JP2009025600A - Electrophotographic developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic developer which comprises a toner having a glass transition temperature of 20-45°C and a carrier, and does not cause fogging, deterioration in transferability, carrier deposition and toner and carrier scattering even after printing on a large number of sheets (e.g., 200,000 sheets) using the electrophotographic developer. <P>SOLUTION: The electrophotographic developer comprising the toner and carrier is characterized in that the toner has a glass transition temperature of 20-45°C and the carrier is produced by injecting a resin into voids in a core material, wherein a core material having a void ratio of 10-60% is used as the above core material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic developer comprising a toner and a carrier.

  In recent years, there has been an increasing need to reduce the amount of power and waste consumed by the entire image forming apparatus for the purpose of saving energy and resources.

  In the entire image forming apparatus, the amount of power consumed by the fixing device is large, and reduction of this amount of power is effective as a measure for energy saving. As a resource saving, it is effective to reduce the amount of developer discarded by extending the life of the developer.

  Currently, the adoption of low-temperature fixing toner to reduce the amount of power consumed by the fixing device and the use of a long-life developer as a developer to reduce the amount of waste are being studied.

  In order to obtain a toner capable of reducing the amount of electric power, studies have been made to lower the glass transition point of the toner (see, for example, Patent Document 1).

  However, the toner with a low glass transition point design has a soft toner surface, and when the toner is stirred in the developing machine, the external additive on the surface of the toner particle is buried, so that the external additive on the surface of the toner particle is pre- and post-printing. The change in the state of existence has become large. As a result, the function of the external additive has been lost, and there has been a problem of deterioration in transferability during durability.

  Further, in recent years, as the speed of the image forming apparatus is increased, particularly the speed of the color image forming apparatus is increased, the stirring strength in the developing machine has increased, and the stirring energy received by the developer has increased. As a result, the deterioration of the toner has been promoted and the toner has been cracked. Along with this, the decrease in charge amount and the burying of external additives began to occur remarkably. As a result, fogging, transferability deterioration, carrier adhesion and toner / carrier scattering have become prominent.

  As countermeasures, the carrier has been reduced in specific gravity and a magnetic material dispersion type carrier has been proposed. However, there has been a problem that it is likely to be cracked or deformed by impact. (For example, refer to Patent Document 2).

Also, as the agitation energy received by the developer increases as the printing speed increases, in the carrier having the resin coating layer on the surface of the carrier particles, the film of the resin coating layer peels off, resulting in the resistance of the carrier. There was a problem that the value was extremely lowered. The film peeling depends on how the film-forming property of the resin coating layer at the time of carrier production, that is, how the adhesion between the carrier core material and the resin coating layer can be enhanced.
JP 2001-175025 A JP-A-8-248684

  In the present invention, even when a large number of sheets (for example, 200,000 sheets) are printed using an electrophotographic developer comprising a toner having a glass transition point of 20 to 45 ° C. and a carrier, fogging, transferability is reduced, and the carrier An object of the present invention is to provide a developer that does not cause adhesion or toner / carrier scattering.

  The present invention is achieved by adopting the following configuration.

1. In an electrophotographic developer comprising a toner and a carrier,
The toner has a glass transition point of 20 to 45 ° C.
The carrier is prepared by injecting a resin into the gap of the core material.
An electrophotographic developer using a core material having a porosity of 10 to 60% as the core material.

  The electrophotographic developer comprising a toner and a carrier having a glass transition point of 20 to 45 ° C. according to the present invention generates fog, deteriorates transferability, causes carrier adhesion and toner even when a large number of sheets (for example, 200,000 sheets) are printed. -It has an excellent effect that carrier scattering does not occur.

  The present inventors have examined a developer having excellent durability that does not cause the above-described problem even when a large number of sheets are printed using toner having a low glass transition point.

  Therefore, in the present invention, the carrier is reduced in specific gravity and reduced in weight to reduce the stress (stirring energy) received by the toner in the developing machine, and even when using a toner having a low glass transition point, the deterioration of the toner is suppressed. The production of a highly durable developer was studied.

  As a result of the study, the carrier having a low specific gravity is obtained by using a toner having a low glass transition point when a carrier having a low specific gravity is prepared by injecting a resin into a void of a core material having a porosity of 10 to 60%. It was also found that toner deterioration is suppressed and a highly durable developer can be obtained.

  This developer consisting of low specific gravity carrier and low glass transition point toner can suppress the deterioration of the toner because the stress applied to the toner is reduced even when a large number of sheets are printed in a high-speed image forming apparatus. It became so.

  The low specific gravity carrier also has good fluidity, and the charge amount and the like can be easily controlled by selecting the resin to be injected. Furthermore, since this low specific gravity carrier has higher strength than the magnetic powder-dispersed carrier, it has excellent characteristics without cracking, deformation and melting due to heat and impact.

  The reason why the fluidity has improved is that when the resin is injected into the core material, the concave portion of the core material is filled with the resin, so the shape of the carrier is smooth and the fluidity of the carrier is improved. Estimated. In addition, since a resin film is formed on the surface of the core material when the resin is injected into the voids of the core material, the carrier surface is less likely to be spent by the toner, contributing to a longer life of the developer.

  Hereinafter, the present invention will be described in detail.

《Career》
First, the carrier used in the present invention will be described.

  The carrier used in the present invention is produced by injecting a resin into a void of a core material having a specific porosity.

  When this carrier is used, even if it is combined with a toner having a glass transition point of 20 to 45%, no spent is generated on the carrier surface over a long period of time, and high-quality print image quality can be obtained. Can be prevented.

  Further, the carrier may be produced by injecting a resin into the core material and further providing a resin coating on the surface thereof.

  Hereinafter, the core material and resin used for producing the carrier, and the method for producing the carrier will be described.

<Core>
The core material used in the present invention has a porosity of 10 to 60%, preferably 20 to 40%. By setting the porosity to the above range, the specific gravity can be reduced even when the resin is injected, and the strength is improved by injecting the resin into the void and the carrier is not destroyed during printing.

  The porosity of the core material referred to in the present invention is the ratio of the void portion to the total area of the core material cross section.

  The porosity of the core material is obtained by photographing a cross section of the core material with a metal microscope, a scanning microscope, etc., and then analyzing the obtained image using image analysis software (Image-Pro Plus, manufactured by Media Cybernetics). . Specifically, the particle area (A) connected by a line enveloping the irregularities on the surface of the core material particles is measured, and then the area (B) of the core material portion included in the particle screen is measured. Here, the porosity is calculated using the following formula (1).

Formula (1)
Porosity (%) = (Envelope particle area (A) −Core material area (B)) / Envelope particle area (A) × 100
The void ratio calculated by this formula (1) is a void ratio obtained by combining voids continuous from the surface of the core material and voids independently existing inside the core material.

  Specifically, a cross section near the center of the 10 core members is photographed with a scanning electron microscope, and the obtained image is image-analyzed to obtain the porosity from the average.

  Further, as a core material used for the porosity measurement, 2 g of carrier from which the toner is separated from the developer and 15 ml of methyl ethyl ketone are stirred with a wave rotor for 10 minutes, and the coating resin layer and a part of the injected resin are removed. To do.

The core material used in the present invention has a true density of preferably 3.0 to 5.5 g / cm ³ , more preferably 4.0 to 5.5 g / cm ³ . By setting the true density within the above range, the charging speed is lowered, the magnetization per particle is not lowered too much, and carrier adhesion does not occur, so that it is preferable to extend the life.

  The true density of the core material and the carrier is a value obtained by measurement using a pycnometer according to JIS R9301-2-1.

The apparent density of the core material used in the present invention is preferably 0.7 to 2.5 g / cm ³ , more preferably 0.9 to 2.3 g / cm ³ . By making the apparent density within the above range, the strength is maintained and the carrier is not destroyed, and the weight can be reduced and the life can be increased, which is preferable.

  The apparent density is measured according to JIS-Z2504 (Apparent density test method for metal powder).

The core material used in the present invention preferably has an average particle diameter of 15 to 80 μm, more preferably 20 to 60 μm, in terms of volume-based median diameter (D ₅₀ ). By setting the average particle size in the above range, carrier adhesion does not occur and a high quality image can be obtained, which is preferable.

The median diameter (D ₅₀ ) based on the volume of the carrier can be measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympathic) equipped with a wet disperser.

The core material used in the present invention has an electric resistance of preferably 10 ² to 10 ¹² Ω, more preferably 10 ³ to 10 ¹¹ Ω. By setting the electric resistance in the above range, it is preferable that a charge leak of a carrier produced by injecting a resin hardly occurs and an electric resistance is not excessively high, and a high-density image can be obtained.

The core material used in the present invention is preferably made of ferrite, and more preferably represented by the general formula (MO) x (Fe ₂ O ₃ ) y (where y is 30 to 95 mol%). Here, M is preferably one or more selected from Fe, Mn, Mg, Sr, Ca, Ti, Cu, Zn, Ni, Li, Al, Si, Zr, and Bi.

