JP2013231840A - Manufacturing method of carrier core material for electrophotographic developer, carrier core for electrophotographic developer, carrier for electrophotographic developer, and electrophotographic developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a carrier core capable of manufacturing a carrier core capable of providing good images over long-term use, while achieving high chargeability and low density.SOLUTION: A manufacturing method of a carrier core according to the present invention includes: a granulation step (A) of mixing a raw material including manganese and a raw material including iron, and granulating the resulting mixture; a calcination step (B) of calcining the granules granulated in the granulation step within a temperature range of 1050°C to 1300°C; and removal step (G) of removing components present in a grain boundary part of calcined crystals from among obtained calcined powder.

Description

  The present invention relates to a method for producing a carrier core material for an electrophotographic developer (hereinafter sometimes simply referred to as “carrier core material”), a carrier core material for an electrophotographic developer, and a carrier for an electrophotographic developer (hereinafter simply referred to as “a carrier core material”). And electrophotographic developer (hereinafter sometimes simply referred to as “developer”), and in particular, an electrophotographic developer used in a copying machine, an MFP (Multifunctional Printer), and the like. The present invention relates to an electrophotographic developer carrier core material, a method for producing the same, an electrophotographic developer carrier provided in the electrophotographic developer, and an electrophotographic developer.

  In a copying machine, MFP, etc., as a dry development method in electrophotography, a one-component developer using only toner as a component of developer and a two-component developer using toner and carrier as components of developer are provided. is there. In any of the development methods, toner charged to a predetermined charge amount is supplied to the photoreceptor. Then, the electrostatic latent image formed on the photosensitive member is visualized with toner and transferred to a sheet. Thereafter, the visible image with toner is fixed on the paper to obtain a desired image.

  Here, the development in the two-component developer will be briefly described. A predetermined amount of toner and a predetermined amount of carrier are accommodated in the developing device. The developing device includes a rotatable magnet roller in which a plurality of S poles and N poles are alternately provided in the circumferential direction, and a stirring roller that stirs and mixes the toner and the carrier in the developing device. A carrier made of magnetic powder is carried by a magnet roller. A linear magnetic brush made of carrier particles is formed by the magnetic force of the magnet roller. A plurality of toner particles adhere to the surface of the carrier particles by frictional charging by stirring. Toner is supplied to the surface of the photoconductor by rotating the magnet roller so that the magnetic brush is applied to the photoconductor. In a two-component developer, development is performed in this way.

  As for the toner, the toner in the developing device is sequentially consumed by fixing to the paper, so new toner corresponding to the consumed amount is supplied from time to time to the developing device from the toner hopper attached to the developing device. The On the other hand, the carrier is not consumed by development and is used as it is until the end of its life. The carrier that is a constituent material of the two-component developer includes a toner charging performance and an insulating property for efficiently charging the toner by frictional charging by stirring, a toner transporting ability to appropriately transport and supply the toner to the photoreceptor, etc. Various functions are required. For example, from the viewpoint of improving the charging ability of the toner, the carrier is required to have an appropriate electrical resistance value (hereinafter also simply referred to as a resistance value).

  In recent years, the above-described carrier is composed of a core material, that is, a carrier core material constituting a core portion, and a coating resin provided so as to cover the surface of the carrier core material. A technique related to the carrier core material is disclosed in Japanese Patent Laid-Open No. 3-229271 (Patent Document 1).

JP-A-3-229271

  As described above, the carrier core material is coated with the coating resin. This coating resin imparts main characteristics as a carrier, such as toner charging performance. Here, the carrier core material itself before coating with the coating resin is also required to have a high function of charging the toner efficiently by frictional charging, that is, a high toner charging performance.

  For this, for example, the following cases can be considered. With regard to a developer obtained by stirring and mixing a predetermined amount of carrier and a predetermined amount of toner, the image quality and the development characteristics are kept good in the initial stage of the use of the developer due to the above-described characteristics of the coating resin. It is. However, if the developer is used for a long period of time and the carrier continues to be used as it is in the developing device, for example, a region where the coating resin is not coated due to part of the coating resin peeling or chipping or cracking of the carrier. May be exposed on the surface of the carrier core material. In such a case, the characteristics of the carrier core material itself, that is, the toner charging performance of the carrier core material itself is directly reflected in the image quality and the development characteristics. Therefore, when it is desired to obtain a good image over a long period of time, the carrier core material itself is required to have high toner charging performance.

  Further, as described above, the carrier in which the carrier core material is coated with the coating resin is used for a long time in the developing device, and is stirred for a long time. Under such circumstances, it is required to reduce the stirring torque in the developing device. As a characteristic required as a carrier for reducing the stirring torque, a specific gravity is light, that is, a so-called low density carrier is required. In this case, the amount of the resin portion used is generally small, and the specific gravity of the resin itself is low. Therefore, in order to reduce the density of the carrier, it is required to reduce the density of the carrier core material itself that is a member constituting the carrier.

  Here, Patent Document 1 discloses a carrier in which the surface of a carrier core particle having a pore area of less than 10% including a major axis is corrugated by being corroded with acid or alkali, and the surface is coated with a resin. Although disclosed, the conventional carrier core material represented by Patent Document 1 may be insufficient for long-term use. Specifically, for example, although a certain level of performance is obtained in the early stage of use as a developer, the ratio of occurrence of cracks and chipping of the carrier core material becomes relatively high with long-term use, or coating In some cases, the ratio of part of the resin to be peeled off becomes relatively large, and the image quality and the like of the image to be formed deteriorates, causing problems. Also, the specific gravity itself was insufficient.

  An object of the present invention is for an electrophotographic developer capable of producing a carrier core material for an electrophotographic developer capable of obtaining a good image even in long-term use while achieving high chargeability and low density. It is providing the manufacturing method of a carrier core material.

  Another object of the present invention is to provide a carrier core material for an electrophotographic developer capable of obtaining a good image even during long-term use while achieving high chargeability and low density.

  Still another object of the present invention is to provide a carrier for an electrophotographic developer capable of obtaining a good image even after long-term use.

  Still another object of the present invention is to provide an electrophotographic developer capable of obtaining a good image even after long-term use.

  The inventors of the present application first considered that manganese and iron are the main components in order to ensure good magnetic properties. A carrier core material mainly composed of manganese and iron has good magnetic properties. Furthermore, the electrical characteristics are basically good.

  The inventors of the present application have made extensive studies to reduce the density of the carrier core material while maintaining good electrical characteristics and magnetic characteristics. And the following composition was found. That is, first, in order to maintain good electrical characteristics and magnetic characteristics, it was considered essential to sufficiently promote the sintering reaction of the raw materials in the firing process. Then, from the viewpoint of reducing the density, attention was focused on the crystal grain boundary portion of the sintered powder that sufficiently promoted the sintering reaction. For this part, the degree of sintering is somewhat insufficient compared to the crystalline part of the sintered powder that has sufficiently promoted the sintering reaction, and the electrical and magnetic properties of the carrier core material are kept good. We thought that the degree to contribute to was low. Therefore, the inventors of the present application positively removed this part, specifically, the grain boundary part between the crystals formed by the sintering reaction, and the other part, specifically, sufficient In order to reduce the density of the carrier core material itself while positively leaving the crystal part that promoted the sintering reaction and maintaining good electrical and magnetic properties, the configuration of the present invention was achieved. is there.

