Image forming system and image forming method

Abstract

To provide an image forming system and an image forming method for reducing an image defect to form a high-quality image.SOLUTION: An image forming system of the present invention comprises an image forming apparatus of an electrophotographic system having photoreceptors, and a toner for electrostatic charge image development. The photoreceptors each have a photosensitive layer. The photosensitive layer contains polyarylate. The toner for electrostatic charge image development includes, as external additives, inorganic particles A and inorganic particles B treated with silicone oil. The number average primary particle diameter of the inorganic particles A is within a range of 5 nm or more and less than 60 nm. The number average primary particle diameter of the inorganic particles B is within a range of 60 nm or more and 150 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming system and an image forming method. [Background technology]

[0002] From the viewpoint of achieving higher image resolution, improvements have been proposed, such as sharpening the particle size distribution of toner, making toner spherical, and reducing the diameter of toner. However, spherical toner or small-diameter toner is likely to slip through the blade during cleaning and remain on the photoreceptor. Furthermore, if the blade pressure is increased to prevent the toner from remaining, the photoreceptor is prone to wear and deterioration due to the blade, which can reduce its durability. A technology that incorporates polyarylate into a photoreceptor to reduce wear and deterioration is known (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2022-181419 Summary of the Invention [Problem to be solved by the invention]

[0004] Although the above technology has improved the durability of the photoconductor, it has been found that toner still tends to remain on the photoconductor. Even if the pressure of the blade during cleaning is increased, some toner still slips through, and the toner remaining on the photoconductor causes image defects.

[0005] The present invention has been made in view of the above problems and circumstances, and an object of the present invention is to provide an image forming system and an image forming method that form high-quality images with reduced image defects. [Means for solving the problem]

[0006] The present inventors have investigated the causes of the above problems in order to solve the above problems. In an image forming system, an image forming apparatus has a photoreceptor containing polyarylate, and a toner for developing electrostatic images contains inorganic particles A and inorganic particles B as specific external additives. This makes it possible to form high-quality images with reduced image defects. The present inventors have found the above and arrived at the present invention. That is, the above-described problems according to this embodiment are solved by the following means.

[0007] 1. An image forming system comprising an electrophotographic image forming apparatus having a photosensitive member and a toner for developing an electrostatic image, the photoreceptor has a photosensitive layer, the photosensitive layer contains polyarylate, the toner for developing electrostatic images contains, as external additives, inorganic particles A and inorganic particles B treated with silicone oil, the number average primary particle diameter of the inorganic particles A is in the range of 5 nm or more and less than 60 nm, The number average primary particle diameter of the inorganic particles B is in the range of 60 nm or more and 150 nm or less. An image forming system comprising:

[0008] 2. The inorganic particles A and the inorganic particles B are silica particles 2. The image forming system according to claim 1,

[0009] 3. The inorganic particles B are silica particles having a shape factor SF-2 of 116 or less. 3. The image forming system according to claim 1 or 2,

[0010] 4. The number average primary particle size of the inorganic particles B is in the range of 80 nm or more and 120 nm or less. 3. The image forming system according to claim 1 or 2,

[0011] 5. The toner for developing electrostatic images contains toner base particles, The toner base particles have a volume average particle size in the range of 3 μm or more and 7 μm or less. 3. The image forming system according to claim 1 or 2,

[0012] 6. The volume average particle size of the toner base particles is in the range of 3 μm or more and 5 μm or less. 6. The image forming system according to claim 5,

[0013] 7. The toner base particles have a core-shell structure 6. The image forming system according to claim 5,

[0014] 8. The average circularity of the toner base particles is 0.940 or more and 0.980 or less. 6. The image forming system according to claim 5,

[0015] 9. The photosensitive layer has an outermost layer, The outermost layer contains the polyarylate. 3. The image forming system according to claim 1 or 2,

[0016] 10. The photosensitive layer has a charge transport layer; The charge transport layer contains the polyarylate. 3. The image forming system according to claim 1 or 2,

[0017] 11. The polyarylate has a structural unit derived from a dicarboxylic acid and represented by the following structural formula (1): 3. The image forming system according to claim 1 or 2,

[0018] [ka]

[0019] 12. The polyarylate has a structural unit derived from a dicarboxylic acid and represented by the following structural formula (2): 3. The image forming system according to claim 1 or 2,

[0020] [ka]

[0021] 13. The image forming apparatus has a cleaning unit that removes the electrostatic image developing toner on the photosensitive member by contacting a blade. 3. The image forming system according to claim 1 or 2,

[0022] 14. Using the image forming system described in paragraph 1 or 2 An image forming method comprising: [Effects of the Invention]

[0023] The above-described means of the present invention can provide an image forming system or the like that forms high-quality images with reduced image defects.

[0024] 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.

[0025] Many toners contain external additives in addition to toner base particles for the purpose of improving fluidity, charging properties, etc. The particle size of the external additives is smaller than that of the toner base particles. Therefore, the external additives tend to adhere to the photoreceptor. Furthermore, the external additives tend to slip through the blade during cleaning of the photoreceptor and remain on the photoreceptor.

[0026] As described above, the photoreceptor contains polyarylate, which improves its hardness and durability, allowing for a stronger blade pressure during cleaning of the photoreceptor, making it easier to remove external additives from the photoreceptor with the blade.

[0027] In addition, the present invention uses inorganic particles treated with silicone oil as the external additive. This allows the silicone oil to be supplied to the surface of the toner base particles when the external additive and the toner base particles are mixed to prepare the toner. Furthermore, when the toner adheres to the photoreceptor, the silicone oil is supplied to the surface of the photoreceptor by the external additive. As a result, the adhesive force between the photoreceptor and the toner is weakened, making it easier to remove the external additive from the photoreceptor with the blade. This reduces the friction between the blade and the photoreceptor, suppressing vibration (stick-slip) at the tip of the cleaning blade and preventing the toner and external additive from slipping through.

[0028] The inorganic particles used are a combination of small particle size inorganic particle A and large particle size inorganic particle B. For the same mass, small particle size inorganic particle A has a larger surface area than large particle size inorganic particle B. Therefore, by using small particle size inorganic particle A, silicone oil can be efficiently supplied to the surface of the photoreceptor.

[0029] The larger inorganic particles B are relatively easy to separate from the toner base particles and can polish the surface of the photoreceptor when they come into contact with it. This allows the smaller inorganic particles A to be removed from the photoreceptor while silicone oil is being supplied to the surface of the photoreceptor. Furthermore, since the photoreceptor contains polyarylate and has high hardness, the surface of the photoreceptor is less likely to wear down when polished with the inorganic particles B.

[0030] It is believed that the above-mentioned features can reduce image defects caused by external additives remaining on the photoreceptor, and high-quality images can be formed. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of an image forming apparatus. [Figure 2] FIG. 2 is a cross-sectional view of a photoreceptor. [Figure 3] FIG. 10 is a schematic diagram showing an example of streak-like adhesion occurring on a photosensitive member. [Figure 4]FIG. 10 is a schematic diagram showing an example of streak-like adhesion occurring on a photosensitive member. DETAILED DESCRIPTION OF THE INVENTION

[0032] The image forming system of the present invention is an image forming system comprising an electrophotographic image forming apparatus having a photoreceptor, and a toner for developing electrostatic images. The photoreceptor has a photosensitive layer. The photosensitive layer contains polyarylate. The toner for developing electrostatic images contains, as external additives, inorganic particles A and inorganic particles B treated with silicone oil. The number average primary particle diameter of inorganic particles A is in the range of 5 nm or more and less than 60 nm. The number average primary particle diameter of inorganic particles B is in the range of 60 nm or more and 150 nm or less. The image forming system of the present invention is characterized as above. The above features are technical features common to or corresponding to the following embodiments.

[0033] In an embodiment of the present invention, from the viewpoint of reducing image defects due to streak-like adhesion, the inorganic particles A and the inorganic particles B are preferably silica particles.

[0034] In an embodiment of the present invention, from the viewpoint of reducing image defects due to streak-like adhesion, the inorganic particles B are preferably silica particles having a shape factor SF-2 of 116 or less.

[0035] In an embodiment of the present invention, from the viewpoint of reducing image defects due to streaky adhesion, the number average primary particle diameter of the inorganic particles B is preferably in the range of 80 nm or more and 120 nm or less.

[0036] In an embodiment of the present invention, from the viewpoint of forming a high-resolution image, it is preferable that the toner for developing electrostatic images contains toner base particles, and that the volume average particle size of the toner base particles is in the range of 3 μm or more and 7 μm or less.

[0037] In an embodiment of the present invention, from the viewpoint of forming a high-definition image, it is preferable that the volume average particle size of the toner base particles is in the range of 3 μm or more and 5 μm or less.

[0038] In an embodiment of the present invention, from the viewpoint of forming a high-definition image, it is preferable that the toner base particles have a core-shell structure.

[0039] In an embodiment of the present invention, from the viewpoint of forming a high-definition image, it is preferable that the average circularity of the toner base particles is 0.940 or more and 0.980 or less.

[0040] In an embodiment of the present invention, from the viewpoint of reducing image defects due to streak-like adhesion, it is preferred that the photosensitive layer has an outermost layer, and that the outermost layer contains the polyarylate.

[0041] In an embodiment of the present invention, from the viewpoint of reducing image defects due to streak-like adhesion, it is preferred that the photosensitive layer has a charge transport layer, and that the charge transport layer contains the polyarylate.

[0042] In an embodiment of the present invention, from the viewpoint of reducing image defects due to streak-like adhesion, the polyarylate preferably has a structural unit derived from a dicarboxylic acid and represented by the above structural formula (1).

[0043] In an embodiment of the present invention, from the viewpoint of reducing image defects due to streak-like adhesion, the polyarylate preferably has a structural unit derived from a dicarboxylic acid and represented by the above structural formula (2).

[0044] In an embodiment of the present invention, from the viewpoint of reducing image defects caused by streak-like adhesion, it is preferable that the image forming apparatus has a cleaning unit that removes the electrostatic image developing toner on the photosensitive member by contacting a blade.

[0045] The image forming method of this embodiment is characterized by using the image forming system.

[0046] Hereinafter, one or more embodiments of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the disclosed embodiments. In this application, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0047] 1. Image forming system The image forming system of this embodiment includes a toner for developing electrostatic images and an electrophotographic image forming apparatus having a photoreceptor. The toner for developing electrostatic images contains inorganic particles A and inorganic particles B treated with silicone oil as external additives. The number average particle diameter of inorganic particles A is in the range of 5 nm or more and less than 60 nm. The number average particle diameter of inorganic particles B is in the range of 60 nm or more and 150 nm or less. The photoreceptor has a photosensitive layer. The photosensitive layer contains polyarylate. The image forming system of this embodiment is characterized as described above.

[0048] The toner for developing electrostatic images of this embodiment includes toner particles having toner base particles and external additives disposed on the surfaces of the toner base particles. Hereinafter, the toner for developing electrostatic images will also be simply referred to as "toner." In this specification, "toner base particles" refer to the base of "toner particles," and "toner base particles" are called "toner particles" when external additives are added. "Toner" refers to an aggregate of toner particles. The toner for developing electrostatic images and the image forming apparatus will be described below in order.

[0049] 2. Toner for developing electrostatic images The toner for developing electrostatic images of the present embodiment contains toner particles having toner base particles and external additives. The external additives and toner base particles will be described below.

[0050] (1) External additives The external additive according to this embodiment contains inorganic particles A and inorganic particles B treated with silicone oil. The number-average particle size of inorganic particles A is in the range of 5 nm or more and less than 60 nm, and the number-average particle size of inorganic particles B is in the range of 60 nm or more and 150 nm or less. The external additive may further contain particles other than inorganic particles A and inorganic particles B.

[0051] The external additive according to this embodiment contains at least two types of inorganic particles. Here, the term "type" refers to different types of inorganic particles if they have different number-average primary particle diameters. In other words, even if the material is the same, if the number-average primary particle diameters are different, they are considered to be different types. The material and surface modifier of the two types of inorganic particles may be the same or different.

[0052] (1.1) Material Examples of materials for the inorganic particles include inorganic oxides (silica, aluminum oxide, titanium oxide, etc.), inorganic stearic acid compounds (aluminum stearate, zinc stearate, etc.), inorganic titanic acid compounds (strontium titanate, zinc titanate, etc.), etc. Among these, from the viewpoints of toner fluidity, charge rise properties, etc., the material for the inorganic particles is preferably silica or aluminum oxide, and particularly preferably silica.

[0053] (1.1.1) Silica particles The inorganic particles according to this embodiment are preferably silica particles. In this embodiment, "silica particles" refers to particles containing silica (SiO2). The content of silica in inorganic particles is not particularly limited, but it is preferable that silica is the main component. The term "main component" refers to a content of 55% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more, of the total mass of the inorganic particles.

