Electrostatic charge image developer, process cartridge, image forming apparatus, and image forming method

Abstract

To provide an electrostatic charge image developer excellent in stability of image density.SOLUTION: An electrostatic charge image developer includes a carrier and a toner, the carrier has magnetic particles, a resin coating layer, and inorganic particles, and an element ratio of metal and semimetal constituting the inorganic particles is analyzed in a depth direction by X-ray photoelectron spectroscopy. The value of B-A is from 0. 5atm% to 3. 0atm%, where A is the element ratio at 0 seconds of etching and B is the element ratio at 300 seconds of etching, and the toner particles of the toner have a minimum value tan δ (min) of a loss tangent at from 50 °C. to 80 °C. and the minimum value tan δ (min) of the loss tangent is from 0.50 to 1.00 in dynamic viscoelasticity measurement when the temperature is increased from 30 °C. to 120 °C.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a toner A containing silica particles (A) containing a nitrogen-containing compound containing molybdenum element and a binder resin and resin particles, and a carrier B having a core material and a coating resin layer containing inorganic particles that coats the core material, and the net intensity N of molybdenum element measured by fluorescent X-ray analysis of the silica particles (A) is Mo and the net strength of silicon element N Si Ratio to N Mo / N Si is 0.035 or more and 0.45 or less.

[0003] Patent Document 2 discloses an electrostatic image developing carrier having magnetic particles and a resin layer containing silica particles that coat the magnetic particles and have an average particle size of 50 nm to 200 nm, wherein the ratio Si1 of the Si element in a region from the surface of the resin layer to the interior at a distance of 0.1 μm to 0.2 μm, and the ratio S2 of the Si element in a region from the surface of the magnetic particles to the surface of the resin layer at a distance of 0.0 μm to 0.1 μm, satisfy the formula 1-1: 0.005≦Si1≦2 and the formula 2-1: 1≦Si1 / Si2≦1000.

[0004] Patent Document 3 describes a carrier having a core material and a resin layer covering the core material, and the carrier is defined by the formula (1): 1≦(S×r×D) / 3≦1.5 [S is the BET specific surface area (m 2 / g), r is the average particle radius of the carrier (m), and D is the density of the carrier (g / m 3 ) is disclosed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-046535 [Patent Document 2] Japanese Patent Publication No. 2022-181065 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-093629 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide an electrostatic image developer that has excellent stability in image density. [Means for solving the problem]

[0007] Specific means for solving the above problems include the following aspects: Each formula is the same as the formula with the same number described below.

[0008] <1> An electrostatic image developer comprising a carrier and a toner, the carrier has magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer, and the element ratio of metals and metalloids that constitute the inorganic particles is analyzed in the depth direction by X-ray photoelectron spectroscopy, and when the element ratio at 0 seconds of etching is defined as A and the element ratio at 300 seconds of etching is defined as B, the value of B A is 0.5 atm% or more and 3.0 atm% or less; the toner contains toner particles, and in a dynamic viscoelasticity measurement when the toner particles are heated from 30°C to 120°C, the toner particles have a minimum value of loss tangent tanδ(min) between 50°C and 80°C, and the minimum value of loss tangent tanδ(min) is between 0.50 and 1.00; Electrostatic image developer. <2> The inorganic particles are at least one selected from the group consisting of silica particles, titania particles, and alumina particles. <1> Electrostatic image developer according to claim 1. <3> The inorganic particles are silica particles whose surfaces have been hydrophobized. <1> or <2> Electrostatic image developer according to claim 1. <4> The proportion of the inorganic particles in the resin coating layer is 15% by mass or more and 35% by mass or less. <1> ~ <3> 10. The electrostatic image developer according to claim 9, wherein the electrostatic image developer is a developer containing a fluorine atom or a methyl acrylate. <5> The value of B is 3.5 atm% or more and 12.0 atm% or less, <1> ~ <4> 10. The electrostatic image developer according to claim 9, wherein the electrostatic image developer is a developer containing a fluorine atom or a methyl acrylate. <6> The BA value is 1.2 atm% or more and 2.3 atm% or less, <1> ~ <5> 10. The electrostatic image developer according to claim 9, wherein the electrostatic image developer is a developer containing a fluorine atom or a methyl acrylate. <7> The minimum value of the loss tangent tanδ(min) is 0.60 or more and 0.96 or less. <1> ~ <6> 10. The electrostatic image developer according to claim 9, wherein the electrostatic image developer is a developer containing a fluorine atom or a methyl acrylate. <8> The ratio tanδ(90) / tanδ(min) of the minimum value tanδ(min) of the loss tangent to the loss tangent tanδ(90) at a temperature of 90°C is 2.5 or less. <1> ~ <7> 10. The electrostatic image developer according to claim 9, wherein the electrostatic image developer is a developer containing a fluorine atom or a methyl acrylate. <9> the toner particles contain an amorphous polyester resin as a binder resin, the amorphous polyester resin comprises an amorphous polyester resin (S) having at least one of a structural unit represented by formula (A) and a structural unit represented by formula (B), the total proportion of the structural units represented by formula (A) and the structural units represented by formula (B) in the total structural units constituting the amorphous polyester resin contained in the toner particles is 0.5 mol % or more and 10.0 mol % or less; <1> ~ <8> 10. The electrostatic image developer according to claim 9, wherein the electrostatic image developer is a developer containing a fluorine atom or a methyl acrylate. <10> the proportion of the structural unit represented by formula (A) in the total carboxylic acid units constituting the amorphous polyester resin contained in the toner particles is 2.0 mol % or more and 15.0 mol % or less; <9> Electrostatic image developer according to claim 1. <11> <1> ~ <10> a developing device that contains the electrostatic image developer according to any one of the preceding items and develops an electrostatic image formed on a surface of an image carrier into a toner image by using the electrostatic image developer, Attached to and detached from the image forming apparatus, Process cartridge. <12> an image carrier; a charging device that charges the surface of the image carrier; an electrostatic image forming device for forming an electrostatic image on the charged surface of the image carrier; <1> ~ <10> a developing device that contains the electrostatic image developer according to any one of the above items and develops the electrostatic image formed on the surface of the image carrier into a toner image by using the electrostatic image developer; a transfer device that transfers the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing device that fixes the toner image transferred onto the surface of the recording medium, Image forming device. <13> a charging step of charging the surface of the image carrier; an electrostatic image forming step of forming an electrostatic image on the charged surface of the image carrier; <1> ~ <10> a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image by using the electrostatic image developer according to any one of the above items; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing step of fixing the toner image transferred onto the surface of the recording medium, Image forming method. [Effects of the Invention]

[0009] <1> , <2> or <3> According to the method, an electrostatic image developer having excellent image density stability is provided, compared to an electrostatic image developer containing a carrier having a BA value of less than 0.5 atm% or more than 3.0 atm%, or an electrostatic image developer containing toner particles having a minimum loss tangent value tanδ(min) of less than 0.50 or more than 1.00. <4> According to the present invention, an electrostatic image developer having excellent stability of image density is provided compared to electrostatic image developers in which the proportion of inorganic particles in the resin coating layer of the carrier is less than 15% by mass or more than 35% by mass. <5> According to the method, an electrostatic image developer having excellent stability of image density is provided compared to an electrostatic image developer containing a carrier in which the value of B is less than 3.5 atm % or more than 12.0 atm %. <6> According to the method, an electrostatic image developer having excellent stability of image density is provided compared to an electrostatic image developer containing a carrier having a BA value of less than 1.2 atm % or more than 2.3 atm %. <7> According to the method, an electrostatic image developer having excellent stability of image density is provided compared to an electrostatic image developer containing toner particles having a minimum value of loss tangent tanδ(min) of less than 0.60 or more than 0.96. <8> According to the method, an electrostatic image developer having excellent image density stability is provided compared to an electrostatic image developer containing toner particles having a ratio tanδ(90) / tanδ(min) of the minimum value of loss tangent tanδ(min) to the loss tangent tanδ(90) at a temperature of 90°C of more than 2.5. <9> According to the present invention, an electrostatic image developer having excellent image density stability is provided, compared to an electrostatic image developer containing a toner in which the total proportion of the structural units represented by formula (A) and the structural units represented by formula (B) in all structural units constituting the amorphous polyester resin contained in the toner particles is less than 0.5 mol % or more than 10.0 mol %. <10> According to the method, an electrostatic image developer having excellent image density stability is provided, compared to an electrostatic image developer containing a toner in which the proportion of the structural unit represented by formula (A) in all carboxylic acid units constituting the amorphous polyester resin contained in the toner particles is less than 2.0 mol % or more than 15.0 mol %. <11> According to the method, a process cartridge having excellent image density stability is provided compared to a process cartridge containing an electrostatic image developer containing a carrier having a BA value of less than 0.5 atm% or more than 3.0 atm%, or a process cartridge containing an electrostatic image developer containing toner particles having a minimum loss tangent value tanδ(min) of less than 0.50 or more than 1.00. <12> According to the present invention, an image forming apparatus is provided that has excellent stability of image density compared to an image forming apparatus that contains an electrostatic image developer containing a carrier whose BA value is less than 0.5 atm% or more than 3.0 atm%, or an electrostatic image developer containing toner particles whose minimum value of loss tangent, tanδ(min), is less than 0.50 or more than 1.00. <13> According to the present invention, an image forming method is provided which is superior in stability of image density compared to an image forming method using an electrostatic image developer containing a carrier whose BA value is less than 0.5 atm % or more than 3.0 atm %, or an image forming method using an electrostatic image developer containing toner particles whose minimum value of loss tangent, tanδ(min), is less than 0.50 or more than 1.00. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating an example of a process cartridge that is detachably mounted to an image forming apparatus according to an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] In this disclosure, "developer" refers to "electrostatic image developer," "carrier" refers to "electrostatic image developing carrier," and "toner" refers to "electrostatic image developing toner."

[0020] <Electrostatic image developer> The developer of the present disclosure includes the following carrier and the following toner.

[0021] Carrier: Comprising magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer, the element ratio of the metals and metalloids that make up the inorganic particles is analyzed in the depth direction by X-ray photoelectron spectroscopy, and when the element ratio at 0 seconds of etching is defined as A and the element ratio at 300 seconds of etching is defined as B, the value of BA is 0.5 atm% or more and 3.0 atm% or less.

[0022] For the resin coating layer of the carrier of the present disclosure, carbon black is not an inorganic particle.

[0023] Toner: Contains toner particles, and in dynamic viscoelasticity measurement when the toner particles are heated from 30°C to 120°C, the toner particles have a minimum value of loss tangent tanδ(min) between 50°C and 80°C, and the minimum value of loss tangent tanδ(min) is between 0.50 and 1.00.