  That is, the method for producing a carrier core material for an electrophotographic developer according to the present invention is a method for producing a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, the raw material containing manganese, and iron A granulation step of mixing raw materials containing the granulation, a firing step of firing the granulated product granulated by the granulation step within a temperature range of 1050 ° C to 1300 ° C, and a firing step, A removal step of removing a component present in the grain boundary portion of the sintered crystal from the obtained sintered powder.

  According to such a method for producing a carrier core material for an electrophotographic developer, the obtained carrier core material contains manganese and iron as a core composition, and a sintering temperature of 1050 ° C. to 1300 ° C. is sufficient in the firing step. Since the sintering reaction is promoted, the magnetic characteristics are good and the electrical characteristics are also good. And since the component which exists in the grain boundary part of the sintered crystal | crystallization is removed, the density reduction can be achieved. In this case, since the sintered crystals formed with sufficient promotion of the sintering reaction are actively left and the components present in the grain boundary portions of the sintered crystals are actively removed, The obtained carrier core material can be reduced in density while maintaining good electrical characteristics and magnetic characteristics. That is, it is possible to efficiently reduce the density without impairing the electrical characteristics and magnetic characteristics.

  Here, for the carrier core material to be manufactured, the sintering temperature is set to a low temperature, that is, about 700 ° C. to 1050 ° C., so that the sintering reaction is not sufficiently promoted, and irregularities are formed on the surface of the obtained carrier core material. Therefore, there is a method for reducing the density. That is, this is a technique for obtaining a so-called porous carrier core material. However, according to such a low temperature sintering method, the sintering reaction is not sufficiently promoted, so that the magnetic characteristics and electrical characteristics of the sintered powder become insufficient. Specifically, the chargeability of the carrier core material is low, or the residual magnetization value is high. In some cases, the apparent density (AD) is high, so that the density cannot be sufficiently reduced. In other words, the basic performance of the carrier core material that is required recently is insufficient. Such a carrier core material having no basic performance is insufficient as a carrier constituting a developer mounted on a copying machine, a printer, or the like that is required to have a high speed and a long life. . Further, in such a sintering reaction at a low temperature, the sintering reaction proceeds temporarily, but it is very difficult to control the so-called porous shape, size, and volume. Moreover, there are many temperature irregularities at the time of a sintering reaction, and as a result, the dispersion | variation in the crystal growth between particle | grains will become large. Such a situation is not preferable from the viewpoint of productivity.

  According to the carrier core material obtained according to the present invention, the sintering temperature is set to 1050 ° C. to 1300 ° C. to promote sufficient sintering reaction at a high temperature, and the sintering reaction can be promoted almost uniformly. The degree of variation in crystal growth can be greatly reduced. That is, it is possible to improve the productivity of the carrier core material with a reduced density while maintaining good electrical characteristics and magnetic characteristics. In other words, the method for producing a carrier core material according to the present invention is excellent from the viewpoint of productivity to obtain a carrier core material having good characteristics. Then, with respect to the carrier core material, while maintaining good electrical characteristics and magnetic characteristics, the density is reduced, and a developer including a carrier in which such a carrier core material is coated with a resin is provided in the developing device. In addition to reducing the stress of agitation, even if part of the coating resin is peeled off or cracked or chipped due to long-term use, the image quality is improved by the good electrical and magnetic properties of the carrier core itself. Etc., and a longer life is achieved.

  Moreover, you may comprise so that a removal process may be a process which melt | dissolves and removes the component which exists in the grain boundary part of the sintered crystal | crystallization. By carrying out like this, a grain boundary part can be removed substantially uniformly with respect to the surface of particulate-form sintered powder, and appropriate and efficient removal can be performed.

  In the removing step, the sintered powder is immersed in hydrochloric acid having a concentration of 4.8 mol / l (liter) or more and 11.0 mol / l or less and 35 ° C. or more in a time range of 2 hours or more and 20 hours or less. You may comprise so that it may be a process to do. The hydrochloric acid used in the removal step has a certain degree of correlation with the degree of removal with respect to temperature, concentration, and immersion time. By adjusting the temperature, concentration, and immersion time, the degree of removal, that is, the density can be adjusted, and a carrier core material having a desired density can be obtained relatively easily. For example, according to the binding property with the coating resin and the amount of the coating resin to be used, the density can be adjusted while maintaining good electrical characteristics and magnetic characteristics, which is very effective.

  In another aspect of the present invention, the carrier core material for an electrophotographic developer is a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, the raw material containing manganese, and iron The raw materials to be mixed are granulated, and the obtained granulated powder is fired within a temperature range of 1050 ° C. to 1300 ° C., and among the obtained sintered powder, the grain boundaries of the sintered crystals are formed. Manufactured by removing existing components.

In still another aspect of the present invention, the carrier core material for an electrophotographic developer is a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, and the charge amount is 20 μC / g and the apparent density value is 2.1 g / cm ³ or less.

  In still another aspect of the present invention, the carrier core material for an electrophotographic developer is a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, and the carrier core material for an electrophotographic developer When the particles of the material are spherical, when the structure is observed by cutting along a plane passing through the center of the particles of the carrier core material, the maximum value of the upper limit of the pore diameter is 2.3 μm or more, The maximum value of the upper limit value of the pore depth is 7.6 μm or more.

  In still another aspect of the present invention, the carrier core material for an electrophotographic developer is a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, and the carrier core material for an electrophotographic developer When the particles of the material are made into a spherical body, when the structure is observed by cutting along the plane passing through the center of the particle of the carrier core material, the area ratio of the area of the sintered portion is electrophotographic development. It is 83.0% or less of the area of a circle centering on the center of the particle of the carrier core material for an agent and having the outer diameter surface of the particle of the carrier core material for an electrophotographic developer as a diameter.

  Such a carrier core material can obtain a good image even in long-term use while achieving high chargeability and low density.

  In still another aspect of the present invention, an electrophotographic developer carrier is an electrophotographic developer carrier used for an electrophotographic developer, and the carrier core material for an electrophotographic developer described above, And a resin that covers the surface of the carrier core material for an electrophotographic developer.

  Such a carrier for an electrophotographic developer can obtain a good image in long-term use.

  In still another aspect of the present invention, the electrophotographic developer is an electrophotographic developer used for electrophotographic development, and includes the above-described electrophotographic developer carrier and the electrophotographic developer carrier. And a toner capable of being charged in electrophotography by frictional charging.

  Such an electrophotographic developer can obtain a good image in long-term use.

  According to the method for producing a carrier core material for an electrophotographic developer according to the present invention, a carrier core for an electrophotographic developer capable of obtaining a good image even in long-term use while achieving high chargeability and low density. The material can be manufactured.

  Further, the carrier core material for an electrophotographic developer according to the present invention can obtain a good image even in long-term use while achieving high chargeability and low density.

  In addition, the carrier for an electrophotographic developer according to the present invention can obtain a good image in long-term use.

  In addition, the electrophotographic developer according to the present invention can obtain a good image in long-term use.

