JP4298614B2 - Magnetic toner - Google Patents

Description

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

  Many methods are known as electrophotographic methods. Generally, an electrostatic latent image is formed on an electrostatic charge image carrier (hereinafter also referred to as a “photosensitive member”) by using a photoconductive substance by various means. Then, the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a recording medium such as paper, and then the toner image is fixed on the recording medium by heat or pressure. To obtain a copy. Examples of such an image forming apparatus include a copying machine and a printer.

  These printers and copiers have recently moved from analog to digital, and there is a strong demand for reduction in power consumption to be used as well as excellent reproducibility of latent images and high resolution.

  Here, for example, when focusing on the printer, the ratio of the power consumption in the fixing process to the total power consumption is considerably large, and the power consumption increases as the fixing temperature increases. Further, when the fixing temperature becomes high, problems such as curling of the printout paper after fixing also occur, and there is a great demand for lowering the fixing temperature. Furthermore, there is a demand for various materials, and a toner having good fixability in a wide temperature range is demanded.

  In contrast, many studies have been made on the low-temperature fixing of toners, and it has been reported that both low-temperature fixing and high-temperature offset resistance can be achieved by controlling the molecular weight distribution and THF-insoluble matter. Yes (see, for example, Patent Document 1).

  In addition, many studies have been made on the low softening point substance added to the toner, and by treating the surface of the magnetic powder with the low softening point substance, the dispersibility of the magnetic powder in the toner is improved, and along with that, Techniques for improving the fixability have also been proposed (see, for example, Patent Documents 2 to 4).

However, even if such a magnetic powder is used, there is still room for improvement in coexistence of low-temperature fixing and high-temperature offset resistance, and improvement in fixing properties is still insufficient.
JP-A-5-297630 JP-A-9-319137 JP-A-1-259369 JP-A-1-259372

  An object of the present invention is to provide a magnetic toner that is excellent in low-temperature fixability and has good fixability in a wide temperature range.

  Another object of the present invention is to provide a magnetic toner capable of forming a high-definition image free from image defects such as fogging and toner fusion.

The present invention is a magnetic toner having at least a binder resin and a magnetic material and having a weight average particle diameter of 3 to 10 μm,
The magnetic material is obtained by surface-treating magnetic fine particles with a low softening point substance (A),
The compression ratio of the magnetic material obtained from the following formula (1) is 35 or more,
Compression rate = {1- (apparent density / tap density)} × 100 Formula (1)
The softening point Ts when the magnetic toner is measured with a flow tester is 40 to 85 ° C.,
The magnetic toner has a THF (tetrahydrofuran) insoluble content of a resin component of 1 to 60% by mass.

  According to the present invention, a good image can be obtained, and a toner having excellent low temperature fixability and good fixability in a wide temperature range can be obtained.

  As a result of intensive studies by the present inventors, a magnetic material uniformly surface-treated with a low softening point substance is used, and a toner having a specific softening point and a THF insoluble content is used to greatly improve low temperature fixability and resistance. Both high temperature offset properties are possible and the present invention has been achieved.

  First, considering the behavior of the toner at the time of fixing, the toner in contact with the high-temperature fixing member transfers heat from the toner surface to the inside, and the resin part is plasticized and deformed, and the contained low softening point material melts and exudes. This improves the releasability from the fixing member, and is considered to fix without offset.

  Here, considering the magnetic toner, the magnetic toner has a large amount of magnetic substance inside. Since this magnetic material has a larger specific heat than the resin, it absorbs part of the heat received by the toner during fixing, and the heat from the fixing device is effectively used for plasticity / deformation of the resin and melting of the low softening point material. Hard to break.

  The present inventors uniformly treat the surface of the magnetic fine particles with a low softening point material (A) (the low softening point material used for the surface treatment of the magnetic fine particles is referred to as “low softening point material (A)”). Thus, before the magnetic material (in the present invention, the surface of the “magnetic fine particles” treated with the low softening point material is called “magnetic material”) the amount of heat received during fixing is taken away by the low softening point material ( It was considered that the fixability was improved by melting and exuding A).

Then, when the surface treatment and fixing property of the magnetic fine particles with the low softening point substance (A) were examined, the following formula (1)
Compression rate = {1− (apparent density) / (tap density)} × 100 (1)
It was proved that the magnetic material obtained from No. 1 had a compression ratio of 35 or more had good low-temperature fixability.

  A high compression ratio represented by the above formula means that the “apparent density” is low or the “tap density” is high. However, even if the low-softening point substance (A) is treated on the surface of the magnetic fine particles by various methods, the apparent density does not change so much, and the fluctuation of the compressibility is mainly caused by the fluctuation of the tap density. I understood.

  Then, when the variation of the tap density was considered, the following knowledge was obtained.

  By simply mixing and stirring a submicron-order magnetic fine particle using a low softening point substance of several μm to several hundreds of μm in size, the magnetic fine particle is simply treated with the low softening point substance (A). Since the magnetic fine particles are only attached to the low-softening point substance (A) having a large diameter, such a magnetic material does not clog tightly even if tapped, resulting in a low tap density. . In addition, even when the magnetic fine particles are tightly agglomerated by the treatment with the low softening point substance, even if tapped, the tap density is lowered because the magnetic fine particles are not tightly packed. On the other hand, when the surface of each magnetic fine particle is uniformly coated with the low softening point substance (A), the magnetic material is densely packed by tapping, so that the tap density is increased, resulting in a compression ratio. Becomes higher.

  That is, the high compression rate of the magnetic material can be considered as an index indicating that the surface treatment of the magnetic fine particles with the low softening point substance (A) is performed uniformly.

  Further, the high tap density of the magnetic material indicates that the magnetic materials after processing have less aggregation and excellent fluidity, and the magnetic material is well dispersed in the toner particles.

  For this reason, in the toner of the present invention, since the magnetic material whose surface is uniformly coated with the low softening point substance (A) is well dispersed in the toner particles, the amount of heat received at the time of fixing is low (the softening point substance ( It is used effectively for melting and exudation of A), and it is considered that the fixing property of the toner is improved.

  On the other hand, when a magnetic material having a compression ratio of less than 35 is used, that is, when it seems that the magnetic fine particles are attached to the low softening point substance (A), the low temperature fixability of the toner is reduced. The effect of improving cannot be obtained sufficiently. In addition, in a toner having a small particle diameter of 10 μm or less as in the present invention, it is difficult to uniformly disperse the magnetic material, and the magnetic material tends to exist as an aggregate in the toner particles. Then, since the fluidity is inferior, poor dispersion of the magnetic material becomes more prominent. For this reason, the low softening point substance (A) cannot be melted and exuded well, and the effect of improving the low-temperature fixability is further reduced. In addition, in the state where the magnetic powder adheres to the low softening point substance (A), not only the above-mentioned effect cannot be expected, but also the suspension polymerization method (which can suitably produce the toner of the present invention ( In the later-described case, it is difficult to encapsulate the low softening point substance (A), or the low softening point substance (A) is present in a state of being released from the toner, and the toner carrier is likely to be fused. In addition, an increase in fog is caused, which is not preferable.

  As described above, the magnetic material surface-treated with the low softening point substance (A) and having a compression rate of 35 or more, more preferably 38 or more, the low softening point substance (A) is fixed at the time of fixing. We believe that it will be possible to exude well.

  In addition, in the magnetic material in which the surface of the magnetic fine particles is coated with the low softening point material (A), the relationship between the tap density between the magnetic fine particles before the treatment with the low softening point material (A) and the magnetic material after the treatment is as follows. Particularly preferred is the case.

(Tap density of magnetic material / tap density of magnetic fine particles)
= 0.80 to 1.00 (more preferably 0.90 to 1.00)
When the above relationship is satisfied, it is considered that the treatment with respect to the individual magnetic fine particles by the low softening point substance (A) is performed in an extremely uniform state, and the effect of improving the low-temperature fixability becomes more remarkable.

  Next, regarding the softening point Ts of the toner when measured with a flow tester, this indicates the temperature at which the toner is softened when heat is applied. The lower the softening point, the lower the plasticity and deformation at lower temperatures. It means easy. For this reason, those having a softening point higher than 85 ° C. inhibit the low-temperature fixability because the toner itself is hardly plasticized or deformed even if the low softening point substance (A) exudes well.

  On the other hand, when the softening point Ts of the toner as measured with a flow tester is less than 40 ° C., the low-temperature fixability is good, but the storage stability is poor and the toner is fused to the toner carrier during development. This is not preferable because the toner tends to be deteriorated and toner deterioration is likely to occur due to long-term use.

  For this reason, in the present invention, the softening point Ts of the toner as measured by a flow tester needs to be 40 to 85 ° C., more preferably 45 to 80 ° C.

  Next, regarding the THF (tetrahydrofuran) insoluble component of the binder resin component of the toner, it is important that the THF insoluble component is 1 to 60% by mass in the present invention. When the THF-insoluble content is 1% by mass or more, it is possible to prevent the melt viscosity of the toner from becoming too low at the time of fixing at a high temperature, and a synergistic effect with the seepage of the low softening point substance (A) present on the surface of the magnetic material. Therefore, the high temperature offset resistance can be improved, and an excellent fixability can be obtained in a wide temperature range. However, if the THF-insoluble content of the binder resin component of the toner exceeds 60% by mass, the low-temperature fixability tends to deteriorate due to the low plasticity and melting resin content, making it difficult to obtain good fixability. It becomes.

  Therefore, in the present magnetic toner, it is important that the THF-insoluble content of the resin component is 1 to 60% by mass, preferably 10 to 55% by mass.

As I have said,
(1) By using a magnetic material uniformly treated with a low softening point substance, bleeding of the low softening point substance (A) during fixing is very good;
(2) Since the softening point Ts is 40 to 85 ° C., the toner is easily plasticized and deformed;
(3) Since the THF-insoluble content is 1 to 60%, the high-temperature offset resistance is excellent;
These three synergistic effects are considered to be excellent in low-temperature fixability and high-temperature offset resistance, and have good fixability in a wide fixing temperature range.

  The apparent density and tap density of the magnetic material are measured according to JIS K5101. Further, the tap density is measured with the tapping frequency set to 600 times. For the measurement of the apparent density and the tap density, for example, a powder tester manufactured by Hosokawa Micron can be used.

