JP2008015248A - Magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic toner which excels in low-temperature fixability, does not cause contamination of a fixing member even in long-term use, and ensures stable image density and few image defects regardless of the use environment. <P>SOLUTION: The magnetic toner contains a magnetic toner base containing at least a binder resin, a magnetic material and wax and inorganic fine powder, wherein (i) the magnetic toner has a weight average particle diameter of 4-9 μm, (ii) an amount of heat of fusion given by the wax in the magnetic toner is 8.0-20 J/g, (iii) in a wettability test of the magnetic toner with a methanol/water mixed solvent, when light transmittance at 780 nm wavelength is 50%, methanol concentration is 50-70 vol.%, and (iv) a coverage of the magnetic toner base with the inorganic fine powder is 0.4-0.9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Conventional electrophotography uses a photoconductive material, forms an electrical latent image on a photoreceptor by various means, and then develops the latent image with toner, and if necessary, a transfer material such as paper. A method is known in which after a toner image is transferred to the toner image, the toner image is fixed by heating, pressurizing, pressure heating or solvent vapor.

  In the method of developing the toner, a magnetic one-component developing system using a magnetic toner is preferably used because it does not require a carrier and is advantageous in downsizing the apparatus. In the magnetic toner used in the magnetic one-component development system, a considerable amount of fine powdery magnetic powder, wax, and the like are mixed and dispersed, and a part of the magnetic substance and wax is exposed on the surface of the toner particles. . For this reason, the presence state of a part of the magnetic substance and the wax greatly affects the properties such as the fluidity, environmental stability, and triboelectric chargeability of the toner.

  In the one-component development method, charging is applied by passing toner through a gap between the developing sleeve and the regulating member. At this time, a great stress is applied to the toner, so that a problem of so-called toner deterioration such as that the processing agent added externally to the toner base is buried in the toner, is detached from the toner, or the toner base is missing occurs. To do. When such deterioration progresses, when it is used repeatedly, the charge amount decreases, or the generated fine powder adheres to the developing sleeve or the regulating member, so that an image defect due to charging failure is likely to occur.

  In order to prevent such a phenomenon, attempts have been made to improve the durability of the magnetic toner by making the toner spherical and enhancing the surface smoothness (Patent Document 1). However, this method still has a problem in stabilizing charging characteristics due to environmental fluctuations.

  Various methods and apparatuses have been developed for the fixing process, but the most common method at present is a pressure heating method using a heated roller, film or belt. In the pressure heating method, a toner image surface of a fixing sheet is applied to a pressure member on the surface of a fixing member having a heating source whose surface is formed of a material releasable with respect to toner (silicone rubber or fluororesin). Fixing is carried out by passing the film while contacting under pressure. In this method, since the surface of the heating body and the toner image of the fixing sheet are in contact with each other under pressure, the thermal efficiency when fusing the toner image on the fixing sheet is extremely good, and the fixing is performed quickly. This is very effective in a high-speed electrophotographic copying machine. However, in the above method, since the surface of the heating body and the toner image are in pressure contact in a molten state, a part of the toner image may adhere to and transfer to the surface of the heating body, so that the next fixing sheet is soiled (so-called so-called). "Offset phenomenon"). For this reason, preventing the toner from adhering to the heating member is one of the essential conditions of the pressure heating method.

For this reason, for the purpose of preventing offset, a method of supplying oil such as silicone oil to the fixing member and covering the fixing member uniformly is also being studied.
Further, a large number of toner particles containing a release agent are disclosed (for example, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 7, Patent Document 8, and Patent Document 9). Patent Document 10 and Patent Document 11).
The release agent is used for improving the offset resistance at the time of fixing the toner at a low temperature or at a high temperature and for improving the fixability at the time of fixing at a low temperature. On the other hand, the developing property is reduced by reducing the blocking resistance of the toner, the developing property of the toner is lowered by the temperature rise in the machine, or the release agent oozes out on the toner particle surface when the toner is left for a long period of time. Or drop.

  In order to improve such a decrease in developability, it has also been studied to improve the developability by adding inorganic fine powder to the toner surface (Patent Document 12). However, by covering the toner base with the inorganic fine powder, the charging characteristics are improved, but the fixability is deteriorated, and there is still a problem regarding the compatibility between the charging characteristics and the fixability.

Japanese Patent Laid-Open No. 11-295925 Japanese Patent Laid-Open No. 3-50559 Japanese Patent Laid-Open No. 2-79860 JP-A-1-109359 Japanese Patent Laid-Open No. Sho 62-14166 JP-A-61-273554 JP 61-94062 A JP-A-61-138259 JP-A-60-252361 JP-A-60-252360 JP-A-60-217366 JP 2005-70758 A

  An object of the present invention is to provide a magnetic toner that solves the above-described problems. A specific object of the present invention is to provide a magnetic toner that has excellent low-temperature fixability and does not cause fouling of fixing members even during long-term use. Another object of the present invention is to provide a magnetic toner having a stable image density and less image defects regardless of the use environment.

  By optimizing the amount of heat of fusion of the wax contained in the magnetic toner and the presence of the wax and inorganic fine powder existing on the magnetic toner shape and the magnetic toner surface, the inventors The inventors have found that a magnetic toner having stable charging characteristics and excellent low-temperature fixability and member contamination can be obtained, and the present invention has been completed.

That is, the present invention is as follows.
(1) A magnetic toner comprising at least a binder resin, a magnetic substance, and a magnetic toner base containing a wax, and an inorganic fine powder,
(I) the magnetic toner has a weight average particle diameter of 4 to 9 μm;
(Ii) The heat of fusion exhibited by the wax in the magnetic toner is 8.0 J / g or more and 20 J / g or less,
(Iii) In the wettability test of the magnetic toner with respect to the methanol / water mixed solvent, the methanol concentration when the light transmittance at a wavelength of 780 nm is 50% is 50 to 70% by volume,
(Iv) A magnetic toner wherein the coverage of the inorganic fine powder on the magnetic toner base is 0.4 to 0.9.
(2) The magnetic toner according to (1), wherein the average circularity of particles having an equivalent circle diameter (number basis) of 2 μm or more is 0.94 or more.
(3) The wax is a hydrocarbon wax in which an endothermic main peak appears in the region of 50 to 90 ° C. in the obtained DSC curve when the magnetic toner containing the wax is measured with a differential scanning calorimeter. The magnetic toner according to (1) or (2), wherein
(4) In the wettability test of the magnetic toner base with respect to a methanol / water mixed solvent, the methanol concentration when the light transmittance at a wavelength of 780 nm is 50% is 30 to 50% by volume. The magnetic toner according to any one of (3).
(5) The binder resin contains at least a polyester resin, and the acid value of the polyester resin is 3 to 10 mgKOH / g, according to any one of (1) to (4), Magnetic toner.
(6) The magnetic toner matrix is a magnetic toner matrix obtained by polymerizing a polymerizable monomer composition in an aqueous medium, (1) to (5), Magnetic toner.

  According to the present invention, it is possible to provide a magnetic toner that can obtain a stable image density regardless of the use environment, and is excellent in low-temperature fixability and does not cause fusing member contamination.

Hereinafter, the present invention will be described in detail.
In the magnetic toner, as the amount of the wax contained as a release agent is increased, the sharp melt property and the releasability of the magnetic toner tend to improve, while the ratio of exposure to the surface increases. The charging characteristics tend to be reduced. In addition, the charging characteristics are improved by the inorganic fine powder added to the magnetic toner base. However, when the coverage on the surface of the magnetic toner base is increased, the fixability and the like tend to be adversely affected.

  In the present invention, by controlling the wettability and shape of the magnetic toner, it becomes possible to reduce the coverage of the inorganic fine powder on the magnetic toner base even when the amount of wax in the magnetic toner is large. It has been found that can be solved.

  In the present invention, it is necessary to add the wax so that the heat of fusion of the wax in the magnetic toner is 8 J / g or more, preferably 10 J / g or more and 20 J / g or less. The heat of fusion of the wax in the toner corresponds to the sharp melt property at the time of heat melting and can be used as an index for fixing property. This is because when the heat of fusion of the wax is 8 J / g or less, the effect of improving the fixing property and the effect of suppressing the contamination of the fixing member due to long-term use are insufficient. On the other hand, when the heat of fusion is 20 J / g or more, the influence of the wax on the charging characteristics increases, and the developability tends to deteriorate.