2 is an electron micrograph showing the appearance of a carrier core material of Example 1. FIG. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. FIG. 3 is a schematic view in which a region where crystals are present and a region where voids are present are separated by lines in the cross section of the carrier core material shown in FIG. 2. It is a flowchart which shows a typical process among the manufacturing methods of the carrier core material which concerns on one Embodiment of this invention. 4 is an electron micrograph showing the appearance of a carrier core material of Example 2. FIG. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 4 is an electron micrograph showing the appearance of a carrier core material of Example 3. FIG. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 4 is an electron micrograph showing the appearance of a carrier core material of Example 4. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 6 is an electron micrograph showing the appearance of a carrier core material of Example 5. FIG. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 6 is an electron micrograph showing the appearance of a carrier core material of Example 6. FIG. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 4 is an electron micrograph showing the appearance of a carrier core material of Comparative Example 1. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 4 is an electron micrograph showing the appearance of a carrier core material of Comparative Example 2. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 6 is an electron micrograph showing the appearance of a carrier core material of Comparative Example 3. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 6 is an electron micrograph showing the appearance of a carrier core material of Comparative Example 4. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 6 is an electron micrograph showing the appearance of a carrier core material of Comparative Example 5. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG. 14 is an electron micrograph showing the appearance of a carrier core material of Comparative Example 6. It is an electron micrograph which shows the cross section of the carrier core material shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. First, a carrier core material according to an embodiment of the present invention will be described. FIG. 1 is an electron micrograph showing the appearance of a carrier core material according to an embodiment of the present invention. FIG. 1 shows a carrier core material according to Example 1 described later. FIG. 2 is an electron micrograph showing a cross section of the carrier core shown in FIG. FIG. 2 corresponds to a case where the carrier core material having a spherical shape is cut along a plane passing through substantially the center. FIG. 1 shows a state in which the appearance of the carrier core material is enlarged by 3000 times, and FIG. 2 shows a state in which the cross section of the carrier core material is enlarged by 2700 times. In the electron micrographs shown in FIGS. 5 to 26 described later, the magnification is shown in the electron micrograph or described later. For easy understanding, FIG. 3 shows a schematic diagram in which a region where crystals are present and a region where voids are present are separated by lines in the cross section of the carrier core shown in FIG. The carrier core material illustrated in FIGS. 1 to 3 refers to the carrier core particle itself. In FIG. 2, a portion indicated by a black region of what appears to be a particle shape represents a void in a so-called carrier core material.

  1 to 3, the outer shape of the carrier core material 11 according to one embodiment of the present invention is a substantially spherical shape. The particle diameter of the carrier core material 11 according to an embodiment of the present invention is about 35 μm. In addition, the group of carrier core materials in which the particles of the carrier core material 11 gather has an appropriate particle size distribution. The above-mentioned particle diameter means a volume average particle diameter. The particle size and particle size distribution are arbitrarily set depending on required developer characteristics, yield in the manufacturing process, and the like. The carrier core material 11 is formed with a minute uneven shape mainly formed in a firing step described later.

  The carrier core material 11 has a gap 12 therein. The void 12 is formed by removing components present in the grain boundary portion of the sintered crystal from the sintered powder obtained by sintering in the manufacturing process of the carrier core material 11 described later. is there. That is, the void 12 is mainly located between the sintered crystals 13. The void 12 here mainly indicates a region formed from the surface 14 of the particle of the carrier core material 11 to a considerable extent inside the particle. For example, the void 12 is formed on the surface of the sintered crystal 13. It does not mainly show minute irregularities. The sintered crystal 13 is indicated by a hatched region in FIG.

  Here, when the particles of the carrier core material 11 are formed into a spherical body, the region of the sintered crystal 13 is obtained when the structure is observed by cutting along a plane passing through the center 15 of the particles of the carrier core material 11. The area ratio of the carrier core material 11 is 83.0% or more of the area of the circle centering on the particle center 15 of the carrier core material 11 and having the diameter of the outer diameter surface 16 of the carrier core material 11 particle. . The outer diameter surface is indicated by a dotted line in FIG.

  In addition, although illustration is abbreviate | omitted, also about the carrier which concerns on one Embodiment of this invention, the outer shape of the carrier core material 11 is a substantially spherical shape. The carrier is obtained by thinly coating the surface of the carrier core material 11 with a resin, that is, the particle diameter is almost the same as that of the carrier core material 11. Unlike the carrier core material 11, the carrier surface is almost completely covered with a resin.

  An electrophotographic developer according to an embodiment of the present invention includes the above-described carrier and toner. The outer shape of the toner is also substantially spherical. The toner is mainly composed of a styrene acrylic resin or a polyester resin, and contains a predetermined amount of pigment, wax or the like. Such a toner is manufactured by, for example, a pulverization method or a polymerization method. For example, a toner having a particle diameter of about 5 μm, which is about 1/7 of the particle diameter of the carrier, is used. Further, the mixing ratio of the toner and the carrier is also arbitrarily set according to the required developer characteristics and the like. Such a developer is produced by mixing a predetermined amount of carrier and toner with an appropriate mixer.

  Next, a method for manufacturing a carrier core material according to an embodiment of the present invention will be described. FIG. 4 is a flowchart showing typical steps in the method for manufacturing the carrier core material according to the embodiment of the present invention. Hereinafter, the manufacturing method of the carrier core material according to the present invention will be described with reference to FIG.

  First, a raw material containing manganese and a raw material containing iron are prepared. At this time, the calcined raw material may be used as the raw material to be used. Examples of the calcining conditions include heating for 1 to 10 hours at a temperature of 800 to 1100 ° C. in an air atmosphere.

The prepared raw materials are blended at an appropriate blending ratio according to required characteristics and mixed. About the iron raw material which comprises the carrier core material which concerns on one Embodiment of this invention, what is necessary is just metallic iron or its oxide. Specifically, Fe ₂ O ₃ , Fe ₃ O ₄ , Fe, and the like that exist stably at normal temperature and pressure are preferably used. The manganese raw material may be metal manganese or an oxide thereof. Specifically, metals Mn, MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , and MnCO ₃ that exist stably at normal temperature and pressure are preferably used. In addition, you may calcine and grind | pulverize the raw material which mixed the said raw material (iron raw material, manganese raw material) so that it might become the target composition, and may use it as a raw material. Moreover, about the above-mentioned iron raw material and manganese raw material, magnesium etc. are contained as an inevitable impurity though it is a trace amount.

  Next, the mixed raw material is slurried. That is, these raw materials are weighed according to the target composition of the carrier core material and mixed to obtain a slurry raw material.

  In the manufacturing process for manufacturing the carrier core material according to the present invention, a reducing agent may be further added to the above-described slurry raw material in order to advance the reduction reaction in the baking process described later. As the reducing agent, carbon powder, polycarboxylic acid organic substance, polyacrylic acid organic substance, maleic acid, acetic acid, polyvinyl alcohol (PVA (polyvinyl alcohol)) organic substance, and a mixture thereof are preferably used.

  Water is added to the slurry raw material described above and mixed and stirred, so that the solid concentration is 40% by weight or more, preferably 50% by weight or more. If the solid content concentration of the slurry raw material is 50% by weight or more, it is preferable because the strength of the granulated pellet can be maintained.

  Then, the slurryed raw material is granulated (FIG. 4A). That is, a raw material containing manganese and a raw material containing iron are mixed together with a reducing agent contained in a ratio of 0.10 to 1.00% by weight with respect to the total amount of the raw material containing manganese and the raw material containing iron. Granulate. Granulation of the slurry obtained by mixing and stirring is performed using a spray dryer. In addition, it is also preferable to further wet-grind the slurry before granulation.