Here, when M is Fe, it means iron ferrite, that is, magnetite. Compared to magnetite, ferrite is a higher-order oxide, and its characteristics are not easily changed by stress. Also, it is easy to reduce the specific gravity. When Fe ₂ O ₃ is less than 30 mol%, it is difficult to obtain desired magnetization, and carrier adhesion tends to occur. In particular, ferrite using a specific metal oxide as a raw material has little composition variation among particles, and easily obtains desired characteristics. In addition, when the above-described elements are used, it is easier to inject the resin than the other elements, although the reason is not clear.

  In consideration of the trend of environmental load reduction including recent waste regulations, it is preferable that substantially no heavy metals such as Cu, Zn and Ni are contained.

  For the above reasons, M is preferably one or more selected from Mn, Mg, Sr, Ca, Ti, Li, Al, Si, Zr, Bi, and Mn, Mg, Sr, Ca, Li, Zr, One type or two or more types selected from Bi are particularly preferable.

  In the production of the core material used in the present invention, an appropriate amount of the raw material is weighed and then pulverized and mixed for 0.5 hour or more, preferably 1 to 20 hours, with a ball mill or a vibration mill. 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, the mixture is further pulverized by a ball mill or vibration mill, and then water and, if necessary, a dispersant, a binder and the like are added. After adjusting the viscosity, granulation is performed, and the oxygen concentration is controlled. Hold for ˜24 hours and perform main firing. 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 or vibration mill is not particularly limited. However, 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. By making the thickness of the oxide film within the above range, the effect of the oxide film layer can be obtained, and it is easy to obtain desired characteristics without becoming too high resistance. Moreover, you may reduce | restore before an oxide film process as needed.

  As described above, as a method for controlling the porosity and continuous porosity of the core material, the apparent density, and the true density, the raw material type to be blended, the pulverization degree of the raw material, the presence or absence of calcination, the calcination temperature, the calcination time, It can be performed by various methods such as the amount of binder, the amount of moisture, the degree of drying, the firing method, the firing temperature, the firing time, the pulverization method, the reduction with hydrogen gas, etc. during granulation with a spray dryer. These control methods are not particularly limited, but an example is shown below.

  That is, the use of hydroxides or carbonates as raw material species to be blended tends to increase the porosity and continuous porosity compared to the case of using oxides. In addition, compared to oxides of heavy metals such as Cu, Ni, and Zn, the true density is higher when oxides such as Mn, Mg, Ca, Sr, Li, Ti, Al, Si, Zr, and Bi are used. And apparent density tends to be low.

  In addition, the porosity and continuous porosity are higher when the preliminary firing is not performed, and the apparent density is lower. Even when the preliminary firing is performed, the lower the temperature is, the higher the porosity and continuous porosity are. It tends to be low.

  In granulation with a spray dryer, increasing the amount of water when slurrying the raw material increases the number of voids, the porosity and the continuous void ratio are high, the apparent density tends to be low, and the temperature is lowered during firing. However, the porosity and continuous porosity are high, and the apparent density tends to be low.

  In order to obtain a desired porosity, continuous porosity, true density, and apparent density, these control methods can be used alone or in combination. In general, those having a high porosity and continuous porosity tend to have a lower true density and apparent density.

  However, since the degree of influence of each control factor on each characteristic varies, it is composed of ferrite that has characteristics such as high porosity and high apparent density, low porosity and low density, etc. by using them in combination. A core material can be obtained.

<Injected resin>
The injection resin to be injected into the gap in the core material is not particularly limited. For example, fluororesin, acrylic resin, epoxy resin, polyamide resin, polyamideimide resin, polyester resin, unsaturated polyester resin, urea resin, melamine resin, alkyd Modified with each resin such as resin, phenol resin, fluoroacrylic resin, acrylic-styrene resin, silicone resin or acrylic resin, polyester resin, epoxy resin, polyamide resin, polyamideimide resin, alkyd resin, urethane resin, fluororesin A silicone resin etc. are mentioned. 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 injection 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 the electrical resistance becomes relatively high due to resin injection, the charging ability may decrease, 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 addition, a conductive agent can be added to the resin to be injected for the purpose of controlling the electric resistance, charge amount, and charging speed of the carrier. Since the electrical resistance of the conductive agent itself is low, if the addition amount is too large, it causes a sudden charge leak. Therefore, the addition amount is preferably 0.25 to 20 relative to the solid content of the injected resin. It is 0.0 mass%, More preferably, it is 0.5-15.0 mass%. Examples of the conductive agent include conductive carbon, oxides such as titanium oxide and tin oxide, and various organic conductive agents.

<Carrier manufacturing method>
The carrier used in the present invention is produced by injecting a resin into the gap of the core material.

  The carrier is obtained by injecting 6 to 30% by mass, more preferably 8 to 25% by mass of the injected resin with respect to 100 parts by mass of the core material. By setting the resin injection amount in the above range, it is preferable that the desired specific gravity can be reduced and the effect of extending the life can be obtained, and that the electric resistance of the carrier is not excessively high and an image with a high density can be obtained.

  The carrier used in the present invention has a porosity, that is, a portion where resin is not injected and exists as voids, preferably 1 to 50%, more preferably 1.5 to 40%. Even if the resin is sufficiently injected, there are 1% or more voids. In addition, by injecting resin near the surface and leaving as much void as possible inside, it becomes easy to obtain a low specific gravity without extremely increasing the resistance of the carrier. However, when the porosity exceeds 50%, the strength of the carrier tends to be lowered, and the carrier is easily destroyed during use.

  Next, a method for manufacturing a carrier according to the present invention will be described.

  The method for producing a carrier by injecting a resin into the core material is not particularly limited, and various methods can be mentioned. Specific examples include a dry method, a spray-dry method using a fluidized bed, a rotary dry method, an immersion drying method using a universal agitator, and the like. As these methods, appropriate methods are selected depending on the core material and resin to be used.

  After injecting the resin, the resin is heated by various methods as necessary to bring the injected resin into close contact with the core material. The heating method may be either an external heating method or an internal heating method, and may be, for example, a fixed or fluid electric furnace, a rotary electric furnace, a burner furnace, or a microwave baking. The temperature varies depending on the resin to be injected, but a temperature higher than the melting point or glass transition point is necessary. With a thermosetting resin or a condensation-crosslinking resin, it is strong against impact by raising the temperature to a point where the curing proceeds sufficiently. You can get a career.

  A carrier prepared by injecting a resin into the core and then further coating the resin can be used. As a method for further coating the resin, it can be coated by a known method such as a brush coating method, a dry method, a spray drying method using a fluidized bed, a rotary drying method, an immersion drying method using a universal stirrer, or the like. In order to improve the coverage, a fluidized bed method is preferred.

  In the case of baking after coating, either an external heating method or an internal heating method may be used, for example, a fixed or fluid electric furnace, a rotary electric furnace, a burner furnace, or microwave baking may be used. . When a UV curable resin is used, a UV heater is used. Although the baking temperature varies depending on the resin to be used, a temperature equal to or higher than the melting point or the glass transition point is necessary. For a thermosetting resin or a condensation-crosslinking resin, it is necessary to raise the temperature to a point where the curing proceeds sufficiently.

  The resin for forming the coating layer can be appropriately selected depending on the toner to be combined. 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 consideration of detachment of the resin coating layer 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 carrier is preferably 0.01 to 10.0% by mass, more preferably 0.3 to 7.0% by mass, and further preferably 0.5 to 5% with respect to 100 parts by mass of the carrier after resin injection. 0.0% by mass. By setting the coating amount within the above range, a uniform coating layer can be formed on the surface of the carrier without causing aggregation between carriers, and fluctuations in developer characteristics such as fluidity or charge amount in the actual machine can be suppressed to a minimum. Can be preferable.

(Magnetic properties)
The measurement of magnetic characteristics (magnetization) is performed using an integral BH tracer BHU-60 type (manufactured by Riken Denshi Co., Ltd.). A magnetic field measuring H coil and a magnetization measuring 4πI coil are placed between the electromagnets. In this case, the sample is placed in a 4πI coil. The outputs of the H coil and the 4πI coil whose magnetic field H is changed by changing the current of the electromagnet are respectively integrated, and the H output is drawn on the X axis, the output of the 4πI coil is drawn on the Y axis, and a hysteresis loop is drawn on the recording paper. Here, the measurement conditions are sample injection amount: about 1 g, sample injection cell: inner diameter 7 mmφ ± 0.02 mm, height 10 mm ± 0.1, 4πI coil: values obtained by measurement with 30 turns. .

"toner"
Next, the toner will be described.

  The toner used in the present invention has a glass transition point of 20 to 45 ° C., preferably 20 to 40 ° C., and is excellent in low-temperature fixing characteristics.

  The glass transition point of the toner can be changed by selecting a polymerizable monomer used when producing a binder resin constituting the toner.

  Toner that is strong against stress (pressure) can be achieved by adopting a core-shell structure and making the glass transition point of the resin forming the shell higher than the glass transition point of the resin forming the core particles.

  The toner used in the present invention can be prepared by mixing an external additive with toner base particles (hereinafter also referred to as colored particles) containing a binder resin, a colorant, and a release agent.

  The method for producing the toner is not particularly limited, but a method using an emulsion association method is preferably used. Particularly preferred is a production method in which resin particles having a multi-stage polymerization structure formed by emulsion polymerization of miniemulsion polymerized particles are associated (aggregated / fused).

