JP5219682B2 - Magnetic carrier and two-component developer - Google Patents

Description

  The present invention relates to a magnetic carrier contained in a developer used for electrophotography and electrostatic recording, and a two-component developer having the magnetic carrier and a toner.

  Electrophotographic development methods include a one-component development method using only toner and a two-component development method using a mixture of toner and magnetic carrier. In the two-component development method, a magnetic carrier that is a charge imparting member and a toner are mixed and used as a two-component developer. The two-component developer has many opportunities for contact between the magnetic carrier, which is a charge imparting member, and the toner, is stable in charging characteristics, and is advantageous for maintaining high image quality. In addition, the magnetic carrier supplies toner to the development site, and its supply amount is large and easy to control, so it is often used especially for high-speed machines. In recent years, in order to apply an electrophotographic development method to print on demand (POD), it is essential to support three basic elements of printing: high speed, high image quality, and low running cost. Furthermore, when considering the application of a two-component developer to the POD market, it is possible to output an image with no image defects, high quality, and no change in color tone or density over a long period of time. Component developers are desired.

In order to suppress concentration fluctuation due to long-term use, a carrier having irregularities based on fine crystal particles on the surface of spherical ferrite particles has been proposed (for example, Patent Document 1). It is a carrier coated with a resin so that the convex part of the core is exposed, and is less dependent on the environment, so that fluctuations in image density can be reduced by long-term use. However, the apparent density of the carrier is as large as 2.66 g / cm ^3, and the stress received by the carrier increases in a high-speed development process corresponding to POD. In addition, since the coating resin layer is designed to be thin, the carrier may have a low resistance due to scraping of the coating resin. Further, since the coating resin is directly bonded to the spherical ferrite core, the adhesion between the coating resin and the core is insufficient, the coating resin is peeled off, and the carrier may have a low resistance. Due to the low resistance of the carrier, a charge injection phenomenon occurs from the developing sleeve to the electrostatic latent image carrier through the magnetic carrier, the latent image of the electrostatic latent image carrier is disturbed, and the halftone part is scratched. There was a case.

  On the other hand, in order to improve the stress resistance of the carrier, there has been proposed a resin-filled ferrite carrier that achieves low specific gravity and low magnetic force by filling a resin in the voids of the porous ferrite core (Patent Document 2). . Although low specific gravity and low magnetic force can improve the durability of the carrier and improve the image quality, it may have poor developability. The cause of the decrease in developability is due to a decrease in electrode effect due to the increased resistance of the carrier. As a result, the toner at the rear end of the halftone part is scraped off at the boundary between the halftone part and the solid part, resulting in white streaks, and an image defect in which the edge of the solid part is emphasized (hereinafter referred to as white spot) occurs. Sometimes. Further, in order to compensate for the lack of developability, if the development bias Vpp (peak-to-peak voltage), which is an alternating bias voltage, is set high, the lack of developability can be compensated. In some cases, an image defect phenomenon in which a pattern of spots or spots is generated. In general, when the toner flies from the carrier surface in the development process, a charge having the opposite polarity to the toner is generated on the surface of the carrier particle. This is referred to as counter charge. However, when the resistance of the carrier is increased, the counter charge accumulated in the magnetic carrier particles is less likely to move to the developer carrier. As a result, the counter charge remaining on the surface of the magnetic carrier particles and the charge of the toner attract each other, resulting in a large adhesion force, making it difficult for the toner to fly from the carrier particles and lowering the image density.

  As described above, methods for improving the stability and stress resistance of the two-component developer have been studied. However, the developer and durability stability are satisfied, and a high-quality image free from image defects is provided over a long period of time. Two-component developers have not yet been obtained.

JP-A-4-93954 Patent 4001606

  An object of the present invention is to provide a magnetic carrier and a two-component developer that have solved the above problems.

  Another object of the present invention is to provide a magnetic carrier and a two-component developer that have excellent developability and can obtain a high-quality image free from image defects over a long period of time.

  That is, an object of the present invention is to provide a magnetic carrier and a two-component developer that are excellent in developability, have little fluctuation in image density, and can obtain an image free from image defects such as white spots and carrier adhesion. It is in.

  As a result of intensive studies, the inventors of the present invention have used a magnetic carrier and a two-component developer described below, which are excellent in developability and capable of obtaining a high-quality image free from image defects over a long period of time. It has been found that a component developer can be obtained.

  The above object is achieved by using the magnetic carrier and the two-component developer described below.

That is, a magnetic carrier having magnetic carrier particles containing at least porous magnetic ferrite core particles and a resin,
The area of the resin portion on the projection surface of the reflected electron image of the magnetic carrier particles photographed at an acceleration voltage of 2.0 kV using a scanning electron microscope is 92.0 area% or more with respect to the magnetic carrier particle projection surface. 99.5 area% or less,
Wherein the porous electric field intensity just before the break-down of the magnetic ferrite core particles state, and are less 300 V / cm or more 1388 V / cm,
On the projection plane of the reflected electron image of the magnetic carrier particles, the average area value of the portion derived from the metal oxide, related to the magnetic carrier, wherein at 0.45 [mu] m ² or more 1.40 .mu.m ² or less.

Furthermore, the present invention is, at least a portion of the voids of the porous magnetic core particles, relates to magnetic carrier resin is characterized Tei Rukoto filled.

Further, in the present invention, the magnetic carrier particles are filled with the first resin in at least a part of the voids of the porous magnetic core particles, and the surface thereof is the same as the first resin. Further, the present invention relates to a magnetic carrier characterized by being coated with a second resin which may be different from each other .

  Furthermore, the present invention relates to a two-component developer containing at least the magnetic carrier and a toner.

  Further, according to the present invention, the toner has an equivalent circle diameter of 0.500 μm or more measured by a flow type particle image measuring apparatus having an image processing resolution of 512 × 512 pixels (0.37 μm × 0.37 μm per pixel). The present invention relates to a two-component developer characterized in that particles having a particle size of 985 μm or less are 30% by number or less.

Furthermore, the present invention, the toner is about two-component developer which is characterized by containing inorganic particles having an extremely Daine to 300nm below the range of 50nm in the particle size distribution of number distribution criteria.

  By using the magnetic carrier and the two-component developer of the present invention, it is possible to obtain a high-quality image with excellent developability and no image defects over a long period of time.

  That is, it is possible to provide a magnetic carrier and a two-component developer that are excellent in developability, have little fluctuation in image density, and can obtain an image free from image defects such as white spots and carrier adhesion.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  The magnetic carrier of the present invention is a magnetic carrier having magnetic carrier particles containing at least porous magnetic core particles and a resin, and the reflection of the magnetic carrier particles taken by a scanning electron microscope with an acceleration voltage of 2.0 kV. The area of the resin portion on the projection plane of the electronic image is 92.0 area% or more and 99.5 area% or less with respect to the projection plane of the magnetic carrier particles, and is about to break down the porous magnetic core particles. The magnetic carrier has a field strength of 300 V / cm or more and 1500 V / cm or less.

  In the magnetic carrier of the present invention, the insulating resin portion is optimally distributed on the surface of the magnetic carrier particle containing at least the porous magnetic core particle and the resin, and the electric field strength just before the breakdown of the porous magnetic core particle is defined. It is what. By adjusting to the range specified in the present invention, it was possible to obtain a magnetic carrier having both high charge imparting ability and high developability. Since high developability is obtained, development can be performed by setting the development bias, which is an alternating bias voltage, to a lower Vpp (peak-to-peak voltage) than before, and a ring-like or spot-like pattern that is problematic at high Vpp. It is possible to suppress the occurrence of image defects that cause the occurrence of image defects. In addition, even with continuous use, the image density is maintained, the amount of change in charge is small, and an image free from image defects such as leakage and fog can be obtained.

  Usually, in order to increase the charge imparting ability, the resin composition on the surface of the magnetic carrier related to charge imparting is optimized, the resin ratio is increased, the resistance of the magnetic carrier is increased, or a charge control material is added to the resin component. Etc. are taken. However, as the charge imparting ability is increased, the adhesion between the toner and the magnetic carrier increases. As a result, the toner becomes difficult to fly, the developability is lowered, and the required image density may not be obtained. Therefore, in order to ensure high developability, the resistance of the magnetic carrier is lowered. By reducing the resistance of the magnetic carrier, the developability can be improved by the electrode effect of the magnetic brush on the developer carrying member. Lowering the resistance of the magnetic carrier advantageously works to improve developability, but leads to a decrease in charge imparting ability and makes it difficult to achieve both the charge imparting ability. Further, a magnetic carrier having high developability capable of developing at a low Vpp is more preferable because it does not cause an image defect phenomenon in which a ring-like or spot-like pattern is generated on a recording paper that occurs under a high Vpp developing condition.

  Therefore, it is important to achieve both high charge imparting ability and high developability.

  The magnetic carrier of the present invention is a carrier having high developability that enables development at a lower Vpp than before while having high charge imparting ability.

  It is presumed that the magnetic carrier behaves transiently as a low-resistance magnetic carrier during development, expresses high developability, and has a sufficient charge-providing ability while maintaining a certain level of resistance before and after development. In order to achieve both high chargeability and high developability, the inventors have found that there is a relationship between the resin area% on the surface of the magnetic carrier and the electric field strength just before the breakdown of the porous magnetic core.

  The reason why the magnetic carrier of the present invention exhibits such an excellent effect is not clear, but the present inventors consider as follows.

  In the magnetic carrier of the present invention, the area of the resin portion on the projection surface of the reflected electron image of the acceleration voltage of 2.0 kV photographed by the scanning electron microscope of the magnetic carrier particle is 92 with respect to the projection surface of the magnetic carrier particle. It is 0.0 area% or more and 99.5 area% or less, preferably 94.5 area% or more and 98.0 area% or less.

  When the area of the resin part is 92.0 area% or more and 99.5 area% or less on the projected surface of the reflected electron image with an acceleration voltage of 2.0 kV, the resin part that is insulative and participates in charging is applied to the surface of the magnetic carrier particle. It exists optimally, provides high charge imparting ability, and does not cause image defects such as toner scattering and fogging.

  However, when the area of the resin portion on the projection surface of the reflected electron image with an acceleration voltage of 2.0 kV is smaller than 92.0 area%, the magnetic carrier has a low resistance, and charge injection into the electrostatic latent image carrier causes The electrostatic latent image may be disturbed, resulting in an image with a halftone portion. In addition, the charge amount is insufficient, and an image with gradation can be written or toner scattering may occur.

  On the other hand, if the area of the resin part exceeds 99.5% by area on the projection surface of the reflected electron image with an acceleration voltage of 2.0 kV, the charge amount becomes too large or the charge is increased, so Since the electric adhesion force increases, the image density may decrease.

  In the magnetic carrier of the present invention, the electric field strength immediately before breakdown of the porous magnetic core particles is 300 V / cm or more and 1500 V / cm or less. When the electric field strength just before breakdown of the porous magnetic core particles is 300 V / cm or more and 1500 V / cm or less, it becomes a magnetic carrier having high developability capable of developing at low Vpp, and at the same time, an image such as white spots It became possible to improve the defects.

  Normally, when the toner flies from the magnetic carrier particles during development, a counter charge is generated on the surface of the magnetic carrier particles. As the counter charge accumulates, the adhesion between the toner and the magnetic carrier particles increases, and the image density decreases. Further, the counter charge acts as a force that pulls the toner once developed on the electrostatic latent image carrier to the magnetic carrier side, and thus may cause white spots.

  Therefore, it is necessary to quickly attenuate the countercharge generated on the surface of the magnetic carrier particles.

  The magnetic carrier of the present invention exhibits high developability even when the electric field strength just before breakdown of the porous magnetic core particles is 300 V / cm or more and 1500 V / cm or less, while exhibiting high developability. The effect of improvement was recognized. Although details of the breakdown in the present invention will be described later, it is defined that an overcurrent flows when an electric field strength of a certain level or more is applied to the porous magnetic core particles. If the porous magnetic core particles are considered to have a low resistance at a stroke when an electric field strength of a certain level or more is applied, the magnetic carrier comprising the porous magnetic core particles of the present invention is developed at the time of development to which a high development electric field is applied. It is presumed that the resistance was lowered transiently. Because the counter charge was smoothly leaked to the developer carrier through the low-resistance magnetic carrier particles, it had high developability while having a high charge amount, and white spot was improved by quick decay of the counter charge. Conceivable.

  If the electric field strength just before the breakdown is less than 300 V / cm, there may be a problem that charge injection occurs and a pinhole is opened in the electrostatic latent image carrier. Further, the toner cannot be sufficiently charged, and image defects such as fogging occur.

  When the electric field strength just before the breakdown exceeds 1500 V / cm, the counter charge on the surface of the magnetic carrier particles is not sufficiently attenuated, and white spots occur or carrier adhesion occurs.

  The resin portion of the present invention is a portion having low brightness (appears dark and black on the image) in an image (FIG. 1) obtained by visualizing mainly reflected electrons taken under a predetermined acceleration voltage by a scanning electron microscope. It points to that. The scanning electron microscope is a device that visualizes the surface and composition information of a sample by irradiating the sample with an accelerated electron beam and detecting secondary electrons and reflected electrons emitted from the sample. In observation with a scanning electron microscope, it is known that the amount of reflected electrons emitted is larger for heavy elements. For example, in the case of a sample in which an organic compound and iron are distributed on a plane, the amount of reflected electrons emitted from the iron is large, so that the iron portion appears bright (high brightness, white) on the image. On the other hand, since the amount of reflected electrons from the organic compound composed of light elements is not large, it appears dark (low brightness and black) on the image.

  In the sample in which the resin portion which is an organic compound and the porous magnetic core portion which is a metal oxide are present as in the magnetic carrier particle surface of the present invention, the resin portion is dark and the metal oxide portion is bright. Obtained as a projected image with a large contrast difference. FIG. 2 schematically shows the distribution of the metal oxide portion and the resin portion on the surface of the magnetic carrier in FIG.

  In the present invention, first, magnetic carrier particles are extracted from the projected image of the magnetic carrier in FIG. 1 to determine the area of the magnetic carrier particles. In FIG. 5, white portions are portions extracted as magnetic carrier particle portions from the projected image of FIG. 1. Subsequently, on the projected image of the magnetic carrier particle part in FIG. 1, the part excluding the white part is the resin part (FIG. 4). In the present invention, in FIG. 4, the area of the magnetic carrier particle part is the area of the part excluding the white part, and the area of the resin part is the area difference. The area of the magnetic carrier particles and the area of the resin portion are respectively obtained by image processing, and the ratio of the area of the resin portion to the area of the magnetic carrier particles is calculated. Details of observation conditions, imaging conditions, and image processing procedures using an electron microscope will be described later. In fact, it can be confirmed with an elemental analyzer attached to the electron microscope that the low luminance portion is a resin portion.

