JP2003043735A - Magnetic toner and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic toner having preferable fixing property, high transfer efficiency, little fog, excellent electrification stability and high image density even for long-term use in a high temperature and high humidity environment, and hardly causing ghost or trailing, and to provide a method for manufacturing the magnetic toner. SOLUTION: The magnetic toner contains at least a binder resin, magnetic powder and a sulfur-containing polymer and has 3 to 10 μm weight average particle size, >=0.970 average circularity and 5 to 60 mass% tetrahydrofuran insoluble content of the resin component. The ratio of E/A, wherein A is the amount of carbon element present on the surface and E is the amount sulfur element present on the surface satisfies the relation of 3×10<-4> <=E/A<=50×10<-4> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic toner for visualizing an electrostatic latent image in an image forming method such as an electrophotographic method, an electrostatic recording method, a magnetic recording method and a toner jet method, and the magnetic toner. Manufacturing method.

[0002]

2. Description of the Related Art In recent years, image forming apparatuses are required to have higher performance and smaller size, and in order to satisfy such requirements, the image forming apparatus, the image forming process, and related products are required. Various techniques have been proposed for elements and the like. Further, in order to satisfy such requirements, there is a demand for a toner that is a developer, which has a small particle size and has high transfer efficiency and less fog.

However, as the toner particle size becomes smaller, stable triboelectric charging of the toner powder becomes an important technique. That is, unless the individual fine toner particles have a uniform charge amount, the image stability is more likely to decrease significantly. This is because the particle size of the toner is simply reduced,
In addition to the Coulomb force applied to the toner particles in the transfer process, the adhesion force of the toner particles to the photoconductor (mirror image force, van der Waals force, etc.) is increased, and as a result, the transfer residual toner is increased. This is because, as the toner diameter is reduced, the fluidity is deteriorated, so that the charge amount of each toner particle tends to be non-uniform, and fog and toner particles having poor transferability increase.

Further, from the viewpoint of improving the toner characteristics, it is desired to expose the magnetic powder or to improve the magnetic powder itself, but there is still a point to be improved that the charging property and the toner fluidity are compatible with each other. For example, various proposals have been made to improve the conventionally known magnetic powder, but it is difficult to suppress the charging leak by only improving the magnetic powder itself, and there are still points to be improved as a small particle size magnetic toner. is doing.

On the other hand, from the viewpoint of exposing the magnetic powder,
Attempts have been made to solve the problem by improving the toner manufacturing method.

In the conventional toner, a binder resin, a colorant, and the like are melt-mixed, uniformly dispersed, and then pulverized by a fine pulverizer,
Although a toner having a desired particle size has been classified (classified by a classifier) to be manufactured (pulverization method), there is a limitation in the selection range of materials for making the toner into a fine particle size. For example, the resin colorant dispersion must be sufficiently brittle to be comminuted in an economically available manufacturing apparatus. From this requirement, in order to make the resin colorant dispersion brittle, it is often further pulverized or pulverized when used as a developing toner in a copying machine or the like.

Further, since a considerable amount of fine powdery magnetic powder is mixed and dispersed in the toner and a part of the magnetic powder is exposed on the surface of the toner particle, the fluidity of the magnetic toner and the The frictional electrification property is affected, and as a result, various characteristics required for the magnetic toner such as developing characteristics and durability of the magnetic toner are fluctuated or deteriorated. It is considered that this is caused by the presence of magnetic powder fine particles having a resistance relatively lower than that of the resin forming the toner on the surface of the magnetic toner. Further, the chargeability of the toner has a great influence on development and transfer, and the above-mentioned problems have not been solved.

In order to overcome such problems of the toner by the pulverization method, a method for producing the toner by the polymerization method has been proposed. Toner produced by the polymerization method (hereinafter, polymerized toner) is
The toner can be easily made into fine particles, and further, since the shape of the obtained toner is spherical, it has excellent fluidity,
It is advantageous for high image quality.

Further, a step such as a seed polymerization method in which a monomer or the like is further added and polymerized during the production of the polymer particles or after the completion of the polymerization to cover the particle surfaces with a resin is also possible, and the exposure of the colorant can be suppressed. it can. However, when the magnetic powder is contained in the polymerized toner, the fluidity and the charging property are rather lowered, and the developability cannot be satisfied. This is because the magnetic particles are generally hydrophilic and therefore tend to exist on the toner surface.

In order to solve this problem, it is important to modify the surface characteristics of the magnetic powder. In order to improve the dispersibility and inclusion of the magnetic powder in the polymerized toner, many proposals have been made regarding the surface modification of the magnetic powder. For example, JP-A-59-200254 and JP-A-59-20025.
6, JP-A 59-200257, JP-A 5
Various silane coupling agent treatment techniques for magnetic powder have been proposed in Japanese Patent Application Laid-Open No. 9-224102 and the like.
Japanese Patent No. 50660 discloses a technique of treating magnetic particles containing elemental silicon with a silane coupling agent.

However, although these treatments can suppress the exposure in the toner to some extent, it is difficult to uniformly make the surface of the magnetic powder uniform, and the exposure of the magnetic powder to the toner surface is suppressed. Therefore, the solution of the above problems is not sufficient.

On the other hand, regarding the amount of magnetic powder on the toner surface, a toner having a special structure in which magnetic fine particles are not present in the toner surface layer is disclosed in JP-A-7-209904 by means such as the above-mentioned seed (swelling) polymerization method. Has been made. This toner is excellent in the inclusion of the magnetic powder and the magnetic powder is not exposed on the surface of the toner.

However, in the toner of such a form, the charge control agent, which should be present on the surface of the toner particles, is also completely covered, so the chargeability of the toner is poor under high humidity, and as shown in FIG. A so-called ghost may appear on the image.

Further, a toner having a poor charging property is likely to have a rough ears on the toner carrier, and causes tailing at the time of development due to deterioration of the toner during long-term use under high humidity.

As described above, various improvements have been disclosed regarding the existence state of magnetic powder and the magnetic powder itself.
The chargeability of the small particle size magnetic toner was still insufficient.

Attempts have been made to solve these problems by improving the charge control agent. For example, as a negative charge control agent, salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid, metal compounds of aromatic carboxylic acids such as dicarboxylic acids, metal salts or metal complexes of azo dyes or azo pigments, sulfonic acid or carboxylic acid groups. Polymer compounds having a side chain of, boron compounds, urea compounds, silicon compounds, calixarenes, quaternary ammonium salts as positive charge control agents, polymer compounds having a quaternary ammonium salt in the side chain, guanidine Various charge control agents such as compounds, nigrosine compounds and imidazole compounds are disclosed in JP-B-45-26478, JP-A-59-62870 and JP-A-62-2620.
No. 55, etc.

However, when the above-mentioned charge control agent is used for the magnetic toner, the chargeability tends to be low because the magnetic particles function as charge leakage sites, and the transferability is deteriorated especially in the case of a small particle size toner. In that case, it is necessary to make the conditions of the transfer process excessively strong, and as a result, transfer scattering is likely to occur.

Of these, a polar polymer charge control agent has recently been attracting attention because it has excellent compatibility with other components and can be uniformly charged. For example, JP-A-63-18476.
No. 2, JP-A-3-56974, JP-A-8-1.
No. 79564, JP-A No. 11-184165,
JP-A-11-28126, JP-A-11-3272
No. 08 and Japanese Patent Application Laid-Open No. 2000-56518 disclose toners using a monomer containing a sulfonic acid group or a similar functional group as an essential component. However, even when these charge control agents are used, when the magnetic toner having a small particle size is used, the toner has a wider charge distribution than the case where other metal compound-based charge control agents are added. I understand.

As a result of studies conducted by the present inventors, this is because the charge control agent itself is a polymer although it has a sufficient performance in charging, but tends to be easily charged up. It has been found that the body leaks charge, and is easily affected by poor dispersion in toner particles and toner particle size distribution.

Further, the charge control agent itself affects the dispersibility of the colorant in the toner and the fluidity of the toner. Therefore, when a sufficient amount of the charge control agent is added, excessive slip occurs and the charge distribution It is also known that it will be a wide toner. Furthermore, in order to improve these, for example, when a charge control agent of a polar polymer and a charge control agent of an inorganic metal complex are used in combination, each charge control agent expresses each charging performance due to its chemical structure. Therefore, the toner has a wider charge distribution. As a result, the toner is non-uniformly charged, and phenomena such as ghost, fogging, and transfer scattering occur.

As described above, the improvement of the charge control agent for the small particle size magnetic toner is still insufficient at present.

Further, as a combination of the above-mentioned polymerized toner and these charge control agents, JP-A-11-184165, JP-A-11-288129, and JP-A-11-3 are used.
No. 27208 and Japanese Patent Laid-Open No. 2000-56518 disclose the technology of a polymerized toner having a sulfonic acid group-containing resin. Further, JP-A-1-193748 discloses a toner having a charge controllable functional group on its surface by dissolving a water-soluble monomer having a charge controllable functional group in a suspension dispersion and polymerizing the solution. The technology of the manufacturing method is disclosed.

However, these examples are all about the non-magnetic toner, and the relation with the performance required for the magnetic toner as described above is not described.

[0024]

SUMMARY OF THE INVENTION The present invention is intended to provide a magnetic toner and a method for producing the same, which solves the above-mentioned problems of the prior art, and an object of the present invention is to provide a good fixing property. Magnetic toner with high transfer efficiency, low fog, excellent charge stability, high image density even during long-term use in a high temperature and high humidity environment, and less likely to cause phenomena such as ghost and tailing. It is to provide a method for manufacturing a toner.

[0025]

The present invention provides a magnetic toner containing at least a binder resin, a magnetic powder, and a sulfur-containing polymer, as a means for achieving the above object.
The weight average particle diameter is 3 to 10 μm, and the average circularity is 0.
970 or more, tetrahydrofuran insoluble content of the resin component is 5 to 60 mass%, and the amount of carbon element present on the surface is A, and the amount of sulfur element present on the surface is E , A, which is the ratio of E to A, satisfies the following formula (1).

[Equation 4] 3 × 10 ⁻⁴ ≦ E / A ≦ 50 × 10 ⁻⁴ (1)

The present invention also provides a method for producing a magnetic toner of the present invention, wherein particles having at least magnetic powder are dispersed in an aqueous medium, and then a mixture of a polymerizable monomer and a sulfur-containing polymer is added. Provided is a method for producing a magnetic toner, which comprises adding and polymerizing.

In the present invention, it is preferable that the intensity of magnetization in a magnetic field of 79.6 kA / m is 10 to 50 Am ² / kg.

In the present invention, the mode circularity is 0.99.
The above is preferable.

In the present invention, the E / A is expressed by the following formula (2)
It is preferable to satisfy the following, and it is more preferable to satisfy the following formula (3).

[Equation 5] 3 × 10 ^-4 ≤ E / A ≤ 35 × 10 ^-4 (2)

[Equation 6] 3 × 10 ^-4 ≤ E / A ≤ 25 × 10 ^-4 (3)

In the present invention, the sulfur-containing polymer preferably contains sulfonic acid group-containing (meth) acrylamide.

In the present invention, the amount of carbon element present on the surface is A, and the amount of iron element present on the surface is B.
And B / A, which is the ratio of B to A, is 0.0
It is preferably less than 01.

In the present invention, when the projected area equivalent diameter of the magnetic toner is C and the minimum value of the distance between the magnetic toner surface and the magnetic powder is D, the relationship of D / C≤0.02 is satisfied. The magnetic toner content is preferably 50% by number or more.

In the present invention, the magnetic toner preferably contains a release agent in an amount of 1 to 30% by mass based on the binder resin.
The release agent has an endothermic peak of 40 to 110 by differential thermal analysis.
C., and more preferably 45 to 90.degree.

Further, in the present invention, the tetrahydrofuran-insoluble content of the resin component of the magnetic toner is preferably 8 to 50% by mass.

In the present invention, the magnetic powder is preferably hydrophobized with a coupling agent, and more preferably the surface is hydrophobized while hydrolyzing the coupling agent in an aqueous medium. .

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the present inventors have a close relationship between the exposure of magnetic powder and the charge distribution of magnetic toner, and the charge distribution greatly depends on the toner shape. From the above, we investigated in detail the relationship between the charge control substance and the physical properties of the toner.
It has been found that the ghost and the tailing can be improved by controlling the amount of the insoluble matter and the specific element existing on the toner surface.

That is, the magnetic toner of the present invention is a magnetic toner containing at least a binder resin, a magnetic powder, and a sulfur-containing polymer, and has a weight average particle diameter of 3 to 10 μm.
The average circularity is 0.970 or more, the tetrahydrofuran (THF) insoluble content of the resin component is 5 to 60% by mass, and the existing amount of the carbon element existing on the surface is A,
When the amount of elemental sulfur present on the surface is E, A
The ratio of E to E is 3 × 10 ⁻⁴ ≦ E / A ≦ 5
It has been found that by satisfying 0 × 10 ⁻⁴ , it is possible to suppress the ghost and the tailing that occur during long-term use in a high temperature and high humidity environment, and have reached the present invention. The reason for this is considered as follows.