  Measurement of the THF-insoluble content of the resin component of the toner is performed as follows.

1 g of toner is precisely weighed and charged in a cylindrical filter paper, and extracted with 200 ml of THF for 20 hours with Soxhlet. Thereafter, the cylindrical filter paper is taken out, vacuum-dried at 40 ° C. for 20 hours, the residue mass is measured, and the THF-insoluble matter is calculated from the following formula. The resin component of the toner is a component obtained by removing components other than the resin such as magnetic fine particles, a charge control agent, a release agent component (including a low softening point substance (A)), an external additive, and a pigment from the toner. Yes, when measuring the THF-insoluble content, the THF-insoluble content is calculated based on the resin component in consideration of whether these contents are soluble or insoluble in THF.
THF insoluble content (%) = (W2-W3) / (W1-W3-W4) × 100
Here, W1 is the mass of the toner, W2 is the mass of the residue, W3 is the mass of a component insoluble in THF other than the resin component of the toner, and W4 is the mass of a component soluble in THF other than the resin component of the toner.

  The THF-insoluble content of the resin component of the toner can be arbitrarily adjusted depending on the binder resin used and the kneading conditions when the toner is produced by the pulverization method. Further, in the polymerization method, it can be arbitrarily adjusted by a combination of the initiator used, the kind and amount of the crosslinking agent, and the like. It can also be adjusted by using a chain transfer agent or the like.

The softening point (Ts) of the toner of the present invention was measured with a flow tester CFT-500D type (manufactured by Shimadzu Corporation). About 1.5 g of a 60-mesh (aperture 250 μm) pass toner is weighed as a sample, and this is pressurized for 1 minute with a load of 100 kg / cm ² (9800 kPa) using a molding machine.

  A load of 10 kgf (98 N) was applied to this sample, and the plunger drop amount of the flow tester was measured by a temperature rising method with a temperature rising temperature of 4.0 ° C./min, a die diameter of 1.0 mm, and a die length of 1.0 mm. A flow curve as shown in FIG. 1 is obtained to obtain the softening point (Ts).

  The low softening point substance (A) used for the surface treatment of magnetic fine particles is a substance having an endothermic peak at the time of temperature rise in differential scanning calorimetry (DSC) measurement, and the peak top of the endothermic peak is 80 to 150 ° C. It is preferable that it is 80-130 degreeC. When the peak top is higher than 150 ° C., the low softening point substance itself hardly melts unless the temperature is high, and the low-temperature fixability is poor. On the other hand, when the endothermic peak top is less than 80 ° C., in the suspension polymerization suitably used in the present invention, a part of the low softening point substance is eluted into the polymerizable monomer system, and the effect of the treatment is reduced. This is not preferable.

  The amount of the low softening point substance (A) used for the treatment of the magnetic fine particles is preferably 0.3 to 15 parts by mass with respect to 100 parts by mass of the magnetic fine particles. When the amount of the low softening point material used for the treatment is less than 0.3 parts by mass, sufficient releasability cannot be obtained, and the fixability becomes poor. On the other hand, when the amount is more than 15 parts by mass, the aggregation of the magnetic substance tends to occur during the surface treatment with the low softening point substance (A), and the free low softening point substance (A) increases, which is not preferable.

The liberation rate of the low softening point substance (A) of the magnetic material is preferably 25% or less, more preferably 15% or less. The liberation rate of the low softening point substance (A) is obtained by the following formula (2). The larger the value, the easier the low softening point substance (A) is detached from the surface of the magnetic material, or the lower the liberation point. It means that there are many softening point substances (A). In this case, for example, in the suspension polymerization, the granulation property is deteriorated, so that the particle size distribution of the obtained toner is widened. Further, since a part of the free low softening point substance is present in a state free from the toner, it is not preferable because it causes the toner carrier to be fused and fogging easily deteriorates. The liberation rate of the low softening point substance of the magnetic material depends on the processing method, conditions, melting point, amount, particle size, etc. of the low softening point substance used.
Release rate = (1-B / A) × 100 Formula (2)
Here, A is an endothermic amount of the magnetic material, and is a value measured by DSC (differential scanning calorimeter). B is an endothermic amount measured by DSC after adding 10 g of magnetic substance to 200 ml of methanol and dispersing for 30 minutes with an ultrasonic disperser, collecting the magnetic substance with a magnet and drying it.

  The endothermic amount and endothermic peak top of the magnetic material are measured according to “ASTM D 3417-99”. For the measurement, for example, DSC-7 manufactured by PerkinElmer, DSC2920 manufactured by TA Instruments, or Q1000 manufactured by TA Instruments can be used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, and an empty pan is set as a control. The sample is heated up to 200 ° C. once to remove the heat history, then rapidly cooled, and again at a heating rate of 10 ° C./min. DSC curve measured when the temperature is raised in the range of 30 to 200 ° C. is used. The same measurement was performed in the examples described later.

  As the low softening point material (A) for treating the surface of the magnetic fine particles, known waxes and crystalline polyesters can be used.

  Examples of the wax include, for example, paraffin wax, microcrystalline wax, petroleum wax such as petrolatum and derivatives thereof, montan wax and derivatives thereof, hydrocarbon waxes and derivatives thereof according to the Fischer-Tropsch method, polyolefin waxes represented by polyethylene and derivatives thereof Natural waxes such as carnauba wax and candelilla wax and derivatives thereof. Derivatives here include oxides, block copolymers with vinyl monomers, and graft modified products. Furthermore, higher aliphatic alcohols, higher fatty acids or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant-based waxes, and animal waxes can also be used.

  Crystalline polyester can be obtained by the reaction of a divalent or higher polyvalent carboxylic acid and a diol. Among these, polyesters mainly composed of aliphatic diols and aliphatic dicarboxylic acids are preferable because of high crystallinity.

  Examples of alcohol monomers for obtaining such a crystalline polyester include ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, trimethylene glycol, and tetramethylene glycol. , Pentamethylene glycol, hexamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, neopentyl glycol, cyclohexane dimetatool, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, and others.

  Examples of the carboxylic acid monomer for obtaining the crystalline polyester include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, peric acid, glutaconic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decane. Dicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, anhydrides or lower alkyl esters of these acids, and the like.

  As an apparatus for processing the low softening point material (A) on the surface of the magnetic fine particles, an apparatus capable of applying a shearing force is preferable. In particular, an apparatus capable of simultaneously performing shearing, spatula and compression, for example, a wheel A shape kneader, a ball type kneader, and a roll type kneader can be suitably used. Among these, the use of a wheel-type kneader is particularly preferable from the viewpoint of uniform treatment. When a wheel-type kneader is used, it becomes possible to rub, adhere and stretch the low softening point substance on the surface of the magnetic fine particles, and to uniformly cover the surface of the magnetic fine particles with the low softening point substance.

  Specific examples of the wheel-type kneader include edge runners, multi-mills, stotz mills, wet pan mills, conner mills, ring mullers, and the like, preferably edge runners, multi-mals, stotz mills, wet pan mills, ring mullers, An edge runner is more preferable. The ball type kneader includes a vibration mill, and the roll type kneader includes an extruder.

  When an edge runner is used, the line load in the treated portion should be 19.6 to 1960 N / cm (2 to 200 kg / cm) so that the low softening point material can be uniformly treated / coated on the surface of the magnetic fine particles. More preferably, it is 98-1470 N / cm (10-150 kg / cm), More preferably, it is 147-980 N / cm (15-100 kg / cm). The treatment time is 15 to 180 minutes, preferably 30 to 150 minutes. If the treatment time is short, the low softening point substance (A) cannot be completely treated on the surface of the magnetic powder, and the liberation rate of the low softening point substance (A) increases. On the other hand, if the treatment time is longer than 180 minutes, heat is generated by the treatment. As a result, agglomeration occurs, and the compression rate decreases. In addition, what is necessary is just to adjust process conditions suitably in the range of stirring speed 2-2000rpm, Preferably 5-1000rpm, More preferably, it is 10-800rpm.

  The low softening point substance (A) used for the treatment of the magnetic fine particles preferably has a particle size of 500 μm or less, and if it is larger than this, uniform treatment becomes difficult and the liberation rate becomes large. . The particle size of the low softening point substance (A) was measured using a laser diffraction / scattering type particle size distribution analyzer LA-920 (manufactured by Horiba, Ltd.), and the volume average particle size of the low softening point substance (A) was measured. The particle size.

  The magnetic material used in the toner of the present invention is preferably one obtained by subjecting the magnetic fine particles to a surface treatment with a coupling agent and further treating with a low softening point substance (A).

  As described above, the magnetic substance of the present invention is obtained by treating the surface of magnetic fine particles with the low softening point substance (A). Since the magnetic fine particles are inorganic and the low softening point substance (A) is an organic compound, it is difficult to uniformly cover the surface of the magnetic fine particles with the low softening point substance (A) even if the above processing equipment is used. Therefore, it is possible to easily treat the low softening point substance (A) uniformly through the coupling agent by previously treating the surface of the magnetic fine particles with the coupling agent.

  In suspension polymerization, treatment with a coupling agent increases the degree of hydrophobicity of the magnetic material itself and can increase the degree of encapsulation of the magnetic material, so that developability can be improved.

  Here, as a method for treating the surface of the magnetic fine particles with a coupling agent, there are generally two methods, dry treatment and wet treatment, but in the present invention, either method may be used. It can process with the apparatus similar to the processing apparatus suitable for processing (A).

  In the case of wet processing, it is preferable to use a method in which the surface treatment is performed while hydrolyzing the coupling agent while dispersing the magnetic fine particles in the aqueous medium so as to have a primary particle size. It is more preferable to perform the hydrophobizing treatment after washing without drying.

  Here, the aqueous medium is a medium containing water as a main component. Specific examples include water itself, water added with a small amount of surfactant, water added with a pH adjuster, and water added with an organic solvent. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5.0% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid. Examples of the organic solvent include alcohols.