[0054] Silica particles can be produced by known methods such as a sol-gel method, a gas phase method (gas combustion method), a melting method, hydrothermal synthesis, etc. Among these, the sol-gel method or the gas phase method is preferred from the viewpoint of producing silica particles that are nearly spherical.

[0055] The sol-gel method includes, for example, a method in which a raw material, tetraalkoxysilane, is supplied in the presence of an alcohol containing an alkali catalyst, and the tetraalkoxysilane is reacted to produce silica particles. The use of the sol-gel method makes it easy to control the particle size distribution and shape of the produced silica particles.

[0056] An example of a gas phase method (gas combustion method) is a method in which a siloxane gas obtained by vaporizing a siloxane compound is introduced into a burner together with a carrier gas such as nitrogen, and the siloxane gas is diffused and mixed with a combustion-supporting gas such as oxygen to combust, thereby producing silica particles. Examples of siloxane compounds that are vaporized to obtain the siloxane gas include hexamethylcyclotrisiloxane and octamethylcyclotetrasiloxane.

[0057] Another example of a gas phase method is a method in which silicon tetrachloride is burned at high temperature together with a mixed gas of oxygen, hydrogen, nitrogen or other diluent gas to produce silica particles (fumed silica).

[0058] The melting method includes a method in which a slurry of metal silicone fine particles is sprayed into a flame and spheroidized while undergoing an oxidation reaction, thereby producing silica particles.

[0059] The silica particles may contain a metal component in addition to silica. As a method for incorporating a metal component, a method using a siloxane compound containing a metal component can be mentioned.

[0060] (1.1.2) Aluminum oxide particles The inorganic particles according to this embodiment may be aluminum oxide particles. The crystalline form of aluminum oxide may be α-type, γ-type, σ-type, a mixture thereof, etc. By controlling the crystalline form, the particle shape can be controlled.

[0061] The aluminum oxide particles can be produced by known methods such as the sol-gel method, hydrolysis method, vapor phase synthesis method, flame hydrolysis method, underwater spark discharge method, etc. Among these, the sol-gel method is preferred from the viewpoint of producing aluminum oxide particles that are nearly spherical.

[0062] (1.2) Surface modification The inorganic particles according to this embodiment are surface-modified with silicone oil, which improves the toner's fluidity, chargeability (charge rise time, charge stability, etc.), heat-resistant storage properties, environmental stability, etc. Furthermore, silicone oil can be supplied to the surface of the photoreceptor.

[0063] The silicone oil is not particularly limited as long as it can be released when attached to the surface of the inorganic particles, and any known silicone oil can be used. Examples of silicone oils include dimethyl silicone oil, alkyl-modified silicone oil, amino-modified silicone oil, carboxy-modified silicone oil, epoxy-modified silicone oil, fluorine-modified silicone oil, alcohol-modified silicone oil, polyether-modified silicone oil, methylphenyl silicone oil, methylhydrogen silicone oil, mercapto-modified silicone oil, higher fatty acid-modified silicone oil, phenol-modified silicone oil, methacrylic acid-modified silicone oil, polyether-modified silicone oil, methylstyryl-modified silicone oil, etc. Among these, dimethyl silicone oil is preferred from the viewpoint of ease of handling. The silicone oils may be used alone or in combination of two or more.

[0064] The kinematic viscosity of silicone oil at 25°C is 50 to 500 mm 2 It is preferable that the kinematic viscosity at 25°C is in the range of 50mm / s. 2 / s or more, the silicone oil easily migrates to the surface of the photoreceptor. 2 / s or less, the silicone oil that has migrated to the surface of the photoreceptor is likely to remain on the surface of the photoreceptor. The kinematic viscosity at 25°C can be measured by a method in accordance with JIS K2283.

[0065] The surface modifiers used for the inorganic particles A and the inorganic particles B may be the same or different. However, from the viewpoint that it is preferable that one type of silicone oil is uniformly applied to the surface of the photoreceptor, it is preferable that the surface modifiers are the same.

[0066] The method for surface-modifying inorganic particles is not particularly limited, and known methods can be used, such as a spray-drying method, a wet method, and a mixing method. In the spray-drying method, a surface modifier or a solution containing a surface modifier is sprayed onto inorganic particles suspended in a gas phase. In the wet method, inorganic particles are immersed in a solution containing a surface modifier and then dried. In the mixing method, a surface modifier and inorganic particles are mixed in a mixer.

[0067] (1.2.1) Release rate In the inorganic particles according to this embodiment, the liberation rate of the surface modifier of inorganic particle A is preferably greater than that of inorganic particle B. By making the liberation rate of the surface modifier of inorganic particle A greater than that of inorganic particle B, inorganic particle A can impart (supply) the surface modifier to the carrier in a relatively short time, and inorganic particle B can suppress aggregation of inorganic particle A. The term "liberation" will be described in more detail below.

[0068] In this embodiment, "free" refers to the surface modifier being desorbed from the surface of the inorganic particles and becoming freely mobile under the extraction and rinsing conditions described below. On the other hand, a surface modifier that is not free is attached to the surface of the inorganic particles by chemical adsorption or physical adsorption. "Chemical adsorption" refers to relatively strong adsorption due to the formation of chemical bonds. On the other hand, "physical adsorption" refers to relatively weak adsorption due to van der Waals forces (intermolecular forces).

[0069] In particular, when inorganic particle is silica particle and surface modifier is silicone oil, silicone oil is adsorbed on the surface of silica particle with relatively weak adsorption force.Silicone oil can be separated from the surface of silica particle by hydrocarbon organic solvent such as hexane.In this case, the silicone oil that is not in free state can remain attached to the surface of silica particle.

[0070] In the present invention, the term "free rate" refers to the ratio of the amount of surface modifier in a free state after the extraction and rinsing described below to the total amount of surface modifier attached to the inorganic particles before the extraction and rinsing described below.

[0071] When the inorganic particles are silica particles and the surface modifier is silicone oil, the liberation rate can be measured by the following method. More specifically, the "liberation rate" here refers to the liberation rate of silicone oil-derived carbon atoms in the silica particles.

[0072] For example, a Soxhlet extraction apparatus (manufactured by BUCHI) is used for the release. 0.7 g of silica particle sample surface-modified with silicone oil is placed in a cylindrical filter paper with a diameter of 28 mm. Hexane is used as the extraction solvent, and the silicone oil contained in the silica particle sample is released under the following conditions: extraction time 60 minutes, rinse time 30 minutes, and temperature 25°C.

[0073] The carbon content (number of carbon atoms) of the silica particle sample before and after the extraction and release of silicone oil is measured. For example, a CHN elemental analyzer "CHN Coder MT-5" (manufactured by Yanaco Analytical Industry Co., Ltd.) can be used for the measurement.

[0074] The carbon atom-based liberation rate of silicone oil-derived silica particles is calculated using the following formula: The liberation rate here is expressed as a ratio based on the number of carbon atoms, that is, an atomic number ratio. (Formula) Release rate=(C0-C1) / C0×100(atm%) C0: Carbon content (number of carbon atoms) in the silica particle sample before extraction and release of silicone oil C1: Carbon content (number of carbon atoms) in the silica particle sample after extraction and release of silicone oil

[0075] (1.3) Shape (1.3.1) Number-average primary particle size The number-average primary particle size of inorganic particles A according to this embodiment is in the range of 5 nm or more and less than 60 nm. The number-average primary particle size of inorganic particles B is in the range of 60 nm or more and 150 nm or less. This allows inorganic particles A to have a larger surface area than inorganic particles B, allowing silicone oil to be efficiently supplied to the photoreceptor surface. As a result, the toner particles remaining on the photoreceptor surface can be reduced. This also allows inorganic particles B to be suitably detached from the toner base particles, and the inorganic particles B detached from the toner base particles can polish the photoreceptor surface. As a result, the toner particles remaining on the photoreceptor surface can be reduced. On the other hand, inorganic particles A are less likely to be detached from the toner base particles than inorganic particles B, thereby reducing fluctuations in the toner charge amount.

[0076] The number average primary particle size of the inorganic particles can be measured by the following method. For example, a scanning electron microscope (SEM) "JEM-7401F" (manufactured by JEOL Ltd.) is used to take an SEM photograph of toner particles magnified 30,000 times. The external additives of the toner particles in the photographic image are visually observed, and particle groups with approximately the same particle size are determined to be the same type. An image processing analyzer "LUZEX AP" (manufactured by Nireco Corporation) is used to binarize the external additives present on the toner surface in the photographic image. The horizontal Feret diameters of 100 particles per type of external additive are calculated, and the average value is taken as the number-average primary particle diameter. Here, the horizontal Feret diameter refers to the length of the side parallel to the x-axis of the circumscribing rectangle when the image of the external additive is binarized. Note that if the number-average primary particle diameter of the external additive is small and it exists on the toner surface as an aggregate, the particle diameter of the aggregate is treated as the particle diameter of the external additive.

[0077] The number average primary particle size of inorganic particles A is more preferably within a range of 10 to 60 nm, and even more preferably within a range of 10 to 50 nm.The number average primary particle size of inorganic particles B is more preferably within a range of 80 to 120 nm, and even more preferably within a range of 80 to 100 nm.

[0078] (1.3.2) Shape factor The shape of the inorganic particles is not particularly limited, but is preferably a sphere with a gently sloping surface. The shape of the inorganic particles can be expressed by the shape factor SF-2. The shape factor SF-2 can be measured by the following method. For example, a scanning electron microscope (SEM) "JEM-7401F" (manufactured by JEOL Ltd.) is used to take an SEM photograph of toner particles magnified 30,000 times. An image processing analyzer "LUZEX AP" (manufactured by Nireco Corporation) is used to binarize the external additives present on the toner surface of the photograph. The shape factor SF-2 is calculated for 100 particles per type of external additive, and the average value is taken as the shape factor SF-2. The larger the value of the shape factor SF-2, the more irregular and irregular the shape of the particle.

[0079] The shape factor SF-2 of the inorganic particles B is preferably equal to or less than 116, and more preferably equal to or less than 112. This can enhance the polishing effect on the surface of the photoreceptor.

[0080] (1.4) Content The content of inorganic particles is preferably within a range of 0.5 to 5.0 parts by mass relative to 100 parts by mass of toner base particles. By setting the content to 0.5 parts by mass or more, the inorganic particles can be uniformly added to the surface of the toner base particles. Furthermore, by setting the content to 5.0 parts by mass or less, aggregation of the inorganic particles can be suppressed.

[0081] The content of inorganic particles A is preferably within a range of 0.1 to 3.0 parts by mass per 100 parts by mass of toner base particles. This allows silicone oil to be efficiently supplied to the surface of the photoreceptor. The content of inorganic particles B is preferably within a range of 0.3 to 3.0 parts by mass per 100 parts by mass of toner base particles. This allows for an improved polishing effect on the surface of the photoreceptor.

[0082] When other external additives are used in addition to the inorganic particles, the total amount of the inorganic particles and other external additives is preferably within the range of 0.5 to 3.0% by mass relative to the total mass of the toner base particles.

[0083] (1.5) Other external additives The toner according to the present embodiment may further contain other external additives in addition to the two types of inorganic particles. The other external additives are not particularly limited, and known external additives can be used. Examples of the other external additives include the inorganic particles, organic particles, and lubricants.

[0084] Examples of organic particles include particles of homopolymers such as styrene and methyl methacrylate, and copolymers thereof. The number average primary particle size of the organic particles is preferably within the range of 10 to 2000 nm, and the particles are preferably spherical.

[0085] Lubricants are used for the purpose of further improving cleaning properties and transfer properties. There are no particular limitations on the lubricant, and known lubricants can be used. Examples of lubricants include metal salts of higher fatty acids. Examples of metal salts of higher fatty acids include salts of zinc, aluminum, copper, magnesium, calcium, etc. with stearic acid; salts of zinc, manganese, iron, copper, magnesium, etc. with oleic acid; salts of zinc, copper, magnesium, etc. with palmitic acid; salts of zinc, calcium, etc. with linoleic acid; salts of zinc, calcium, etc. with ricinoleic acid; and the like.

[0086] These particles may be surface-modified using a surface modifier such as a silane coupling agent, a titanium coupling agent, a higher fatty acid, or a silicone oil.

[0087] (2) Toner base particles The toner base particles according to this embodiment preferably contain a binder resin, a colorant, a release agent, and the like, and may also contain other components as required.

[0088] (2.1) Structure The structure of the toner base particle is not particularly limited, but is preferably a core-shell structure in which the surface of a core particle is coated with a shell layer. Due to the existence of an interface between the core and shell, if the compatibility between the components of the core particle and the components of the shell layer is low, the charge generated during toner charging can be efficiently trapped, preventing charge leakage. Furthermore, by adjusting the compatibility, the degree of charge leakage can be controlled. The shell layer does not necessarily have to completely cover the core particle, and a portion of the core particle may be exposed.