First, regarding the average circularity, the magnetic toner having an average circularity of 0.970 or more has a spherical toner shape, and the toner shapes are relatively uniform. It is considered that the triboelectrification of the particles becomes uniform and the variation in the charge amount is small. Further, since the ears of the toner on the toner carrier become uniform, the control at the developing unit becomes easy. Also, because of the spherical toner,
The fluidity is also good. On the other hand, the average circularity is 0.9
When it is less than 70, the uniformity of triboelectrification and the formation of ears may be impaired.

The magnetic toner of the present invention has a fog characteristic,
Very good transferability. The reason for this is that since the average circularity is as high as 0.970 or more, the contact area between the toner particles and the photoconductor is small, and the adhesion force of the toner particles to the photoconductor due to the image force, van der Waals force, etc. Is likely to be transferred, and the toner particles are uniformly triboelectrically charged, so that the variation in the charge amount is small. The average circularity of the magnetic toner can be adjusted by a manufacturing method adopted, for example, by using a polymerization method such as a suspension polymerization method, and the manufactured particles are deformed by a mechanical impact method or the like. Can be adjusted by.

The average circularity in the present invention is a simple one that quantitatively expresses the shape of particles, and indicates the degree of unevenness of the magnetic toner. When the magnetic toner has a perfect spherical shape, it shows 1.000, and the more the surface shape of the magnetic toner becomes complicated, the smaller the average circularity becomes. The average circularity is obtained by calculating the circularity (Ci) of each particle by the following formula (4), and further calculating the sum of the circularity of all the particles as shown in the following formula (5). Value (C) divided by (m)
Is.

[0041]

[Equation 7]

[Equation 8]

The magnetic toner of the present invention preferably has a modal circularity of 0.99 or more in the circularity distribution of the magnetic toner. The 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-mentioned action becomes more remarkable, which is preferable.

The mode circularity is 0.40.
To 1.00 are divided into 61 by 0.01, and the circularity of the measured particles is assigned to each division range according to the circularity, and the circularity of the peak with the maximum frequency value in the circularity frequency distribution. Is.

The average circularity in the present invention is the flow type particle image analyzer "FPIA-100" manufactured by Toa Medical Electronics.
0 ”can be used for measurement, and in this case, 3 μ
The measurement is performed on a particle group having a circle equivalent diameter of m or more.

The measuring procedure is as follows. A dispersion liquid was prepared by dispersing about 5 mg of the magnetic toner in 10 ml of water in which about 0.1 mg of the surfactant was dissolved, and the dispersion liquid was irradiated with ultrasonic waves (20 KHz, 50 W) for 5 minutes to adjust the dispersion liquid concentration. The number of particles is set to 5000 to 20,000 / μl, and the measurement is performed by the above-mentioned apparatus to obtain the average circularity and the mode circularity of the particle group having a circle equivalent diameter of 3 μm or more.

The reason why the average degree is measured only for the particle group having a circle equivalent diameter of 3 μm or more in this measurement is 3 μm.
This is because the particle group having an equivalent circle diameter of less than m includes a large number of particles of the external additive that exist independently of the toner particles, and the average degree of the toner particle group cannot be accurately estimated due to the influence thereof. .

In addition, the measuring device "FPIA-1000" used in the present invention was used after calculating the circularity of each particle.
In calculating the average circularity and the mode circularity, the particles are divided into 61 classes by dividing the circularity 0.40 to 1.00 according to the circularity obtained, and the average circularity is calculated using the center value and frequency of the division points. And a calculation method for calculating the mode circularity is used. However, the error between each value of the average circularity and mode circularity calculated by this calculation method, and each value of the average circularity and mode circularity calculated by the calculation formula that directly uses the circularity of each particle described above. Is very small and is substantially negligible, and in the present invention, the circular shape of each particle described above is used for the reason of handling data such as short-circuiting of calculation time and simplification of calculation calculation formula. The calculation method that directly uses the degree may be used, and such a calculation method that is partially modified may be used.

Next, the tetrahydrofuran (THF) insoluble content of the resin component of the magnetic toner is 5 to 60% by mass.
And preferably 8 to 50% by mass. Due to the presence of tetrahydrofuran insoluble matter in the magnetic toner,
The strength of the magnetic toner increases, and toner deterioration is unlikely to occur during long-term use in a high temperature environment. For this reason, when the tetrahydrofuran insoluble content is less than 5% by mass, the strength of the magnetic toner is insufficient and deterioration is likely to occur. On the other hand, if the tetrahydrofuran insoluble content exceeds 60% by mass, the fixability is likely to be impaired, which is not preferable.

The THF insoluble content of the resin component of the magnetic toner can be measured as follows. 1g of magnetic toner is precisely weighed and charged into a cylindrical filter paper.
Soxhlet extract for 20 hours in ml. After that, the cylindrical filter paper is taken out, vacuum dried at 40 ° C. for 20 hours, and the mass of the residue is measured, and calculated by the following formula. The resin component of the magnetic toner is a component obtained by removing the magnetic powder, the charge control agent, the release agent component, the external additive, and the pigment from the magnetic toner. When measuring the THF insoluble matter, these contents should be TH
Considering whether it is soluble or insoluble in F, T based on the resin component
HF insoluble matter is calculated.

[Equation 9] THF insoluble matter (%) = (W2-W3) / (W1
−W3−W4) × 100 where W1 is the mass of the magnetic toner, W2 is the mass of the residue, and W
3 is the mass of the THF-insoluble component other than the resin component of the magnetic toner, and W4 is the mass of the THF-soluble component other than the resin component of the magnetic toner.

The THF insoluble content of the resin component of the magnetic toner is
It can be arbitrarily changed depending on the combination of the type and amount of the initiator and the crosslinking agent used. It can also be adjusted by using a chain transfer agent or the like.

Further, the amount of sulfur element (E) relative to the amount of carbon element (A) existing on the surface of the magnetic toner particles.
Ratio (E / A) of 3 × 10 ⁻⁴ ≦ E / A ≦ 50 × 10 ⁻⁴
Is important, preferably 3 × 10 ⁻⁴ ≦ E / A
≦ 35 × 10 ⁻⁴ , more preferably 3 × 10 ⁻⁴ ≦ E
/ A ≦ 25 × 10 ⁻⁴ . Although the measurement of A and E will be described in detail later, they can be measured by X-ray photoelectron spectroscopy analysis.

By controlling E / A as described above, it is possible to obtain a magnetic toner which has a quick charge rise and has a sufficient charge amount. This means that a charge controllable substance containing a sulfur element is evenly present on the surface of the magnetic toner. If the E / A value is low, the charge amount is insufficient, and the charge uniformity is low. Tends to be damaged. On the other hand, when the E / A is larger than 50 × 10 ⁻⁴ , the charge rises sufficiently quickly, but the charge amount of the toner is too high, which causes a so-called charge-up tendency, and the charge amount distribution becomes broad. A ghost is likely to occur. Further, it becomes difficult to control the amount of toner on the toner carrier, and the ears of the toner on the toner carrier may become long or rough.

By controlling E / A as described above and setting the average circularity of the magnetic toner to 0.970 or more, the durability of the magnetic toner is further improved. It is considered that this is because the magnetic toner is uniformly charged, and thus the magnetic toner ears on the toner carrier are rough and thick due to electrostatic repulsion, and are unlikely to deteriorate. further,
By setting the THF insoluble content of the magnetic toner within the above range, this effect becomes very large.

The inventors of the present invention have found that the synergistic effect of these actions, that is, high fluidity due to the high average circularity of the magnetic toner,
Charge uniformity is improved, uniform ears can be formed, toner deterioration is suppressed by the presence of tetrahydrofuran insoluble matter of 5 to 60%, and chargeability of the magnetic toner is improved by E / A being in an appropriate range. Due to the synergistic effect of the above three points, it is considered that ghost does not occur even during long-term use in a high temperature and high humidity environment.

Further, such magnetic toner does not cause development tailing. With regard to the development tailing, in the one-component magnetic development method, the magnetic toner is developed in a chain shape (generally called “brush”) at the time of development, so that the magnetic toner is removed from the image portion in a state of a brush. This is the development that sticks out. This can be improved by making the spikes of the magnetic toner on the toner carrier shorter. However,
A magnetic toner having an average circularity of 0.970 or more has a smooth toner surface, and thus is particularly susceptible to toner deterioration at high temperatures. In addition, the deteriorated magnetic toner cannot form uniform ears on the toner carrier, and the ears become long and rough. Therefore, it is considered that development tailing occurs in long-term use at high temperature and high humidity.

However, as described above, the magnetic toner of the present invention does not deteriorate even when used for a long period of time in a high temperature and high humidity environment, and has a good charging property, so that the magnetic toner remains on the toner carrier even after a long period of use. It is thought that tailing does not occur because the thin and short ears can be formed uniformly.

The magnetic toner of the present invention is required to have a weight average particle diameter of 3 to 10 μm in order to improve the image quality and to faithfully develop finer latent image dots. It is more preferably 9 μm. In the case of a magnetic 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 abrasion of the photoconductor and toner fusion in the contact charging step. Further, in addition to the increase in the surface area of the magnetic toner as a whole, the fluidity and agitation property of the powder are lowered, and it becomes difficult to uniformly charge the individual toner particles. It is not preferable because it becomes worse.

The weight average particle diameter of the magnetic toner is 10 μm.
When it exceeds m, the characters and line images are likely to scatter, and it is difficult to obtain high resolution. Further, as the resolution of the apparatus becomes higher, the reproduction of one dot tends to deteriorate with toner of 10 μm or more. The weight average particle diameter of the magnetic toner can be adjusted by a granulation condition or the like in a classification step in the manufacturing process, or in suspension polymerization which is a preferable toner manufacturing method of the present invention.

Here, the weight average particle size and particle size distribution of the magnetic toner can be measured by various methods such as Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter Co.), but in the present invention, Coulter Multi Using a sizer (manufactured by Coulter), number distribution,
It is preferable to measure with an apparatus connected to an interface (made by Nikkaki) that outputs the volume distribution and a PC9801 personal computer (made by NEC). An electrolyte solution is used for this measurement. As the electrolyte solution, a 1% NaCl aqueous solution prepared using primary sodium chloride, for example, ISOTON R-II (manufactured by Coulter Scientific Japan Co.) is used. it can.

The measuring method is as follows:
0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 150 ml,
Further, 2 to 20 mg of the measurement sample is added. The electrolytic solution in which the sample is suspended is dispersed by an ultrasonic disperser for about 1 to 3 minutes, and the volume and the number of toner particles of 2 μm or more are measured by the Coulter Multisizer using a 100 μm aperture as an aperture. The distribution and the 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 carried out in Examples described later.

The magnetic toner of the present invention has a magnetic field of 79.6 kA.
/ M (1000 oersted) has a magnetization intensity of 1
It is preferably 0 to 50 Am ² / kg (emu / g). This is because by providing a magnetic force generating means in the developing device, it is possible to prevent leakage of the magnetic toner from the developing device, not only enhance the transportability or agitability of the magnetic toner, but also prevent the magnetic toner from scattering. It will be easy.

However, if the strength of the magnetization in the magnetic field of 79.6 kA / m is less than 10 Am ² / kg, the above effect cannot be obtained, and when a magnetic force is applied to the toner carrier, the spikes of the magnetic toner rise. Instability, fogging, uneven image density due to uneven charging of the magnetic toner,
Image defects such as ghosts are likely to occur. On the other hand, magnetic field 7
Magnetization strength at 9.6 kA / m is 50 Am ² / kg
If it is larger than the above value, when magnetic force is applied to the magnetic toner, the fluidity of the magnetic toner is significantly reduced due to magnetic aggregation, the developability is reduced, the magnetic toner is easily damaged, and the toner is significantly deteriorated. Further, the developing property is deteriorated, and the spikes on the toner carrying member become long, so that the development tailing is likely to occur.

The strength of magnetization of magnetic toner (saturation magnetization) is
It can be arbitrarily changed depending on the amount of the magnetic powder contained and the saturation magnetization of the magnetic powder. The saturation magnetization of the magnetic powder is 30 to 120 Am ² / k in a magnetic field of 796 kA / m.
It is preferably g.

In the present invention, the saturation magnetization of the magnetic toner is
It can be measured using a vibrating magnetometer VSM P-1-10 (manufactured by Toei Industry Co., Ltd.), and is measured at a room temperature of 25 ° C. and an external magnetic field of 79.6 kA / m. Also, regarding the magnetic characteristics of the magnetic powder, the vibration type magnetometer VSM P-1-10
(Manufactured by Toei Industry Co., Ltd.)
It measures at room temperature of 25 ° C. and an external magnetic field of 796 kA / m.

Monomers having a sulfur element for producing the sulfur-containing polymer used in the present invention are styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamido-2-methylpropanesulfone. Acid, vinyl sulfonic acid, methacryl sulfonic acid and the like. The sulfur-containing polymer used in the present invention may be a homopolymer of the above monomer or a copolymer of the above monomer and another monomer.

However, among them, a polymer containing a sulfonic acid group-containing (meth) acrylamide is preferable because the chargeability of the magnetic toner becomes very good.

In this case, when the sulfonic acid group-containing (meth) acrylamide is 0.1 to 5.0% by mass, more preferably 0.1 to 4.0% by mass, the E / A value is controlled. It is preferable because it is easy to do.

