JP2009086093A - Method of manufacturing resin-filled carrier for electrophotographic developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a resin-filled carrier for an electrophotographic developer, by which a developer preventing an image defect while retaining advantages of the resin-filled carrier can be obtained, and developer has high strength, high production yield and preferable production stability. <P>SOLUTION: The method of manufacturing the resin-filled carrier for an electrophotographic developer, the carrier obtained by filling a porous ferrite core material with a resin, is characterized by setting the pore volume of the porous ferrite core material and the amount of the filling resin such that the filling amount ranges from 80 to 120% of the maximum filling amount (theoretical value) expressed by the formula of: maximum filling amount C (g/g, which is a resin amount (g) per one gram of the core material)=A×B, wherein A represents the pore volume (cm<SP>3</SP>/g) of the ferrite core material and B represents the density (g/cm<SP>3</SP>) of the filling resin. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a resin-filled ferrite carrier used in a two-component electrophotographic developer used in a copying machine, a printer, and the like, and more specifically, a developer that prevents image defects is obtained and has excellent strength. The present invention relates to a method for producing a resin-filled ferrite carrier for an electrophotographic developer having a high yield and good production stability.

  The electrophotographic development method is a method in which toner particles in a developer are attached to an electrostatic latent image formed on a photoreceptor and developed, and the developer used in this method is composed of toner particles and carrier particles. The two-component developer and the one-component developer using only toner particles.

  Among these developers, as a developing method using a two-component developer composed of toner particles and carrier particles, the cascade method has been used in the past, but at present, the magnetic brush method using a magnet roll is the mainstream. It is.

  In the two-component developer, the carrier particles are agitated together with the toner particles in the developing box filled with the developer, thereby imparting a desired charge to the toner particles, and thus being charged. A carrier material for transporting toner particles to the surface of the photoreceptor to form a toner image on the photoreceptor. The carrier particles remaining on the developing roll holding the magnet are returned to the developing box from the developing roll, mixed and stirred with new toner particles, and used repeatedly for a certain period.

  Unlike the one-component developer, the two-component developer has the function of mixing and stirring the carrier particles with the toner particles, charging the toner particles, and further transporting the toner particles. Good controllability. Therefore, the two-component developer is suitable for a full-color developing device that requires high image quality and a device that performs high-speed printing that requires image maintenance reliability and durability.

  In the two-component developer used in this manner, image characteristics such as image density, fog, vitiligo, gradation, and resolving power show predetermined values from the initial stage, and these characteristics are in the printing life period. It needs to be kept stable without fluctuating inside. In order to maintain these characteristics stably, it is necessary that the characteristics of the carrier particles contained in the two-component developer are stable.

  Conventionally, various types of iron powder carriers, ferrite carriers, resin-coated ferrite carriers, magnetic powder-dispersed resin carriers, and the like have been used as carrier particles for forming a two-component developer.

  Recently, the networking of offices has progressed and evolved from the single-function copying machine to the multifunctional machine, and the service system has been changed from a system in which contracted service personnel regularly perform maintenance and replace developer etc. However, there has been a shift to the era of maintenance-free systems, and the demand for further extending the life of the developer is increasing from the market.

  Under such circumstances, for the purpose of reducing the weight of carrier particles and extending the developer life, Patent Document 1 (Japanese Patent Laid-Open No. 5-40367) discloses that fine magnetic fine particles are dispersed in a resin. Many magnetic powder dispersed carriers have also been proposed.

  Such a magnetic powder-dispersed carrier can reduce the true density by reducing the amount of magnetic fine particles, and can reduce stress due to stirring, so it can prevent the film from being scraped or peeled off, and is stable over a long period of time. Image characteristics can be obtained.

  However, the magnetic powder-dispersed carrier has a high carrier resistance because the binder resin covers the magnetic fine particles. Therefore, there is a problem that it is difficult to obtain a sufficient image density.

  In addition, the magnetic powder-dispersed carrier is obtained by solidifying magnetic fine particles with a binder resin. The magnetic fine particles are detached due to agitation stress or impact in a developing machine, or the conventional iron powder carrier or ferrite carrier is used. In some cases, the mechanical strength may be inferior, or the carrier particles may be broken. The detached magnetic fine particles and broken carrier particles may adhere to the photoreceptor and cause image defects.

  Furthermore, since the magnetic powder-dispersed carrier uses fine magnetic fine particles, there are disadvantages that the residual magnetization and the coercive force are increased and the fluidity of the developer is deteriorated. In particular, when a magnetic brush is formed on a magnet roll, since the residual magnetization and the coercive force are present, the ears of the magnetic brush become hard and it is difficult to obtain high image quality. In addition, even when the magnet roll is separated, the magnetic aggregation of the carrier is not loosened and the toner is not quickly mixed with the replenished toner, so that the charge amount rises poorly and causes image defects such as toner scattering and fogging. was there.

