Electrostatic charge image developing carrier, electrostatic charge image developer, process cartridge, image forming apparatus, and image forming method

Abstract

An electrostatic charge image developing carrier, an electrostatic charge image developer, a process cartridge, an image forming apparatus, and an image forming method, the electrostatic charge image developing carrier having magnetic particles and a resin coating layer coating the magnetic particles, the resin coating layer containing inorganic particles, the inorganic particles are characterized in that the element ratio of a metal and a semimetal constituting the inorganic particles is analyzed in the depth direction by X-ray photoelectron spectroscopy, and the value of B-A is 0.5-3.0 atm% (inclusive), where A is the element ratio at 0 seconds of etching and B is the element ratio at 300 seconds of etching.

Description

Technical Field

[0001] The present invention relates to an electrostatic image developing carrier, an electrostatic image developer, a processing box, an image forming device and an image forming method. Background Art

[0002] As a carrier for electrostatic image development, a resin-coated carrier having a resin coating layer on the surface of magnetic particles is known. As the resin-coated carrier, for example, the following carriers are disclosed.

[0003] Patent document 1 discloses a carrier for electrostatic image development, which has magnetic particles and a resin layer containing silica particles with an average particle size of not less than 50 nm and not more than 200 nm, and the proportion Si1 of the Si element in the region at a distance of not less than 0.1 μm and not more than 0.2 μm from the surface of the resin layer toward the interior and the proportion Si2 of the Si element in the region at a distance of not less than 0.0 μm and not more than 0.1 μm from the surface of the magnetic particles toward the surface of the resin layer satisfy Formulas 1-1 and 2-1.

[0004] Formula 1-1: 0.005≤Si1≤2

[0005] Formula 2-1: 1≤Si1 / Si2≤1000

[0006] Patent Document 2 discloses an electrophotographic carrier comprising a core material and a resin layer covering the core material, and satisfying the formula (1).

[0007] Formula (1): 1≤(S×r×D) / 3≤1.5

[0008] In formula (1), S represents the BET specific surface area (m 2 / g), r represents the average particle radius of the electrophotographic carrier (m), and D represents the density of the electrophotographic carrier (g / m 3 ).

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2022-181065

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2012-93629 Summary of the Invention

[0011] The present invention provides a carrier for electrostatic image development, wherein a resin coating layer contains inorganic particles, and the element ratio of metals and semi-metals constituting the inorganic particles is analyzed along the depth direction by X-ray photoelectron spectroscopy. 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 image density stability in the obtained image is excellent compared to a case where the value of B A is less than 0.5 atm% or exceeds 3.0 atm%.

[0012] Means for solving the above-mentioned problems include the following.

[0013] <1> A carrier for electrostatic image development, comprising magnetic particles and a resin coating layer coating the magnetic particles, wherein:

[0014] The resin coating layer contains inorganic particles,

[0015] The element ratio of the metal and semi-metal constituting the inorganic particles was analyzed along the depth direction by X-ray photoelectron spectroscopy. When the element ratio at 0 seconds of etching was set to A and the element ratio at 300 seconds of etching was set to B, the value of BA was greater than 0.5 atm% and less than 3.0 atm%.

[0016] <2> The electrostatic image developing carrier according to <1>, wherein the inorganic particles are at least one selected from the group consisting of silica particles, titania particles, and alumina particles.

[0017] <3> The electrostatic image developing carrier according to <1> or <2>, wherein the inorganic particles are silica particles.

[0018] <4> The electrostatic image developing carrier according to any one of <1> to <3>, wherein the inorganic particles are surface-treated inorganic particles.

[0019] <5> The electrostatic image developing carrier according to any one of <1> to <3>, wherein the inorganic particles are inorganic particles whose surfaces have been subjected to a hydrophobic treatment.

[0020] <6> The electrostatic image developing carrier according to any one of <1> to <5>, wherein the content of the inorganic particles in the resin coating layer is 15% by mass or more and 35% by mass or less relative to the total mass of the resin coating layer.

[0021] <7> The electrostatic image developing carrier according to any one of <1> to <6>, wherein the value of B is 3.5 atm % or more and 12.0 atm % or less.

[0022] <8> The electrostatic image developing carrier according to any one of <1> to <7>, wherein the value of A is 2.0 atm % or more and 10.0 atm % or less.

[0023] <9> The electrostatic image developing carrier according to any one of <1> to <8>, wherein the value of BA is 1.2 atm % or more and 2.3 atm % or less.

[0024] <10> The electrostatic image developing carrier according to any one of <1> to <9>, wherein the resin coating layer further contains resin particles, and the ratio D1 / D2 of the average primary particle size D1 of the inorganic particles contained in the resin coating layer to the average primary particle size D2 of the resin particles is greater than or equal to 0.01 and less than or equal to 0.15.

[0025] <11> The electrostatic image developing carrier according to any one of <1> to <10>, wherein the resin coating layer further contains resin particles, and the average primary particle size D2 of the resin particles contained in the resin coating layer is 100 nm to 400 nm.

[0026] <12> An electrostatic image developer comprising the electrostatic image developing carrier according to any one of <1> to <11> and a toner.

[0027] <13> A process cartridge comprising a developing device that contains the electrostatic image developer according to <12> and develops an electrostatic image formed on a surface of an image holding member into a toner image using the electrostatic image developer,

[0028] The process cartridge is attachable to and detachable from the image forming apparatus.

[0029] <14> An image forming apparatus comprising:

[0030] Image holding body;

[0031] a charging device for charging the surface of the image holding member; and an electrostatic image forming device for forming an electrostatic image on the charged surface of the image holding member.

[0032] a developing device that accommodates the electrostatic image developer described in <12> and develops the electrostatic image formed on the surface of the image holding member into a toner image using the electrostatic image developer;

[0033] a transfer device that transfers the toner image formed on the surface of the image holding member to the surface of a recording medium; and

[0034] The fixing device fixes the toner image transferred onto the surface of the recording medium.

[0035] <15> An image forming method comprising:

[0036] a charging process for charging the surface of the image holding member;

[0037] an electrostatic image forming step of forming an electrostatic image on the charged surface of the image holding member;

[0038] a developing step of developing the electrostatic image formed on the surface of the image holding member into a toner image using the electrostatic image developer described in <12>;

[0039] a transfer step of transferring the toner image formed on the surface of the image holding member to the surface of a recording medium; and

[0040] The fixing step fixes the toner image transferred onto the surface of the recording medium.

[0041] Effects of the Invention

[0042] According to <1> or <2>, there is provided a carrier for developing an electrostatic image, wherein the carrier exhibits excellent image density stability in an obtained image compared to a case where the BA value is less than 0.5 atm % or exceeds 3.0 atm %.

[0043] According to <3>, there is provided a carrier for electrostatic image development, wherein the obtained image has better image density stability than when the inorganic particles are titanium dioxide particles or aluminum oxide particles.

[0044] According to <4> or <5>, there is provided a carrier for electrostatic image development, wherein the obtained image has better image density stability than when the inorganic particles are not surface-treated.

[0045] According to <6>, there is provided an electrostatic image developing carrier having an image having better image density stability than when the content of the inorganic particles in the resin coating layer is less than 15% by mass or more than 35% by mass relative to the total mass of the resin coating layer.

[0046] According to <7>, there is provided a carrier for developing an electrostatic image, wherein the obtained image has a more excellent image density stability than when the value of B is less than 3.5 atm % or exceeds 12.0 atm %.

[0047] According to <8>, there is provided a carrier for developing an electrostatic image, wherein the obtained image has a more excellent image density stability than when the value of A is less than 2.0 atm % or exceeds 10.0 atm %.

[0048] According to <9>, there is provided a carrier for developing an electrostatic image, wherein the obtained image has a more excellent image density stability than when the BA value is less than 1.2 atm % or exceeds 2.3 atm %.

[0049] According to <10>, there is provided a carrier for electrostatic image development, wherein the obtained image has better image density stability than when the ratio D1 / D2 of the average primary particle size D1 of the inorganic particles contained in the resin coating layer to the average primary particle size D2 of the resin particles is less than 0.01 or exceeds 0.15.

[0050] According to <11>, there is provided an electrostatic image developing carrier having an image density stability that is more excellent than when the average primary particle size D2 of the resin particles contained in the resin coating layer is less than 100 nm or exceeds 400 nm.

[0051] According to <12>, there is provided an electrostatic image developer having excellent image density stability in an obtained image compared to a case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %.

[0052] According to <13>, there is provided a process cartridge in which the image density stability of an obtained image is excellent compared with a case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %.

[0053] According to <14>, there is provided an image forming apparatus in which the obtained image has excellent image density stability compared to a case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %.

[0054] According to <15>, there is provided an image forming method in which the obtained image has excellent image density stability compared to a case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Embodiments of the present invention will be described in detail with reference to the following drawings.

[0056] Figure 1 This is a schematic configuration diagram showing an example of the image forming apparatus according to the present embodiment.

[0057] Figure 2 This is a schematic structural diagram showing an example of a process cartridge that is attached to and detached from the image forming apparatus according to the present embodiment.

[0058] Explanation of symbols

[0059] 1Y, 1M, 1C, 1K - photoreceptor (an example of an image holding member), 2Y, 2M, 2C, 2K - charging roller (an example of a 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 (an example of a developing device), 5Y, 5M, 5C, 5K - primary transfer roller (an example of a primary transfer device), 6Y, 6M, 6C, 6K - Photoreceptor cleaning device (an example of a 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-driving roller, 24-support roller, 26-secondary transfer roller (an example of a secondary transfer device), 28-fixing device (an example of a fixing device), 30-intermediate transfer body cleaning device, P-recording paper (an example of a recording medium).

[0060] 107-photoreceptor (an example of an image holding member), 108-charging roller (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-transfer device (an example of a transfer device), 113-photoreceptor cleaning device (an example of a cleaning device), 115-fixing device (an example of a fixing device), 116-mounting guide rail, 117-housing, 118-opening for exposure, 200-processing box, 300-recording paper (an example of a recording medium). DETAILED DESCRIPTION

[0061] Hereinafter, embodiments of the present invention will be described. These descriptions and examples are provided to illustrate the embodiments and do not limit the scope of the embodiments.