As a monomer forming a copolymer with a monomer having a sulfur element, there is a vinyl-based polymerizable monomer, and a monofunctional polymerizable monomer or a polyfunctional polymerizable monomer is used. Can be used.

As the monofunctional polymerizable monomer, styrene; α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p- n-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy Styrene, styrene derivatives such as p-phenylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso
-Butyl acrylate, tert-butyl acrylate, n-amyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, cyclohexyl acrylate, benzyl acrylate, dimethyl phosphate ethyl acrylate, diethyl phosphate ethyl Acrylic polymerizable monomers such as acrylate, dibutyl phosphate ethyl acrylate, 2-benzoyloxyethyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert
-Butyl methacrylate, n-amyl methacrylate,
Methacrylic polymerizable monomers such as n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, diethyl phosphate ethyl methacrylate, and dibutyl phosphate ethyl methacrylate; methylene aliphatic monocarboxylic acid ester; acetic acid Vinyl esters such as vinyl, vinyl propionate, vinyl butyrate, vinyl benzoate, vinyl formate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropyl ketone Can be mentioned.

As the polyfunctional polymerizable monomer, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, 1,6
-Hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 2,2'-bis (4- (acryloxydiethoxy) phenyl) propane, trimethylolpropane triacrylate, tetramethylolmethane Tetraacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate,
1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2′-bis (4- (methacryloxydiethoxy) phenyl) propane, 2,
2'-bis (4-methacryloxy polyethoxy) phenyl) propane, trimethylolpropane trimethacrylate, tetramethylolmethane tetramethacrylate, divinylbenzene, divinylnaphthalene, divinyl ether and the like can be mentioned.

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

The polymer having a sulfonic acid group has a structure represented by the following general formula.

Embedded image X (SO ₃ ⁻ ) _n · mY ^{k +} (X represents a polymer moiety derived from the polymerizable monomer,
Y ⁺ represents a counter ion, k is the valence of the counter ion, m and n are integers, and n = k × m. )

As counter ions, hydrogen ions,
It is preferably sodium ion, potassium ion, calcium ion, ammonium ion or the like, and more preferably hydrogen ion.

The weight average molecular weight (Mw) of the sulfur-containing polymer is preferably 2,000 to 100,000. If the weight average molecular weight (Mw) is less than 2000, the fluidity of the magnetic toner tends to be poor and the transferability tends to be poor. If it exceeds 100,000, it will take time to dissolve it in the monomer, and it tends to be difficult for the elemental sulfur to uniformly exist on the surface of the magnetic toner. The weight average molecular weight can be measured using gel permeation chromatography (GPC).

The glass transition point (Tg) of the sulfur-containing polymer is 5
0 ° C to 100 ° C is preferable. When the glass transition point is lower than 50 ° C., the magnetic toner may have poor fluidity and storability, and may also have poor transferability. When the glass transition point is higher than 100 ° C., the fixability of an image having a large toner printing rate may be poor. The glass transition point can be measured using a differential scanning calorimeter (DSC).

The acid value (mgKOH / g) of the sulfur-containing polymer is preferably 3 to 80, more preferably 5 to 40, and further preferably 5 to 30. When the acid value is less than 3, it is difficult to obtain a sufficient charge control action as mentioned in the present invention. On the other hand, when the acid value exceeds 50, the hygroscopicity increases, and it is difficult to obtain sufficient chargeability under high humidity.

The acid value is calculated as follows. The basic operation conforms to JIS-K0070. The acid value means the number of mg of potassium hydroxide required to neutralize free fatty acids, resin acids and the like contained in 1 g of a sample, and can be measured by the following test.

(1) Reagent (a) Solvent Ethyl ether-ethyl alcohol mixed solution (1
+1 or 2 + 1) or benzene-ethyl alcohol mixed solution (1 + 1 or 2 + 1), and these solutions are neutralized with N / 10 potassium hydroxide ethyl alcohol solution using phenolphthalein as an indicator immediately before use. (B) Phenolphthalein solution 1 g of phenolphthalein was added to 100 m of ethyl alcohol (95 v / v%).
dissolve in l. (C) N / 10 potassium hydroxide-ethyl alcohol solution 7.0 g of potassium hydroxide is dissolved in as little water as possible, ethyl alcohol (95 v / v%) is added to make 1 liter, and the mixture is left for 2 to 3 days and then filtered. JIS K
8006 (basic items regarding titration during reagent content test)
Carry out according to.

(2) Correctly weigh 1 to 20 g of the operation sample, and add 100 parts of the solvent to it.
Add ml and a few drops of phenolphthalein solution as an indicator and shake well until the sample is completely dissolved. For solid samples, heat on a water bath to dissolve. After cooling, this is N / 10
Titrate with potassium hydroxide ethyl alcohol solution, and make the end point of neutralization when indicator light red color continues for 30 seconds.

(3) Calculation formula The acid value is calculated by the following formula.

[Equation 10] Here, A is the acid value, B is the amount of the N / 10 potassium hydroxide ethyl alcohol solution used (ml), f is the factor of the N / 10 potassium hydroxide ethyl alcohol solution, and S is the sample (g).

In the measurement of various physical properties of the sulfur-containing polymer, the extraction of the sulfur-containing polymer from the magnetic toner is not particularly limited and can be performed by any method. The above-mentioned physical properties of the sulfur-containing polymer can be adjusted by various conditions such as the amount and type of the monomer used and the control of polymerization conditions.

Using such a sulfur-containing polymer, the amount of sulfur element (E) relative to the amount of carbon element (A) present on the surface of the magnetic toner particles measured by X-ray photoelectron spectroscopy analysis of the toner. Ratio (E / A) of 3 × 10 ⁻⁴ ≦ E /
In order to satisfy A ≦ 50 × 10 ⁻⁴ , a spray dry method,
Using a method such as a seed polymerization method, it is preferable to cover the particle surface with a sulfur-containing polymer, in order to obtain a uniform surface state,
It is more preferable to produce the magnetic toner by the seed polymerization method.

E / A is the amount of the sulfur-containing polymer used,
The content of elemental sulfur in the polymer and the seed polymerization method, which is a preferred production method of the present invention, can be arbitrarily changed depending on the timing of seed polymerization, that is, the conversion rate of the core particles.

When the resin layer is formed on the core particles as in the seed polymerization method, the amount of the sulfur-containing polymer forming the shell part is 0.05 based on 100 parts by mass of the core particles.
It is preferably ˜20 parts by mass, more preferably 0.1 to 10 parts by mass. Further, the amount of the polymerizable monomer that dissolves the polymer is not particularly limited as long as it is an amount that dissolves the polymer.

Further, at the time of forming the shell, the above-mentioned sulfur-containing polymer is dissolved in the polymerizable monomer in advance, and this solution is put into the dispersion liquid in which the core particles are dispersed all at once.
Alternatively, it can be added continuously or intermittently using a metering pump or the like. Further, the solution of the sulfur-containing polymer may be added to an aqueous medium such as water, finely dispersed using an ultrasonic emulsifier, etc., and the resulting dispersion may be added to the liquid of the core particles. .

Regarding the timing of adding the solution containing the sulfur-containing polymer, the conversion rate of the polymerizable monomer in the core particles is 10-9.
It is preferably 5% and more preferably 20 to 90%. If a solution of the polymer is added when the polymerization conversion rate of the core particles is low, the polymer will get into the toner particles, making it difficult to obtain the desired performance. On the other hand, when the polymerization conversion rate of the core particles is 95% or more, the polymerizable monomer dissolving the polymer is less likely to soak into the core particles, so that the sulfur-containing polymer is not exposed to the toner surface. It is not preferable because it tends to be uniform and tends to cause an increase in fine powder.

The polymerization conversion rate can be measured by gas chromatography as follows. As a specific measuring method, about 500 toner suspensions are put in a sample bottle.
mg is precisely weighed, about 15 g of precisely weighed acetone is added thereto, and the mixture is thoroughly mixed and irradiated with ultrasonic waves for 30 minutes using an ultrasonic cleaner. After that, filtration is performed using a membrane filter (for example, Disposable Membrane Filter 25JP020AN manufactured by Advantech Toyo Co., Ltd.),
2 μL of the filtrate are analyzed by gas chromatography. Then, the polymerization conversion rate is calculated from a calibration curve prepared in advance using a monomer such as styrene.

Specifically, the analysis is performed under the following conditions. GC: HP company 6890GC column: HP company INNOWax (200 μm × 0.
40 μm × 25 m) Carrier gas: He (Constant pressure mode: 20 psi) Oven: 50 ° C .: Hold for 10 minutes, 2 at 10 ° C./minute
Temperature rises to 00 ° C, 200 ° C: Hold for 5 minutes. INJ: 200 ° C., pulsed splitless mode (20 → 40 psi, until 0.5 minutes) Split ratio: 5.0: 1.0 DET: 250 ° C. (FID)

Examples of the polymerizable monomer used when the sulfur-containing polymer is dissolved include styrene, o-methylstyrene, p-methylstyrene, m-methylstyrene and p-
Styrene monomers such as methoxystyrene and p-ethylstyrene, acrylic acid, methacrylic acid, and methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-acrylate. Octyl, dodecyl acrylate, acrylic acid 2-
Ethylhexyl, stearyl acrylate, acrylic acid 2
-Acrylic acid esters such as chloroethyl, 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,
Examples thereof include methacrylic acid esters such as dimethylaminoethyl methacrylate and diethylaminoethyl methacrylate, and other monomers such as acrylonitrile, methacrylonitrile and acrylamide.

These monomers may be used alone or in combination. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in a mixture with other monomers, since the adsorptivity to polymer particles is enhanced and the durability is enhanced.

As the polymerization initiator used in the seeding step of the present invention, any known one such as a water-soluble initiator and an oil-soluble initiator can be used, and one kind or a combination of two or more kinds can be used. .

These polymerization initiators are used in the range of 0.01 to 10% by mass, preferably 0.05 to 5% by mass, based on the polymerizable monomer usually used in the coating step. When the amount of the polymerization initiator added exceeds 10% by mass, not only is it uneconomical due to the increase in the amount used, but also the molecular weight does not increase and toner deterioration tends to occur. Further, if it is less than 0.01% by mass, a sufficient degree of polymerization tends not to be obtained.

In the seed step of producing the magnetic toner of the present invention, 0.001 to 0.1 based on the polymerizable monomer is added in order to stabilize the emulsion of the dropped polymerizable monomer composition.
Mass% surfactants may be used. This is for promoting the emulsification and dispersion of the polymerizable monomer composition, and specific examples thereof include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium stearate, and calcium oleate. Etc.

In the magnetic toner of the present invention, it is preferable that the magnetic powder is not substantially 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 amount of carbon element existing on the surface is A,
It is defined that the ratio of B to A, B / A, is less than 0.001, where B is the amount of iron element present on the surface. Since the magnetic powder is not substantially exposed, the flowability and triboelectric chargeability of the magnetic toner are improved, and various performances required for the magnetic toner such as fog suppression, transferability improvement, and ghost suppression are satisfied. Like Further, such effects are further enhanced by combining with the above-mentioned sulfur-containing polymer.

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 present on the toner surface. The ratio (E / A) of the content (E) of the elemental sulfur to (A) can be calculated based on the analysis result of the surface composition analysis by ESCA (X-ray photoelectron spectroscopy analysis).

Preferred examples of the ESCA device and measurement conditions are as follows. Device used: PHI (Physical Elect)
tronics Industries, Inc. ) Made
1600S type X-ray photoelectron spectrometer measuring conditions: X-ray source MgKα (400 W), spectral region 800 μmφ In the present invention, from the measured peak intensity of each element,
It is preferable to calculate the surface atomic concentration (atomic%) using the relative sensitivity factor provided by PHI.

The range of the measurement peak top of each element used for measurement is as follows: carbon element: 283 to 293 eV,
Iron element: 706 to 730 eV, Sulfur element: 166 to 17
It is 2 eV.

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

The magnetic toner of the present invention has a relationship of D / C ≦ 0.02, where C is the projected area equivalent diameter of the magnetic toner and D is the minimum value of the distance between the magnetic toner surface and the magnetic powder. It is preferable that the number of magnetic toners to be filled is 50% by number or more.

The projected area equivalent diameter is a diameter in a projected image of magnetic toner particles or an image similar thereto (for example, a sectional image). For example, the area of the projected image is obtained, and the diameter of a circle of this area is equivalent to the projected area. It can be calculated as the diameter. The number of toners satisfying the relationship of D / C ≦ 0.02 is 50
% Means that the dispersion state of the magnetic powder in the magnetic toner varies widely, the physical properties of the toner are likely to change due to long-term use, and the charging uniformity of the magnetic toner is impaired. It is not preferable because pulling or ghost is likely to occur. The D / C can be measured by using a TEM (transmission electron microscope).

In the present invention, specific D by TEM
As a method of measuring / C, the particles to be observed are sufficiently dispersed in a room temperature curable epoxy resin and then cured for 2 days in an atmosphere at a temperature of 40 ° C. A method of observing as a flaky sample with a microtome equipped with diamond teeth is preferable.

