JP2006133734A - Magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic toner which is excellent in durability and developability even in the case of being applied to high-speed developing process or being used in a large-capacity process cartridge whose amount of toner is increased, and which has high degree of blackness. <P>SOLUTION: The magnetic toner has magnetic toner particles containing at least a binder resin and magnetic material particles each comprising a predetermined amount of a titanium compound, wherein the magnetic material particles (1) have a predetermined amount of adsorbed water under a relative water vapor pressure of 50% and (2) ensures a reduced difference between an amount of water adsorbed on the magnetic material particles in an adsorption process in which the relative water vapor pressure is increased and an amount of water adsorbed on the magnetic material particles in a desorption process in which the relative water vapor pressure is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotography, an image forming method for developing an electrostatic image, and a magnetic toner used in a toner jet.

  In recent years, in addition to high definition, high quality, and high image quality, image forming apparatuses are required to have higher speed and higher reliability over a long period of time. In order to achieve a high-resolution and high-definition development system, the toner particle size is reduced and the particle size distribution is sharpened. However, simply reducing the particle size of the toner tends to affect the toner performance due to the dispersibility of other internal additives in the binder resin.

  In particular, in the case of a magnetic toner having magnetic toner particles used in a one-component development method that is advantageous for downsizing of an image forming apparatus, the dispersion state of the magnetic particles contained in the magnetic toner particles depends on the development characteristics and durability. This may affect various properties required for magnetic toners such as properties.

If the dispersion of the magnetic particles in the magnetic toner particles is insufficient, the total amount of the magnetic particles exposed on the surface of the magnetic toner particles varies greatly for each individual magnetic toner particle. If there are few magnetic particles on the surface of the magnetic toner particles, the surface of the magnetic toner particles may be charged up and charged up when frictionally charged with the charging member (developing sleeve).
On the other hand, if the magnetic particles are excessively present on the surface of the magnetic toner particles, the electric charge is likely to leak and it becomes difficult to obtain a high charge amount, and the reverse is caused by the contact between the magnetic particles and the binder resin. Polar toner is likely to be generated, the width of the charge distribution is expanded, and image quality may be deteriorated.

  On the other hand, a contact charging method in which a photosensitive member is charged by a contact charging member without using a corona charger that generates ozone is often employed. If the magnetic particles are not uniformly dispersed in the magnetic toner particles, the magnetic toner in which the magnetic particles are excessively present on the surface may cause mechanical pressure or electrical compression at the contact portion between the contact charging member and the photoreceptor surface. As a result, the surface of both members is strongly rubbed, the photoconductor is easily scratched, and image defects may be caused. On the other hand, when the magnetic toner having a small amount of magnetic particles on the surface and apparently increased surface viscoelasticity is rubbed against both the contact charging member and the photosensitive member, the toner is likely to be fused to the photosensitive member, Photoconductor contamination such as filming is likely to occur.

  In order to improve the fluidity of the magnetic toner, it is common to add an external additive to the magnetic toner particles. However, when the magnetic toner is deteriorated by repeating the printing process over a long period of time, the external additive is embedded in the magnetic toner particles, and the influence of the magnetic particles exposed on the surface of the magnetic toner particles becomes large. Problems are likely to manifest themselves.

  Further, the expansion of the width of the charge distribution due to poor dispersion of the magnetic particles as described above facilitates so-called selective development in which toner having a certain amount of charge amount distribution is preferentially consumed, and at the same time Moving forward makes it easier to promote various problems.

  For example, not only the charging characteristics of the magnetic toner are easily affected by the environment, but also the fluidity of the magnetic toner is reduced, the toner is insufficiently supplied to the developing sleeve, and the toner layer on the developing sleeve is unevenly charged. The “fogging” in which the non-image portion is developed with toner is likely to occur, and in a high-temperature and high-humidity environment, the phenomenon of “fading” in which the image density becomes thin in a band shape is likely to occur.

  Further, when toner is transferred from the photosensitive member to the transfer material, if there is excessively charged toner, a phenomenon that the toner scatters around characters and line images such as “scattering” occurs. If the toner is not sufficiently charged in order to suppress the scattering, a toner that is insufficiently charged is generated, so that developability and fogging may occur. In order to reduce the fog, an attempt has been made to further sharpen the toner particle size distribution, but this may cause an increase in cost due to a decrease in yield in toner production.

  In particular, in order to cope with the recent increase in speed and life, the above-mentioned problem becomes more prominent by using a large-capacity process cartridge with increased process speed or increased toner filling amount in the developing device. There was a need for immediate improvement.

  Patent Document 1 and Patent Document 2 disclose that the particle diameter of the magnetic particles and the particle size distribution are narrowed in order to uniformly disperse the magnetic particles in the magnetic toner particles. Certainly, these treatments tend to make the dispersion of the magnetic particles in the magnetic toner particles uniform, but if the magnetic toner is made smaller in size in order to achieve high image quality, the fog becomes worse. Therefore, there is room for improvement in the dispersibility of the magnetic particles in the magnetic toner particles.

Moreover, there is a problem that the blackness is lowered by making the magnetic particles fine. Conventionally, it is known that the blackness of magnetic particles depends on the content of FeO (or Fe ²⁺ ). However, the content of FeO (or Fe ²⁺ ) in the magnetic particles decreases as the deterioration with time due to oxidation after production proceeds, and as a result, the blackness decreases. Needless to say, the deterioration with time greatly depends on the environment in which the magnetic particles are placed, but is also promoted by making the magnetic particles fine.

  The finely divided magnetic particles are not only easily changed with time but also easily affected by heat. In the magnetic toner production process, in order to uniformly disperse the magnetic particles in the magnetic toner particles, it is preferable to set the melt kneading temperature to a high temperature and knead the binder resin in a melted and soft state. . In particular, when using a binder resin containing a hard component such as a THF-insoluble component, it is preferable to uniformly disperse the magnetic particles by softening and kneading the binder resin at a high temperature. For this reason, even with magnetic particles having high blackness, depending on the particle size of the magnetic particles and the melt kneading temperature at the time of toner production, the magnetic particles are oxidized, and finally the toner looks reddish. There was a case.

  In general, from the viewpoint of obtaining a toner having excellent low-temperature fixability, it is preferable to use a polyester resin as a binder resin rather than a styrene resin. However, since the polyester resin has many functional groups that show acidity in the molecular structure, the magnetic particles present in the polyester resin are placed in an acidic environment during kneading, and the oxidation of the magnetic particles is particularly likely to proceed. .

  In order to solve these problems, many proposals have conventionally been made to add various elements to the magnetic particles contained in the magnetic toner particles.

  Patent Documents 3 and 4 describe magnetic particles coated with a coating layer containing an element selected from the group consisting of Si, Al, and Ti.

However, the magnetic particles intended for uniform dispersion in the magnetic toner particles are insufficient in preventing the blackness from being lowered and improving the heat resistance. When kneaded at a high temperature, it may oxidize, and depending on the additive element, not only affects the magnetic properties of the magnetic particles, but also the elements elute from the magnetic particles, especially when used in combination with a resin with a relatively high acid value. In some cases, defects related to development other than blackness may be caused.

  In addition, one or two or more metal elements selected from the group consisting of Mn, Zn, Ni, Cu, Al, and Ti are contained in Fe. On the other hand, magnetic particles containing 0 to 10 atomic% are known (see, for example, Patent Documents 5 and 6). According to the magnetic particles, the magnetic characteristics and charging characteristics of the magnetic toner are improved. However, there is room for improvement in terms of compatibility between developability and image quality in a high-speed development system by simply adding the above-described metal. It is left.

  Further, Zn, Mn, Cu, Ni, Co, Cr, Cd, which contains a silicon component continuously from the center to the surface of the magnetic particles, the silicon component is exposed on the surface of the magnetic particles, and is bonded to the silicon component. There is known a magnetic particle in which the outer shell of the particle is coated with a metal compound composed of at least one metal component selected from the group consisting of Al, Sn, Mg, and Ti (see, for example, Patent Document 7). However, the use of such magnetic particles shows good developability at the beginning of durability, but particularly in a high-speed development system, in order to improve the deterioration in image quality and developability due to fog deterioration caused by long-term use. It has not yet been reached and has further improvements.

  Furthermore, Zn, Mn, Cu, Ni, Co, Cr, containing a silicon component and an aluminum component continuously from the center of the particle, exposing these components on the particle surface, and bonding to the silicon component and the aluminum component, A magnetic particle in which the outer shell of the particle is coated with a metal compound composed of at least one metal component selected from the group consisting of Cd, Al, Sn, Mg, and Ti is known (see, for example, Patent Document 8). . However, the use of the magnetic particles has not yet provided sufficient charging stability to the magnetic toner.

  Patent Document 9 describes magnetic particles having an oxide containing an element selected from the group consisting of Fe, Al, Ti, Zr and Si on the surface, and Patent Document 10 describes Zn, Mn, Cu. , Ni, Co, Mg, Cd, Al, Cr, V, Mo, Ti, and magnetic particles having an element selected from the group consisting of Sn are described. Patent Document 11 describes Si, Al, Ti. , Magnetic particles having an element selected from the group consisting of Zr, Mn, Mg and Zn on the surface are described.

Further, Patent Document 12 contains 0.10 to 1.00% by mass of silicon element inside the spherical particles, and there is a coprecipitate of silica and alumina on the surface of the spherical particles. At least one non-magnetic oxide fine particle powder or non-magnetic hydrated oxide fine particle powder of an element selected from the group consisting of Fe, Ti, Zr, Si and Al is fixed on the sediment by 0.1 to 10% by weight. Magnetic particles are disclosed.
Patent Document 13 contains 0.9 atomic% or more and less than 1.7 atomic% of silicon with respect to Fe, and one or more selected from the group consisting of Mn, Zn, Ti, Zr, Si, and Al on the particle surface. A hexahedral magnetic particle having an adherent layer made of an oxide of two or more elements, a hydroxide, a hydrated oxide, or a mixture thereof is disclosed.

  Patent Document 14 discloses magnetic particles having an isoelectric point of 5 to 6.5, and Patent Document 15 discloses toners using magnetic particles having an isoelectric point of 5 to 9, respectively. ing.

  Further, Patent Document 16 discloses a toner that defines an adsorbed moisture amount and an average circularity.

  Moreover, patent documents 17-20 are mentioned as an example of the magnetic body in which a titanium compound exists in the inside or the surface of particle | grains.

  Each of the toners containing the magnetic particles has good developability. However, all of them have a high process speed, and when applied to a high-speed development system using a large capacity cartridge, further improvement in developability and durability is often desired. Furthermore, if the amount of element added is too large, or if the amount of adsorbed water becomes too large due to the loss of smoothness on the surface of the magnetic particles, the photoconductor may be damaged, filming may occur, Various problems caused by the fluidity and chargeability of the magnetic toner such as fogging, fading and image scattering occur. Further, there is still room for improvement in the oxidation resistance in the production process of toner particles and the mixing with a resin having a relatively high acid value such as a polyester resin.