It is possible to improve fluidity and charging characteristics by adding inorganic fine powder to the magnetic toner base. However, if a large amount of inorganic fine powder is added to increase the surface coverage on the magnetic toner, fixing Sometimes the effect of the wax tends to be hindered when the magnetic toner melts. In particular, when a large amount of wax is present on the surface of the magnetic toner base, even if the inorganic fine powder is added, the inorganic fine powder is easily embedded in the toner surface by repeated use, and the durability of the magnetic toner is deteriorated.
The coverage ratio of the external additive on the surface of the magnetic toner was obtained by randomly sampling 100 toner images using Hitachi FE-SEM (S-800), and the image information was sent to an image analysis apparatus (manufactured by Nicole) via the interface ( Luzex 3). The obtained image information is binarized because the brightness of the toner particle surface and the external additive portion are different, and the area SG of the external additive portion and the area of the toner particle portion (including the area of the external additive portion) ST It calculates | requires by dividing and calculates by the following formula.

  In the present invention, the coverage of the inorganic fine powder on the magnetic toner surface is in the range of 0.4 to 0.9, preferably 0.45 to 0.8. If it becomes 0.4 or less, the fluidity of the magnetic toner is lowered, and a part of the inorganic fine powder is embedded in or released from the surface of the magnetic toner base material due to durable use to maintain stable charging characteristics. Becomes difficult. When the coverage is 0.9 or more, the seepage of wax on the surface of the magnetic toner base during fixing is inhibited and the releasability is lowered, so that the contamination of the member due to repeated use deteriorates and the low temperature fixability Will also be inhibited.

  In the present invention, in the wettability test of a magnetic toner with a methanol / water mixed solvent, the methanol concentration (TA) when the light transmittance at a wavelength of 780 nm is 50% of the initial value is 50 to 70% by volume, preferably 55 to 55%. 65% by volume. When TA is less than 50% by volume, the affinity with water becomes too high, and the charging characteristics in a high-humidity environment are likely to deteriorate.

  Conversely, when TA is greater than 70% by volume due to exposure or modification of the release agent on the magnetic toner surface, or when TA exceeds 90% by volume due to increased hydrophobicity and addition of a large amount of inorganic fine powder, Since the aqueous solution is too high, problems such as deterioration of the coating uniformity of the developing sleeve due to the charge-up phenomenon, thin image density, and toner adhesion to the charge imparting member and the photoreceptor occur particularly in a low humidity environment.

  In the present invention, in the wettability test of the magnetic toner base to a methanol / water mixed solvent, the methanol concentration (TB) when the light transmittance at a wavelength of 780 nm is 50% of the initial value is 30 to 50% by volume, preferably 35. It is preferable that it is -55 volume%. When the TB is less than 30% by volume, the charging characteristics of the magnetic toner base particles themselves are lowered, and when the coverage of the inorganic fine powder is in the above range, the image density is lowered in a high humidity environment. Is likely to occur.

  On the contrary, when TB is larger than 50 volume% due to the exposure of the wax to the magnetic toner surface, the environmental stability of the charging characteristics is reduced and the adhesion to the member is increased. Image defects are likely to occur due to adhesion to the surface.

  In the present invention, the average circularity of the magnetic toner is preferably 0.94 or more, more preferably 0.95 or more. When the value is lower than this range, a phenomenon such as a decrease in charge amount and contamination of the developing sleeve is caused during long-term repeated use, and problems such as a decrease in image density are likely to occur.

  The magnetic toner of the present invention has a weight average particle diameter of 4 to 9 μm. When the weight average particle diameter of the magnetic toner exceeds 9 μm, the reproducibility of the fine dot image is lowered. On the other hand, when the weight average particle size of the magnetic toner is smaller than 4 μm, external additives such as inorganic fine powder are likely to be deteriorated due to a decrease in fluidity, and problems such as fogging due to poor charging, low density, etc. Is likely to occur. In the toner of the present invention, effects such as improvement in charging stability and fluidity appear more remarkably in the case of a weight average particle size of 4 to 9 μm. ˜8.0 μm is preferred.

Next, a method for producing a magnetic toner in the present invention will be described.
The toner of the present invention can be produced by a pulverization method, but the pulverization method requires a multi-step process in order to satisfy the circularity and wettability of the present invention. This is disadvantageous.

On the other hand, in a method for producing a toner obtained by directly polymerizing a polymerizable monomer system (polymerizable monomer composition) in an aqueous medium (hereinafter referred to as polymerization method), the affinity with the aqueous medium From the viewpoint of the above, localization / separation is likely to occur between polar and nonpolar components, so that the circularity and wettability of the present invention can be obtained in one step, which is preferable.

  Conventionally known magnetic materials are used as the magnetic material used in the magnetic toner of the present invention. Examples of magnetic materials contained in the magnetic toner include iron oxides such as magnetite, maghemite, and ferrite, and iron oxides including other metal oxides; metals such as Fe, Co, Ni, or these metals and Al, Co, Cu , Pb, Mg, Ni, Sn, Zn, Sb, Be, Bi, Cd, Ca, Mn, alloys with metals such as Se, Ti, W, and V; and mixtures thereof.

Specifically, iron tetroxide (Fe ₃ O ₄ ), iron sesquioxide (γ-Fe ₂ O ₃ ), zinc iron oxide (ZnFe ₂ O ₄ ), iron yttrium oxide (Y ₃ Fe ₅ O ₁₂ ), Iron cadmium oxide (CdFe ₂ O ₄ ), iron gadolinium oxide (Gd ₃ Fe ₅ O ₁₂ ), copper iron oxide (CuFe ₂ O ₄ ), lead iron oxide (PbFe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄₎ ), Iron neodymium (NdFe ₂ O ₃ ), iron barium oxide (BaFe ₁₂ O ₁₉ ), iron magnesium oxide (MgFe ₂ O ₄ ), iron manganese oxide (MnFe ₂ O ₄ ), iron lanthanum oxide (LaFeO ₃ ), Examples thereof include iron powder (Fe), cobalt powder (Co), and nickel powder (Ni). In the present invention, at least magnetic iron oxide is contained as a magnetic material, and one or two or more other metals can be arbitrarily selected and used as necessary.

Such magnetic iron oxide preferably has a BET specific surface area of ² to 30 m ² / g, particularly preferably 3 to 28 m ² / g, and a Mohs hardness of 5 to 7 by a nitrogen adsorption method.
In addition, the shape of magnetic iron oxide includes octahedron, hexahedron, spherical shape, needle shape, scale shape, etc., but those having low anisotropy such as octahedron, hexahedron, spherical shape, and indefinite shape have a high image density. It is preferable in terms of enhancement. Such a shape can be confirmed by a scanning electron microscope (FE-SEM: scanning electron microscope S-4700 manufactured by Hitachi, Ltd.) or the like.
As the particle size of the magnetic iron oxide, the number average particle size is 0.1 to 0.3 μm and the particle size is 0.03 to 0.03 μm in the particle size measurement for particles having a particle size of 0.03 μm or more. The number of 0.1 μm particles is preferably 40% by number or less.

  When an image is obtained from a magnetic toner using magnetic iron oxide having a number average particle size of less than 0.1 μm, the color of the image shifts to red, and the blackness of the image is insufficient. It is generally not preferable, such as a tendency to feel a strong taste. Further, since the surface area of the magnetic iron oxide is increased, the dispersibility is lowered and the energy required for the production is increased, which is not efficient. Further, the effect of magnetic iron oxide as a colorant is weakened, and the image density may be insufficient, which is not preferable.

  On the other hand, if the number average particle diameter of the magnetic iron oxide exceeds 0.3 μm, the mass per particle increases, so the probability of exposure to the toner surface increases due to the difference in specific gravity with the binder resin during production, This is not preferable because the possibility of significant wear of the production apparatus increases and the sedimentation stability of the dispersion decreases.

  In addition, when the number of particles of 0.1 μm or less of the magnetic iron oxide in the magnetic toner exceeds 40% by number, the surface area of the magnetic iron oxide particles is increased and the dispersibility is lowered, and agglomerates are easily generated in the toner. Therefore, the number is preferably 40% by number or less because there is a high possibility that the charging characteristics of the magnetic toner will be impaired or the coloring power will be reduced. Furthermore, if it is 30% by number or less, the tendency becomes smaller, which is preferable.

Magnetic iron oxide having a particle size of less than 0.03 μm has a low probability of appearing on the surface of the magnetic toner particles because the stress applied during the production of the magnetic toner is small due to the small particle size. Further, even if it is exposed on the surface of the magnetic toner particles, it hardly acts as a leak site, so that there is substantially no problem. Therefore, in the present invention, attention is paid to magnetic iron oxide particles having a particle size of 0.03 μm or more, and the number% is defined.