The specific method for determining the proportion of the corresponding number of particles is as follows. For the 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 included particles are the applicable particles, and the minimum value (D) of the distance from the surface of the magnetic particles is measured for the applicable particles.
Calculate / C. Further, the ratio of particles having a D / C value of 0.02 or less is calculated for 100 corresponding particles. The micrograph at this time is preferably 10,000 to 20,000 times in magnification in order to perform highly accurate measurement. In the present invention, it is preferable to use a transmission electron microscope (H-600 type manufactured by Hitachi) as an apparatus, observe at an accelerating voltage of 100 kV, and observe and measure using a micrograph with a magnification of 10,000 times.

The ratio of the magnetic toner satisfying D / C ≦ 0.02 includes the amount of the toner additive, the treating agent and the treating method of the magnetic powder, the amount of the polymerizable monomer at the time of seed polymerization, and the like. It can be arbitrarily changed depending on the amount of the sulfur polymer, the polymerization conversion rate of the core particles, and the like.

Here, even if the polymerized toner contains normal magnetic powder, the above-mentioned B / A should be controlled to less than 0.001, that is, the magnetic powder is not substantially exposed on the toner surface. However, it is difficult to obtain fluidity of toner particles and uniform triboelectrification. Further, it is difficult to obtain a toner having an average circularity of 0.970 or more due to the strong interaction between the magnetic powder and water during the production of the suspension polymerization toner.

This is because (1) the magnetic powder is generally hydrophilic so that it easily exists on the toner surface, and (2) the magnetic powder moves randomly during stirring in an aqueous solvent, and It is considered that the cause is that the surface of suspended particles consisting of is dragged and the shape is distorted and is unlikely to be circular. In order to solve these problems, it is effective to modify the surface characteristics of magnetic powder.

Many proposals have been made regarding the surface modification of the magnetic powder used for the polymerized toner. As described above, JP-A-59-200254 and JP-A-59-2
00256, JP-A-59-200257,
Japanese Patent Application Laid-Open No. 59-224102 and the like propose various techniques for treating magnetic powder with a silane coupling agent, and Japanese Patent Application Laid-Open No. 63-250660 discloses a technique for treating magnetic particles containing a silicon element with a silane coupling agent. The technology is disclosed.

However, although these treatments suppress the exposure of the magnetic powder to the toner surface to some extent,
There is a problem that it is difficult to uniformly make the surface of the magnetic powder hydrophobic. Therefore, coalescence of the magnetic powders and generation of non-hydrophobicized magnetic powder cannot be avoided, and the toner surface May be exposed, the dispersibility of the magnetic powder may not be sufficient, and the particle size distribution may be broad.

As an example of using hydrophobized 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 various electrophotographic characteristics of the toner, the surface activity of the magnetic iron oxide is originally small, and coalesced particles are generated at the treatment stage and the hydrophobicity is nonuniform. However, it is not always satisfactory. Further, when a magnetic powder having a small particle size is used, uniform treatment becomes more difficult, and further improvement is required for application to the present invention. Furthermore, in order to improve the encapsulation property of the magnetic powder, when a large amount of treating agent is used or a highly viscous treating agent is used, the degree of hydrophobicity is certainly increased, but coalescence of particles occurs. On the contrary, the dispersibility may be deteriorated.

The toner produced using such magnetic powder has non-uniform triboelectrification, which may result in poor fog, transferability, ghost, and tailing. In addition, as described above, the polymerized toner using the conventional surface-treated magnetic powder does not always achieve both the hydrophobicity and the dispersibility, and such a polymerized toner can stably obtain a high-definition image. Is difficult

Therefore, the magnetic powder used in the magnetic toner of the present invention is preferably subjected to a uniform hydrophobic treatment with a coupling agent. When hydrophobizing the surface of the magnetic powder, it is very preferable to use a method of performing surface treatment while hydrolyzing the coupling agent while dispersing the magnetic powder to have a primary particle size in an aqueous medium. In this hydrophobic treatment method, coalescence between magnetic powders is less likely to occur than in the gas phase, and the electrostatic repulsion action between the magnetic powders due to the hydrophobic treatment works so that the magnetic powders are almost in the state of primary particles. Is surface treated 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 such as chlorosilanes or silazanes that generates a gas. Furthermore, the magnetic powder can be easily coalesced with each other in the gas phase, and a highly viscous coupling agent, which has been difficult to be processed well, can be used, and the effect of hydrophobization is great.

Examples of coupling agents that can be used in the surface treatment of the magnetic powder according to the present invention include silane coupling agents and titanium coupling agents. A silane coupling agent is more preferably used and is represented by the following general formula.

Embedded image R _m SiY _n [wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents an alkyl group, a vinyl group, a glycidoxy group,
A hydrocarbon group such as a methacryl group is shown, and n is an integer of 1 to 3. ]

Examples of such silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (βmethoxyethoxy) silane, β- (3,4epoxycyclohexyl) ethyltrimethoxysilane, γ-glycid. Xypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-
Phenyl-γ-aminopropyltrimethoxysilane, γ
-Methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane , N-butyltrimethoxysilane, n-hexyltrimethoxysilane, isobutyltrimethoxysilane, trimethylmethoxysilane, n-decyltrimethoxysilane, hydroxypropyritrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane Silane etc. can be mentioned. These coupling agents may be used alone or in combination of two or more.

Among these, it is more preferable to use at least one alkyltrialkoxysilane coupling agent represented by the following general formula in order to impart sufficient hydrophobicity to the magnetic powder.

Embedded image 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 hydrophobic treatment becomes easy, but it is difficult to impart sufficient hydrophobicity, and it is difficult to suppress the exposure of the magnetic particles from the toner particles. Become. If p is greater than 20, the hydrophobicity will be sufficient, but the coalescence of the magnetic powder particles will increase, making it difficult to disperse the magnetic powder particles sufficiently and impairing the charging uniformity. It will be easier.

When q is larger than 3, the reactivity of the silane coupling agent is lowered and it becomes difficult to sufficiently hydrophobize the silane coupling agent. Particularly, an alkyltrialkoxysilane cup in which p 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 better to use a ring agent.

The total treatment amount of these coupling agents is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the magnetic powder.
It is preferable to adjust the amount of the treating agent according to the reactivity of the coupling agent.

Here, the aqueous medium is a medium containing water as a main component. Specifically, water itself as an aqueous medium, water with a small amount of a surfactant added, and water pH
The thing which added the preparation agent and the thing which added the organic solvent to water are mentioned. The surfactant is preferably a nonionic surfactant such as polyvinyl alcohol. The surfactant is preferably added in an amount of 0.1 to 5 wt% with respect to water.
Examples of the pH adjusting agent include inorganic acids such as hydrochloric acid, and examples of the organic solvent include alcohols.

For the stirring, for example, a mixer having a stirring blade can be used, and it is preferable to carry out the stirring sufficiently so that the magnetic powder particles become primary particles in the aqueous medium.

When a plurality of types of silane coupling agents are used, a plurality of types of coupling agents are added at the same time or with a time difference, and the magnetic powder is treated.

In the magnetic powder thus obtained, no particle agglomeration is observed and the surface of each particle is uniformly hydrophobized, so that it is possible to obtain a magnetic toner having excellent charging uniformity and free from ghost and tailing. Obtainable.

The magnetic powder used in the magnetic toner of the present invention may contain elements such as phosphorus, cobalt, nickel, copper, magnesium, manganese, aluminum and silicon. These magnetic powders are BET produced by the nitrogen adsorption method.
The specific surface area is preferably ² to 30 m ² / g, particularly 3 to 28
It is preferably m ² / g and further has a Mohs hardness of 5 to 7.

The shape of the magnetic powder may be a polyhedron, an octahedron, a hexahedron, a sphere, a needle, a scaly shape, etc. It is preferable for increasing the image density. The shape of such magnetic powder can be confirmed by SEM (scanning electron microscope) or the like. The volume average particle size of the magnetic powder is 0.0
5 to 0.4 μm is preferable, and more preferably 0.1 to
It is 0.3 μm.

When the volume average particle size is less than 0.05 μm,
The blackness is markedly reduced, the coloring power is insufficient as a colorant for black and white toners, and the magnetic powders are strongly aggregated with each other, so that the dispersibility tends to be deteriorated. Also,
Uniformity treatment of the magnetic powder surface tends to be very difficult. On the other hand, if the volume average particle diameter exceeds 0.4 μm, the coloring power becomes insufficient as in the case of general colorants. In addition, when a magnetic powder having a volume average particle size of more 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 each toner particle. This is probabilistically difficult, and the uniform charging property of the magnetic toner is likely to be impaired.

The magnetic powder used in the magnetic toner of the present invention is 10 parts by mass to 2 parts by mass with respect to 100 parts by mass of the binder resin.
It is preferable to use 100 parts by mass. It is more preferable to use 20 to 180 parts by mass. If it is less than 10 parts by mass, the coloring power of the magnetic toner is poor and it is difficult to suppress fog. On the other hand, when the amount exceeds 200 parts by mass, the holding force due to the magnetic force on the toner carrier is increased and the developability is lowered,
Not only is it difficult to uniformly disperse the magnetic powder in each toner particle, but also the fixing property tends to deteriorate.

The content of the magnetic powder contained in the magnetic toner was measured by a thermal analysis device manufactured by Perkin Elmer Co., T
It can be measured with GA7. As a specific example of the measuring method, the toner is heated from room temperature to 900 ° C. at a temperature rising rate of 25 ° C./min in a nitrogen atmosphere, and 100 ° C. to 75 ° C.
The weight loss% up to 0 ° C. is taken as the binder resin amount, and the remaining weight is taken as the magnetic powder amount approximately.

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

To the ferrous iron salt aqueous solution, an alkali such as sodium hydroxide is added in an amount equivalent to or more than the amount of the iron component,
An aqueous solution containing ferrous hydroxide is prepared. Air is blown while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 to 14), the ferrous hydroxide is oxidized while the aqueous solution is heated to 70 ° C. or higher, and the core of the magnetic iron oxide particles is added. First, a seed crystal that becomes

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 air is blown in, and magnetic iron oxide particles are grown around the seed crystal.

The pH of the liquid shifts to the acidic side as the oxidation reaction progresses, but the pH of the liquid is preferably not less than 6. The pH of the solution is adjusted at the end of the oxidation reaction, and the magnetic iron oxide is sufficiently stirred to form primary particles, a coupling agent is added, and the mixture is thoroughly mixed and stirred, and after stirring, filtered, dried, and lightly crushed. By doing so, hydrophobically treated magnetic iron oxide particles are obtained. Alternatively, after completion of the oxidation reaction, iron oxide particles obtained by washing and filtering are re-dispersed in another aqueous medium without being dried, and then the pH of the re-dispersion liquid is adjusted, and the silane is sufficiently stirred. You may add a coupling agent and may perform a coupling process. In any case, it is preferable to apply the surface treatment to the magnetic toner of the present invention after the completion of the oxidation reaction without passing through a drying step.

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

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 in view of preventing the viscosity from increasing during the reaction and the solubility of iron sulfate.
Generally, the thinner the concentration of iron sulfate, the finer the particle size of the product tends to be. Also, in the reaction, the larger the amount of air,
Further, the lower the reaction temperature, the more easily the particles become fine.

By using the magnetic toner made of the hydrophobic magnetic powder thus produced as a material, it is preferable to achieve stable toner chargeability, high transfer efficiency, high image quality and high stability. .

The magnetic toner of the present invention preferably contains a releasing agent in order to improve the fixing property, and the amount thereof is preferably 1 to 30% by mass based on the binder resin. More preferably, it is 3 to 25 mass%. If the content of the release agent is less than 1% by mass, the effect of adding the release agent is not sufficient and the effect of suppressing the offset is also insufficient. On the other hand, 30
When the content is more than 100% by mass, the long-term storability is deteriorated, 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. In addition, the release agent component also exudes, and the durability under high temperature and high humidity tends to deteriorate. Further, since a large amount of wax is included, the toner shape is likely to become distorted.

Generally, the toner image transferred onto the recording medium is then fixed on the transfer material by energy such as heat and pressure, and a semi-permanent image is obtained. At this time, hot roll type fixing is generally used. As described above, an extremely high-definition image can be obtained by using a magnetic toner having a weight average particle diameter of 10 μm or less. However, the toner particles having a small particle diameter are different from those of paper when a recording medium such as paper is used. The fibers enter the gaps and the heat from the heat fixing roller is insufficiently received, so that low temperature offset is likely to occur. However, in the magnetic toner according to the present invention, by containing an appropriate amount of the release agent, it becomes possible to achieve both high image quality and fixability.

Examples of the releasing agent usable for the magnetic toner according to the present invention include petroleum waxes such as paraffin wax, microcrystalline wax and petrolactam and their derivatives, montan wax and its derivatives, and hydrocarbon wax by the Fischer-Tropsch method. And its derivatives, polyolefin wax represented by polyethylene and its derivatives, carnauba wax, natural wax such as candelilla wax and its derivatives, which are oxides, block copolymers with vinyl monomers,
Including graft modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide wax, ester wax, ketone, hydrogenated castor oil and its derivatives, plant wax,
Animal wax can also be used.