  The atmospheric temperature during spray drying may be about 100 to 300 ° C. Thereby, the granulated powder whose particle diameter is 10-200 micrometers can be obtained in general. The obtained granulated powder takes into consideration the final particle size of the product, removes coarse particles and fine powder using a vibrating sieve or the like, and adjusts the particle size at this point. That is, classification is performed. This classification process is the first classification process (FIG. 4B).

  Thereafter, the granulated product is fired (FIG. 4C). Specifically, the obtained granulated powder is put into a furnace heated to a temperature of about 1050 ° C. to 1300 ° C. as a firing temperature, and is fired by holding for 0.5 to 10 hours to generate a desired fired product. . At this time, the oxygen concentration in the firing furnace is specifically fired under a flow state in a nitrogen atmosphere in which the oxygen concentration of the introduced gas is adjusted to be 100 ppm to 50000 ppm.

  For the sintered product obtained by lowering the temperature to the room temperature level after firing, it is desirable to further adjust the particle size at this stage. For example, the sintered product is coarsely pulverized with a hammer mill or the like. That is, the granulated material is pulverized (FIG. 4D). After that, classification is performed using a vibrating screen. That is, classification is performed on the pulverized granular material. This classification step is the second classification step (FIG. 4E). By carrying out like this, the particle | grains of the carrier core material with a desired particle size can be obtained.

  Next, the classified granular material is oxidized (FIG. 4F). That is, the particle surface of the carrier core material obtained at this stage is heat-treated (oxidation treatment). And the dielectric breakdown voltage of particle | grains is raised and an electrical resistance value is made into an appropriate electrical resistance value. By doing so, carrier scattering due to charge leakage can be prevented. This oxidation step may not be performed according to the value of electrical resistance required for the carrier core material. That is, this oxidation step can be omitted if necessary.

  Specifically, the oxidation is held at 200 to 700 ° C. for 0.1 to 24 hours in an atmosphere having an oxygen concentration of 10 to 100%. More preferably, it is 0.5 to 20 hours at 250 to 600 ° C, and more preferably 1 to 12 hours at 300 to 550 ° C.

  Thereafter, the components present in the grain boundary portion of the sintered crystal are removed (FIG. 4G). This step is a removal step of removing components present in the grain boundary portion of the sintered crystal from the sintered powder. As this removal process, you may comprise so that the component which exists in the grain boundary part of the sintered crystal | crystallization may be melt | dissolved and removed chemically. By carrying out like this, a grain boundary part can be removed substantially uniformly with respect to the surface of particulate-form sintered powder, and appropriate and efficient removal can be performed.

  Further, in the removing step, the sintered powder is immersed in hydrochloric acid having a concentration of 4.8 mol / l (liter) or more and 11.0 mol / l or less and 35 ° C. or more in a time range of 2 hours or more and 20 hours or less. You may comprise so that it may be a process to do. By doing so, it is possible to more reliably remove the components present in the grain boundary portion of the sintered crystal.

  Here, the hydrochloric acid used in the removal step has a certain degree of correlation with the degree of removal with respect to temperature, concentration, and immersion time. By adjusting the temperature, concentration, and immersion time, the degree of removal, that is, the density can be adjusted, and a carrier core material having a desired density can be obtained relatively easily. For example, according to the binding property with the coating resin and the amount of the coating resin to be used, the density can be adjusted while maintaining good electrical characteristics and magnetic characteristics, which is very effective.

  An example of a specific removal process will be described. A beaker is prepared, hydrochloric acid having a concentration of 4.8 mol / l (liter) to 11.0 mol / l and a temperature of 35 ° C. or more is prepared. Put in. Thereafter, the sintered powder is put into the beaker. Then, within the above-described time range, stirring is appropriately performed, and for example, heat is continuously applied from the lower side of the beaker so that the temperature is not lower than 35 ° C., and the removing step is performed. Thereafter, the fired powder that has been processed is taken out from the beaker, washed with water, and dried.

  Thus, the carrier core material according to one embodiment of the present invention is manufactured. That is, the method for producing a carrier core material for an electrophotographic developer according to an embodiment of the present invention is a method for producing a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, and includes manganese. A granulation step in which a raw material and a raw material containing iron are mixed and granulated, a firing step in which the granulated product granulated in the granulation step is sintered within a temperature range of 1050 ° C. to 1300 ° C., and a firing step After performing this, the removal process which removes the component which exists in the grain boundary part of the sintered crystal | crystallization among the obtained sintered powder is provided.

  According to such a method for producing a carrier core material for an electrophotographic developer, the obtained carrier core material includes manganese and iron as a core composition, and a sintering temperature of 1050 ° C. to 1300 ° C. is sufficient in the firing step. Therefore, the magnetic characteristics are good and the electrical characteristics are good. And since the component which exists in the grain boundary part of the sintered crystal | crystallization is removed, the density reduction can be achieved. In this case, the sintered crystals formed by sufficiently promoting the sintering reaction were positively retained, and the components present in the grain boundary portions of the sintered crystals were removed, so that the obtained The carrier core material can be reduced in density while maintaining good electrical characteristics and magnetic characteristics. That is, efficient density reduction can be achieved without impairing electrical characteristics and magnetic characteristics.

  The carrier core material for an electrophotographic developer is a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, and is mixed with a raw material containing manganese and a raw material containing iron for granulation. The obtained granulated powder is fired within a temperature range of 1050 ° C. to 1300 ° C., and the obtained sintered powder is manufactured by removing components present at the grain boundary portion of the sintered crystal. The

  The carrier core material configured as described above is mainly composed of manganese and iron and has good magnetic characteristics and electrical characteristics. Further, the density can be reduced.

  The carrier core material thus obtained is coated with a resin (FIG. 4H). Specifically, the obtained carrier core material according to the present invention is covered with a silicone resin, an acrylic resin, or the like. By doing so, it is possible to obtain an electrophotographic developer carrier by imparting chargeability and improving durability. A coating method such as silicone resin or acrylic resin can be performed by a known method. That is, an electrophotographic developer carrier according to an embodiment of the present invention is an electrophotographic developer carrier used for an electrophotographic developer, and includes the above-described carrier core material for an electrophotographic developer, and electrophotography. And a resin that covers the surface of the carrier core material for developer.

  In addition, about such a carrier core material, the quantity of resin taken in in a space | gap increases. However, in the carrier core material, since crystals that have undergone a sufficient sintering reaction remain, the degree of causing a decrease in chargeability based on an increase in the amount of resin is very small.

  Next, a predetermined amount of the carrier and toner thus obtained are mixed (FIG. 4I). Specifically, the electrophotographic developer carrier according to the present invention and an appropriate known toner are mixed. Thus, the electrophotographic developer according to the present invention can be obtained. For the mixing, for example, an arbitrary mixer such as a ball mill is used. That is, an electrophotographic developer according to an embodiment of the present invention includes the above-described electrophotographic developer carrier and a toner that can be charged in electrophotography by frictional charging of the electrophotographic developer carrier.