  In the present invention, it is preferable that 10% by number or less of particles having a particle size of 0.3 μm or more in the magnetic iron oxide particles. If it exceeds 10% by number, the coloring power tends to decrease and the image density tends to decrease. In addition, even if the amount used is the same, the number is small, so that it can be present near the surface of the magnetic toner particles. It is not preferable that a uniform number is contained in the magnetic toner particles, which is stochastically difficult. In the magnetic iron oxide particles, the number of particles having a particle size of 0.3 μm or more is more preferably 5% by number or less.

The magnetic characteristics of these magnetic iron oxides when 79.58 kA / m (1 k Oersted) is applied are such that the coercive force is 1.5 kA / m to 12 kA / m, and the saturation magnetization is 30 to 120 Am ² / kg (preferably 40 to 80 Am). ² / kg) and a remanent magnetization of 1 to 10 Am ² / kg is preferable. The magnetic properties of the magnetic material can be measured using a vibration magnetometer such as VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.) under the conditions of 25 ° C. and an external magnetic field of 79.6 kA / m.

  The magnetic iron oxide particles used as the magnetic material in the magnetic toner of the present invention are preferably those subjected to a hydrophobic treatment. By adjusting this hydrophobization treatment, the existence state of magnetic iron oxide in the magnetic toner can be strictly controlled.

  There are two methods of treating the surface of magnetic iron oxide with a coupling agent or the like, ie, dry treatment and wet treatment. In the present invention, either method may be used, but the wet processing method in the aqueous medium is less likely to cause the coalescence of the magnetic iron oxide particles as compared with the dry processing in the gas phase, and the hydrophobic processing is performed. The repulsive action between the magnetic iron oxide particles works, and the magnetic iron oxide is preferable because it is surface-treated with the coupling agent in the state of almost primary particles.

  Examples of the coupling agent that can be used for the surface treatment of magnetic iron oxide in 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 following general formula (A).

  [Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents an alkyl group, a vinyl group, a methacryl group, a phenyl group, an amino group, an epoxy group, a mercapto group, or a derivative thereof. n shows the integer of 1-3. ]

  Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane. Dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.

  In particular, it is preferable to hydrophobize the magnetic iron oxide surface using an alkyltrialkoxysilane coupling agent represented by the following formula (B).

  [Wherein p represents an integer of 2 to 20, and q represents an integer of 1 to 3]

  If p in the above formula is smaller than 2, the hydrophobization treatment is easy, but it may be difficult to impart sufficient hydrophobicity. If p is larger than 20, the hydrophobicity will be sufficient. However, the coalescence of the magnetic iron oxide particles increases, and it may be difficult to sufficiently disperse the magnetic iron oxide in the magnetic toner. On the other hand, when q is larger than 3, the reactivity of the silane coupling agent is lowered, and the hydrophobicity may not be sufficiently performed.

  Therefore, 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). It is preferred to use a coupling agent. The treatment amount is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the magnetic iron oxide particles before the treatment.

  In the present invention, as a method for controlling the hydrophobicity of magnetic iron oxide, a method of treating with two or more types of silane coupling agents having different p in the above coupling agent can be mentioned. By appropriately adjusting the type of the coupling agent and the ratio of the treatment amount, it is possible to obtain magnetic iron oxide having a distribution in the degree of the hydrophobic treatment.

In order to treat the surface of the magnetic iron oxide with a coupling agent in an aqueous medium, a method of stirring an appropriate amount of magnetic iron oxide and the coupling agent in the aqueous medium can be mentioned.
An aqueous medium is a medium containing water as a main component. Specific examples of the aqueous medium include water itself, water added with a small amount of a surfactant, water added with a pH adjusting agent, and water added with an organic solvent. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid.

  Stirring is sufficiently performed by, for example, a mixer having a stirring blade (specifically, a high shear force mixing device such as an attritor or a TK homomixer) so that the magnetic iron oxide particles become primary particles in the aqueous medium. Good to do.

  Since the surface of the magnetic iron oxide obtained in this way is uniformly hydrophobized, the dispersibility in the polymerizable monomer composition is very good, and a magnetic toner base with a uniform content of magnetic iron oxide is obtained. Be able to get.

The magnetic iron oxide used in the toner of the present invention is produced, for example, by the following method.
An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide in an amount equivalent to or higher than the iron component to an aqueous ferrous salt solution such as an aqueous ferrous sulfate solution. Air was blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 to 10), the ferrous hydroxide was oxidized while heating the aqueous solution to 70 ° C. or higher, and the core of the magnetic iron oxide particles First, a seed crystal is formed.

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 10, the reaction of ferrous hydroxide proceeds while blowing air to grow magnetic iron oxide particles with the seed crystal as the core. 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. At the end of the oxidation reaction, the pH of the solution is adjusted and sufficiently stirred so that the magnetic iron oxide becomes primary particles. A coupling agent is added and mixed and stirred sufficiently. After stirring, the mixture is filtered, dried, and lightly crushed to obtain a hydrophobized magnetic iron oxide. Alternatively, after the oxidation reaction is completed, the iron oxide obtained by washing and filtering is redispersed in another aqueous medium without drying, and then the pH of the redispersion is adjusted and the silane is stirred well. A coupling agent may be added to perform the coupling treatment.

  In any case, it is preferable that the untreated magnetic iron oxide formed in the aqueous solution is hydrophobized in the state of the water-containing slurry before passing through the drying step. This is because if untreated magnetic iron oxide is dried as it is, coalescence between particles cannot be avoided. Even if wet-hydrophobic treatment is performed on such agglomerated powder, uniform hydrophobization treatment is possible. Because it is difficult.

  The ferrous salt used in the ferrous salt aqueous solution in the production of magnetic iron oxide particles is generally iron sulfate produced as a by-product in the production of sulfuric acid titanium, and iron sulfate produced as a by-product when the steel sheet is cleaned. In addition to ferrous sulfate, iron chloride or the like can be used.

  In the method for producing magnetic iron oxide by the aqueous solution method, a ferrous sulfate aqueous solution having an iron concentration of 0.5 to 2 mol / liter is generally used from the viewpoint of preventing increase in viscosity during reaction and solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the product particle size. In the reaction, the larger the amount of air and the lower the reaction temperature, the finer the particle size.

In the present invention, it is preferable to use the hydrophobic magnetic iron oxide thus produced.
The magnetic iron oxide used in the toner of the present invention is preferably used in an amount of 10 to 200 parts by weight, more preferably 20 to 180 parts by weight, and still more preferably 40 to 160 parts by weight with respect to 100 parts by weight of the binder resin. . When the blending amount of the magnetic iron oxide is less than 10 parts by mass, the coloring power of the developer is poor, and it is difficult to suppress fogging. On the other hand, when the blending amount of the magnetic iron oxide exceeds 200 parts by mass, Not only does the retention by magnetic force increase and the developability deteriorates, and it becomes difficult to uniformly disperse the magnetic iron oxide in the individual toner bases, but also the fixability of the magnetic toner may deteriorate.

Moreover, the following are mentioned as a polymerizable monomer which is used for this invention and comprises the polymerizable monomer type | system | group used as binder resin.
Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, and p-ethylstyrene; methyl acrylate, ethyl acrylate, Acrylic esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate Class: Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenolic methacrylate , Dimethylaminoethyl methacrylate, such as methacrylic acid esters of diethylaminoethyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide.

  These polymerizable monomers can be used alone or in combination. Among the polymerizable monomers described above, styrene or a styrene derivative is preferably used alone or mixed with other polymerizable monomers from the viewpoint of the development characteristics and durability of the magnetic toner.

