JP5455444B2 - Magnetic toner - Google Patents

Description

The present invention relates to a magnetic toner used for electrophotography, electrostatic recording, and the like.

  As a general electrophotographic image forming method, for example, a photoconductive material is used, an electric latent image is formed on an electrostatic latent image carrier by various means, and then the latent image is developed into a developing device. It is visualized by developing it into a toner image. Next, if necessary, the toner image is transferred to a transfer material such as paper and then fixed by heating, pressure, or heating and pressing to obtain a toner image. Examples of such an image forming apparatus include a copying machine and a printer.

  As a developing device in such an electrophotographic method, generally, a developing blade made of rubber or metal as a toner regulating member for regulating the toner coat amount is brought into contact with the surface of a developing sleeve as a toner carrier. There are known devices comprising:

  By the friction between the developing blade and the toner and / or the friction between the toner carrier and the toner, a positive or negative charge is given to the toner. Further, a method is generally employed in which a toner carrier having toner thinly applied on the surface thereof by a developing blade is used to develop the image by flying and adhering to the electrostatic latent image on the surface of the electrostatic latent image carrier facing the toner carrier. ing.

Among such developing methods, a magnetic one-component developing system using magnetic toner is preferably used because it does not require a carrier and is advantageous in downsizing the apparatus.
In recent years, the technical direction of image forming apparatuses is required to increase the speed, improve the reliability during long-term use, and improve the fixability. Among them, the characteristics required of magnetic toners are to improve the stress resistance of magnetic toners in order to increase speed and improve reliability during long-term use. It is necessary to reduce the amount of change in characteristics. For this reason, specifically, the external additive added to the magnetic toner particles is prevented from being embedded in the magnetic toner particles. Alternatively, it is necessary to reduce the amount of change in magnetic toner characteristics even when the magnetic toner particles are embedded or peeled off.

  On the other hand, as a characteristic required for a magnetic toner for improving the fixing property, the magnetic toner is deformed at a low temperature or a light pressure, so that the thermoplasticity of the magnetic toner is improved. Specifically, there are lower molecular weight and lower Tg of the binder resin, and improvement of the release agent. Among them, a technique in which lowering the molecular weight of the binder resin is effective in order to reduce adverse effects on developability. As mentioned.

Thus, in order to satisfy the improvement of the stress resistance of the magnetic toner, the reduction of the change in the magnetic toner characteristics during long-term use, and the improvement of the fixing property, various studies have been made as the magnetic toner.
For example, Patent Document 1 proposes a magnetic capsule toner in which polyester is unevenly distributed on the surface of a core material containing magnetic fine particles and an outer shell is formed, and a high-quality image with good developability and transferability is proposed. An obtained electrostatic image developing toner having excellent fixability is obtained. However, there is an insufficient amount of change in toner characteristics especially during long-term use, and there is still room for improvement in terms of compatibility with stress resistance and fixing properties.

Patent Document 2 proposes a method for increasing the reaction efficiency of a polymerization initiator by adding a reducing agent for redox initiator in an aqueous dispersion medium in a granulation process or a polymerization process, and further adding a reducing agent. Thus, a dry toner excellent in high-resolution and high-definition image formation has been obtained. However, in particular, the compatibility between stress resistance and low-temperature fixability is insufficient, and there is still room for improvement.

Japanese Patent No. 3765593 JP 2004-184721 A

An object of the present invention is to provide a magnetic toner that solves the above problems.
That is, an object of the present invention is to improve image density and halftone uniformity during long-term use by improving the stress resistance of magnetic toner and reducing the amount of change in magnetic toner characteristics. Furthermore, it is to obtain good image characteristics by improving the low-temperature fixability.

And the magnetic toner particles of organic binder resin, a magnetic material and a release agent, a magnetic toner organic and inorganic fine powder,
The magnetic toner particles have an outer shell on the surface thereof;
The outer shell contains a polyester resin;
The polyester resin content is 8 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.
(1) The Total Energy (TEA100) when the stirring speed measured by the powder flowability measuring device of the magnetic toner particles is 100 revolutions is 650 mJ or more and 800 mJ or less,
(2) When the weight-average molecular weight Mw and the inertial square radius Rw were measured for the ortho-dichlorobenzene soluble content of the magnetic toner by size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS), the weight-average molecular weight Mw There is 2 00000 or less on 50000 or more, in the inertial square radius Rw of relationship between the weight average molecular weight Mw, Rw / Mw is, 1.0 × ^{10 -4} or more on 4. Magnetic toner satisfying 0 × 10 ⁻⁴ or less.

  According to the present invention, by improving the stress resistance of magnetic toner and reducing the amount of change in magnetic toner characteristics, the image density and halftone uniformity during long-term use are improved, and the low-temperature fixability is further improved. Magnetic toner can be provided.

1 is a schematic diagram illustrating an example of an image forming apparatus used in an embodiment of the present invention. It is an enlarged view of a developing unit. It is explanatory drawing of the external appearance (a) of the propeller-type blade of a powder fluidity | liquidity measuring apparatus, and the twist angle (b) of a blade outermost edge part.

Hereinafter, the present invention will be described in detail.
The present invention relates to a magnetic toner, and an image forming method and a fixing method can be applied with a conventionally known electrophotographic process, and are not particularly limited.

The present invention is a magnetic toner having at least a magnetic toner particle having at least a binder resin, a magnetic material and a release agent, and an inorganic fine powder,
(1) Total Energy (TEA100) when the stirring speed measured by the powder fluidity measuring apparatus for magnetic toner particles is 100 revolutions is 500 mJ or more and 1000 mJ or less,
(2) When the weight-average molecular weight Mw and the inertial square radius Rw were measured for the ortho-dichlorobenzene soluble content of the magnetic toner by size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) , the weight-average molecular weight Mw but 50,000 or more and 200,000 or less, in the inertial square radius Rw of relationship between the weight average molecular weight ^{Mw, 1.0 × 10 -4 ≦ Rw} / Mw ≦ 4.0 × 10 - and satisfies the ⁴ The present invention relates to a magnetic toner.

  According to the study by the present inventors, it is not sufficient to simply increase the surface hardness of the magnetic toner in order to improve the stress resistance of the magnetic toner and reduce the amount of change in magnetic toner characteristics during long-term use. I understood that.

  So far, methods for increasing the surface hardness of the magnetic toner include a method for increasing the strength of the binder resin, and a method for forming an outer shell such as polyester on the core material in the wet manufacturing method. The present inventors also prepared a magnetic toner by such a conventional method and examined the problems to be solved by the present invention. As a result, the stress resistance was improved, and the toner characteristics during long-term use were changed. The amount tended to decrease. However, the magnetic toner produced by the conventional method is still insufficient in terms of stress resistance, and the magnetic toner is deteriorated, so-called external additives are peeled off or embedded. As a result, a decrease in powder fluidity and charge amount with respect to the initial magnetic toner was observed. Further, in particular, the magnetic toner with the increased strength of the binder resin deteriorated the fixing property, and it was found that the fixing was poor and the image was rough. For this reason, it is necessary to further suppress the exfoliation or embedding of the external additive, or to find a method that exhibits the same magnetic toner characteristics as the initial magnetic toner even when the external additive is exfoliated or embedded. It was also found that it was necessary to satisfy the low-temperature fixability.

  Thus, the inventors of the present invention diligently studied and found that it is important to develop physical properties similar to those of the initial toner even when the external additive is peeled off or embedded. For this purpose, it has been found that it is most effective to improve the powder fluidity in the state of magnetic toner particles to which no external additive is added. It is also clear that by increasing the powder fluidity in the state of magnetic toner particles, it is possible to suppress the exfoliation and embedding of external additives and to maintain the powder fluidity of magnetic toner for a long time. It became.

  First, in order to improve the powder fluidity of the magnetic toner particles, it is important that a strong outer shell exists on the surface of the magnetic toner particles. The magnetic toner particles having an outer shell on the surface increase the hardness of the particles and increase the fluidity. Further, since the magnetic toner particles have an outer shell on the surface thereof, embedding of the external additive can be suppressed, so that the stress resistance can be improved and the amount of change in magnetic toner characteristics during long-term use can be reduced.

  However, when forming a strong outer shell on the surface of the magnetic toner particles, the thickness of the outer shell layer between the magnetic toner particles is not only increased by increasing the strength of the outer shell or by increasing the thickness of the outer shell. It was important that the variation in thickness was minimized and that the outer layer had no exposure of the binder resin and the layer thickness was uniform. In order to form such an outer shell on the surface of the magnetic toner particles, for example, in the case of a wet manufacturing method of magnetic toner, a magnetic toner particle is formed by simply mixing the material that becomes the outer shell, or a core material is formed. It is not sufficient to add the outer shell material later, and it is necessary to control the mutual relationship with the binder resin. That is, for the first time by adjusting the weight average molecular weight Mw and inertial square radius Rw of the soluble part of the ortho-dichlorobenzene of the magnetic toner, and appropriately controlling the type and amount of the binder resin having a branched structure and the outer shell material. Since the outer shell material uniformly covers the surface of the magnetic toner particles and the outer shell has an appropriate thickness, a uniform and strong outer shell can be formed on the surface of the magnetic toner particles. By doing so, the magnetic toner characteristics of the present invention can be expressed. That is, the powder fluidity is improved from the beginning, and the powder fluidity can be maintained even during long-term use. As a result, stress resistance is improved, and the amount of change in magnetic toner characteristics during long-term use can be greatly reduced, making it possible to obtain images with high image density and high halftone uniformity over a long period of time. Fixability can be improved.

  The present inventors examined an index indicating such a good magnetic toner characteristic. As a result, the total energy (TEA 100) when the stirring speed measured by the powder fluidity measuring apparatus for magnetic toner particles was 100 revolutions was adjusted. I found it important to do. As described above, in order to reduce the amount of change in magnetic toner characteristics, it is important to improve the fluidity of the magnetic toner. Regarding the fluidity of the initial magnetic toner, in addition to controlling the circularity of the magnetic toner, the fluidity can be increased relatively easily by the type and amount of inorganic fine powder added externally to the magnetic toner particles. Become. However, the fluidity during long-term use cannot be controlled only by adjusting the type and amount of inorganic fine powder added externally, and it is important to maintain fluidity in a state where the external additive is embedded or peeled off. That is, the fluidity during long-term use is greatly related to the fluidity of the magnetic toner particles themselves, and it is important to improve the fluidity of the magnetic toner particles themselves. The index is TEA100 when the stirring speed measured by the powder fluidity measuring device for magnetic toner particles is 100 revolutions, and the magnetic toner flows on the toner carrier in the developing device during long-term use. Corresponds to the state. In addition, the total energy (TEB100) when the stirring speed measured by a powder flowability measuring device for magnetic toner described later is 100 revolutions, the magnetic toner flows on the toner carrier in the initial developing device. It corresponds to the state. Furthermore, the total energy (TEB10) when the stirring speed measured by the powder flowability measuring device of the magnetic toner is 10 rotations corresponds to the flow state in the toner storage portion in the initial developing device.