[0024] With conventional developers, heat is easily generated at the contact points between the toner and carrier, and when image formation is performed that involves a long period of mechanical load (for example, forming a large number of low-density images (for example, image density of 0.5%) in a high-temperature, high-humidity environment (for example, temperature 25°C and relative humidity 90%), the external additives are embedded in the toner and the resin coating layer of the carrier is peeled off, causing fluctuations in the triboelectric charge of the toner; and when a large number of high-density images (for example, image density of 100%) are then formed in a low-temperature, low-humidity environment (for example, temperature 10°C and relative humidity 15%), the image density can become unstable. In contrast, the developer of the present disclosure has excellent stability of image density due to the combination of the carrier and toner described above.

[0025] If the BA value of the carrier is less than 0.5 atm%, when the carrier surface is scraped off due to stress in the developing device, there will be too few inorganic particles on the carrier surface, which will easily generate heat at the point where the toner and carrier come into contact, promoting the embedding of external additives in the toner and peeling off of the carrier's resin coating layer, impairing the good agitation properties of the toner and carrier, causing fluctuations in the triboelectric charge of the toner, and resulting in unstable image density. From the viewpoint of suppressing this phenomenon, the BA value of the carrier is 0.5 atm% or more, preferably 0.8 atm% or more, more preferably 1.0 atm% or more, and even more preferably 1.2 atm% or more.

[0026] If the BA value of the carrier exceeds 3.0 atm%, when the carrier surface is scraped off due to stress in the developing device, too many inorganic particles will appear on the carrier surface, making the carrier surface too hard and promoting the embedding of external additives in the toner, impairing good agitation between the toner and carrier, causing fluctuations in the triboelectric charge of the toner, and possibly resulting in unstable image density. From the viewpoint of suppressing this phenomenon, the BA value of the carrier is 3.0 atm% or less, preferably 2.7 atm% or less, more preferably 2.5 atm% or less, and even more preferably 2.3 atm% or less.

[0027] If the minimum value of the loss tangent of the toner particles, tanδ(min), is less than 0.50, the external additives tend to be buried due to the synergistic effect of excessive viscosity of the toner and heat generated at the contact point between the toner and carrier due to stress in the developing machine, impairing the good agitation properties of the toner and carrier, causing fluctuations in triboelectric charge, and resulting in unstable image density. From the viewpoint of suppressing this phenomenon, the minimum value of the loss tangent of the toner particles, tanδ(min), is 0.50 or more, preferably 0.60 or more, and more preferably 0.70 or more.

[0028] If the minimum value of the loss tangent of the toner particles, tanδ(min), exceeds 1.00, the external additives are likely to be liberated due to excessive elasticity of the toner, which may contaminate the carrier and cause a decrease in charge, and may impair the good agitation properties of the toner and carrier, causing fluctuations in triboelectric charge and unstable image density. From the viewpoint of suppressing this phenomenon, the minimum value of the loss tangent of the toner particles, tanδ(min), is 1.00 or less, preferably 0.96 or less, and more preferably 0.90 or less.

[0029] The developer of the present disclosure is a two-component developer in which toner and carrier are mixed at an appropriate ratio. The mixing ratio (mass ratio) of toner to carrier is preferably toner:carrier=1:100 to 30:100, and more preferably 3:100 to 20:100.

[0030] The carrier and toner will be described in detail below.

[0031] <Electrostatic image developing carrier> [BA value] The carrier of the present disclosure is 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 and the elemental ratio at 300 seconds of etching is defined as B, the BA value is 0.5 atm% or more and 3.0 atm% or less.

[0032] From the viewpoint of image density stability, the BA value 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.

[0033] The method for elemental analysis in the depth direction by X-ray photoelectron spectroscopy (XPS) and the method for measuring the element ratios A and B are as follows. The carrier 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 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 when etching is performed for 0 seconds is A (atm %), and the ratio of the above element when etching is performed for 300 seconds is B (atm %). Etching for 0 seconds means that no etching is performed.

[0034] 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

[0035] 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.

[0036] [Element ratio A value] From the viewpoint of image density stability, the value of element ratio A is preferably 2.0 atm% to 10.0 atm%, more preferably 2.5 atm% to 8.0 atm%, and even more preferably 3.0 atm% to 6.0 atm%. When the element ratio A is within the above range, the inorganic particles form fine irregularities on the carrier surface, and the inorganic particles moderately harden the carrier surface, thereby suppressing wear due to stress within the developing device, resulting in stable image density.

[0037] [Element ratio B value] From the viewpoint of image density stability, the value of element ratio B 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. When the element ratio B is 3.5 atm% or more, the amount of inorganic particles exposed when the carrier surface is scraped off due to stress in the developing device is not too small, and the charge does not increase too much, resulting in stable image density. When the element ratio B is 12.0 atm % or less, the amount of inorganic particles exposed when the carrier surface is scraped off due to stress in the developing device is not too large, and the charge does not decrease too much, resulting in stable image density.

[0038] [How to control the BA value] The BA value 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 BA value 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, the conditions for forming the resin coating layer, and the like. 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.

[0039] [Resin coating layer] -resin- The carrier of the present disclosure has a resin coating layer on the surface of the 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.

[0040] From the viewpoint of controlling the BA value and image density stability, 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. From the viewpoint of image density stability, the acrylic resin having a structural unit with an aliphatic cyclic structure preferably contains 80% by 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. From the viewpoint of image density stability, the acrylic resin having a structural unit having an amino group preferably contains the structural unit having an amino group in an amount of 0.05% by mass to 5% by mass, more preferably 0.1% by mass to 2% by mass.

[0041] -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.

[0042] 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 that the inorganic particles appearing on the surface in an appropriate amount easily exhibit the effect of preventing abnormal increases or decreases in charge.

[0043] From the viewpoint of image density stability, 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] Examples of the silazane compound used for the hydrophobic treatment of the surfaces of inorganic particles include dimethyldisilazane, trimethyldisilazane, tetramethyldisilazane, pentamethyldisilazane, and hexamethyldisilazane.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] The ratio of the amount of inorganic particles on the carrier surface (element ratio A, atm %) to the content of inorganic particles in the resin coating layer (mass %) (element ratio A / content of inorganic particles, atm % / mass %) is preferably 0.05 to 0.60, more preferably 0.08 to 0.40, and even more preferably 0.10 to 0.30. When the ratio of the amount of inorganic particles on the carrier surface (element ratio A, atm %) to the content of inorganic particles in the resin coating layer (mass %) is within the above range, the carrier surface is appropriately hardened by the inorganic particles, and the inorganic particles are appropriately unevenly distributed below the resin coating layer.

[0056] -Resin particles- From the viewpoint of image density stability, the resin coating layer preferably contains resin particles. 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.

[0057] From the viewpoint of image density stability, 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.

[0058] From the viewpoint of image density stability, 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. 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] From the viewpoint of image density stability, the content of resin particles in the resin coating layer is preferably smaller than the content of inorganic particles. From the viewpoint of image density stability, 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.

[0063] -Carbon black- From the viewpoint of image density stability, the resin coating layer preferably contains carbon black. From the viewpoint of image density stability, the average primary particle size of 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.

[0064] 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. When the resin coating layer is formed by a wet process, the carbon black rises to the top of the resin coating layer, and as a result, the inorganic particles tend to be positioned below the resin coating layer.

[0065] 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.

[0066] From the viewpoint of image density stability, 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 image density stability, 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 image density stability, the content of carbon black in the resin coating layer is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 13% by mass or less, and even more preferably 2% by mass or more and 10% by mass or less, relative to the total mass of the resin coating layer.

[0067] From the viewpoint of image density stability, the resin coating layer preferably contains silica particles and melamine resin particles, and more preferably contains silica particles, melamine resin particles and carbon black.

[0068] [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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] [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.

[0074] 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 it is believed that the presence of calcium or strontium on the surface of ferrite particles suppresses 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 developer, 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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 )

[0082] [Career characteristics] The volume average particle size of the carrier 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.

[0083] The volume average particle size of a carrier 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 a 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.

[0084] The magnetic force of the carrier 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.

[0085] The volume resistivity of the carrier (at 25°C) is, for example, 1 x 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.

[0086] The exposed ratio of the magnetic particles on the surface of the carrier is preferably 2% to 20%, more preferably 3% to 15%, and even more preferably 4% to 12%.

[0087] The exposed ratio of the magnetic particles on the surface of the carrier 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.

[0088] The exposed ratio of the magnetic particles on the surface of the carrier 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.

[0089] <Toner for developing electrostatic images> [Dynamic viscoelasticity of toner particles] The toner particles contained in the toner of the present disclosure have a minimum value of loss tangent tanδ(min) at a temperature of 50°C or higher and 80°C or lower, in dynamic viscoelasticity measurement when heated from 30°C to 120°C, and the minimum value of loss tangent tanδ(min) is 0.50 or higher and 1.00 or lower.

[0090] From the viewpoint of image density stability, the minimum value of the loss tangent, tan δ(min), is 0.50 or more and 1.00 or less, preferably 0.60 or more and 0.96 or less, and more preferably 0.70 or more and 0.90 or less.

[0091] From the viewpoint of achieving superior image density stability, the toner particles contained in the toner of the present disclosure preferably have a ratio tanδ(90) / tanδ(min) of the minimum value of the loss tangent tanδ(min) to the loss tangent tanδ(90) at a temperature of 90°C of 2.5 or less, more preferably 2.2 or less, and even more preferably 2.0 or less.

[0092] The dynamic viscoelasticity of the toner particles is measured as follows. The toner particles are formed into tablets at room temperature (25°C) using a press molding machine, and these are used as samples. Since the loss tangent tanδ of the toner particles is not affected by external additives, the toner may also be used as a sample. The sample is placed in the measuring device and left at 120°C for 20 minutes. It is then cooled to 60°C and held at 60°C for 1 hour, then cooled to room temperature. Dynamic viscoelasticity is measured under the following measurement conditions to measure the storage modulus and loss modulus. The loss tangent tanδ is calculated from the storage modulus and loss modulus, and a graph showing the relationship between measurement temperature and loss tangent tanδ is drawn. Measurement equipment: Rheometer ARES (TA Instruments Japan Co., Ltd.) Measurement jig: 8mm parallel plate Gap: Adjusted to 3mm Frequency: 6.28rad / s Heating conditions: Starting temperature 30°C, End temperature 120°C, Heating rate 2°C / min

[0093] Methods for controlling the minimum value of the loss tangent tanδ(min) and the ratio tanδ(90) / tanδ(min) within the above ranges include, for example, the following methods (1) and (2). (1) Adding crosslinked resin particles to toner particles The crosslinked resin particles are preferably resin particles having an appropriate glass transition temperature. (2) The amount of metal ions contained in the toner particles is adjusted to control the degree of crosslinking of the binder resin by the metal ions. The metal ions are preferably at least one selected from the group consisting of Al ions, Mg ions, and Ca ions.

[0094] [Toner particles] The toner particles contain at least a binder resin, and may further contain a colorant, a release agent, internally added crosslinked resin particles, and various internal additives. From the viewpoint of controlling dynamic viscoelasticity, the toner particles preferably contain crosslinked resin particles.

