JP4479576B2 - Toner for developing electrostatic image, image forming apparatus, and image forming method - Google Patents

Description

  The present invention relates to an electrostatic image developing toner, an image forming apparatus and an image forming method using the electrostatic image developing toner.

  As an electrophotographic image forming technique, digital image formation is becoming mainstream in recent years. In digital image formation, fine dot images can be faithfully reproduced. For example, photographic images that have conventionally been difficult to reproduce can be reproduced with toner. As a means for outputting such a high-definition image on a recording medium, a reduction in the diameter of the toner has been studied, and a chemical toner represented by a polymerized toner that can be subjected to various controls in the manufacturing process is attracting attention. (For example, refer to Patent Document 1).

  On the other hand, recently, the influence of the image forming apparatus on the global environment has been studied, and a technique for reducing the environmental load by creating a print is being promoted. For example, it is considered to reduce the environmental load by reducing the amount of toner consumed, and a toner recycling technique that enables the toner remaining on the photoreceptor to be collected and reused for image formation is a representative example (for example, Patent Document 2).

  Further, a technique for reducing the power consumption of the fixing device has been studied, and an induction heating type fixing device using an induction coil has been adopted as one means for energy saving (see, for example, Patent Document 3). ).

  Furthermore, the toner is required to have a certain level of durability for smooth image formation. In other words, it is necessary that the toner inherently has no performance when it passes through a predetermined image forming process or is input and stored in the developing device. Therefore, the toner is required to have sufficient durability to withstand the usage environment. In particular, in order to improve performance such as charging properties, a substance called an external additive is applied to the toner surface, but the external additive is detached from the toner surface or embedded in the toner during image formation. This has a problem of affecting the image quality.

  To solve this problem, a technique for improving the durability of the toner by improving the external additive has been studied. For example, by using metal oxide particles having a specific structure as the external additive, the external additive can be removed from the toner surface. There is a toner technique that eliminates separation (see, for example, Patent Document 4).

  In addition, in the induction heating type fixing device, there has been a concern about the generation of vibration and noise generated from the induction heating coil, but these problems can be solved and stable by controlling energization to the induction heating coil. Fixing can be performed (see, for example, Patent Document 5).

As described above, in the electrophotographic image forming technology, it is required to achieve both of the two themes of high image quality and consideration for the global environment, and the development of an apparatus that simultaneously satisfies these two issues is advanced. Has been.
JP 2000-214629 A Japanese Patent Laid-Open No. 2001-060054 JP 2002-233416 A JP 2004-110006 A JP 2005-49815 A

  By the way, recently, it has become possible to create a high-definition image such as a photographic image with toner using the aforementioned small-diameter toner. As one example, there is a business of creating a small amount of printed matter on demand with an electrophotographic image forming apparatus instead of the conventional printing. Small print production in the printing industry is much more than the amount of documents created in the office, and there is a strong demand for toner recycling and reduction of device power consumption for reasons such as reducing production costs. It was done. However, a toner that can sufficiently cope with such on-demand print creation has not yet been found.

  For example, the toner disclosed in Patent Document 4 has improved durability compared to the conventional one. However, in a recycling type image forming apparatus, the external additive is detached from the toner surface due to the stress applied to the toner during collection. It was confirmed that it was easy. It was also confirmed again that fine line reproducibility was not sufficiently developed when induction heating fixing was used.

  An object of the present invention is to provide a stable toner that can withstand use in a toner recycling type image forming apparatus. In other words, in an image forming apparatus that employs toner recycling, even when printing on several hundred thousand sheets, it is possible to form a toner image with little fluctuation in image density, good transfer rate, and no fogging. An object of the present invention is to provide a new toner.

  It is another object of the present invention to provide a toner that can exhibit stable fine line reproducibility even when using an induction heating fixing type fixing device.

  The present invention is achieved by adopting the following configuration.

(Claim 1)
In the electrostatic image developing toner obtained by adding an external additive to the base particles obtained by agglomerating and fusing the resin particles,
As the external additive,
Inorganic particles having a number average primary particle size of 10 to 50 nm;
Inorganic particles having a number average primary particle size of 70 to 150 nm;
Metal oxide particles having a domain matrix structure containing two or more kinds of metal elements having a number average primary particle diameter of 70 to 150 nm;
A toner for developing electrostatic images, characterized in that

(Claim 2)
The toner for developing an electrostatic charge image according to claim 1, wherein the addition amount of the metal oxide particles is 0.1 to 3.0% by mass.

(Claim 3)
The toner for developing an electrostatic charge image according to claim 1, wherein an addition amount of the inorganic particles having a number average primary particle diameter of 10 to 50 nm is 1.0 to 2.5% by mass.

(Claim 4)
The electrostatic charge image according to any one of claims 1 to 3, wherein an addition amount of the inorganic particles having a number average primary particle diameter of 70 to 150 nm is 0.1 to 2.0 mass%. Developing toner.

(Claim 5)
Developing means for developing the electrostatic latent image formed on the photoreceptor with a developer having the electrostatic charge image developing toner according to any one of claims 1 to 4 to form a toner image;
Transfer means for transferring a toner image formed on the photoreceptor to a transfer material;
Separating means for separating the transfer material onto which the toner image has been transferred from the photoreceptor;
Fixing means for fixing the toner image transferred onto the transfer material by the transfer means;
An image forming apparatus comprising: a toner recycling unit that collects toner remaining on the photosensitive member after transfer and returns the toner to the developing unit.

(Claim 6)
The image forming apparatus according to claim 5, wherein the fixing unit includes an induction coil that generates a magnetic field by applying an alternating current, and a heating roller that is heated by the action of the magnetic field generated by the induction coil. apparatus.

(Claim 7)
A developing step of forming a toner image by developing the electrostatic latent image formed on the photoreceptor with a developer having the electrostatic charge image developing toner according to any one of claims 1 to 4.
A transfer step of transferring the toner image formed on the photoreceptor to a transfer material;
A separation step of separating the transfer material onto which the toner image has been transferred from the photoreceptor;
A fixing step of fixing the toner image transferred to the transfer material to the transfer material;
An image forming method comprising: a toner recycling step for collecting toner remaining on a photosensitive member after transfer and returning the toner to the developing step.