The breakdown will be described. In the specific resistance measurement using the apparatus schematically shown in FIG. 3, an electrometer (for example, Kessley 6517A manufactured by Kessley) is used with an electrode area of 2.4 cm ² and a magnetic carrier thickness of about 1.0 mm. Screening is performed by applying a voltage of 1V, 2V, 4V, 8V, 16V, 32V, 64V, 128V, 256V, 512V, and 1000V for 1 second at a maximum applied voltage of 1000V using the auto range function of the electrometer. At that time, the electrometer determines whether or not up to 1000 V can be applied, and when an overcurrent flows, “VOLTAGE SOURCE OPARATE” flashes. Then, the applied voltage is lowered, the applicable voltage is further screened, and the maximum value of the applied voltage is automatically determined. Then, this measurement is performed. The resistance value is measured from the current value after holding the voltage obtained by dividing the maximum voltage value into five steps for 30 seconds.

  A porous magnetic core used in Example 1 described later will be described as an example. Table 1 shows the results of measuring the porous magnetic core.

  In the table, the applied voltage (V), the electric field strength (V / cm) obtained by dividing the applied voltage by the sample thickness d, and the specific resistance (Ω · cm) at that time are shown. A graph shown in FIG. 4 is obtained by plotting the sixth and subsequent steps in the table by the electric field strength and the specific resistance. In the graph, the point of 669 V / cm when 68.2 V is applied to the porous magnetic core 1 is defined as the electric field strength just before breakdown. At the time of screening, the voltage values determined to be able to be applied to 17.1V, 34.1V, 51.2V, 68.2V, 85.3V and a maximum of 85.3V. At 85.3V, an overcurrent flowed. In the present invention, it is defined as a breakdown that the resistance cannot be measured at a voltage of 85.3 V or more and the measured value becomes zero. Further, the electric field strength just before breakdown is defined as the electric field strength value at which “VOLTAG SOURCE OVERRATE” blinks or the maximum electric field strength value plotted on the specific resistance.

Further, in the magnetic carrier of the present invention, the average area value of the portion derived from the metal oxide on the projection plane of the reflected electron image at an acceleration voltage of 2.0kV is, is a 0.45 [mu] m ² or more 1.40 .mu.m ² or less, more preferably, it is 0.70 .mu.m ² or more 1.00 .mu.m ² or less. Average area value of the portion derived from the metal oxide on the projection plane of the reflected electron image at an acceleration voltage of 2.0kV is, in the case of 0.45 [mu] m ² or more 1.40 .mu.m ² or less, thereby improving the developing property.

  The two-component developer forms magnetic spikes on the developer carrier, but the average area value of the portion derived from the metal oxide on the projected surface of the reflected electron image with an acceleration voltage of 2.0 kV is within the scope of the present invention. Thus, it is presumed that the magnetic carrier particles can have contacts through the metal oxide portion. It is considered that a conduction path from the surface of the magnetic carrier particle at the tip of the magnetic spike to the developer carrier is secured, and the counter charge on the surface of the magnetic carrier particle generated during development is easily attenuated. As a result, it is considered that the toner separation from the magnetic carrier is improved. In addition, image defects such as white spots are less likely to occur. In addition, although the detail of the measuring method of the average area value of the part originating in a metal oxide on the projection surface of the reflected electron image of acceleration voltage 2.0kV is mentioned later, the projection surface of the reflection electron image of acceleration voltage 2.0kV is used. It can be obtained by image processing.

  There are various methods for controlling the presence of the resin on the surface of the magnetic carrier particles, such as the composition and filling amount of the resin contained in the porous magnetic ferrite particles, the filling method, the composition of the coating resin, the amount of the coating resin, and the coating method. Can be adjusted. It is possible to control the presence of the core and the presence of the resin by filling and coating multiple times with filling resin solutions and coating resin solutions with different solid content concentrations, and adjusting the viscosity of the resin solution being processed. it can.

  The porous magnetic ferrite particles are structurally easy to control the presence of the resin on the surface of the magnetic carrier particles.

  The method for controlling the breakdown voltage of the porous magnetic ferrite particles can be controlled by controlling the internal structure according to the raw material composition, raw material particle size, pretreatment conditions, firing conditions, and posttreatment conditions.

  The porous magnetic core particle of the present invention can be produced by the following steps.

  Examples of the material for the porous magnetic core particles include the following. 1) Iron powder with oxidized surface 2) Unoxidized iron powder 3) Metal particles such as lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium and rare earth elements 4) Iron, lithium Alloy particles of metals such as calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium and rare earth elements, or oxide particles containing these elements, 5) magnetite particles or ferrite particles.

A ferrite particle is a sintered body represented by the following formula.
(M1 ₂ O) _u (M2O) _v (M3 ₂ O ₃ ) _w (M4O ₂ ) _x (M5 ₂ O ₅ ) _y (Fe ₂ O ₃ ) _z
(In the formula, M1 is monovalent, M2 is divalent, M3 is trivalent, M4 is tetravalent, M5 is pentavalent metal, and u, v, w, x, and x when u + v + w + x + y + z = 1.0. y is 0 <(u, v, w, x, y) ≦ 0.8, respectively, and z is 0.2 <z <1.0.)

In the above formula, M1 to M5 are at least Li, Fe, Zn, Ni, Mn, Mg, Co, Cu, Ba, Sr, Ca, Si, V, Bi, In, Ta, Zr, B, One or more selected from the group consisting of Mo, Na, Sn, Ti, Cr, Al, Sc, Y, La, Ce, Pr, NdSm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu Represents a metal element. For example, magnetic Li-based ferrite (for example, (Li ₂ O) _a (Fe ₂ O ₃ ) _b (0.0 <a <0.4, 0.6 ≦ b <1.0, a + b = 1)), Mn based ferrite (for example, (MnO) _a (Fe ₂ O ₃ ) _b (0.0 <a <0.5, 0.5 ≦ b <1.0, a + b = 1)), Mn—Mg based ferrite ( For example, (MnO) _a (MgO) _b (Fe ₂ O ₃ ) _c (0.0 <a <0.5, 0.0 <b <0.5, 0.5 ≦ c <1.0, a + b + c = 1)), Mn—Mg—Sr ferrite (for example, (MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d (0.0 <a <0.5, 0.0 <b < 0.5, 0.0 <c <0.5, 0.5 ≦ d <1.0, a + b + c + d = 1), Cu—Zn ferrite (for example, (CuO) _a (ZnO) _b (Fe ₂ O ₃ ) _c (0. <A <0.5, 0.0 <b <0.5, 0.5 ≦ c <1.0, a + b + c = 1) The above ferrite represents the main element, and other trace metals are used. It contains what it contains.

  From the viewpoint of easy control of crystal growth rate, Mn-based ferrite, Mn-Mg-based ferrite, and Mn-Mg-Sr-based ferrite containing Mn element are preferable.

  Below, the manufacturing process in the case of using a ferrite particle as a porous magnetic carrier particle is demonstrated in detail.

Process 1 (weighing / mixing process):
The ferrite raw materials are weighed and mixed.

  Examples of the ferrite raw material include the following. Li, Fe, Zn, Ni, Mn, Mg, Co, Cu, Ba, Sr, Y, Ca, Si, V, Bi, In, Ta, Zr, B, Mo, Na, Sn, Ti, Cr, Al, Rare earth metal particles, oxides, hydroxides, oxalates, carbonates.

  Examples of the mixing apparatus include the following. Ball mill, planetary mill, Giotto mill, vibration mill. A ball mill is particularly preferable from the viewpoint of mixing properties. Specifically, a weighed ferrite raw material and balls are placed in a ball mill, and pulverized and mixed for 0.1 to 20.0 hours.

Step 2 (temporary firing step):
The ferrite raw material thus pulverized and mixed is calcined in the atmosphere at a firing temperature of 700 ° C. or higher and 1000 ° C. or lower for 0.5 hour or more and 5.0 hours or less to form a ferrite. For firing, for example, the following furnace is used. Burner type incinerator, rotary type incinerator, electric furnace.

Step 3 (grinding step):
The calcined ferrite produced in step 2 is pulverized with a pulverizer.

  The pulverizer is not particularly limited as long as a desired particle size can be obtained. Examples include the following. Crusher, hammer mill, ball mill, bead mill, planetary mill, Giotto mill.

  The volume-based 50% particle size (D50) of the calcined ferrite finely pulverized product is preferably 0.5 μm or more and 5.0 μm or less.

  In order to make the finely pulverized ferrite product have the above particle size, for example, it is preferable to control the material, particle size, and operation time of balls and beads used in a ball mill and a bead mill. The particle size of the ball or bead is not particularly limited as long as a desired particle size / distribution is obtained. For example, a ball having a diameter of φ5 mm or more and φ60 mm is preferably used. Further, beads having a diameter of φ0.03 mm or more and less than φ5 mm are preferably used. Further, in the ball mill and the bead mill, the wet type is higher than the dry type in that the pulverized product does not rise in the mill and the pulverization efficiency is high. For this reason, the wet type is more preferable than the dry type.

Process 4 (granulation process):
Water, a binder, and, if necessary, a gap adjusting agent are added to the pulverized product of calcined ferrite. Examples of the gap adjusting agent include a foaming agent and resin fine particles.

  Examples of the foaming agent include sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, ammonium hydrogen carbonate, sodium carbonate, potassium carbonate, lithium carbonate, and ammonium carbonate.

  Examples of resin fine particles include polyester, polystyrene, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, and styrene-α-chloromethacrylic acid. Styrene copolymers such as acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Polyvinyl chloride, phenolic resin, modified phenolic resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin; aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol and Polyester resin having monomers selected from phenols as structural units; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, hybrid resin having polyester unit and vinyl polymer unit Fine particles.

  For example, polyvinyl alcohol is used as the binder.

  The obtained ferrite slurry is dried and granulated using a spray dryer in a heated atmosphere of 100 ° C. or higher and 200 ° C. or lower. The spray dryer is not particularly limited as long as a desired porous magnetic core particle size can be obtained. For example, a spray dryer can be used.

Process 5 (main baking process):
Next, the granulated product is fired at 800 ° C. to 1400 ° C. for 1 hour to 24 hours.

  By increasing the firing temperature or increasing the firing time, firing proceeds, and as a result, the void volume inside the porous magnetic core particles decreases. Moreover, the specific resistance of the porous magnetic carrier core particles can be adjusted to a preferable range by controlling the firing atmosphere. For example, the specific resistance of the porous magnetic core particles can be lowered by lowering the oxygen concentration or reducing atmosphere (in the presence of hydrogen).

Process 6 (screening process):
After pulverizing the particles fired as described above, coarse particles and fine particles may be removed by classification or sieving as necessary.

  The volume distribution reference 50% particle diameter (D50) of the porous magnetic core particles is more preferably 18.0 μm or more and 68.0 μm or less in order to prevent carrier adhesion to the image and the suppression of roughness.

  Furthermore, the magnetic carrier particles of the present invention are preferably magnetic carriers in which at least a part of the voids of the porous magnetic core particles is filled with a resin.

  The porous magnetic core particles may have a low physical strength depending on the internal void volume, and in order to increase the physical strength as the magnetic carrier particles, at least a part of the voids of the porous magnetic core particles may contain a resin. Filling is preferred. The amount of the resin filled with the magnetic carrier particles of the present invention is preferably 6% by mass or more and 25% by mass or less with respect to the porous magnetic core particles. If there is little variation in the resin content for each magnetic carrier particle, even if the resin is filled only in a part of the internal voids, the resin is filled only in the voids near the surface of the porous magnetic core particles, and the voids are formed inside. Even if it remains, the internal space may be completely filled with resin.

  The specific filling method is not particularly limited, but as a method of filling the voids in the porous magnetic core particles with resin, porous magnetic cores can be formed by a coating method such as dipping, spraying, brushing, and fluidized bed. A method of impregnating the core particles into the resin solution and then volatilizing the solvent can be mentioned. A method of filling a void of porous magnetic core particles with a resin solution in which a resin and a solvent are mixed is preferable. As a method for filling the voids in the porous magnetic core particles with the resin, a method in which the resin is diluted with a solvent and added to the voids in the porous magnetic core particles can be employed. The solvent used here should just be what can melt | dissolve resin. When the resin is soluble in an organic solvent, examples of the organic solvent include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. In the case of a water-soluble resin or an emulsion type resin, water may be used as a solvent.

  The resin that fills the voids of the porous magnetic core particles is not particularly limited, and either a thermoplastic resin or a thermosetting resin may be used. It is preferable that the resin has a high affinity for the porous magnetic core particles. When a resin having a high affinity is used, the surface of the porous magnetic core particles is simultaneously filled with the resin in the voids of the porous magnetic core particles. It becomes easy to cover with resin.

  As the resin to be filled, examples of the thermoplastic resin include the following. Polystyrene, polymethyl methacrylate, styrene-acrylic resin; styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, polyvinylpyrrolidone, petroleum Resin, novolak resin, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, polyarylate, polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, polyetherketone resin.

  Moreover, the following are mentioned as said thermosetting resin. Phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy resin, unsaturated polyester obtained by polycondensation of maleic anhydride, terephthalic acid and polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin , Toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, polyimide, polyamideimide resin, polyetherimide resin, polyurethane resin.

  Further, a resin obtained by modifying these resins may be used. Of these, fluorine-containing resins such as polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, or solvent-soluble perfluorocarbon resin, acrylic-modified silicone resin, or silicone resin are preferable because of their high affinity for porous magnetic core particles.

  Among the above resins, a thermosetting resin is preferable because the strength of the magnetic carrier can be increased. Among these, a silicone resin is preferable because it can reduce the adhesion between the magnetic carrier particles and the toner and improve developability.

  For example, the following are mentioned as a commercial item. For straight silicone resins, KR271, KR255, KR152 manufactured by Shin-Etsu Chemical Co., Ltd., SR2400, SR2405, SR2410, SR2411 manufactured by Toray Dow Corning Co., Ltd. are used. Among the modified silicone resins, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified), SR2110 (alkyd) manufactured by Toray Dow Corning Co., Ltd. Denatured).