[0095] -Binder resin- The binder resin preferably contains an amorphous polyester resin, and more preferably contains a crystalline resin, and the crystalline resin is preferably a crystalline polyester resin.

[0096] The "crystalline" nature of a resin refers to the presence of a clear endothermic peak rather than a stepwise change in endothermic heat in differential scanning calorimetry (DSC). Specifically, this refers to the half-width of the endothermic peak being within 10°C when measured at a heating rate of 10°C / min. The term "amorphous" for a resin means that the half-width exceeds 10°C, that the endothermic amount exhibits a stepwise change, or that no clear endothermic peak is observed.

[0097] The amorphous polyester resin preferably contains an amorphous polyester resin (S) having at least one of a constitutional unit represented by the following formula (A) and a constitutional unit represented by the following formula (B).

[0098] [ka]

[0099] In formula (A), nA is an integer of 2 or more and 12 or less. In formula (B), nB is an integer of 2 or more and 12 or less.

[0100] In formula (A), nA is preferably an integer of 3 or more and 11 or less, more preferably an integer of 3 or more and 10 or less, and even more preferably an integer of 4 or more and 10 or less.

[0101] In formula (B), nB is preferably an integer of 3 or more and 11 or less, more preferably an integer of 3 or more and 10 or less, and even more preferably an integer of 4 or more and 10 or less.

[0102] The total proportion of the structural units represented by formula (A) and the structural units represented by formula (B) in all structural units constituting the amorphous polyester resin contained in the toner particles is preferably 0.5 mol % or more and 10.0 mol % or less, more preferably 1.5 mol % or more and 8.0 mol % or less, and even more preferably 2.5 mol % or more and 6.0 mol % or less, from the viewpoint of achieving better image density stability.

[0103] The proportion of the constituent units represented by formula (A) in all carboxylic acid units constituting the amorphous polyester resin contained in the toner particles is preferably 2.0 mol % or more and 15.0 mol % or less, more preferably 3.0 mol % or more and 10.0 mol % or less, and even more preferably 3.2 mol % or more and 9.5 mol % or less, from the viewpoint of achieving better image density stability.

[0104] The proportion of the structural unit represented by formula (A) and the proportion of the structural unit represented by formula (B) in all structural units constituting the amorphous polyester resin contained in the toner particles are determined by the following measurement method. The toner is dissolved in a solvent such as tetrahydrofuran in which the binder resin is soluble, the insoluble matter is removed, and the soluble matter is dried. The dried product is dissolved in a solvent in which the amorphous polyester resin is soluble but the crystalline resin is insoluble, the insoluble matter is removed, and the soluble matter is dried. Differential scanning calorimetry is used to confirm that the dried product does not have an endothermic peak due to the crystalline resin. After confirmation, NMR is performed. 1 Obtain a H-NMR spectrum. 1 The 1 H-NMR spectrum is analyzed, and the proportion of the constitutional unit represented by formula (A) and the proportion of the constitutional unit represented by formula (B) are determined from the chemical shift and integral value ratio.

[0105] From the viewpoint of achieving superior image density stability, the amorphous polyester resin (S) preferably has, in addition to the structural units represented by formula (A) and the structural units represented by formula (B), a structural unit derived from an aromatic polycarboxylic acid and / or a structural unit derived from an aromatic polyhydric alcohol. From the viewpoint of achieving superior image density stability, the amorphous polyester resin (S) is preferably a resin having at least a structural unit represented by formula (A), a structural unit derived from an aromatic polycarboxylic acid, and a structural unit derived from an aromatic polyhydric alcohol, and more preferably a resin having a structural unit represented by formula (A), a structural unit represented by formula (B), a structural unit derived from terephthalic acid, and a structural unit derived from an aromatic polyhydric alcohol.

[0106] From the viewpoints of easy availability and low cost, the amorphous polyester resin (S) is preferably a resin having only the structural unit represented by formula (A) among the structural units represented by formula (A) and the structural units represented by formula (B).

[0107] Examples of aliphatic dicarboxylic acids that provide the structural unit represented by formula (A) include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, azelaic acid, dodecanedioic acid, etc., and anhydrides thereof. These may be used alone or in combination of two or more.

[0108] Examples of aromatic polycarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, anhydrides thereof, and lower alkyl esters thereof (for example, having 1 to 5 carbon atoms). A trivalent or higher carboxylic acid that forms a crosslinked or branched structure may be used together with the dicarboxylic acid. Examples of the trivalent or higher carboxylic acid include trimellitic acid, pyromellitic acid, anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The polycarboxylic acids may be used alone or in combination of two or more.

[0109] Examples of aliphatic diols that provide the structural unit represented by formula (B) include ethylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, undecanediol, etc. These may be used alone or in combination of two or more.

[0110] Examples of aromatic polyhydric alcohols include ethylene oxide adducts of bisphenol A and propylene oxide adducts of bisphenol A. A trihydric or higher polyhydric alcohol that forms a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher polyhydric alcohols include glycerin, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more.

[0111] The glass transition temperature (Tg) of the amorphous polyester 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), specifically, 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."

[0112] The weight average molecular weight (Mw) of the amorphous polyester 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 amorphous polyester resin is preferably 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the amorphous polyester 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). GPC is performed using a measuring device HLC-8120GPC (Tosoh Corporation) and a column TSKgel SuperHM-M (diameter 15 cm, Tosoh Corporation) in tetrahydrofuran solvent. The weight-average molecular weight and number-average molecular weight are calculated using a molecular weight calibration curve prepared using monodisperse polystyrene standard samples.

[0113] The amorphous polyester resin preferably uses two or more amorphous polyesters having different molecular weights in combination, and preferably uses a low molecular weight amorphous polyester resin in combination with a high molecular weight amorphous polyester resin. The low molecular weight amorphous polyester resin preferably has a weight average molecular weight of 9,000 or more and 20,000 or less. The high molecular weight amorphous polyester resin preferably has a weight average molecular weight of 25,000 or more and 70,000 or less. The low molecular weight amorphous polyester resin preferably has an acid value of 13 mgKOH / g or more and 20 mgKOH / g or less. The high molecular weight amorphous polyester resin preferably has an acid value of 10 mgKOH / g or more and 15 mgKOH / g or less.

[0114] The binder resin of the toner particles preferably contains a crystalline resin in addition to the amorphous polyester resin. Examples of the crystalline resin include crystalline polyester resin, crystalline vinyl resin (for example, polyalkylene resin, long-chain alkyl (meth)acrylate resin, etc.) As the crystalline resin, crystalline polyester resin is preferred from the viewpoint of low-temperature fixability of the toner.

[0115] The crystalline polyester resin is preferably a polycondensate using a monomer having a straight chain rather than a monomer having an aromatic ring, since it easily forms a crystalline structure.

[0116] Examples of polycarboxylic acids include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalene-2,6-dicarboxylic acid), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). A trivalent or higher carboxylic acid that forms a crosslinked or branched structure may be used together with the dicarboxylic acid. Examples of the trivalent carboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), anhydrides thereof, and lower alkyl esters thereof (e.g., having 1 to 5 carbon atoms). The dicarboxylic acid may be used in combination with a dicarboxylic acid having a sulfonic acid group or a dicarboxylic acid having an ethylenic double bond. The polycarboxylic acids may be used alone or in combination of two or more.

[0117] Examples of polyhydric alcohols include aliphatic diols (for example, straight-chain aliphatic diols having 7 to 20 carbon atoms in the main chain). Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanedecanediol. Among these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred as aliphatic diols. Trihydric or higher alcohols that form a crosslinked or branched structure may be used in combination with the diol. Examples of trihydric or higher alcohols include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. The polyhydric alcohols may be used alone or in combination of two or more. The proportion of the aliphatic diol in the polyhydric alcohol is preferably 80 mol % or more, more preferably 90 mol % or more.

[0118] The melting temperature of the crystalline polyester resin is preferably 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower, and even more preferably 60°C or higher and 85°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."

[0119] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0120] 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. From the viewpoint of low-temperature fixability of the toner, the proportion of the crystalline resin in the binder resin is preferably 2% by mass or more and 40% by mass or less, more preferably 5% by mass or more and 35% by mass or less, even more preferably 10% by mass or more and 30% by mass or less, and particularly preferably 15% by mass or more and 30% by mass or less.

[0121] -Internally added crosslinked resin particles- The internally added crosslinked resin particles are resin particles contained inside toner particles, and the resin has a crosslinked structure. The internally added crosslinked resin particles are particles that exist in the toner particles in a state in which they are incompatible with the binder resin.

[0122] Examples of the internally crosslinked resin particles include crosslinked resin particles crosslinked by ionic bonds, crosslinked resin particles crosslinked by covalent bonds, etc. As the internally crosslinked resin particles, crosslinked resin particles crosslinked by covalent bonds are preferred.

[0123] Examples of resins constituting the internally crosslinked resin particles include polyolefin resins (polyethylene, polypropylene, etc.), styrene resins (polystyrene, α-polymethylstyrene, etc.), (meth)acrylic resins (polymethyl methacrylate, polyacrylonitrile, etc.), epoxy resins, polyurethane resins, polyurea resins, polyamide resins, polycarbonate resins, polyether resins, polyester resins, and copolymer resins thereof. These resins may be used alone or in combination of two or more.

[0124] The resin constituting the internally added crosslinked resin particles is preferably a styrene-acrylic copolymer. The proportion of the styrene-acrylic copolymer in the internally added crosslinked resin particles is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably substantially all of the resin particles are styrene-acrylic copolymer.

[0125] The total of the styrene-acrylic monomer and (meth)acrylic monomer constituting the styrene-acrylic copolymer is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, with the remainder being a crosslinking agent described below.

[0126] Examples of styrene-based monomers constituting the styrene-acrylic copolymer include styrene, α-methylstyrene, vinylnaphthalene, alkyl-substituted styrenes having alkyl chains such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene, halogen-substituted styrenes such as 2-chlorostyrene, 3-chlorostyrene, and 4-chlorostyrene, and fluorine-substituted styrenes such as 4-fluorostyrene and 2,5-difluorostyrene, etc. Among these, styrene and α-methylstyrene are preferred.

[0127] Examples of (meth)acrylic monomers constituting styrene-acrylic copolymers include (meth)acrylic acid, n-methyl (meth)acrylate, n-ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isopentyl (meth)acrylate, and (meth)acrylic acid. Examples of suitable acrylates include amyl acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, t-butylphenyl (meth)acrylate, terphenyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-carboxyethyl (meth)acrylate, (meth)acrylonitrile, and (meth)acrylamide. Among these, n-butyl (meth)acrylate and 2-carboxyethyl (meth)acrylate are preferred.

