HK1176126B - Carrier core material for electrophotography developer, carrier for electrophotography developer, and electrophotography developer - Google Patents

Abstract

A carrier core material for electrophotography developers has as a principal component a core composition represented by the general formula（MnxMgyCaz）FewO4+v（x+y+z+w=3、-0.003＜v）, with the following relationship being satisfied therein: 0.05≤y≤0.35, and 0.005≤z≤0.024.

Description

Carrier core material for electrophotographic developer, carrier for electrophotographic developer, and electrophotographic developer

Technical Field

The present invention relates to a carrier core material for an electrophotographic developer (hereinafter also simply referred to as "carrier core material"), a carrier for an electrophotographic developer (hereinafter also simply referred to as "carrier"), and an electrophotographic developer (hereinafter also simply referred to as "developer"), and particularly relates to a carrier core material for an electrophotographic developer provided in an electrophotographic developer used in a copying machine, an MFP (multi functional Printer), or the like, a carrier for an electrophotographic developer provided in an electrophotographic developer, and an electrophotographic developer.

Background

In copiers, MFPs, and the like, dry development methods in electrophotography include a one-component developer containing only toner as a developer component, and a two-component developer containing toner and a carrier as developer components. In any of the developing methods, toner with a fixed charge amount is supplied to the photoreceptor. Then, the electrostatic latent image formed on the photoreceptor is visualized with toner and transferred onto paper. After that, the visible image formed with the toner is fixed on paper to obtain a desired image.

Here, the development of the two-component developer will be briefly described. The developer contains a predetermined amount of toner and a predetermined amount of carrier. The developing device includes a rotatable magnetic roller in which a plurality of S poles and N poles are alternately arranged in a circumferential direction, and an agitating roller for agitating and mixing the toner and the carrier in the developing device. The carrier made of magnetic powder is carried by a magnetic roller. The magnetic force of the magnetic roller forms a linear magnetic brush composed of carrier particles. On the surfaces of the carrier particles, a plurality of toner particles are adhered by triboelectric charging caused by stirring. The magnetic brush is brought into contact with the photoreceptor by rotation of the magnetic roller, and toner is supplied to the surface of the photoreceptor. In the two-component developer, development is performed as described above.

Since toner in the developing device is gradually consumed by fixing the paper, new toner corresponding to the amount of consumption is supplied from a toner hopper mounted in the developing device to the developing device as needed. On the other hand, the carrier is not consumed by development, and can be used as it is until its lifetime is reached. Various functions such as a toner charging function of effectively charging toner by triboelectric charging caused by stirring, an insulating property, and a toner conveying ability of appropriately conveying and supplying toner to a photoreceptor are required for a carrier which is a constituent material of a two-component type developer. For example, from the viewpoint of improving the toner charging ability, the resistance value (hereinafter also simply referred to as resistance value) of the carrier is required to be appropriate, and the insulation property is required to be appropriate.

Recently, the carrier is composed of a carrier core material, the core of which is a core portion, and a resin coating layer provided to coat the surface of the carrier core material.

Here, as basic characteristics of the carrier core material, it is desirable that the magnetic characteristics thereof are good. In brief, in the developing device, as described above, the carrier is carried on the magnetic roller by magnetic force. In such a situation, if the magnetism of the carrier core particles themselves, specifically, if the magnetization of the carrier core particles themselves is low, the holding force for the magnetic roller is weak, and there is a possibility that a problem such as so-called carrier scattering occurs. In particular, in recent years, in order to meet the demand for high image quality of formed images, the particle diameter of toner particles tends to be reduced, and in response thereto, the particle diameter of carrier particles also tends to be reduced. If the carrier is made smaller in particle size, the carrying force of each carrier particle may be reduced. Therefore, a more effective solution to the carrier scattering problem is desired.

Various technologies relating to carrier core particles have been disclosed, but a technology for preventing carrier scattering is disclosed in japanese patent application laid-open No. 2008-241742 (patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2008-241742

Disclosure of Invention

Technical problem to be solved by the invention

In addition, the magnetic properties are required to be high not only in the magnetization value in the external magnetic field or the saturation magnetization value that is finally reached, but also in the rising property of magnetization. That is, even in an environment with a low external magnetic field, high magnetization is required. Such a demand is from the viewpoint of further preventing the scattering of the carrier.

In addition, the carrier core material is desired to have good electrical characteristics, specifically, a high electrical charge or a high dielectric breakdown voltage, and from the above viewpoint, the carrier core material itself is desired to have an appropriate electrical resistance value. In particular, the charging performance of the carrier core material itself tends to be strongly desired nowadays.

Although the copying machine is generally installed and used in offices of offices and the like, various office environments exist in various countries. For example, the present invention may be used in a high temperature environment of about 30 ℃, or in a high humidity environment with a relative humidity of about 75%, or conversely, in a low temperature environment of about 10 ℃, or in a low humidity environment with a relative humidity of about 35%. Even in such a situation where the temperature or the relative humidity changes, it is desired to reduce the change in the characteristics of the developer in the developer provided in the copying machine, and the carrier core particles constituting the carrier are also required to have a small change in the characteristics in the case of environmental change, that is, to have a small environmental dependency.