[0062] In the present invention, a numerical range expressed using “to” indicates a range including the numerical values before and after “to” as the minimum value and the maximum value, respectively.

[0063] In the numerical ranges described in stages in the present invention, the upper limit or lower limit described in one numerical range may be replaced by the upper limit or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in the present invention, the upper limit or lower limit of the numerical range may be replaced by the value shown in the Examples.

[0064] In the present invention, "A and / or B" has the same definition as "at least one of A and B." That is, "A and / or B" may mean only A, only B, or a combination of A and B.

[0065] In the present invention, the word "process" is included not only in an independent process but also in a case where it cannot be clearly distinguished from other processes as long as the purpose of the process can be achieved.

[0066] In the present invention, when the embodiments are described with reference to the drawings, the structures of the embodiments are not limited to those shown in the drawings. Furthermore, the sizes of the components in the drawings are conceptual, and the relative sizes of the components are not limited thereto.

[0067] In the present invention, each component may also include multiple corresponding substances. In the present invention, when referring to the amount of each component in the composition, when multiple substances corresponding to each component are present in the composition, unless otherwise specified, it refers to the total amount of the multiple substances present in the composition.

[0068] In the present invention, multiple types of particles corresponding to each component may be included. When multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for the mixture of the multiple types of particles present in the composition unless otherwise specified.

[0069] In the present invention, when a compound is represented by a structural formula, the symbols (C and H) representing carbon atoms and hydrogen atoms in a hydrocarbon group and / or hydrocarbon chain may be omitted.

[0070] In the present invention, “(meth)acrylic acid” is a term encompassing both acrylic acid and methacrylic acid, and “(meth)acrylate” is a term encompassing both acrylate and methacrylate.

[0071] In the present invention, “developer” means “electrostatic image developer”, “carrier” means “carrier for electrostatic image development”, and “toner” means “toner for electrostatic image development”.

[0072] <Carrier for electrostatic image development>

[0073] The carrier according to this embodiment includes magnetic particles and a resin coating layer that coats the magnetic particles, and the resin coating layer contains inorganic particles.

[0074] In the resin coating layer of the carrier according to the present embodiment, it is assumed that carbon black is not inorganic particles.

[0075] The carrier involved in this embodiment is analyzed by X-ray photoelectron spectroscopy along the depth direction to analyze the element ratio of metals and semi-metals constituting the inorganic particles. When the element ratio at 0 seconds of etching is set to A and the element ratio at 300 seconds of etching is set to B, the value of BA is greater than 0.5atm% and less than 3.0atm%.

[0076] In conventional carriers, when a high-density image is output after a low-density image is output in a low-temperature, low-humidity environment, excessive charging (charging) occurs, resulting in a decrease in image density.

[0077] The carrier according to this embodiment, with a BA value of 0.5 atm% or more and 3.0 atm% or less, appropriately forms inorganic particles on the surface of the carrier when the carrier surface is abraded by stress within the developing device, thereby preventing abnormal increases or decreases in charging. This effectively maintains image density more consistently, resulting in excellent image density stability. This effect is particularly pronounced when outputting a high-density image after outputting a low-density image in a low-temperature, low-humidity environment.

[0078] Hereinafter, the structure of the carrier according to this embodiment will be described in detail.

[0079] [BA value]

[0080] The carrier involved in this embodiment is analyzed by X-ray photoelectron spectroscopy to analyze the element ratio of metals and semi-metals contained in the inorganic particles contained in the resin coating layer along the depth direction. When the element ratio at 0 seconds of etching is set to A and the element ratio at 300 seconds of etching is set to B, the value of BA is greater than 0.5atm% and less than 3.0atm%.

[0081] From the viewpoint of image density stability of the obtained image, the BA value is, for example, preferably 0.8 atm% to 2.7 atm%, more preferably 1.0 atm% to 2.5 atm%, and even more preferably 1.2 atm% to 2.3 atm%.

[0082] The element analysis in the depth direction by X-ray photoelectron spectroscopy (XPS) and the measurement method of the element ratios A and B are as follows.

[0083] The carrier is set as the XPS sample, and the elements are analyzed while etching. The elements analyzed are carbon, nitrogen, oxygen, iron, manganese, and the metals and semi-metals that constitute the inorganic particles. In the case where the metals and semi-metals that constitute the inorganic particles are unclear, all element analysis of the carrier is performed in advance to determine the metals and semi-metals that constitute the inorganic particles. Examples of the metal elements that constitute the inorganic particles include aluminum and titanium. Examples of the semi-metal elements that constitute the inorganic particles include silicon, boron, germanium, arsenic, antimony, and tellurium.

[0084] The ratio of the total amount of metals and semimetals constituting the inorganic particles to the total amount of all elements to be analyzed is defined as the element ratio (atm%) of metals and semimetals constituting the inorganic particles. Specifically, the element ratio (atm%) of metals and semimetals constituting the inorganic particles = (total amount of metals and semimetals constituting the inorganic particles) / (total amount of carbon, nitrogen, oxygen, iron, manganese, and metals and semimetals constituting the inorganic particles) × 100.

[0085] The ratio of the above elements at the time of etching for 0 seconds is A (atm%), and the ratio of the above elements at the time of etching for 300 seconds is B (atm%). Etching for 0 seconds means that no etching is performed.

[0086] The above-mentioned XPS was performed using the following apparatus and conditions. Analysis was performed after baseline correction.

[0087] XPS device: PHI5000 Versa Probe II (ULVAC-PHI, INC.)

[0088] X-ray source: monochromated AlKα rays

[0089] Beam voltage: 15kV

[0090] Emission current: 3mA

[0091] Etching gun: Argon cluster ion gun

[0092] Vacuum degree: 1×10 -5 Pa~1×10 -6 Pa

[0093] Pass Energy: 23.5eV

[0094] Scanning area: 300μm×300μm

[0095] Time Per Step: 50 seconds

[0096] Cycle: 5 times

[0097] Sweep: 10 times

[0098] When analyzing the carrier contained in the developer, as a method of separating the carrier from the developer, there is a method of removing the toner from the developer by blowing air using an arbitrary filter.

[0099] [Value of element ratio A]

[0100] From the viewpoint of image density stability, the value of the element ratio A is, for example, 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%.

[0101] When the element ratio A is within the above range, fine irregularities are formed on the carrier surface by the inorganic particles, and the carrier surface is appropriately hardened by the inorganic particles, thereby suppressing wear caused by stress in the developing device, resulting in stable image density.

[0102] [Value of element ratio B]

[0103] From the viewpoint of image density stability, the value of the element ratio B is, for example, preferably 3.5 atm% to 12.0 atm%, more preferably 4.3 atm% to 9.8 atm%, and even more preferably 4.8 atm% to 7.8 atm%.

[0104] When the element ratio B is 3.5 atm % or more, the amount of inorganic particles exposed when the carrier surface is abraded by stress in the developing device will not be too small, and charging will not increase excessively, resulting in a stable image density.

[0105] When the element ratio B is 12.0 atm % or less, the amount of inorganic particles exposed when the carrier surface is abraded by stress in the developing device does not become excessive, and charging does not decrease excessively. As a result, the image density is stabilized.

[0106] [BA value control method]

[0107] The value of BA can be controlled by utilizing, for example, the precipitation phenomenon of particles and / or the Brazil nut phenomenon when forming the resin coating layer.

[0108] Particle sedimentation is a phenomenon in which the sedimentation rate varies depending on factors such as particle size and shape, density differences and affinity between the particles and the dispersion medium, density differences and affinity between the particles and other components, and particle concentration. Generally speaking, the smaller the particle size and the greater the density of the particles in a liquid, the faster the sedimentation rate. The Brazil nut phenomenon occurs when a collection of particles of varying sizes is vibrated, causing the larger particles to rise.

[0109] When the resin coating layer is formed by a wet method, the above phenomenon can be utilized because the particles can move freely in the liquid in which the resin is dissolved.

[0110] By utilizing the above phenomenon, the BA value can be controlled by adjusting the material, particle size, density and / or concentration of the inorganic particles, the presence or absence of other particles, the type of resin of the resin coating layer, the formation conditions of the resin coating layer, and the like.

[0111] If the particle size of the inorganic particles is set within an appropriate range, it is easy to appropriately bias towards the lower side of the resin coating. As other particles, particles with a particle size larger than that of the inorganic particles are used, so that the inorganic particles are more likely to be biased towards the lower side of the resin coating. When the other particles are particles with a density lower than that of the inorganic particles and / or particles with different polarities, the inorganic particles are more likely to be biased towards the lower side of the resin coating. If the concentration of the inorganic particles is set within an appropriate range, it is easy to appropriately bias the inorganic particles towards the lower side of the resin coating. If the concentration of the other particles is set within an appropriate range, it is also easy to appropriately bias the inorganic particles towards the lower side of the resin coating.

[0112] [Resin coating]

[0113] -Resin-

[0114] The carrier according to this embodiment has a resin coating layer on the surface of the magnetic particles.

[0115] Examples of the resin constituting the resin coating layer include styrene-acrylic acid copolymers; polyolefin resins such as polyethylene and polypropylene; polyvinyl or polyvinylidene resins such as polystyrene, acrylic resins, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone; vinyl chloride-vinyl acetate copolymers; linear silicone resins composed of organosiloxane bonds or modified products thereof; fluororesins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyesters; polyurethanes; polycarbonates; amino resins such as urea-formaldehyde resins; epoxy resins, and the like.

[0116] These resins may be used alone or in combination of two or more.

[0117] From the perspective 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 containing a structural unit having an aliphatic cyclic structure and a structural unit having an amino group.

[0118] As the aliphatic cyclic structure, for example, a cycloalkyl group is preferred, and a cyclohexyl group is more preferred.

[0119] Examples of the acrylic resin having a cyclohexyl group include homopolymers of a (meth)acrylic monomer having a cyclohexyl group, copolymers of a (meth)acrylic monomer having a cyclohexyl group and other monomers, etc. Examples of the (meth)acrylic monomer having a cyclohexyl group include cyclohexyl acrylate and cyclohexyl methacrylate.