  The amount of the resin solid content in the resin solution is preferably 1% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 30% by mass or less. When a resin solution having a resin amount larger than 50% by mass is used, the resin solution is difficult to uniformly penetrate into the voids of the porous magnetic core particles because of its high viscosity. Further, if the amount is less than 1% by mass, the amount of resin is small, and the adhesion force of the resin to the porous magnetic core particles may be low.

The solvent used for the filling resin solution is preferably toluene, and the viscosity of the resin in a 20% by weight toluene solution is 1.0 × 10 ⁻⁶ m ² / s or more and 1.0 × 10 ⁻³ m ² / s or less. Is more preferable because it is easily filled.

  The magnetic carrier of the present invention more preferably covers the surface with a resin after filling the voids of the porous magnetic core particles with the resin.

  Covering the surfaces of the magnetic carrier particles with a resin is more preferable because the ratio of the resin portion and the average area of the metal oxide portion can be controlled more precisely. In addition, the surface is coated with a resin in order to control the releasability of the toner from the surface of the magnetic carrier particles, the contamination of the toner and external additives on the surface of the magnetic carrier particles, the ability to impart charge to the toner, and the magnetic carrier resistance. It is preferable to do.

  The method for coating the surface of the magnetic carrier particles with a resin is not particularly limited, and examples thereof include a coating method such as a dipping method, a spray method, a brush coating method, a dry method, and a fluidized bed. Among these, the dipping method is more preferable from the viewpoint of controlling the ratio of the resin portion on the surface of the magnetic carrier particles and controlling the average area of the portion derived from the metal oxide.

  The amount of the resin to be coated is 0.1 parts by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the porous magnetic core particles in controlling the ratio of the resin part on the surface of the magnetic carrier particles. preferable.

  The resin to be coated can be used alone or in combination. The resin to be coated may be the same as or different from the resin used for filling, and may be a thermoplastic resin or a thermosetting resin. In addition, a curing agent or the like can be mixed with a thermoplastic resin and cured for use. In particular, it is preferable to use a resin having higher releasability.

  The following are mentioned as said thermoplastic resin. Polystyrene, polymethyl methacrylate, styrene-acrylic resin; styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, polyvinylpyrrolidone, petroleum Resin, novolak resin, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, polyarylate, polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, polyetherketone resin.

  The following are mentioned as said thermosetting resin. Phenolic resin, modified phenolic resin, maleic resin, alkyd resin, epoxy resin, unsaturated polyester obtained by polycondensation of maleic anhydride, terephthalic acid and polyhydric alcohol, urea resin, melamine resin, urea-melamine resin, xylene resin , Toluene resin, guanamine resin, melamine-guanamine resin, acetoguanamine resin, gliptal resin, furan resin, silicone resin, polyimide, polyamideimide resin, polyetherimide resin, polyurethane resin.

  Further, a resin obtained by modifying these resins may be used. Examples of resins obtained by modifying these resins include the following. Fluorine-containing resins such as polyvinylidene fluoride resins, fluorocarbon resins, perfluorocarbon resins or solvent-soluble perfluorocarbon resins, and acrylic-modified silicone resins.

  Of the above-described resins, silicone resins are particularly preferable. As the silicone resin, conventionally known silicone resins can be used.

  For example, the following are mentioned as a commercial item. For straight silicone resins, KR271, KR255, KR152 manufactured by Shin-Etsu Chemical Co., Ltd., SR2400, SR2405, SR2410, SR2411 manufactured by Toray Dow Corning Co., Ltd. are used. Among the modified silicone resins, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified), SR2110 (alkyd) manufactured by Toray Dow Corning Co., Ltd. Denatured).

  Further, the resin may contain conductive particles or charge controllable particles. Examples of the conductive particles include carbon black, magnetite, graphite, zinc oxide, and tin oxide.

  The particles having charge controllability include organometallic complex particles, organometallic salt particles, chelate compound particles, monoazo metal complex particles, acetylacetone metal complex particles, hydroxycarboxylic acid metal complex particles, and polycarboxylic acid. Metal complex particles, polyol metal complex particles, polymethyl methacrylate resin particles, polystyrene resin particles, melamine resin particles, phenol resin particles, nylon resin particles, silica particles, titanium oxide particles, alumina particles Etc.

  The magnetic carrier of the present invention has a volume distribution standard 50% particle size (D50) of 20.0 μm or more and 70.0 μm or less, which suppresses carrier adhesion and toner spent, and is stable even for long-term use. Can be used.

The magnetic carrier of the present invention has a magnetization strength at 1000 / 4π (kA / m) of 40 Am ² / kg or more and 65 Am ² / kg or less, which improves dot reproducibility and prevents carrier adhesion. It is also preferable for obtaining a stable image by preventing toner spent.

The magnetic carrier of the present invention preferably has a true specific gravity of 3.2 g / cm ³ or more and 5.0 g / cm ³ or less in order to prevent toner spent and maintain a stable image over a long period of time. More preferably, it is 3.4 g / cm ³ or more and 4.2 g / cm ³ or less, which prevents carrier adhesion and is more excellent in durability.

  In the present invention, it is preferable to use a two-component developer containing at least the magnetic carrier and toner because a high-quality image can be obtained.

  The toner used in the two-component developer of the present invention will be described.

  The toner used in the present invention has an equivalent circle diameter of 0.500 μm or more and 1.985 μm or less measured by a flow type particle image measuring apparatus having an image processing resolution of 512 × 512 pixels (0.37 μm × 0.37 μm per pixel). It is preferable that a certain particle (hereinafter also referred to as small particle toner) is 30% by number or less.

  The proportion of the small particle toner is more preferably 20% by number or less, still more preferably 10% by number or less, and the amount of the small particle toner is preferably smaller. When the ratio of the small particle toner is 30% by number or less, the mixing property of the developer and the toner in the developing device is good and the adhesion of the small particle toner to the magnetic carrier particles can be reduced. Thus, the charging stability at the time of toner replenishment can be maintained.

  This is because the use of the magnetic carrier can reduce the stress between the toner and the magnetic carrier particles in the developing device, thereby further suppressing the adhesion of the small particle toner to the magnetic carrier particles. For this reason, it is possible to maintain the charging stability during toner replenishment over a long period of time, and the occurrence of image defects such as fogging can be suppressed.

  Furthermore, the weight average diameter (D4) of the toner used in the present invention is preferably 3.0 μm or more and 8.0 μm or less.

  When the weight average diameter of the toner is larger than 8.0 μm, the releasability between the toner and the magnetic carrier becomes too high, so that the developer slips on the developer carrier and easily causes poor conveyance. There is a case. Further, when the weight average diameter of the toner is less than 3.0 μm, the developability may be deteriorated because the adhesive force between the toner and the magnetic carrier particles is too high.

  As the toner of the present invention, a toner having toner particles containing a binder resin and a colorant is used.

  Examples of the binder resin contained in the toner include the following. Polyester, polystyrene; polymer of styrene derivatives such as poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic Acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrene copolymers such as styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenol resin, modified phenol resin, maleic resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin; Polyester resin having as a structural unit a monomer selected from aliphatic polyhydric alcohol, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, aromatic dialcohol and diphenol; polyurethane resin, polyamide resin, polyvinyl butyral, terpene resin, A hybrid resin having coumarone indene resin, petroleum resin, polyester unit and vinyl polymer unit.

  The polyester resin used in the present invention is obtained by condensation polymerization of an alcohol monomer and a carboxylic acid monomer.

The following are mentioned as an alcohol monomer.
Polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2. 0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6) alkylene oxide adducts of bisphenol A such as -2,2-bis (4-hydroxyphenyl) propane, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1 , 4-butanediol, neopentyl glycol, 1,4-butenediol 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A, sorbitol, 1,2 , 3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropane Triol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene.

The following are mentioned as a carboxylic acid monomer.
Aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid or their anhydrides; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid or their anhydrides; alkyl group or alkenyl having 6 to 18 carbon atoms Group-substituted succinic acid or anhydride; unsaturated dicarboxylic acids such as fumaric acid, maleic acid and citraconic acid or anhydrides thereof.

Moreover, the following are mentioned as another monomer.
Glycerin, sorbit, sorbitan, and polyhydric alcohols such as oxyalkylene ethers of novolac-type phenol resins; polyhydric carboxylic acids such as trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid and anhydrides thereof.

  Among these, in particular, a bisphenol derivative represented by the following general formula (1) is a dihydric alcohol monomer component, and a carboxylic acid component comprising a divalent or higher carboxylic acid or an acid anhydride thereof, or a lower alkyl ester thereof ( For example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) are used as acid monomer components, and resins obtained by condensation polymerization with these polyester unit components have good charging characteristics. Therefore, it is preferable.

（式中、Ｒはエチレン又はプロピレン基を示し、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乃至１０である。）

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

  Examples of monomers used for vinyl resins such as polystyrene and styrene derivatives include the following.

  Styrene; o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert- Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-crawler styrene, 3, Styrene and its derivatives such as 4-dicroller styrene, m-nitrostyrene, o-nitrostyrene, p-nitrostyrene; styrene unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; unsaturated such as butadiene and isoprene Polyenes; vinyl chloride, vinylidene chloride, vinyl bromide Vinyl halides such as vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacryl Α-methylene aliphatic monocarboxylic acid esters such as n-octyl acid, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate; methyl acrylate; Ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, acrylic Acid 2-crawler ethyl, acrylic esters such as phenyl acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone; N -N-vinyl compounds such as vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide.

  The hybrid resin used in the present invention means a resin in which a polyester unit and a vinyl polymer unit are chemically bonded. Specifically, a polyester unit and a vinyl polymer unit obtained by polymerizing a monomer having a carboxylic acid ester group such as (meth) acrylic acid ester may be formed by a transesterification reaction. Monomers that undergo both addition polymerization and condensation polymerization reactions having at least a double bond and a carboxyl group (for example, unsaturated dibasic compounds such as maleic acid, citraconic acid, itaconic acid, alkenyl succinic acid, fumaric acid, and mesaconic acid) Acid; an unsaturated dibasic acid anhydride such as maleic acid anhydride, citraconic acid anhydride, itaconic acid anhydride, alkenyl succinic acid anhydride), and a vinyl polymerization monomer is added and polymerized. It may be a dish.

  The binder resin used in the present invention has a molecular weight distribution peak molecular weight (Mp) of 2,000 to 50,000, as measured by gel permeation chromatography (GPC), in order to achieve both toner storage stability and low-temperature fixability. It is preferable that the number average molecular weight (Mn) is 1500 or more and 30000 or less, the weight average molecular weight (Mw) is 2000 or more and 1000000 or less, and the glass transition point (Tg) is 40 ° C. or more and 80 ° C. or less.

  Examples of the colorant contained in the toner of the present invention include the following.

  Examples of the black colorant include carbon black; a magnetic material; a black colorant using a yellow colorant, a magenta colorant, and a cyan colorant.

  As the colorant, a pigment may be used alone, but it is more preferable from the viewpoint of the image quality of a full-color image to improve the sharpness by using a dye and a pigment together.

  Examples of the color pigment for magenta toner include the following. C. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269; I. Pigment violet 19; C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35.

  Examples of the magenta toner dye include the following. C. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; I. Disper thread 9; I. Solvent violet 8, 13, 14, 21, 27; C.I. I. Oil-soluble dyes such as Disper Violet 1; I. B. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; I. Basic dyes such as Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

  Examples of the color pigment for cyan toner include the following. C. I. Pigment blue 2, 3, 15: 3, 15: 4, 16, 17; I. Bat Blue 6; C.I. I. Acid Blue 45, a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on the phthalocyanine skeleton.

  Examples of the coloring dye for cyan include C.I. I. There is Solvent Blue 70.

  Examples of the color pigment for yellow include the following. C. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; I. Bat yellow 1, 3, 20

  Examples of the coloring dye for yellow include C.I. I. There is Solvent Yellow 162.

  The amount of the colorant used is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, most preferably 100 parts by mass of the binder resin. 3 parts by mass or more and 15 parts by mass or less.

  The wax is preferably used in an amount of 0.5 to 20 parts by mass per 100 parts by mass of the binder resin. Preferably they are 2 to 8 mass parts. The peak temperature of the maximum endothermic peak of the wax is preferably 45 ° C. or higher and 140 ° C. or lower. It is preferable because both the storage stability of the toner and the hot offset property can be achieved.

  Examples of the wax include the following. Low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymer, hydrocarbon wax such as microcrystalline wax, paraffin wax, Fischer-Tropsch wax; oxide of hydrocarbon wax such as oxidized polyethylene wax or block copolymer thereof; Waxes composed mainly of fatty acid esters such as carnauba wax, behenic acid behenate wax, and montanic acid ester wax; fatty acid esters such as deoxidized carnauba wax that have been partially or fully deoxidized.

  Furthermore, the following are mentioned. Saturated linear fatty acids such as palmitic acid, stearic acid and montanic acid; unsaturated fatty acids such as brassic acid, eleostearic acid and valinalic acid; stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauvyl alcohol, seryl alcohol, Saturated alcohols such as sil alcohols; polyhydric alcohols such as sorbitol; fatty acids such as palmitic acid, stearic acid, behenic acid, montanic acid, and stearyl alcohol, aralkyl alcohol, behenyl alcohol, carnauvyl alcohol, seryl alcohol, Esters with alcohols such as sil alcohols; Fatty acid amides such as linoleic acid amide, oleic acid amide, lauric acid amide; Methylene bis stearic acid amide, ethylene biscapric acid Saturated fatty acid bisamides such as amide, ethylene bis lauric acid amide, hexamethylene bis stearic acid amide; ethylene bis oleic acid amide, hexamethylene bis oleic acid amide, N, N 'dioleyl adipic acid amide, N, N' dioleyl Unsaturated fatty acid amides such as sebacic acid amides; aromatic bisamides such as m-xylene bis-stearic acid amide, N, N ′ distearyl isophthalic acid amide; calcium stearate, calcium laurate, zinc stearate, magnesium stearate Aliphatic metal salts such as those commonly referred to as metal soaps; waxes grafted to aliphatic hydrocarbon waxes using vinylic monomers such as styrene and acrylic acid; fatty acids such as behenic acid monoglycerides Price Partial esters of Lumpur; methyl ester compounds having hydroxyl groups obtained by hydrogenation of vegetable fats and oils.

  The toner may contain a charge control agent as necessary. As the charge control agent contained in the toner, known ones can be used. In particular, a metal compound of an aromatic carboxylic acid that is colorless, has a high toner charging speed, and can stably maintain a constant charge amount is preferable.