  In addition, depending on the type and amount of additive element, the amount of moisture adsorbed by the magnetic particles becomes too large, or the adsorbed moisture becomes difficult to desorb, and the chargeability after being left in a high temperature and high humidity environment is particularly high. Problems such as a significant decrease were likely to occur.

Thus, even when applied to a high-speed development system using a high-capacity cartridge with a high process speed, in order to obtain a magnetic toner having excellent durability stability and developability and at the same time high blackness, further investigation is required. There is room for it.
Japanese Patent Laid-Open No. 3-101743 JP-A-3-101744 JP-A-8-133744 JP-A-8-133745 Japanese Patent Laid-Open No. 9-59024 JP-A-9-59025 JP 11-157843 A Japanese Patent Laid-Open No. 11-189420 JP 7-239571 A JP-A-7-267646 Japanese Patent Laid-Open No. 10-72218 JP 7-240306 A JP-A-10-171157 JP 2003-195560 A JP 2004-139071 A JP 2004-78055 A JP-A-8-34617 JP-A-3-2276 JP 2003-192352 A JP 2003-162089 A

  Accordingly, an object of the present invention is to provide a magnetic toner that solves the problems as described above.

  That is, the object of the present invention is to show excellent durability stability and developability both when the process speed is increased and when a large-capacity process cartridge with an increased toner filling amount is used. And providing a magnetic toner exhibiting high blackness at the same time.

As a result of intensive studies, the present inventors have found that the magnetic toner has magnetic toner particles containing magnetic particles containing at least a binder resin and a titanium compound, and includes I) a temperature of 28 ° C. and a relative water vapor pressure of 50. %) The ratio A [mass%] of the moisture content adsorbed on the magnetic particles to the mass of the magnetic particles is 0.25 to 0.80 [mass%], and II) the relative water vapor pressure is increased at a constant temperature. The difference in the relative water vapor pressure between the adsorbed water mass to the magnetic particles in the adsorption process and the adsorbed water mass to the magnetic particles in the desorption process to decrease the relative water vapor pressure at the same temperature is the magnetic The ratio B [mass%] of the mass converted to TiO _{2 of the} titanium compound to the mass of the magnetic particles is 0.1 to 10.0 based on the mass of the body particles. [mass% ] Has been found that the object of the present invention can be achieved, and the present invention has been completed.

  According to the magnetic toner of the present invention, even when the process speed is increased, or when a large-capacity process cartridge with an increased amount of toner filled in the developing unit is used, the toner scatters around the character. Deterioration of fog in the latter half of durability can be suppressed.

  Furthermore, even when the process speed is increased and when the contact charging method is adopted, it is possible to suppress the occurrence of photoconductor scratches and filming.

  Further, by using the magnetic particles in the present invention, a magnetic toner having excellent blackness can be obtained even when the kneading step in the production of the magnetic toner is performed at a high temperature.

The magnetic toner of the present invention contains at least a binder resin and magnetic particles.
The inventors of the present invention have found that the object of the present invention can be achieved by using magnetic particles exhibiting a specific moisture adsorption and desorption behavior.

Specifically, the magnetic particles exhibiting a specific moisture adsorption and desorption behavior include magnetic particles satisfying the following two points.
(1) The mass of water adsorbed on the magnetic particles at a temperature of 28 ° C. and a relative water vapor pressure of 50% is 0.25 to 0.80 mass% with respect to the mass of the magnetic particles.
(2) The amount of moisture adsorbed on the magnetic particles in the adsorption process that increases the relative water vapor pressure at a constant temperature and the amount of water adsorbed on the magnetic particles in the desorption process that decreases the relative water vapor pressure at the same constant temperature, The mass difference at an arbitrary relative water vapor pressure is 0.10% by mass or less with respect to the mass of the magnetic particles. Here, the “constant temperature” is preferably 28 ° C., and the “arbitrary relative water vapor pressure” is preferably in the range of 5% to 90%. That is, the maximum value of the mass difference at a relative vapor pressure of 5 to 90% is preferably 0.10% by mass or less with respect to the mass of the magnetic particles.

The larger the difference between the "adsorbed water mass on the magnetic particles in the adsorption process" and the "adsorbed water mass on the magnetic particles in the desorption process", the more the surface of the magnetic particles desorbs the water once adsorbed. It means having a property or structure that is difficult to do.
That is, (1) the ratio of the mass of water adsorbed to the magnetic particles at a relative water vapor pressure of 50% to the mass of the magnetic particles is 0.25 to 0.80 mass%, and (2) “in the adsorption process The ratio of the mass difference between the “adsorbed moisture mass to the magnetic particles” and the “adsorbed moisture mass to the magnetic particles in the desorption process” to the magnetic particle mass is 0.10% by mass or less. It shows that the surface of the magnetic particles can hold an appropriate amount of moisture with a high degree of freedom of adsorption and desorption.

The magnetic toner containing magnetic particles satisfying the conditions (1) and (2) has very good environmental stability. That is, even when a large-capacity process cartridge is used in which the process speed is increased or the amount of toner filled in the developing device is increased, the chargeability is hardly lowered and the selective development can be suppressed.

  A magnetic toner containing magnetic particles having a ratio of moisture adsorbed to magnetic particles at a relative water vapor pressure of 50% to the mass of magnetic particles (hereinafter also referred to as ratio A) is less than 0.25% by mass is particularly low in humidity. After long-term durability in the environment, fogging and scattering are likely to occur, which may cause image quality deterioration.

  On the other hand, even if a) the magnetic particles having a ratio A exceeding 0.80% by mass, or b) the ratio A is 0.25% to 0.80% by mass, “adsorption to the magnetic particles in the adsorption process” The magnetic substance in which the ratio of the difference between the “water mass” and the “moisture content adsorbed on the magnetic particles in the desorption process” to the magnetic particle mass (hereinafter also referred to as the ratio ΔA) exceeds 0.10% by mass. The magnetic toner containing particles is likely to have problems such as deterioration in charging characteristics particularly under high humidity, a slow rise in charging, and a lack of concentration at the beginning of durability.

The mass of moisture adsorbed on the magnetic particles at a relative water vapor pressure of 50% can be controlled by adjusting the average particle size of the magnetic particles and the content of the titanium compound, for example.
The difference between the “adsorption moisture mass in the adsorption process” and the “adsorption moisture mass in the desorption process” on the magnetic particles is, for example, the content of the titanium compound and the pH of the aqueous suspension when the titanium compound is contained. It can be controlled by adjusting.

  The adsorbed water mass on the magnetic particles in the present invention is made to reach a solid-gas equilibrium under the condition that only the target gas (water vapor in the present invention) exists, and the solid mass and vapor pressure at this time are measured. It can be determined by the device that performs. Examples of such an apparatus include an adsorption equilibrium measuring apparatus (EAM-02; manufactured by JT Toshi Co., Ltd.). In the examples described later, the adsorbed water mass of the magnetic particles was determined by this apparatus.

  The adsorbed water mass on the magnetic particles of the present invention is determined from the adsorption / desorption isotherm. Adsorption / desorption isotherms are automatically performed for a) measurement of dry matter amount, b) degassing of dissolved air in water, c) measurement of adsorption equilibrium pressure, and d) measurement of adsorption amount at each relative vapor pressure. Can be obtained by performing automatically. The outline of the measurement is described in the operation manual issued by JT Toshi Co., Ltd., and is as follows.

  First, about 5 g of toner is filled in the sample container in the adsorption tube, and then the thermostat temperature and the sample portion temperature are set to 28 ° C. Thereafter, V1 (main valve) and V2 (exhaust valve) are opened to operate the vacuum exhaust unit, and the sample container is depressurized to about 0.01 mmHg to dry the sample. The mass at the time when the weight of the sample does not change is defined as “dry matter amount”.

  Since air is dissolved in the solvent liquid (water in the present invention), deaeration is performed. First, a solvent liquid (hereinafter referred to as water) is placed in a liquid reservoir, V1 and V3 are closed, V2 is opened, the evacuation unit is operated, V2 is closed and V3 is opened, and air is supplied between V2 and V3. After that, V3 is closed, then V2 is opened, and after deaeration, V2 is closed. Thus, the operation of alternately opening and closing V2 and V3 is repeated several times, and the deaeration is completed when no bubbles are seen in the water.

  Following dry matter measurement and water deaeration, the V1 (main valve) and V2 (exhaust valve) are closed and the V3 (reservoir valve) is opened while the sample container is kept under vacuum. Then, steam is introduced between V1 and V3, and V3 (container valve) is closed.

Next, by opening V1 (main valve), water vapor is introduced into the sample container, and the pressure is measured by a pressure sensor. If the pressure in the sample container does not reach the set pressure, the above operation is repeated to set the pressure in the sample container to the set pressure. When equilibrium is reached, the pressure and mass in the sample container become constant, and the pressure and temperature at that time and the sample mass are measured as equilibrium data.

  Furthermore, by changing the pressure of water vapor, an isotherm of adsorption / desorption can be obtained. In actual measurement, a relative water vapor pressure for measuring the adsorbed water mass is set in advance. For example, when the set pressure is 5%, 30%, 60%, 80%, and 90%, the “adsorption process” means that the relative water vapor pressure is increased from 5% and the adsorbed water mass at each set pressure is measured. This is a process of creating an isotherm (adsorption isotherm). The “desorption process” is performed subsequent to the adsorption process. In contrast to the adsorption process, the relative water vapor pressure is lowered from 90%, It means the process of creating an isotherm (desorption isotherm) by measuring the adsorbed water mass at a set pressure.

The absorption / desorption isotherm of a normal magnetic toner becomes a loop in which the “desorption isotherm” of the subsequent desorption process is shifted to the side where the adsorbed moisture mass is larger than the “adsorption isotherm” of the adsorption process. May show “hysteresis”.
The magnetic toner of the present invention is characterized in that the difference between the “adsorption isotherm” and the “desorption isotherm” of the adsorption / desorption isotherm is small. Specifically, the mass difference between the adsorption moisture mass indicated by the “adsorption isotherm” and the adsorption moisture mass indicated by the “desorption isotherm” at an arbitrary relative water vapor pressure is 0.10 with respect to the magnetic particle mass. It is characterized by being not more than mass%. Here, the arbitrary relative water vapor pressure is preferably in the range of 5% to 90%. That is, it is preferable that the maximum value of the mass difference at a relative water vapor pressure of 5% to 90% is 0.10% by mass or less with respect to the mass of the magnetic particles.

  In this apparatus, the pressure is set as a relative water vapor pressure (%), and an adsorption / desorption isotherm of the adsorption amount (%) and the relative water vapor pressure (%) is displayed. Calculation formulas for the amount of adsorption and relative water vapor pressure are shown below.

