JP4434967B2 - Magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic toner which exhibits good fixing property, excels in offset resistance even in a SURF (Surface Rapid Fusing) fixing system, excels also in charge stability, provides high image density even in long-term use in a high temperature and high humidity environment, and causes no ghost. <P>SOLUTION: The magnetic toner having a weight average particle diameter of 3-10 &mu;m is manufactured by polymerizing a monomer composition containing at least a polymerizable monomer, magnetic iron oxide and a release agent. The magnetic toner has an average circularity of &ge;0.970 and the inertia radius Rw and absolute molecular weight Mw of the magnetic toner on size exclusion chromatography-online-multiple angle light scattering (SEC-MALLS) measurement of an o-dichlorobenzene-soluble component satisfy the expression (1): 0.1&times;10<SP>-4</SP>&le;Rw/Mw&le;5.0&times;10<SP>-4</SP>. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a toner used for developing an electrostatic image formed in an image forming method such as an electrophotographic method, an electrostatic recording method, a magnetic recording method, and a toner jet recording method.

  Fixing performance is the most important performance required for toners in digital printers and high-definition image copying. Various methods and apparatuses have been developed for the fixing process, but the most common method is a thermocompression bonding method using a heat roller. This thermocompression bonding method using a heating roller performs fixing by allowing the toner image surface of a fixing sheet to pass through the surface of a heat roller formed with a material having releasability with respect to the toner while being in contact with pressure. It is. In this method, since the surface of the heat roller and the toner image of the fixing sheet are brought into contact with each other under pressure, the thermal efficiency at the time of fusing the toner image on the fixing sheet is extremely good, and the fixing can be performed quickly. This is very effective in a high-speed electrophotographic copying machine.

  In recent years, it has been demanded to realize a fixing method having a short wait time and low power consumption, and a surf fixing method is used as a representative one. The surf fixing method is a method in which fixing is performed under light pressure through a film provided with a heating device, and power consumption is remarkably low because the heat capacity of the film is small. Furthermore, since the waiting time can be short, it is preferably used mainly for medium and low speed printers.

  There is also a demand for a toner that can realize fixing at a lower temperature while preventing offset development. However, in the case of magnetic toner, since a considerable amount of fine magnetic powder is mixed and dispersed in the toner, the toner is hard and hardly deformed due to the filler effect of the magnetic powder. For this reason, although a certain degree of fixing performance is exhibited in the thermocompression bonding method using a heating roller, in the surf fixing method, the toner is not easily crushed due to light pressure, and the heat is not easily transmitted. A low temperature offset in which only one surface of the image melts extremely and adheres to the fixing film, that is, a so-called one-off offset is likely to occur. This problem becomes even more pronounced with toners where the magnetic powder is significantly exposed to or released from the toner particle surfaces. This is presumably because the magnetic powder having a large heat capacity first absorbs heat from the fixing device. As described above, it has been difficult to obtain sufficient fixing performance in the surf fixing of magnetic toner.

  As the simplest and most general method for solving this problem, it is known that a wax is contained in the toner as a release agent. However, if the toner simply contains a wax having a low softening point, it tends to adversely affect the developing characteristics, charging properties, durability, and storage properties of the toner. In addition, various types of waxes have been proposed to be included in the toner. Regardless of which method is used, low-temperature fixability, offset resistance, and toner durability stability can be achieved only by using a release agent. It is one more thing to make sex compatible, and further improvement was desired.

  Conventionally, as a method for obtaining a polymerized toner excellent in fixability, a method in which a polymerizable monomer containing a colorant and a charge control agent is subjected to suspension polymerization in the presence of a macromonomer has been proposed (for example, Patent Document 1). ). The macromonomer is an oligomer or polymer having a polymerizable functional group at the molecular chain end. According to this method, since the macromonomer is incorporated as a monomer unit in the molecular chain of the resulting polymer, a polymer in which the macromonomer is grafted into the molecular chain is obtained. In the resulting polymer, entanglement of macromonomer units as branches, that is, so-called physical cross-linking occurs between polymer molecules, and an apparently high molecular weight polymer is obtained, so that offset resistance is improved. Furthermore, this physical cross-linking is a loose cross-linking structure, unlike chemical cross-linking with a cross-linking agent such as divinylbenzene, so that the cross-linking structure tends to be broken by heating. Therefore, the polymerized toner is easily melted at the time of fixing using a heating roller, and thus has excellent fixability. However, this polymerized toner tends to cause aggregation between the toners during storage, and the storage stability is not satisfactory.

  As a means for improving storage stability, a method of suspension polymerization in the presence of a macromonomer having a glass transition temperature higher than that of a polymer obtained by polymerizing a monomer composition has been proposed (for example, Patent Document 2). According to this method, polymer particles having a pseudo capsule structure can be obtained, so that the storage stability can be improved while maintaining the low-temperature fixability.

  In addition, the polymerizable monomer composition is subjected to suspension polymerization in the presence of an oil-soluble polymerization initiator until the polymerization conversion is within the range of 30 to 97%, and then suspended by adding a water-soluble polymerization initiator. There has also been proposed a method of obtaining a polymerized toner in which a polymer film is formed on the toner surface by polymerization and in which a low melting point release agent is encapsulated (for example, Patent Document 3). By using this method, it is possible to obtain a toner that is excellent in low-temperature fixability, storage stability, and durability, and is less likely to cause fogging and density reduction.

  However, as a result of investigations by the present inventors, it has been found that the above-described method is not specialized for magnetic toner, and thus the occurrence of offset cannot be further suppressed in the surf fixing method. Furthermore, it is difficult to keep the charging property sufficiently stable during long-term use in a high-temperature and high-humidity environment, resulting in deterioration of transferability and ghosting.

  As described above, although various methods have been proposed for the fixing property of magnetic toner, it has not been sufficient, and further improvement has been demanded.

Japanese Patent Laid-Open No. 3-136005 Japanese Patent Laid-Open No. 10-20547 JP-A-11-160909

  An object of the present invention is to provide a magnetic toner that solves the above-mentioned problems of the prior art.

  That is, an object of the present invention is to provide a magnetic toner that exhibits good fixability and is excellent in offset resistance even in the surf fixing method.

  Another object of the present invention is to provide a magnetic toner having excellent charging stability, high image density and no ghost even when used for a long time in a high temperature and high humidity environment.

The present invention, at least a polymerizable monomer, magnetic iron oxide, and the weight average particle size which is produced by polymerizing a polymerizable monomer composition containing a release agent is located in the magnetic toner of 3 to 10μm ,
The average circularity of the magnetic toner is 0.970 or more,
The inertial radius Rw and absolute molecular weight Mw in the size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) measurement of the o-dichlorobenzene soluble matter of the magnetic toner are expressed by the following formulae.
0.25 × 10 ⁻⁴ ≦ Rw / Mw ≦ 4.0 × 10 ⁻⁴ (Formula 1)
It is related with the magnetic toner characterized by satisfying.

  The magnetic toner of the present invention has good fixability and is excellent in offset resistance even in the surf fixing system.

  Further, by using the magnetic toner of the present invention, an image having a high image density and no ghost can be obtained even in a long-term use in a high temperature and high humidity environment.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention.

  The inventors determined the ratio of the inertia radius Rw to the absolute molecular weight Mw and the value of Rw / Mw in the size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) measurement of the o-dichlorobenzene soluble matter of the magnetic toner. It was found that by controlling it, good fixing performance and charging stability can be realized, and the present invention has been achieved.

  The inertia radius Rw indicates the spread of the polymer chain, and the relationship between the inertia radius and the absolute molecular weight is closely related to the degree of branching and the crosslinking density of the molecule. Although details are not clear, when the present inventors examined, the ratio between the radius of inertia Rw and the absolute molecular weight Mw is greatly increased in toner melting and offset resistance during fixing, particularly in the offset property in the surf fixing method. It turns out that it is involved. The reason for this is as follows.

