum endothermic peak in the region of 40 ° C. or more and 140 ° C. or less at the time of temperature rise in the DSC curve measured by a differential diffractometer are preferable, and more preferably 45 ° C. or more and 120 ° C. What has in the following area | regions is more preferable. Having the maximum endothermic peak in the above temperature range is preferable because good fixability can be imparted to the toner and exudation of the release agent component can be suppressed. When the maximum endothermic peak is less than 40 ° C., the self-aggregating force of the release agent component becomes weak, and as a result, the release agent component tends to ooze out and the charging uniformity of the toner is lowered. On the other hand, when the maximum endothermic peak exceeds 140 ° C., in the suspension polymerization method which is a preferred production method of the present invention, the solubility of the release agent in the polymerizable monomer becomes extremely poor. This is not preferable because the dispersibility of the resin is lowered.

  The endothermic peak top of the release agent is measured according to ASTM D 3417-99. The glass transition temperature (Tg) of the toner and the amorphous polyester is measured according to ASTM D 3418-99. For example, DSC-7 manufactured by PerkinElmer, DSC2920 manufactured by TA Instruments, and TA Instruments manufactured by TA Instruments. Q1000 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.

  DSC measured when the sample is heated to 200 ° C. once, the thermal history is removed, rapidly cooled, and then heated again at a temperature rising rate of 10 ° C./min. Use curves. The same measurement was performed in the examples described later.

  In the toner of the present invention, conventionally known azo polymerization initiators, peroxide polymerization initiators and the like can be used as the polymerization initiator. As the azo polymerization initiator, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile) ), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile and the like. Examples of peroxide polymerization initiators include t-butyl peroxyacetate, t- Butyl peroxylaurate, t-butyl peroxypivalate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl peroxyneodecanoate, t-hexyl per Oxyacetate, t-hexylperoxylaurate, t-hexylperoxypivalate, t-hexylperoxy-2-ethyl Xanoate, t-hexylperoxyisobutyrate, t-hexylperoxyneodecanoate, t-butylperoxybenzoate, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecano 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylper Oxyneodecanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylper Oxyisopropyl monocarbonate, t-butyl peroxyisopropyl monocar Nate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxy-m-toluoylbenzoate, Bis (t-butylperoxy) isophthalate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, 2,5-dimethyl-2,5-bis (m -Toluoyl peroxide) Peroxyesters such as hexane, diacyl peroxides such as benzoyl peroxide, lauroyl peroxide, isobutyryl peroxide, diisopropyl peroxydicarbonate, bis (4-t-butylcyclohexyl) peroxydicarbonate , G-se peroxydicarbonates such as c-butylperoxydicarbonate, 1,1-di-t-butylperoxycyclohexane, 1,1-di-t-hexylperoxycyclohexane, 1,1-di-t-butylpercarbonate Peroxyketals such as oxy-3,3,5-trimethylcyclohexane, 2,2-di-t-butylperoxybutane, di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, etc. Examples of the dialkyl peroxide include t-butyl peroxyallyl monocarbonate, and two or more of these initiators can be used as necessary.

  In the present invention, a crosslinking agent may be added, and a preferable addition amount is 0.001 part by mass or more and 10 parts by mass or less 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, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; for example, ethylene glycol diacrylate, ethylene Carboxylic acid esters having two double bonds such as glycol dimethacrylate, 1,3-butanediol dimethacrylate; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide, divinylsulfone; and three or more vinyl groups Are used alone or as a mixture.

In the method for producing the toner of the present invention by a polymerization method, generally a composition containing at least the above-mentioned polymerizable monomer, release agent, and crystalline polyester is appropriately added, and a homogenizer, ball mill, colloid mill, ultrasonic disperser is added. A polymerizable monomer composition uniformly dissolved or dispersed by a dispersing machine such as the like is suspended in an aqueous medium containing a dispersion stabilizer. At this time, it is easier to sharpen the particle size of the obtained toner particles by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size all at once. 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. Further, a polymerization initiator dissolved in a polymerizable monomer or a 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.

  When the toner of the present invention is produced by a polymerization method, 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 polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, carbonates such as calcium carbonate and magnesium carbonate, calcium metasuccinate, calcium sulfate and barium sulfate. Inorganic oxides such as inorganic salts, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina can be mentioned.

  These inorganic dispersants are preferably used in an amount of 0.2 parts by mass or more and 20 parts by mass or less alone or in combination of two or more with respect to 100 parts by mass of the polymerizable monomer. Furthermore, you may use together 0.001 mass part or more and 0.1 mass part or less surfactant.

  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 in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed under high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, water-soluble sodium chloride is by-produced. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and ultrafine toner is generated by emulsion polymerization. This is more convenient. The inorganic dispersant can be almost completely removed by dissolution with an acid or an alkali after completion of the polymerization.

  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.

  In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 ° C. or higher and 90 ° C. or lower. When polymerization is carried out in this temperature range, the release agent to be sealed inside the toner particles becomes easier to be introduced into the toner due to phase separation, and the encapsulation becomes more complete. Inferred.

  After the polymerization is completed, the polymerized toner particles are filtered, washed and dried by a known method, and if necessary, inorganic fine powder is mixed and adhered to the surface, whereby the toner of the present invention can be obtained. It is also possible to put a classification step into the manufacturing process and cut coarse powder and fine powder.