[0089] The core-shell structure can be confirmed by observing the cross-sectional structure of the toner using a known device such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM).

[0090] (2.2) Constituents (2.2.1) Binder resin The toner base particles according to this exemplary embodiment preferably contain a binder resin. The term "binder resin" refers to a resin that serves as a medium or matrix (parent body) for dispersing internal additives (colorants, release agents, etc.) and external additives contained in toner particles, and also has the function of adhering to a recording medium (e.g., paper) during the fixing process of a toner image. Binder resins are also called binder resins.

[0091] The binder resin is not particularly limited, but is preferably an amorphous resin from the viewpoint of image storage stability, etc., and known amorphous resins can be used. In the case of a core-shell structure, it is preferable that both the core particle and the shell layer are amorphous resins, but if necessary, a crystalline resin may also be contained.

[0092] An amorphous resin refers to a resin that does not show a clear endothermic peak in differential scanning calorimetry (DSC) and has a relatively high glass transition temperature (Tg). Specifically, the Tg of the amorphous resin measured by a differential scanning calorimetry device is preferably in the range of 35 to 70°C, and more preferably in the range of 50 to 65°C. When the Tg of the amorphous resin is 35°C or higher, the toner can be given sufficient thermal strength, and sufficient heat-resistant storage stability can be obtained. Furthermore, when the Tg of the amorphous resin is 70°C or lower, sufficient low-temperature fixability can be obtained.

[0093] The glass transition temperature (Tg) of a resin is measured, for example, using a differential scanning calorimeter "Diamond DSC" (manufactured by PerkinElmer) under the following measurement conditions (heating and cooling conditions): In the first heating step, the resin is heated from 0°C to 100°C at a heating rate of 10°C / min and isothermally held at 100°C for 1 minute; in the cooling step, the resin is cooled from 100°C to 0°C at a cooling rate of 10°C / min and isothermally held at 0°C for 1 minute; in the second heating step, the resin is heated from 0°C to 100°C at a heating rate of 10°C / min.

[0094] The measurement procedure involves sealing 5.0 mg of a resin sample in an aluminum pan and setting it in the sample holder of the Diamond DSC. An empty aluminum pan is used as a reference.

[0095] In the DSC curve obtained during the first temperature rise using a differential scanning calorimeter, a baseline shift is observed, and the intersection of an extension of the baseline before the shift and a tangent showing the maximum slope of the shifted portion of the baseline is taken as the glass transition temperature (Tg). If an endothermic peak due to enthalpy relaxation is observed in the DSC curve, an extension of the baseline before the rise of the endothermic peak is drawn with a tangent showing the maximum slope from the rise of the endothermic peak to the peak apex, and the intersection is taken as the glass transition temperature.

[0096] Examples of amorphous resins include polyester, vinyl resin, urethane resin, and urea resin.

[0097] In particular, in the case of a core-shell structure, it is preferable that the shell layer contains an amorphous polyester as the main component, where "main component" means that the amorphous polyester accounts for 55% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more of the total mass of the binder resin contained in the toner base particles.

[0098] The content of the binder resin is preferably within a range of 50 to 95% by mass, more preferably within a range of 60 to 90% by mass, and even more preferably within a range of 70 to 90% by mass, based on the total mass of the toner base particles. By being within the above range, a colorant, a release agent, etc. can be dispersed and contained in the toner base particles.

[0099] (2.2.1.1) Amorphous polyester The toner base particles according to this embodiment preferably contain an amorphous polyester as a binder resin. In particular, by containing an amorphous polyester in the shell layer of the core-shell structure, the toner base particles have appropriate toughness. Therefore, the toner base particles can easily retain external additives, and the effects of the external additives can be stably obtained.

[0100] Polyesters are produced by polycondensation reaction of polycarboxylic acid monomers (derivatives) and polyhydric alcohol monomers (derivatives) in the presence of an appropriate catalyst.

[0101] Examples of the polycarboxylic acid monomer derivatives include alkyl esters, acid anhydrides, and acid chlorides of polycarboxylic acid monomers. Examples of the polyhydric alcohol monomer derivatives include ester compounds of polyhydric alcohol monomers and hydroxycarboxylic acids.

[0102] Examples of dicarboxylic acid monomers among polycarboxylic acid monomers 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, and phthalic acid. , isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, 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, etc. Among the polycarboxylic acid monomers, examples of tricarboxylic acid monomers include trimellitic acid, pyromellitic acid, naphthalene tricarboxylic acid, naphthalene tetracarboxylic acid, pyrene tricarboxylic acid, pyrene tetracarboxylic acid, etc.

[0103] Among them, the polycarboxylic acid monomer is preferably an unsaturated aliphatic dicarboxylic acid such as fumaric acid, maleic acid, mesaconic acid, etc. The polycarboxylic acid monomer may also be an anhydride of a dicarboxylic acid such as maleic anhydride.

[0104] Examples of dihydric alcohols among the polyhydric alcohol monomers include 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. Examples of trihydric or higher polyols among the polyhydric alcohol monomers include glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and tetraethylolbenzoguanamine.

[0105] The mass average molecular weight (Mw) of the polyester is preferably within a range of 10000 to 100000. The mass average molecular weight (Mw) can be measured using the same method as that for the styrene-(meth)acrylic resin described below.

[0106] The glass transition temperature (Tg) of the polyester is preferably within a range of 30 to 65° C. When the glass transition temperature (Tg) is 30° C. or higher, the external additive is less likely to be embedded in the toner base particles. When the glass transition temperature (Tg) is 65° C. or lower, the toner base particles can easily retain the external additive, i.e., the external additive is less likely to migrate, and the effect of the external additive can be stably obtained.

[0107] (2.2.1.2) Amorphous vinyl resin The toner base particles according to the present embodiment preferably contain an amorphous vinyl resin as a binder resin. In particular, by containing an amorphous vinyl resin in the core particles of a core-shell structure, the charge retention of the toner is improved, and good charging characteristics can be obtained.

[0108] The vinyl resin is not particularly limited as long as it is a polymer of a vinyl compound. Examples of the vinyl resin include (meth)acrylic acid ester resin, styrene-(meth)acrylic acid ester resin, ethylene-vinyl acetate resin, etc. These may be used alone or in combination of two or more.

[0109] Among them, from the viewpoint of plasticity during thermal fixation, styrene-(meth)acrylic acid ester resin is preferable. Hereinafter, styrene-(meth)acrylic acid ester resin as an amorphous resin will be described. Hereinafter, styrene-(meth)acrylic acid ester resin will also be referred to as "styrene-(meth)acrylic resin".

[0110] Styrene-(meth)acrylic resins are synthesized by addition polymerization of at least a styrene monomer and a (meth)acrylic acid ester monomer. Here, "styrene monomer" includes not only styrene represented by the structural formula CH2=CH-C6H5, but also compounds having a structure in which a known side chain or functional group is present in the styrene structure.

[0111] Here, the term "(meth)acrylic acid ester monomer" includes an acrylic acid ester or a methacrylic acid ester represented by CH2=CHCOOR (R is an alkyl group). The term "(meth)acrylic acid ester monomer" also includes esters having a known side chain or functional group in the structure of an acrylic acid ester derivative or a methacrylic acid ester derivative. In this specification, the term "(meth)acrylic acid ester monomer" refers collectively to "acrylic acid ester monomer" and "methacrylic acid ester monomer."

[0112] Examples of the styrene monomer and (meth)acrylic acid ester monomer used in the synthesis of the styrene-(meth)acrylic resin are shown below.

[0113] Specific examples of styrene 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, etc. These may be used alone or in combination of two or more.

[0114] Specific examples of acrylic acid ester monomers include 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. Specific examples of methacrylic acid ester monomers include 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. These may be used alone or in combination of two or more.

[0115] The content of structural units derived from styrene monomers in the styrene-(meth)acrylic resin is preferably within a range of 40 to 90% by mass relative to the total mass of the styrene-(meth)acrylic resin, and the content of structural units derived from (meth)acrylic acid ester monomers in the styrene-(meth)acrylic resin is preferably within a range of 10 to 60% by mass relative to the total mass of the styrene-(meth)acrylic resin.

[0116] Furthermore, the styrene-(meth)acrylic resin may contain the following monomer compounds in addition to the above-mentioned styrene monomer and (meth)acrylic acid ester monomer. Examples of such monomer compounds include compounds having a carboxy group (acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, etc.) and compounds having a hydroxy group (2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.). These may be used alone or in combination of two or more.

[0117] The content of the structural units derived from the above-mentioned monomer compounds in the styrene-(meth)acrylic resin is preferably within a range of 0.5 to 20% by mass relative to the total mass of the styrene-(meth)acrylic resin.

[0118] The mass average molecular weight (Mw) of the styrene-(meth)acrylic resin is preferably within the range of 10,000 to 100,000.

[0119] The mass average molecular weight (Mw) of the styrene-(meth)acrylic resin can be calculated from the molecular weight distribution measured by gel permeation chromatography (GPC).

[0120] The mass average molecular weight (Mw) can be measured, for example, by the following method. The mass average molecular weight (Mw) can be calculated using a calibration curve of monodisperse polystyrene standard particles by gel permeation chromatography (GPC) measurement under the following conditions. The calibration curve is used for the molecular weights of 6.00 × 10 2 , 2.10×10 3 , 4.00×10 3 , 1.75×10 4 , 5.10×10 4 , 1.10×10 5 , 3.90×10 5, 8.60×10 5 , 2.00×10 6 , 4.48×10 6 Ten polystyrene standard particles (manufactured by Pressure Chemical Co.) are measured and prepared.

[0121] The sample was added to tetrahydrofuran (THF) to a concentration of 1 mg / mL, dispersed for 5 minutes using an ultrasonic disperser at room temperature, and then passed through a membrane filter with a pore size of 0.2 μm.

[0122] Apparatus: GPC apparatus "HLC-8220GPC" (Tosoh Corporation) Column: "TSKguard column + TSKgel (registered trademark) Super HZM-M triple column" (manufactured by Tosoh Corporation) Carrier solvent: tetrahydrofuran (THF) Detector: Differential refractive index detector (RI detector) Column temperature: 40℃ Flow rate: 0.2mL / min Sample: 10 μL

[0123] The method for producing the styrene-(meth)acrylic resin is not particularly limited. Examples of suitable methods include using any polymerization initiator (peroxide, persulfide, persulfate, azo compound, etc.) commonly used in the polymerization of the above-mentioned monomers and carrying out polymerization by a known polymerization method (bulk polymerization, solution polymerization, emulsion polymerization, miniemulsion, dispersion polymerization, etc.). Furthermore, commonly used chain transfer agents can be used to adjust the molecular weight. Examples of chain transfer agents include, but are not limited to, alkyl mercaptans (n-octyl mercaptan, etc.) and mercapto fatty acid esters.

[0124] (2.2.1.3) Crystalline polyester The toner base particles according to this exemplary embodiment can improve the low temperature fixability of the toner by containing a crystalline polyester as a binder resin in the core particles.

[0125] A crystalline resin is a resin that exhibits a clear endothermic peak rather than a stepwise endothermic change in differential scanning calorimetry (DSC). Specifically, a "clear endothermic peak" refers to a peak whose half-width is 15°C or less when measured at a heating rate of 10°C / min in differential scanning calorimetry (DSC).

[0126] The melting point of the crystalline polyester is preferably in the range of 55 to 90°C, more preferably in the range of 60 to 85°C. By keeping it in the above range, sufficient low-temperature fixability and excellent image storage stability can be obtained. The melting point of the crystalline polyester can be controlled by the resin composition.

[0127] The melting point of the crystalline polyester is the peak-top temperature of the melting peak in the second heating process in the DSC curve obtained by the above-mentioned differential scanning calorimetry. When there are multiple melting peaks in the DSC curve, the peak-top temperature of the melting peak with the largest endothermic amount is taken as the melting point.

[0128] The content of the crystalline polyester is preferably in the range of 5 to 30% by mass, more preferably in the range of 5 to 20% by mass, based on the total mass of the binder resin. When the content is 5% by mass or more, sufficient low-temperature fixability can be obtained, and when the content is 30% by mass or less, the crystalline polyester can be reliably introduced into the toner during toner production.

[0129] (2.2.2) Colorants The toner base particles according to this embodiment may contain a colorant. As the colorant, any of dyes, pigments, carbon black, magnetic materials, etc. can be used. From the viewpoint of being usable as a color toner, the colorant is preferably a dye or a pigment.

[0130] Examples of dyes include CI Solvent Red 1, 49, 52, 58, 63, 111, and 122. Examples of dyes include CI Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, and 162. Examples of dyes include CI Solvent Blue 25, 36, 60, 70, 93, and 95. These may be used alone or in combination of two or more.