  Having an appropriate crosslink density means having an appropriate distance between crosslink points. Such toner easily exudes wax during fixing and has excellent heat transfer. Furthermore, having an appropriate distance between cross-linking points means that the gel is flexible and soft and easily deforms the toner. Due to the above effects, it is considered that there is no further offset in surf fixing, and that a wide fixing area is provided.

In the magnetic toner of the present invention, the radius of inertia Rw and the absolute molecular weight Mw in the size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) measurement of o-dichlorobenzene soluble component are expressed by the following formula: 0.1 × 10 ⁻⁴ ≦ Rw / Mw ≦ 5.0 × 10 ⁻⁴ (Formula 1)
And preferably satisfies 0.25 × 10 ⁻⁴ ≦ Rw / Mw ≦ 4.0 × 10 ⁻⁴ . When Rw / Mw is less than 0.1 × 10 ⁻⁴ , the crosslink density is too high, so that the oozing of the wax is insufficient, and the toner is difficult to deform because the gel is hard. As a result, offset is more likely to occur during surf fixing. On the contrary, when Rw / Mw exceeds 5.0 × 10 ⁻⁴ , exudation of wax other than during fixing occurs, and developability and durability deteriorate.

In the SEC-MALLS measurement, o-dichlorobenzene is used as a solvent. Although the detailed measurement method will be described later, by using o-dichlorobenzene as a solvent and treating at a high temperature (135 ° C.), it is possible to analyze high molecular weight components that do not dissolve in THF. It became possible.

  The absolute molecular weight and radius of inertia determined from SEC-MALLS will be described.

  The molecular weight distribution measured by SEC is the molecular size and the intensity is its abundance, whereas SEC-MALLS (the SEC and the multi-angle light scattering detector are combined as a separation means, and the absolute molecular weight and molecular size are measured. (The inertial square radius can be measured), and the light scattering intensity obtained increases with the molecular size. However, the presence of a peak due to the elution time in SEC-MALLS measurement means that a polymer having a molecular spread (molecular size) at the molecular weight exists with a number distribution.

  In the conventional SEC method, when a molecule to be measured passes through a column, the molecule is subjected to a molecular sieving effect and eluted according to the molecular size, and the molecular weight is measured. In this case, the linear polymer and the branched polymer having the same molecular weight are eluted earlier because the former has a larger molecular size in the solution. Therefore, the molecular weight of the branched polymer measured by the SEC method is measured smaller than the true molecular weight.

  On the other hand, the light scattering method of the present invention uses the Rayleigh scattering of the measurement molecule, measures the dependence of the incident angle of the light on the intensity of the scattered light and the sample concentration, and analyzes it by the Zimm method, the Berry method, etc. True molecular weight (absolute molecular weight) can be determined in all molecular forms of the polymer and branched polymer (in the present invention, the absolute molecular weight was calculated by the Zim method by the SEC-MALLS measurement method (described later)), and shows higher performance. Toner molecular design is now possible.

  The average circularity of the toner of the present invention is 0.970 or more. A magnetic toner having an average circularity of 0.970 or more has a spherical shape, and the toner shapes are relatively uniform. Therefore, charging is likely to be uniform and effective in suppressing fogging and sleeve ghosting. Further, since the toner ears on the toner carrying member become uniform, control at the developing unit is facilitated. Further, since the toner is spherical, it has good fluidity and is not easily subjected to stress in the developing device, so that the chargeability is not easily lowered even when used for a long time under high humidity.

  The magnetic toner of the present invention preferably has a mode circularity of 0.99 or more in the circularity distribution of the toner. A mode circularity of 0.99 or more means that most of the toner particles have a shape close to a true sphere, and the above action becomes more remarkable, which is preferable.

  As described above, the toner having a nearly spherical shape tends to apply heat and pressure uniformly to the whole toner during fixing. For this reason, an extremely heat-absorbing portion or an extremely cooled portion that can cause an offset is unlikely to occur, and the effect of the toner of the present invention becomes more remarkable.

  The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of the particles. In the present invention, the flow type particle image analyzer “FPIA-1000” manufactured by Toago Medical Electronics is used. Measurement was performed, and the circularity (Ci) of each particle measured for a particle group having an equivalent circle diameter of 3 μm or more was obtained by the following formula (1), and further measured as shown by the following formula (2) The value obtained by dividing the sum of the circularity by the total number of particles (m) is defined as the average circularity (C).

  In addition, the mode circularity is obtained by dividing the circularity from 0.40 to 1.00 into 61 units every 0.01, and assigning the measured particle circularity to each divided range according to each circularity. This is the circularity of the peak having the maximum frequency value in the frequency distribution.

  In addition, “FPIA-1000”, which is a measuring apparatus used in the present invention, calculates the circularity of each particle and then calculates the average circularity and the mode circularity. A calculation method is used in which 0.40 to 1.00 is divided into 61 classes, and the average circularity and mode circularity are calculated using the center value and frequency of the dividing points. However, an error between each value of the average circularity and the mode circularity calculated by this calculation method and each value of the average circularity and the mode circularity calculated by the calculation formula that directly uses the circularity of each particle described above. Is very small and substantially negligible, and in the present invention, for the reasons of data handling such as short calculation time and simplified calculation formula, Such a calculation method that is partially changed by using the concept of a calculation formula that directly uses the circularity may be used.

  The measurement procedure is as follows.

  A dispersion is prepared by dispersing about 5 mg of a magnetic toner in 10 ml of water in which about 0.1 mg of a surfactant is dissolved, and ultrasonic waves (20 KHz, 50 W) are irradiated to the dispersion for 5 minutes to adjust the concentration of the dispersion. Measurement is performed with the above apparatus at 5000 to 20,000 / μl, and the average circularity and mode circularity of a particle group having a circle-equivalent diameter of 3 μm or more are obtained.

  The average circularity in the present invention is an index of the degree of unevenness of the magnetic toner, and is 1.000 when the magnetic toner is perfectly spherical, and the average circularity becomes smaller as the surface shape of the magnetic toner becomes more complicated. Become.

  In this measurement, the reason why the circularity is measured only for the particle group having an equivalent circle diameter of 3 μm or more is that the particle group of the external additive existing independently of the toner particles in the particle group having an equivalent circle diameter of less than 3 μm. This is because the circularity of the toner particle group cannot be accurately estimated due to the influence of such a large amount.

  The magnetic toner of the present invention needs to have a weight average diameter of 3 to 10 μm in order to develop finer latent image dots faithfully in order to improve image quality. In a toner having a weight average particle size of less than 3 μm, the transfer residual toner on the photoconductor increases due to a decrease in transfer efficiency, and it becomes difficult to suppress the photoconductor scraping and toner fusion in the contact charging step. Furthermore, in addition to an increase in the surface area of the entire toner, the fluidity and agitation as a powder decrease, and it becomes difficult to uniformly charge individual toner particles, so ghost, fog, and transferability tend to deteriorate. It is not preferable. On the other hand, when the weight average particle diameter of the toner exceeds 10 μm, the characters and line images are likely to be scattered and high resolution is difficult to obtain. Also, as the device becomes higher in resolution, the reproduction of one dot tends to deteriorate. Furthermore, when the weight average particle diameter of the toner is 10 μm or more, the offset is further deteriorated.

  Here, the average particle size and particle size distribution of the toner can be measured by various methods such as Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter Co.). In the present invention, Coulter Multisizer (manufactured by Coulter Co.). Are connected to an interface (manufactured by Nikka) and a PC9801 personal computer (manufactured by NEC), and a 1% NaCl aqueous solution is prepared using first grade sodium chloride. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used.

  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 electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of toner particles of 2 μm or more are measured using the 100 μm aperture as the aperture by the Coulter Multisizer. Distribution and number distribution are calculated. Then, the volume-based weight average particle diameter (D4) obtained from the volume distribution and the number-based length average particle diameter obtained from the number distribution, that is, the number average particle diameter (D1) are obtained. The same measurement was performed in the examples described later.

