Image forming system

Abstract

To provide an image forming system that can prevent deterioration of fixability due to slip of a roller member of a fixing device during high-speed operation and deterioration of the roller member and a belt member, and can obtain good images even in a low temperature environment.SOLUTION: An image forming system of the present invention has a fixing device that fixes a toner image to a recording medium, and the fixing device includes a belt member and a roller member that stretches the belt member, or further includes a roller member that is arranged in pressure-contact rotatably from an outer peripheral surface of the belt member. At least one of the roller members has a substrate including aluminum as a main component. The substrate contains silicon in an amount exceeding 0.60 mass%. The standard deviation of the shape factor of toner base particles is 0.045 or less. The coefficient of variation of the volume average particle diameter of the toner base particles is 28.0% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming system, and more particularly to an image forming system that can suppress deterioration of fixing performance due to slippage of roller members of a fixing device and deterioration of roller members and belt members during high-speed operation, and can obtain good images even in low-temperature environments. [Background technology]

[0002] In recent years, emphasis has been placed on energy conservation and productivity in electrophotographic image forming systems. Particularly in high-speed printing areas, fixing belts made of materials with low heat capacity are used to ensure smooth recovery from sleep mode. Furthermore, image forming systems equipped with so-called belt-type fixing devices, in which the belt is heated from the inside or outside by a heating roller made of aluminum with good thermal conductivity, have become mainstream. However, in such belt-type fixing systems, the rotation of the heating roller cannot keep up with the rotation of the belt during high-speed operation, which can cause the roller to slip, resulting in poor fixing performance and deterioration of the belt material over long periods of use. To address this issue, roughening the surface of the aluminum roller is effective. The raised areas on the surface caused by the roughening act as anchors to the belt substrate, allowing the roller to rotate more easily and follow the movement of the belt.

[0003] In addition, using a heated roller with a resin coating layer or rubber layer on the surface of an aluminum substrate is also effective in improving belt conformability. In this case, the resin coating layer or rubber layer may peel off during long-term use. However, by roughening the surface of the aluminum substrate, the anchor effect makes the resin coating layer or rubber layer less likely to peel off, allowing belt conformability to be maintained even during long-term use. Known methods for roughening the surface of an aluminum substrate include machining or blasting the aluminum substrate. However, these methods often require additional steps for the surface roughening treatment, which can result in a decrease in productivity. To achieve a surface roughening treatment without reducing productivity, it is desirable to chemically obtain a roughened structure during the existing process.

[0004] Incidentally, aluminum alloys used for heating rollers and their substrates often contain silicon, as disclosed in, for example, Patent Documents 1 and 2. When an aluminum alloy with a high silicon content is used, convex portions are formed on the surface of the aluminum substrate due to the eutectic of Si and Al, and an anchoring effect can be expected without surface roughening treatment. However, silicon reduces thermal conductivity, so increasing the amount of silicon can lead to a deterioration in fixation. In particular, in low-temperature environments, heat from the heat source and heat once transferred to the belt is easily absorbed by the air, making it difficult for the belt surface temperature to recover, resulting in a significant deterioration in fixation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 04-110439 [Patent Document 2] Japanese Patent Application Publication No. 01-263244 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems and circumstances. The problem to be solved by the present invention is to provide an image forming system that can suppress deterioration of fixing performance due to slippage of the roller members of the fixing device and deterioration of the roller members and belt members during high-speed operation, and can obtain good images even in low-temperature environments. [Means for solving the problem]

[0007] The present inventors have investigated the causes of the above problems in order to solve the above problems, and have found that by specifying the silicon content in the aluminum-based substrate of the roller member and using toner with little variation in shape and particle size, it is possible to suppress deterioration of the fixing ability and degradation of the roller member and belt member, and to obtain good images even in low-temperature environments. That is, the above-mentioned problems of the present invention are solved by the following means.

[0008] 1. An image forming system having a fixing device for fixing a toner image to a recording medium, the fixing device includes a belt member and a roller member that stretches the belt member, or further includes a roller member that is rotatably pressed against the outer circumferential surface of the belt member, At least one of the roller members has an aluminum-based substrate; the substrate contains greater than 0.60 wt. % silicon; The standard deviation of the shape factor of the toner base particles is 0.045 or less, and The coefficient of variation of the volume average particle diameter of the toner base particles is 28.0% or less. An image forming system comprising:

[0009] 2. The substrate contains more than 0.80% by mass of silicon. 2. The image forming system according to claim 1,

[0010] 3. A pressure roller is provided on the outside of the belt member so as to sandwich the belt member and form a nip portion, and a pad is provided on the inside of the belt member facing the pressure roller. 2. The image forming system according to claim 1,

[0011] 4. A heat source for heating the belt member is provided inside at least one of the roller members. 2. The image forming system according to claim 1,

[0012] 5. A resin coating layer or a rubber layer is provided on the surface of at least one of the roller members. 2. The image forming system according to claim 1,

[0013] 6. Before the toner image is fixed to the recording medium, the toner image is heated in a non-contact manner by a heater. 2. The image forming system according to claim 1.

[0014] 7. The toner base particles contain 5.0 to 20% by mass of a crystalline resin among the binder resins. 2. The image forming system according to claim 1,

[0015] 8. Strontium titanate particles having a number average particle size in the range of 10 to 60 nm are added as an external additive to the toner base particles. 2. The image forming system according to claim 1, [Effects of the Invention]

[0016] The above-mentioned means of the present invention can provide an image forming system that can suppress deterioration of fixing performance due to slippage of the roller members of the fixing device during high-speed operation, and deterioration of the roller members and belt members, and can also obtain good images even in low-temperature environments. The mechanism by which the effects of the present invention are manifested or the mechanism of action is not clear, but is speculated as follows. In the present invention, at least one roller member has a substrate primarily composed of aluminum, and the substrate contains more than 0.60% by mass of silicon, so that Al-Si eutectic crystal portions (protrusions) are formed on the substrate surface. The anchor effect originating from these protrusions suppresses deterioration of fixation due to slippage of the roller member. Furthermore, deterioration of the roller member and belt member can be prevented even during long-term use. In particular, even when a resin coating layer or rubber layer is applied to the surface of the roller member to prevent slippage of the roller member, the presence of crystalline portions (convex portions) made of Al-Si eutectic on the surface of the base body has an anchoring effect that prevents the resin coating layer or rubber layer from peeling off during long-term use. Furthermore, in order to address the decrease in thermal conductivity caused by the inclusion of a large amount of silicon in the base, it is effective to reduce the standard deviation of the shape factor of the toner base particles and the coefficient of variation of the volume average particle diameter of the toner base particles. By keeping the standard deviation at a certain level or less, irregularly shaped particles are reduced, and the difference in contact area with the belt member between particles is reduced, which reduces the variation in the melting speed of the toner base particles and prevents deterioration of fixability in harsh environments. Furthermore, by setting the coefficient of variation of the volume average particle diameter of the toner base particles to a certain value or less, the particle diameter variation is reduced, and therefore, toner base particles that are easy to dissolve and toner base particles that are difficult to dissolve are not mixed together, and deterioration of fixability in low-temperature environments is prevented. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic side view of a fixing device according to a first embodiment; [Figure 2] 10 is a schematic side view of a fixing device according to a second embodiment. [Figure 3] 10 is a schematic side view of a fixing device according to a third embodiment. [Figure 4A] FIG. 10 is a schematic side view illustrating a state in which a sheet passes through the fixing device according to the fourth embodiment. [Figure 4B] FIG. 10 is a schematic side view showing a state during warm-up of a fixing device according to a fourth embodiment; [Figure 5] Perspective view of the switching mechanism [Figure 6] 1 is a schematic side view of a fixing device and a non-contact heating unit according to a first embodiment; [Figure 7] 1 is a schematic diagram illustrating an example of the overall configuration of an image forming apparatus; DETAILED DESCRIPTION OF THE INVENTION

[0018] The image forming system of the present invention is an image forming system having a fixing device that fixes a toner image to a recording medium, wherein the fixing device comprises a belt member and a roller member that stretches the belt member, or further comprises a roller member that is rotatably pressed against the outer peripheral surface of the belt member, and at least one of the roller members has a substrate whose main component is aluminum, the substrate contains silicon in an amount exceeding 0.60% by mass, the standard deviation of the shape factor of the toner base particles is 0.045 or less, and the coefficient of variation of the volume average particle diameter of the toner base particles is 28.0% or less. This feature is a technical feature common to or corresponding to each of the following embodiments.

[0019] In an embodiment of the present invention, the substrate preferably contains more than 0.80 mass % of silicon, in view of good processability and a uniform surface of the substrate.

[0020] It is preferable that a pressure roller is provided on the outer side of the belt member and a pad is provided on the inner side of the belt member facing the pressure roller so that a nip is formed across the belt member, thereby widening the nip area, providing sufficient heating and improving fixability.

[0021] It is preferable that a heat source for heating the belt member is provided inside at least one of the roller members, in order to ensure sufficient heating and good fixability.

[0022] It is preferable that a resin coating layer or a rubber layer is provided on the surface of at least one of the roller members, in order to prevent the roller members from slipping.

[0023] It is preferable to heat the toner image in a non-contact manner using a heater before fixing the toner image to the recording medium, since this allows for sufficient heating and improves fixability.

[0024] It is preferable that the toner base particles contain 5.0 to 20% by mass of a crystalline resin in the binder resin, as this improves the sharp melting properties of the toner and makes it less likely that delays in melting of the toner base particles will occur. By making the crystalline resin 5.0% by mass or more, good low-temperature fixability is achieved. Furthermore, by making the crystalline resin 20% by mass or less, excellent heat-resistant storage stability is achieved.

[0025] It is preferable to add strontium titanate particles having a number-average particle size of 10 to 60 nm as an external additive to the toner base particles. The abrasive effect of the strontium titanate particles can prevent small-diameter toner particles, which melt easily, from adhering to the belt member. As a result, the durability of the belt member is improved.

[0026] The present invention, its components, and embodiments and modes for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as lower and upper limits.

[0027] [Outline of the image forming system of the present invention] The image forming system of the present invention is an image forming system having a fixing device that fixes a toner image to a recording medium, wherein the fixing device comprises a belt member and a roller member that stretches the belt member, or further comprises a roller member that is rotatably pressed against the outer peripheral surface of the belt member, and at least one of the roller members has a substrate whose main component is aluminum, the substrate contains silicon in an amount exceeding 0.60% by mass, the standard deviation of the shape factor of the toner base particles is 0.045 or less, and the coefficient of variation of the volume average particle diameter of the toner base particles is 28.0% or less.

[0028] In this specification, the term "toner" refers to a toner for developing electrostatic images. The toner includes toner particles having toner base particles and an external additive disposed on the surface of the toner base particles. "Toner base particles" are particles that constitute the base of "toner particles." The "toner base particles" according to the present invention contain at least a binder resin, and may contain other components such as a colorant, a release agent (wax), and a charge control agent, as necessary. "Toner base particles" become "toner particles" when external additives are added. "Toner" refers to an aggregate of toner particles. The term "toner image" refers to a state in which toner is collected in an image form.

[0029] <Roller parts> In the present invention, at least one roller member constituting the fixing device has a substrate whose main component is aluminum (Al). "Containing aluminum as a main component" means that the Al content is 80 mass % or more relative to the total mass of the entire substrate. In particular, the Al content is preferably within the range of 85 to 99 mass % relative to the total mass of the entire substrate.

[0030] Furthermore, the substrate contains silicon (Si). The silicon content is in the range of more than 0.60 mass % relative to the total mass of the entire substrate. If the silicon content in the substrate is 0.60% by mass or less, processability deteriorates and the surface becomes uneven. Therefore, from the viewpoint of processability, the silicon content is preferably more than 0.60% by mass, more preferably more than 0.80% by mass. Furthermore, in order to obtain a sufficient amount of protrusions derived from silicon crystals, the silicon content is more preferably 1.50% by mass or more, and particularly preferably 1.80% by mass or more. On the other hand, if the silicon content exceeds 12.6% by mass, coarse crystals due to the eutectic crystal of alumina and silicon are likely to occur. As a result, the belt member and the resin coating layer and rubber layer formed on the substrate are likely to deteriorate due to pressure contact with the protrusions made of coarse crystals on the substrate surface. Therefore, the silicon content is preferably 12.6% by mass or less. Furthermore, if the silicon content exceeds 3.0% by mass, the impact on the deterioration of fixation becomes significant, so 3.0% by mass or less is more preferable.

[0031] The silicon content in the substrate is measured by high frequency inductively coupled plasma emission spectrometry. Inductively Coupled Plasma Atomic Emission Spectroscopy is a method in which a solution sample of metals dissolved in acid or alkali is sprayed into Ar plasma, the excited light is separated into individual wavelengths, and the type and content of elements are quantified from the light intensity. This method has a linear relationship between light intensity and content from trace to high concentrations, allowing each element to be analyzed simultaneously. The measurement device for high-frequency inductively coupled plasma optical emission spectrometry can be the "ULTIMA2000 (manufactured by Horiba, Ltd.)." The measurement can also be performed using an optical emission spectrometer with an argon atmosphere discharge optical emission stand, an optical emission spectrometer with an atmospheric discharge optical emission stand, a glow discharge mass spectrometer (GD-MS), an X-ray fluorescence spectrometer (XRF), or the like. If a coating layer such as a resin is present on the substrate, it is removed appropriately with a solvent before measurement.

[0032] The substrate is preferably made of an aluminum alloy, which may contain Fe, Cu, Mn, Mg, Ti, and the like in addition to Al and Si. It is preferable that Fe is 0.7 mass % or less, Cu is in the range of 0.05 to 0.2 mass %, Mn is 0.9 mass % or less, and Ti, Zn and Cr are 0.1 mass % or less, based on the total mass of the entire substrate. In the present invention, the term "aluminum alloy" refers to an alloy in which the content of aluminum (Al) is 50 mass % or more relative to the total alloy.

[0033] In the present invention, it is preferable that a resin coating layer or a rubber layer is provided on the surface of at least one of the roller members, in order to prevent slippage of the roller members. The surface of the roller member may be provided with both a resin coating layer and a rubber layer. In this case, it is preferable that the rubber layer and the resin coating layer are provided on the surface of the roller member in this order.

[0034] (Resin coating layer) The resin coating layer is preferably made of a heat-resistant resin (heat-resistant resin) or a fluorine-based resin. The term "heat resistance" as used herein means that the toner does not deform at temperatures used for fixing a toner image to a recording medium in electrophotographic image formation, and exhibits the desired physical properties with sufficient stability. The temperature is, for example, within the range of 150 to 220°C.

[0035] The heat-resistant resin is suitably selected from resins that do not substantially denature or deform at the above-mentioned use temperatures, and may be used alone or in combination of two or more kinds.

