Electrostatic charge image developer set, image forming apparatus, and image forming method

Abstract

To provide an electrostatic charge image developer set that suppresses the occurrence of filming on the surface of an image holder located downstream in a tandem type image forming apparatus.SOLUTION: The electrostatic charge image developer set is a set of a developer (1) and a developer (2) which both include a toner and a carrier, the carrier (1) of the developer (1) includes magnetic particles, a resin coating layer which coats the magnetic particles, and inorganic particles which are included in the resin coating layer, the carrier (2) of the developer (2) includes magnetic particles and a resin coating layer which coats the magnetic particles, in each of the carrier (1) and the carrier (2), an element ratio of metal and metalloid configuring the inorganic particles of the carrier (1) is analyzed by X-ray photoelectron spectroscopic analysis, when the element ratio on the surface of the carrier (1) is A (1) and the element ratio on the surface of the carrier (2) is A (2), the value of A (1) / A (2) is 17 or more and 105 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to an electrostatic image developer set, an image forming apparatus, and an image forming method. [Background technology]

[0002] Patent Document 1 discloses a carrier for developing electrostatic images, which has a coating resin layer containing magnetic particles and silica particles, and in which the ratio of Si on the surface of the coating resin layer determined by X-ray photoelectron spectroscopy is 6 atom % or more and 12 atom % or less.

[0003] Patent Document 2 describes a two-component developer containing toner particles and carrier particles, in which the toner particles contain at least a binder resin, a colorant, a charge control agent, and an external additive, and the carrier particles have a coating layer made of resin, and the thickness of the coating layer is equal to or greater than the color carrier thickness d c is the black carrier film thickness d bk The carrier resistance of the color carrier is the same as or 10 times smaller than that of the black carrier. -2 Sub-Ωcm two-component developers are disclosed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-147733 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-219321 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide an electrostatic image developer set that suppresses filming on the surface of an image carrier located downstream in a tandem image forming apparatus. [Means for solving the problem]

[0006] Specific means for solving the above problems include the following aspects. <1> Both are a set of developer (1) and developer (2) containing toner and carrier, The carrier (1) of the developer (1) has magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer, The carrier (2) of the developer (2) has magnetic particles and a resin coating layer that coats the magnetic particles, The carrier (1) and the carrier (2) are each analyzed by X-ray photoelectron spectroscopy to analyze the element ratio of metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio on the surface of the carrier (1) is defined as A(1) and the element ratio on the surface of the carrier (2) is defined as A(2), the value of A(1) / A(2) is 17 or more and 105 or less. Electrostatic image developer set. <2> The carrier (1) is analyzed in the depth direction by X-ray photoelectron spectroscopy to determine the element ratio of metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio at 0 seconds of etching is defined as A(1) and the element ratio at 300 seconds of etching is defined as B(1), the value of B(1) - A(1) is 0.5 atm% or more and 3.0 atm% or less. <1> 10. An electrostatic image developer set according to claim 19. <3> The carrier (2) is analyzed in the depth direction by X-ray photoelectron spectroscopy to determine the element ratio of the metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio at 0 seconds of etching is defined as A(2) and the element ratio at 300 seconds of etching is defined as B(2), the value of B(2) - A(2) is 0.3 atm% or less. <1> or <2> 10. An electrostatic image developer set according to claim 19. <4> The inorganic particles of the carrier (1) include at least one selected from the group consisting of silica particles, alumina particles, and titania particles. <1> ~ <3> 10. An electrostatic image developer set according to claim 9. <5> the volume average particle size of the inorganic particles contained in the resin coating layer of the carrier (1) is 5 nm or more and 40 nm or less; <1> ~ <4> 10. An electrostatic image developer set according to claim 9. <6> The mass ratio of the inorganic particles in the resin coating layer of the carrier (1) is 15 mass% or more and 35 mass% or less. <1> ~ <5> 10. An electrostatic image developer set according to claim 9. <7> the carrier (1) contains a nitrogen atom-containing resin in the resin coating layer, and the mass ratio of the nitrogen atom-containing resin in the resin coating layer is R(1), When the carrier (2) contains a nitrogen atom-containing resin in the resin coating layer and the mass ratio of the nitrogen atom-containing resin in the resin coating layer is R(2), The value of R(1) / R(2) is between 0.2 and 4.0. <1> ~ <6> 10. An electrostatic image developer set according to claim 9. <8> a first image forming unit that forms a yellow image; a second image forming unit that forms a magenta image; a third image forming unit that forms a cyan image; a fourth image forming unit that forms a black image, <1> ~ <7> and a storage container containing the electrostatic image developer set according to any one of the above items. the developing devices of the first image forming unit, the second image forming unit, and the third image forming unit each contain the developer (1); The developing device of the fourth image forming unit contains the developer (2). Image forming device. <9> a first image forming step of forming a yellow image; a second image forming step of forming a magenta image; a third image forming step of forming a cyan image; a fourth image forming step of forming a black image, <1> ~ <7> 2. Using the electrostatic image developer set according to any one of the preceding items, the first image forming step, the second image forming step, and the third image forming step each use the developer (1); the developing step of the fourth image forming step uses the developer (2); Image forming method. [Effects of the Invention]

[0007] <1> , <3> or <4> According to the present invention, an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the value of A(1) / A(2) is less than 17 or more than 105. <2> According to the present invention, an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the value of B(1)-A(1) is less than 0.5 atm% or more than 3.0 atm%. <5> According to the present invention, an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the volume average particle size of inorganic particles contained in the resin coating layer of the carrier (1) is less than 5 nm or more than 40 nm. <6> According to the present invention, an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the mass proportion of inorganic particles in the resin coating layer of the carrier (1) is less than 15 mass % or more than 35 mass %. <7> According to the present invention, an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the value of R(1) / R(2) is less than 0.2 or more than 4.0. <8> According to the present invention, an image forming apparatus is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an image forming apparatus which applies an electrostatic image developer set in which the value of A(1) / A(2) is less than 17 or more than 105. <9> According to the present invention, an image forming method is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an image forming method which applies an electrostatic image developer set in which the value of A(1) / A(2) is less than 17 or more than 105. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments of the present disclosure. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

[0010] In the present disclosure, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0011] In the present disclosure, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B.

[0012] In the present disclosure, the term "step" includes not only an independent step but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

[0013] When embodiments of the present disclosure are described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each drawing are conceptual, and the relative size relationships between the components are not limited to these.

[0014] In the present disclosure, each component may contain multiple corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified. In the present disclosure, the composition may contain multiple types of particles corresponding to each component. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified.

[0015] In the present disclosure, when a compound is represented by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in the hydrocarbon group and / or hydrocarbon chain may be omitted.

[0016] In the present disclosure, "(meth)acrylic" is an expression that includes both acrylic and methacrylic, and "(meth)acrylate" is an expression that includes both acrylate and methacrylate.

[0017] In this disclosure, "developer set" refers to "electrostatic image developer set," "developer" refers to "electrostatic image developer," "carrier" refers to "electrostatic image developing carrier," and "toner" refers to "electrostatic image developing toner."

[0018] <Electrostatic image developer set> The developer set of the present disclosure is a set of developer (1) and developer (2), each of which contains a toner and a carrier. That is, developer (1) and developer (2) are each two-component developers.

[0019] In this disclosure, the toner constituting the developer (1) is referred to as "toner (1)," and the carrier constituting the developer (1) is referred to as "carrier (1)." In this disclosure, the toner constituting the developer (2) is referred to as "toner (2)," and the carrier constituting the developer (2) is referred to as "carrier (2)."

[0020] The developer (1) is a two-component developer obtained by mixing the toner (1) and the carrier (1) at an appropriate mixing ratio. The mixing ratio (mass ratio) of the toner (1) and the carrier (1) is preferably toner (1):carrier (1) = 1:100 to 30:100, more preferably 3:100 to 20:100.

[0021] The developer (2) is a two-component developer obtained by mixing the toner (2) and the carrier (2) at an appropriate mixing ratio. The mixing ratio (mass ratio) of the toner (2) to the carrier (2) is preferably toner (2):carrier (2) = 1:100 to 30:100, more preferably 3:100 to 20:100.

[0022] The carrier (1) of the developer (1) has magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer. Carbon black is not an inorganic particle in the resin coating layer of the carrier (1). The carrier (2) of the developer (2) has magnetic particles and a resin coating layer that coats the magnetic particles. Carbon black is not an inorganic particle in the resin coating layer of the carrier (2).

[0023] In the developer set of the present disclosure, the element ratios of metals and metalloids constituting the inorganic particles of carrier (1) are analyzed by X-ray photoelectron spectroscopy for each of carrier (1) and carrier (2), and when the element ratio on the surface of carrier (1) is defined as A(1) and the element ratio on the surface of carrier (2) is defined as A(2), the value of A(1) / A(2) is 17 or more and 105 or less.

[0024] The "inorganic particles" of the "metals and metalloids constituting inorganic particles" that are the analysis targets of X-ray photoelectron spectroscopy for carrier (1) and carrier (2) are the inorganic particles contained in the resin coating layer of carrier (1). For carrier (2), the element ratios of the metals and metalloids constituting the inorganic particles contained in the resin coating layer of carrier (1) are also analyzed. When the carrier (2) does not contain inorganic particles in the resin coating layer, the A(2) value derived from the carrier (2) itself is zero. However, inorganic particles (e.g., silica particles, alumina particles, titania particles) that are external additives to the toner (2) may adhere to the surface of the carrier (2), so the A(2) value may not be zero.

[0025] The developer set of the present disclosure is applied to a tandem image forming apparatus, in which developer (1) is used in an image forming unit located upstream of the tandem image forming apparatus, and developer (2) is used in an image forming unit located downstream of the tandem image forming apparatus.

[0026] Conventionally, when an image forming apparatus is used for a long period of time, the cleaning member for the image carrier deteriorates, the surface of the image carrier is not sufficiently cleaned, and filming (a phenomenon in which toner components form a film) occurs on the surface of the image carrier. In particular, filming can occur on the surface of the image carrier located downstream in a tandem image forming apparatus. In contrast, the developer set of the present disclosure suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus.