  An example of a procedure for preparing the toner used in the present invention is shown below.

The toner used in the present invention is produced through the following steps. That is,
(1) Dissolution / dispersion step in which wax is dissolved or dispersed in radical polymerizable monomer (2) Polymerization step in which polymerizable monomer is polymerized to produce a dispersion of resin particles (3) Resin in aqueous medium Aggregation / fusion process for producing core particles (aggregated particles) by agglomerating and fusing particles and colorant particles (4) First aging process for adjusting the shape by aging associated particles with thermal energy (5) Shelling step of forming colored particles having a core / shell structure by adding resin particles for a shell to a dispersion of core particles and aggregating and fusing the resin particles for the shell on the surface of the core particles (6) Core A second aging step for adjusting the shape of the core-shell structured colored particles by aging the shell-structured colored particles with thermal energy. (7) Cooling the colored particles dispersion of the core-shell structured and cooling the colored particles. Colored particles from the dispersion And liquid separation, it the separated washing step (8) washing the treated colored particles to remove the surface active agent than the colored particles from the drying step of drying, after drying if necessary,
(9) There may be a case of having an external additive treatment step of adding an external additive to the dried colored particles. The “colored particles” referred to in the above process means toner base particles, and the toner is used as it is when no external additive treatment is performed.

  When producing the toner used in the present invention, first, resin particles and colorant particles are associated and fused to produce particles serving as a core (hereinafter referred to as core particles). Next, resin particles are added to the core particle dispersion, and the resin particles are aggregated and fused on the surface of the core particles to coat the surface of the core particles to produce colored particles having a core / shell structure. As described above, the toner used in the present invention forms a core-shell structure by adding resin particles to a dispersion of core particles prepared by various manufacturing methods and fusing the resin particles to the core particles. .

  The core part constituting the toner used in the present invention can be formed through the following steps, for example. That is, the wax component is dissolved or dispersed in the polymerizable monomer that forms the resin. This is mechanically dispersed finely in an aqueous medium, and a polymerizable monomer is polymerized by a miniemulsion polymerization method. In this way, composite resin particles containing the wax component are formed.

  And a core part is formed by carrying out the salting-out / fusing which the composite resin particle and colorant particle which were produced in the said procedure mention later. When the wax component is dissolved in the polymerizable monomer, the wax component may be dissolved and melted or melted and dissolved.

  Hereinafter, each process mentioned above is demonstrated.

(1) Dissolution / dispersion step This step is a step of preparing a radical polymerizable monomer solution in which a wax is mixed by dissolving or dispersing a wax in a radical polymerizable monomer.

(2) Polymerization step In a preferred example of this polymerization step, a radical polymerizable monomer solution in which a wax is dissolved or dispersed in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less is used. Add and apply mechanical energy to form droplets. Next, a water-soluble radical polymerization initiator is added to advance the polymerization reaction in the droplet. The droplets may contain an oil-soluble radical polymerization initiator. In such a polymerization step, it is indispensable to forcibly emulsify (form droplets) by applying mechanical energy. Examples of means for imparting such mechanical energy include means for imparting strong stirring action such as homomixer, ultrasonic wave, and Manton gorin and ultrasonic vibration.

  By this polymerization step, resin particles (also referred to as composite resin particles) containing a wax and a binder resin are obtained. Such resin particles may be colored particles or uncolored particles. Colored resin particles can be obtained by polymerizing a monomer composition containing a colorant. In the case of non-colored resin particles, the resin particles are colored by fusing the resin particles and the colorant particles by adding a dispersion of the colorant particles to the resin particle dispersion in the aggregation / fusion process described later. Particles are obtained.

  The mass average particle diameter (dispersed particle diameter) of the resin particles obtained in the polymerization step is preferably in the range of 10 to 1000 nm, more preferably in the range of 30 to 300 nm. The mass average particle diameter is a value measured using an electrophoretic light scattering photometer “ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)”.

(3) Aggregation / fusion process The aggregation / fusion process is a process of forming core particles (association particles) by associating resin particles obtained in the polymerization process. A typical method for agglomerating and fusing the resin particles is a salting-out / fusing method. In addition, in the aggregation / fusion process, it is possible to aggregate and fuse the internal particles such as wax particles and charge control agent together with the resin particles and the colorant particles.

  Here, “salting out / fusion” is to stop the particle growth by adding the aggregation terminator when the particles are aggregated and fused in parallel and grown to a desired particle size.

  In addition, the “aqueous medium” in the aggregation / fusion process refers to a material in which the main component (50% by mass or more) is made of water. Examples of components other than water that constitute the aqueous medium include organic solvents that dissolve in water, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran.

  Colorant particles can be prepared by dispersing a colorant in an aqueous medium. The dispersion treatment of the colorant is performed in a state where the surfactant concentration is set to a critical micelle concentration (CMC) or more in water. Although the disperser used for the dispersion | distribution process of a coloring agent is not specifically limited, For example, the following are mentioned. That is, a pressure disperser such as an ultrasonic disperser, a mechanical homogenizer, a manton gourin or a pressure homogenizer, a media grinder such as a sand grinder, a Getzman mill, or a diamond fine mill.

  Further, as the usable surfactant, the same surfactants as those described above can be used. The colorant (particles) may be surface-modified. In the surface modification method of the colorant, the colorant is dispersed in a solvent, the surface modifier is added to the dispersion, and the system is reacted by raising the temperature. After completion of the reaction, the colorant is filtered off, washed and filtered with the same solvent, and dried to obtain a colorant (pigment) treated with the surface modifier.

  The salting out / fusion method, which is a representative example of the method of agglomerating and fusing the resin particles, comprises the following steps. First, in a water-based medium in which resin particles and colorant particles are present, a salting-out agent composed of an alkali metal salt, an alkaline earth metal salt, a trivalent salt, or the like is used as a flocculant, and the water content exceeds a critical coagulation concentration. Add amount. Next, salting is advanced by heating to a temperature above the glass transition point of the resin particles and above the melting peak temperature of the mixture, and at the same time, the particles are fused. Alkali metal salts and alkaline earth metal salts which are salting-out agents include lithium, potassium, sodium and the like as alkali metals, and examples of alkaline earth metals include magnesium, calcium, strontium and barium, preferably Examples include potassium, sodium, magnesium, calcium, and barium.

  When agglomeration and fusion are performed by the salting-out / fusion method, it is preferable to shorten the time after addition of the salting-out agent as much as possible. This is because there is a concern that the aggregation state of the particles, the particle size distribution, and the surface performance of the toner may be affected by the passage of time after the salting out. Further, the temperature at which the salting-out agent is added must be at least the glass transition point of the resin particles. This is because if the temperature at which the salting-out agent is added is equal to or higher than the glass transition point of the resin particles, although the salting-out / fusion of the resin particles proceeds quickly, it becomes difficult to control the particle size. This is because the formation of particles is a concern. The temperature range when the salting-out agent is added may be equal to or lower than the glass transition point of the resin, but is generally 5 to 55 ° C, preferably 10 to 45 ° C.

  Also, after adding the salting-out agent below the glass transition point of the resin particles, the temperature is raised as quickly as possible to a temperature above the glass transition point of the resin particles and above the melting peak temperature of the mixture. Heat. The time until this temperature rise is preferably less than 1 hour. Furthermore, it is necessary to quickly raise the temperature, and the rate of temperature rise is preferably 0.25 ° C./min or more. The upper limit of the rate of temperature rise is not particularly clear, but if the temperature is increased instantaneously, salting out proceeds rapidly, and particle size control becomes difficult, so 5 ° C./min or less is preferable. In this way, a dispersion liquid of associated particles (core particles) formed by subjecting arbitrary particles such as resin particles and a colorant to salting out / fusion is obtained through the aggregation / fusion process.

(4) First aging step This step is a step of adjusting the shape of the particles by aging the associated particles by supplying thermal energy to the dispersion liquid of the associated particles formed in the above-described aggregation / fusion step. It is.

  In the present invention, the shape of the core particles can be controlled by controlling the heating temperature and time in the first aging process in addition to the control of the heating temperature in the aggregation / fusion process. By performing such aging, the particle size of the core particles can be kept constant and the particle size distribution can be controlled within a narrow range. In addition, the surface of the formed core particles can be smoothed, and at the same time, the shape can be controlled to be uniform. Specifically, by lowering the heating temperature in the agglomeration / fusion process and suppressing the progress of fusion between the resin particles, the uniformization of the particle size is promoted, and the heating temperature is lowered in the first aging process. And it controls so that time may be lengthened and the shape of a core particle may be equalized.

(5) Shelling step The shelling step is performed by adding the resin particle dispersion for the shell to the core particle dispersion, and aggregating and fusing the shell resin particles on the core particle surface. Is a step of forming colored particles having a core-shell structure in which a shell is coated with a shell.

  Specifically, the temperature of the core particle dispersion is maintained at the same temperature as the above-described aggregation / fusion step and the first aging step, and the dispersion of the resin particles for shells is added in this state. Then, colored particles are formed by slowly covering the core particle surfaces with the resin particles for shells over several hours while continuing the heating and stirring. The heating and stirring time is preferably 1 hour to 7 hours, particularly preferably 3 hours to 5 hours.