Therefore, the present inventors have conducted intensive studies on the cause of the change in the physical properties of the support, specifically, the change in the charge amount or the resistance value, depending on the use environment. As a result, it was found that the change in the physical properties of the carrier core particles greatly affects the physical properties of the coated carrier. Therefore, it is found that the conventional carrier core particles represented by patent document 1 are insufficient in the above-described environmental dependency. Specifically, in an environment with a high relative humidity, the charge amount or the resistance value may be greatly reduced. Such a carrier core material has a large influence due to environmental changes, and may affect image quality.

The purpose of the present invention is to provide a carrier core material for an electrophotographic developer which has excellent electrical and magnetic properties and is less dependent on the environment.

Another object of the present invention is to provide a carrier for an electrophotographic developer which is excellent in electrical and magnetic characteristics and has little environmental dependency.

It is a further object of the present invention to provide an electrophotographic developer which can form images of good quality under various environments.

Means for solving the problems

The present inventors considered that, as a means for obtaining a carrier core material having excellent electrical and magnetic properties and small environmental dependence of the carrier core material itself, it is first necessary to ensure excellent magnetic properties as basic properties, and manganese and iron are used as main components of the core composition. Since it is desired to further improve the magnetic properties, the electrical properties, or the environmental dependency, magnesium (Mg) and calcium (Ca) are added as metal elements in predetermined amounts as components of the carrier core material.

Thus, the electrical and magnetic properties of the carrier core particles can be improved by the following mechanism, and the environmental dependency can be reduced. The carrier core material inevitably contains a very small amount of silicon element (Si) even if it is not positively added. The oxide (SiO) of the silicon element (Si) is present in an extremely small amount in the surface layer portion of the carrier core material₂). It is considered that the silicon element (Si) in the oxide adsorbs and contains a large amount of moisture in an environment with a high relative humidity to promote leakage of electric charges, and as a result, the resistance value is lowered in an environment with a high relative humidity. However, as described above, by adding Ca and Mg, at least one of the Ca and Mg reacts with Si, which is an oxide present in the surface layer portion of the carrier core material, to form a metal composite oxide. Further, it is considered that the metal composite oxide of Si can suppress charge leakage in an environment with high relative humidity, and prevent a decrease in the resistance value of the carrier core material, and as a result, can reduce environmental dependency.

In addition, since the ionic radius is small, a part of at least one of Mg and Ca added in a predetermined amount is dissolved in a spinel structure in a crystal structure of a main component of the core composition. Thus, the crystal structure of the core composition of the carrier core particle is relatively stabilized. Thus, Fe in the carrier component formed by oxidation₂O₃Hardly separated out, as a resultThe movement of the magnetic domain wall corresponding to the change in the magnetic field is easily promoted, and the rise of magnetization is improved. Therefore, it is considered that a prescribed amount of Mg or Ca is added, and for example, the charge amount has a tendency to increase as the Ca content increases, but, with regard to magnetization, has a tendency to slightly decrease. Therefore, by adding an appropriate amount of Mg or Ca, both the electrical and magnetic properties can be improved. In the present specification, the content of Mg and the like in the carrier core particles may be expressed in terms of a molar ratio.

In order to further reduce the environmental dependency, the oxygen content in the core composition is made excessive, that is, the oxygen content is made excessive with respect to the carrier core material.

That is, the carrier core material for electrophotographic developer of the present invention has the general formula (Mn)_xMg_yCa_z）Fe_wO_4+v(x + y + z + w =3, -0.003 < v) and has a relationship of 0.05. ltoreq. y.ltoreq.0.35 and 0.005. ltoreq. z.ltoreq.0.024.

The carrier core material having the above structure is first prepared by the general formula (Mn)_xMg_yCa_z）Fe_wO_4+v(x + y + z + w =3, -0.003 < v). That is, the oxygen content in the carrier core material was slightly excessive as-0.003 < v. The carrier core particles satisfying such a v value can be obtained, for example, by a method for producing a carrier core particle for an electrophotographic developer described later. Such a carrier core particle can suppress a decrease in the resistance value in an environment with a high relative humidity. In addition, in the carrier core material, the content of Mg in the structure is more than or equal to 0.05 and less than or equal to 0.35, and the content of Ca in the structure is more than or equal to 0.005 and less than or equal to z and less than or equal to 0.024. By forming the carrier core material in such a structure that Mg and Ca are contained in predetermined amounts within the above ranges, it is possible to obtain a carrier core material having excellent initial electrical and magnetic properties and small environmental dependency.

In addition, in the above general formula (Mn)_xMg_yCa_z）Fe_wO_4+vIn the core composition shown, the parenthesis is (Mn)_xMg_yCa_z) Part, mainly consisting ofAccording to the A site in the crystal structure, with respect to the Fe portion, the B site in the crystal structure is mainly occupied. And the sum of x and y and z is close to 1, i.e. has a relationship of x + y + z ≈ 1.

Here, a method of calculating the oxygen content v will be explained. In the invention of the present application, in calculating the oxygen content v, the valence of Mn is assumed to be 2. Then, first, the average valence of Fe is calculated. With respect to the average valence state of Fe, Fe may be performed by redox titration²⁺The quantitative amount of (3) and the quantitative amount of total Fe consisting of Fe²⁺Amount and Fe³⁺The average valence of Fe is obtained from the calculation result of the amount. Here, for Fe²⁺The method for determining total Fe and the method for determining total Fe are described in detail.