[0128] Examples of crosslinking agents for crosslinking the resin that constitutes the internally crosslinked resin particles include aromatic polyvinyl compounds such as divinylbenzene and divinylnaphthalene; polyvinyl esters of aromatic polycarboxylic acids such as divinyl phthalate, divinyl isophthalate, divinyl terephthalate, divinyl homophthalate, divinyl trimesate, trivinyl trimesate, divinyl naphthalenedicarboxylate, and divinyl biphenylcarboxylate; divinyl esters of nitrogen-containing aromatic compounds such as divinyl pyridinedicarboxylate; vinyl esters of unsaturated heterocyclic carboxylic acids such as vinyl pyromethane, vinyl furancarboxylate, vinyl pyrrole-2-carboxylate, and vinyl thiophenecarboxylate; butanediol diacrylate, butanediol dimethacrylate, hexanediol diacrylate, hexanediol dimethacrylate, octanediol diacrylate, octanediol dimethacrylate, nonanediol diacrylate, nonanediol dimethacrylate, decanediol diacrylate, decanediol diacrylate, (Meth)acrylic acid esters of linear polyhydric alcohols such as dodecanediol dimethacrylate, dodecanediol diacrylate, and dodecanediol dimethacrylate; (meth)acrylic acid esters of branched or substituted polyhydric alcohols such as neopentyl glycol dimethacrylate and 2-hydroxy, 1,3-diacryloxypropane; polyethylene glycol di(meth)acrylate, polypropylene polyethylene glycol di(meth)acrylates, divinyl succinate, divinyl fumarate, and maleic acid Examples of the crosslinking agent include polyvalent vinyl esters of polyvalent carboxylic acids such as vinyl, divinyl maleate, divinyl diglycolate, vinyl itaconate, divinyl itaconate, divinyl acetonedicarboxylate, divinyl glutarate, divinyl 3,3'-thiodipropionate, divinyl trans-aconitate, trivinyl trans-aconitate, divinyl adipate, divinyl pimelate, divinyl suberate, divinyl azelaate, divinyl sebacate, divinyl dodecanedioate, and divinyl brassylate. One type of crosslinking agent may be used alone, or two or more types may be used in combination.

[0129] From the viewpoint of controlling the crosslinking density and elasticity of the internally crosslinked resin particles, the crosslinking agent is preferably a bifunctional alkyl acrylate having an alkylene chain with 6 or more carbon atoms. That is, the internally crosslinked resin particles preferably have a bifunctional alkyl acrylate as a constituent unit, and the alkylene chain in the bifunctional alkyl acrylate preferably has 6 or more carbon atoms.

[0130] From the viewpoint of adjusting the crosslink density within an appropriate range, the number of carbon atoms in the alkylene chain of the bifunctional alkyl acrylate is preferably 6 or more, more preferably 6 to 12, and even more preferably 8 to 12. Examples of bifunctional alkyl acrylates include 1,6-hexanediol acrylate, 1,6-hexanediol methacrylate, 1,8-octanediol diacrylate, 1,8-octanediol dimethacrylate, 1,9-nonanediol diacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol diacrylate, 1,10-decanediol dimethacrylate, 1,12-dodecanediol diacrylate, and 1,12-dodecanediol dimethacrylate. Of these, 1,10-decanediol diacrylate and 1,10-decanediol dimethacrylate are preferred.

[0131] The crosslinking agent may also be 2-carboxyethyl acrylate. It is preferable to use at least one of a bifunctional alkyl acrylate and 2-carboxyethyl acrylate as the crosslinking agent.

[0132] When the internally crosslinked resin particles are polymer particles of a composition containing a styrene-based monomer, a (meth)acrylic monomer, and a crosslinking agent, the elasticity of the internally crosslinked resin particles can be controlled by adjusting the amount of crosslinking agent contained in the composition. The amount of crosslinking agent is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 3.0 parts by mass or less, and even more preferably 0.8 parts by mass or more and 2.5 parts by mass or less, per 100 parts by mass of the total of the styrene-based monomer, the (meth)acrylic monomer, and the crosslinking agent.

[0133] The glass transition temperature Tg of the internally added crosslinked resin particles is preferably 0° C. or more and 40° C. or less, more preferably 5° C. or more and 35° C. or less, from the viewpoint of controlling the loss tangent tan δ of the toner particles. The glass transition temperature Tg of the internally crosslinked resin particles is determined from a DSC curve obtained by differential scanning calorimetry (DSC). Specifically, it is determined from the "extrapolated glass transition onset temperature" described in the method for determining the glass transition temperature in JIS K7121-1987 "Method for measuring the transition temperature of plastics." The internally crosslinked resin particles are obtained by dissolving the toner in a solvent such as tetrahydrofuran in which the binder resin is soluble, recovering the insoluble matter, and drying the insoluble matter.

[0134] The average dispersed diameter of the internally added crosslinked resin particles is preferably 50 nm or more and 300 nm or less, more preferably 80 nm or more and 300 nm or less, and further preferably 100 nm or more and 250 nm or less, from the viewpoint of controlling the loss tangent tan δ of the toner particles.

[0135] The method for measuring the average dispersed diameter of the internally added crosslinked resin particles is as follows. Toner particles or toner are mixed and embedded in epoxy resin, and the epoxy resin is solidified. The solidified material is cut using an ultramicrotome to prepare thin section samples with a thickness of 80 nm to 130 nm. The thin section samples are stained with ruthenium tetroxide for 3 hours in a desiccator at 30°C. SEM images of the stained thin section samples are obtained using an ultra-high-resolution field emission scanning electron microscope (FE-SEM). Since the release agent, styrene-acrylic resin, and polyester resin are most easily stained by ruthenium tetroxide in this order, each component is identified by the shade resulting from the degree of staining. If the shade is difficult to distinguish due to the condition of the sample, adjust the staining time. In the cross section of a toner particle, the colorant domains are smaller than the release agent domains and resin particle domains, so they are distinguished by size. In the SEM image, 30 toner cross sections whose maximum length is 85% or more of the volume average particle diameter of the toner particles are selected, and a total of 100 dyed internally added cross-linked resin particles (i.e., styrene acrylic resin domains) are observed. The maximum length of each internally added cross-linked resin particle is measured, and the arithmetic average of the maximum lengths is used as the average dispersion diameter.

[0136] The average dispersion diameter of the internally-added crosslinked resin particles can be adjusted by, for example, adjusting the volume average particle diameter of the internally-added crosslinked resin particles contained in the internally-added crosslinked resin particle dispersion liquid used when producing toner particles by the aggregation-coalescence method; preparing a plurality of internally-added crosslinked resin particle dispersion liquids with different volume average particle diameters and using them in combination; or the like.

[0137] The content of the internally added crosslinked resin particles is preferably 2% by mass to 20% by mass, more preferably 5% by mass to 15% by mass, based on the total toner mass, from the viewpoint of controlling the loss tangent tan δ of the toner particles.

[0138] -Method of manufacturing internally crosslinked resin particles- Examples of methods for producing the internally-added crosslinked resin particles include known methods such as emulsion polymerization, melt-kneading using a Banbury mixer or a kneader, suspension polymerization, spray drying, etc. As a method for producing the internally-added crosslinked resin particles, emulsion polymerization is preferred from the viewpoint of unevenly distributing units derived from a styrene-based monomer on the particle surface.

[0139] The internally crosslinked resin particles are preferably produced by emulsion polymerization using a styrene-based monomer and a (meth)acrylic monomer in the presence of a crosslinking agent. The emulsion polymerization is preferably carried out in multiple batches. The method for producing the internally crosslinked resin particles by emulsion polymerization will be described below.

[0140] The method for producing the internally crosslinked resin particles includes the steps of: a step of obtaining an emulsion containing a monomer, a crosslinking agent, a surfactant, and water (emulsion preparation step); a step of adding a polymerization initiator to the emulsion and heating to polymerize the monomers (first emulsion polymerization step); a step (second emulsion polymerization step) of adding an emulsion containing a monomer and a crosslinking agent to the reaction solution after the first emulsion polymerization step and heating the mixture to polymerize the monomer; It is preferred that it contains In the second emulsion polymerization step, emulsions with different ratios of styrene-based monomer and (meth)acrylic monomer may be added multiple times in order to adjust the composition of the particle surfaces.

[0141] ·Emulsion preparation process This is a process for obtaining an emulsion containing a monomer, a crosslinking agent, a surfactant, and water. For example, the monomer, crosslinking agent, surfactant, and water are emulsified using an emulsifier. Examples of emulsifiers include rotary mixers equipped with propeller, anchor, paddle, or turbine-type agitating blades; static mixers such as static mixers; rotor-stator emulsifiers such as homogenizers and Clearmix; mill-type emulsifiers equipped with grinding functions; high-pressure emulsifiers such as Manton-Gaulin pressure emulsifiers; high-pressure nozzle-type emulsifiers that generate cavitation under high pressure; high-pressure collision-type emulsifiers such as microfluidizers that apply shear force by colliding liquids under high pressure; ultrasonic emulsifiers that generate cavitation using ultrasound; and membrane emulsifiers that emulsify through fine pores.

[0142] The monomer is preferably a styrene-based monomer or a (meth)acrylic-based monomer. The crosslinking agent is preferably the crosslinking agent described above.

[0143] Examples of surfactants include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Nonionic surfactants may be used in combination with anionic surfactants or cationic surfactants. Of these, anionic surfactants are preferred. One surfactant may be used alone, or two or more surfactants may be used in combination.

[0144] The emulsion may contain a chain transfer agent. As the chain transfer agent, a compound having a thiol component is preferable. Specifically, alkyl mercaptans such as hexyl mercaptan, heptyl mercaptan, octyl mercaptan, nonyl mercaptan, decyl mercaptan, and dodecyl mercaptan are preferable.

[0145] The mass ratio of the styrene-based monomer to the (meth)acrylic monomer in the emulsion (styrene-based monomer / (meth)acrylic monomer) is preferably 0.2 or more and 1.1 or less. The content of the crosslinking agent in the entire emulsion is preferably 0.5% by mass or more and 3% by mass or less.

[0146] ·First emulsion polymerization process This is a step in which a polymerization initiator is added to the emulsion and heated to polymerize the monomers. As the polymerization initiator, ammonium persulfate is preferably used.

[0147] In the first emulsion polymerization step, the emulsion (reaction solution) containing the polymerization initiator is preferably stirred with a stirrer, such as a rotary stirrer equipped with a propeller-type, anchor-type, paddle-type, or turbine-type stirring blade.

[0148] ·Second emulsion polymerization process In this step, a monomer-containing emulsion is added to the reaction solution obtained after the first emulsion polymerization step, and the mixture is heated to polymerize the monomer. The monomer-containing emulsion can be obtained, for example, by emulsifying the monomer, surfactant, and water using an emulsifier.

[0149] In the second emulsion polymerization step, emulsions with different ratios of styrene-based monomer and (meth)acrylic monomer may be added multiple times in order to adjust the composition of the particle surfaces. In the second emulsion polymerization step, it is preferable to stir the reaction solution in the same manner as in the first emulsion polymerization step.

[0150] -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, ultramarine blue, and the like. Examples of the dyes include various pigments such as phosphorus blue, chalco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate, and various 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.