  By performing such an operation, a shell having a thickness of 100 to 300 nm is formed on the surface of the core particle in the shelling step. And particle growth is stopped by adding stop agents, such as sodium chloride, in the stage in which colored particles became a predetermined particle size.

(6) Second ripening step In this step, after the colored particles have reached a predetermined particle size by shelling, a stopper is added to stop particle growth, and then the dispersion of the colored agent particles is heated and stirred. Is a process that continues for several hours. In the second aging step, by continuing the heating and stirring, the fusion of the resin particles for the shell adhered to the surface of the core particles is advanced, and the adhesion of the resin particles for the shell to the surface of the core particles is strengthened. . At the same time, the colored particles after the shell formation are rounded and have a uniform shape.

  In the present invention, it is possible to control the shape of the colored particles in the true sphere direction by setting the time of the second aging step longer or by setting the aging temperature higher.

(7) Washing process In this process, the colored particle dispersion liquid having the core / shell structure that has undergone the second aging process is cooled, and the colored particles are subjected to solid-liquid separation treatment from the cooled colored particle dispersion liquid, thereby being separated. This is a step of washing the colored particles in order to remove the surfactant and the like from the particles.

  First, the core-shell structured colored particle dispersion is rapidly cooled. The cooling process condition is cooling at a cooling rate of 1 to 20 ° C./min. The specific cooling treatment method is not particularly limited, for example, a method of cooling the colorant dispersion by supplying a refrigerant from the outside of the reaction vessel, a method of cooling by directly introducing cold water into the reaction system, etc. Is mentioned.

  Next, the colored particles are subjected to solid-liquid separation from the dispersion of colored particles cooled to a predetermined temperature by the cooling treatment (solid-liquid separation treatment). The colored particles in the wet state separated by the solid-liquid separation process take the form of an aggregate aggregated in a cake form called a toner cake. Further, a cleaning process is performed to remove deposits such as surfactants and salting-out agents from the surface of the colored particles taking the form of a toner cake. Examples of the solid-liquid separation treatment include a centrifugal separation method, a vacuum filtration method using Nutsche and the like, a filtration method using a filter press and the like.

  In order to reliably remove the deposits from the surface of the colored particles, it is also preferable to repeat the solid-liquid separation process and the cleaning process.

(8) Drying step This step is a step of obtaining dried colored particles by drying the toner cake prepared by the solid-liquid separation process after the final washing process. Examples of the drying apparatus that can be used in this step include a spray dryer, a vacuum freeze dryer, a vacuum dryer, and the like, and a stationary shelf dryer, a mobile shelf dryer, a fluidized bed dryer, a rotary dryer, and the like. It is preferable to use a dryer, a stirring dryer, or the like. The water content of the colored particles after the drying treatment is preferably 5% by mass or less, and more preferably 2% by mass or less. Incidentally, the dried colored particles may aggregate due to weak interparticle attractive force. In such a case, the aggregate may be crushed. Examples of the crushing treatment apparatus include mechanical crushing apparatuses such as a jet mill, a Henschel mixer, a coffee mill, and a food processor.

  Through the above steps, colored particles constituting the toner according to the present invention can be produced. In addition, when it is not necessary to add an external additive to be described later, the colored particles after the drying process become the toner.

(9) External Addition Treatment Step This step is a step of adding and mixing an external additive to the colored particles that have been dried, if necessary. Examples of apparatuses that can be used for the external addition treatment include mechanical mixing apparatuses such as a Henschel mixer and a coffee mill.

<Materials that make up toner>
Next, materials constituting the toner, such as resins, colorants, waxes, and external additives that can be used in the toner used in the present invention, will be described with specific examples.

(resin)
First, resins that can be used in the toner used in the present invention will be described. The resin that can be used for the toner is not particularly limited as long as the glass transition point of the toner can be within a range of 20 to 45 ° C.

The resin that can be used in the toner used in the present invention is produced by polymerizing a polymerizable monomer typified by a vinyl monomer as shown in the following (1) to (10), and has a glass transition. It is a polymer having a point in the range of 20 to 45 ° C. That is, examples of the resin that can be used for the toner used in the present invention include those obtained by polymerizing the following vinyl monomers alone or in combination.
(1) Styrene or styrene derivatives Styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-chloro styrene, 3,4-dichloro styrene, p-phenyl styrene, p-ethyl styrene 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, etc. (2) Methacrylic acid ester derivatives Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate , Lauryl methacrylate , Phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, etc. (3) Acrylic acid ester derivatives Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate N-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, and the like.
(4) Olefins Ethylene, propylene, isobutylene, etc. (5) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate, etc. (6) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, etc. (7) Vinyl ketones Vinyl methyl ketone, Vinyl ethyl ketone, vinyl hexyl ketone, etc. (8) N-vinyl compounds N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, etc. (9) Vinyl compounds Vinyl naphthalene, vinyl pyridine, etc. (10) Acrylic acid or methacrylic acid Derivatives Acrylonitrile, methacrylonitrile, acrylamide, etc.

  Moreover, it is also possible to use combining the polymerizable monomer which has an ionic dissociation group as a polymerizable monomer which comprises resin. Examples of the ionic dissociation group include substituents such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and the polymerizable monomer having an ionic dissociation group has these substituents.

  Specific examples of the polymerizable monomer having an ionic dissociation group are given below.

  Acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfone Acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxypropyl methacrylate and the like.

  Furthermore, it is also possible to use a polyfunctional vinyl as a polymerizable monomer constituting the resin to obtain a resin having a crosslinked structure. Specific examples of the polyfunctional vinyls are listed below.

  Divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, and the like.

(Coloring agent)
Next, examples of the colorant that can be used in the toner used in the present invention include the following known colorants.

  Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, and magnetic powder such as magnetite and ferrite.

  Examples of the colorant for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48; 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the colorant for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Further, as a colorant for green or cyan, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15; 2, C.I. I. Pigment blue 15; 3, C.I. I. Pigment blue 15; 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66, C.I. I. And CI Pigment Green 7.

  These colorants can be used alone or in combination of two or more as required. The addition amount of the colorant is set in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

(wax)
Next, the wax that can be used for the toner used in the present invention will be described. Examples of the wax that can be used in the toner used in the present invention include conventionally known waxes. Specific examples include the following.
(1) Long-chain hydrocarbon wax Polyolefin wax such as polyethylene wax and polypropylene wax, paraffin wax, sazole wax, etc. (2) Ester wax Trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrasteare Rate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitic acid, distearyl maleate, etc. (3) Amide wax Ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. (4) Dialkyl ketone waxes, distearyl ketone, etc. (5) Others Carnaubawack , Montan waxes, and the like.

  The melting point of the wax is usually 40 to 160 ° C, preferably 50 to 120 ° C, more preferably 60 to 90 ° C. By keeping the melting point of the wax within the above range, the heat-resistant storage stability of the toner is ensured, and at the same time, stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

(External additive)
The toner used in the present invention may be used by mixing so-called external additives with colored particles for the purpose of improving fluidity, chargeability and cleaning properties. These external additives are not particularly limited, and various inorganic fine particles, organic fine particles and lubricants can be used.

  A conventionally well-known thing can be used as an inorganic fine particle. Specifically, silica, titania, alumina, strontium titanate fine particles and the like can be preferably used. These inorganic fine particles may be hydrophobized if necessary. Specific silica fine particles include, for example, commercially available products R-805, R-976, R-974, R-972, R-812, R-809 manufactured by Nippon Aerosil Co., Ltd., HVK-2150, H- manufactured by Hoechst. 200, commercial products TS-720, TS-530, TS-610, H-5, MS-5 and the like manufactured by Cabot Corporation.

  As titania fine particles, for example, commercially available products T-805 and T-604 manufactured by Nippon Aerosil Co., Ltd., commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, JA- 1. Commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium Co., Ltd. Commercial products IT-S, IT-OA, IT-OB, IT- manufactured by Idemitsu Kosan Co., Ltd. OC etc. are mentioned.

  Examples of the alumina fine particles include commercial products RFY-C and C-604 manufactured by Nippon Aerosil Co., Ltd. and commercial products TTO-55 manufactured by Ishihara Sangyo Co., Ltd.

  As the organic fine particles, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. Specifically, homopolymers such as styrene and methyl methacrylate and copolymers thereof can be used.

  The addition amount of these external additives is preferably 0.1 to 10.0% by mass with respect to the whole toner. Examples of the method of adding the external additive include a method of adding using various known mixing devices such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer.

  The toner is mixed with a carrier and used as a two-component developer. As the carrier, a carrier produced by injecting a resin into the gap of the core material described later is used. The particle diameter of the carrier is preferably 20 to 100 μm, and more preferably 25 to 80 μm.

  The particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

[Toner glass transition point (Tg)]
The glass transition point (Tg) of the toner used in the present invention is 20 to 45 ° C. By setting Tg within the above range, there is no problem in heat-resistant storage stability and excellent low-temperature fixability.

  In order to make Tg into the range of 20-45 degreeC, the kind and quantity of the polymerizable monomer which form copolymer resin are adjusted. Propyl acrylate, propyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and the like are polymerizable monomers that lower Tg, and styrene, methyl methacrylate, methacrylic acid, and the like are polymerizable monomers that increase Tg.