  The tetrahydrofuran (THF) insoluble content of the toner resin component of the present invention is preferably 5 to 70% by mass, more preferably 8 to 60% by mass. Due to the presence of tetrahydrofuran-insoluble matter in the toner, the strength of the toner increases, and the toner is unlikely to deteriorate during long-term use under high temperature and high humidity. For this reason, when the tetrahydrofuran insoluble content is less than 5% by mass, the toner strength is insufficient and the toner deteriorates. On the other hand, if the tetrahydrofuran-insoluble content exceeds 70% by mass, the fixability is impaired, which is not preferable.

  In the magnetic toner of the present invention, it is preferable that substantially no magnetic powder is exposed on the toner surface. In the present invention, the fact that the magnetic powder is not substantially exposed on the toner surface means that the iron element content relative to the carbon element content (A) present on the toner particle surface measured by X-ray photoelectron spectroscopic analysis. The ratio (B / A) of the quantity (B) is defined as being less than 0.001. Since the magnetic powder is not substantially exposed, the fluidity and triboelectricity of the magnetic toner are improved, so as to satisfy various performances required for the toner, such as suppression of fogging, improvement of transferability, suppression of ghost, etc. become. When (B / A) is 0.001 or more, not only the fluidity and triboelectric chargeability of the toner are lowered, but also the surf fixing film is damaged by the magnetic powder exposed on the toner surface, which is not preferable. Furthermore, since the magnetic powder having a large heat capacity absorbs heat from the fixing device first, offset is more likely to occur.

  In the present invention, the ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the toner surface and the carbon element content (A) present on the toner surface. The ratio (E / A) of the content (E) of sulfur element was calculated by performing surface composition analysis by ESCA (X-ray photoelectron spectroscopy).

In the present invention, the ESCA apparatus and measurement conditions are as follows.
Equipment used: 1600S type X-ray photoelectron spectrometer manufactured by PHI (Physical Electronics Industries, Inc.) Measurement conditions: X-ray source MgKα (400 W)
Spectral region 800μmφ

  In the present invention, the surface atomic concentration (atomic%) was calculated from the measured peak intensity of each element using a relative sensitivity factor provided by PHI.

  As the measurement sample, toner is used. When an external additive is added to the toner, the toner is washed with a solvent that does not dissolve the toner, such as isopropanol, and the measurement is performed after removing the external additive. Do.

  In the toner of the present invention, when the projected area equivalent diameter of the toner is C and the minimum value of the distance between the iron oxide and the toner surface in the cross-sectional observation of the toner using a transmission electron microscope (TEM) is D, D / The number of toners satisfying the relationship of C ≦ 0.02 is preferably 50% or more.

  When the number of toners satisfying the relationship of D / C ≦ 0.02 is less than 50%, it means that the dispersion state of the magnetic powder in the toner has a large variation, and the toner physical properties are likely to change due to long-term use. In addition, the charging uniformity of the toner is impaired, and tailing and ghosting are likely to occur, which is not preferable.

  In the present invention, as a specific method for measuring D / C by TEM, particles to be observed can be sufficiently dispersed in a room temperature curable epoxy resin and then cured in an atmosphere at a temperature of 40 ° C. for 2 days. The cured product is preferably observed as it is or as a flaky sample with a microtome equipped with diamond teeth after freezing.

  A specific method for determining the ratio of the number of corresponding particles is as follows. For particles for determining D / C by TEM, the equivalent circle diameter is obtained from the cross-sectional area in the micrograph, and the value is within ± 10% of the number average particle diameter (D1) measured by a Coulter counter. The contained particles are regarded as the corresponding particles, and the minimum value (D) of the distance from the magnetic particle surface is measured for the corresponding particles, and D / C is calculated. In addition, the ratio of particles having a D / C value of 0.02 or less is calculated for 100 corresponding particles. In this case, a magnification of 10,000 to 20,000 times is suitable for the microphotograph to perform measurement with high accuracy. In the present invention, a transmission electron microscope (H-600 model manufactured by Hitachi) is used as an apparatus, and observation is performed at an accelerating voltage of 100 kV, and observation and measurement are performed using a micrograph having a magnification of 10,000.

  Here, even when normal magnetic powder is contained in the polymerized toner, the aforementioned (B / A) is controlled to be less than 0.001, that is, the magnetic powder is not substantially exposed on the toner surface. It is difficult to obtain fluidity of toner particles and uniform triboelectric charging. Furthermore, since the interaction between the magnetic powder and water is strong during the production of the suspension polymerization toner, it is difficult to obtain a toner having an average circularity of 0.970 or more. This is because (1) the magnetic powder is generally hydrophilic and thus easily present on the toner surface. Further, as described above, (2) the magnetic powder moves randomly when the aqueous solvent is stirred, This is probably because the surface of suspended particles composed of the body is dragged, the shape is distorted, and it is difficult to form a circle. In order to solve these problems, it is important to modify the surface characteristics of the magnetic powder.

  Many proposals have been made regarding the surface modification of magnetic powders used in polymerized toners. For example, Japanese Patent Application Laid-Open No. 63-250660 discloses a technique for treating silicon element-containing magnetic particles with a silane coupling agent. However, although the exposure of the magnetic powder to the toner surface is suppressed to some extent by these treatments, there is a problem that it is difficult to make the magnetic powder surface hydrophobic uniformly. The generation of the magnetic powder that is not united or hydrophobized cannot be avoided, exposure to the toner surface occurs, the dispersibility of the magnetic powder is not sufficient, and the particle size distribution becomes wide.

  As an example of using hydrophobic magnetic iron oxide, Japanese Patent Application Laid-Open No. 54-84731 proposes a toner containing magnetic iron oxide treated with alkyltrialkoxysilane. Although the addition of this magnetic iron oxide has certainly improved the electrophotographic properties of the toner, the surface activity of the magnetic iron oxide is inherently small, and coalesced particles are formed at the processing stage, and the hydrophobicity is not uniform. It is not always satisfactory. Further, when a magnetic powder having a small particle diameter is used, uniform processing becomes more difficult, and further improvement is required to apply to the present invention. Furthermore, in order to improve the inclusion of magnetic powder, when a large amount of treatment agent is used, or when a highly viscous treatment agent is used, the degree of hydrophobicity will surely increase, but the particles will coalesce. On the contrary, dispersibility deteriorates.

  The toner produced using such a magnetic powder has non-uniform frictional chargeability, resulting in poor fog, transferability, ghosting and tailing.

  Thus, the conventional polymerized toner using the surface-treated magnetic powder does not necessarily achieve both hydrophobicity and dispersibility, and such polymerized toner can stably obtain a high-definition image. difficult.

  Therefore, it is preferable that the magnetic powder used in the magnetic toner of the present invention is uniformly hydrophobized with a coupling agent. When hydrophobizing the surface of the magnetic powder, it is very preferable to use a method in which the surface treatment is performed while hydrolyzing the coupling agent while dispersing the magnetic powder to have a primary particle size in an aqueous medium. This hydrophobic treatment method is less likely to cause coalescence between the magnetic powders than in the gas phase, and the repulsive action between the magnetic powders due to the hydrophobic treatment works, and the magnetic powder is almost in the form of primary particles. Surface treatment with.

  The method of treating the surface of the magnetic powder while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates gas such as chlorosilanes and silazanes. In the gas phase, the magnetic powders can be easily combined with each other, and a highly viscous coupling agent that has been difficult to be treated can be used, so that the hydrophobizing effect is great.