  Furthermore, the magnetic powder-dispersed carrier can be made by two methods, a pulverization method and a polymerization method, but the pulverization method has a low yield, and the polymerization method has a complicated manufacturing process. There's a problem.

  As an alternative to a magnetic powder-dispersed carrier, a resin-filled carrier has been proposed in which a void in a porous carrier core material is filled with a resin. For example, in Patent Document 2 (Japanese Patent Laid-Open No. 11-295933) and Patent Document 3 (Japanese Patent Laid-Open No. 11-295935), a soft magnetic core or a hard magnetic core, a polymer contained in the pores of the core, and a core A carrier including an overlying coating is described. These resin-filled carriers are said to provide a carrier with less impact, desired fluidity, a wide triboelectric charge range, desired conductivity, and a volume average particle diameter in a certain range. Yes.

  Here, Patent Document 2 states that various appropriate porous solid core carrier materials such as a known porous core can be used as the core material. Of particular importance is described as being porous and having the desired fluidity, and notable properties include softness and porosity and volume average particle size as indicated by the BET area.

However, as described in the Examples of the same document, with a porosity having a BET area of about 1600 cm ² / g, it is not possible to achieve a sufficiently low specific gravity even if the resin is filled. It was not able to meet the demand for life extension.

  Furthermore, as described in the same document, it is difficult to accurately control the specific gravity and mechanical strength of the carrier after filling with the resin simply by controlling the porosity expressed by the BET area. .

  The measurement principle of the BET area is to measure physical adsorption and chemical adsorption of a specific gas and does not correlate with the porosity of the core material. In other words, even if the core material has few pores, it is common for the BET area to change depending on the particle size, particle size distribution, surface material, etc., and the porosity is controlled by the BET area thus measured. Even so, it cannot be said that the core material can be sufficiently filled with resin. Although the BET area value is high, if you try to fill a large amount of resin into a core material that is not porous or insufficiently porous, the resin that could not be filled alone will not be in close contact with the core material. In addition, it is possible to obtain stable characteristics such as floating in the carrier, large amount of aggregation between particles, poor fluidity, and large change in charging characteristics when aggregation is released during the actual use period. Is difficult.

  In addition, the same document states that it is preferable to use a porous core, and the total content of the resin filling the core and the resin covering the surface thereof is about 0.5 to about 10% by weight of the carrier. ing. Furthermore, in the examples of the document, those resins are less than 6% by weight based on the carrier. With such a small amount of resin, a desired low specific gravity cannot be realized, and only the same performance as that of a resin-coated carrier that has been used conventionally can be obtained.

  Patent Document 4 (Japanese Patent Application Laid-Open No. Sho 54-78137) describes pores and surface dents in magnetic particles having a smaller bulk specific gravity or a larger surface roughness than those substantially nonporous. An electrostatic image developer carrier filled with a fine powder of an electrically insulating resin is disclosed.

  Patent Document 5 (Japanese Patent Laid-Open No. 2006-337579) discloses a resin-filled carrier obtained by filling a ferrite core material having a porosity of 10 to 60% with a resin, as disclosed in Patent Document 6 (Japanese Patent Laid-Open No. 2007-57943). (Patent Publication) proposes a resin-filled carrier having a three-dimensional laminated structure. In these documents, various methods can be used as a method for filling a resin-filled carrier core material with a resin. Examples of the methods include a dry method, a spray-dry method using a fluidized bed, a rotary dry method, and a universal agitator. It is disclosed that an appropriate method is selected depending on the core material and resin to be used.

  Further, in Patent Document 6, when filling the resin, it is preferable to reduce the pressure inside the filling device, and it is difficult to fill the gap with the resin under normal pressure or in a pressurized state. There is a disclosure that by reducing the pressure, the voids inside the particles can be efficiently and sufficiently filled with resin, and a three-dimensional laminated structure can be easily formed.

  In the porous magnetic powders described in these patent documents, there is an example in which the pore volume of the core material is examined by BET or oil absorption. However, BET is a surface area to the last, and the actual porosity is not known from the value. The amount of oil absorption reflects the pore volume to some extent, but considering the measurement principle, the gap between particles is also measured and is not an actual pore volume. In general, the void volume between the particles is larger than the actual void volume in the particle, and the index when attempting to fill the resin without excessive excess or deficiency is not accurate. It was.

  When an appropriate amount of resin is filled using such a core material, if there is too much resin filling amount relative to the core material void volume, the resin that could not be filled is present as floating resin. Induces poor charging with toner and leads to image defects.