Example 1
As raw materials, Fe ₂ O ₃ (average particle size 0.6 μm) 10.75 kg (67.3 mol), Mn ₃ O ₄ (average particle size 2.0 μm) 4.25 kg (19.0 mol) and water 5 Disperse in 0.0 kg, 90 g of an ammonium polycarboxylate dispersant as a dispersant, 45 g of carbon black as a reducing agent, and 30 g (0.25 mol) of colloidal silica (solid content concentration 50%) as an SiO ₂ raw material are added. To make a mixture. When the solid content concentration at this time was measured, it was 75% by weight. This mixture was pulverized by a wet ball mill (media diameter 2 mm) to obtain a mixed slurry. This mixed slurry was sprayed into hot air at about 130 ° C. with a spray dryer to obtain a dry granulated product having a particle size of 10 to 200 μm. From this granulated product, coarse particles were separated using a sieve mesh having a mesh size of 54 μm, and fine particles were separated using a sieve mesh having a mesh size of 33 μm. This granulated powder was put into an electric furnace in a nitrogen atmosphere in which the oxygen concentration was adjusted to 8000 to 12000 ppm and fired at 1240 ° C. for 3 hours. The obtained sintered powder was pulverized and then classified using a vibration sieve to obtain ferrite particles having an average particle diameter of 35 μm. 60 g of this ferrite particle was put into 100 ml of hydrochloric acid (9.6 mol / l) and immersed for 12 hours at 90 ° C. with appropriate stirring. Then, it washed with water and dried and obtained the carrier core material which concerns on Example 1 which removed the component which exists in a grain-boundary part.

Tables 1, 2 and 3 show the material properties, electrical properties, and actual machine performance of the obtained carrier core material. Here, with respect to material properties, pore diameter (upper / lower limit, average) (μm), pore depth (upper / lower limit, average) (μm), apparent density (AD) (g / cm ³ ), tap density ( g / cm ³ ) and pore volume (cm ³ / g), and the electrical characteristics indicate the charge amount (μC / g). The measurement of each physical property will be described later. The same applies to the following.

(Example 2)
A carrier core material according to Example 2 was obtained in the same manner as in Example 1 except that the immersion time in hydrochloric acid was changed to 5 hours. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 5, and the electron micrograph of the cross section of the carrier core material shown in FIG. 5 is shown in FIG.

(Example 3)
A carrier core material according to Example 3 was obtained in the same manner as in Example 1 except that the immersion time in hydrochloric acid was 2 hours. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 7, and the electron micrograph of the cross section of the carrier core material shown in FIG. 7 is shown in FIG.

Example 4
A carrier core material according to Example 4 was obtained in the same manner as in Example 1 except that the temperature of hydrochloric acid was 35 ° C. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 9, and the electron micrograph of the cross section of the carrier core material shown in FIG. 9 is shown in FIG.

(Example 5)
A carrier core material according to Example 5 was obtained in the same manner as in Example 1 except that the temperature of hydrochloric acid was 50 ° C. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 11, and the electron micrograph of the cross section of the carrier core material shown in FIG. 11 is shown in FIG.

(Example 6)
A carrier core material according to Example 6 was obtained in the same manner as in Example 1 except that the concentration of hydrochloric acid was 4.8 mol / l. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 13, and the electron micrograph of the cross section of the carrier core material shown in FIG. 13 is shown in FIG.

(Comparative Example 1)
A carrier core material according to Comparative Example 1 was obtained in the same manner as in Example 1, except that the concentration of hydrochloric acid was 2.4 mol / l. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 15, and the electron micrograph of the cross section of the carrier core material shown in FIG. 15 is shown in FIG.

(Comparative Example 2)
A carrier core material according to Comparative Example 2 was obtained in the same manner as in Example 1 except that the immersion time in hydrochloric acid was 1 hour. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 17, and the electron micrograph of the cross section of the carrier core material shown in FIG. 17 is shown in FIG.

(Comparative Example 3)
A carrier core material according to Comparative Example 3 was obtained in the same manner as in Example 1 except that the temperature of hydrochloric acid was 10 ° C. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 19, and the electron micrograph of the cross section of the carrier core material shown in FIG. 19 is shown in FIG. Note that FIG. 19 shows a state where the appearance of the carrier core material is magnified 3000 times.

(Comparative Example 4)
15.0 kg (93.9 mol) of Fe ₂ O ₃ (average particle diameter 0.6 μm) as raw materials, 2.6 kg (32.6 mol) of CuO, 2.2 kg (26.9 mol) of ZnO, Mn ₃ O ₄ was dispersed in 0.15 kg (1.1 mol) of water in 4.0 kg, and 160 g of an ammonium polycarboxylate dispersant was added as a dispersant to obtain a mixture. The solid concentration at this time was measured and found to be 82% by weight. This mixture was pulverized by a wet ball mill (media diameter 2 mm) to obtain a mixed slurry. This mixed slurry was sprayed into hot air at about 130 ° C. with a spray dryer to obtain a dry granulated product having a particle size of 10 to 200 μm. From this granulated product, coarse particles were separated using a sieve mesh having a mesh size of 103 μm, and fine particles were separated using a sieve mesh having a mesh size of 67 μm. This granulated powder was put into an electric furnace in an air atmosphere and fired at 1170 ° C. for 3 hours. The obtained sintered powder was pulverized and then classified using a vibration sieve to obtain ferrite particles having an average particle diameter of 80 μm. 60 g of this ferrite particle was put into 100 ml of hydrochloric acid (2.4 mol / l), and immersed for 0.5 hour with appropriate stirring at 10 ° C. Then, it washed with water and dried and the carrier core material which concerns on the comparative example 4 was obtained. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 21, and the electron micrograph of the cross section of the carrier core material shown in FIG. 21 is shown in FIG. This Comparative Example 4 corresponds to Example 1 of Patent Document 1 described above. FIG. 21 shows a state in which the appearance of the carrier core material is enlarged 1500 times, and FIG. 22 shows a state in which the cross section of the carrier core material is enlarged 1500 times.

(Comparative Example 5)
A carrier core material according to Comparative Example 5 was obtained in the same manner as in Example 1 except that the treatment with hydrochloric acid was not performed. Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Further, an electron micrograph of the appearance of the obtained carrier core material is shown in FIG. 23, and an electron micrograph of a cross section of the carrier core material shown in FIG. 23 is shown in FIG. FIG. 23 shows a state where the appearance of the carrier core material is enlarged 2700 times, and FIG. 24 shows a state where the cross section of the carrier core material is enlarged 2700 times. In addition, about this comparative example 5, in the manufacturing method of the carrier core material which concerns on this invention, it corresponds to the removal process, specifically, what is not immersed in hydrochloric acid. For Comparative Example 5 and Comparative Example 6 described later, “-” in Table 1 means that removal treatment with hydrochloric acid is not performed.

(Comparative Example 6)
A carrier core material according to Comparative Example 6 was obtained in the same manner as in Comparative Example 5 except that the oxygen concentration was adjusted to 300 to 500 ppm in an electric furnace under a nitrogen atmosphere and the firing temperature was 875 ° C. . Tables 1 to 3 show the material characteristics, electrical characteristics, and actual machine performance of the obtained carrier core material. Moreover, the electron micrograph of the external appearance of the obtained carrier core material is shown in FIG. 25, and the electron micrograph of the cross section of the carrier core material shown in FIG. 25 is shown in FIG. FIG. 25 shows a state where the appearance of the carrier core material is enlarged 2500 times, and FIG. 26 shows a state where the cross section of the carrier core material is enlarged 2500 times. The comparative example 6 corresponds to the conventional low temperature sintering method for obtaining a porous carrier core material. Further, this Comparative Example 6 also corresponds to a removal step, specifically, a case where immersion in hydrochloric acid is not performed in the method for manufacturing a carrier core material according to the present invention.