Examples of the coupling agent that can be used in the surface treatment of the magnetic fine particles according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, which is represented by the following formula.
R _m SiY _n
[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a functional group such as an alkyl group, a vinyl group, an epoxy group, or a (meth) acryl group, and n represents 1 to 3] Indicates an integer. However, m + n = 4. ]
Examples of the silane coupling agent represented by the above formula include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-glycol. Sidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxy Silane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiet Sisilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, trimethylmethoxysilane, n-hexyltrimethoxysilane, n-decyltrimethoxysilane, hydroxypropyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltri Examples include methoxysilane.

Among these, from the viewpoint of obtaining high hydrophobicity, it is preferable to use an alkyltrialkoxysilane coupling agent represented by the following formula.
_{C p H 2p + 1 -Si- (} OC q H 2q + 1) 3
[In formula, p shows the integer of 2-20, q shows the integer of 1-3. ]
When p in the above formula is smaller than 2, it is difficult to sufficiently impart hydrophobicity, and when p is larger than 20, the hydrophobicity is sufficient, but the coalescence between the magnetic fine particles increases, which is not preferable. . Furthermore, when q is larger than 3, the reactivity of the silane coupling agent is lowered and the hydrophobicity is not sufficiently performed. Moreover, p in the formula represents an integer of 3 to 15, and q is more preferably an integer of 1 or 2.

  In addition, when using the said silane coupling agent, it is possible to process independently, or to process in combination of several types, and when using together, each coupling agent is processed separately or processed simultaneously. I can do it.

  The total amount of the coupling agent used is 0.05 to 20.0 parts by mass, preferably 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the magnetic fine particles. It is preferable to adjust the amount of the treatment agent according to reactivity or the like.

  The magnetic fine particles used in the magnetic toner of the present invention are preferably those containing iron oxide as a main component, such as triiron tetroxide, γ-iron oxide, and phosphorus, cobalt, nickel, copper, magnesium, manganese. Further, elements such as aluminum and silicon may be included. Further, two or more kinds of magnetic fine particles may be used in combination.

  The shape of the magnetic fine particle includes a polyhedron, octahedron, hexahedron, sphere, needle shape, scale shape, and the like, but a polyhedron, octahedron, hexahedron, sphere and the like having low anisotropy increase the image density. Is preferable.

Moreover, as a magnetic body, 2-30 m < ² > / g of BET specific surface area by a nitrogen adsorption method is preferable, and 3-28 m < ² > / g is especially more preferable. Further, those having a Mohs hardness of 5 to 7 are preferred.

  The volume average particle size of the magnetic material is preferably 0.05 to 0.40 μm. When the volume average particle size is less than 0.05 μm, the decrease in blackness becomes remarkable, the coloring power is insufficient as a colorant for black toner, and the magnetic substance is likely to aggregate, and a low softening point substance is used. The uniformity of the treatment tends to be inferior. On the other hand, when the volume average particle diameter exceeds 0.40 μm, the coloring power becomes insufficient. In addition, particularly when used as a colorant for a toner having a small particle diameter, it is stochastically difficult to uniformly disperse the magnetic material in individual toner particles, and the dispersibility tends to deteriorate, which is not preferable.

  The volume average particle diameter of the magnetic material can be measured using a transmission electron microscope. Specifically, after adding 10 g of magnetic substance to 200 ml of methanol and dispersing for 30 minutes with an ultrasonic disperser, the magnetic substance was collected with a magnet and the dried product was sufficiently dispersed in an epoxy resin, 100 pieces of cured products obtained by curing in an atmosphere of 40 ° C. for 2 days as samples on a thin piece by a microtome in a transmission electron microscope (TEM) at a magnification of 10,000 to 40,000 times in a field of view The particle diameter of the magnetic material is measured. Then, the volume average particle diameter was calculated based on the equivalent diameter of a circle equal to the projected area of the magnetic material. It is also possible to measure the particle size with an image analyzer. In the measurement of the average particle diameter of the magnetic material, the low softening point substance that is in a free state with respect to the magnetic fine particles is removed by treatment with an ultrasonic disperser.

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

  The magnetic material used in the magnetic toner of the present invention is preferably used in an amount of 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. More preferably, 20 to 180 parts by mass are used. If the amount is less than 10 parts by mass, the fixability is improved, but the coloring power of the toner is poor, and it is difficult to suppress fogging. On the other hand, when the amount exceeds 200 parts by mass, the fixing ability is deteriorated and the holding force by the magnetic force of the toner carrier is increased, so that the developing property is lowered.

  Note that the content of the magnetic substance in the toner can be approximately measured using a thermal analysis apparatus manufactured by Perkin Elmer, TGA7. In the measurement method, the toner is heated from room temperature to 900 ° C. at a temperature rising rate of 25 ° C./min in a nitrogen atmosphere, and the weight loss from 100 ° C. to 750 ° C. is defined as the binder resin amount, and the remaining weight is approximated. The amount of magnetic material is calculated from the ratio of both.

  When magnetic iron oxide is used as the magnetic fine particles used in the magnetic toner of the present invention, it can be produced, for example, by the following method.

  An aqueous solution containing ferrous hydroxide is prepared by adding an alkali such as sodium hydroxide to the ferrous salt aqueous solution in an amount equivalent to or greater than the iron component. While maintaining the prepared aqueous solution at pH 7 or higher (preferably pH 8 to 14), air was blown in, and the aqueous solution was heated to 70 ° C. or higher to oxidize ferrous hydroxide. First, a seed crystal is formed.

  Next, an aqueous solution containing about 1 equivalent of ferrous sulfate is added to the slurry-like liquid containing seed crystals based on the amount of alkali added previously. While maintaining the pH of the solution at 6 to 14, the reaction of ferrous hydroxide is promoted while blowing air, and the magnetic iron oxide powder is grown around the seed crystal. At this time, it is possible to control the shape of the magnetic powder by selecting an arbitrary pH. As the oxidation reaction proceeds, the pH of the liquid shifts to the acidic side, but the pH of the liquid is preferably not less than 6.

  When the surface treatment of the obtained magnetic iron oxide is performed, it is performed as follows. When the surface treatment is performed dry after the oxidation reaction, the magnetic powder that has been washed, filtered and dried is treated with a coupling agent or a low softening point material. In addition, when the coupling agent treatment is performed in a wet manner, after the oxidation reaction is completed, the dried product is redispersed, or after the oxidation reaction is completed, the iron oxide obtained by washing and filtering is not dried and is separated. Re-dispersion in aqueous medium, pH of re-dispersed liquid is set to acidic range, silane coupling agent is added with sufficient stirring, temperature is increased after hydrolysis, or coupling treatment is performed by setting pH to alkaline range Can also be done. After the surface treatment with the coupling agent in this manner, the surface treatment with the low softening point substance is performed by the method as described above.

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

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

The toner of the present invention preferably has a magnetization intensity of 10 to 50 Am ² / kg (emu / g) in a magnetic field of 79.6 kA / m (1000 oersted). In the case of using magnetic toner, a technique for preventing leakage of magnetic toner by providing a magnetic force generating means in the developing device is generally used. However, if the strength of magnetization is 10 Am ² / kg or more, Toner leakage can be sufficiently suppressed, and sufficient effects can be obtained from the viewpoints of toner transportability and agitation, and suppression of toner scattering. However, if the magnetization intensity of the toner at a magnetic field of 79.6 kA / m is less than 10 Am ² / kg, the above effect cannot be obtained sufficiently, and in addition, if a magnetic force is applied to the toner carrier, the ear of the toner Standing becomes unstable and uneven image density is likely to occur. In addition, since the toner cannot be uniformly charged, fog is increased.

On the other hand, if the magnetic strength of the toner at a magnetic field of 79.6 kA / m is larger than 50 Am ² / kg, when the magnetic force is applied to the toner, the fluidity of the toner is remarkably lowered due to magnetic aggregation, and the developability is lowered. This is not preferable because the toner deteriorates significantly.

  The strength of magnetization of the toner can be arbitrarily changed depending on the type and amount of the magnetic powder contained.

  In the present invention, the strength of magnetization of the magnetic toner is measured using a vibration magnetometer VSM P-1-10 (manufactured by Toei Kogyo Co., Ltd.) at a room temperature of 25 ° C. and an external magnetic field of 79.6 kA / m. This is because the magnetic force of the developing pole of the magnet roller fixed in the toner carrying member is around 1000 oersted, and the toner behavior in the developing region can be considered by measuring with an external magnetic field of 79.6 kA / m. Because you can.

  The toner of the present invention has a weight average particle diameter of 3 to 10 [mu] m, more preferably 4 to 9 [mu] m in order to faithfully develop finer latent image dots in order to improve image quality. . Also, the smaller the toner particle size, the better the fixing property. From this viewpoint, the toner particle size must be 10 μm or less.

  The reason for this is not clear, but if the toner particle size is small, the number of toners per unit mass increases and the contact point between the toners also increases. For this reason, it is thought that the fixability is improved because the plasticized and deformed toner is easily adhered to each other by the heat from the fixing device.

  For the above reasons, it is preferable that the weight average particle size is small to some extent. However, when the weight average particle size is less than 3 μm, the fluidity and agitation as a powder decrease, and the individual toner particles are uniformly charged. In addition to difficulty, it causes an increase in fog and is undesirable.

  In the magnetic toner of the present invention, the coefficient of variation in the number distribution is preferably 40 or less, more preferably 30 or less. When the coefficient of variation in the number distribution is larger than 40, it means that the toner particle size distribution is wide, and selective development occurs, toner charge uniformity is inferior, and fog increases. End up.

Here, the variation coefficient of the number distribution is a value obtained by the following equation (3).
Coefficient of variation = {(standard deviation of number distribution) / (number average particle diameter of toner)} × 100 Formula (3)
The weight average particle size and particle size distribution of the toner can be measured by various methods such as Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter). In the present invention, Coulter Multisizer (manufactured by Coulter) is used. The interface for outputting the number distribution and the volume distribution (manufactured by Nikka) and the PC9801 personal computer (manufactured by NEC) are connected, and 1% NaCl aqueous solution is prepared using first-grade sodium chloride as the electrolyte. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used.

  As a measuring method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the number distribution of toner particles of 2 μm or more is measured using the 100 μm aperture as an aperture by the Coulter Multisizer. Is calculated. Then, the number-based length average particle diameter obtained from the number distribution, that is, the number average particle diameter and the standard deviation of the number distribution are obtained. The same measurement was performed in the examples described later.