(Claim 8)
In the fixing step of fixing the toner image transferred to the transfer material to the transfer material, the heating roller is heated by the action of a magnetic field generated in the induction coil by application of an alternating current,
In the nip formed between the heated heating roller and the pressure roller,
The image forming method according to claim 7, wherein the transfer material is conveyed to melt and fix the toner image.

  In the present invention, stable image formation can be performed with an image forming apparatus having a toner recycling means by using the toner prepared by adding the above external additive to the surface of the toner base obtained through the process of aggregating and fusing the resin particles. The toner can be provided. That is, even when printing on several hundred thousand sheets, the image density variation is small, a good transfer rate is maintained, and stable image formation without fogging can be performed.

  For example, by providing an electrophotographic image forming apparatus to a printer who seeks a system for producing a small amount of printed matter on demand, it becomes possible to produce a necessary number of printed matter without causing a plate. This makes it possible to greatly improve work efficiency.

  Further, a toner image having good fine line reproducibility can be stably provided by an image forming apparatus equipped with an induction heating type fixing device. Accordingly, it is possible to reduce the power consumption required for creating the printed matter, thereby reducing the running cost, and to provide a printed matter with a beautifully finished toner image like a photograph.

  As described above, according to the present invention, an image forming apparatus that enables high-quality toner image formation, takes into consideration the global environment, and also takes into account the production efficiency required for print creation by a print creator. Made it possible to provide

  The present invention uses inorganic particles of 10 to 50 nm and particles of 70 to 150 nm as external additives to be added to the toner, and the composite metal oxide having inorganic particles and domain matrix structure for the external additives of 70 to 150 nm. It is a combination of particles. And it discovered that the above-mentioned effect was show | played by this invention by combining an external additive in this way.

  The reason why the toner according to the present invention is able to exhibit durability against the stress applied to the image forming apparatus of the toner recycling method is that the toner of a large external additive is probably due to the addition of 10 to 50 nm inorganic particles. It is presumed that the stabilization on the surface was promoted. In other words, the presence of small inorganic particles around the large external additive holds the large external additive firmly, and it is presumed that the toner surface does not roll off and desorb even under some stress. The Similarly, since the large external additive is firmly held on the toner surface due to the presence of the small external additive, it is assumed that the large external additive is not embedded in the toner even under stress.

  In addition, according to the toner of the present invention, it has become possible to reproduce fine line reproducibility satisfactorily with an induction heating type fixing device, but probably due to the addition of multiple types of external additives having different sizes. It is estimated that the toner is no longer affected by the induction heating coil. That is, in the conventional toner, a minute repulsive force is generated between the toners due to the influence of the magnetic field generated by the induction heating coil, and the effect of the toner image formed in the repelled state appears on a minute image such as a fine line. It is guessed. In the present invention, the density of the external additive on the toner surface is increased and the influence of the magnetic field is shielded. As a result, no repulsive force is generated between the toners, and good fine line reproducibility can be expressed. The

  Hereinafter, the present invention will be described in detail.

  First, the external additive will be described.

  In the present invention, inorganic particles having a number average primary particle size of 10 to 50 nm (hereinafter also referred to as small-sized inorganic fine particles) and particles having a number average primary particle size of 70 to 150 nm are used as external additives.

  Particles having a number average primary particle diameter of 70 to 150 nm are 70 to 150 nm inorganic particles (hereinafter also referred to as large-diameter inorganic fine particles) and 70 to 150 nm of metal oxide particles containing two or more kinds of metal elements (hereinafter referred to as “particles”). The metal oxide particles have a domain-matrix structure.

  A method for measuring the number average primary particle size of the inorganic particles and metal oxide particles will be described.

  First, a 30,000-magnification photograph of toner is taken with a scanning electron microscope (SEM), and this photograph image is taken into an image analysis apparatus “Luzex AP” (manufactured by Nireco Corporation) with a scanner.

  The external additives (inorganic particles, metal oxide particles) existing on the toner surface of the captured photographic image are binarized, and the horizontal ferret diameter is calculated for 100 of each external additive. The value is the number average primary particle size.

  When the number average primary particle diameter of the external additive is small and exists as an aggregate on the toner surface, the particle diameter of the primary particles forming the aggregate is measured.

  Moreover, about 70-150 nm particle | grains, since discrimination | determination with an inorganic particle and a metal oxide particle is hard to stick from a SEM photograph, it shall measure in the form which included both as a particle | grain of large particle diameter.

  The horizontal ferret diameter according to the present invention represents the maximum length in one arbitrary direction of each external additive particle in the plurality of external additive particles photographed by the electron microscope.

  FIG. 1 is a conceptual diagram illustrating a method for measuring the ferret diameter in the horizontal direction.

  In FIG. 1, an arbitrary direction 201 is defined for a photograph 300 of an external additive particle 200 using an electron microscope. The ferret diameter 203 in the horizontal direction is a distance between the two straight lines 202 that are perpendicular to the arbitrary one direction 201 and are in contact with the external additive particles 200.

  Next, the particles used as each external additive will be described.

<Small-diameter inorganic particles>
As the material constituting the small-diameter inorganic particles, various inorganic oxides, carbides, nitrides, borides and the like are preferably used.

  Specifically, silicon dioxide, aluminum oxide, titanium dioxide, zirconium dioxide, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, calcium titanate, zinc oxide, chromium oxide, cerium oxide, antimony oxide, oxidation Examples include tungsten, tin oxide, tellurium oxide, manganese oxide, boron oxide, boron carbide, titanium carbide, silicon nitride, titanium nitride, and boron nitride. Moreover, you may use what gave the hydrophobic treatment of the said compound. Among these, silicon dioxide and titanium dioxide are preferable, and a mixture thereof is also preferable.