（1）Fe²⁺Quantitative determination of

First, ferrite containing an iron element is dissolved in a hydrochloric acid (HCl) solution which is a reducing acid in a state where carbon dioxide gas is bubbled. Then, potentiometric titration was carried out with a potassium permanganate solution, and the Fe in the solution was quantitatively analyzed²⁺The amount of ions, Fe²⁺The amount of titration of (c).

(2) Quantification of total Fe

Weighing and Fe²⁺The ferrite containing iron element in the same amount as the ferrite in the quantitative determination was dissolved in a mixed acid solution of hydrochloric acid and nitric acid. After the solution was evaporated and dried, an aqueous sulfuric acid solution was added to redissolve the solution, thereby volatilizing the excess hydrochloric acid and nitric acid. Adding solid Al to the solution to remove Fe in the solution³⁺Reduction to Fe²⁺. Then, by reacting with the above Fe²⁺The solution was measured by the same analytical method as used for the quantitative determination to determine the titration amount.

(3) Calculation of the average valence of Fe

In the above (1), Fe²⁺Quantitative determination, ((2) titration amount- (1) titration amount) represents Fe³⁺The average valence of Fe is thus calculated by the following formula.

Average valence of Fe = {3 × ((2) titration amount- (1) titration amount) +2 × (1) titration amount }/(2) titration amount

In addition to the above-mentioned methods, different redox titration methods are also conceivable as a method for quantifying the valence state of an iron element, but the method is excellent because the reaction used in the analysis is simple, the obtained result is easily explained, sufficient accuracy can be obtained with a reagent and an apparatus which are generally used, and a skilled operation by an analyst is not required.

Further, according to the principle of electroneutrality, in the structural formula, since the relationship of the valence state of Mn (+ 2-valent) × x + average valence state of Fe × (3-x) = oxygen valence state (-2-valent) × (4 + w) holds, the value of w can be calculated from the above equation.

Further, a method for analyzing Si, Mn, Ca, and Mg in the carrier core particles in the present invention will be described.

（SiO₂Analysis of content and Si content

SiO in carrier core material₂The content was quantitatively determined by the silica weight method described in JIS M8214-1995. SiO of carrier core material described in the present invention₂The content of SiO obtained by the gravimetric analysis of the silica₂And (4) content.

(analysis of Mn)

The Mn content in the carrier core particles was quantitatively analyzed by ferromanganese analysis (potentiometric titration) according to JIS G1311-1987. The Mn content of the carrier core material described in the present invention is a Mn content quantitatively analyzed by the ferromanganese analysis method (potentiometric titration).

(analysis of Mg and Ca)

The contents of Mg and Ca in the carrier core particles were analyzed by the following methods. The carrier core material in the present invention was dissolved in an acid solution, and quantitative analysis was performed by ICP. The contents of Mg and Ca in the carrier core particles described in the present invention are the contents of Mg and Ca obtained by the ICP quantitative analysis. For the analysis of ICP, an ICP emission spectrometer (model: ICPS-7510, product of Shimadzu corporation) was used.

Preferably has a relationship of 0.10. ltoreq. y.ltoreq.0.25 and 0.007. ltoreq. z.ltoreq.0.015. With such a configuration, the electrical and magnetic characteristics can be improved.

In another aspect of the present invention, a carrier for an electrophotographic developer is a carrier for an electrophotographic developer used in a developer for electrophotography, having a carrier core material for an electrophotographic developer represented by the general formula (Mn) and a resin covering a surface of the carrier core material for an electrophotographic developer_xMg_yCa_z）Fe_wO_4+v(x + y + z + w =3, -0.003 < v) and has a relationship of 0.05. ltoreq. y.ltoreq.0.35 and 0.005. ltoreq. z.ltoreq.0.024.

Such a carrier for electrophotographic developer has good electrical and magnetic properties and little environmental dependency because it has the carrier core material for electrophotographic developer having the above-described structure.

In another aspect of the present invention, an electrophotographic developer is an electrophotographic developer used in electrophotographic development, having a carrier for electrophotographic developer having a carrier core material for electrophotographic developer and a resin covering a surface of the carrier core material for electrophotographic developer, and a toner chargeable in electrophotography by frictional charging with the carrier for electrophotographic developer, the carrier core material for electrophotographic developer being represented by the general formula (Mn)_xMg_yCa_z）Fe_wO_4+v(x + y + z + w =3, -0.003 < v) and has a relationship of 0.05. ltoreq. y.ltoreq.0.35 and 0.005. ltoreq. z.ltoreq.0.024.

Such an electrophotographic developer can form an image of good quality in various environments due to the electrophotographic developer carrier having the above-described structure.

Effects of the invention

The carrier core material for electrophotographic developers of the present invention is excellent in electrical and magnetic properties and has little environmental dependency.

Further, the carrier for an electrophotographic developer of the present invention is excellent in electric and magnetic characteristics and has little environmental dependency.

In addition, the electrophotographic developer of the present invention can form images of good quality in various environments.

Drawings

Fig. 1 is a flowchart showing typical steps in a method for producing a carrier core material according to an embodiment of the present invention.