  The average circularity of the magnetic toner of the present invention is preferably 0.960 to 1.000. When the average circularity of the toner is 0.960 or more, the magnetic toner can form uniform and thin spikes at the developing portion and can develop faithfully to the latent image, so that a high-definition image can be obtained. Become. Further, it is preferable to use such a toner because there are few voids in the toner layer after development (easy to close packing), and the contact points between the toners are increased and the fixing property is improved.

  Further, in the circularity distribution of the toner, when the mode circularity is 0.99 or more, it means that most of the toner particles have a shape close to a true sphere, and the above action becomes more remarkable. preferable.

  The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of the particles. In the present invention, the flow type particle image analyzer “FPIA-1000” manufactured by Toago Medical Electronics is used. Measurement was performed, and the circularity (Ci) of each particle measured for a particle group having a circle-equivalent diameter of 3 μm or more was obtained by the following equation (4), and further measured by the following equation (5). The value obtained by dividing the sum of the circularity by the total number of particles (m) is defined as the average circularity (C).

  In addition, the mode circularity is divided into 61 parts every 0.01 from 0.40 to 1.00 (that is, 0.40 or more and less than 0.41, 0.41 or more and less than 0.42,. -0.99 or more and less than 1.00 and 1.00), the circularity of the peak in which the frequency value is maximum in the circularity frequency distribution is assigned to each divided range according to the circularity of the measured particles. Degree. The numerical value of the mode circularity is the lower limit value of each divided range.

  In addition, “FPIA-1000”, which is a measuring apparatus used in the present invention, calculates the circularity of each particle, and then calculates the average circularity. 1.00 is divided into 61 classes described above, and a calculation method is used in which the average circularity is calculated using the center value and frequency of the dividing points. However, there is very little error between the average circularity value calculated by this calculation method and the average circularity value calculated by the above-described calculation formula that directly uses the circularity of each particle. In the present invention, the concept of the calculation formula that directly uses the circularity of each particle described above is used in the present invention for reasons of data handling such as a short calculation time and simplification of the calculation calculation formula. It is also possible to use such a calculation method that is used and partially changed.

  The measurement procedure is as follows.

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

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

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

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

  As a method of adding a charge control agent to the toner, there is a method of adding it inside the toner particles. For example, when suspension polymerization is performed, a method of adding a charge control agent to the polymerizable monomer composition before granulation is generally performed, and the polymerization is performed by forming oil droplets in water. During or after polymerization, seed polymerization may be performed by adding a polymerizable monomer in which a charge control agent is dissolved and suspended, thereby uniformly covering the toner surface. In addition, when externally added to the toner particles, an organometallic compound can be used as the charge control agent, and the toner particles and the compound can be introduced into the toner by mixing and stirring the mixture.

  The amount of use of these charge control agents is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, but is not uniquely limited. When added, it is preferably used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin. Further, when externally added, the amount is preferably 0.005 to 1.0 part by mass, more preferably 0.01 to 0.3 part by mass with respect to 100 parts by mass of the toner.

  The magnetic toner of the present invention preferably further comprises 1 to 20 parts by mass of a low softening point substance (B) with respect to 100 parts by mass of the binder resin in order to further improve the fixability. More preferably, it is 40-80 degreeC. The melting point of the low softening point substance (B) is preferably 5 ° C. or more lower than the melting point of the low softening point substance (A). In the present invention, the surface of the magnetic material is treated with the low softening point substance (A). However, the amount of the low softening point substance that oozes out by adding the low softening point substance (B) increases the fixability. Can be improved. In particular, when the endothermic peak top of the low softening point material (A) for treating the surface of the magnetic fine particles as described above is 80 to 150 ° C., the endothermic peak top is further 40 to 80 ° C. as the low softening point material (B). When the amount of the low softening point substance to be added is less than 1 part by mass with respect to 100 parts by mass of the binder resin, the low softening point substance (B) On the other hand, if the amount exceeds 20 parts by mass, the long-term storage stability is deteriorated and the toner charging uniformity is deteriorated due to, for example, oozing out to the toner surface. Further, since a large amount of wax is included, the toner shape tends to become distorted.

  Further, as the low softening point substance (B) to be added, a known mold release agent can be used. Petroleum wax such as paraffin wax, microcrystalline wax, petrolatum and derivatives thereof, montan wax and derivatives thereof, carbonization by the Fischer-Tropsch method Hydrogen wax and derivatives thereof, polyolefin waxes and derivatives thereof typified by polyethylene, natural waxes and derivatives such as carnauba wax, candelilla wax, etc., which include oxides, block copolymers with vinyl monomers, grafts Includes modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes and the like can also be used.

  The measurement of the peak top temperature of the endothermic peak of such a low softening point substance (B) is performed according to “ASTM D 3417-99”.

  The toner of the present invention preferably has a peak top of the main peak in the molecular weight range of 5000 to 50000 in the molecular weight distribution measured by gel permeation chromatography (GPC) of the THF soluble resin component of the toner. Preferably it is the range of 8000-40000. When the peak top has a molecular weight of less than 5,000, a problem occurs in the storage stability of the toner, or the toner deteriorates remarkably when a large number of sheets are printed out. On the contrary, when the peak top exceeds the molecular weight of 50000, there is a problem in low-temperature fixability, which is not preferable.

  The molecular weight of the resin component soluble in THF by GPC is measured as follows.

  A solution obtained by allowing the toner to stand in THF at room temperature for 24 hours and dissolving it is filtered through a solvent-resistant membrane filter having a pore diameter of 0.2 μm to obtain a sample solution, and measurement is performed under the following conditions. In addition, sample preparation adjusts the quantity of THF so that the density | concentration of the component soluble in THF may be 0.4-0.6 mass%.

Equipment: High-speed GPC HLC8120 GPC (manufactured by Tosoh Corporation)
Column: Shodex KF-801, 802, 803, 804,
Seven series of 805, 806, 807 (made by Showa Denko KK)
Eluent: THF
Flow rate: 1.0 ml / min
Oven temperature: 40.0 ° C
Sample injection volume: 0.10 ml
In calculating the molecular weight of the sample, standard polystyrene resin (TSO standard polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F- manufactured by Tosoh Corporation) was used. 10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500).

  Further, the glass transition point (Tg) of the toner of the present invention is preferably 30 to 80 ° C, more preferably 35 to 70 ° C. When the Tg is lower than 30 ° C., the storage stability of the toner is lowered, and when it is higher than 80 ° C., the fixing property is inferior. For example, the glass transition point of the toner is measured with a differential scanning calorimeter, and the measurement method is performed according to ASTM D 3418-99. In the measurement, the DSC curve measured when the temperature of the sample is once raised and the history is taken, then rapidly cooled, and the temperature is raised again in the range of a temperature rising rate of 10 ° C./min and a temperature of 10 to 200 ° C. is used.

  The magnetic toner of the present invention can be produced by any known method. First, in the case of producing by a pulverization method, for example, binder resin, magnetic material, and other components such as a release agent (low softening point substance (B)), a charge control agent, a colorant, and other additives as necessary. Magnetic materials, etc., after mixing the agents sufficiently with a mixer such as a Henschel mixer, ball mill, etc., and then melting and kneading them using a heat kneader such as a heating roll, kneader, extruder Other magnetic toner materials can be dispersed or dissolved, cooled, solidified, pulverized, classified, and subjected to surface treatment as necessary to obtain toner base particles. When performing the surface treatment, either the classification or the surface treatment may be performed first. In the classification process, it is preferable to use a multi-division classifier in terms of production efficiency. The toner base particles may be used as toner as they are, or may be used as toner by adding an external additive to the toner base particles.

  The pulverization step can be performed by a method using a known pulverizer such as a mechanical impact type or a jet type. Further, in order to obtain a toner having a preferable circularity (0.960 or more) of the present invention, it is preferable to further apply heat to pulverize or to supplementarily apply a mechanical impact. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.

  As a means for applying mechanical impact force, for example, a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. or a turbo mill manufactured by Turbo Industry Co., a mechano-fusion system manufactured by Hosokawa Micron Co., Ltd. There is a method of applying a mechanical impact force to the toner by a force such as a compressive force or a frictional force by pressing the toner against the inside of the casing by a centrifugal force with a blade rotating at high speed, as in a device such as a hybridization system manufactured by the manufacturer.

  In the case where the mechanical impact force is used, a thermomechanical impact in which the processing temperature is a temperature in the vicinity of the glass transition point Tg (Tg ± 10 ° C.) of the toner is preferable from the viewpoint of preventing aggregation and productivity. More preferably, it is particularly effective to improve the transfer efficiency to carry out at a temperature in the range of the glass transition point Tg ± 5 ° C. of the toner.

  As a binder resin when the toner according to the present invention is produced by a pulverization method, styrene such as polystyrene and polyvinyltoluene and a homopolymer of a substituted product thereof; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, Styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylamino acrylate Ethyl copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinylmethyl Ether copolymer, styrene-vinylethyl Styrene copolymer such as ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Combined; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin can be used alone or in combination I can do it. Of these, styrene copolymers and polyester resins are particularly preferred from the standpoints of development characteristics and fixability.

  The magnetic toner of the present invention can be produced by the pulverization method as described above, but the toner obtained by this pulverization method is generally indefinite, and the average circularity suitably used in the present invention is low. In order to obtain a physical property of 0.960 or more, it is necessary to perform mechanical / thermal or some special treatment, resulting in poor productivity. Therefore, the toner of the present invention is preferably produced with toner base particles in a wet medium such as a dispersion polymerization method, an association aggregation method, or a suspension polymerization method. In particular, the suspension polymerization method easily satisfies the suitable physical properties of the present invention. Highly preferred.

  The suspension polymerization method includes a polymerizable monomer and a magnetic substance (colorant), and further, a polymerization initiator, a crosslinking agent, a release agent, a charge control agent, and other additives (for example, a plasticizer, (Polymer) is uniformly dissolved or dispersed to prepare a polymerizable monomer composition, and then the polymerizable monomer composition is contained in a continuous layer (for example, an aqueous phase) containing a dispersion stabilizer. The toner base particles having a desired particle diameter are obtained by dripping the solution onto the toner particles and dispersing them using a suitable disperser and simultaneously carrying out a polymerization reaction. In addition, after granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented. The toner obtained by this suspension polymerization method (hereinafter, polymerized toner) has an average circularity of 0.960 or more and a mode circularity of 0.99 or more because the shape of individual toner base particles is almost spherical. It is easy to obtain a toner satisfying the physical property requirements suitable for the present invention. Further, since such a toner has a relatively uniform charge amount distribution, an improvement in image quality can be expected.