  The number average primary particle size is 10 to 50 nm, preferably 10 to 40 nm.

  The addition amount is preferably 1.0 to 2.5% by mass, and more preferably 1.2 to 2.0% by mass with respect to the toner mass.

《Large diameter inorganic particles》
As the inorganic material constituting the large-diameter inorganic particles, various inorganic oxides, carbides, nitrides, borides and the like are preferably used.

  Specifically, silicon dioxide, aluminum oxide, titanium dioxide, zirconium dioxide, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, calcium titanate, zinc oxide, chromium oxide, cerium oxide, antimony oxide, oxidation Examples include tungsten, tin oxide, tellurium oxide, manganese oxide, boron oxide, boron carbide, titanium carbide, silicon nitride, titanium nitride, and boron nitride. Moreover, you may use what gave the hydrophobic treatment of the said compound. Among these, silicon dioxide and titanium dioxide are preferable, and a mixture thereof is also preferable.

  The number average primary particle diameter is 70 to 150 nm, preferably 90 to 130 nm.

  The addition amount is preferably 0.1 to 2.0% by mass and more preferably 0.3 to 1.7% by mass with respect to the toner mass.

《Metal oxide particles》
Although there is no restriction | limiting in particular as a metal element which comprises a metal oxide particle, Si, Ti, Mg, Al, Sn, Ge, Zr, Zn etc. are mentioned as a preferable metal element. Among these, Si, Ti, Al, and Zr are more preferable.

  The number average primary particle diameter of the metal oxide particles is 70 to 150 nm, preferably 90 to 130 nm.

  The addition amount is preferably 0.1 to 3.0% by mass, and more preferably 0.3 to 0.9% by mass with respect to the toner mass.

  Next, the domain matrix structure will be described.

  The metal oxide particles used in the present invention have a domain matrix structure.

  FIG. 2 is a cross-sectional view showing an example of metal oxide particles having a domain / matrix structure.

  In FIG. 2, 1 is a metal oxide particle, 2 is a matrix (also referred to as the sea), which is a continuous phase region, and 3 is a domain (also referred to as an island).

  The domain-matrix structure is also called a sea-island structure, and is one of phase separation structures formed by a substance containing a plurality of incompatible components. That is, among the incompatible components, a component with a high ratio forms a continuous phase (a continuous phase is a matrix and is a region representing the sea), and a component with a low ratio is a closed interface (phase). An island-like phase having a boundary between and a phase is formed to form such a structure.

  That is, the metal oxide particles according to the present invention are composed of a plurality of components incompatible with each other in the metal oxide particles, and each forms an independent phase (domain (island), matrix (sea)). One is an island-like phase and the other is a sea-like phase to form a domain matrix structure (sea-island structure).

  Thus, the metal oxide particles used in the present invention are composed of incompatible metal oxides. One of the incompatible metal oxides is higher than the other so as to form a domain / matrix phase.

  For example, for metal oxide particles that are preferably used, Si, Ti, Al, and Zr are listed above. However, in the case of a metal oxide composed of an oxide of Si and an oxide of Ti, the proportion of Si oxide is increased. In the present invention, metal oxide particles having a high Si oxide ratio are preferable.

  That is, the metal oxide particles used in the present invention have a domain-matrix structure having a domain phase formed of Ti, Al, Zr oxide in a matrix phase formed of Si oxide. preferable. In forming the metal oxide particles having a domain / matrix structure, the ratio of the metal oxide forming the domain phase is preferably 10 to 45% by mass. When particles having a number average primary particle diameter of 70 to 150 nm are formed at this ratio, a domain having a size of 1 to 60 nm is formed.

  The domain / matrix structure of the metal oxide particles according to the present invention is confirmed by confirming the particles using a field emission transmission electron microscope (FE-TEM) and mapping the target element. Can be performed.

  The horizontal ferret diameter of the domain can be obtained by analyzing an image taken with a transmission electron microscope with an image analysis apparatus “Luzex AP” (manufactured by Nireco Corporation).

  Next, a method for producing metal oxide particles will be described.

  The metal oxide particles according to the present invention can be produced by a flame combustion method or a wet method, but are preferably produced by a flame combustion method.

  The basic production method of the flame combustion method is not limited, but as a highly reproducible and preferable method, a halogen-free silane coupling agent and an organometallic compound such as a metal coupling agent are mixed in a liquid state, It is a method of spraying into a flame from a burner.

  FIG. 3 is a flowchart showing an example of a production apparatus for producing metal oxide particles.

  In FIG. 3, a raw material (metal coupling agent mixture) 210 is guided from a raw material tank 220 through a feed pipe 250 to a main burner 260 having a spray nozzle attached at the tip thereof and sprayed. The raw material 210 is sprayed inside the combustion furnace 270 and ignited by an auxiliary flame, whereby a combustion flame 280 is formed. The metal oxide particles generated by the combustion are cooled by the flue 290 together with the exhaust gas, separated by the cyclone 300 and the bag filter 330, and collected by the collectors 310 and 330. The exhaust gas is exhausted by the exhaust fan 340.

  The number average primary particle size of the metal oxide particles can be changed by controlling the composition and amount of the raw material used, the amount of sprayed air, the amount of propane, the amount of oxygen supplied, and adjusting the flame temperature for combustion.

  Specifically, the number average primary particle size of the metal oxide particles increases when the flame temperature is adjusted higher, the number of primary particles of the metal oxide particles decreases when the amount of spray of the raw material is reduced and the flame temperature is adjusted lower. Becomes smaller.

  The domain diameter can be controlled by the amount of halogen contained in the raw material. When the halogen is increased, the domain diameter becomes finer, and when it is excessive, phase separation does not occur and a domain / matrix structure is not formed. The amount of halogen is preferably 0 to 4% by mass. Further, the domain can be made crystalline or non-crystalline by controlling the temperature at the time of flame combustion, the residence time in the flame, and the like. In general, if the temperature during flame combustion is controlled at a high temperature and the residence time is lengthened, crystals tend to form. Specifically, the flame temperature is set to 1700 ° C. or more, and the residence time varies depending on the apparatus scale, but it is preferably 1.5 to 7 times that in the case of producing silicon dioxide.