  Specifically, the TEA100 of the magnetic toner particles needs to be 500 mJ or more and 1000 mJ or less. When the TEA 100 is 500 mJ or more and 1000 mJ or less, the fluidity is sufficient, and the amount of change in the magnetic toner fluidity during long-term use can be reduced. In order to make the TEA 100 500 mJ or more and 1000 mJ or less, it is not sufficient to increase the average circularity of the magnetic toner or to form an outer shell on the surface of the magnetic toner particle. It is indispensable to form a uniform and thick shell. As described above, the outer shell of the surface of the magnetic toner particle is formed by adjusting the weight-average molecular weight Mw and the inertial square radius Rw of the soluble part of the magnetic toner, and the binder resin having an appropriately branched structure. By controlling the type and amount of the shell material, it can be formed uniformly thick. When TEA100 is greater than 1000 mJ, it indicates that the fluidity is low, and the amount of change in the magnetic toner fluidity during long-term use increases, which causes a decrease in image quality and image density. On the other hand, when TEA100 is smaller than 500 mJ, the magnetic toner fluidity during long-term use becomes very high and the amount of change in the magnetic toner physical properties can be reduced. It becomes difficult to reduce the image density from the beginning.

  The TEB100 of the magnetic toner is preferably 300 mJ or more and 800 mJ or less. When TEB100 is 300 mJ or more, the fluidity of the magnetic toner is improved and the initial developability tends to be improved. When TEB100 is 800 mJ or less, the magnetic toner tends to be uniformly charged in the developing device, and the image quality tends to be improved.

  Next, in the Total Energy measured by the magnetic toner particle and the magnetic toner powder fluidity measuring apparatus, (TEA100-TEB100) is 300 (mJ) or less, that is, (TEA100-TEB100) ≦ 300 (mJ). It is preferable that the formula (2) is satisfied. (TEA100-TEB100) indicates the difference between the total energy of the magnetic toner particles and the magnetic toner, and corresponds to the difference in fluidity between the initial magnetic toner and the magnetic toner during long-term use on the toner carrier in the developing device. . When (TEA100-TEB100) is 300 (mJ) or less, the difference in fluidity between the initial use and long-term use becomes small, so the amount of change in toner physical properties during long-term use becomes small, and stable image density and image quality can be achieved. Can be obtained.

Further, it is preferable that TEB10 / TEB100 is not less than 1.00 and not more than 1.50, that is, 1.00 ≦ TEB10 / TEB100 ≦ 1.50 is satisfied. TEB10 / TEB100 is the ratio of Total Energy when the stirring speed is 10 revolutions and 100 revolutions. Within the developing container, different stirring states exist depending on the stirring member, the magnetic toner carrier, and the like. At that time, the closer the fluidity of the magnetic toner is to a certain level, the more easily the shearing is more likely to occur, and the triboelectric charge tends to be uniform. When TEB10 / TEB100 is 1.00 or more and 1.50 or less, since the ratio of fluidity in different stirring states is small, it becomes easy to hang the share uniformly, the triboelectric charge becomes uniform, and the image quality is improved. Even during long-term use, the amount of change in physical properties of the magnetic toner tends to be small.
The TEB 10 and TEB 100 can be adjusted by controlling the outer shell of the magnetic toner particles and the circularity of the magnetic toner, and by adjusting the kind, addition amount, and addition conditions of the inorganic fine powder added to the magnetic toner particles. .

Next, the wettability of the magnetic toner particles to the methanol / water mixed solvent is preferably 20% by volume or more and 50% by volume or less at which the methanol concentration at which the transmittance of light having a wavelength of 780 nm is 50%. When the magnetic toner particles have wettability to a methanol / water mixed solvent and the methanol concentration at which the light transmittance at a wavelength of 780 nm is 50% is 20% by volume or more, the outer shell material of the magnetic toner particles uniformly covers the surface. This means that durability stability is easily improved. Similarly, when the wettability of the magnetic toner particles to the methanol / water mixed solvent is 50% by volume or less at which the light transmittance at a wavelength of 780 nm is 50%, a material other than the outer shell material such as a release agent is used. Since it is not exposed, the stress resistance is easily improved.
The wettability with respect to the methanol / water mixed solvent can be adjusted by controlling the layer thickness and uniformity of the outer shell by the method used for preparing the outer shell on the surface of the magnetic toner particles.

Next, it is indispensable to adjust the molecular weight of the magnetic toner in order to satisfy the low-temperature fixability while reducing the stress resistance and the amount of change in magnetic toner characteristics during long-term use. Specifically, the weight-average molecular weight Mw when the ortho-dichlorobenzene soluble part of the magnetic toner is measured by size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) is 50,000 to 200,000, and the weight It is important that the average molecular weight Mw and the inertial square radius Rw satisfy 1.0 × 10 ⁻⁴ ≦ Rw / Mw ≦ 4.0 × 10 ⁻⁴ formula (1).

  Conventionally, the molecular weight distribution of a magnetic toner is determined by measuring the tetrahydrofuran soluble content of the toner by gel permeation chromatography (GPC). In the present invention, the measurement by SEC-MALLS is because the molecular size of the binder resin is more important.

Here, the absolute molecular weight and inertial square radius determined from SEC-MALLS will be described.
The molecular weight distribution measured by SEC is the molecular size and the intensity is its abundance. On the other hand, the light scattering intensity obtained with SEC-MALLS (by combining SEC and a multi-angle light scattering detector as a separation means and measuring the absolute molecular weight and molecular size (square of inertia square)) is the molecular size. Increases strength. However, the presence of a peak due to the elution time in SEC-MALLS measurement means that a polymer having a molecular spread (molecular size) at the molecular weight exists with a number distribution.

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

On the other hand, in the light scattering method used in the present invention, Rayleigh scattering of the measurement molecule was used.
Measure the dependence of the incident angle of the light and the sample concentration on the intensity of the scattered light, and analyze it with the Zimm method, the Berry method, etc., and the true molecular weight (absolute molecular weight) can be obtained for all molecular forms of linear polymers and branched polymers. Can be determined. (In the present invention, the absolute molecular weight was calculated by the Zim method by the SEC-MALLS measurement method (described later)). As a result, the molecular design of the magnetic toner can be precisely performed.

  First, when the weight average molecular weight Mw obtained by using the SEC-MALLS measurement method is 50000 or more and 200000 or less, the magnetic toner has high thermoplasticity, and it is easy to promote deformation of the magnetic toner even at a low temperature, and low temperature fixability is obtained. improves. In addition, the stress resistance of the magnetic toner is easily improved, and the amount of change in physical properties of the magnetic toner during long-term use can be easily reduced.

When the weight average molecular weight Mw is less than 50,000, the magnetic toner has high thermoplasticity, but the stress resistance of the magnetic toner tends to be lowered, and the change in physical properties of the magnetic toner during long-term use tends to be large. On the other hand, when the weight average molecular weight Mw is larger than 200000, the thermoplasticity of the magnetic toner is lowered, the fixing property is insufficient, and the image quality is lowered.
In the present invention, the weight average molecular weight Mw can be adjusted by the kind of polymerization initiator, the amount added, and the polymerization temperature. A preferable adjustment method is to add a peroxide-based polymerization initiator after the addition of the peroxide-based polymerization initiator and when the polymerization addition rate of the polymerizable monomer is 30 to 60%, or redox An additional reducing agent is added.

Next, it is important that the weight average molecular weight Mw and the inertial square radius Rw are 1.0 × 10 ⁻⁴ ≦ Rw / Mw ≦ 4.0 × 10 ⁻⁴ . Rw / Mw represents the spread or branched state per molecule forming the binder resin. A large Rw / Mw means a large inertial square radius per molecular weight, that is, a linear molecule with a small degree of branching. On the other hand, a small Rw / Mw means that the molecule has a high degree of branching and is a three-dimensional molecule. In the present invention, Rw / Mw is 1.0 × 10 ⁻⁴ or more and 4.0 × 10 ⁻⁴ or less. When Rw / Mw is 1.0 × 10 ⁻⁴ or more and 4.0 × 10 ⁻⁴ or less, the molecule has a suitable molecular size, the dispersibility of each material contained in the toner is improved, and the sharpness is increased. Both melt properties can be achieved. Therefore, both stress resistance and low-temperature fixability can be achieved. When Rw / Mw is smaller than 1.0 × 10 ⁻⁴ , the molecule has a branched structure and the molecular size increases, so that the dispersibility of each material contained in the toner is likely to be reduced, and frictional charging is not uniform. As a result, the image quality is lowered and the fixing property is also lowered.

On the other hand, when Rw / Mw is larger than 4.0 × 10 ⁻⁴ , the degree of branching is small and linear molecules tend to be improved, but the fixability tends to be improved. It tends to be low and stress resistance is reduced.
Furthermore, as a new finding obtained in the present invention, the weight average molecular weight Mw is 50000 or more and 200000 or less, and the weight average molecular weight Mw and the inertial square radius Rw are 1.0 × 10 ⁻⁴ ≦ Rw / Mw ≦ 4. 0.times.10.sup.- ⁴ , and by controlling the type, molecular weight, acid value, etc. of the outer shell material, the resin component and the outer shell material interact, and the outer shell material uniformly covers the surface of the magnetic toner particles. I found out that

The mechanism is considered as follows. For example, when magnetic toner particles are produced by a suspension polymerization method, a colorant, a release agent, and an outer shell material are dispersed and dissolved in a polymerizable monomer, and then they are liquidated in an aqueous medium in a granulation process. Droplets are formed, and the droplets are polymerized in the reaction process to produce magnetic toner particles. In the initial stage of this reaction process, while the outer shell material is exposed on the surface of the magnetic toner particles, the polymerization of the polymerizable monomer proceeds in parallel, and a binder resin is generated. Here, due to the polymerization rate of the droplets and the spread and stericity per molecule of the polymerized binder resin,
The motility of the outer shell material is different.

From such a mechanism, the weight average molecular weight Mw is 50,000 or more and 200,000 or less, and the weight average molecular weight Mw and the inertial square radius Rw are 1.0 × 10 ⁻⁴ ≦ Rw / Mw ≦ 4.0 × 10 ^−4. It is important to meet. By doing so, the resin component in the initial stage of the reaction process and the outer shell material have a suitable balance, which suggests that the outer shell material can be uniformly exposed on the surface of the magnetic toner particles.