  Further, in the present invention, it is also a preferred form that the toner is added with an inorganic fine powder having a number average primary particle size of 4 nm or more and 80 nm or less, more preferably 6 nm or more and 40 nm or less as a fluidizing agent. The inorganic fine powder is added to improve the fluidity of the toner and to make the charge of the toner particles uniform. However, adjustment of the charge amount of the toner, improvement of environmental stability, etc. by treatment such as hydrophobizing the inorganic fine powder. It is also a preferable form to provide the function.

  When the number average primary particle size of the inorganic fine powder is larger than 80 nm, or when the inorganic fine powder of 80 nm or less is not added, good toner fluidity cannot be obtained, and charging to the toner particles can be imparted. It tends to be non-uniform, resulting in an increase in fog and a decrease in image density. On the other hand, when the number average primary particle size of the inorganic fine powder is smaller than 4 nm, the fineness of the inorganic fine powder becomes stronger, and the particle size distribution has strong agglomeration that is difficult to break even by crushing treatment instead of the primary particles. This is not preferable because it tends to behave as a wide aggregate, and image defects are likely to occur due to development of the aggregate, damage to the image carrier or magnetic toner carrier, and the like.

  In the present invention, the number average primary particle size of the inorganic fine powder is measured by a photograph of the toner magnified by a scanning electron microscope, and further by an elemental analysis means such as XMA attached to the scanning electron microscope. Measure 100 or more primary particles of inorganic fine powder adhering to or leaving the toner surface while contrasting the photograph of the toner mapped with the elements contained in the body. It can be measured by determining the diameter and number average primary particle size.

Silica, titanium oxide, alumina, etc. can be used as the inorganic fine powder used in the present invention. As the silicate fine powder, for example, both a so-called dry method produced by vapor phase oxidation of silicon halide or dry silica called fumed silica, and so-called wet silica produced from water glass can be used. However, dry silica having less silanol groups on the surface and inside the silica fine powder and less production residue such as Na ₂ O and SO ₃ ²⁻ is more preferable. In dry silica, it is also possible to obtain composite fine powders of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride and titanium chloride together with silicon halogen compounds in the production process. Is also included.

  The addition amount of the inorganic fine powder having a number average primary particle size of 4 nm or more and 80 nm or less is preferably 0.1% by mass or more and 3.0% by mass or less with respect to the toner particles, and the addition amount is less than 0.1% by mass. However, the effect is not sufficient, and if it is 3.0% by mass or more, the fixing property is deteriorated. The amount of the inorganic fine powder having a number average primary particle size of 4 nm to 80 nm is in the range of 0.1% by mass to 3.0% by mass with respect to the toner particles. It can be used without inhibiting the effect.

  Further, the content of the inorganic fine powder can be quantified using a calibration curve prepared from a standard sample using fluorescent X-ray analysis.

  In the present invention, the inorganic fine powder is preferably a hydrophobized product because environmental stability is improved. When the inorganic fine powder added to the toner absorbs moisture, the charge amount of the toner particles is remarkably reduced, the charge amount is likely to be non-uniform, and toner scattering is likely to occur.

  As the treating agent used for the hydrophobizing treatment, treating agents such as silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, and organic titanium compounds may be used alone or You may process together.

  Among them, those treated with silicone oil are preferable, and more preferably, the inorganic particles are hydrophobized with a silane compound, or are treated with silicone oil and then treated with silicone oil, even in a high humidity environment. In order to prevent toner scattering.

  As a method for treating such inorganic fine powder, for example, as a first-stage reaction, a silanization reaction is performed with a silane compound, silanol groups are eliminated by chemical bonds, and then a hydrophobic reaction is performed on the surface with silicone oil as a second-stage reaction. The thin film can be formed.

The silicone oil has a viscosity 10 mm ² / s or more 200,000 mm ² / s or less at 25 ° C., more 3,000 mm ² / s or more 80, 000 mm ² / s or less being preferred. Is less than the viscosity 10 mm ² / s at 25 ° C. of the silicone oil, the stability of the inorganic fine powder is not, by thermal and mechanical stresses, tend to image quality deteriorates, if it exceeds 200,000 mm ² / s is Uniform treatment tends to be difficult.

  As the silicone oil used, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are particularly preferable.

  As a method for treating the inorganic fine powder with silicone oil, for example, the inorganic fine powder treated with the silane compound and the silicone oil may be directly mixed using a mixer such as a Henschel mixer, or the inorganic fine powder may be mixed with the inorganic fine powder. A method of spraying silicone oil may be used. Alternatively, after dissolving or dispersing silicone oil in an appropriate solvent, inorganic fine powder may be added and mixed to remove the solvent. A method using a sprayer is more preferable in that the formation of inorganic fine powder aggregates is relatively small.

  The treatment amount of the silicone oil is 1 to 40 parts by mass, preferably 3 to 35 parts by mass with respect to 100 parts by mass of the inorganic fine powder. If the amount of silicone oil is too small, good hydrophobicity cannot be obtained, and if it is too large, problems such as fogging tend to occur.