[0131] Examples of pigments include CI Pigment Red 5, 48:1, 48:3, 53:1, 57:1, 81:4, 122, 139, 144, 149, 166, 177, 178, and 222. Examples of pigments include CI Pigment Orange 31, 43, CI Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, and 185. Examples of pigments include CI Pigment Green 7, CI Pigment Blue 15:3, 15:4, and 60. These pigments may be used alone or in combination of two or more.

[0132] Examples of white colorants include inorganic pigments (e.g., titanium white, zinc white, titanium strontium white, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, talc, calcium sulfate, barium sulfate, zinc oxide, magnesium oxide, magnesium carbonate, amorphous silica, colloidal silica, white carbon, kaolin, calcined kaolin, delaminated kaolin, aluminosilicate, sericite, bentonite, smexite, etc.), and organic pigments (e.g., polystyrene resin particles, urea formalin resin particles, etc.).

[0133] Examples of carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black.

[0134] The toner according to the present embodiment may be a magnetic toner. Examples of magnetic materials include ferromagnetic metals (iron, nickel, cobalt, etc.), alloys containing ferromagnetic metals, and compounds of ferromagnetic metals (ferrite, magnetite, etc.).

[0135] The content of the colorant is not particularly limited. From the viewpoint of ensuring color reproducibility of the image, the content of the colorant is preferably in the range of 1 to 30% by mass, more preferably in the range of 2 to 20% by mass, based on the total mass of the toner base particles.

[0136] The volume average particle size of the colorant is preferably within a range of 10 to 1000 nm, more preferably within a range of 50 to 500 nm, and even more preferably within a range of 80 to 300 nm.

[0137] (2.2.3) Release agents The toner base particles according to this embodiment preferably contain a release agent. By containing a release agent, low-temperature fixability can be improved. Furthermore, contamination of the heat roller during fixation can be reduced, i.e., release properties can be improved. Hereinafter, the release agent is also referred to as "wax."

[0138] The release agent is not particularly limited, but preferably does not have any interaction with the binder resin, such as being compatible with it. Examples of the release agent include polyolefin waxes (polyethylene wax, polypropylene wax, etc.), branched-chain hydrocarbon waxes (microcrystalline wax, etc.), long-chain hydrocarbon waxes (paraffin wax, sazol wax, etc.), dialkyl ketone waxes (distearyl ketone, etc.), ester waxes (carnauba wax, montan wax, behenyl behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, tristearyl trimellitate, distearyl maleate, etc.), and amide waxes (ethylenediamine behenylamide, tristearyl trimellitate amide, etc.). Among these, from the viewpoint of fixability, the release agent is preferably a hydrocarbon wax. These may be used alone or in combination of two or more.

[0139] From the viewpoint of low-temperature fixability and releasability, the release agent preferably has a low melting point, specifically, the melting point is preferably within the range of 50 to 95°C.

[0140] The content of the release agent is preferably in the range of 0.1 to 30% by mass, more preferably in the range of 1 to 10% by mass, relative to the total mass of the binder resin. By being in this range, it is possible to achieve both dispersibility in the binder resin and fixability to a recording medium.

[0141] As a method for introducing the release agent into the toner base particles, there is a method in which particles consisting of only the release agent are aggregated and fused together with amorphous resin particles in an aqueous medium in the aggregation and fusion step of the toner manufacturing method described below. The release agent particles can be obtained as a dispersion liquid in which the release agent is dispersed in an aqueous medium.

[0142] The dispersion of release agent particles can be prepared by the following method: An aqueous medium containing a surfactant is heated to a temperature higher than the melting point of the release agent. A molten solution of the release agent is added to the heated aqueous medium. Mechanical energy, ultrasonic energy, or the like is applied to the resulting mixture to finely disperse the release agent, and the mixture is then cooled.

[0143] (2.2.4) Charge control agent The toner base particles according to this exemplary embodiment preferably contain a charge control agent, which allows the chargeability of the toner to be controlled.

[0144] The charge control agent may be any known charge control agent that can be dispersed in an aqueous medium, such as nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, metal salicylate salts, and metal salicylate complexes.

[0145] The content of the charge control agent is preferably in the range of 0.1 to 10% by mass, and more preferably in the range of 0.5 to 5% by mass, based on the total mass of the binder resin.

[0146] The number average primary particle size of the charge control agent is preferably within the range of 10 to 1000 nm, more preferably within the range of 50 to 500 nm, and even more preferably within the range of 80 to 300 nm.

[0147] (2.3) Shape (2.3.1) Volume average particle size The volume average particle diameter of the toner base particles according to this embodiment is preferably in the range of 3 to 7 μm, and more preferably in the range of 3 to 5 μm. When the particle diameter is 3 μm or more, the adhesion of the toner to the photoreceptor is not too strong, and the toner adhering to the surface of the photoreceptor can be sufficiently removed by cleaning. Furthermore, when the particle diameter is 5 μm or less, high-resolution images can be formed.

[0148] For example, when toner is produced by the emulsion aggregation method described below, the average particle size of the toner particles can be controlled by the concentration of the aggregating agent, the amount of organic solvent added, the fusion time, the composition of the polymer, and the like.

[0149] The volume-based median diameter can be measured, for example, using a measuring device that connects a precision particle size distribution measuring device "Multisizer 3" (manufactured by Beckman Coulter, Inc.) to a computer system equipped with data processing software "Software V3.51."

[0150] Specifically, 0.02 g of toner sample was added to 20 mL of surfactant solution, and the mixture was allowed to mix. Then, ultrasonic dispersion was performed for 1 minute to prepare a toner particle dispersion. The surfactant solution used here was a solution prepared by diluting a neutral detergent containing surfactant components 10 times with pure water, for example, for the purpose of dispersing toner particles. The prepared toner particle dispersion was pipetted into a beaker containing ISOTON® II (manufactured by Beckman Coulter, Inc.) in the sample stand until the measurement device indicated a concentration of 8%. Setting the concentration within this range ensures reproducible measurements. The measurement device was set to a particle count of 25,000 and an aperture diameter of 100 μm. The measurement range of 2 to 60 μm was divided into 256 sections to calculate the frequency value, and the particle size with the highest volumetric fraction (50%) was determined as the volume-based median diameter.

[0151] (2.3.2) Average circularity The toner base particles according to this embodiment preferably have an average circularity in the range of 0.940 to 0.980, and more preferably in the range of 0.960 to 0.980. Having an average circularity of 0.940 or more allows for the formation of high-resolution images. Furthermore, having an average circularity of 0.980 or less allows the toner base particles to be less than perfectly spherical and to have some irregularities. These irregularities allow the toner base particles to be more easily caught by a cleaning blade, allowing for sufficient removal of toner adhering to the surface of the photoreceptor.

[0152] The average circularity of the toner base particles can be measured using, for example, a flow type particle image analyzer "FPIA-3000" (manufactured by Sysmex Corporation).

[0153] Specifically, the toner base particle sample is soaked in an aqueous solution containing a surfactant and dispersed by ultrasonic dispersion for 1 minute. Then, using a flow particle image analyzer "FPIA-3000" (Sysmex Corporation), images are taken in HPF (high magnification imaging) mode under measurement conditions at an appropriate density of 3,000 to 10,000 HPF detections. The circularity of each toner base particle is calculated according to the following formula. The calculated circularity of each toner base particle is added up and divided by the total number of toner particles to calculate the average circularity.

[0154] (Formula) Circularity = (perimeter of a circle with the same projected area as the particle image) / (perimeter of the particle projected image)

[0155] (3) Physical properties of toner for developing electrostatic images (3.1) Toner glass transition temperature (Tg) The glass transition temperature (Tg) of the toner according to this embodiment is preferably within the range of 30 to 65° C. When the glass transition temperature (Tg) is within the above range, the low-temperature fixability of the toner can be improved. The glass transition temperature (Tg) of the toner can be measured by the same procedure as that for the glass transition temperature (Tg) of the resin.

[0156] (3.2) Softening point of toner From the viewpoint of low-temperature fixability, the softening point of the toner is preferably within a range of 80 to 120°C, and more preferably within a range of 90 to 110°C. The softening point of the toner can be measured by the flow tester described below.

[0157] Specifically, 1.1 g of a toner sample was placed in a petri dish under an environment of 20°C and 50% RH, flattened, and left for 12 hours or more. Then, the toner sample was pressed under a pressure of 3820 kg / cm using a molding machine "SSP-10A" (manufactured by Shimadzu Corporation). 2 A pressure of 1000 psi is applied for 30 seconds to produce a cylindrical molded sample with a diameter of 1 cm.

[0158] Next, this molded sample is extruded from the end of preheating using a flow tester "CFT-500D" (Shimadzu Corporation) under the following conditions at 24°C and 50% RH, using a piston with a diameter of 1 cm: load 196 N (20 kgf), starting temperature 60°C, preheating time 300 seconds, and temperature rise rate 6°C / min. The offset temperature Toffset measured using the temperature rise melting temperature measurement method with an offset value set to 5 mm is taken as the softening point.

[0159] (4) Manufacturing method of toner for developing electrostatic images The method for producing the toner according to the present embodiment 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 particle size uniformity and shape controllability.

[0160] In the emulsion aggregation method for toner production, a dispersion of binder resin particles dispersed with surfactants, dispersion stabilizers, etc. is mixed with a dispersion of colorant particles as needed, and the mixture is aggregated to a desired toner particle size. In addition, in the emulsion aggregation method, the shape of the binder resin particles is controlled by fusing them together. The binder resin particles may optionally contain a release agent, a charge control agent, etc.

[0161] 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.

[0162] [1] A step of preparing an additive particle dispersion liquid in which various additives are dispersed in an aqueous medium (additive particle dispersion liquid preparation step) [2] A step of preparing a binder resin particle dispersion for core particles and a binder resin particle dispersion for shell layers in which binder resin particles are dispersed in an aqueous medium (binder resin particle dispersion preparation step). [3] A step of mixing an additive particle dispersion and a binder resin particle dispersion for core particles to obtain a resin particle dispersion for aggregation, and aggregating and fusing the additive particles and the binder resin particles for core particles in the presence of an aggregating agent to form aggregated particles as core particles (core particle formation step). [4] A step of adding a dispersion of binder resin particles for the shell layer to a dispersion containing core particles, and aggregating and fusing the binder resin particles for the shell layer onto the surfaces of the core particles to form toner base particles with a core-shell structure (shell layer formation step). [5] A step of filtering the toner base particles from the toner base particle dispersion and removing surfactants, etc. (filtration step) [6] Drying the toner base particles (drying process) [7] Step of adding external additives to toner base particles (external additive addition step)

[0163] In producing toner particles having a core-shell structure, core particle binder resin particles and additive particles are first aggregated and fused to form core particles. Next, shell layer binder resin particles are added to the core particle dispersion, and the shell layer binder resin particles are aggregated and fused to the core particle surfaces to form a shell layer that covers the core particle surfaces. The toner base particles according to this embodiment may be single-layer particles. Single-layer particles can be produced, for example, by omitting the step [4] above.

[0164] In this embodiment, 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 water-soluble organic solvents include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran. The organic solvent is preferably an alcohol-based organic solvent that does not dissolve the resulting resin.

[0165] [1] Additive particle dispersion preparation process The additive particle dispersion liquid can be prepared by dispersing additives (colorant, release agent, charge control agent, etc.) in an aqueous medium. From the viewpoint of uniform dispersion, the dispersion treatment of the additives 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 the dispersion treatment of the additives.

[0166] (surfactant) Examples of surfactants include anionic surfactants (alkyl sulfate salts, polyoxyethylene (n) alkyl ether sulfate salts, alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, etc.), amine salt-type cationic surfactants (alkylamine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, imidazolines, etc.), quaternary ammonium salt-type cationic surfactants (alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, etc.), nonionic surfactants (fatty acid amide derivatives, polyhydric alcohol derivatives, etc.), and amphoteric surfactants (alanine, dodecyldi(aminoethyl)glycine, di(octylaminoethyl)glycine, N-alkyl-N,N-dimethylammonium betaine, etc.). Fluoroalkyl group-containing anionic or cationic surfactants can also be used.

[0167] In this step, the dispersion diameter of the additive particles in the additive particle dispersion liquid prepared is preferably in the range of 10 to 300 nm in volume median diameter. The volume median diameter of the colorant particles in the additive particle dispersion liquid can be measured using, for example, an electrophoretic light scattering photometer "ELS-800" (manufactured by Otsuka Electronics Co., Ltd.).

[0168] The additives may be incorporated into the toner base particles by dissolving or dispersing them in advance in a monomer solution for forming a resin using a mini-emulsion method in the binder resin particle dispersion preparation step described below.

[0169] [2] Binder resin particle dispersion preparation process Methods for dispersing a binder resin in an aqueous medium include the aqueous direct dispersion method, the dissolution-emulsification-desolvation method, and the phase inversion emulsification method. In the aqueous direct dispersion method, the binder resin is dispersed in an aqueous medium to which a surfactant has been added by ultrasonic dispersion, bead mill dispersion, or the like. In the dissolution-emulsification-desolvation method, the binder resin is dissolved in a solvent, and this solution is dispersed in an aqueous medium to form emulsified particles (oil droplets), and then the solvent is removed.