[Equation 1]
M = (Wk−Wc) / Wc × 100 (11)
Pk = Q / Q0 × 100 (12)

In the formula (11), M represents an adsorption amount (%), Wk (mg) represents a sample mass, and Wc (mg) represents a dry substance amount of the sample.
In Equation (12), Pk is the relative water vapor pressure (%), Q0 (mmHg) is the saturated water vapor pressure obtained from the temperature Tk (° C.) at the time of adsorption / desorption equilibrium by the Antoine equation, and Q (mmHg) is measured as equilibrium data. Pressure (equilibrium water vapor pressure), respectively.

  Furthermore, the isoelectric point of the magnetic particles in the present invention is preferably in the range of pH 4.1 to 8.0, and more preferably in the range of pH 4.5 to 6.5. The isoelectric point of the magnetic particles in the present invention is the hydrogen ion concentration at which the zeta potential measured when the magnetic particles are dispersed in water becomes zero.

  In the case of magnetic particles having an isoelectric point of less than pH 4.1, the adsorption / desorption behavior of adsorbed moisture on the surface of the magnetic particles may not be preferably controlled in order to achieve the object of the present invention.

  Magnetic particles having an isoelectric point greater than 8.0 at pH not only may not preferably control the adsorption and desorption behavior of adsorbed moisture, but also lower the fluidity. In addition, the dispersibility in the magnetic toner may deteriorate or the heat resistance may decrease. Further, when the process speed is increased or when the contact charging method is adopted, the photoconductor scratches and filming are likely to occur.

  The isoelectric point of the magnetic particles is, for example, the type of the magnetic substance, the type and amount of the non-magnetic material blended in the magnetic particle, the type and amount of the material that coats the magnetic particle, and the control of the coating state. Can be adjusted by.

The isoelectric point of the magnetic particles can be measured by the following method.
First, the magnetic particles are dissolved or dispersed in ion exchange water at 25 ° C., and the sample concentration is adjusted to 1.8 vol%. Using an ultrasonic zeta potential measurement device DT-1200 (manufactured by Dispersion Technology), titration with 1N HCl is performed to measure the zeta potential. The isoelectric point is the pH when the zeta potential is 0 mV.

Furthermore, the magnetic particles in the present invention contain a titanium compound, and the mass of the titanium compound converted to TiO ₂ is 0.1% by mass to 10.0% by mass with respect to the mass of the magnetic material particles. More preferably, it is 5 mass%-9.0 mass%.

  As a result of intensive studies, the present inventors have found that a) a titanium compound is contained in the above range, b) moisture on the particle surface causes the above-described absorption / desorption phenomenon, and c) an isoelectric point in the above range. It has been found that the magnetic particles controlled to have a preferential presence of the titanium compound on the surface of the magnetic particles. And it discovered that such a magnetic body particle | grain could demonstrate the effect made into the objective of this invention to the maximum.

  That is, since the magnetic particles have a titanium compound preferentially in the vicinity of the surface, components of the magnetic particles other than the titanium compound (for example, iron oxide with high hardness) are unlikely to exist near the surface of the magnetic particles. Become. Therefore, even when the magnetic toner is deteriorated by repeating the printing process of the contact charging method for a long time, the component other than the titanium compound in the magnetic particles exposed on the surface of the magnetic toner directly contacts the photoconductor. As a result, the photoconductor becomes difficult to be damaged.

  In addition, magnetic particles containing a titanium compound are excellent in fluidity and low in agglomeration between the magnetic particles, so that the dispersibility in the toner particles is excellent. Therefore, an appropriate amount of magnetic particles exposed on the surface of the magnetic toner can suppress filming of the magnetic toner on the photoconductor and fading in a high humidity environment.

  Furthermore, by preferentially presenting an appropriate amount of the titanium compound in the vicinity of the surface in this way, it is possible to improve heat resistance and oxidation resistance without deteriorating the original magnetic properties and chargeability of the magnetic particles. For this reason, such magnetic particles are less likely to be oxidized even in a melt-kneading process at a high temperature in the production of toner particles. Furthermore, a resin having a relatively high acid value can be used as the toner resin, and it is possible to obtain a magnetic toner with excellent blackness utilizing the characteristics of the resin.

The ratio of the mass of the titanium compound contained in the magnetic particles to TiO ₂ to the mass of the magnetic particles (hereinafter also referred to as “ratio B”) is less than 0.1% by mass. Moisture absorption / desorption behavior and isoelectric point are difficult to control properly. Therefore, the magnetic toner containing such magnetic particles tends to cause fogging and filming. Furthermore, since such magnetic particles often have low heat resistance, the blackness of a magnetic toner containing the magnetic particles may decrease.
Magnetic particles having a ratio B higher than 10.0% by mass not only make it difficult to control the moisture absorption / desorption behavior on the surface, but also may reduce the magnetic properties. Tends to cause bad effects on image quality such as fog.

The content of the titanium compound in the magnetic particles in the present invention can be measured by performing fluorescent X-ray analysis in accordance with JIS K0119 “General rules for fluorescent X-ray analysis”. Examples of the measuring device include a fluorescent X-ray analyzer SYSTEM 3080 (manufactured by Rigaku Corporation).

The average particle size of the magnetic particles in the present invention is preferably 0.08 to 0.25 μm from the viewpoints of dispersibility, blackness, magnetic properties, and the like. Magnetic particles having an average particle size of less than 0.08 μm are not preferred because they may cause poor dispersion due to reaggregation in the magnetic toner, and the blackness may be lowered.
Magnetic particles having an average particle size larger than 0.25 μm have excellent blackness, but are not preferable because they may not be sufficiently dispersed in the toner particles.

  Here, the average particle diameter of the magnetic particles is 100 particles randomly selected from the particles copied in the transmission electron micrograph (magnification 30,000 times), the particle diameter is measured, and the average value is obtained. It can obtain | require by setting it as an average particle diameter. Further, the average particle diameter of the magnetic particles can be adjusted by controlling the initial alkali concentration and the particle generation process by the oxidation reaction, for example.

The magnetic properties of the magnetic particles in the present invention include a saturation magnetization of 10 to 200 Am ² / kg (more preferably 70 to 100 Am ² / kg) and a residual magnetization of 1 to 100 Am ² / kg at a magnetic field of 795.8 kA / m. (more preferably 2~20Am ² / kg), coercivity is preferably 1~30kA / m (more preferably 2~15kA / m) is. A magnetic toner containing magnetic particles having such magnetic properties can have good developability with a good balance between image density and fog.

The magnetic properties of the magnetic particles can be measured under an external magnetic field of 795.8 kA / m using, for example, “vibrating sample magnetometer VSM-3S-15” (manufactured by Toei Kogyo Co., Ltd.).
The magnetic properties of the magnetic particles can be adjusted, for example, depending on the type and average particle size of the magnetic particles and the type and amount of the nonmagnetic material added to the magnetic particles.

  Examples of components other than the titanium compound of the magnetic particles in the present invention include magnetic iron oxides such as magnetite, maghemite, and ferrite containing different elements and mixtures thereof. Preferably, magnetite having a high FeO content is used. The main component. Magnetite particles are generally obtained by oxidizing a ferrous hydroxide slurry obtained by neutralizing and mixing a ferrous salt aqueous solution and an alkaline solution.

  The magnetic particles in the present invention are preferably composed of base magnetic particles and a compound that adheres to the surface of the base magnetic particles.

In the present invention, the base magnetic particle serving as the base of the magnetic particle preferably contains Si element. The Si element is preferably present both inside and on the surface of the base magnetic particle, and more preferably preferentially present on the surface. In the process of producing the base magnetic particles, Si elements can be preferentially present on the surface of the base magnetic particles by adding Si elements in stages.
When Si element exists on the surface of the base magnetic particles, a large number of pores are formed on the surface of the base magnetic particles. Therefore, when the outer shell is coated with a titanium compound, the surface of the base magnetic particles is a titanium compound. Can be more strongly fixed.

  The content of Si element is preferably 0.1% by mass to 1.5% by mass and more preferably 0.2% by mass to 1.0% by mass with respect to Fe element. When the amount is less than 0.1% by mass, the fixing force of the titanium compound to the surface of the base magnetic particle may be insufficient. When the amount is more than 1.5% by weight, the surface of the base magnetic particle is smooth. Sex is easily lost.

  The magnetic particles in the present invention should be adjusted to a specific adsorbed water mass and isoelectric point that can achieve the object of the present invention after obtaining base magnetic particles using a general method for producing magnetite particles. It is obtained by containing a titanium compound.

  The pre-stage base magnetic particles containing the titanium compound can be manufactured by using a known magnetic particle manufacturing method, but the base magnetic particles having Si element preferentially on the surface are manufactured by the following method, for example. The

Reaction comprising ferrous hydroxide colloid by reacting an aqueous ferrous salt solution with 0.90 to 0.99 equivalent of an aqueous alkali hydroxide solution with respect to Fe ^{2+ in} the aqueous ferrous salt solution An aqueous solution is obtained.
Here, 0.1 to 1.5% by mass of water-soluble silicic acid in terms of Si element with respect to iron element, in either the aqueous alkali hydroxide solution or the ferrous salt containing ferrous hydroxide colloid Add 50-99% of the salt (total content).
A matrix containing Si element from a ferrous hydroxide colloid by heating an aqueous reaction solution to which water-soluble silicate is added in a temperature range of 85 to 100 ° C., and performing an oxidation reaction by aeration of an oxygen-containing gas. Magnetic nucleate particles are generated. At this time, it is preferable to carry out an oxidation reaction under the condition of pH 6.0 to 7.0.

1.00 equivalent or more of an alkali hydroxide aqueous solution with respect to Fe ²⁺ remaining in the suspension after completion of the oxidation reaction, and the remaining water-soluble silicate [total content (0.1 to 1.5 mass %) To 1-50%]. Further, the oxidation reaction is carried out while heating in a temperature range of 85 to 100 ° C. At this time, it is preferable to carry out an oxidation reaction under conditions of pH 8.0 to 10.5.

  Next, the base magnetic particles in the present invention are obtained by filtration, washing with water, drying and crushing by a known method. Furthermore, in order to adjust the smoothness and specific surface area of the base magnetic particles to a preferable range, it is preferable to compress, shear, or spatulate using a “mix muller” or “leak machine”.

  Examples of the water-soluble silicate used for the production of the above-described base magnetic particles include commercially available silicates such as sodium silicate and silicic acid such as sol-like silicic acid generated by hydrolysis.

  Examples of the ferrous salt used in the production of the above-mentioned parent magnetic particles include iron sulfate generally produced as a by-product in the production of titanium oxide by the sulfuric acid method, iron sulfate produced as a by-product with the surface cleaning of the steel sheet, Includes iron chloride and the like.

  According to the above-described production method, it is possible to produce magnetic particles mainly composed of spherical particles formed of curved surfaces having no plate-like surface and containing almost no octahedral particles. The magnetic particles contained in the magnetic toner of the present invention preferably have such a particle shape. The particle shape of the magnetic particles can be observed by a transmission electron micrograph (H-7500; manufactured by Hitachi, Ltd.).