FIG. 2 is a graph showing the Mg content and σ₅₀₀A graph of the relationships.

FIG. 3 is a graph showing the relationship between Ca content and core charge amount.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, a carrier core material in one embodiment of the present invention will be described.

In the carrier core material according to one embodiment of the present invention, the outer shape thereof is approximately spherical. The carrier core particles in one embodiment of the present invention have a particle size of about 35 μm and an appropriate particle size distribution. The particle diameter refers to a volume average particle diameter. The particle diameter and the particle size distribution can be arbitrarily set according to the required developer characteristics, the yield in the production process, and the like. Fine irregularities mainly formed in a baking step described later are formed on the surface of the carrier core particles.

The carrier in one embodiment of the present invention is also similar to the carrier core material, and its outer shape is approximately spherical. The carrier is formed by thinly coating, i.e., covering, the surface of the carrier core material with a resin, and the particle diameter thereof is almost unchanged from that of the carrier core material. The surface of the carrier is almost completely covered with the resin, unlike the carrier core material.

An electrophotographic developer according to an embodiment of the present invention is composed of the above carrier and toner. The external shape of the toner is also approximately spherical. The toner is mainly composed of a styrene acrylic resin or a polyester resin, and a predetermined amount of a pigment, wax, or the like is mixed therein. Such a toner is produced by, for example, a pulverization method or a polymerization method. The particle diameter of the toner is, for example, about one-seventh of the particle diameter of the carrier, about 5 μm. The ratio of the toner to the carrier may be set arbitrarily according to the required properties of the developer. Such a developer can be prepared by mixing prescribed amounts of the carrier and the toner with an appropriate mixer.

Next, a method for producing a carrier core material in one embodiment of the present invention will be described. Fig. 1 is a flowchart showing typical steps in a method for producing a carrier core material according to an embodiment of the present invention. Hereinafter, a method for producing a carrier core particle according to this embodiment of the present invention will be described with reference to fig. 1.

First, a raw material containing calcium, a raw material containing magnesium, a raw material containing manganese, and a raw material containing iron are prepared. The prepared raw materials are mixed in an appropriate ratio according to the required characteristics (fig. 1 a). Here, the appropriate compounding ratio means that the carrier core particles finally obtained are in a compounding ratio described later.

The iron material constituting the carrier core particles in one embodiment of the present invention may be metallic iron or an oxide thereof. Particularly suitable for using Fe stably existing at normal temperature and normal pressure₂O₃、Fe₃O₄Or Fe, etc. Further, the manganese source may be metallic manganese or an oxide thereof. Particularly suitable for using metal Mn and MnO which stably exist at normal temperature and normal pressure₂、Mn₂O₃、Mn₃O₄、MnCO₃. In addition, as the raw material containing calcium, it is suitable to useCalcium metal or an oxide thereof. Specifically, CaCO as a carbonate may be mentioned₃Ca (OH) as a hydroxide₂Or CaO as an oxide. As the raw material containing magnesium, metallic magnesium or an oxide thereof is suitably used. Specifically, MgCO as a carbonate may be mentioned₃Mg (OH) as a hydroxide₂Or MgO as an oxide. In addition, the above-described raw materials (iron raw material, manganese raw material, calcium raw material, magnesium raw material) may be separately calcined and pulverized as raw materials, or raw materials mixed to have a desired composition may be calcined and pulverized as raw materials. The iron or manganese raw material contains magnesium in a very small amount.

Subsequently, the mixed raw materials are slurried (fig. 1B). That is, these raw materials are weighed in a composition targeted for the carrier core particles, and mixed to form a slurry raw material.

In the preparation step of the carrier core material in the present invention, a reducing agent may be further added to the above-mentioned slurry raw material in order to perform a reduction reaction in a partial firing step described later. Carbon powder, polycarboxylic organic compounds, polyacrylic organic compounds, maleic acid, acetic acid, polyvinyl alcohol (pva) organic compounds, and mixtures thereof are suitably used as the reducing agent.

Water is added to the slurry material, and the mixture is stirred until the solid content concentration is 40 wt% or more, preferably 50 wt% or more. It is preferable that the slurry material has a solid content concentration of 50 wt% or more because the strength of the granulated particles can be ensured.

Subsequently, the slurried raw material is granulated (fig. 1C). The slurry obtained by the above mixing and stirring was granulated by using a spray dryer. Further, it is preferable to further wet-grind the slurry before granulation.

The environment temperature during spray drying can be about 100-300 ℃. This can substantially obtain granulated powder having a particle size of 10 to 200 μm. In consideration of the final particle diameter of the product, it is desirable to remove coarse particles or fine particles using a vibrating screen or the like and to adjust the particle size of the granulated powder obtained at this time.

Then, the granulated substance is fired (fig. 1 (D)). Specifically, the obtained granulated powder is put into a furnace heated to about 900-1500 ℃, and is kept for roasting for 1-24 hours to generate a target roasted product. In this case, the oxygen concentration in the baking furnace may be set to a condition that promotes the ferrite reaction, and specifically, the baking is performed in a flowing state by adjusting the oxygen concentration of the introduced gas to 10 to 7% or more and 3% or less at 1200 ℃.