  As the disperser, a disperser such as a homogenizer, a ball mill, a colloid mill, or an ultrasonic disperser can be used. At this time, a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser is used at once. The desired toner base particle size makes the particle size of the obtained toner base particles sharper. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. In addition, a polymerization initiator dissolved in a polymerizable monomer or solvent can be added immediately after granulation and before starting the polymerization reaction.

  In the production of the polymerized toner according to the present invention, examples of the polymerizable monomer constituting the polymerizable monomer composition include the following.

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

  In the production of the polymerized toner according to the present invention, the polymerization may be performed by adding a resin to the polymerizable monomer composition. For example, it contains hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups that cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the polymerizable monomer component into the toner, a random copolymer of these and a vinyl compound such as styrene or ethylene, a block copolymer, or a graft copolymer, and the like, Alternatively, it can be used in the form of a polycondensate such as polyester or polyamide, or a polyaddition polymer such as polyether or polyimine. By adding such a high molecular polymer containing a polar functional group to the toner, the high molecular polymer is unevenly distributed on the toner surface, and a toner having good blocking resistance and developability can be obtained.

  Among these resins, the effect is greatly increased by containing a polyester resin. I think this is because of the following reasons. Since the polyester resin contains many ester bonds having relatively high polarity, the polarity of the resin itself becomes high. Due to its high polarity, polyester tends to be unevenly distributed on the surface of the droplets in the aqueous dispersion medium, polymerization proceeds while maintaining this state, and toner base particles are generated. For this reason, the polyester resin is unevenly distributed on the surface of the toner base particles, the surface state and surface composition of the toner base particles are uniform, the charging property is uniform, and the release agent is encapsulated well. Therefore, very good developability can be obtained by the synergistic effect of both.

  The polyester resin used in the present invention is, for example, a saturated polyester resin, an unsaturated polyester resin, or both are appropriately selected and used for controlling physical properties such as charging property, durability, and fixing property of the toner. Is possible.

  As the polyester resin used in the present invention, a normal resin composed of an alcohol component and an acid component can be used, and both components are exemplified below.

  As alcohol components, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexane Diol, neopentyl glycol, 2-ethyl-1,3-hexanediol, cyclohexanedimethanol, butenediol, octenediol, cyclohexenedimethanol, hydrogenated bisphenol A, and bisphenol derivatives represented by the following formula (I);

［式中、Ｒはエチレンまたはプロピレン基であり、ｘ，ｙはそれぞれ１以上の整数であり、かつｘ＋ｙの平均値は２〜１０である。］
、あるいは式（Ｉ）の化合物の水添物、また、下式（ＩＩ）示されるジオール；

[Wherein, R is 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. ]
Or hydrogenated compounds of formula (I), and diols of formula (II) below;

、あるいは式（ＩＩ）の化合物の水添物のジオールが挙げられる。

Or diols of hydrogenated compounds of the formula (II).

  Divalent carboxylic acids include benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid, or anhydrides thereof; Furthermore, succinic acid substituted with an alkyl or alkenyl group having 6 to 18 carbon atoms or an anhydride thereof; unsaturated dicarboxylic acid such as fumaric acid, maleic acid, citraconic acid or itaconic acid, or an anhydride thereof.

  In addition, polyhydric alcohols such as glycerin, pentaerythritol, sorbit, sorbitan, and oxyalkylene ethers of novolac type phenol resins can be cited as the alcohol component, and trimellitic acid, pyromellitic acid, 1,2,3,4- Examples thereof include polyvalent carboxylic acids such as butanetetracarboxylic acid, benzophenonetetracarboxylic acid and anhydrides thereof.

  Among the polyester resins, the alkylene oxide adduct of bisphenol A, which is excellent in charging characteristics and environmental stability and balanced in other electrophotographic characteristics, is preferably used. In the case of this compound, the average number of added moles of alkylene oxide is preferably 2 to 10 in terms of fixability and toner durability.

  It is preferable that 45-55 mol% of the polyester resin in this invention is an alcohol component, and 55-45 mol% is an acid component in all the components.

  In the magnetic toner of the present invention, the polyester resin preferably has an acid value of 0.1 to 50 mgKOH / resin in order to be present on the surface of the toner particles and to exhibit stable chargeability. . If the amount is less than 0.1 mgKOH / resin 1 g, the amount existing on the toner surface tends to be absolutely insufficient, and if it exceeds 50 mgKOH / resin 1 g, the chargeability of the toner is adversely affected. Furthermore, in this invention, it is more preferable to have the acid value of the range of 5-35 mgKOH / resin 1g.

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

  Moreover, when using the high molecular polymer containing such a polar functional group, the number average molecular weight is preferably 5,000 or more. If it is less than 5,000, especially 4,000 or less, the present polymer tends to concentrate in the vicinity of the surface, so that developability, blocking resistance, and durability tend to deteriorate, which is not preferable. Moreover, it is preferable that ratio (Mw / Mn) of a weight average molecular weight and a number average molecular weight is 1.2-10.0 from a viewpoint of fixability and blocking resistance. The number average molecular weight and the weight average molecular weight can be measured by the GPC described above.

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

  As the polymerization initiator used in the production of the magnetic toner by the polymerization method, those having a half-life of 0.5 to 30 hours at the temperature during the polymerization reaction are preferable. Such a polymerization initiator is used as a polymerizable monomer. It is preferable to use it with the addition amount of 0.5-20 mass parts with respect to. When the polymerization reaction is carried out under such conditions, a polymer having a maximum between 10,000 and 100,000 in molecular weight can be obtained, and the toner can have desirable strength and suitable melting characteristics.

  As polymerization initiators, 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile), Azo or diazo polymerization initiators such as 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene Examples thereof include peroxide polymerization initiators such as hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, t-butylperoxy 2-ethylhexanoate, and t-butylperoxypivalate.

  When the magnetic toner is produced by the polymerization method, a crosslinking agent may be added, and the preferable addition amount is 0.001 to 15 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

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

  When toner base particles are produced by a polymerization method, known surfactants, organic dispersants, and inorganic dispersants can be used as a dispersion stabilizer. In particular, inorganic dispersants are less likely to produce harmful ultrafine powders, and because of their steric hindrance, dispersion stability is obtained, so even if the reaction temperature is changed, stability is not easily lost, and washing is easy and does not adversely affect the toner. Therefore, it can be preferably used. Examples of such inorganic dispersants include tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, phosphate polyvalent metal salts such as hydroxyapatite, carbonates such as calcium carbonate and magnesium carbonate, calcium metasuccinate, calcium sulfate, Examples thereof include inorganic salts such as barium sulfate and inorganic compounds such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide.

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

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

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

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

  The polymerized toner base particles are filtered, washed and dried by a known method after the polymerization is completed, and if necessary, external additives are mixed and adhered to the surface to obtain the magnetic toner of the present invention. It is also possible to put a classification step into the manufacturing process and cut coarse powder and fine powder. As described above, the toner base particles obtained by the polymerization method may be used as the toner as they are, or an external additive may be added to the toner base particles and used as the toner.

  In the present invention, whether the toner base particles are produced by a pulverization method or a polymerization method, the number average primary particle size is 4 to 80 nm, more preferably 6 to 6 as an external additive. It is preferable that 40 nm inorganic fine powder is added. Inorganic fine powder is added to improve the fluidity of the toner and to make the charge uniform. However, the inorganic fine powder is treated to make it hydrophobic, etc. to adjust the charge amount of the toner and improve the environmental stability. It is also possible to give this function.

  When the number average primary particle size of the inorganic fine powder is larger than 80 nm, or when the inorganic fine powder of 80 nm or less is not added, good toner fluidity cannot be obtained, and charge imparting to the toner particles is not possible. It tends to be non-uniform, and problems such as an increase in fog, a decrease in image density, and an increase in consumption cannot be avoided. On the other hand, when the number average primary particle size of the inorganic fine powder is smaller than 4 nm, the fineness of the inorganic fine powder becomes stronger, and the particle size distribution has strong cohesiveness that is difficult to break even by crushing treatment instead of the primary particles. This is not preferable because it tends to behave as a wide aggregate, and image defects are likely to occur due to development of the aggregate, damage to the image carrier or magnetic toner carrier, and the like.

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

  Silica, titanium oxide, alumina, etc. can be used as the inorganic fine powder used in the present invention.

As the silica, for example, both a so-called dry method produced by vapor phase oxidation of silicon halide or dry silica called fumed silica, and so-called wet silica produced from water glass or the like can be used. Further, dry silica having less silanol groups on the surface and inside of the silica fine powder and less production residue such as Na ₂ O, SO ₃ ²⁻ is more preferable. In dry silica, it is also possible to obtain composite fine powders of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride and titanium chloride together with silicon halogen compounds in the production process. Is also included.

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

  In the present invention, the inorganic fine powder is preferably a hydrophobized product from the viewpoint of improving environmental stability. When the inorganic fine powder added to the toner absorbs moisture, the charge amount of the toner is remarkably reduced, the charge amount is likely to be non-uniform, and toner scattering is likely to occur.

  As the treating agent used for the hydrophobizing treatment, treating agents such as silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, and organic titanium compounds may be used alone or You may process together.

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

  As a method for treating such inorganic fine powder, for example, as a first-stage reaction, a silanization reaction is performed with a silane compound and silanol groups are eliminated by chemical bonding, and then a hydrophobic reaction is performed on the surface with silicone oil as a second-stage reaction. The thin film can be formed.

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

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

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

  The treatment amount of the silicone oil is 1 to 40 parts by mass, preferably 3 to 35 parts by mass with respect to 100 parts by mass of the inorganic fine powder. If the amount of silicone oil is too small, good hydrophobicity cannot be obtained, and if it is too large, problems such as fogging tend to occur.