[0027] In a tandem image forming apparatus, the carrier (1) contained in the developer (1) used by the upstream image forming unit (1) may be mixed into the developer (2) used by the downstream image forming unit (2). In this case, the carrier (1) moves along the following path: The carrier (1) contained in the developer (1) is mixed into the toner image (1) formed on the image carrier (1) by the developer (1). The toner image (1) mixed with the carrier (1) is transferred from the image carrier (1) to a transfer recipient (for example, an intermediate transfer member in an intermediate transfer method, or a recording medium in a direct transfer method). When the toner image (2) on the image carrier (2) is transferred to the transfer recipient, the carrier (1) mixed into the toner image (1) migrates from the transfer recipient to the image carrier (2). The carrier (1) that has migrated to the image carrier (2) migrates from the image carrier (2) to the developing device (2) and is mixed into the developer (2). In the event that the carrier (1) is mixed into the developer (2), the developer set of the present disclosure is presumed to suppress the occurrence of filming on the surface of the image carrier (2) by the following mechanism. Carrier (1) has a fine unevenness due to the inorganic particles being exposed on the surface of its resin coating layer, giving it a lower surface energy than carrier (2). When this carrier (1) is mixed into developer (2), a magnetic brush is formed in the developing device (2) by both carrier (1), which has a relatively low surface energy, and carrier (2), which has a relatively high surface energy. Due to the relative difference in surface energy, carrier (1) is more likely to be removed from the magnetic brush than carrier (2) and migrate to image carrier (2). It is believed that carrier (1) is more selectively transferred to image carrier (2) when only a small amount of carrier (1) is mixed into carrier (2) than when a predetermined amount of carrier (1) and carrier (2) are mixed together. Then, carrier (1) reaches the cleaning nip of image carrier (2), where carrier (1), which has inorganic particles in its resin coating layer, exerts a polishing effect and removes filming on the surface of image carrier (2).

[0028] If the value of A(1) / A(2) of the developer set is less than 17, the difference in surface energy between the carrier (1) and the carrier (2) is too small, making it difficult for the carrier (1) to selectively migrate from the magnetic brush formed in the developing device (2) to the image carrier (2), which may result in filming on the surface of the image carrier (2). Therefore, the value of A(1) / A(2) of the developer set is 17 or more, preferably 25 or more, and more preferably 30 or more.

[0029] If the value of A(1) / A(2) of the developer set exceeds 105, the surface energy of the carrier (1) itself is too small, making it difficult for the carrier (1) to transfer from the transfer recipient to the image carrier (2) and the developing device (2), and the abrasive action of the carrier (1) on the image carrier (2) cannot be expected, which may result in filming on the surface of the image carrier (2). Therefore, the value of A(1) / A(2) of the developer set is 105 or less, preferably 80 or less, and more preferably 60 or less.

[0030] The element ratio A(1) on the surface of the carrier (1) is synonymous with the element ratio A(1) at 0 seconds of etching, which will be described later, and the measurement method and preferred values ​​are also the same. The element ratio A(2) on the surface of the carrier (2) is synonymous with the element ratio A(2) at 0 seconds of etching, which will be described later, and the measurement method and preferred values ​​are also the same.

[0031] Carrier (1), carrier (2), toner (1) and toner (2) will be described in detail below.

[0032] <Career (1)> The carrier (1) has magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer.

[0033] [B(1)-A(1)] The carrier (1) is preferably analyzed by X-ray photoelectron spectroscopy to determine the elemental ratio of metals and metalloids constituting the inorganic particles contained in the resin coating layer in the depth direction, and when the elemental ratio at 0 seconds of etching is defined as A(1) and the elemental ratio at 300 seconds of etching is defined as B(1), the value of B(1) - A(1) is preferably 0.5 atm% or more and 3.0 atm% or less.

[0034] From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the value of B(1) - A(1) is preferably 0.8 atm% or more and 2.7 atm% or less, more preferably 1.0 atm% or more and 2.5 atm% or less, and even more preferably 1.2 atm% or more and 2.3 atm% or less.

[0035] The method of elemental analysis in the depth direction by X-ray photoelectron spectroscopy (XPS) and the method of measuring the element ratio A(1) and the element ratio B(1) are as follows. The carrier (1) is separated from the developer (1). As a method for separating the carrier, there is a method of removing the toner from the developer by air blowing using any mesh. The carrier (1) is used as an XPS sample, and elements are analyzed while etching. The elements analyzed are carbon, nitrogen, oxygen, iron, manganese, and the metals and metalloids that make up the inorganic particles. If the metals and metalloids that make up the inorganic particles are unknown, a full elemental analysis of the carrier (1) is performed in advance to identify the metals and metalloids that make up the inorganic particles. Examples of metal elements that make up the inorganic particles include aluminum and titanium. Examples of metalloid elements that make up the inorganic particles include silicon, boron, germanium, arsenic, antimony, and tellurium. The ratio of the total amount of metals and metalloids constituting inorganic particles to the total amount of all elements to be analyzed is defined as the element ratio (atm%) of metals and metalloids constituting inorganic particles. That is, the element ratio (atm%) of metals and metalloids constituting inorganic particles = (total amount of metals and metalloids constituting inorganic particles) / (total amount of carbon, nitrogen, oxygen, iron, manganese, and metals and metalloids constituting inorganic particles) × 100. The ratio of the above element at 0 seconds of etching is A(1) (atm %), and the ratio of the above element at 300 seconds of etching is B(1) (atm %). Etching for 0 seconds means that no etching is performed.

[0036] The XPS is performed using the following equipment and conditions. Analysis is performed after baseline correction. XPS equipment: PHI5000 Versa Probe II (ULVAC-PHI, Inc.) X-ray source: Monochromated AlKα rays Beam voltage: 15kV Emission current: 3mA Etching gun: Argon gas cluster ion gun ·Vacuum degree: 1×10 -5 Pa~1×10 -6 Pa Pass Energy: 23.5 eV ·Sweep area: 300μm×300μm Time Per Step: 50 seconds Cycle: 5 times Sweep: 10 times

[0037] [Element ratio A(1) value] From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the value of element ratio A(1) is preferably 2.0 atm% or more and 10.0 atm% or less, more preferably 2.5 atm% or more and 8.0 atm% or less, and even more preferably 3.0 atm% or more and 6.0 atm% or less.

[0038] [Element ratio B(1) value] From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the value of element ratio B(1) is preferably 3.5 atm% or more and 12.0 atm% or less, more preferably 4.3 atm% or more and 9.8 atm% or less, and even more preferably 4.8 atm% or more and 7.8 atm% or less.

[0039] [How to control the value of B(1)-A(1)] The value of B(1)-A(1) can be controlled, for example, by utilizing the particle settling phenomenon and / or the Brazil nut phenomenon when forming the resin coating layer. The particle settling phenomenon is a phenomenon in which the settling speed of particles changes depending on the particle size and shape, the density difference and affinity between the particle and the dispersion medium, the density difference and affinity between the particle and other components, the particle concentration, etc. Generally, the smaller the particle size and the higher the density of particles in a liquid, the faster the settling speed. The Brazil nut phenomenon is a phenomenon in which larger particles rise when a collection of multiple types of particles with different particle sizes is vibrated. When the resin coating layer is formed by a wet process, the particles can move freely in the liquid in which the resin is dissolved, and the above phenomenon can be utilized. By utilizing the above phenomenon, the value of B(1) - A(1) can be controlled by the material, particle size, density and / or concentration of the inorganic particles, whether or not other particles are added, the type of resin in the resin coating layer, and the conditions for forming the resin coating layer. When the particle size of the inorganic particles is within an appropriate range, they tend to be unevenly distributed to the lower side of the resin coating layer. When particles having a particle size larger than the inorganic particles are used as other particles, the inorganic particles tend to be unevenly distributed to the lower side of the resin coating layer. When the other particles have a lower density than the inorganic particles and / or have a different polarity than the inorganic particles, the inorganic particles tend to be unevenly distributed to the lower side of the resin coating layer. When the concentration of the inorganic particles is within an appropriate range, the inorganic particles tend to be unevenly distributed to the lower side of the resin coating layer. When the concentration of the other particles is within an appropriate range, the inorganic particles tend to be unevenly distributed to the lower side of the resin coating layer.

[0040] [Resin coating layer] -resin- The carrier (1) has a resin coating layer on the surface of magnetic particles. Resins that can be used to form the resin coating layer include styrene-acrylic acid copolymers; polyolefin resins such as polyethylene and polypropylene; polyvinyl or polyvinylidene resins such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone; vinyl chloride-vinyl acetate copolymers; straight silicone resins or modified silicone resins consisting of organosiloxane bonds; fluororesins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyesters; polyurethanes; polycarbonates; amino resins such as urea-formaldehyde resins; and epoxy resins. These resins may be used alone or in combination of two or more.

[0041] From the viewpoint of controlling the value of B(1)-A(1), the resin coating layer preferably contains an acrylic resin having an aliphatic cyclic structure and an amino group, and more preferably contains an acrylic resin having a structural unit having an aliphatic cyclic structure and a structural unit having an amino group. The aliphatic cyclic structure is preferably a cycloalkyl group, more preferably a cyclohexyl group. Examples of acrylic resins having a cyclohexyl group include homopolymers of (meth)acrylic monomers having a cyclohexyl group, copolymers of (meth)acrylic monomers having a cyclohexyl group and other monomers, etc. Examples of (meth)acrylic monomers having a cyclohexyl group include cyclohexyl acrylate and cyclohexyl methacrylate. As the structural unit having an aliphatic cyclic structure, a structural unit derived from cyclohexyl (meth)acrylate is preferred. The acrylic resin having a structural unit with an aliphatic cyclic structure preferably contains 80 mass % or more of the structural unit with an aliphatic cyclic structure. As the (meth)acrylic monomer having an amino group, dialkylaminoalkyl (meth)acrylate is preferred, and dimethylaminoethyl (meth)acrylate is more preferred. The acrylic resin having a structural unit having an amino group preferably contains 0.05% by mass or more and 5% by mass or less of the structural unit having an amino group, and more preferably 0.1% by mass or more and 2% by mass or less.

[0042] -Inorganic particles- The resin coating layer contains inorganic particles. Examples of inorganic particles include particles of metal compounds such as silica (silicon dioxide), titania (titanium oxide), alumina (aluminum oxide), zinc oxide, tin oxide, barium sulfate, aluminum borate, potassium titanate, antimony-doped tin oxide, tin-doped indium oxide, and aluminum-doped zinc oxide; particles of metals such as gold, silver, and copper; and resin particles coated with a metal. The inorganic particles may be used alone or in combination of two or more kinds.

[0043] As the inorganic particles, at least one type selected from the group consisting of silica particles, titania particles, and alumina particles is preferred, and silica particles are more preferred, from the viewpoints that they have excellent dispersibility in the resin and are likely to exhibit the effect of preventing abnormal increase or decrease in charge when an appropriate amount of inorganic particles appears on the surface.