The inorganic fine powder used in the present invention preferably has a specific surface area measured by the BET method by nitrogen adsorption in the range of 20 m ² / g or more and 350 m ² / g or less in order to impart good fluidity to the toner. More preferably, those of 25 m ² / g or more and 300 m ² / g or less are even better.

  In accordance with the BET method, the specific surface area is obtained by adsorbing nitrogen gas to the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) and calculating the specific surface area using the BET multipoint method.

  The toner used in the present invention may further contain other additives such as Teflon (registered trademark) powder, zinc stearate powder, polyvinylidene fluoride powder, or cerium oxide within a range that does not substantially adversely affect the toner. Abrasives such as powders, silicon carbide powders, strontium titanate powders, fluidity-imparting agents such as titanium oxide powders and aluminum oxide powders, anti-caking agents, and organic fine particles and inorganic fine particles of opposite polarity are improved in developability. A small amount can be used as an agent. These additives can also be used after hydrophobizing the surface.

  An example of an image forming apparatus that can suitably use the toner of the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus, and FIG. 2 is a schematic cross-sectional view showing the configuration of the developing device portion of FIG. The image forming apparatus of FIG. 1 is an electrophotographic apparatus adopting a developing method using a one-component magnetic toner, and is a drum-shaped photosensitive member (photosensitive drum) 100 as an image carrier and charging means disposed around the drum-shaped photosensitive member. A developing unit 140 as a developing unit, a transfer charging roller 114 as a transfer unit, a cleaner 116 as a cleaning unit, a paper feed roller 124, and the like.

  First, the photoreceptor 100 is charged to, for example, −600 V by the primary charging roller 117. (Applied voltage is AC voltage -1.7 kVpp, DC voltage -620 Vdc) Then, the photosensitive member 100 is exposed by irradiating the laser beam 123 emitted from the laser generator 121 and electrostatic in accordance with the image to be formed. A latent image is formed on the photoreceptor 100.

  The electrostatic latent image formed on the photoreceptor 100 is developed with the one-component magnetic toner as the toner of the present invention by the developing device 140, and becomes a toner image. The formed toner image on the photoconductor 100 is transferred onto the transfer material by the transfer roller 114 in contact with the photoconductor via the transfer material. The transfer material on which the toner image is placed is conveyed to a fixing device 126 as fixing means by the conveyance belt 125 or the like and fixed on the transfer material. Further, the toner that is not transferred onto the transfer material and is partially left on the photosensitive member is cleaned by the cleaner 116.

  As shown in FIG. 2, the developing device 140 has a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel, which is disposed in the vicinity of the photosensitive member 100. The gap between the photosensitive member 100 and the developing sleeve 102 is maintained at a predetermined distance (for example, about 270 μm) by a sleeve / photosensitive member gap holding member (not shown). A magnet roller 104 is fixed and arranged concentrically with the developing sleeve 102 in the developing sleeve. However, the developing sleeve 102 is rotatable. The magnet roller 104 has complicated magnetic poles as shown in the figure, and S1 influences development, N1 restricts the amount of toner coating, S2 takes in / conveys toner, and N2 affects toner blowout prevention. The toner is applied onto the developing sleeve 102 by the toner application roller 141, and is adhered and conveyed. As a member that regulates the amount of toner conveyed, the elastic blade 103 is disposed so as to contact the developing sleeve 102, and the amount of toner conveyed to the developing region is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. The In the developing region which is the closest portion between the surface of the photoconductor 100 and the surface of the developing sleeve 102, a DC and AC developing bias is applied between the photoconductor 100 and the developing sleeve 102, and the toner on the developing sleeve is electrostatic latent image. In response to this, it flies over the photoconductor 100 and becomes a visible image.

  Next, it describes regarding the measuring method of each physical property which concerns on this invention.

Average Circularity The average circularity and mode circularity of the toner are measured using a flow type particle image measuring device “FPIA-2100 type” (manufactured by Sysmex Corporation), and calculated using the following equations.

  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).

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

また、モード円形度は円形度頻度分布において、もっとも頻度が高い円形度の値である。 The average circularity C, which means the average value of the circularity frequency distribution, is calculated from the following equation, where ci is the circularity (center value) at the dividing point i of the particle size distribution and m is the number of measured particles.

The mode circularity is a circularity value having the highest frequency in the circularity frequency distribution.

  In addition, “FPIA-2100”, which is a measuring apparatus used in the present invention, calculates the circularity of each particle, and then calculates the average circularity and the circularity standard deviation. A degree of 0.4 or more and 1.0 or less is divided into equally divided classes every 0.01, and the average circularity and circularity standard deviation are calculated using the center value of the dividing points and the number of measured particles.

  The measurement procedure is as follows. A dispersion is prepared by dispersing about 5 mg of magnetic toner in 10 ml of water in which about 0.1 mg of a surfactant is dissolved, and the dispersion is irradiated with ultrasonic waves (20 kHz, 50 W) for 5 minutes. The average circularity of a particle group having a circle-equivalent diameter of 3 μm or more is determined by measuring with the above apparatus at 5000 / μl or more and 20,000 / μl or less.