  On the other hand, when the weight average molecular weight Mw is small or when Rw / Mw is large, the molecular motion during the polymerization reaction increases, so that the outer shell material is easily taken into the magnetic toner particles, and the surface of the uniform magnetic toner particles is reduced. It becomes difficult to form the outer shell. Also, when the weight average molecular weight Mw is large or when Rw / Mw is small, the molecular motion during the polymerization reaction becomes too small, so that the interaction with the outer shell material becomes smaller and the coating state of the outer shell material between the magnetic toner particles Variation tends to occur.

  Rw / Mw can be adjusted as follows. Rw / Mw as described above represents the degree of branching of the binder resin. In the present invention, it is essential that the binder resin has an appropriate degree of branching. For this reason, for example, when the magnetic toner of the present invention is produced by suspension polymerization (described later), it is necessary to adjust the polymerization conditions. Specifically, since the binder resin has a branched structure, there are means such as causing a hydrogen abstraction reaction during polymerization and branching by this.

  In order to cause the hydrogen abstraction reaction, it can be achieved by means such as rapidly increasing the radical concentration during the polymerization. As these means, for example, a polymerization initiator having a lower half-life temperature of 10 ° C. or more, more preferably 15 ° C. or more, is added during the polymerization, or an oxidation-reduction reaction (redox reaction) at a higher polymerization temperature. And so on. Usually, the oxidation-reduction reaction has the merit that the polymerization temperature can be lowered and the polymerization can proceed under mild conditions. However, the oxidation-reduction reaction at a high temperature causes the polymerization to proceed vigorously and the hydrogen abstraction reaction becomes active. Will happen.

  In these means, it is possible to arbitrarily change the degree of branching of the resin by changing the timing for rapidly increasing the radical concentration. Specifically, it is preferable to perform an oxidation-reduction reaction when the conversion rate of the polymerizable monomer is 30% or more and 60% or less, or to add a polymerization initiator having a low half-life temperature.

Further, in the magnetic toner of the present invention, the number average molecular weight Mn and the weight average molecular weight Mw when the ortho-dichlorobenzene soluble part of the magnetic toner is measured by size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) are obtained. It is preferable to satisfy Mw / Mn ≦ 7.2. When Mw / Mn is 7.2 or less, the molecular weight distribution becomes sharp, so that the balance with the outer shell material is easily fixed, and a more uniform outer shell is easily formed on the surface of the magnetic toner particles. In addition, the thermoplasticity of the binder resin is easily improved, and the low-temperature fixability is easily improved.
In the present invention, the number average molecular weight Mn can be adjusted by the kind of polymerization initiator, the amount added, and the polymerization temperature. A preferable adjustment method is to add a peroxide-based polymerization initiator after the addition of the peroxide-based polymerization initiator and when the polymerization addition rate of the polymerizable monomer is 30 to 60%, or redox An additional reducing agent is added.

  Next, the magnetic toner of the present invention preferably has a high average circularity. Since the average circularity of the magnetic toner is high, the powder fluidity is increased, and it is easy to uniformly and frictionally charge in the developing device, so that the image characteristics during initial and long-term use tend to be high.

Specifically, the average circularity of the magnetic toner is preferably 0.960 or more.
When the average circularity is 0.960 or more, the initial powder fluidity increases, and even when the external additive is peeled off or embedded during long-term use, the powder fluidity is easily maintained. Become. In addition, when the average circularity of the magnetic toner is increased, a uniform share is applied during long-term use, so that embedding of the external additive tends to be uniform, and the magnetic toner characteristics vary among the magnetic toner particles having the external additive. Since it tends to be small, it becomes easy to stabilize. In the present invention, the average circularity of the magnetic toner can be adjusted by the kind and amount of the additive material of the magnetic toner particles and the manufacturing method of the magnetic toner particles. As a method for producing magnetic toner particles, specifically, in a method for producing magnetic toner particles in an aqueous medium such as an emulsion aggregation method, a dissolution suspension method, and a suspension polymerization method, the temperature and pH can be adjusted. preferable. Further, when magnetic toner particles are produced by a pulverization method, it is preferable to perform a spheronization treatment with heat or a solvent after the pulverization step.

  The magnetic toner of the present invention can be produced by any known method. However, in order to obtain a suitable Total Energy of the magnetic toner according to the present invention and a physical property of an average circularity of 0.960 or more which is a preferable condition, an aqueous medium such as a dispersion polymerization method, an association aggregation method, a suspension polymerization method, etc. Among them, it is preferable to produce magnetic toner particles. In particular, a suspension polymerization method produced by polymerizing a polymerizable monomer composition in an aqueous medium is preferable because it easily satisfies the preferred conditions of the present invention.

  The suspension polymerization method is a polymerizable monomer system in which a polymerizable monomer and a colorant (and a polymerization initiator, a crosslinking agent, a charge control agent, and other additives as necessary) are uniformly dissolved or dispersed. And This polymerizable monomer system is dispersed in a continuous layer (for example, an aqueous phase) containing a dispersion stabilizer by using a suitable stirrer and simultaneously undergoes a polymerization reaction to obtain toner particles having a desired particle size. is there.

  Magnetic toner particles obtained by this suspension polymerization method (hereinafter referred to as polymerized magnetic toner particles) have an almost spherical shape, so that it is easy for stress to be applied to the polymerized magnetic toner particles uniformly. Therefore, it is easy to obtain a magnetic toner having good stress resistance. In addition, since the particle size distribution and the charge amount distribution are relatively uniform, the toner amount in the development nip is regulated and the magnetic toner is uniformly triboelectrically charged.

  However, as described above, even if a normal magnetic substance is contained in the polymerized magnetic toner particles, a large number of free magnetic substances are present, and the triboelectric charging characteristics of the polymerized magnetic toner particles are deteriorated. Further, the powder fluidity of the polymerized magnetic toner particles tends to deteriorate, and it is difficult to satisfy the total energy that is an essential requirement of the present invention. Furthermore, due to the strong interaction between the magnetic substance and water during the production of the polymerized magnetic toner particles by the suspension polymerization method, it is difficult to obtain polymerized magnetic toner particles having a high degree of circularity, and the magnetic toner has a wide particle size distribution. .

  This is as follows. 1. The magnetic substance is generally hydrophilic and therefore tends to be present on the surface of the polymerized magnetic toner particles. This is probably because the magnetic substance moves randomly during the aqueous phase stirring, and the suspended particle surface made of the monomer is dragged, and the shape is distorted to make it difficult to form a circle. In order to solve these problems, it is important to modify the surface characteristics of the magnetic material.

  Therefore, the magnetic material used in the magnetic toner of the present invention is preferably subjected to a hydrophobic treatment with a coupling agent. When hydrophobizing the surface of the magnetic material, it is more preferable to use a method in which the surface treatment is performed while hydrolyzing the coupling agent while dispersing the magnetic material to have a primary particle size in an aqueous medium. Furthermore, it is very preferable that the magnetic material produced in an aqueous solution is washed and then subjected to a hydrophobic treatment without drying.

In the hydrophobization method in water, the magnetic materials are less likely to coalesce than in the gas phase, and more uniform treatment can be performed. Moreover, since the thing which hydrophobizes without passing through a drying process does not occur the aggregation which arises at the time of drying, since it is disperse | distributed to the primary particle diameter at the time of a process, a very uniform surface treatment can be performed.

Examples of the coupling agent that can be used in the surface treatment of the magnetic material according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, which is represented by the general formula (I).
RmSiYn (I)
[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, or a methacryl group, and n represents an integer of 1 to 3. Show. However, m + n = 4. ]

  Examples of the silane coupling agent represented by the general formula (I) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, Vinyltriacetoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyl Diethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, trimethylmethoxysilane, n-hexyltrimethoxysilane, n-decyltrimethoxysilane, hydroxypropyltrimethoxysilane, n-hexadecyltrimethoxysilane, n- Examples include octadecyltrimethoxysilane.

  The treatment amount is preferably such that the total amount of the silane coupling agent is 0.5 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the magnetic substance, the surface area of the magnetic substance, and the reactivity of the coupling agent. It is preferable to adjust the amount of the treatment agent according to the above.

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

The magnetic material used in the magnetic toner of the present invention is preferably used in an amount of 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. More preferably, 20 parts by mass or more and 180 parts by mass or less are used. When the amount is 10 parts by mass or more, the coloring power of the magnetic toner is improved, and fog tends to be suppressed.
On the other hand, when the amount is 200 parts by mass or less, the magnetic material is easily dispersed uniformly in each magnetic toner particle.
The content of the magnetic substance in the magnetic toner can be measured using a thermal analysis apparatus manufactured by Perkin Elmer, TGA7. The measurement method is to heat the magnetic toner from room temperature to 900 ° C. at a temperature rising rate of 25 ° C./min in a nitrogen atmosphere, and use the weight loss part between 100 ° C. and 750 ° C. as the binder resin amount to approximate the remaining mass. The amount of magnetic material is used.

For example, in the case of magnetite, the magnetic material used in the magnetic toner of the present invention is produced by the following method.
An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide to the ferrous salt aqueous solution in an amount equivalent to or greater than the iron component. Air is blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 8 or higher, 14 or lower), and ferrous hydroxide is oxidized while heating the aqueous solution to 70 ° C. or higher. Magnetic iron oxide powder First, seed crystals that form the core of the body are generated.
Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals based on the amount of alkali added previously. The pH of the liquid is maintained at 6 or more and 14 or less, ferrous hydroxide is reacted while blowing air, and a magnetic iron oxide powder is grown with the seed crystal as a core. At this time, the shape of the magnetic material can be controlled by selecting an arbitrary pH. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but the pH of the liquid is preferably not less than 6.

  After completion of the oxidation reaction, the iron oxide powder obtained by washing and filtering is re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersed liquid is set to the acidic region, and the silane is stirred well. It is preferable to add a coupling agent and adjust the temperature and pH after hydrolysis to perform a coupling treatment. In any case, it is important to perform the surface treatment without passing through the drying step after the oxidation reaction, and if it is dried before the coupling treatment, it is difficult to uniformly disperse the magnetic substance in the aqueous medium, Uniform processing cannot be performed.

As the ferrous salt, iron sulfate generally produced as a by-product in the production of sulfuric acid titanium, iron sulfate produced as a by-product with the surface cleaning of the steel sheet can be used, and iron chloride or the like can be used.
In general, a method for producing magnetic iron oxide by an aqueous solution method uses an iron concentration of 0.5 mol / l or more and 2 mol / l or less from the viewpoint of preventing the viscosity from increasing during the reaction and the solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the particle size of the product. Further, in the reaction, the larger the amount of air and the lower the reaction temperature, the easier the atomization.