  Tg can be measured by a differential scanning calorimetry method. Specifically, the DSC-7 differential scanning calorimeter (manufactured by PerkinElmer) and a TAC7 / DX thermal analyzer controller (manufactured by PerkinElmer) are used. be able to.

  As a measurement procedure, 4.5 to 5.0 mg of toner is precisely weighed to 0.01 mg, sealed in an aluminum pan (KITNO.0219-0041), and set in a DSC-7 sample holder. The reference used an empty aluminum pan. As measurement conditions, the measurement temperature is 0 to 200 ° C., the temperature increase rate is 10 ° C./min, the temperature decrease rate is 10 ° C./min, and the heat-cool-heat control is performed, and the analysis is performed based on the data in the 2nd Heat. Do.

  Tg draws an extension line of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum inclination between the rising portion of the first endothermic peak and the peak apex, and the intersection is defined as Tg.

[Molecular weight of resin]
The resin constituting the toner preferably has a weight average molecular weight (Mw) of 10,000 to 100,000, a number average molecular weight (Mn) of 5,000 to 50,000, and Mw / Mn of 2 to 4.

  By adjusting the kind and amount of the polymerizable monomer, and adjusting the molecular weight of the resin obtained by polymerizing the polymerizable monomer within these ranges, a toner having Tg as defined in the present invention is obtained. be able to. In addition, when a material having a wide molecular weight distribution is used, it becomes difficult to melt partially, which may cause poor fixing.

  The molecular weight of the resin can be measured by GPC by the following method.

  As a method for measuring the molecular weight of a resin by GPC (gel permeation chromatography), a sample is dissolved in tetrahydrofuran so as to be 1 mg / ml. As dissolution conditions, it is carried out at room temperature for 5 minutes using an ultrasonic disperser. Next, after processing with a membrane filter having a pore size of 0.2 μm, 10 μl of sample solution is injected into GPC.

  The measurement conditions for GPC are shown below.

Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKguardcolum + TSKgelSuperHZM-M 3 series (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Solvent: Tetrahydrofuran Flow rate: 0.2 ml / min Detector: Refractive index detector (RI detector)
In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrenes for calibration curve measurement were used.

(Toner particle size)
The toner used in the present invention preferably has a particle diameter of 3 to 8 μm in terms of a median diameter (D ₅₀ ) on a volume basis. When toner having this particle size range is used, a high-quality image corresponding to high image quality can be reproduced.

The median diameter (D ₅₀ ) on the volume basis of the toner is obtained by measuring with the following measuring method.

  Specifically, measurement and calculation are performed using a device in which a computer system (manufactured by Coulter) equipped with data processing software “Software V3.51” is connected to Coulter Multisizer 3 (manufactured by Coulter).

  As a measurement procedure, 0.02 g of toner is blended with 20 ml of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner). After that, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is injected into a beaker containing ISOTON II (manufactured by Coulter) in a sample stand with a pipette until the display density of the measuring instrument becomes 5% to 10%. By setting this concentration range, a reproducible measurement value can be obtained. In the measuring machine, the measurement particle count is 25000, the aperture diameter is 50 μm, and the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256 parts. The particle diameter of 50% from the larger volume integrated fraction is defined as the volume-based median diameter.

<Developer>
Next, the developer of the present invention will be described.

  The developer of the present invention is prepared by mixing a toner having a glass transition point of 20 to 45 ° C. and a carrier prepared by injecting a resin into a void of a core material having a void of 10 to 60%. is there.

  The mixing ratio of the toner and the carrier is preferably 2 to 10 parts by mass of the toner with respect to 100 parts by mass of the carrier.

  The toner and carrier may be mixed as long as they can be mixed without applying stress to the toner and carrier, and can be performed using a known mixer. Specific examples include a V-type mixer, a Nauta mixer, and a Henschel mixer.

<Image formation>
Next, an image forming method in which the developer of the present invention can be used will be described. The developer of the present invention is preferably used in, for example, a high-speed full-color image forming apparatus having a printing speed of 300 mm / sec or higher (65 sheets / min output performance in terms of A4 paper) level or higher. Specifically, a printer or the like that can create a large amount of documents on demand in a short time can be mentioned. The present invention can also be applied to an image forming method in which the temperature of the fixing roller is set to 150 ° C. or lower, preferably 125 ° C. or lower.

  FIG. 1 is a schematic view showing an example of an image forming apparatus in which the developer of the present invention is preferably used.

  In FIG. 1, 1Y, 1M, 1C and 1K are photosensitive members, 4Y, 4M, 4C and 4K are developing means, 5Y, 5M, 5C and 5K are primary transfer rollers as primary transfer means, and 5A is a secondary transfer means. Secondary transfer rollers 6Y, 6M, 6C and 6K are cleaning means, 7 is an intermediate transfer body unit, 24 is a heat roll type fixing device, and 70 is an intermediate transfer body.

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer body unit 7 as a transfer unit, and a recording member P. An endless belt-shaped sheet feeding / conveying means 21 and a heat roll type fixing device 24 as a fixing means. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y as a first photoconductor, and a periphery of the photoconductor 1Y. A charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roller 5Y as a primary transfer unit, and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image as another different color toner image is disposed around a drum-shaped photoconductor 1M as a first photoconductor, and the photoconductor 1M. A charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, and a cleaning unit 6M. In addition, an image forming unit 10C that forms a cyan image as one of other different color toner images is arranged around a drum-shaped photoconductor 1C as a first photoconductor, and around the photoconductor 1C. The charging unit 2C, the exposure unit 3C, the developing unit 4C, the primary transfer roller 5C as the primary transfer unit, and the cleaning unit 6C are provided. Further, an image forming unit 10K that forms a black image as one of other different color toner images is disposed around a drum-shaped photosensitive member 1K as a first photosensitive member, and the photosensitive member 1K. It has a charging unit 2K, an exposure unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit 6K.

  The endless belt-shaped intermediate transfer body unit 7 has an endless belt-shaped intermediate transfer body 70 as an intermediate transfer endless belt-shaped second image carrier that is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred and synthesized on the rotating endless belt-shaped intermediate transfer body 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K. A color image is formed. A recording member P such as a sheet as a transfer material accommodated in the sheet feeding cassette 20 is fed by the sheet feeding / conveying means 21, passes through a plurality of intermediate rollers 22 A, 22 B, 22 C, 22 D, and a registration roller 23, and is secondary. A color image is transferred onto the recording member P at a time by being conveyed to a secondary transfer roller 5 </ b> A as a transfer unit. The recording member P to which the color image has been transferred is fixed by a heat roller type fixing device 24, is sandwiched between paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording member P by the secondary transfer roller 5A, the residual toner is removed from the endless belt-shaped intermediate transfer body 70 from which the recording member P is separated by the curvature by the cleaning means 6A.

  During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rollers 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5A comes into pressure contact with the endless belt-shaped intermediate transfer body 70 only when the recording member P passes through the secondary transfer roller 5A and the secondary transfer is performed.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10K, and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, and 76, primary transfer rollers 5Y, 5M, 5C, and 5K, and a cleaning unit 6A. It consists of.

  The image forming units 10Y, 10M, 10C, and 10K and the endless belt-shaped intermediate transfer body unit 7 are integrally pulled out from the main body A by the drawer operation of the housing 8.

  In this way, toner images are formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer body 70, and are collectively applied to the recording member P. The image is transferred, and fixed by pressing and heating with a heat roll type fixing device 24 and fixed. The photoreceptors 1Y, 1M, 1C, and 1K after transferring the toner image to the recording member P clean the toner remaining on the photoreceptor at the time of transfer by the cleaning device 6A, and supply and supply the fatty acid metal salt to the surface of the photoreceptor. After the formed fatty acid metal salt is spread to form a film of the fatty acid metal salt on the surface of the photoreceptor, the charging, exposure and development cycle described above is entered, and the next image formation is performed.

  In the present invention, as a fixing device for fixing a toner image to a recording member, a device equipped with a heating roller and a heating belt is preferably used.

  The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

<Creation of carrier>
A carrier was produced as follows.

<Manufacture of core material>
(Preparation of core material 3)
MnO: 35 mol%, MgO: 14.5 mol%, Fe2O3: 50 mol% and SrO: 0.5 mol% Weighed the raw materials, mixed with water, and then pulverized with a wet media mill for 5 hours Obtained.

  The obtained slurry was dried with a spray dryer to obtain true spherical particles.

  In order to adjust the porosity and the continuous porosity, manganese carbonate was used as the MnO raw material, and magnesium hydroxide was used as the MgO raw material. After adjusting the particle size, the particles were heated at 950 ° C. for 2 hours to be pre-baked. Next, in order to obtain an appropriate fluidity while increasing the porosity, after pulverizing with a wet ball mill for 1 hour using a stainless steel bead having a diameter of 0.3 cm, further pulverizing with a stainless steel bead having a diameter of 0.15 cm for 4 hours did. An appropriate amount of a dispersant is added to the slurry, and 1% by mass of PVA as a binder is added as a binder for the purpose of ensuring the strength of the granulated particles and adjusting the porosity and continuous porosity. Granulation and drying were performed with a spray dryer, and the main firing was performed in an electric furnace at a temperature of 1100 ° C. and an oxygen concentration of 0% by volume for 3.5 hours.