Examples of the release agent that can be used in the magnetic toner of the present invention include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, and paraffin wax; aliphatic hydrocarbon waxes such as oxidized polyethylene wax. Oxides or block copolymers thereof; waxes based on fatty acid esters such as carnauba wax, sazol wax and montanic acid ester wax; part or all of fatty acid esters such as deoxidized carnauba wax Deoxidized; saturated linear fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brandic acid, eleostearic acid, and valinalic acid; stearyl alcohol, aralkyl alcohol, behenyl alcohol, and carnauvir Alcohol, seri Saturated alcohols such as alcohol and melyl alcohol; polyhydric alcohols such as sorbitol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis Saturated fatty acid bisamides such as lauric acid amide and hexamethylene bis stearic acid amide; ethylene bis oleic acid amide, hexamethylene bis oleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid Unsaturated fatty acid amides such as amides; Aromatic bisamides such as m-xylene bis-stearic acid amide and N, N′-distearylisophthalic acid amide; Calcium stearate, calcium furate, zinc stearate, magnesium stearate Aliphatic metal salts such as those commonly referred to as metal soaps; waxes grafted with aliphatic hydrocarbon waxes using vinyl monomers such as styrene and acrylic acid; fatty acids such as behenic acid monoglycerides And a partially esterified product of polyhydric alcohol; a methyl ester compound having a hydroxyl group obtained by hydrogenation of vegetable oil or the like; a long-chain alkyl alcohol or a long-chain alkyl carboxylic acid having 12 or more carbon atoms;

The magnetic toner of the present invention contains a wax as a release agent.
Examples of the wax as a release agent that is particularly preferably used in the present invention include aliphatic hydrocarbon waxes. As such an aliphatic hydrocarbon wax, for example, a low molecular weight alkylene polymer obtained by radical polymerization of alkylene at a high pressure or a Ziegler catalyst at a low pressure; a high molecular weight alkylene polymer is thermally decomposed. Alkylene polymers obtained; synthetic hydrocarbon waxes obtained from the distillation residue of hydrocarbons obtained by the age method from synthesis gas containing carbon monoxide and hydrogen, and synthetic hydrocarbon waxes obtained by hydrogenating them; these aliphatics And hydrocarbon waxes separated by press sweating, solvent method, vacuum distillation and fractional crystallization.

  Examples of the hydrocarbon as the base of the aliphatic hydrocarbon wax include those synthesized by the reaction of carbon monoxide and hydrogen using a metal oxide catalyst (often a multi-component system of two or more types) (for example, Hydrocarbon compounds synthesized by the Gintor method and Hydrocol method (using a fluidized catalyst bed); Up to several hundred carbon atoms can be obtained by the Age method (using an identified catalyst bed) in which many waxy hydrocarbons are obtained Hydrocarbons; hydrocarbons obtained by polymerizing alkylene such as ethylene with a Ziegler catalyst. Among such hydrocarbons, in the present invention, it is preferable that the hydrocarbon is a linear hydrocarbon having a small number of branches and a long saturation, and particularly a hydrocarbon synthesized by a method not based on polymerization of alkylene has a molecular weight distribution. Is also preferable.

  In the present invention, the wax as the release agent is used in the magnetic toner so that an endothermic main peak appears in the region of 50 to 90 ° C. in the obtained DSC curve when the magnetic toner containing the wax is measured with a differential scanning calorimeter. It is preferable that the toner be contained in terms of low-temperature fixability and high-temperature offset resistance of the toner. When the endothermic main peak is present in a region of less than 50 ° C. in DSC measurement, the wax component tends to ooze out and storage stability is deteriorated. On the other hand, if the endothermic main peak is present in a region exceeding 90 ° C., the fixing temperature becomes high and low temperature offset tends to occur, which is not preferable. Further, when a magnetic toner is directly obtained in an aqueous medium by a polymerization method, if the temperature of the endothermic region is high, adding a large amount of wax causes problems such as precipitation of a wax component during granulation, which is not preferable.

  The endothermic peak temperature can be measured according to ASTM D3418-82 using a highly accurate internal heat input compensation type differential scanning calorimeter, for example, DSC-7 manufactured by PerkinElmer, Inc. The appearing temperature can be adjusted by using a wax whose melting point, glass transition point, polymerization degree and the like are appropriately adjusted. The DSC-7 is applied to the measurement of the temperature indicating the thermal properties of the magnetic toner particles and the magnetic toner particle materials such as the glass transition point of the binder resin, the softening point, and the melting point of the wax in addition to the peak temperature. can do.

  Specific examples of the wax that can be used as a release agent in the present invention include Biscol (registered trademark) 330-P, 550-P, 660-P, TS-200 (Sanyo Chemical Industries), high wax 400P, 200P. , 100P, 410P, 420P, 320P, 220P, 210P, 110P (Mitsui Chemicals), Sazol H1, H2, C80, C105, C77 (Schumann Sazol), HNP-1, HNP-3, HNP-9, HNP -10, HNP-11, HNP-12 (Nippon Seiwa Co., Ltd.), Unilin (registered trademark) 350, 425, 550, 700, Unicid (registered trademark), Unicid (registered trademark) 350, 425, 550, 700 ( Toyo Petrolite), wood wax, beeswax, rice wax, candelilla wax, carnauba wax Available), and the like by the Corporation Cerarica NODA.

  In the present invention, it is necessary to adjust the amount of the wax added so that the heat of fusion in the magnetic toner is 8 J / g or more and 20 J / g or less. Specifically, it can be adjusted to a preferable range by appropriately adjusting the amount of the wax added according to the heat of fusion of the wax used.

  In this invention, you may superpose | polymerize by adding resin to the polymerizable monomer system used as binder resin. For example, 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 a monomer component containing styrene into a magnetic toner, a random copolymer, a block copolymer, or a graft copolymer of these and a vinyl compound such as styrene or ethylene is formed into a copolymer. Or 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 a magnetic toner, the above-described wax component is phase-separated, and the encapsulation becomes stronger, and the magnetic property is excellent in offset resistance, blocking resistance, and low-temperature fixability. Toner can be obtained. As the usage-amount, 1-20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers. If the amount used is less than 1 part by mass, the effect of addition is small. On the other hand, if the amount used exceeds 20 parts by mass, it becomes difficult to design various physical properties of the magnetic toner produced by the polymerization method. Moreover, as a high molecular polymer containing these polar functional groups, those having an average molecular weight of 3000 or more are preferably used. If the molecular weight is less than 3000, particularly 2000 or less, the present polymer tends to concentrate near the surface of the magnetic toner, and this is not preferred because it tends to adversely affect developability and blocking resistance. Also, if a polymer having a molecular weight different from the molecular weight range of the magnetic toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a magnetic toner having a wide molecular weight distribution and high offset resistance can be obtained. be able to.

In the magnetic toner of the present invention, it is preferable to add a polyester resin as a resin to be added to the polymerizable monomer system as a binder resin.
As a dihydric or higher alcohol monomer component which is a polyester unit component, specifically, as a dihydric alcohol monomer component, polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, poly Oxypropylene (3.3) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0 ) -Polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane and other alkylene oxides of bisphenol A Adduct, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-pro Lenglycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, Examples include dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, and hydrogenated bisphenol A.

  Examples of the trivalent or higher alcohol monomer component include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol. 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, etc. Is mentioned.

  The divalent or higher carboxylic acid monomer component includes aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid or their anhydrides; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid, or their anhydrides. Succinic acid substituted with an alkyl group or alkenyl group having 6 to 18 carbon atoms or an anhydride thereof; unsaturated dicarboxylic acids such as fumaric acid, maleic acid and citraconic acid or the anhydride thereof; In particular, isophthalic acid is preferably used because of its high reactivity.

  Other monomers include glycerin, sorbit, sorbitan, and polyhydric alcohols such as oxyalkylene ethers of novolak type phenol resins; trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid and anhydrides thereof, etc. And polyvalent carboxylic acids.

  Among these, in particular, a bisphenol derivative represented by the following general formula (1) is a dihydric alcohol monomer component, and a carboxylic acid component comprising a divalent or higher carboxylic acid or an acid anhydride thereof, or a lower alkyl ester thereof ( For example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) are used as acid monomer components, and resins obtained by condensation polymerization with these polyester unit components have good charging characteristics. Therefore, it is preferable.

(In the formula, R represents 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.)

  The acid value (mgKOH / g) of the polyester resin used in the present invention is preferably 3 or more and 10 or less in order to control the wettability of the magnetic toner base. The acid value (mgKOH / g) of the polyester resin can be adjusted by appropriately adjusting the type and amount of the monomer used.

  The magnetic toner of the present invention may contain a charge control agent in order to stabilize charging characteristics. As the charge control agent, known ones can be used, but a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable.

  Further, the charge control agent used in the production of the magnetic toner using the direct polymerization method is particularly preferably one having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous dispersion medium. Specific compounds include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid and dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, sulfones Examples thereof include a polymer compound having an acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, and an imidazole compound. These charge control agents are preferably used in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the binder resin. However, the developer related to the image forming method of the present invention does not require the addition of a charge control agent, and the magnetic toner can be obtained by positively utilizing frictional charging of the developer with the layer pressure regulating member or the developer carrier. It is not always necessary to include a charge control agent therein.