  Here, for the measurement of the pore diameter and the pore depth, the cross section polisher: SM-09010 (JEOL) Voltage: 6 kV, the particles were cut in 4 hours, and the obtained cross section was subjected to SEM (electron microscope): JSM -6510LA type Acceleration voltage: 5 kV, spot size: 45, and the pore diameter and pore depth were measured from the distance between two points. Regarding the measurement of the pore diameter and the pore depth, first, 20 particles were measured. The highest value among the upper limit values for each of the 20 particles was taken as the upper limit value for the example, and the lowest value among the lower limit values for each of the 20 particles was taken as the lower limit value for the example. Moreover, about the average value, the average value of the pore diameter and pore depth in each particle | grain was calculated | required, respectively, and the average value for 20 particles was averaged, and the average value in the example was obtained. In Table 1, for example, the upper and lower limits “0.3 to 3.0” of the pore diameter shown in Example 1 mean 0.3 μm as the lower limit and 3.0 μm as the upper limit. Is. In addition, “−” of the pore diameter and the pore depth in Comparative Example 5 in Table 1 means that none corresponding to the pores was found.

  The apparent density was measured according to JIS-Z2504 (2000).

  Regarding the measurement of tap density, A. B. The density was measured by tapping 180 times with a D powder characteristic measuring instrument (Tsutsui Rikagakuki).

The pore volume was measured as follows. As an evaluation apparatus, POREMASTER-60GT manufactured by Quantachrome was used. Specifically, the measurement conditions include Cell Stem Volume: 0.5 ml, Headpressure: 20 PSIA, Mercury surface tension: 485.00 erg / cm ² , Mercury contact angle: 130.00 degrees, High-pressure measurement mode: Fixed Rate, Motor Speed: 1, high pressure measurement range: 20.00 to 10000.00 PSI, 1.200 g of sample was weighed and filled in a 0.5 ml (cc) cell for measurement. The value obtained by subtracting the volume A (ml / g) at 100 PSI from the volume B (ml / g) at 10000.00 PSI was defined as the pore volume.

The charge amount in Table 1 refers to the charge amount of the carrier core material. Here, the measurement of the charge amount will be described. 9.5 g of carrier core material and 0.5 g of commercially available full-color toner are put into a 100 ml stoppered glass bottle and left to stand for 12 hours in an environment of 25 ° C. and 50% relative humidity to adjust the humidity. Here, as the toner, specifically, a black toner mounted on Bizhub PRO1050 manufactured by Konica Minolta Co. was used. The conditioned carrier core material and toner are shaken for 30 minutes with a shaker and mixed. Here, the shaker was performed at a rate of 200 ° / min and an angle of 60 ° using a NEW-YS type manufactured by Yayoi Co., Ltd. 500 mg of the mixed carrier core material and toner were weighed, and the charge amount was measured with a charge amount measuring device. In this embodiment, STC-1-C1 type manufactured by Nippon Piotech Co., Ltd. was used, suction pressure was 5.0 kPa, and a mesh for suction was performed with 795 mesh manufactured by SUS. Two measurements were performed on the same sample, and the average of these values was used as the charge amount of each core. Regarding the calculation formula of the core charge amount, core charge amount (μC (Coulomb) / g) = actual charge (nC) × 10 ³ × coefficient (1.00083 × 10 ⁻³ ) ÷ toner weight (weight before suction (g) -Weight after suction (g)).

  The area ratio is also shown in Table 1. The ratio of the area of the sintered portion to the area of the circle centered on the center of the carrier core particle and having the diameter of the outer diameter surface of the carrier core particle, ie, the area of the carrier core / carrier core The area of the circumscribed circle of the material was measured with SEM (electron microscope): JSM-6510LA type acceleration voltage: 5 kV, spot size: 45, and the measured image was analyzed with image analysis software Image Pro Plus, and the carrier core The area of the circle circumscribing the material and the area of the carrier core material excluding the voids were determined, and the ratio was calculated. In Table 1, “area ratio” (%) is shown.

About the measurement of the magnetic characteristic, ie, the magnetization which shows the magnetic characteristic in Table 2, magnetization was measured using VSM (the Toei industry Co., Ltd. make, VSM-P7). Here, in Table 2, for example, “σ ₁₀₀₀ ” is the magnetization when the external magnetic field is 1000 Oe (Oersted). “Σs” is saturation magnetization, “σr” is residual magnetization, and “Hc” is coercivity.

  The actual machine evaluation was performed as follows. First, a silicone resin (SR2411 manufactured by Toray Dow Corning) was dissolved in toluene to prepare a coating resin solution. Then, the carrier core material and the resin solution are respectively loaded in a stirrer at a ratio of carrier core material: resin solution = 9: 1 by weight ratio, and the temperature is set to 150 to 250 ° C. while the carrier core material is immersed in the resin solution. The mixture was heated and stirred for 3 hours.

  The resin-coated carrier core material manufactured in this way is placed in a hot-air circulating heating device, heated at 250 ° C. for 5 hours to cure the coated resin layer, and the magnetic carrier according to Example 1 is obtained. Obtained.

  This carrier and a toner having a particle size of about 5 μm were mixed for a predetermined time using a pot mill to obtain a two-component electrophotographic developer according to Example 1. Using this two-component electrophotographic developer, a 60-sheet machine adopting a digital reversal development method is used as an evaluation machine. For each item, after initial 100K image formation and 200K image formation Was evaluated. Also in Examples 2-6 and Comparative Examples 1-6, the carrier according to Example 2 and the electrophotographic developer according to Example 2 were obtained in the same manner. K represents 1000, 100K sheets means 100,000 sheets, and 200K sheets mean 200000 sheets.

(1) Evaluation of Image Density and Fog Using the 60 sheet machine described above as an evaluation machine, image density of a two-component electrophotographic developer was evaluated. Specifically, the evaluation of the image density was performed by measuring the density of the solid black image portion at 10 locations using a reflection densitometer “TC-6D” (manufactured by Tokyo Denshoku Co., Ltd.) and evaluating the average density. . An image density of 1.20 or more was considered acceptable.

  The fog was evaluated by measuring the density of a solid white image portion at 10 locations, and taking the value obtained by subtracting the density measured for unused blank paper from this average value as the fog density. A fog density of less than 0.006 was accepted.

(2) Evaluation of white spot Using the above-described 60 sheet machine as an evaluator, carrier scattering regarding a two-component electrophotographic developer was evaluated. Specifically, the level of carrier scattering (white spot) on the image was evaluated in the following four stages. The results are shown in Table 3.

  (Double-circle): It is a level without a white spot in 10 sheets of A3 paper.

  A: A level where 1 to 5 white spots are present on each of 10 A3 sheets.

  (Triangle | delta): It is a level which has 6-10 white spots in each 1 sheet of 10 A3 sheets.

  X: A level where 11 or more white spots are present on each of 10 A3 sheets.

(3) Evaluation of fine line reproducibility Using the 60 sheet machine described above as an evaluation machine, fine line reproducibility of a two-component electrophotographic developer was evaluated. Specifically, the level of fine line reproducibility on the image was evaluated in the following four stages. The results are shown in Table 3.