[0036] Examples of heat-resistant resins applicable to the present invention include silicone resins, polyphenylene sulfide, polyarylate, and polysulfone. Examples of the heat-resistant resin include polyethersulfone, polyetherimide, polyimide, polyamideimide, and polyetheretherketone. Among these, polyimide and silicone resins are preferred as heat-resistant resins from the viewpoint of heat resistance.

[0037] Polyimide can be obtained, for example, by heating its precursor, polyamic acid, at 200° C. or higher, or by promoting dehydration and cyclization (imidization) reaction using a catalyst. The polyamic acid may be produced by dissolving a tetracarboxylic dianhydride and a diamine compound in a solvent, mixing them, and heating them to cause a polycondensation reaction, or a commercially available product may be used. Examples of the diamine compound and tetracarboxylic dianhydride include the compounds described in paragraphs (0123) to (0130) of JP-A No. 2013-25120.

[0038] The silicone resin is preferably a mixture of an addition reaction type silicone and a catalyst. Examples of commercially available products of the addition reaction type silicone include "SD7333" (manufactured by Dow Corning Toray Co., Ltd.). Examples of commercially available products of the catalyst include "SRX212" (manufactured by Dow Corning Toray Co., Ltd.).

[0039] The content of the heat-resistant resin is preferably within a range of 40 to 100% by mass based on the entire resin coating layer.

[0040] Examples of the fluorine-based resin contained in the resin coating layer include perfluoroalkoxy fluorine-based resin (PFA) and tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and examples of the fluorine-based resin include tetrafluoroethylene-ethylene copolymer (ETFE) and perfluoropolyether compound (PFPE). The fluororesin is preferably a perfluoroalkoxy fluororesin (PFA), which is a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene. Specifically, the fluororesin is a film-shaped or tubular perfluoroalkoxy fluororesin (PFA), and for example, a tubular soft PFA manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd. can be used. Furthermore, as a commercially available fluorine-based resin, for example, fluorinated acrylic "Novec2702" (manufactured by 3M) can be used.

[0041] The content of the fluorine-based resin is preferably within the range of 10 to 100% by mass based on the entire resin coating layer.

[0042] The thickness of the resin coating layer is preferably within a range of 5 to 500 μm, more preferably within a range of 10 to 200 μm, from the viewpoint of sufficiently exhibiting heat conductivity and elasticity.

[0043] (rubber layer) The rubber layer is made of, for example, an elastic material. An example of an elastic material applicable to the present invention is an elastic resin material, including silicone rubber, thermoplastic elastomer, and rubber material. Among them, the elastic material is preferably silicone rubber from the viewpoint of heat resistance as well as desired elastic properties.

[0044] The silicone rubber may be used alone or in combination of two or more kinds. Examples of silicone rubbers that can be used in the present invention include polyorganosiloxanes or heat-cured products thereof, and the addition reaction type silicone rubbers described in JP-A-2009-122317.

[0045] A representative example of such polyorganosiloxane is dimethylpolysiloxane, which is described in JP-A-2008-255283 and has both ends blocked with trimethylsiloxane groups and vinyl groups on the side chains.

[0046] The thickness of the rubber layer is preferably within a range of 5 to 1000 μm, more preferably within a range of 50 to 500 μm, from the viewpoint of sufficiently exhibiting heat conductivity and elasticity.

[0047] The rubber layer may further contain components other than the elastic resin material as long as the intended effects of the present invention can be obtained. For example, the rubber layer may contain, in addition to the elastic material, a thermally conductive filler to enhance the thermal conductivity of the elastic layer. Examples of the filler material include silica, metal silicon, alumina, zinc, aluminum nitride, boron nitride, silicon nitride, silicon carbide, carbon, and graphite. The form of the filler is not limited and may be, for example, a spherical powder, an irregular powder, a flat powder, or a fibrous form.

[0048] The content of the elastic resin material in the elastic material constituting the rubber layer is preferably within a range of 60 to 100% by volume of the total volume of the rubber layer, from the viewpoint of achieving both heat conductivity and elasticity.

[0049] <Shape factor of toner base particles> The standard deviation of the shape factor of the toner base particles according to the present invention is 0.045 or less, more preferably 0.035 or less, and particularly preferably 0.030 or less, from the viewpoint of uniform contact with the belt. The shape factor of the toner base particles is preferably in the range of 0.920 to 0.995, and more preferably in the range of 0.940 to 0.975.

[0050] The shape factor of a toner base particle indicates the degree of roundness of the toner base particle, and is calculated by taking a 2000x magnified photograph of the toner base particle using a scanning electron microscope and analyzing the image using an image analysis system such as the image processing analyzer "LUZEX AP" (manufactured by Nireco Corporation). At this time, toner particles that are not entirely visible, such as those that are overlapping other toner base particles or those at the edge of the field of view, are excluded. Then, 100 toner base particles are randomly selected from those whose entire particles are visible and measured. Note that this is for toner base particles excluding fine particles of 2 μm or less. From the photographic image obtained above, the shape factor is calculated using the following formula: Shape factor = (perimeter of a circle with the same projected area as the particle image) / (perimeter of the projected particle image) After calculating the shape factors for 100 toner base particles, the average shape factor is calculated. The average shape factor is the arithmetic mean value obtained by adding up the shape factors of each particle and dividing by the total number of particles measured. This average shape factor is the shape factor of the toner base particle according to the present invention. The average shape factor in the examples described below was also calculated by the above-mentioned method. In addition to the above method, the shape factor can also be measured using, for example, a flow particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation). In this case, toner base particles obtained by removing fine particles of 2 μm or less from the toner particles are used, or the shape factor is determined by removing the measurement values ​​of particles of 2 μm or less from the measurement results of the toner particles.

[0051] The standard deviation can be calculated from the shape coefficient of the toner particles calculated as described above using the following formula (1).

number

[0052] In chemical methods such as emulsion aggregation and suspension polymerization, the coefficient of variation of the shape factor of the toner base particles can be adjusted by, for example, the content of surfactant, the pH of the dispersion medium, the acid value of the resin, stirring conditions, etc. On the other hand, in pulverization methods, the coefficient of variation can be adjusted by, for example, air flow conditions such as the temperature of the cold air, the type and content of the release agent, etc. Regardless of the manufacturing method, the coefficient of variation of the shape factor can also be adjusted by mixing toner particles having different average circularities. In addition, in the emulsion aggregation method, the shape factor of the toner base particles can be adjusted by the heating temperature and heating time, the content of the surfactant, the pH of the dispersion medium, the acid value of the resin, the molecular weight of the resin, the composition of the resin, the stirring conditions, etc.

[0053] For example, in the emulsion aggregation method, increasing the rotation speed during dispersion slows down the aggregation rate, making it easier to achieve uniform aggregation, thereby reducing the coefficient of variation of the shape factor of the toner base particles.On the other hand, decreasing the rotation speed during dispersion speed increases the aggregation rate, making it easier to achieve non-uniform aggregation, thereby increasing the coefficient of variation of the shape factor of the toner base particles. In addition, in the emulsion aggregation method, increasing the amount of surfactant added slows down the aggregation rate and facilitates uniform aggregation, thereby reducing the coefficient of variation of the shape factor of the toner base particles, whereas decreasing the amount of surfactant added increases the aggregation rate and facilitates non-uniform aggregation, thereby increasing the coefficient of variation of the shape factor of the toner base particles.

[0054] In the pulverization method, the control range varies greatly depending on the type of pulverizer. To reduce the shape factor of the toner base particles, it is preferable to use a jet mill. To increase the shape factor of the toner base particles, it is preferable to use a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.). When a jet mill is used, the shape factor can be controlled by adjusting the airflow conditions such as the cold air temperature. Similarly, when using a turbo mill, the shape factor can be controlled by adjusting the airflow requirements, such as the cold air temperature. In both the jet mill and turbo mill, the lower the temperature, the lower the shape factor. It is preferable to use dehumidified dry air as the cool air, as lowering the temperature can cause condensation, making it necessary to use dry air.

[0055] As for the airflow conditions of the jet mill, the cold air temperature is preferably within the range of -15 to 5°C. As for the airflow conditions of the turbo mill, the cold air temperature is preferably within the range of -15 to 5°C.

[0056] In addition, in order to promote spheronization, the shape factor of the toner base particles can be increased by processing them in a spheronization processing device, such as Angmill (manufactured by Hosokawa Micron Corporation). When the temperature is increased, the resin softens, and the shape of the toner base particles becomes rounder, that is, the shape factor increases.

[0057] <Volume average particle size of toner base particles> The coefficient of variation of the volume average particle size (volume-based median size) of the toner base particles according to the present invention is 28.0% or less, preferably 24.0% or less, particularly preferably 22.0% or less, from the viewpoint of uniform melting of the toner base particles. The volume average particle size of the toner base particles is preferably within the range of 3.0 to 10.0 μm.

[0058] The volume average particle diameter of the toner base particles is measured and calculated using a device consisting of a "Coulter Counter Multisizer 3" (manufactured by Beckman Coulter) connected to a computer system (manufactured by Beckman Coulter) equipped with data processing software "Software V3.51." The measurement procedure involves soaking 0.02 g of toner in 20 ml of surfactant solution, followed by ultrasonic dispersion for 1 minute to prepare a toner dispersion. The surfactant solution is prepared by diluting, for example, a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner. The prepared toner dispersion is pipetted into a beaker containing ISOTON II (manufactured by Beckman Coulter) in the sample stand until the concentration indicated by the measuring instrument is 5% to 10%. By keeping the concentration within this range, reproducible measurement values ​​can be obtained. The measuring instrument counts 25,000 particles and sets the aperture diameter to 100 μm. The measurement range of 2.0 to 60 μm is divided into 256 parts to calculate the frequency value, and the particle diameter of the 50% with the largest volume cumulative fraction is taken as the volume-based median diameter (volume D 50 % diameter).

[0059] From the volume average particle diameter of the toner base particles calculated as described above, the coefficient of variation of the volume average particle diameter can be calculated by the following formula (2). Equation (2): Coefficient of variation of volume average particle size (%) = (Si / K) × 100 In the above formula, Si represents the standard deviation of the volume average particle diameter of 100 toner base particles, and K represents the average value of the volume average particle diameter of 100 toner base particles. The standard deviation of the volume average particle diameter can also be calculated based on the formula (1) in the same manner as the standard deviation of the shape factor of the toner base particles.

[0060] In chemical methods such as emulsion aggregation and suspension polymerization, the coefficient of variation of the volume average particle size of the toner base particles can be adjusted by, for example, the content of surfactant, the pH of the dispersion medium, the acid value of the resin, stirring conditions, etc. On the other hand, in pulverization methods, the coefficient of variation can be adjusted by, for example, air flow conditions such as the temperature of the cold air, the resin composition, the type and content of the release agent, etc. Regardless of the production method, the volume average particle diameter can also be adjusted by mixing toner particles having different volume average particle diameters. In order to satisfy the coefficient of variation of the shape factor and the coefficient of variation of the volume average particle diameter specified in the present invention, in a chemical method such as emulsion aggregation or suspension polymerization, the coefficients can be adjusted by, for example, the content of a surfactant, the pH of the dispersion medium, the acid value of the resin, the molecular weight of the resin, the composition of the resin, stirring conditions, etc. For example, in the chemical method, increasing the rotation speed during dispersion slows down the aggregation rate, making it easier for the particles to aggregate uniformly, thereby reducing the variation in the volume average particle diameter of the toner base particles.On the other hand, decreasing the rotation speed during dispersion speeds up the aggregation rate, making it easier for the aggregation to become non-uniform, thereby increasing the variation in the volume average particle diameter of the toner base particles. In the chemical method, increasing the amount of surfactant added slows down the aggregation rate and facilitates uniform aggregation, thereby reducing the variation in the volume average particle size of the toner base particles, whereas decreasing the amount of surfactant added increases the aggregation rate and facilitates non-uniform aggregation, thereby increasing the variation in the volume average particle size of the toner base particles. In the pulverization method, the temperature can be adjusted by adjusting the airflow conditions such as the cold air temperature, the resin composition, the type and content of the release agent, and the like.

[0061] The shape factor of the toner base particles is approximately the same as the shape factor of toner particles to which external additives are added, excluding particles with a circle-equivalent diameter of 2 μm or less. Furthermore, the volume average particle diameter of the toner base particles is also approximately the same as the volume average particle diameter of the toner particles, and therefore can be treated as the same.

[0062] [Fixing device] (1) First embodiment FIG. 1 is a schematic side view of a fixing device according to a first embodiment of the present invention. The fixing device shown in Fig. 1 has a heating roller 31, an upper pressure roller 32, a lower pressure roller 33, and an endless belt member (also called a "fixing belt") 34. In the figure, arrow F indicates the transport direction of paper (recording medium). This is the same in other figures. The heating roller 31 and the upper pressure roller 32 correspond to the "roller member" according to the present invention. At least one of the heating roller 31 and the upper pressure roller 32 has a substrate mainly composed of aluminum, and the substrate contains more than 0.60 mass % of silicon. The constituent materials of the heating roller 31 and the upper pressure roller 32 will be described later.

[0063] The heating roller 31 has a rotatable sleeve that serves as the base, and a heater (heat source) 35 disposed inside the sleeve. The heating roller 31 heats the belt member 34 with the heater 35. The heater 35 may be, for example, a halogen heater.

[0064] The upper pressure roller 32 presses the belt member 34 toward the fixing nip (nip portion) 36 . A fixing nip 36 is formed by the portion of the belt member 34 pressed by the upper pressure roller 32 and the lower pressure roller 33 .

[0065] The lower pressure roller 33 rotates in synchronization with the rotation of the upper pressure roller 32 . The lower pressure roller 33 presses the paper passing through the fixing nip 36 toward the belt member 34. A driving force from a drive source is transmitted to the upper pressure roller 32 and the lower pressure roller 33, and the upper pressure roller 32 and the lower pressure roller 33 rotate synchronously. The heating roller 31 is rotated by the movement of the belt member 34, which moves in accordance with the rotation of the upper pressure roller 32.

[0066] The belt member 34 is an endless belt that is in contact with and stretched over the heating roller 31 and the upper pressure roller 32. The belt member 34 is preferably configured, for example, by forming a silicone rubber layer on a polyimide base material, and further forming a fluorine material as a surface layer, the details of which will be described later. The belt member 34 is heated by the heating roller 31, and as the belt member 34 moves, the heat is transferred to the fixing nip 36, and the paper being sandwiched and transported in the fixing nip 36 is heated and pressurized, thereby fixing the unfixed toner image to the paper.