  FIG. 3 is a flowchart showing an example of a production apparatus for producing metal oxide particles.

  In FIG. 3, a raw material (metal coupling agent mixture) 210 is guided from a raw material tank 220 through a feed pipe 250 to a main burner 260 having a spray nozzle attached at the tip thereof and sprayed. The raw material 210 is sprayed inside the combustion furnace 270 and ignited by an auxiliary flame, whereby a combustion flame 280 is formed. The metal oxide particles generated by the combustion are cooled by the flue 290 together with the exhaust gas, separated by the cyclone 300 and the bag filter 330, and collected by the collectors 310 and 330. The exhaust gas is exhausted by the exhaust fan 340.

  Titanium sulfate, titanium tetrachloride, triisostearylpropyl titanate, etc. as the metal oxide raw material, zirconium source, zirconium dioxide, zirconium oxychloride, zirconium tetrachloride, zirconium sulfate, zirconium nitrate, etc. as the aluminum source Includes aluminum chloride, aluminum sulfate, sodium aluminate, and the like. Examples of calcium sources include calcium carbonate and calcium sulfate. These can be used alone or in any combination. Examples of the silicon source include hexamethyldisiloxane and γ-glycidoxypropyltrimethoxysilane.

The toner of the present invention has a median particle diameter (D ₅₀ ) on a volume basis of preferably 3 to 8 μm, and more preferably 4 to 7 μm.

The measurement of the median particle size (D ₅₀ ) on a volume basis is performed as follows.

  Measurement and calculation are performed using a device in which a computer system for data processing (manufactured by Beckman Coulter) is connected to "Coulter Multisizer III" (manufactured by Beckman Coulter). As a measuring means, 0.02 g of toner was conditioned with 20 g of a surfactant solution (for example, a surfactant solution in which a neutral detergent containing a surfactant was diluted 10 times with pure water for the purpose of dispersing the toner). Thereafter, 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 Beckman Coulter, Inc.) in a sample stand with a pipette until a measurement concentration of 5 to 10% by mass, and the measuring machine count is set to 2500. To do. An aperture diameter of 50 μm was used.

  Next, a method for producing the toner of the present invention will be described.

  The toner of the present invention is obtained by aggregating and fusing resin particles, and preferably has a small particle size and a uniform distribution.

  The toner production method is not particularly limited as long as it is a production method including a step of agglomerating and fusing resin particles. Specifically, the suspension polymerization method, emulsion association method, dispersion polymerization method, dissolution method Suspension method etc. can be mentioned.

  Hereinafter, the emulsion association method will be described.

<Emulsion association method>
The emulsion association method is a method in which resin particles are prepared by agglomeration and fusion in an aqueous medium. The method is not particularly limited, and examples thereof include methods disclosed in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904. That is, dispersed particles of constituent materials such as resin particles and a colorant, or a method of aggregating and fusing a plurality of particles composed of a resin and a colorant, especially after dispersing them in water using an emulsifier, A coagulant with a critical coagulation concentration or higher is added for salting out, and at the same time, the formed polymer itself is heated and fused at a temperature above the glass transition temperature to gradually grow the particle size while forming fused particles. When the particle size is reached, add a large amount of water to stop particle size growth, further smooth the particle surface while heating and stirring, control the shape, and heat and dry the particles in a fluidized state while containing water. Thus, the toner of the present invention can be formed.

  In the toner manufacturing method of the present invention, a release agent is dissolved or dispersed in a polymerizable monomer, and then finely dispersed in an aqueous medium, and the polymerizable monomer is polymerized by a miniemulsion polymerization method. A method of aggregating and fusing the composite resin particles formed through the process and the colorant particles is preferably used.

  In addition, as a method for producing the toner of the present invention, a step of aggregating and fusing the composite resin particles obtained by the multistage polymerization method and the colorant particles is preferably used.

  Next, an example of a preferable toner production method (emulsion polymerization association method) will be described in detail.

This manufacturing method includes
(1) Dissolution / dispersion step for dissolving or dispersing the release agent in the radical polymerizable monomer (2) Polymerization step for preparing a dispersion of resin particles (3) Resin particles and colorant particles in an aqueous medium (4) Cooling step for cooling the dispersion of the toner base (5) Solidifying the toner base from the cooled dispersion of the toner base Liquid separation and washing step for removing surfactants from the toner base (6) Drying step for drying the washed toner base If necessary (7) Adding an external additive to the dried toner base A process may be included.

  Hereinafter, each step will be described.

[Dissolution / dispersion process]
This step is a step of preparing a radical polymerizable monomer solution of the release agent by dissolving or dispersing the release agent in the radical polymerizable monomer.

[Polymerization process]
In a preferred example of this polymerization step, a radical polymerizable monomer solution in which the release agent is dissolved or dispersed is added to an aqueous medium containing a surfactant, and mechanical energy is applied to form droplets. Then, the polymerization reaction is allowed to proceed in the droplets by radicals from the water-soluble radical polymerization initiator. In addition, you may add the resin particle as a core particle in the said aqueous medium.

  By this polymerization step, resin particles containing a release agent and a binder resin are obtained. Such resin particles may be colored particles or non-colored particles. The colored resin particles can be obtained by polymerizing a monomer composition containing a colorant. Further, when using resin particles that are not colored, in the fusion step described later, the dispersion of the colorant particles is added to the dispersion of the resin particles to fuse the resin particles and the colorant particles. Thus, a toner base can be obtained.

[Aggregation / fusion process]
As the aggregation / fusion method, an aggregation / fusion method using resin particles (colored or non-colored resin particles) obtained by the polymerization step is preferable. In the agglomeration / fusion step, resin particles and colorant particles can be agglomerated / fused together with release agent particles and internal additive particles such as charge control agents.