The inorganic fine powder used in the present invention preferably has a specific surface area measured by the BET method by nitrogen adsorption in the range of ²⁰ to 350 m ² / g in order to impart good fluidity to the toner, more preferably 25. it is those of ~300m ² / g.

  In accordance with the BET method, the specific surface area is obtained by adsorbing nitrogen gas to the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics) and calculating the specific surface area using the BET multipoint method.

The magnetic toner of the present invention has a primary particle size of more than 30 nm (preferably a specific surface area of less than 50 m ² / g), more preferably a primary particle size of 50 nm or more (preferably a specific surface area of 30 m) for the purpose of improving cleaning properties. It is one of preferable modes to further add inorganic or organic fine particles close to spherical shape (less than ² / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.

  The magnetic toner used in the present invention may further contain other additives, for example, a lubricant powder such as a polyfluorinated ethylene powder, a zinc stearate powder, a polyvinylidene fluoride powder, or a cerium oxide powder within a range that does not have a substantial adverse effect. Abrasives such as silicon carbide powder and strontium titanate powder, or fluidity-imparting agents such as titanium oxide powder and aluminum oxide powder, anti-caking agents, and organic fine particles having opposite polarity and inorganic fine particles as developability improvers A small amount can be used. These additives can also be used after hydrophobizing the surface.

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

  In FIG. 2, reference numeral 100 denotes a photoconductor as an image carrier, and a primary charging roller 117, a developing device 140, a transfer charging roller 114, and a cleaner 116 are provided around the photoconductor. The photoreceptor 100 is charged to −600 V by a primary charging roller 117 to which an AC voltage of 2.0 kV (Vpp) and a DC voltage of −620 V (Vdc) are applied, for example. Next, exposure is performed by irradiating the photoconductor 100 with a laser beam 123 by a laser generator 121. The electrostatic latent image on the photoconductor 100 is developed with a one-component magnetic toner by the developing device 140 and transferred onto the transfer material by the transfer roller 114 in contact with the photoconductor via the transfer material. The transfer material on which the toner image is placed is conveyed to the fixing device 126 by the conveying belt 125 or the like and fixed on the transfer material. In addition, toner remaining on a part of the photoconductor is cleaned by the cleaning unit 116. Reference numeral 124 denotes a register roller.

  In the developing device 140, a cylindrical toner carrier 102 (hereinafter referred to as a developing sleeve) made of a nonmagnetic metal such as aluminum or stainless steel is disposed in the vicinity of the photosensitive member 100 as shown in FIG. Yes. For example, the gap between the photoconductor 100 and the developing sleeve 102 is maintained at about 280 μm by a sleeve / photoconductor gap holding member (not shown) or the like. A magnet roller 104 is fixed and arranged concentrically with the developing sleeve 102 in the developing sleeve. However, the developing sleeve 102 is rotatable. The magnet roller 104 is provided with a plurality of magnetic poles as shown in the figure. S1 affects development, N1 regulates the toner coat amount, S2 takes in / conveys toner, and N2 affects toner blowout prevention. An elastic blade 103 is disposed in contact with the developing sleeve 102 as a member that regulates the amount of magnetic toner that adheres to the developing sleeve 102 and is conveyed. In the developing region, a DC and AC developing bias is applied between the photoconductor 100 and the developing sleeve 102, and the toner on the developing sleeve flies onto the photoconductor 100 in accordance with the electrostatic latent image and becomes a visible image.

  Hereinafter, the present invention will be specifically described with reference to production examples and examples, but this does not limit the present invention in any way. In addition, all the parts in the following mixing | blending are mass parts.

<Production of crystalline polyester>
In a reactor equipped with a stirrer, a thermometer, and an outflow cooler, 118.1 parts by mass (1.0 mol part) of succinic acid and 94.6 parts by mass (1.05 mol part) of 1,4-butanediol Then, 0.50 part by mass of tetrabutyl titanate was added, and an esterification reaction was performed at 190 ° C. Thereafter, the temperature was raised to 220 ° C., the pressure inside the system was gradually reduced, and a polycondensation reaction was performed at 150 Pa to obtain a crystalline polyester. The peak top temperature of the endothermic peak of the crystalline polyester was 112 ° C., the number average molecular weight was 4000, the weight average molecular weight was 6000, and the acid value was 0.4 mgKOH / g. The obtained crystalline polyester was coarsely pulverized and then finely pulverized, and the volume average particle size was 28 μm.

<Manufacture of magnetic body 1>
In aqueous ferrous sulfate solution, 1.0 to 1.1 equivalents of caustic soda solution with respect to iron element, 1.5 mass% sodium hexametaphosphate in terms of phosphorus element with respect to iron element, silicon element with respect to iron element An aqueous solution containing ferrous hydroxide was prepared by mixing 1.5 mass% sodium silicate in terms of conversion.

  While maintaining the aqueous solution at pH 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.

Subsequently, after adding ferrous sulfate aqueous solution so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH 8 and air is supplied. The oxidation reaction was promoted while blowing to obtain a slurry liquid containing magnetic iron oxide. After this slurry was filtered and washed, the water-containing slurry was once taken out. At this time, a small amount of water-containing sample was collected and the water content was measured. Next, this water-containing sample was re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersion was adjusted to about 4.5, and n-hexyltrimethoxysilane was magnetically oxidized with sufficient stirring. To 100 parts by mass of iron, 2.0 parts by mass (the amount of magnetic iron oxide was calculated as a value obtained by subtracting the water content from the water-containing sample) was added for hydrolysis. Thereafter, the pH of the dispersion was adjusted to about 10, a condensation reaction was performed, and a coupling treatment was performed. The produced hydrophobic magnetic fine particles were washed, filtered and dried by a conventional method, and the resulting particles were crushed. The obtained magnetic fine particles had a volume average particle size of 0.20 μm and a tap density of 1.87 g / cm ³ .

  7 parts by mass of polyethylene wax (volume average particle size: 52 μm, Mn: 650) as a low softening point substance (A) was added to 100 parts by mass of the magnetic fine particles thus obtained, and a linear pressure of 45 kg / kg was obtained using an edge runner. Treatment was performed for 2 hours while cooling the system temperature to 60 ° C. or less, and a spherical magnetic body 1 having a volume average particle diameter of 0.23 μm was obtained. The volume average particle diameter after the treatment is increased by 0.03 μm with respect to the volume average particle diameter of the magnetic fine particles before the treatment, and considering this, the added low softening point substance (A) is almost satisfactory. It seems to have been treated on the surface. The physical properties of the obtained magnetic body 1 are shown in Table 1.

<Manufacture of magnetic body 2>
In aqueous ferrous sulfate solution, 1.0 to 1.1 equivalents of caustic soda solution with respect to iron element, 1.5 mass% sodium hexametaphosphate in terms of phosphorus element with respect to iron element, silicon element with respect to iron element An aqueous solution containing ferrous hydroxide was prepared by mixing 1.5 mass% sodium silicate in terms of conversion.

  While maintaining the aqueous solution at pH 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to prepare a slurry liquid for generating seed crystals.

Subsequently, after adding ferrous sulfate aqueous solution so that it may become 0.9-1.2 equivalent with respect to the original alkali amount (sodium component of caustic soda) to this slurry liquid, the slurry liquid is maintained at pH 8 and air is supplied. The oxidation reaction was promoted while blowing to obtain a slurry liquid containing magnetic iron oxide. This slurry was filtered, washed and dried, and then crushed. To this, 2.0 parts by mass of n-octyltriethoxysilane was added and treated with an edge runner for 60 minutes to hydrophobize the surface of the magnetic fine particles. . The obtained magnetic fine particles had a volume average particle size of 0.20 μm and a tap density of 1.87 g / cm ³ .

  5 parts by mass of Fischer-Tropsch wax (volume average particle size: 34 μm, Mn: 750) is added as a low softening point substance (A) to 100 parts by mass of the magnetic fine particles thus obtained, and the magnetic substance 1 is obtained using an edge runner. The spherical magnetic body 2 having a volume average particle diameter of 0.22 μm was obtained under the same conditions as in the production of the above. The physical properties of the obtained magnetic body 2 are shown in Table 1.

<Manufacture of magnetic body 3>
In the production of the magnetic substance 2, the crystalline polyester (volume average particle size: 28 μm) produced as described above was used as the low softening point substance (A) instead of the Fischer-Tropsch wax. The magnetic body 3 was obtained in the same manner as in the production. The physical properties of the obtained magnetic body 3 are shown in Table 1.

<Manufacture of magnetic body 4>
In the production of the magnetic body 2, the magnetic body 4 was obtained in the same manner as the production of the magnetic body 2 except that the Fischer-Tropsch wax was changed to polypropylene wax (volume average particle size: 138 μm, Mn: 960). The physical properties of the obtained magnetic body 4 are shown in Table 1.

<Manufacture of magnetic body 5>
In the production of the magnetic body 2, the magnetic body 5 was obtained in the same manner as the production of the magnetic body 2 except that the Fischer-Tropsch wax was changed to paraffin wax (volume average particle size: 57 μm, Mn: 430). Table 1 shows the physical properties of the obtained magnetic body 5.

<Manufacture of magnetic powder 6>
In the production of the magnetic body 2, the magnetic body 6 was obtained in the same manner as the production of the magnetic body 2 except that the amount of Fischer-Tropsch wax was changed from 5 parts by mass to 0.2 parts by mass. The physical properties of the obtained magnetic body 6 are shown in Table 1.

<Manufacture of magnetic body 7>
In the production of the magnetic body 2, the magnetic body 7 was obtained in the same manner as the production of the magnetic body 2 except that the amount of the Fischer-Tropsch wax was changed from 5 parts by mass to 16 parts by mass. Table 1 shows the physical properties of the magnetic body 7 obtained.

<Manufacture of magnetic body 8>
In the production of the magnetic body 2, the magnetic body 8 was obtained in the same manner as the production of the magnetic body 2 except that the treatment with the n-octyltriethoxysilane coupling agent was not performed. The physical properties of the obtained magnetic body 8 are shown in Table 1.

<Manufacture of magnetic body 9>
In the production of the magnetic body 2, the magnetic body 9 was obtained in the same manner as in the production of the magnetic body 2 except that the average particle diameter of the used Fischer-Tropsch wax was changed to 534 μm. The physical properties of the obtained magnetic body 9 are shown in Table 1.