In addition, the reducing atmosphere required for the ferrite formation may be controlled by adjusting the reducing agent. Further, from the viewpoint of obtaining a reaction rate that can ensure sufficient productivity in industrial production, a temperature of 900 ℃ or higher is most preferable. On the other hand, when the firing temperature is 1500 ℃ or lower, the particles do not excessively sinter to each other, and a fired product in the form of a powder can be obtained.

In this case, as one means for controlling the oxygen content in the core composition to be slightly excessive, it is conceivable to control the oxygen concentration at the time of cooling in the firing step to be a predetermined amount or more. That is, in the baking step, when cooling to about room temperature, the oxygen concentration is controlled to a predetermined concentration, and the cooling may be performed in an atmosphere of more than 0.03%, for example. Specifically, the oxygen concentration of the introduced gas introduced into the electric furnace may be higher than 0.03% and the introduction may be performed in a flowing state. With such a structure, the oxygen content in the ferrite can be made excessive in the inner layer of the carrier core material. That is, as the value of v, it is possible to set-0.003 < v. On the other hand, if the content is 0.03% or less, the oxygen content in the inner layer is relatively reduced. That is, the v value may be reduced to-0.003 or less. Therefore, the cooling is performed in an environment of the above oxygen concentration.

The resulting calcined product is more desirably subjected to particle size adjustment at this stage. For example, the calcined material is coarsely pulverized by a hammer mill or the like. That is, the fired pellets were disaggregated (fig. 1 (E)). Then, classification is performed with a vibrating screen or the like. That is, the granulated substance after the granulation is classified (fig. 1 (F)). This can provide particles of the carrier core material having a desired particle diameter.

Next, the classified particulate matter is oxidized (fig. 1G). That is, the particle surfaces of the carrier core particles obtained at this stage are subjected to heat treatment (oxidation treatment). Then, the dielectric breakdown voltage of the particles was increased to 250V or more to make the resistance an appropriate resistance value of 1X 10⁶~1×10¹³Omega cm. By increasing the resistance value of the carrier core material by the oxidation treatment, the possibility of carrier scattering due to charge leakage can be reduced.

Specifically, the target carrier core material is obtained by keeping the temperature of the target carrier core material at 200-700 ℃ for 0.1-24 hours in an atmosphere with the oxygen concentration of 10-100%. More preferably, the temperature is maintained at 250 to 600 ℃ for 0.5 to 20 hours, and still more preferably at 300 to 550 ℃ for 1 to 12 hours. In this way, the carrier core material according to one embodiment of the present invention is prepared. In addition, such an oxidation treatment step may be optionally performed as needed.

Next, the carrier core particles obtained above are covered with a resin (fig. 1H). Specifically, the carrier core material of the present invention obtained is covered with a silicone resin, an acrylic resin, or the like. Thus, a carrier for an electrophotographic developer according to an embodiment of the present invention was obtained. The coating method of the silicone resin, the acrylic resin, and the like can be performed by a known method. That is, the carrier for an electrophotographic developer of the present invention has a carrier core material for an electrophotographic developer represented by the general formula (Mn)_xMg_yCa_z）Fe_wO_4+v(x + y + z + w =3, -0.003 < v) and has a relationship of 0.05. ltoreq. y.ltoreq.0.35 and 0.005. ltoreq. z.ltoreq.0.024.

Such a carrier for electrophotographic developer has good electrical and magnetic properties and little environmental dependency because it has the carrier core material for electrophotographic developer having the above-described structure.

Then, the amount is determined every timeThe thus-obtained support and toner were mixed (fig. 1 (I)). Specifically, the carrier for an electrophotographic developer in one embodiment of the present invention prepared by the above method and a suitable known toner are mixed. Thus, an electrophotographic developer in one embodiment of the present invention can be obtained. For mixing, an arbitrary mixer such as a ball mill is used. The electrophotographic developer of the present invention is an electrophotographic developer used in development of electrophotography, having a carrier for electrophotographic developer having a carrier core material for electrophotographic developer and a resin covering the surface of the carrier core material for electrophotographic developer, and a toner chargeable in electrophotography by frictional charging with the carrier for electrophotographic developer, the carrier core material for electrophotographic developer being represented by the general formula (Mn)_xMg_yCa_z）Fe_wO_4+v(x + y + z + w =3, -0.003 < v) and has a relationship of 0.05. ltoreq. y.ltoreq.0.35 and 0.005. ltoreq. z.ltoreq.0.024.

Such an electrophotographic developer can form an image of good quality in various environments because of the carrier for an electrophotographic developer having the above-described structure.

Examples

Example 1

Dispersing 27.3kg Fe in 15kg water₂O₃(average particle diameter: 0.6 μm) 13.05kg of Mn₃O₄(average particle diameter: 2 μm) and 4.65kg of MgFeO₄270g of a polyvalent ammonium carboxylate dispersant as a dispersant, 135g of carbon black as a reducing agent and 225g of CaCO were added₃And forming a mixture. The solid content concentration at this time was measured, and found to be 75% by weight. This mixture was pulverized by a wet ball mill (medium diameter 2 mm) to obtain a mixed slurry.