  On the other hand, the base magnetic particles used in the present invention preferably have a low total content of Al, P, S, Cr, Mn, Co, Ni, Cu, Zn and Mg, for example, 1% by mass or less. In many cases, the above components are contained as inevitable components derived from raw materials at the time of producing magnetic particles. In consideration of maintaining the blackness and magnetic properties of the magnetic toner, the effect of the present invention is more easily exhibited when the total content of the above components in the base magnetic particles is small.

The magnetic particles in the present invention contain a titanium compound. Titanium may be incorporated in the iron oxide crystal lattice, or may be incorporated in the iron oxide as titanium oxide, but preferably the magnetic particles. Exists as titanium oxide or titanium hydroxide.

In particular, the effects of the present invention can be maximized by coating the base magnetic particles with TiO ₂ by the method described below.

The aqueous suspension containing the parent magnetic particles at a concentration of 50 to 200 g / l is maintained at 60 to 80 ° C. A sodium hydroxide aqueous solution or dilute sulfuric acid is added to this suspension aqueous solution to adjust the pH to 4.0 to 6.0. While stirring this suspension aqueous solution, an aqueous solution of titanium sulfate having a concentration of 50 to 150 g / l in terms of TiO _{2 was} equivalent to 0.1 to 10.0% by mass in terms of TiO ₂ / Fe ₃ O ₄ , Add over about 1 hour. During this addition, an aqueous sodium hydroxide solution is added so that the pH of the aqueous suspension is maintained at 4.0-6.0. After completion of the addition, an aqueous sodium hydroxide solution is added to make the suspended aqueous solution neutral. This is washed, filtered, dried and crushed to obtain titania-coated magnetic particles.

  The content of the magnetic particles in the magnetic toner of the present invention is 50 to 150 parts by mass, preferably 60 to 120 parts by mass with respect to 100 parts by mass of the binder resin. When the amount is less than 50 parts by mass, not only the fogging and scattering are worsened, but also the coloring power of the magnetic toner may be insufficient, which is not preferable. When the content is larger than 150 parts by mass, it is not preferable because the charge imparting member (developing sleeve) cannot sufficiently fly to the photoconductor during development, which may cause a decrease in image density.

Further, the magnetic particles included in the present invention preferably have the following physical properties.
That is, a magnetic material having a ratio A (mass%) of the mass of water adsorbed to magnetic particles at a relative water vapor pressure of 50% to the mass of magnetic particles and the mass converted to TiO ₂ of a titanium compound contained in the magnetic particles. The ratio B to the particle mass preferably satisfies the following relationship. As above-mentioned, A (mass%) is 0.25-0.80 (mass%), B is 0.1-10.00 (mass%).

[Equation 2]
0.50 ≧ A / B ≧ 0.05 (1)

  The ratio A / B of “the ratio A of the mass of adsorbed water to the mass of the magnetic particles” to the “ratio B of the content mass of the titanium compound to the mass of the magnetic particles” is controlled to 0.05 to 0.50. Body particles are coated with a titanium compound with a smooth and dense coating on the surface of the particles. As a result, the characteristics of the magnetic particles in the present invention, such as heat resistance and dispersibility in toner particles, can be exhibited to the maximum without impairing the magnetic properties and chargeability of the magnetic particles.

  When the A / B value is larger than 0.50 and the content of the titanium compound is large, the smoothness of the surface of the magnetic particles coated with the titanium compound is lowered, so that the amount of adsorbed water increases. This is likely to cause a decrease in the fluidity of the magnetic particles. Further, when the value of A / B is larger than 0.50 and the content of the titanium compound is small, the area of the portion not covered with the titanium compound is increased, so that the magnetic toner containing it is used as the photoreceptor. Scratches and filming are likely to occur, and the heat resistance may be particularly poor.

  On the other hand, if the value of A / B is less than 0.05, the magnetic particles are insufficient in the amount of adsorbed moisture with respect to the content of the titanium compound, and the magnetic toner containing the particles can be charged up or in a low humidity environment. May cause fogging.

In addition, the content of Fe ²⁺ in the magnetic particles in the present invention is preferably 17% by mass or more based on the mass of the magnetic particles from the viewpoint of obtaining magnetic particles having sufficient blackness and magnetic properties. .

Furthermore, the Fe ²⁺ content in the magnetic particles after the heat treatment is preferably 60% or more, and more preferably 70% or more with respect to the Fe ²⁺ content in the magnetic particles before the heat treatment. Hereinafter, the ratio of "content of Fe ²⁺ in the magnetic particles after the heat treatment" to "the content of Fe ²⁺ in the magnetic particles before heat treatment", also referred to as "retention of Fe ^2+". The heat treatment is heat treatment at 160 ° C. for 1 hour in air.
The magnetic particles having an “Fe ²⁺ retention ratio” of 60% or more are excellent in heat resistance, and are therefore not easily oxidized during the melt-kneading process during the production of the toner. From the viewpoint of finally obtaining a magnetic toner with high blackness. Even more preferred.

The content of Fe ^{2+ in} the magnetic particles can be measured, for example, by dissolving a sample (magnetic particles) with sulfuric acid and performing oxidation-reduction titration using a potassium permanganate standard solution.
In addition, the content of Fe ^{2+ in} the magnetic particles is, for example, the type of magnetic particles, the type and amount of non-magnetic material blended in the magnetic particles, the type and amount of coating of the material covering the magnetic particles, and the coating amount. It can be adjusted by controlling the state.

  Further, the constitution of a preferable magnetic toner for achieving the object of the present invention will be described in detail below.

  The binder resin contained in the magnetic toner of the present invention may be various resin compounds conventionally known as toner binder resins. Examples of binder resins include vinyl resins, phenolic resins, natural resin-modified phenolic resins, natural resin-modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethanes, polyamide resins, furans. Resins, epoxy resins, xylene resins, polyvinyl butyral, terpene resins, coumaroindene resins, petroleum resins and the like are included.

  The binder resin contained in the magnetic toner of the present invention preferably has an acid value, more preferably has an acid value of 1 to 50 mgKOH / g, and still more preferably has an acid value of 4 to 40 mgKOH / g.

  The inventors of the present invention have a considerable influence on the charge amount distribution on the surface of the magnetic toner and the charge stability of the magnetic toner. If the charge amount distribution is uneven, the charge leaks locally, It has been found that charging stability of the magnetic toner tends to be impaired by charging up. And, by using a binder resin having an acid value in the above-mentioned range, it is possible to reduce the difference in the amount of adsorbed moisture between the magnetic particle portion exposed on the surface of the magnetic toner and the binder resin portion. It was found that the charge amount distribution on the surface of the magnetic toner can be made uniform, and the above-mentioned problems can be solved.

  When the acid value of the binder resin is less than 1 mgKOH / g or more than 50 mgKOH / g, not only is it difficult to control the amount of adsorbed moisture of the magnetic toner, but also the charging environment of the magnetic toner. There is a tendency for fluctuations to increase.

  The OH value (hydroxyl value) of the binder resin is preferably 60 mgKOH / g or less, and more preferably 45 mgKOH / g or less. This is because, as the number of terminal groups of the molecular chain increases, the environmental dependency of the charging characteristics of the magnetic toner increases, so the fluidity, electrostatic adhesion, and developer surface resistance (influence of adsorbed water) of the magnetic toner fluctuate, This is because image quality may be degraded.

  The binder resin contained in the toner of the present invention preferably has at least a polyester unit. Since the polyester unit increases the water absorption of the resin, the surface of the toner particles made of the resin having the polyester unit can hold a relatively large amount of adsorbed moisture. The magnetic toner of the present invention containing a resin having a polyester unit as a binder resin has an extremely large amount of adsorbed moisture between the magnetic particle portion exposed on the surface of the magnetic toner and the polyester resin portion, and the adsorption and desorption behavior is extremely high. Therefore, it is easy to make the charge amount distribution on the surface of the magnetic toner more uniform.

  The “polyester unit” refers to a portion derived from polyester. That is, the “resin having a polyester unit” refers to a resin having at least a repeating unit having an ester bond.

Here, if the water content of the binder resin becomes too large, the physical properties of the magnetic toner will vary greatly depending on the environment. Therefore, by using a resin having an acid value in the above range (preferably a resin having a polyester unit), the ratio of the moisture content adsorbed to the magnetic toner at a relative water vapor pressure of 50% is 0.05 mass. It is preferable to adjust to% to 0.60 mass%.
When the ratio of the adsorbed water mass to the magnetic toner is less than 0.05% by mass, even if the magnetic particles of the present invention are used, the magnetic toner is likely to be charged up and to cause image quality problems such as fogging and scattering. Sometimes. On the other hand, if the ratio of the adsorbed water mass to the magnetic toner exceeds 0.60% by mass, the chargeability tends to decrease, and the magnetic toner may not form an image having a sufficient density.

The adsorbed water mass to the magnetic toner can be measured in the same manner as the adsorbed water mass to the magnetic particles described above.
The amount of moisture adsorbed to the magnetic toner can be adjusted by the type of binder resin, the acid value and hydroxyl value of the binder resin, the type of magnetic particles, the amount of moisture adsorbed by the magnetic particles, and the like.

  The acid value of the binder resin is determined by the following operations 1) to 5). Basic operation conforms to JIS K0070.

1) The sample is used by removing additives other than the binder resin (polymer component) in advance, or the content of components other than the binder resin in the sample is obtained. Weigh accurately 0.5 to 2.0 g of the pulverized product of magnetic toner or binder resin. The mass of the binder resin component at this time is defined as W (g).
2) A sample is put into a 300 (ml) beaker, and a mixed solution 150 (ml) of toluene / ethanol (mass ratio: 4/1) is added and dissolved.
3) Titrate with 0.1 mol / l KOH in ethanol. This titration can be automatically titrated using, for example, a potentiometric titration measuring device AT-400 (winworkstation) manufactured by Kyoto Electronics Co., Ltd. and an ABP-410 electric burette.
4) Let the amount of KOH solution used in this titration be S (ml). On the other hand, a blank containing no resin is titrated, and the amount of KOH solution used in this titration is B (ml).
5) Calculate the acid value according to the following formula. In the following formula, f is a factor of KOH.

[Equation 3]
Acid value (mgKOH / g) = {(SB) × f × 5.61} / W

  The OH value is determined by the following operations 1) to 8). Basic operation conforms to JIS K0070.