[0067] Furthermore, the fixing device 30 is preferably provided with a temperature sensor 37 that is in contact with the belt member 34 and measures the temperature. The temperature sensor 37 is disposed near the fixing nip 36 to measure the temperature of the fixing nip 36. A signal from the temperature sensor 37 is sent to a control unit (not shown). The temperature sensor 37 may be disposed in any position where it can measure the temperature of the fixing nip 36, and is not limited to being disposed downstream in the movement direction of the belt member 34. For example, the temperature sensor 37 may be disposed upstream in the movement direction of the fixing nip 36. The temperature sensor 37 may also be a non-contact type.

[0068] The control unit controls the output of the halogen heater based on a signal from the temperature sensor 37, that is, the heating temperature during fixing.

[0069] <Materials of the heating roller and upper pressure roller> At least one of the heating roller 31 and the upper pressure roller 32, which are roller members according to the present invention, has a substrate mainly composed of aluminum, and the substrate contains more than 0.60% by mass of silicon. In the present invention, it is preferred that both the heating roller 31 and the upper pressure roller 32 have a substrate mainly composed of aluminum, and the substrate contains more than 0.60% by mass of silicon. Furthermore, it is preferable that a resin coating layer or a rubber layer is provided on the surface of at least one of the roller members, in order to prevent the roller members from slipping.

[0070] Specifically, the sleeve of the heating roller 31 is preferably made of the above-mentioned base body, and a resin coating layer or a rubber layer is provided on the surface of the base body. The sleeve of the upper pressure roller 32 is also made of the above-mentioned base material, and it is preferable that a resin coating layer or a rubber layer is provided on the surface of the base material. The resin coating layer and the rubber layer are as described above, and therefore, a description thereof will be omitted here.

[0071] The lower pressure roller 33 is preferably configured, for example, by forming a silicone rubber layer on the surface of an aluminum or stainless steel core, and coating the surface of the silicone rubber layer with a fluorine material. As with the upper pressure roller, the lower pressure roller 33 may also use a base material as the core, which is primarily composed of aluminum and contains more than 0.60 mass% silicon.

[0072] <Constituent materials of belt components> The belt member 34 preferably has at least a base material, an elastic layer, and a thermoplastic resin layer in this order. The belt member 34 may have an adhesive layer having an adhesive function between the elastic layer and the outermost layer.

[0073] (base material) The base material constituting the belt member is made of a resin having heat resistance (heat-resistant resin). The heat-resistant resin is suitably selected from resins that do not substantially denature or deform at the temperature of use (about 150 to 220° C.), and one type may be used, or two or more types may be used in combination.

[0074] Examples of heat-resistant resins that can be used in the present invention include the same heat-resistant resins as those used in the resin coating layer of the roller member described above, and polyimide is particularly preferred. The heat-resistant resin is a main material constituting the substrate, and its content may be an amount sufficient to form the substrate. From the viewpoint of formability during substrate production, the content of the heat-resistant resin in the substrate is preferably 40 to 100% by volume of the total volume of the substrate.

[0075] The substrate may further contain components other than the heat-resistant resin as long as the intended effects of the present invention are obtained. For example, the substrate may contain a filler in addition to the heat-resistant resin as a constituent material. The filler is a component that contributes to improving at least one of the performances of the substrate, such as hardness, thermal conductivity, and electrical conductivity. The filler may be of one type or of two or more types, and examples of the filler include carbon black, ketjen black, nanocarbon, and graphite.

[0076] In the present invention, if the filler content in the substrate is too high, the toughness of the substrate may decrease, resulting in poor fixability and separability of the belt member. Also, if the filler content is too low, the desired effects of the filler, such as imparting appropriate conductivity, may be insufficient. From this perspective, the filler content in the substrate is preferably 3% by mass or more, more preferably 4% by mass or more, and even more preferably 5% by mass or more. From the above perspective, the upper limit of the filler content in the substrate is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0077] (elastic layer) The elastic layer constituting the belt member according to the present invention is a layer having elasticity that contributes to improving contact between the surface of the belt member at the nip portion and a recording medium bearing an unfixed toner image. The elastic layer is made of, for example, an elastic material. An example of an elastic material applicable to the present invention is an elastic resin material, which may be the same as the elastic resin material used for the rubber layer of the roller member described above, and is particularly preferably silicone rubber.

[0078] The thickness of the elastic layer is preferably within a range of 5 to 500 μm, more preferably within a range of 50 to 400 μm, from the viewpoint of sufficiently exhibiting heat conductivity and elasticity.

[0079] The elastic layer, like the rubber layer of the roller member, may further contain components other than the elastic resin material, for example, a heat-conductive filler.

[0080] The content of the elastic resin material in the elastic material constituting the elastic layer is preferably within a range of 60 to 100% by volume of the total volume of the elastic layer, from the viewpoint of achieving both thermal conductivity and elasticity, more preferably 75 to 100% by volume, and even more preferably 80 to 100% by volume of the total volume of the elastic layer.

[0081] (Thermoplastic resin layer: outermost layer) In the thermoplastic resin layer constituting the outermost layer of the belt member according to the present invention (hereinafter simply referred to as the outermost layer), one of the thermoplastic resins is preferably a fluorine-based resin.

[0082] (thermoplastic resin) In the present invention, the thermoplastic resin constituting the outermost layer of the belt member is not particularly limited as long as it has the necessary heat resistance and releasability. Examples of the thermoplastic resin include vinyl thermoplastic resins (e.g., polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, etc.), polystyrene thermoplastic resins (e.g., polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer (ABS), polyethylene, ethylene-vinyl acetate copolymer, etc.), polypropylene, polyacetal, acrylic thermoplastic resins (e.g., polymethyl methacrylate, methacrylic-styrene copolymer, etc.), polycarbonate, polyamide thermoplastic resins, polyurethane thermoplastic resins, and fluorine-based thermoplastic resins (e.g., trifluorochloroethylene (PCTFE), tetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), perfluoroalkoxy fluorine-based resins (PFA), perfluoropolyether compounds (PFPE), etc.).

[0083] As for the heat resistance required for the thermoplastic resin, from the viewpoint of low temperature fixation of the toner, a fluorine-based resin is particularly preferred since high releasability is required at temperatures of about 150° C. or more continuously.

[0084] (2) Second embodiment FIG. 2 is a schematic side view of a fixing device according to a second embodiment of the present invention. 2 includes a heating roller 31, an upper pressure roller 32, a lower pressure roller 33, and an endless belt member 34, similar to the fixing device 30 shown in FIG.

[0085] The fixing device 30A further includes an auxiliary roller 38 that changes the position of the belt member 34. The auxiliary roller 38 is disposed near the upper pressure roller 32. Depending on the position of the auxiliary roller 38, the width of the fixing nip 36 can be changed without changing the tension of the belt member 34. The auxiliary roller 38 also has a base whose main component is aluminum, similar to the heating roller 31, and the base may contain more than 0.60% by mass of silicon. Furthermore, a resin coating layer or a rubber layer may be provided on the surface of the base.

[0086] (3) Third embodiment FIG. 3 is a schematic side view of a fixing device according to a third embodiment of the present invention. 1, the fixing device 30B shown in FIG. 3 includes a heating roller 31, an upper pressure roller 32, a lower pressure roller 33, and an endless belt member .

[0087] The fixing device 30B further includes two tension rollers 39a and 39b that stretch the belt member , and a second heating roller 31a that is disposed outside the belt member . The second heating roller 31a is disposed so as to be rotatable and press against the outer circumferential surface of the belt member , and heats the outer circumferential surface of the belt member .

[0088] The two tension rollers 39a, 39b and the second heating roller 31a also have a substrate mainly composed of aluminum, similar to the heating roller 31, and the substrate may contain more than 0.60 mass% of silicon. Furthermore, a resin coating layer or a rubber layer may be provided on the surface of the substrate.

[0089] (4) Fourth embodiment 4A and 4B are schematic side views of a fixing device according to a fourth embodiment of the present invention. The fixing device 40 shown in FIGS. 4A and 4B includes a lower pressure roller 33, a fixing pad 4, and a belt member .

[0090] The lower pressure roller 33 is the same as the lower pressure roller 33 of the fixing device 30 shown in FIG. 1, and the belt member 34 is the same as the belt member 34 of the fixing device 30 shown in FIG.

[0091] A lower pressure roller 33 is provided on the outside of the belt member 34 so that a fixing nip 36 is formed across the belt member 34, and a fixing pad 4 is provided on the inside of the belt member 34 facing the lower pressure roller 33. In other words, the fixing nip 36 is formed by the portion of the belt member 34 that is pressed by the fixing pad 4 and the lower pressure roller 33. The fixing pad 4 presses the belt member 34 toward the fixing nip 36. By providing the fixing pad 4 instead of the upper pressure roller 31 of the fixing device 30 shown in FIG. 1, the fixing nip 36 can be made wider. As a result, heating is sufficient, resulting in good fixability.

[0092] The fixing pad 4 has a pad member 4a that contacts the inside of the belt member 34, and a pad base material 4b that supports the pad member 4a from behind. The pad member 4a is plate-shaped. The pad member 4a is preferably constructed by stacking an insulating layer (low thermal conductivity layer) 4c made of a highly insulating material and a heat transfer layer (high thermal conductivity layer) 4d having better thermal conductivity than the insulating layer. The heat insulating layer 4c can be made of a material with relatively low thermal conductivity. Examples of materials with low thermal conductivity include low-thermal-conductivity silicone rubber, PPS (polyphenylene sulfide), LCP (liquid crystal polymer), PET (polyethylene terephthalate), and other heat-resistant resin materials. A porous material with a particularly low heat capacity is advantageous for shortening the warm-up time. The heat transfer layer 4d is preferably made of a material with relatively high thermal conductivity, such as metals such as aluminum (Al), copper (Cu), and iron (Fe), or a graphite sheet. The thermal conductivity of the heat insulating layer 4c is preferably 1.0 W / m·K or less, and the thermal conductivity of the heat transfer layer 4d is preferably 50 W / m·K or more.

[0093] In this embodiment, it is preferable to provide a switching mechanism for switching the surfaces of the heat insulating layer 4c and the heat conducting layer 4d of the pad member 4a that come into contact with the belt member .

[0094] FIG. 5 is a perspective view of the switching mechanism. 5, the switching mechanism 10 has an actuator 12 formed by connecting a drive shaft 11 to the pad member 4a. The axis of the drive shaft 11 extends in the direction perpendicular to the paper plane of FIGS. 4A and 4B. The actuator 12 is fixed to the frame of the image forming apparatus and drives the drive shaft 11 in the direction of arrow A to insert or remove the pad member 4a, and rotates the drive shaft 11 in the direction of arrow B to rotate the pad member 4a in the reverse direction. The pad substrate 4b is made of a metal such as Al, Fe, or stainless steel.

[0095] Here, during the warm-up operation shown in Figure 4B, it is preferable that the surface of the heat insulating layer 4c of the pad member 4a be in the first position (a position where the surface of the low thermal conductive layer is inscribed in the belt member 34) facing the lower pressure roller 33 with the belt member 34 sandwiched therebetween. At this time, the heat insulating layer 4c is in contact with the belt member 34, but the heat transfer layer 4d is not in contact with it. This suppresses the transfer of heat from the belt member 34 to the pad member 4a, shortening the warm-up time, thereby shortening the start-up time and achieving energy savings.

[0096] In contrast, during the printing operation shown in Figure 4A, it is preferable that the surface of the heat transfer layer 4d of the pad member 4a be in the second position (a position where the surface of the high heat transfer layer is inscribed in the belt member) facing the lower pressure roller 33 with the belt member 34 sandwiched therebetween. At this time, the heat transfer layer 4d is in contact with the belt member 34, but the heat insulating layer 4c is not in contact with it. Therefore, when small-sized sheets are continuously fed, which requires suppressing temperature unevenness in the width direction of the sheet, heat is smoothly transferred from the belt member 34 to the pad member 4a, and temperature rise in the non-passing portions can be effectively suppressed, thereby suppressing printing unevenness and forming high-quality images. In other words, it is possible to achieve both the conflicting goals of suppressing heat transfer to the pad member 4a during warm-up and maintaining heat conduction in the paper feed width direction during printing. Although the belt member 34 does not contact the heat transfer layer 4d at the first position and does not contact the heat insulating layer 4c at the second position, it may be arranged so that only a small area of ​​contact is made between them so as not to affect heat transfer.

[0097] (5) Other FIG. 6 is a cross-sectional view of the main parts of the fixing device 30 and the non-contact heating unit 160 according to the first embodiment. In FIG. 6, a non-contact heating section 160 for fixing the toner image T on the paper before the toner image T on the paper is fixed by the fixing device 30 is provided upstream of the fixing device 30 in the conveying direction. 6 has the same configuration as the fixing device 30 shown in FIG. 1, so its description will be omitted and only the non-contact heating section 160 will be described here.

[0098] The non-contact heating unit 160 includes a non-contact heater 161, a heat insulating cover 162, and a paper transport means. The non-contact heater 161 heats the image surface of the paper without contacting it. Heat insulating cover 162 covers the non-contact heater 161 except for the image surface side. The paper transport means is disposed vertically below the paper path of non-contact heater 161. The non-contact heater 161 is disposed inside a heat insulating cover 162, and the surface temperature is controlled to a desired temperature by a control means (not shown).

[0099] Considering the differences in light absorption between the black, yellow, magenta, and cyan toners and non-image areas, it is preferable that the non-contact heater 161 has a long wavelength. Furthermore, taking into consideration the balance with energy density, a ceramic heater or a halogen heater is suitable for the non-contact heater 161. A light-collecting reflector 63 is provided above the non-contact heater 161 to increase heating efficiency. The reflector 163 may be made of aluminum or the like that has been processed to a mirror finish.

[0100] A highly insulating and heat-resistant material such as ceramic fiber may be used for the insulating cover 162 used to maintain a high temperature around the non-contact heater 161. Furthermore, to improve the volatilization efficiency of the carrier liquid, it is necessary to lower the saturated vapor pressure of the volatilized carrier liquid. For this purpose, an airflow means (not shown) may be provided directly below the non-contact heater 161 to ventilate the volatilized carrier liquid (vapor) from the periphery of the non-contact heater 161 to the outside.

[0101] In this embodiment, the paper transport means is a suction belt 165. The suction belt 165 is arranged vertically below the paper path as seen from the non-contact heater 161, and has suction holes made of a highly heat-resistant rubber material such as silicone rubber. The suction belt 165 is wound around a drive roller 166 and a driven roller 167. The drive roller 166 is driven to rotate at a predetermined peripheral speed in the clockwise direction in FIG. 6 by a drive mechanism (not shown).

[0102] The driving roller 166 and the driven roller 167 may be metal rollers made of aluminum or the like, and their positional relationship with respect to the paper transport direction may be reversed. A suction fan 168 is disposed inside the suction belt 165 (between the drive roller 166 and the driven roller 167), and sucks the paper being conveyed.

[0103] In the non-contact heating unit 160, the toner image T and the paper are heated mainly by radiation from the non-contact heater 161. After passing through the non-contact heating section 160 , the toner image T on the paper reaches the fixing device 30 .