  Thereafter, the mixture was crushed, further classified to adjust the particle size, and then the low-magnetic force product was separated by magnetic separation, thereby obtaining a core material. The porosity of the obtained core material 3 was 60%. The porosity was measured by the above method.

(Preparation of core material 1)
Instead of manganese carbonate used in the preparation of the core material 3, trimanganese tetroxide is used, the amount of binder added is 0.8% by mass, and instead of stainless steel beads having a diameter of 0.15 cm, 0.5 mm zirconia is added. “Core 1” was prepared in the same manner as in preparation of the core 3 except that the beads were used and were held in an electric furnace at a temperature of 1200 ° C. and an oxygen concentration of 0.5 vol% for 5 hours and subjected to main firing. Produced. The porosity of the obtained core material 1 was 20%.

(Preparation of core material 2)
Manganese dioxide is used in place of the manganese carbonate used in the preparation of the core material 3, the amount of the binder to be added is 0.5% by mass, and the temperature is 1200 ° C. and the oxygen concentration is 1.5% by volume in an electric furnace for 6 hours. A “core material 2” was produced in the same manner as in the production of the core material 3 except that it was held and subjected to main firing. The porosity of the obtained core material 2 was 10%.

(Preparation of core material 4)
The core material except that the temporary firing temperature for preparation of the core material 3 was changed from 950 ° C. to 1100 ° C., the subsequent pulverization time was 12 hours, the main firing was performed at 1300 ° C. for 2 hours, and the oxygen concentration was 2.5%. In the same manner as in No. 3, “Core 4” was produced. The porosity of the obtained core material 4 was 7%.

(Preparation of core material 5)
The temperature condition of the electric furnace for producing the core material 1 was changed from 1100 ° C. to 1150 ° C., kept at an oxygen concentration of 0% by volume for 3.5 hours, and subjected to the main firing in the same manner as the production of the core material 1 “Core 5” was produced. The porosity of the obtained core material 5 was 65%.

(Preparation of core material 6)
Instead of manganese carbonate used in the preparation of the core material 3, trimanganese tetraoxide was used, the amount of binder added was 0.8% by mass, and instead of 0.15 cm stainless beads, 0.5 mm zirconia beads were used. A “core material 6” was produced in the same manner as in the production of the core material 3 except that it was held in an electric furnace at a temperature of 1150 ° C. and held at an oxygen concentration of 0.5 vol% for 4 hours and subjected to main firing. . The porosity of the obtained core material 6 was 40%.

<Preparation of injection resin solution>
The injection resin solution was prepared as follows.

(Preparation of injection resin solution 1)
In 1000 parts by mass of toluene, 5.5 parts by mass of a thermoplastic acrylic resin (BR-52, manufactured by Mitsubishi Rayon Co., Ltd.) was dissolved to prepare “injected resin solution 1”.

(Preparation of injection resin solution 2)
11000 parts by mass of a thermoplastic acrylic resin (BR-52, manufactured by Mitsubishi Rayon Co., Ltd.) was dissolved in 1000 parts by mass of toluene to prepare “injected resin solution 2”.

(Preparation of injection resin solution 3)
In 1000 parts by mass of toluene, 2.75 parts by mass of a thermoplastic acrylic resin (BR-52, manufactured by Mitsubishi Rayon Co., Ltd.) was dissolved to prepare “injected resin solution 3”.

(Preparation of injection resin solution 4)
To 1000 parts by mass of toluene, 20 parts by mass of a solidification conversion type silicone resin (SR-2411, manufactured by Toray Dow Corning Co., Ltd.) and 2 parts by mass of γ-aminopropyltriethoxysilane were dissolved. Solution 4 "was prepared.

<Creation of carrier>
Resin was inject | poured into the core material produced above as follows, and the carrier was produced.

(Preparation of carrier 1)
100 parts by weight of “Core 1” was placed in a uniaxial indirect heating type dryer, and the entire amount of “Injected Resin Solution 1” was dropped while stirring at 75 ° C. After confirming that toluene was sufficiently volatilized, the temperature was raised to 150 ° C. while continuing stirring, and was maintained for 2 hours. Thereafter, the particles were taken out from the dryer, and the aggregated particles were crushed to adjust the particle size. Thereafter, low magnetic products were separated by magnetic separation, and “Carrier 1” was produced.

(Preparation of carrier 2)
“Carrier 2” was produced in the same manner as Carrier 1, except that “Core 1” used in the production of Carrier 1 was changed to “Core 2”.

(Preparation of carrier 3)
A “carrier 2” was produced in the same manner as the carrier 1 except that the “core material 1” used in the production of the carrier 1 was changed to the “core material 3”.

(Preparation of carrier 4)
100 parts by mass of “Core 6” was placed in a uniaxial indirect heating type dryer, and the entire amount of “Injected Resin Solution 4” was added dropwise while stirring at 75 ° C. After confirming that toluene was sufficiently volatilized, the temperature was raised to 200 ° C. while continuing stirring, and was maintained for 2 hours. Thereafter, the particles were taken out from the dryer, and the aggregated particles were crushed to adjust the particle size. Thereafter, low-magnetic force products were separated by magnetic separation, and “Carrier 4” was produced.

(Preparation of carrier 5)
“Carrier 5” was prepared in the same manner except that “injection resin solution 4” used in preparation of carrier 4 was changed to “injection resin solution 2”.

(Preparation of carrier 6)
“Carrier 6” was prepared in the same manner except that “injection resin solution 4” used in preparation of carrier 4 was changed to “injection resin solution 3”.

(Preparation of carrier 7)
Using a spray coater, a solution for a resin coating layer in which 1.0 part by mass of a thermoplastic acrylic resin (BR-52, manufactured by Mitsubishi Rayon Co., Ltd.) is dissolved in 100 parts by mass of toluene on carrier 6 (100 parts by mass). “Carrier 7” was prepared by spray coating.

(Preparation of carrier 8)
A “carrier 8” was produced in the same manner as the carrier 1 except that the “core material 1” used in the production of the carrier 1 was changed to the “core material 4”.

(Preparation of carrier 9)
A “carrier 9” was produced in the same manner as the carrier 1 except that the “core material 1” used in the production of the carrier 1 was changed to the “core material 5”.

(Carrier 10)
The “core material 6” used in the production of the carrier 6 as it is (without resin injection) is referred to as “carrier 10”.

(Carrier 11)
The particle size of 100 parts by mass of alkoxy-modified silicone (SR-2402, manufactured by Toray Dow Corning Co., Ltd.), 15 parts by mass of γ-aminopropyltriethoxysilane and 4 parts by mass of dibutyltin laurate was adjusted to a volume average particle size of 0.75 μm. A paste was prepared by kneading with a kneader together with 300 parts by mass of magnetite fine particles.

  2 parts by mass of calcium phosphate was dispersed in 20 parts by mass of ion-exchanged water, 1 part by mass of the paste was added, and the mixture was stirred for 2 minutes with a homogenizer. The suspension after stirring was heated at 80 ° C. for 2 hours and then cooled to 25 ° C. Then, hydrochloric acid was added to dissolve calcium phosphate and filtered to obtain a residue. The obtained filtrate was dried, cured at 80 ° C. for 2 hours, and then crushed to produce a magnetic powder-dispersed carrier “Carrier 11”. The porosity of the obtained carrier 11 was 1.2%.

<Production of toner>
A toner was prepared by the following method.

<Preparation of resin particles for core>
(Preparation of core resin particle 1)
(1) First-stage polymerization A reaction mixture equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction apparatus was charged and mixed to prepare a mixed solution.

Styrene 110.9 parts by mass n-butyl acrylate 52.8 parts by mass Methacrylic acid 12.3 parts by mass
After adding 93.8 parts by mass of paraffin wax “HNP-57 (Nippon Seiki Co., Ltd.)”, it was heated to 80 ° C. and dissolved to prepare a polymerizable monomer solution.

  On the other hand, a surfactant solution was prepared by dissolving 2.9 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate in 1340 parts by mass of ion-exchanged water. After heating the surfactant solution to 80 ° C., the polymerizable monomer solution is added, and the polymerizable monomer is added by a mechanical disperser “CLEAMIX (manufactured by M Technique)” having a circulation path. The solution was mixed and dispersed for 2 hours. Then, a dispersion of emulsified particles (oil droplets) having an average particle size of 245 nm was prepared.

  Next, after adding 1460 parts by mass of ion-exchanged water, an initiator solution in which 6 parts by mass of a polymerization initiator (potassium persulfate) is dissolved in 142 parts by mass of ion-exchanged water, 1.8 parts by mass of n-octyl mercaptan, Was added to bring the temperature to 80 ° C. This system was heated and stirred at 80 ° C. for 3 hours to perform polymerization (first stage polymerization) to produce resin particles. This is designated as “resin particle C1”.