The slurry was sprayed in hot air at about 130 ℃ by a spray dryer to obtain dry granulated powder. At this time, granulated powder other than the target particle size distribution is removed by a sieve. The granulated powder was charged into an electric furnace and calcined at 1090 ℃ for 3 hours. At this time, the oxygen concentration in the electric furnace was 0.8%, that is, the atmosphere was adjusted so that the oxygen concentration was 8000 ppm. The cooling temperature during firing was 200 ℃ per hour. Here, the cooling temperature at the time of firing, that is, the rate of cooling to room temperature after completion of firing, is preferably 200 ℃/hr or less, and particularly preferably 120 ℃/hr or less. The resultant calcined product was pulverized and classified with a sieve so that the average particle size was 25 μm. The carrier core particles thus obtained were kept at 465 ℃ for 1 hour in the atmosphere and subjected to oxidation treatment, thereby obtaining carrier core particles of example 1. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method. Further, the particle size was measured using a Model9320-X100 microturbine manufactured by Nikkiso K.K. Further, as for the oxygen concentration, the oxygen concentration in the furnace atmosphere was measured using a zirconia oxygen analyzer (ECOAZ TB-11F-S, product of first thermal research Co., Ltd.).

Example 2

Dispersing 9.1kg Fe in 7kg water₂O₃、4.35kg Mn₃O₄And 3.67kg of MgFeO₄103g of a polyvalent ammonium carboxylate dispersant as a dispersant, 51g of carbon black as a reducing agent, and 86g of CaCO₃Except for this, the carrier core particles of example 2 were produced in the same manner as in example 1. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method.

Example 3

Dispersing 9.1kg Fe in 8.1kg water₂O₃、4.35kg Mn₃O₄And 6.33kg of MgFeO₄119g of ammonium polycarboxylic acid dispersant as a dispersant, 59gCarbon black as a reducing agent, and 99g CaCO₃Except for this, the carrier core particles of example 3 were produced in the same manner as in example 1. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method.

Example 4

Dispersing 9.1kg Fe in 5kg water₂O₃、4.35kg Mn₃O₄And 1.55kg of MgFeO₄90g of an ammonium polycarboxylic acid dispersant as a dispersant, 45g of carbon black as a reducing agent, and 30g of silica gel (solid content concentration: 50% by weight) as SiO were added₂Raw materials, and 37.5g CaCO₃Except for this, the carrier core particles of example 4 were produced in the same manner as in example 1. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method.

Example 5

Dispersing 9.1kg Fe in 5kg water₂O₃、4.35kg Mn₃O₄And 1.55kg of MgFeO₄90g of an ammonium polycarboxylic acid dispersant as a dispersant, 45g of carbon black as a reducing agent, and 30g of silica gel (solid content concentration: 50% by weight) as SiO were added₂Raw materials, and 75g CaCO₃Except for this, the carrier core particles of example 5 were produced in the same manner as in example 1. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method.

Example 6

30.61kg of Fe was mixed by a vibration mill₂O₃、13.16kg Mn₃O₄、1.02kg MgO、0.22kg（220g）CaCO₃Thereafter, the mixture was calcined at 900 ℃ for 2 hours in the atmosphere. Then, the mixture was pulverized by a vibration pulverizer to a volume average particle diameter of 1.5 μm and a residual component on a sieve of 45 μm of 0.5 wt% or less, and this was used as a calcination raw material. A carrier core material of example 6 was produced in the same manner as in example 1 except that 45.2kg of the calcined material was dispersed in 15kg of water, 270g of an ammonium polycarboxylic acid-based dispersant was added as a dispersant, and 135g of carbon black was added as a reducing agent. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method. The raw material proportions before calcination are shown in parentheses in table 1.

Comparative example 1

10.8kg of Fe were dispersed in 5kg of water₂O₃、4.2kg Mn₃O₄90g of an ammonium polycarboxylic acid dispersant as a dispersant, 45g of carbon black as a reducing agent, and 30g of silica gel (solid content concentration: 50% by weight) as SiO were added₂Raw materials, and 75g CaCO₃Except for this, the carrier core particles of comparative example 1 were produced in the same manner as in example 1. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method. Here, it is considered that magnesium present in the composition of the carrier core particle of comparative example 1 is an extremely small amount of magnesium contained in the iron raw material or the manganese raw material.

Comparative example 2

10.8kg of Fe were dispersed in 5kg of water₂O₃、4.2kg Mn₃O₄90g of an ammonium polycarboxylic acid dispersant as a dispersant, 45g of carbon black as a reducing agent, and 30g of silica gel (solid content concentration: 50% by weight) as SiO were added₂Raw material, and 127g of MgCO₃Otherwise, the same as example 1In the same manner, the carrier core material of comparative example 2 was prepared. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method.

Comparative example 3

Dispersing 9.1kg Fe in 5kg water₂O₃、4.35kg Mn₃O₄、1.55kg MgFeO₄90g of an ammonium polycarboxylic acid dispersant as a dispersant, 45g of carbon black as a reducing agent, and 30g of silica gel (solid content concentration: 50% by weight) as SiO were added₂The carrier core particles of comparative example 3 were produced in the same manner as in example 1 except for the raw materials. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method.