1) The sample is used by removing additives other than the binder resin (polymer component) in advance, or the content of components other than the binder resin in the sample is obtained. 0.5-2.0 g of the pulverized toner or binder resin is precisely weighed into a 200 ml flat bottom flask.
2) To this is added 5 ml of an acetylating reagent (25 g of acetic anhydride is weighed into a flask (100 ml) and pyridine is added to bring the total amount to 100 ml, followed by sufficient stirring). If the sample is difficult to dissolve, add a small amount of pyridine, or add xylene or toluene to dissolve.
3) Place a small funnel in the mouth of the flask and immerse the bottom of about 1 cm in a glycerin bath at a temperature of 95-100 ° C. and heat. In order to prevent the temperature of the neck of the flask from rising due to the heat of the glycerin bath, a cardboard disc with a round hole in it is put on the base of the neck of the flask.
4) After 1 hour, remove the flask from the glycerin bath, allow to cool, add 1 ml of water from the funnel, and shake it to decompose acetic anhydride.
5) Further, in order to completely decompose acetic anhydride, the flask is again immersed in a glycerin bath and heated for 10 minutes. After cooling, the funnel and the flask wall are washed with 5 ml of ethanol.
6) A few drops of phenolphthalein solution is added as an indicator, titrated with 0.5 kmol / m ³ potassium hydroxide ethanol solution, and the end point is when the indicator is light red for about 30 seconds.
7) Perform 2) to 6) as blank tests without adding resin.
8) Calculate the OH number by the following formula.

[Equation 4]
A = [{(BC) × 28.05 × f} / S] + D
(However, A is a hydroxyl value (mgKOH / g), B is the amount (ml) of 0.5 kmol / m ³ potassium hydroxide ethanol solution used in the blank test, and C is 0.5 kmol used for titration. / M ^{3 of} potassium hydroxide ethanol solution (ml), f is a factor of 0.5 kmol / m ³ potassium hydroxide ethanol solution, and S is the amount of binder resin (g) contained in the sample. Yes, D is the acid value of the sample, where “28.05” is the formula weight of potassium hydroxide (56.11 × 1/2)).

  The acid value and hydroxyl value of the binder resin can be adjusted by, for example, the types of monomers constituting the binder resin and their blending amounts.

  In the polyester resin contained in the magnetic toner of the present invention, it is preferable that 45 to 55 mol% of all components is an alcohol component and 55 to 45 mol% is an acid component.

  Examples of the alcohol component include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6 -Hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, bisphenol derivatives represented by the following general formula (B); diols represented by the following general formula (C); or Polyhydric alcohols such as glycerin, sorbit, sorbitan and the like are included.

  In the general formula (B), R represents an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10.

  In the general formula (C), R ′ represents any of the following structural formulas, which may be the same or different.

  As the acid component, carboxylic acid can be preferably exemplified, and examples of the divalent carboxylic acid include benzenedicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and phthalic anhydride, or anhydrides thereof; succinic acid Alkyldicarboxylic acids such as adipic acid, sebacic acid and azelaic acid or anhydrides thereof; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid and itaconic acid or anhydrides thereof; Examples of trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid and anhydrides thereof.

  Examples of particularly preferred alcohol components of the polyester resin include bisphenol derivatives represented by the formula (B). Examples of particularly preferred acid components include phthalic acid, terephthalic acid, isophthalic acid or anhydrides thereof, succinic acid, Examples include dicarboxylic acids such as n-dodecenyl succinic acid or its anhydride, fumaric acid, maleic acid and maleic anhydride; trimellitic acid or its tricarboxylic acid. This is because a magnetic toner using a polyester resin obtained from these acid components and alcohol components as a binder resin has good fixability and excellent offset resistance.

  In the magnetic toner of the present invention, the following vinyl resin may be used as the binder resin.

  Examples of vinyl resins include styrene; o-methylstyrene, m-methylstyrene, p-methylenestyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p- Ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl Styrene derivatives such as styrene and pn-dodecylstyrene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; unsaturated polyenes such as butadiene; vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride Vinyl halides such as: vinyl acetate, vinyl propionate, repose Vinyl esters such as vinyl acid; methyl methacrylate, ethyl methacrylate, propyl methacrylate, -n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, methacryl Α-methylene aliphatic monocarboxylic acid esters such as stearyl acid, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic Acrylate esters such as propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N N-vinyl compounds such as vinyl pyrrolidone; vinyl naphthalenes: acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; esters of α, β-unsaturated acids, diesters of dibasic acids; acrylic acid, Acrylic acid such as methacrylic acid, α-ethylacrylic acid, crotonic acid, cinnamic acid, vinyl acetic acid, isocrotonic acid, angelic acid, and α- or β-alkyl derivatives thereof; fumaric acid, maleic acid, citraconic acid, alkenyl succinic acid Polymers using vinyl monomers such as unsaturated dicarboxylic acids such as acid, itaconic acid, mesaconic acid, dimethylmaleic acid and dimethylfumaric acid and monoester derivatives or anhydrides thereof are included.

  The said vinyl resin is manufactured from the vinyl monomer mentioned above individually or in combination of 2 or more types. Examples of preferred vinyl resins include styrene copolymers and styrene-acrylic copolymers.

  Further, the binder resin contained in the magnetic toner of the present invention may be a polymer or copolymer cross-linked with a cross-linkable monomer as exemplified below if necessary.

  As the crosslinkable monomer, a monomer having at least two crosslinkable unsaturated bonds can be used. As such a crosslinkable monomer, various monomers as shown below are conventionally known and can be suitably used for the magnetic toner of the present invention.

  Examples of the crosslinkable monomer include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, and 1,5-pentanediol. Diacrylate compounds linked by alkyl chains such as diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate and the above compounds in which acrylate is replaced by methacrylate; diethylene glycol diacrylate, triethylene glycol diacrylate , Tetraethylene glycol diacrylate, polyethylene glycol # 400 diacrylate, polyethylene glycol # 600 diacrylate, dipropylene glycol diacrylate And diacrylate compounds linked by an alkyl chain containing an ether bond, such as those obtained by replacing acrylates of the above compounds with methacrylates; polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane diacrylate , Polyoxyethylene (4) -2,2-bis (4-hydroxyphenyl) propane diacrylate and di-linked by a chain containing an aromatic group and an ether bond such as those obtained by replacing acrylate of the above compound with methacrylate Acrylate compounds; polyester type diacrylates such as trade name MANDA (Nippon Kayaku);

Examples of polyfunctional crosslinkers having three or more crosslinkable unsaturated bonds include pentaerythritol triacrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate and more Compounds in which the acrylate of the compound is replaced with methacrylate; triallyl cyanurate, triallyl trimellitate and the like are included.

  The amount of these crosslinking agents used is preferably adjusted according to the type of monomer to be crosslinked, the desired physical properties of the binder resin, etc., but generally 100 parts by mass of other monomer components constituting the binder resin In contrast, 0.01 to 10.00 parts by mass (more preferably 0.03 to 5.00 parts by mass) of a crosslinking agent can be used.

  Among these cross-linkable monomers, examples that are preferably used from the viewpoint of developer fixing property and offset resistance include aromatic divinyl compounds (particularly divinylbenzene), a chain containing an aromatic group and an ether bond. Diacrylate compounds.

  The binder resin contained in the magnetic toner particles of the magnetic toner of the present invention includes a vinyl monomer homopolymer or copolymer, polyester, polyurethane, epoxy resin, polyvinyl butyral, rosin, modified rosin, if necessary. Other resins such as terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, and aromatic petroleum resin may be mixed. When two or more kinds of resins are mixed and used as a binder resin, it is preferable to mix those having different molecular weights at an appropriate ratio.

  Furthermore, the glass transition temperature (Tg) of the binder resin used in the present invention is preferably 45 to 80 ° C., more preferably 55 to 70 ° C., and the number average molecular weight (Mn) is 2,500 to 50,000, weight. The average molecular weight (Mw) is preferably 10,000 to 1,000,000.

  The number average molecular weight and weight average molecular weight of the binder resin are obtained by dissolving the binder resin in tetrahydrofuran (THF). This solution is used for measurement by gel permeation chromatography (GPC). The number average molecular weight and the weight average molecular weight can be determined from the count number (retention time) measured from the sample (binder resin) and the logarithmic value of a calibration curve prepared from several monodisperse polystyrene standard samples. it can. Further, the molecular weight of the binder resin can be adjusted by polymerization conditions, use of a crosslinking agent, kneading of the binder resin, and the like.

The glass transition temperature of the binder resin is preferably 45 to 80 ° C., and the glass transition temperature can be adjusted by selecting a constituent material (polymerizable monomer) of the binder resin. Here, the glass transition temperature is a theoretical glass transition temperature described in publication polymer handbook 2nd edition III-p139-192 (manufactured by John Wiley & Sons).
The glass transition temperature of the binder resin can be measured according to ASTM D3418-82 using a differential scanning calorimeter, for example, DSC-7 manufactured by PerkinElmer or DSC2920 manufactured by TA Instruments Japan. If the glass transition temperature of the binder resin is lower than the above range, the storage stability of the magnetic toner may be insufficient, and if the glass transition temperature of the binder resin is higher than the above range, the fixability of the magnetic toner will be reduced. May be insufficient.

  A method for synthesizing a binder resin made of a vinyl polymer or copolymer is not particularly limited, and various conventionally known production methods can be used. For example, a bulk polymerization method, a solution polymerization method, a suspension method can be used. A polymerization method such as a polymerization method or an emulsion polymerization method can be used. When a carboxylic acid monomer or an acid anhydride monomer is used, it is preferable to use a bulk polymerization method or a solution polymerization method because of the properties of the monomer.

The magnetic toner of the present invention may contain a wax.
Examples of the wax contained in the magnetic toner of the present invention include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; Oxides of aliphatic hydrocarbon waxes such as polyethylene wax; or block copolymers thereof; plant waxes such as candelilla wax, carnauba wax, wood wax, jojoba wax; animals such as beeswax, lanolin, whale wax Waxes; mineral waxes such as ozokerite, ceresin, petrolatum; waxes based on aliphatic esters such as montanate ester wax and castor wax; aliphatic esters such as deoxidized carnauba wax Part or all include those deoxidized.

  Further, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group; unsaturated fatty acids such as brassic acid, eleostearic acid, parinaric acid; stearyl alcohol Saturated alcohol such as eicosyl alcohol, behenyl alcohol, cannavir alcohol, seryl alcohol, melyl alcohol, or alkyl alcohol having a long chain alkyl group; polyhydric alcohol such as sorbitol; linoleic acid amide, oleic acid amide, lauric acid Aliphatic amides such as acid amides; saturated aliphatic bisamides such as methylene bisstearic acid amide, ethylene biscapric acid amides, ethylene bislauric acid amides, hexamethylene bisstearic acid amides; ethylene Unsaturated fatty acid amides such as soleic acid amide, hexamethylenebisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; m-xylene bisstearic acid amide, N, Aromatic bisamides such as N'-distearylisophthalamide; aliphatic metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (commonly referred to as metal soap); aliphatic hydrocarbons Wax grafted with a vinyl monomer such as styrene or acrylic acid; Partial esterified product of fatty acid and polyhydric alcohol such as behenic acid monoglyceride; Hydroxyl group obtained by hydrogenating vegetable oil Methyl ester compound And the like.