[0120] As the structural unit having an aliphatic cyclic structure, for example, a structural unit derived from cyclohexyl (meth)acrylate is preferred.

[0121] From the viewpoint of image density stability, the acrylic resin containing a structural unit having an aliphatic cyclic structure preferably contains, for example, 80% by mass or more of a structural unit having an aliphatic cyclic structure.

[0122] As the (meth)acrylic monomer having an amino group, for example, dialkylaminoalkyl (meth)acrylate is preferred, and dimethylaminoethyl (meth)acrylate is more preferred.

[0123] From the viewpoint of image density stability, the acrylic resin containing a structural unit having an amino group preferably contains, for example, 0.05% by mass to 5% by mass, and more preferably 0.1% by mass to 2% by mass.

[0124] -Inorganic particles-

[0125] The resin coating layer contains inorganic particles.

[0126] Examples of inorganic particles include particles of metal compounds such as silica (silicon dioxide), titanium dioxide (titanium oxide), alumina (aluminum oxide), zinc oxide, tin oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide doped with antimony, indium oxide doped with tin, and zinc oxide doped with aluminum; particles of metals such as gold, silver, and copper; and resin particles coated with metals.

[0127] The inorganic particles may be used alone or in combination of two or more.

[0128] From the viewpoint of excellent dispersibility in the resin and the ability of inorganic particles to appropriately appear on the surface to prevent abnormal charge increase or decrease, the inorganic particles are preferably at least one selected from the group consisting of silica particles, titania particles and alumina particles, and more preferably silica particles.

[0129] From the perspective of image concentration stability, the average primary particle size of the inorganic particles is, for example, preferably greater than 1 nm and less than 100 nm, more preferably greater than 5 nm and less than 60 nm, further preferably greater than 5 nm and less than 40 nm, further preferably greater than 6 nm and less than 30 nm, and particularly preferably greater than 7 nm and less than 20 nm.

[0130] When the average primary particle size of the inorganic particles is 1 nm or more, the inorganic particles are less likely to aggregate with each other when forming the resin coating layer, and as a result, the inorganic particles are more likely to be concentrated on the lower side of the resin coating layer.

[0131] When the average primary particle size of the inorganic particles is 100 nm or less, exposure of the inorganic particles to the surface of the resin coating layer can be suppressed.

[0132] In the present embodiment, the primary particle size of the inorganic particles refers to the diameter of a circle having the same area as the primary particle image (so-called equivalent circle diameter), and the average primary particle size of the inorganic particles refers to the particle size that becomes the cumulative 50% from the smaller diameter side in the number-based distribution of the primary particle size. The primary particle size of the inorganic particles is obtained by performing image analysis on at least 300 inorganic particles.

[0133] The inorganic particles contained in the resin coating layer may be the inorganic particles themselves, or may be particles on which the surface of the inorganic particles (sometimes referred to as mother particles) has been subjected to a hydrophobic treatment. From the viewpoint of preventing the inorganic particles from aggregating with each other, improving the affinity between the inorganic particles and the resin of the resin coating layer, and appropriately appearing on the surface of the inorganic particles to prevent abnormal charging from increasing or decreasing, for example, inorganic particles with a surface treatment are preferably used, and more preferably inorganic particles with a surface treatment having been subjected to a hydrophobic treatment.

[0134] The surface treatment of the inorganic particles is performed, for example, by preparing a treatment solution comprising a silicon-containing organic compound as a hydrophobizing agent and a solvent, mixing the inorganic particles and the treatment solution under stirring, and further continuing the stirring. After the surface treatment, a drying process is performed to remove the solvent from the treatment solution.

[0135] Examples of silicon-containing organic compounds used for surface treatment of inorganic particles include alkoxysilane compounds, silazane compounds, and silicone oils. Among these, alkoxysilane compounds and silazane compounds are preferred, and silazane compounds are more preferred, from the perspective of easily achieving the effect of improving the dispersibility of the inorganic particles and preventing aggregation through appropriate steric hindrance, resulting in the inorganic particles being appropriately present on the surface, thereby preventing abnormal charge increase or decrease.

[0136] Examples of the alkoxysilane compound used in the hydrophobic treatment of the surface of the inorganic particles include tetramethoxysilane, tetraethoxysilane; methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, hexyltrimethoxysilane, n-octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, butyltriethoxysilane, Hexyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane, phenyltriethoxysilane, benzyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane; trimethylmethoxysilane, trimethylethoxysilane.

[0137] Examples of the silazane compound used for the hydrophobic treatment of the surface of the inorganic particles include dimethyldisilazane, trimethyldisilazane, tetramethyldisilazane, pentamethyldisilazane, and hexamethyldisilazane.

[0138] Examples of the silicone oil used in the surface treatment of the inorganic particles include silicone oils such as dimethylpolysiloxane, diphenylpolysiloxane, and benzylpolysiloxane; and reactive silicone oils such as amino-modified polysiloxane, epoxy-modified polysiloxane, carboxyl-modified polysiloxane, carbinol-modified polysiloxane, fluorine-modified polysiloxane, methacrylic acid-modified polysiloxane, mercapto-modified polysiloxane, and phenol-modified polysiloxane.

[0139] As the solvent used in the preparation of the treatment liquid, for example, when the silicon-containing organic compound is an alkoxysilane compound or a silazane compound, alcohols (for example, methanol, ethanol, propanol, butanol) are preferred, and when the silicon-containing organic compound is silicone oil, hydrocarbons (for example, benzene, toluene, n-hexane, n-heptane) are preferred.

[0140] The concentration of the silicon-containing organic compound in the treatment liquid is, for example, preferably 1 mass % to 50 mass %, more preferably 5 mass % to 40 mass %, and further preferably 10 mass % to 30 mass %.

[0141] The amount of the silicon-containing organic compound used in the surface treatment is, for example, preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 5 to 30 parts by mass, relative to 100 parts by mass of the inorganic particles.

[0142] The content of the inorganic particles in the resin coating layer is preferably, for example, 15% by mass or more and 35% by mass or less, more preferably 17% by mass or more and 30% by mass or less, and even more preferably 20% by mass or more and 25% by mass or less relative to the total mass of the resin coating layer. If the content of the inorganic particles is within the above range, the particles are easily and appropriately positioned on the lower side of the resin coating layer.

[0143] The ratio of the amount of inorganic particles on the carrier surface (element ratio A, atm%) to the content (mass %) of inorganic particles in the resin coating layer (element ratio A / content of inorganic particles, atm% / mass%) is, for example, preferably from 0.05 to 0.60, more preferably from 0.08 to 0.40, and even more preferably from 0.10 to 0.30. If the ratio of the amount of inorganic particles on the carrier surface (element ratio A, atm%) to the content (mass %) of inorganic particles in the resin coating layer is within the above range, it means that the carrier surface is suitably hardened by the inorganic particles, and the inorganic particles are suitably biased toward the lower side of the resin coating layer.

[0144] -Resin particles-

[0145] From the viewpoint of image density stability, the resin coating layer preferably contains resin particles, for example.

[0146] Examples of the resin particles include (meth)acrylic resins obtained by polymerizing dimethylaminoethyl (meth)acrylate, dimethylacrylamide, acrylonitrile, and the like; amino resins such as urea, melamine, guanamine, and aniline; amide resins; urethane resins; and copolymers of these resins. The resin particles may be used alone or in combination of two or more.

[0147] 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 melamine resin particles.

[0148] Melamine resin particles have a different polarity from inorganic particles, so it is believed that the Brazil nut phenomenon is more effective.

[0149] From the viewpoint of image density stability, the average primary particle size of the resin particles is, for example, preferably 100 nm or more and 400 nm or less, and more preferably 150 nm or more and 350 nm or less.

[0150] 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 can be easily concentrated on the lower side of the resin coating layer.

[0151] In this embodiment, the primary particle size of the resin particles refers to the diameter of a circle having the same area as the primary particle image (so-called equivalent circle diameter), and the average primary particle size of the resin particles refers to the particle size at which the cumulative 50% distribution of primary particle sizes from the smallest diameter side is achieved. The primary particle size of the resin particles is determined by image analysis of at least 300 resin particles.

[0152] The value of the ratio D1 / D2 of the average primary particle size D1 of the inorganic particles contained in the resin coating layer to the average primary particle size D2 of the resin particles is preferably, for example, 0.01 to 0.15, and more preferably 0.02 to 0.10.

[0153] When the value of 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 can be easily concentrated on the lower side of the resin coating layer.

[0154] The density ratio of the inorganic particles to the resin particles (density of the inorganic particles / density of the resin particles) is preferably, for example, 1.0 or greater and 5.0 or less. If this density ratio is within the above range, when the resin coating layer is formed by a wet process, the degree of sedimentation in the liquid is likely to vary, and the inorganic particles are likely to be arranged on the lower side of the resin coating layer.

[0155] From the viewpoint of image density stability, the content of the resin particles in the resin coating layer is preferably smaller than the content of the inorganic particles, for example.

[0156] From the viewpoint of image density stability, the content of the resin particles in the resin coating layer is preferably, for example, not less than 5 mass % and not more than 30 mass %, more preferably not less than 6 mass % and not more than 20 mass %, and further preferably not less than 7 mass % and not more than 15 mass %, relative to the total mass of the resin coating layer.

[0157] -Carbon black-

[0158] From the viewpoint of image density stability, the resin coating layer preferably contains carbon black, for example.

[0159] From the viewpoint of image density stability, the average primary particle size of carbon black is, for example, preferably 10 nm to 70 nm, more preferably 20 nm to 60 nm, and even more preferably 30 nm to 50 nm.

[0160] The value of 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, for example, 0.1 or more and 1.0 or less.

[0161] If the ratio D1 / D3 is within the above range, the particle size difference between the inorganic particles and the carbon black becomes appropriate, and the Brazil nut phenomenon is easily expressed. When the resin coating layer is formed by a wet method, the carbon black floats to the upper side of the resin coating layer. As a result, the inorganic particles are easily arranged on the lower side of the resin coating layer.