<Manufacture of magnetic body 10>
In the production of the magnetic body 2, the magnetic body 10 was obtained in the same manner as the production of the magnetic body 2 except that the average particle diameter of the Fischer-Tropsch wax used was 1.1 mm. The physical properties of the obtained magnetic body 10 are shown in Table 1.

<Manufacture of magnetic body 11>
In the production of the magnetic body 2, the magnetic body 11 was obtained in the same manner as the production of the magnetic body 2 except that the treatment time was changed to 4 hours by the edge runner. The physical properties of the obtained magnetic body 11 are shown in Table 1.

<Manufacture of magnetic body 12>
In the manufacture of the magnetic body 2, the magnetic body 12 was obtained in the same manner as the manufacture of the magnetic body 2 except that the processing was performed by changing the processing time by the edge runner to 6 hours. Table 1 shows the physical properties of the magnetic body 12 obtained.

<Manufacture of magnetic body 13>
In the manufacture of the magnetic body 2, the magnetic body 13 was obtained in the same manner as the manufacture of the magnetic body 2 except that the processing was performed by changing the processing time by the edge runner to 10 minutes. Table 1 shows the physical properties of the magnetic body 13 obtained.

<Manufacture of magnetic body 14>
In the production of the magnetic body 2, 100 parts by mass of the coupling agent-treated magnetic fine particles and 5 parts by mass of Fischer-Tropsch wax were mixed with a Henschel mixer for 30 minutes at a peripheral speed of the stirring blade at 50 m / sec. A magnetic body 14 was obtained in the same manner as in the manufacture of the magnetic body 2 except that. The physical properties of the obtained magnetic body 14 are shown in Table 1.

<Manufacture of magnetic body 15>
Similarly to the magnetic body 2, the surface of the magnetic fine particles was subjected to a hydrophobic treatment with n-octyltriethoxysilane.

  5 parts by mass of Fischer-Tropsch wax was dissolved by heating in 50 parts by mass of toluene, and the toluene solution of the obtained wax was added dropwise to 100 parts by mass of magnetic particles treated with a coupling agent while stirring vigorously. Subsequently, the slurry was gradually heated to completely distill off the toluene, thereby obtaining a magnetic body 15 having an average particle diameter of 0.21 μm. Table 1 shows the physical properties of the magnetic body 15 obtained.

<Manufacture of magnetic body 16>
The oxidation reaction proceeded in the same manner as in the production of the magnetic body 2 to obtain a slurry liquid containing magnetic iron oxide. This slurry was filtered, washed and dried, and then sufficiently crushed to obtain a magnetic body 16. The physical properties of the obtained magnetic body 16 are shown in Table 1.

  <Table 1: Physical properties of magnetic material>

<Manufacture of magnetic toner 1>
After adding 450 parts by mass of 0.1 mol / l-Na ₃ PO ₄ aqueous solution to 720 parts by mass of ion-exchanged water and heating to 60 ° C., 67.7 parts by mass of 1.0 mol / l-CaCl ₂ aqueous solution was added. Thus, an aqueous medium containing a dispersion stabilizer was obtained.
Styrene 74 parts by mass n-butyl acrylate 26 parts by mass divinylbenzene 0.55 parts by mass saturated polyester resin 10 parts by mass (Mn = 11000, Mw / Mn = 2.6, acid value = 12 mgKOH / g, Tg = 72 ° C)
Charge control agent (Azo dye iron complex: T-77 (Hodogaya Chemical Co., Ltd.) 1 part by mass Magnetic substance 101.6 parts by mass (including 6.6 parts of polyethylene)
The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.). This was heated to 60 ° C., 5 parts by mass of ester wax (maximum endothermic peak 62 ° C. in DSC) was added, mixed and dissolved therein, and polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was added thereto. ) 3 parts by mass was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition was charged into the aqueous medium, and the mixture was granulated by stirring at 12,000 rpm for 10 minutes in a TK homomixer (Special Machine Industries Co., Ltd.) in an N ₂ atmosphere at 60 ° C. . Thereafter, the mixture was reacted at 60 ° C. for 10 hours while stirring with a paddle stirring blade. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve the dispersion stabilizer, filtered, washed with water, and dried to obtain toner base particles 1.

100 parts by weight of this toner base particle 1 and a hydrophobic silica fine powder (silica base having a number average primary particle size of 12 nm treated with hexamethyldisilazane and then treated with silicone oil, the BET ratio after treatment 1.0 part by mass of surface area = 120 m ^{2 /} g) was mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to obtain magnetic toner 1 having a weight average particle diameter of 6.8 μm. The obtained toner had a softening point Ts of 51.9 ° C., a THF insoluble content of 38%, and a peak top molecular weight of 19000 in a THF soluble content. Table 2 shows the physical properties of the magnetic toner 1.

<Manufacture of magnetic toners 2 to 16>
Magnetic toners 2 to 16 were obtained in the same manner as the magnetic toner 1 except that the magnetic materials 2 to 16 were used in place of the magnetic material 1 and the addition amount was adjusted. Table 2 shows the physical properties of the magnetic toners 2 to 16. The addition amount of the magnetic substance was adjusted so that the content in the toner as the magnetic fine particles (including the coupling agent) excluding the low softening point substance was 95 parts with respect to 100 parts of the binder resin.

  <Table 2: Physical properties of toner 1>

In addition, the magnetic strength of each magnetic toner at a magnetic field of 79.6 kA / m was in the range of 29.5 to 30.5 Am ² / kg for all the magnetic toners.
[Example 1]

<Image forming apparatus>
As an image forming apparatus, LBP-1760 was remodeled and the same as that shown in FIG. A rubber roller charger 117 in which conductive carbon is dispersed as a charging member and coated with nylon resin is brought into contact with the image carrier (photosensitive member) 100 (contact pressure 60 g / cm), and an AC voltage of 2.620V is applied to a DC voltage of −620V. A bias superimposed with 0 kVpp is applied to uniformly charge the photosensitive member. Subsequent to charging, the image portion is exposed with a laser beam 123 to form an electrostatic latent image (the dark portion potential Vd is −600 V and the light portion potential VL is −120 V).

The gap between the photoconductor 100 and the developing sleeve 102 is 280 μm. As a magnetic toner carrier, on a 16 mm diameter aluminum cylinder with a blasted surface, the layer thickness of the following configuration is about 7 μm, and JIS centerline average roughness (Ra). Using a developing sleeve 102 having a resin layer of 1.0 μm, a developing magnetic pole 95 mT (950 gauss), a toner regulating member 103 having a thickness of 1.0 mm and a free length 0.70 mm urethane blade of 39.2 N / m ( 40 g / cm).
-Phenol resin 100 parts by mass-Graphite (particle size: about 7 µm) 90 parts by mass-Carbon black 10 parts by mass Next, a DC voltage Vdc of -420 V was used as a developing bias, 1.6 kVpp and a frequency of 2400 Hz were used as an alternating electric field to be superimposed. The peripheral speed of the developing sleeve was 110% (103 mm / sec) in the forward direction with respect to the peripheral speed of the photosensitive member (94 mm / sec).

Under this condition, the magnetic toner 1 was used and an image printing test of 2000 sheets was performed in a normal temperature and normal humidity environment (23 ° C., 60% RH). As the recording medium, A4 75 g / m ² paper was used. As a result, there was no fog on the non-image area before and after endurance, the image density was 1.4 or more, and a high-definition image could be obtained.

Also, a solid image was formed on A4 75 g / m ² paper so that the toner mass per unit area would be 0.6 mg / cm ² , and the temperature at which the offset was offset at low and high temperatures was investigated by changing the temperature of the fixing device. As a result, the magnetic toner 1 started to be fixed from 130 ° C. (fixing start temperature), and the high temperature side did not cause an offset up to 240 ° C. (maximum fixing temperature), and showed good fixability in a wide temperature range. The evaluation results are shown in Table 3.

  The evaluation method and evaluation criteria for each evaluation item shown in Table 3 are described below.

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

<Fog>
A white image was output and the fog on paper was measured and judged according to the following criteria. In addition, the measurement of fog was performed using a REFECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku Co., Ltd. The filter used was a green filter, and fog was calculated from the following equation.
Fog (%) = reflectance of standard paper (%)-reflectance of sample outputting white image (%)
The determination criteria for fogging are as follows.
A: Very good (less than 1.5%)
B: Good (1.5% or more, less than 2.5%)
C: Normal (2.5% or more and less than 4.0%)
D: Poor (4% or more)
<Image quality>
The image quality criterion is a comprehensive evaluation of the halftone image uniformity and fine line reproducibility.
A: A clear image excellent in fine line reproducibility and image uniformity.
B: A good image although fine line reproducibility and image uniformity are slightly inferior.
C: An image at a level where there is no practical problem.
D: Unfavorable image with poor fine line reproducibility and image uniformity.

[Examples 2 to 11]
An image printing test and a fixing test were conducted in the same manner as in Example 1 using magnetic toners 2 to 11. As a result, each of the toners gave an image of a level that was not problematic for practical use and exhibited good fixability in a wide temperature range. The evaluation results are shown in Table 3.

[Comparative Examples 1-5]
Using the magnetic toners 12 to 16, the image output test was performed in the same manner as the magnetic toner 1.

  As a result, in Comparative Example 1 using the magnetic toner 12 and Comparative Example 4 using the magnetic toner 15, an image having no practical problem was obtained, but the fixing start temperature was 160 ° C. or higher, and the low temperature fixing property was obtained. It was inferior result. In Comparative Example 2 using the magnetic toner 13 and Comparative Example 3 using the magnetic toner 14, the low-temperature fixability was poor and the image was greatly inferior, and the toner carrier was fused with toner. It was happening. In Comparative Example 5 using the magnetic toner 16, the low-temperature fixability was inferior and the image was also greatly inferior. The evaluation results are shown in Table 3.

  <Table 3: Test result 1>

<Manufacture of magnetic toner 17>
Magnetic toner 17 was produced in the same manner as magnetic toner 1 except that the amounts of styrene and n-butyl acrylate used in the production of magnetic toner 1 were changed to 70 parts by mass and 30 parts by mass, respectively. Table 4 shows the physical properties of the magnetic toner 17.