[0170] 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. The volume-based median diameter can be measured using, for example, "UPA-EX150" (manufactured by Microtrack Bell Co., Ltd.).

[0171] When the binder resin is an amorphous vinyl resin, a binder resin particle dispersion can be prepared, for example, by the following method. A polymerizable monomer for forming an amorphous vinyl resin is added to an aqueous medium containing a surfactant at or below its critical micelle concentration (CMC). Next, a liquid in which a release agent, a charge control agent, etc., is dissolved or dispersed as needed is added to the aqueous medium, and mechanical energy is applied to form droplets. Thereafter, a water-soluble radical polymerization initiator is added to the aqueous medium, and a polymerization reaction is allowed to proceed in the droplets. Note that the droplets may also contain a hydrophobic polymerization initiator.

[0172] This process requires the application of mechanical energy to emulsify the emulsion, i.e., to form droplets. Examples of devices for applying mechanical energy include devices that apply strong stirring, such as a homomixer, ultrasonic wave, or Manton-Gaulin mixer, or devices that apply ultrasonic vibration energy.

[0173] In this step, the binder resin particles may have a multilayer structure of two or more layers 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 resin particle dispersion prepared by a conventional emulsion polymerization treatment (first-stage polymerization), and the system is further polymerized (second-stage polymerization, third-stage polymerization).

[0174] When a surfactant is used, the surfactants described above can be used.

[0175] (Polymerization initiator) The polymerization initiator is not particularly limited, and known initiators can be used. Examples of the polymerization initiator include peroxides (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, triphenyl peracetic acid tert-hydroperoxide, tert-butyl performate, and tetralin hydroperoxide. Examples of suitable azo compounds include tert-butyl acetate, 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).

[0176] Among these, the polymerization initiator is preferably water-soluble. Examples of the water-soluble polymerization initiator include ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide, 2,2′-azobis(2-amidinopropane) hydrochloride, 2,2′-azobis(2-amidinopropane) nitrate, 1,1′-azobis(1-methylbutyronitrile-3-sodium sulfonate), and 4,4′-azobis-4-cyanovaleric acid.

[0177] As the polymerization initiator, a redox polymerization initiator (such as a combination of persulfate and metabisulfite, or a combination of hydrogen peroxide and ascorbic acid) can also be used.

[0178] (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 for the purpose of adjusting the molecular weight of the binder resin. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.

[0179] 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. The volume-based median diameter can be measured using, for example, "UPA-EX150" (manufactured by Microtrack Bell Co., Ltd.).

[0180] [3] Core particle formation process This step is a step in which the additive particles and binder resin particles contained in each particle dispersion liquid formed in the above steps are aggregated and fused in an aqueous medium.

[0181] Specific methods for aggregating and fusing the additive particles and binder resin particles include, for example, the following methods. First, an aggregating agent is added to an aqueous medium containing each particle dispersion to a concentration equal to or higher than the critical aggregating concentration. Next, the aqueous medium is heated to a temperature equal to or higher than the glass transition temperature of the binder resin particles and the melting peak temperature of the release agent, thereby promoting salting out of the additive particles and the binder resin particles and simultaneously promoting fusion. When the particles formed by aggregation and fusion have grown to the desired particle size, an aggregation terminator is added to the aqueous medium to stop the particle growth. Furthermore, the aqueous medium is continuously heated as needed to control the particle shape.

[0182] In this method, it is preferable to keep the time left as short as possible after adding the flocculant to the aqueous medium and quickly heat the aqueous medium to a temperature equal to or higher than the glass transition temperature of the binder resin. Although the reason for this is not clear, shortening the time left after salting out can reduce fluctuations in the particle aggregation state, which can lead to unstable particle size distribution and fluctuations 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.

[0183] The temperature rise rate is preferably 1°C / min or more. There is no particular upper limit to the temperature rise rate, but it is preferably 15°C / min or less in order to prevent the generation of coarse particles due to rapid fusion. Furthermore, after the reaction system reaches a temperature equal to or higher than the glass transition temperature, it is essential to maintain the temperature of the reaction system for a certain period of time to allow fusion to continue. This effectively promotes the growth and fusion of the toner base particles, thereby improving the durability of the final toner.

[0184] (flocculant) The flocculant is not particularly limited, but is preferably a metal salt. Examples of monovalent metal salts include salts of alkali metals (sodium, potassium, lithium, etc.). Examples of divalent metal salts include salts of calcium, magnesium, manganese, copper, etc. Examples of trivalent metal salts include salts of iron, aluminum, etc. Specific examples of metal salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, polyaluminum chloride, aluminum sulfate, etc. Among these, it is more preferable to use trivalent metal salts because they can promote flocculation with a small amount and the flocculation properties can be easily controlled. These may be used alone or in combination of two or more.

[0185] When a surfactant is used, the surfactants described above can be used.

[0186] [4] Shell layer formation process In this step, the binder resin particles for the shell layer are aggregated and fused to the surface of the core particles in the same procedure as in the above-mentioned core particle formation step [3] to form toner base particles having a core-shell structure.

[0187] [5] Filtration and washing process The filtration and washing steps can be carried out by known methods.

[0188] [6] Drying process The drying step can be carried out by a known method.

[0189] [7] External additive addition process This step is a step of adding the external additive according to the present embodiment to the dried toner base particles.

[0190] The external additive may be added by a dry method in which a powdered external additive is added to dried toner base particles and mixed in. Examples of the mixing device include mechanical mixers such as a Henschel mixer, a Nauta mixer, a Turbula mixer, and a coffee mill.

[0191] In particular, by using a mixing device capable of applying shear force to the particles being processed, such as a Henschel mixer, and lengthening the mixing time or increasing the rotational peripheral speed of the stirring blades, the external additive can be firmly attached to each toner base particle.

[0192] 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 external additives.

[0193] (5) Two-component developer The toner according to the present embodiment may be mixed with a carrier and used as a two-component developer. By using the toner according to the present embodiment as a two-component developer, it can be made into a non-magnetic toner, and can be made into a color toner by adding a colorant. The carrier is not particularly limited, and known carriers can be used.

[0194] 3. Image forming device The image forming apparatus according to this embodiment has a photoreceptor 1, which will be described later. The image forming apparatus according to this embodiment is an electrophotographic type, and preferably has a first charging unit, an exposure unit, a developing unit, a transfer unit, a second charging unit, and a cleaning unit.

[0195] The first charging section charges the surface of the photoreceptor 1 . The exposure section irradiates the surface of the photoreceptor 1 with light to form an electrostatic image. The developing unit develops the electrostatic image with toner to form a toner image. The transfer section transfers the toner image onto a transfer material, which is an image support such as plain paper or a transparent sheet. The second charging section charges the surface of the photoreceptor 1 after the toner image is transferred onto the transfer material. The cleaning unit removes residual toner from the photoreceptor 1 .

[0196] FIG. 1 is a schematic diagram showing an example of the configuration of an image forming apparatus according to the present embodiment. The image forming apparatus 100 is a so-called tandem color image forming apparatus, and includes four sets of image forming units 10Y, 10M, 10C, and 10Bk, an intermediate transfer unit 7, a paper feed unit 21, a fixing unit 24, etc. An original image reading device SC is located on top of the device body A of the image forming apparatus 100.

[0197] The image forming unit 10Y, which forms a yellow image, has a first charging section 2Y, an exposure section 3Y, a developing section 4Y, a primary transfer roller 5Y, a second charging section 9Y, and a cleaning section 6Y, which are arranged in sequence around the drum-shaped photoreceptor 1Y in the direction of rotation of the photoreceptor 1Y.

[0198] Image forming unit 10M, which forms magenta images, has a first charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M, a second charging unit 9M, and a cleaning unit 6M around a drum-shaped photosensitive member 1M, which are positioned sequentially along the rotation direction of photosensitive member 1M.

[0199] Image forming unit 10C, which forms a cyan image, has a first charging section 2C, an exposure section 3C, a developing section 4C, a primary transfer roller 5C, a second charging section 9C, and a cleaning section 6C, which are arranged sequentially around a drum-shaped photoreceptor 1C in the direction of rotation of the photoreceptor 1C.

[0200] Image forming unit 10Bk, which forms black images, has a drum-shaped photoconductor 1Bk and a first charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk, a second charging unit 9Bk, and a cleaning unit 6Bk, which are arranged in sequence along the rotation direction of photoconductor 1Bk.

[0201] The photoconductor 1 described later is used as the photoconductors 1Y, 1M, 1C, and 1Bk.

[0202] The only difference between the image forming units 10Y, 10M, 10C, and 10Bk is the color of the toner images they form on the photoconductors 1Y, 1M, 1C, and 1Bk. Therefore, the image forming unit 10Y will be described in detail as an example, and a description of the image forming units 10M, 10C, and 10Bk will be omitted.

[0203] In the image forming unit 10Y, a first charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roller 5Y, a second charging unit 9Y, and a cleaning unit 6Y are located around the photoreceptor 1Y, which is an image forming body. The image forming unit 10Y forms a yellow (Y) toner image on the photoreceptor 1Y. In this embodiment, at least the photoreceptor 1Y, the first charging unit 2Y, the developing unit 4Y, the second charging unit 9Y, and the cleaning unit 6Y of the image forming unit 10Y are provided integrally.

[0204] The first charging section 2Y applies a uniform potential to the photosensitive member 1Y. As the first charging section 2Y, for example, a corona discharge type charger is used.

[0205] The exposure unit 3Y exposes the photoconductor 1Y, which has been given a uniform potential by the first charging unit 2Y, based on an image signal (yellow), to form an electrostatic charge image corresponding to the yellow image. The exposure unit 3Y includes, for example, an LED in which light-emitting elements are arranged in an array in the axial direction of the photoconductor 1Y, and an imaging element. The exposure unit 3Y also includes, for example, a laser optical system.

[0206] The developing unit 4Y develops the electrostatic image formed on the photoreceptor 1Y with toner to form a toner image. The developing unit 4Y includes, for example, a developing sleeve and a voltage application device. The developing sleeve has a built-in magnet and rotates while holding developer. The voltage application device applies a bias voltage between the photoreceptor 1Y and the developing sleeve. The bias voltage may be either DC or AC, or both.

[0207] The primary transfer roller 5Y transfers the toner image formed on the photosensitive member 1Y onto an endless belt-like intermediate transfer member 70. The primary transfer roller 5Y is positioned in contact with the intermediate transfer member 70.

[0208] The second charging section 9Y is provided as a pre-cleaning member that charges (de-electrifies) the surface of the photosensitive member 1Y after the toner image is transferred to the intermediate transfer member 70. As the second charging section 9Y, for example, a corona discharge type charger is used.

[0209] The cleaning unit 6Y removes toner remaining on the photoreceptor 1 after a toner image has been transferred to the intermediate transfer body 70 or after pre-cleaning. The cleaning unit 6Y includes, for example, a blade and a brush roller provided upstream of the blade. The toner remaining on the photoreceptor 1 can be removed by bringing the blade into contact with the photoreceptor 1. In this embodiment, by using the photoreceptor 1 described below, wear on the photoreceptor 1 can be reduced even when the blade is pressed strongly.

[0210] The intermediate transfer unit 7 has an intermediate transfer member 70 as a second image carrier. The intermediate transfer member 70 is a semiconductive endless belt that is wound around and rotatably supported by multiple rollers 71, 72, 73, and 74. The intermediate transfer unit 7 is equipped with a cleaning section 6b that removes toner from the intermediate transfer member 70.

[0211] The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk, and the intermediate transfer unit 7. The housing 8 can be pulled out from the apparatus main body A via support rails 82L and 82R.

[0212] The image forming apparatus 100 includes a secondary transfer roller 5b that transfers a color image formed on the intermediate transfer body 70 onto a transfer material P. A paper feed unit 21 supplies the transfer material P to the secondary transfer roller 5b. The paper feed unit 21 includes a paper feed cassette 20 that stores the transfer material P, a plurality of intermediate rollers 22A, 22B, 22C, and 22D that transport the transfer material P to the secondary transfer roller 5b, and a registration roller 23.

[0213] The fixing unit 24 fixes the color image transferred onto the transfer material P onto the transfer material P. The fixing unit 24 includes, for example, a heat roller and a pressure roller of a heat roller fixing system. The heat roller has a heat source inside. The heat roller and the pressure roller are provided in a state of pressure contact so as to form a fixing nip portion.

[0214] The image forming apparatus 100 has a paper discharge tray 26 for removing the transfer material P on which an image has been formed. The image forming apparatus 100 also has a paper discharge roller 25 downstream of the fixing unit 24 for transporting the transfer material P that has been subjected to the fixing process to the paper discharge tray 26.