[0162] The density ratio of the inorganic particles to the carbon black (density of the inorganic particles / density of the carbon black) is preferably, for example, 1.0 or greater and 5.0 or less. If this density ratio is within the above range, when the resin coating layer is formed by a wet method, the degree of sedimentation in the liquid is likely to vary, and the inorganic particles are likely to be arranged on the lower side of the resin coating layer.

[0163] From the viewpoint of image density stability, the content of carbon black in the resin covering layer is preferably smaller than the content of inorganic particles in the resin covering layer, for example.

[0164] From the viewpoint of image density stability, the content of carbon black in the resin covering layer is preferably smaller than the content of resin particles in the resin covering layer, for example.

[0165] From the viewpoint of image concentration stability, the content of carbon black in the resin coating layer is preferably, for example, not less than 0.5 mass % and not more than 15 mass %, more preferably not less than 1 mass % and not more than 13 mass %, and further preferably not less than 2 mass % and not more than 10 mass %, relative to the total mass of the resin coating layer.

[0166] From the viewpoint of image density stability, the resin coating layer preferably contains, for example, silica particles and melamine resin particles, and more preferably contains silica particles, melamine resin particles, and carbon black.

[0167] [Method for forming resin coating layer]

[0168] Methods for forming a resin coating layer on the surface of magnetic particles include a wet method and a dry method. The wet method is a method using a solvent that dissolves or disperses the resin constituting the resin coating layer. For example, the wet method is preferred because it can utilize precipitation or the Brazil nut phenomenon to control the arrangement of inorganic particles.

[0169] As wet production methods, for example, there can be cited an immersion method in which the magnetic particles are immersed in a resin liquid for forming a resin coating layer for coating; a spraying method in which the resin liquid for forming a resin coating layer is sprayed onto the surface of the magnetic particles; a fluidized bed method in which the resin liquid for forming a resin coating layer is sprayed while the magnetic particles are allowed to flow in a fluidized bed; a kneading coating method in which the magnetic particles and the resin liquid for forming a resin coating layer are mixed in a kneading coater and the solvent is removed, etc.

[0170] The resin solution for forming the resin coating layer used in the wet 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 dissolves or disperses the resin; examples include aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; and ethers such as tetrahydrofuran and dioxane.

[0171] In the examples described below, the resin coating layer is formed by a wet process in multiple steps, but the method for forming the resin coating layer is not limited thereto.

[0172] The thickness of the resin coating layer is, for example, 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.

[0173] [Magnetic particles]

[0174] The magnetic particles are not particularly limited, and known magnetic particles used as core materials for carriers can be used. Specifically, examples of 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 obtained by impregnating porous magnetic powder with a resin; and magnetic powder-dispersed resin particles obtained by dispersing magnetic powder in a resin.

[0175] In this embodiment, the magnetic particles are preferably ferrite particles, for example.

[0176] In this embodiment, the ferrite particles preferably contain at least one selected from calcium oxide and strontium oxide, for example. Calcium oxide and strontium oxide are easily contained on the surface of the ferrite particles. If calcium or strontium is present on the surface of the ferrite particles, the leakage of charge from the ferrite particles is suppressed, and it is inferred that the surface charge of the carrier is relatively high. According to this carrier, the low charge of the toner in the developer is suppressed, and as a result, the fog is further suppressed, and the reproducibility of the fine line becomes good (for example, the fine line is suppressed from becoming thicker, collapsing or blurring). This effect is significant when a low-density image is formed with the same color after repeatedly forming a high-concentration and high-density monochrome image at a higher speed.

[0177] In this embodiment, the ferrite particles contain at least one selected from calcium oxide and strontium oxide, for example. The combined 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 combined 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 effectively suppressed. When the combined 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 uniform, and the resistance and magnetic susceptibility are within appropriate ranges. As a result, fogging is further suppressed, and further, fine line reproducibility is improved (for example, thickening, collapse, or blurring of fine lines is suppressed).

[0178] From the above viewpoints, the total content of calcium and strontium relative to the total amount of ferrite particles is, for example, preferably 0.1 mass % to 2.0 mass %, more preferably 0.2 mass % to 1.5 mass %, and even more preferably 0.5 mass % to 1.2 mass %.

[0179] In this embodiment, the ferrite particles contain, for example, calcium oxide, and the calcium content is preferably 0.2% by mass or more and 2.0% by mass or less relative to the total mass of the ferrite particles. When the calcium content is 0.2% by mass or more relative to the total mass of the ferrite particles, charge leakage from the ferrite particles is effectively suppressed. When the calcium content is 2.0% by mass or less relative to the total mass of the ferrite particles, the crystal structure of the ferrite particles is uniform, and the resistance and magnetic susceptibility are within appropriate ranges. As a result, fogging is further suppressed, and further, fine line reproducibility is improved (for example, thickening, collapse, or blurring of fine lines is suppressed).

[0180] From the above viewpoints, the content of calcium element is preferably 0.2 mass % to 2.0 mass % based on the total amount of ferrite particles, more preferably 0.5 mass % to 1.5 mass %, and even more preferably 0.5 mass % to 1.0 mass %.

[0181] In this embodiment, the ferrite particles contain, for example, 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 effectively 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 uniform, and the resistance and magnetic susceptibility are within appropriate ranges. As a result, fogging is further suppressed, and further, fine line reproducibility is improved (for example, thickening, collapse, or blurring of fine lines is suppressed).

[0182] From the above viewpoints, the strontium content relative to the total amount of the ferrite particles is, for example, 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 %.

[0183] The contents of calcium and strontium contained in the ferrite particles were measured by fluorescent X-ray analysis. The fluorescent X-ray analysis of the ferrite particles was performed by the following method.

[0184] Qualitative and quantitative analysis was performed using a fluorescent X-ray analyzer (XRF1500, manufactured by Shimadzu Corporation) under the conditions of X-ray output: 40 V / 70 mA, measurement area: 10 mm diameter, and measurement time: 15 minutes. The elements analyzed were selected based on the elements detected by qualitative analysis. Iron (Fe), manganese (Mn), magnesium (Mg), calcium (Ca), strontium (Sr), oxygen (O), and carbon (C) were primarily selected. The mass ratio (%) of each element was calculated by referring to a separately prepared calibration curve data.

[0185] The volume average particle size of the magnetic particles is, for example, preferably 20 μm or more and 50 μm or less, more preferably 25 μm or more and 45 μm or less, and still more preferably 30 μm or more and 40 μm or less.

[0186] The saturation magnetization of the magnetic force of the magnetic particles in a magnetic field of 3000 oersteds is, for example, 50 emu / g or more, preferably 60 emu / g or more. The above-mentioned saturation magnetization is measured using a vibrating sample type magnetic measuring device VSMP10-15 (manufactured by TOEI INDUSTRY CO., LTD.). The measurement sample is placed in a groove with an inner diameter of 7 mm and a height of 5 mm and is placed in the device. In addition to applying a magnetic field during measurement, the measurement is scanned to a maximum of 3000 oersteds. Then, the applied magnetic field is reduced and a hysteresis curve is produced on a recording paper. According to the data of the curve, the saturation magnetization, residual magnetization, and coercive force are obtained.

[0187] The volume resistance (volume resistivity) of the magnetic particles is, for example, 1×10 5 Ω·cm or more and 1×10 9 Ω·cm or less, preferably 1×10 7 Ω·cm or more and 1×10 9 Ω·cm or less.

[0188] The volume resistivity (Ω·cm) of the magnetic particles was measured as follows: The object to be measured was placed flat on a plate with a 20 cm 2 The 20 cm electrode plate was placed on the surface of the circular fixture to form a layer. 2 The electrode plates are placed on the layers and the layers are clamped. In order to eliminate the gaps between the objects to be measured, a load of 4 kg is applied to the electrode plates arranged on the layers, and then the thickness of the layers (cm) is measured. An electrometer and a high-voltage power supply generator are connected to the upper and lower electrodes of the layers. A high voltage is applied to the two electrodes so that the electric field becomes 103.8 V / cm, and the current value (A) flowing at this time is read. The measurement environment is set to a temperature of 20°C and a humidity of 50% RH. The calculation formula for the volume resistivity (Ω·cm) of the object to be measured is shown below.

[0189] R=E×20 / (I-I0) / L

[0190] In the above formula, R represents the volume resistance of the object to be measured (Ω·cm), E represents the applied voltage (V), I represents the current value (A), I0 represents the current value (A) under the condition of applied voltage 0V, and L represents the thickness of the layer (cm). The coefficient 20 represents the area of the electrode plate (cm 2 ).

[0191] [Characteristics of the carrier]

[0192] The volume average particle size of the carrier is, for example, preferably 20 μm or more and 52 μm or less, more preferably 25 μm or more and 47 μm or less, and still more preferably 30 μm or more and 42 μm or less.

[0193] The volume average particle size of the carrier refers to the particle size at which the cumulative total of the smallest particles in the volume-based particle size distribution is 50%. The particle size distribution of the carrier is measured using a laser diffraction / scattering particle size distribution analyzer.

[0194] When analyzing the carrier contained in the developer, as a method of separating the carrier from the developer, there is a method of removing the toner from the developer by blowing air using an arbitrary filter.

[0195] The magnetic force of the carrier has a saturation magnetization of, for example, 40 emu / g or more, preferably 50 emu / g or more in a magnetic field of 1000 oersted. The saturation magnetization is measured in the same manner as the saturation magnetization of the magnetic particles, but scanned to a maximum of 1000 oersted.

[0196] The volume resistance (25°C) of the carrier is, for example, 1×10 7 Ω·cm or more and 1×10 15 Ω·cm or less, preferably 1×10 8 Ω·cm or more and 1×10 14 Ω·cm or less, more preferably 1×10 8 Ω·cm or more and 1×10 13 The volume resistivity of the carrier is measured in the same manner as the volume resistivity of the magnetic particles.

[0197] The exposure ratio of the magnetic particles on the surface of the carrier is, for example, preferably 2% to 20%, more preferably 3% to 15%, and even more preferably 4% to 12%.

[0198] The exposure ratio of the magnetic particles on the surface of the carrier is determined by the following method using X-ray photoelectron spectroscopy (XPS).