  Regarding the evaluation criteria, ◎ (double circle) was a very good level, ○ (circle) was a good level, Δ (triangle) was usable level, and x (cross) was unusable level. Here, the evaluation of ○ mark is the same level as the high-performance electrophotographic developer that is currently in practical use, and the evaluation of ○ or more was determined to be acceptable.

(4) Evaluation of image quality Using the 60 sheet machine described above as an evaluation machine, the image quality level for the two-component electrophotographic developer was evaluated in the following four stages. The results are shown in Table 3.

  A: The test image is reproduced very well.

  ○: The test image is almost reproduced.

  Δ: The test image is hardly reproduced.

  X: The test image is not reproduced at all.

With reference to Tables 1 to 2 and FIGS. 1 to 26, first, attention is paid to the apparent density and the tap density, which are indicators of density. In Examples 1 to 6, the value of the apparent density is 2.06 g / cm ³ at the maximum value, and the other examples are less than this value. That is, it is at least 2.1 g / cm ³ or less. On the other hand, in Comparative Examples 1 to 5, the minimum value is 2.33 g / cm ³ , and the other comparative examples are equal to or higher than this value. Also, the tap density value is 2.54 g / cm ³ at the maximum value, and the other values are below this value. On the other hand, for Comparative Examples 1 to 5, the minimum value is 2.76 g / cm ³ , and the other comparative examples are above this value. That is, in the first to sixth embodiments, the density can be reduced. In Comparative Example 6, the apparent density value is 1.63 g / cm ³ and the tap density value is 2.06 g / cm ^3, which is low at the same level as in Examples 1 to 6. Is.

  Next, attention is paid to the value of the charge amount that serves as an index of electrical characteristics. In Examples 1 to 6, the charge amount is 21.5 μC / g at the minimum, and the other examples are equal to or higher than this value. That is, it is at least 21 μC / g or more. On the other hand, in Comparative Examples 1 to 6, the maximum is 18.3 μC / g, and other Comparative Examples are below this value. In Comparative Example 6, it was 8.2 μC / g, which is less than half of the lowest value in the examples. Therefore, in Examples 1 to 6, good electrical characteristics can be achieved. Further, Comparative Example 6 is insufficient from the viewpoint of electrical characteristics.

That is, the carrier core material according to the present invention is a carrier core material containing manganese and iron as the core composition, the charge amount value is 20 μC / g or more, and the apparent density value is 2.1 g. / Cm ³ or less.

Here, paying attention to Example 1, Example 2, and Example 3, Example 1 has an immersion time of 12 hours in hydrochloric acid, Example 2 has an immersion time of 5 hours in hydrochloric acid, In Example 3, the immersion time in hydrochloric acid is 2 hours. Looking at the apparent density, Example 1 is 1.60 g / cm ³ , Example 2 is 1.76 g / cm ³ , and Example 3 is 2.05 g / cm ³ . is there. In terms of the charge amount, Example 1 is 29.4 μC / g, Example 2 is 24.6 μC / g, and Example 3 is 23.6 μC / g. Therefore, when a low apparent density value is desired or a high charge amount is desired, the immersion time in hydrochloric acid may be increased. The change in the outer shape in this case can be grasped by the electron micrographs shown in FIGS. 1, 2, and 5 to 8. Here, when considering the removal state of the grain boundary part of Examples 1 to 3, first, the part located at the grain boundary is preferentially removed, and then removed according to the length of the immersion time. It can be understood that there is a tendency to be removed from the centered portion. That is, it can be considered that in the crystal of the carrier core material, a portion far from the portion where the grain boundary originally existed is selectively left.

Further, focusing on Example 1, Example 5, and Example 4, Example 1 has a hydrochloric acid temperature of 90 ° C., Example 5 has a hydrochloric acid temperature of 50 ° C., and Example 4 The temperature of hydrochloric acid is 35 ° C. When looking at the apparent density, Example 1 is 1.60 g / cm ³ , Example 5 is 1.91 g / cm ³ , and Example 3 is 2.06 g / cm ³ . is there. In terms of the charge amount, Example 1 is 29.4 μC / g, Example 5 is 24.4 μC / g, and Example 3 is 23.4 μC / g. Therefore, when a low apparent density value is desired or a high charge amount is desired, the hydrochloric acid temperature may be increased. The change in the outer shape in this case can be grasped from the electron micrographs shown in FIGS. 1, 2, and 9 to 12. Here, when considering the removal state of the grain boundary part of Example 1, Example 5, and Example 4, the part located at the grain boundary is first removed preferentially, and then the temperature of hydrochloric acid is increased. Accordingly, it can be understood that the removed portion tends to be removed from the center. That is, it can be considered that in the crystal of the carrier core material, a portion far from the portion where the grain boundary originally existed is selectively left.

Further, focusing on Example 1 and Example 6, Example 1 has a hydrochloric acid concentration of 9.6 mol / l, and Example 6 has a hydrochloric acid concentration of 4.8 mol / l. Then, looking at the apparent density, Example 1 is 1.60 g / cm ^3, Example 6 is 1.90 g / cm ^3. In terms of the charge amount, Example 1 is 29.4 μC / g, and Example 6 is 21.5 μC / g. Therefore, the concentration of hydrochloric acid may be increased when a low apparent density value or a high charge amount is desired. The change in the outer shape in this case can be grasped from the electron micrographs shown in FIGS. 1, 2, 13, and 14. FIG. Here, when considering the removal state of the grain boundary part of Example 1 and Example 6, first, the part located at the grain boundary is preferentially removed, and then, according to the high concentration of hydrochloric acid, It can be grasped that there is a tendency to be removed from the removed part. That is, it can be considered that in the crystal of the carrier core material, a portion far from the portion where the grain boundary originally existed is selectively left.

In addition, about the value of pore volume, in Example 1- Example 6, the value is settled in the range of 0.025-0.031 cm < ³ > / g. On the other hand, about the comparative example 1-the comparative example 4, it exists in the range of 0.003-0.008 cm < ³ > / g, and is a very small value. The value for Comparative Example 5 is 0 cm ³ / g, and the value for Comparative Example 6 is 0.106 cm ³ / g. When the values of Examples 1 to 6 and Comparative Examples 1 to 5 are compared, it can be understood that the removal of the grain boundary portion is effectively performed for Examples 1 to 6. Note that the value of Comparative Example 6 is very large.

The pore diameter is as follows. As for the pore diameter, when the cross section shown in FIG. 3 described above, ie, when the carrier core particle is a spherical body, the structure is cut by a plane passing through the center of the carrier core particle and the structure is observed. a dimension indicated by arrow D ₁ of the in Figure 3, shows the size of the so-called voids. In Example 1 to Example 6, the minimum value of the upper limit value of the pore diameter is 2.3 μm. On the other hand, in Comparative Examples 1 to 4 and Comparative Example 6, the maximum value of the upper limit value of the pore diameter is 1.1 μm, and the values of the other comparative examples are less than this value. That is, it can be understood that Comparative Examples 1 to 4 and Comparative Example 6 have very small pore diameters. On the other hand, the pore depth is as follows. Regarding the pore depth, when the cross section shown in FIG. 3 described above, that is, when the carrier core particle is a spherical body, the structure was observed by cutting along the plane passing through the center of the carrier core particle. when a dimension indicated by the arrow D ₂ in FIG. 3, it illustrates the depth of the air gap from the surface of the so-called carrier core material. In Examples 1 to 6, the minimum value of the upper limit value of the pore depth is 7.6 μm. On the other hand, in Comparative Examples 1 to 4 and Comparative Example 6, the maximum value of the upper limit value of the pore depth is 4.0 μm, and the values of the other comparative examples are less than this value. . That is, for Comparative Examples 1 to 4 and Comparative Example 6, it can be understood that the pores are only very shallow. In Comparative Example 5, the values of the pore diameter and the pore depth are both 0 μm, and the value of the pore volume is 0 cm ³ / g. Is considered to be almost nonexistent.