  More specifically, for negative charging, for example, Spiron Black TRH, T-77, T-95 (Hodogaya Chemical Co., Ltd.), BONTRON (registered trademark) S-34, S-44, S-54, E-84. , E-88, E-89 (Orient Chemical Co., Ltd.) are more preferable, and for positive charging, for example, TP-302, TP-415 (Hodogaya Chemical Co., Ltd.), BONTRON (registered trademark) N-01, N-04, N-07, P-51 (Orient Chemical Co.) and Copy Blue PR (Clariant) are preferable.

  In the present invention, the magnetic iron oxide particles may serve as a colorant, but other colorants other than the magnetic iron oxide particles may be used in combination. Examples of coloring materials 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, rare earth elements to these, hematite, titanium black, nigrosine dye / pigment, carbon black, Examples include phthalocyanine. These may also be used after treating the surface.

  When the toner of the present invention is produced by a polymerization method, a polymerization initiator having a half-life of 0.5 to 30 hours during the polymerization reaction is used in an addition amount of 0.5 to 20% by mass of the polymerizable monomer. When the polymerization reaction is carried out, a polymer having a maximum between 10,000 and 100,000 in molecular weight can be obtained, and the toner can have a desired strength and appropriate melting characteristics. Examples of polymerization initiators include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile ), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo or diazo polymerization initiators such as azobisisobutyronitrile; benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Peroxide polymerization initiators such as cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide.

  In the present invention, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% 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.

Next, the production of the magnetic toner by the suspension polymerization method which is one of the direct polymerization methods will be described. A magnetic toner produced by a suspension polymerization method is very preferable because it easily satisfies the preferable conditions for the average circularity of the present invention. In the suspension polymerization method, a magnetic substance, a wax as a release agent, and a polymerization initiator, a crosslinking agent, a charge control agent, a colorant, and other additives are added to the polymerizable monomer that becomes a binder resin. Add an appropriate agent, for example, an organic solvent to be added to reduce the viscosity of the polymer produced by the polymerization reaction, a dispersion stabilizer, etc., and uniformly dissolve or disperse with a disperser such as a homogenizer, ball mill, colloid mill, or ultrasonic disperser. Disperse. The polymerizable monomer system (polymerizable monomer composition) thus obtained is suspended in an aqueous medium containing a dispersion stabilizer. At this time, the particle size distribution of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size at a stretch. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Also, a polymerization initiator dissolved in a polymerizable monomer or solvent can be added immediately after granulation and before starting the polymerization reaction.
After granulation, stirring may be performed using an ordinary stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented.

  In the suspension polymerization method, known surfactants and organic / inorganic dispersion stabilizers can be used as dispersion stabilizers. Among them, the use of inorganic dispersion stabilizers makes it difficult to produce harmful ultrafine powders, and the steric hindrance makes dispersion stable. Therefore, even if the reaction temperature is changed, the stability is not easily lost, the washing is easy and the toner is not adversely affected. Examples of such inorganic dispersion stabilizers 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. And inorganic salts such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina.

  When these inorganic dispersion stabilizers are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersion stabilizer particles may be generated and used 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 with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, water-soluble sodium chloride salt is produced as a by-product. However, if 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. However, since this sodium chloride salt becomes an obstacle when removing the remaining polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersion stabilizer can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.

  These inorganic dispersion stabilizers are preferably used in an amount of 0.2 to 20 parts by mass alone or in combination of two or more with respect to 100 parts by mass of the polymerizable monomer. When the purpose is to produce a more finely divided magnetic toner having a weight average particle diameter of 5 μm or less, 0.001 to 0.1 parts by mass of a surfactant may be used in combination.

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

  In the polymerization step, it is preferable to carry out the polymerization at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent to be sealed inside is precipitated by phase separation, and the encapsulation becomes more complete. In order to consume the remaining polymerizable monomer, it is possible to raise the reaction temperature to 90 to 150 ° C. at the end of the polymerization reaction.

  The magnetic toner of the present invention is used by externally adding various materials according to the type of magnetic toner to the magnetic toner base described above. Examples of the externally added material include a fluidity improver that improves the fluidity of the toner, such as inorganic fine powder, and a conductive fine powder that adjusts the charging characteristics of the toner, such as metal oxide fine particles. And other external additives.

  Examples of the fluidity improver include those that can improve the fluidity of the toner by external addition to the magnetic toner matrix. Such fluidity improvers include, for example, wet-process silica, fine-powder silica such as dry-process silica, fine-powder titanium oxide, fine-powder alumina; these can be surfaced with silane coupling agents, titanium coupling agents, silicone oils, etc. Treated silica, treated titanium oxide, treated alumina; and the like.

The fluidity improver preferably has a BET specific surface area by nitrogen adsorption measured by the BET method of 30 m ² / g or more, and more preferably 50 m ² / g or more. Although the fluidity improver varies depending on the type, for example, it is preferable to mix 0.01 to 8 parts by mass with respect to 100 parts by mass of the magnetic toner base, and more preferably 0.1 to 4 parts by mass. .

  A preferred fluidity improver is a fine powder produced by vapor phase oxidation of a silicon halogen compound, and is referred to as dry process silica or fumed silica. Such silica is produced, for example, by utilizing a thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen, and the basic reaction formula is represented by the following formula (2): It is.

  In this production process, it is also possible to obtain a composite fine powder of silica and another metal oxide by using other metal halogen compounds such as aluminum chloride or titanium chloride together with silicon halogen compounds. The silica fine powder used as an improving agent also includes them. The particle size is preferably in the range of 0.001 to 2 μm as the primary average particle size, and more preferably in the range of 0.002 to 0.2 μm.

Examples of commercially available silica fine powders produced by vapor phase oxidation of silicon halogen compounds include those sold under the following trade names: AEROSIL (Nippon Aerosil Co., Ltd.) 130, 200, 300, 380, TT600, MOX170, MOX80, COK84; Ca—O—SiL (CABOT Co.) M-5, MS-7, MS-75, HS-5, EH-5; Wacker HDK N 20 (WACKER-CHEMIE GMBH) V15, N20E, T30, T40; DC Fine Silica (Dow Corning CO.); Franco1 (Fransil).

In the present invention, the silica fine powder is preferably subjected to a hydrophobic treatment on the surface. In addition, the silica fine powder is obtained by treating the silica fine powder so that the degree of hydrophobicity measured by a methanol titration test is in the range of 30 to 80 degrees. preferable. The degree of hydrophobicity is expressed as a percentage of methanol in a liquid mixture of methanol and water at the end of sedimentation of the silica fine powder by dropping methanol onto a predetermined amount of the silica fine powder stirred in water. Examples of the method for hydrophobizing the surface of the silica fine powder include a method of chemically treating the silica fine particles with an organosilicon compound or silicone oil that reacts with the silica fine powder or physically adsorbs to the silica fine particles. More preferably, it is a hydrophobic treatment with an organosilicon compound. Here, as the organosilicon compound, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane , Bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyl Dimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divirtetramethyldisiloxa , 1,3-diphenyltetramethyldisiloxane, and dimethylpolysiloxane having 2 to 12 siloxane units per molecule and having a hydroxyl group bonded to Si in the terminal unit. These may be used alone or as a mixture of two or more.

  In the hydrophobization treatment of the silica fine powder, it is possible to use one or more silane coupling agents having a nitrogen atom among the organosilicon compounds. Examples of such nitrogen-containing silane coupling agents include aminopropyltrimethoxysilane, aminopropyltriethoxysilane, dimethylaminopropyltrimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyltrimethoxysilane, dibutylaminopropyltrimethoxysilane. Methoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyldimethoxysilane, dibutylaminopropyldimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyltriethoxysilane, trimethoxysilyl-γ-propylphenylamine, trimethoxysilyl -Γ-propylbenzylamine and the like.

  In the present invention, a preferable silane coupling agent is hexamethyldisilazane (HMDS).

  As the silicone oil preferably used in the surface hydrophobization treatment of the silica fine powder, the kinematic viscosity at 25 ° C. is preferably 0.5 to 10000 centistokes, more preferably 1 to 1000 centistokes, More preferably, it is 10-200 centistokes. Particularly preferred silicone oils include, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, and fluorine modified silicone oil.

  As a method for surface hydrophobization treatment of silica fine powder using silicone oil, for example, silica fine powder treated with a silane coupling agent and silicone oil are directly mixed using a mixer such as a Henschel mixer; A method in which silicone oil is sprayed onto a silica fine powder; a method in which silicone oil is dissolved or dispersed in a suitable solvent, and then the silica fine powder is added and mixed to remove the solvent.