[0199] Prepare a carrier and magnetic particles from which the resin coating has been removed. Methods for removing the resin coating from the carrier include dissolving the resin component with an organic solvent and removing the resin coating by heating to approximately 800°C to eliminate the resin component. The carrier and the magnetic particles from which the resin coating has been removed are each used as a measurement sample. Fe (atomic %) is quantified by XPS, and the ratio (Fe on the carrier) ÷ (Fe on the magnetic particles) × 100 is calculated as the exposure ratio (%) of the magnetic particles.

[0200] The exposure 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. The greater the amount of resin relative to the amount of magnetic particles, the smaller the exposure ratio.

[0201] <Electrostatic image developer>

[0202] The developer according to this embodiment includes a toner and the carrier according to this embodiment.

[0203] The developer according to this embodiment is prepared by mixing a toner and a carrier according to this embodiment at an appropriate mixing ratio. The mixing ratio (mass ratio) of toner to carrier is preferably, for example, toner:carrier = 1:100 to 30:100, and more preferably 3:100 to 20:100.

[0204] [Toner for electrostatic image development]

[0205] There are no particular limitations on the toner, and known toners can be used. Examples include colored toners comprising toner particles containing a binder resin and a colorant, and infrared-absorbing toners using an infrared absorber in place of a colorant. Toners may also contain a release agent and various internal and external additives.

[0206] [Toner particles]

[0207] -Binding resin-

[0208] Examples of the binder resin include vinyl resins composed of homopolymers of monomers such as styrenes (e.g., styrene, p-chlorostyrene, α-methylstyrene, etc.), (meth)acrylates (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), or copolymers obtained by combining two or more of these monomers.

[0209] Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures thereof with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these resins.

[0210] These binder resins may be used alone or in combination of two or more.

[0211] As the binder resin, for example, polyester resin, styrene acrylic resin, and styrene acrylic modified polyester resin are preferred, and polyester resin is more preferred.

[0212] The glass transition temperature (Tg) of the resin is, for example, preferably 50° C. or higher and 80° C. or lower, and more preferably 50° C. or higher and 65° C. or lower.

[0213] The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, according to the "extrapolated glass transition onset temperature" method described in JIS K7121-1987 "Plastics - Determination of Transition Temperatures".

[0214] The weight average molecular weight (Mw) of the resin is preferably, for example, 5,000 or more and 1,000,000 or less, and more preferably 7,000 or more and 500,000 or less. The number average molecular weight (Mn) of the resin is preferably, for example, 2,000 or more and 100,000 or less. The molecular weight distribution Mw / Mn of the resin is preferably, for example, 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less.

[0215] The weight average molecular weight and number average molecular weight were measured by gel permeation chromatography (GPC). In the molecular weight measurement based on GPC, a GPC HLC-8120GPC (TOSOH CORPORATION) was used as the measuring apparatus, a TSKgel SuperHM-M (15 cm diameter, TOSOH CORPORATION) was used as the chromatographic column, and the measurement was performed in THF solvent. The weight average molecular weight and number average molecular weight were calculated using a molecular weight calibration curve prepared from the measurement results and using a monodisperse polystyrene standard sample.

[0216] The content of the binder resin is, for example, preferably 40 mass % to 95 mass % inclusive, more preferably 50 mass % to 90 mass % inclusive, and further preferably 60 mass % to 85 mass % inclusive, based on the total amount of the toner particles.

[0217] -Colorant-

[0218] Examples of the colorant include carbon black, chrome yellow, Hansa yellow, benzidine yellow, vat yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, sulfur-resistant orange, saffron carmine, permanent red, brilliant carmine 3B, brilliant carmine 6B, Dupont Oil Red, pyrazolone red, lithocyanine, rhodamine B Lake, Red Lake C, pigment red, rose Bengal, aniline blue, ultramarine blue, copper oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, and malachite green oxalate; and dyes such as acridines, xanthenes, azos, benzoquinones, azines, anthraquinones, thioindigos, dioxazines, thiazines, azomethines, indigos, phthalocyanines, nigrosines, polymethines, triphenylmethanes, diphenylmethanes, and thiazoles.

[0219] The coloring agents may be used alone or in combination of two or more.

[0220] The colorant may be a surface-treated colorant as needed, and may be used in combination with a dispersant. Furthermore, multiple colorants may be used in combination.

[0221] The content of the colorant is, for example, preferably 1 mass % or more and 30 mass % or less, and more preferably 3 mass % or more and 15 mass % or less, based on the total amount of the toner particles.

[0222] -Release agent-

[0223] Examples of the release agent include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic waxes such as montan wax, or mineral / petroleum waxes, and ester waxes such as fatty acid esters and montanic acid esters. The release agent is not limited thereto.

[0224] The melting temperature of the release agent is, for example, preferably 50° C. or higher and 110° C. or lower, and more preferably 60° C. or higher and 100° C. or lower.

[0225] The melting temperature is determined based on the “melting peak temperature” described in the method for determining the melting temperature in JIS K7121-1987 “Determination of Transition Temperatures of Plastics” from a DSC curve obtained by differential scanning calorimetry (DSC).

[0226] The content of the release agent is, for example, preferably 1 mass % or more and 20 mass % or less, and more preferably 5 mass % or more and 15 mass % or less, based on the total amount of the toner particles.

[0227] -Other additives-

[0228] Examples of other additives include known additives such as magnetic materials, charge control agents, and inorganic powders. These additives are contained in the toner particles as internal additives.

[0229] [Characteristics of Toner Particles]

[0230] The toner particles may be single-layer toner particles or so-called core-shell toner particles composed of a core (core particle) and a coating layer (shell layer) that covers the core. The core-shell toner particles preferably include, for example, a core composed of a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer composed of a binder resin.

[0231] The volume average particle diameter (D50v) of the toner particles is, for example, preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

[0232] The volume average particle size (D50v) of the toner particles is measured using a Coulter Multisizer II (BECKMAN COULTER) and an ISOTON-II (BECKMAN COULTER) electrolyte. During the measurement, 0.5 mg to 50 mg of the sample is added to 2 ml of a 5% by mass aqueous solution of a surfactant (e.g., preferably sodium alkylbenzene sulfonate) as a dispersant. This sample is then added to 100 ml to 150 ml of the electrolyte. The electrolyte containing the sample is dispersed for 1 minute using an ultrasonic disperser. The particle size distribution of particles with a diameter of 2 μm to 60 μm is measured using a Coulter Multisizer II with an aperture of 100 μm. A total of 50,000 particles are sampled.

[0233] [External additives]

[0234] Examples of external additives include inorganic particles. Examples of such inorganic particles include SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, K2O·(TiO2) n , Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, SrTiO3, etc.

[0235] As the surface of the inorganic particles of the external additive, for example, a hydrophobic treatment is preferably implemented. 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 for example, silane coupling agents, silicone oils, titanate coupling agents, aluminum coupling agents, etc. can be cited. They can be used alone or in combination of two or more.

[0236] The amount of the hydrophobizing agent is preferably, for example, 1 part by mass or more and 30 parts by mass or less relative to 100 parts by mass of the inorganic particles.

[0237] Examples of external additives include resin particles (polystyrene, polymethyl methacrylate, melamine resin, and other resin particles), cleaning aids (for example, metal salts of higher fatty acids such as zinc stearate, and particles of fluorine-based high molecular weight substances).

[0238] The amount of the external additive added is, for example, preferably from 0.01 mass % to 10 mass % inclusive, and more preferably from 0.01 mass % to 5 mass % inclusive, based on the toner particles.

[0239] [Method for producing toner]

[0240] Toner is obtained by adding an external additive to the toner particles after they are manufactured. Toner particles can be produced by any of dry methods (e.g., kneading and pulverization methods) or wet methods (e.g., coagulation, suspension polymerization, and dissolution suspension methods). These methods are not particularly limited, and known methods can be employed. Among these, toner particles are preferably produced by the coagulation method.

[0241] <Image Forming Apparatus and Image Forming Method>

[0242] An image forming apparatus and an image forming method according to this embodiment will be described.

[0243] The image forming apparatus according to this embodiment includes: an image holder; a charging device for charging the surface of the image holder; an electrostatic image forming device for forming an electrostatic image on the surface of the charged image holder; a developing device for storing an electrostatic image developer and developing the electrostatic image formed on the surface of the image holder into a toner image using the electrostatic image developer; a transfer device for transferring the toner image formed on the surface of the image holder to the surface of a recording medium; and a fixing device for fixing the toner image transferred to the surface of the recording medium. The electrostatic image developer according to this embodiment can be used as the electrostatic image developer.

[0244] In the image forming device involved in this embodiment, an image forming method (the image forming method involved in this embodiment) is implemented, which includes the following processes: a charging process, in which the surface of the image retaining body is charged; an electrostatic image forming process, in which an electrostatic image is formed on the surface of the charged image retaining body; a developing process, in which the electrostatic image formed on the surface of the image retaining body is developed into a toner image by the electrostatic image developer involved in this embodiment; a transfer process, in which the toner image formed on the surface of the image retaining body is transferred to the surface of the recording medium; and a fixing process, in which the toner image transferred to the surface of the recording medium is fixed.

[0245] The image forming device involved in this embodiment can be applicable to the following well-known image forming devices: a device of a direct transfer method in which a toner image formed on the surface of an image retaining body is directly transferred to a recording medium; a device of an intermediate transfer method in which a toner image formed on the surface of an image retaining body is transferred to the surface of an intermediate transfer body for the first time, and the toner image transferred to the surface of the intermediate transfer body is transferred to the surface of a recording medium for a second time; a device having a cleaning device for cleaning the surface of the image retaining body after transferring the toner image but before charging; a device having an electrostatic elimination device for eliminating static electricity by irradiating the surface of the image retaining body with electrostatic elimination light after transferring the toner image and before charging, etc.

[0246] In the case where the image forming device involved in this embodiment is an intermediate transfer device, the transfer device can, for example, be applicable to the following structure, which includes: an intermediate transfer body that transfers the toner image to the surface; a primary transfer device that transfers the toner image formed on the surface of the image retaining body to the surface of the intermediate transfer body for the first time; and a secondary transfer device that transfers the toner image transferred to the surface of the intermediate transfer body for the second time to the surface of the recording medium.