  In addition, these waxes have a sharp molecular weight distribution using a press perspiration method, a solvent method, a recrystallization method, a vacuum distillation method, a supercritical gas extraction method or a melt liquid crystal deposition method, a low molecular weight solid fatty acid, a low A molecular weight solid alcohol, a low molecular weight solid compound, and other impurities are preferably used.

In addition, a charge control agent may be added to the magnetic toner of the present invention.
Specific examples of the negative charge control agent include metal compounds of monoazo dyes described in JP-B-41-20153, JP-B-44-6397, JP-B-45-26478, and the like. Nitrohumic acid and its salts described in JP-A-50-133838 or C.I. I. Dyes and pigments such as 14645, salicylic acid, naphthoic acid, dicarboxylic acid Zn, Al, Co, described in JP-B-55-42752, JP-B-58-41508, JP-B-59-7385, etc. Examples thereof include metal compounds such as Cr, Fe, and Zr, sulfonated copper phthalocyanine pigment, nitro group, styrene oligomer introduced with halogen, and chlorinated paraffin. In particular, the azo metal compound represented by the general formula (I) and the basic organic acid metal compound represented by the general formula (II) are excellent in dispersibility and effective in reducing the image density stability and fog. preferable.

  In general formula (I), M represents a coordination center metal and represents Cr, Co, Ni, Mn, Fe, Ti, or Al. Ar is an arylene group such as a phenylene group or a naphthylene group, and may have a substituent. In this case, examples of the substituent include a nitro group, a halogen group, a carboxyl group, an anilide group, an alkyl group having 1 to 18 carbon atoms, and an alkoxy group having 1 to 18 carbon atoms. X, X ′, Y, and Y ′ are —O—, —CO—, —NH—, and —NR— (R represents an alkyl group having 1 to 4 carbon atoms). A + represents hydrogen, sodium ion, potassium ion, ammonium ion or aliphatic ammonium ion.

In general formula (II), M represents a coordination center metal and represents Cr, Co, Ni, Mn, Fe, Ti, Zr, Zn, Si, B, or Al. (B) represents any one of the following structural formulas (1) to (8) which may have a substituent such as an alkyl group, and may be the same or different. A ′ ⁺ represents a hydrogen ion, a sodium ion, a potassium ion, an ammonium ion, or an aliphatic ammonium ion. Z represents -O- or any one of the following structural formula (9), and may be the same or different.

  In the general formulas (7) and (8), R represents a hydrogen atom, a C1-C18 alkyl group, or a C2-C18 alkenyl group.

  Of these charge control agents, the azo-based metal compound represented by the above general formula (I) is more preferable, and in particular, the azo-based compound represented by the following general formula (III) or (IV) whose central metal is Fe. Iron compounds are most preferred.

In the general formula (III), _{X 2} and _{X 3} represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a nitro group or a halogen atom. k and k ′ each represent an integer of 1 to 3. Y ₁ and Y ₃ are hydrogen atom, C1-C18 alkyl group, C2-C18 alkenyl group, sulfonamide group, mesyl group, sulfonic acid group, carboxyester group, hydroxy group, C1-C18 alkoxy group, acetylamino A group, a benzoyl group, an amino group or a halogen atom; l and l ′ each represent an integer of 1 to 3. Y ₂ and Y ₄ represent a hydrogen atom or a nitro group. A ″ ⁺ represents an ammonium ion, a sodium ion, a potassium ion, a hydrogen ion or a mixed ion thereof, preferably a mixed ion containing 75 to 98 mol% of an ammonium ion.
X ₂ and X ₃ , k and k ′, Y ₁ and Y ₃ , l and l ′, and Y ₂ and Y ₄ may be the same or different.

In general formula (IV), R < ₁ > -R < ₂₀ > shows a hydrogen atom, a halogen atom, or an alkyl group, and may be same or different, respectively. A ⁺ represents an ammonium ion, a sodium ion, a potassium ion, a hydrogen ion, or a mixed ion thereof.

  Next, specific examples of the azo-based iron compound represented by the general formula (III) will be shown.

  Specific examples of the charge control agent having a structure represented by the above formulas (I), (II), and (IV) are shown below.

  These metal complex compounds can be used alone or in combination of two or more. The amount of these charge control agents used is preferably 0.1 to 5.0 parts by mass per 100 parts by mass of the binder resin from the viewpoint of the charge amount of the magnetic toner.

  Preferable examples of the charge control agent for negative charging include Spiron Black TRH, T-77, T-95 (Hodogaya Chemical Co., Ltd.), BONTRON (registered trademark) S-34, S-44, S-54, E- 84, E-88, E-89 (Orient Chemical). Preferred examples of the positive charge control agent include TP-302, TP-415 (Hodogaya Chemical Co., Ltd.), BONTRON (registered trademark) N-01, N-04, N-07, P-51 (Orient Chemistry). Co., Ltd.) and Copy Blue PR (Clariant).

  On the other hand, examples of the charge control agent for controlling the toner to be positively charged include modified products of nigrosine and fatty acid metal salts, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate and the like. Quaternary ammonium salts of these compounds, and onium salts such as phosphonium salts thereof and their lake pigments, triphenylmethane dyes and lake lake pigments (the rake agents include phosphotungstic acid, phosphomolybdic acid, phosphorus Tungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide, etc.), metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; DOO, dioctyl tin borate, diorgano tin borate such as dicyclohexyl tin borate; includes. These can be used alone or in combination of two or more.

  The magnetic toner of the present invention is preferably mixed with inorganic fine powder or hydrophobic inorganic fine powder. For example, silica fine powder is preferably externally added to the magnetic toner of the present invention.

  The silica fine powder mixed (preferably externally added) to the magnetic toner of the present invention includes so-called dry silica or fumed silica produced by vapor phase oxidation of a silicon halogen compound, and water. Any of so-called wet silica produced from glass or the like may be used. However, dry silica having fewer silanol groups on the surface and inside and having no production residue is preferred.

  Further, the silica fine powder used in the present invention is preferably hydrophobized. The hydrophobic treatment of the silica fine powder is performed by chemically treating with an organosilicon compound that reacts or physically adsorbs with the silica fine powder. Examples of a preferred method include a method of treating a dry silica fine powder produced by vapor phase oxidation of a silicon halogen compound with an organosilicon compound such as silicone oil after treating with the silane compound or simultaneously with the silane compound. included.

  Examples of silane compounds used for hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, Bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, Diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldi Siloxane and 1,3-diphenyltetramethyldisiloxane are included.

Examples of the organosilicon compound used for the hydrophobizing treatment include silicone oil. Preferred silicone oils have a viscosity at 25 ° C. of about 3 × 10 ⁻⁵ to 1 × 10 ⁻³ m ² / s. Examples of preferable silicone oil include dimethyl silicone oil, methyl hydrogen silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like.

  The treatment with silicone oil is performed, for example, by directly mixing silica powder treated with a silane compound and silicone oil using a mixer such as a Henschel mixer, or by injecting silicone oil onto the base silica. It can be broken. Alternatively, it may be carried out by dissolving or dispersing silicone oil in an appropriate solvent, mixing the silica fine powder of the base, and further removing the solvent.

  External additives other than silica fine powder may be added to the magnetic toner of the present invention as required. Examples of such other external additives include resin fine particles and inorganic fine particles that function as a charging aid, a conductivity imparting agent, a fluidity imparting agent, an anti-caking agent, a lubricant, an abrasive, and the like. A small amount of these can be used.

More specific examples of other external additives include the following.
Lubricants such as polyfluorinated ethylene, zinc stearate and polyvinylidene fluoride, especially polyvinylidene fluoride; abrasives such as cerium oxide, silicon carbide and strontium titanate, especially strontium titanate; fluidity imparting such as titanium oxide and aluminum oxide Agents, especially hydrophobic ones; anti-caking agents; conductivity imparting agents such as carbon black, zinc oxide, antimony oxide, tin oxide; developability improvers such as white particles and black particles of opposite polarity.

  The amount of the inorganic fine powder or hydrophobic inorganic fine powder mixed with the magnetic toner is 0.1 to 5.0 parts by mass (preferably 0.1 to 3.0 parts by mass) with respect to 100 parts by mass of the magnetic toner. It is preferable that

  In order to produce the magnetic toner of the present invention, a mixture containing at least a binder resin and magnetic particles is used as a material. In addition, other materials such as a wax, a charge control agent, and a known colorant are used as necessary. These additives are used.

The method for producing the magnetic toner of the present invention is not particularly limited, and can be produced by a known method. For example, it can be produced as follows.
The aforementioned magnetic toner materials are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill, and then melted, kneaded and kneaded using a heat kneader such as a roll, a kneader and an extruder to make the resins compatible with each other. Let me. Magnetic particles, pigments or dyes are dispersed or dissolved in the obtained compatible material, cooled and solidified, then pulverized and classified, and external additives such as inorganic fine powder are mixed with the mixer as necessary. Thus, the magnetic toner of the present invention can be obtained.

  Examples of mixers include Henschel mixer (made by Mitsui Mining); Super mixer (made by Kawata); Ribocorn (made by Okawara Seisakusho); Nauter mixer, turbulizer, cyclomix (made by Hosokawa Micron); Spiral pin Mixer (manufactured by Taiheiyo Kiko Co., Ltd.);

Examples of the kneader include KRC kneader (manufactured by Kurimoto Iron Works); Bus Co. kneader (Buss)
TEM type extruder (manufactured by TOSHIBA MACHINERY CO., LTD.); TEX twin-screw kneader (manufactured by Nippon Steel Works); PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.); Nidex (manufactured by Mitsui Mining Co., Ltd.); MS pressure kneader, Nider Ruder (manufactured by Moriyama Seisakusho); Banbury mixer (manufactured by Kobe Steel), and the like.

  Examples of the pulverizer include counter jet mill, micron jet, inomizer (manufactured by Hosokawa Micron); IDS type mill, PJM jet pulverizer (manufactured by Nippon Pneumatic Industry); cross jet mill (manufactured by Kurimoto Iron Works); Ur Max (manufactured by Nisso Engineering Co., Ltd.); SK Jet Oh Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.); Super Rotor (Nisshin Engineering).

  Examples of classifiers include: Classy, Micron Classifier, Spedic Classifier (manufactured by Seishin Enterprise); Turbo Classifier (manufactured by Nissin Engineering); Micron Separator, Turboplex (ATP), TSP Separator (Hosokawa Micron) Elbow Jet (manufactured by Nippon Steel Mining Co., Ltd.), dispersion separator (manufactured by Nippon Pneumatic Industrial Co., Ltd.), YM micro cut (manufactured by Yaskawa Shoji Co., Ltd.) and the like.