[0215] In this embodiment, the image forming apparatus 100 is a color laser printer, but the image forming apparatus 100 may also be a monochrome laser printer, a copier, a multifunction machine, or the like.

[0216] The photoreceptor according to this embodiment will be described in detail below.

[0217] (1) Photoreceptor The photoreceptor according to this embodiment has a photosensitive layer on a conductive support. The "photosensitive layer" refers to a layer that absorbs light to generate or transport electric charges. The number of layers in the photosensitive layer is not particularly limited, and may be one layer or multiple layers.

[0218] 2 is a cross-sectional schematic diagram of a photoreceptor according to this embodiment. For example, when the photosensitive layer 103 has two layers, the photosensitive layer 103 has a charge generation layer 103a and a charge transport layer 103b in this order from the conductive support 101 side. If necessary, an intermediate layer 102 may be provided between the conductive support 101 and the photosensitive layer 103. If necessary, a protective layer (not shown) may be further provided on the charge transport layer 103b. If the protective layer has the function of transporting charges, the protective layer is also included in the photosensitive layer 103 in this embodiment.

[0219] (1.1) Photosensitive layer The photosensitive layer according to this embodiment contains polyarylate as a binder resin. This improves the hardness of the photosensitive layer and the abrasion resistance of the photoreceptor. Furthermore, since photoreceptor wear is likely to occur due to strong pressure from a blade during cleaning, the layer containing polyarylate is preferably the outermost layer of the photoreceptor, and is preferably a charge transport layer. Polyarylate may be contained in the entire photosensitive layer, or in only a portion of the layer.

[0220] (1.1.1) Polyarylate The polyarylate according to this embodiment is obtained by synthesis of a dicarboxylic acid and a diol, and therefore has a structure including structural units derived from the dicarboxylic acid and structural units derived from the diol.

[0221] The dicarboxylic acid preferably contains an aromatic dicarboxylic acid as a main component. The diol preferably contains an aromatic diol as a main component. Here, "main component" refers to a component that is contained in an amount of 60 mass% or more based on the total mass of the dicarboxylic acid. The dicarboxylic acid may contain, for example, an aliphatic dicarboxylic acid, an alicyclic dicarboxylic acid, etc., which does not have an aromatic ring in its structure. The diol may contain, for example, an aliphatic diol, an alicyclic diol, etc., which does not have an aromatic ring in its structure.

[0222] In the synthesis of polyarylate, dicarboxylic acids may be used in the form of derivatives, specifically, the carboxyl groups of dicarboxylic acids may be substituted with more reactive substituents (such as acid halide groups).

[0223] An aromatic dicarboxylic acid has at least one aromatic ring and two carboxy groups in its structure. The aromatic ring may be two or more. The carboxy group is preferably directly bonded to the aromatic ring. Alternatively, an acid halide group may be used instead of the carboxy group. The "acid halide group" refers to a group in which the hydroxy group in the carboxy group is substituted with a halogen atom.

[0224] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, chlorophthalic acid, nitrophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, methyl terephthalic acid, 4,4'-biphenyldicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 4,4'-diphenylisopropylidenedicarboxylic acid, 1,2-bis(4-carboxyphenoxy)ethane, 5-sodium sulfoisophthalic acid, and diphenic acid. Examples of aromatic dicarboxylic acids include derivatives thereof, such as acid halides. These aromatic dicarboxylic acids may be used alone or in combination.

[0225] From the viewpoint of obtaining a polyarylate having high hardness, the aromatic dicarboxylic acid preferably has two aromatic rings in one molecule in its structure, and particularly preferably includes 4,4'-biphenyldicarboxylic acid or 4,4'-diphenyletherdicarboxylic acid.

[0226] The structural unit derived from 4,4'-biphenyldicarboxylic acid is represented by the following structural formula (1).

[0227] [ka]

[0228] The structural unit derived from 4,4'-diphenyl ether dicarboxylic acid is represented by the following structural formula (2).

[0229] [ka]

[0230] The aromatic diol has at least one aromatic ring and two hydroxy groups in its structure. The aromatic ring may be two or more. The hydroxy groups are preferably directly bonded to the aromatic ring.

[0231] Examples of aromatic diols include 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(3-methyl-4-hydroxyphenyl)propane (bisphenol C), 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 1,1-bis(4-hydroxyphenyl)-1-phenylethane (bisphenol AP), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3 ,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxybiphenyl [4,4'-biphenol], 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC), 4,4'-(1,3-dimethylbutylidene)diphenol, resorcinol, etc. These aromatic diols may be used alone or in combination of two or more.

[0232] From the viewpoint of obtaining a polyarylate having high hardness, the aromatic diol preferably has two aromatic rings in one molecule in its structure, and among them, the aromatic dicarboxylic acid preferably contains 1,1-bis(4-hydroxyphenyl)-2-ethylhexane.

[0233] The structural unit derived from 1,1-bis(4-hydroxyphenyl)-2-ethylhexane is represented by the following structural formula (3).

[0234] [ka]

[0235] In the synthesis of polyarylate, the molar ratio of dicarboxylic acid monomer to diol is preferably within the range of 48:52 to 52:48, and more preferably 50:50.

[0236] In the synthesis of polyarylate, a trifunctional or higher polyvalent monomer may be further used. By using a trifunctional or higher polyvalent monomer, a branched structure can be introduced into the polyarylate. Examples of trifunctional or higher polyvalent monomers include tricarboxylic acids (1,3,5-benzenecarboxylic acid, etc.) and triol components (4,4',4''-trihydroxytriphenylmethane, etc.).

[0237] In the synthesis of polyarylate, the content of the trifunctional or higher polyvalent monomer is not particularly limited, but is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the total amount of the dicarboxylic acid and the diol.

[0238] In the synthesis of polyarylate, a terminal blocking agent may be used to adjust the molecular weight. Examples of terminal blocking agents include monohydric phenols (phenol, cresol, p-tert-butylphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, cumylphenol, etc.), monohydric acid chlorides (benzoic acid chloride, methanesulfonyl chloride, phenyl chloroformate, etc.), monohydric alcohols (methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, phenethyl alcohol, etc.), and monohydric carboxylic acids (acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, p-methoxyphenylacetic acid, etc.). These may be used alone or in combination of two or more.

[0239] In the synthesis of polyarylate, the content of the end-capping material is not particularly limited, but the content is, for example, preferably in the range of 0.2 to 20 parts by mass, more preferably in the range of 0.6 to 10 parts by mass, and even more preferably in the range of 2 to 5 parts by mass, relative to 100 parts by mass of the diol.

[0240] (1.1.2) Charge generation layer The charge generating layer contains a charge generating agent and a binder resin for the charge generating layer, and the above-mentioned polyarylate may be used as the binder resin for the charge generating layer.

[0241] The charge generating material is not particularly limited, and known charge generating materials may be used. Examples of charge generating materials include azo pigments, quinone pigments, indigo pigments, polycyclic quinone pigments, and phthalocyanine pigments. Examples of azo pigments include Sudan Red and Diane Blue. Examples of quinone pigments include pyrenequinone and anthanthrone. Examples of indigo pigments include quinocyanine pigments, perylene pigments, indigo, and thioindigo. Examples of polycyclic quinone pigments include pyranthrone and diphthaloylpyrene. Among these, polycyclic quinone pigments or titanyl phthalocyanine pigments are preferred. These may be used alone or in combination.

[0242] The binder resin for the charge generation layer other than polyarylate is not particularly limited, and known resins may be used. Examples of binder resins for the charge generation layer include polystyrene, polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral, epoxy resin, polyurethane, phenolic resin, polyester, alkyd resin, polycarbonate, silicone resin, and melamine resin. Examples of binder resins for the charge generation layer include copolymers containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin). These may be used alone or in combination of two or more.

[0243] The content of the charge generating agent in the charge generating layer is preferably within a range of 1 to 600 parts by mass, and more preferably within a range of 50 to 500 parts by mass, per 100 parts by mass of the binder resin for the charge generating layer.

[0244] The thickness of the charge generating layer varies depending on the characteristics of the charge generating agent, the characteristics and content of the binder resin for the charge generating layer, etc., but is preferably in the range of 0.01 to 5 μm, more preferably in the range of 0.05 to 3 μm.

[0245] (1.1.3) Charge transport layer The charge transport layer contains a charge transport material and a binder resin for the charge transport layer, and the above-mentioned polyarylate may be used as the binder resin for the charge transport layer.

[0246] The charge transport material is not particularly limited, and may be a known charge transport material.As the charge transport material, for example, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, triphenylamine derivatives, etc. may be mentioned.These may be used alone or in combination of two or more.

[0247] The binder resin for the charge transport layer is not particularly limited, and known resins may be used. Examples of the binder resin for the charge transport layer include polycarbonate, polyacrylate, polyester, polystyrene, styrene-acrylonitrile copolymer, polymethacrylic acid ester, and styrene-methacrylic acid ester copolymer. These may be used alone or in combination of two or more.

[0248] The content of the charge transport agent in the charge transport layer is preferably within a range of 10 to 500 parts by weight, more preferably within a range of 20 to 250 parts by weight, per 100 parts by weight of the binder resin for the charge transport layer.

[0249] The thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics and content of the binder resin for the charge transport layer, etc., but is preferably within the range of 5 to 40 μm, more preferably 10 to 30 μm.

[0250] The charge transport layer may contain an antioxidant, an electronic conductive agent, a stabilizer, silicone oil, etc. The antioxidant is preferably a compound disclosed in JP-A-2000-305291. The electronic conductive agent is preferably a compound disclosed in JP-A-50-137543 or JP-A-58-76483.

[0251] (1.2) Conductive support The conductive support may be any support that is conductive. Examples of the conductive support include a metal such as aluminum, copper, chromium, nickel, zinc, or stainless steel formed into a drum or sheet shape. The conductive support may be a plastic film laminated with a metal foil containing aluminum, copper, or the like. The conductive support may be a plastic film onto which aluminum, indium oxide, tin oxide, or the like is vapor-deposited. The conductive support may be a metal, plastic film, paper, or the like, on which a conductive layer is provided by applying a conductive substance alone or together with a binder resin.

[0252] (1.3) Middle class The intermediate layer can improve the barrier property and adhesiveness between the conductive support and the photosensitive layer. The intermediate layer contains a binder resin for the intermediate layer and, if necessary, conductive particles, metal oxide particles, etc.

[0253] The binder resin for the intermediate layer is not particularly limited, and known resins may be used. Examples of binder resins for the intermediate layer include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane, and gelatin. Among these, alcohol-soluble polyamide is preferred.

[0254] The intermediate layer may contain various conductive particles or metal oxide particles for the purpose of adjusting resistance. Examples of metal oxide particles include alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, and zirconium oxide. Examples of metal oxide particles include particles of composite metal oxides such as tin-doped indium oxide and antimony-doped tin oxide. The metal oxide particles may also be particles of composite oxides having a perovskite structure, such as strontium titanate.

[0255] The number average primary particle size of the metal oxide particles is preferably within a range of 10 to 300 nm, and more preferably within a range of 20 to 100 nm.

[0256] The conductive particles and the metal oxide particles may each be used alone or in combination of two or more kinds. When two or more kinds are used in combination, they may be in the form of a solid solution or fused particles.

[0257] The content of the conductive particles and metal oxide particles in the intermediate layer is preferably within a range of 20 to 400 parts by mass, and more preferably within a range of 50 to 350 parts by mass, per 100 parts by mass of the binder resin.

[0258] The thickness of the intermediate layer is preferably within a range of 0.1 to 15 μm, and more preferably within a range of 0.3 to 10 μm. The intermediate layer may have a laminated structure of two or more layers depending on the function. The intermediate layer may contain an electron transport agent.

[0259] (1.4) Manufacturing method The method for producing the photoreceptor is not particularly limited, and known production methods may be used. The photoreceptor can be produced, for example, by sequentially forming each layer constituting the photoreceptor on a conductive support. Specifically, first, a coating liquid containing solid components (raw material components) constituting each layer and a solvent is prepared. Next, the prepared coating liquid is applied to the conductive support to form a coating film. Thereafter, the formed coating film is cured.

[0260] 4.Image forming method In the image forming method according to this embodiment, an image is formed using the image forming system that combines the electrostatic image developing toner with the image forming apparatus 100 that includes the photoreceptor 1. This allows for a combination of toner that is less likely to remain and the photoreceptor, and the photoreceptor has high wear resistance. Therefore, even when printing at high speed for a long period of time, high-quality images can be formed with few image defects.

[0261] The steps of the image forming method are not particularly limited, and an example will be described below. Note that the image forming unit 10Y will be described in detail as an example, and descriptions of the image forming units 10M, 10C, and 10Bk will be omitted.