By using the magnetic toner made of the hydrophobic magnetic material produced as described above, stable charging property of the magnetic toner can be obtained, transfer efficiency is high, and high image quality and high development stability can be achieved.
Such magnetic iron oxide preferably has a BET specific surface area by nitrogen adsorption method of 2 m ² / g or more and 30 m ² / g or less, particularly 3 m ² / g or more and 28 m ² / g or less, and a Mohs hardness of 5 Above, 7 or less is preferable.
In addition, the shape of magnetic iron oxide includes octahedron, hexahedron, spherical shape, needle shape, scale shape, etc., but those having low anisotropy such as octahedron, hexahedron, spherical shape, and indefinite shape have a high image density. It is preferable in terms of enhancement. Such a shape can be confirmed by SEM or the like.

  As the particle size of magnetic iron oxide, the number average particle size is 0.1 μm or more and 0.3 μm or less and 0.03 μm or more in the particle size measurement for particles having a particle size of 0.03 μm or more, The number of particles having a size of 0.1 μm or less is preferably 40% by number or less.

  The magnetic toner of the present invention preferably has substantially no magnetic powder exposed on the toner surface. In the present invention, the fact that the magnetic powder is not substantially exposed on the toner surface means that the iron element content relative to the carbon element content (A) present on the toner particle surface measured by X-ray photoelectron spectroscopic analysis. The ratio (B / A) of the quantity (B) is defined as being less than 0.001. When the magnetic powder is not substantially exposed, the fluidity and triboelectric chargeability of the magnetic toner are improved, and a high density transition and image quality are likely to be improved during long-term use.

  When the projected area equivalent diameter of the magnetic toner of the present invention is C and D is the minimum distance between the iron oxide and the toner surface in the cross-sectional observation of the toner using a transmission electron microscope (TEM), D / C ≦ 0. The number of toners satisfying the relationship of .02 is preferably 50% or more.

  When the number of toners satisfying the relationship of D / C ≦ 0.02 is 50% or more, the dispersion state of the magnetic powder in the toner becomes small, and it becomes easy to suppress changes in toner physical properties due to long-term use. In addition, the charging uniformity of the toner is easily improved.

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

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

The magnetic toner of the present invention may contain a release agent for improving fixability, and preferably contains 1 part by mass or more and 30 parts by mass or less, more preferably 100 parts by mass of the binder resin. 3 parts by mass or more and 25 parts by mass or less.
Low-temperature offset property improves that content of a mold release agent is 1 mass part or more. When the amount is 30 parts by mass or less, toner fluidity during long-term use is easily improved.

  Release agents usable for the magnetic toner according to the present invention include petroleum waxes such as paraffin wax, microcrystalline wax, petrolactam and derivatives thereof, montan wax and derivatives thereof, hydrocarbon waxes and derivatives thereof according to the Fischer-Tropsch method, Polyolefin waxes represented by polyethylene and derivatives thereof, natural waxes and derivatives thereof such as carnauba wax and candelilla wax, and the derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, plant waxes, animal waxes, and the like can also be used.

  Among these release agent components, those having an endothermic peak of 40 ° C. or more and 110 ° C. or less by differential thermal analysis, that is, 40 ° C. or more and 110 ° C. at the time of temperature rise in a DSC curve measured by a differential differential calorimeter. Those having the maximum endothermic peak in the following regions are preferred. Furthermore, what has in the area | region of 45 to 90 degreeC is more preferable. Having the maximum endothermic peak in the temperature range is preferable because it has good fixability and can suppress exudation of the release agent component.

  The melting point of the release agent and the endothermic peak top of the release agent can be measured by differential scanning calorimetry. More specifically, it is performed according to ASTM D 3417-99. For example, DSC-7 manufactured by PerkinElmer, DSC2920 manufactured by TA Instrument, and Q1000 manufactured by TA Instrument can be used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, and an empty pan is set for control and measured.

In the magnetic toner of the present invention, since the binder resin and the release agent are easily compatible with each other when heated, the modulated mode is used and measured under the following conditions. The melting point was determined.

<Modulated mode measurement conditions>
• Equilibrate at 20 ° C for 1 minute.
-Apply a modulation of 1.5 ° C / min and raise the temperature to 180 ° C at 2 ° C / min.
• Equilibrate at 180 ° C for 10 minutes.
・ Apply a modulation of 1.5 ° C / min and lower the temperature to 20 ° C at 2 ° C / min.

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

  As a method of incorporating the charge control agent into the magnetic toner, there are a method of adding it inside the magnetic toner particles and a method of adding it externally. The amount of these charge control agents used is determined by the method of producing magnetic toner particles including the type of binder resin, the presence or absence of other additives, and the dispersion method. Absent. When these charge control agents are added internally, preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.1 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binder resin. Used in a range. When externally added, the amount is preferably 0.005 parts by mass or more and 1.0 parts by mass or less, more preferably 0.01 parts by mass or more and 0.3 parts by mass or less, with respect to 100 parts by mass of the magnetic toner particles. .

  However, in the magnetic toner of the present invention, the addition of a charge control agent is not essential, and the charge control agent is not necessarily contained in the magnetic toner by actively utilizing frictional charging with the layer thickness regulating member of the magnetic toner or the toner carrier. Need not be included.

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

The magnetic toner of the present invention may be polymerized by adding a resin to the polymerizable monomer system. For example, it contains hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups that cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the polymerizable monomer component into the toner, a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, and the like, Alternatively, it can be used in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. When such a polymer containing a polar functional group is allowed to coexist in the magnetic toner particles, the above-described wax component is phase-separated and the encapsulation becomes stronger, and a magnetic toner having good blocking resistance and developability can be obtained. Can do.
Among these resins, the effect is greatly increased by containing a polyester resin. I think this is because of the following reasons. Since the polyester resin contains many ester bonds which are functional groups having relatively high polarity, the polarity of the resin itself is increased. Due to its polarity, polyester tends to be unevenly distributed on the surface of the droplets in the aqueous dispersion medium, and polymerization proceeds while maintaining this state, resulting in magnetic toner particles. Here, by controlling the interrelationship with the binder resin, the polyester resin tends to be unevenly distributed on the surface of the magnetic toner particles, and the surface composition becomes uniform. As a result, the chargeability becomes uniform and the mold release agent. Very good developability can be obtained by a synergistic effect with the good encapsulating property.

  The polyester resin used in the present invention is, for example, appropriately selected from saturated polyester resin, unsaturated polyester resin, or both for controlling physical properties of magnetic toner such as triboelectric chargeability, durability and fixability. Is possible.

  The polyester resin used in the present invention is, for example, appropriately selected from saturated polyester resin, unsaturated polyester resin, or both for controlling physical properties of magnetic toner such as triboelectric chargeability, durability and fixability. Is possible.

  As the polyester resin used in the present invention, an ordinary resin composed of an alcohol component and an acid component can be used.

In the polyester resin in the present invention, it is preferable that 45 mol% or more and 55 mol% or less of all components are alcohol components, and 55 mol% or more and 45 mol% or less are acid components.
In the magnetic toner of the present invention, the polyester resin has an acid value of 0.1 to 30 mg KOH / resin 1 g so that the magnetic toner particles obtained on the surface of the magnetic toner particles exhibit stable chargeability. Is preferred. When the amount is less than 0.1 mgKOH / resin 1 g, the amount existing on the toner surface is absolutely insufficient, and when it exceeds 30 mgKOH / resin 1 g, the triboelectric charging property of the magnetic toner is adversely affected.

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

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

The content of the polyester resin with respect to 100 parts by mass of the binder resin is preferably 8 parts by mass or more and 30 parts by mass or less.
By being 8 mass parts or more, it becomes easy to express the effect as an outer shell of the polyester resin, the chargeability is improved, and the stress resistance is improved. On the other hand, if it is 30 parts by mass or less, the production stability is improved, the circularity of the toner tends to be high, and the dispersibility of the magnetic substance and the like tends to be improved.

  In addition, resins other than those described above may be added to the monomer system for the purpose of improving the dispersibility and fixing properties of the material or image characteristics. Examples of the resin used include styrene such as polystyrene and polyvinyltoluene. And styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-methacrylic acid Acid butyl copolymer, styrene-dimethylaminoethyl methacrylate copolymer Polymer, Styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether copolymer, Styrene-vinyl methyl ketone copolymer, Styrene-butadiene copolymer, Styrene-isoprene copolymer, Styrene-maleic acid copolymer Styrene copolymers such as styrene-maleic acid ester copolymer; polymethyl methacrylate and polybutyl methacrylate can be used alone or in combination. As addition amount of these resin, 1-20 mass parts is preferable with respect to 100 mass parts of polymerizable monomers.

Furthermore, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the polymerizable monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. I can do it.
The polymerization initiator used in the production of the magnetic toner of the present invention has a half-life of 0.5 to 30 hours during the polymerization reaction, and 0.5 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. It is preferable to carry out the polymerization reaction with an added amount of. In the present invention, it is essential that the binder resin has an appropriate degree of branching, and it is preferable to cause a hydrogen abstraction reaction or the like during the polymerization. As a means for causing a hydrogen abstraction reaction, for example, a polymerization initiator having a lower half-life temperature of 10 ° C. or more, more preferably 15 ° C. or more is preferably added during the polymerization, or an oxidation-reduction reaction at a higher polymerization temperature. (Redox reaction) is performed.

  The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Further, after the granulation, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added before starting the polymerization reaction or during the polymerization reaction.

As the polymerization initiator used in the present invention, conventionally known azo polymerization initiators, peroxide polymerization initiators and the like may be used in combination. As the azo polymerization initiator, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile) ), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, etc., and examples of the peroxide polymerization initiator include t-butyl hydroperoxide, di- t-butyl hydroperoxide, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxyacetate, t-butyl peroxylaurate, t-butyl peroxyneoheptanoate, t-butyl peroxypivalate, t -Butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy Cineodecanoate, t-hexylperoxyacetate, t-hexylperoxylaurate, t-hexylperoxypivalate, t-hexylperoxy-2-ethylhexanoate, t-hexylperoxyisobutyrate, t-hexylperoxyneodecanoate, t-butylperoxybenzoate, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetra Methylbutylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, 2,5-dimethyl -2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclo Xyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2 , 5-bis (benzoylperoxy) hexane, t-butylperoxy-m-toluoylbenzoate, bis (t-butylperoxy) isophthalate, t-butylperoxymaleic acid, t-butylperoxy-3 , 5,5-trimethylhexanoate, 2,5-dimethyl-2,5-bis (m-toluoylperoxy) hexane and other peroxyesters, benzoyl peroxide, dilauroyl peroxide, isobutyryl peroxide, etc. Diacyl peroxide, Peroxydicarbonates such as diisopropyl peroxydicarbonate and bis (4-t-butylcyclohexyl) peroxydicarbonate, 1,1-di-t-butylperoxycyclohexane, 1,1-di-t-hexylperoxy Peroxyketals such as cyclohexane, 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,2-di-t-butylperoxybutane, dicumyl peroxide, t-butyl kumi Dialkyl peroxides such as ruperoxide and others include t-butyl peroxyallyl monocarbonate, hydrogen peroxide and the like.