  On the other hand, when the resin filling amount is too small with respect to the core hole volume, the dielectric breakdown voltage is low, leading to image defects. Moreover, since the void | hole is not fully filled with resin, it is inferior to intensity | strength.

  For this reason, in the past, in order to properly fill the resin without excessive excess or deficiency, a plurality of experiments were repeated to determine the resin filling amount. However, such a method has a problem that yield is poor and production stability is poor.

JP-A-5-40367 JP 11-295933 A JP-A-11-295935 JP 54-78137 A JP 2006-337579 A JP 2007-57943 A

  Thus, while maintaining the advantages of the above-described resin-filled type carrier, an appropriate amount of resin is filled with respect to the core material void volume to obtain a developer that prevents image defects, and has excellent strength. There is a need for a method for producing a resin-filled carrier for an electrophotographic developer having a high yield and good production stability.

  Accordingly, an object of the present invention is to provide a developer that prevents image defects while maintaining the advantages of a resin-filled carrier, and has excellent strength, high yield, and good production stability. The object is to provide a method for producing a resin-filled carrier for a developer.

  As a result of intensive studies to solve the above problems, the present inventors have found that 80% to 120% of the maximum filling amount (theoretical value) indicated by the product of the ferrite core hole volume and the density of the filling resin. Thus, it has been found that the above problem can be solved by setting the ferrite core material void volume and the amount of the filling resin, and the present invention has been achieved.

That is, the present invention is a method for producing a resin-filled carrier for an electrophotographic developer obtained by filling a porous ferrite core material with a resin, and has a maximum filling amount (theoretical value) of 80 represented by the following formula. An object of the present invention is to provide a method for producing a resin-filled carrier for an electrophotographic developer, wherein the pore volume of the porous ferrite core material and the amount of the filling resin are set so as to be ˜120%.

  In the method for producing a resin-filled carrier for an electrophotographic developer according to the present invention, in the step of filling the resin, the porous ferrite core material and the filled resin are mixed and stirred under reduced pressure while the porous ferrite core is mixed. It is preferable to fill the pores of the core material with resin.

  In the method for producing a resin-filled carrier for an electrophotographic developer according to the present invention, the step of filling the resin is preferably performed in a plurality of times.

  In the method for producing a resin-filled carrier for an electrophotographic developer according to the present invention, it is preferable to provide a step of releasing aggregated particles after the step of filling the resin.

  In the method for producing a resin-filled carrier for an electrophotographic developer according to the present invention, it is preferable to perform a process of removing fine particles after the step of filling the resin or the step of releasing the aggregated particles.

  In the method for producing a resin-filled carrier for an electrophotographic developer according to the present invention, it is preferable to provide a surface coating step with a resin after the step of filling the resin, the step of releasing the agglomerated particles, or the treatment of removing fine particles. .

  Since the resin-filled ferrite carrier for an electrophotographic developer obtained by the production method according to the present invention is a resin-filled ferrite carrier, the true density is lightened and a long life can be achieved, the fluidity is excellent, the charge amount, etc. Can be easily controlled, and has higher strength than the magnetic powder-dispersed carrier, and does not crack, deform or melt due to heat or impact. In addition, since the resin filling amount is appropriate, there is no floating resin, so there is no image defect due to poor charging with the toner, and there is no image defect due to low dielectric breakdown voltage. It does not occur and has high strength. And the manufacturing method of this invention has a high yield, and the said resin filling type | mold carrier is obtained with the outstanding production stability.

Hereinafter, the best mode for carrying out the present invention will be described.
<Method for producing resin-filled ferrite carrier for electrophotographic developer according to the present invention>
A method for producing a resin-filled ferrite carrier for an electrophotographic developer according to the present invention will be described.

  In the method for producing a resin-filled ferrite carrier for an electrophotographic developer according to the present invention, in order to produce a porous ferrite carrier core material, first, an appropriate amount of raw materials are weighed, and then, measured with a ball mill or a vibration mill. Grind and mix for 5 hours or more, preferably 1 to 20 hours.

  The raw material is not particularly limited, and various ferrite materials are used, but it is preferable to include at least one selected from Mn, Mg, Li, Ca, Sr, Cu, Zn, Zr, Bi, Ti, and Al. Considering the recent trend of reducing environmental burdens including waste regulations, it is preferable not to include heavy metals such as Cu, Zn and Ni beyond the range of inevitable impurities (accompanying impurities).

  The pulverized material thus obtained is pelletized using a pressure molding machine or the like, and then calcined at a temperature of 700 to 1200 ° C. You may grind | pulverize without using a pressure molding machine, add water to make a slurry, and granulate using a spray dryer. After calcination, after further pulverizing with a ball mill or a vibration mill, water and, if necessary, a dispersant, a binder, etc. are added, after adjusting the viscosity, granulated with a spray dryer, the oxygen concentration is controlled, 1000-1500 The firing is performed at a temperature of 1 ° C. for 1 to 24 hours. When pulverizing after calcination, water may be added and pulverized by a wet ball mill, a wet vibration mill or the like.