  Examples of sieving devices used for sieving coarse particles include Ultrasonic (manufactured by Sakae Sangyo Co., Ltd.); Resonator Sheave, Gyroshifter (manufactured by Deoksugakusho Co., Ltd.); Vibrasonic System (manufactured by Dalton Co., Ltd.); (Shinto Kogyo Co., Ltd.); Turbo screener (Turbo Kogyo Co., Ltd.); Micro shifter (Ogino Sangyo Co., Ltd.);

  The weight average particle size of the magnetic toner particles in the present invention is preferably 4.5 μm to 10.0 μm. A magnetic toner having a weight average particle size exceeding 10.0 μm is not preferable because it has a problem in terms of high image quality due to the size of the toner particles themselves. A magnetic toner having a weight average particle size of less than 4.5 μm is not preferable because even if the magnetic particles of the present invention are used, fogging and scattering may be deteriorated.

The weight average particle diameter can be measured using a Coulter Multisizer II (trade name, manufactured by Coulter, Inc.) which is a particle diameter measuring instrument. For example, the Coulter Multisizer II can be connected to an interface (manufactured by Nikka) for outputting the number distribution and volume distribution and a personal computer PC9801 (trade name, manufactured by NEC).

  As an electrolytic solution used for the preparation of a test sample, a 1% NaCl aqueous solution in which a reagent primary sodium chloride is dissolved in water can be used. In addition, as the electrolytic solution, for example, ISOTONR-II (trade name, manufactured by Coulter Scientific Japan Co., Ltd.) can be used.

The test sample is a surfactant, preferably 0.1 to 5.0 ml of an alkyl benzene sulfonate as a dispersant in 100 to 150 ml of the electrolyte solution, and 2 to 20 mg of a developer sample. For about 1 to 3 minutes.
In the measurement of the weight average particle diameter by the Coulter Multisizer, a 100 μm aperture can be used as the aperture.

  The number of magnetic toner particles contained in each channel (having a particle diameter of 2 μm or more) and the volume of each particle are measured, and the volume distribution and number distribution are calculated. The weight average particle diameter is the weight average particle diameter obtained from the volume distribution. The center value of each channel is set as the representative value of each channel.

  The weight average particle diameter of the magnetic toner particles can be adjusted, for example, by pulverizing / classifying the magnetic toner or mixing a classified product having an appropriate particle diameter.

  The magnetic toner of the present invention is suitably used as a one-component developer. The magnetic toner of the present invention includes, for example, a developing device for one-component jumping development, and a developing and cleaning device that supplies (develops) magnetic toner to the photosensitive member and collects transfer residual toner from the photosensitive member. For example, it is used for image formation by a known image forming apparatus for a one-component developer. In addition, the magnetic toner of the present invention has at least a developing device in which the magnetic toner of the present invention is accommodated, and a photoreceptor on which an electrostatic latent image that is developed as a toner image with the magnetic toner of the present invention is formed, It can also be suitably used for a process cartridge that is integrally attached to the image forming apparatus main body.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

(Production Example 1 of Magnetic Particles)
In the ferrous sulfate aqueous solution, 0.965 equivalent sodium hydroxide aqueous solution was mixed with Fe ²⁺ to produce a ferrous salt aqueous solution containing Fe (OH) ₂ .

Then, sodium silicate was added so that it might become 0.3 mass% in conversion of Si element with respect to Fe element. Next, air was passed through the aqueous ferrous salt solution containing Fe (OH) ₂ at a temperature of 90 ° C. to cause an oxidation reaction under the condition of pH 6.5.

Furthermore, by adding a sodium hydroxide aqueous solution in which 0.1% by mass of sodium silicate is dissolved to this suspension, sodium silicate is converted to Si element with respect to Fe ²⁺ remaining in the suspension. 1.05 equivalent was added. Further, while heating at a temperature of 90 ° C., an oxidation reaction was carried out under the condition of pH 9.0, and washing, filtration and drying were carried out by a conventional method to obtain base magnetic particles A.

Next, the base magnetic particles A were dispersed in water, and a suspension aqueous solution having a concentration of 100 g / l was maintained at 70 ° C. Sodium hydroxide aqueous solution or dilute sulfuric acid was added to adjust the pH of the suspension aqueous solution to 5.0. While stirring this suspended aqueous solution, about 1 hour was added thereto, and an aqueous titanium sulfate solution having a concentration of 80 g / l as TiO ₂ was added in an amount corresponding to 1.0% by mass as TiO ₂ / Fe ₃ O ₄ . At this time, an aqueous sodium hydroxide solution was simultaneously added so that the pH of the aqueous suspension was maintained at 5.0. Then, an aqueous sodium hydroxide solution was added to make the pH of the suspended aqueous solution neutral. This was washed, filtered, dried, and crushed by ordinary methods to obtain magnetic particles 1 coated with TiO ₂ . The average particle diameter of the magnetic particles 1 was 0.15 μm. Table 1 shows the physical properties of the magnetic particles.

(Production Example 2 of magnetic particles)
Magnetic material coated with TiO ₂ in the same manner as in Production Example 1 except that in Example 1 of production of magnetic particles, an aqueous titanium sulfate solution was added in an amount corresponding to 5.3% by mass as TiO ₂ / Fe ₃ O _4. Body particles 2 were obtained. Table 1 shows the physical properties of the magnetic particles 2.

(Production Example 3 of Magnetic Particles)
In Production Example 1 of magnetic particles, the average particle size of the base magnetic particles before being coated with TiO ₂ was 0.12 μm, and the titanium sulfate aqueous solution was 9.0% by mass as TiO ₂ / Fe ₃ O _4. A magnetic particle 3 coated with TiO ₂ having an average particle size of 0.12 μm was obtained in the same manner as in Production Example 1 except that a considerable amount was added. Table 1 shows the physical properties of the magnetic particles 3.

(Magnetic particle production example 4)
In Production Example 1 of magnetic particles, the pH in the production process of the parent magnetic particles before being coated with TiO ₂ was adjusted to obtain magnetic particles having an octahedral shape with an average particle diameter of 0.27 μm, and sulfuric acid. Magnetic particles 4 coated with TiO ₂ were obtained in the same manner as in Production Example 1, except that an equivalent amount of 0.5% by mass of titanium aqueous solution was added as TiO ₂ / Fe ₃ O ₄ . Table 1 shows the physical properties of the magnetic particles 4.

(Production Examples 5 to 7 of magnetic particles)
In Production Example 1 of magnetic particles, the average particle size of the base magnetic particles before being coated with TiO ₂ was adjusted, and the addition amount of the titanium sulfate aqueous solution was changed, as in Production Example 1, Magnetic particles 5 to 7 coated with TiO ₂ were obtained. Table 1 shows the physical properties of the magnetic particles 5 to 7.

(Production Examples 8 and 9 for comparative magnetic particles)
In Production Example 1 of magnetic particles, the average particle size of the base magnetic particles before being coated with TiO ₂ was adjusted, and the addition amount of the titanium sulfate aqueous solution was changed, as in Production Example 1, The comparative magnetic particles 8 and 9 coated with TiO ₂ were obtained. Table 1 shows the physical properties of the magnetic particles 8 and 9.

(Comparative magnetic particle production example 10)
In the magnetic particle production example 4, the titanium sulfate aqueous solution was coated with TiO ₂ in the same manner as in the production example 4 except that 9.8% by mass of TiO ₂ / Fe ₃ O ₄ was added. Magnetic particles 10 for use were obtained. Table 1 shows the physical properties of the magnetic particles 10.

(Production Example 11 for Comparative Magnetic Particles)
In the magnetic particle production example 1, the magnetic particles for comparison coated with TiO ₂ in the same manner as in production example 1 except that sodium silicate is not added in the process of producing the parent magnetic particle. 11 was obtained. Table 1 shows the physical properties of the magnetic particles 11.

In Table 1,
“A” represents “a ratio (mass%) of the adsorbed water mass at 28 ° C. relative water vapor pressure of 50% to the mass of magnetic particles”;
“ΔA” is “a magnetic particle having a maximum mass difference between an adsorption moisture mass in the adsorption process at 28 ° C. and an adsorption moisture mass in the desorption process at 28 ° C. at a relative water vapor pressure of 5% to 90%. "Ratio to mass (mass%)"
“B” represents “a ratio (mass%) of the mass of the titanium compound in the magnetic particle converted to TiO ₂ to the mass of the magnetic particle”.
“Fe ²⁺ retention” represents “ratio of the content of Fe ²⁺ in the magnetic particles after the heat treatment to the content of Fe ²⁺ in the magnetic particles before the heat treatment”.

(Binder resin production example 1)
40 parts by mass of PO (propylene oxide) 2 mol adduct of bisphenol A, 30 parts by mass of EO (ethylene oxide) 2 mol adduct of bisphenol A, 25 parts by mass of terephthalic acid, 4 parts by mass of fumaric acid, anhydrous 5 parts by mass of trimellitic acid and 0.5 parts by mass of dibutyltin oxide were added, and these were subjected to condensation polymerization at 220 ° C. to obtain a polyester binder resin 1. The acid value of this resin is 22 mgKOH / g, and the hydroxyl value is 32 mgKOH.
/ G, Tg was 59 ° C., the weight average molecular weight [Mw] was 220,000, and the THF-insoluble content was 14% by mass.

  The amount of THF-insoluble matter in the binder resin was determined from the residue when the binder resin was extracted with a Soxhlet extractor using tetrahydrofuran (THF) as a solvent. More specifically, the weighed binder resin is put into a cylindrical filter paper (for example, No. 86R size 28 × 10 mm, manufactured by Toyo Filter Paper Co.), 200 ml of THF is used as a solvent, and the extraction cycle of THF is about 4 to 5 minutes. The sample was extracted for 16 hours at a reflux rate of once, and after the extraction, the cylindrical filter paper was taken out and weighed, and the THF-insoluble content in the binder resin was determined from the following formula.

[Equation 5]
THF insoluble matter (mass%) = W2 / W1 × 100

  In the above formula, W1 represents the weight (g) of the binder resin placed in the cylindrical filter paper, and W2 represents the weight (g) of the binder resin in the cylindrical filter paper after extraction.

(Binder resin production example 2)
In Binder Resin Production Example 1, the monomer composition is 40 parts by mass of PO2 mol adduct of bisphenol A, 70 parts by mass of EO2 mol adduct of bisphenol A, 50 parts by mass of terephthalic acid, 1 part by mass of trimellitic anhydride, and dibutyltin. Except for using 0.5 parts by mass of oxide, condensation polymerization was carried out in the same manner as in Binder Resin Production Example 1 to obtain a polyester binder resin 2. The acid value of this resin was 3.6 mgKOH / g, the hydroxyl value was 22 mgKOH / g, Tg was 65 ° C., Mw was 50,000, and the THF insoluble content was 4% by mass.

(Binder resin production example 3)
In Binder Resin Production Example 1, the monomer composition is 100 parts by mass of PO2 mol adduct of bisphenol A, 32 parts by mass of isophthalic acid, 12 parts by mass of terephthalic acid, 1 part by mass of trimellitic anhydride and 0.5 mass of dibutyltin oxide. The polyester was subjected to condensation polymerization in the same manner as in Binder Resin Production Example 1 to obtain a polyester binder resin 3. The acid value of this resin was 2.0 mgKOH / g, the hydroxyl value was 54 mgKOH / g, Mw was 60,000, Tg was 52 ° C., and the THF insoluble content was 0% by mass.