[0151] The colorant may be surface-treated as needed, and may be used in combination with a dispersant.

[0152] The content of the colorant is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0153] -Mold release agent- Examples of the release agent 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. The release agents may be used alone or in combination of two or more.

[0154] 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 K 7121-1987 "Method for measuring transition temperatures of plastics."

[0155] The content of the release agent is, for example, preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the total mass of the toner particles.

[0156] -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.

[0157] [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 part (core particle) and a coating layer (shell layer) that coats the core part. The toner particles having a core-shell structure may be composed of, for example, a core containing a binder resin, internally added crosslinked resin particles, and optionally other additives such as a colorant and a release agent, and a coating layer containing the binder resin.

[0158] 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.

[0159] The volume average particle size of the toner particles is measured using a Coulter Multisizer II (manufactured by Beckman Coulter), and the electrolyte is measured using an ISOTON-II (manufactured by Beckman Coulter). For the measurement, 0.5 mg to 50 mg of the sample to be measured is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant, and this is then added to 100 ml to 150 ml of the electrolyte. The electrolyte solution containing the suspended sample is dispersed for 1 minute using an ultrasonic disperser, and the particle size distribution of particles with a particle size range of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture diameter of 100 μm. The number of particles sampled is 50,000. The particle size that is 50% cumulative from the smallest diameter side in the volume-based particle size distribution is defined as the volume average particle size.

[0160] The average circularity of the toner particles is preferably 0.90 or more and 1.00 or less, and more preferably 0.92 or more and 0.98 or less. The average circularity of toner particles is (perimeter of a circle with the same projected area as the particle image) / (perimeter of the particle projected image). Analysis of the particle projected image is performed using a flow particle image analyzer (FPIA-3000, Sysmex Corporation). 3,500 toner particles are sampled. When the toner contains external additives, the toner is dispersed in water containing a surfactant, and then ultrasonically treated to obtain toner particles from which the external additives have been removed.

[0161] The toner particles preferably contain at least one metal ion selected from the group consisting of Al ions, Mg ions, and Ca ions. The ratio AV1 / M1 of the total amount M1 of these metal ions to the acid value AV1 of the binder resin is 1.0×10 3 Over 4.0 x 10 3 Preferably, it is 1.5 x 10 or less. 3 Over 3.8 x 10 3 Less than 2.0 x 10 is preferable. 3 Over 3.5 x 10 3 The following is more preferable: By setting the ratio AV1 / M1 in the above range, an appropriate crosslinked structure is imparted to the binder resin, and the loss tangent tan δ of the toner particles becomes easy to control. The amount of the metal ions is preferably 0.0015% by mass or more and 0.0150% by mass or less, and more preferably 0.0020% by mass or more and 0.010% by mass or less, based on the mass of the toner particles.

[0162] Examples of sources of at least one metal ion selected from the group consisting of Al ions, Mg ions, and Ca ions (compounds to be contained in toner particles as additives) include metal salts, inorganic metal salt polymers, metal complexes, etc. These compounds are used, for example, as aggregating agents when producing toner particles by an aggregation-coalescence method. Examples of metal salts include aluminum sulfate, aluminum chloride, magnesium chloride, magnesium sulfate, calcium chloride, and calcium sulfate. Examples of inorganic metal salt polymers include polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples of metal complexes include aluminum salts, magnesium salts and calcium salts of known chelating agents such as ethylenediaminetetraacetic acid, propanediaminetetraacetic acid, nitriletriacetic acid, triethylenetetraminehexaacetic acid and diethylenetriaminepentaacetic acid. These metal ion sources may be added simply as additives rather than as flocculants.

[0163] The metal ion is preferably an Al ion. The source of the metal ion is preferably an aluminum salt (e.g., aluminum sulfate, aluminum chloride, etc.) or an aluminum salt polymer (e.g., polyaluminum chloride, polyaluminum hydroxide, etc.). The source of the metal ion is preferably an inorganic metal salt polymer, and the source of the metal ion is particularly preferably an aluminum salt polymer (e.g., polyaluminum chloride, polyaluminum hydroxide, etc.).

[0164] The amount of metal ions can be quantified by measuring the fluorescent X-ray intensity of the toner particles. A resin and a metal ion source are mixed to obtain a resin mixture with a known amount of metal ions. 200 mg of this resin mixture is formed into a tablet with a diameter of 13 mm to obtain a sample. The mass of the sample is precisely weighed, and the fluorescent X-ray intensity of the sample is measured to determine the peak intensity. A calibration curve is created from the measurement results of samples with different amounts of metal ions. The fluorescent X-ray intensity of the toner particles to be measured is similarly measured, and the amount of metal ions is quantified from the calibration curve.

[0165] Examples of methods for adjusting the amount of metal ions include the following (1) and (2). (1) Adjust the amount of metal ion source added. (2) When toner particles are produced by the aggregation and coalescence method, an aggregating agent (e.g., a metal salt or a metal salt polymer) is added as a source of metal ions, and then an appropriate amount of a chelating agent (e.g., ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, etc.) is added to form a metal complex, and the metal complex is then removed in a toner particle washing process.

[0166] The acid value of the binder resin is measured in accordance with JIS K0070-1992 "Test methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products." The binder resin is obtained by dissolving the toner in a solvent in which the binder resin is soluble, such as tetrahydrofuran, removing the insoluble matter, and drying the soluble matter.

[0167] [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.

[0168] 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.

[0169] 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).

[0170] The amount of the external additive added is, for example, preferably 0.01% by mass to 10% by mass, and more preferably 0.01% by mass to 5% by mass, based on the toner particles.

[0171] [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. An embodiment of the aggregation and coalescence method will be described below.

[0172] An example of an embodiment of the aggregation and coalescence method is as follows: a step of mixing an amorphous polyester resin particle dispersion, a crystalline resin particle dispersion, an internally crosslinked resin particle dispersion, a release agent particle dispersion, and a colorant dispersion, and aggregating the particles and the colorant in the resulting dispersion to form first aggregated particles (first aggregated particle forming step); a step of mixing the dispersion in which the first aggregated particles are dispersed with an amorphous polyester resin particle dispersion, and aggregating the amorphous polyester resin particles onto the surfaces of the first aggregated particles to form second aggregated particles (second aggregated particle forming step); and a step of heating the dispersion liquid in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles to form toner particles (fusion and coalescence step).

[0173] Each step will be described in detail below.

[0174] -Dispersion liquid preparation process- The dispersions to be used in the aggregation-coalescence method are prepared: an amorphous polyester resin particle dispersion, a crystalline resin particle dispersion, an internally crosslinked resin particle dispersion, a release agent particle dispersion, and a colorant dispersion.

[0175] The resin particle dispersion is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

[0176] Examples of the dispersion medium used in the resin particle dispersion include aqueous media. Examples of aqueous media include water such as distilled water and ion-exchanged water, and alcohols. These may be used alone or in combination of two or more.

[0177] Examples of surfactants include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soap-based surfactants; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, anionic surfactants and cationic surfactants are preferred. Nonionic surfactants may be used in combination with anionic or cationic surfactants. The surfactants may be used alone or in combination of two or more.

[0178] In resin particle dispersions, resin particles can be dispersed in a dispersion medium using common dispersion methods such as a rotary shear homogenizer, a ball mill with media, a sand mill, or a Dynomill. Depending on the type of resin particles, the resin particles may be dispersed in a dispersion medium using a phase inversion emulsification method. The phase inversion emulsification method involves dissolving the resin to be dispersed in a hydrophobic organic solvent in which the resin is soluble, adding a base to the organic continuous phase (O phase) to neutralize it, and then introducing an aqueous medium (W phase) to invert the phase from W / O to O / W, thereby dispersing the resin in particulate form in the aqueous medium.

[0179] The volume average particle size of the resin particles dispersed in the resin particle dispersion is, for example, preferably 0.01 μm to 1 μm, more preferably 0.08 μm to 0.8 μm, and even more preferably 0.1 μm to 0.6 μm. The volume average particle size of the resin particles is measured using a laser diffraction particle size distribution analyzer (e.g., LA-700, Horiba, Ltd.). The particle size that is 50% cumulative from the small particle size side in the volume-based particle size distribution is defined as the volume average particle size. The volume average particle sizes of particles in other dispersions are measured in the same manner.

[0180] The content of resin particles contained in the resin particle dispersion is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less.

[0181] The internally crosslinked resin particle dispersion, the release agent particle dispersion, and the colorant dispersion are also prepared in the same manner as the resin particle dispersion. The dispersion medium, dispersion method, particle content, and volume average particle diameter of the particles in the resin particle dispersion are the same for the internally crosslinked resin particle dispersion, the release agent particle dispersion, and the colorant dispersion.

[0182] -First agglomerated particle formation process- Amorphous polyester resin particle dispersion, crystalline resin particle dispersion, internally crosslinked resin particle dispersion, release agent particle dispersion, and colorant dispersion are mixed together, and the particles and colorant are aggregated in the mixed dispersion to form first aggregated particles.

[0183] An aggregating agent is added to a mixed dispersion obtained by mixing the individual dispersions, and the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 or more and 5 or less), and a dispersion stabilizer is added as necessary.Then, the temperature is maintained at 20°C or more and 50°C or less to form first aggregated particles. In the first aggregate particle formation step, for example, the mixed dispersion may be stirred with a rotary shear homogenizer, an aggregating agent may be added at room temperature (e.g., 25°C), the pH of the mixed dispersion may be adjusted to an acidic value (e.g., pH 2 or more and 5 or less), a dispersion stabilizer may be added as needed, and then the mixture may be heated.

[0184] Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant contained in the mixed dispersion, an inorganic metal salt, and a divalent or higher metal complex. When a metal complex is used as the flocculant, the amount of surfactant used can be reduced, and the charging characteristics can be improved. If necessary, an additive that forms a complex or a similar bond with the metal ions of the flocculant may be used, and a chelating agent is preferred as this additive.

[0185] Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples of the chelating agent include hydroxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA). The amount of the chelating agent added is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass, relative to 100 parts by mass of the resin particles.

[0186] -Second agglomerated particle formation process- The dispersion of the first aggregated particles and the dispersion of the amorphous polyester resin particles are mixed. The amorphous polyester resin in the second aggregated particle forming step may be the same type as or different from the amorphous polyester resin in the first aggregated particle forming step.

[0187] In a dispersion containing the first aggregate particles and the amorphous polyester resin particles, the amorphous polyester resin particles are aggregated on the surfaces of the first aggregate particles. A release agent particle dispersion may also be added to aggregate the amorphous polyester resin particles and the release agent particles on the surfaces of the first aggregate particles.

[0188] In the second aggregated particle formation step, for example, when the first aggregated particles reach a desired particle size, an amorphous polyester resin particle dispersion is added to the first aggregated particle dispersion, and the mixture is heated at a temperature equal to or lower than the glass transition temperature of the amorphous polyester resin. Thereafter, the pH of the dispersion is adjusted to, for example, a range of about 6.5 to 8.5 to stop the aggregation.