  Negative charge control agents include salicylic acid metal compounds, naphthoic acid metal compounds, dicarboxylic acid metal compounds, sulfonic acid or polymer compounds having carboxylic acid in the side chain, sulfonates or sulfonated products in the side chain. Examples thereof include a polymer compound having a carboxylate or a carboxylate ester compound in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene.

  Examples of the positive charge control agent include quaternary ammonium salts, polymer compounds having the quaternary ammonium salt in the side chain, guanidine compounds, and imidazole compounds. The charge control agent may be added internally or externally to the toner particles.

  The addition amount of the charge control agent is preferably 0.2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  Further, the toner used in the present invention has at least one maximum value of the particle size distribution in the range of 50 nm or more and 300 nm or less based on the number distribution as spacer particles for improving the releasability between the toner and the carrier particles. It is preferable to contain inorganic particles. In order to more effectively suppress the detachment of the inorganic particles from the toner while functioning as the spacer particles, it is more preferable to add inorganic particles having at least one maximum value in the range of 80 nm to 150 nm. preferable.

  Further, an external additive may be added to the toner to improve fluidity. As the external additive, inorganic fine powders such as silica, titanium oxide and aluminum oxide are preferable. The inorganic fine powder is preferably hydrophobized with a hydrophobizing agent such as a silane compound, silicone oil or a mixture thereof. The external additive preferably has at least one maximum value in the range of 20 nm to 50 nm in the particle size distribution based on the number distribution.

  The total content of the inorganic particles and the external additive is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, and 0.8 parts by mass or more and 4.0 parts by mass with respect to 100 parts by mass of the toner particles. It is more preferable that the amount is not more than parts. Among them, the content of the inorganic particles having at least one maximum value in the range of 50 nm to 300 nm in the particle size distribution based on the number distribution is 0.1 parts by mass or more and 2.5 parts by mass or less, more preferably 0. 0.5 parts by mass or more and 2.0 parts by mass or less. Within this range, the effect as spacer particles becomes more prominent.

  The surfaces of the inorganic particles and the external additive are preferably hydrophobized with a hydrophobizing agent such as a silane compound, silicone oil, or a mixture thereof. The hydrophobizing treatment is preferably carried out by various titanium coupling agents, coupling agents such as silane coupling agents; fatty acids and metal salts thereof; silane compounds; silicone oils;

  As a titanium coupling agent, the following are mentioned, for example. Tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, bis (dioctyl pyrophosphate) oxyacetate titanate.

  Moreover, as a silane coupling agent or a silane compound, the following are mentioned, for example. γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) γ -Aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyl Trimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane.

  Examples of the fatty acid include the following. Long chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, arachidonic acid. Examples of the metal of these fatty acid metal salts include zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

  Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.

  The hydrophobization treatment is performed by adding a hydrophobizing agent of 1% by mass to 30% by mass (more preferably 3% by mass to 7% by mass) with respect to the particles to be treated. It is preferable to carry out by coating.

  The degree of hydrophobization of the hydrophobized inorganic particles and the external additive is not particularly limited. For example, the hydrophobization degree after the treatment is preferably 40 or more and 98 or less. The degree of hydrophobicity indicates the wettability of a sample to methanol and is an index of hydrophobicity.

  For mixing the toner particles with the inorganic particles and the external additive, a known mixer such as a Henschel mixer can be used.

  The toner of the present invention can be obtained by a kneading and pulverizing method, a dissolution suspension method, a suspension polymerization method, an emulsion aggregation polymerization method or an associative polymerization method, and its production method is not particularly limited.

  Examples of the method for producing toner particles include a pulverization method in which a binder resin and a colorant are melt-kneaded and the kneaded product is cooled and then pulverized and classified; the binder resin and the colorant are dissolved or dispersed in a solvent. The suspension solution is introduced into an aqueous medium, suspended and granulated, and the solvent is removed to obtain toner particles; the suspension polymerization method is used to directly produce toner particles; Solvent, but directly forms toner particles using a water-soluble organic solvent and a monomer that becomes insoluble when a polymer is formed. Produces toner particles directly using a water-soluble organic solvent that is soluble in the resulting polymer and is insoluble in the monomer. A dispersion polymerization method; an emulsion polymerization method in which toner particles are directly polymerized in the presence of a water-soluble polar polymerization initiator; a step of agglomerating at least polymer fine particles and colorant fine particles to form fine particle aggregates; Emulsion aggregation method obtained through the aging step to cause fusion between fine particles in the body; and the like.

  A procedure for producing toner by the pulverization method will be described.

  In the raw material mixing step, as a material constituting the toner particles, for example, a predetermined amount of other components such as a binder resin, a colorant and a wax, and a charge control agent as necessary are mixed and mixed. Examples of the mixing apparatus include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a mechano hybrid (manufactured by Mitsui Mining Co., Ltd.).

  Next, the mixed material is melt-kneaded to disperse the colorant and the like in the binder resin. In the melt-kneading process, a batch kneader such as a pressure kneader or a Banbury mixer or a continuous kneader can be used, and a single-screw or twin-screw extruder has become the mainstream because of the advantage of continuous production. ing. For example, KTK type twin screw extruder (manufactured by Kobe Steel Co., Ltd.), TEM type twin screw extruder (manufactured by Toshiba Machine Co., Ltd.), PCM kneader (manufactured by Ikekai Tekko), twin screw extruder (manufactured by Kay Sea Kay Co., Ltd.) ), Ko Kneader (Bus), Needex (Mitsui Mining).

  Furthermore, the colored resin composition obtained by melt-kneading may be rolled with two rolls or the like and cooled with water or the like in the cooling step.

  Next, the cooled kneaded product is pulverized to a desired particle size in a pulverization step. In the pulverization step, for example, after coarse pulverization with a pulverizer such as a crusher, a hammer mill, or a feather mill, for example, a kryptron system (manufactured by Kawasaki Heavy Industries), a super rotor (manufactured by Nisshin Engineering), a turbo mill Finely pulverize with a turbomill (made by Turbo Industries) or air jet type fine pulverizer.

  Then, if necessary, classification such as inertial class elbow jet (manufactured by Nippon Steel & Mining Co., Ltd.), centrifugal classification turboplex (manufactured by Hosokawa Micron), TSP separator (manufactured by Hosokawa Micron), Faculty (manufactured by Hosokawa Micron) The toner particles are obtained by classification using a machine or a sieving machine.

  Further, if necessary, after the pulverization, the toner particle surface modification treatment such as spheroidization treatment can be performed using a hybridization system (manufactured by Nara Machinery Co., Ltd.) or a mechano-fusion system (manufactured by Hosokawa Micron Co., Ltd.). .

  In the two-component developer of the present invention, the mixing ratio of the toner and the magnetic carrier is preferably 2 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the magnetic carrier, and preferably 5 parts by mass or more and 20 parts by mass or less. Is preferred. By setting it within the above range, high image density can be achieved and toner scattering can be reduced.

  The two-component developer containing the magnetic carrier and the toner of the present invention supplies the developer for replenishment containing the toner and the magnetic carrier to the developer, and at least the excess magnetic carrier inside the developer. It can also be used in a two-component development method discharged from a developing device, and can be used as the replenishment developer. In the replenishing system, when the two-component developer of the present invention is used as a replenishing developer, the toner is added in an amount of 2 parts by mass or more with respect to 1 part by mass of the magnetic carrier from the viewpoint of enhancing the durability of the developer. A blending ratio of 50 parts by mass or less is preferable.

  A method for measuring various physical properties of the magnetic carrier and toner will be described below.

<Area% of resin part on carrier surface>
The area% of the resin portion on the surface of the magnetic carrier particle of the present invention can be determined by observing a reflected electron image (FIG. 7) with a scanning electron microscope and subsequent image processing.

  The area% of the resin portion on the surface of the magnetic carrier particles used in the present invention was performed using a scanning electron microscope (SEM) and S-4800 (manufactured by Hitachi, Ltd.). The area% of the resin portion is calculated from image processing of an image that visualizes reflected electrons mainly when the acceleration voltage is 2.0 kV. In observation with a scanning electron microscope, it is known that the amount of reflected electrons emitted from a sample is larger as a heavy element. As in the carrier surface of the present invention, in the sample in which the metal oxide portion derived from the resin portion and the core is present, the metal oxide portion is bright (high brightness, white) and the resin portion is dark (low brightness, black) ) So that images with large contrast differences can be obtained.

Specifically, the carrier particles are fixed in a single layer with a carbon tape on a sample stage for observation with an electron microscope, and scanning electron microscope S-4800 (Hitachi) is used under the following conditions without performing deposition with platinum. (Manufactured by Seisakusho). Observe after performing the flushing operation.
SignalName = SE (U, LA80)
AcceleratingVoltage = 2000Volt
EmissionCurrent = 10000nA
Working distance = 6000um
LensMode = High
Condencer1 = 5
ScanSpeed = Slow4 (40 seconds)
Magnification = 600
DataSize = 1280x960
ColorMode = Grayscale

The reflected electron image is adjusted to brightness of “Contrast 5 and Brightness-5” on the control software of the scanning electron microscope S-4800, the capture speed / total number of images “Slow 4 is 40 seconds”, and the image size is 1280 × 960 pixels of 8 bits. A projection image of the magnetic carrier was obtained as a 256 gray scale gray scale image (FIG. 7). From the scale on the image, the length of 1 pixel is 0.1667 μm, and the area of 1 pixel is 0.0278 μm ² .

  Subsequently, the area% of the resin portion was calculated for 50 magnetic carrier particles using the obtained projected image of reflected electrons. Details of the method of selecting 50 magnetic carrier particles to be analyzed will be described later. Image processing software Image-Pro Plus 5.1J (manufactured by Media Cybernetics) was used for the area% of the resin portion.

  First, the character string at the bottom of the image in FIG. 7 is unnecessary for image processing, and unnecessary portions were deleted and cut into a size of 1280 × 895 (FIG. 8).

  Next, the magnetic carrier particle part was extracted, and the size of the extracted magnetic carrier particle part was counted. Specifically, first, in order to extract the magnetic carrier particles to be analyzed, the magnetic carrier particles and the background portion are separated. Select “Measurement”-“Count / Size” of Image-Pro Plus 5.1J. In “Brightness range selection” of “Count / Size”, the brightness range was set to a range of 50 to 255, and the low-brightness carbon tape portion reflected in the background was excluded, and magnetic carrier particles were extracted. (FIG. 9). When the magnetic carrier particles are fixed by a method other than the carbon tape, there is no possibility that the background does not necessarily have a low luminance area or that the luminance is partially the same as that of the magnetic carrier particles. However, the boundary between the magnetic carrier particles and the background can be easily distinguished from the backscattered electron observation image. When performing the extraction, select 4 connections in the “Count / Size” extraction option, enter a smoothness of 5, enter a check for fill in holes, and check for particles or other points on all boundaries (peripheries) of the image. Particles overlapping with particles were excluded from the calculation. Next, in the “count / size” measurement item, the area and the ferret diameter (average) were selected, and the area selection range was set to a minimum of 300 pixels and a maximum of 10000000 pixels (FIG. 10). Further, the selection range is set so that the ferret diameter (average) is within a range of ± 25% of the measured value of the volume distribution reference 50% particle diameter (D50) of the magnetic carrier, which will be described later, and the magnetic carrier particles subjected to image analysis are selected. Extracted (FIG. 11). The size (pixel number) of the portion derived from the extracted magnetic carrier particles was determined as (ja), the sum of the extracted portions (Σja = Ja), and the number of extracted portions (Jc). The same operation was repeated for the projected magnetic carrier particle image of another field until the number Jc of the extracted carrier particles reached Jc = 50.

Next, the area of the resin portion on the particle selected at the time of image analysis of the area of the magnetic carrier particle was calculated. In “Brightness range selection” of “Count / Size” of Image-Pro Plus 5.1J, the brightness range was set to a range of 140 to 255, and a portion with high brightness on the carrier particles was extracted. The area selection range was set to a minimum of 10 pixels and a maximum of 10000 pixels, and portions other than the resin portion on the surface of the magnetic carrier particles were extracted (FIG. 12). Further, similarly to the extraction of the magnetic carrier part, particles located on the outer periphery of the image and those deviating from the range of ± 25% diameter of the measured value of 50% particle diameter (D50) were excluded from the calculation. The size (pixel number) (ma) other than the resin portion and the sum (Ma) of the respective extracted portions were used. The area of the resin part was calculated by subtracting the area other than the resin part from the carrier particle area, and the area% of the resin part was calculated according to the following formula.
Area% of resin part
= (Carrier particle area-area other than resin portion) / carrier particle area × 100
= ((Ja-Ma) / Ja) × 100

<Average area of part derived from metal oxide>
Similar to calculating the area% of the resin part on the surface of the magnetic carrier particle, the size (number of pixels) derived from the metal oxide part (= other than the resin part) (ma), The sum (Ma) was determined.

  Moreover, the number (mc) of the part derived from a metal oxide part was counted, and the average area of the part derived from a metal oxide was calculated according to the following formula.

Average area of parts derived from metal oxide = Ma / mc
<Field strength just before breakdown of porous magnetic core>
The electric field strength and specific resistance just before breakdown of the porous magnetic core particles are measured using a measuring apparatus schematically shown in FIG.

The resistance measuring cell A includes a cylindrical PTFE resin container 1 having a hole with a cross-sectional area of 2.4 cm ² , a lower electrode (made of stainless steel) 2, a support base (made of PTFE resin) 3, and an upper electrode (made of stainless steel) 4. Composed. The cylindrical PTFE resin container 1 is placed on the support pedestal 3, the porous magnetic core particles 5 are filled in a range of about 0.5 to 1.3 g, the upper electrode 4 is placed on the filled sample 5, and the sample Measure the thickness. If the thickness when there is no sample in advance is d1 (blank), and the thickness d2 (sample) when a sample of about 0.5 to 1.3 g is filled, the actual thickness d of the sample can be expressed by the following equation.
d = d2 (sample) −d1 (blank)

  At this time, it is important to appropriately change the amount of the sample so that the thickness of the sample becomes 0.95 mm or more and 1.04 mm.

  By applying a voltage between the electrodes and measuring the current flowing at that time, the electric field strength just before the breakdown of the porous magnetic carrier core particles can be obtained. For the measurement, an electrometer 6 (Kesley 6517A, manufactured by Kesley) and a computer 7 are used for control.

This is performed by software using a control system and control software (manufactured by LabVEIW National Instruments) manufactured by National Instruments for the control computer. As measurement conditions, a measured value d is inputted so that the contact area S of the sample and the electrode is S = 2.4 cm ² and the thickness of the sample is 0.95 mm or more and 1.04 mm or less. The upper electrode load is 120 g and the maximum applied voltage is 1000 V.