Comparative example 4

Dispersing 18.2kg Fe in 10kg water₂O₃、8.7kg Mn₃O₄、3.1kg MgFeO₄180g of an ammonium polycarboxylic acid dispersant as a dispersant, 90g of carbon black as a reducing agent, and 60g of silica gel (solid content concentration: 50% by weight) as SiO were added₂The carrier core particles of comparative example 4 were produced in the same manner as in example 1 except for the raw materials. The proportions of the raw materials and the composition of the carrier core particles are shown in table 1, and the electrical and magnetic properties of the obtained carrier core particles are shown in table 2. The carrier core particle composition shown in table 1 is obtained as a result of measurement of the obtained carrier core particle by the above analysis method.

The core charge amount in the table means the charge amount of the core, i.e., the carrier core material. Here, measurement of the charged amount will be described. 9.5g of the carrier core and 0.5g of toner from a commercially available full-color machine were put in a 100ml glass bottle with a stopper, and left to stand at 25 ℃ under an atmosphere of a relative humidity of 50% for 12 hours for humidity adjustment. The carrier core material and the toner after the conditioning were vibrated for 30 minutes by a vibrator and mixed. Here, the vibrator was made at an angle of 60 ℃ at 200 cycles/min using NEW-YS type manufactured by YAYOI, K.K. 500mg of the mixed carrier core material and toner were weighed, and the charge amount was measured by a charge amount measuring device. In this embodiment, the operation was carried out using STC-1-C1 model manufactured by Piotech corporation, Japan, using a 795 mesh suction screen manufactured by SUS and having a suction pressure of 5.0 KPa. The same sample was subjected to two measurements, and the average value was taken as the charge amount of each core. The calculation formula for the core charge amount is: core charge amount (μ C (coulomb)/g) = measured charge (nC) × 10³X coefficient (1.0083X 10)^-3) Toner weight (pre-attraction weight (g) -post-attraction weight (g)).

Next, measurement of the resistance value will be described. The carrier core particles were subjected to humidity control for one day and night in an environment (HH environment) of 30 ℃ and a relative humidity of 75%, and then measured in this environment. First, two pieces of sus (jis) 304 plates each having an electrolytically polished surface and a plate thickness of 2mm were disposed as electrodes on an insulating plate placed horizontally, for example, an acrylic plate coated with Teflon (registered trademark), and the distance between the electrodes was set to 1 mm. At this time, the normal directions of the two electrode plates are set to be horizontal directions. After loading 200 + -1 mg of powder to be measured into the gap between two electrode plates, a cross-sectional area of 240mm was arranged behind each electrode plate²The magnet (2) forms a bridge of the powder to be measured between the electrodes. In this state, voltages were applied between the electrodes in order of decreasing voltage, and the value of the current flowing through the powder to be measured was measured by a two-terminal method to calculate the resistance value. Further, here, a super insulation meter SM-8215 available from japanese electrical machinery corporation was used. In addition, electricityThe resistance value is calculated by the formula: resistance value (Ω · cm) = actually measured resistance (Ω) × cross-sectional area (2.4 cm)²) Distance between electrodes (0.1 cm). And the resistance value (Ω · cm) at the time of voltage application was measured in the case where each voltage in the table was applied. In addition, although various magnets can be used as long as the powder can form a bridge, in this embodiment, a permanent magnet having a surface magnetic flux density of 1000 gauss or more, for example, a ferrite magnet is used.

In addition, for the measurement of magnetization representing magnetic properties, the magnetic susceptibility was measured using VSM (VSM-P7, manufactured by Toyobo industries, Ltd.). In the table, "σ s" represents saturation magnetization, "σ_1000（1K）"represents the magnetization in the case of an external magnetic field of 1000 (1K) Oe," σ₅₀₀"represents magnetization in the case where the external magnetic field is 500 Oe.

Here, the y value is the Mg content and σ₅₀₀The relationship between them is shown in fig. 2. FIG. 2 is a graph showing the Mg content and σ₅₀₀A graph of the relationship between. In FIG. 2, the vertical axis represents σ₅₀₀The horizontal axis represents the y value (Mg content). Further, the relationship between the z value, i.e., the Ca content, and the core charge amount is shown in FIG. 3. FIG. 3 is a graph showing the relationship between Ca content and core charge amount. In fig. 3, the vertical axis represents the value of the core charge amount, and the horizontal axis represents the z value (Ca content). In fig. 2, σ considered to correspond to each y value is shown by a broken line with reference to the examples and comparative examples₅₀₀The value of (c). In fig. 3, values of core charge amounts considered to correspond to the respective z values are shown by broken lines with reference to examples and comparative examples.

Here, σ in the magnetic properties is defined as the amount of dispersion of the carrier which increases with the increase in the speed of the copying machine₅₀₀The value of (b) is required to be 38emu/g or more. And, as σ₅₀₀The value of (b) is preferably 38.5emu/g or more. In addition, the amount of charge as a core in the electrical characteristics is charged as a core in order to suppress the change in the physical properties of the carrier due to the long-term use of the developer, specifically, the change in the physical properties of the carrier due to the peeling of the resin coating layer on the surface of the carrier due to the long-term useThe amount of the surfactant is required to be 13. mu.C/g or more. Further, the value of the core charge amount is preferably 16. mu.C/g or more.