[0189] -Fusion / unification process- The second aggregate particle dispersion liquid containing the second aggregate particles is heated to fuse and coalesce the second aggregate particles, for example, to a temperature equal to or higher than the glass transition temperature of the amorphous polyester resin (for example, a temperature 10°C to 30°C higher than the glass transition temperature).

[0190] Through the above steps, toner particles are obtained. The first aggregated particles may be fused and coalesced to form toner particles without performing the second aggregated particle forming step. The second aggregated particle forming step may be repeated multiple times. In the second aggregated particle forming step, a crystalline resin particle dispersion and / or an internally crosslinked resin particle dispersion and / or a release agent particle dispersion may be used.

[0191] After the fusion and coalescence process is completed, the toner particles in the dispersion are subjected to a known washing process, solid-liquid separation process, and drying process to obtain dried toner particles. In the washing process, from the viewpoint of chargeability, it is preferable to perform sufficient substitution washing with ion-exchanged water. In the solid-liquid separation process, from the viewpoint of productivity, it is preferable to perform suction filtration, pressure filtration, etc. In the drying process, from the viewpoint of productivity, it is preferable to perform freeze drying, flash drying, fluidized drying, vibration-type fluidized drying, etc.

[0192] The toner is produced, for example, by adding an external additive to the obtained dry toner particles and mixing them. The mixing can be carried out using, for example, a V blender, a Henschel mixer, a Loedige mixer, etc. If necessary, coarse particles from the toner can be removed using a vibrating sieve, an air sieve, etc.

[0193] <Image forming apparatus and image forming method> An image forming apparatus and an image forming method according to this embodiment will be described. The image forming apparatus according to the present embodiment includes an image carrier, a charging device that charges the surface of the image carrier, an electrostatic image forming device that forms an electrostatic image on the surface of the charged image carrier, a developing device that contains an electrostatic image developer and develops the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer, a transfer device that transfers the toner image formed on the surface of the image carrier to the surface of a recording medium, and a fixing device that fixes the toner image transferred to the surface of the recording medium. The electrostatic image developer according to the present embodiment is used as the electrostatic image developer.

[0194] The image forming apparatus according to this embodiment carries out an image forming method (the image forming method according to this embodiment) that includes a charging step of charging the surface of an image carrier, an electrostatic image forming step of forming an electrostatic image on the surface of the charged image carrier, a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer according to this embodiment, a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium, and a fixing step of fixing the toner image transferred to the surface of the recording medium.

[0195] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; an intermediate transfer type apparatus that primarily transfers a toner image formed on the surface of an image carrier to the surface of an intermediate transfer medium, and then secondarily transfers the toner image transferred to the surface of the intermediate transfer medium to the surface of a recording medium; an apparatus equipped with a cleaning device that cleans the surface of the image carrier after the transfer of the toner image but before charging; and an apparatus equipped with a static elimination device that irradiates the surface of the image carrier with static elimination light to eliminate static after the transfer of the toner image but before charging. When the image forming apparatus according to this embodiment is an intermediate transfer type apparatus, the transfer device is configured to have, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer device that performs primary transfer of the toner image formed on the surface of the image carrier onto the surface of the intermediate transfer body, and a secondary transfer device that performs secondary transfer of the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0196] In the image forming apparatus according to the present embodiment, for example, the portion including the developing device may have a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge equipped with a developing device that accommodates the electrostatic image developer according to the present embodiment is preferably used.

[0197] 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.

[0198] FIG. 1 is a schematic diagram showing the configuration of an image forming apparatus according to this embodiment. The image forming apparatus shown in Fig. 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.

[0199] 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.

[0200] 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.

[0201] 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).

[0202] 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). -6The 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] 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.

[0211] <Process cartridge> The process cartridge according to this embodiment will be described. The process cartridge according to this embodiment is a process cartridge that is detachably attached to an image forming apparatus and that contains the electrostatic image developer according to this embodiment and is equipped with a developing device that develops an electrostatic image formed on the surface of an image carrier using the electrostatic image developer into a toner image.

[0212] The process cartridge according to this embodiment is not limited to the above configuration, but may also be configured to include a developing device and, if necessary, at least one other device selected from the group consisting of an image carrier, a charging device, an electrostatic image forming device, and a transfer device.

[0213] An example of a process cartridge 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.

[0214] FIG. 2 is a schematic diagram showing the configuration of the process cartridge according to the present embodiment. The process cartridge 200 shown in FIG. 2 is configured to integrally combine and hold a photosensitive member 107 (an example of an image carrier), a charging roll 108 (an example of a charging device) provided around the photosensitive member 107, a developing device 111 (an example of a developing device), and a photosensitive member cleaning device 113 (an example of a cleaning device), which are held by a housing 117 having, for example, a mounting rail 116 and an opening 118 for exposure, and is formed into a cartridge. In FIG. 2, 109 denotes an exposure device (an example of an electrostatic image forming device), 112 denotes a transfer device (an example of a transfer device), 115 denotes a fixing device (an example of a fixing device), and 300 denotes recording paper (an example of a recording medium). [Example]

[0215] The present embodiment will be described in detail below 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.

[0216] In the following description, synthesis, processing, manufacturing, testing, etc. were carried out at room temperature (25°C ± 3°C) unless otherwise specified.

[0217] <Creating the carrier> [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.

[0218] [Preparation of Coating Agent for First Layer and Coating Agent for Second Layer] In this example, the BA value is controlled by forming the resin coating layer in multiple steps. This example is an example of a method for controlling the BA value, and the method for controlling the BA value is not limited to this.

[0219] 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:

[0220] 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

[0221] 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)

[0222] Resin particles (M1): Melamine resin particles (Eposter FS, Nippon Shokubai Co., Ltd., average primary particle size 250 nm) Resin particles (M2): Melamine resin particles (Eposter SS, Nippon Shokubai Co., Ltd., average primary particle size 70 nm) Resin particles (M3): Melamine resin particles (Eposter S, Nippon Shokubai Co., Ltd., average primary particle size 100 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) Resin particles (M4): Melamine resin particles (Eposter S6, Nippon Shokubai Co., Ltd., average primary particle size 400 nm) Resin particles (M5): Melamine resin particles (Eposter S12, Nippon Shokubai Co., Ltd., average primary particle size 900 nm) CB: Carbon black (VXC72, Cabot Corporation)

[0223] [Creating carriers (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) to (40) and comparative carriers (C1) to (C2), respectively. For the comparative carrier (C3), a Spira Coater (Okada Seiko Co., Ltd.) was used to apply a first layer coating agent 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 30 parts relative to the ferrite core material, and then the coating agent was dried. The dried powder was removed from the Spira Coater and crushed using a sieve with 75 μm openings to obtain a comparative carrier (C3).

[0224] [Creating carriers (2)] -Materials (1)- Ferrite particles (1): 1000 parts 4.6 parts of cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer resin particles (copolymerization ratio 97 mol:3 mol) Surface-treated silica (S1): 4.0 parts ·CB: 0.4 parts ·Resin particles (M1): 1.0 part -Materials (2)- 14.7 parts of cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer resin particles (copolymerization ratio 97 mol:3 mol) Surface-treated silica (S1): 2.0 parts ·CB: 1.3 parts ·Resin particles (M1): 2.0 parts The above material (1) was placed in a high-speed mixer with a stirring blade and stirred at a temperature of 125°C and an air speed of 10 m / s for 45 minutes. Next, the above material (2) was added and stirred at a temperature of 125°C and an air speed of 10 m / s for 45 minutes. A resin coating layer was formed on the surface of the ferrite particles by the action of mechanical impact force. The air speed was then reduced to 2 m / s, and the mixture was cooled to room temperature to obtain a comparative carrier (C4).

[0225] [Creating carriers (3)] 19.3 parts of cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer resin particles (copolymerization ratio 97 mol:3 mol) Surface-treated silica (S7): 6.0 parts ·CB: 1.7 parts ·Resin particles (M1): 3.0 parts Toluene: 386.7 parts The above material was applied to 1,000 parts of ferrite particles (1) and dried to obtain a comparative carrier (C5). The application and drying were carried out using a fluidized bed coating device in which the temperature in the fluidized bed was controlled at 70°C.

[0226] [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) to (40) and the comparative carriers (C5) to (C5) was 36 μm.

[0227] [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%).

[0228] 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

[0229] <Toner Production> [Preparation of emulsion (1-1)] Styrene: 80 parts n-Butyl acrylate: 120 parts 1,10-decanediol diacrylate (crosslinking agent): 4 parts Anionic surfactant (Newcol 271A, Nippon Nyukazai Co., Ltd.): 2.2 parts Ion-exchanged water: 197.8 parts The above materials were placed in a mixing vessel equipped with a stirrer and stirred to prepare an emulsion (1-1).

[0230] [Preparation of emulsion (1-2)] Styrene: 75 parts n-Butyl acrylate: 25 parts 1,10-decanediol diacrylate (crosslinking agent): 1.0 part Anionic surfactant (Newcol 271A, Nippon Nyukazai Co., Ltd.): 1.1 parts Ion-exchanged water: 97.7 parts The above materials were placed in a mixing vessel equipped with a stirrer and stirred to prepare an emulsion (1-2).

[0231] [Preparation of Internally Added Crosslinked Resin Particle Dispersion (1)] A reaction vessel equipped with a stirrer and a nitrogen inlet tube was purged with nitrogen, and then 0.5 parts of an anionic surfactant (Newcol 271A, Nippon Nyukazai Co., Ltd.) and 200 parts of ion-exchanged water were added. The reaction solution was heated in an oil bath while stirring, and the temperature of the reaction solution was raised to 65°C. 10 parts of emulsion (1-1) were added, followed by 10 parts of a 10% by mass aqueous ammonium persulfate solution, and the mixture was maintained for 30 minutes. While maintaining the temperature of the reaction solution at 65°C, 390 parts of emulsion (1-1) were added dropwise to the reaction vessel over 60 minutes. Next, 200 parts of emulsion (1-2) were added dropwise over 30 minutes. After completion of the dropwise addition, the mixture was maintained at 65°C for 60 minutes. Next, 2 parts of 10% by mass ammonium persulfate were added, and the mixture was maintained at 65°C for 3 hours. Next, the mixture was cooled to room temperature, and ion-exchanged water was added to adjust the solids concentration to 20% by mass, to obtain an internally-added crosslinked resin particle dispersion (1). The resin particles had a volume average particle size of 165 nm and a glass transition temperature of 17°C.

[0232] [Preparation of Internally Added Crosslinked Resin Particle Dispersions (2) to (7)] Internally-added crosslinked resin particles (2) to (7) were prepared in the same manner as for the internally-added crosslinked resin particle dispersion (1), except that the amounts of materials used were changed as shown in Table 2.