  The colorant particles can be prepared by dispersing the 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. The disperser used for the dispersion treatment of the colorant is not particularly limited, but preferably an ultrasonic disperser, a mechanical homogenizer, a pressure disperser such as a manton gorin or a pressure homogenizer, a sand grinder, a Getzmann mill, a diamond fine mill, or the like. A medium type disperser is mentioned.

[Cooling process]
This step is a step of cooling (rapid cooling) the dispersion of the toner base. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

[Solid-liquid separation and washing process]
In this solid-liquid separation / washing step, a solid-liquid separation process for solid-liquid separation of the toner base from the dispersion of the toner base cooled to a predetermined temperature in the above-described step, and a solid-liquid separated toner cake (in a wet state) A cleaning process is performed to remove deposits such as a surfactant and a salting-out agent from an aggregate obtained by agglomerating a toner base in a cake form. Here, the filtration method is not particularly limited, such as a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like.

[Drying process]
In this step, the washed toner cake is dried to obtain a dried toner base. Examples of the dryer used in this step include a spray dryer, a vacuum freeze dryer, and a vacuum dryer, and a stationary shelf dryer, a mobile shelf dryer, a fluidized bed dryer, and a rotary dryer. It is preferable to use a stirring dryer or the like. The moisture content of the dried toner base is preferably 5% by mass or less, and more preferably 2% by mass or less. In addition, when the toner bases subjected to the drying treatment are aggregated with weak interparticle attraction, the aggregate may be crushed. Here, as the crushing treatment device, a mechanical crushing device such as a jet mill, a Henschel mixer, a coffee mill, a food processor, or the like can be used.

[External process]
In this step, an external additive is mixed with the dried toner base to produce a toner.

  As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  Here, the toner base is a material before an external additive is added to obtain a toner.

  Next, the compounds (binder resin, colorant, release agent, charge control agent, external additive, lubricant) constituting the toner will be described.

(Binder resin)
As the polymerizable monomer constituting the binder resin, known monomers can be used. Specifically, it is preferable to use a combination of styrene, acrylic acid or methacrylic acid derivatives, and those having an ionic dissociation group.

(Coloring agent)
As the colorant used in the present invention, a known inorganic or organic colorant can be used. These colorants may 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.

(Release agent)
A known compound can be used as the release agent used in the present invention. When the release agent is contained in an amount of 1 to 15% by mass, preferably 3 to 12% by mass, based on the whole toner, good results can be obtained.

(Charge control agent)
A charge control agent can be added to the toner of the present invention as necessary. A known compound can be used as the charge control agent.

(External additive)
In the present invention, it is an essential requirement to use the external additive according to the present invention, but the following conventionally known external additives may be mixed and used.

  Examples of inorganic particles that can be used as conventionally known external additives include conventionally known particles. Specifically, silica fine particles, titania fine particles, alumina fine particles and the like can be preferably used. These inorganic particles are preferably hydrophobic.

  Examples of the organic fine particles that can be used as the external additive include spherical fine particles having a number average primary particle diameter of about 10 to 2000 nm. Examples of the constituent material of the organic fine particles include polystyrene, polymethyl methacrylate, styrene-methyl methacrylate copolymer, and the like.

<Developer>
The toner of the present invention can be used as a one-component developer or a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. As the carrier, conventionally known magnetic particles such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. Ferrite particles are particularly preferable. 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.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The coating resin is not particularly limited, and for example, an olefin resin, a styrene resin, a styrene-acrylic resin, a silicon resin, an ester resin, a fluorine-containing polymer resin, or the like is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is used. be able to. Among these, a coat carrier coated with a styrene-acrylic resin is more preferable because it can prevent the external additive from being detached and ensure durability.

<< Image forming apparatus and image forming method >>
The toner of the present invention is suitably used in an image forming apparatus having a toner recycling unit.

  The toner of the present invention is suitably used for an image forming apparatus for fixing a toner image by a dielectric heating fixing unit. Specifically, it is possible to accurately form a minute dot image such as a thin line that has been difficult to achieve with conventional toner.

  FIG. 4 is a cross-sectional view of an image forming apparatus having toner recycling means.

  The image forming apparatus shown in FIG. 4 collects toner remaining on the photosensitive member after the transfer step by a cleaning unit, and supplies the collected toner to the developing unit so that the recovered toner can be reused. An image forming apparatus having a path is configured such that toner and a carrier are appropriately supplied to the developing device by a trickle method.

  In FIG. 4, reference numeral 10 denotes a photosensitive drum as an electrostatic latent image carrier, which is, for example, an organic photosensitive member (OPC photosensitive member) applied on a conductive drum and is grounded and rotated clockwise. Reference numeral 11 denotes a scorotron charger that applies negative uniform charging to the circumferential surface of the photosensitive drum 10 by corona discharge to give a potential of VH. Prior to charging by the scorotron charger 11, the history of the photosensitive body up to the previous print is removed. For this purpose, the peripheral surface of the photosensitive member is neutralized by performing exposure with PCL 11A, which is a pre-charging exposure means using a light emitting diode or the like.

  After the photosensitive drum 10 is uniformly charged, the laser writing device 12 performs image exposure based on the image signal. In this image exposure, an image signal input from a computer or an image reading device is processed by an image signal processing unit, and then input to a laser writing device 12 to perform image exposure, and an electrostatic latent image is formed on the photosensitive drum 10. Form.

  The laser writing device 12 performs main scanning by bending the optical path by a plurality of reflecting mirrors 12d through a rotating polygon mirror 12a, an fθ lens 12b, and the like that rotate using a laser diode (not shown) as a light source, and the rotation of the photosensitive drum 10 is performed. An electrostatic latent image is formed by sub-scanning. In this embodiment, the image portion is exposed based on the image signal, and the exposure portion forms a reverse latent image having a low potential absolute value VL.

  A developing device 14 containing a two-component developer composed of a negatively charged conductive toner and a magnetic carrier is provided around the periphery of the photosensitive drum 10. The developing device 14 has a built-in magnet body and holds the developer to rotate. Reversal development is performed by the developing sleeve.