^{Examples of the} reducing agent used in the present invention include Fe ²⁺ salts, sulfites, alcohols, amines (polyamines, tertiary amines), naphthenates, mercaptans, and the like. Among these, an organic compound containing no sulfur or nitrogen element is preferable, and a salt of ascorbic acid is more preferable.

  As a particularly preferable method for adding a polymerization initiator when using the suspension polymerization method in the present invention, the polymerization addition rate of the polymerizable monomer after addition of 2,2′-azobisisobutyronitrile is 30 to 60%. At this point, additional t-butyl peroxyneoheptanoate is added. The polymerization initiator and the reducing agent are a combination in which Na ascorbate is additionally added when the polymerization addition rate of the polymerizable monomer is 30 to 60% after the addition of dilauroyl peroxide.

  When the magnetic toner of the present invention is produced, a crosslinking agent may be added, and a preferable addition amount is 0.001 part by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the polymerizable monomer. .

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

  In the method for producing the magnetic toner of the present invention by a polymerization method, generally, the above-described toner composition or the like is appropriately added, and uniformly dissolved or dispersed by a dispersing machine such as a homogenizer, a ball mill, a colloid mill, or an ultrasonic dispersing machine. . The resulting polymerizable monomer system is suspended in an aqueous medium containing a dispersion stabilizer. At this time, by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser, the toner particle size is sharpened by setting the desired toner particle size at once. After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and the particles are prevented from floating and settling.

  In the production of the magnetic toner of the present invention, a known surfactant, organic dispersant, or inorganic dispersant can be used as a dispersion stabilizer. Among these, inorganic dispersants can be preferably used because they have dispersion stability due to their steric hindrance, and therefore, stability is not easily lost even when the reaction temperature is changed, and washing is easy and does not adversely affect the toner. Examples of such inorganic dispersants include tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, phosphate polyvalent metal salts such as hydroxyapatite, carbonates such as calcium carbonate and magnesium carbonate, calcium metasuccinate, calcium sulfate, Examples thereof include inorganic salts such as barium sulfate and inorganic compounds such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide.

  These inorganic dispersants are desirably used in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer. Moreover, the said dispersion stabilizer may be used independently and may be used together in multiple types. Furthermore, you may use together 0.001 mass part or more and 0.1 mass part or less surfactant.

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

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

  In the polymerization step, the polymerization is preferably performed at a polymerization temperature of 40 ° C. or higher, generally 50 ° C. or higher and 90 ° C. or lower, particularly 5 ° C. from the 10-hour half-life temperature of the polymerization initiator used. As described above, it is preferable to set the temperature to 20 ° C. or lower. When the polymerization is carried out in this temperature range, the release agent and wax to be sealed inside are precipitated by phase separation, and the encapsulation is more complete. In order to consume the remaining polymerizable monomer, the reaction temperature can be raised to 90 ° C. or higher and 150 ° C. or lower at the end of the polymerization reaction.

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

  In the present invention, in order to control the powder fluidity of the magnetic toner, it is an essential condition to add inorganic fine powder to the magnetic toner particles. In addition, both organic fine powders and inorganic fine powders can be added, and all known ones can be used.

In particular, the inorganic fine powder used in the present invention preferably contains at least one kind of hydrophobic silica.
As a preferable hydrophobizing treatment of silica, there is a method of preparing by treating with hexamethyldisilazane and then treating with silicone oil.
As described above, it is preferable to treat silica with a silane compound and subsequently oil-treat, since the hydrophobicity can be effectively increased.

The magnetic toner of the present invention may be externally added with additives other than silica, if necessary.
Examples thereof include resin fine particles and inorganic fine particles that act as charging aids, conductivity imparting agents, fluidity imparting agents, anti-caking agents, mold release agents at the time of hot roll fixing, lubricants, and abrasives.
The fine resin particles preferably have an average particle size of 0.03 to 1.0 μm.

  Other fine particles include lubricants such as poly (ethylene fluoride), zinc stearate and polyvinylidene fluoride (polyvinylidene fluoride is preferred); abrasives such as cerium oxide, silicon carbide and strontium titanate (especially strontium titanate). Fluidity-imparting agents such as titanium oxide and aluminum oxide (especially hydrophobic ones are preferred); anti-caking agents; and conductivity-imparting agents such as carbon black, zinc oxide, antimony oxide and tin oxide. . Further, a small amount of white fine particles and black fine particles having a polarity opposite to that of the toner may be used as a developability improver.

The amount of the external additive added to the magnetic toner particles is preferably 0.1 to 3.0% by mass.
The magnetic toner particles and the inorganic fine powder are sufficiently mixed by a mixer such as a Henschel mixer to produce the magnetic toner according to the present invention.

An example of an image forming apparatus that can suitably use the magnetic toner of the present invention will be specifically described with reference to the drawings.
In the image forming apparatus of FIG. 2, reference numeral 100 denotes a photosensitive drum, and a primary charging roller 117, a developing device 140, a transfer charging roller 114, a cleaner 116, a register roller 124, and the like are provided around the photosensitive drum. The photoreceptor 100 is charged to, for example, −700 V by the primary charging roller 117 (applied voltages are AC voltage −2.0 kVpp, DC voltage −700 Vdc). Then, exposure is performed by irradiating the photosensitive member 100 with a laser beam 123 by the laser generator 121. The electrostatic latent image on the photoconductor 100 is developed by the developing device 140 and transferred onto the transfer material by the transfer charging roller 114 in contact with the photoconductor via the transfer material. The transfer material on which the toner image is placed is conveyed to the fixing device 126 by the conveying belt 125 or the like and fixed on the transfer material. In addition, toner partially remaining on the photoconductor is cleaned by a cleaner 116. As shown in FIG. 3, the developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive member 100. The gap between the photosensitive member 100 and the developing sleeve 102 is maintained at about 300 μm by a sleeve / photosensitive member gap holding member (not shown). A magnet roller 104 is fixed and arranged concentrically with the developing sleeve 102 in the developing sleeve. However, the developing sleeve 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure, and S1 influences development, N1 regulates the amount of toner coating, S2 takes in / conveys toner, and N2 affects toner blowout prevention. The toner is applied to the developing sleeve 102 by the toner application roller 141, and is adhered and conveyed. An elastic blade 103 is provided as a member for regulating the amount of toner conveyed, and the amount of toner conveyed to the development region is controlled by the contact pressure of the elastic blade 103 against the developing sleeve 102. In the developing region, a DC and AC developing bias is applied between the photosensitive member 100 and the developing sleeve 102, and the developer on the developing sleeve flies on the photosensitive member 100 in accordance with the electrostatic latent image and becomes a visible image. Become.

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

<Measuring method of weight average particle diameter (D4) and number average particle diameter (D1)>
The weight average particle diameter (D4) and the number average particle diameter (D1) of the magnetic toner are calculated as follows. As a measuring device, a precise particle size distribution measuring device “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.) using a pore electrical resistance method equipped with a 100 μm aperture tube is used. For setting the measurement conditions and analyzing the measurement data, the attached dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.) is used. Note that the measurement is performed with 25,000 effective measurement channels.

As the electrolytic aqueous solution used for the measurement, special grade sodium chloride is dissolved in ion-exchanged water so as to have a concentration of about 1% by mass, for example, “ISOTON II” (manufactured by Beckman Coulter, Inc.) can be used.
Prior to measurement and analysis, the dedicated software was set as follows.
On the “Change Standard Measurement Method (SOM)” screen of the dedicated software, set the total count in the control mode to 50,000 particles, set the number of measurements once, and set the Kd value to “standard particles 10.0 μm” (Beckman Coulter Set the value obtained using By pressing the “Threshold / Noise Level Measurement Button”, the threshold and noise level are automatically set. In addition, the current is set to 1600 μA, the gain is set to 2, the electrolyte is set to ISOTON II, and the “aperture tube flush after measurement” is checked.

In the “Pulse to particle size conversion setting” screen of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin is set to 256 particle size bin, and the particle size range is set to 2 μm to 60 μm.
The specific measurement method is as follows.

(1) About 200 ml of the electrolytic aqueous solution is put in a glass 250 ml round bottom beaker exclusively for Multisizer 3, set on a sample stand, and the stirrer rod is stirred counterclockwise at 24 rotations / second. Then, the dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the dedicated software.

(2) About 30 ml of the electrolytic aqueous solution is put into a glass 100 ml flat bottom beaker. In this, "Contaminone N" (nonionic surfactant, anionic surfactant, 10% by weight aqueous solution of neutral detergent for pH7 precision measuring instrument cleaning, made by organic builder, manufactured by Wako Pure Chemical Industries, Ltd. About 0.3 ml of a diluted solution obtained by diluting 3) with ion-exchanged water is added.

(3) Two oscillators with an oscillation frequency of 50 kHz are incorporated with the phase shifted by 180 degrees, and an ultrasonic disperser “Ultrasonic Dissipation System Tetora 150” (manufactured by Nikki Bios Co., Ltd.) having an electrical output of 120 W is prepared. About 3.3 l of ion-exchanged water is placed in the water tank of the ultrasonic disperser, and about 2 ml of Contaminone N is added to the water tank.

(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. And the height position of a beaker is adjusted so that the resonance state of the liquid level of the electrolyte solution in a beaker may become the maximum.

(5) In a state where the electrolytic aqueous solution in the beaker of (4) is irradiated with ultrasonic waves, about 10 mg of toner is added to the electrolytic aqueous solution little by little and dispersed. Then, the ultrasonic dispersion process is continued for another 60 seconds. In the ultrasonic dispersion, the temperature of the water tank is appropriately adjusted so as to be 10 ° C. or higher and 40 ° C. or lower.

(6) To the round bottom beaker of (1) installed in the sample stand, the electrolyte solution of (5) in which the toner is dispersed is dropped using a pipette, and the measurement concentration is adjusted to about 5%. . The measurement is performed until the number of measured particles reaches 50,000.