  In this measurement, the reason why the circularity is measured only for the particle group having an equivalent circle diameter of 3 μm or more is that the particle group of the external additive existing independently of the toner particles in the particle group having an equivalent circle diameter of less than 3 μm. This is because the circularity of the toner particles can be obtained more accurately. In order to suppress variation in circularity, the installation environment of the apparatus is controlled at 23 ° C. ± 0.5 ° C. for a certain period of time so that the in-machine temperature of the flow type particle image analyzer FPIA-2100 is 26 ° C. or higher and 27 ° C. or lower. In other words, the autofocus is preferably performed every 2 hours using 2 μm latex particles.

  Furthermore, “FPIA-2100”, which is a measuring apparatus used in the present invention, improves the magnification of the processed particle image as compared with “FPIA-1000” conventionally used for calculating the shape of the toner. Further, the accuracy of toner shape measurement has been improved by improving the processing resolution of the captured image (256 × 256 → 512 × 512), thereby achieving more reliable capture of fine particles. Therefore, when it is necessary to measure the shape more accurately as in the present invention, the FPIA 2100 that can obtain information on the shape more accurately is more useful.

(2) Measurement of weight average particle diameter and number% of low specific gravity particles of number average particle diameter of 4 μm or less The weight average particle diameter (D4) of the magnetic toner of the present invention is a Coulter Counter TA-II type or Coulter Multisizer (Coulter Corporation). In the present invention, a Coulter Multisizer (manufactured by Coulter Inc.) is used, and an interface (manufactured by Nikkiki) that outputs a number distribution and volume distribution and a PC9801 personal computer (manufactured by NEC). And 1% NaCl aqueous solution is prepared using 1st grade sodium chloride as the electrolytic solution. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used.

  As a measurement method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolyte solution in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the number distribution of toner particles of 2 μm or more is measured using the 100 μm aperture as the aperture by the Coulter Multisizer. calculate. Based on this, the weight average particle diameter is determined.

  The number% of 4 μm or less of the low specific gravity particles of the present invention is also measured by the same measuring method as described above, the number of toner particles of 4 μm or less is measured to calculate the number distribution, and the number% is calculated.

(Example)
Hereinafter, the present invention will be specifically described with reference to production examples and examples, but this does not limit the present invention in any way. In addition, the number of parts or% used in an Example shows a mass part or mass%.

<1> Manufacture of magnetic body (manufacture of surface-treated magnetic body 1)
An aqueous solution containing ferrous hydroxide was prepared by mixing 1.0 to 1.1 equivalents of a caustic soda solution with respect to iron ions in the ferrous sulfate aqueous solution. While maintaining the pH of the aqueous solution at 10, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry for generating seed crystals.
Subsequently, after adding ferrous sulfate aqueous solution to this slurry liquid so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda), the slurry liquid is maintained at pH 9, and air is supplied. The oxidation reaction was advanced while blowing to obtain a slurry liquid containing magnetic iron oxide. After filtration and washing, the water-containing slurry was once taken out. Next, the water-containing sample was re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersed liquid was adjusted to about 4.1, and the silane coupling agent (n-C ₁₀ was thoroughly stirred. 2.0 parts of H ₂₁ Si (OCH ₃ ) ₃ ) was added to 100 parts of magnetic iron oxide for hydrolysis. At that time, the pH of the dispersion was set to about 10, a condensation reaction was performed, and a coupling treatment was performed. The produced hydrophobic magnetic powder was washed, filtered and dried by a conventional method, and the resulting particles were sufficiently crushed to obtain a spherical surface-treated magnetic material 1 having an average particle size of 0.18 μm.

(Manufacture of surface-treated magnetic body 2)
In the production of the surface-treated magnetic body 1, a surface-treated magnetic body 2 was obtained in the same manner except that the amount of the coupling treatment agent was 1.3 parts by mass.

(Manufacture of surface-treated magnetic body 3)
In the production of the surface-treated magnetic body 1, a surface-treated magnetic body 3 was obtained in the same manner except that the amount of the coupling treatment agent was 0.6 parts by mass.

<2> Production of low specific gravity particles (production of low specific gravity particles 1)
427 parts by mass of 0.1 M Na ₃ PO ₄ aqueous solution is added to 720 parts by mass of ion-exchanged water and heated to 60 ° C., and then 64.0 parts by mass of 1.0 M CaCl ₂ aqueous solution is added to add a dispersion stabilizer. An aqueous medium containing was obtained.
Styrene 79.0 parts by mass n-butyl acrylate 21.0 parts by mass Divinylbenzene 0.48 parts by mass Negative charge control agent (monoazo dye-based Fe compound) 1.5 parts by mass Amorphous polyester 1 3.0 parts by mass

  The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.). This monomer composition was heated to 60 ° C., and 15 parts by mass of paraffin wax (melting point: 78 ° C.) was added and dissolved therein. To this, a polymerization initiator 2,2′-azobis- (2,4-dimethylvalero) was added. (Nitrile) 7 parts by mass was dissolved.

The polymerizable monomer composition was charged into the aqueous medium, and granulated by stirring at 15000 rpm for 10 minutes in Claremix (manufactured by M Technique) in an N ₂ atmosphere at 60 ° C. The mixture was then reacted at 70 ° C. for 5 hours while stirring with a paddle stirring blade, and then stirred for 2 hours. After completion of the reaction, the suspension is cooled, acid-washed with hydrochloric acid, filtered, washed with water and dried, and the weight-average particle size is 7.56 μm, and the number percent of 4 μm or less is 13.40 number-% low specific gravity particles. 1 was obtained.