[0104] [Image forming equipment] The "image forming system" of the present invention refers to an assembly that is composed of devices or apparatuses having predetermined functions as means elements required for each step of image formation, toner for developing electrostatic images, etc., and that performs the function of image formation as a whole. Note that each means element may be individually located in different locations, or may be gathered together in a certain space as a single device and integrated into a system device.

[0105] The image forming system of the present invention is a system that forms an image using the fixing device described above and a toner for developing an electrostatic image, which will be described later. In the following description, for the sake of convenience, the device section having the image forming section and the fixing device, etc., which will be described later, will be referred to as the "electrophotographic image forming apparatus." A typical electrophotographic image forming apparatus that can be used in the present invention will be described below. Note that the electrophotographic image forming apparatus is also simply referred to as an "image forming apparatus."

[0106] FIG. 7 is a schematic diagram showing an example of the overall configuration of an image forming apparatus applicable to the present invention. The image forming apparatus according to this embodiment has the fixing device for fixing an unfixed toner image formed on a recording medium by an electrophotographic method to the recording medium by applying heat and pressure. The image forming apparatus may be configured in the same manner as a known image forming apparatus, except that the fixing device described above is employed. An example of the image forming apparatus according to this embodiment will be described below with reference to FIG.

[0107] As shown in FIG. 7, the image forming apparatus 50 includes an image forming unit, an intermediate transfer unit, a fixing device 30, an image reading unit, and a recording medium conveying unit. The image forming section includes, for example, four image forming units corresponding to the colors yellow, magenta, cyan, and black. As shown in FIG. 7, the image forming unit includes a photosensitive drum 51, a charging device 52 that charges the photosensitive drum 51, an exposure device 53 that irradiates the charged photosensitive drum 51 with light to form an electrostatic latent image, a developing device 54 that supplies toner to the photosensitive drum 51 on which the electrostatic latent image has been formed to form a toner image corresponding to the electrostatic latent image, and a cleaning device 55 that removes residual toner from the photosensitive drum 51.

[0108] The photosensitive drum 51 is, for example, a negatively charged organic photosensitive member having photoconductivity. The charging device 52 is, for example, a corona charger. The charging device 52 may be a contact charging device that charges the photosensitive drum 51 by bringing a contact charging member such as a charging roller, a charging brush, or a charging blade into contact with the photosensitive drum 51. The exposure device 53 is composed of, for example, a semiconductor laser. The developing device 54 is, for example, a known developing device used in an electrophotographic image forming apparatus.

[0109] The intermediate transfer section includes a primary transfer unit and a secondary transfer unit. The primary transfer unit includes an intermediate transfer belt 61 , a primary transfer roller 62 , a backup roller 63 , a plurality of support rollers 64 , and a cleaning device 65 . The intermediate transfer belt 61 is an endless belt. The intermediate transfer belt 61 is stretched in a loop shape by a backup roller 63 and a support roller 64 . At least one of the backup roller 63 and the support roller 64 is driven to rotate, so that the intermediate transfer belt 61 runs in one direction on an endless track at a constant speed.

[0110] The secondary transfer unit includes a secondary transfer belt 66 , a secondary transfer roller 67 , and a plurality of support rollers 68 . The secondary transfer belt 66 is also an endless belt. The secondary transfer belt 66 is stretched in a loop shape by a secondary transfer roller 67 and a support roller 68 .

[0111] The fixing device 30 may be, for example, the fixing device 30 shown in FIG. 1, but other fixing devices such as the fixing devices 30A, 30B, 40, etc. may also be used. The paper S corresponds to a recording medium.

[0112] The image reading section includes a paper feeder 81, a scanner 82, a CCD sensor 83, and an image processing section 84. The recording medium transport section has three paper feed tray units 91 and a plurality of registration roller pairs 92 . The paper feed tray unit 91 accommodates paper sheets S (standard paper, special paper) identified based on basis weight, size, etc., according to preset types. The pair of registration rollers 92 are arranged to form a desired transport path. The image forming system 500 is a system that forms an image using a fixing device 30 and toner for developing an electrostatic image, which will be described later.

[0113] [Image forming method] The image forming method according to the present embodiment includes a step of fixing an unfixed toner image formed on a recording medium by electrophotography to the recording medium by applying heat and pressure using the fixing device described above. The image forming method can be performed by the image forming apparatus 50 described above. As an example of the image forming method, the formation of an image by the image forming apparatus 50 will be described below.

[0114] The scanner 82 optically scans and reads the document D on the contact glass sent from the paper feeder 81 . The light reflected from the document D is read by the CCD sensor 83 and becomes input image data. The input image data is subjected to predetermined image processing in the image processing unit 84 and sent to the exposure device 53 .

[0115] On the other hand, the photosensitive drum 51 rotates at a constant peripheral speed corresponding to a printing speed of 60 sheets per minute or more on an A4 size recording medium.

[0116] The charging device 52 uniformly charges the surface of the photosensitive drum 51 to a negative polarity. The exposure device 53 irradiates the photosensitive drum 51 with laser light corresponding to the input image data of each color component. In this way, an electrostatic latent image is formed on the surface of the photosensitive drum 51. The developing device 54 makes the electrostatic latent image visible by attaching toner to the surface of the photosensitive drum 51. In this way, a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 51 . The toner image on the surface of the photosensitive drum 51 is transferred to an intermediate transfer belt 61 . Residual toner remaining on the photosensitive drum 51 after transfer is removed by a cleaning device 55 . The toner images of the respective colors formed on the respective photosensitive drums 51 are transferred onto the intermediate transfer belt 61 in order to be superimposed on one another.

[0117] On the other hand, the secondary transfer roller 67 presses the secondary transfer belt 66 toward the backup roller 63 and brings it into pressure contact with the intermediate transfer belt 61 . This forms a secondary transfer nip. On the other hand, a sheet S is transported from a sheet feed tray unit 91 to the secondary transfer nip portion via a pair of registration rollers 92 . The pair of registration rollers 92 corrects the inclination of the sheet S and adjusts the timing of conveyance.

[0118] When the paper S is transported to the secondary transfer nip, a transfer voltage is applied to the secondary transfer roller 67, and the toner image on the intermediate transfer belt 61 is transferred onto the paper S. The paper S onto which the toner image has been transferred is transported to a fixing device 70 by a secondary transfer belt 66 . Residual toner remaining on the intermediate transfer belt 61 after transfer is removed by a cleaning device 65 .

[0119] In the fixing device 30, the belt member 34 rotates at a constant speed corresponding to a printing speed of 60 sheets per minute or more for A4 size recording media. When the paper S is transported, as described above, the lower pressure roller 33 forms a fixing nip 36 with the belt member 34. The paper S is heated and pressurized in the fixing nip 36, and then guided and discharged toward the outside of the image forming apparatus 50. In this manner, a toner image is formed on the paper S, and the paper S is discharged outside the apparatus.

[0120] [Electrostatic image developing toner] Next, the toner used in the image forming system of the present invention will be described. As described above, the toner according to the present invention has a standard deviation of the shape factor of the toner base particles of 0.045 or less, and a coefficient of variation of the volume average particle diameter of the toner base particles of 28.0% or less. The methods for calculating the standard deviation of the shape factor of the toner base particles and the coefficient of variation of the volume average particle diameter are as described above.

[0121] The toner according to the present invention includes toner particles comprising toner base particles and an external additive that is externally added to the toner base particles. It is also preferable that the toner base particles contain crystalline resin in the binder resin in the range of 5.0 to 20% by mass. Furthermore, it is preferable to add strontium titanate particles having a number-average particle size in the range of 10 to 60 nm as an external additive to the toner base particles, in that abrasive power can be effectively exerted.

[0122] <Toner base particles> The toner base particles contain a binder resin. The binder resin is a resin that functions to bind toner particles to a recording medium. The toner base particles according to the present invention preferably contain an amorphous resin and a crystalline resin as a binder resin. The binder resin may be composed of only an amorphous resin, but it is preferable that the binder resin contains a crystalline resin in an amount of 5.0 to 20% by mass.

[0123] <Amorphous resin> The amorphous resin preferably contains a vinyl resin, a urethane resin, a urea resin, or the like. In the present invention, the amorphous resin is particularly preferably a vinyl resin. This is because the vinyl resin has a main chain composed of a carbon chain and therefore is less compatible with the crystalline polyester resin, which is preferably used as the crystalline resin described below, and the compatibility between the amorphous resin and the crystalline resin can be further suppressed.

[0124] In the present invention, an amorphous resin is a resin that does not have a melting point and has a relatively high glass transition temperature (Tg) when differential scanning calorimetry (DSC) is performed on the resin.

[0125] In DSC measurement, when the glass transition temperature during the first temperature rise is defined as Tg1 and the glass transition temperature during the second temperature rise is defined as Tg2, the Tg1 of the amorphous resin is preferably 35 to 80°C. The Tg1 is particularly preferably 45 to 65°C. The Tg2 of the amorphous resin is preferably 20 to 70°C, particularly preferably 30 to 55°C.

[0126] (vinyl resin) The vinyl resin is a resin obtained by polymerization using at least a vinyl monomer.

[0127] Specific examples of amorphous vinyl resins include acrylic resins and styrene-acrylic resins, etc. Among these, styrene-acrylic resins formed using styrene monomers and (meth)acrylic acid ester monomers are preferred as amorphous vinyl resins. Specific examples of styrene monomers and (meth)acrylic acid ester monomers that can be used to form styrene-acrylic resins are shown below, but the styrene-acrylic resins that can be used in the present invention are not limited to those shown below.

[0128] (1) Styrene-based monomers Examples of styrene-based monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, and derivatives thereof. These styrene-based monomers can be used alone or in combination of two or more.

[0129] (2) (Meth)acrylic acid ester monomers Examples of the (meth)acrylic acid ester monomer include acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, and phenyl acrylate; and methacrylic acid esters such as 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, and dimethylaminoethyl methacrylate.

[0130] The content of the styrene-acrylic resin is preferably 70% by mass or more of the total amount of the binder resin, which is sufficient to achieve the effect of improving the chargeability.

[0131] In addition to the above, a third polymerizable monomer can also be used as the polymerizable monomer. Examples of the third polymerizable monomer include acid monomers such as acrylic acid, methacrylic acid, maleic anhydride, and vinylacetic acid. Examples of the third polymerizable monomer include acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene vinyl chloride, N-vinylpyrrolidone, and butadiene. The third polymerizable monomer may further be a polyfunctional vinyl monomer, such as diacrylates of ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, etc., and dimethacrylates and trimethacrylates of tertiary or higher alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane.

[0132] (Method of manufacturing styrene-acrylic resin) Styrene-acrylic resins are preferably produced by emulsion polymerization. Emulsion polymerization can be achieved by dispersing and polymerizing polymerizable monomers such as styrene and acrylic esters in an aqueous medium, as described below. A surfactant is preferably used to disperse the polymerizable monomers in the aqueous medium, and known polymerization initiators and chain transfer agents can be used for polymerization.

[0133] (Polymerization initiator) As the polymerization initiator, various known polymerization initiators can be suitably used. Specific examples of the polymerization initiator include hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, di-t-butyl peroxide, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, triphenylacetic acid tert-hydroperoxide, and performic acid tert-butyl peroxide. peroxides such as tert-butyl peracetate, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl permethoxyacetate, and tert-butyl per-N-(3-toluyl)palmitate; and azo compounds such as 2,2'-azobis(2-aminodipropane) hydrochloride, 2,2'-azobis(2-aminodipropane) nitrate, 1,1'-azobis(1-methylbutyronitrile-3-sodium sulfonate), 4,4'-azobis-4-cyanovaleric acid, and poly(tetraethylene glycol-2,2'-azobisisobutyrate).

[0134] (chain transfer agent) The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as octyl mercaptan, dodecyl mercaptan, alkyl mercaptan, and t-dodecyl mercaptan. Also usable as the chain transfer agent are mercaptopropionic acids such as n-octyl-3-mercaptopropionate and stearyl-3-mercaptopropionate, mercapto fatty acid esters, and styrene dimers. These can be used alone or in combination of two or more.

[0135] The molecular weight of the amorphous resin measured by gel permeation chromatography (GPC) is preferably in the range of weight average molecular weight (Mw) of 10,000 to 100,000. In the present invention, the molecular weight of the amorphous resin measured by GPC is a value measured as follows. The measurement sample (amorphous resin) was dissolved in tetrahydrofuran at room temperature for 5 minutes using an ultrasonic disperser to a concentration of 1 mg / mL. The solution was then filtered through a 0.2 μm pore membrane filter to obtain a sample solution. A Tosoh HLC-8120GPC system and a Tosoh TSKguard column with a triple column TSKgel Super HZM-M column were used. The column temperature was maintained at 40°C, and tetrahydrofuran (THF) was used as the carrier solvent at a flow rate of 0.2 mL / min. 10 μL of the sample solution prepared above was injected into the system along with the carrier solvent. The measurement sample was then detected using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample was calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrene samples were used for the calibration curve measurement.

[0136] Furthermore, when a hybrid crystalline polyester resin described below is contained as the crystalline resin, it is preferable that the amorphous resin contained is the same type of resin as the amorphous resin used in the hybrid crystalline polyester resin.

[0137] Here, "same type of resin" means that the repeating units contain common characteristic chemical bonds. Here, "characteristic chemical bonds" are in accordance with the "polymer classification" listed in the Materials Database of the National Institute for Materials Science (NIMS). The substance and materials database is available at http: / / polymer.nims.go.jp / PoLyInfo / guide / jp / term_polymer.html.

[0138] That is, the chemical bonds that make up polymers classified into a total of 22 types, including polyacrylic, polyamide, polyanhydride, polycarbonate, polydiene, polyester, polyhaloolefin, polyimide, polyimine, polyketone, polyolefin, polyether, polyphenylene, polyphosphazene, polysiloxane, polystyrene, polysulfide, polysulfone, polyurethane, polyurea, polyvinyl, and other polymers, are called "characteristic chemical bonds." Furthermore, when the resin is a copolymer, "same type of resin" refers to resins that share a characteristic chemical bond when the monomer species having the above-mentioned chemical bond are used as constituent units in the chemical structures of the multiple monomer species that make up the copolymer. Therefore, even if the properties exhibited by the resins themselves are different from each other or the molar component ratios of the monomer species that make up the copolymer are different from each other, they are considered to be the same type of resin as long as they share the characteristic chemical bond.

[0139] For example, a resin (or resin segment) formed from styrene, butyl acrylate, and acrylic acid and a resin (or resin segment) formed from styrene, butyl acrylate, and methacrylic acid have at least a chemical bond constituting polyacrylic, and therefore, they are the same type of resin. Further, for example, a resin (or resin segment) formed from styrene, butyl acrylate, and acrylic acid and a resin (or resin segment) formed from styrene, butyl acrylate, acrylic acid, terephthalic acid, and fumaric acid have at least a chemical bond constituting polyacrylic as a mutually shared chemical bond. Therefore, they are the same type of resin.