[0233] [Preparation of amorphous polyester resin particle dispersion (1)] Terephthalic acid: 25 parts by mole Isophthalic acid: 19 mole parts Adipic acid: 3 mole parts Trimellitic anhydride: 2 mole parts Bisphenol A propylene oxide 2 mole adduct: 31 mole parts Bisphenol A propylene oxide 3 mole adduct: 20 mole parts The above materials were charged into a reaction vessel equipped with a stirrer, nitrogen inlet tube, temperature sensor, and distillation column. The temperature was raised to 190°C over 1 hour, and 1.2 parts of dibutyltin oxide was added per 100 parts of the above materials. The temperature was raised to 240°C over 6 hours while distilling off the generated water, and the dehydration condensation reaction was continued for 3 hours while maintaining the temperature at 240°C. The reaction solution was then cooled to room temperature to obtain amorphous polyester resin (1). The amorphous polyester resin (1) had an acid value of 10 mgKOH / g, a glass transition temperature of 61°C, and a weight-average molecular weight of 25,000.

[0234] Amorphous polyester resin (1): 100 parts Methyl ethyl ketone: 60 parts Isopropanol: 10 parts 10% aqueous ammonia solution: 3.5 parts The above materials were placed in a jacketed reactor equipped with a condenser, thermometer, water dripper, and anchor blade. The liquid temperature was maintained at 50°C in a water-circulating thermostatic bath while stirring and mixing at 100 rpm to dissolve the amorphous polyester resin (1). The water-circulating thermostatic bath was then set to 40°C, and a total of 300 parts of ion-exchanged water maintained at 40°C was added dropwise at a rate of 3 parts / min to induce phase inversion and produce an emulsion. The emulsion was placed in an eggplant flask and placed in an evaporator equipped with a vacuum control unit via a trap bulb. The eggplant flask was heated in a hot water bath at 60°C while rotating. The pressure was reduced to 7 kPa while taking care to prevent bumping, and the solvent was removed. The pressure was then returned to normal, and the eggplant flask was water-cooled to obtain a dispersion. Ion-exchanged water was added to the dispersion to obtain an amorphous polyester resin particle dispersion (1) with a solids content of 20% by mass. The volume average particle size of the amorphous polyester resin particles was 180 nm.

[0235] [Preparation of amorphous polyester resin particle dispersions (2) to (19)] Amorphous polyester resin particle dispersions (2) to (19) were prepared in the same manner as for the amorphous polyester resin particle dispersion (1), except that the amounts of materials used were changed as shown in Table 3-1. The details of the abbreviations for each component listed in Table 3-1 are as follows: Monomer (A): an aliphatic dicarboxylic acid for forming a structural unit represented by formula (A) Monomer (B): an aliphatic diol for forming a structural unit represented by formula (B) TPA: Terephthalic acid IPA: Isophthalic acid TMA: Trimellitic anhydride BPA-2PO: Bisphenol A propylene oxide 2 mole adduct BPA-3PO: Bisphenol A propylene oxide 3 mole adduct BPA-2EO: Bisphenol A ethylene oxide 2 mole adduct

[0236] [Preparation of Crystalline Polyester Resin Particle Dispersion (1)] Dodecanedioic acid: 50 parts by mole 1,6-Hexanediol: 50 parts by mole The above materials were charged into a reaction vessel equipped with a stirrer, nitrogen inlet tube, temperature sensor, and distillation column. The temperature was raised to 160°C over 1 hour, and 0.8 parts of dibutyltin oxide was added per 100 parts of the above materials. The temperature was raised to 180°C over 6 hours while distilling off the resulting water. The reaction proceeded under reflux in the vessel while maintaining the temperature at 180°C for 5 hours and stirring. The temperature was then gradually raised to 230°C under reduced pressure (3 kPa) and maintained at 230°C for 2 hours. The reaction mixture was then cooled, solid-liquid separated, and the solid was dried to obtain crystalline polyester resin (1). The acid value of crystalline polyester resin (1) was 8.8 mgKOH / g and the weight-average molecular weight was 29,000.

[0237] Crystalline polyester resin (1): 100 parts Methyl ethyl ketone: 70 parts Isopropanol: 12 parts 10% ammonia solution: 3 parts The above materials were placed in a jacketed reactor equipped with a condenser, thermometer, water dripper, and anchor blade. The liquid temperature was maintained at 80°C in a water-circulating thermostatic bath while stirring and mixing at 100 rpm to dissolve the crystalline polyester resin (1). The water-circulating thermostatic bath was then set to 60°C, and a total of 300 parts of ion-exchanged water maintained at 60°C was added dropwise at a rate of 3 parts / min to induce phase inversion, resulting in an emulsion. The emulsion was placed in an eggplant flask and placed in an evaporator equipped with a vacuum control unit via a trap bulb. The eggplant flask was heated in a hot water bath at 60°C while rotating. The pressure was reduced to 7 kPa, taking care to prevent bumping, to remove the solvent. The pressure was then returned to normal, and the eggplant flask was water-cooled to obtain a dispersion. Ion-exchanged water was added to the dispersion to obtain a crystalline polyester resin particle dispersion (1) with a solids content of 20% by mass. The volume average particle size of the crystalline polyester resin particles was 160 nm.

[0238] [Preparation of release agent particle dispersion] Fischer-Tropsch wax (Sasolwax H1, Sasol): 100 parts Anionic surfactant (Neopelex G-65, Kao Corporation): 6 parts Ion-exchanged water: 300 parts The above materials were mixed and heated to 100°C, and dispersed using a homogenizer (Ultra Turrax T50). Further dispersion was performed using a Manton-Gaulin high-pressure homogenizer, and ion-exchanged water was added to the dispersion to obtain a release agent particle dispersion with a solid content of 20% by mass. The volume average particle size of the release agent particles was 230 nm.

[0239] [Preparation of colorant dispersion] Carbon black (Regel 330, Cabot Corporation): 110 parts Anionic surfactant (Neopelex G-65, Kao Corporation): 6 parts Ion-exchanged water: 300 parts The above materials were mixed and dispersed for 10 minutes using a homogenizer (Ultra Turrax T50). Ion-exchanged water was added to the dispersion to obtain a colorant particle dispersion with a solid content of 20% by mass. The volume average particle size of the colorant particles was 220 nm.

[0240] [Preparation of Toner (1)] Amorphous polyester resin particle dispersion (1): 61.7 parts Crystalline polyester resin particle dispersion (1): 15.4 parts ·Internally added crosslinked resin particle dispersion (1): 10 parts Colorant dispersion: 6.9 parts Release agent particle dispersion: 6.0 parts Anionic surfactant (Eleminol MON-2, Sanyo Chemical Industries, Ltd.): 1.6 parts Ion-exchanged water: 80 parts The above materials were placed in a reaction vessel equipped with a thermometer, pH meter, and stirrer, and the temperature of the reaction vessel was maintained at 20°C while stirring at 150 rpm for 30 minutes. Next, a 0.3 N aqueous nitric acid solution was added to adjust the pH to 5.0, and then 12 parts of a 1% aqueous aluminum sulfate solution were added while dispersing with a homogenizer (Ultra-Turrax T50). Next, the temperature was raised to 45°C at a rate of 0.4°C / min while stirring, and the mixture was maintained for 30 minutes. Next, 29 parts of amorphous polyester resin particle dispersion (1) was added and the mixture was maintained for 30 minutes. Next, 0.62 parts of Chelest 40 (Chilesto Corporation, 40% content) was added. Next, a 0.1N aqueous sodium hydroxide solution was added to adjust the pH to 8.5 and maintained for 15 minutes. After that, the mixture was heated to 80°C at a rate of 1°C / min while continuing to stir, and maintained at 80°C for 5 hours. The mixture was then cooled, solid-liquid separated, and the solid matter was washed with ion-exchanged water. Then, the mixture was dried in a vacuum freeze dryer for 24 hours to obtain toner particles (1) having a volume average particle size of 5.5 μm. 100 parts of the toner particles (1) and 2.0 parts of hydrophobic silica (RY200, Nippon Aerosil Co., Ltd.) were mixed in a Henschel mixer to obtain toner (1).

[0241] [Preparation of Toners (2) to (41) and Comparative Toners (C1) to (C2)] Toners (2) to (41) and comparative toners (C1) and (C2) were obtained in the same manner as toner (1), except that the type and amount of each resin particle dispersion was changed as shown in Table 4-1. The solid content of each resin particle dispersion was set to 20% by mass.

[0242] Tables 4-2 and 4-3 show various properties of the toner particles measured by the above-mentioned measurement methods.

[0243] <Preparation of developer> [Examples 1-1 to 1-40 and Comparative Examples 1-1 to 1-5] The type of toner was fixed, and the type of carrier was changed as shown in Table 1-1 to prepare developers of Examples 1-1 to 1-40 and Comparative Examples 1-1 to 1-5. 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.

[0244] [Examples 2-1 to 2-41 and Comparative Examples 2-1 to 2-2] The type of carrier was fixed and the type of toner was changed as shown in Table 4-3 to prepare developers of Examples 2-1 to 2-41 and Comparative Examples 2-1 and 2-2. 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.

[0245] <Performance evaluation> [Image density stability] The developer was filled into a developing device of a modified image forming apparatus Apeos C4030 (FUJIFILM Business Innovation Co., Ltd.) Image formation was carried out on A4 size plain paper in the following order (1) to (3). (1) One image with 100% image density was printed in an environment with a temperature of 25°C and a relative humidity of 90%. (2) Print 10,000 images with an image density of 0.5% in an environment with a temperature of 25°C and a relative humidity of 90%. (3) Print 10,000 images with 100% image density in an environment with a temperature of 10°C and a relative humidity of 15%. The image density of one sheet in (1) and the image density of the last sheet in (3) were measured using an image densitometer (X-Rite 938, X-Rite Corporation), the image density difference Δ was calculated, and the value of the image density difference Δ was classified as follows. The smaller the image density difference Δ, the more desirable it is. The evaluation results are shown in Tables 1-2 and 4-3.

[0246] A: 0.00 or more, less than 0.05 B++: 0.05 or more, less than 0.07 B+: 0.07 or more, less than 0.09 B: 0.09 or more, less than 0.12 C++: 0.12 or higher, less than 0.14 C+: 0.14 or more, less than 0.16 C: 0.16 or more, less than 0.20 D: 0.20 or more, less than 0.25 E: 0.25 or more

[0247] [Table 1-1]

[0248] [Table 1-2]

[0249] [Table 2]

[0250] [Table 3-1]

[0251] [Table 3-2]

[0252] [Table 4-1]

[0253] [Table 4-2]

[0254] [Table 4-3]

[0255] The electrostatic image developer, process cartridge, image forming apparatus, and image forming method of the present disclosure include the following aspects: Each formula is the same as the formula with the same number described above.