(Production of low specific gravity particles 2)
In the production of the low specific gravity particles 1, 386 parts by weight of 0.1 M Na ₃ PO ₄ aqueous solution was added and heated to 60 ° C., and then 57.9 parts by weight of 1.0 M CaCl ₂ aqueous solution was added to add a dispersion stabilizer. A low specific gravity particle 2 having a weight average particle diameter of 8.88 μm and a number% of 4 μm or less of 11.22 number% was obtained in the same manner except that an aqueous medium containing the same was obtained.

(Production of low specific gravity particles 3)
In the production of the low specific gravity particles 1, 443 parts by mass of 0.1 M Na ₃ PO ₄ aqueous solution was added and heated to 60 ° C., and then 66.5 parts by mass of 1.0 M CaCl ₂ aqueous solution was added to add a dispersion stabilizer. A low specific gravity particle 3 having a weight average particle diameter of 6.94 μm and a number% of 4 μm or less of 36.21 number% was obtained in the same manner except that an aqueous medium containing the same was obtained.

(Production of low specific gravity particles 4)
In the production of the low specific gravity particles 1, 378 parts by mass of 0.1 M Na ₃ PO ₄ aqueous solution was added and heated to 60 ° C., and then 56.6 parts by mass of 1.0 M CaCl ₂ aqueous solution was added to add a dispersion stabilizer. A low specific gravity particle 4 having a weight average particle diameter of 8.9 μm and a number% of 4 μm or less of 9.37 number% was obtained in the same manner except that an aqueous medium containing the same was obtained.

(Production of low specific gravity particles 5)
Styrene / n-butyl acrylate copolymer (mass ratio 79/21) 100 parts by weight Paraffin wax (melting point 78 ° C.) 15.0 parts by weight Negative charge control agent (monoazo dye-based Fe compound) 1.5 parts by weight

  The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 120 ° C., the cooled kneaded product is coarsely pulverized with a hammer mill, the coarsely pulverized product is finely pulverized with a jet mill, and then a hybridizer is used. , 3 treatments at 6000 rpm for 3 times, and the resulting finely pulverized product was subjected to air classification to obtain low specific gravity particles 5 having a weight average particle size of 7.34 μm and a number percentage of 4 μm or less of 66.37%. .

<3> Manufacture of magnetic toner (manufacture of magnetic toner 1)
Into 720 parts by mass of ion-exchanged water, 410 parts by mass of a 0.1M Na ₃ PO ₄ aqueous solution was added and heated to 60 ° C., and then 61.6 parts by mass of a 1.0M CaCl ₂ aqueous solution was added to add a dispersion stabilizer. An aqueous medium containing was obtained.
Styrene 79.0 parts by mass n-butyl acrylate 21.0 parts by mass Surface-treated magnetic material 1 90.0 parts by mass Divinylbenzene 0.48 parts by mass Negative charge control agent (monoazo dye-based Fe compound) 1.5 parts by mass Amorphous Polyester (number average molecular weight 10,000, acid value 10mgKOH / g)
3.0 parts by mass

  The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.). This monomer composition was heated to 60 ° C., and 15 parts by mass of paraffin wax (melting point: 78 ° C.) was added and dissolved therein. To this, a polymerization initiator 2,2′-azobis- (2,4-dimethylvalero) was added. (Nitrile) 7 parts by mass was dissolved.

The polymerizable monomer composition was charged into the aqueous medium, and granulated by stirring at 15000 rpm for 10 minutes in Claremix (manufactured by M Technique) in an N ₂ atmosphere at 60 ° C. The mixture was then reacted at 70 ° C. for 5 hours while stirring with a paddle stirring blade, and then stirred for 2 hours. After completion of the reaction, the suspension was cooled, acid washed with hydrochloric acid, filtered, washed with water and dried to obtain magnetic toner particles 1. 100 parts by mass of the magnetic toner particles 1 and 0.004 parts by mass of the low specific gravity particles 1 are mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.), and a magnetic toner having a weight average particle diameter of 8.02 μm. 1 was obtained. Table 1 shows the physical properties of the magnetic toner 1 obtained.

(Manufacture of magnetic toner 2)
In the production of the magnetic toner 1, after obtaining the magnetic toner particles 2 in the same manner until the magnetic toner particles are obtained, the magnetic toner particles 2 are 100 parts by mass, the low specific gravity particles 1 are 0.004 parts by mass, the average primary particle diameter of 9nm of fine powder treated with silicone oil after processing with hexamethyldisilazane, BET value after processing 200 meters 2 / ^g of hydrophobic silica fine powder 0.6 parts of a Henschel mixer (Mitsui The magnetic toner 2 having a weight average particle diameter of 7.9 μm was obtained by mixing with Miike Chemical Industries, Ltd. Table 2 shows the physical properties of the magnetic toner 2 obtained.

(Manufacture of magnetic toner 3)
A magnetic toner 3 having a weight average particle diameter of 8.10 μm was obtained in the same manner as the magnetic toner 1 except that the surface-treated magnetic body 2 was used instead of the surface-treated magnetic body 1 in the production of the magnetic toner 1. Table 1 shows the physical properties of the magnetic toner 3.