[0247] In the image forming apparatus of the present embodiment, for example, the portion including the developing device may be a cartridge structure (processing cartridge) that is detachably mounted on the image forming apparatus. As the processing cartridge, for example, a processing cartridge having a developing device that accommodates the electrostatic image developer of the present embodiment may be preferably used.

[0248] An example of the image forming apparatus according to the present embodiment is shown below, but the present invention is not limited thereto. In the following description, the main parts shown in the figure are described, and the description of other parts is omitted.

[0249] Figure 1 FIG. 1 is a diagram schematically showing the configuration of an image forming apparatus according to this embodiment.

[0250] Figure 1 The image forming apparatus shown includes first to fourth electrophotographic image forming units 10Y, 10M, 10C, and 10K that output images in yellow (Y), magenta (M), cyan (C), and black (K) based on color-decomposed image data. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side by side, separated from each other by a predetermined distance in the horizontal direction. These units 10Y, 10M, 10C, and 10K may be process cartridges that are attachable to and detachable from the image forming apparatus.

[0251] An intermediate transfer belt (an example of an intermediate transfer member) 20 extends above each of the units 10Y, 10M, 10C, and 10K. The intermediate transfer belt 20 is wound around a drive roller 22 and a support roller 24, and travels from the first unit 10Y toward the fourth unit 10K. The support roller 24 is biased away from the drive roller 22 by a spring (not shown), thereby applying tension to the intermediate transfer belt 20 wound around the drive roller 22. An intermediate transfer member cleaning device 30 is provided on the outer circumference of the intermediate transfer belt 20, facing the drive roller 22.

[0252] Yellow, magenta, cyan, and black toners contained in toner cartridges 8Y, 8M, 8C, and 8K are supplied to developing devices (an example of developing devices) 4Y, 4M, 4C, and 4K of the respective units 10Y, 10M, 10C, and 10K.

[0253] The first to fourth units 10Y, 10M, 10C, and 10K have the same structure and operation, and therefore the first unit 10Y disposed upstream in the traveling direction of the intermediate transfer belt and forming a yellow image will be described as a representative.

[0254] The first unit 10Y includes a photoreceptor 1Y that functions as an image holder. Sequentially arranged around the photoreceptor 1Y are: a charging roller (an example of a charging device) 2Y, which charges the surface of the photoreceptor 1Y to a predetermined potential; an exposure device (an example of an electrostatic image forming device) 3, which forms an electrostatic image by exposing the charged surface to a laser beam 3Y based on a color-decomposed image signal; a developing device (an example of a developing device) 4Y, which supplies charged toner to the electrostatic image to develop the electrostatic image; a primary transfer roller (an example of a primary transfer device) 5Y, which transfers the developed toner image to the intermediate transfer belt 20; and a photoreceptor cleaning device (an example of a cleaning device) 6Y, which removes toner remaining on the surface of the photoreceptor 1Y after the primary transfer.

[0255] The primary transfer roller 5Y is disposed inside the intermediate transfer belt 20 and is positioned opposite the photoreceptor 1Y. A bias power supply (not shown) for applying a primary transfer bias is connected to each of the primary transfer rollers 5Y, 5M, 5C, and 5K in each unit. Each bias power supply changes the value of the transfer bias applied to each primary transfer roller under the control of a control unit (not shown).

[0256] Next, the operation of forming a yellow image in the first unit 10Y will be described.

[0257] First, before the operation is performed, the surface of the photoreceptor 1Y is charged to a potential of -600 V to -800 V by the charging roller 2Y.

[0258] The photoreceptor 1Y is conductive (for example, the volume resistivity is 1×10 -6 The photosensitive layer is formed by laminating a photosensitive layer on a substrate having a resistance of 100 Ω·cm or less. This photosensitive layer typically has a high electrical resistance (the electrical resistance of a typical resin), but when irradiated with a laser beam, the resistivity of the portion exposed to the laser beam changes. Therefore, based on yellow image data transmitted from a control unit (not shown), the exposure device 3 irradiates the surface of the charged photoreceptor 1Y with a laser beam 3Y. This forms an electrostatic image of a yellow image pattern on the surface of the photoreceptor 1Y.

[0259] An electrostatic image refers to an image formed on the surface of the photoreceptor 1Y by charging, and is a so-called negative latent image. It is formed by the resistivity of the irradiated portion of the photosensitive layer being reduced by the laser beam 3Y, and the charged charge on the surface of the photoreceptor 1Y flowing, while on the other hand, the charge of the portion not irradiated by the laser beam 3Y remains.

[0260] As the photoreceptor 1Y travels, the electrostatic image formed on the photoreceptor 1Y rotates to a predetermined developing position. At the developing position, the electrostatic image on the photoreceptor 1Y is developed by the developing device 4Y and visualized as a toner image.

[0261] The developing device 4Y contains, for example, an electrostatic image developer containing at least yellow toner and a carrier. The yellow toner is triboelectrically charged by being stirred within the developing device 4Y, resulting in a charge of the same polarity (negative) as the charge on the photoreceptor 1Y and being retained on the developer roller (an example of a developer retainer). The surface of the photoreceptor 1Y then passes through the developing device 4Y, whereupon the yellow toner electrostatically adheres to the de-electrostaticized latent image on the surface of the photoreceptor 1Y, developing the latent image with the yellow toner. The photoreceptor 1Y, with the yellow toner image formed on it, continues to travel at a predetermined speed, and the developed toner image on the photoreceptor 1Y is transported to a predetermined primary transfer position.

[0262] When the yellow toner image on the photoreceptor 1Y reaches the primary transfer position, a primary transfer bias is applied to the primary transfer roller 5Y. Electrostatic force from the photoreceptor 1Y toward the primary transfer roller 5Y acts on the toner image, thereby transferring the toner image on the photoreceptor 1Y to 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 by a control unit (not shown) in the first unit 10Y to, for example, +10 μA.

[0263] On the other hand, the toner remaining on the photoreceptor 1Y is removed and recovered by the photoreceptor cleaning device 6Y.

[0264] The primary transfer bias applied to the primary transfer rollers 5M, 5C, and 5K after the second unit 10M is also controlled in accordance with the first unit.

[0265] In this manner, the intermediate transfer belt 20 to which the yellow toner image has been transferred in the first unit 10Y is sequentially transported through the second to fourth units 10M, 10C, and 10K, so that the toner images of the respective colors are superimposed and multi-transferred.

[0266] The intermediate transfer belt 20, to which four color toner images have been multiply transferred by the first through fourth units, reaches the secondary transfer section, which is comprised of the intermediate transfer belt 20, a backup roller 24 in contact with the inner surface of the intermediate transfer belt 20, and a secondary transfer roller (an example of a secondary transfer device) 26 disposed on the outer circumference of the intermediate transfer belt 20. Meanwhile, recording paper (an example of recording medium) P is fed into the gap between the secondary transfer roller 26 and the intermediate transfer belt 20 via a feed mechanism at a predetermined timing, and a secondary transfer bias is applied to the backup roller 24. The applied transfer bias has a (-) polarity, the same as the 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 to the recording paper P. The secondary transfer bias is determined based on the resistance detected by a resistance detection device (not shown) that detects the resistance of the secondary transfer section and is voltage-controlled.

[0267] Then, the recording paper P is fed into a pressure-contact portion (nip portion) of a pair of fixing rollers in a fixing device (an example of a fixing device) 28 , where the toner image is fixed on the recording paper P, thereby forming a fixed image.

[0268] Examples of the recording paper P to which the toner image is transferred include plain paper used in electrophotographic copy machines, printers, etc. Examples of the recording medium include, in addition to the recording paper P, OHP sheets and the like.

[0269] To further improve the smoothness of the image surface after fixing, the surface of the recording paper P is preferably smooth. For example, coated paper obtained by coating the surface of plain paper with a resin or coated paper for printing can be preferably used.

[0270] The recording paper P on which the color image has been fixed is conveyed toward the discharge portion, thereby completing a series of color image forming operations.

[0271] <Processing cartridge>

[0272] The process cartridge according to this embodiment will be described.

[0273] The processing box involved in this embodiment is a processing box that includes a developing device and is loaded and unloaded from an image forming device. The developing device accommodates the electrostatic image developer involved in this embodiment and develops the electrostatic image formed on the surface of the image holding body into a toner image through the electrostatic image developer.

[0274] The process cartridge according to this embodiment is not limited to the above-described configuration, and may include a developing device and, if necessary, at least one other device selected from an image holder, a charging device, an electrostatic image forming device, and a transfer device.

[0275] An example of the process cartridge according to the present embodiment is shown below, but the present invention is not limited thereto. In the following description, the main parts shown in the drawings are described, and description of other parts is omitted.

[0276] Figure 2 It is a diagram schematically showing the structure of a process cartridge according to this embodiment.

[0277] Figure 2 The processing box 200 shown is constructed by, for example, integrally combining and holding a photosensitive body 107 (an example of an image holding body), a charging roller 108 (an example of a charging device) provided around the photosensitive body 107, a developing device 111 (an example of a developing device), and a photosensitive body cleaning device 113 (an example of a cleaning device) using a shell 117 having a mounting guide 116 and an opening 118 for exposure, and making it into a box.

[0278] exist Figure 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).

[0279] Example

[0280] Hereinafter, the present embodiment will be described in detail with reference to Examples, but the present embodiment is not limited to these Examples. In the following description, "parts" and "%" are based on mass unless otherwise specified.

[0281] In the following description, unless otherwise specified, synthesis, handling, production, testing, etc. were carried out at room temperature (25°C ± 3°C).