Among these releasing agent components, those having an endothermic peak by differential thermal analysis of 40 to 110 ° C., that is, in the region of 40 to 110 ° C. at the time of heating in the DSC curve measured by a differential scanning calorimeter. Those having a maximum endothermic peak are preferable, and those having a maximum endothermic peak are more preferable. By having the maximum endothermic peak in the above temperature range, releasability is effectively exhibited 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 tends to deteriorate. Further, the release agent is likely to exude, the charge amount of the toner is reduced, and the durability under high temperature and high humidity is likely to be reduced. On the other hand, when the maximum endothermic peak exceeds 110 ° C., the fixing temperature becomes high and low-temperature offset easily occurs, which is not preferable. Further, when granulating / polymerizing in an aqueous medium to directly obtain a toner by a polymerization method, when the maximum endothermic peak temperature is high, problems such as precipitation of a release agent component mainly occur during granulation. This is not preferable because the dispersibility of the mold agent is likely to deteriorate.

The maximum endothermic peak temperature of the release agent is "AST
M D 3418-8 ". For this measurement, for example, Perkin Elmer DSC-7 is used.
The melting point of indium and zinc is used to correct the temperature of the device detection unit, and the heat of fusion of indium is used to correct the amount of heat. An aluminum pan was used as a measurement sample, an empty pan was set as a control, the sample was heated to 200 ° C. once to remove the heat history, and then rapidly cooled, and the temperature rising rate was 10 ° C. again.
The DSC curve measured when the temperature is raised in the range of 30 to 200 ° C./min is used. The same measurement was carried out in Examples described later.

The magnetic toner of the present invention is TH of the magnetic toner.
In the molecular weight distribution measured by gel permeation chromatography (GPC) of the F-soluble content, it is preferable that the main peak has a peak top in the range of molecular weight of 5,000 to 50,000, and more preferably 8,000.
It is in the range of 40,000. If the peak top is less than 5,000, the storage stability of the magnetic toner may be problematic, or the toner may be significantly deteriorated when many sheets are printed out. Conversely, the peak top is 500
If it exceeds 00, a problem in low temperature fixability may occur, and it may be difficult to set the average circularity of the toner to 0.970 or more due to a rapid increase in droplet viscosity during polymerization.

The molecular weight of the resin component soluble in THF by GPC may be measured as follows. A solution obtained by dissolving the magnetic toner in THF at room temperature for 24 hours is filtered through a solvent-resistant membrane filter having a pore size of 0.2 μm to obtain a sample solution, and the sample solution is measured under the following conditions. In the sample preparation, the amount of THF is adjusted so that the concentration of the THF-soluble component is 0.4 to 0.6% by mass. Device: High-speed GPC HLC8120 GPC (manufactured by Tosoh Corporation) Column: Shodex KF-801, 802, 80
7, 804, 805, 806, and 807 (manufactured by Showa Denko KK) Eluent: THF Flow rate: 1.0 ml / min Oven temperature: 40.0 ° C. Sample injection amount: 0.10 ml

In calculating the molecular weight of the sample,
Standard polystyrene resin (TSK standard polystyrene F-850, F-450, F-28 manufactured by Tosoh Corporation)
8, F-128, F-80, F-40, F-20, F-
10, F-4, F-2, F-1, A-5000, A-2
500, A-1000, A-500) is used.

The molecular weight of the magnetic toner can be arbitrarily changed by the combination of the type and amount of the initiator and the crosslinking agent used. It can also be adjusted by using a chain transfer agent or the like.

The magnetic toner of the present invention may further contain a charge control agent in addition to the sulfur-containing polymer. As the charge control agent, known ones can be used, but when the toner is produced by 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 present. Charge control agents not listed in are particularly preferred.

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 acids, metal salts or metal salts of azo dyes or azo pigments. Complex, polymer type compound having sulfonic acid or carboxylic acid group in side chain, boron compound, urea compound,
Examples thereof include silicon compounds and calixarene. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer type compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, an imidazole compound, and the like.

The amount of these charge control agents used is determined by the type of binder resin, the presence or absence of other additives, and the toner manufacturing method including the dispersion method, and is not uniquely limited. However, it is preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 100 parts by mass of the binder resin.
It is used in the range of 5 parts by mass. However, the magnetic toner of the present invention does not necessarily require the addition of the above charge control agent.

Next, a method of manufacturing the magnetic toner according to the present invention will be described. The production of the magnetic toner of the present invention is as described above.
It is preferably produced by a seed polymerization method, but as a method for producing the core particles, a suspension polymerization method or an association / dispersion method after emulsion polymerization is used.
It can be produced by a salting-out method (hereinafter referred to as an association polymerization method), an interfacial polymerization method, a dispersion polymerization method, or the like. Among them, in order to obtain the physical property that the magnetic toner according to the present invention has an average circularity of 0.970 or more, which is an essential requirement, the suspension polymerization method is particularly preferable.

When the magnetic toner of the present invention is produced by the suspension polymerization method, magnetic powder, a release agent, a plasticizer,
A charge control agent, a cross-linking agent, a colorant in some cases, a component necessary for a magnetic toner and other additives, for example, a high-molecular polymer, a dispersant, etc. are appropriately added and uniformly dissolved by a disperser or the like. A dispersed polymerizable monomer system is obtained. Next, the obtained polymerizable monomer system is suspended in an aqueous medium containing a dispersion stabilizer to carry out polymerization (formation of core particles). Further, when the conversion rate of the core is 10 to 95% as described above, a solution obtained by previously dissolving the sulfur-containing polymer in the polymerizable monomer is added to the core particle solution and polymerized to obtain magnetic properties. Toner can be manufactured.

In the production of core particles, the polymerizable monomers constituting the polymerizable monomer composition for core particles include the following.

Examples of the polymerizable monomer include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene and p-ethylstyrene, methyl acrylate and acryl. Ethyl acetate, n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, etc. Acrylic esters, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacrylic acid Phenyl, dimethylaminoethyl methacrylate, methacrylic acid esters other acrylonitrile such as diethylaminoethyl methacrylate,
Examples thereof include monomers such as methacrylonitrile and acrylamide. These monomers may be used alone or in combination. Among the above-mentioned monomers, it is preferable to use styrene or a styrene derivative alone or in a mixture with other monomers, from the viewpoint of developing characteristics and durability of the magnetic toner.

In the production of core particles, a resin may be added to the polymerizable monomer composition for polymerization. For example, a monomer is water-soluble and cannot be used because it dissolves in an aqueous suspension to cause emulsion polymerization, and thus a polymerizable monomer containing a hydrophilic functional group such as an amino group, a carboxylic acid group, a hydroxyl group, a glycidyl group, or a nitrile group cannot be used. When you want to introduce the monomer component into the magnetic toner,
Random copolymers, block copolymers, or graft copolymers of these with vinyl compounds such as styrene or ethylene, in the form of copolymers, or polycondensates of polyesters, polyamides, polyethers, polyimines, etc. It can be used in the form of a polyaddition polymer. When such a high molecular polymer containing a polar functional group is allowed to coexist in a magnetic toner, the above wax component is phase-separated, the inclusion becomes stronger, and a magnetic toner having good blocking resistance and developability can be obtained. it can.

Further, a resin other than the above may be added to the monomer composition for the purpose of improving the dispersibility and fixing property of the material, the image characteristics and the like. Examples of the resin used include polystyrene and polystyrene. A homopolymer of styrene such as polyvinyltoluene and its substitution product; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, a styrene-vinylnaphthalene copolymer, a styrene-methyl acrylate copolymer, a styrene-acrylic acid. Ethyl copolymer,
Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene -Butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene Styrene-based copolymers such as copolymers, styrene-isoprene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene , Po Vinyl butyral, silicone resin,
Polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, tempel resin, phenol resin, aliphatic or alicyclic hydrocarbon resin,
Aromatic petroleum resins 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 tends to be difficult to design various physical properties of the polymerized toner.

Further, if a polymer having a molecular weight different from the molecular weight range of the magnetic toner obtained by polymerizing a polymerizable monomer is dissolved in the monomer and polymerized, a wide molecular weight distribution and offset resistance can be obtained. It is even more effective in obtaining a high magnetic toner.

The polymerization initiator used in the production of the core particles relating to the magnetic toner of the present invention has a half-life of 0.5 to 30 hours during the polymerization reaction, and is 0.5 to the polymerizable monomer. It is preferable to carry out the polymerization reaction with an addition amount of ˜20 parts by mass in order to obtain a polymer in which the peak top of the main peak in GPC is present between 5,000 and 50,000.

As the above-mentioned polymerization initiator, there are conventionally known azo-based polymerization initiators, peroxide-based polymerization initiators, etc., and as the azo-based polymerization initiator, 2,2′-azobis- (2,4
-Dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvalero Nitriles, azobisisobutyronitrile, etc. are exemplified, and as the peroxide-based polymerization initiator, t-butylperoxyacetate, t-butylperoxylaurate, t-butylperoxypivalate, t-butylperoxy. 2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxyneodecanoate, t-hexylperoxyacetate, t-hexylperoxylaurate, t-
Hexylperoxypivalate, t-hexylperoxy-2-ethylhexanoate, t-hexylperoxyisobutyrate, t-hexylperoxyneodecanoate, t-butylperoxybenzoate, α,
α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxy neodecanoate, 1,
1,3,3-Tetramethylbutylperoxy-2-ethylhexanoate, 1,1,3,3-Tetramethylbutylperoxy neodecanoate, 1-Cyclohexyl-
1-methylethyl peroxy neodecanoate, 2,5
-Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-
Butyl peroxyisopropyl monocarbonate, t-
Butyl peroxy 2-ethylhexyl monocarbonate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxy-m-toluoyl benzoate, bis (t- Butyl peroxy) isophthalate, t
-Butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate,
Peroxyesters such as 2,5-dimethyl-2,5-bis (m-toluoylperoxy) hexane, diacyl peroxides such as benzoyl peroxide, lauroyl peroxide and isobutyryl peroxide,
Diisopropyl peroxydicarbonate, bis (4-
Peroxydicarbonates such as t-butylcyclohexyl) peroxydicarbonate, 1,1-di-t-butylperoxycyclohexane, 1,1-di-t-hexylperoxycyclohexane, 1,1-di-t- Peroxyketals such as butylperoxy-3,3,5-trimethylcyclohexane and 2,2-di-t-butylperoxybutane, di-t-butylperoxide, dicumylperoxide, t-butylcumylperoxide Dialkyl peroxide such as t-
Butyl peroxyallyl monocarbonate and the like can be mentioned, and 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 important to add a cross-linking agent to generate a THF-insoluble matter. The preferable addition amount of the cross-linking agent is 100 It is 0.001 to 15 mass% with respect to mass parts.

As the cross-linking 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 dimethacrylate,
A carboxylic acid ester having two double bonds such as 1,3-butanediol dimethacrylate; a divinyl compound such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and a compound having three or more vinyl groups; Are used alone or as a mixture.

In the method for producing the magnetic toner of the present invention, generally, the magnetic powder, the polymerizable monomer, the toner composition such as the releasing agent and the like described above are appropriately added, and a homogenizer, a ball mill,
The polymerizable monomer composition uniformly dissolved or dispersed by a disperser such as a colloid mill or an ultrasonic 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 make the size of the desired toner particles at a stretch. Regarding the timing of addition of the polymerization initiator, it 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. It is also possible to add a polymerization initiator dissolved in a polymerizable monomer or a solvent immediately after granulation and before starting the polymerization reaction.

After the granulation, an ordinary stirrer may be used to perform stirring to the extent that the particle state is maintained and the particles are prevented from floating and settling.

When producing the magnetic toner of the present invention,
As the dispersion stabilizer, known surfactants, organic dispersants and inorganic dispersants can be used. Among them, the inorganic dispersant is less likely to produce harmful ultrafine powder, and because it has dispersion stability due to its steric hindrance, it is difficult to lose stability even when the reaction temperature is changed, and it is easy to wash and adversely affects the magnetic toner. Since it is difficult, it can be preferably used. Examples of such inorganic dispersants include calcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, and other polyvalent metal salts of phosphates, calcium carbonate, carbonates such as magnesium carbonate, calcium meta silicate, calcium sulfate, and barium sulfate. Examples thereof include inorganic salts, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite, and inorganic oxides such as 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 may be formed in an aqueous medium and used. For example, in the case of calcium phosphate, a water-insoluble calcium phosphate can be produced by mixing an aqueous solution of sodium phosphate and an aqueous solution of calcium chloride under high-speed stirring, and more uniform and fine dispersion is possible. This time,
At the same time, a water-soluble sodium chloride salt is by-produced, but when the water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and ultrafine toner particles due to emulsion polymerization are less likely to occur. Therefore, it is more convenient.

When removing the remaining polymerizable monomer at the end of the polymerization reaction, it becomes an obstacle.
It is better to desalt with ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving it with an acid or an alkali after completion of the polymerization.

Further, it is desirable to use 0.2 to 20 parts by mass of these inorganic dispersants per 100 parts by mass of the polymerizable monomer, but it is difficult to generate ultrafine particles. Since there are cases where the atomization is insufficient, 0.001 to 0.1 parts by mass of a surfactant may be used together.

As the surfactant, for example, sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate,
Examples thereof include sodium oleate, sodium laurate, sodium stearate, potassium stearate and the like.

In the core particle and the polymerization step after seeding, 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 within this temperature range, the release agent and waxes to be sealed inside are precipitated by phase separation and the encapsulation becomes more complete. In order to consume the remaining polymerizable monomer, at the end of the polymerization reaction,
It is possible to raise the reaction temperature to 90-150 ° C.