(Manufacture of magnetic toner 4)
A magnetic toner 4 having a weight average particle size of 8.34 μm was obtained in the same manner as the magnetic toner 1 except that the surface-treated magnetic body 3 was used instead of the surface-treated magnetic body 1 in the production of the magnetic toner 1. Table 1 shows the physical properties of the magnetic toner 4.

(Manufacture of magnetic toner 5)
Styrene 65.0 parts by mass 2-ethylhexyl acrylate 35.0 parts by mass Divinylbenzene 0.5 parts by mass Surface treatment magnetic powder 1 90.0 parts by mass Amorphous polyester (number average molecular weight 10,000, acid value 10mgKOH / g)
3.0 parts by mass

  The above formulation was uniformly dispersed and mixed using an attritor. Thereafter, the mixture was heated to 60 ° C., 10 parts by mass of ester wax and 3.5 parts by mass of 2,2′-azobisisobutyronitrile were added and dissolved.

Next, after heating 650 parts by mass of an aqueous colloidal solution of 4% by mass of tricalcium phosphate to 60 ° C., 222.3 parts by mass of the polymerizable monomer composition was added, and Claremix (M Technique) ) At room temperature at a rotational speed of 10,000 rpm for 3 minutes.
Thereafter, the reaction was carried out at 85 ° C. for 10 hours while continuing stirring in a nitrogen atmosphere, and then cooled to room temperature to obtain a magnetic toner particle dispersion.

Next, separately, 13.0 parts by mass of styrene, 7.0 parts by mass of 2-ethylhexyl acrylate, 0.4 parts by mass of 2,2′-azobisisobutyronitrile, 0.2 parts by mass of divinylbenzene, sodium lauryl sulfate 0.1 part by mass was added to 20 parts by mass of water and dispersed using an ultrasonic homogenizer.
This was dropped into the magnetic toner particle dispersion to swell the particles. Then, it stirred in nitrogen atmosphere and reacted for 10 hours at 85 degreeC. Thereafter, the suspension was cooled, washed, filtered and dried in the same manner as magnetic toner 1, and then subjected to air classification to obtain magnetic toner particles 5.

  100 parts by mass of the magnetic toner particles 5 and 0.004 parts by mass of the low specific gravity particles 1 are mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.), and a magnetic toner having a weight average particle size of 8.21 μm. 5 was obtained. Table 1 shows the physical properties of the magnetic toner 5 obtained.

(Manufacture of magnetic toner 6)
In the production of magnetic toner 1, 435 parts by mass of 0.1M Na ₃ PO ₄ aqueous solution was added to 720 parts by mass of ion-exchanged water, heated to 60 ° C., and then 65.3 parts by mass of 1.0M CaCl ₂ aqueous solution was added. The weight average particle diameter was the same as in the production of the magnetic toner 1 except that an aqueous medium containing a dispersion stabilizer was obtained by addition and 0.001 part by mass of the low specific gravity particles 2 was used instead of the low specific gravity particles 1. Was 6.89 μm of magnetic toner 6. Table 1 shows the physical properties of the magnetic toner 6.

(Manufacture of magnetic toner 7)
In the production of the magnetic toner 1, 394 parts by weight of 0.1 M Na ₃ PO ₄ aqueous solution was added to 720 parts by weight of ion-exchanged water, heated to 60 ° C., and then 59.1 parts by weight of 1.0 M CaCl ₂ aqueous solution was added. The weight average particle diameter was the same as in the production of the magnetic toner 1 except that an aqueous medium containing a dispersion stabilizer was obtained by addition and that 0.4 parts by mass of the low specific gravity particles 3 were used instead of the low specific gravity particles 1. Was 8.51 μm of magnetic toner 7. Table 1 shows the physical properties of the magnetic toner 7.

(Manufacture of magnetic toner 8)
A magnetic toner 8 having a weight average particle diameter of 7.89 μm was obtained in the same manner as the magnetic toner 1 except that the low specific gravity particles 4 were used instead of the low specific gravity particles 1 in the production of the magnetic toner 1. Table 1 shows the physical properties of the magnetic toner 8.

(Manufacture of magnetic toner 9)
Styrene / n-butyl acrylate copolymer (mass ratio 79/21)
100 parts by mass / amorphous polyester (number average molecular weight 10,000, acid value 10 mgKOH / g)
3.0 parts by mass, divinylbenzene 0.5 parts by mass, surface-treated magnetic powder 1 90 parts by mass, negative charge control agent (monoazo dye-based Fe compound) 1.5 parts by mass
-Paraffin wax (melting point 78 ° C) 15.0 parts by mass

  The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 110 ° C., the cooled kneaded product is coarsely pulverized with a hammer mill, and the coarsely pulverized product is finely pulverized with a jet mill. The pulverized product was subjected to air classification to obtain magnetic toner particles 9. 100 parts by mass of the magnetic toner particles 9 and 0.004 parts by mass of the low specific gravity particles 5 are mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to obtain a magnetic toner having a weight average particle diameter of 7.94 μm. 9 was obtained. Table 1 shows the physical properties of the magnetic toner 9 obtained.