[0282] <Toner Production>

[0283] [Preparation of Resin Particle Dispersion (1)]

[0284] Ethylene glycol (FUJIFILM Wako Pure Chemical Corporation): 37 parts

[0285] Neopentyl glycol (FUJIFILM Wako Pure Chemical Corporation): 65 parts

[0286] 1,9-Nonanediol (FUJIFILM Wako Pure Chemical Corporation): 32 parts

[0287] Terephthalic acid (FUJIFILM Wako Pure Chemical Corporation): 96 parts

[0288] The above materials were placed in a flask and heated to 200°C over 1 hour. After ensuring uniform stirring within the reaction system, 1.2 parts of dibutyltin oxide were added. While distilling off the generated water, the temperature was raised to 240°C over 6 hours and stirred at 240°C for 4 hours to obtain a polyester resin (acid value 9.4 mgKOH / g, weight-average molecular weight 13,000, glass transition temperature 62°C). The polyester resin was transferred to an emulsifier (Cavitron CD1010, EUROTEC LIMITED) in a molten state at a rate of 100 g per minute. Separately, a 0.37% concentration of dilute ammonia water, obtained by diluting reagent ammonia water with ion-exchanged water, was placed in a tank and heated to 120°C using a heat exchanger. The mixture was then transferred to the emulsifier at a rate of 0.1 liter per minute, simultaneously with the polyester resin. The rotor speed was 60 Hz and the pressure was 5 kg / cm3. 2 The emulsifying disperser was operated under the conditions of , and a resin particle dispersion (1) having a volume average particle size of 160 nm and a solid content of 30% was obtained.

[0289] [Preparation of Resin Particle Dispersion (2)]

[0290] Sebacic acid (Tokyo Chemical Industry Co., Ltd.): 81 parts

[0291] Hexanediol (FUJIFILM Wako Pure Chemical Corporation): 47 parts

[0292] The above materials were placed in a flask and the temperature was raised to 160°C over 1 hour. After confirming uniform stirring within the reaction system, 0.03 parts of dibutyltin oxide was added. While distilling off the generated water, the temperature was raised to 200°C over 6 hours and stirred at 200°C for 4 hours. The reaction solution was then cooled, solid-liquid separation was performed, and the solid matter was dried at 40°C under reduced pressure to obtain a polyester resin (C1) (melting point 64°C, weight-average molecular weight 15,000).

[0293] Polyester resin (C1): 50 parts

[0294] Anionic surfactant (NEOGEN SC, DKS Co. Ltd.): 2 parts

[0295] Ion exchange water: 200 parts

[0296] The above materials were heated to 120°C, fully dispersed with a homogenizer (ULTRA TURRAX T50, IKA), and then dispersed with a pressure jet homogenizer. When the volume average particle size reached 180 nm, the dispersion was recovered to obtain a resin particle dispersion (2) with a solid content of 20%.

[0297] [Preparation of Colorant Particle Dispersion (1)]

[0298] Cyan pigment (Pigment Blue 15:3, Dainichiseika Color & Chemicals Mfg. Co., Ltd.): 10 parts

[0299] Anionic surfactant (NEOGEN SC, DKS Co. Ltd.): 2 parts

[0300] Ion exchange water: 80 parts

[0301] The above materials were mixed and dispersed for 1 hour using a high-pressure impact disperser (ULTIMAIZER HJP30006, SUGINOMACHINE LIMITED) to obtain a colorant particle dispersion (1) having a volume average particle size of 180 nm and a solid content of 20%.

[0302] [Preparation of Release Agent Particle Dispersion (1)]

[0303] Paraffin wax (HNP-9, NIPPON SEIRO CO., LTD.): 50 parts

[0304] Anionic surfactant (NEOGEN SC, DKS Co. Ltd.): 2 parts

[0305] Ion exchange water: 200 parts

[0306] The above materials were heated to 120°C, fully dispersed with a homogenizer (ULTRA TURRAX T50, IKA), and then dispersed with a pressure jet homogenizer. When the volume average particle size reached 200 nm, the particles were recovered to obtain a release agent particle dispersion (1) having a solid content of 20%.

[0307] [Preparation of Toner (1)]

[0308] Resin particle dispersion (1): 150 parts

[0309] Resin particle dispersion (2): 50 parts

[0310] Colorant particle dispersion (1): 25 parts

[0311] Release agent particle dispersion (1): 35 parts

[0312] Polyaluminium chloride: 0.4 parts

[0313] Ion exchange water: 100 parts

[0314] The above materials were placed in a round stainless steel flask and thoroughly mixed and dispersed using a homogenizer (ULTRA TURRAX T50, IKA). The flask was then stirred and heated to 48°C in a heating oil bath. The reaction system was kept at 48°C for 60 minutes, and then 70 parts of the resin particle dispersion (1) were slowly added. Next, the pH was adjusted to 8.0 using a 0.5 mol / L sodium hydroxide aqueous solution, the flask was sealed, the stirring shaft was magnetically sealed, and the mixture was heated to 90°C and maintained for 30 minutes while continuing to stir. Next, the mixture was cooled at a cooling rate of 5°C / min, solid-liquid separation was performed, and the mixture was thoroughly washed with ion exchange water. Next, the mixture was solid-liquid separation was performed, the mixture was dispersed again in ion exchange water at a temperature of 30°C, stirred at a rotation speed of 300 rpm (revolutions per minute) for 15 minutes, and washed. This washing operation was repeated six times. When the pH of the filtrate reached 7.54 and the conductivity reached 6.5 μS / cm, solid-liquid separation was performed. Vacuum drying was continued for 24 hours to obtain toner particles (1) having a volume average particle size of 5.7 μm.

[0315] 100 parts of the toner particles (1) and 2.5 parts of silica particles (surface hydrophobized with hexamethyldisilazane, average primary particle size 40 nm) were mixed with a Henschel mixer to obtain a toner (1).

[0316] <Preparation of Carrier and Developer: Examples 1 to 40 and Comparative Examples 1 to 5>

[0317] [Production of ferrite particles (1)]

[0318] Fe2O3: 1597 parts

[0319] Mn(OH)2: 712 parts

[0320] Mg(OH)2: 116 parts

[0321] SrCO3: 20 parts

[0322] CaCO3: 30 parts

[0323] The above materials were mixed, dispersant, water and zirconia beads with a diameter of 1 mm were added, and the mixture was decomposed, crushed and mixed using a sand mill. The zirconia beads were filtered out, and the filtrate was dried, and then temporarily calcined using a rotary kiln at a speed of 20 rpm / temperature of 970°C / 2 hours. Dispersant and water were added to the obtained pre-calcined product, and 8 parts of polyvinyl alcohol were further added, and the mixture was crushed and mixed using a wet ball mill for 5 hours. The volume average particle size of the obtained crushed product was 1.2 μm. Then, a spray dryer was used to granulate the product to a particle size of 40 μm. The obtained granulated product was formally calcined using an electric furnace at a temperature of 1,400°C / 4 hours in an oxygen-nitrogen mixed atmosphere with an oxygen concentration of 1% by volume. The obtained calcined product was crushed and classified to obtain ferrite particles (1). The volume average particle size of the ferrite particles (1) was 35 μm.

[0324] [Preparation of the First Layer Coating Agent and the Second Layer Coating Agent]

[0325] In this embodiment, the value of BA is controlled by forming the resin coating layer in multiple steps. This embodiment is just one example of a method for controlling the value of BA, and the method for controlling the value of BA is not limited to this.

[0326] The components listed in Tables 1 and 2 at the mass ratios listed in Table 1 and glass beads (1 mm in diameter, the same amount as toluene) were placed in a sand mill and stirred at 190 rpm for 30 minutes to prepare first and second layer coating agents, respectively.

[0327] The details of the abbreviations of the components of the coating agents described in Tables 1 and 2 are as follows.

[0328] Resin (1): Cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer (copolymerization ratio 97 mol:3 mol)

[0329] Resin (2): Cyclohexyl methacrylate / methyl methacrylate copolymer (copolymerization ratio 95 mol:5 mol)

[0330] Resin (3): Methyl methacrylate polymer

[0331] Surface-treated silica (S1): silica particles (HM20S, TOKUYAMA, average primary particle size 12 nm, surface treatment agent hexamethyldisilazane)

[0332] Surface-treated silica (S2): silica particles (NX90S, NIPPON AEROSIL CO., LTD., average primary particle size 22 nm, surface treatment agent: hexamethyldisilazane)

[0333] Surface-treated silica (S3): silica particles (RY200, NIPPON AEROSIL CO., LTD., average primary particle size 12 nm, surface treatment agent: silicone oil)

[0334] Surface-treated silica (S4): silica particles (HM30S, TOKUYAMA, average primary particle size 7 nm, surface treatment agent: hexamethyldisilazane)

[0335] Surface-treated silica (S5): silica particles (average primary particle size 30 nm, dry-process silica, surface-treated with hexamethyldisilazane)

[0336] Surface-treated silica (S6): silica particles (average primary particle size 40 nm, dry-process silica, surface-treated with hexamethyldisilazane)

[0337] Surface-treated silica (S7): silica particles (RX50, NIPPON AEROSIL CO., LTD., average primary particle size 65 nm, surface treatment agent hexamethyldisilazane)

[0338] · Non-surface treated silica (Sn): silica particles (QS-20, TOKUYAMA, average primary particle size 12 nm)

[0339] Surface-treated alumina (A): alumina particles (AluC805, NIPPON AEROSIL CO., LTD., average primary particle size 22 nm, surface treatment agent octylsilane)

[0340] Surface-treated titanium dioxide (T): titanium dioxide particles (T805, NIPPON AEROSIL CO., LTD., average primary particle size 20 nm, surface treatment agent octylsilane)

[0341] Resin particles (M1): melamine resin particles (EPOSTAR FS, NIPPON SHOKUBAI CO., LTD., average primary particle size 250 nm)

[0342] Resin particles (M2): melamine resin particles (EPOSTAR SS, NIPPON SHOKUBAI CO., LTD., average primary particle size 70 nm)

[0343] Resin particles (M3): melamine resin particles (EPOSTAR S, NIPPON SHOKUBAI CO., LTD., average primary particle size 100 nm)

[0344] Resin particles (A1): acrylic resin particles (MP-1441, SOKEN CHEMICAL ASIA CO., LTD., average primary particle size 150 nm)

[0345] Resin particles (A2): acrylic resin particles (MP-2200, SOKEN CHEMICAL ASIA CO., LTD., average primary particle size 350 nm)

[0346] Resin particles (M4): melamine resin particles (EPOSTAR S6, NIPPON SHOKUBAI CO., LTD., average primary particle size 400 nm)

[0347] Resin particles (M5): melamine resin particles (EPOSTAR S12, NIPPON SHOKUBAI CO., LTD., average primary particle size 900 nm)

[0348] CB: Carbon black (VXC72, Cabot Corporation)

[0349] [Preparation of carrier (1)]

[0350] Using a spin coater (OKADA SEIKO CO., LTD.), a first layer coating agent was applied to the surface of 1000 parts of ferrite particles (1) at a rate of 30 g / min in an atmosphere of 70°C so that the composition of the resin coating layer was 15 parts relative to the ferrite core material. Subsequently, a second layer coating agent was applied at a rate of 30 g / min so that the composition of the resin coating layer was 15 parts relative to the ferrite particles (1), and then dried. The dried powder was removed from the spin coater and crushed using a sieve with an aperture of 75 μm to obtain carriers of Examples 1 to 40 and Comparative Examples 1 and 2, respectively.