  The voltage application conditions are as follows: 1 V, 2 V, 4 V, 8 V, 16 V, 32 V, 64 V, 128 V, using the automatic range function of the electrometer using the IEEE-488 interface for control between the control computer and the electrometer. Screening is performed by applying voltages of 256V, 512V, and 1000V for 1 second each. At that time, the electrometer determines whether it is possible to apply up to 1000 V (the electric field strength is about 10000 V / cm), and when the overcurrent flows, “VOLTAGE SOURCE OPARATE” flashes. Then, the applied voltage is lowered, the applicable voltage is further screened, and the maximum value of the applied voltage is automatically determined. Then, this measurement is performed. The resistance value is measured from the current value after holding the voltage obtained by dividing the maximum voltage value into five steps for 30 seconds. For example, when the maximum applied voltage is 1000 V, the voltage is increased in 200 V increments after 200 V, 400 V, 600 V, 800 V, 1000 V, 1000 V, 800 V, 600 V, 400 V, 200 V, and then applied in order of decreasing. At each step, the resistance value is measured from the current value after holding for 30 seconds.

Further, for example, as shown in Table 1, in the case of the porous magnetic carrier core used in Example 1 described later, the maximum applied voltage is 85.3V at the time of screening, and 17.1V, 34.1V, 51 .2V, 68.2V, 85.3V, 85.3V, 68.2V, 51.2V, 34.1V, 17.1V in this order. The current value obtained there is processed by a computer, and the electric field strength and specific resistance are calculated from the sample thickness and electrode area, and plotted on a graph. In that case, five points (from the sixth step to the tenth step in Table 1) are plotted for decreasing the voltage from the maximum applied voltage. In the measurement at each step, “VOLTAGE SOURCE OPARATE” blinks, and when an overcurrent flows, the resistance value is displayed as 0 for measurement. This phenomenon is defined as breakdown. This “VOLTAGE SOURCE OPARATE” blinks and is defined as the electric field strength just before the breakdown. Therefore, “VOLTAGE SOURCE OPARATE” blinks and the point at which the maximum electric field strength of the above-described profile is plotted is defined as the electric field strength just before the breakdown. When “VOLTAGE SOURCE OPARATE” blinks when the maximum applied voltage is applied, if the resistance value does not become 0 and plotting is possible, the electric field strength is set to the point just before breakdown. In the case of the porous magnetic carrier core of Example 1 shown in Table 1, breakdown occurs at 85.3 V, the voltage immediately before breakdown is 68.2 V, and the electric field strength immediately before breakdown is 669 V / cm. This is indicated by an arrow in FIG.
In addition, specific resistance and electric field strength are calculated | required by a following formula.
Specific resistance (Ω · cm) = (applied voltage (V) / measured current (A)) × S (cm ² ) / d (cm)
Electric field strength (V / cm) = applied voltage (V) / d (cm)

  FIG. 4 shows the result of plotting the porous magnetic carrier core used in Example 1.

<Measurement Method of Volume Distribution Standard 50% Particle Size (D50) of Magnetic Carrier Particles and Porous Magnetic Core Particles>
The particle size distribution was measured with a laser diffraction / scattering particle size distribution measuring apparatus “Microtrack MT3300EX” (manufactured by Nikkiso Co., Ltd.).

  For measurement of 50% particle size (D50) based on the volume distribution of magnetic carrier particles and porous magnetic core particles, a sample feeder for dry measurement “One-shot dry sample conditioner Turbotrac” (manufactured by Nikkiso Co., Ltd.) is installed. went. As the supply conditions of Turbotrac, a dust collector was used as a vacuum source, the air volume was about 33 liters / sec, and the pressure was about 17 kPa. Control is automatically performed on software. For the particle size, a 50% particle size (D50), which is a cumulative value based on volume, is obtained. Control and analysis are performed using attached software (version 10.3.3-202D).

  The measurement conditions are: SetZero time 10 seconds, measurement time 10 seconds, number of measurements once, particle refractive index 1.81, particle shape non-spherical, measurement upper limit 1408 μm, measurement lower limit 0.243 μm. The measurement is performed in a normal temperature and humidity environment.

<Measurement of Ratio of Particles (Small Particles) whose Toner Equivalent Diameter is 0.500 μm or more and 1.985 μm or less>
The ratio of particles (small particles) having an equivalent circle diameter of 0.500 μm or more and 1.985 μm or less of the toner is measured by a flow type particle image measuring device “FPIA-3000 type” (manufactured by Sysmex Corporation) during calibration. Measurement was performed under analysis conditions.

  The measurement principle of the flow-type particle image measuring device “FPIA-3000 type” (manufactured by Sysmex Corporation) is to capture flowing particles as a still image and perform image analysis. The sample added to the sample chamber is fed into the flat sheath flow cell by a sample suction syringe. The sample fed into the flat sheath flow is sandwiched between sheath liquids to form a flat flow. The sample passing through the flat sheath flow cell is irradiated with strobe light at 1/60 second intervals, and the flowing particles can be photographed as a still image. Further, since the flow is flat, the image is taken in a focused state. The particle images are picked up by a CCD camera, and the picked-up image is 512 pixels × 512 pixels in one field of view, and image processing is performed at an image processing resolution of 0.37 × 0.37 μm per pixel, and the contour of each particle image Extraction is performed, and the projected area and perimeter of the particle image are measured.

  Next, the projected area S and the perimeter L of each particle image are obtained. The equivalent circle diameter is obtained using the area S and the peripheral length L. The circular equivalent diameter is a diameter of a circle having the same area as the projected area of the particle image.

  As a specific measurement method, 0.02 g of a surfactant, preferably an alkylbenzene sulfonate, is added to 20 ml of ion-exchanged water, and then 0.02 g of a measurement sample is added, an oscillation frequency of 50 kHz, electrical output. Dispersion treatment was carried out for 2 minutes using a 150 W tabletop type ultrasonic cleaner / disperser (for example, “VS-150” (manufactured by VervoCrea Co., Ltd.)) to obtain a dispersion for measurement. It cools suitably so that temperature may become 10 to 40 degreeC.

  The flow type particle image analyzer equipped with a standard objective lens (10 × numerical aperture 0.40) was used for measurement, and a particle sheath “PSE-900A” (manufactured by Sysmex Corporation) was used as the sheath liquid. The dispersion liquid prepared according to the above procedure was introduced into the flow type particle image measuring device, and 3000 toner particles were measured in the total count mode in the HPF measurement mode. In addition, by setting the binarization threshold at the time of particle analysis to 85% and specifying the analysis particle diameter, the number ratio (%) of particles in the range can be calculated. The ratio of particles (small particles) having an equivalent circle diameter of 0.500 μm or more and 1.985 μm or less is such that the analyzed particle diameter range of the equivalent circle diameter is 0.500 μm or more and 1.985 μm or less, and the number of particles included in the range The percentage (%) was calculated.

  In the measurement, automatic focus adjustment is performed using standard latex particles (for example, Duke Scientific 5200A diluted with ion-exchanged water) before the measurement is started. Thereafter, it is preferable to perform focus adjustment every two hours from the start of measurement.

  In the embodiment of the present application, a flow type particle image measuring apparatus which has been issued a calibration certificate issued by Sysmex Corporation, which has been calibrated by Sysmex Corporation, has an analysis particle diameter of 0.500 μm or more, 1 The measurement was performed under the measurement and analysis conditions when the calibration certificate was received, except for being limited to .985 μm or less.

<Measurement of weight average particle diameter (D4) of toner>
The weight average particle diameter (D4) of the toner is determined based on the precise particle size distribution measuring apparatus “Coulter Counter Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.) having a 100 μm aperture tube. Using the attached dedicated software “Beckman Coulter Multisizer 3 Version 3.51” (manufactured by Beckman Coulter, Inc.) for setting and analyzing the measurement data, the measurement data is measured with 25,000 effective channels. Analysis was performed and calculated.

  As the electrolytic aqueous solution used for the measurement, special grade sodium chloride is dissolved in ion-exchanged water so as to have a concentration of about 1% by mass, for example, “ISOTON II” (manufactured by Beckman Coulter, Inc.) can be used.

  Prior to measurement and analysis, the dedicated software was set as follows.

  In the “Standard measurement method (SOM) change screen” of the dedicated software, set the total count in the control mode to 50000 particles, the number of measurements is 1 and the Kd value is “standard particles 10.0 μm” (Beckman Coulter Set the value obtained using The threshold and noise level are automatically set by pressing the threshold / noise level measurement button. Also, the current is set to 1600 μA, the gain is set to 2, the electrolyte is set to ISOTON II, and the aperture tube flash after measurement is checked.

  In the “pulse to particle size conversion setting screen” of the dedicated software, the bin interval is set to logarithmic particle size, the particle size bin is set to 256 particle size bin, and the particle size range is set to 2 μm or more and 60 μm or less.

The specific measurement method is as follows.
(1) About 200 ml of the electrolytic solution is placed in a glass 250 ml round bottom beaker exclusively for Multisizer 3, set on a sample stand, and the stirrer rod is stirred counterclockwise at 24 rpm. Then, dirt and bubbles in the aperture tube are removed by the “aperture flush” function of the analysis software.
(2) About 30 ml of the electrolytic aqueous solution is put in a glass 100 ml flat bottom beaker, and "Contaminone N" (nonionic surfactant, anionic surfactant, organic builder pH 7 precision measurement is used as a dispersant therein. About 0.3 ml of a diluted solution obtained by diluting a 10% by weight aqueous solution of a neutral detergent for washing a vessel (made by Wako Pure Chemical Industries, Ltd.) 3 times with ion-exchanged water is added.
(3) Two oscillators with an oscillation frequency of 50 kHz are incorporated in a state where the phase is shifted by 180 degrees, and placed in a water tank of an ultrasonic dispersion device “Ultrasonic Dissipation System Tetora 150” (manufactured by Nikki Bios Co., Ltd.) having an electrical output of 120 W. A fixed amount of ion-exchanged water is added, and about 2 ml of the above-mentioned Contaminone N is added to this water tank.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. And the height position of a beaker is adjusted so that the resonance state of the liquid level of the electrolyte solution in a beaker may become the maximum.
(5) In a state where the electrolytic aqueous solution in the beaker of (4) is irradiated with ultrasonic waves, about 10 mg of toner is added to the electrolytic aqueous solution little by little and dispersed. Then, the ultrasonic dispersion process is continued for another 60 seconds. In the ultrasonic dispersion, the temperature of the water tank is appropriately adjusted so as to be 10 ° C. or higher and 40 ° C. or lower.
(6) To the round bottom beaker of (1) installed in the sample stand, the electrolyte solution of (5) in which the toner is dispersed is dropped using a pipette, and the measurement concentration is adjusted to about 5%. . Measurement is performed until the number of measured particles reaches 50,000.
(7) The measurement data is analyzed with the dedicated software attached to the apparatus, and the weight average particle diameter (D4) is calculated. The “average diameter” on the analysis / volume statistics (arithmetic average) screen when the graph / volume% is set with the dedicated software is the weight average particle diameter (D4).

<Measurement method of resin peak molecular weight (Mp), number average molecular weight (Mn), weight average molecular weight (Mw)>
The molecular weight distribution of the resin is measured by gel permeation chromatography (GPC) as follows.

First, the resin is dissolved in tetrahydrofuran (THF) at room temperature over 24 hours. The obtained solution is filtered through a solvent-resistant membrane filter “Maescho Disc” (manufactured by Tosoh Corporation) having a pore diameter of 0.2 μm to obtain a sample solution. The sample solution is adjusted so that the concentration of the component soluble in THF is about 0.8% by mass. Using this sample solution, measurement is performed under the following conditions.
Apparatus: HLC8120 GPC (detector: RI) (manufactured by Tosoh Corporation)
Column: Seven series of Shodex KF-801, 802, 803, 804, 805, 806, 807 (manufactured by Showa Denko KK)
Eluent: Tetrahydrofuran (THF)
Flow rate: 1.0 ml / min
Oven temperature: 40.0 ° C
Sample injection volume: 0.10 ml

  In calculating the molecular weight of the sample, standard polystyrene resin (for example, trade name “TSK Standard Polystyrene F-850, F-450, F-288, F-128, F-80, F-40, F-20, F— 10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500 ", manufactured by Tosoh Corporation) are used.

<Peak temperature of maximum endothermic peak of wax, glass transition temperature Tg of binder resin>
The peak temperature of the maximum endothermic peak of the wax is measured according to ASTM D3418-82 using a differential scanning calorimeter “Q1000” (manufactured by TA Instruments).

  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.

  Specifically, about 10 mg of wax is precisely weighed, placed in an aluminum pan, an empty aluminum pan is used as a reference, and the temperature rise rate is within a measurement temperature range of 30 to 200 ° C. Measurement is performed at 10 ° C./min. In the measurement, the temperature is once raised to 200 ° C., subsequently lowered to 30 ° C., and then the temperature is raised again. The maximum endothermic peak of the DSC curve in the temperature range of 30 to 200 ° C. in the second temperature raising process is defined as the maximum endothermic peak of the wax of the present invention.

  Further, the glass transition temperature (Tg) of the toner and the binder resin is measured by precisely weighing about 10 mg of the binder resin as in the case of the wax measurement. Then, a specific heat change is obtained in the temperature range of 40 ° C to 100 ° C. At this time, the intersection point between the line of the midpoint of the baseline before and after the change in specific heat and the differential heat curve is defined as the glass transition temperature Tg of the binder resin.

<Measurement of particle size based on number distribution of inorganic particles>
The particle size based on the number distribution of the inorganic particles was measured by the following procedure.

  Using a scanning electron microscope S-4800 (manufactured by Hitachi, Ltd.), toner is applied in an undeposited state at an acceleration voltage of 2.0 kV. The reflected electron image is observed at 50,000 times. Since the amount of reflected electrons emitted depends on the atomic number of the substance constituting the sample, the contrast between the inorganic particles and the organic substance such as the toner particle matrix can be achieved. The highlight (white) component particles from the toner particle matrix can be judged as inorganic particles. Then, 500 fine particles having a particle diameter of 5 nm or more are extracted at random. The major and minor axes of the extracted particles are measured with a digitizer, and the average value of the major and minor axes is taken as the particle size of the fine particles. In the particle size distribution of 500 extracted particles (using column histograms with column widths divided every 10 nm such as 5 to 15 nm, 15 to 25 nm, 25 to 35 nm,...), The center value of the column Draw a histogram with a particle size of. From the histogram, it is determined whether the maximum particle size is in the range of 50 nm to 300 nm. In the histogram, the maximum particle size may be single or plural, and the peak in the range of 50 nm to 300 nm may or may not take the maximum value.