[0044] From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the average primary particle size of the inorganic particles is preferably 1 nm or more and 100 nm or less, more preferably 5 nm or more and 60 nm or less, even more preferably 5 nm or more and 40 nm or less, still more preferably 6 nm or more and 30 nm or less, and particularly preferably 7 nm or more and 20 nm or less. If the average primary particle size of the inorganic particles is 1 nm or more, the inorganic particles are less likely to aggregate when forming the resin coating layer, and as a result, the inorganic particles tend to be unevenly distributed on the lower side of the resin coating layer. When the average primary particle size of the inorganic particles is 100 nm or less, the exposure of the inorganic particles to the surface of the resin coating layer is suppressed.

[0045] In the present disclosure, the primary particle size of inorganic particles is the diameter of a circle having the same area as the primary particle image (so-called circle equivalent diameter), and the average primary particle size of inorganic particles is the particle size that is the cumulative 50% from the smallest diameter side in the number-based distribution of primary particle sizes. The primary particle size of inorganic particles is determined by image analysis of at least 300 inorganic particles.

[0046] The inorganic particles contained in the resin coating layer may be inorganic particles themselves, or may be inorganic particles (sometimes referred to as mother particles) whose surfaces have been hydrophobized. Surface-treated inorganic particles are preferred, and inorganic particles whose surfaces have been hydrophobized are more preferred, from the viewpoint of being highly effective in preventing aggregation of inorganic particles and being more effective in preventing abnormal increases or decreases in charge when the affinity with the resin of the resin coating layer is increased and the inorganic particles appear appropriately on the surface.

[0047] The surface treatment of inorganic particles is carried out, for example, by preparing a treatment liquid by mixing a silicon-containing organic compound, which is a hydrophobic treatment agent, with a solvent, and mixing the inorganic particles with the treatment liquid under stirring, and then continuing to stir. After the surface treatment, a drying treatment is carried out to remove the solvent from the treatment liquid.

[0048] Examples of silicon-containing organic compounds used for the surface treatment of inorganic particles include alkoxysilane compounds, silazane compounds, silicone oils, etc. Among these, alkoxysilane compounds or silazane compounds are preferred, and silazane compounds are more preferred, from the viewpoint that they provide an effect of improving the dispersibility of inorganic particles and preventing aggregation through appropriate steric hindrance, and as a result, the inorganic particles appear appropriately on the surface, which makes it easier to exert the effect of preventing abnormal increase or decrease in charge.

[0049] Examples of alkoxysilane compounds used for the hydrophobic treatment of the surfaces of inorganic particles include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, and hexyltriethoxysilane. Examples of suitable silanes include dimethylsilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, trimethylmethoxysilane, and trimethylethoxysilane.

[0050] Examples of the silazane compound used for the hydrophobic treatment of the surfaces of inorganic particles include dimethyldisilazane, trimethyldisilazane, tetramethyldisilazane, pentamethyldisilazane, and hexamethyldisilazane.

[0051] Examples of silicone oils used for the surface treatment of inorganic particles include silicone oils such as dimethylpolysiloxane, diphenylpolysiloxane, and phenylmethylpolysiloxane; and reactive silicone oils such as amino-modified polysiloxane, epoxy-modified polysiloxane, carboxyl-modified polysiloxane, carbinol-modified polysiloxane, fluorine-modified polysiloxane, methacryl-modified polysiloxane, mercapto-modified polysiloxane, and phenol-modified polysiloxane.

[0052] As the solvent used in preparing the treatment liquid, when the silicon-containing organic compound is an alkoxysilane compound or a silazane compound, an alcohol (e.g., methanol, ethanol, propanol, butanol) is preferred, and when the silicon-containing organic compound is a silicone oil, a hydrocarbon (e.g., benzene, toluene, normal hexane, normal heptane) is preferred.

[0053] In the treatment liquid, the concentration of the silicon-containing organic compound is preferably from 1 to 50% by mass, more preferably from 5 to 40% by mass, and even more preferably from 10 to 30% by mass.

[0054] The amount of the silicon-containing organic compound used for the surface treatment is preferably 1 part by mass to 50 parts by mass, more preferably 5 parts by mass to 40 parts by mass, and even more preferably 5 parts by mass to 30 parts by mass, per 100 parts by mass of the inorganic particles.

[0055] The content of inorganic particles in the resin coating layer is preferably 15% by mass to 35% by mass, more preferably 17% by mass to 30% by mass, and even more preferably 20% by mass to 25% by mass, based on the total mass of the resin coating layer. When the content of inorganic particles is within the above range, they tend to be unevenly distributed to the lower side of the resin coating layer.

[0056] In the carrier (1), the ratio of the amount of inorganic particles on the carrier surface (element ratio A(1), atm%) to the content (mass%) of inorganic particles in the resin coating layer (element ratio A(1) / content of inorganic particles, atm% / mass%) is preferably 0.05 or more and 0.60 or less, more preferably 0.08 or more and 0.40 or less, and even more preferably 0.10 or more and 0.30 or less. When the ratio of the amount of inorganic particles on the carrier surface (element ratio A(1), atm%) to the content (mass%) of inorganic particles in the resin coating layer is within the above range, the carrier surface is moderately hardened by the inorganic particles, and the inorganic particles are moderately unevenly distributed below the resin coating layer.

[0057] -Resin particles- The resin coating layer preferably contains resin particles from the viewpoint of suppressing the occurrence of filming on the surface of the image carrier located downstream in the tandem image forming apparatus. Examples of resin particles include particles of (meth)acrylic resins obtained by polymerizing dimethylaminoethyl (meth)acrylate, dimethylacrylamide, acrylonitrile, etc.; amino resins such as urea, melamine, guanamine, and aniline; amide resins; urethane resins; copolymers of the above resins; etc. One type of resin particle may be used alone, or two or more types may be used in combination.

[0058] The resin particles are preferably at least one selected from the group consisting of acrylic resin particles, amino resin particles, and urethane resin particles, more preferably amino resin particles, and even more preferably contain melamine resin particles. Melamine resin particles have a different polarity from inorganic particles, so the Brazil nut phenomenon is thought to be more effective.

[0059] The average primary particle size of the resin particles is preferably 100 nm or more and 400 nm or less, and more preferably 150 nm or more and 350 nm or less, from the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus. When the average primary particle size of the resin particles is within the above range, the difference in particle size between the resin particles and the inorganic particles becomes appropriate, and the inorganic particles tend to be unevenly distributed on the lower side of the resin coating layer.

[0060] In the present disclosure, the primary particle size of resin particles is the diameter of a circle having the same area as the primary particle image (so-called circle equivalent diameter), and the average primary particle size of resin particles is the particle size that is the cumulative 50% from the smallest diameter side in the number-based distribution of primary particle sizes. The primary particle size of resin particles is determined by image analysis of at least 300 resin particles.

[0061] The ratio D1 / D2 of the average primary particle size D1 of the inorganic particles to the average primary particle size D2 of the resin particles contained in the resin coating layer is preferably 0.01 or more and 0.15 or less, more preferably 0.02 or more and 0.10 or less. When the ratio D1 / D2 is within the above range, the difference in particle size between the inorganic particles and the resin particles becomes appropriate, and the inorganic particles tend to be unevenly distributed on the lower side of the resin coating layer.

[0062] The density ratio between the inorganic particles and the resin particles (density of the inorganic particles / density of the resin particles) is preferably 1.0 or more and 5.0 or less. When the density ratio is within the above range, differences in the degree of settling in the liquid tend to occur when the resin coating layer is formed by a wet manufacturing method, and the inorganic particles tend to be located on the lower side of the resin coating layer.

[0063] The content of resin particles in the resin coating layer is preferably less than the content of inorganic particles, from the viewpoint of suppressing the occurrence of filming on the surface of the image carrier located downstream in a tandem image forming apparatus. From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the content of resin particles in the resin coating layer is preferably 5% by mass or more and 30% by mass or less, more preferably 6% by mass or more and 20% by mass or less, and even more preferably 7% by mass or more and 15% by mass or less, relative to the total mass of the resin coating layer.

[0064] -Carbon black- The resin coating layer preferably contains carbon black from the viewpoint of suppressing the occurrence of filming on the surface of the image carrier located downstream in a tandem image forming apparatus. From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the average primary particle size of the carbon black is preferably 10 nm or more and 70 nm or less, more preferably 20 nm or more and 60 nm or less, and even more preferably 30 nm or more and 50 nm or less.

[0065] The ratio D1 / D3 of the average primary particle size D1 of the inorganic particles contained in the resin coating layer to the average primary particle size D3 of the carbon black is preferably 0.1 or more and 1.0 or less. When the ratio D1 / D3 is within the above range, the particle size difference between the inorganic particles and the carbon black becomes appropriate, making it easier for the Brazil nut phenomenon to occur, and when the resin coating layer is formed by a wet process, the carbon black rises to the top of the resin coating layer, resulting in the inorganic particles being more likely to be positioned below the resin coating layer.

[0066] The density ratio between the inorganic particles and the carbon black (density of the inorganic particles / density of the carbon black) is preferably 1.0 or more and 5.0 or less. When the density ratio is within this range, differences in the degree of settling in the liquid tend to occur when the resin coating layer is formed by a wet process, and the inorganic particles tend to be located on the lower side of the resin coating layer.

[0067] The content of carbon black in the resin coating layer is preferably less than the content of inorganic particles in the resin coating layer, from the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus. The content of carbon black in the resin coating layer is preferably less than the content of resin particles in the resin coating layer, from the viewpoint of suppressing the occurrence of filming on the surface of the image carrier located downstream in a tandem image forming apparatus. From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the content of carbon black in the resin coating layer is preferably from 0.5% by mass to 15% by mass, more preferably from 1% by mass to 13% by mass, and even more preferably from 2% by mass to 10% by mass, relative to the total mass of the resin coating layer.

[0068] From the viewpoint of suppressing the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, the resin coating layer preferably contains silica particles and melamine resin particles, and more preferably contains silica particles, melamine resin particles, and carbon black.

[0069] The resin coating layer of the carrier (1) preferably contains a nitrogen atom-containing resin, which may be a binder resin and / or resin particles. As the nitrogen atom-containing binder resin, an acrylic resin having a structural unit having an amino group is preferred, and as the (meth)acrylic monomer having an amino group, a dialkylaminoalkyl (meth)acrylate is preferred, and dimethylaminoethyl (meth)acrylate is more preferred. As the nitrogen atom-containing resin particles, amino resin particles are preferred, and melamine resin particles are more preferred.

[0070] When the mass proportion of the nitrogen atom-containing resin in the total mass of the resin coating layer of the carrier (1) is defined as R(1), the value of R(1) is preferably 2 mass% or more and 25 mass% or less, more preferably 5 mass% or more and 23 mass% or less, and even more preferably 8 mass% or more and 22 mass% or less.