  Next, the transfer material P onto which the toner image has been transferred is neutralized by the pointed electrode 16c arranged with a slight gap, separated from the circumferential surface of the photosensitive drum 10, and conveyed to the fixing device 17, and the heating roller 17a already described. When the pressure roller 17b is heated and pressed, the transferred toner image is melted, fixed on the transfer material P, and then discharged to the tray portion 54 by the discharge roller.

  The transfer roller 16a is retracted away from the circumferential surface of the photosensitive drum 10 after the transfer material P passes through until the next toner image is transferred.

  On the other hand, the photosensitive drum 10 having the toner image transferred to the transfer material P is discharged from the rubber material that reaches the cleaning device 20 and contacts the photosensitive drum 10 after being discharged by the charge eliminator 19 using an AC corona discharger. The residual toner remaining on the peripheral surface by the cleaning blade 20a is scraped into the cleaning device 20, and the collected toner scraped off is sent to the developing device 14 through a collected toner conveyance path 21 containing a screw or the like.

  The photosensitive drum 10 from which the residual toner has been removed by the cleaning device 20 is exposed by the PCL 11A, and then uniformly charged by the charger 11, and enters the next image forming cycle.

  Fixing by the induction heating fixing method can be performed by changing the heating roll fixing devices 17 and 17b of FIG. 4 to the induction heating fixing device shown in FIG.

  FIG. 5 is a cross-sectional view showing an example of an induction heating fixing device using an induction heating fixing method.

  In FIG. 5, 1 is a transfer material, 2 is a heating element, 3 is a coil assembly, 4 is an insulating holding member, 5 is a pressure roller, 6 is a nip portion, and 8 and 9 are temperature detection means.

  The induction heating and fixing apparatus shown in FIG. 5 heats and melts the toner held on the transfer material 1 and fixes it to the transfer material 1. The induction heat fixing device includes a release layer having releasability with respect to the toner on the surface. A hollow cylindrical heating body 2 made of a rigid material that accommodates a core made of a magnetic material having a high magnetic permeability, a coil assembly 3 for inductively heating the heating body 2 by generating an induction current in the heating body 2, and a coil assembly 3 A high-frequency AC power supply unit 7 for supplying power to the heater, an insulating holding member 4 that holds the coil assembly 3 and is fixedly installed inside the heating body 2, and a transfer material 1 that holds unfixed toner. 2 is arranged to detect the temperature of the heating body 2 before and after the pressure roller 5 rotating with the heating body 2 while being sandwiched between the heating body 2 and the nip portion 6 where the heating roller 2 is pressed against the pressure roller 5. Temperature detecting means 8, 9 and the temperature And a control means for controlling a supply power amount based on information from the detection means 8, 9.

  In the following, each part will be described in detail. The heating element 2 is pressure-bonded to a pressure roller 5 via a bearing such as a ball bearing and is pivotally mounted on a fixing device frame not shown in the drawing. The heating element refers to a hollow cylindrical rigid roller and a hollow flexible sleeve that house the coil assembly 3 therein. A flexible sleeve includes a belt.

  The heating element 2 has an elastic layer made of silicon rubber, fluorine rubber or the like having high heat resistance on a rigid base material such as ceramic or heat-resistant resin, and is thin, electrically conductive and magnetic, made of nickel, aluminum, iron or the like. A hollow cylindrical rigid roller composed of layers. It is preferable to use a conductive ferromagnetic material that effectively generates an eddy current by the alternating magnetic flux from the coil assembly 3. By using a ferromagnetic material for the heating element 2, a large amount of magnetic flux passes through the heating element 2, so that the heat generation efficiency is further improved. On the outer peripheral surface of the heating body 2, a release layer having good release properties and heat resistance with respect to the toner is formed by coating with a fluororesin in order to make it easy to separate the transfer material 1. .

<Transfer material>
The transfer material used in the present invention is a support for holding a toner image, and is usually called an image support, a recording material or transfer paper. Specifically, various transfer materials such as plain paper and fine paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. However, it is not limited to these.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Preparation and production of external additives]
<Small-diameter inorganic particles>
Silicon dioxide particles and titanium dioxide particles were mixed as shown in Table 1 to prepare “inorganic particles 1-1 to 1-6”.

  Table 1 shows the materials used and their number average primary particle size.

《Large diameter inorganic particles》
“Inorganic particles 2-1 to 2-5” made of titanium dioxide having different number average primary particle sizes were prepared.

  Table 2 shows the number average primary particle size of the prepared materials.

<< Manufacture of metal oxide particles >>
<Manufacture of metal oxide particles 3-1>
The apparatus shown in FIG. 3 was used for the production of metal oxide particles.

  A raw material liquid prepared by mixing the following raw materials at room temperature is supplied to a burner provided at the top of the vertical combustion furnace, and fine droplets are generated from the spray nozzle attached to the tip of the burner by the air of the spray medium. Sprayed and burned with an auxiliary flame from the combustion of propane. Oxygen and air were supplied from the burner as combustion-supporting gas.

Incidentally, the atomizing air control 4 Nm ³ / hr, the amount of propane 0.4 Nm ³ / hr, the supply amount of oxygen air to 100 Nm ³ / hr, burned by adjusting the flame temperature to 2500 ° C., a cyclone and a bag filter And collected.

Raw material Hexamethyldisiloxane 72 parts by mass γ-glycidoxypropyltrimethoxysilane 14 parts by mass Triisostearyl isopropyl titanate 14 parts by mass As a result of observing the metal oxide particles produced above using a transmission electron microscope, It was confirmed that it had a matrix structure. The number average primary particle size of the metal oxide particles was 104 nm as a result of taking a transmission electron micrograph and measuring it with an image analyzer “Luzex AP” (manufactured by Nireco Corporation).

<Production of metal oxide particles 3-2 to 3-6>
The “metal oxide particles 3-2” were prepared in the same manner except that the raw materials used in the production of the “metal oxide particles 3-1” were changed as shown in Table 3, and the flame temperature was adjusted as shown in Table 3 to cause combustion. ˜3-6 ”.