Examples of the coupling agent that can be used in the surface treatment of the magnetic powder according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, which has the general formula Rm SiYn
[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, or a methacryl group, and n represents an integer of 1 to 3. Show. ]
It is shown by. For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyl Diethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxy Silane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, n-butyltrimethoxysilane, n-he Sill trimethoxysilane, isobutyl trimethoxysilane, trimethyl methoxy silane, n- decyl trimethoxysilane, hydroxypropyl Ritori silane, n- hexadecyl trimethoxy silane, can be mentioned n- octadecyl trimethoxysilane.

  These coupling agents may be used alone or in combination of two or more.

However, among these, it is more preferable to use at least one alkyltrialkoxysilane coupling agent represented by the following formula in order to make the magnetic powder sufficiently hydrophobic.
_{C p H 2p + 1 -Si- (} OC q H 2q + 1) 3
[Wherein p represents an integer of 2 to 20, and q represents an integer of 1 to 3]

  When p in the above formula is smaller than 2, the hydrophobizing treatment is easy, but it is difficult to sufficiently impart hydrophobicity, and it becomes difficult to suppress the exposure of the magnetic particles from the toner particles. On the other hand, if p is larger than 20, the hydrophobicity is sufficient, but the coalescence of the magnetic powder particles increases, making it difficult to sufficiently disperse the magnetic powder particles, and the charging uniformity is impaired. End up.

  On the other hand, when q is larger than 3, the reactivity of the silane coupling agent is lowered and the hydrophobicity is not sufficiently performed.

  In particular, p in the formula represents an integer of 2 to 20 (more preferably an integer of 3 to 15), and q represents an integer of 1 to 3 (more preferably an integer of 1 or 2). A coupling agent should be used.

  The total processing amount of these coupling agents 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 powder, and the surface area of the magnetic powder and the reaction of the coupling agent It is preferable to adjust the amount of the treatment agent according to the property.

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

  Stirring is preferably performed sufficiently, for example, with a mixer having stirring blades so that the magnetic powder particles become primary particles in the aqueous medium.

  In the case where a plurality of types of silane coupling agents are used, a plurality of types of coupling agents are added simultaneously or with a time difference to process the magnetic powder.

  In the magnetic powder thus obtained, no particle aggregation is observed, and the surface of each particle is uniformly hydrophobized, so that it is excellent in charging uniformity and a toner having no ghost and tailing can be obtained.

The magnetic powder used in the toner of the present invention may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum, and silicon. The magnetic powder is mainly composed of iron oxide such as triiron tetroxide and γ-iron oxide, and these are used alone or in combination of two or more. These magnetic powders preferably have a BET specific surface area of ² to 30 m ² / g, particularly 3 to 28 m ² / g, and a Mohs hardness of 5 to 7 by the nitrogen adsorption method.

  The shape of the magnetic powder includes polyhedron, octahedron, hexahedron, spherical shape, needle shape, scale shape, and the like, but those having less anisotropy such as polyhedron, octahedron, hexahedron, and spherical shape increase the image density. Preferred above. The shape of such magnetic powder can be confirmed by SEM or the like. The volume average particle size of the magnetic powder is preferably 0.05 to 0.4 μm, more preferably 0.1 to 0.3 μm. When the volume average diameter is less than 0.05 μm, the decrease in blackness becomes remarkable, the coloring power becomes insufficient as a colorant for black-and-white toner, and the cohesion between magnetic powders becomes strong. Gets worse. In addition, it is very difficult to treat the surface of the magnetic powder. On the other hand, when the volume average particle diameter exceeds 0.4 μm, the coloring power becomes insufficient as in the case of a general colorant. In addition, when a magnetic powder having a volume average particle size larger than 0.4 μm is used, when used as a colorant for a small particle size toner as in the present invention, the magnetic particles are uniformly dispersed in individual toner particles. This is difficult to achieve, and the uniform chargeability of the toner is impaired.

  The magnetic powder used in the toner of the present invention is preferably used in an amount of 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. More preferably, 20 to 180 parts by mass are used. If it is less than 10 parts by mass, the coloring power of the toner is poor, and it is difficult to suppress fogging. On the other hand, when the amount exceeds 200 parts by mass, not only the retention by the magnetic force on the toner carrier is increased and the developability is lowered, but it is difficult not only to uniformly disperse the magnetic powder into individual toner particles, but also the fixability. It will decline.

  The content of the magnetic powder in the toner was measured with a thermal analysis device manufactured by Perkin Elmer, TGA7. In the measurement method, the toner is heated from normal temperature to 900 ° C. at a temperature increase rate of 25 ° C./min in a nitrogen atmosphere, and the weight loss from 100 ° C. to 750 ° C. is defined as the binder resin amount, and the residual mass is approximately The amount of magnetic powder was used.

  For example, in the case of magnetite, the magnetic powder used in the magnetic toner according to the present invention is produced by the following method.

  An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide in an amount equivalent to or higher than the iron component to the ferrous salt aqueous solution. Air was blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 to 14), and iron oxide was oxidized while heating the aqueous solution to 70 ° C. or higher. 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 14, the reaction of ferrous hydroxide is promoted while blowing air, and magnetic iron oxide particles are grown around the seed crystal. 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. Adjust the pH of the solution at the end of the oxidation reaction, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, stir well, stir, filter, dry, and lightly crush after stirring By doing so, hydrophobic treated magnetic iron oxide particles can be obtained. Alternatively, after completion of the oxidation reaction, the iron oxide particles obtained by washing and filtering are 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 important to perform the surface treatment after the oxidation reaction without passing through the drying step, which is an important point in the toner of the present invention.

  As the ferrous salt, iron sulfate generally produced as a by-product in the production of sulfuric acid titanium, iron sulfate produced as a by-product with the surface cleaning of the steel sheet can be used, and iron chloride or the like can be used.

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

  By using the magnetic toner made of the hydrophobic magnetic powder produced as described above, stable toner charging property can be obtained, transfer efficiency is high, and high image quality and high stability are possible.

  The magnetic toner of the present invention preferably has a release agent for improving fixability, and the amount thereof preferably contains 1 to 30% by mass with respect to the binder resin. More preferably, it is 3 to 25% by mass. When the content of the release agent is less than 1% by mass, the effect of adding the release agent is not sufficient, and further, the offset suppressing effect is also insufficient. On the other hand, if it exceeds 30% by mass, the long-term storage stability is deteriorated and the dispersibility of the toner material such as the release agent and the magnetic powder is deteriorated, and the fluidity of the magnetic toner is deteriorated and the image characteristics are deteriorated. Leads to. Further, exudation of the releasing agent component other than during fixing occurs, and the durability under high temperature and high humidity is inferior. Further, since a large amount of wax is included, the toner shape tends to become distorted.

  Examples of the release agent that can be used in the magnetic toner according to the present invention include petroleum waxes such as paraffin wax, microcrystalline wax, and petrolactam and derivatives thereof, montan wax and derivatives thereof, and hydrocarbon waxes and derivatives thereof according to the Fischer-Tropsch method. Polyolefin waxes and their derivatives typified by polyethylene, natural waxes and their derivatives such as carnauba wax and candelilla wax, and the derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. Above all, when the paraffin wax or Fischer-Tropsch wax is graft-modified with a styrene monomer or an unsaturated carboxylic acid monomer, the compatibility between the modified portion and the toner resin component is high and the wax is less likely to be detached. preferable. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes and the like can also be used.

  These release agents may be used alone or in combination of two or more. When two types of waxes are used, it is preferable to add an ester wax having a low melting point and a Fischer-Tropsch wax or polyethylene wax having a high melting point (Tm of 100 ° C. or higher) at the same time.