[0071] [Method for forming resin coating layer] Methods for forming a resin coating layer on the surface of magnetic particles include wet and dry processes. The wet process uses a solvent to dissolve or disperse the resin that constitutes the resin coating layer, and is preferred from the viewpoint of being able to control the arrangement of inorganic particles by utilizing the sedimentation phenomenon or the Brazil nut phenomenon.

[0072] Examples of wet manufacturing methods include an immersion method in which magnetic particles are immersed in a resin liquid for forming a resin coating layer to coat them; a spray method in which a resin liquid for forming a resin coating layer is sprayed onto the surface of magnetic particles; a fluidized bed method in which magnetic particles are fluidized in a fluidized bed and a resin liquid for forming a resin coating layer is sprayed onto them; and a kneader coater method in which magnetic particles and a resin liquid for forming a resin coating layer are mixed in a kneader coater and the solvent is removed.

[0073] The resin liquid for forming the resin coating layer used in the wet manufacturing method is prepared by dissolving or dispersing the resin and other components in a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the resin, and examples of the solvent that can be used include aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, and ethers such as tetrahydrofuran and dioxane.

[0074] In the examples described below, the resin coating layer is formed in multiple steps by a wet process, but the method for forming the resin coating layer is not limited to this.

[0075] The thickness of the resin coating layer is preferably 0.5 μm or more and 2.0 μm or less, and more preferably 0.7 μm or more and 1.4 μm or less.

[0076] [Magnetic particles] The magnetic particles are not particularly limited, and known magnetic particles used as a core material of a carrier can be used. Specific examples of the magnetic particles include particles of magnetic metals such as iron, nickel, and cobalt; particles of magnetic oxides such as ferrite and magnetite; resin-impregnated magnetic particles in which porous magnetic powder is impregnated with resin; and magnetic powder-dispersed resin particles in which magnetic powder is dispersed in resin.

[0077] In the present disclosure, ferrite particles are preferred as magnetic particles. In the present disclosure, the ferrite particles preferably contain at least one selected from calcium oxide and strontium oxide. Calcium oxide and strontium oxide are easily incorporated into the surface of ferrite particles, and the presence of calcium or strontium on the surface of ferrite particles is thought to suppress charge leakage from the ferrite particles, thereby resulting in a relatively high charge on the carrier surface. This carrier suppresses low charge on the toner in the developing device, thereby further suppressing fogging and improving thin line reproducibility (e.g., suppressing thickening, crushing, or blurring of thin lines). This effect is particularly noticeable when forming a low-density image of the same color after repeatedly forming a high-density, monochromatic image at a higher speed.

[0078] In the present disclosure, the ferrite particles contain at least one selected from calcium oxide and strontium oxide, and the total content of calcium and strontium is preferably 0.1% by mass or more and 2.0% by mass or less relative to the total mass of the ferrite particles. When the total content of calcium and strontium is 0.1% by mass or more relative to the total mass of the ferrite particles, charge leakage from the ferrite particles is efficiently suppressed. When the total content of calcium and strontium is 2.0% by mass or less relative to the total mass of the ferrite particles, the crystal structure of the ferrite particles is well-ordered, and the resistivity and magnetic susceptibility fall within appropriate ranges. As a result, fogging is further suppressed, and thin line reproducibility is improved (e.g., thickening, crushing, or blurring of thin lines is suppressed). From the above viewpoints, the total content of calcium element and strontium element is preferably 0.1 mass % or more and 2.0 mass % or less, more preferably 0.2 mass % or more and 1.5 mass % or less, and even more preferably 0.5 mass % or more and 1.2 mass % or less, based on the entire ferrite particles.

[0079] In the present disclosure, the ferrite particles contain calcium oxide, and the calcium content is preferably 0.2 mass% or more and 2.0 mass% or less relative to the total mass of the ferrite particles. When the calcium content is 0.2 mass% or more relative to the total mass of the ferrite particles, charge leakage from the ferrite particles is efficiently suppressed. When the calcium content is 2.0 mass% or less relative to the total mass of the ferrite particles, the crystal structure of the ferrite particles is well-ordered, and the resistivity and magnetic susceptibility fall within appropriate ranges. As a result, fogging is further suppressed, and thin line reproducibility is improved (for example, thickening, crushing, or blurring of thin lines is suppressed). From the above viewpoints, the calcium element content is preferably 0.2 to 2.0 mass %, more preferably 0.5 to 1.5 mass %, and even more preferably 0.5 to 1.0 mass %, based on the total mass of the ferrite particles.

[0080] In the present disclosure, the ferrite particles contain strontium oxide, and the strontium content is preferably 0.1% by mass or more and 1.0% by mass or less relative to the total mass of the ferrite particles. When the strontium content is 0.1% by mass or more relative to the total mass of the ferrite particles, charge leakage from the ferrite particles is efficiently suppressed. When the strontium content is 1.0% by mass or less relative to the total mass of the ferrite particles, the crystal structure of the ferrite particles is well-ordered, and the resistivity and magnetic susceptibility fall within appropriate ranges. As a result, fogging is further suppressed, and thin line reproducibility is improved (for example, thickening, crushing, or blurring of thin lines is suppressed). From the above viewpoints, the content of strontium element is preferably 0.1 mass % to 1.0 mass %, more preferably 0.4 mass % to 1.0 mass %, and even more preferably 0.5 mass % to 0.8 mass %, based on the total mass of the ferrite particles.

[0081] The contents of calcium and strontium contained in the ferrite particles are measured by X-ray fluorescence analysis. The X-ray fluorescence analysis of the ferrite particles is performed by the following method. Qualitative and quantitative analysis is performed using an X-ray fluorescence analyzer (XRF1500, Shimadzu Corporation) under the following conditions: X-ray output: 40 V / 70 mA, measurement area: 10 mm diameter, measurement time: 15 minutes. The elements to be analyzed are selected based on the elements detected in the qualitative analysis. The main elements selected are iron (Fe), manganese (Mn), magnesium (Mg), calcium (Ca), strontium (Sr), oxygen (O), and carbon (C). The mass percentage (%) of each element is calculated by referring to separately prepared calibration curve data.

[0082] The volume average particle size of the magnetic particles is preferably 20 μm or more and 50 μm or less, more preferably 25 μm or more and 45 μm or less, and even more preferably 30 μm or more and 40 μm or less.

[0083] The magnetic force of the magnetic particles is, for example, 50 emu / g or more, preferably 60 emu / g or more, in terms of saturation magnetization in a magnetic field of 3000 oersteds. The saturation magnetization is measured using a vibrating sample magnetic measuring device VSMP10-15 (Toei Kogyo Co., Ltd.). The measurement sample is placed in a cell with an inner diameter of 7 mm and a height of 5 mm and set in the device. The measurement is performed by applying a magnetic field and sweeping up to a maximum of 3000 oersteds. The applied magnetic field is then reduced, and a hysteresis curve is created on recording paper. The saturation magnetization, remanent magnetization, and coercive force are determined from the curve data.

[0084] The volume resistivity of the magnetic particles is, for example, 1×10 5 Ω cm or more 1×10 9 Ω·cm or less, 1×10 7 Ω cm or more 1×10 9 Ω·cm or less is preferable. The volume resistivity (Ω·cm) of magnetic particles is measured as follows: 2 The object to be measured is placed flat on the surface of the circular jig on which the electrode plate is arranged, with a thickness of 1 mm to 3 mm, to form a layer. 2 The layer is sandwiched between two electrode plates. To eliminate any gaps between the objects being measured, a 4 kg load is placed on the electrode plates placed on the layer, and then the layer thickness (cm) is measured. The electrodes above and below the layer are connected to an electrometer and a high-voltage power supply generator. A high voltage is applied to both electrodes so that the electric field becomes 103.8 V / cm, and the current value (A) that flows at this time is read. The measurement environment is a temperature of 20°C and a humidity of 50% RH. The formula for calculating the volume electrical resistivity (Ω·cm) of the object being measured is as shown below. R=E×20 / (I-I0) / L In the above formula, R represents the volume electrical resistance (Ω·cm) of the object to be measured, E represents the applied voltage (V), I represents the current value (A), I0 represents the current value (A) at an applied voltage of 0 V, and L represents the layer thickness (cm). The coefficient 20 is the area of ​​the electrode plate (cm 2 )

[0085] [Characteristics of Carrier (1)] The volume average particle size of the carrier (1) is preferably 20 μm or more and 52 μm or less, more preferably 25 μm or more and 47 μm or less, and even more preferably 30 μm or more and 42 μm or less.

[0086] The volume average particle size of the carrier (1) is the particle size that is the cumulative 50% from the smallest diameter side in the volume-based particle size distribution. The particle size distribution of the carrier is measured using a laser diffraction / scattering particle size distribution measuring device. When analyzing the carrier contained in the developer, a method for separating the carrier from the developer includes a method of removing the toner from the developer by air blowing using any mesh.

[0087] The magnetic force of the carrier (1) is, for example, 40 emu / g or more, preferably 50 emu / g or more, in terms of saturation magnetization in a magnetic field of 1000 oersted. The saturation magnetization is measured in the same manner as for measuring the saturation magnetization of magnetic particles, except that the magnetic field is swept up to 1000 oersted.

[0088] The volume electrical resistance (25°C) of the carrier (1) is, for example, 1×10 7 Ω cm or more 1×10 15 Ω·cm or less, 1×10 8 Ω cm or more 1×10 14 Ω·cm or less is preferable, and 1×10 8 Ω cm or more 1×10 13 It is more preferable that the volume resistivity of the carrier is Ω·cm or less. The volume resistivity of the carrier is measured in the same manner as that of the magnetic particles.

[0089] The exposed ratio of the magnetic particles on the surface of the carrier (1) is preferably 2% to 20%, more preferably 3% to 15%, and even more preferably 4% to 12%.

[0090] The exposed ratio of the magnetic particles on the surface of the carrier (1) is determined by X-ray photoelectron spectroscopy (XPS) using the following method. The target carrier and magnetic particles with the resin coating layer removed from the target carrier are prepared. Methods for removing the resin coating layer from the carrier include, for example, dissolving the resin component in an organic solvent to remove the resin coating layer, or heating to about 800°C to eliminate the resin component and remove the resin coating layer. The carrier and the magnetic particles with the resin coating layer removed are each used as measurement samples, and the Fe (atomic %) is quantified using XPS. The exposed percentage (%) of the magnetic particles is calculated as (Fe in the carrier) ÷ (Fe in the magnetic particles) × 100.

[0091] The exposed ratio of the magnetic particles on the surface of the carrier (1) can be controlled by the amount of resin used to form the resin coating layer, and the greater the amount of resin relative to the amount of magnetic particles, the smaller the exposed ratio.