[0140] <Crystalline resin> The crystalline resin according to the present invention preferably contains a hybrid crystalline polyester resin in which a crystalline polyester resin and an amorphous resin are chemically bonded.

[0141] When the toner of the present invention contains a hybrid crystalline polyester resin, the hybrid crystalline polyester resin is preferably contained in the toner base particles in an amount of 5 to 30% by mass, and more preferably in an amount of 10 to 20% by mass. When the toner base particles contain 30% by mass or less of the hybrid crystalline polyester resin, the presence of polyester resin whose crystals cannot fully grow can be avoided, allowing the crystals to grow sufficiently during fixing. On the other hand, if the toner base particles contain 5% by mass or more of the hybrid crystalline polyester resin, a sufficient amount of the hybrid crystalline polyester resin necessary for crystallization can be secured, and as a result, the crystals can grow sufficiently during fixing.

[0142] The crystalline resin is a resin that exhibits a clear endothermic peak rather than a stepwise endothermic change in differential scanning calorimetry (DSC). Specifically, the clear endothermic peak means a peak whose half-width is within 15°C when measured at a heating rate of 10°C / min in differential scanning calorimetry (DSC).

[0143] <Crystalline polyester resin> The crystalline polyester resin is a crystalline resin obtained by a polycondensation reaction between a divalent or higher carboxylic acid (a polycarboxylic acid compound) and a divalent or higher alcohol (a polyhydric alcohol compound).

[0144] The polycarboxylic acid compound is a compound having two or more carboxy groups in one molecule, and alkyl esters, acid anhydrides and acid chlorides of the polycarboxylic acid compound can be used. Examples of polycarboxylic acid compounds include oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, and p-carboxyphenylacetic acid. , p-phenylene diacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, dodecenyl succinic acid, and other dicarboxylic acids; and trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid, naphthalene tricarboxylic acid, naphthalene tetracarboxylic acid, pyrene tricarboxylic acid, and pyrene tetracarboxylic acid.

[0145] A polyhydric alcohol compound is a compound having two or more hydroxy groups in one molecule. Examples of polyhydric alcohol compounds include dihydric alcohols such as ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, an ethylene oxide adduct of bisphenol A, and a propylene oxide adduct of bisphenol A; and trihydric or higher polyols such as glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and tetraethylolbenzoguanamine.

[0146] As a catalyst for synthesizing the crystalline polyester resin, various known catalysts can be used, such as an esterification catalyst. Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamine. The esterification promoter may, for example, be gallic acid. The amount of the esterification catalyst used is preferably 0.01 to 1.5 parts by mass, more preferably 0.1 to 1.0 part by mass, per 100 parts by mass of the total amount of the polyhydric alcohol compound, polycarboxylic acid compound, and bireactive monomer component. The amount of the esterification promoter used is preferably 0.001 to 0.5 parts by mass, more preferably 0.01 to 0.1 parts by mass, per 100 parts by mass of the total amount of the polyhydric alcohol compound, polycarboxylic acid compound, and bireactive monomer component.

[0147] Examples of combinations of polycarboxylic acid compounds and polyhydric alcohol compounds for forming crystalline polyester resins that can be used in the present invention include 1,12-dodecanediol (having 12 carbon atoms) and sebacic acid (having 10 carbon atoms), ethylene glycol (having 2 carbon atoms) and sebacic acid (having 10 carbon atoms), 1,6-hexanediol (having 6 carbon atoms) and dodecanedioic acid (having 12 carbon atoms), 1,9-nonanediol (having 9 carbon atoms) and dodecanedioic acid (having 12 carbon atoms), and 1,6-hexanediol (having 6 carbon atoms) and sebacic acid (having 10 carbon atoms).

[0148] The melting point Tm of the crystalline polyester resin particles is preferably within a range of 65 to 90° C., more preferably within a range of 70 to 80° C. When the melting point Tm of the crystalline polyester resin particles is within a range of 65 to 90° C., the low-temperature fixability is not impaired and the heat-resistant storage stability is improved.

[0149] (Measuring method for melting point of crystalline polyester resin) The melting point of the crystalline polyester resin can be measured by a differential scanning calorimeter (DSC). For example, this can be done using a DSC-7 Differential Scanning Calorimeter (PerkinElmer) and a TAC7 / DX Thermal Analyzer Controller (PerkinElmer). Specifically, 4.50 mg of sample is sealed in an aluminum pan (KIT No. 0219-0041). This is placed in the sample holder of the DSC-7, and an empty aluminum pan is used for reference measurements. The measurement temperature is 0 to 200°C, with a heating rate of 10°C / min and a cooling rate of 10°C / min. Temperature control is performed using a heat-cool-heat cycle, and data is obtained from the second heat. The melting point is the temperature at the top of the endothermic peak. The method for measuring the melting point of the crystalline polyester resin can also be applied to measuring the melting point of crystalline resins other than the crystalline polyester resin.

[0150] <Hybrid crystalline polyester resin> A hybrid crystalline polyester resin is a resin formed by chemically bonding a crystalline polyester resin and an amorphous resin. In the following description, the portion derived from the crystalline polyester resin in the hybrid crystalline polyester resin is referred to as a "first resin segment," and the portion derived from the amorphous resin is referred to as a "second resin segment." The first resin segment and the second resin segment are preferably formed by chemical bonding via a bireactive monomer, and the first resin segment is composed of a crystalline polyester resin.

[0151] (First resin segment) The first resin segment constituting the hybrid resin is composed of a crystalline polyester resin produced by polycondensation of a polycarboxylic acid and a polyhydric alcohol in the presence of a catalyst, the specific types of which are as described above.

[0152] (Second resin segment) The second resin segment constituting the hybrid crystalline resin is composed of a resin obtained by polymerizing a monomer that forms the second resin. Here, the monomer that forms the second resin is not particularly limited as long as it is a monomer that forms an amorphous resin, and for example, known monomers such as the vinyl monomers described above that form vinyl resins can be used.

[0153] The content of the second resin segment relative to the hybrid crystalline polyester resin (hybrid ratio) is preferably within the range of 0.1 to 30% by mass. A more preferred range for this content is 0.5 to 10% by mass. If this content is 0.1% by mass or more, the effect of promoting crystallization is more easily achieved. Furthermore, if this content is 30% by mass or less, an increase in compatibility is suppressed, and similarly, the effect of promoting crystallization is more easily achieved. The hybrid ratio is the proportion of the second resin in the total amount of the first resin, the second resin, and the structure derived from the bireactive monomer in the hybrid crystalline polyester resin.

[0154] The "ambireactive monomer" is a monomer that bonds a segment of a first resin with a segment of a second resin. The ambireactive monomer is a monomer that has, in its molecule, both a group selected from a hydroxy group, a carboxy group, an epoxy group, a primary amino group, and a secondary amino group that forms a segment of the first resin, and an ethylenically unsaturated group that forms a segment of the second resin. The ambireactive monomer is preferably a monomer having a hydroxy group or a carboxy group and an ethylenically unsaturated group. It is more preferably a monomer having a carboxy group and an ethylenically unsaturated group. That is, it is preferably a vinyl-based carboxylic acid. Specific examples of the bireactive monomer include acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc., and may further include hydroxyalkyl (having 1 to 3 carbon atoms) esters of these. However, from the viewpoint of reactivity, acrylic acid, methacrylic acid, or fumaric acid is preferred as the bireactive monomer. The first resin segment and the second resin segment are bonded via this bireactive monomer. The amount of the bireactive monomer used is preferably 1 to 10 parts by mass, more preferably 4 to 8 parts by mass, per 100 parts by mass of the total amount of the monomers constituting the second resin segment. By setting the amount of the bireactive monomer used within the above range, the low-temperature fixability, high-temperature offset resistance, and durability of the toner are improved.

[0155] (Method for producing hybrid crystalline resin) The hybrid crystalline resin can be produced by any of the existing general schemes. The following three typical methods are available: (1) A method in which a segment of a first resin is polymerized in advance, and then a bireactive monomer is reacted with the segment of the first resin, followed by a monomer for forming a segment of a second resin (e.g., an aromatic vinyl monomer and a (meth)acrylic acid ester monomer) to form a hybrid crystalline resin. (2) A method in which a segment of a second resin is polymerized in advance, a bireactive monomer is reacted with the segment of the second resin, and a polycarboxylic acid and a polyhydric alcohol for forming a segment of a first resin are further reacted to form the segment of the first resin. (3) A method in which the first resin segment and the second resin segment are polymerized in advance, and then reacted with a bireactive monomer to bond the two together.

[0156] In the present invention, any of the above production methods can be used, but the method in item (2) above is preferred. Specifically, a polycarboxylic acid and a polyhydric alcohol that form the first resin segment are mixed with a monomer and a bireactive monomer that form the second resin segment. Next, a polymerization initiator is added to perform addition polymerization of the monomer that forms the second resin segment and the bireactive monomer to form the second resin segment. Thereafter, an esterification catalyst is preferably added to carry out a polycondensation reaction. Here, various conventionally known catalysts can be used as catalysts for synthesizing the first resin segment. Examples of esterification catalysts include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamine. Examples of esterification promoters include gallic acid (3,4,5-trihydroxybenzoic acid).

[0157] <Coloring agent> A colorant can be added to the toner of the present invention, and known colorants such as those shown below can be used as the colorant.

[0158] Examples of colorants contained in the yellow toner include CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162, and CI Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, and 185. These may be used alone or in combination of two or more. Among these, CI Pigment Yellow 74 is particularly preferred. The content of the colorant contained in the yellow toner is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the binder resin.

[0159] Examples of colorants contained in magenta toner include CI Solvent Red 1, 49, 52, 58, 63, 111, and 122, CI Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178, and 222. These may be used alone or in combination of two or more. Among these, CI Pigment Red 122 is particularly preferred. The content of the colorant contained in the magenta toner is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the binder resin.

[0160] An example of a colorant contained in a cyan toner is CI Pigment Blue 15:3. The content of the colorant contained in the cyan toner is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the binder resin.

[0161] Examples of colorants contained in black toner include carbon black, magnetic materials, and titanium black. Examples of carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. Examples of magnetic materials include ferromagnetic metals such as iron, nickel, and cobalt, alloys containing these ferromagnetic metals, ferromagnetic metal compounds such as ferrite and magnetite, and alloys that do not contain ferromagnetic metals but become ferromagnetic when heat treated. Examples of alloys that become ferromagnetic when heat treated include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, and chromium dioxide. The content of the colorant contained in the black toner is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the binder resin.

[0162] <Release agent> A release agent can be added to the toner base particles according to the present invention. As the release agent, various known waxes can be used. Examples of waxes include polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, long-chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, ester waxes such as behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, and distearyl maleate, and amide waxes such as ethylenediamine behenylamide and tristearyl trimellitate amide.

[0163] The content of the release agent is preferably 0.1 to 30 parts by mass, more preferably 1 to 10 parts by mass, relative to 100 parts by mass of the binder resin.

[0164] <Charge control agent> A charge control agent can be added to the toner base particles according to the present invention, if necessary.

[0165] The charge control agent is not particularly limited as long as it is a substance that can impart positive or negative charge by frictional charging, and various known positive charge control agents and negative charge control agents can be used. The content of the charge control agent is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the binder resin.

[0166] <External additives> The external additives function to control the fluidity and chargeability of the toner particles. The toner particles according to the present invention preferably contain strontium titanate particles as an external additive, in that they can effectively exert abrasive power. The strontium titanate particles preferably have a number average particle size within the range of 10 to 60 nm.

[0167] The number average particle diameter is measured as follows. After external additives are added (dispersed) to the toner base particles, 100 primary particles of the external additive are observed at 40,000x magnification using a scanning electron microscope "JSM-7401F" (manufactured by JEOL Ltd.). The longest and shortest diameters of each particle are measured by image analysis of the primary particles, and the median value is used to determine the spherical equivalent diameter. The average of the 100 measured primary particle diameters is then taken as the number-average primary particle diameter (number-average particle diameter).

[0168] The toner particles may contain only one kind of external additive, or may contain two or more kinds of external additives. Examples of the external additive other than the strontium titanate particles include silica particles, titania particles, alumina particles, zirconia particles, zinc oxide particles, chromium oxide particles, and cerium oxide particles, and examples of the external additive also include antimony oxide particles, tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles.

[0169] The surface of the external additive is preferably subjected to a hydrophobic treatment. A known surface treatment agent is used for the hydrophobic treatment. One type of surface treatment agent may be used alone, or two or more types may be used in combination. Examples of the surface treatment agent include silane coupling agents, silicone oils, titanate-based coupling agents, aluminate-based coupling agents, fatty acids, fatty acid metal salts, esters thereof, and rosin acids.

[0170] Examples of the silane coupling agent include dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, and decyltrimethoxysilane. Examples of the silicone oil include cyclic compounds, and linear or branched organosiloxanes. More specifically, silicone oils include organosiloxane oligomers, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, tetravinyltetramethylcyclotetrasiloxane, and the like.

[0171] Examples of the silicone oil include highly reactive silicone oils with modified groups at least at the end, such as those in the side chain, one end, both ends, one end of the side chain, or both ends of the side chain. The type of the modified group may be one or more. Examples of the modified group include alkoxy, carboxyl, carbinol, higher fatty acid modified, phenol, epoxy, (meth)acryloyl, and amino.

[0172] The content of the external additive is preferably 0.1 to 10.0% by mass, more preferably 1.0 to 3.0% by mass, based on the total amount of the toner particles.

[0173] [Toner manufacturing method] The method for producing the toner according to the present invention is not particularly limited, and known methods such as emulsion aggregation, pulverization, and suspension polymerization can be used. The method for producing the toner according to the present invention is not particularly limited, and examples thereof include known methods such as a kneading and pulverization method, a suspension polymerization method, an emulsion aggregation method, a solution suspension method, a polyester elongation method, and a dispersion polymerization method. Among these, the emulsion aggregation method is preferred from the viewpoints of uniformity of particle size and controllability of particle shape.

[0174] The toner of the present invention can be specifically produced by a production method including the following steps: However, this is merely an example, and the production method of the toner of the present invention is not limited to the following production method.

[0175] The emulsion aggregation method in toner production is a method in which a dispersion of binder resin particles (hereinafter also referred to as "binder resin particles") dispersed with a surfactant or a dispersion stabilizer is mixed with a dispersion of colorant particles (hereinafter also referred to as "colorant particles") as needed, and the particles are aggregated to a desired toner particle size, and the shape is controlled by fusing the binder resin particles together. The binder resin particles may optionally contain a release agent, a charge control agent, etc.