  The pulverizer such as the above-mentioned ball mill and vibration mill is not particularly limited, but in order to disperse the raw materials effectively and uniformly, it is preferable to use fine beads having a particle diameter of 1 mm or less for the medium to be used. Further, the degree of grinding can be controlled by adjusting the diameter, composition and grinding time of the beads used.

  The fired product thus obtained is pulverized and classified. As a classification method, the particle size is adjusted to a desired particle size using an existing air classification, mesh filtration method, sedimentation method, or the like.

  Then, if necessary, the surface can be heated at a low temperature to perform an oxide film treatment to adjust the electric resistance. The oxide film treatment can be performed by heat treatment at, for example, 300 to 700 ° C. using a general rotary electric furnace, batch electric furnace or the like. The thickness of the oxide film formed by this treatment is preferably 0.1 nm to 5 μm. If the thickness is less than 0.1 nm, the effect of the oxide film layer is small, and if it exceeds 5 μm, the magnetization is lowered or the resistance becomes too high, so that it is difficult to obtain desired characteristics. Moreover, you may reduce | restore before an oxide film process as needed.

  In the present invention, the resin-filled ferrite carrier core material (porous ferrite core material) for electrophotographic developer thus obtained is filled with resin. Various methods can be used as the filling method. Examples of the method include a dry method, a spray drying method using a fluidized bed, a rotary drying method, an immersion drying method using a universal stirrer, and the like.

  The resin used here is not particularly limited and can be appropriately selected depending on the toner to be combined, the environment in which it is used, and the like. For example, fluorine resin, acrylic resin, epoxy resin, polyamide resin, polyamideimide resin, polyester resin, unsaturated polyester resin, urea resin, melamine resin, alkyd resin, phenol resin, fluorine acrylic resin, acrylic-styrene resin, silicone resin, Alternatively, modified silicone resins modified with resins such as acrylic resin, polyester resin, epoxy resin, polyamide resin, polyamideimide resin, alkyd resin, urethane resin, and fluororesin can be used. In view of the detachment of the resin due to mechanical stress during use, a thermosetting resin is preferably used. Specific examples of thermosetting resins include epoxy resins, phenol resins, silicone resins, unsaturated polyester resins, urea resins, melamine resins, alkyd resins, and resins containing them.

  A conductive agent can be added to the filled resin for the purpose of controlling the electrical resistance, charge amount, and charging speed of the ferrite carrier. Since the conductive agent itself has a low electric resistance, an excessive amount of the conductive agent tends to cause an abrupt charge leak. Therefore, the addition amount is 0.25 to 20.0% by weight, preferably 0.5 to 15.0% by weight, particularly preferably 1.0 to 10.0% by weight, based on the solid content of the filled resin. It is. Examples of the conductive agent include conductive carbon, oxides such as titanium oxide and tin oxide, and various organic conductive agents.

  In addition, the charge resin can contain a charge control agent. Examples of the charge control agent include various charge control agents generally used for toners and various silane coupling agents. This is because, when a large amount of resin is filled, the charge imparting ability may be lowered, but it can be controlled by adding various charge control agents and silane coupling agents. The types of charge control agents and coupling agents that can be used are not particularly limited, but charge control agents such as nigrosine dyes, quaternary ammonium salts, organometallic complexes, and metal-containing monoazo dyes, aminosilane coupling agents, and fluorine-based silane couplings. An agent or the like is preferable.

In the present invention, when filling the porous ferrite core material with resin, the porous ferrite core material pore volume and the maximum filling amount (theoretical value) represented by the following formula are 80% to 120%. Set the amount of filled resin.

Here, the pore volume (cm ³ / g) of the ferrite core material and the density (g / cm ³ ) of the filled resin are measured as follows.

(Ferrite core hole volume)
It measured using mercury porosimeter Pascal140 and Pascal240 (Thermo Fisher Scientific company make). CD3P (for powder) was used as the dilatometer, and the sample was placed in a dilatometer in a commercially available gelatin capsule with a plurality of holes. After degassing with Pascal 140, it was filled with mercury and the low pressure region (0 to 400 Kpa) was measured to obtain 1st Run. Next, deaeration and measurement of the low pressure region (0 to 400 Kpa) were performed again to obtain 2nd Run. After 2nd Run, the combined weight of the dilatometer, mercury, capsule and sample was measured. Next, the high pressure region (0.1 Mpa to 200 Mpa) was measured with Pascal240. The mercury intrusion amount obtained by the measurement of the high pressure part was defined as the ferrite core material void volume.