(7) The measurement data is analyzed with the dedicated software attached to the apparatus, and the weight average particle diameter (D4) and the number average particle diameter (D1) are calculated. The “average diameter” on the “analysis / volume statistic (arithmetic average)” screen when the graph / volume% is set in the dedicated software is the weight average particle size (D4). When the number% is set, the “average diameter” on the “analysis / number statistics (arithmetic average)” screen is the number average particle diameter (D1).

<Average circularity of magnetic toner>
The average circularity of the toner particles is measured by a flow type particle image analyzer “FPIA-3000” (manufactured by Sysmex Corporation) under the measurement and analysis conditions during the calibration operation.
A specific measurement method is as follows. First, about 20 ml of ion-exchanged water from which impure solids are removed in advance is put in a glass container. In this, "Contaminone N" (nonionic surfactant, anionic surfactant, 10% by weight aqueous solution of neutral detergent for pH7 precision measuring instrument cleaning, made by organic builder, manufactured by Wako Pure Chemical Industries, Ltd. About 0.2 ml of a diluted solution obtained by diluting the solution with ion exchange water about 3 times by mass. Further, about 0.02 g of a measurement sample is added, and dispersion treatment is performed for 2 minutes using an ultrasonic disperser to obtain a dispersion for measurement. In that case, it cools suitably so that the temperature of a dispersion liquid may become 10 to 40 degreeC. As the ultrasonic disperser, a desktop type ultrasonic cleaner disperser (for example, “VS-150” (manufactured by VervoCrea)) having an oscillation frequency of 50 kHz and an electric output of 150 W is used. Ion exchange water is added, and about 2 ml of the above-mentioned Contaminone N is added to this water tank.
For the measurement, the flow type particle image analyzer equipped with “UPlanApro” (magnification: 10 ×, numerical aperture: 0.40) as an objective lens is used. It was used. The dispersion prepared in accordance with the above procedure is introduced into the flow type particle image analyzer, and 3000 toner particles are measured in the HPF measurement mode and in the total count mode. Then, the binarization threshold at the time of particle analysis is set to 85%, the analysis particle diameter is limited to the circle equivalent diameter of 1.985 μm or more and less than 39.69 μm, and the average circularity of the toner particles is obtained.
In the measurement, before starting the measurement, standard latex particles (for example, Duke Science)
Automatic focusing is performed using “RESEARCH AND TEST PARTICLES Latex Microsphere Suspensions 5200A” manufactured by tific. Thereafter, it is preferable to perform focus adjustment every two hours from the start of measurement.
In the examples of the present application, a flow-type particle image analyzer that has been issued a calibration certificate issued by Sysmex Corporation, which has been calibrated by Sysmex Corporation, was used. Measurement was performed under the measurement and analysis conditions when the calibration certificate was received, except that the analysis particle size was limited to a circle equivalent diameter of 1.985 μm or more and less than 39.69 μm.

The measurement principle of the flow-type particle image analyzer “FPIA-3000” (manufactured by Sysmex Corporation) is to capture flowing particles as a still image and perform image analysis. The sample added to the sample chamber is fed into the flat sheath flow cell by a sample suction syringe. The sample fed into the flat sheath flow is sandwiched between sheath liquids to form a flat flow. The sample passing through the flat sheath flow cell is irradiated with strobe light at 1/60 second intervals, and the flowing particles can be photographed as a still image. Further, since the flow is flat, the image is taken in a focused state. The particle image is captured by a CCD camera, and the captured image is subjected to image processing at an image processing resolution of 512 × 512 (0.37 × 0.37 μm per pixel), and the contour of each particle image is extracted, The projected area S, the peripheral length L, and the like are measured.
Next, the equivalent circle diameter and the circularity are obtained using the area S and the peripheral length L. The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particle image, and the circularity C is a value obtained by dividing the circumference of the circle obtained from the equivalent circle diameter by the circumference of the projected particle image. And is calculated by the following formula.
Circularity C = 2 × (π × S) ^1/2 / L
When the particle image is circular, the degree of circularity is 1, and the degree of unevenness on the outer periphery of the particle image increases, and the degree of circularity decreases. After calculating the circularity of each particle, the circularity is 0.200 to 1.000.
Is divided into 800, and an arithmetic average value of the obtained circularity is calculated, and the value is defined as an average circularity.

<Total Energy of Magnetic Toner Particles and Magnetic Toner>
In the present invention, Total Energy (TEA100) when the stirring speed of the magnetic toner particles is 100 revolutions, and Total when the stirring speed of the magnetic toner is 10 revolutions.
Energy (TEB10), Total Energy (TEB100) when the stirring speed of the magnetic toner is 100 revolutions, is a powder rheometer FT-4 (manufactured by Freeman Technology) (hereinafter abbreviated as FT-4). Is measured).

  Specifically, the measurement is performed by the following operation. In all operations, the propeller type blade is a 48 mm diameter blade dedicated to FT-4 measurement (see FIG. 3; there is a rotation axis in the normal direction at the center of the 48 mm × 10 mm blade plate. The outer edge portion (24 mm from the rotation axis) is smoothly twisted counterclockwise such that the outer edge portion (24 mm from the rotation axis) is 70 °, and the 12 mm portion from the rotation axis is 35 °, and the material is made of SUS. May be abbreviated as blade).

  23 for a cylindrical split container (model number: C203, 82 mm in height from the bottom of the container to the split part. The material is glass. Hereinafter, it may be abbreviated as a container). A toner powder layer is formed by adding 100 g of magnetic toner particles or magnetic toner that has been left in a 60 ° C., 60% environment for 3 days or more.

(1) Conditioning operation (a) The rotational speed of the blade in the clockwise direction with respect to the powder layer surface (the direction in which the powder layer is loosened by the rotation of the blade) is set to the peripheral speed 60 at the outermost edge of the blade. (Mm / sec), and the angle between the trajectory drawn by the outermost edge of the moving blade and the surface of the powder layer is a speed of 5 (deg) (hereinafter referred to as the vertical approach speed to the powder layer). In some cases, the angle formed may be abbreviated as an angle formed from the bottom surface of the toner powder layer to the position of 10 mm from the surface of the powder layer. Thereafter, in the clockwise rotation direction with respect to the powder layer surface, the rotation speed of the blade is 60 (mm / sec), and the angle forming the vertical entry speed to the powder layer is 2 (deg). After performing an operation to enter the position 1 mm from the bottom of the magnetic toner powder layer at a speed, the blade rotation speed is 60 (mm / sec) in the clockwise rotation direction with respect to the powder layer surface, and the powder The angle forming the extraction speed from the body layer is moved to a position of 100 mm from the bottom surface of the magnetic toner powder layer at a speed of 5 (deg) to perform extraction. When the extraction is completed, the magnetic toner adhering to the blade is wiped off by rotating the blade alternately in small clockwise and counterclockwise directions.
(B) By performing the series of operations (1) to (a) five times, air trapped in the magnetic toner powder layer is removed, and a stable magnetic toner powder layer is formed.

(2) Split operation A magnetic toner powder layer having the same volume is formed by grinding the magnetic toner powder layer at the split portion of the above-described FT-4 measurement dedicated cell and removing the magnetic toner on the upper part of the powder layer.

(3) Measurement operation (i) Measurement of TEA 100 and TEB 100 (a) A conditioning operation similar to (1) to (a) above is performed once. Next, the rotation speed of the blade is set to 100 (mm / sec) in the counterclockwise rotation direction (direction in which the powder layer is pushed in by rotation of the blade) with respect to the surface of the magnetic toner powder layer, The approach speed in the vertical direction is made to enter a position 10 mm from the bottom surface of the magnetic toner powder layer at a speed at which the angle formed is 5 (deg). Thereafter, the rotation speed of the blade is set to 60 (mm / sec) in the clockwise rotation direction with respect to the surface of the magnetic toner powder layer, and the angle formed by the vertical entry speed to the magnetic toner powder layer is 2 After performing an operation of entering the position 1 mm from the bottom of the magnetic toner powder layer at a speed of (deg), the rotation speed of the blade is set to 60 in the clockwise rotation direction with respect to the surface of the magnetic toner powder layer. (Mm / sec), extraction is performed from the bottom surface of the magnetic toner powder layer to a position of 100 mm at a speed at which the angle forming the vertical extraction speed from the magnetic toner powder layer is 5 (deg). When the extraction is completed, the magnetic toner adhering to the blade is wiped off by rotating the blade alternately in small clockwise and counterclockwise directions.
(B) The above series of operations is repeated seven times, and the measurement is started from the position of 100 mm from the bottom surface of the magnetic toner powder layer at the seventh rotation speed of the blade of 100 (mm / sec). The sum of the rotational torque and the vertical load that is obtained when approaching to a position 10 mm from the bottom is defined as TEA100 or TEB100.
(Ii) Measurement of TEB10 (a) Using the magnetic toner powder layer for which the measurement of TEB100 has been completed, the above operations (3)-(i)-(a) are performed once.
(B) Next, in the series of operations in (3)-(i)-(a), the blade rotation speed was set to 100 (mm / sec) and the magnetic toner powder layer was made to enter 70. (Mm / sec) is used for measurement.
(C) Subsequently, the measurement was performed by sequentially reducing the rotational speed to 40 (mm / sec) and 10 (mm / sec) in the same manner as in (3)-(ii)-(b), and the rotational speed was 10 (mm / sec). sec), the measurement is started from the position of 100 mm from the bottom surface of the magnetic toner powder layer, and the sum of the rotational torque and the vertical load obtained when entering the position of 10 mm from the bottom surface is defined as TEB10.

<Measurement of methanol wettability of magnetic toner particles>
In the present invention, when the magnetic toner particles are infiltrated into a methanol / water mixed solvent, the methanol concentration at which the transmittance is 50% is determined from the methanol dropping transmittance curve obtained as follows.
First, 70 ml of water is put into a cylindrical glass container having a diameter of 5 cm and a thickness of 1.75 mm, and dispersed for 5 minutes with an ultrasonic disperser in order to remove bubbles and the like in the measurement sample.
Next, the magnetic toner particles are shaken with a mesh having an opening of 150 μm, and 0.1 g of the magnetic toner particles passing through the mesh are precisely weighed and added to the container containing the water to prepare a sample solution for measurement. .
Then, the measurement sample solution is set in a powder wettability tester “WET-100P” (manufactured by Reska). The sample liquid for measurement is stirred at a speed of 6.7 s ⁻¹ (400 rpm) using a magnetic stirrer. As the rotor of the magnetic stirrer, a spindle type rotor having a length of 25 mm and a maximum barrel diameter of 8 mm coated with a fluororesin is used.

  Next, methanol is continuously added to the measurement sample solution through the apparatus at a dropping rate of 1.3 ml / min. The transmittance is measured with light having a wavelength of 780 nm, and the methanol concentration at which the transmittance is 50% is defined as the methanol concentration at which the transmittance is 50% in the methanol / water mixed solvent of the magnetic toner particles.