  Among these release agent components, those having an endothermic peak by differential thermal analysis of 40 to 130 ° C., that is, the maximum endotherm in the region of 40 to 130 ° C. at the time of temperature rise in the DSC curve measured by the differential differential calorimeter. What has a peak is preferable, and what has in a 45-120 degreeC area | region is more preferable. By having the maximum endothermic peak in the above temperature range, the mold releasability is effectively expressed while greatly contributing to low-temperature fixing. When the maximum endothermic peak is less than 40 ° C., the self-aggregating force of the release agent component becomes weak, and as a result, the high temperature offset resistance deteriorates. Further, exudation of the release agent is likely to occur at times other than during fixing, and the charge amount of the toner is reduced, and the durability under high temperature and high humidity is reduced. On the other hand, if the maximum endothermic peak exceeds 130 ° C., the fixing temperature becomes high and low temperature offset is likely to occur, which is not preferable. Further, when granulation / polymerization is performed in an aqueous medium and a toner is obtained directly by the polymerization method, if the maximum endothermic peak temperature is high, a problem such as precipitation of a release agent component mainly occurs during granulation. Dispersibility of the mold is deteriorated, which is not preferable.

  The maximum endothermic peak temperature of the release agent is measured according to “ASTM D 3418-8”. For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, and an empty pan is set as a control. The sample is heated up to 200 ° C. once to remove the heat history, then rapidly cooled, and again at a heating rate of 10 ° C./min. DSC curve measured when the temperature is raised in the range of 30 to 200 ° C. is used. The same measurement was performed in the examples described later.

  The magnetic toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, known ones can be used. However, when the toner is produced using the direct polymerization method as in the present invention, the polymerization inhibitory property is low, and the solubilized product in the aqueous dispersion medium is substantially reduced. Especially preferred are charge control agents which are not present. 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.

  The amount of use of these charge control agents is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.

  However, the addition of the charge control agent as described above is not essential for the magnetic toner of the present invention.

  Next, a toner manufacturing method according to the present invention will be described.

  The polymerized toner according to the present invention is generally a toner composition, that is, a polymerizable monomer that becomes a binder resin, a magnetic powder, a release agent, a plasticizer, a charge control agent, a cross-linking agent, and optionally a colorant. Components necessary for the toner and other additives such as a polymer and a dispersant are appropriately added to obtain a polymerizable monomer system uniformly dissolved or dispersed by a disperser or the like. Subsequently, it suspends in the aqueous medium containing a dispersion stabilizer, and superposes | polymerizes.

  The following are mentioned as a polymerizable monomer which comprises a polymerizable monomer type | system | group.

  Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethylstyrene, methyl acrylate, ethyl acrylate, Acrylate esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, Methacrylic acid dimethyl aminoethyl, methacrylic acid esters other acrylonitrile such as diethylaminoethyl methacrylate, methacrylonitrile, and the like monomers acrylamide. These monomers can be used alone or in combination. Among the above-mentioned monomers, styrene or a styrene derivative is preferably used alone or mixed with other monomers from the viewpoint of the developing characteristics and durability of the toner.

  Further, polymerization may be performed by adding a resin to the polymerizable monomer system. For example, monomers that are water-soluble and cannot be used because they dissolve in an aqueous suspension and cause emulsion polymerization, so that polymerizable monomers containing hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, glycidyl groups, and nitrile groups cannot be used. When it is desired to introduce the monomer component into the toner, it is in the form of a copolymer such as a random copolymer, a block copolymer, or a graft copolymer of these and a vinyl compound such as styrene or ethylene, or a polyester or polyamide. It can be used in the form of polycondensates such as polyaddition polymers such as polyethers and polyimines. When such a polymer containing a polar functional group is allowed to coexist in the toner, the above-described wax component is phase-separated, the encapsulation becomes stronger, and a toner having good blocking resistance and developability can be obtained.

  In addition, resins other than those described above may be added to the monomer system for the purpose of improving the dispersibility and fixing properties of the material, or image characteristics. Examples of the resin used include styrene such as polystyrene and polyvinyltoluene, and the like. Monomer of the substituted product: styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene -Butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene- Butyl methacrylate copolymer, styrene-dimethylamino methacrylate Copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid Styrene copolymers such as copolymers and styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resins, polyester resins, polyamide resins, epoxy resins Polyacrylic acid resin, rosin, modified rosin, terper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin and the like can be used alone or in combination. The addition amount of these resins is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. If it is less than 1 part by mass, the effect of addition is small, while if it is added in an amount of 20 parts by mass or more, it becomes difficult to design various physical properties of the polymerized toner.

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

  Examples of the polymerization initiator used in the present invention include conventionally known azo polymerization initiators and peroxide polymerization initiators. As the azo polymerization initiator, 2,2′-azobis- (2, 4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethyl Examples include valeronitrile, azobisisobutyronitrile, and peroxide polymerization initiators include t-butyl peroxyacetate, t-butyl peroxylaurate, t-butyl peroxypivalate, t-butyl peroxy Oxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxyneodecanoate, t-hexylperoxyacetate, t- Xylperoxylaurate, t-hexylperoxypivalate, t-hexylperoxy-2-ethylhexanoate, t-hexylperoxyisobutyrate, t-hexylperoxyneodecanoate, t-butylper Oxybenzoate, α, α′-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 1, 1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) ) Hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoe T-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis ( Benzoylperoxy) hexane, t-butylperoxy-m-toluoylbenzoate, bis (t-butylperoxy) isophthalate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5- Peroxyesters such as trimethylhexanoate, 2,5-dimethyl-2,5-bis (m-toluoylperoxy) hexane, diacyl peroxides such as benzoyl peroxide, lauroyl peroxide, isobutyryl peroxide, diisopropyl Peroxydicarbonates such as pyrperoxydicarbonate and bis (4-t-butylcyclohexyl) peroxydicarbonate, 1,1-di-t-butylperoxycyclohexane, 1,1-di-t-hexylperoxy Peroxyketals such as cyclohexane, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,2-di-t-butylperoxybutane, di-t-butyl peroxide, dioctyl Examples thereof include dialkyl peroxides such as milperoxide and t-butylcumyl peroxide, and t-butylperoxyallyl monocarbonate as the others. If necessary, two or more of these initiators can be used.

  When the magnetic toner of the present invention is produced by a polymerization method, it is preferable to add a cross-linking agent to generate a THF-insoluble matter. The preferable addition amount of the cross-linking agent is 100 parts by mass of a polymerizable monomer. It is 0.001-15 mass parts with respect to.

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

  Further, when producing the magnetic toner of the present invention, it is preferable to carry out a polymerization reaction by adding a reactive resin together with a polymerizable monomer. Here, the reactive resin is a so-called macromonomer having an unsaturated double bond capable of undergoing a polymerization reaction at the molecular chain terminal. As described above, since it is incorporated as a monomer unit in the molecular chain of the resulting polymer, a large number of branches resulting from long linear molecules of the reactive resin occur in the molecular chain. When the physical cross-linking by the entanglement of the branched chains and the chemical cross-linking by the above-mentioned cross-linking agent are used in combination, a soft gel having appropriate hardness can be obtained, so that both durability and fixability can be achieved.

  The reactive resin is preferably an oligomer or polymer having a number average molecular weight of 1000 to 20000. If the number average molecular weight of the reactive resin is less than 1000, the distance between cross-linking points due to physical cross-linking becomes short because the branched chain is short, and the oozing of the wax at the time of fixing becomes insufficient. When the number average molecular weight of the reactive resin is larger than 20000, the molecular weight of the produced polymer becomes high, so that the low-temperature fixability is lowered.

  As the reactive resin, styrene, a styrene derivative, acrylic acid esters, methacrylic acid esters, acrylonitrile, methacrylonitrile, acrylamide, etc. alone or a polymer obtained by polymerizing two or more kinds is preferably used. Among these, a reactive resin having polystyrene as a main component is preferable because it has good compatibility with the polymerizable monomer composition and thus improves dispersion in the toner. A preferable addition amount of the reactive resin is 2 to 28 parts by mass, more preferably 5 to 25 parts by mass with respect to 100 parts by mass of the polymerizable monomer. If the addition amount is less than 2 parts by mass, the effect of addition of the reactive resin is not sufficient. On the other hand, if it exceeds 28 parts by mass, the molecular weight of the resulting resin increases and the low-temperature fixability decreases.