(Filled resin density)
In a thermosetting resin, if the resin is cured, for example, if it is a silicone resin, it is held at 150 to 250 ° C. for 1 hour to cure the resin. In a thermoplastic resin, it hold | maintains, for example in 60 degreeC on a petri dish for 2 hours so that the solvent contained may fully volatilize. The obtained resin solid was pulverized using a mortar to obtain resin powder. The density of the resin powder was measured using a pycnometer in accordance with JIS R9301-2-1.

  The maximum filling amount (theoretical value) represented by the above formula is the amount of resin that can be filled without any excess or deficiency in terms of the theoretical maximum filling amount. However, there are actually vacancies that remain unfilled. There is also an outermost surface of the ferrite core material, that is, a resin to be coated instead of being filled.

  Regarding such fluctuations, it was found that the extreme excess or deficiency as described above does not occur when the maximum filling amount (theoretical value) is in the range of 80% to 120%.

  If the filling amount exceeds 120% of the maximum filling amount (theoretical value), the resin filling amount is too much with respect to the core material pore volume, and thus the resin that cannot be filled is present as a floating resin. This induces a charging failure with the toner, leading to image defects. On the other hand, if the filling amount is less than 80% of the maximum filling amount (theoretical value), the resin filling amount is too small with respect to the core hole volume, so that the dielectric breakdown voltage is low, leading to image defects. Moreover, since the void | hole is not fully filled with resin, it is inferior to intensity | strength.

  In the production method of the present invention, in the step of filling the resin, it is preferable to fill the pores of the porous ferrite core material with the resin while mixing and stirring the porous ferrite core material and the filling resin under reduced pressure. By filling the resin under reduced pressure in this way, it is possible to efficiently fill the hole portion with the resin. The degree of decompression is preferably 500 mmHg or less. If it exceeds 500 mmHg, the effect of depressurizing is lost, so that efficient filling cannot be performed.

  In the production method of the present invention, in the step of filling the resin, the porous ferrite core material and the filling resin are preferably mixed and stirred at a temperature not higher than the boiling point of the dilution solvent of the resin solution. When mixing and stirring at a temperature exceeding the boiling point of the diluting solvent, the resin filling is performed in a state where the resin solution is boiled, so that efficient filling cannot be performed. For example, when using toluene as a diluting solvent, the mixture is stirred at a temperature of the boiling point of toluene of 110.6 ° C. or lower.

  In the production method of the present invention, the step of filling the resin is preferably performed in a plurality of times. It is possible to fill the resin in a single filling step. There is no need to divide it multiple times. However, depending on the type of resin, when a large amount of resin is filled at once, particle aggregation may occur. When aggregation occurs, when it is used as a carrier in a developing machine, the aggregation may be released due to agitation stress of the developing device. In such a case, the agglomerated particle interface has a large charging characteristic. In such a case, the particles can be filled in a plurality of times, and can be filled without excessive excess or deficiency while preventing aggregation.

  In the production method of the present invention, it is preferable to further provide a step of breaking the aggregated particles after the filling step. By performing filling as described above, filling can be performed without agglomeration or excessive excess or deficiency, but some agglomeration may occur. Since such agglomeration may cause fluctuations in the developer characteristics in the developing machine during use, it is preferable to break up the agglomerated particles after the filling step when heat treatment is performed. . Various methods and apparatuses can be used as a method for solving such agglomeration. For example, a vibration sieve, an ultrasonic vibration sieve, a vibration mill, a hammer mill, a roll mill, or the like can be used.

  In the production method of the present invention, it is desirable to perform a process of removing fine particles after the step of filling the resin or the step of breaking the aggregated particles. Fine particles may be generated in the filling step or the step of removing aggregation. This is because a part of the core material particles is broken or excessive filling resin becomes resin fine particles due to physical stress in each step. Such fine particles may cause image defects such as vitiligo, cause fluctuations in developer characteristics, and cause charging failure. Therefore, it is more preferable to perform a process for removing such fine particles. Various methods and apparatuses can be used as the method and apparatus for removing the fine particles. For example, a vibration sieve, an ultrasonic vibration sieve, an air classifier, or the like can be used.

  In the production method of the present invention, it is desirable to provide a resin surface covering step after the step of filling the resin, the step of breaking up the agglomerated particles, or the treatment of removing the fine particles. Carrier characteristics, particularly electrical characteristics such as charging characteristics, are often affected by materials and properties existing on the carrier surface. Therefore, the desired carrier characteristics can be adjusted with high accuracy by coating the surface with an appropriate resin.