[0092] <Career (2)> The carrier (2) has magnetic particles and a resin coating layer that coats the magnetic particles. The carrier (2) preferably has the same structure as the carrier (1) except that the resin coating layer does not contain inorganic particles.

[0093] The magnetic particles constituting the carrier (2) may be the same as those constituting the carrier (1), and the specific and preferred forms are also the same.

[0094] The resin coating layer constituting the carrier (2) may be the same as the resin coating layer constituting the carrier (1), and the specific and preferred forms are also the same.

[0095] The method for forming the resin coating layer of the carrier (2) may be the same as the method for forming the resin coating layer of the carrier (1), except that inorganic particles are not used.

[0096] [B(2)-A(2)] The carrier (2) is preferably analyzed by X-ray photoelectron spectroscopy to determine the elemental ratio of metals and metalloids constituting the inorganic particles contained in the resin coating layer of the carrier (1) in the depth direction, and when the elemental ratio at 0 seconds of etching is defined as A(2) and the elemental ratio at 300 seconds of etching is defined as B(1), the value of B(2) - A(2) is preferably 0.3 atm% or less.

[0097] In the present disclosure, the "inorganic particles" of the "metals and metalloids constituting inorganic particles" that are the analysis targets of X-ray photoelectron spectroscopy for carriers refer to the inorganic particles contained in the resin coating layer of carrier (1). For carrier (2), the element ratios of the metals and metalloids constituting the inorganic particles contained in the resin coating layer of carrier (1) are also analyzed. When the carrier (2) does not contain inorganic particles in the resin coating layer, the values ​​of A(2) and B(2) derived from the carrier (2) itself are zero. However, inorganic particles (e.g., silica particles, alumina particles, titania particles) that are external additives to the toner (2) may adhere to the surface of the carrier (2) or may be embedded in the resin coating layer of the carrier (2), so the values ​​of A(2) and B(2) may not be zero.

[0098] The value of B(2) - A(2) is more preferably 0.3 atm% or less, and even more preferably 0.2 atm% or less, from the viewpoint of suppressing the occurrence of filming on the surface of the image carrier located downstream in a tandem image forming apparatus.

[0099] The method of elemental analysis in the depth direction by XPS and the method of measuring the element ratio A(2) and the element ratio B(2) in the carrier (2) are the same as the method of elemental analysis in the depth direction by XPS and the method of measuring the element ratio A(1) and the element ratio B(1) in the carrier (1).

[0100] The resin coating layer of the carrier (2) preferably contains a nitrogen atom-containing resin, which may be a binder resin and / or resin particles. As the nitrogen atom-containing binder resin, an acrylic resin having a structural unit having an amino group is preferred, and as the (meth)acrylic monomer having an amino group, a dialkylaminoalkyl (meth)acrylate is preferred, and dimethylaminoethyl (meth)acrylate is more preferred. As the nitrogen atom-containing resin particles, amino resin particles are preferred, and melamine resin particles are more preferred.

[0101] When the mass proportion of the nitrogen atom-containing resin in the total mass of the resin coating layer of the carrier (2) is defined as R(2), the value of R(2) is preferably 5 mass% or more and 20 mass% or less, more preferably 7 mass% or more and 18 mass% or less, and even more preferably 10 mass% or more and 16 mass% or less.

[0102] The ratio R(1) / R(2) of R(1) of carrier (1) to R(2) of carrier (2) is preferably 0.2 or more and 4.0 or less, more preferably 0.4 or more and 3.0 or less, and even more preferably 1.0 or more and 1.7 or less, from the viewpoint of suppressing the occurrence of filming on the surface of the image carrier located downstream in a tandem image forming apparatus.

[0103] The volume average particle size, magnetic force, volume electrical resistivity and degree of exposed magnetic particles of the carrier (2) are the same as those of the carrier (1), and the preferred ranges of the values ​​are also the same.

[0104] <Toner (1) and Toner (2)> It is preferable that the toner (1) and the toner (2) have the same composition except for the color, and hereinafter, the toner (1) and the toner (2) will be collectively referred to as "toner."

[0105] The toner is not particularly limited, and known toners can be used. For example, a colored toner containing toner particles containing a binder resin and a colorant can be used, and an infrared absorbing toner using an infrared absorbing agent instead of a colorant can also be used. The toner may contain a release agent, various internal additives, external additives, etc.

[0106] [Toner particles] -Binder resin- Examples of binder resins include homopolymers of monomers such as styrenes (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid esters (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), and vinyl resins made of copolymers of two or more of these monomers. Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These binder resins may be used alone or in combination of two or more.

[0107] As the binder resin, polyester resin, styrene-acrylic resin, and styrene-acrylic modified polyester resin are preferred, and polyester resin is more preferred.

[0108] The glass transition temperature (Tg) of the resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower. The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), and more specifically, is determined from the "extrapolated glass transition onset temperature" described in the method for determining glass transition temperature in JIS K7121-1987 "Method for measuring transition temperature of plastics."

[0109] The weight average molecular weight (Mw) of the resin is preferably 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution (Mw / Mn) of the resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less. The weight-average molecular weight and number-average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight measurements by GPC are performed using a GPC·HLC-8120GPC (Tosoh Corporation) as the measuring device and a TSKgel SuperHM-M (diameter 15 cm, Tosoh Corporation) as the column, with THF as the solvent. The weight-average molecular weight and number-average molecular weight are calculated from the measurement results using a molecular weight calibration curve prepared with monodisperse polystyrene standard samples.

[0110] The content of the binder resin is preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 85% by mass, based on the total mass of the toner particles.

[0111] -Coloring agent- Examples of colorants include carbon black, chrome yellow, Hansa Yellow, benzidine yellow, threne yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, Balkan orange, watch young red, permanent red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil red, pyrazolone red, lithol red, rhodamine B lake, lake red C, pigment red, rose bengal, aniline blue, Examples of suitable dyes include pigments such as ultramarine blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate; and dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes. The colorant may be used alone or in combination of two or more kinds.

[0112] The colorant may be surface-treated as needed, or may be used in combination with a dispersant. Furthermore, a plurality of colorants may be used in combination.

[0113] The content of the colorant is preferably from 1% by mass to 30% by mass, and more preferably from 3% by mass to 15% by mass, based on the total mass of the toner particles.

[0114] -Mold release agent- Examples of release agents include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic or mineral / petroleum waxes such as montan wax, and ester waxes such as fatty acid esters and montanic acid esters, but are not limited thereto.

[0115] The melting temperature of the release agent is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) by using the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for measuring transition temperatures of plastics."

[0116] The content of the release agent is preferably from 1% by mass to 20% by mass, and more preferably from 5% by mass to 15% by mass, based on the total mass of the toner particles.

[0117] -Other additives- Examples of other additives include known additives such as magnetic materials, charge control agents, inorganic powders, etc. These additives are contained in the toner particles as internal additives.

[0118] [Characteristics of toner particles] The toner particles may be toner particles of a single layer structure, or may be toner particles of a so-called core-shell structure composed of a core (core particle) and a coating layer (shell layer) that coats the core. The toner particles of the core-shell structure may be composed of, for example, a core composed of a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer composed of a binder resin.

[0119] The volume average particle size (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less. The volume average particle size (D50v) of toner particles is measured using a Coulter Multisizer II (Beckman Coulter, Inc.) and an ISOTON-II (Beckman Coulter, Inc.) electrolyte. For measurement, 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5% by weight aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant. This is then added to 100 ml to 150 ml of electrolyte. The electrolyte containing the suspended sample is dispersed in an ultrasonic disperser for 1 minute, and the particle size distribution of particles ranging from 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. 50,000 particles are sampled.

[0120] [External additives] Examples of external additives include inorganic particles, such as SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, and K2O·(TiO2). n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, SrTiO3, etc.

[0121] The surfaces of inorganic particles as external additives are preferably subjected to a hydrophobic treatment. The hydrophobic treatment is carried out, for example, by immersing the inorganic particles in a hydrophobic treatment agent. The hydrophobic treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more. The amount of the hydrophobic treatment agent is preferably, for example, 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

[0122] Examples of external additives include resin particles (resin particles such as polystyrene, polymethyl methacrylate, and melamine resin), cleaning agents (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based polymers).

[0123] The amount of the external additive added is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.01% by mass or more and 5% by mass or less, based on the toner particles.

[0124] [Toner manufacturing method] The toner is obtained by producing toner particles and then externally adding an external additive to the toner particles. The toner particles may be produced by either a dry production method (e.g., a kneading and pulverization method) or a wet production method (e.g., an aggregation and coalescence method, a suspension polymerization method, a dissolution and suspension method). There are no particular restrictions on these production methods, and any known production method may be used. Among these, it is preferable to obtain toner particles by the aggregation and coalescence method.

[0125] <Image forming apparatus and image forming method> The developer set of the present disclosure is applied to a tandem image forming apparatus. A tandem image forming apparatus has two or more image forming units. Examples of the tandem image forming apparatus include the following configurations (1) and (2). In the following description, yellow will be represented as "Y", magenta as "M", cyan as "C", black as "K", and special colors (for example, white, green, orange, pink, gold, silver) as "S".

[0126] Configuration (1): Four-series tandem image forming device with YMCK lined up in order from upstream Y is developer (1), K is developer (2), and MC are preferably both developer (1).

[0127] Configuration (2): A tandem image forming apparatus of five or more series in which YMCK are arranged in order from the upstream, and at least one S is further arranged upstream and / or downstream of the YMCK. Y is developer (1), K is developer (2), and MC are preferably both developer (1). Since S is used less frequently, either developer (1) or developer (2) may be used, but when S is located upstream of YMCK, developer (1) is preferred, and when S is located downstream of YMCK, developer (2) is preferred.

[0128] Representative examples of the image forming apparatus according to this embodiment are as follows. a first image forming unit that forms a yellow image; a second image forming unit that forms a magenta image; a third image forming unit that forms a cyan image; a fourth image forming unit that forms a black image, containing a developer set according to the present disclosure; Each of the developing devices of the first image forming unit, the second image forming unit, and the third image forming unit contains a developer (1), The developing device of the fourth image forming unit contains the developer (2). Image forming device.

[0129] In the above embodiment, the developers (1) contained in the developing devices of the first image forming unit, the second image forming unit, and the third image forming unit are developers (1) of different colors.

[0130] Representative examples of the image forming method according to this embodiment are as follows. a first image forming step of forming a yellow image; a second image forming step of forming a magenta image; a third image forming step of forming a cyan image; a fourth image forming step of forming a black image, Using the developer set of the present disclosure, Each of the development steps of the first image forming step, the second image forming step, and the third image forming step uses a developer (1), The development step of the fourth image forming step uses developer (2). Image forming method.