[0256] (Addendum) (((1))) An electrostatic image developer comprising a carrier and a toner, the carrier has magnetic particles, a resin coating layer that coats the magnetic particles, and inorganic particles contained in the resin coating layer, and the element ratio of metals and metalloids that constitute the inorganic particles is analyzed in the depth direction by X-ray photoelectron spectroscopy, and when the element ratio at 0 seconds of etching is defined as A and the element ratio at 300 seconds of etching is defined as B, the value of B A is 0.5 atm% or more and 3.0 atm% or less; the toner contains toner particles, and in a dynamic viscoelasticity measurement when the toner particles are heated from 30°C to 120°C, the toner particles have a minimum value of loss tangent tanδ(min) between 50°C and 80°C, and the minimum value of loss tangent tanδ(min) is between 0.50 and 1.00; Electrostatic image developer. (((2))) The electrostatic image developer according to (((1))), wherein the inorganic particles are at least one kind selected from the group consisting of silica particles, titania particles, and alumina particles. (((3))) The electrostatic image developer according to (((1))) or (((2))), wherein the inorganic particles are silica particles whose surfaces have been subjected to a hydrophobic treatment. (((4))) The electrostatic image developer according to any one of (((1))) to (((3))), wherein the inorganic particles account for 15% by mass or more and 35% by mass or less of the resin coating layer. (((5))) The electrostatic image developer according to any one of (((1))) to (((4))), wherein the value of B is 3.5 atm % or more and 12.0 atm % or less. (((6))) The electrostatic image developer according to any one of (((1))) to (((5))), wherein the BA value is 1.2 atm % or more and 2.3 atm % or less. (((7))) The electrostatic image developer according to any one of (((1))) to (((6))), wherein the minimum value of the loss tangent, tan δ(min), is 0.60 or more and 0.96 or less. (((8))) The electrostatic image developer according to any one of (((1))) to (((7))), wherein the ratio tanδ(90) / tanδ(min) of the minimum value of the loss tangent tanδ(min) to the loss tangent tanδ(90) at a temperature of 90°C is 2.5 or less. (((9))) the toner particles contain an amorphous polyester resin as a binder resin, the amorphous polyester resin comprises an amorphous polyester resin (S) having at least one of a structural unit represented by formula (A) and a structural unit represented by formula (B), the total proportion of the structural units represented by formula (A) and the structural units represented by formula (B) in the total structural units constituting the amorphous polyester resin contained in the toner particles is 0.5 mol % or more and 10.0 mol % or less; The electrostatic image developer according to any one of (((1))) to (((8))). (((10))) The electrostatic image developer according to (((9))), wherein the proportion of the structural units represented by formula (A) in the total carboxylic acid units constituting the amorphous polyester resin contained in the toner particles is 2.0 mol % or more and 15.0 mol % or less. (((11))) a developing device that contains the electrostatic image developer according to any one of (((1))) to (((10))) and develops an electrostatic image formed on the surface of an image carrier into a toner image by using the electrostatic image developer, Attached to and detached from the image forming apparatus, Process cartridge. (((12))) an image carrier; a charging device that charges the surface of the image carrier; an electrostatic image forming device for forming an electrostatic image on the charged surface of the image carrier; a developing device that contains the electrostatic image developer according to any one of (((1))) to (((10))) and develops the electrostatic image formed on the surface of the image carrier into a toner image by using the electrostatic image developer; a transfer device that transfers the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing device that fixes the toner image transferred onto the surface of the recording medium, Image forming device. (((13))) a charging step of charging the surface of the image carrier; an electrostatic image forming step of forming an electrostatic image on the charged surface of the image carrier; a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer according to any one of (((1))) to (((10))); a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing step of fixing the toner image transferred onto the surface of the recording medium, Image forming method.

[0257] According to (((1))), (((2))) or (((3))), an electrostatic image developer is provided which is excellent in image density stability compared to an electrostatic image developer containing a carrier whose BA value is less than 0.5 atm% or more than 3.0 atm%, or an electrostatic image developer containing toner particles whose minimum loss tangent value tanδ(min) is less than 0.50 or more than 1.00. According to (((4))), an electrostatic image developer having excellent image density stability is provided compared to electrostatic image developers in which the proportion of inorganic particles in the resin coating layer of the carrier is less than 15% by mass or more than 35% by mass. According to (((5))), an electrostatic image developer having excellent stability of image density is provided compared to an electrostatic image developer containing a carrier in which the value of B is less than 3.5 atm % or more than 12.0 atm %. According to (((6))), an electrostatic image developer having excellent stability of image density is provided compared to electrostatic image developers containing carriers having a BA value of less than 1.2 atm % or more than 2.3 atm %. According to (((7))), an electrostatic image developer having excellent stability of image density is provided compared to an electrostatic image developer containing toner particles having a minimum value of loss tangent, tanδ(min), of less than 0.60 or more than 0.96. According to (((8))), an electrostatic image developer is provided which has excellent image density stability compared to electrostatic image developers containing toner particles in which the ratio tanδ(90) / tanδ(min) of the minimum value of the loss tangent tanδ(min) to the loss tangent tanδ(90) at a temperature of 90°C is greater than 2.5. According to (((9))), an electrostatic image developer having excellent image density stability is provided compared to an electrostatic image developer containing a toner in which the total proportion of the structural units represented by formula (A) and the structural units represented by formula (B) in all structural units constituting the amorphous polyester resin contained in the toner particles is less than 0.5 mol % or more than 10.0 mol %. According to (((10))), an electrostatic image developer having excellent stability of image density is provided, compared to an electrostatic image developer containing a toner in which the proportion of the constituent units represented by formula (A) in all carboxylic acid units constituting the amorphous polyester resin contained in the toner particles is less than 2.0 mol % or more than 15.0 mol %. According to (((11))), a process cartridge is provided which is superior in image density stability compared to a process cartridge containing an electrostatic image developer containing a carrier whose BA value is less than 0.5 atm% or more than 3.0 atm%, or a process cartridge containing an electrostatic image developer containing toner particles whose minimum loss tangent value tanδ(min) is less than 0.50 or more than 1.00. According to (((12))), an image forming apparatus is provided that has excellent stability of image density compared to an image forming apparatus that contains an electrostatic image developer containing a carrier whose BA value is less than 0.5 atm% or more than 3.0 atm%, or an image forming apparatus that contains an electrostatic image developer containing toner particles whose minimum value of loss tangent, tanδ(min), is less than 0.50 or more than 1.00. According to (((13))), an image forming method is provided which is superior in stability of image density compared to an image forming method using an electrostatic image developer containing a carrier whose BA value is less than 0.5 atm% or more than 3.0 atm%, or an image forming method using an electrostatic image developer containing toner particles whose minimum value of loss tangent, tanδ(min), is less than 0.50 or more than 1.00. [Explanation of symbols]

[0258] 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)

[0259] 107 Photosensitive body (an example of an image carrier) 108 Charging roll (an example of a charging device) 109 Exposure device (an example of an electrostatic image forming device) 111 Developing device (an example of a developing device) 112 Transcription device (an example of a transcription device) 113 Photosensitive drum cleaning device (an example of a cleaning device) 115 Fixing device (an example of a fixing device) 116 Mounting Rail 117 Cabinet 118 Exposure opening 200 Process Cartridge 300 Recording paper (an example of a recording medium)

Claims

1. An electrostatic image developer comprising a carrier and a toner, the carrier has magnetic particles, a resin coating layer coating the magnetic particles, and inorganic particles contained in the resin coating layer, and when the element ratio of metals and metalloids constituting the inorganic particles is analyzed in the depth direction by X-ray photoelectron spectroscopy, the element ratio at 0 seconds of etching is defined as A and the element ratio at 300 seconds of etching is defined as B, the value of B-A is 0.5 atm% or more and 3.0 atm% or less, the toner contains toner particles, and in a dynamic viscoelasticity measurement when the temperature of the toner particles is increased from 30°C to 120°C, the toner particles have a minimum value tanδ (min) of loss tangent at a temperature of 50°C to 80°C, and the minimum value tanδ (min) of loss tangent is 0.50 to 1.00; Electrostatic image developer.

2. 2. The electrostatic image developer according to claim 1, wherein the inorganic particles are at least one kind selected from the group consisting of silica particles, titania particles, and alumina particles.

3. 2. The electrostatic image developer according to claim 1, wherein said inorganic particles are silica particles whose surfaces have been treated to be hydrophobic.

4. 2. The electrostatic image developer according to claim 1, wherein the inorganic particles account for 15% by mass or more and 35% by mass or less of the resin coating layer.

5. 2. The electrostatic image developer according to claim 1, wherein the value of B is 3.5 atm % or more and 12.0 atm % or less.

6. 2. The electrostatic image developer according to claim 1, wherein the value of B-A is 1.2 atm % or more and 2.3 atm % or less.

7. 2. The electrostatic image developer according to claim 1, wherein the minimum value tan δ (min) of the loss tangent is 0.60 or more and 0.96 or less.

8. 2. The electrostatic image developer according to claim 1, wherein the ratio tan δ(90) / tan δ(min) of the minimum value tan δ(min) of the loss tangent to the loss tangent tan δ(90) at a temperature of 90° C. is 2.5 or less.

9. the toner particles contain an amorphous polyester resin as a binder resin, The amorphous polyester resin includes an amorphous polyester resin (S) having at least one of a structural unit represented by the following formula (A) and a structural unit represented by the following formula (B), the total proportion of the structural units represented by the following formula (A) and the structural units represented by the following formula (B) in all structural units constituting the amorphous polyester resin contained in the toner particles is 0.5 mol % or more and 10.0 mol % or less:

2. The electrostatic image developer according to claim 1. 【Chemistry 1】 In formula (A), nA is an integer of 2 or more and 12 or less. In formula (B), nB is an integer of 2 or more and 12 or less.

10. 10. The electrostatic image developer according to claim 9, wherein the proportion of the structural unit represented by formula (A) in all carboxylic acid units constituting the amorphous polyester resin contained in the toner particles is 2.0 mol % or more and 15.0 mol % or less.

11. a developing device containing the electrostatic image developer according to any one of claims 1 to 10 and developing an electrostatic image formed on a surface of an image carrier into a toner image by using the electrostatic image developer; Attached to and detached from the image forming apparatus, Process cartridge.

12. an image carrier; a charging device that charges the surface of the image carrier; an electrostatic image forming device for forming an electrostatic image on the charged surface of the image carrier; a developing device containing the electrostatic image developer according to any one of claims 1 to 10 and developing the electrostatic image formed on the surface of the image carrier into a toner image by the electrostatic image developer; a transfer device that transfers the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing device that fixes the toner image transferred onto the surface of the recording medium, Image forming device.

13. a charging step of charging the surface of the image carrier; an electrostatic image forming step of forming an electrostatic image on the charged surface of the image carrier; a developing step of developing the electrostatic image formed on the surface of the image carrier as a toner image using the electrostatic image developer according to any one of claims 1 to 10; a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of a recording medium; a fixing step of fixing the toner image transferred onto the surface of the recording medium, Image forming method.

Images