  The coating resin is not particularly limited. For example, fluorine resin, acrylic resin, epoxy resin, polyamide resin, polyamideimide resin, polyester resin, unsaturated polyester resin, urea resin, melamine resin, alkyd resin, phenol resin, fluorine acrylic resin, acrylic-styrene resin, silicone resin, Alternatively, modified silicone resins modified with resins such as acrylic resin, polyester resin, epoxy resin, polyamide resin, polyamideimide resin, alkyd resin, urethane resin, and fluororesin can be used. In view of the detachment of the resin due to mechanical stress during use, a thermosetting resin is preferably used. Specific examples of thermosetting resins include epoxy resins, phenol resins, silicone resins, unsaturated polyester resins, urea resins, melamine resins, alkyd resins, and resins containing them. The coating amount of the resin is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the filled ferrite carrier (before resin coating).

  These coating resins can also contain a conductive agent and a charge control agent for the same purpose as described above. The kind and addition amount of the conductive agent and the charge control agent are the same as in the case of the above filling resin.

<Resin-filled ferrite carrier for electrophotographic developer obtained by the production method according to the present invention>
The resin-filled ferrite carrier for an electrophotographic developer obtained by the production method of the present invention preferably has an average particle size of 20 to 50 μm. In this range, carrier adhesion is prevented and good image quality is obtained. It is done. An average particle size of less than 20 μm is not preferable because carrier adhesion tends to occur. If the average particle size exceeds 50 μm, the image quality tends to deteriorate, which is not preferable.

The resin-filled ferrite carrier for an electrophotographic developer obtained by the production method of the present invention preferably has an electric resistance of 1 × 10 ⁷ Ω or more at an applied voltage of 100V. If the electric resistance is less than 1 × 10 ⁷ Ω, charge leakage and dielectric breakdown voltage are likely to occur in actual use, which is not preferable.

  The resin-filled ferrite carrier for an electrophotographic developer obtained by the production method of the present invention preferably has a transmittance of 90% or more. The higher the transmittance, the less floating resin. If the transmittance is less than 90%, white spots and poor charging are generated in actual use, which is not preferable.

  The resin-filled ferrite carrier for an electrophotographic developer obtained by the production method of the present invention preferably has a charge amount of 20 μC / g or more. The level of the charge amount itself is a design item, so there is no range that is uniquely determined, but in general, it is designed to be 20 μC / g or more. If the charge amount is too low, toner scattering and fogging are likely to occur, which is not preferable.

  In the resin-filled ferrite carrier for an electrophotographic developer obtained by the production method of the present invention, it is desirable that aggregated particles and fine particles are not observed. The presence of aggregated particles and fine particles is not preferable because problems such as poor charging, characteristic variation during use, and white spots occur.

<Measurement method>
The measuring method of each characteristic of the resin-filled ferrite carrier obtained by the production method according to the present invention is shown below.

(Average particle size)
The average particle size is measured using a Microtrac particle size analyzer (Model 9320-X100) manufactured by Nikkiso Co., Ltd. Water was used as the dispersion medium. Place 10 g of sample and 80 ml of water in a 100 ml beaker and add 2-3 drops of dispersant (sodium hexametaphosphate). Subsequently, using an ultrasonic homogenizer (UH-150 type manufactured by SMT.CO.LTD.), The output level was set to 4 and dispersion was performed for 20 seconds. Thereafter, bubbles formed on the beaker surface were removed, and the sample was put into the apparatus. The volume% of particles less than 24 μm was also measured and calculated in the same manner.

(Electric resistance)
A non-magnetic parallel plate electrode (10 mm × 40 mm) is made to oppose with an inter-electrode spacing of 1.0 mm, and 200 mg of a sample is weighed and filled between them. A sample is held between the electrodes by attaching a magnet (surface magnetic flux density: 1500 Gauss, area of the magnet in contact with the electrode: 10 mm × 30 mm) to the parallel plate electrodes, a voltage of 100 V is applied, and the resistance is measured by an insulation resistance meter (SM- 8210, manufactured by Toa Decay Co., Ltd.). Note that the measurement was performed in a constant temperature and humidity room controlled at a room temperature of 25 ° C. and a humidity of 55%.

(Charging characteristics)
The charge amount was determined by measuring a mixture of carrier and toner with a suction charge amount measuring device (Epping q / m-meter, manufactured by PES-Laboratorium). As the toner, a commercially available negative polarity toner (cyan toner, for DocuPrint C3530 manufactured by Fuji Xerox Co., Ltd.) used in a full color printer was used, and the toner concentration was adjusted to 5% by weight. The adjusted developer was put in a 50 cc glass bottle and stirred at a rotation speed of 100 rpm. Note that the measurement was performed in a constant temperature and humidity room controlled at a room temperature of 25 ° C. and a humidity of 55%.