[0131] In the above embodiment, the developers (1) used in the first image forming process, the second image forming process, and the third image forming process are developers (1) of different colors.

[0132] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. In the following description, the main parts shown in the drawings will be described, and the description of the rest will be omitted.

[0133] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to this embodiment, and is a diagram showing a four-tandem type and intermediate transfer type image forming apparatus. The image forming apparatus shown in Figure 1 includes first through fourth electrophotographic image forming units 10Y, 10M, 10C, and 10K that output images in the colors yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side by side horizontally spaced apart by predetermined distances. These units 10Y, 10M, 10C, and 10K may be process cartridges that are detachably attached to the image forming apparatus.

[0134] An intermediate transfer belt (an example of an intermediate transfer body) 20 is provided above each of the units 10Y, 10M, 10C, and 10K and extends through each unit. The intermediate transfer belt 20 is provided wrapped around a drive roll 22 and a support roll 24, and runs in a direction from the first unit 10Y to the fourth unit 10K. A force is applied to the support roll 24 by a spring or the like (not shown) in a direction away from the drive roll 22, and tension is applied to the intermediate transfer belt 20 wrapped around them. An intermediate transfer body cleaning device 30 is provided on the outer circumferential surface of the intermediate transfer belt 20, facing the drive roll 22. The developing devices (examples of developing devices) 4Y, 4M, 4C, and 4K of the units 10Y, 10M, 10C, and 10K are supplied with yellow, magenta, cyan, and black toner contained in toner cartridges 8Y, 8M, 8C, and 8K, respectively.

[0135] Since the first to fourth units 10Y, 10M, 10C, and 10K have the same configuration and operation, we will explain here the first unit 10Y, which forms a yellow image and is arranged upstream in the direction of travel of the intermediate transfer belt.

[0136] The first unit 10Y has a photoreceptor 1Y that acts as an image carrier. Around the photoreceptor 1Y, there are arranged in this order: a charging roll (an example of a charging device) 2Y that charges the surface of the photoreceptor 1Y to a predetermined potential; an exposure device (an example of an electrostatic image forming device) 3 that exposes the charged surface to a laser beam 3Y based on a color-separated image signal to form an electrostatic image; a developing device (an example of a developing device) 4Y that supplies charged toner to the electrostatic image to develop it; a primary transfer roll (an example of a primary transfer device) 5Y that transfers the developed toner image onto the intermediate transfer belt 20; and a photoreceptor cleaning device (an example of a cleaning device) 6Y that removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer. The primary transfer roll 5Y is disposed inside the intermediate transfer belt 20 and is provided at a position facing the photoreceptor 1Y. A bias power supply (not shown) that applies a primary transfer bias is connected to the primary transfer rolls 5Y, 5M, 5C, and 5K of each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roll under the control of a control unit (not shown).

[0137] The operation of forming a yellow image in the first unit 10Y will be described below. First, prior to operation, the surface of the photosensitive member 1Y is charged to a potential of −600V to −800V by the charging roll 2Y. The photoconductor 1Y has conductivity (for example, a volume resistivity of 1×10 at 20°C). -6 The photosensitive layer is formed by laminating a photosensitive layer on a substrate with a resistivity of Ωcm or less. This photosensitive layer normally has a high resistance (the resistance of ordinary resins), but when irradiated with a laser beam, the resistivity of the irradiated portion changes. Therefore, the exposed surface of the photosensitive element 1Y is irradiated with a laser beam 3Y from the exposure device 3 in accordance with image data for yellow sent from a control unit (not shown). This forms an electrostatic charge image of a yellow image pattern on the surface of the photosensitive element 1Y.

[0138] An electrostatic image is an image formed on the surface of the photosensitive element 1Y by charging it; the laser beam 3Y reduces the resistivity of the irradiated portion of the photosensitive layer, causing the charged charges on the surface of the photosensitive element 1Y to flow, while the charges remain in the portions not irradiated by the laser beam 3Y, forming a so-called negative latent image. The electrostatic image formed on the photoreceptor 1Y rotates to a predetermined development position as the photoreceptor 1Y moves, and at this development position, the electrostatic image on the photoreceptor 1Y is developed into a toner image by the developing device 4Y and made visible.

[0139] The developing device 4Y contains an electrostatic image developer containing, for example, at least yellow toner and a carrier. The yellow toner is frictionally charged by being stirred inside the developing device 4Y, and is held on a developer roll (an example of a developer holder) with a charge of the same polarity (negative polarity) as the charge on the photoreceptor 1Y. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the yellow toner electrostatically adheres to the discharged latent image portion on the surface of the photoreceptor 1Y, and the latent image is developed with the yellow toner. The photoreceptor 1Y on which the yellow toner image has been formed continues to travel at a predetermined speed, and the toner image developed on the photoreceptor 1Y is transported to a predetermined primary transfer position.

[0140] When the yellow toner image on the photoreceptor 1Y is transported to the primary transfer position, a primary transfer bias is applied to the primary transfer roll 5Y, and an electrostatic force from the photoreceptor 1Y to the primary transfer roll 5Y acts on the toner image, causing the toner image on the photoreceptor 1Y to be transferred onto the intermediate transfer belt 20. The transfer bias applied at this time has a (+) polarity opposite to the (-) polarity of the toner, and is controlled to, for example, +10 μA by a control unit (not shown) in the first unit 10Y. On the other hand, the toner remaining on the photoreceptor 1Y is removed and collected by the photoreceptor cleaning device 6Y.

[0141] The primary transfer bias applied to the primary transfer rolls 5M, 5C, and 5K of the second unit 10M and subsequent units is also controlled in accordance with the first unit. In this way, the intermediate transfer belt 20 onto which the yellow toner image has been transferred by the first unit 10Y is conveyed sequentially through the second to fourth units 10M, 10C, and 10K, and the toner images of each color are superimposed and transferred.

[0142] The intermediate transfer belt 20, onto which the four-color toner images have been multiplex-transferred through the first to fourth units, reaches a secondary transfer section composed of the intermediate transfer belt 20, a support roll 24 in contact with the inner surface of the intermediate transfer belt, and a secondary transfer roll (an example of a secondary transfer device) 26 arranged on the outer circumferential surface of the intermediate transfer belt 20. Meanwhile, recording paper (an example of a recording medium) P is fed via a feed mechanism into the gap between the secondary transfer roll 26 and the intermediate transfer belt 20 at a predetermined timing, and a secondary transfer bias is applied to the support roll 24. The transfer bias applied at this time has a negative polarity, the same as the negative polarity of the toner. Electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, transferring the toner image on the intermediate transfer belt 20 onto the recording paper P. The secondary transfer bias at this time is determined based on resistance detected by a resistance detection device (not shown) that detects resistance in the secondary transfer section, and is voltage-controlled.

[0143] Thereafter, the recording paper P is sent to a pressure contact portion (nip portion) of a pair of fixing rolls in a fixing device (an example of a fixing device) 28, where the toner image is fixed onto the recording paper P, forming a fixed image.

[0144] Examples of the recording paper P onto which the toner image is transferred include plain paper used in electrophotographic copiers, printers, etc. In addition to the recording paper P, examples of the recording medium include overhead projector sheets and the like. To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth. For example, coated paper in which the surface of plain paper is coated with resin or the like, or art paper for printing, etc., is preferably used.

[0145] The recording paper P on which the color image has been fixed is conveyed toward the discharge section, and the series of color image forming operations is completed. [Example]

[0146] Hereinafter, the present embodiment will be described in detail with reference to examples, but the present embodiment is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass.

[0147] In the following description, synthesis, processing, manufacturing, testing, etc. were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0148] <Production of black toner> [Preparation of Resin Particle Dispersion (1)] Ethylene glycol: 37 parts Neopentyl glycol: 65 parts 1,9-nonanediol: 32 parts Terephthalic acid: 96 parts The above materials were charged into a flask, and the temperature was raised to 200°C over 1 hour. After confirming uniform stirring within the reaction system, 1.2 parts of dibutyltin oxide was added. The temperature was raised to 240°C over 6 hours while distilling off the resulting water. Stirring was continued at 240°C for 4 hours, yielding a polyester resin (acid value 9.4 mgKOH / g, weight-average molecular weight 13,000, glass transition temperature 62°C). This polyester resin was transferred in its molten state to an emulsifier / disperser (Cavitron CD1010, Eurotech) at a rate of 100 g / min. Separately, a 0.37% concentration dilute ammonia water, prepared by diluting reagent ammonia water with ion-exchanged water, was placed in a tank and heated to 120°C in a heat exchanger. The emulsifier / disperser was operated at a rotor speed of 60 Hz and a pressure of 5 kg / cm. 2 The operation was carried out under the conditions of (a) to (c) to obtain a resin particle dispersion (1) having a volume average particle size of 160 nm and a solid content of 30%.

[0149] [Preparation of Resin Particle Dispersion (2)] Decanedioic acid: 81 parts Hexanediol: 47 parts The above materials were charged into a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide was added. The temperature was raised to 200°C over 6 hours while distilling off the produced water, and stirring was continued at 200°C for 4 hours. The reaction liquid was then cooled, solid-liquid separation was performed, and the solid was dried at 40°C under reduced pressure to obtain polyester resin (C1) (melting point 64°C, weight average molecular weight 15,000).

[0150] Polyester resin (C1): 50 parts Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku Co., Ltd.): 2 parts Ion-exchanged water: 200 parts The above materials were heated to 120°C and thoroughly dispersed using a homogenizer (Ultra Turrax T50, IKA), and then dispersed using a pressure discharge homogenizer. When the volume average particle size reached 180 nm, the particles were collected to obtain a resin particle dispersion (2) with a solid content of 20%.

[0151] [Preparation of Colorant Particle Dispersion (1)] Black pigment (Regel 330, Cabot Corporation): 10 parts Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku Co., Ltd.): 2 parts Ion-exchanged water: 80 parts The above materials were mixed and dispersed for 1 hour using a high-pressure impact disperser (Ultimizer HJP30006, Sugino Machine Co., Ltd.) to obtain a colorant particle dispersion (1) with a volume average particle size of 180 nm and a solid content of 20%.

[0152] [Preparation of Release Agent Particle Dispersion (1)] Paraffin wax (HNP-9, Nippon Seiro Co., Ltd.): 50 parts Anionic surfactant (Neogen SC, Daiichi Kogyo Seiyaku Co., Ltd.): 2 parts Ion-exchanged water: 200 parts The above materials were heated to 120°C and thoroughly dispersed using a homogenizer (Ultra Turrax T50, manufactured by IKA), and then dispersed using a pressure discharge homogenizer. When the volume average particle size reached 200 nm, the particles were collected to obtain a release agent particle dispersion (1) with a solid content of 20%.