After the polymerization, the polymerized toner particles are filtered, washed and dried by a known method, and if necessary, inorganic fine powder is mixed and attached to the surface to obtain the magnetic toner of the present invention. In addition, it is possible to cut a coarse powder or a fine powder by adding a classification process to the manufacturing process.

In the present invention, the magnetic toner is also preferably added with an inorganic fine powder having a number average primary particle diameter of 4 to 80 nm as a fluidizing agent. The inorganic fine powder is added to improve the fluidity of the magnetic toner and to make the toner particles evenly charged, but the inorganic fine powder is subjected to a treatment such as a hydrophobic treatment to adjust the charge amount of the magnetic toner and environmental stability. It is also a preferable mode to add a function of improving

The number average primary particle diameter of the inorganic fine powder is 80 nm.
If it is larger than the above value or if the inorganic fine powder having a particle size of 80 nm or less is not added, the transfer residual toner is apt to adhere to the charging member when it adheres to the charging member, and stable and good charging characteristics are obtained. Can be difficult. In addition, it is difficult to obtain good fluidity of the magnetic toner, the toner particles are apt to be unevenly charged, and fog increases.
Problems such as reduction in image density and toner scattering tend to be unavoidable.

When the number average primary particle size of the inorganic fine powder is smaller than 4 nm, the inorganic fine powder has a strong cohesive property, and has a strong cohesive property which is not easily broken by the crushing process and is not a primary particle. The particles tend to act as aggregates of distribution, and image defects are likely to occur due to development of the aggregates, damage to the image carrier, the magnetic toner carrier, and the like. In order to make the charge distribution of the toner particles more uniform, the number average primary particle size of the inorganic fine powder is more preferably 6 to 35 nm.

In the present invention, the number average primary particle size of the inorganic fine powder is measured by a photograph of a magnetic toner magnified by a scanning electron microscope, and an element analysis means such as XMA attached to the scanning electron microscope. By contrasting the photographs of the magnetic toner mapped with the elements contained in the inorganic fine powder, 100 or more primary particles of the inorganic fine powder adhering to or detaching from the toner surface were measured, and the number-based It can be measured by determining the average primary particle diameter and the number average primary particle diameter.

As the inorganic fine powder used in the present invention,
Silica, titanium oxide, alumina and the like can be used, and they may be used alone or in combination of two or more. As the silica, for example, both a so-called dry method produced by vapor phase oxidation of a silicon halide or a dry silica called fumed silica, and a so-called wet silica produced from water glass or the like can be used. , The surface and the inside of the fine silica powder have few silanol groups, and N
Dry silica having less production residue such as a ₂ O and SO ₃ ²⁻ is preferable. Further, in the case of dry silica, it is also possible to obtain a composite fine powder of silica and other metal oxide by using other metal halogen compound such as aluminum chloride and titanium chloride together with the silicon halogen compound in the manufacturing process. Also includes.

The addition amount of the inorganic fine powder having a number average primary particle diameter of 4 to 80 nm is preferably 0.1 to 3.0% by mass with respect to the toner particles. If the addition amount is less than 0.1% by mass, the effect is not sufficient, and if it is 3.0% by mass or more, the fixing property tends to deteriorate. The content of the inorganic fine powder can be quantified using fluorescent X-ray analysis and a calibration curve prepared from a standard sample.

In addition, in the present invention, the inorganic fine powder is preferably one which has been subjected to a hydrophobizing treatment in view of the characteristics under a high temperature and high humidity environment. When the inorganic fine powder added to the magnetic toner absorbs moisture, the charge amount of the toner particles is remarkably reduced, and toner scattering easily occurs.

Examples of the treatment agent used for the hydrophobic treatment include silicone varnishes, various modified silicone varnishes, silicone oils, various modified silicone oils, silane compounds, silane coupling agents, and other treatment agents such as organic silicon compounds and organic titanium compounds. They may be used alone or in combination.

Among them, those treated with silicone oil are preferable, and more preferably, those treated with silicone oil at the same time as or after the inorganic fine powder is subjected to hydrophobic treatment with a silane compound are toner particles even in a high humidity environment. It is good for maintaining the high charge amount and preventing toner scattering.

As a method of treating such an inorganic fine powder, for example, as a first step reaction, a silylation reaction is performed with a silane compound to eliminate silanol groups by a chemical bond, and then a second step reaction is performed with a silicone oil on the surface. A hydrophobic thin film can be formed on.

The above silicone oil preferably has a viscosity at 25 ° C. of 10 to 200,000 mm ² / s, more preferably 3,000 to 80,000 mm ² / s. If it is less than 10 mm ² / s, the inorganic fine powder is not stable and the image quality tends to deteriorate due to heat and mechanical stress. If it exceeds 200,000 mm ² / s, uniform treatment tends to be difficult.

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

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

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

The inorganic fine powder used in the present invention is preferably silica, alumina or titanium oxide in order to impart good fluidity to the magnetic toner, and among them, silica is particularly preferable. Further, the specific surface area of silica measured by the BET method by nitrogen adsorption is preferably in the range of ²⁰ to 350 m ² / g, more preferably 25 to 300 m ² / g.
The ones are even better.

The above-mentioned specific surface area is measured according to the BET method by a specific surface area measuring apparatus Autosorb 1 (manufactured by Yuasa Ionics Co., Ltd.).
Nitrogen gas is adsorbed on the surface of the sample using, and it can be calculated using the BET multipoint method.

Further, in the magnetic toner of the present invention, for the purpose of improving the cleaning property and the like, it is also preferable to further add inorganic or organic spherical particles having a primary particle size of 30 nm or more, more preferably 50 nm or more. It is one. For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.

In the magnetic toner used in the present invention, other additives may be added within a range that does not have a substantial adverse effect, for example, lubricant powders such as Teflon (registered trademark) powder, zinc stearate powder, and polyvinylidene fluoride powder. , Or an abrasive such as cerium oxide powder, silicon carbide powder, strontium titanate powder, or titanium oxide powder,
A fluidity-imparting agent such as aluminum oxide powder, an anti-caking agent, organic fine particles of opposite polarity, and inorganic fine particles may be used in a small amount as a developing property improver. It is also possible to use these additives after the surface is hydrophobized.

Next, an image forming apparatus which can suitably use the magnetic toner of the present invention will be described. The magnetic toner of the present invention can be used in an image forming apparatus that develops an electrostatic latent image formed on a photoconductor. Hereinafter, an example of an image forming apparatus to which the magnetic toner of the present invention can be applied will be specifically described with reference to the drawings.

The image forming apparatus is an image forming apparatus adopting a one-component jumping system and a contact charging system as shown in FIG. 2, and includes a rotatable cylindrical photoconductor 100,
The conductive primary charging roller 117 arranged in contact with the photoconductor 100 and the laser beam 12 applied to the charged photoconductor 100.
3, a laser generator 121, which is an electrostatic latent image forming means for forming an electrostatic latent image by irradiating 3 and an electrostatic latent image formed on the photoconductor 100 containing the magnetic toner of the present invention is developed by the magnetic toner. Developing device 140, a transfer roller 114 for transferring the toner image formed on the photoconductor 100 by this development to a transfer material, a fixing device 126 for fixing an unfixed toner image on the transfer material to the transfer material, and a transfer device after transfer. Photoconductor 1
Blade-type cleaning means 116 for removing the transfer residual toner remaining on the photoconductor 100 from the photoconductor 100, and the register roller 117 for conveying the transfer material to the transfer roller 114.
And a conveyor belt 125 that conveys the transfer material after the transfer.

The photosensitive member 100 is charged to -700V by the primary charging roller 117. (Applied voltage is AC voltage −
It is exposed by irradiating the photoconductor 100 with a laser beam 123 by the laser generator 121. Photoconductor 100
The above electrostatic latent image is developed with a one-component magnetic toner by the developing device 140, and is transferred onto the transfer material by the transfer roller 114 that is in contact with the photoconductor through the transfer material. The transfer material on which the toner image is placed is fixed to a fixing device 126 by a conveyor belt 125 or the like.
And is fixed on the transfer material. Further, the magnetic toner partially left on the photoconductor is cleaned by the cleaning unit 116.

The developing device 140, as shown in FIG.
00, a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a non-magnetic metal such as aluminum or stainless is disposed, and a gap between the photoconductor 100 and the developing sleeve 102 is not shown. It is maintained at about 230 μm by a photoconductor gap holding member or the like. A magnet roller (not shown) is concentrically fixed to and arranged in the developing sleeve 102. However, the developing sleeve 102 is rotatable.

The magnet roller is provided with a plurality of magnetic poles such as S1, S2, and N1, and S1 is for development and N
1 is the regulation of the coating amount of the magnetic toner, S2 is the taking in / conveying of the magnetic toner, and N2 is the prevention of the blowing of the magnetic toner. The developing device 140 includes a developing sleeve 102.
An elastic blade is arranged as a member for regulating the amount of magnetic toner attached to and conveyed to the developing sleeve 102, and the contact pressure of the elastic blade against the developing sleeve 102 controls the amount of magnetic toner conveyed to the developing area. In the developing area, a DC and AC developing bias is applied between the photoconductor 100 and the developing sleeve 102, and the magnetic toner on the developing sleeve flies on the photoconductor 100 according to the electrostatic latent image to form a visible image. Become.

[0191]

EXAMPLES The present invention will be specifically described below with reference to production examples and examples, but the present invention is not limited thereto. In the following formulation, all parts are parts by mass.

<Production Example 1 of surface-treated magnetic powder> An aqueous solution containing ferrous hydroxide was prepared by mixing 1.0 to 1.1 equivalents of caustic soda solution with iron ion in an aqueous solution of ferrous sulfate. Was prepared. While maintaining the pH of this aqueous solution at around 8,
Air was blown in and an oxidation reaction was carried out at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.

Next, the slurry liquid contained 0.9-1..1 with respect to the initial amount of alkali (sodium component of caustic soda).
After adding an aqueous ferrous sulfate solution to 2 equivalents, the slurry solution was maintained at a pH of around 8 to promote the oxidation reaction while blowing air, and the magnetic iron oxide particles produced after the oxidation reaction were washed and filtered once. I took it out. At this time, a small amount of water sample was taken and the water content was measured.

Next, the water-containing sample was re-dispersed in another aqueous medium without being dried, and then the pH of the re-dispersion liquid was adjusted to about 6, and n-hexyltrimethoxysilane coupling was performed with sufficient stirring. 2.0 parts by mass of the agent was added to 100 parts by mass of magnetic iron oxide (the amount of magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample), and the coupling treatment was performed. The produced hydrophobic iron oxide particles were washed, filtered, and dried by a conventional method, and then the particles slightly aggregated were crushed to obtain surface-treated magnetic powder 1 having an average particle diameter of 0.19 μm.

<Production Example 1 of Magnetic Powder> In the same manner as in Production Example 1 of surface-treated magnetic powder, the oxidation reaction was advanced, and the magnetic powder produced after the completion of the oxidation reaction was washed, filtered, dried, and aggregated. Particles with a mean particle size of 0.19μm
Got

<Production Example 2 of Surface-treated Magnetic Powder> The magnetic powder 1 obtained in Production Example 1 of the magnetic powder was redispersed in another aqueous medium, and the pH of the redispersion liquid was adjusted. Prepared to about 6,
While stirring, 2.0 parts by mass of the n-hexyltrimethoxysilane coupling agent was added to the magnetic powder 1 to perform a coupling treatment. The obtained magnetic particle slurry was washed, filtered, and dried by a conventional method, and the aggregated particles were crushed to obtain surface-treated magnetic powder 2 having an average particle size of 0.19 μm.

<Production Example 3 of Surface-treated Magnetic Powder> The magnetic powder 1 obtained in Production Example 1 of magnetic powder was used in an amount of 2.0 parts by mass of n-hexyltrimethoxysilane cup. By surface-treating with a ring agent in the gas phase, surface-treated magnetic powder 3 having an average particle diameter of 0.19 μm was obtained.

<Production Example 1 of Sulfur-Containing Polymer> In a pressurizable reaction vessel equipped with a reflux tube, a stirrer, a thermometer, a nitrogen introducing tube, a dropping device and a decompression device, methanol 250 was used as a solvent.
Parts, 150 parts of 2-butanone and 100 parts of 2-propanol
Parts, 83 parts of styrene as a monomer, 12 parts of butyl acrylate, and 5 parts of 2-acrylamido-2-methylpropanesulfonic acid (hereinafter abbreviated as AMPS) were added and heated to a reflux temperature with stirring. To this, t-butylperoxy-2-ethylhexanoate, which is a polymerization initiator, was added.
A solution prepared by diluting 45 parts with 20 parts of 2-butanone was added dropwise over 30 minutes and stirring was continued for 5 hours, and 0.28 parts of t-butylperoxy-2-ethylhexanoate was further added with 20 parts of 2-butanone. Add the diluted solution dropwise over 30 minutes,
The polymerization was completed by further stirring for 5 hours.

The polymer obtained after distilling off the polymerization solvent under reduced pressure was roughly pulverized to 100 μm or less using a cutter mill equipped with a 150-mesh screen. The obtained polymer had a Tg of about 70 ° C. Table 1 shows the physical properties of the obtained sulfur-containing polymer.