<Measurement method of magnetization intensity of magnetic carrier>
The magnetization strength of the magnetic carrier and the magnetic core can be obtained by a vibrating magnetic field measuring device (Vibrating sample magnetometer) or a direct current magnetization characteristic recording device (BH tracer). In the examples described later, the measurement is performed by the following procedure using an oscillating magnetic field type magnetic property measuring apparatus BHV-30 (manufactured by Riken Electronics Co., Ltd.).

  A sample in which a cylindrical plastic container is sufficiently densely packed with a magnetic carrier or a magnetic core is used. The actual mass of the sample filled in the container is measured. Thereafter, the sample in the plastic container is bonded so that the sample is not moved by the instantaneous adhesive.

  Calibration of the external magnetic field axis and the magnetization moment axis at 5000 / 4π (kA / m) is performed using a standard sample.

The strength of magnetization was measured from a loop of magnetization moment to which an external magnetic field of 1000 / 4π (kA / m) was applied at a sweep rate of 5 min / loop. From these, the magnetization strength (Am ² / kg) of the magnetic carrier and the magnetic core is obtained by dividing by the sample weight.

<Measurement method of true density of porous magnetic core>
The true density of the porous magnetic core is measured using a dry automatic densimeter AccuPick 1330 (manufactured by Shimadzu Corporation). First, 5 g of a sample sample left in an environment of 23 ° C. and 50% RH for 24 hours is precisely weighed, placed in a measurement cell (10 cm ³ ), and inserted into the main body sample chamber. The measurement can be automatically performed by inputting the sample sample mass into the main body and starting the measurement.

The measurement conditions for the automatic measurement were: helium gas adjusted at 20.000 psig (2.392 × 10 ² kPa), purged 10 times in the sample chamber, and then the pressure change in the sample chamber was 0.005 psig / min (3 .447 × 10 ⁻² kPa / min) is the equilibrium state, and helium gas is repeatedly purged until the equilibrium state is reached. Measure the pressure in the sample chamber in the equilibrium state. The sample sample volume can be calculated from the pressure change when the equilibrium state is reached (Boil's law).

Since the sample sample volume can be calculated, the true specific gravity of the sample sample can be calculated by the following equation.
True specific gravity of sample sample (g / cm ³ ) = Sample sample mass (g) / Sample sample volume (cm ³ )

The average of the values measured five times by this automatic measurement is defined as the true specific gravity (g / cm ³ ) of the magnetic carrier and the porous magnetic core.

<Measurement method of apparent density of porous magnetic core>
According to JIS-Z2504 (Apparent density test method of metal powder), the apparent density of the magnetic carrier and the porous magnetic core is determined by using a magnetic carrier and a porous magnetic core instead of the metal powder.

<Measuring method of number average particle diameter of external additives (inorganic particles and silica fine particles)>
The measurement is performed using a scanning electron microscope S-4700 (manufactured by Hitachi, Ltd.). The photographing magnification is set to 50,000 times, and the photographed photograph is enlarged twice and then measured from the FE-SEM photograph image. The diameter of spherical particles and the maximum diameter (major axis diameter) of elliptical spherical particles are used as the particle size of the particles, 100 inorganic fine particles are measured, the average value is obtained, and the number average particle size is calculated. .

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely with reference to an Example, this invention is not limited only to these Examples.

Production Example 1 of Porous Magnetic Core Particle
Process 1 (weighing / mixing process):
Fe ₂ O ₃ 61.1% by mass
MnCO ₃ 33.5% by mass
Mg (OH) ₂ 4.5% by mass
SrCO ₃ 0.9% by mass
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls.

Step 2 (temporary firing step):
After pulverization and mixing, firing was performed in the atmosphere at 950 ° C. for 2 hours using a burner-type firing furnace to prepare calcined ferrite. The composition of ferrite is as follows.
(MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d
In the above formula, a = 0.39, b = 0.10, c = 0.01, d = 0.50

Step 3 (grinding step):
After pulverizing to about 0.5 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using zirconia beads (φ1.0 mm), and pulverized with a wet bead mill for 4 hours to obtain a ferrite slurry. .

Process 4 (granulation process):
To the ferrite slurry, 2.0 parts by mass of polyvinyl alcohol was added as a binder with respect to 100 parts by mass of calcined ferrite, and granulated into 36 μm spherical particles with a spray dryer (manufacturer: Okawahara Chemical).

Process 5 (main baking process):
In order to control the firing atmosphere, firing was performed at 1050 ° C. for 4 hours in a nitrogen atmosphere (oxygen concentration 0.02% by volume) in an electric furnace.

Process 6 (screening process):
After the agglomerated particles were crushed, coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain porous magnetic core particles 1. The physical properties were D50 = 34.5, specific resistance at 300 v / cm = 6.0 × 10 ⁶ , true specific gravity = 4.8, and apparent specific gravity = 1.2. The physical properties of the porous magnetic core particle 1 are summarized in Table 2.

Production example 2 of porous magnetic core particles
Process 1 (weighing / mixing process):
Fe ₂ O ₃ 80.3 mass%
MnCO ₃ 28.3 mass%
Mg (OH) ₂ 1.4% by mass
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls. The composition of ferrite is as follows.
(MnO) _a (MgO) _b (Fe ₂ O ₃ ) _C
In the above formula, a = 0.36, b = 0.05, c = 0.59

  Subsequent steps were performed in the same manner as in Production Example 1 of porous magnetic core particles, to obtain porous magnetic core particles 2. The physical properties of the porous magnetic core particle 2 are summarized in Table 2.

Production Example 3 of Porous Magnetic Core Particle
Porous magnetic core particles 3 were obtained in the same manner as in Production Example 2 of porous magnetic core particles, except that the nitrogen atmosphere of the firing conditions in step 5 was changed to an oxygen concentration of less than 0.01% by volume. The physical properties of the porous magnetic core particle 3 are summarized in Table 2.

Production example 4 of porous magnetic core particles
The pulverization time with zirconia beads (φ1.0 mm) in Step 3 of Production Example 1 of porous magnetic core particles was changed to 3 hours. Further, under the firing conditions in Step 5, the electric furnace was used in a nitrogen atmosphere (oxygen concentration less than 0.01% by volume). In addition, porous magnetic core particles 4 were obtained in the same manner as in Production Example 1 of porous magnetic core particles, except that firing was performed at 1100 ° C. for 4 hours. Table 2 summarizes the physical properties of the porous magnetic core particles 4.

Production Example 5 of Porous Magnetic Core Particle
Porous magnetic core particles 5 were obtained in the same manner as in Production Example 4 of porous magnetic core particles, except that the oxygen concentration in the atmosphere was 0.30% by volume under the firing conditions in Step 5. Table 2 summarizes the physical properties of the porous magnetic core particles 5.

Production Example 6 of Porous Magnetic Core Particle
Manufacture of porous magnetic core particles except that the pulverization time with zirconia beads (φ1.0 mm) in step 3 was changed to 2 hours, and the oxygen concentration in the atmosphere was 0.05 vol% under the firing conditions in step 5. In the same manner as in Example 4, porous magnetic core particles 6 were obtained. Table 2 summarizes the physical properties of the porous magnetic core particles 6.

Production Example 7 of Porous Magnetic Core Particle
Porous magnetic core particles 7 were obtained in the same manner as in Production Example 6 of porous magnetic core particles except that the oxygen concentration in the atmosphere was changed to 0.20% by volume under the firing conditions in Step 5. Table 2 summarizes the physical properties of the porous magnetic core particles 7.

Production Example 8 of Porous Magnetic Core Particle
Porous magnetic core particles were produced in the same manner as in Production Example 6 of the porous magnetic core particle except that firing was performed in an electric furnace under a nitrogen atmosphere (oxygen concentration of less than 0.01% by volume) at 1150 ° C. for 4 hours. The magnetic core particle 8 was obtained. The physical properties of the porous magnetic core particles 8 are summarized in Table 2.

Production Example 9 of Porous Magnetic Core Particle
Porous magnetic core particles 9 were obtained in the same manner as in Production Example 8 of porous magnetic core particles, except that the oxygen concentration in the atmosphere was 0.30% by volume under the firing conditions in Step 5. Table 2 summarizes the physical properties of the porous magnetic core particles 9.

Production Example 10 of Porous Magnetic Core Particle
Porous magnetic core particles 10 were obtained in the same manner as in Production Example 8 of porous magnetic core particles, except that the oxygen concentration in the atmosphere was changed to 0.50% by volume under the firing conditions in Step 5. Table 2 summarizes the physical properties of the porous magnetic core particles 10.

Production example 11 of porous magnetic core particles
Process 1 (weighing / mixing process):
Fe ₂ O ₃ 61.6% by mass
MnCO ₃ 31.6% by mass
Mg (OH) ₂ 5.7% by mass
SrCO ₃ 0.7% by mass
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 5 hours by a wet ball mill using zirconia (φ10 mm) balls. Thereafter, it was dried with a spray dryer to obtain spherical particles.

Step 2 (temporary firing step):
Spherical particles were fired in the atmosphere at 950 ° C. for 2 hours using a burner-type firing furnace to prepare calcined ferrite. The composition of ferrite is as follows.
(MnO) _a (MgO) _b (SrO) _c (Fe ₂ O ₃ ) _d
In the above formula, a = 0.36, b = 0.13, c = 0.01, d = 0.50

Step 3 (grinding step):
After crushing to about 0.5 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using stainless beads (φ3 mm), and pulverized with a wet ball mill for 1 hour. The slurry was pulverized with a wet bead mill using stainless beads (φ1.0 mm) for 4 hours to obtain a ferrite slurry.

Process 4 (granulation process):
To the ferrite slurry, 1.0 part by mass of polyvinyl alcohol was added as a binder to 100 parts by mass of calcined ferrite, and granulated to 35 μm spherical particles with a spray dryer (manufacturer: Okawara Kako).

Process 5 (main baking process):
In order to control the firing atmosphere, firing was performed at 1100 ° C. for 4 hours in an electric furnace at an oxygen concentration of 0.5 vol%.

Process 6 (screening process):
After the aggregated particles were crushed, coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain porous magnetic core particles 11. Table 2 summarizes the physical properties of the porous magnetic core particles 11.

Production example 12 of magnetic core particles
Step 1:
Fe ₂ O ₃ 71.0 mass%
CuO 12.5 mass%
ZuO 16.5% by mass
The ferrite raw material was weighed so that Thereafter, the mixture was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls.

Step 2:
After pulverization and mixing, firing was performed at 950 ° C. for 2 hours in the air to prepare calcined ferrite. The composition of ferrite is as follows.
(CuO) _a (ZnO) _b (Fe ₂ O ₃ ) _c
In the above formula, a = 0.25, b = 0.20, c = 0.55

  In addition, the said ferrite shows the main element and the thing containing the trace metal other than that is also included.

Step 3:
After crushing to about 0.5 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using a stainless steel ball (φ10 mm), and pulverized with a wet ball mill for 2 hours. The slurry was further pulverized by a wet bead mill using stainless beads (φ1.0 mm) for 4 hours to obtain a ferrite slurry.

Step 4:
To the ferrite slurry, 0.5 part by mass of polyvinyl alcohol was added as a binder to 100 parts by mass of calcined ferrite, and granulated to 75 μm spherical particles with a spray dryer (manufacturer: Okawara Chemical).

Step 5:
Firing was performed at 1300 ° C. for 4 hours in the air.

Step 6:
After the aggregated particles were crushed, coarse particles were removed by sieving with a sieve having an opening of 250 μm to obtain magnetic core particles 12. The physical properties of the magnetic core particle 12 are shown in Table 2.

Production example 13 of magnetic core particles
In the production example of the magnetic core particles 12, after crushing to about 0.5 mm by a crusher in Step 3, pulverization was performed for 6 hours by a wet ball mill using stainless balls (φ10 mm). Furthermore, the magnetic core particle 13 was obtained in the same manner as the magnetic core particle 12 except that it was granulated into 39 μm spherical particles in Step 4. The physical properties of the magnetic core particle 13 are shown in Table 2.

(Preparation of resin solution A)
Silicone varnish (SR2410 manufactured by Toray Dow Corning Co., Ltd., solid content concentration: 20% by mass) 75.8 parts by mass γ-aminopropyltriethoxysilane 1.5 parts by mass Toluene 22.7 parts by mass 1.2 × 10 ⁻⁴ m ² / sec).

(Preparation of resin solutions B and C)
Resin solutions B and C were prepared according to Table 3. The viscosities of the resin solutions B and C were 1.1 × 10 ⁻⁴ m ² / sec and the viscosity was 1.2 × 10 ⁻⁴ m ² / sec, respectively.

(Preparation of resin solution D)
According to Table 3, each material was mixed. After adding 3 mm glass beads as media particles and dispersing for 1 hour in a sand mill, the beads were separated using a sieve to obtain Resin Solution D.

(Example of production of filled core particle 1)
100 parts by mass of the porous magnetic core particle 1 is put into a universal stirring mixer (manufactured by Dalton), heated to 80 ° C., and corresponds to 15 parts by mass as a filling resin component with respect to 100 parts by mass of the porous magnetic core particle 1. Resin solution A was added, and the organic solvent which volatilized was stirred while exhausting. Heating and stirring were continued at 80 ° C. for 2 hours to remove the solvent. The obtained sample was transferred to a Julia mixer (Tokuju workshop), heat-treated at 200 ° C. for 2 hours in a nitrogen atmosphere, and classified with a mesh having an opening of 70 μm to obtain filled core particles 1 (resin filling amount 15.0). Parts by mass).

(Example of production of filled core particles 2, 3, 7, 9)
According to Table 4, the magnetic core type and the resin solution type to be used were changed, and the resin core was filled in such a manner that 100 parts by mass of each magnetic core material was filled with the resin so as to have the resin filling amount shown in Table 4. In the same manner as in the production example, filled core particles 2, 3, 7, and 9 were obtained.

(Production example of filled core 4)
100 parts by mass of the porous magnetic carrier core particles 5 were put into a universal stirring mixer (manufactured by Dalton) and heated to 50 ° C. under reduced pressure. The resin liquid A corresponding to 11 parts by mass as a filling resin component was added to 100 parts by mass of the porous magnetic carrier core particles 5 and maintained at 50 ° C. for 2 hours, followed by stirring to impregnate the resin. Thereafter, the temperature was raised to 80 ° C. to remove the solvent. The obtained sample was transferred to a Julia mixer (Tokuju workshop), heat-treated at 200 ° C. for 2 hours in a nitrogen atmosphere, and classified with a mesh having an opening of 70 μm to obtain filled core particles 4.