[0153] [Preparation of Toner (K)] ·Resin particle dispersion (1): 150 parts ·Resin particle dispersion (2): 50 parts Colorant particle dispersion (1): 25 parts Release agent particle dispersion (1): 35 parts Polyaluminum chloride: 0.4 parts Ion-exchanged water: 100 parts The above materials were placed in a round stainless steel flask and thoroughly mixed and dispersed using a homogenizer (Ultra-Turrax T50, IKA). The flask was then heated to 48°C in an oil bath while stirring. The reaction system was maintained at 48°C for 60 minutes, after which 70 parts of resin particle dispersion (1) was slowly added. The pH was then adjusted to 8.0 using a 0.5 mol / L aqueous sodium hydroxide solution. The flask was then sealed, the stirring shaft was magnetically sealed, and the mixture was heated to 90°C with continued stirring and maintained for 30 minutes. The mixture was then cooled at a rate of 5°C / min, solid-liquid separated, and thoroughly washed with ion-exchanged water. The solid-liquid separated product was then redispersed in ion-exchanged water at 30°C and washed with stirring at 300 rpm (revolutions per minute) for 15 minutes. This washing operation was repeated six more times, and when the pH of the filtrate reached 7.54 and the electrical conductivity reached 6.5 μS / cm, solid-liquid separation was performed, and vacuum drying was continued for 24 hours to obtain toner particles (K) with a volume average particle size of 5.7 μm.

[0154] 100 parts of the toner particles (K) and 2.5 parts of silica particles (surface hydrophobized with hexamethyldisilazane, average primary particle size 40 nm) were mixed in a Henschel mixer to obtain toner (K).

[0155] <Preparation of Yellow Toner> Toner (Y) was prepared in the same manner as in the preparation of black toner, except that in the preparation of the colorant particle dispersion, the black pigment was changed to a yellow pigment (CI Pigment Yellow 74, Clariant Japan KK).

[0156] <Preparation of magenta toner> Toner (M) was produced in the same manner as in the production of black toner, except that in the preparation of the colorant particle dispersion, the black pigment was changed to a magenta pigment (CI Pigment Red 122, DIC Corporation).

[0157] <Preparation of Cyan Toner> Toner (C) was prepared in the same manner as in the preparation of the black toner, except that in the preparation of the colorant particle dispersion, the black pigment was changed to a cyan pigment (CI Pigment Blue 15:3, Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

[0158] <Preparation of carrier (1)> [Preparation of ferrite particles (1)] ·Fe2O3: 1597 parts ·Mn(OH)2: 712 parts ·Mg(OH)2: 116 parts ·SrCO3: 20 parts ·CaCO3: 30 parts The above materials were mixed, and a dispersant, water, and zirconia beads with a diameter of 1 mm were added, followed by crushing and mixing using a sand mill. The zirconia beads were filtered off, and the filtrate was dried and then pre-fired using a rotary kiln at a rotation speed of 20 rpm and a temperature of 970°C for 2 hours. The dispersant and water were added to the pre-fired product, and 8 parts of polyvinyl alcohol were then added, followed by crushing and mixing using a wet ball mill for 5 hours. The volume average particle size of the resulting crushed product was 1.2 μm. Next, the product was granulated using a spray dryer to a particle size of 40 μm. The resulting granulated product was fired in an electric furnace under an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1% by volume at a temperature of 1,400°C for 4 hours. The resulting fired product was crushed and classified to obtain ferrite particles (1). The volume average particle size of the ferrite particles (1) was 35 μm.

[0159] [Preparation of Coating Agent for First Layer and Coating Agent for Second Layer] In this embodiment, the value of B(1)-A(1) is controlled by forming the resin coating layer in multiple steps. This embodiment is an example of a method for controlling the value of B(1)-A(1), and the method for controlling the value of B(1)-A(1) is not limited to this.

[0160] Each of the components shown in Tables 1-1 and 1-2 was added to a sand mill in the mass ratio shown in Table 1-1 along with glass beads (1 mm in diameter, the same amount as toluene) and stirred at a rotation speed of 190 rpm for 30 minutes to prepare a coating agent for the first layer and a coating agent for the second layer, respectively. Details of the abbreviations for each component of the coating agent shown in Tables 1-1 and 1-2 are as follows:

[0161] Resin (1): Cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer (copolymerization ratio 97 mol:3 mol) Resin (2): Cyclohexyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 95 mol:5 mol) Resin (3): Methyl methacrylate polymer Resin (4): Cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer (copolymerization ratio 99.5 mol:0.5 mol)

[0162] Surface-treated silica (S1): Silica particles (HM20S, Tokuyama Corporation, average primary particle size 12 nm, surface treatment agent hexamethyldisilazane) Surface-treated silica (S2): Silica particles (NX90S, Nippon Aerosil Co., Ltd., average primary particle size 22 nm, surface treatment agent hexamethyldisilazane) Surface-treated silica (S3): Silica particles (RY200, Nippon Aerosil Co., Ltd., average primary particle size 12 nm, surface treatment agent silicone oil) Surface-treated silica (S4): Silica particles (HM30S, Tokuyama Corporation, average primary particle size 7 nm, surface treatment agent hexamethyldisilazane) Surface-treated silica (S5): Silica particles (average primary particle size 30 nm, dry-process silica, surface treatment agent hexamethyldisilazane) Surface-treated silica (S6): Silica particles (average primary particle size 40 nm, dry-process silica, surface treatment agent hexamethyldisilazane) Surface-treated silica (S7): Silica particles (RX50, Nippon Aerosil Co., Ltd., average primary particle size 65 nm, surface treatment agent hexamethyldisilazane) Untreated silica (Sn): Silica particles (QS-20, Tokuyama Corporation, average primary particle size 12 nm) Surface-treated alumina (A): Alumina particles (AluC805, Nippon Aerosil Co., Ltd., average primary particle size 22 nm, surface treatment agent octylsilane) Surface-treated titania (T): Titania particles (T805, Nippon Aerosil Co., Ltd., average primary particle size 20 nm, surface treatment agent octylsilane)

[0163] Resin particles (M1): Melamine resin particles (Eposter FS, Nippon Shokubai Co., Ltd., average primary particle size 250 nm) Resin particles (M4): Melamine resin particles (Eposter S6, Nippon Shokubai Co., Ltd., average primary particle size 400 nm) Resin particles (A1): Acrylic resin particles (MP-1441, Soken Chemical & Engineering Co., Ltd., average primary particle size 150 nm) Resin particles (A2): Acrylic resin particles (MP-2200, Soken Chemical & Engineering Co., Ltd., average primary particle size 350 nm) CB: Carbon black (VXC72, Cabot Corporation)

[0164] [Creating a carrier - Part 1] Using a Spira Coater (Okada Seiko Co., Ltd.), a first layer coating agent was applied to the surface of 1,000 parts of ferrite particles (1) at a rate of 30 g / min in an atmosphere of 70°C so that the components of the resin coating layer were 15 parts relative to the ferrite core material. Next, a second layer coating agent was applied at a rate of 30 g / min so that the components of the resin coating layer were 15 parts relative to the ferrite particles (1), and then dried. The dried powder was removed from the Spira Coater and crushed using a sieve with 75 μm openings to obtain carriers (1-1) to (1-36) and carriers (1-C1) to (1-C2), respectively.

[0165] [Measurement of the volume average particle size of the carrier] The particle size of the carrier was measured using a laser diffraction / scattering particle size analyzer (LS Particle Size Analyzer: LS13 320, Beckman Coulter, Inc.) as a sample. The particle size (μm) representing the cumulative 50% smallest diameter in the volume-based particle size distribution was determined. The volume average particle diameter of each of the carriers (1-1) to (1-36) and the carriers (1-C1) to (1-C2) was 36 μm.

[0166] [Elemental analysis by XPS] Using the carrier as a sample, carbon, nitrogen, oxygen, iron, manganese, and metals and metalloids constituting the inorganic particles were analyzed by XPS using an etching method. When the inorganic particles were silica particles, carbon, nitrogen, oxygen, iron, manganese and silicon were analyzed. When the inorganic particles were alumina particles, carbon, nitrogen, oxygen, iron, manganese and aluminum were analyzed. When the inorganic particles were titania particles, carbon, nitrogen, oxygen, iron, manganese and titanium were analyzed. The element ratio (atm%) of metals and metalloids that make up the inorganic particles to the total amount of all elements analyzed was calculated. The element ratio at 0 seconds of etching is A (atm%), and the element ratio at 300 seconds of etching is B (atm%).

[0167] XPS was performed using the following equipment and conditions. Analysis was performed after baseline correction. XPS equipment: PHI5000 Versa Probe II (ULVAC-PHI, Inc.) X-ray source: Monochromated AlKα rays Beam voltage: 15kV Emission current: 3mA Etching gun: Argon gas cluster ion gun ·Vacuum degree: 1×10 -5 Pa~1×10 -6 Pa Pass Energy: 23.5 eV ·Sweep area: 300μm×300μm Time Per Step: 50 seconds Cycle: 5 times Sweep: 10 times

[0168] <Preparation of carrier (2)> Each of the components listed in Table 2 was placed in a sand mill in the mass ratio listed in Table 2 along with glass beads (1 mm diameter, same amount as toluene) and stirred at a rotation speed of 190 rpm for 30 minutes to prepare each coating agent. 1000 parts of the ferrite particles (1) and 125 parts of the coating agent were placed in a kneader and mixed at room temperature (25°C) for 20 minutes, then heated to 70°C and dried under reduced pressure. The dried product was cooled to room temperature (25° C.), and 125 parts of the coating agent was added and mixed at room temperature (25° C.) for 20 minutes, followed by heating to 70° C. and drying under reduced pressure. Next, the dried product was taken out of the kneader and sieved through a mesh with 75 μm openings to remove coarse powder, thereby preparing carriers (2-1) to (2-8). The composition of the coating agent is as shown in Table 2. Details of the abbreviations for each component of the coating agent are as described above.

[0169] The particle size of the carrier was measured using a laser diffraction / scattering particle size analyzer (LS Particle Size Analyzer: LS13 320, Beckman Coulter, Inc.) as a sample. The particle size (μm) representing the cumulative 50% smallest diameter in the volume-based particle size distribution was determined. The volume average particle diameter of each of the carriers (2-1) to (2-8) was 36 μm.