(Transmissivity (floating resin amount))
The transmittance indicating the amount of floating resin was measured by the following method.
As a measuring device, a visible spectrophotometer Mod6100 (manufactured by Ogawa Seiki Co., Ltd.) was used. 3 ml of 2-butanone was placed in a glass cell (MG-10, Fujiwara Seisakusho) and set in a cell holder. In wavelength selection, 500 nm was selected. The sample chamber was closed and the Calibrate button was pressed (the transmittance obtained by this operation was set to 100%).

  15 g of the carrier sample was weighed and placed in a 50 ml sample bottle, and 20 ml of 2-butanone was added to the lid. This sample bottle was set on a rotary stirrer and stirred at 150 rpm for 20 minutes. Next, a magnet was attached to the bottom of the sample bottle, the carrier was submerged, and the sample bottle was shaken by hand three times in that state. 3 ml of the supernatant was placed in an empty glass cell.

The cell containing the sample (supernatant liquid) was placed in a cell holder, and the sample chamber was closed. The transmittance was measured by reading the value displayed on the display of the measuring device.
It shows that there are many amounts of floating resin, so that the value of the transmittance | permeability is low. If the transmittance is less than 90%, the amount of floating resin is large, and if it is less than 85%, it is very large.

(Agglomerated particles and fine particles)
This was done by observing the carrier with an electron microscope.

  Hereinafter, the present invention will be specifically described based on examples and the like.

MnO: 35mol%, MgO: 14.5mol %, Fe 2 O 3: 50mol% and SrO: materials were weighed so that 0.5 mol%, to obtain a slurry was pulverized for 5 hours by a wet media mill. The obtained slurry was dried with a spray dryer to obtain true spherical particles. Trimanganese tetraoxide was used as the MnO raw material, magnesium hydroxide was used as the MgO raw material, and strontium carbonate was used as the SrO raw material. After adjusting the particle size, the particles were heated at 950 ° C. for 2 hours to be pre-baked. Next, the mixture was pulverized with a wet ball mill for 1 hour using 1/8 inch diameter stainless steel beads, and further pulverized for 4 hours with 1/16 inch diameter stainless steel beads. A suitable amount of a dispersant is added to this slurry, and 0.6% by weight of PVA as a binder is added to the solid content for the purpose of ensuring the strength of the granulated particles and adjusting the degree of voids, and then spray dryer The mixture was granulated and dried, and held in an electric furnace at a temperature of 1140 ° C. and an oxygen concentration of 0% by volume for 4 hours, followed by firing. Thereafter, the mixture was crushed, further classified to adjust the particle size, and then the low magnetic product was separated by magnetic separation, thereby obtaining a core material of porous ferrite particles. The ferrite core material had a volume average particle size of 35.1 μm. Moreover, when the void | hole volume of this ferrite core material was measured, it was 0.082 cm < ³ > / g.

A condensation-crosslinked silicone resin (weight average molecular weight: about 8000) comprising T units and D units was prepared. The density of the cured silicone resin was measured and found to be 1.26 cm ³ / g. 5500 g of this silicone resin solution (because the resin solution concentration is 20%, solid content is 1100 g, diluent solvent: toluene, boiling point 110.6 ° C.) and 10 kg of the above porous ferrite particles are mixed and stirred at 70 ° C. under a reduced pressure of 200 mmHg Then, while volatilizing toluene, the resin was permeated and filled inside the porous ferrite.

  After confirming that toluene was sufficiently volatilized, stirring was continued for another 30 minutes, and toluene was almost completely removed.

  The product was taken out from the filling device, placed in a container, placed in a hot-air heating oven, and heat-treated at 250 ° C. for 2 hours.

  Then, it cooled to room temperature, the ferrite particle | grains by which resin was hardened were pick_out | removed, the aggregation of the particle | grains was released with the vibrating sieve of 150M opening, and the nonmagnetic thing was removed using the magnetic separator. Thereafter, coarse particles and fine particles were removed again with a vibrating sieve to obtain a carrier filled with resin.

  The surface of the obtained resin-filled carrier was coated with 0.5% by weight of the same resin as the filled resin. Here, the coating was performed at 60 ° C. under normal pressure by using an immersion drying method with a universal stirrer.

  After coating, it was placed in a hot air heating type oven and heat-treated at 250 ° C. for 2 hours. Then, it cooled to room temperature, the ferrite particle | grains by which resin was hardened were pick_out | removed, the aggregation of the particle | grains was released with the vibrating sieve of 150M opening, and the nonmagnetic thing was removed using the magnetic separator. Thereafter, coarse particles were again removed with a vibrating sieve to obtain a resin-filled carrier whose surface was coated with a resin.