(Production example of filled cores 5, 6, 8, 11)
According to Table 4, the magnetic core type and the resin solution type to be used were switched, and the resin was filled so that the resin filling amount shown in Table 4 was obtained with respect to 100 parts by mass of the magnetic core material. Other than that was carried out similarly to the manufacture example of the filling core particle 4, and obtained the filling core particle 5,6,8,11.

(Manufacturing example of the filling core 10)
100 parts by mass of the porous magnetic core particle 11 was put into a uniaxial indirect heating dryer, and the liquid A corresponding to 13 parts by mass was dropped as a filling resin component while stirring at 75 ° C. while stirring. Then, it heated up to 200 degreeC and hold | maintained for 2 hours. Classification was performed with a mesh having an opening of 70 μm to obtain filled core particles 10.

[Production example of magnetic carrier 1]
100 parts by mass of packed core particles 1 were put into a Nauta mixer (manufactured by Hosokawa Micron Corporation) and heated to 70 ° C. under reduced pressure while stirring under the conditions of a screw rotation speed of 100 min ⁻¹ and a rotation speed of 3.5 min ⁻¹ . Subsequently, the resin solution C is diluted with toluene so that the solid content concentration becomes 10% by mass, and the resin solution is added so as to be 1.5 parts by mass as a coating resin component with respect to 100 parts by mass of the filled core particles 1 did. Solvent removal and coating operation were performed over 2 hours. Thereafter, the temperature was raised to 180 ° C., stirring was continued for 2 hours, and then the temperature was lowered to 70 ° C. Furthermore, using resin solution C, the resin solution was added to 100 parts by mass of filled core particles 1 so as to be 1.0 part by mass as a coating resin component, and the solvent was removed and the coating operation was performed over 2 hours. . The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated for 4 hours at a temperature of 180 ° C. in a nitrogen atmosphere, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 1. Table 4 shows the physical properties of the magnetic carrier 1 obtained.

[Example of manufacturing magnetic carrier 2]
A magnetic carrier 2 was obtained in the same manner as the magnetic carrier 1 except that the filled core particle 2 was used as the filled core particle and the resin solution A was used. Table 4 shows the physical properties of the magnetic carrier 2.

[Production example of magnetic carrier 3]
100 parts by mass of packed core particles 3 were put into a Nauta mixer (manufactured by Hosokawa Micron) and heated to 70 ° C. under reduced pressure while stirring under the conditions of a screw rotation speed of 100 min ⁻¹ and a screw revolution speed of 3.5 min ⁻¹ . . Subsequently, the resin solution A is diluted with toluene so that the solid content concentration is 15% by mass, and the resin solution is added so as to be 1.0 part by mass as a coating resin component with respect to 100 parts by mass of the filled core particle 3 did. Solvent removal and coating operation were performed over 2 hours. Thereafter, the temperature was raised to 180 ° C., stirring was continued for 2 hours, and then the temperature was lowered to 70 ° C. Furthermore, the resin solution A is adjusted so that the coating resin component is 0.5 parts by mass with respect to 100 parts by mass of the filled core particles 1 with the screw rotation speed of 70 min ⁻¹ and the screw revolution speed of 2.0 min ^−1. The solvent was removed and the coating operation was performed over 2 hours. The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated at a temperature of 180 ° C. for 4 hours under a nitrogen atmosphere, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 3. Table 4 shows the physical properties of the magnetic carrier 3 obtained.

[Production example of magnetic carrier 4]
100 parts by mass of packed core particles 4 were charged into a Nauta mixer (manufactured by Hosokawa Micron Corporation) and heated to 70 ° C. under reduced pressure while stirring under the conditions of a screw rotation speed of 100 min ⁻¹ and a screw revolution speed of 3.5 min ⁻¹ . . Subsequently, the resin solution A is diluted with toluene so that the solid content concentration becomes 10% by mass, and the resin solution is added so as to be 0.5 parts by mass as a coating resin component with respect to 100 parts by mass of the filled core particles 4 did. Solvent removal and coating operation were performed over 2 hours. Thereafter, the temperature was raised to 180 ° C., stirring was continued for 2 hours, and then the temperature was lowered to 70 ° C. Furthermore, the resin solution A diluted so that the solid content concentration is 15% by mass is added, and the solvent is removed over 2 hours so that the resin component A is 100 parts by mass with respect to 100 parts by mass of the filled core particles 4 as the coating resin component. And application | coating operation was performed. The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated at a temperature of 180 ° C. for 4 hours in a nitrogen atmosphere, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 4. Table 4 shows the physical properties of the magnetic carrier 4 obtained.

[Production example of magnetic carrier 5]
100 parts by mass of packed core particles 5 were put into a Nauta mixer (manufactured by Hosokawa Micron), and heated to 70 ° C. under reduced pressure while stirring under the conditions of a screw rotation speed of 100 min ⁻¹ and a rotation speed of 3.5 min ⁻¹ . Subsequently, the resin solution A is diluted with toluene so that the solid content concentration is 15% by mass, and the resin solution is added so that the resin component A becomes 0.5 parts by mass as a coating resin component with respect to 100 parts by mass of the filled core particles 5. did. Solvent removal and coating operation were performed over 2 hours. Thereafter, the temperature was raised to 180 ° C. and stirring was continued for 2 hours. Further, the temperature is lowered to 70 ° C., and the resin solution A diluted to a solid content concentration of 15% by mass is added to 100 parts by mass of the filled core particles 5 as a coating resin component to 0.5 parts by mass. Solvent removal and coating operation were performed over 2 hours. Thereafter, the temperature was raised to 180 ° C., stirring was continued for 2 hours, and then the temperature was lowered to 70 ° C. Furthermore, with respect to 100 parts by mass of the filled core particles 5, the resin solution A diluted so that the solid content concentration becomes 10% by mass as the coating resin component is added, and the solvent is removed over 2 hours. And application | coating operation was performed. The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated at a temperature of 180 ° C. for 4 hours under a nitrogen atmosphere, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 5. Table 4 shows the physical properties of the magnetic carrier 5 obtained.

[Production example of magnetic carrier 6]
The filled core particles 6 were not subjected to a resin coating operation, and were used as they were for evaluation as the magnetic carrier 6. The physical properties of the magnetic carrier 6 are also shown in Table 4.

[Magnetic carrier 7]
The filled core particle 1 was not subjected to a resin coating operation, and was used as it was for evaluation as a magnetic carrier 7. The physical properties of the magnetic carrier 7 are also shown in Table 4.

[Production example of magnetic carrier 8]
100 parts by mass of packed core particles 7 were put into a Nauta mixer (manufactured by Hosokawa Micron Corporation) and heated to 70 ° C. under reduced pressure while stirring under the conditions of a screw rotation speed of 100 min ⁻¹ and a rotation speed of 3.5 min ⁻¹ . Subsequently, the resin solution C is diluted with toluene so that the solid content concentration is 5% by mass, and the solid content concentration is 1.5 parts by mass as a coating resin component with respect to 100 parts by mass of the filled core particles 8. A resin solution diluted to 5% by mass was added. Solvent removal and coating operation were performed over 6 hours. Thereafter, the temperature was raised to 180 ° C., stirring was continued for 2 hours, and then the temperature was lowered to 70 ° C. The resin solution A diluted to a solid content concentration of 10% by mass is added to 100 parts by mass of the filled core particles 7 as a coating resin component, and the solvent is removed and applied over 6 hours. The operation was performed. The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated in a nitrogen atmosphere at a temperature of 180 ° C. for 4 hours, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 8. Table 4 shows the physical properties of the magnetic carrier 8 obtained.

[Production example of magnetic carrier 9]
The filled core particles 8 were not subjected to resin coating operation, and were used as they were for evaluation as magnetic carriers 9. The physical properties of the magnetic carrier 9 are also shown in Table 4.

[Production Example of Magnetic Carrier 10]
The porous magnetic core 3 100 parts by weight was charged into Nauta Mixer (manufactured by Hosokawa Micron Corporation), the rotation speed 50min ^-1 screw, the revolution speed of the screw was heated with stirring to 70 ° C. under conditions of 1.0 min ^-1. Subsequently, the resin solution was added so that the resin solution C was 1.5 parts by mass as a coating resin component with respect to 100 parts by mass of the porous magnetic core 3 and stirred for 2 hours. Under reduced pressure, the solvent was removed and the coating operation was performed over 2 hours. Thereafter, the temperature was raised to 180 ° C., stirring was continued for 2 hours, and then the temperature was lowered to 70 ° C. With respect to 100 parts by mass of the porous magnetic core 11, the resin solution A diluted to a solid content concentration of 10% so as to be 2.5 parts by mass as the coating resin component is added, and the solvent is removed and applied for 6 hours. Went. The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated for 4 hours at a temperature of 180 ° C. in a nitrogen atmosphere, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 10. Table 4 shows the physical properties of the magnetic carrier 10 thus obtained.

[Production Example of Magnetic Carrier 11]
100 parts by mass of packed core particles 9 were put into a Nauta mixer (manufactured by Hosokawa Micron) and heated to 70 ° C. under reduced pressure while stirring under the conditions of a screw rotation speed of 100 min ⁻¹ and a screw revolution speed of 2.0 min ⁻¹ . . Subsequently, the resin solution C was added so that the resin solution C was 0.7 parts by mass as a coating resin component with respect to 100 parts by mass of the filled core particles 9. Solvent removal and coating operation were performed over 2 hours. Thereafter, the temperature was raised to 180 ° C., stirring was continued for 2 hours, and then the temperature was lowered to 70 ° C. The resin solution A diluted to a solid content concentration of 10% so as to be 0.3 parts by mass as a coating resin component is charged with respect to 100 parts by mass of the filled core particles 9 and the solvent removal and coating operation are performed over 6 hours. went. The obtained sample was transferred to a Julia mixer (manufactured by Tokuju Kogakusha Co., Ltd.), heat-treated for 4 hours at a temperature of 180 ° C. in a nitrogen atmosphere, and then classified with a mesh having an opening of 70 μm to obtain a magnetic carrier 11. Table 4 shows the physical properties of the magnetic carrier 11 thus obtained.

[Production Example of Magnetic Carrier 12]
While stirring using a fluidized bed heated to 80 ° C. using the resin solution D, the coating operation and the solvent were performed so that the coating resin component was 1.3% by mass with respect to 100 parts by mass of the filled core particles 10. Removal was performed. Went. Thereafter, heat treatment was performed at 220 ° C. for 2 hours, followed by classification with a mesh having an opening of 70 μm to obtain the magnetic carrier 12. Table 4 shows the physical properties of the magnetic carrier 12 obtained.

[Production Example of Magnetic Carrier 13]
The coating operation and solvent removal were performed in a fluidized bed heated to 80 ° C. using the resin solution B so that the coating resin component was 0.5% by mass with respect to 100 parts by mass of the magnetic core particles 12. Thereafter, heat treatment was performed at 220 ° C. for 2 hours, followed by classification with a mesh having an opening of 70 μm to obtain a magnetic carrier 13. Table 4 shows the physical properties of the magnetic carrier 13 obtained.

[Production Example of Magnetic Carrier 14]
The filled core particles 11 were not subjected to resin coating operation, and were used as they were for evaluation as magnetic carriers 14. The physical properties of the magnetic carrier 14 are also shown in Table 4.

[Production Example of Magnetic Carrier 15]
The coating operation and solvent removal were performed in a fluidized bed heated to 80 ° C. using the resin solution A so that the coating resin component was 1.0% by mass with respect to 100 parts by mass of the magnetic core particles 13. After removing the coating solvent, stirring was continued at 80 ° C. for 2 hours, and the resin solution A was used so that the coating resin component was 1.5% by mass with respect to 100 parts by mass of the magnetic core particles 13. Application operation and solvent removal were performed on the floor. After performing heat treatment at 200 ° C. for 2 hours, the magnetic carrier 15 was obtained by classification with a mesh having an opening of 70 μm. Table 4 shows the physical properties of the magnetic carrier 15 obtained.

[Production example of resin A (hybrid resin)]
1.9 mol of styrene, 0.21 mol of 2-ethylhexyl acrylate, 0.15 mol of fumaric acid, 0.03 mol of dimer of α-methylstyrene, and 0.05 mol of dicumyl peroxide were placed in a dropping funnel. In addition, 7.0 mol of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane; 0 mol, 3.0 mol of terephthalic acid, 2.0 mol of trimellitic anhydride, 5.0 mol of fumaric acid and 0.2 g of dibutyltin oxide are placed in a 4-liter four-necked flask made of glass, a thermometer, a stirring rod, a condenser and nitrogen The introduction tube was installed and placed in a mantle heater. Next, after the inside of the flask was replaced with nitrogen gas, the temperature was gradually raised while stirring, and while stirring at a temperature of 145 ° C., the monomer of the vinyl resin, the crosslinking agent and the polymerization initiator were added from the previous dropping funnel for 5 hours. It was dripped over. Next, the temperature was raised to 200 ° C. and reacted at 200 ° C. for 4.0 hours to obtain a hybrid resin (resin A). The molecular weight of this resin A by GPC was weight average molecular weight (Mw) 64,000, number average molecular weight (Mn) 4500, and peak molecular weight (Mp) 7000.

[Production example of inorganic particles (sol-gel silica fine particles)]
The mixture was heated to 35 ° C. in the presence of methanol, water and ammonia water, and tetramethoxysilane was added dropwise with stirring to obtain a suspension of silica fine particles. Solvent substitution was performed, and hexamethyldisilazane was added to the obtained dispersion as a hydrophobizing agent at room temperature, followed by heating to 130 ° C. for reaction, thereby hydrophobizing the surface of the silica fine particles. After passing through a sieve in a wet manner to remove coarse particles, the solvent was removed and dried to obtain inorganic particles A (sol-gel silica fine particles). The particle size based on the number distribution of the inorganic particles A was 110 nm. Similarly, inorganic particles (sol-gel silica fine particles) B to E having number average particle diameters of 43 nm, 50 nm, 280 nm, and 330 nm were prepared by appropriately changing the reaction temperature and the stirring speed.

<Manufacture of magenta master batch>
-Resin A 60 parts by mass-Magenta pigment (Pigment Red-57 20 parts by mass)-Magenta pigment (Pigment Red-122) 20 parts by mass The above materials were melted and kneaded by a kneader mixer to prepare a magenta master batch.