  Table 3 shows the raw materials used for the production of “metal oxide particles 3-1 to 3-6” and their mixing ratios.

  Table 4 shows the raw material composition and production conditions of the “metal oxide particles 3-1 to 3-6”, the structure of the obtained particles, the number average primary particle diameter, and the horizontal ferret diameter based on the number of domains.

[Production of toner]
<Production of toner base>
(Preparation of core resin particles)
First stage polymerization (mini-emer polymerization)
Into a reaction vessel equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introducing device, the following monomer mixture solution is added, and 100 g of pentaerythritol tetrabehenate is added thereto, heated to 70 ° C. and dissolved. A monomer solution was prepared.

175.0 g of styrene
n-Butyl acrylate 60.0g
Methacrylic acid 15.0 g
n-octyl-3-mercaptopropionate 7.0 g
On the other hand, a surfactant solution prepared by dissolving 2 g of polyoxyethylene (2) sodium dodecyl ether sulfate in 1350 g of ion-exchanged water is heated to 70 ° C., added to and mixed with the monomer solution, and then a machine having a circulation path. An emulsified dispersion was prepared by mixing and dispersing at 70 ° C. for 30 minutes using a type disperser “CLEARMIX” (manufactured by M Technique).

  Next, an initiator solution prepared by dissolving 7.5 g of potassium persulfate in 150 g of ion exchange water was added to this dispersion, and polymerization was performed by heating and stirring the system at 78 ° C. for 1.5 hours. Resin particles were prepared. This is referred to as “resin particles (1H)”.

Second-stage polymerization To the “resin particles (1H)” obtained as described above, an initiator solution in which 12 g of potassium persulfate is dissolved in 220 g of ion-exchanged water is added, and under a temperature condition of 80 ° C.,
Styrene 320.0g
n-Butyl acrylate 100.0g
Methacrylic acid 35.0 g
n-octyl-3-mercaptopropionate 7.5 g
A monomer mixture consisting of was added dropwise over 1 hour. After completion of the dropping, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to obtain resin particles. This is referred to as “core resin particles”.

(Preparation of resin particles for shell)
A reaction vessel equipped with a stirrer, a temperature sensor, a condenser, and a nitrogen introducing device was charged with a surfactant solution in which 8 g of sodium dodecyl sulfate was dissolved in 3000 g of ion-exchanged water, and stirred at a stirring speed of 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C.

  To this surfactant solution, a surfactant solution in which 10 g of potassium persulfate was dissolved in 200 g of ion-exchanged water was added, the temperature of the solution was adjusted to 80 ° C., and the following monomer mixture was added dropwise over 100 minutes. The system was polymerized by heating and stirring at 80 ° C. for 2 hours to prepare “resin particles for shell”.

Styrene 570.0g
n-Butyl acrylate 165.0g
Methacrylic acid 70.0g
n-octyl-3-mercaptopropionate 5.5 g
(Preparation of colorant dispersion)
90 g of sodium dodecyl sulfate was dissolved in 1600 g of ion-exchanged water with stirring. While stirring this solution, 400 g of carbon black “Regal 330R” (manufactured by Cabot) is gradually added, and then dispersed by using a stirrer “Claremix” (manufactured by M Technique Co., Ltd.). A dispersion of agent particles was prepared. This is referred to as a “colorant dispersion”. The particle diameter of the colorant particles in this colorant dispersion was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm.

(Aggregation / fusion process)
In a reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introduction device, the following materials were placed and stirred. After adjusting the liquid temperature to 30 ° C., 5N sodium hydroxide aqueous solution was added to this solution to adjust the pH. Adjusted to 10.

Core resin particles 2000 g (300 g in terms of solid content)
Ion exchange water 1400g
Colorant dispersion 1 420 g
Next, an aqueous solution in which 60 g of magnesium chloride hexahydrate was dissolved in 60 g of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was started to rise, and the system was heated to 98 ° C. over 60 minutes for agglomeration to grow the particle size and carry out an association reaction. In this state, the particle size of the associated particles was measured with “Coulter Multisizer III” (manufactured by Beckman Coulter), and when the median particle size (D ₅₀ ) on the volume basis became 5 μm, sodium chloride 8. An aqueous solution in which 5 g was dissolved in 35 g of ion-exchanged water was added to stop particle growth, and the mixture was stirred for 6 hours for fusion.

  Further, in order to fuse the particles, the particles are heated and stirred at a liquid temperature of 98 ° C., and the fusion between the particles is allowed to proceed until the circularity becomes 0.965 as measured by “FPIA-2100” (manufactured by Sysmex Corporation). “Agglomerated particles of core resin particles” were obtained.

  Further, 530 g of “shell resin particles” was added, and heating and stirring were continued for 4 hours to fuse “shell resin particles” to the surface of “aggregated particles of core resin particles”. Here, after 17 g of sodium chloride was added to stop the particle growth, the mixture was heated and stirred at 97 ° C. for 2 hours in order to fuse the “shell resin particles”. Thereafter, the mixture was cooled to 30 ° C., hydrochloric acid was added to adjust the pH to 2.0, stirring was stopped, and a “toner base dispersion” was prepared.

(Washing / drying process)
The “toner matrix dispersion” produced in the aggregation / fusion process is solid-liquid separated with a basket-type centrifuge “MARKIII model number 60 × 40” (Matsumoto Kikai Co., Ltd.), and “wet toner particle wet cake” Formed. The wet cake is washed with water using the basket-type centrifuge, and then transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). The wet cake is dried until the water content becomes 0.5% by mass to obtain a “toner base”. Produced.

(External additive mixing process)
The external additives listed in Table 1 were added to 100 parts by weight of the above “toner base”, mixed for 10 minutes with a “Henschel mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.), and then coarse with a sieve having an opening of 45 μm. The particles were removed to prepare “Toners 1 to 21”. These are referred to as “Examples 1 to 11” and “Comparative Examples 1 to 10”.