<SEC-MALLS measurement of magnetic toner>
The mass average molecular weight Mn, the weight average molecular weight Mw, and the inertial square radius Rw of the magnetic toner of the present invention were determined by SEC-MALLS measurement.

0.03 g of magnetic toner is dispersed and dissolved in 10 ml of o-dichlorobenzene, and then dissolved at 25 ° C. for 24 hours.
Shake with a time shaker, filter with a 0.2 μm filter, and use the filtrate as a sample.

[Analysis conditions]
Separation column: Shodex (TSK GMHHR-H HT20) × 2
Column temperature: 135 ° C
Mobile phase solvent: o-dichlorobenzene mobile phase flow rate: 1.0 ml / min.
Sample concentration: about 0.3%
Injection volume: 300 μl
Detector 1: Multi-angle light scattering detector Wyatt DAWN EOS
Detector 2: Differential refractive index detector Shodex RI-71
[Measurement theory]
(LS) = (dn / dc) ² × C × Mw × KLS (1)
(LS); Measurement voltage value of the detector (v)
(Dn / dc): Increment of refractive index per 1 g of sample (ml / g)
C: concentration (g / ml)
KLS: Coefficient of measurement voltage and scattering intensity (reduction Rayleigh ratio) (equipment constant)
In the present invention, (dn / dc) was set to 0.068 ml / g from the literature value of polystyrene.

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

<B / A measurement of magnetic toner>
The ratio (B / A) of the iron element content (B) to the carbon element content (A) present on the surface of the magnetic toner particles in the present invention is determined by surface composition analysis by ESCA (X-ray photoelectron spectroscopy). Calculated.
In the present invention, the ESCA apparatus and measurement conditions are as follows.
Equipment used: 1600S type X-ray photoelectron spectrometer manufactured by PHI (Physical Electronics Industries, Inc.) Measurement conditions: X-ray source MgKα (400 W)
Spectral region 800μmφ
In the present invention, the surface atomic concentration (atomic%) was calculated from the measured peak intensity of each element using a relative sensitivity factor provided by PHI.
As the measurement sample, magnetic toner is used. When an external additive is added to the magnetic toner particles, the magnetic toner is washed with a solvent that does not dissolve the magnetic toner particles, such as isopropanol, and the external additive is added. Measure after removing.

<GPC measurement>
The molecular weight distribution of a polymer having a polar functional group such as a polyester resin in the present invention is measured by gel permeation chromatography (GPC) as follows.
First, a magnetic toner or resin is dissolved in tetrahydrofuran (THF) over 24 hours at room temperature. The obtained solution is filtered through a solvent-resistant membrane filter “Maescho Disc” (manufactured by Tosoh Corporation) having a pore diameter of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of the component soluble in THF is about 0.8% by mass. Using this sample solution, measurement is performed under the following conditions.

Apparatus: HLC8120 GPC (detector: RI) (manufactured by Tosoh Corporation)
Column: Seven series of Shodex KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko KK)
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 ml / min
Oven temperature: 40.0 ° C
Sample injection volume: 0.10 ml
In calculating the molecular weight of the sample, standard polystyrene resin (for example, trade name “TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F— 10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500 ", manufactured by Tosoh Corporation) are used.

<Acid value of a polymer containing a polar functional group>
The acid value is the number of mg of potassium hydroxide necessary for neutralizing the acid contained in 1 g of the sample. The acid value of the polyester resin is measured according to JIS K 0070-1992. Specifically, it is measured according to the following procedure.

(1) Preparation of Reagent 1.0 g of phenolphthalein is dissolved in 90 ml of ethyl alcohol (95 vol%), and ion exchanged water is added to make 100 ml to obtain a phenolphthalein solution.
7 g of special grade potassium hydroxide is dissolved in 5 ml of water, and ethyl alcohol (95 vol%) is added to make 1 l. In order not to touch carbon dioxide, etc., put in an alkali-resistant container and let stand for 3 days, then filter to obtain a potassium hydroxide solution. The obtained potassium hydroxide solution is stored in an alkali-resistant container. The factor of the potassium hydroxide solution was as follows: 25 ml of 0.1 mol / l hydrochloric acid was placed in an Erlenmeyer flask, a few drops of the phenolphthalein solution were added, titrated with the potassium hydroxide solution, and the hydroxide required for neutralization. Determined from the amount of potassium solution. As the 0.1 mol / l hydrochloric acid, one prepared according to JIS K 8001-1998 is used.

(2) Operation (A) Main test A polyester resin sample (2.0 g) is precisely weighed in a 200 ml Erlenmeyer flask, and 100 ml of a toluene / ethanol (2: 1) mixed solution is added and dissolved over 5 hours. Subsequently, several drops of the phenolphthalein solution is added as an indicator, and titration is performed using the potassium hydroxide solution. The end point of titration is when the light red color of the indicator lasts for about 30 seconds.
(B) Blank test Titration is performed in the same manner as above except that no sample is used (that is, only a mixed solution of toluene / ethanol (2: 1) is used).

(3) The acid value is calculated by substituting the obtained result into the following formula.
A = [(C−B) × f × 5.61] / S
Here, A: acid value (mgKOH / g), B: addition amount (ml) of a potassium hydroxide solution in a blank test, C: addition amount (ml) of a potassium hydroxide solution in this test, f: potassium hydroxide Solution factor, S: sample (g).

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

<Synthesis of polyester resin 1>
The following components were placed in a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introduction tube, and reacted for 10 hours while distilling off the water produced at 230 ° C. under a nitrogen stream.
Bisphenol A EO 2 mol adduct 350 parts Bisphenol A PO 2 mol adduct 326 parts terephthalic acid 278 parts
Titanium-based catalyst (titanium dihydroxybis (triethanolamate)) 2 parts Next, the reaction was carried out under reduced pressure of 5 to 20 mmHg, and when the acid value became 2 or less, the mixture was cooled to 180 ° C., and 62 parts of trimellitic anhydride was added. In addition, the polyester resin 1 was obtained by reacting for 2 hours under normal pressure sealing, taking out, cooling to room temperature, and pulverizing. The obtained polyester resin 1 had Mw = 10500, Mn = 3800, and an acid value of 6.

<Synthesis of polyester resin 2>
369.5 g of propylene oxide adduct of bisphenol A (hereinafter abbreviated as BPA · PO, added mole number is 3 on average), 146.4 g of ethylene oxide adduct of bisphenol A (hereinafter abbreviated as BPA · EO), terephthalic acid 126 0.0 g (hereinafter abbreviated as TPA), 40.2 g of dodecenyl succinic acid (hereinafter abbreviated as DSA), and 77.7 g of trimellitic anhydride (hereinafter abbreviated as TMA) are placed in a 2-liter glass four-necked flask. A thermometer, a stainless steel stirring bar, a flow-down condenser, and a nitrogen introduction tube were attached, and the reaction was carried out at 220 ° C. under a nitrogen stream in a mantle heater.
The degree of polymerization was tracked from the softening point according to ASTM E28-67, and the reaction was terminated when the softening point reached 110 ° C. This resin is designated as polyester resin 2.

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

Subsequently, the ferrous sulfate aqueous solution was added to this slurry liquid so that it might become 1.0 equivalent with respect to the original alkali amount (sodium component of caustic soda). The slurry was maintained at pH 8 and the oxidation reaction was advanced while blowing air, and the pH was adjusted to about 6 at the end of the oxidation reaction. As a silane coupling agent, 0.6 part of n-C ₆ H ₁₃ Si (OCH ₃ ) ₃ was added to 100 parts of magnetic iron oxide and sufficiently stirred. The produced hydrophobic iron oxide particles were washed, filtered and dried by a conventional method. After the aggregated particles were crushed, heat treatment was performed at a temperature of 70 ° C. for 5 hours to obtain magnetic iron oxide.
The average particle diameter of the magnetic iron oxide 0.26 .mu.m, saturation magnetization and the residual magnetization in a magnetic field 79.6 kA / m (1000 oersteds) is ^{67.3Am 2 /kg(emu/g),4.0Am 2 / kg (emu} / g).

<Manufacture of magnetic toner 1>
An aqueous system containing a dispersion stabilizer by adding 450 parts of a 0.1 M Na ₃ PO ₄ aqueous solution to 720 parts of ion-exchanged water and heating to 60 ° C. and then adding 67.7 parts of a 1.0 M CaCl ₂ aqueous solution. A medium was obtained.
Styrene 75 parts n-Butyl acrylate 25 parts Divinylbenzene 0.5 part Polyester resin 1 15 parts Negative charge controller T-77 (Hodogaya Chemical) 1 part Magnetic iron oxide 90 parts

  The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.). This monomer composition was heated to a temperature of 60 ° C., and 15 parts by mass of HNP-9 (polyethylene wax, DSC endothermic main peak = 78 ° C .; manufactured by Nippon Seiwa Co., Ltd.), 6.5 parts of dilauroyl peroxide. The parts were mixed and dissolved to obtain a polymerizable monomer composition.

The polymerizable monomer composition is charged into the aqueous medium, and is stirred at 10,000 rpm for 15 minutes in a TK homomixer (Special Machine Industries Co., Ltd.) at a temperature of 60 ° C. and in an N ₂ atmosphere. Granulated.
Then, the reaction process was performed by stirring with a paddle stirring blade at a temperature of 70 ° C. When the polymerization addition rate of the polymerizable monomer was 50%, 2.0 parts by mass of sodium ascorbate was additionally added, and the reaction was further performed. The reaction process was completed when the reaction time was 360 minutes.
After completion of the reaction, the suspension was cooled and hydrochloric acid was added to dissolve the dispersant, followed by filtration, washing with water and drying to obtain magnetic toner particles 1.
Hydrophobic silica fine powder 1 having 100 parts of magnetic toner particles 1 and silica having a primary particle diameter of 12 nm treated with hexamethyldisilazane and then treated with silicone oil, and a BET specific surface area value of 120 m ² / g after treatment. 0.0 part was mixed using a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare magnetic toner 1. Table 2 shows the physical properties of the magnetic toner 1.

<Manufacture of magnetic toners 2 to 23>
In the production of magnetic toner 1, as shown in Table 1, the amounts of polyester resin 1, magnetic iron oxide, and polymerization initiator were changed, and the reaction conditions were changed to obtain magnetic toners 2 to 23. Table 2 shows the physical properties of the magnetic toners 2 to 23.