(Manufacture of magnetic toner 10)
In the production of the magnetic toner 1, a magnetic toner 10 having a weight average particle diameter of 8.55 μm was obtained in the same manner as in the production of the magnetic toner 1 except that 25 parts by mass of paraffin wax was used. Table 1 shows the physical properties of the magnetic toner 10.

(Manufacture of magnetic toner 11)
In the production of the magnetic toner 1, the magnetic toner 11 having a weight average particle diameter of 8.92 μm was obtained in the same manner as in the production of the magnetic toner 1 except that 48 parts by mass of the magnetic material was used. Table 1 shows the physical properties of the magnetic toner 11.

(Manufacture of magnetic toner 12)
In the production of the magnetic toner 1, the magnetic toner 12 having a weight average particle diameter of 7.34 μm was obtained in the same manner as in the production of the magnetic toner 1 except that 123 parts by mass of the magnetic material was used. Table 1 shows the physical properties of the magnetic toner 12.

(Manufacture of magnetic toner 13)
In the production of the magnetic toner 1, the magnetic toner 13 having a weight average particle diameter of 8.03 μm was obtained in the same manner as in the production of the magnetic toner 1 except that 0.0009 parts of the low specific gravity particles 1 were used. Table 1 shows the physical properties of the magnetic toner 13.

(Production of Magnetic Toner 14) In the production of the magnetic toner 1, the magnetic toner 14 having a weight average particle diameter of 7.87 μm was obtained in the same manner as the production of the magnetic toner 1 except that 0.12 parts of the low specific gravity particles 1 were used. Obtained. Table 1 shows the physical properties of the magnetic toner 14.

(Manufacture of magnetic toner 15)
A magnetic toner 15 having a weight average particle diameter of 7.89 μm was obtained in the same manner as in the production of the magnetic toner 1 except that 0.51 part of the low specific gravity particles 1 was used in the production of the magnetic toner 1. Table 1 shows the physical properties of the magnetic toner 15.
(Manufacture of magnetic toner 16)
A magnetic toner 16 having a weight average particle size of 8.04 μm was obtained in the same manner as the magnetic toner 1 except that the low specific gravity particles 2 were used instead of the low specific gravity particles 1 in the production of the magnetic toner 1. Table 1 shows the physical properties of the magnetic toner 16.
(Manufacture of magnetic toner 17)
A magnetic toner 17 having a weight average particle diameter of 8.05 μm was obtained in the same manner as the magnetic toner 1 except that the low specific gravity particles 3 were used instead of the low specific gravity particles 1 in the production of the magnetic toner 1. Table 1 shows the physical properties of the magnetic toner 17.

(Example 1)
<Image forming apparatus>
As the image forming apparatus, LBP-1760 (manufactured by Canon Inc.) was remodeled so that development and transfer bias could be changed. A DC voltage Vdc-450 V was used as the developing bias, 1550 Vpp was used as the overlapping alternating electric field, and a frequency of 2200 Hz.

Under this condition, the magnetic toner 1 is used, in a normal temperature and humidity environment (23 ° C., 60% RH), in a high temperature and high humidity environment (30 ° C., 80% RH), in a low temperature and low humidity environment (15 ° C., 10% RH). ), An image print test of 9000 sheets was performed in a continuous mode with an image consisting of only a vertical line with a printing rate of 4%, and the following evaluation items were evaluated in each environment. Note that Letter 75 g / m ² paper was used as the recording medium. As a result, even after the endurance of 9000 sheets, cleaning failure does not occur in a normal temperature and humidity environment, the solid image in a high temperature and high humidity environment is uniform, and fogging to a non-image area is not observed in all environments. A good image was obtained. Various evaluation results are shown in Table 2.

  The evaluation items described in Examples and Comparative Examples of the present invention and the criteria for the evaluation are described below.

<Image density>
The image density formed a solid image portion, and this solid image was measured with a Macbeth reflection densitometer (manufactured by Macbeth).

<Fog>
A white image was output and the fog on paper was measured and judged according to the following criteria. The fog was measured using REFLECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. The filter used was a green filter, and fog was calculated according to the following formula.
Fog (reflectance) (%) = reflectance of standard paper (%) − reflectance of sample non-image area (%)
The determination criteria for fogging are as follows.
A: Very good (less than 1.5%)
B: Good (1.5% or more, less than 2.5%)
C: Normal (2.5% or more and less than 4.0%)
D: Poor (4.0% or more)

<Image quality and solid uniformity>
The image quality criterion is a comprehensive evaluation of image uniformity and fine line reproducibility.
The uniformity of the image was judged by the uniformity of the solid black image and the halftone image.
A: A clear image excellent in fine line reproducibility and image uniformity.
B: A good image although the fine line reproducibility and image uniformity are slightly inferior.
C: Image quality with no practical problem.
D: An image unfavorable for practical use due to poor fine line reproducibility and image uniformity.
The following evaluation was used for the uniformity of the solid black image.
A: A solid black image with excellent uniformity and a clear image.
B: Good image although the uniformity of the solid black image is slightly inferior.
C: Image quality with no practical problem.
D: A solid black image having poor uniformity, which is not preferable for practical use.