  Therefore, also from these tendencies, in Example 1 to Example 6, it is considered that the grain boundaries can be sufficiently removed, and low density and good electrical characteristics can be achieved. Moreover, about the comparative example 1- comparative example 6, the grain boundary has not fully removed, but the comparative example 1- comparative example 5 are inadequate in both density reduction and an electrical property. In Comparative Example 6, sintering was performed at a low temperature, and the sintering reaction did not proceed sufficiently in the first place, and almost no grain boundary was formed. As a result, although the density reduction was achieved, The magnetic properties and magnetic properties are insufficient.

  That is, the carrier core material for an electrophotographic developer is a carrier core material for an electrophotographic developer containing manganese and iron as a core composition, and the carrier core material for the electrophotographic developer is formed into a spherical body. When the structure is observed by cutting along a plane passing through the center of the carrier core particle, the maximum value of the upper limit of the pore diameter is 2.3 μm or more, and the maximum value of the upper limit of the pore depth is Is 7.6 μm or more.

  In addition, from the result in Table 1, about Example 1-Example 6, the ratio of the area of the area | region of the sintered crystal | crystallization is comprised so that it may become 83.0% or more of the area of a circumscribed circle. Here, about Example 1, Example 2, Example 5, and Example 6, those area ratios are much less than 80%. Further, except for Comparative Example 6, the Comparative Examples 1 to 5 have an area ratio of 90% or more.

Next, attention is focused on the value of magnetization that is an index of magnetic characteristics. About Example 1- Example 6, it is 82.2 emu / g at the minimum as saturation magnetization, and is a high value. The values of σ ₁₀₀₀ , σ ₅₀₀ , remanent magnetization, and coercive force are at a level with no problem. On the other hand, Comparative Example 6 has a remanent magnetization value of 2.0 emu / g, which is insufficient as the characteristics of the carrier core material used recently. Similarly, the coercive force value in Comparative Example 6 is insufficient.

  In addition, although the resistance value in the carrier core material which concerns on Example 1- Example 6 and Comparative Example 1- Comparative Example 6 was measured just in case, it is a level without a problem in particular.

  Next, referring to Table 3, with respect to actual machine characteristics, for Examples 1 to 6 and Comparative Examples 1 to 6, in the initial evaluation, image density, fog, white spot, fine line reproducibility, and Both are good in image quality. However, in the evaluation after the image formation of 100K sheets, most of Examples 1 to 6 are good evaluations, but in Comparative Examples 1 to 6, some of the comparatively inferior levels are observed. . In the evaluation after the 200K images were formed, in Examples 1 to 6, a good state was maintained in most evaluation items. On the other hand, about the comparative example 1-the comparative example 6, it has reached the level inferior and the level which cannot be actually used in most evaluation items.

  That is, according to the carrier core material of the present invention, it is possible to obtain a good image even when used for a long period of time while improving the magnetic characteristics and achieving high chargeability and low density.

  As mentioned above, in the manufacturing method of the carrier core material concerning this invention, the carrier core material for electrophotographic developers which can obtain a favorable image in the use over a long term can be manufactured. The carrier core material for an electrophotographic developer, the carrier for an electrophotographic developer, and the electrophotographic developer according to the present invention can obtain a good image in long-term use.

  In the above embodiment, hydrochloric acid is used for chemical dissolution and removal. However, physical treatment such as vibration may be applied to perform physical chemical removal. .

  Although the embodiments of the present invention have been described with reference to the drawings, the present invention is not limited to the illustrated embodiments. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

  The method for producing a carrier core material for an electrophotographic developer according to the present invention, the carrier core material for an electrophotographic developer, the carrier for an electrophotographic developer, and the electrophotographic developer are applied to a copying machine or the like used for a long time. It is effectively used when

  11 Carrier core material, 12 gap, 13 crystal, 14 surface, 15 center, 16 outer diameter surface.

Claims (9)

A method for producing a carrier core material for an electrophotographic developer containing manganese and iron as a core composition,
A granulation step in which a raw material containing manganese and a raw material containing iron are mixed and granulated;
A firing step of firing the granulated product granulated in the granulation step within a temperature range of 1050 ° C. to 1300 ° C .;
A method for producing a carrier core material for an electrophotographic developer, comprising: removing a component present in a grain boundary portion of a sintered crystal from the obtained sintered powder after performing the firing step. . The method for producing a carrier core material for an electrophotographic developer according to claim 1, wherein the removing step is a step of chemically dissolving and removing a component present in a grain boundary portion of the sintered crystal. . In the removing step, the sintered powder is immersed in hydrochloric acid having a concentration of 4.8 mol / l (liter) to 11.0 mol / l and a temperature of 35 ° C. or more within a time range of 2 hours to 20 hours. The manufacturing method of the carrier core material for electrophotographic developers of Claim 2 which is a process to perform. A carrier core material for an electrophotographic developer containing manganese and iron as a core composition,
The raw material containing manganese and the raw material containing iron are mixed and granulated, and the obtained granulated powder is fired within a temperature range of 1050 ° C. to 1300 ° C., and the sintered powder obtained is sintered. A carrier core material for an electrophotographic developer produced by removing a component present in a grain boundary portion of the produced crystal. A carrier core material for an electrophotographic developer containing manganese and iron as a core composition,
A carrier core material for an electrophotographic developer having a charge amount value of 20 μC / g or more and an apparent density value of 2.1 g / cm ³ or less. A carrier core material for an electrophotographic developer containing manganese and iron as a core composition,
When the particles of the carrier core material for the electrophotographic developer are spherical, when the structure is observed by cutting along a plane passing through the center of the particles of the carrier core material, the maximum upper limit of the pore diameter A carrier core material for an electrophotographic developer having a value of 2.3 μm or more and a maximum value of the upper limit value of the pore depth of 7.6 μm or more. A carrier core material for an electrophotographic developer containing manganese and iron as a core composition,
When the particles of the carrier core material for the electrophotographic developer are formed into a spherical body, the region of the sintered portion is observed when the structure is observed by cutting along a plane passing through the center of the particles of the carrier core material. 83.0% of the area of the circle whose center is the center of the particle of the carrier core material for electrophotographic developer and whose diameter is the outer diameter surface of the particle of the carrier core material for electrophotographic developer A carrier core material for an electrophotographic developer, which is the following. A carrier for an electrophotographic developer used in an electrophotographic developer,
A carrier core material for an electrophotographic developer according to any one of claims 4 to 7,
An electrophotographic developer carrier comprising: a resin that covers a surface of the carrier core material for the electrophotographic developer. An electrophotographic developer used for electrophotographic development,
The carrier for an electrophotographic developer according to claim 8,
An electrophotographic developer comprising: toner capable of being charged in electrophotography by frictional charging with the carrier for electrophotographic developer.