As the core material, porous ferrite having a pore volume of 0.104 cm ³ / g fired at a firing temperature of 1120 ° C. is used, the resin filling amount is 1500 g as a solid content, and fine particles are removed by air classification after the resin filling step. A resin-filled carrier having a resin-coated surface was obtained in the same manner as in Example 1 except that the steps were added.

The same procedure as in Example 1 was performed except that porous ferrite having a pore volume of 0.130 cm ³ / g fired at a firing temperature of 1100 ° C. was used as the core material, and the resin filling amount was 1500 g as a solid content. Thus, a resin-filled carrier whose surface was coated with a resin was obtained.

  A resin-filled carrier was obtained in the same manner as in Example 3 except that the resin filling amount was 1800 g as a solid content, filling was performed in three portions of 1200 g, 500 g, and 100 g, and surface coating was not performed.

  A resin-filled carrier was obtained in the same manner as in Example 2 except that the resin filling amount was 1700 g as the solid content, and filling was performed in two batches of 1500 g and 200 g.

Comparative example

[Comparative Example 1]
A resin-filled carrier was obtained in the same manner as in Example 3 except that the resin filling amount was 1200 g as a solid content and no surface coating was applied. Here, as in Example 3, coarse particles were removed using a vibrating sieve, but the treatment for removing fine particles was not performed.

[Comparative Example 2]
The same core material as that used in Example 1 was used, and the resin filling amount was 1300 g as a solid content. In addition, a resin-filled carrier was obtained without performing the crushing step for breaking the aggregated particles, the treatment for removing the fine particles, and the surface coating step.

  Table 1 shows the production conditions of Examples 1 to 5 and Comparative Examples 1 and 2. Table 2 shows each characteristic (electric resistance, floating resin amount and charge amount) and evaluation result (carrier observation) of the obtained resin-filled carrier.

  As is clear from the results shown in Table 2, the resin-filled ferrite carriers shown in Examples 1 to 5 have high transmittance values indicating the amount of resin floating without being in close contact with the ferrite core material. It can be seen that there is almost no floating resin. In addition, there is no noticeable charging failure and electrical resistance is high.

  On the other hand, although the carrier shown in Comparative Example 1 has a small amount of floating resin, since the resin filling amount is small, there are many fine particles estimated as core particles crushed during the agglomerated particle crushing step, and electric resistance is also high. Extremely low. In addition, the charge amount is low, and it is assumed that charging failure has occurred.

  The carrier obtained in Comparative Example 2 has a very large amount of floating resin, and there is charge inhibition due to this, so the charge amount is extremely low. Many agglomerated particles and fine particles were observed.

  When the carriers obtained in Comparative Examples 1 and 2 are actually used, the charge amount fluctuates significantly due to stress in the actual machine, and image defects such as white spots due to charge leakage and fine particles are likely to occur, and good image quality is achieved. It is easily imagined that it cannot be maintained stably.

  The resin-filled ferrite carrier for an electrophotographic developer obtained by the production method according to the present invention provides a developer that prevents image defects while maintaining the advantages of the resin-filled carrier and is excellent in strength. In addition, according to the production method of the present invention, the filled ferrite carrier can be produced with a high yield and good production stability.

  Therefore, the method for producing a resin-filled ferrite carrier for an electrophotographic developer according to the present invention is widely used in fields such as a full-color machine requiring high image quality and a high-speed machine requiring image maintenance reliability and durability. Is possible.

Claims (6)

A method for producing a resin-filled carrier for an electrophotographic developer obtained by filling a porous ferrite core material with a resin so that the maximum filling amount (theoretical value) represented by the following formula is 80 to 120%. A method for producing a resin-filled carrier for an electrophotographic developer, characterized in that the pore volume of the porous ferrite core material and the amount of the filling resin are set.

2. The electrophotographic developer according to claim 1, wherein in the step of filling the resin, the pores of the porous ferrite core material are filled with the resin while mixing and stirring the porous ferrite core material and the filled resin under reduced pressure. For producing resin-filled carrier for use in a vehicle. The method for producing a resin-filled carrier for an electrophotographic developer according to claim 1 or 2, wherein the step of filling the resin is performed in a plurality of times. The method for producing a resin-filled carrier for an electrophotographic developer according to claim 1, wherein a step of releasing aggregated particles is provided after the step of filling the resin. The method for producing a resin-filled carrier for an electrophotographic developer according to any one of claims 1 to 4, wherein a treatment for removing fine particles is performed after the step of filling the resin or the step of breaking the aggregated particles. The resin-filled carrier for an electrophotographic developer according to any one of claims 1 to 5, wherein a surface coating step with a resin is provided after the step of filling the resin, the step of breaking up the agglomerated particles, or the treatment of removing fine particles. Method.