<Manufacture of Magnetic Toner 24>
Styrene 65.0 parts 2-Ethylhexyl acrylate 35.0 parts Divinylbenzene 0.8 parts Iron trioxide (M-0902: σs = 93.9 emu / g (5 kOe), σr = 7.7 emu / g (5 kOe), Hc = 76 Oe (5 kOe), pH = 7.5, oil absorption amount: 21 ml / 100 g, manufactured by Mitsui Mining & Smelting Co., Ltd. 98.0 parts Polyester resin 2 10 parts

Add 3.5 parts by weight of 2,2′-azobisisobutyronitrile, and put into an attritor (“MA-01SC type”, manufactured by Mitsui Miike Chemical Co., Ltd.) and disperse at 10 ° C. for 5 hours. As a result, a polymerizable composition was obtained.
Next, 212.3 g of the polymerizable composition was added to 650 g of an aqueous colloidal solution of 6% by weight of tricalcium phosphate prepared in advance in a 2 liter glass separable flask. Using a TK homomixer (M type, manufactured by Tokushu Kika Kogyo Co., Ltd.), the mixture was emulsified and dispersed at room temperature at a rotation speed of 10,000 rpm for 2 minutes.

Next, a four-necked glass lid was capped, and a reflux condenser, a thermometer, a nitrogen inlet tube, and a stainless steel stirring rod were attached and installed in an electric heating mantle heater. While continuing stirring under nitrogen, the temperature was raised to 85 ° C. as the first stage polymerization and reacted for 10 hours to obtain seed particles. This was cooled to room temperature to obtain precursor particles.
Next, 13.0 parts by weight of styrene prepared with an ultrasonic oscillator (US-150, manufactured by Nippon Seiki Seisakusho Co., Ltd.) and 7.0 weights of 2-ethylhexyl acrylate in an aqueous suspension of the precursor particles. 40.7 parts by weight of water emulsion consisting of 0.4 parts by weight of 2,2'-azobisisobutyronitrile, 0.22 parts by weight of divinylbenzene, 0.1 parts by weight of sodium lauryl sulfate, and 20 parts by weight of water Part was dropped to swell the precursor particles. While continuing stirring under nitrogen, the temperature was raised to 85 ° C. as the second stage polymerization, and the reaction was carried out for 10 hours. After cooling, the dispersion medium is dissolved in a 10% hydrochloric acid aqueous solution, filtered, washed with water, air-dried, dried at 45 ° C. for 12 hours under reduced pressure at 20 mmHg, classified with an air classifier, and magnetized with an average particle size of 6.5 μm. Toner particles were obtained.
A magnetic toner 24 was obtained by adding 0.4 parts by weight of hydrophobic silica fine particles “Aerosil R-972” (manufactured by Nippon Aerosil Co., Ltd.) to 100 parts by weight of the magnetic toner particles.

<Manufacture of magnetic toner 25>
Polyester resin 1 100 parts by mass Magnetic iron oxide 90 parts by mass Monoazo iron complex (T-77: manufactured by Hodogaya Chemical Co., Ltd.) 2 parts by mass HNP9 5 parts by mass After the above mixture was premixed with a Henschel mixer, it was heated to 110 ° C. 2 The kneaded material was melt-kneaded with a shaft extruder and the cooled kneaded material was coarsely pulverized with a hammer mill to obtain a coarsely pulverized toner product. The obtained coarsely pulverized product was coated with a mechanical pulverizer turbo mill (manufactured by Turbo Kogyo Co., Ltd .; coated with chromium alloy plating containing chromium carbide on the rotor and stator surfaces (plating thickness 150 μm, surface hardness HV1050)). And then pulverized by mechanical pulverization. The finely pulverized product was classified and removed at the same time by a multi-division classifier (Elbow Jet Classifier manufactured by Nittetsu Mining Co., Ltd.) using the Coanda effect to obtain magnetic toner particles.

Hydrophobic silica fine powder 1 having 100 parts by mass of the magnetic toner particles and silica having a number average primary particle size of 12 nm treated with hexamethyldisilazane and then with silicone oil, and a BET value after treatment of 120 m ² / g. 0.0 part by mass was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to obtain a magnetic toner 25 having a weight average particle diameter (D4) of 6.4 μm. Table 2 shows the physical properties of the magnetic toner 25.

<Example 1>
As the image forming apparatus, LBP-3410 was used with the process speed modified to 220 mm / sec.
Under these conditions, the magnetic toner 1 was used, and an endurance test was performed on an image with a 1% printing rate using 8-point A characters in a normal temperature and humidity environment (temperature 25.0 ° C., humidity 50% RH). It was. The endurance test was performed for 2000 sheets per day in the intermittent mode, and the endurance test was performed for 10,000 sheets over 5 days. As the recording medium, A4 75 g / m ² paper was used. As a result, a high image density was obtained through the durability test, and the halftone uniformity was also good. The image density at the end of the durability was 1.5 or more, and a high-quality image could be obtained. Further, similarly, an endurance test was performed in a high temperature and high humidity environment (temperature 32.5 ° C., humidity 80% RH). As a result, a high image density was obtained through the durability test, and the halftone uniformity was also good. The image density at the end of the durability was 1.5 or more, and a high-quality image could be obtained.
Further, a similar image forming apparatus is modified so that the fixing temperature of the fixing unit can be adjusted, and magnetic toner 1 is used, and Xerox is 75 g / m in a normal temperature and humidity environment (temperature 25.0 ° C., humidity 50% RH). ^The fixing property was evaluated using ^two papers. As a result, the minimum fixing temperature was less than 180 ° C., and good low-temperature fixability was obtained. The results are shown in Table 3.

Here, the evaluation items and judgment criteria described in the examples of the present invention and comparative examples will be described.
a) Image density A solid image portion was formed and evaluated at the initial stage and after 10000 printouts were completed. The image density was measured by using a “Macbeth reflection densitometer” (manufactured by Macbeth Co.), which is an image density measuring device, to measure a relative density with respect to a printout image of a white background portion having a document density of 0.00. If the image density is 1.30 or more, the image has no practical problem.

b) Uniformity of halftone Using a 1 dot-2space halftone image, visual judgment was made according to the following criteria.
A: Halftone image with no unevenness and excellent uniformity B: Uniform halftone image with slight unevenness C: Halftone image with a level that does not cause any practical problems although unevenness occurs D: Halftone unevenness is generated, which is not preferable for practical use

c) Low-temperature fixability After adjusting the amount of toner in the unfixed image to be 0.6 mg / cm ² , the fixing temperature is set at a temperature range of 160 ° C. to 230 ° C. at intervals of 5 ° C. 9 points of 5 cm square solid images were output. The image was reciprocated five times with sylbon paper applied with a load of 4.9 kPa, and the temperature at which the density reduction rate was 15% or more was evaluated as the minimum fixing temperature.
A: Fixing lower limit temperature is less than 180 ° C. B: Fixing lower limit temperature is 180 ° C. or more and less than 190 ° C. C: Fixing lower limit temperature is 190 ° C. or more and less than 200 ° C. D: Fixing lower limit temperature is 200 ° C. or more.

<Examples 2 to 21>
Magnetic toners 2 to 21 were used as magnetic toners, and development durability evaluation and fixing performance evaluation were performed under the same conditions as in Example 1. As a result, there was no problem in the initial image characteristics, and no problem was obtained until the end of the durability. Table 3 shows the results of durability evaluation under a normal temperature and humidity environment and the results of durability evaluation under a high temperature and high humidity environment.
Examples 4 to 21 are referred to as Reference Examples 4 to 21.

<Comparative Examples 1 to 4>
Magnetic toners 22 to 25 were used as magnetic toners, and development durability evaluation and fixing performance evaluation were performed under the same conditions as in Example 1. As a result, the magnetic toner 17 had poor image density and halftone uniformity level during long-term use (after 10,000 sheets) in a high temperature and high humidity environment. Also, in the evaluation of the magnetic toners 18 to 21, the image deteriorated during long-term use and the minimum fixing temperature increased, and the image was problematic in practice. Table 3 shows the results of durability evaluation under a normal temperature and humidity environment and the results of durability evaluation under a high temperature and high humidity environment.

  DESCRIPTION OF SYMBOLS 100 Photoconductor, 102 Developing sleeve (toner carrier), 103 Elastic blade (regulating blade), 104 Magnet roller, 114 Transfer charging roller, 116 Cleaner, 117 Primary charging roller, 123 Laser light, 126 Fixing device, 140 Developing device, 141 Toner application roller

Claims (6)

And the magnetic toner particles of organic binder resin, a magnetic material and a release agent, a magnetic toner organic and inorganic fine powder,
The magnetic toner particles have an outer shell on the surface thereof;
The outer shell contains a polyester resin;
The polyester resin content is 8 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin.
(1) The Total Energy (TEA100) when the stirring speed measured by the powder flowability measuring device of the magnetic toner particles is 100 revolutions is 650 mJ or more and 800 mJ or less,
(2) When the weight-average molecular weight Mw and the inertial square radius Rw were measured for the ortho-dichlorobenzene soluble component of the magnetic toner by size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS),
The weight average molecular weight Mw is 2 00000 or less on 50,000 or more,
The weight average molecular weight Mw and the inertial square radius Rw is, 1.0 × ^{10 -4} ≦ that satisfy the following formula (1) (Rw / Mw) ≦ 4.0 × 10 -4 (1)
Magnetic toner characterized by the above. The magnetic average circularity of the toner is magnetic toner according to 請 Motomeko 1 Ru der least 0.960. The magnetism of the in the magnetic toner particles and the magnetic Total Energy measured by powder flowability measuring apparatus of the toner, the magnetic toner TotalEnergy when agitation speed is 10 revolutions and TEB10, when agitation speed is 100 rpm When the total energy of the toner is TEB100,
Wherein TEB100 is no more than 300mJ than on 8 mJ,
The TEA100, the TEB10 and the TEB100 are you satisfies the following formula (2) and (3) (TEA100-TEB100) ≦ 300 (mJ) (2)
1.00 ≦ (TEB10 / TEB100) ≦ 1.50 (3)
The magnetic toner according to claim 1. In the magnetic methanol concentration of the methanol / water mixed solvent when the transmittance of the toner particles having a wavelength of 780nm in methanol / water mixed solvent infiltrated with light is 50%, the 20 vol% or 5 0 vol% a magnetic toner according to any one of Ah Ru請 Motomeko 1-3. The number average molecular weight Mn and the weight average molecular weight Mw when the ortho-dichlorobenzene soluble content of the magnetic toner is measured by size exclusion chromatography-online-multi-angle light scattering (SEC-MALLS) are : Mw / Mn ≦ 7. a magnetic toner according to any one of 請 Motomeko 1 that satisfy the second relation-4. The magnetic toner particles, the magnetic toner according to any one of Ah Ru claim 1-5 in the magnetic toner particles produced by suspension polymerization.

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