[0170] <Preparation of Developer (Y), Developer (M), and Developer (C)> Toner (Y), toner (M), and toner (C) were combined with one of carriers (1-1) to (1-36) and carriers (1-C1) to (1-C2) to prepare yellow developer (Y), magenta developer (M), and cyan developer (C). 100 parts of the carrier and 6 parts of the toner were charged into a V-blender and stirred for 20 minutes, after which the mixture was sieved through a sieve with 212 μm openings to obtain a developer.

[0171] <Preparation of Developer (K)> The toner (K) was combined with one of the carriers (2-1) to (2-8) to prepare a black developer (K). 100 parts of the carrier and 6 parts of the toner were charged into a V-blender and stirred for 20 minutes, after which the mixture was sieved through a sieve with 212 μm openings to obtain a developer.

[0172] <Performance evaluation> [Black photosensitive filming] A modified Color 1000 Press (Fujifilm Business Innovation Co., Ltd.), a four-tandem image forming apparatus, was prepared. The four colors were arranged in the order of YMCK from the upstream. Each color developer was accommodated in its own developing device. In each image forming unit, the contact angle θ between the photosensitive member (an example of an image carrier) and the photosensitive member cleaning blade was set to 11°, and the pressing pressure N of the photosensitive member cleaning blade against the photosensitive member was set to 2.5 gf / mm. 2 was set to. An image with an average image density of 5% for each of the YMCK colors was printed on 10,000 sheets of A4 plain paper at a temperature of 28°C and a relative humidity of 85%. Next, an image with an average image density of 5% for each of the YMCK colors was printed on 1,000 sheets of A4 plain paper at a temperature of 10°C and a relative humidity of 15%. After repeating the above print cycle twice, an image with an average image density of 40% for each of the YMCK colors was printed on 10,000 sheets of A4 plain paper at a temperature of 10°C and a relative humidity of 15%. The surface of the black photoreceptor (the most downstream photoreceptor) was then analyzed using a laser microscope, and the area percentage of filming within a 300 μm x 250 μm field of view was classified as follows. The results are shown in Table 3.

[0173] A: Less than 5% B+: 5% or more, less than 15% B: 15% or more, less than 25% B-: 25% or more, less than 35% C: 35% or more, less than 50% C-: 50% or more, less than 60% D: 60% or more, less than 75% E: 75% or more

[0174] [Table 1-1]

[0175] [Table 1-2]

[0176] [Table 2]

[0177] [Table 3]

[0178] The electrostatic image developer set, image forming apparatus, and image forming method of the present disclosure include the following aspects.

[0179] (Addendum) (((1))) Both are a set of developer (1) and developer (2) containing toner and carrier, The carrier (1) of the developer (1) has magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer, The carrier (2) of the developer (2) has magnetic particles and a resin coating layer that coats the magnetic particles, The carrier (1) and the carrier (2) are each analyzed by X-ray photoelectron spectroscopy to analyze the element ratio of metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio on the surface of the carrier (1) is defined as A(1) and the element ratio on the surface of the carrier (2) is defined as A(2), the value of A(1) / A(2) is 17 or more and 105 or less. Electrostatic image developer set. (((2))) The carrier (1) is analyzed in the depth direction by X-ray photoelectron spectroscopy to determine the element ratio of metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio at 0 seconds of etching is defined as A(1) and the element ratio at 300 seconds of etching is defined as B(1), the value of B(1) - A(1) is 0.5 atm% or more and 3.0 atm% or less. The electrostatic image developer set according to (((1))). (((3))) The carrier (2) is analyzed in the depth direction by X-ray photoelectron spectroscopy to determine the element ratio of the metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio at 0 seconds of etching is defined as A(2) and the element ratio at 300 seconds of etching is defined as B(2), the value of B(2) - A(2) is 0.3 atm% or less. The electrostatic image developer set according to (((1))) or (((2))). (((4))) The inorganic particles of the carrier (1) include at least one selected from the group consisting of silica particles, alumina particles, and titania particles. The electrostatic image developer set according to any one of (((1))) to (((3))). (((5))) the volume average particle size of the inorganic particles contained in the resin coating layer of the carrier (1) is 5 nm or more and 40 nm or less; The electrostatic image developer set according to any one of (((1))) to (((4))). (((6))) The mass ratio of the inorganic particles in the resin coating layer of the carrier (1) is 15 mass% or more and 35 mass% or less. The electrostatic image developer set according to any one of (((1))) to (((5))). (((7))) the carrier (1) contains a nitrogen atom-containing resin in the resin coating layer, and the mass ratio of the nitrogen atom-containing resin in the resin coating layer is R(1), When the carrier (2) contains a nitrogen atom-containing resin in the resin coating layer and the mass ratio of the nitrogen atom-containing resin in the resin coating layer is R(2), The value of R(1) / R(2) is between 0.2 and 4.0. The electrostatic image developer set according to any one of (((1))) to (((6))). (((8))) a first image forming unit that forms a yellow image; a second image forming unit that forms a magenta image; a third image forming unit that forms a cyan image; a fourth image forming unit that forms a black image, The electrostatic image developer set according to any one of (((1))) to (((7))) is contained therein, the developing devices of the first image forming unit, the second image forming unit, and the third image forming unit each contain the developer (1); The developing device of the fourth image forming unit contains the developer (2). Image forming device. (((9))) a first image forming step of forming a yellow image; a second image forming step of forming a magenta image; a third image forming step of forming a cyan image; a fourth image forming step of forming a black image, Using the electrostatic image developer set according to any one of (((1))) to (((7))), the first image forming step, the second image forming step, and the third image forming step each use the developer (1); the developing step of the fourth image forming step uses the developer (2); Image forming method.

[0180] According to (((1))), (((3))), or (((4))), an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the value of A(1) / A(2) is less than 17 or more than 105. According to (((2))), an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the value of B(1)-A(1) is less than 0.5 atm% or more than 3.0 atm%. According to (((5))), an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the volume average particle size of the inorganic particles contained in the resin coating layer of the carrier (1) is less than 5 nm or more than 40 nm. According to (((6))), an electrostatic image developer set is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an electrostatic image developer set in which the mass proportion of inorganic particles in the resin coating layer of the carrier (1) is less than 15 mass % or more than 35 mass %. According to (((7))), an electrostatic image developer set is provided which, compared to an electrostatic image developer set in which the value of R(1) / R(2) is less than 0.2 or more than 4.0, suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus. According to (((8))), an image forming apparatus is provided which suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus, compared to an image forming apparatus which applies an electrostatic image developer set in which the value of A(1) / A(2) is less than 17 or more than 105. According to (((9))), an image forming method is provided which, compared to an image forming method using an electrostatic image developer set in which the value of A(1) / A(2) is less than 17 or more than 105, suppresses the occurrence of filming on the surface of an image carrier located downstream in a tandem image forming apparatus. [Explanation of symbols]

[0181] 1Y, 1M, 1C, 1K Photoconductor (an example of an image carrier) 2Y, 2M, 2C, 2K Charging roll (example of charging device) 3. Exposure device (an example of an electrostatic image forming device) 3Y, 3M, 3C, 3K laser beam 4Y, 4M, 4C, 4K developing device (example of developing device) 5Y, 5M, 5C, 5K Primary transfer roll (an example of a primary transfer device) 6Y, 6M, 6C, 6K Photoconductor cleaning device (example of cleaning device) 8Y, 8M, 8C, 8K toner cartridges 10Y, 10M, 10C, 10K image forming units 20 Intermediate transfer belt (an example of an intermediate transfer body) 22 Drive Roll 24 Support Roll 26 Secondary transfer roll (an example of a secondary transfer device) 28 Fixing device (example of fixing device) 30 Intermediate transfer body cleaning device P Recording paper (an example of a recording medium)

Claims

1. A set of developer (1) and developer (2) each containing toner and carrier, The carrier (1) of the developer (1) has magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer, the carrier (2) of the developer (2) has magnetic particles and a resin coating layer that coats the magnetic particles, The carrier (1) and the carrier (2) are each analyzed by X-ray photoelectron spectroscopy to analyze the element ratio of metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio on the surface of the carrier (1) is defined as A(1) and the element ratio on the surface of the carrier (2) is defined as A(2), the value of A(1) / A(2) is 17 or more and 105 or less. Electrostatic image developer set.

2. The carrier (1) is analyzed in the depth direction by X-ray photoelectron spectroscopy to determine the element ratio of metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio at 0 seconds of etching is defined as A(1) and the element ratio at 300 seconds of etching is defined as B(1), the value of B(1) - A(1) is 0.5 atm% or more and 3.0 atm% or less.

2. The electrostatic image developer set according to claim 1.

3. The carrier (2) is analyzed in the depth direction by X-ray photoelectron spectroscopy to determine the element ratio of the metals and metalloids constituting the inorganic particles of the carrier (1), and when the element ratio at 0 seconds of etching is defined as A(2) and the element ratio at 300 seconds of etching is defined as B(2), the value of B(2) - A(2) is 0.3 atm% or less.

2. The electrostatic image developer set according to claim 1.

4. The inorganic particles of the carrier (1) include at least one selected from the group consisting of silica particles, alumina particles, and titania particles.

2. The electrostatic image developer set according to claim 1.

5. the volume average particle size of the inorganic particles contained in the resin coating layer of the carrier (1) is 5 nm or more and 40 nm or less; 2. The electrostatic image developer set according to claim 1.

6. the mass ratio of the inorganic particles in the resin coating layer of the carrier (1) is 15 mass% or more and 35 mass% or less; 2. The electrostatic image developer set according to claim 1.

7. the carrier (1) contains a nitrogen atom-containing resin in the resin coating layer, and the mass ratio of the nitrogen atom-containing resin in the resin coating layer is R(1), When the carrier (2) contains a nitrogen atom-containing resin in the resin coating layer and the mass ratio of the nitrogen atom-containing resin in the resin coating layer is R(2), The value of R(1) / R(2) is 0.2 or more and 4.0 or less.

2. The electrostatic image developer set according to claim 1.

8. a first image forming unit for forming a yellow image; a second image forming unit that forms a magenta image; a third image forming unit that forms a cyan image; a fourth image forming unit that forms a black image, The electrostatic image developer set according to any one of claims 1 to 7 is housed therein, the developing devices of the first image forming unit, the second image forming unit, and the third image forming unit each contain the developer (1); The developing device of the fourth image forming unit contains the developer (2). Image forming device.

9. a first image forming step of forming a yellow image; a second image forming step of forming a magenta image; a third image forming step of forming a cyan image; a fourth image forming step of forming a black image, Using the electrostatic image developer set according to any one of claims 1 to 7, each of the developing steps of the first image forming step, the second image forming step, and the third image forming step uses the developer (1); the developing step of the fourth image forming step uses the developer (2); Image forming method.

Images