  When the surface of the silica fine powder is hydrophobized with silicone oil, the silica fine powder is heated to 200 ° C or higher (more preferably 250 ° C or higher) in an inert gas after the silicone oil treatment to stabilize the surface coating. More preferably.

  In the present invention, it is possible to use both the silane coupling agent and the silicone oil described above for the surface hydrophobization treatment of the silica fine powder. As a method for such surface hydrophobization treatment, a method in which silica fine powder is previously treated with a silane coupling agent and then treated with silicone oil, or a method in which silica fine powder is simultaneously treated with a silane coupling agent and silicone oil, etc. Is mentioned.

Further, an external additive other than the fluidity improver may be added to the magnetic toner in the present invention, if necessary.
For example, for the purpose of improving the cleaning property, the primary average particle diameter exceeds 30 nm (preferably the BET specific surface area is less than 50 m ² / g), more preferably the primary average particle diameter is 50 nm or more (preferably the BET ratio). It is also a preferred embodiment to add inorganic particles or organic particles having a surface area of less than 30 m ² / g and a nearly spherical shape to the magnetic toner base. For example, spherical silica particles, spherical polymethylsilsesquioxane particles, and spherical resin particles are preferably used.

  Still other external additives, for example, lubricant powders such as polyethylene fluoride powder, zinc stearate powder, polyvinylidene fluoride powder; or abrasives such as cerium oxide powder, silicon carbide powder, strontium titanate powder; For example, a conductivity imparting agent such as carbon black powder, zinc oxide powder or tin oxide powder; organic fine particles having opposite polarity and inorganic fine particles can be added in small amounts as a developability improver. These external additives can also be used after hydrophobizing the surface.

  The external additives as described above are preferably used in an amount of 0.1 to 2 parts by mass (preferably 0.1 to 1.5 parts by mass) with respect to 100 parts by mass of the magnetic toner base in terms of fixing properties and charging characteristics. .

  When the magnetic toner base of the present invention is produced by a pulverization method, a known method can be used. For example, binder resin, magnetic material, wax and other additives as required are mixed thoroughly by a mixer such as a Henschel mixer or ball mill, and then melted, kneaded and kneaded using a heat kneader such as a kneader or an extruder. It is preferable to obtain a magnetic toner base material by meat and making the resins compatible with each other, cooling and solidifying the melt-kneaded product, and then pulverizing the solidified product and classifying the pulverized product. A magnetic toner can be obtained by sufficiently mixing the magnetic toner base and an external additive such as a fluidity improver as required by a mixer such as a Henschel mixer.

  In the production of the magnetic toner of the present invention, the classification can be performed at any time after the toner particles are generated. For example, the classification may be performed after mixing with an external additive.

  Examples of devices that can be generally used as toner manufacturing devices are listed below, but are not limited thereto. Table 1 shows an example of a pulverizing device for toner production, Table 2 shows an example of a classification device for toner production, Table 3 shows an example of a sieve device for toner production, and Table 4 shows an example of a mixing device for toner production. Table 5 gives examples of kneading apparatuses for toner production.

  In the present invention, in order to control the circularity of the magnetic toner, it is preferably pulverized by a method of applying a mechanical impact force. Examples of the treatment that gives mechanical impact force include a method using a mechanical pulverizer such as a pulverizer KTM manufactured by Kawasaki Heavy Industries, Ltd., a turbo mill manufactured by Turbo Industrial Co., Ltd., a mechano-fusion system manufactured by Hosokawa Micron, and Nara Machinery Co., Ltd. The method of processing with apparatuses, such as a manufactured hybridization system, is mentioned. These apparatuses can be used as they are or after being appropriately improved. By controlling the conditions for applying such a mechanical impact, it is possible to control the circularity of the magnetic toner produced by the pulverization method.

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 shown in the figure is an electrophotographic apparatus adopting a developing method using a one-component magnetic toner, and 100 is an electrostatic charge image carrier (photosensitive drum) around which a primary charging roller 117, a developing device 140, a transfer A charging roller 114, a cleaner 116, a register roller 124, and the like are provided. The photosensitive drum 100 is charged to, for example, −700 V by the primary charging roller 117 (applied voltages are AC voltage −2.0 kVpp, DC voltage −700 Vdc). Then, exposure is performed by irradiating the photosensitive drum 100 with laser light 123 by the laser generator 121, and an electrostatic latent image corresponding to an image to be formed is formed on the photosensitive drum 100. The electrostatic latent image formed on the photosensitive drum 100 is developed with a one-component magnetic developer by the developing device 140 and 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 the fixing device 126 by the conveying belt 125 and fixed on the transfer material. In addition, toner remaining on a part of the photoconductor is cleaned by the cleaning unit 116. As shown in FIG. 2, the developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive drum 100. The gap between the drum 100 and the developing sleeve 102 is maintained at a predetermined distance (for example, about 300 μm) by a sleeve / photosensitive drum 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 is provided with a plurality of magnetic poles as shown in the figure, and S1 influences development, N1 regulates the amount of toner coating, S2 takes in / conveys toner, and N2 affects toner blowout prevention. The toner is applied to the developing sleeve 102 by the toner application roller 141, and is adhered and conveyed. An elastic blade 103 is provided as a member that regulates the amount of toner conveyed. The amount of toner conveyed to the developing area is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. In the development region, a DC and AC development bias is applied between the photosensitive drum 100 and the developing sleeve 102, and the developer on the developing sleeve flies onto the photosensitive drum 100 in accordance with the electrostatic latent image to become a visible image. .

  The measuring method of each physical property in the present invention is described in detail below.

(1) Measurement of weight average particle size of magnetic toner The particle size distribution can be measured by various methods, but in the present invention, it is performed using a multisizer of a Coulter counter.
The measuring device is a Coulter Counter Multisizer II (manufactured by Coulter), connected to an interface (manufactured by Nikkiki) that outputs number distribution and volume distribution, and a computer for analysis. The electrolyte is a special grade or first grade sodium chloride. Is used to prepare a 1% NaCl aqueous solution. As a measuring method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the above electrolytic aqueous solution, and further 2 to 20 mg of a measurement sample is added. The electrolytic solution in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and when measuring the toner particle size as an aperture with the Coulter Counter Multisizer II, use a 100 μm aperture. taking measurement. The volume and number of toners are measured, and the volume distribution and number distribution are calculated. Then, the weight-based weight average particle diameter obtained from the volume distribution is obtained.

(2) Measurement of number average particle size of inorganic fine powder The number average particle size of inorganic fine powder was selected by randomly selecting 300 particles on the photograph from a transmission electron micrograph (magnification 30,000 times). It can be determined by measuring and taking the average value as the number average particle diameter.

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

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.

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.

  Further, the circularity standard deviation SD is calculated from the following equation where the average circularity C, the circularity ci of each particle, and the number of measured particles are m.

  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. The degree 0.4 to 1.0 is divided into classes equally divided every 0.01, and the average circularity and the circularity standard deviation are calculated using the center value of the division points and the number of measured particles.

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

  To measure the circularity of the toner particles, the flow type particle image measuring device is used, and the concentration of the dispersion is readjusted so that the toner particle concentration at the time of measurement is 3000 to 10,000 particles / μl. Measure more than one. After the measurement, using this data, data having an equivalent circle diameter of less than 2 μm is cut to determine the average circularity of the toner particles.

  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. Furthermore, the accuracy of toner shape measurement is 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.

(4) Water / methanol wettability test method Using a powder wettability tester WET-100P manufactured by Reska Co., Ltd., a methanol dropping transmittance curve measured under the following conditions and procedures is used.
First, 50 ml of a methanol / water mixed solvent (methanol concentration 0%) is placed in a flask and the transmittance is measured. The transmittance is measured with the transmittance at this time being 100% and the state in which no light is transmitted at all being 0%. That is, the methanol mass% when the transmitted light intensity at the time of measurement is half the transmitted light intensity when the methanol / water mixed solvent (methanol concentration 0%) is transmitted is defined as the wettability of the present invention.