<Production Examples 2 to 6 of Sulfur-Containing Polymer> In Production Example 1 of the sulfur-containing polymer, the monomers used were changed to those shown in Table 1, and the amount of the polymerization initiator, the polymerization temperature or the polymerization time was changed. Sulfur-containing polymers 2 to 6 were obtained in the same manner as the sulfur-containing polymer 1 except that the molecular weight was controlled by adjusting. Table 1 shows the composition and physical properties of the obtained sulfur-containing polymer.

<Production Example 7 of Sulfur-Containing Polymer> In the same manner as in Production Example 1 of sulfur-containing polymer, except that 5 parts of AMPS used was 0.25 part of styrenesulfonic acid, the same procedure as that of the sulfur-containing polymer 1 was carried out. Sulfur polymer 7 was obtained. Table 1 shows the physical properties of the obtained sulfur-containing polymer.

[0202]

[Table 1]

<Production Example of Magnetic Toner 1> Deionized Water 7
After warming the 0.1M-Na ₃ PO ₄ aqueous solution 451 parts of the closing and 60 ° C. to 09 parts, 1.0 M-CaCl ₂ aqueous solution 6
7.7 parts was added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

On the other hand, styrene 78 parts n-butyl acrylate 22 parts divinylbenzene 0.5 part saturated polyester resin 2 parts surface-treated magnetic powder 1 80 parts The above formulation was used with an attritor (Mitsui Miike Kakoki Co., Ltd.). And uniformly mixed. This monomer composition was heated to 60 ° C., 8 parts of ester wax (maximum value of endothermic peak in DSC 72 ° C.) was added and mixed therein, and a polymerization initiator t-butylperoxy 2-ethyl was added thereto. Hexanoate (4 parts by mass) was dissolved.

The above polymerizable monomer composition was charged in the above aqueous medium, and the mixture was 10,000 rpm in a TK type homomixer (Tokushu Kika Kogyo Co., Ltd.) at 60 ° C. under N ₂ atmosphere.
Stir for 15 minutes and granulate. Then, the mixture was reacted at 80 ° C. for 1.5 hours while stirring with a paddle stirring blade. The polymerization conversion rate at this time was about 70%.

On the other hand, the following mixture was uniformly dissolved and added dropwise to the above suspension at 80 ° C., and polymerization was further carried out for 4.5 hours. Styrene 10 parts Sulfur-containing polymer 4 3 parts 2,2'-azobis (2,4-dimethylvaleronitrile) 0.3 parts

After completion of the reaction, distillation was further carried out at 80 ° C. for 2 hours, after which the suspension was cooled and hydrochloric acid was added to dissolve the dispersant, followed by filtration, washing with water and drying to give a weight average particle diameter of 7.1 μm. To obtain black particles 1.

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

<Production Example of Magnetic Toner 2> Sulfur-containing polymer 4
A magnetic toner 2 was obtained in the same manner as in the production example of the magnetic toner 1 except that the sulfur-containing polymer 5 was used instead of. Table 2 shows the physical properties of the magnetic toner 2.

<Production Example of Magnetic Toner 3> Sulfur-containing polymer 4
A magnetic toner 3 was obtained in the same manner as in the production example of the magnetic toner 1 except that the sulfur-containing polymer 3 was used instead of. Table 2 shows the physical properties of the magnetic toner 3.

<Production Example of Magnetic Toner 4> Sulfur-containing polymer 4
A magnetic toner 4 was obtained in the same manner as in the production example of the magnetic toner 1 except that the sulfur-containing polymer 2 was used instead of. Table 2 shows the physical properties of the magnetic toner 4.

<Production Example of Magnetic Toner 5> Sulfur-containing polymer 4
A magnetic toner 5 was obtained in the same manner as in the production example of the magnetic toner 1 except that the sulfur-containing polymer 7 was used instead of. Table 2 shows the physical properties of the magnetic toner 5.

<Production Example of Magnetic Toner 6> Sulfur-containing polymer 4
A magnetic toner 6 was obtained in the same manner as in the production example of the magnetic toner 1 except that the sulfur-containing polymer 1 was used instead of. Table 2 shows the physical properties of the magnetic toner 6.

<Production Example of Magnetic Toner 7> Sulfur-containing polymer 4
A magnetic toner 7 was obtained in the same manner as in the production example of the magnetic toner 1 except that the sulfur-containing polymer 6 was used instead of. Table 2 shows the physical properties of the magnetic toner 7.

<Production Example of Magnetic Toner 8> Styrene 65.0 parts by mass 2-ethylhexyl acrylate 35.0 parts by mass Divinylbenzene 0.5 parts by mass Magnetic powder 1 98.0 parts by mass Saturated polyester used in Magnetic Toner 1 10 parts by mass The above formulation was uniformly dispersed and mixed using an attritor. Then, the mixture was heated to 60 ° C., and 8 parts by mass of the ester wax used in the production of the magnetic toner 1 and 3.5 parts by mass of 2,2′-azobisisobutyronitrile were added and dissolved.

Next, 650 parts by mass of an aqueous colloidal solution containing 4% by mass of tricalcium phosphate was heated to 60 ° C., then 222 parts by mass of the above polymerizable monomer composition was added, and the mixture was mixed with a TK homomixer. Rotation speed 10,000 rp at room temperature
emulsified and dispersed for 3 minutes.

Thereafter, the reaction was carried out at 85 ° C. for 10 hours while continuing stirring in a nitrogen atmosphere, and then cooled to room temperature to obtain a magnetic toner particle dispersion liquid. The polymerization conversion rate at this time was about 100%.

Next, 13.0 parts by mass of styrene, 7.0 parts by mass of 2-ethylhexyl acrylate, 0.4 parts by mass of 2,2'-azobisisobutyronitrile, 0.2 parts by mass of divinylbenzene, and lauryl sulfate. 0.1 part by mass of sodium was added to 20 parts by mass of water and dispersed using an ultrasonic homogenizer to obtain 40.7 parts by mass of a water emulsion.

This was dropped into the magnetic toner particle dispersion liquid to swell the particles. Then, the mixture was stirred under a nitrogen atmosphere and reacted at 85 ° C. for 10 hours. Then, the suspension was cooled and hydrochloric acid was added to dissolve the dispersion medium, followed by filtration, washing with water and drying to obtain black particles 2 having a weight average particle diameter of 7.8 μm.

Magnetic toner 8 was prepared by mixing 100 parts by weight of the black particles 2 with 1.0 part by weight of silica used in the production of the magnetic toner 1 by a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.). Table 2 shows the physical properties of Toner 8.

[0221]

[Table 2]

The magnetic field of each magnetic toner is 79.6 k.
The strength of the magnetization at A / m is 25 to 27 Am in all cases.
It was ² / kg. In addition, the peak tops of the molecular weights of each magnetic toner measured by GPC are 22,000-
It was 30,000.

Example 1 In this example, the above-described magnetic toner was applied to the image forming apparatus shown in FIG. 2 by modifying LBP-1760, and the obtained image was evaluated. The conditions for image formation and the evaluation method in this embodiment will be described below.

In the image forming apparatus described above, the potential of the electrostatic image carrier is as follows: dark portion potential Vd = -620V, light portion potential VL.
= -130V. The gap between the electrostatic image carrier and the developing sleeve (toner carrier) was 260 μm.

The developing sleeve was provided with a resin layer having the following constitution on an aluminum cylinder having a diameter of 16 mm, the surface of which was blasted, with a layer thickness of about 7 μm and JIS center line average roughness (Ra).
A developing sleeve formed to 1.0 μm was used. A roll-shaped magnet, which is a magnetic field generating means, is fixedly arranged in the cylinder of the developing sleeve to form a developing magnetic pole of 85 mT (850 Gauss), while the developing sleeve has a peripheral surface of 1.0 mm in thickness as a toner regulating member. A urethane blade having a free length of 0.5 mm was brought into contact with the linear pressure of 39.2 N / m (40 g / cm). Phenolic resin 100 parts Graphite (particle size about 7 μm) 90 parts Carbon black 10 parts

As the developing bias, a DC bias component Vdc = -450V and an AC bias component Vp- to be superimposed.
p = 1500V and f = 2300Hz were used. Further, the peripheral speed of the developing sleeve was set to 110% (103 mm / sec) in the forward direction with respect to the peripheral speed (94 mm / sec) of the photoconductor that is the electrostatic image carrier. The transfer bias was set to DC 1.5 kV.

For fixing, instead of the fixing device usually provided in LBP-1760, a fixing device having a system of heating and pressurizing with a heater through a film and having no oil coating function was used. At this time, the pressure roller used has a surface layer of fluorocarbon resin, and the diameter of the roller is 30 mm.
Met. The fixing temperature is 185 ° C and the nip width is 7m.
set to m.

First, the magnetic toner 1 is loaded into the cartridge 3
Filled with 00 g, and under high temperature and high humidity (30 ° C., 80% RH), an image pattern consisting of only horizontal lines with a print rate of 2% was obtained.
An image output test of 000 sheets was performed, and 7 items described below were evaluated. As the transfer material, 90 g / m ² paper was used. Regarding the fixing property, after the initial image is displayed, Fo
Using a x River Bond paper, a halftone image was obtained and evaluated.

As a result, when the magnetic toner 1 was used, high transferability was exhibited at the initial stage and after printing 6000 sheets, and a good image without fog on the non-image area was obtained. In addition, there was no ghosting or tailing. Further, the fixability and offset resistance were also good. The evaluation results are shown in Table 3. The evaluation items and the criteria for judging the evaluation items in this embodiment will be described.

<Image Density> The image density was measured by forming a solid image portion and measuring the solid image with a Macbeth reflection densitometer (manufactured by Macbeth Co.).

<Transfer Efficiency> The transfer efficiency is as follows. The transfer residual toner on the photoconductor after the transfer of the solid black image is taped off with a Mylar tape and stripped off, and the value of the Macbeth density of what is stuck on the paper is C, and the value after the transfer and before the fixing is fixed. When the Macbeth density of the Mylar tape stuck on the paper on which the toner is placed is D and the Macbeth density of the Mylar tape stuck on the unused paper is E, it was approximately calculated by the following formula.

[Equation 11]

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> Fog is measured by REFLECTMETER MODEL TC-6D manufactured by Tokyo Denshoku Co., Ltd.
It was measured using S. A green filter was used as a filter, and fog was calculated from the following formula.

[Equation 12]

The reflectance obtained from the above calculation results was judged according to the following criteria. A: Very good (less than 1.5%) B: Good (1.5% or more and less than 2.5%) C: Normal (2.5% or more and less than 4.0%) D: Poor (4% that's all)

<Ghost> For the ghost, the image shown in FIG. 1 was output and visually judged based on the following criteria. A: No ghost has occurred. B: A good image although a slight ghost is generated. C: Although the ghost is generated, there is practically no problem in image quality. D: Image having bad ghost and not preferable for practical use.

<Tailing> Tailing is a condition in which the machine is stopped during development and the state of character portions on the electrostatic charge image bearing member after development is visually determined according to the following criteria. A: No tailing has occurred. B: A good image although a slight trailing has occurred. C: Image quality with no problem in practical use, although trailing has occurred. D: An image which is not preferable in practical use because of its severe trailing.

<Fixability> The fixability is 5 for a halftone image.
Applying a load of 0 g / cm ² and rubbing the fixed image 5 times back and forth with a soft thin paper, the reduction rate (%) of the image density before and after rubbing
It was evaluated by. A: less than 10% B: 10% or more and less than 20% C: 20% or more and less than 30% D: 30% or more

<Offset resistance> The offset resistance was evaluated by the degree of stain on the image and the back of the paper after the durability test. A: Dirt has not occurred. B: Slight stains are seen. C: Some dirt is seen. D: Remarkable stain is generated.

<Examples 2 to 5> Magnetic toners 2 to 5 were used as toners, and an image forming test and durability evaluation were performed under the same conditions as in Example 1. As a result, in the image forming test under high temperature and high humidity, the result without any big problem was obtained. The results are shown in Table 3.

<Comparative Examples 1 to 3> Magnetic toners 6 to 8 were used as toners, and an image forming test and durability evaluation were performed under the same conditions as in Example 1. As a result, after the durability test, ghost and tailing occurred, and fog and transferability deteriorated. The results are shown in Table 3.

[0241]

[Table 3]

<Production Example of Magnetic Toner 9> Deionized Water 7
After warming the 0.1M-Na ₃ PO ₄ aqueous solution 451 parts of the closing and 60 ° C. to 09 parts, 1.0 M-CaCl ₂ aqueous solution 6
7.7 parts was added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

On the other hand, styrene 78 parts n-butyl acrylate 22 parts divinylbenzene 0.5 part saturated polyester resin 2 parts surface-treated magnetic powder 1 80 parts The above formulation was used with an attritor (Mitsui Miike Kakoki Co., Ltd.). And uniformly mixed. This monomer composition was heated to 60 ° C., 8 parts of ester wax (maximum value of endothermic peak in DSC 72 ° C.) was added and mixed therein, and a polymerization initiator t-butylperoxy 2-ethyl was added thereto. Hexanoate (4 parts by mass) was dissolved.