  The method for producing the magnetic toner of the present invention generally includes a toner composition such as the above-mentioned magnetic powder, polymerizable monomer, mold release agent, etc., as appropriate, homogenizer, ball mill, colloid mill, ultrasonic disperser, etc. The polymerizable monomer system uniformly dissolved or dispersed by the disperser is suspended in an aqueous medium containing a dispersion stabilizer. At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size all at once. The polymerization initiator may be added at the same time as other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Also, a polymerization initiator dissolved in a polymerizable monomer or solvent can be added immediately after granulation and before starting the polymerization reaction.

  After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and the particles are prevented from floating and settling.

  In the production of the magnetic toner of the present invention, a known surfactant, organic dispersant, or inorganic dispersant can be used as a dispersion stabilizer. In particular, inorganic dispersants do not easily generate harmful ultrafine powders, and because of their steric hindrance, dispersion stability is obtained, so stability does not collapse even when the reaction temperature is changed, and cleaning is easy and adversely affects the toner. Since it is difficult to give, it can be preferably used. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, carbonates such as calcium carbonate and magnesium carbonate, calcium metasuccinate, calcium sulfate, barium sulfate and the like. And inorganic oxides such as calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina.

  When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated and used in an aqueous medium. For example, in the case of 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, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine toner by emulsion polymerization is produced. It is more convenient because it is less likely to occur. When removing the residual polymerizable monomer at the end of the polymerization reaction, it becomes an obstacle, so it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.

  These inorganic dispersants are desirably used alone in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. Since it is slightly weak, 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, potassium stearate and the like.

  The polymerization is carried out at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, it becomes more complete whether the separation economy to be sealed inside or the kind of wax does not precipitate due to phase separation. 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.

  After the polymerization reaction, the polymerized toner particles are filtered, washed, and dried by a known method, and if necessary, inorganic fine powder is mixed and adhered to the surface to obtain the magnetic toner of the present invention. Moreover, it is also possible to put a classification process in the manufacturing process and cut coarse powder and differentiation.

  In order to improve the image quality, it is preferable that a fluidity improver is externally added to the toner particles of the present invention.

  As the fluidity improver, inorganic fine powders such as silicate fine powder, titanium oxide, and aluminum oxide are preferable. The inorganic fine powder is preferably hydrophobized with a hydrophobizing agent such as a silane coupling agent, silicone oil or a mixture thereof.

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

  In FIG. 2, reference numeral 100 denotes a photosensitive drum, around which a primary charging roller 117, a developing device 140, a transfer charging roller 114, a cleaner 116, a register roller 124, and the like are provided. The photoreceptor 100 is charged to −700 V by the primary charging roller 117. (Applied voltage is AC voltage -2.0 kVpp, DC voltage -700 Vdc) Then, exposure is performed by irradiating the photoconductor 100 with laser light 123 by the laser generator 121. The electrostatic latent image on the photoconductor 100 is developed with a one-component magnetic toner by the developing device 140 and 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 or the like 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 member 100. The gap between 100 and the developing sleeve 102 is maintained at about 230 μm by a sleeve / photoreceptor 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, S1 is developing, N1 is the toner coating amount regulation, S2 is toner intake / conveyance, and N2 is the toner blowing prevention. An elastic blade 103 is provided as a member for regulating the amount of magnetic toner that adheres to the developing sleeve 102 and is conveyed, and the amount of toner conveyed to the developing region is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. . In the developing region, a DC and AC developing bias is applied between the photoconductor 100 and the developing sleeve 102, and the toner on the developing sleeve flies onto the photoconductor 100 in accordance with the electrostatic latent image and becomes a visible image.

  The inertial radius Rw, absolute molecular weight Mw, and THF-insoluble content of the magnetic toner of the present invention were measured as follows.

(1) SEC-MALLS measurement After 0.03 g of toner is dispersed in 10 ml of o-dichlorobenzene and dissolved, it is shaken with a shaker at 135 ° C. for 24 hours, filtered with a 0.2 μm filter, and the filtrate is used as a sample.

[Analysis conditions]
Separation column: Shodex (TSK GMHHR-H HT20) × 2
Column temperature: 135 ° C
Mobile phase solvent: o-dichlorobenzene mobile phase flow rate: 1.0 ml / min.
Sample concentration: about 0.3%
Injection volume: 300 μl
Detector 1: Multi-angle light scattering detector Wyatt DAWN EOS
Detector 2: Differential refractive index detector Shodex RI-71

[Measurement theory]
(LS) = (dn / dc) ² × C × Mw × KLS (1)
(LS); Measurement voltage value of the detector (v)
(Dn / dc): Increment of refractive index per 1 g of sample (ml / g)
C: concentration (g / ml)
K _LS ; Coefficient of measurement voltage and scattering intensity (reduction Rayleigh ratio) (equipment constant)

  In the present invention, (dn / dc) was set to 0.068 ml / g from the literature value of polystyrene.

In SEC-MALLS, the molecular size is separated by the molecular sieve of the SEC column, and Mw (absolute molecular weight) and C (concentration) are changed and eluted, so it is necessary to separately measure the concentration detector in combination with MALLS. The signal intensity is converted into a concentration C to determine the molecular weight Mw. In the present invention, a differential refractive index detector (RI) is used as a concentration detector, and the signal intensity (RI) of the RI detector is converted into a concentration C and used.
(RI) = (dn / dc) × C × KRI (2)
KRI: Coefficient of measurement voltage and refractive index (RI constant, calibrated with polystyrene standard)

  The molecular size (radius of inertia) was calculated by Debye Plot.

(2) Amount of THF-insoluble matter A polyester resin or toner is weighed, put into a cylindrical filter paper (for example, No. 86R size 28 × 10 mm, manufactured by Toyo Filter Paper Co., Ltd.), and applied to a Soxhlet extractor. Extraction is performed for 16 hours using 200 ml of THF as a solvent. At this time, extraction is performed at a reflux rate such that the extraction cycle of THF is about once every 4 to 5 minutes. After completion of the extraction, the cylindrical filter paper is taken out and weighed to obtain an insoluble content of the polyester resin or toner.

When the toner contains a THF-insoluble component such as a magnetic substance or pigment other than the resin component, the weight of the toner put in the cylindrical filter paper is W1 g, and the extracted THF-soluble resin component is W2 g. When the mass of the THF-insoluble component other than the resin component contained in the toner is W3 g, the content of the THF-insoluble component of the resin component in the toner can be obtained from the following formula.
THF insoluble matter (mass%) = [(W1- (W3 + W2)) / (W1-W3)] × 100

  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.

(Production Example 1 of hydrophobic magnetic iron oxide)
An aqueous solution containing ferrous hydroxide was prepared by mixing 1.0 to 1.1 equivalents of a caustic soda solution with respect to iron ions in an aqueous ferrous sulfate solution. While maintaining the aqueous solution at pH 8, air was blown in, and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals. Then, after adding ferrous sulfate aqueous solution so that it becomes 0.9 to 1.2 equivalent to the initial alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH = 8, The oxidation reaction was advanced while blowing air, and the pH was adjusted to about 6 at the end of the oxidation reaction to complete the oxidation reaction. The produced iron oxide particles are washed, filtered, and once taken out, re-dispersed in another water without drying, the pH of the re-dispersed liquid is adjusted, and the n-hexyltrimethoxysilane coupling agent is sufficiently stirred. Was added to 100 parts of magnetic iron oxide and stirred sufficiently. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method, and then the aggregated particles were crushed to obtain hydrophobic magnetic iron oxide 1 having an average particle size of 0.19 μm.