The transmittance is measured as follows.
A magnetic stirrer is placed in a beaker containing 50 m of a methanol / water mixed solvent (methanol concentration 0%). Then, 0.1 g of toner or toner particles sieved with a mesh having a mesh size of 150 μm is precisely weighed and put into the flask. Next, stirring was started with a magnetic stirrer at a stirring speed of 300 rpm (5 revolutions / second), and methanol was continuously added into the sample solution for measurement at a rate of 1.3 ml / min with a glass tube while a wavelength of 780 nm was added. The light transmittance is measured and a methanol dropping transmittance curve is prepared. In this case, methanol is used as a titration solvent because it is less affected by elution of dyes, pigments, charge control agents and the like contained in the toner, and the surface state of the toner can be observed more accurately.
In this measurement, a glass beaker having a diameter of 5 cm was used as the beaker, and a magnetic stirrer having a spindle shape of 25 mm in length and a maximum diameter of 8 mm and coated with Teflon (registered trademark) was used. .

(5) Melting point measurement / measurement device for release agent: differential scanning calorimeter (DSC), MDSC-2920 (manufactured by TA Instruments)
Measured according to ASTM D3418-82.

  The measurement sample is precisely weighed in an amount of 2 to 10 mg, preferably 3 mg. This is put into an aluminum pan, and an empty aluminum pan is used as a reference, and measurement is performed at a temperature rise rate of 10 ° C./min at a temperature rise rate of 30 ° C. to 200 ° C. at normal temperature and humidity. The analysis is performed with a DSC curve in the temperature range of 30 to 200 ° C. obtained in the second temperature raising process. For the melting point of the wax, the temperature value of the endothermic main peak of the obtained DSC curve is used.

(6) Measurement of acid value of binder resin The acid value is determined as follows. Basic operation conforms to JIS-K0070.
(A) Reagent (a) As the solvent, an ethyl ether-ethyl alcohol mixed solution (1 + 1 or 2 + 1) or a benzene-ethyl alcohol mixed solution (1 + 1 or 2 + 1) was used, and these solutions were mixed with phenolphthalein as an indicator immediately before use. Neutralize with 1 mol / liter potassium hydroxide ethyl alcohol solution.
(B) Phenolphthalein solution: 1 g of phenolphthalein is dissolved in 100 ml of ethyl alcohol (95% by volume).
(C) 0.1 mol / liter potassium hydroxide-ethyl alcohol solution: Dissolve 7.0 g of potassium hydroxide in as little water as possible, add ethyl alcohol (95% by volume) to 1 liter, leave it for 2 to 3 days, and filter To do. The standardization is performed according to JIS K8006 (basic matters regarding titration during the reagent content test).
(B) Operation: 1-20 g of a sample (magnetic toner or binder resin) is weighed correctly, 100 ml of a solvent and a few drops of a phenolphthalein solution as an indicator are added thereto, and shaken sufficiently until the sample is completely dissolved. In the case of a solid sample, dissolve it by heating on a water bath. After cooling, this is titrated with a 0.1 mol / liter potassium hydroxide ethyl alcohol solution, and the end point of neutralization is taken when the indicator is slightly red for 30 seconds.
(C) Calculation formula The acid value is calculated by the following formula.

here,
A: Acid value (mgKOH / g)
B: Amount of 0.1 mol / liter potassium hydroxide ethyl alcohol solution (ml)
f: 0.1 mol / liter of potassium hydroxide ethyl alcohol solution, factor S: sample (g)

  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, all the parts in the following mixing | blending are a mass part.

<Example of production of magnetic material (magnetic iron oxide 1)>
A ferrous sulfate aqueous solution is mixed with 1.0 to 1.1 equivalents of a caustic soda solution (containing 1 mass% sodium hexametaphosphate in terms of P with respect to Fe) with respect to iron ions, and ferrous hydroxide An aqueous solution containing was prepared. While maintaining the aqueous solution at pH 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.

Subsequently, after adding ferrous sulfate aqueous solution so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH 8 and air is supplied. The oxidation reaction proceeds while blowing, the pH is adjusted to about 6 at the end of the oxidation reaction, and n-C ₈ H ₁₇ Si (OC ₂ H ₅ ) ₃ is used as a silane coupling agent with respect to 100 parts by mass of magnetic iron oxide. 1.2 parts by mass of each was added and sufficiently stirred. The produced hydrophobic magnetic iron oxide particles were washed, filtered and dried by a conventional method, and then the agglomerated particles were pulverized to obtain magnetic iron oxide 1. The number average particle size of the magnetic iron oxide 1 0.28 .mu.m, saturation magnetization and the residual magnetization in a magnetic field 79.6 kA / m (1000 oersteds) is 67.6Am ² /kg(emu/g),3.9 Am ² / kg (Emu / g).

<Manufacture of magnetic toner A>
After adding 451 parts by mass of 0.1 mol / L-Na ₃ PO ₄ aqueous solution to 709 parts by mass of ion-exchanged water and heating to 60 ° C., 67.7 parts by mass of 1.0 mol / L-CaCl ₂ aqueous solution was gradually added. Thus, an aqueous medium containing Ca ₃ (PO ₄ ) ₂ was obtained.
On the other hand, the following prescription was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).
Styrene 74 parts by mass n-butyl acrylate 26 parts by mass Saturated polyester resin (1) 3 parts by mass (monomer composition; bisphenol A propylene oxide adduct / terephthalic acid / isophthalic acid, acid value; 7 mg KOH / g, Tg (glass Transition temperature) = 69 ° C., Mn (number average molecular weight) = 4200, Mw (weight average molecular weight) = 9000)
・ Negative charge controller 2 parts by mass (T-77; monoazo dye-based Fe compound (Hodogaya Chemical Co., Ltd.))
・ 90 parts by mass of magnetic iron oxide 1

This monomer composition was heated to 60 ° C., and 18 parts by mass of HNP-9 (polyethylene wax, DSC endothermic main peak = 78 ° C.) manufactured by Nippon Seiwa Co., Ltd. was mixed and dissolved therein. A polymerizable monomer system was obtained by dissolving 2 parts by mass of butyl peroxide.

The polymerizable monomer system was put into the aqueous medium, and the mixture was granulated by stirring at 12,000 rpm for 15 minutes with Claremix (manufactured by M Technique) in an N ₂ atmosphere at 60 ° C. Thereafter, the mixture was reacted at 80 ° C. for 1 hour while stirring with a paddle stirring blade. Thereafter, stirring was continued for another 10 hours. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ , filtered, washed with water, and dried to obtain a magnetic toner base.
Hydrophobic silica fine powder having a BET specific surface area of 140 m ² / g after treatment with hexamethyldisilazane and then with silicone oil (primary average particle size of 14 nm, hydrophobization degree of 85), and 100 parts by mass of the magnetic toner base. The magnetic toner A (weight average particle diameter 7.5 μm) shown in Table 6 was prepared by mixing 0.5 part by mass of the body (i) with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.).

<Manufacture of magnetic toners B to C>
In the production example of the magnetic toner A, except that the amount of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution / 1.0 mol / liter-CaCl ₂ aqueous solution to be added was appropriately adjusted and the weight average particle size of the magnetic toner was changed. Magnetic toners B to C were obtained in the same manner as in the production of the magnetic toner A. Table 6 shows the physical properties of the magnetic toners B to C.

<Manufacture of magnetic toner D>
In the production example of the magnetic toner A, the weight average particle diameter of the magnetic toner and the hydrophobic silica fine powder (ii) (hexamethyldisilazane treated and then treated with silicone oil, the treated BET specific surface area is 200 m ² / g, A magnetic toner D was obtained in the same manner as in the production of the magnetic toner A except that the primary average particle size was changed to 8 nm and the degree of hydrophobicity was 82). Table 6 shows the physical properties of the magnetic toner D.

<Manufacture of magnetic toners E to F>
Magnetic toners E to F were obtained in the same manner as in the production of the magnetic toner A except that the amount of wax added was changed in the production example of the magnetic toner A. Table 6 shows the physical properties of the magnetic toners E to F.

<Manufacture of magnetic toner G>
In the production example of the magnetic toner A, the magnetic toner A was prepared in the same manner as in the production of the magnetic toner A except that the weight average particle diameter of the magnetic toner and the wax to be added were changed to C105 (DSC endothermic main peak = 105 ° C.) manufactured by Sazol. Toner G was obtained. Table 6 shows the physical properties of the magnetic toner G.

<Manufacture of magnetic toners H and I>
Magnetic toners H and I were obtained in the same manner as in the production of magnetic toner A except that the weight average particle diameter of the magnetic toner and the amount and type of polyester resin added were changed in the production example of magnetic toner A. Table 6 shows the physical properties of the magnetic toners H to I.