[0176] As a preferred method for producing a toner, an example of a case where toner particles having a core-shell structure are obtained by emulsion aggregation will be described below.

[0177] (1) A step of preparing a colorant particle dispersion in which colorant particles are dispersed in an aqueous medium. (2) A step of preparing a binder resin particle dispersion (for core particles / for shell layer) in which binder resin particles containing internal additives (releasing agents, charge control agents, etc.) as needed are dispersed in an aqueous medium. (3) A colorant particle dispersion and a binder resin particle dispersion for core particles are mixed to obtain a resin particle dispersion for aggregation. Thereafter, the colorant particles and the binder resin particles for core particles are aggregated and fused in the presence of an aggregating agent to form aggregated particles as core particles (aggregation and fusion process). (4) A process of adding a dispersion of binder resin particles for the shell layer containing binder resin particles for the shell layer to a dispersion of core particles, and aggregating and fusing the binder resin particles for the shell layer to the surface of the core particles to form toner base particles with a core-shell structure (aggregation and fusion process). (5) A process of cooling the toner base particles after the aggregation and fusion process (cooling process) (6) A process of filtering the toner base particles from the dispersion of the toner base particles (toner base particle dispersion) and removing surfactants and the like (filtration and washing process). (7) Step of drying the toner base particles (drying step) (8) If necessary, a step of mixing multiple types of toner base particles (classified products) having different coefficients of variation of shape coefficients and coefficients of variation of volume average particle diameter to obtain toner base particles having a desired shape coefficient and a desired coefficient of variation of volume average particle diameter. (9) A step of adding an external additive to the toner base particles (an external additive treatment step)

[0178] Toner particles having a core-shell structure are first prepared by aggregating and fusing binder resin particles for the core particles and colorant particles to form core particles. Next, binder resin particles for the shell layer are added to a dispersion of the core particles, and the binder resin particles for the shell layer are aggregated and fused to the surface of the core particles to form a shell layer that covers the surface of the core particles. However, toner particles formed from a single layer of particles can also be produced by the same method, for example, by not adding a dispersion of binder resin particles for the shell layer in step (4) above.

[0179] In the present invention, the term "aqueous medium" refers to a medium composed of 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. Preferably, the water-soluble organic solvent is an alcohol-based organic solvent that does not dissolve the resulting resin.

[0180] (1) A step of preparing a colorant particle dispersion in which colorant particles are dispersed in an aqueous medium. The colorant particle dispersion can be prepared by dispersing the colorant in an aqueous medium. From the viewpoint of uniform dispersion, the colorant dispersion treatment is preferably carried out in a state in which the surfactant concentration in the aqueous medium is equal to or higher than the critical micelle concentration (CMC). Various known dispersers can be used for dispersing the colorant.

[0181] (surfactant) Examples of surfactants include anionic surfactants such as alkyl sulfates, polyoxyethylene(n) alkyl ether sulfates, alkylbenzene sulfonates, α-olefin sulfonates, and phosphate esters; cationic surfactants such as alkylamine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, and imidazolines; and cationic surfactants such as quaternary ammonium salts, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, and benzethonium chloride; nonionic surfactants such as fatty acid amide derivatives and polyhydric alcohol derivatives; and amphoteric surfactants such as alanine, dodecyldi(aminoethyl)glycine, di(octylaminoethyl)glycine, and N-alkyl-N,N-dimethylammonium betaine. Also useful are anionic and cationic surfactants containing fluoroalkyl groups.

[0182] In this step, the dispersed diameter of the colorant particles in the prepared colorant particle dispersion is preferably in the range of 10 to 300 nm in volume median diameter. The volume median diameter of the colorant particles in the colorant particle dispersion can be measured using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.).

[0183] The colorant may be incorporated into the toner base particles by dissolving or dispersing it in advance in a monomer solution for forming the resin using a mini-emulsion method in the binder resin particle dispersion preparation step described below.

[0184] (2) A step of preparing a binder resin particle dispersion (for core particles / for shell layer) in which binder resin particles containing internal additives (releasing agents, charge control agents, etc.) as needed are dispersed in an aqueous medium. Examples of a method for dispersing a binder resin in an aqueous medium include an aqueous direct dispersion method in which the binder resin is dispersed in an aqueous medium to which a surfactant has been added by ultrasonic dispersion or bead mill dispersion. Examples of the dispersion method include a dissolution-emulsification-desolvation method and a phase inversion emulsification method in which a binder resin is dissolved in a solvent, and the resulting solution is dispersed in an aqueous medium to form emulsified particles (oil droplets), and then the solvent is removed.

[0185] In this step, the average particle size of the binder resin particles obtained is preferably, for example, in the range of 50 to 500 nm in terms of volume-based median diameter, which is measured using a Coulter Multisizer 3 (manufactured by Beckman Coulter, Inc.).

[0186] In this process, a treatment for emulsification (formation of droplets) by applying mechanical energy is essential. Examples of means for applying mechanical energy include means for applying strong stirring or ultrasonic vibration energy using a homomixer, ultrasonic wave, or Manton-Gaulin mixer.

[0187] In this step, the binder resin particles can be configured to have two or more layers made of resins with different compositions. In this case, a method can be used in which a polymerization initiator and a polymerizable monomer are added to a dispersion of resin particles prepared by a conventional emulsion polymerization treatment (first-stage polymerization), and this system is further polymerized (second-stage polymerization, third-stage polymerization).

[0188] When a surfactant is used, the same surfactants as those described above can be used.

[0189] (Polymerization initiator) The polymerization initiator is not particularly limited, and known initiators can be used, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, triphenylacetic acid-tert-hydroperoxide, and performic acid-tert peroxides such as tert-butyl peracetate, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl permethoxyacetate, and tert-butyl per-N-(3-toluyl)palmitate; and azo compounds such as 2,2'-azobis(2-amidinopropane) hydrochloride, 2,2'-azobis(2-amidinopropane) nitrate, 1,1'-azobis(1-methylbutyronitrile-3-sodium sulfonate), 4,4'-azobis-4-cyanovaleric acid, and poly(tetraethylene glycol-2,2'-azobisisobutyrate).

[0190] Among these, preferred examples of the water-soluble polymerization initiator include ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, 2,2'-azobis(2-amidinopropane) hydrochloride, and 2,2'-azobis(2-amidinopropane) nitrate. Furthermore, preferred examples of the water-soluble polymerization initiator include 1,1'-azobis(1-methylbutyronitrile-3-sodium sulfonate) and 4,4'-azobis-4-cyanovaleric acid.

[0191] As the polymerization initiator, redox polymerization initiators such as persulfate and metabisulfite, hydrogen peroxide and ascorbic acid, etc. may also be used. Furthermore, di-tert-butyl peroxide can also be used as the polymerization initiator.

[0192] (chain transfer agent) In this step, particularly when an amorphous vinyl resin is used as the binder resin, a commonly used chain transfer agent can be used to adjust the molecular weight of the resin. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.

[0193] (3) A step of mixing a colorant particle dispersion and a resin particle dispersion for core particles to obtain a resin particle dispersion for aggregation, and aggregating and fusing the colorant particles and binder resin particles in the presence of an aggregating agent to form aggregated particles as core particles (aggregation and fusion step).

[0194] This step is a step of aggregating and fusing the colorant particles and binder resin particles contained in each dispersion liquid formed in the above step in an aqueous medium. In this step, a binder resin particle dispersion liquid and a colorant particle dispersion liquid are added to an aqueous medium to which a surfactant has been added, and these particles are aggregated and fused. The surfactant used may be the same as the surfactant described above. The amount of surfactant added is preferably within a range of 1.0 to 5.0 parts by mass per 100 parts by mass of the resin (solid content).

[0195] As a specific method for aggregating and fusing the colorant particle dispersion and the binder resin particle dispersion, for example, an aggregating agent is added to the aqueous medium so that the concentration becomes equal to or higher than the critical aggregating concentration. Next, the mixture is heated to a temperature equal to or higher than the glass transition temperature of the binder resin particles and equal to or higher than the melting peak temperature of the release agent. This allows the salting out of the colorant particles and the binder resin particles to proceed while simultaneously fusion, and when the particles have grown to a desired particle size, an aggregation terminator is added to stop the particle growth. Furthermore, if necessary, heating may be continued to control the particle shape.

[0196] In this method, it is preferable to leave the mixture after adding the aggregating agent for as short a time as possible and quickly heat it to a temperature equal to or higher than the glass transition temperature of the binder resin. The reason for this is not clear, but it is because there is a concern that depending on the time left after salting out, the aggregation state of the particles may change, resulting in an unstable particle size distribution or changes in the surface properties of the fused particles. The time until this temperature rise is usually preferably within 30 minutes, and more preferably within 10 minutes.

[0197] The temperature rise rate is preferably 0.05 to 1° C. / min. Furthermore, after the reaction system reaches a temperature equal to or higher than the glass transition temperature, it is important to maintain the temperature of the reaction system for a certain period of time to continue the fusion process, thereby effectively promoting the growth and fusion of the toner base particles and improving the durability of the final toner.

[0198] (flocculant) The flocculant is not particularly limited, but is preferably a metal salt. Examples of the metal salt include monovalent metal salts such as salts of alkali metals such as sodium, potassium, and lithium; divalent metal salts such as calcium, magnesium, manganese, and copper; and trivalent metal salts such as iron and aluminum. Specific metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, and aluminum sulfate. Among these, it is more preferable to use a divalent metal salt because a small amount can promote flocculation and the flocculation property can be easily controlled. These may be used alone or in combination of two or more.

[0199] (4) A process of adding a dispersion of resin particles for the shell layer, which contains binder resin particles for the shell layer, to a dispersion of core particles, and aggregating and fusing the particles for the shell layer onto the surface of the core particles to form toner base particles with a core-shell structure (aggregation and fusion process). This step is similar to the step (3) of aggregating and fusing colorant particles and binder resin particles in the presence of an aggregating agent to form aggregated particles as core particles (aggregation and fusion step), in which particles for the shell layer are aggregated and fused to the surface of the core particles to form toner base particles with a core-shell structure.

[0200] (5) A process of cooling the toner base particles after the aggregation and fusion process (cooling process) In this step, the toner base particles are cooled at a temperature decreasing rate of 5 to 15° C. / min when the shape factor of the obtained toner base particles reaches a range of 0.940 to 0.973.

[0201] (6) A process of filtering the toner base particles from the toner base particle dispersion (toner base particle dispersion) and removing surfactants and the like (filtering and washing process) (7) Step of drying the toner base particles (drying step) The filtration, washing and drying steps can be carried out by known methods.

[0202] (8) If necessary, a step of mixing multiple types of toner base particles (classified products) having different coefficients of variation of shape coefficients and coefficients of variation of volume average particle diameter to obtain toner base particles having a desired shape coefficient and a desired coefficient of variation of volume average particle diameter. Specifically, multiple types of toner base particles having different standard deviations of volume average particle diameter and shape factor are prepared in advance, and then these multiple types of toner base particles are combined and mixed to adjust the coefficients of variation of the shape factor and the volume average particle diameter to satisfy the coefficients of variation specified in the present invention.

[0203] (9) A step of adding an external additive to the toner base particles (an external additive treatment step) This step is a step of adding and mixing an external additive to the toner base particles obtained above.

[0204] As described above, the external additive used is preferably strontium titanate particles, and the number average particle size of the strontium titanate particles is preferably within the range of 10 to 60 nm.

[0205] The external additive may be added by a dry method in which a powder external additive is added to and mixed with dried toner base particles. As the mixing device, a mechanical mixing device such as a Henschel mixer, a Nauta mixer, a Turbula mixer, or a coffee mill can be used.

[0206] In particular, it is preferable to use a mixing device capable of applying shear force to the particles to be processed, such as a Henschel mixer, and to increase the mixing time or the rotational peripheral speed of the stirring blades, which allows the external additive to adhere firmly to each toner base particle.

[0207] When a plurality of types of external additives are used, all of the external additives may be mixed with the toner base particles at once, or may be mixed in separate batches depending on the type of external additive.

[0208] [Developer] The toner according to the present invention can be suitably used as the following developer. For example, the toner may be used as a one-component magnetic toner by incorporating a magnetic substance, as a two-component developer by mixing with a carrier, or as a non-magnetic toner by itself. The toner according to the present invention can be suitably used in any of the above cases.

[0209] As the magnetic material, for example, magnetite, γ-hematite, or various ferrites can be used. As the carrier constituting the two-component developer, magnetic particles made of conventionally known materials such as metals such as iron, steel, nickel, cobalt, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. As the carrier, it is preferable to use a coated carrier in which the surface of magnetic particles is coated with a coating agent such as resin, or a so-called resin-dispersed carrier in which magnetic powder is dispersed in a binder resin.

[0210] The resin for coating is not particularly limited, but examples thereof include olefin resin, styrene resin, styrene-acrylic resin, silicone resin, polyester resin, and fluororesin. The resin for constituting the resin dispersion-type carrier is not particularly limited and may be any known resin, such as acrylic resin, styrene-acrylic resin, polyester resin, fluororesin, or phenolic resin.

[0211] The volume-based median diameter of the carrier is preferably within the range of 20 to 100 μm, and more preferably within the range of 25 to 60 μm. The volume-based median diameter of the carrier can be measured typically by a laser diffraction particle size distribution analyzer equipped with a wet disperser. An example of the laser diffraction particle size distribution analyzer is "HELOS" (manufactured by SYMPATEC). The amount of toner mixed with the carrier is preferably within the range of 2 to 10% by mass, with the total mass of the toner and carrier being 100% by mass. [Example]

[0212] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. In the following examples, unless otherwise specified, operations were carried out at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively.

[0213] [Manufacture of heating roller 1] (1) Preparation of aluminum alloy substrate A cylindrical substrate (outer diameter φ40 mm, length 360 mm) made of an aluminum alloy containing 0.61 mass % silicon was prepared. (2) Formation of resin coating layer A silicone resin (a mixture of addition reaction type silicone (product name: SD7333, manufactured by Dow Corning Toray Co., Ltd.) and catalyst (product name: SRX212, manufactured by Dow Corning Toray Co., Ltd.)) was applied to the surface of the substrate at a coating amount of 0.05 g / m.2 The resin coating layer was applied so as to have a thickness of 500 μm and then dried to obtain a heating roller 1.

[0214] [Manufacture of Heating Rollers 2 to 12, 14 and 16] Heating rollers 2 to 12, 14 and 16 were produced in the same manner as in the production of heating roller 1, except that the silicon content of the aluminum alloy substrate was changed as shown in Table I below.

[0215] [Manufacture of heating roller 13] (1) Preparation of aluminum alloy substrate A cylindrical substrate (outer diameter φ40 mm, length 360 mm) made of an aluminum alloy containing 2.90 mass % silicon was prepared. (2) Formation of elastic rubber layer (rubber layer) A cylindrical mold was placed over the aluminum alloy substrate, and the substrate and the cylindrical mold were held coaxially, forming a cavity between them. A silicone rubber material was then injected into the cavity and cured by heating to form a 200 μm-thick elastic silicone rubber layer.