<Cleanability>
For the evaluation of the cleaning property, the degree of contamination on the solid white image in a room temperature and humidity environment and the degree of contamination on the image carrier after the solid white image was produced were evaluated.
A: Clean image quality with no problem on the image and no stain on the image carrier.
B: A cleaning property in which an image having no problem on the image can be obtained, but the image carrier is slightly stained.
C: Cleanability with no problem in practical use.
D: Dirt is observed on the image and the image bearing member, and cleaning properties which are not preferable for practical use.

(Examples 2 to 13)
Using magnetic toners 2 to 5 and 10 to 17, image printing and durability tests were performed under the same conditions as in Example 1. As a result, even after the endurance of 9000 sheets, an image having no practical problem was obtained in evaluation under a normal temperature and normal humidity environment, a high temperature and high humidity environment, and a low temperature and low humidity environment. Table 2 shows the evaluation results in each environment.

(Comparative Example 1)
Using the magnetic toner 6, an image forming test and durability evaluation were performed under the same conditions as in Example 1. The results are shown in Table 2. As a result, fogging in a low temperature and low humidity environment was bad. This is probably because the charge distribution of the low specific gravity particles is sharp and the charge imparting ability to the toner tends to be too high, causing charge-up in a low temperature and low humidity environment and causing fogging.
(Comparative Example 2)
Using the magnetic toner 7, an image printing test and durability evaluation were performed under the same conditions as in Example 1. The results are shown in Table 2. As a result, the cleanability in a normal temperature and normal humidity environment was poor, and the density of a solid image was low in a high temperature and high humidity environment, resulting in poor uniformity. This is thought to be because the charge distribution of the low specific gravity particles becomes broad, so that the formation of the electrostatic aggregates as described above is suppressed, and as a result, the toner slips through and the cleaning property is impaired. In addition, it is considered that the charge distribution effect of the low specific gravity particles is broad, so that the charge imparting effect as described above is hardly obtained, and the uniformity of the solid image in a high temperature and high humidity environment is inferior.
(Comparative Example 3)
Using the magnetic toner 8, an image printing test and durability evaluation were performed under the same conditions as in Example 1. The results are shown in Table 2. As a result, fogging in a low temperature and low humidity environment was bad. This is probably because the charge distribution of the low specific gravity particles is sharp and the charge imparting ability to the toner tends to be too high, causing charge-up in a low temperature and low humidity environment and causing fogging.

(Comparative Example 4)
Using the magnetic toner 9, an image printing test and durability evaluation were performed under the same conditions as in Example 1. The results are shown in Table 2. As a result, the cleanability in a normal temperature and normal humidity environment was poor, and the solid image density in a high temperature and high humidity environment was a faint result. This is thought to be because the charge distribution of the low specific gravity particles becomes broad, so that the formation of the electrostatic aggregates as described above is suppressed, and as a result, the toner slips through and the cleaning property is impaired. In addition, it is considered that the charge distribution effect of the low specific gravity particles is broad, so that the charge imparting effect as described above is hardly obtained, and the uniformity of the solid image in a high temperature and high humidity environment is inferior.

1 is a diagram illustrating an outline of an example of an image forming apparatus to which a toner of the present invention is applied. FIG. 2 is a sectional view of a cartridge of the image forming apparatus shown in FIG. 1.

Explanation of symbols

100 photoconductor (image carrier, charged body)
102 Development sleeve (magnetic toner carrier)
103 Elastic blade
104 Magnet roller
114 Transfer charging roller (transfer member)
116 cleaner
117 Primary charging roller (contact charging member)
121 Laser light emitting device (latent image forming means, exposure device)
123 laser light
124 Feed roller
125 Conveyor belt (conveying member)
126 Fuser
140 Developer toner application roller (stirring member)

Claims (7)

In a magnetic toner containing at least a binder resin and a magnetic material, the average circularity of the magnetic toner is 0.950 or more, 1 g of the magnetic toner is dispersed in 50 ml of an electrolytic solution, and the magnetic toner is collected on the bottom of the container. The weight average particle diameter (D4e) of the particles present in the supernatant and the weight average particle diameter (D4t) of the magnetic toner are expressed by the following formula (1):
0.80 ≦ (D4t / D4e) ≦ 1.20 (1)
And a ratio of particles having a number average particle diameter of 4 μm or less in the supernatant liquid is 10.0% by number or more and 50.0% by number or less.   2. The magnetic toner according to claim 1, wherein the ratio of particles having a number average particle diameter of 4 μm or less in the supernatant liquid is 10.0% by number or more and 35.0% by number or less.   3. The magnetic toner according to claim 1, wherein a liberation rate of iron and an iron compound of the magnetic toner is 0.05% or more and 3.00% or less.   The magnetic toner according to claim 1, wherein an average circularity of the magnetic toner is 0.960 or more.   The magnetic toner according to claim 1, wherein the magnetic toner has a mode circularity of 0.98 or more.   6. The magnetic toner according to claim 1, wherein the magnetic toner contains a magnetic material in an amount of 50 parts by mass to 120 parts by mass with respect to 100 parts by mass of the binder resin. 7. The magnetic toner according to claim 1, wherein the weight of the particles present in the supernatant liquid is 0.001 part by mass or more and 0.5 part by mass or less with respect to 100 parts by mass of the magnetic toner.

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