(2) Second stage polymerization (formation of outer layer)
An initiator solution prepared by dissolving 5.1 parts by mass of potassium persulfate in 197 parts by mass of ion-exchanged water is added to the “resin particle C1”, and the following polymerizable monomer is mixed under a temperature condition of 80 ° C. The monomer mixture obtained was added dropwise over 1 hour. The monomer mixture is
Styrene 282.2 parts by mass n-butyl acrylate 134.4 parts by mass Methacrylic acid 31.4 parts by mass n-octyl mercaptan 4.93 parts by mass (Formation of outer layer) was performed. Then, it cooled to 28 degreeC and obtained "resin particle 1 for cores".

  The formed “core resin particle 1” had a weight average molecular weight of 21,300, a mass average particle diameter of 180 nm, and a glass transition point of 39 ° C. The weight average molecular weight and mass average particle diameter were determined by the above methods. The glass transition point was measured by the same method as the measurement of Tg of the toner obtained by filtering and drying the core resin particles 1.

(Preparation of core resin particles 2)
In the preparation of “core resin particles 1”, the amount of the polymerizable monomer charged in the first stage polymerization is
Styrene 90.8 parts by mass n-butyl acrylate 72.7 parts by mass Methacrylic acid 12.3 parts by mass, the addition amount of the polymerizable monomer in the second stage polymerization,
Styrene 274.1 parts by mass n-butyl acrylate 168.6 parts by mass A “core resin particle 2” was prepared in the same manner except that it was changed to 5.2 parts by mass of methacrylic acid. The “core resin particle 2” had a weight average molecular weight of 22,000, a mass average particle diameter of 180 nm, and a glass transition point of 20.1 ° C.

(Preparation of core resin particle 3)
In the preparation of “core resin particle 1”, the addition amount of the polymerizable monomer in the first stage polymerization is
Styrene 115.3 parts by weight n-butyl acrylate 48.4 parts by weight Methacrylic acid 12.3 parts by weight, the polymerizable monomer mixture in the second stage polymerization,
Styrene 293.4 parts by mass n-butyl acrylate 123.2 parts by mass Methacrylic acid 3 Core parts were prepared in the same manner except for changing to 31.4 parts by mass. The “core resin particle 3” had a weight average molecular weight of 22,500, a mass average particle diameter of 180 nm, and a glass transition point of 44 ° C.

(Preparation of core resin particles 4)
In the preparation of “core resin particles 1”, the amount of the polymerizable monomer charged in the first stage polymerization is
Styrene 103.5 parts by mass n-butyl acrylate 70.4 parts by mass Methacrylic acid 2.1 parts by mass, the polymerizable monomer mixture in the second stage polymerization,
Styrene 263.4 parts by mass n-butyl acrylate 179.2 parts by mass A “core resin particle 4” was prepared in the same manner except that the amount was changed to 5.4 parts by mass of methacrylic acid. The “core resin particles 4” had a weight average molecular weight of 22,500, a mass average particle diameter of 180 nm, and a glass transition point of 18 ° C.

(Preparation of core resin particles 5)
In the preparation of “core resin particles 1”, the amount of the polymerizable monomer charged in the first stage polymerization is
Styrene 119.7 parts by mass n-butyl acrylate 44.0 parts by mass Methacrylic acid 12.3 parts by mass, the polymerizable monomer mixture in the second stage polymerization,
Styrene 304.6 parts by mass n-Butyl acrylate 112.0 parts by mass Methacrylic acid 3 Core parts were prepared in the same manner except for changing to 31.4 parts by mass. The “core resin particles 5” had a weight average molecular weight of 22,500, a mass average particle diameter of 180 nm, and a glass transition point of 49 ° C.

<Preparation of resin particles for shell>
A surfactant solution in which 2.0 parts by mass of polyoxyethylene (2) sodium dodecyl ether sulfate was dissolved in 3000 parts by mass of ion-exchanged water was charged into a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device. The internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

A polymerizable monomer obtained by adding an initiator solution in which 10 parts by mass of a polymerization initiator (potassium persulfate: KPS) is dissolved in 200 parts by mass of ion-exchanged water to this surfactant solution and mixing the following compounds. The mixed solution was added dropwise over 3 hours. The polymerizable monomer mixed solution is
Styrene 528 parts by mass n-butyl acrylate 176 parts by mass Methacrylic acid 120 parts by mass n-octyl mercaptan 22 parts by mass After dropping the polymerizable monomer mixed solution, the system was heated and stirred at 80 ° C. for 1 hour to carry out polymerization to prepare resin particles. This is referred to as “shell resin particles”.

  The “shell resin particles” had a weight average molecular weight of 12,000, a mass average particle size of 120 nm, and a glass transition point of 53 ° C. The weight average molecular weight and mass average particle diameter were determined by the above methods. The glass transition point was measured by the same method as the Tg measurement of the toner obtained by filtering and drying the shell resin particles.

<Preparation of colorant dispersion>
(Preparation of colorant dispersion Bk1)
While stirring 900 parts by weight of an aqueous solution of 10% by weight of sodium dodecyl sulfate, 100 parts by weight of a colorant “Regal 330R” (Cabot) is gradually added, and then a stirring device “Clearmix” (made by M Technique) ) To prepare a dispersion of colorant particles. This is designated as “colorant dispersion Bk1”. The average dispersion diameter of the colorant particles in the colorant dispersion was measured using a dynamic light scattering particle size analyzer “Microtrack UPA150” (manufactured by Nikkiso Co., Ltd.), and found to be 150 nm.

(Preparation of colorant dispersion C1)
In the production of the colorant dispersion Bk1, the colorant particles were similarly prepared except that 420 parts by weight of the colorant “Regal 330R” (Cabot Corporation) was changed to 210 parts by weight of “CI Pigment Blue 15: 3”. A dispersion was prepared. This is designated as “colorant dispersion C1”. The average dispersion diameter of the colorant particles in the colorant dispersion was measured using a dynamic light scattering particle size analyzer “Microtrack UPA150” (manufactured by Nikkiso Co., Ltd.), and found to be 150 nm.

(Preparation of colorant dispersion M1)
In the preparation of the colorant dispersion Bk1, the colorant particles were similarly prepared except that 420 parts by mass of the colorant “Regal 330R” (Cabot Corporation) was changed to 357 parts by mass of “CI Pigment Red 122”. A dispersion was prepared. This is designated as “colorant dispersion M1”. The average dispersion diameter of the colorant particles in the colorant dispersion was measured using a dynamic light scattering particle size analyzer “Microtrack UPA150” (manufactured by Nikkiso Co., Ltd.), and found to be 150 nm.

(Preparation of colorant dispersion Y1)
In the preparation of the colorant dispersion Bk1, the dispersion of the colorant particles was similarly performed except that 420 parts by weight of the colorant “Regal 330R” (Cabot Corporation) was changed to 378 parts by weight of “CI Pigment Yellow 74”. A liquid was prepared. This is designated as “colorant dispersion Y1”. The average dispersion diameter of the colorant particles in the colorant dispersion was measured using a dynamic light scattering particle size analyzer “Microtrack UPA150” (manufactured by Nikkiso Co., Ltd.), and found to be 150 nm.

<Preparation of colored particles Bk1>
(Salting out / fusion (association / fusion) process) (core formation)
420.7 parts by mass (solid content conversion) of “core resin particles 1”, 900 parts by mass of ion-exchanged water and 200 parts by mass of “colorant particle dispersion Bk1”, a temperature sensor, a cooling pipe, a nitrogen introducing device, The mixture was stirred in a reaction vessel equipped with a stirrer. After adjusting the temperature in the container to 30 ° C., 5 mol / L sodium hydroxide aqueous solution was added to this solution to adjust the pH to 9.

Next, an aqueous solution obtained by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was raised and the system was heated to 65 ° C. over 60 minutes. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter), and when the median system (D ₅₀ ) on the volume basis of the particles became 5.5 μm, sodium chloride 40. An aqueous solution in which 2 parts by mass is dissolved in 1000 parts by mass of ion-exchanged water is added to stop the growth of the particle size, and further, the fusion is continued by heating and stirring at a liquid temperature of 70 ° C. for 1 hour as an aging treatment. Core part 1 "was formed.

  The circularity of the “core part 1” was measured by “FPIA2100” (manufactured by Systex) and found to be 0.930.

(Formation of shell layer (shelling operation))
Next, at 65 ° C., 50 parts by mass (in terms of solid content) of “resin particles for shell” is added, and an aqueous solution in which 2 parts by mass of magnesium chloride hexahydrate is dissolved in 1000 parts by mass of ion-exchanged water is added over 10 minutes. After the addition, the temperature was raised to 70 ° C. (shelling temperature), and stirring was continued for 1 hour to fuse the “resin particles for shell” onto the surface of “core part 1”. Thereafter, an aging treatment was carried out at 75 ° C. for 20 minutes to form a shell layer.

  Here, 40.2 parts by mass of sodium chloride was added and cooled to 30 ° C. under the condition of 8 ° C./min to obtain “an aqueous solution containing colored particles”.

(Washing and drying process)
The aqueous solution containing the colored particles was subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40” (manufactured by Matsumoto Kikai Co., Ltd.) to form a colored particle wet cake. The wet cake was washed with water using the basket-type centrifuge until the electric conductivity of the filtrate reached 5 μS / cm, and then transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). % Was dried to produce “colored particles Bk1”. The obtained colored particle Bk1 was a particle having a core-shell structure with a median diameter (D ₅₀ ) of 6.0 μm and a Tg of 39.5 ° C. on a volume basis. The Tg was measured by the method described above.