(Binder resin production example 4)
In Binder Production Example 1, the monomer composition is 40 parts by mass of an EO2 molar adduct of bisphenol A, 12 parts by mass of terephthalic acid, 7 parts by mass of trimellitic anhydride, 5 parts by mass of dodecenyl succinic acid, and 0.5 parts of dibutyltin oxide. Except for the mass part, condensation polymerization was carried out in the same manner as in Binder Resin Production Example 1 to obtain a polyester binder resin 4. The acid value of this resin was 42 mgKOH / g, the hydroxyl value was 4.8 mgKOH / g, Mw was 280,000, Tg was 55 ° C., and the THF-insoluble content was 5% by mass.

(Binder resin production example 5)
Into a four-necked flask, 300 parts by mass of xylene is charged, heated to reflux, and mixed with 80 parts by mass of styrene, 20 parts by mass of acrylate-n-butyl and 2 parts by mass of di-tert-butyl peroxide. Was dropped over 5 hours to obtain a low molecular weight polymer (L-1) solution having an Mw of 15,000.

On the other hand, 180 parts by mass of degassed water and 20 parts by mass of a 2% by weight aqueous solution of polyvinyl alcohol were charged into a four-necked flask, and then 75 parts by mass of styrene, 25 parts by mass of acrylic acid-n-butyl, 0.005 of divinylbenzene. A mixed solution of 0.1 part by mass and 2,2-bis (4,4-di-tert-butylperoxycyclohexyl) propane (half-life 10 hours temperature; 92 ° C.) is added, stirred and suspended. It was. After sufficiently substituting the inside of the flask with nitrogen, the temperature was raised to 85 ° C. to polymerize, and after maintaining for 24 hours, 0.1 part by mass of benzoyl peroxide (half-life 10 hours temperature; 72 ° C.) was added, Furthermore, it was maintained for 12 hours to complete the polymerization of the high molecular weight polymer (H-1).

  25 parts by mass of the high molecular weight polymer (H-1) was added to 300 parts by mass of the homogeneous solution of the low molecular weight polymer (L-1), and after mixing well under reflux, the organic solvent was distilled off. A styrene-based binder resin 5 was obtained. The acid value of this binder resin was 0 mgKOH / g, the hydroxyl value was 0 mgKOH / g, Tg was 57 ° C., Mw was 300,000, and the THF insoluble content was 0% by mass.

(Magnetic toner production example 1)
Binder resin 1: 100 parts by mass Wax: 3 parts by mass (low molecular weight polyethylene, DSC maximum peak temperature: 102 ° C., Mn: 850)
Magnetic particles 1: 95 parts by mass Azo-based iron compound (1): 2 parts by mass (the counter ion is NH ₄ ⁺ )
After the above raw materials were premixed with a Henschel mixer (Mitsui Mining Co., Ltd.) as a mixer, the resulting premixture was directly mixed at a temperature of 150 near the outlet of the kneaded product by a twin-screw kneading extruder set at 200 rpm. The preset temperature was adjusted so that the temperature was 160 ° C. to kneading. The obtained kneaded product is cooled and coarsely pulverized with a cutter mill, and then the obtained coarsely pulverized product is finely pulverized using a turbo mill (manufactured by Turbo Kogyo Co., Ltd.) as a pulverizer, and divided into multiple parts utilizing the Coanda effect. Classification was performed using a classifier to obtain negatively chargeable magnetic toner particles 1 having a weight average particle diameter (D4) of 6.3 μm.

  1.0 part by mass of hydrophobic silica fine particles was added to 100 parts by mass of the magnetic toner particles 1 and externally mixed with a Henschel mixer (Mitsui Mining Co., Ltd.) as a mixer to obtain a magnetic toner 1. Table 2 shows the physical properties of this magnetic toner 1.

(Production Examples 2 to 7 of magnetic toner)
In magnetic toner production example 1, as shown in Table 2, the binder resin and magnetic particles were changed, and the weight average particle diameter of the toner particles was adjusted in the pulverization and classification process, as in production example 1. Thus, magnetic toners 2 to 7 were obtained. Table 2 shows the physical properties of the magnetic toners 2 to 7.

(Comparative magnetic toner production examples 8 to 11)
In magnetic toner production example 1, as shown in Table 2, the binder resin and magnetic particles were changed, and the weight average particle diameter of the toner particles was adjusted in the pulverization and classification process, as in production example 1. Thus, comparative magnetic toners 8 to 11 were obtained.

[Example 1]
(Evaluation 1)
A commercially available LBP printer (Laser Jet 4300, manufactured by HP) was modified to have an A4 size of 55 sheets / minute (process speed of 325 mm / sec), and a modified process cartridge that doubled the capacity of the toner filling unit was mounted. .

  With this as an image testing machine, the machine temporarily stops between jobs with a horizontal line pattern of 1% printing rate in a high-temperature and high-humidity environment of 35 ° C and 85% RH as 2 sheets / job. A print test was conducted.

  After the durability of 20,000 sheets, the image density was measured and compared with the image density at the initial stage of durability. As a result, the reflection density before durability was 1.50, and the reflection density after durability was 1.48, and the density stability was good. The results are shown in Table 3.

  The image density was measured by measuring the reflection density of a solid black image of 5 mm square using an SPI filter with a Macbeth densitometer (Macbeth Co.) which is a reflection densitometer. The evaluation standard of image density is shown below.

A: The reduction rate of the reflection density before and after durability is less than 2%.
B: The decrease rate of the reflection density before and after durability is 2% or more and less than 4%.
C: The reduction rate of the reflection density before and after durability is 4% or more and less than 8%.
D: The reduction rate of the reflection density before and after durability is 8% or more.

  After the image density evaluation, 10 halftone patterns with a printing rate of 25% were output, and the occurrence of fading was confirmed. As a result, even when a halftone image having a high printing rate was output, fading did not occur and an image without unevenness was obtained. The results are shown in Table 3. The evaluation criteria for fading are shown below.

A: No occurrence.
B: There is a slightly thin part.
C: The density is clearly reduced in a band shape.

  After the above evaluation was completed, the occurrence of scratches and filming on the surface of the photoreceptor was visually confirmed to confirm the influence on the image. As a result, the occurrence of photoconductor scratches and filming was not confirmed. The results are shown in Table 3. The evaluation criteria are shown below.

A: Very good.
B: Good. Although slight scratches or filming is observed on the photoreceptor, there is almost no influence on the image.
C: Practical use is possible. Scratches or filming is observed on the photoreceptor, but the influence on the image is small.
D: Not practical. Causes image defects.

(Evaluation 2)
Move the image printing test machine used in Evaluation 1 to a low-temperature, low-humidity environment at 15 ° C. and 10% RH, and leave it overnight. In a mode in which the machine is temporarily stopped during the job, a test was performed to print another 1000 sheets. Thereafter, fog and scattering were evaluated.

  For fog, the amplitude of the AC component of the development bias is set to 1.8 kV (conditions that make fog worse. Default is 1.6 kV), two solid whites are printed, and the second fog is printed by the following method. It was measured.

  Using a reflection densitometer (reflectometer model TC-6DS manufactured by Tokyo Denshoku Co., Ltd.), the transfer material before and after the image formation is measured, and the reflection density worst value after the image formation is Ds, and the reflection average density of the transfer material before the image formation. Was taken as Dr, Ds-Dr was determined, and this was evaluated as the amount of fogging. The smaller the number, the less the fog. As a result, the fog amount was good at 0.2. The results are shown in Table 3.

The scattering was evaluated by visual observation of toner scattering around the character when printed on cardboard (105 g / m ² ). As a result, almost no scattering was observed, and a sharp character image was obtained.

The evaluation standard of fog is shown below.
A: Less than 0.5.
B: 0.5 or more and less than 1.0.
C: 1.0 or more and less than 2.5.
D: 2.5 or more.

The evaluation criteria for scattering are shown below.
A: It is hardly seen.
B: Scattering is seen but I don't care.
C: Scattering is remarkable.

(Evaluation 3)
The color tone of the solid black image was measured, and the blackness of the magnetic toner was quantitatively evaluated.
Subsequent to Evaluation 2, after adjusting the development contrast so that the transmission density of the solid black image was 1.7, one solid black image was output on A4 paper, and the color tone was measured. The transmission density is Macbe
It is a value measured using th Density Densitometer RD914 type.

The color tone was measured quantitatively based on the color system definition defined by the International Commission on Illumination (CIE) in 1976. A spectrocolorimeter type 938 manufactured by X-Rite was used as the measuring device, the observation light source was a C light source, and the viewing angle was 2 °.
As a result, a ^* was +0.31, b ^* was −0.37, and L ^* was +20.5.

[Examples 2 to 7]
Evaluation was performed in the same manner as in Example 1 using magnetic toners 2 to 7. The evaluation results are shown in Table 3.

[Comparative Examples 1-4]
Evaluation was performed in the same manner as in Example 1 using comparative magnetic toners 8 to 11. The evaluation results are shown in Table 3.

Claims (7)

A magnetic toner having magnetic toner particles containing magnetic particles containing at least a binder resin and a titanium compound,
I) The ratio A [mass%] of the moisture content adsorbed to the magnetic particles at a temperature of 28 ° C. and a relative water vapor pressure of 50% is 0.25 to 0.80 [mass%],
II) The amount of moisture adsorbed on the magnetic particles in the adsorption process in which the relative water vapor pressure is increased at a temperature of 28 ° C. and the amount of water adsorbed on the magnetic particles in the desorption process in which the relative water vapor pressure is decreased at the same temperature. The difference in any relative water vapor pressure is 0.10% by mass or less based on the mass of the magnetic particles, and
III) The magnetic toner, wherein the ratio B [mass%] of the mass of the titanium compound converted to TiO ₂ to the mass of the magnetic particles is 0.10 to 10.0 [mass%].   The magnetic toner according to claim 1, wherein an isoelectric point of the magnetic particles is pH 4.1 to 8.0. The magnetic toner according to claim 1, wherein the ratio A [mass%] and the ratio B [mass%] satisfy the following formula (1).
[Equation 1]
0.50 ≧ A / B ≧ 0.05 Formula (1)   The magnetic toner according to claim 1, wherein the magnetic particles have an average particle size of 0.08 μm to 0.25 μm. When the magnetic particles are heat-treated at 160 ° C. for 1 hour in air,
The magnetic toner according to any one of claims 1 to 4, wherein a ratio of the Fe ²⁺ content in the magnetic particles after the heat treatment to the Fe ²⁺ content in the magnetic particles before the heat treatment is 60% or more. .   The magnetic toner according to claim 1, wherein the binder resin has an acid value of 1 mgKOH / g to 50 mgKOH / g.   The magnetic toner according to claim 1, wherein the binder resin is a resin having at least a polyester unit.