The above polymerizable monomer composition was charged into the above aqueous medium, and the mixture was 10,000 rpm in a TK homomixer (Tokushu Kika Kogyo Co., Ltd.) at 60 ° C. under N ₂ atmosphere.
Stir for 15 minutes and granulate. Then, the mixture was stirred at 80 ° C. for 5 hours while stirring with a paddle stirring blade. The polymerization conversion rate at this time was about 100%.

On the other hand, the following mixture was uniformly dissolved and added dropwise to the above suspension at 80 ° C., and polymerization was further carried out for 4 hours. Styrene 20 parts Sulfur-containing polymer 1 6 parts 2,2′-azobis (2,4-dimethylvaleronitrile) 0.6 parts

After completion of the reaction, distillation was further carried out at 80 ° C. for 2 hours, after which the suspension was cooled and hydrochloric acid was added to dissolve the dispersant, followed by filtration, washing with water and drying to obtain a weight average particle diameter of 7.2 μm. To obtain black particles 3.

100 parts by weight of the black particles and 1.0 part by weight of the silica used in the production of the magnetic toner 1 were mixed by using a Henschel mixer (Mitsui Miike Kakoki Co., Ltd.) to obtain a magnetic toner 9
Was prepared. Table 4 shows the physical properties of the magnetic toner 9.

<Production Example of Magnetic Toner 10> A magnetic toner 10 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 2 was used in place of the surface-treated magnetic powder 1. Table 4 shows the physical properties of the magnetic toner 10.

<Production Example of Magnetic Toner 11> A magnetic toner 11 was obtained in the same manner as in the production example of the magnetic toner 1 except that the surface-treated magnetic powder 3 was used in place of the surface-treated magnetic powder 1. Table 4 shows the physical properties of the magnetic toner 11.

<Production Example of Magnetic Toner 12> A magnetic toner 12 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of the surface-treated magnetic powder was 40 parts by mass. Magnetic toner 1
The physical properties of No. 2 are shown in Table 4.

<Production Example of Magnetic Toner 13> A magnetic toner 13 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of the surface-treated magnetic powder was 150 parts by mass. Table 4 shows the physical properties of the magnetic toner 13.

<Production Example of Magnetic Toner 14> A magnetic toner 14 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of the ester wax was 0.8 part by mass. Table 4 shows the physical properties of the magnetic toner 14.

<Production Example of Magnetic Toner 15> A magnetic toner 15 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of the ester wax was changed to 35 parts by mass. Magnetic toner 1
The physical properties of No. 5 are shown in Table 4.

<Production Example of Magnetic Toner 16> Magnetic Toner 1 was prepared in the same manner as in Production Example of Magnetic Toner 1 except that 8 parts by mass of ester wax was changed to 4 parts by mass of polyethylene wax.
Got 6. Table 4 shows the physical properties of the magnetic toner 16.

<Production Example of Magnetic Toner 17> A magnetic toner 17 was obtained in the same manner as in the production example of the magnetic toner 1 except that divinylbenzene was not used. Table 4 shows the physical properties of the magnetic toner 17.

<Production Example of Magnetic Toner 18> A magnetic toner 18 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of divinylbenzene was changed to 0.1 part by mass. Table 4 shows the physical properties of the magnetic toner 18.

<Production Example of Magnetic Toner 19> Magnetic Toner 1 except that the amount of divinylbenzene was changed to 0.15 parts by mass.
Magnetic toner 19 was obtained in the same manner as in the manufacturing example of. Table 4 shows the physical properties of the magnetic toner 19.

<Production Example of Magnetic Toner 20> A magnetic toner 20 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of divinylbenzene was changed to 1.0 part by mass. Table 4 shows the physical properties of the magnetic toner 20.

<Production Example of Magnetic Toner 21> A magnetic toner 21 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of divinylbenzene was 1.2 parts by mass. Table 4 shows the physical properties of the magnetic toner 21.

<Production Example of Magnetic Toner 22> A magnetic toner 22 was obtained in the same manner as in the production example of the magnetic toner 1 except that the amount of divinylbenzene was changed to 1.5 parts by mass. Table 4 shows the physical properties of the magnetic toner 22.

<Production Example of Magnetic Toner 23> Styrene / n-butyl acrylate copolymer (mass ratio 78/22) 100 parts by mass saturated polyester resin 2 parts by mass sulfur-containing polymer 1 10 parts by mass Surface-treated magnetic powder 1 80 parts by mass Ester wax used in Example 1 8 parts by mass The above materials were mixed with a blender, melt-kneaded with a twin-screw extruder heated to 110 ° C., and the cooled kneaded material was coarsely crushed with a hammer mill to obtain a coarse kneaded product. After finely pulverizing the pulverized product with a jet mill, the obtained finely pulverized product was classified by wind force to obtain a toner having a weight average particle diameter of 8.1 μm. To 100 parts of this toner, 1.0 part of the silica used in Production Example 1 of magnetic toner was added and mixed using a Henschel mixer to prepare magnetic toner 23. Table 4 shows the physical properties of the magnetic toner 23.

[0262]

[Table 4]

The magnetic field of each magnetic toner is 79.6 k.
The magnetic strength at A / m is 16.
² Am ² / kg, and the magnetic toner 13 is 34.4 Am ²
/ Kg, and the others are 25 to 27 Am ² / k
It was g. Further, the peak tops of the molecular weight of each magnetic toner measured by GPC are all 12000 to 330.
It was 00.

<Examples 6 to 17> Magnetic toners 9 to 16 and 18 to 21 were used as toners, and an image forming test and durability evaluation were performed under the same conditions as in Example 1. as a result,
Even in the image forming test under high temperature and high humidity, the result without any big problem was obtained. The results are shown in Table 5.

<Comparative Examples 4 to 6> Magnetic toners 17, 22, and 23 were used as toners, and an image forming test and durability evaluation were performed by the same image forming method as in Example 1. As a result, the magnetic toners 17 and 22 were inferior in fixing property or anti-offset property as compared with the case of using other magnetic toners. Further, the magnetic toner 23 had poor transferability as compared with the case of using another magnetic toner. The results are shown in Table 5.

[0266]

[Table 5]

[0267]

The present invention is a magnetic toner containing at least a binder resin, magnetic powder, and a sulfur-containing polymer, having a weight average particle diameter of 3 to 10 μm and an average circularity of 0.9.
When it is 70 or more, the tetrahydrofuran insoluble matter of the resin component is 5 to 60 mass%, and the existing amount of carbon element existing on the surface is A and the existing amount of sulfur element existing on the surface is E. , E / A, which is the ratio of E to A, is a magnetic toner that satisfies the above formula (1). Therefore, by using this magnetic toner, good fixability, excellent transferability, and no fog occur. You can get an image. Further, even in a long-term use under a high temperature and high humidity environment, an image without ghost or trailing can be obtained.

The present invention also provides a magnetic toner characterized in that particles having at least magnetic powder are dispersed in an aqueous medium, and then a mixture of a polymerizable monomer and a sulfur-containing polymer is added and polymerized. Since it is a manufacturing method, it is possible to manufacture a magnetic toner having the above-described performance.

In the magnetic toner of the present invention, a magnetic field of 79.
The strength of magnetization at 6 kA / m is 10 to 50 Am ² / k
When g is g, it is more effective in preventing the toner scattering in the developing device and appropriately controlling the bristling on the toner carrying member to prevent the development tailing.

In the magnetic toner of the present invention, if the mode circularity is 0.99 or more, it is more effective in further improving the fog characteristic, transfer property and charging uniformity.

In the magnetic toner of the present invention, the E / A
Satisfying the above formula (2) is more effective in controlling the charging characteristics of the magnetic toner, and E / A is more effective in controlling the charging characteristics of the magnetic toner. Target.

Further, in the magnetic toner of the present invention, the sulfur-containing polymer preferably contains a sulfonic acid group-containing (meth) acrylamide.

In the magnetic toner of the present invention, when the amount of carbon element present on the surface is A and the amount of iron element present on the surface is B, the ratio of B to A is B.
When / A is less than 0.001, it is more effective in improving the fluidity, charging characteristics, transfer characteristics and the like of the magnetic toner and suppressing fog and ghost.

In the magnetic toner of the present invention, D / C ≦ 0.02, where C is the projected area equivalent diameter of the magnetic toner and D is the minimum value of the distance between the magnetic toner surface and the magnetic powder.
When the magnetic toner satisfying the relationship of 50% by number or more,
It is even more effective in achieving a good dispersion state of the magnetic powder in the magnetic toner.

In the magnetic toner of the present invention, if the release agent is contained in the binder resin in an amount of 1 to 30% by mass, it is more effective in achieving good fixing properties and storability of the magnetic toner. Furthermore, the release agent has an endothermic peak of 4 by differential thermal analysis.
When it is 0 to 110 ° C., and further 45 to 90 ° C., it is much more effective in improving the fixability and releasability at low temperatures.

Further, in the magnetic toner of the present invention, when the tetrahydrofuran component of the resin component is 8 to 50% by mass,
It is even more effective in suppressing toner deterioration.

Further, in the magnetic toner of the present invention, when the magnetic powder is subjected to a hydrophobic treatment with a coupling agent, it is more effective in controlling the dispersion state of the magnetic powder in the magnetic toner, and further, It is even more effective if the surface is hydrophobized while hydrolyzing the coupling agent in an aqueous medium.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a ghost image.

FIG. 2 is a schematic configuration diagram showing an example of an image forming apparatus to which the magnetic toner of the present invention is applied.

[Explanation of symbols]

100 photoconductor 102 developing sleeve (toner carrier) 114 transfer roller 116 Cleaning means 117 Primary charging roller 121 Laser generator 123 laser light 124 register roller 125 conveyor belt 126 Fixer 140 developer 141 stirring member

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takehiko Chiba             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Keiji Kawamoto             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Akira Hashimoto             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation (72) Inventor Tatsuya Nakamura             Kyano, 3-30-2 Shimomaruko, Ota-ku, Tokyo             Within the corporation F-term (reference) 2H005 AA01 AA03 AA06 AB06 CA02                       CA14 CA25 EA02 EA03 EA05                       EA10 FA06

Claims (16)

[Claims] 1. A magnetic toner containing at least a binder resin, magnetic powder, and a sulfur-containing polymer, having a weight average particle diameter of 3 to 10 μm and an average circularity of 0.
970 or more, tetrahydrofuran insoluble content of the resin component is 5 to 60 mass%, and the amount of carbon element present on the surface is A, and the amount of sulfur element present on the surface is E , E / A, which is the ratio of E to A, satisfies the following formula (1). [Equation 1] 3 × 10 ^-4 ≤ E / A ≤ 50 × 10 ^-4 (1) 2. Strong magnetization in a magnetic field of 79.6 kA / m
10 to 50 Am ²/ Kg / kg
The magnetic toner according to claim 1. 3. The magnetic toner according to claim 1, wherein the mode circularity is 0.99 or more. 4. The magnetic toner according to claim 1, wherein the E / A satisfies the following expression (2). [Equation 2] 3 × 10 ^-4 ≤ E / A ≤ 35 × 10 ^-4 (2) 5. The magnetic toner according to claim 1, wherein the E / A satisfies the following expression (3). [Equation 3] 3 × 10 ^-4 ≤ E / A ≤ 25 × 10 ^-4 (3) 6. The magnetic toner according to claim 1, wherein the sulfur-containing polymer contains a sulfonic acid group-containing (meth) acrylamide. 7. When the abundance of the carbon element existing on the surface is A and the abundance of the iron element existing on the surface is B,
7. The magnetic toner according to claim 1, wherein B / A, which is the ratio of B to A, is less than 0.001. 8. A magnetic toner satisfying the relationship of D / C ≦ 0.02, where C is the projected area equivalent diameter of the magnetic toner and D is the minimum value of the distance between the magnetic toner surface and the magnetic powder. Is 50% by number or more, and the magnetic toner according to any one of claims 1 to 7. 9. The magnetic toner contains a release agent in an amount of 1 to 30% by mass based on the binder resin.
9. The magnetic toner according to any one of items 8 to 8. 10. The magnetic toner according to claim 9, wherein the release agent has an endothermic peak by differential thermal analysis of 40 to 110 ° C. 11. The release agent has an endothermic peak by differential thermal analysis of 45 to 90 ° C.
The magnetic toner described in 1. 12. The magnetic toner according to claim 1, wherein the resin component of the magnetic toner has a tetrahydrofuran insoluble content of 8 to 50 mass%. 13. The magnetic powder is hydrophobized with a coupling agent, according to any one of claims 1 to 12.
The magnetic toner according to any one of 1. 14. The magnetic toner according to claim 13, wherein the surface of the magnetic powder is hydrophobized while the coupling agent is hydrolyzed in an aqueous medium. 15. A method for producing a magnetic toner, wherein particles having at least magnetic powder are dispersed in an aqueous medium, and then a mixture of a polymerizable monomer and a sulfur-containing polymer is added and polymerized. 16. A polymerizable monomer composition containing at least a polymerizable monomer and a magnetic powder is dispersed in an aqueous medium to produce particles of the polymerizable monomer composition, which is polymerized and converted. A mixture of a polymerizable monomer and a sulfur-containing polymer is added and polymerized when the ratio is 10% to 95%.
5. The method for producing a magnetic toner according to item 5.