[0216] [Manufacture of heating roller 15] A cylindrical substrate (outer diameter φ40 mm, length 360 mm) made of an aluminum alloy containing 2.90 mass % silicon was prepared. This was designated as heating roller 15.

[0217] [Manufacture of heating roller 17] Heating roller 17 was manufactured in the same manner as in manufacturing the heating roller 14, except that fluorinated acrylic Novec 2702 (solvent: Novec 7200) manufactured by 3M was used instead of the silicone resin. The thickness of the fluororesin coating layer was 500 μm.

[0218] [Manufacture of heating roller 18] (1) Preparation of aluminum alloy substrate A cylindrical substrate (outer diameter φ40 mm, length 360 mm) made of an aluminum alloy containing 2.90 mass % silicon was prepared. (2) Formation of resin coating layer A fluororesin (uncured) manufactured by Chemours was applied to the surface of the substrate by a known application method, and then the outer circumferential surface of the substrate was covered with the inner circumferential surface of a PFA tube manufactured by Mitsui-Chemours Products. Next, the PFA tube was heat-shrunk by heating to produce a heated roller 18 having a PFA tube layer on its surface. The thickness of the PFA tube layer was 500 μm.

[0219] [Manufacture of heating roller 19] (1) Preparation of aluminum alloy substrate A cylindrical substrate (outer diameter φ40 mm, length 360 mm) made of an aluminum alloy containing 2.90 mass % silicon was prepared. (2) Formation of a rubber elastic layer The aluminum alloy substrate was covered with a cylindrical mold that held a 30 μm-thick PFA tube, the inner surface of which was etched. The substrate and the cylindrical mold were held coaxially, and a gap was formed between them. Next, a silicone rubber material was injected into the gap as an elastic layer-forming material and cured by heating to form a 200 μm-thick silicone rubber elastic layer. In this way, a heating roller 19 was produced, which had an aluminum alloy substrate, an elastic silicone rubber layer, and a PFA tube layer in this order. A halogen heater was disposed inside the base of each of the heating rollers 1 to 19. During image formation, which will be described later, the heating temperature of the halogen heater was set to 160°C.

[0220] [Table 1]

[0221] [Configurations 1 to 6 of the fixing device] For the fixing device configurations 1 to 6, the position of the heating roller, the presence or absence of preheating, and the presence or absence of a fixing pad were as shown in Table II below. The position of the heating roller "inside the belt" refers to the case where the heating roller 31 is located inside the belt, as shown in Fig. 1. The position of the heating roller "outside the belt" refers to the case where the second heating roller 31a is located outside the belt, as shown in Fig. 3. Furthermore, "with pre-heating" refers to the case where a non-contact heating section 160 is provided upstream of fixing device 30 in the transport direction, as shown in FIG. 6. In this case, the heating temperature by non-contact heater 161 is set to 80 to 150°C. Furthermore, "with fixing pad" refers to the case where fixing pad 4 is provided, as shown in FIG. 4A. The fixing pad used is made of liquid crystal polymer resin with a fluororesin coating on its surface. The pressure roller and belt member, which are other components of the fixing device, were all the same in Configurations 1 to 6. Specifically, the pressure roller was a cylindrical tube made mainly of stainless steel covered with a PFA tube, and the belt member was a belt made of a polyimide substrate with silicone resin and PFA resin laminated on the surface.

[0222] [Table 2]

[0223] [Preparing Fusing Unit 1] In the configuration 1, the fixing device 1 was prepared by using the heating roller 14 manufactured as described above.

[0224] [Preparation of Fixing Units 2 and 17-20] Fixing devices 2 and 17 to 20 were prepared in the same manner as in preparation of fixing device 1, except that the configuration of the fixing device was as shown in Table III below.

[0225] [Preparation of fixing units 3 to 16 and 21 to 24] In preparing the fixing device 1, the heating rollers used were as shown in Table III below, thereby preparing fixing devices 3 to 16 and 21 to 24.

[0226] [Table 3]

[0227] [Toner manufacturing] <Preparation of Amorphous Polyester Resin Particle Dispersion 1> <Preparation of amorphous polyester resin 1> Bisphenol A ethylene oxide 2.2 mole adduct: 42 mole parts Bisphenol A propylene oxide 2.2 mole adduct: 58 mole parts Dimethyl terephthalate: 59 parts by mole Dimethyl fumarate: 15 parts by mole Dodecenyl succinic anhydride: 21 mole parts Trimellitic anhydride: 5 mole parts A reaction vessel equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet tube was prepared, and the monomers other than dimethyl fumarate and trimellitic anhydride among the above monomers and tin dioctylate were added in an amount of 0.25 parts by mass per 100 parts by mass of the total of the above monomers. After reacting for 6 hours at 235°C under a nitrogen gas flow, the temperature was lowered to 200°C, and dimethyl fumarate and trimellitic anhydride were added and reacted for 1 hour. The temperature was then raised to 220°C over 5 hours, and polymerization was carried out under a pressure of 10 kPa until the desired molecular weight was reached, yielding a pale yellow, transparent amorphous polyester resin 1. Amorphous polyester resin 1 had a weight average molecular weight of 34,500, a number average molecular weight of 7,800, and a glass transition temperature (Tg) of 55.5°C.

[0228] <Preparation of amorphous polyester resin particle dispersion 1> Next, 200 parts by mass of amorphous polyester resin 1, 95 parts by mass of methyl ethyl ketone, 40 parts by mass of isopropyl alcohol, and 7.5 parts by mass of 10% by mass aqueous ammonia solution were placed in a separable flask, and thoroughly mixed and dissolved. Thereafter, while heating and stirring at 40°C, ion-exchanged water was added dropwise at a rate of 8.3 g / min using a liquid-transfer pump, and the addition was stopped when the amount of liquid transferred reached 580 parts by mass. Thereafter, the solvent was removed under reduced pressure to obtain a dispersion of amorphous polyester resin particles. Ion-exchanged water was added to the dispersion to adjust the solid content to 25% by mass, thereby preparing amorphous polyester resin particle dispersion 1. The volume-based median diameter (d 50 ) was measured using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 148 nm.

[0229] <Preparation of Crystalline Resin Particle Dispersion 1> <Preparation of crystalline resin 1> Dodecanedioic acid: 41 mole parts 1,6-Hexanediol: 59 parts by mole A reaction vessel equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet tube was prepared, and the monomer was placed in the reaction vessel, and the atmosphere in the reaction vessel was replaced with dry nitrogen gas. Next, 0.23 parts by mass of titanium tetrabutoxide (Ti(On-Bu)4) was added per 100 parts by mass of the total of the above monomers. The mixture was stirred and reacted at 170°C for 3 hours under a nitrogen gas flow, and then the temperature was further raised to 210°C over 1 hour. The pressure inside the reaction vessel was then reduced to 3 kPa, and the mixture was stirred and reacted under reduced pressure for 13 hours to obtain Crystalline Resin 1. Crystalline Resin 1 had a weight-average molecular weight of 24,500, a number-average molecular weight of 8,300, and a melting point of 71.7°C.

[0230] <Preparation of Crystalline Resin Particle Dispersion 1> Next, 200 parts by mass of this crystalline resin 1, 115 parts by mass of methyl ethyl ketone, and 35 parts by mass of isopropyl alcohol were placed in a separable flask, and these were thoroughly mixed and dissolved at 60° C. Thereafter, 8 parts by mass of a 10% by mass aqueous ammonia solution was added dropwise. The heating temperature was lowered to 67°C, and ion-exchanged water was added dropwise at a rate of 8.5 g / min with stirring using a pump. When the amount of water added reached 580 parts by mass, the addition of ion-exchanged water was stopped. The solvent was then removed under reduced pressure to obtain a crystalline resin particle dispersion. Ion-exchanged water was added to the dispersion to adjust the solid content to 25% by mass, thereby preparing crystalline resin particle dispersion 1. The volume-based median diameter (d 50 ) was measured using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 189 nm.

[0231] <Preparation of Crystalline Resin Particle Dispersion 2> <Preparation of crystalline resin 2> The raw material monomers for the addition polymerization resin, the bireactive monomer, and the radical polymerization initiator listed below were placed in a dropping funnel. Styrene: 51 parts by mass Butyl acrylate: 13 parts by mass Acrylic acid: 6 parts by mass Di-tert-butyl peroxide: 5.5 parts by mass Also, 560 parts by mass of stearyl methacrylate was placed in a four-necked flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and heated to 170° C. to dissolve. Next, the raw material monomers for the addition polymerization resin were added dropwise over 90 minutes while stirring, and the mixture was aged for 60 minutes. After that, unreacted addition polymerization monomers were removed under reduced pressure (8 kPa) to obtain Crystalline Resin 2. The obtained Crystalline Resin 2 had a weight average molecular weight (Mw) of 22,000, a number average molecular weight of 7500, and a melting point of 76°C.

[0232] <Preparation of Crystalline Resin Particle Dispersion 2> Next, 200 parts by mass of this crystalline resin 2, 115 parts by mass of methyl ethyl ketone, and 35 parts by mass of isopropyl alcohol were placed in a separable flask, and these were thoroughly mixed and dissolved at 60° C. Thereafter, 8 parts by mass of a 10% by mass aqueous ammonia solution was added dropwise. The heating temperature was lowered to 67°C, and ion-exchanged water was added dropwise at a rate of 8 g / min using a pump while stirring. When the amount of water being fed reached 580 parts by mass, the addition of ion-exchanged water was stopped. Thereafter, the solvent was removed under reduced pressure to obtain a crystalline resin particle dispersion. Ion-exchanged water was added to the dispersion to adjust the solid content to 25% by mass, thereby preparing crystalline resin particle dispersion 2. The volume-based median diameter (d 50 ) was measured using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 191 nm.

[0233] <Preparation of Release Agent Particle Dispersion 1> Paraffin wax (Nippon Seiro FNP0090, melting temperature 89°C): 268 parts by weight Anionic surfactant (Neogen RK manufactured by Daiichi Kogyo Seiyaku): 15.5 parts by weight (60% active ingredient, 3% release agent) Ion-exchanged water: 21.6 parts by weight The above materials were mixed, and the release agent was dissolved in a pressure discharge homogenizer (Gaulin Homogenizer manufactured by Gaulin Co., Ltd.) at an internal liquid temperature of 120°C. The mixture was then subjected to dispersion treatment at a dispersion pressure of 5 MPa for 120 minutes, followed by 40 MPa for 360 minutes, and then cooled to obtain a dispersion. Ion-exchanged water was added to adjust the solid content to 20%, and this was designated release agent particle dispersion 1. The volume average particle diameter of the particles in release agent particle dispersion 1 was 205 nm.

[0234] <Preparation of Colorant Particle Dispersion> <Preparation of Black Colorant Particle Dispersion 1> Carbon black (Regal (registered trademark) 330, manufactured by Cabot Corporation): 100 parts by weight Anionic surfactant (Neogen SC manufactured by Daiichi Kogyo Seiyaku): 16 parts by weight Ion-exchanged water: 400 parts by weight The above components were mixed and pre-dispersed for 10 minutes using a homogenizer (ULTRA-TURRAX T50, manufactured by IKA). Then, a high-pressure impact disperser, Ultimizer (manufactured by Sugino Machine), was used to perform a dispersion treatment at a pressure of 245 MPa for 30 minutes, yielding an aqueous dispersion of black colorant particles. Ion-exchanged water was further added to the resulting dispersion to adjust the solid content to 15% by mass, thereby preparing Black Colorant Particle Dispersion 1. The volume-based median diameter (d 50 ) was measured using a Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 95 nm.

[0235] <Preparation of Toner Base Particles 1> <Agglomeration, fusion and aging processes> Amorphous polyester resin particle dispersion 1:1008 mass parts ·Crystalline resin particle dispersion 1:156 parts by mass Release agent particle dispersion 1:160 parts by weight Black colorant particle dispersion 1:187 mass parts Anionic surfactant (Dowfax2A1 20% aqueous solution): 40 parts by weight Ion-exchanged water: 1,500 parts by weight The above materials were placed in a 4-liter reaction vessel equipped with a thermometer, a pH meter and a stirrer, and the pH was adjusted to 3.0 by adding 1.0% nitric acid at 25°C. Thereafter, while dispersing at 3000 rpm using a homogenizer (ULTRA-TURRAX T50, manufactured by IKA), 100 parts by mass of a 2% aqueous solution of aluminum sulfate (flocculant) was added over 30 minutes. After the dropwise addition, the mixture was stirred for 10 minutes to thoroughly mix the raw materials and flocculant. A stirrer and mantle heater were then installed in the reactor. The temperature was increased at a rate of 0.2°C / min up to 40°C, and then at a rate of 0.05°C / min after reaching 40°C, while adjusting the stirrer's rotation speed to ensure thorough mixing. Particle size was measured every 10 minutes using a Coulter Multisizer 3 (aperture diameter 100 μm, Beckman Coulter). When the volumetric median diameter reached 5.7 μm, the temperature was maintained and the following premixed mixture was added over 20 minutes. Amorphous polyester resin particle dispersion 1:400 mass parts Anionic surfactant (Dowfax2A1 20% aqueous solution): 15 parts by weight Next, after maintaining the temperature at 50°C for 30 minutes, 9 parts by mass of a 20% EDTA (ethylenediaminetetraacetic acid) solution and a 1 mol / L aqueous sodium hydroxide solution were added to the reaction vessel, and the pH of the raw material dispersion was controlled to 9.0. Thereafter, the temperature was increased to 85°C at a rate of 1°C / min while adjusting the pH to 9.0 every 5°C, and the temperature was maintained at 85°C.

[0236] ≪Cooling process≫ Thereafter, using "FPIA-3000," the dispersion was cooled at a temperature decreasing rate of 10°C / min when the shape factor reached 0.963, and toner base particle dispersion 1 was obtained.

[0237] <Filtration, washing and drying processes> The toner base particle dispersion 1 was filtered and thoroughly washed with ion-exchanged water, and then dried at 40°C to obtain toner base particles 1. The obtained toner base particles 1 had a volume average particle diameter of 5.8 μm, a coefficient of variation of the volume average particle diameter of 21.9%, a shape factor of 0.963, and a standard deviation of the shape factor of 0.030.