Here, referring to FIG. 2, FIG. 3 and Table 2, regarding σ₅₀₀The value of (b) can be grasped as an extremum, that is, a maximum value, when y = 0.13. In comparative example 4,. sigma.₅₀₀The value of (A) was 37.5emu/g, which is low, and it is considered that this is caused by the high Ca content. From the results, it is understood that the magnetization value is increased at a low magnetic field, specifically, σ₅₀₀The value of (A) is 38emu/g or more, and the value of y is required to be 0.05 to 0.35. As for the core charge amount, it can be understood that the core charge amount tends to increase as the z value increases. It is also found that the z value is required to be at least 0.005 or more in order to make the core charge amount 13. mu.C/g or more. On the other hand, in view of maintaining a high magnetization value, z is preferably 0.024 or less.

Further, environmental dependency was examined as follows. The resistance values shown in Table 2 represent the resistance values under a high-temperature and high-humidity environment (30 ℃ C., 75% RH). The resistance value is high, and thus shows that the resistance value does not decrease in a high-temperature and high-humidity environment, that is, the environmental dependency is small. In examples 1 to 6 and comparative example 4, the applied voltage of 1000V was 8.0E +07 (8X 10)⁷) Omega cm or more, and comparative examples 1 to 3 are less than 8.0E +07 (8X 10)⁷) Since Ω · cm, it is understood that the environmental dependency is small in examples 1 to 6 and comparative example 4.

As is clear from the above, the ranges of y and z defined in examples 1 to 6 are excellent in electric and magnetic properties and have little environmental dependency. That is, if y is 0.05. ltoreq. y.ltoreq.0.35 and z is 0.005. ltoreq. z.ltoreq.0.024, the electric and magnetic characteristics are good and the environmental dependency is small.

As described above, the carrier core material for electrophotographic developers and the carrier for electrophotographic developers according to the present invention are excellent in electrical and magnetic properties and have little environmental dependency. In addition, the electrophotographic developer of the present invention is excellent in characteristics.

When further improvement in magnetic and electric characteristics is desired, the following structure is possible. The magnetic property is more than 38.5 emu/g; the electric charge of the electric characteristic core is more than 16 mu C/g, and the range of y is more than or equal to 0.10 and less than or equal to 0.25, and z is more than or equal to 0.007 and less than or equal to 0.015. Thus, if there is a relationship of 0.10. ltoreq. y.ltoreq.0.25 and 0.007. ltoreq. z.ltoreq.0.015, the magnetic properties and the electrical properties can be further improved.

In the above embodiment, the carrier core material of the present invention can be obtained by preparing and mixing a calcium-containing raw material, a magnesium-containing raw material, a manganese-containing raw material, and an iron-containing raw material as the production method, but the present invention is not limited to this, and for example, MnFe is prepared₂O₄Or MgFe₂O₄The carrier core material of the present invention can also be obtained by mixing them.

In the above-described embodiment, the oxygen content v may be such that the oxygen concentration during cooling in the firing step is higher than a predetermined concentration in order to excessively contain the carrier core particles, but is not limited thereto, and for example, the compounding ratio in the raw material mixing step may be adjusted so as to excessively contain the carrier core particles. In the step of carrying out the sintering reaction before cooling, the sintering reaction may be carried out in the same atmosphere as in the cooling step.

The embodiments of the present invention have been described above with reference to the drawings, but the present invention is not limited to the embodiments shown in the drawings. The embodiments shown in the drawings may be modified or changed in various ways within the same scope as or equivalent to the present invention.

Possibility of industrial utilization

The carrier core material for an electrophotographic developer, the carrier for an electrophotographic developer, and the electrophotographic developer according to the present invention can be effectively used when applied to a copying machine or the like used under various environments.

Claims (3)

1. A carrier core material for an electrophotographic developer, characterized by having the general formula (Mn)_xMg_yCa_z）Fe_wO_4+vThe core shown is composed as the main component, where x + y + z + w =3, -0.003 < v, and has the relationship of x + y + z ≈ 1, 0.10 ≦ y ≦ 0.25, and 0.007 ≦ z ≦ 0.015.

2. A carrier for an electrophotographic developer, comprising a carrier core material for an electrophotographic developer and a resin covering the surface of the carrier core material for an electrophotographic developer;

the carrier core material for electrophotographic developer has a general formula (Mn)_xMg_yCa_z）Fe_wO_4+vThe core shown is composed as the main component, where x + y + z + w =3, -0.003 < v, and has the relationship of x + y + z ≈ 1, 0.10 ≦ y ≦ 0.25, and 0.007 ≦ z ≦ 0.015.

3. An electrophotographic developer for use in electrophotographic development, characterized by having a carrier for electrophotographic developer and a toner chargeable in electrophotography by frictional electrification with the carrier for electrophotographic developer;

the carrier for the electrophotographic developer comprises a carrier core material for the electrophotographic developer and a resin covering the surface of the carrier core material for the electrophotographic developer;

the carrier core material for electrophotographic developer has a general formula (Mn)_xMg_yCa_z）Fe_wO_4+vThe core shown is composed as the main component, where x + y + z + w =3, -0.003 < v, and has the relationship of x + y + z ≈ 1, 0.10 ≦ y ≦ 0.25, and 0.007 ≦ z ≦ 0.015.