(Production Example 2 of Hydrophobic Magnetic Powder)
In the same manner as in Production Example 1 of hydrophobic magnetic powder, the oxidation reaction proceeds, the magnetic powder produced after the oxidation reaction is washed, filtered and dried, and the aggregated particles are crushed, and the average particle size is 0. A 19 μm magnetic powder was obtained.

  After re-dispersing the magnetic powder in another aqueous medium, the pH of the re-dispersed liquid is adjusted to about 6, and the n-hexyltrimethoxysilane coupling agent is added to 100 parts of the magnetic powder while stirring. 2.0 parts were added and the coupling process was performed. The obtained magnetic particle slurry was washed, filtered and dried by a conventional method, and then the aggregated particles were pulverized to obtain hydrophobic magnetic powder 2 having an average particle diameter of 0.19 μm.

<Manufacture of magnetic toner 1>
An aqueous medium containing a dispersion stabilizer by adding 450 parts of a 0.1M Na ₃ PO ₄ aqueous solution to 720 parts of ion-exchanged water and heating to 60 ° C., and then adding 67.7 parts of a 1.0 M CaCl ₂ aqueous solution. Got.

Styrene 79 parts n-Butyl acrylate 21 parts Divinylbenzene 0.5 part Reactive resin (styrene macromonomer, Mn = 5700) 10 parts Saturated polyester resin (polycondensate of propylene oxide-modified bisphenol A and isophthalic acid, acid value = 8 mg KOH / g, Tg = 65 ° C., Mn = 6000, Mw = 10000) 6 parts Negative charge control agent (dialkyl salicylic acid aluminum complex compound) 1 part Hydrophobic magnetic iron oxide 1 90 parts Atlite (Mitsui Miike Chemical) And dispersed and mixed uniformly.

  This monomer composition was heated to 60 ° C., and 10 parts of styrene-modified paraffin wax (maximum endothermic peak in DSC 74 ° C.) was added and dissolved therein, and the polymerization initiator t-butyl-oxy 2 was added thereto. -A polymerizable monomer composition was prepared by dissolving 4 parts of ethylhexanoate.

The polymerizable monomer composition was put into the aqueous medium, and stirred at 10,000 rpm for 15 minutes in a TK homomixer (Special Machine Industries Co., Ltd.) at 60 ° C. in an N ₂ atmosphere. Grained. Thereafter, the mixture was reacted at 80 ° C. for 8 hours while stirring with a paddle stirring blade. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the dispersant, the dispersant was dissolved, filtered, washed with water, and dried to obtain toner particles 1.

100 parts of the toner particles and silica having a primary particle diameter of 12 nm are treated with hexamethyldisilazane and then treated with silicone oil, and 1.0 part of hydrophobic silica fine powder having a BET value of 120 m ² / g after the treatment is obtained. Magnetic toner 1 was prepared by mixing using a Henschel mixer (Mitsui Miike Chemical Co., Ltd.). Table 1 shows the physical properties of the magnetic toner 1.

<Manufacture of magnetic toner 2>
A magnetic toner 2 was obtained in the same manner as in the production of the magnetic toner 1 except that no reactive resin was added. Table 1 shows the physical properties of the magnetic toner 2.

<Manufacture of magnetic toner 3>
A magnetic toner 3 was obtained in the same manner as in the production of the magnetic toner 1 except that the amount of the reactive resin was 25 parts. Table 1 shows the physical properties of the magnetic toner 3.

<Manufacture of magnetic toner 4>
Magnetic toner 4 was obtained in the same manner as in the production of magnetic toner 1 except that 0.5 part of α-methylstyrene dimer was further added to the monomer composition. Table 1 shows the physical properties of the magnetic toner 4.

<Manufacture of magnetic toner 5>
A magnetic toner 5 was obtained in the same manner as in the production of the magnetic toner 1 except that the hydrophobic magnetic iron oxide 1 was changed to the hydrophobic magnetic iron oxide 2. Table 1 shows the physical properties of the magnetic toner 5.

<Manufacture of magnetic toner 6>
A magnetic toner 6 was obtained in the same manner as in Production 1 of the magnetic toner 1 except that the amount of styrene-modified paraffin wax was 40 parts. Table 1 shows the physical properties of the magnetic toner 6.

<Manufacture of magnetic toner 7>
A magnetic toner 7 was obtained in the same manner as in the production of the magnetic toner 1 except that the styrene-modified paraffin wax was changed to polyethylene wax (maximum value of endothermic peak in DSC: 135 ° C.). Table 1 shows the physical properties of the magnetic toner 7.

<Manufacture of magnetic toner 8>
A magnetic toner 8 was obtained in the same manner as in the production of the magnetic toner 1 except that the amount of the reactive resin was 30 parts. Table 1 shows the physical properties of the magnetic toner 8.

<Manufacture of magnetic toner 9>
A magnetic toner 9 was obtained in the same manner as in the production of the magnetic toner 1 except that the amount of the reactive resin was 0.3 part and 1.0 part of t-dodecyl mercaptan was further added. Table 1 shows the physical properties of the magnetic toner 9.

<Manufacture of magnetic toner 10>
An aqueous medium containing a dispersion stabilizer by adding 450 parts of a 0.1M Na ₃ PO ₄ aqueous solution to 720 parts of ion-exchanged water and heating to 60 ° C., and then adding 67.7 parts of a 1.0 M CaCl ₂ aqueous solution. Got.

Styrene 79 parts n-Butyl acrylate 21 parts Divinylbenzene 0.5 part Reactive resin (styrene macromonomer, Mn = 5700) 10 parts Saturated polyester resin (polycondensate of propylene oxide-modified bisphenol A and isophthalic acid, acid value = 8 parts KOH / g, Tg = 65 ° C., Mn = 6000, Mw = 10000) 6 parts Hydrophobic magnetic iron oxide 1 90 parts The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.).

  This monomer composition was heated to 60 ° C., and 4 parts of a polymerization initiator t-butyl-oxy-2-ethylhexanoate was dissolved therein to obtain a polymerizable monomer composition.

The polymerizable monomer system was charged into the aqueous medium and granulated by stirring at 10,000 rpm for 15 minutes in a TK homomixer (Special Machine Industries Co., Ltd.) at 60 ° C. in an N ₂ atmosphere. . Thereafter, the mixture was reacted at 80 ° C. for 8 hours while stirring with a paddle stirring blade. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the dispersant, the dispersant was dissolved, filtered, washed with water, and dried to obtain iron oxide-containing resin particles.

next,
100 parts of the iron oxide-containing resin particles negative charge control agent (monoazo dye-based Fe compound) 1 part styrene-modified paraffin wax 3 parts (maximum endothermic peak at DSC of 74 ° C.)
The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 110 ° C., the cooled kneaded product is coarsely pulverized with a hammer mill, and the coarsely pulverized product is finely pulverized with a jet mill. The pulverized product was classified by air to obtain toner particles having a weight average particle diameter of 7.9 μm. To 100 parts of the toner particles, 1.0 part of silica used in the production of the magnetic toner 1 was added and mixed using a Henschel mixer to prepare a magnetic toner 10. Table 1 shows the physical properties of the magnetic toner 10.

<Example 1>
As an image forming apparatus, LBP-1760 was remodeled, and an apparatus having a structure generally shown in FIG. 2 was used.

The potential of the electrostatic charge image carrier (photosensitive drum 100) was set to dark portion potential V _d = −650V and light portion potential V _L = −130V. Further, the gap between the electrostatic charge image carrier 100 and the developing sleeve 102 is 270 μm, and a resin layer having a layer thickness of about 7 μm and a JIS centerline average roughness (RA) of 1.0 μm as a toner carrier is formed on the surface. A developing sleeve formed on an aluminum cylinder with a diameter of 16φ blasted with a developing magnetic pole of 85 mT (850 gauss), a toner regulating member having a thickness of 1.0 mm and a free length of 0.5 mm urethane blade 39.2 N / m The contact was made at a linear pressure of (40 g / cm).
Phenol resin 100 parts Graphite (particle size approx. 7 μm) 90 parts Carbon black 10 parts

Next, a DC bias component V _dc = −450 V, an overlapping AC bias component V _pp = 1600 V, and F = 2200 Hz were used as the developing bias. The peripheral speed of the developing sleeve was 110% (103 mm / sec) in the forward direction with respect to the peripheral speed of the photosensitive member (94 mm / sec). The transfer bias was set to 1.5 kV DC.