<Manufacture of magnetic toner J>
In the magnetic toner A production example, after the polymerizable monomer system was stirred and granulated, the reaction temperature at the time of reaction while stirring with a paddle stirring blade was changed to 70 ° C., and the weight average particle size of the magnetic toner was changed. A magnetic toner J was obtained in the same manner as in the production of the magnetic toner A except for the above. Table 6 shows the physical properties of the magnetic toner J.

<Production example of comparative magnetic toner a>
In the magnetic toner A production example, the magnetic toner A was changed except that the amount of wax added was changed.
A comparative magnetic toner a was obtained in the same manner as in the above. Table 6 shows the physical properties of the comparative magnetic toner a.

<Example of production of magnetic toner b for comparison>
In the production example of the magnetic toner A, a comparative magnetic toner was produced in the same manner as in the production of the magnetic toner A except that the addition amount of the wax, the addition amount of the polyester resin, the addition amount of the inorganic fine powder, and the weight average particle diameter were changed. b was obtained. Table 6 shows the physical properties of the comparative magnetic toner b.

<Example of production of magnetic toner c for comparison>
In the production example of the magnetic toner A, a comparison was made in the same manner as in the production of the magnetic toner A except that the addition amount of the wax, the type and addition amount of the polyester resin, the addition amount of the inorganic fine powder, and the weight average particle diameter were changed. Magnetic toner c was obtained. Table 6 shows the physical properties of the comparative magnetic toner c.

<Manufacturing example of comparative magnetic toners d to e>
In the production example of the magnetic toner A, the comparative magnetic toners d to e are produced in the same manner as in the production of the magnetic toner A except that the weight average particle diameter of the magnetic toner and the addition amount of the inorganic fine powder to be added are changed.
Got. Table 6 shows the physical properties of the comparative magnetic toners d to e.

<Production Example of Comparative Magnetic Toner f>
Styrene acrylic resin 100 parts by mass (styrene, butyl acrylate, monobutyl maleate; glass transition temperature: 63 ° C., softening point: 120 ° C., acid value: 5 mg KOH / g, peak molecular weights: 20,000 and 350,000, weight average molecular weight: 280,000)
-Magnetic iron oxide 1 90 parts by mass-Negative charge control agent <T-77 (Hodogaya Chemical Co., Ltd.)> 2 parts by mass-Polyethylene wax (DSC endothermic main peak = 78 ° C) 18 parts by mass (Nippon Seiwa Co., Ltd., HNP-9)

The above raw materials are mixed with a Henschel mixer for 3 minutes, melt-kneaded with a twin screw extruder PCM-30 heated to 160 ° C, cooled with a cooling belt (cooling water 15 ° C), and then the mixture is coarsely pulverized with a hammer mill. did. The coarsely pulverized product was finely pulverized by a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and the finely pulverized product obtained was classified by an air classifier (Elbow Jet; manufactured by Nittetsu Mining Co., Ltd.) to obtain a magnetic toner base.
Hydrophobic silica fine powder having a BET specific surface area of 140 m ² / g after treatment with hexamethyldisilazane and then with silicone oil (primary average particle size of 14 nm, hydrophobization degree of 85), and 100 parts by mass of the magnetic toner base. 1 part by mass of the body (i) was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare a comparative magnetic toner f (weight average particle diameter 7.5 μm) shown in Table 6. Table 6 shows the physical properties of the comparative magnetic toner f.

<Example 1>
The following evaluation was performed using the magnetic toner A.
Using a commercially available Canon digital copying machine IR6010, the magnetic toner A of the present invention was used to perform a 100,000 sheet passing durability test in a high temperature and high humidity environment (temperature 30 ° C., humidity 80%). Thereafter, 100,000 sheets were further passed through in a low temperature and low humidity environment (temperature 15 ° C., humidity 10%). The document used was a document with an image ratio of 5%. Here, the image density before and after endurance and the toner on the developing sleeve after endurance were cleaned, and sleeve contamination was evaluated visually.

(Image evaluation)
<Durable development evaluation>
1. Image density Image density is measured with a Macbeth densitometer (Macbeth Co., Ltd.) using an SPI filter, and the reflection density of 5mm circle (1.1 density) of the chart is measured before and after the endurance test in the low temperature and low humidity environment and in the high temperature and high humidity environment. Concentration stability was evaluated by comparing before and after the durability test.

2. Sharpness of digital image Using originals including lines and letters, images after durability tests in low-temperature and low-humidity environments and high-temperature and high-humidity environments were evaluated according to the following criteria using visual observation and a magnifying microscope.
◎: Both the character image and the line image are reproduced faithfully to the details. ○: The details are slightly disturbed or scattered, but there is no problem with visual observation. Yes x: Many disturbances and splashes occur, and the document is not reproduced

3. Contamination level of the developing sleeve The contamination level of the developing sleeve was evaluated according to the following criteria.
◎: No problem on the sleeve or image ○: Some contamination on the sleeve is slightly contaminated, but there is no problem on the image △: Some contamination on the sleeve is contaminated, and part of the image has low density, etc. Occurrence ×: The entire sleeve is contaminated and the entire image is thin.

<Fixability evaluation>
The fixing property was evaluated as follows.
1. Low temperature fixability
Using magnetic toner A, a Canon digital copying machine IR3300 is used to adjust the amount of application so that the reflection density by the Macbeth reflection densitometer of the original after fixing is 0.6 to 0.8. / M ^{2 An} unfixed image is obtained on paper. Using an IR3300 external fixing device (taken out the IR3300 fixing device, attached an external drive and fixing device temperature control device, and modified the fixing nip width to 8.0 mm), the fixing image was changed by changing the fixing temperature. Get. The temperature at which the density reduction rate is 20% or less is determined by measuring the density before and after rubbing 5 times with a load of 4900 N / m ² (50 g / cm ² ) on the obtained image. As the evaluation, the following criteria were used.
A: Minimum fixing temperature is less than 145 ° C. O: Minimum fixing temperature is less than 145 to 155 ° C. Δ: Minimum fixing temperature is less than 155 to 165 ° C. x: Minimum fixing temperature is 165 ° C. or more.

2. Contamination of fixing member Using magnetic toner A, the temperature setting of the fixing device of Canon copying machine GP405 was changed to 160 ° C., the fixing roller cleaning web was removed, and a copying test for 100,000 sheets was performed. After durability, the fouling of the pressure roller of the fixing device was evaluated according to the following evaluation criteria.
◎… No stains are seen ○… Some stains are seen on some of the rollers △… Stains are seen on the entire roller, but there are no stains on the transfer paper ×… Stains are seen on the entire roller, transfer Dirt is visible on the entire surface of the paper

As a result of performing the above evaluation, good results were obtained as shown in Table 7.

<Examples 2 to 10 and Comparative Examples 1 to 6>
Using the magnetic toners B to J and the comparative magnetic toners a to f, the same tests as in Example 1 were performed and evaluated. The results are shown in Table 7. As a result, the results shown in Table 7 were obtained.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus used in an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a configuration of a part of a developing device used in an example of the present invention.

Claims (6)

A magnetic toner comprising at least a binder resin, a magnetic toner, and a magnetic toner base containing a wax, and an inorganic fine powder,
(I) the magnetic toner has a weight average particle diameter of 4 to 9 μm;
(Ii) The heat of fusion exhibited by the wax in the magnetic toner is 8.0 J / g or more and 20 J / g or less,
(Iii) In the wettability test of the magnetic toner with respect to the methanol / water mixed solvent, the methanol concentration when the light transmittance at a wavelength of 780 nm is 50% is 50 to 70% by volume,
(Iv) A magnetic toner wherein the coverage of the inorganic fine powder on the magnetic toner base is 0.4 to 0.9. 2. The magnetic toner according to claim 1, wherein an average circularity of particles having an equivalent circle diameter (number basis) of 2 μm or more of the magnetic toner is 0.94 or more. The wax is a hydrocarbon wax in which an endothermic main peak appears in a region of 50 to 90 ° C. in a DSC curve obtained when a magnetic toner containing the wax is measured with a differential scanning calorimeter. The magnetic toner according to claim 1. The methanol concentration when the transmittance of light having a wavelength of 780 nm is 50% in a wettability test of the magnetic toner base with a methanol / water mixed solvent is 30 to 50% by volume. The magnetic toner according to claim 1. The magnetic toner according to claim 1, wherein the binder resin contains at least a polyester resin, and the acid value of the polyester resin is 3 to 10 mg KOH / g. The magnetic toner according to any one of claims 1 to 5, wherein the magnetic toner base is a magnetic toner base obtained by polymerizing a polymerizable monomer composition in an aqueous medium.

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