  Table 5 shows Nos. Of “small-sized inorganic fine particles”, “large-sized inorganic fine particles”, and “metal oxide particles 3” used for toner preparation. And the amount of addition.

[Developer preparation]
Each toner obtained above was mixed with a silicon carrier-coated ferrite carrier having a volume average particle diameter of 50 μm to prepare “Developers 1 to 21” having a toner concentration of 6% by mass.

[Live-action evaluation]
The above-described “Examples 1 to 11” were prepared by replacing the fixing device of the commercially available multifunction machine “7272” (toner recycling method) (manufactured by Konica Minolta Business Technologies) with the induction heating fixing device shown in FIG. ”,“ Comparative Examples 1 to 10 ”in order, an image with a pixel rate of 10% in an environment of 20 ° C. and 55% RH (7% character image, portrait photo, solid white image, solid black image) Were printed on A4 quality paper (64 g / m ² ) over 1 million sheets, and the following evaluation items were evaluated. In the evaluation, ◎, ○, and Δ were acceptable with no problems, and × were unacceptable with problems.

<Image cover>
For image fogging, the density of unprinted transfer material (white paper) is measured at 20 locations, the image density is measured, the average value is used as the white paper density, and then the white background portion of the transfer material on which the plain image is printed is the same. The image density was measured at 20 locations, the average density was calculated, and the value obtained by subtracting the white paper density from the average density was evaluated as the fog density. The measurement was performed using a reflection densitometer “RD-918” (manufactured by Macbeth).

Evaluation Criteria A: Excellent when the image fog density is 0.003 or less. B: Excellent when the image fog density is 0.006 or less. Δ: Level at which the image fog density is 0.010 or less. The fog density is larger than 0.010 and is a practical problem.

<Image density>
The image density was evaluated by measuring the density of a solid black image portion at 12 points using a reflection densitometer “RD-918” (manufactured by Macbeth).

Evaluation Criteria A: Excellent when the image density is 1.35 or more B: Good when the image density is 1.30 or more Δ: Level at which there is no practical problem when the image density is 1.20 or more and 1.30 or less : Image density is less than 1.20, which is a practical problem.

<Transfer rate>
After printing one sheet, 500,000 sheets, and 1 million sheets, a solid image (20 mm × 50 mm) having 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

<Reproducibility of thin lines>
Fine line reproducibility was evaluated after printing 1, 500,000, and 1 million sheets, and how many lines could be resolved by printing a document with 8 black lines and 5 black lines drawn in 1 mm width. .

◎: Resolving up to 8 lines / mm, good reproducibility of fine lines ○: Resolving up to 5 lines / mm, good reproducibility of thin lines first x: Reproduction of thin lines that can resolve 5 lines / mm The nature is bad.

  Table 6 shows the evaluation results.

  As is clear from the evaluation results, “Examples 1 to 11” are excellent in all evaluation items, but “Comparative Examples 1 to 10” have some problems in the evaluation items.

It is a figure explaining the ferret diameter of a horizontal direction. It is sectional drawing which shows an example of the metal oxide particle which has a domain matrix structure. It is a flowchart which shows an example of the manufacturing apparatus which manufactures a metal oxide particle. 1 is a cross-sectional view of an image forming apparatus showing an example of an image forming method using a toner recycling method. It is sectional drawing which shows an example of the induction heating fixing apparatus using the induction heating fixing system.

Explanation of symbols

1 Metal Oxide Particles 2 Matrix that is a Continuous Phase Region

Claims (8)

In the electrostatic image developing toner obtained by adding an external additive to the base particles obtained by agglomerating and fusing the resin particles,
As the external additive,
Inorganic particles having a number average primary particle size of 10 to 50 nm;
Inorganic particles having a number average primary particle size of 70 to 150 nm;
Metal oxide particles having a domain matrix structure containing two or more kinds of metal elements having a number average primary particle diameter of 70 to 150 nm;
A toner for developing electrostatic images, characterized in that The toner for developing an electrostatic charge image according to claim 1, wherein the addition amount of the metal oxide particles is 0.1 to 3.0% by mass. The toner for developing an electrostatic charge image according to claim 1, wherein an addition amount of the inorganic particles having a number average primary particle diameter of 10 to 50 nm is 1.0 to 2.5% by mass. The electrostatic charge image according to any one of claims 1 to 3, wherein an addition amount of the inorganic particles having a number average primary particle diameter of 70 to 150 nm is 0.1 to 2.0 mass%. Developing toner. Developing means for developing the electrostatic latent image formed on the photoreceptor with a developer having the electrostatic charge image developing toner according to any one of claims 1 to 4 to form a toner image;
Transfer means for transferring a toner image formed on the photoreceptor to a transfer material;
Separating means for separating the transfer material onto which the toner image has been transferred from the photoreceptor;
Fixing means for fixing the toner image transferred onto the transfer material by the transfer means;
An image forming apparatus comprising: a toner recycling unit that collects toner remaining on the photosensitive member after transfer and returns the toner to the developing unit. The image forming apparatus according to claim 5, wherein the fixing unit includes an induction coil that generates a magnetic field by applying an alternating current, and a heating roller that is heated by the action of the magnetic field generated by the induction coil. apparatus. A developing step of forming a toner image by developing the electrostatic latent image formed on the photoreceptor with a developer having the electrostatic charge image developing toner according to any one of claims 1 to 4.
A transfer step of transferring the toner image formed on the photoreceptor to a transfer material;
A separation step of separating the transfer material onto which the toner image has been transferred from the photoreceptor;
A fixing step of fixing the toner image transferred to the transfer material to the transfer material;
An image forming method comprising: a toner recycling step for collecting toner remaining on a photosensitive member after transfer and returning the toner to the developing step. In the fixing step of fixing the toner image transferred to the transfer material to the transfer material, the heating roller is heated by the action of a magnetic field generated in the induction coil by application of an alternating current,
In the nip formed between the heated heating roller and the pressure roller,
The image forming method according to claim 7, wherein the transfer material is conveyed to melt and fix the toner image.

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