[0262] The surface of the photoconductor 1Y is discharged and negatively charged by the first charging unit 2Y. The surface of the photoconductor 1Y is exposed to light based on an image signal by the exposure unit 3Y, forming an electrostatic image. The developing unit 4Y applies toner to the surface of the photoconductor 1Y and develops it, forming a toner image.

[0263] The toner image formed on the photosensitive member 1Y is sequentially transferred (primary transfer) by the primary transfer roller 5Y onto the rotating intermediate transfer member 70. The same procedure is used for the image forming units 10M, 10C, and 10Bk, whereby the toner images are sequentially transferred onto the intermediate transfer member 70. As a result, a color image is formed on the intermediate transfer member 70.

[0264] The surface of the photoreceptor 1Y is neutralized by the second charging unit 9Y. The toner remaining on the surface of the photoreceptor 1Y is removed by the cleaning unit 6Y. In preparation for the next image forming process, the photoreceptor 1Y is negatively charged by the charging unit 2Y.

[0265] Meanwhile, a transfer material P is fed from a paper feed cassette 20 by a paper feed unit 21. The transfer material P is transported to a secondary transfer roller 5b via a plurality of intermediate rollers 22A, 22B, 22C, and 22D and a registration roller 23. A color image is transferred (secondary transfer) onto the transfer material P by the secondary transfer roller 5b.

[0266] The transfer material P onto which the color image has been transferred is subjected to a fixing process by the fixing unit 24. The transfer material P is nipped by paper discharge rollers 25 and discharged to the outside of the apparatus, and placed on a paper discharge tray 26. After the transfer material P is separated from the intermediate transfer body 70, the toner remaining on the intermediate transfer body 70 is removed by the cleaning unit 6b.

[0267] An image is formed on the transfer material P through the above steps.

[0268] Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are for purposes of illustration and example only and not limitation, and the scope of the present invention should be interpreted by the following claims. [Example]

[0269] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass." In the following examples, unless otherwise specified, all operations were carried out at room temperature (25°C).

[0270] 1. Toner production (1) Preparation of inorganic particles A (1.1) Preparation of inorganic particles A1 Silica particles with a number-average primary particle size of 40 nm were prepared by a gas phase method. While stirring under a nitrogen atmosphere, the following silicone oil solution was sprayed onto 100.0 parts by mass of the silica particles as a treatment agent. The silicone oil solution had a kinematic viscosity of 100 mm at 25°C. 2 A solution was prepared by diluting 22.0 parts by mass of silicone oil "KF-96-100cs" (polydimethylsiloxane: PDMS, manufactured by Shin-Etsu Chemical Co., Ltd.) having a molecular weight of 1 / s with 50.0 parts by mass of hexane. The resulting reaction mixture was dried by stirring in a nitrogen stream at 320°C for 60 minutes. The reaction mixture was then cooled to obtain inorganic particles A1. The number-average primary particle size was measured by the method described above.

[0271] (1.2) Preparation of inorganic particles A2 to A11 Inorganic particles A2 to A11 were produced in the same manner as inorganic particles A1, except that the particle material, number average primary particle size, and surface modifier were changed as shown in Table I.

[0272] The compositions of inorganic particles A1 to A11 are shown in Table I. Details of the surface treatment agents in Table I are shown below. PDMS: Polydimethylsiloxane "KF-96-100cs" (Shin-Etsu Chemical Co., Ltd.) Alkyl-modified silicone: Side-chain alkyl-modified silicone "KF-414" (Shin-Etsu Chemical Co., Ltd.) Carbinol-modified silicone: Side-chain carbinol silicone "X22-4034" (Shin-Etsu Chemical Co., Ltd.) HMDS: hexamethyldisilazane C8 silane: n-octyltrimethoxysilane C16 silane: n-hexadecyltrimethoxysilane

[0273] [Table 1]

[0274] (2) Preparation of inorganic particles B (2.1) Preparation of inorganic particles B1 The following ingredients were added and mixed in a 3 liter reactor equipped with a stirrer, a dropping funnel, and a thermometer. Methanol 945.0 parts by mass 28% ammonia water 45.0 parts by mass Water 135.0 parts by mass

[0275] The temperature of the resulting solution was adjusted to 35°C, and the following components were added dropwise over 6 hours while stirring. After the addition, stirring was continued for another hour to carry out hydrolysis, yielding a suspension of silica particles. Tetramethoxysilane 405.0 parts by mass

[0276] The solvent was removed from the resulting suspension under reduced pressure to obtain silica particles having a number average primary particle size of 110 nm and a shape factor SF-2 of 112. The number average primary particle size and shape factor SF-2 were measured by the methods described above.

[0277] While stirring under a nitrogen atmosphere, the following silicone oil solution was sprayed as a treatment onto 100.0 parts by mass of the obtained silica particles. The silicone oil solution had a kinematic viscosity of 100 mm at 25°C. 2 A solution was prepared by diluting 22.0 parts by mass of silicone oil "KF-96-100cs" (polydimethylsiloxane: PDMS, manufactured by Shin-Etsu Chemical Co., Ltd.) having a molecular weight of 1 / s with 50.0 parts by mass of hexane. The resulting reaction mixture was dried by stirring under a nitrogen stream at 320°C for 60 minutes. The reaction mixture was then cooled to obtain inorganic particles B1.

[0278] (2.2) Preparation of inorganic particles B2 to B10 Inorganic particles B2 to B10 were produced using the same procedure as inorganic particles B1, except that the number-average primary particle size, shape factor, and surface treatment agent were changed as shown in Table II. The number-average primary particle size and shape factor were adjusted by controlling the mass ratio of each component (alkoxysilane, ammonia, alcohol, and water), reaction temperature, stirring speed, supply rate, etc. in the hydrolysis and polycondensation steps.

[0279] The compositions of inorganic particles B1 to B10 are shown in Table II below. Details of the surface treatment agents in Table II are shown below. PDMS: Polydimethylsiloxane "KF-96-100cs" (Shin-Etsu Chemical Co., Ltd.) HMDS: hexamethyldisilazane

[0280] [Table 2]

[0281] (3) Preparation of toner base particles The toner base particles M1 to M8 were produced by an emulsion aggregation method, and the toner base particle M9 was produced by a kneading and pulverization method.

[0282] (3.1) Preparation of toner base particles M1 (3.1.1) Synthesis of amorphous polyester 1 Bisphenol A ethylene oxide adduct 114.0 parts by mass Bisphenol A propylene oxide adduct 290.0 parts by mass Terephthalic acid 100.0 parts by mass Dodecenyl succinic acid 130.0 parts by mass Trimellitic acid 15.0 parts by mass

[0283] The above monomer components were charged into a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The atmosphere in the reaction vessel was then purged with dry nitrogen gas, and 0.3% by mass of tin dioctanoate, based on the total mass of the above monomer components, was then charged into the reaction vessel. The temperature was raised to 235°C over 1 hour under a nitrogen gas stream, and the above monomers were reacted for 3 hours. The pressure inside the reaction vessel was reduced to 10.0 mmHg, and the reaction was continued with stirring. The reaction was terminated when the reaction product reached the desired molecular weight. The glass transition temperature of the resulting amorphous polyester was 61°C and the weight-average molecular weight was 42,000.

[0284] (3.1.2) Preparation of amorphous polyester dispersion 1 (AP-1) Amorphous polyester 100.0 parts by mass Methyl ethyl ketone 60.0 parts by mass Isopropyl alcohol 15.0 parts by mass The above ingredients were placed in a reaction vessel equipped with a stirrer and dissolved at 60°C.

[0285] 10% aqueous ammonia solution 3.5 parts by mass The reaction vessel was then cooled to 35°C before the above ingredients were added. Ion-exchanged water 300.0 parts by mass The above components were then added dropwise to the reaction vessel over 3 hours. Next, methyl ethyl ketone and isopropyl alcohol were removed using an evaporator to obtain Amorphous Polyester Dispersion 1 (AP-1). The median particle size of the resulting amorphous polyester was 150 nm.

[0286] (3.1.3) Synthesis of crystalline polyester 1 1,10-decanedicarboxylic acid 350.0 parts by mass 1,6-Hexanediol 170.0 parts by mass The above monomer components were charged into a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet tube. The atmosphere in the reaction vessel was then purged with dry nitrogen gas, and 0.3% by mass of tin dioctanoate, based on the total mass of the above monomer components, was then charged into the reaction vessel. The mixture was stirred and reacted at 160°C for 3 hours under a nitrogen gas stream, and the temperature was then further increased to 180°C over 1.5 hours. The pressure in the reaction vessel was then reduced to 3 kPa, and the reaction was terminated when the desired molecular weight was achieved, yielding crystalline polyester 1. The resulting crystalline polyester 1 had a melting point of 73°C and a weight-average molecular weight of 28,000.

[0287] (3.1.4) Preparation of Crystalline Polyester Dispersion 1 (CP-1) Crystalline polyester 1 100.0 parts by mass Methyl ethyl ketone 60.0 parts by mass Isopropyl alcohol 15.0 parts by mass The above ingredients were placed in a reaction vessel equipped with a stirrer and dissolved at 65°C. 10% aqueous ammonia solution 5.0 parts by mass The reaction vessel was then cooled to 60°C before the above ingredients were added. Ion-exchanged water 300.0 parts by mass The above components were then added dropwise to the reaction vessel over 3 hours. Next, methyl ethyl ketone and isopropyl alcohol were removed using an evaporator to obtain Crystalline Polyester Dispersion 1 (CP-1). The median particle size of the resulting crystalline polyester was 150 nm.

[0288] (3.1.5) Preparation of release agent dispersion Paraffin wax "HNP-9" (manufactured by Nippon Seiro Co., Ltd.) 100.0 parts by mass Anionic surfactant "Neogen (registered trademark) RK" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 1.0 parts by mass Ion-exchanged water 350.0 parts by mass The above components were mixed, heated to 100°C, and dispersed using a homogenizer "Ultra Turrax T50" (manufactured by IKA Corporation). After that, a dispersion treatment was carried out using a Manton-Gaulin high-pressure homogenizer (manufactured by Gaulin Corporation) to obtain a release agent dispersion. The median particle diameter of the obtained release agent was 200 nm.

[0289] (3.1.6) Preparation of cyan colorant dispersion Cyan pigment (Dainichiseika Color & Chemicals Co., Ltd., Pigment Blue 15:3 (copper phthalocyanine)) 45.0 parts by mass Anionic surfactant "Neogen (registered trademark) R" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 2.0 parts by mass Ion-exchanged water 250.0 parts by mass The above components were mixed and dispersed using a high-pressure impact disperser, Ultimizer HJP30006 (manufactured by Sugino Machine Co., Ltd.), to obtain a cyan colorant dispersion. The resulting colorant had a median particle size of 150 nm.

[0290] (3.1.7) Formation of toner base particles M1 Amorphous polyester dispersion 1 (AP-1) (solid content equivalent) 54.5 parts by mass Crystalline polyester dispersion 1 (CP-1) (solid content equivalent) 15.0 parts by mass Release agent dispersion (solid content equivalent) 4.5 parts by mass Cyan colorant dispersion (solid content equivalent) 6.0 parts by mass 6.3 parts by mass of 10% aluminum sulfate aqueous solution Ion-exchanged water 650.0 parts by mass

[0291] The above components were placed in a round stainless steel flask. Then, using a homogenizer "Ultra Turrax T50" (manufactured by IKA Corporation), they were mixed and dispersed at 5,000 rpm for 10 minutes. The reaction mixture in the flask was then heated to 40°C while stirring. Thereafter, the temperature was increased at a rate of 0.5°C per minute, and the temperature was maintained when the particle size of the reaction mixture reached 2.5 μm, forming core particles.

[0292] Amorphous polyester dispersion 1 (AP-1) (solid content equivalent) 20.0 parts by mass The above ingredients were then added dropwise over a period of 1 hour.

[0293] Ethylenediaminetetraacetic acid (EDTA) tetrasodium salt "Chilest 40" (manufactured by Chelest Co., Ltd.) 11.0 parts by mass After the above components were added, aqueous sodium hydroxide solution was added to adjust the pH of the reaction solution to 8. The temperature of the reaction solution was then raised to 82.5°C, after which the pH of the reaction solution was lowered by 0.05 every 10 minutes with nitric acid, and stirring was continued for 45 minutes.

[0294] The reaction solution was cooled to below 40°C, stirring was stopped, and the aggregates were removed by filtration using a 45 μm filter. The pH of the reaction solution was adjusted to 4 with hydrochloric acid, and solid-liquid separation was performed. The solid component was then thoroughly washed with ion-exchanged water and dried. This yielded toner base particles M1, which had a shell layer on the surface of the core particles. The volume-average particle size of the toner base particles M1 was 3 μm, and the average circularity was 0.960.

[0295] (3.2) Formation of toner base particles M2 to M8 Toner base particles M2 to M8 were produced using the same procedure as toner base particle M1, except that the volume average particle size and average circularity were changed as shown in Table 3. The volume average particle size and average circularity of the toner base particles were adjusted by controlling the reaction temperature and reaction time during toner base particle formation.