  As a fixing method, there was used a fixing device of LBP-1760 which does not have an oil application function and which is fixed by heating and pressing with a heater through a film. At this time, a pressure roller having a fluororesin surface layer was used, and the diameter of the roller was 30 mm. The fixing temperature was set to 180 ° C., and the nip width was set to 7 mm (the evaluation of the fixing property will be described later).

100 g of magnetic toner 1 is filled in a cartridge, and the image pattern consists of only a horizontal line with a printing rate of 2% in a normal temperature and humidity environment (23 ° C., 60% RH) and a low temperature and low humidity environment (15 ° C., 10% RH). An image printing test of 1000 sheets was performed. Note that 90 g / m ² of paper was used as the transfer material.

  As a result, the toner 1 showed high transferability in the initial stage and after the image was printed on 1000 sheets, and there was no ghost and a good image without fogging on the non-image area was obtained. In addition, it was excellent in low-temperature fixability and offset resistance, and was able to take a wide fixing temperature range. Table 2 shows the evaluation results under a normal temperature and humidity environment, and Table 3 shows the evaluation results under a high temperature and high humidity environment.

  The evaluation items described in the examples of the present invention and the comparative examples and the judgment criteria thereof will be described.

(Fixability)
Using a modified LBP-1760 machine, a fixing test was performed in a normal temperature and humidity environment. The image area ratio at this time was 25%, and the applied toner amount per unit area was set to 0.7 mg / cm ² . The fixing start temperature is measured by adjusting the set temperature of the fixing device every 5 ° C. within a temperature range of 130 to 230 ° C., outputting a fixed image at each temperature, and obtaining the fixed image at 4.9 kPa. The fixing temperature at which the density reduction rate before and after the rubbing was 10% or less was determined as the fixing start temperature by rubbing with a Silbon paper to which a load of (50 g / cm ² ) was applied. As for the offset temperature, the stain on the image and the back of the paper was visually evaluated. The set temperature was increased from 130 ° C., the temperature immediately before the occurrence of further offset was further increased by the offset temperature, and the temperature was further increased, and the temperature at which the high temperature offset occurred was defined as the high temperature offset temperature.

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

(Transfer efficiency)
The transfer efficiency is determined by tapering the transfer residual toner on the photoconductor after the solid black image transfer with a Mylar tape and pasting it on the paper. The Macbeth density value is C, and the Mylar is applied on the paper with the toner after the fixing before the transfer. When the Macbeth concentration of the tape was affixed to D and the Macbeth concentration of the Mylar tape affixed on unused paper was assumed to be E, it was approximately calculated by the following formula.

The transfer efficiency obtained from the above calculation results was judged according to the following criteria.
A: Transfer efficiency is 96% or more.
B: Transfer efficiency is 92% or more and less than 96%.
C: Transfer efficiency is 89% or more and less than 92%.
D: Transfer efficiency is less than 89%.

(Fog)
The fog was measured using a REFECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. The filter used was a green filter, and fog was calculated from the following formula.
Fog (reflectance) (%) = reflectance on standard paper (%) − reflectance of sample non-image area (%)

The criteria for fogging are as follows.
A: Very good (less than 1.5%)
B: Good (1.5% or more to less than 2.5%)
C: Normal (2.5% or more to less than 4.0%)
D: Poor (4% or more)

(ghost)
The ghost criterion is that the image shown in FIG. 1 is output and visually judged according to the following criteria.
A: No ghost is generated.
B: Although a slight ghost is generated, a good image is obtained.
C: Although the ghost is generated, there is no problem in practical use.
D: Image with poor ghost and unpreferable for practical use.

< Reference Examples 1 and 2 and Examples 2 to 5 >
Magnetic toners 2 to 7 were used as toners, and image printing tests, fixing evaluations and durability evaluations were performed under the same conditions as in Example 1. As a result, there were no problems in the initial image characteristics, and no problem was obtained in all of the printed sheets up to 1000 sheets. Table 2 shows the evaluation results under a normal temperature and humidity environment, and Table 3 shows the evaluation results under a high temperature and high humidity environment.

<Comparative Examples 1-3>
As the toner, magnetic toners 8 to 10 were used, and an image printing test, a fixability evaluation, and a durability evaluation were performed under the same conditions as in Example 1. As a result, the transfer efficiency decreased and the ghost deteriorated along with the durability test. Further, the magnetic toners 9 and 10 were further offset even in a relatively high temperature region. Table 2 shows the evaluation results under a normal temperature and humidity environment, and Table 3 shows the evaluation results under a high temperature and high humidity environment.

It is a conceptual diagram of a ghost. 1 is a schematic diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention.

Explanation of symbols

100 photoconductor (image carrier, charged body)
102 Developing sleeve (magnetic toner carrier)
114 Transfer roller (transfer member)
116 Cleaner 117 Charging roller (contact charging member)
121 Laser beam scanner (latent image forming means, exposure device)
124 Feed roller 125 Conveying member 126 Fixing device 140 Developing device 141 Stirring member

Claims (9)

At least a polymerizable monomer, a magnetic toner having a weight average particle diameter of 3 to 10μm is prepared by polymerizing magnetic iron oxide, and a polymerizable monomer composition containing a release agent,
The average circularity of the magnetic toner is 0.970 or more,
The inertial radius Rw and absolute molecular weight Mw in the size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) measurement of the o-dichlorobenzene soluble matter of the magnetic toner are expressed by the following formulae.
0.25 × 10 ⁻⁴ ≦ Rw / Mw ≦ 4.0 × 10 ⁻⁴ (Formula 1)
A magnetic toner characterized by satisfying During the polymerizable monomer composition, the magnetic toner according to claim 1, characterized in Rukoto contain a macromonomer having a polymerizable reactive unsaturated double bond in the molecular chain ends.   The magnetic toner according to claim 1 or 2, wherein the resin component of the magnetic toner has an insoluble content of tetrahydrofuran (THF) of 5 to 70% by mass.   The magnetic toner according to claim 1, wherein the magnetic toner has a mode circularity of 0.99 or more.   The ratio (B / A) of the abundance (B) of the iron element to the abundance (A) of the carbon element present on the surface of the magnetic toner particle as measured by X-ray photoelectron spectroscopy of the magnetic toner is 0.001. The magnetic toner according to claim 1, wherein the magnetic toner is less than or equal to 5.   When the equivalent diameter of the projected area of the magnetic toner is C and the minimum distance between the magnetic powder and the toner particle surface is D in the tomographic surface observation of the magnetic toner using a transmission electron microscope (TEM), D 6. The magnetic toner according to claim 1, wherein the toner satisfying the relationship of /C≦0.02 is 50% by number or more.   The magnetic toner according to claim 1, wherein the magnetic toner contains a release agent in an amount of 1 to 30% by mass based on the polymerizable monomer.   The magnetic toner according to any one of claims 1 to 7, wherein the endothermic peak of the release agent by differential thermal analysis is in the range of 40 to 130 ° C. A charging step for charging the photosensitive member, an electrostatic latent image forming step for forming an electrostatic latent image on the charged photosensitive member, and a developing step for developing the electrostatic latent image using magnetic toner to form a toner image An image forming method comprising a transfer step of transferring the toner image to a transfer material, and a fixing step of fixing the toner image to the transfer material,
9. The image forming method according to claim 1, wherein the fixing step uses a fixing device that heats and pressurizes with a heater through a film, and the magnetic toner is the magnetic toner according to claim 1. .

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