<Toner Production Example 1>
-Resin A 88.3 parts by mass-Refined paraffin wax (maximum endothermic peak: 70 ° C) 5.0 parts by mass-Magenta masterbatch (colorant content 40% by mass) 19.5 parts by mass-Di-tert-butyl salicylic acid Aluminum compound (negative charge control agent)
0.9 parts by mass After the above formulation was mixed with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), a twin-screw kneader (PCM-30 type, Ikegai Iron Works Co., Ltd.) set at a temperature of 150 ° C. Kneaded). The obtained kneaded material was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized material. The obtained coarsely crushed material was finely pulverized with a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.). Classification is performed using a particle design device (product name: Faculty) manufactured by Hosokawa Micron Corporation, and adjustment is performed so that the number of particles (small particles) having an equivalent circle diameter of 0.500 μm or more and less than 1.985 μm is 5% by number. Thus, toner particles 1 having a weight average particle diameter (D4) of 6.2 μm were obtained.

  To 100 parts by mass of the toner particles 1 obtained, 1.0 part by mass of inorganic silica particles (sol-gel silica fine particles) A and 1.0 parts by mass of hydrophobic silica fine particles having a primary average particle diameter of 16 nm and surface-treated with 20% by mass of hexamethyldisilazane. Toner 1 was obtained by mixing with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.).

<Toner Production Example 2>
Toner 2 was obtained in the same manner as in Toner Production Example 1 except that 100 parts by mass of toner particles 1 were changed to 1.0 part by mass of inorganic particles (sol-gel silica fine particles) C.

<Toner Production Example 3>
A toner 3 was obtained in the same manner as in the toner production example 1 except that in the toner 1 production example, 100 parts by weight of the toner particles 1 were changed to 1.0 part by weight of inorganic particles (sol-gel silica fine particles) D.

<Toner Production Example 4>
Toner 4 was obtained in the same manner as in Toner Production Example 1 except that 100 parts by mass of toner particles 1 were changed to 1.0 part by mass of inorganic particles (sol-gel silica fine particles) E in Example 1 of Toner 1.

<Toner Production Example 5>
In Toner Production Example 1, classification was performed using a particle design apparatus (product name: Faculty) manufactured by Hosokawa Micron Corporation, and particles having a circle equivalent diameter of 0.500 μm or more and less than 1.985 μm (small particles) were 28% by number. Toner particles B were obtained in the same manner except that the adjustment was performed. The obtained toner particles B had a weight average particle diameter (D4) of 5.6 μm. In the production example of the toner 1, the same procedure as in the toner production example 1 except that the toner particles B are used and 1.0 part by mass of inorganic particles (sol-gel silica fine particles) E is added to 100 parts by mass of the toner particles B. Toner 5 was obtained.

<Toner Production Example 6>
In Toner Production Example 1, classification was performed using a particle design apparatus (product name: Faculty) manufactured by Hosokawa Micron Corporation, and particles having a circle equivalent diameter of 0.500 μm or more and less than 1.985 μm (small particles) were reduced to 32% by number. A toner particle C was obtained in the same manner except that the adjustment was performed. The obtained toner particles C had a weight average particle diameter (D4) of 5.4 μm. In the production example of the toner 1, the same procedure as in the toner production example 1 except that the toner particles C are used and 1.0 part by mass of inorganic particles (sol-gel silica fine particles) B is added to 100 parts by mass of the toner particles C. Toner 6 was obtained.

  Table 5 shows the ratio of particles (small particles) having an equivalent circle diameter of 0.500 μm or more and less than 1.985 μm of each toner obtained, and the formulation of the externally added inorganic particles.

[Example 1]
To 92 parts by mass of the magnetic carrier 1, 8 parts by mass of the toner 1 was added and shaken for 10 minutes by a V-type mixer to prepare a two-component developer. Table 7 shows the results of the following evaluation using this two-component developer.

As an image forming apparatus, a digital commercial printing printer imagePRESSSC7000VP modified from Canon was used, and the developer was put in a developing device at a cyan position, and image formation was performed in a normal temperature and normal humidity (23 ° C., 50% RH) environment. The remodeling point was remodeled so that the peripheral speed of the developing sleeve with respect to the photosensitive member was 1.5 times, the discharge port of the replenishment developer was closed, and replenishment was limited to toner. An AC voltage and a DC voltage VDC having a frequency of 2.0 kHz and Vpp of 1.3 kV were applied to the developing sleeve. In the image output test, the DC voltage VDC was increased in increments of 50 V under the condition that the toner load on the color laser copier paper (A4, 81.4 g / m ² ) was fixed at Vback 150 V so that the applied toner amount was 0.5 mg / cm ^2. Adjustments were made and the following evaluation items were evaluated. However, the developability was evaluated only before the image printing test. Details will be described later.

For the evaluation, an FFH image (solid image) is formed on a color laser copier paper (A4, 81.4 g / m ² ), and the FFH image is a value in which 256 gradations are displayed in hexadecimal, Is the first gradation (white background part), and FFH is the 256th gradation (solid part).

  (1) In the image output test, an image output test of 100,000 sheets was performed using an image with an image ratio of 5%. After the image output test, the developer was sampled to confirm the toner concentration in the developer. For the developer that has changed from the initial toner concentration of 8%, the toner is consumed by supplying toner to the developing device or by stopping the toner supply and performing image output. The toner density was adjusted to 8%. After adjusting the toner concentration, the following items were evaluated except for developability.

(2) Developability Before performing an image output test, an FFH image (solid image) is formed on a color laser copier paper (A4, 81.4 g / m ² ), and a reflection density is set with a contrast potential of 300 V as a reference. Then, developability was evaluated from Vpp necessary to obtain an image density of 1.30 or more and 1.60 or less and the obtained reflection density. The reflection density was measured using a spectral densitometer 500 series (manufactured by X-Rite).

  When the reflection density of the FFH image (solid image) does not reach 1.30 at 1.3 kVpp, Vpp is increased to increase the toner development amount.

  The FFH image is a value in which 256 gradations are displayed in hexadecimal, and 00H is the first gradation (white background part) and FFH is the 256th gradation (solid part).

  Determination is made based on Vpp and image density under the above conditions.

(Development evaluation criteria)
(A) At Vpp 1.3 kV, the image reflection density is 1.30 to 1.60 (very good)
(B) Vpp 1.5 kV, 1.30 to 1.60 (good)
(C) Vpp 1.8 kV, 1.30 or more and 1.60 or less (acceptable level in the present invention)
(D) Vpp 1.8 kV, less than 1.30 (level unacceptable in the present invention)

(2) Evaluation of image defects (white spots) A chart in which halftone horizontal bands (30H width 10 mm) and solid image horizontal bands (FFH width 10 mm) are alternately arranged in the transfer direction of the transfer paper is output. The image is read by a scanner and binarized. Note that the 30H image is a value representing 256 gradations in hexadecimal notation, and is a halftone image when 00H is a non-image and FFH is a solid image. Take the luminance distribution (256 gradations) of a certain line in the transport direction of the binarized image, draw a tangent line to the luminance of the halftone at that time, and cross the solid image portion luminance at the rear end of the halftone image portion The brightness area (area: sum of the brightness numbers) deviated from the tangent line is defined as the blank area. The white spot level at the start of durability and after 100,000 sheets was evaluated.

(Evaluation criteria for white spots)
A: 50 or less (very good)
B: 51 or more and 150 or less (good)
C: 151 to 300 (acceptable level in the present invention)
D: 301 or more (level unacceptable in the present invention)

(3) Image quality (Gastsuki)
One halftone image (30H) was printed at A4, and the images at the start of durability and after 100,000 sheets were visually observed.

(Evaluation criteria for rustling)
The roughness of the halftone image was visually evaluated.
A: No roughness (very good)
B: Slightly rough (good)
C: acceptable level (acceptable level in the present invention)
D: Severe rustling (unacceptable level in the present invention)

(5) Fog One solid white image was printed at A4 (set to Vback 150V).

  The average reflectance Dr (%) of the paper was measured by a reflectometer (“REFLECTOMETER MODEL TC-6DS” manufactured by Tokyo Denshoku Co., Ltd.).

  The reflectance Ds (%) of the solid white image was measured.

  The fog rate (%) was calculated using the following formula. The fog level at the start of durability and after 100,000 sheets was evaluated according to the following evaluation criteria.

(Fog evaluation criteria)
Fog rate (%) = Dr (%) − Ds (%)
A: Less than 0.5% (very good)
B: 0.5 or more and less than 1.0% (good)
C: 1.0 to less than 2.0% (acceptable level in the present invention)
D: 2.0% or more (level unacceptable in the present invention)

(6) Adherence of carrier At the start of durability and after output of 100,000 sheets, a 00H image was printed, and the part on the photosensitive drum was sampled by sticking a transparent adhesive tape and adhered to the photosensitive drum in 1 cm × 1 cm. The number of magnetic carrier particles was counted, and the number of adhered carrier particles per 1 cm 2 was counted with an optical microscope.

(Evaluation criteria for carrier adhesion)
A: 3 or less (very good)
B: 4 or more and 10 or less (good)
C: 11 or more and 20 or less (acceptable level in the present invention)
D: 21 or more (level not acceptable in the present invention)

(7) Leak test (white pot)
For the initial leak test, a developer having a toner concentration of 4% is prepared in the same manner as the developer used for durability. After the endurance, using the developer for which the endurance evaluation was completed, the toner supply was stopped and the toner was consumed until the toner concentration reached 4%, and then the test was performed by the following method.

  Five continuous (FFH) images are output continuously on A4 plain paper after the initial durability and 100,000 sheets, and the number of white spots with a diameter of 1 mm or more is counted in the image. Evaluate from the total number.

(Leak evaluation criteria)
A: 0 (very good)
B: 1 or more and less than 10 (good)
C: 10 or more and less than 20 (acceptable level in the present invention)
D: 20 or more and less than 100 (level unacceptable in the present invention)

(8) Image density fluctuation An X-Rite color reflection densitometer (500 series: manufactured by X-Rite) was used to measure image density and fog. The difference in image density at the start of durability and after 100,000 sheets was evaluated based on the following criteria.

(Evaluation criteria)
A: 0.00 or more and less than 0.05 B: 0.05 or more and less than 0.10 C: 0.10 or more and less than 0.20 (acceptable level in the present invention)
D: 0.20 or more (level unacceptable in the present invention)

[Examples 2 to 9, Reference Example 1 , Comparative Examples 1 to 8]
Two-component developers were prepared by combining magnetic carriers and toners shown in Table 6. In the same manner as in Example 1, the blending ratio of magnetic carrier 90.0% by mass and toner 10.0% by mass was mixed for 10 minutes with a V-type mixer and used for evaluation. The respective evaluation results are shown in Table 7.

It is an example showing the projection image which visualized the reflected electron image mainly of the magnetic carrier of this invention. It is a schematic diagram for demonstrating the state of the surface of the magnetic carrier of FIG. FIG. 2 is a schematic cross-sectional view of an apparatus for measuring the specific resistance of a porous magnetic carrier core in order to determine the electric field strength just before breakdown of the porous magnetic carrier core of the present invention, and (a) is a blank before putting a sample. It is a figure in the state of this, (b) is a figure which shows a state when a sample is put. It is an example of the graph which shows the measurement result of a specific resistance. The result of having measured the porous magnetic carrier core of Example 1 is shown. It is an example which shows the state which image-processed the magnetic carrier particle of FIG. 1, and extracted the magnetic carrier particle. It is an example which shows the state which image-processed the magnetic carrier particle | grains of FIG. 1, and extracted parts other than the resin part on the magnetic carrier particle surface. It is an example of the projection figure which visualized the reflected electron of the magnetic carrier of this invention mainly with the magnification of 600 times. It is an example of the figure which shows the mode after the pre-process of the image processing of the projection figure which mainly visualized the reflection electron of the magnetic carrier of this invention. It is an example of the figure which shows the state which extracted the magnetic carrier particle from the projection figure which visualized the reflected electron mainly of the magnetic carrier of this invention. It is an example of the figure which shows the state which excluded the carrier particle of the image outer peripheral part from the magnetic carrier particle extracted from the projection figure which visualized the reflected electron mainly of the magnetic carrier of this invention. It is an example of the figure which shows the state which narrowed down the particle | grains to image-process according to a particle size from the magnetic carrier particle | grains extracted in FIG. It is an example of the figure explaining the state which extracted parts other than the resin part on the magnetic carrier particle of this invention.

Explanation of symbols

1 Resin container 2 Lower electrode 3 Support base 4 Upper electrode 5 Sample 6 Electron meter 7 Processing computer A Resistance measurement cell d Sample height d1 (blank) Height without sample d2 (sample) Height with sample The

Claims (6)

A magnetic carrier having magnetic carrier particles containing at least porous magnetic ferrite core particles and a resin,
The area of the resin portion on the projection surface of the reflected electron image of the magnetic carrier particles photographed at an acceleration voltage of 2.0 kV using a scanning electron microscope is 92.0 area% or more with respect to the magnetic carrier particle projection surface. 99.5 area% or less,
Wherein the porous electric field intensity just before the break-down of the magnetic ferrite core particles state, and are less 300 V / cm or more 1388 V / cm,
Wherein on a projection plane of the reflected electron image of the magnetic carrier particles, the magnetic carrier, wherein the average area value of the portion derived from the metal oxide, is 0.45 [mu] m ² or more 1.40 .mu.m ² or less. The magnetic carrier according to claim 1, wherein the magnetic carrier particles are filled with a resin in at least a part of the voids of the porous magnetic ferrite core particles. The magnetic carrier particles are filled with the first resin in at least a part of the voids of the porous magnetic ferrite core particles, and the surface thereof may be the same as or different from the first resin. The magnetic carrier according to claim 1, wherein the magnetic carrier is coated with a good second resin. A two-component developer containing at least a magnetic carrier and a toner, wherein the magnetic carrier is the magnetic carrier according to any one of claims 1 to 3 . The toner has 30 particles having an equivalent circle diameter of 0.500 μm or more and 1.985 μm or less measured by a flow type particle image measuring apparatus having an image processing resolution of 512 × 512 pixels (0.37 μm × 0.37 μm per pixel) The two-component developer according to claim 4 , wherein the two-component developer is at most several percent. The two-component developer according to claim 4 or 5 , wherein the toner contains inorganic particles having a maximum value in a range of 50 nm to 300 nm in a particle size distribution based on a number distribution.

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