<Manufacture of magnetic toner 18>
Magnetic toner 18 was produced in the same manner as magnetic toner 1 except that the amounts of styrene and n-butyl acrylate used in the production of magnetic toner 1 were changed to 66 parts by mass and 34 parts by mass, respectively. Table 4 shows the physical properties of the magnetic toner 18.

<Manufacture of magnetic toner 19>
Magnetic toner 19 was produced in the same manner as magnetic toner 1 except that the amounts of styrene and n-butyl acrylate used in the production of magnetic toner 1 were changed to 87 parts by mass and 13 parts by mass, respectively. Table 4 shows the physical properties of the magnetic toner 19.

<Manufacture of magnetic toner 20>
Magnetic toner 20 was produced in the same manner as magnetic toner 1 except that the amounts of styrene and n-butyl acrylate used in the production of magnetic toner 1 were changed to 90 parts by mass and 10 parts by mass, respectively. Table 4 shows the physical properties of the magnetic toner 20.

<Manufacture of magnetic toner 21>
Magnetic toner 21 was produced in the same manner as magnetic toner 1 except that the amount of divinylbenzene was changed to 0.05 parts by mass in the production of magnetic toner 1. Table 4 shows the physical properties of the magnetic toner 21.

<Manufacture of magnetic toner 22>
In the production of the magnetic toner 1, the magnetic toner 22 was produced in the same manner as the production of the magnetic toner 1 except that the amount of divinylbenzene was changed to 0.20 parts by mass. Table 4 shows the physical properties of the magnetic toner 22.

<Manufacture of magnetic toner 23>
In the production of the magnetic toner 1, the magnetic toner 23 was produced in the same manner as in the production of the magnetic toner 1 except that the amount of divinylbenzene was changed to 1.2 parts by mass. Table 4 shows the physical properties of the magnetic toner 23.

<Manufacture of Magnetic Toner 24>
In the production of the magnetic toner 1, the magnetic toner 24 was produced in the same manner as in the production of the magnetic toner 1 except that the amount of divinylbenzene was changed to 1.3 parts by mass. Table 4 shows the physical properties of the magnetic toner 24.

<Manufacture of magnetic toner 25>
In the production of the magnetic toner 1, the magnetic toner 25 was produced in the same manner as in the production of the magnetic toner 1 except that the amount of ester wax was changed to 0.5 parts by mass. Table 4 shows the physical properties of the magnetic toner 25.

<Manufacture of magnetic toner 26>
In the production of the magnetic toner 1, the magnetic toner 26 was produced in the same manner as in the production of the magnetic toner 1 except that the amount of the ester wax was changed to 25 parts by mass. Table 4 shows the physical properties of the magnetic toner 26.

<Manufacture of magnetic toner 27>
(Preparation of resin fine particle dispersion)
Styrene 303 parts by mass n-butyl acrylate 105 parts by mass Divinylbenzene 2 parts by mass Dodecanethiol 6 parts by mass Carbon tetrabromide 4 parts by mass The above components were mixed and dissolved to prepare a solution.

  Further, 6 parts by mass of a nonionic surfactant and 10 parts by mass of an anionic surfactant are dissolved in 550 parts by mass of ion-exchanged water, added with the above solution, dispersed and emulsified in a flask, and slowly stirred for 10 minutes. While mixing, 50 parts by mass of ion-exchanged water in which 5 parts by mass of ammonium persulfate was dissolved was added. Next, after sufficiently replacing the system with nitrogen, the flask was heated to 70 ° C. in an oil bath while stirring, and emulsion polymerization was continued for 5 hours to contain anionic resin containing resin fine particles having an average particle diameter of 160 nm. A fine particle dispersion 1 was obtained.

(Preparation of magnetic dispersion)
Magnetic body 1 150 parts by weight Nonionic surfactant 10 parts by weight Ion-exchanged water 400 parts by weight The above components were mixed and dissolved, and dispersed for 10 minutes by a homogenizer to obtain a magnetic body dispersion 1.

(Preparation of release agent dispersion)
Paraffin wax (melting point peak temperature 68 ° C.) 50 parts by weight Cationic surfactant 5.5 parts by weight Ion exchange water 200 parts by weight The above components are subjected to a dispersion treatment with a pressure discharge type homogenizer, and a release agent having a center diameter of 0.16 μm. A release agent dispersion liquid 1 containing particles was obtained.

(Manufacture of toner)
Resin fine particle dispersion 1 200 parts by weight Magnetic substance dispersion 1 283 parts by weight Release agent dispersion 1 64 parts by weight Polyaluminum chloride 1.23 parts by weight After sufficiently mixing and dispersing the above components with a homogenizer, an oil bath for heating The flask was heated to an aggregation temperature of 58 ° C. with stirring. Then, after maintaining at 58 ° C. for 60 minutes, 30 parts by mass of the resin fine particle dispersion 1 was further added and gently stirred.

  Thereafter, the pH in the system was adjusted to 7.0 with a 0.5 mol / l sodium hydroxide aqueous solution, and then the flask was sealed and heated to 80 ° C. while continuing stirring. Thereafter, the pH was lowered to 4.0 and held for 6 hours. After completion of the reaction, the mixture was cooled, filtered and sufficiently washed with ion exchange water, and then filtered, washed and dried to obtain magnetic particles. 100 parts by mass of the obtained magnetic particles and 1.0 part by mass of silica used in the production of the magnetic toner 1 were mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.), and the weight average particle diameter was 5.8 μm. A magnetic toner 27 was obtained. Table 4 shows the physical properties of the magnetic toner 27.

  <Table 4: Physical properties of toner 2>

Note that the magnetic strength of each magnetic toner at a magnetic field of 79.6 kA / m was in the range of 29.0 to 31.0 Am ² / kg for all the magnetic toners.

[Examples 12 to 18]
When the image formation test and the fixing test were performed in the same manner as in Example 1 using the magnetic toners 17, 19, 22, 23, and 25 to 27, all of the images were of a level that is not a problem in practical use and excellent fixing. Had sex. The evaluation results are shown in Table 5.

[Comparative Example 6]
When an image forming test and a fixing test were performed using the magnetic toner 18, good fixability was obtained, but due to durability, the toner carrier was fused and fogging deteriorated. there were. The evaluation results are shown in Table 5.

[Comparative Example 7]
When an image forming test and a fixing test were performed using the magnetic toner 20, a good image was obtained, but the fixing start temperature was as high as 165 ° C., and the low temperature fixing property was inferior. The evaluation results are shown in Table 5.

[Comparative Example 8]
When the image forming test and the fixing test were performed using the magnetic toner 21, the fixing start temperature was as good as 130 ° C., but the high temperature offset resistance was poor and a sufficient fixing region could not be obtained. The evaluation results are shown in Table 5.

[Comparative Example 9]
When an image forming test and a fixing test were performed using the magnetic toner 24, a good image could be obtained, but the fixing start temperature was as high as 165 ° C., and the low temperature fixing property was inferior. The evaluation results are shown in Table 5.

  <Table 5: Test result 2>

An example of the flow curve obtained with a flow tester is shown. 1 shows an example of an image forming apparatus used in an embodiment of the present invention. It is an enlarged view of a developing unit.

Explanation of symbols

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

Claims (17)

A magnetic toner having at least a binder resin and a magnetic material and having a weight average particle diameter of 3 to 10 μm,
The magnetic material is obtained by surface-treating magnetic fine particles with a low softening point substance (A),
The compression ratio of the magnetic material obtained from the following formula (1) is 35 or more,
Compression rate = {1- (apparent density / tap density)} × 100 Formula (1)
The softening point Ts when the magnetic toner is measured with a flow tester is 40 to 85 ° C.,
A magnetic toner, wherein a resin component of the magnetic toner is insoluble in THF (tetrahydrofuran) in an amount of 1 to 60% by mass.   2. A ratio A (tap density of magnetic substance / tap density of magnetic fine particles) of a tap density of the magnetic substance and a tap density of the magnetic fine particles is 0.80 to 1.00. The toner described in 1.   The ratio A value (tap density of magnetic substance / tap density of magnetic fine particles) of the tap density of the magnetic substance and the tap density of the magnetic fine particles is 0.90 to 1.00. The toner described in 1.   The magnetic toner according to claim 1, wherein the low softening point substance (A) has an endothermic peak top at 80 ° C. to 150 ° C. in DSC measurement.   The said magnetic body is processed using the low softening point substance (A) of 0.3-15 mass parts with respect to 100 mass parts of magnetic fine particles, The Claim 1 thru | or 4 characterized by the above-mentioned. Magnetic toner.   6. The magnetic toner according to claim 1, wherein a softening point Ts when the magnetic toner is measured with a flow tester is 45 to 80 ° C. 6.   The magnetic toner according to claim 1, wherein a THF-insoluble content of the resin component of the magnetic toner is 10 to 55% by mass.   The magnetic toner according to claim 1, wherein the magnetic toner has an average circularity of 0.960 to 1.000.   The magnetic toner according to any one of claims 1 to 8, wherein the magnetic toner has a mode circularity of 0.99 to 1.00.   The magnetic material according to any one of claims 1 to 9, wherein the magnetic material is obtained by treating the surface of magnetic fine particles with a coupling agent and further treating with the low softening point substance (A). toner.   The magnetic toner according to claim 1, wherein the magnetic material has a compressibility of 38 or more.   The magnetic toner according to claim 1, wherein a liberation rate of the low softening point substance (A) in the magnetic material is 25% or less.   The magnetic toner according to claim 1, wherein a liberation rate of the low softening point substance (A) in the magnetic material is 15% or less.   In addition to the low softening point material (A) used for the surface treatment of the magnetic material, the magnetic toner has 1 to 20 parts by weight of the low softening point material (B) with respect to 100 parts by weight of the binder resin. The magnetic toner according to claim 1.   The magnetic toner according to claim 14, wherein the low softening point substance (B) has a peak top of an endothermic peak at 40 to 80 ° C. in DSC measurement.   16. The magnetic toner according to claim 1, wherein the magnetic toner has a coefficient of variation in number distribution of 40 or less. 16. The magnetic toner according to claim 1, wherein the magnetic toner has a coefficient of variation in number distribution of 30 or less.

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