[0238] <Preparation of Toner Base Particles A> Amorphous polyester resin particle dispersion 1:1008 mass parts ·Crystalline resin particle dispersion 1:156 parts by mass Release agent particle dispersion 1:160 parts by weight Black colorant particle dispersion 1:187 mass parts Anionic surfactant (Dowfax2A1 20% aqueous solution): 20 parts by weight Ion-exchanged water: 1,500 parts by weight The above materials were placed in a 4-liter reaction vessel equipped with a thermometer, pH meter, and stirrer, and 1.0% nitric acid was added at 25°C to adjust the pH to 2.5. Then, while dispersing at 2300 rpm using a homogenizer (ULTRA-TURRAX T50, manufactured by IKA), 150 parts by mass of a 2% aqueous aluminum sulfate (flocculant) solution was added over 30 minutes. After the dropwise addition, the mixture was stirred for 10 minutes to thoroughly mix the raw material and flocculant. A stirrer and mantle heater were then installed in the reactor. The temperature was increased at a rate of 0.2°C / min up to 45°C, and then at a rate of 0.05°C / min after reaching 45°C, while adjusting the stirrer rotation speed to ensure thorough mixing. Particle size was measured every 10 minutes using a Coulter Multisizer 3 (aperture diameter 100 μm, Beckman Coulter). When the volumetric median diameter reached 5.7 μm, the temperature was maintained and the following premixed mixture was added over 20 minutes. Amorphous polyester resin particle dispersion 1:400 mass parts Anionic surfactant (Dowfax2A1 20% aqueous solution): 15 parts by weight Next, after maintaining the temperature at 50°C for 30 minutes, 9 parts by mass of a 20% EDTA (ethylenediaminetetraacetic acid) solution was added to the reaction vessel. Then, a 1 mol / L aqueous sodium hydroxide solution was added to control the pH of the raw material dispersion at 9.0. Further, the temperature was increased to 85°C at a rate of 1°C / min while adjusting the pH to 9.0 every 5°C, and the temperature was maintained at 85°C.

[0239] ≪Cooling process≫ Thereafter, when the shape factor reached 0.963, the dispersion was cooled at a rate of 10° C. / min using the “FPIA-3000,” and a toner base particle dispersion A was obtained.

[0240] <Filtration, washing and drying processes> Thereafter, the toner base particle dispersion A was filtered and thoroughly washed with ion-exchanged water, and then dried at 40°C to obtain toner base particles A. The obtained toner base particles A had a volume average particle diameter of 5.8 μm, a coefficient of variation of the volume average particle diameter of 33.0%, a shape factor of 0.963, and a standard deviation of the shape factor of 0.030.

[0241] <Preparation of Toner Base Particles 2 to 5, 15 and 19> Toner base particles 2 to 5, 15 and 19 were obtained by mixing the toner base particles 1 and the toner base particles A so as to achieve the desired coefficient of variation of the volume average particle diameter shown in Table IV below.

[0242] <Preparation of Toner Base Particles 10> Toner base particles 10 were prepared in the same manner as in the preparation of toner base particles 5, except that crystalline resin 1 was not added when toner base particles 1 and toner base particles A were prepared.

[0243] <Preparation of toner base particles 11 Toner base particles 11 were prepared in the same manner as in the preparation of toner base particles 5, except that crystalline resin 2 was used instead of crystalline resin 1 when preparing toner base particles 1 and toner base particles A.

[0244] <Preparation of Toner Base Particles 12 to 14 and 18> Toner base particles 12 to 14 and 18 were prepared in the same manner as toner base particle 5, except that the amount of crystalline resin 1 added when preparing toner base particle 1 and toner base particle A was changed as shown in Table IV below.

[0245] <Preparation of Toner Base Particles 9> <Agglomeration, fusion and aging processes> Amorphous polyester resin particle dispersion 1:1008 mass parts ·Crystalline resin particle dispersion 1:156 parts by mass Release agent particle dispersion 1:160 parts by weight Black colorant particle dispersion 1:187 mass parts Anionic surfactant (Dowfax 2A1 20% aqueous solution): 40 parts by weight Ion-exchanged water: 1,500 parts by weight The above materials were placed in a 4-liter reaction vessel equipped with a thermometer, a pH meter and a stirrer, and the pH was adjusted to 3.0 by adding 1.0% nitric acid at 25°C. Then, while dispersing at 2800 rpm using a homogenizer (ULTRA-TURRAX T50, manufactured by IKA), 100 parts by mass of a 2% aqueous solution of aluminum sulfate (flocculant) was added over 30 minutes. After the dropwise addition was completed, the mixture was stirred for 10 minutes to thoroughly mix the raw material and flocculant. A stirrer and mantle heater were then installed in the reaction vessel. The stirrer rotation speed was adjusted to ensure sufficient stirring of the slurry. The temperature was increased at a rate of 0.2°C / min up to 40°C, and then at a rate of 0.05°C / min after reaching 40°C. Particle size was measured every 10 minutes using a Coulter Multisizer 3 (aperture diameter 100 μm, Beckman Coulter). When the volumetric median diameter reached 5.7 μm, the temperature was maintained and the following premixed solution was added over 20 minutes. Amorphous polyester resin particle dispersion 1:400 mass parts Anionic surfactant (Dowfax2A1 20% aqueous solution): 40 parts by weight After maintaining the temperature at 50°C for 30 minutes, 9 parts by mass of a 20% EDTA (ethylenediaminetetraacetic acid) solution was added to the reaction vessel. A 1 mol / L aqueous sodium hydroxide solution was then added to adjust the pH of the raw material dispersion to 9.0. The temperature was then increased to 83°C at a rate of 1°C / min while adjusting the pH to 9.0 every 5°C, and the temperature was maintained at 83°C.

[0246] ≪Cooling process≫ Thereafter, when the shape factor reached 0.968, the dispersion was cooled at a rate of 10° C. / min using the “FPIA-3000,” and toner base particle dispersion liquid 9 was obtained.

[0247] <Filtration, washing and drying processes> Thereafter, the toner base particle dispersion 9 was filtered and thoroughly washed with ion-exchanged water, and then dried at 40°C to obtain toner base particles 9. The obtained toner base particles 9 had a volume average particle diameter of 5.7 μm, a coefficient of variation of the volume average particle diameter of 26.0%, a shape factor of 0.968, and a standard deviation of the shape factor of 0.029.

[0248] <Preparation of Toner Base Particles B> Toner base particles B were obtained in the same manner as in the preparation of toner base particles 9, except that in the cooling step, "FPIA-3000" was used and cooling was carried out when the shape factor reached 0.940. The obtained toner base particles B had a volume average particle diameter of 5.7 μm, a coefficient of variation of the volume average particle diameter of 26.0%, a shape factor of 0.940, and a standard deviation of the shape factor of 0.031.

[0249] <Preparation of Toner Base Particles C> Toner base particles B were obtained in the same manner as in the preparation of toner base particles 9, except that in the cooling step, "FPIA-3000" was used and cooling was carried out when the shape factor reached 0.973. The obtained toner base particles B had a volume average particle diameter of 5.7 μm, a coefficient of variation of the volume average particle diameter of 26.0%, a shape factor of 0.973, and a standard deviation of the shape factor of 0.029.

[0250] <Preparation of Toner Base Particles 6 to 8, 16, 17 and 20> The toner base particles 9, the toner base particles B, and the toner base particles C were mixed together so as to achieve a desired standard deviation of the shape coefficient, thereby obtaining toner base particles 6 to 8, 16, 17, and 20.

[0251] [Table 4]

[0252] <Preparation of Toners 1 to 18, 20 and 21> The following external additives were added to the toner base particles 1 to 20 prepared above. Hydrophobic silica (number average primary particle size 12 nm, hydrophobicity 68): 1.0% by mass Strontium titanate (number average primary particle size 40 nm, hydrophobicity 60) 0.8% by mass Spherical silica (average primary particle size 80 nm, hydrophobicity 59) 0.5% by mass Thereafter, the mixture was mixed using a Henschel mixer (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.), and then coarse particles were removed using a sieve with 45 μm openings to produce toners 1 to 18, 20, and 21. The correspondence between toner base particles 1 to 20 and toners 1 to 21 is as shown in Table V below.

[0253] <Preparation of Toner 19> Toner 19 was prepared in the same manner as in the preparation of Toner 1, except that strontium titanate was not added.

[0254] <Creating the carrier> 100 parts by mass of ferrite cores and 5 parts by mass of copolymer resin particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5 / 5) were placed in a high-speed mixer equipped with a stirring blade. The mixture was stirred and mixed at 120°C for 30 minutes, and a resin coating layer was formed on the surface of the ferrite cores by the action of mechanical impact force, yielding a carrier with a volumetric median diameter of 35 μm. The volume-based median diameter of the carrier was measured using a laser diffraction particle size distribution measuring device "HELOS" (manufactured by Sympatec Co., Ltd.) equipped with a wet disperser.

[0255] <Preparation of Developers 1 to 21> Toners 1 to 21 were added to the carrier so that the toner concentration was 6% by mass, and the mixture was placed in a micro V-type mixer (Tsutsui Rikagakuki Co., Ltd.) and mixed for 30 minutes at a rotation speed of 45 rpm to prepare Developers 1 to 21.

[0256] [Table 5]

[0257] [evaluation] <Uneven fixing of initial image quality> A bizhub C250i equipped with the fixing device shown in Table VI below was used, and the developer shown in Table VI below was used. A 30% halftone chart was printed on A4-size fine paper in an environment at room temperature (temperature 20°C, relative humidity 50% RH). The image density of this image was measured at five points in the axial direction of the photoreceptor and evaluated. The image density was measured using an image densitometer (Macbeth RD914). "A," "B," and "C" in the following evaluation criteria were considered acceptable for practical use. (standard) A: Very good, with density variation of less than 10% B: Density variation is 10% or more and less than 15%. C: Density variation is 15% or more and less than 20% D: Density variation is 20% or more

[0258] <Contamination of belt components> Using the evaluation machine used in "<Uneven fixing of initial image>", 500,000 images with a print rate of 5% were printed on A4 size high-quality paper in an environment of room temperature (temperature 20°C, relative humidity 50% RH). Immediately after the completion of the above 500,000 prints, five solid white images were printed and the degree of image contamination was visually evaluated. The evaluation criteria were as follows: "A", "B" and "C" in the following evaluation criteria were considered to be acceptable for practical use. (standard) A: There are no stains in the five images. B: There are less than 10 minor stains in 5 images. C: In five images, there are 10 or more but less than 50 slight stains. D: There are 50 or more minor stains in five images, or there are clearly visible stains in any of the five images.

[0259] <Uneven fixing of image quality after durability test> Using the evaluation machine used in "<Uneven Fixation of Initial Image>", 500,000 copies of a 30% halftone chart were printed on A4 size fine paper in a low temperature and low humidity environment (temperature 10°C, relative humidity 10% RH) (LL environment). The image density of this image was measured at five points in the axial direction of the photoreceptor and evaluated. Note that the image density was measured using an image densitometer (Macbeth RD914). The evaluation criteria were as follows: "A", "B" and "C" in the following evaluation criteria were considered to be acceptable for practical use. (standard) A: Very good, with density variation of less than 10% B: Density variation is 10% or more and less than 15%. C: Density variation is 15% or more and less than 20% D: Density variation is 20% or more

[0260] <LL fixing strength of image quality after durability test> Using the evaluation machine used in "<Uneven Fixing of Initial Images>", the image was printed on A4 size wood-free paper at 5 g / m in a low temperature and low humidity environment (temperature 10°C, relative humidity 10% RH) (LL environment). 2 500,000 images were developed with a toner adhesion amount of 100°C. The transferred paper was then fixed by changing the temperature setting of the fixing heat roller from 100°C to 210°C in 5°C increments. The fixed solid image was then folded using a folding machine, and air at 0.35 MPa was blown onto it. The state of the fold was evaluated on a 5-point scale with reference to a limit sample, and a fixing temperature of rank 3 was designated the lower limit fixing temperature. The evaluation criteria were as follows: "A," "B," and "C" in the following evaluation criteria were considered to be acceptable for practical use. (standard) A: No peeling at the fold B: Some peeling along the fold C: Thin linear peeling along the fold D: Thick peeling along the fold

[0261] <Number of slippages> In the evaluation method for "Contamination of belt member," the number of sheets on which slipping noise occurred among the 500,000 prints was defined as the number of slipping sheets. The evaluation criteria were as follows. "A," "B," and "C" in the following evaluation criteria were considered to be acceptable for practical use. (standard) A: No slip noise B: No slip noise occurs up to 350,000 sheets C: No slip noise occurs up to 200,000 sheets D: Slip noise occurs when printing less than 100,000 sheets

[0262] [Table 6]

[0263] [Table 7]

[0264] As shown by the above results, the present invention can suppress uneven fixing of the initial image quality and the image quality after the durability test compared to the comparative example. Furthermore, it is clear that the fixing strength of the image quality after the durability test in the LL environment is also good, and slippage and staining of the belt member can be reduced. [Explanation of symbols]

[0265] 30, 30A, 30B fixing device 31 Heating roller (roller member) 32 Upper pressure roller (roller member) 33 Lower pressure roller 34 Belt member 35 Heater (heat source) 36 Fixing nip (nip section) 37 Temperature Sensor 4 Fixing pad (pad) 40 Fixing device 50 Image forming device 51 Photosensitive drum 52 Charging device 53 Exposure equipment 54 Developing device 55, 65 Cleaning device 61 Intermediate transfer belt 62 Primary transfer roller 63 Backup roller 64, 68 Support rollers 66 Secondary transfer belt 67 Secondary transfer roller 160 Non-contact heating section 161 Non-contact heater 162 Insulation Cover 500 Image forming system F, S paper (recording media)

Claims

1. An image forming system having a fixing device that fixes a toner image to a recording medium, the fixing device includes a belt member and a roller member that stretches the belt member, or further includes a roller member that is rotatably pressed against the outer circumferential surface of the belt member, At least one of the roller members has an aluminum-based substrate; the substrate contains greater than 0.60 wt. % silicon; The standard deviation of the shape factor of the toner base particles is 0.045 or less, and The coefficient of variation of the volume average particle diameter of the toner base particles is 28.0% or less. An image forming system comprising:

2. The substrate contains silicon in an amount greater than 0.80% by weight.

2. The image forming system according to claim 1.

3. A pressure roller is provided on the outer side of the belt member so as to sandwich the belt member and form a nip portion, and a pad is provided on the inner side of the belt member so as to face the pressure roller.

2. The image forming system according to claim 1.

4. A heat source for heating the belt member is provided inside at least one of the roller members.

2. The image forming system according to claim 1.

5. At least one of the roller members has a surface provided with a resin coating layer or a rubber layer.

2. The image forming system according to claim 1.

6. Before the toner image is fixed to the recording medium, the toner image is heated in a non-contact manner by a heater.

2. The image forming system according to claim 1.

7. The toner base particles contain a crystalline resin in the binder resin in a range of 5.0 to 20% by mass.

2. The image forming system according to claim 1.

8. Strontium titanate particles having a number average particle size in the range of 10 to 60 nm are added as an external additive to the toner base particles.

2. The image forming system according to claim 1.

Images