[0296] (3.3) Formation of toner base particles M9 Amorphous polyester 1 74.5 parts by mass Crystalline polyester 1 15.0 parts by mass Paraffin wax "HNP-9" (manufactured by Nippon Seiro Co., Ltd.) 4.5 parts by mass Cyan pigment (Dainichiseika Color & Chemicals Co., Ltd., Pigment Blue 15:3 (copper phthalocyanine)) 6.0 parts by mass

[0297] The amorphous polyester and crystalline polyester used were the amorphous polyester 1 and crystalline polyester 1 obtained in the preparation of toner base particles M1. The solid components were uniformly mixed for 10 minutes in a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) to obtain a mixture. The obtained mixture was kneaded in a twin-screw extruder while heating to 105°C and then cooled to obtain a kneaded product. The obtained kneaded product was coarsely pulverized in a cutting mill. It was then finely pulverized in an ultrasonic jet mill, and fine powder was removed using a classifier to obtain toner base particles M9. The toner base particles M9 had a volume average particle size of 5 μm and an average circularity of 0.935.

[0298] The shapes of the toner base particles M1 to M9 are shown in Table III below.

[0299] [Table 3]

[0300] (4) Toner production Toner base particles M1 100.0 parts by mass Inorganic particles A1 1.0 parts by mass Inorganic particles B1 1.0 parts by mass The above components were mixed for 20 minutes using a Henschel mixer (manufactured by Nippon Coke & Engineering Co., Ltd.) at a rotor peripheral speed of 40 m / sec and 32° C. After mixing, coarse particles were removed using a sieve with 45 μm openings to obtain Toner T1.

[0301] Toners T2 to T28 were obtained in the same manner as Toner T1, except that the combinations of toner base particles, inorganic particles A, and inorganic particles B were changed as shown in Table IV.

[0302] Table IV below shows combinations of toner base particles, inorganic particles A, and inorganic particles B.

[0303] [Table 4]

[0304] 2. Preparation of the photoreceptor (1) Preparation of photoreceptor P1 (1.1) Preparation of resin for charge transport layer The polyarylates (PAR1) to (PAR3) and polycarbonate (PC1) listed in Table V were prepared. The structures of the dicarboxylic acids (DCA1) to (DCA3) and diol (DO1) listed in Table V are shown below. For PC1, "Z300" (manufactured by Mitsubishi Gas Chemical Company, Inc.) was used.

[0305] [Table 5]

[0306] [ka]

[0307] (1.2) Preparation of the conductive support The surface of the cylindrical aluminum support was machined to form a conductive support.

[0308] (1.3) Formation of the intermediate layer The components of the following composition were mixed together: The mixture was dispersed batchwise for 10 hours using a sand mill as a disperser to obtain a coating liquid for forming an intermediate layer.

[0309] (Composition of Coating Solution for Forming Intermediate Layer) Polyamide "X1010" (manufactured by Daicel-Degussa Co., Ltd.) 10.0 parts by mass Titanium oxide "SMT500SAS" (manufactured by Teika Corporation) 11.0 parts by mass Ethanol 200.0 parts by mass

[0310] The coating solution for forming the intermediate layer was applied onto the conductive support by dip coating, and the resulting coating was dried at 110°C for 20 minutes to form an intermediate layer having a thickness of 2 µm after drying.

[0311] (1.4) Formation of charge generation layer The components of the following composition were mixed. The mixture was dispersed using a circulation ultrasonic homogenizer "RUS-600TCVP (manufactured by Nippon Seiki Seisakusho Co., Ltd.)" to prepare a coating solution for forming a charge generating layer. The dispersion conditions were 19.5 kHz, 600 W, a circulation flow rate of 40 L / H, and 0.5 hours.

[0312] (Composition of the Charge Generating Layer Forming Composition) Charge generating material 24.0 parts by mass Polyvinyl butyral resin "S-LEC BL-1 (manufactured by Sekisui Chemical Co., Ltd.)" 12.0 parts by mass 3-Methyl-2-butanone / cyclohexanone=4 / 1(V / V) 400.0 parts by mass

[0313] The charge-generating substance was a mixed crystal of a 1:1 adduct of titanyl phthalocyanine and (2R,3R)-2,3-butanediol, which had clear peaks at 8.3°, 24.7°, 25.1°, and 26.5° in Cu-Kα characteristic X-ray diffraction spectrum measurement, and unadducted titanyl phthalocyanine.

[0314] The coating solution for forming the charge generating layer was applied onto the intermediate layer by dip coating, and the resulting coating was dried to form a charge generating layer having a thickness of 0.3 μm after drying.

[0315] (1.5) Formation of the charge transport layer The components of the following composition were mixed and dissolved to prepare a coating solution for forming a charge transport layer: The structure of compound CTM-(1) is shown below.

[0316] (Composition of Coating Solution for Forming Charge Transport Layer) Charge transport agent (compound CTM-(1)) 60.0 parts by mass Polyarylate (PAR1) 100.0 parts by mass Antioxidant "Irganox 1010" (manufactured by Ciba Specialty Chemicals Co., Ltd.) 4.0 parts by mass

[0317] [ka]

[0318] The charge transport layer forming coating solution was applied onto the charge generation layer by dip coating, and the resulting coating was dried at 120°C for 70 minutes to form a charge transport layer with a dried thickness of 24 μm, thereby obtaining photoreceptor P1.

[0319] (2) Preparation of photoreceptors P2 to P4 Photoreceptors P2 and P3 were obtained in the same manner as for photoreceptor P1, except that (PAR2) or (PAR3) listed in Table II was used instead of (PAR1) as the resin. Photoreceptor P4 was obtained in the same manner as for photoreceptor P1, except that polycarbonate "Z300" (manufactured by Mitsubishi Gas Chemical Company, Inc.) was used instead of (PAR1) as the resin.

[0320] 3. Evaluation The drum unit of a full-color multifunction printer "bizhub C650i" (manufactured by Konica Minolta, Inc.) was disassembled. For the cyan color in the drum unit, the photoreceptors were replaced with the photoreceptors P1 to P4 prepared above, respectively, to achieve the combinations shown in Table VI. Furthermore, the toner in the developer was replaced with the toners T1 to T28 prepared above, to achieve the combinations shown in Table VI, and image forming systems S1 to S31 were produced.

[0321] Using the resulting image forming systems S1 to S31, an image chart with a cyan solid patch was printed on 100,000 sheets of A4 paper by single-sided printing. The solid patch was a strip measuring 15 mm in the paper feed direction and 290 mm in the direction perpendicular to the feed direction. Image formation was carried out in a low-temperature, low-humidity environment of 10°C and 20% humidity, which are harsh conditions where the charge level is high and external additives tend to adhere to the photoreceptor.

[0322] After image formation, the photoreceptor was inspected over its entire length for the presence or absence of streaky adhesion. A score of 2 was given to areas where cyan streaks were clearly visible to the naked eye, and a score of 1 was given to areas where transparent streaks were visible when illuminated with light. The total score was evaluated according to the following criteria. The lower the total score, the less streaky adhesion occurred, and the better the evaluation.

[0323] A: 5 points or less. B: 6 points or more and 15 points or less. C: 16 points or more and 30 points or less. D: 31 points or more.

[0324] 3 and 4 are schematic diagrams showing an example of streak-like adhesion that has occurred on a photoreceptor. In FIGS. 3 and 4, solid lines represent streaks 110 that are clearly visible to the naked eye. Dotted lines represent transparent streaks 111 that are visible when a light is shone on them. For example, in the example shown in FIG. 3, there are 11 streaks 110 that are clearly visible to the naked eye in the longitudinal direction, so the score is 22 points. In the example shown in FIG. 4, there are two streaks 110 that are clearly visible to the naked eye in the longitudinal direction, and four transparent streaks 111 that are visible when a light is shone on them in the longitudinal direction, so the score is 8 points.

[0325] The following Table VI shows the evaluation results of the image forming systems S1 to S31.

[0326] [Table 6]

[0327] From the examples and comparative examples, it can be seen that the image forming system of this embodiment has less streak-like adhesion on the photosensitive member and can form high-quality images with reduced image defects.

[0328] From Examples 3 and 13, it can be seen that when both inorganic particles A and inorganic particles B are silica particles, streaky adhesion can be further reduced, and high-quality images with reduced image defects can be formed.

[0329] From Examples 3, 14, and 15, it can be seen that when inorganic particles B are silica particles with a shape factor SF-2 of 116 or less, streaky adhesion can be further reduced, and high-quality images with reduced image defects can be formed.

[0330] From Examples 3 and 9 to 12, it can be seen that by setting the number average primary particle diameter of inorganic particles B within the range of 80 nm or more and 120 nm or less, it is possible to further reduce streaky adhesion and form high-quality images with reduced image defects.

[0331] From Examples 1 to 6, it can be seen that by setting the volume average particle size of the toner base particles within the range of 3 μm or more and 7 μm or less, more preferably within the range of 3 μm or more and 5 μm or less, it is possible to further reduce streak-like adhesion and form high-quality images with reduced image defects.

[0332] From Examples 3 and 22, it is clear that when the toner base particles have a core-shell structure, it is possible to further reduce streak-like adhesion and form high-quality images with reduced image defects.

[0333] From Examples 3, 18, and 19, it can be seen that when the average circularity of the toner base particles is 0.940 or more and 0.980 or less, it is possible to further reduce streak-like adhesion and form high-quality images with reduced image defects.

[0334] From Examples 3, 20, and 21, it can be seen that when the polyarylate contained in the photoreceptor has a structural unit derived from a dicarboxylic acid (DCA1 or DCA2), it is possible to further reduce streaky adhesion and form high-quality images with reduced image defects. [Explanation of symbols]

[0335] 1, 1Y, 1M, 1C, 1Bk photoconductor 2Y, 2M, 2C, 2Bk 1st charging section 3Y, 3M, 3C, 3Bk exposure area 4Y, 4M, 4C, 4Bk developing section 5Y, 5M, 5C, 5Bk Primary transfer roller 5b Secondary transfer roller 6Y, 6M, 6C, 6Bk, 6b Cleaning section 7 Intermediate transfer unit 8. Housing 9Y, 9M, 9C, 9Bk Second charging section 10Y, 10M, 10C, 10Bk image forming units 20 Paper cassette 21 Paper feed section 22A, 22B, 22C, 22D Intermediate rollers 23 Resist Roller 24 Fixing section 25 Paper ejection roller 26 Paper output tray 70 Intermediate transfer body 71, 72, 73, 74 Rollers 82L, 82R support rails 100 Image forming device 101 Conductive support 102 Middle Class 103 Photosensitive layer 103a Charge generation layer 103b Charge transport layer P Transfer material

Claims

1. An image forming system including an electrophotographic image forming apparatus having a photosensitive member and a toner for developing an electrostatic image, the photoreceptor has a photosensitive layer, the photosensitive layer contains polyarylate, the toner for developing an electrostatic image contains, as external additives, inorganic particles A and inorganic particles B treated with silicone oil, the number average primary particle diameter of the inorganic particles A is in the range of 5 nm or more and less than 60 nm; The number average primary particle diameter of the inorganic particles B is in the range of 60 nm or more and 150 nm or less. An image forming system comprising:

2. The inorganic particles A and the inorganic particles B are silica particles.

2. The image forming system according to claim 1.

3. The inorganic particles B are silica particles having a shape factor SF-2 of 116 or less.

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer.

4. The number average primary particle diameter of the inorganic particles B is in the range of 80 nm or more and 120 nm or less.

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer.

5. the toner for developing an electrostatic image contains toner base particles, The volume average particle size of the toner base particles is in the range of 3 μm or more and 7 μm or less.

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer.

6. The volume average particle size of the toner base particles is in the range of 3 μm or more and 5 μm or less.

6. The image forming system according to claim 5.

7. The toner base particles have a core-shell structure.

6. The image forming system according to claim 5.

8. The average circularity of the toner base particles is 0.940 or more and 0.980 or less.

6. The image forming system according to claim 5.

9. the photosensitive layer has an outermost layer, The outermost layer contains the polyarylate.

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer.

10. the photosensitive layer has a charge transport layer, The charge transport layer contains the polyarylate.

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer.

11. The polyarylate has a structural unit derived from a dicarboxylic acid and represented by the following structural formula (1):

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer. 【Chemistry 1】

12. The polyarylate has a structural unit derived from a dicarboxylic acid and represented by the following structural formula (2):

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer. 【Chemistry 2】

13. The image forming apparatus has a cleaning unit that removes the electrostatic image developing toner on the photosensitive member by contacting a blade therewith.

3. The image forming system according to claim 1, wherein the image forming apparatus is a printer.

14. The image forming system according to claim 1 or 2 is used. An image forming method comprising:

Images