<Preparation of colored particles Bk2>
In the production of the colored particles Bk1, “colored particles Bk2” were produced in the same manner except that the core resin particles used in the core portion forming step were changed from the core resin particles 1 to the “core resin particles 2”. The volume-based median diameter (D ₅₀ ) of this particle was 6.0 μm, and Tg was 20.5 ° C.

<Preparation of colored particles Bk3>
In the production of the colored particles Bk1, “colored particles Bk3” were produced in the same manner except that the core resin particles used in the core forming step were changed from the core resin particles 1 to the “core resin particles 3”. The volume-based median diameter (D ₅₀ ) of this particle was 6.0 μm, and Tg was 44.5 ° C.

<Preparation of colored particles Bk4>
In the production of the colored particles Bk1, “colored particles Bk4” were produced in the same manner except that the core resin particles used in the core portion forming step were changed from the core resin particles 1 to the “core resin particles 4”. The volume-based median diameter (D ₅₀ ) of this particle was 6.3 μm, and Tg was 19.0 ° C.

<Preparation of colored particles Bk5>
In the production of the colored particles Bk1, “colored particles Bk5” were produced in the same manner except that the core resin particles used in the core portion forming step were changed from the core resin particles 1 to the “core resin particles 5”. The volume-based median diameter (D ₅₀ ) of this particle was 6.1 μm, and Tg was 49.5 ° C.

<Preparation of Toner Bk1>
Hydrophobic silica fine particles (number average primary particle size = 80 nm) are 3.5% by mass and hydrophobic titania fine particles (number average primary particle size = 10 nm) are 0% with respect to 100 parts by mass of the “colored particles Bk1” produced above. Then, 6% by mass was added and mixed using a “Henschel mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.) for 25 minutes at a peripheral speed of 35 m / sec to produce “Toner Bk1”. The glass transition point of the toner Bk1 was 39.5 ° C., which is the same as that of the colored particles 1.

<Preparation of Toner Bk2>
“Toner Bk2” was prepared in the same manner except that the colored particles Bk1 used in the preparation of the toner Bk1 were changed to “colored particles Bk2”. The glass transition point of the toner Bk2 was 20.5 ° C., the same as that of the colored particles 2.

<Preparation of Toner Bk3>
“Toner Bk3” was produced in the same manner except that the colored particles Bk1 used in the production of the toner Bk1 were changed to “colored particles Bk3”. The glass transition point of the toner Bk3 was 44.5 ° C., the same as that of the colored particles 3.

<Preparation of Toner Bk4>
“Toner Bk4” was prepared in the same manner except that the colored particles Bk1 used in the preparation of the toner Bk1 were changed to “colored particles Bk4”. The glass transition point of the toner Bk4 was 18.8 ° C., which is the same as that of the colored particles 4.

  “Toner Bk5” was prepared in the same manner except that the colored particle Bk1 used in the preparation of toner Bk1 was changed to “colored particle Bk5”. The glass transition point of the toner Bk5 was 49.5 ° C., the same as that of the colored particles 5.

<Preparation of Toner C1 to Toner C5>
“Toner C1 to Toner C5” was prepared in the same manner except that the colorant dispersion Bk1 used in the preparation of “Toner Bk1 to Toner Bk5” was changed to “Colorant Dispersion C1”.

<Preparation of Toner M1 to Toner M5>
“Toner M1 to Toner M5” was prepared in the same manner except that the colorant dispersion Bk1 used in the preparation of “Toner Bk1 to Toner Bk5” was changed to “Colorant Dispersion M1”.

<Preparation of Toner Y1 to Toner Y5>
“Toner Y1 to Toner Y5” was prepared in the same manner except that the colorant dispersion Bk1 used in the preparation of “Toner Bk1 to Toner Bk5” was changed to “Colorant Dispersion Y1”.

  The glass transition points of “toner C1 to toner C5”, “toner M1 to toner M5”, and “toner Y1 to toner Y5” were the same as the measurement results of “toner Bk1 to toner Bk5”.

<< Preparation of developer >>
Using each carrier and each toner prepared above, the blending ratio is 8 parts by mass of toner with respect to 100 parts by mass of carrier, and the toner and carrier are in a V blender in a normal temperature and normal humidity (20 ° C., 50% RH) environment. , Blended at a rotation speed of 20 rpm and a stirring time of 20 min, and then sieved with a 125 μm sieving mesh to obtain “Developer Bk1 to Developer Bk15”, “Developer C1 to Developer C15”, “Developer M1 to Developer”. Agent M15 "and" Developer Y1 to Developer Y15 "were prepared.

  Table 1 shows toner and carrier Nos. Used in the production of “Developer Bk1 to Developer Bk15”. Etc.

  Since the developer C, the developer M, and the developer Y other than the developer Bk are the same as the developer Bk, their description is omitted.

<Evaluation>
The developer prepared above was sequentially loaded into the following image evaluation apparatus, printed, and evaluated as follows.

  As an image evaluation apparatus, a digital color multifunction peripheral “bizhub PRO C6500” (manufactured by Konica Minolta Business Technologies) was used.

Printing was performed in 200,000 sheets in an environment of 20 ° C. and 50% RH by sequentially loading the toner and developer prepared above. The print uses an image with a pixel rate of 1% (an original image with a character image 7%, a human face photo, a solid white image, and a solid black image each in quarters) and A4 size fine paper ( 64 g / m ² ). In addition, the evaluation is ◎ and ○ are acceptable.

(Low temperature fixability)
The low temperature fixability is obtained by changing the surface temperature of the heating belt (measured at the center of the heating belt) of the image evaluation apparatus in increments of 5 ° C. within the range of 90 to 150 ° C., and at each surface temperature. An A4 image having a solid black belt image having a width of 5 mm in the vertical direction is conveyed and fixed by vertical feeding, and then an A4 image having a solid black belt image having a width of 5 mm and a halftone image having a width of 20 mm is perpendicular to the conveyance direction. The image was conveyed by lateral feed, and a determination was made based on a temperature region (non-offset region) where image contamination due to fixing offset does not occur.

Evaluation criteria A: The lower limit temperature of the non-offset region is 110 ° C. or lower, and the temperature region is 15 ° C. or higher. ○: The lower limit temperature of the non-offset region is 120 ° C. or lower, and the temperature region is lower than 15 ° C. The lower limit temperature of the region is 125 ° C or higher.

(Transfer rate)
At the initial stage and after the completion of printing 200,000 sheets, a solid image (20 mm × 50 mm) with a pixel density of 1.30 was formed, and the transfer rate was determined by the following formula and evaluated.

Transfer rate (%) = (mass of toner transferred onto transfer material / mass of toner developed on photoreceptor) × 100
Evaluation criteria ○: Transfer rate is 90% or more and good Δ: Transfer rate is 80% or more and practically no problem ×: Transfer rate is less than 80% and practically problematic

(Carrier adhesion)
After the printing of 200,000 sheets with the above evaluation machine, a solid image was printed and the carrier adhesion was evaluated.

  The number of adhering carrier particles found on the solid image was visually measured using a magnifying glass, and judged according to the following criteria.

A: No carrier adhesion on the solid image. O: No carrier problem on the solid image with 5 or less carriers. X: There are more than 5 carrier adhesions on the solid image, and there is a practical problem.

(Toner / carrier scattering)
Toner and carrier scattering was evaluated by visually observing the toner scattering around the developing machine and the contamination inside the machine due to carrier scattering after the completion of printing 200,000 sheets.

Evaluation criteria ◎: No contamination inside the machine due to toner / carrier scattering ○: Although there is slight contamination inside the machine due to toner / carrier scattering, there is no practical problem to the extent that a vacuum cleaner is not required for maintenance ×: Toner / carrier scattering The inside of the machine is very dirty, and the hands need to be cleaned with a dirt cleaner during maintenance, which is a practical problem.

  Table 2 shows the evaluation results.

  As shown in Table 2, “Developers 1 to 9” of Examples 1 to 9 corresponding to the present invention were good in all the evaluation results, whereas those of Comparative Examples 1 to 6 outside the present invention. It was confirmed that “Developers 10 to 15” had problems in any of these evaluation items, and the effects of the present invention were not exhibited.

1 is a schematic diagram illustrating an example of an image forming apparatus in which the developer of the present invention is preferably used.

Explanation of symbols

1Y, 1M, 1C, 1K Photoconductors 4Y, 4M, 4C, 4K Developing means 5Y, 5M, 5C, 5K Primary transfer roller as primary transfer means 5A Secondary transfer roller as secondary transfer means 6Y, 6M, 6C, 6K cleaning means 7 intermediate transfer member unit 24 heat roll type fixing device 70 intermediate transfer member

Claims (1)

In an electrophotographic developer comprising a toner and a carrier,
The toner has a glass transition point of 20 to 45 ° C.
The carrier is prepared by injecting a resin into the gap of the core material.
An electrophotographic developer using a core material having a porosity of 10 to 60% as the core material.

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