[0351] In Comparative Example 3, a first layer coating agent was applied to the surface of 1000 parts of ferrite particles (1) using a spin coater (OKADA SEIKO CO., LTD.) at a rate of 30 g / min in an atmosphere of 70°C so that the resin coating layer had a composition of 30 parts relative to the ferrite core material, and then dried. The dried powder was removed from the spin coater and crushed using a sieve with an aperture of 75 μm to obtain a carrier of Comparative Example 3.

[0352] [Preparation of carrier (2)]

[0353] - Materials (1) -

[0354] Ferrite particles (1): 1000 parts

[0355] 4.6 parts of resin particles of cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer (copolymerization ratio 97 mol:3 mol)

[0356] Surface treated silica (S1): 4.0 parts

[0357] CB: 0.4 parts

[0358] Resin particles (M1): 1.0 part

[0359] -Material (2)-

[0360] 14.7 parts of resin particles of cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer (copolymerization ratio 97 mol:3 mol)

[0361] Surface treated silica (S1): 2.0 parts

[0362] CB: 1.3 parts

[0363] Resin particles (M1): 2.0 parts

[0364] The above-mentioned material (1) was placed in a high-speed mixer equipped with a stirring blade and stirred for 45 minutes at a temperature of 125°C and a wind speed of 10 m / s. Subsequently, the above-mentioned material (2) was added and stirred for 45 minutes at a temperature of 125°C and a wind speed of 10 m / s. Due to the mechanical impact force, a resin coating layer was formed on the surface of the ferrite particles. Subsequently, the wind speed was reduced to 2 m / s, and the mixture was cooled to room temperature to obtain a carrier of Comparative Example 4.

[0365] [Preparation of carrier (3)]

[0366] 19.3 parts of resin particles of cyclohexyl methacrylate / 2-(dimethylamino)ethyl methacrylate copolymer (copolymerization ratio 97 mol:3 mol)

[0367] Surface treated silica (S7): 6.0 parts

[0368] CB: 1.7 parts

[0369] Resin particles (M1): 3.0 parts

[0370] Toluene: 386.7 parts

[0371] The above material was applied to 1000 parts of ferrite particles (1) and dried to obtain a carrier of Comparative Example 5. The coating and drying were performed using a fluidized bed coating apparatus in which the temperature in the fluidized bed was controlled to 70°C.

[0372] [Production of developer]

[0373] 100 parts of the carrier and 6 parts of the toner (1) were placed in a V mixer and stirred for 20 minutes. The mixture was then sieved with a sieve having an aperture of 212 μm to obtain developers of Examples 1 to 40 and Comparative Examples 1 to 5, respectively.

[0374] [Measurement of Volume Average Particle Size of Carrier]

[0375] The carrier particle size was measured using a laser diffraction / scattering particle size analyzer (LS Particle Size Analyzer: LS13320, Beckman Coulter, Inc.) using the carrier as a sample. The particle size (μm) at which the cumulative 50% of the smallest particle size in the volume-based particle size distribution was obtained.

[0376] The volume average particle size of the carriers in Examples 1 to 40 and Comparative Examples 1 to 5 was 36 μm, respectively.

[0377] [Elemental analysis based on XPS]

[0378] Using the support as a sample, carbon, nitrogen, oxygen, iron, manganese, and metals and semi-metals constituting the inorganic particles were analyzed by XPS using an etching method.

[0379] When the inorganic particles were silica particles, carbon, nitrogen, oxygen, iron, manganese, and silicon were analyzed.

[0380] When the inorganic particles were alumina particles, carbon, nitrogen, oxygen, iron, manganese, and aluminum were analyzed.

[0381] When the organic particles were titanium dioxide particles, carbon, nitrogen, oxygen, iron, manganese, and titanium were analyzed.

[0382] The element ratio (atm%) of the metal and semimetal constituting the inorganic particles in the total element amount of all elements analyzed was determined: the element ratio at 0 seconds of etching was A (atm%), and the element ratio at 300 seconds of etching was B (atm%).

[0383] XPS was performed using the following equipment and conditions. Analysis was performed after baseline correction.

[0384] XPS device: PHI5000 Versa Probe II (ULVAC-PHI, INC.)

[0385] X-ray source: monochromated AlKα rays

[0386] Beam voltage: 15kV

[0387] Emission current: 3mA

[0388] Etching gun: Argon cluster ion gun

[0389] Vacuum degree: 1×10 -5 Pa~1×10 -6 Pa

[0390] Pass Energy: 23.5eV

[0391] Scanning area: 300μm×300μm

[0392] Time Per Step: 50 seconds

[0393] Cycle: 5 times

[0394] Sweep: 10 times

[0395] [Evaluation of image density stability]

[0396] The evaluation of each developer was performed using a modified version of the image forming device Apeos C4030 (FUJIFILM Business Innovation). Using A4-sized plain paper, in an environment with a temperature of 10°C and a relative humidity of 15%, one image with an image density of 100% was output, followed by 10,000 images with an image density of 0.5%, and then one image with an image density of 100%. The image density of the first image with an image density of 100% and the image with an image density of 100% after 10,000 images were output was measured using a spectrocolorimeter X-Rite 938 (X-Rite). The image density difference Δ was calculated and classified as follows. For example, the smaller the image density difference Δ, the more preferred. The evaluation results are shown in Table 2.

[0397] A: 0.00 or more and less than 0.05

[0398] B+: 0.05 or higher and less than 0.07

[0399] B: 0.07 or more and less than 0.10

[0400] C: 0.10 or more and less than 0.15

[0401] D: 0.15 or more and less than 0.20

[0402] E: 0.20 or more

[0403] [Table 1]

[0404]

[0405] [Table 2]

[0406]

[0407] As shown in Table 2, the carriers and developers of Examples 1 to 40 were superior to the carriers and developers of Comparative Examples 1 to 5 in image density stability.

[0408] The electrostatic image developing carrier, electrostatic image developer, process cartridge, image forming apparatus, and image forming method of the present invention include the following aspects.

[0409] (Note)

[0410] (1) A carrier for electrostatic image development, comprising magnetic particles and a resin coating layer coating the magnetic particles, wherein:

[0411] The resin coating layer contains inorganic particles,

[0412] The element ratio of metals and semi-metals constituting the inorganic particles was analyzed along the depth direction by X-ray photoelectron spectroscopy. When the element ratio at 0 seconds of etching was set to A and the element ratio at 300 seconds of etching was set to B, the value of BA was greater than 0.5 atm% and less than 3.0 atm%.

[0413] (2) The electrostatic image developing carrier according to (1), wherein the inorganic particles are at least one selected from the group consisting of silica particles, titania particles, and alumina particles.

[0414] (3) The electrostatic image developing carrier according to (1) or (2), wherein the inorganic particles are silica particles.

[0415] (4) The electrostatic image developing carrier according to any one of (1) to (3), wherein the inorganic particles are surface-treated inorganic particles.

[0416] (5) The electrostatic image developing carrier according to any one of (1) to (3), wherein the inorganic particles are inorganic particles whose surfaces have been subjected to a hydrophobic treatment.

[0417] (6) The electrostatic image developing carrier according to any one of (1) to (5), wherein the content of the inorganic particles in the resin coating layer is 15% by mass or more and 35% by mass or less relative to the total mass of the resin coating layer.

[0418] (7) The electrostatic image developing carrier according to any one of (1) to (6), wherein the value of B is 3.5 atm % or more and 12.0 atm % or less.

[0419] (8) The electrostatic image developing carrier according to any one of (1) to (7), wherein the value of A is 2.0 atm % or more and 10.0 atm % or less.

[0420] (9) The electrostatic image developing carrier according to any one of (1) to (8), wherein the value of BA is 1.2 atm % or more and 2.3 atm % or less.

[0421] (10) The electrostatic image developing carrier according to any one of (1) to (9), wherein the resin coating layer further contains resin particles, and the ratio D1 / D2 of the average primary particle size D1 of the inorganic particles contained in the resin coating layer to the average primary particle size D2 of the resin particles is greater than or equal to 0.01 and less than or equal to 0.15.

[0422] (11) The electrostatic image developing carrier according to any one of (1) to (10), wherein the resin coating layer further contains resin particles, and the average primary particle size D2 of the resin particles contained in the resin coating layer is 100 nm or more and 400 nm or less.

[0423] (12) An electrostatic image developer comprising the electrostatic image developing carrier according to any one of (1) to (11) and a toner.

[0424] (13) A process cartridge comprising a developing device that accommodates the electrostatic image developer described in (12) and develops an electrostatic image formed on a surface of an image holding member into a toner image using the electrostatic image developer,

[0425] The process cartridge is attachable to and detachable from the image forming apparatus.

[0426] (14) An image forming apparatus comprising:

[0427] Image holding body;

[0428] a charging device for charging the surface of the image holding member; and an electrostatic image forming device for forming an electrostatic image on the charged surface of the image holding member.

[0429] a developing device that accommodates the electrostatic image developer described in (12) and develops the electrostatic image formed on the surface of the image holding member into a toner image by the electrostatic image developer;

[0430] a transfer device that transfers the toner image formed on the surface of the image holding member to the surface of a recording medium; and

[0431] The fixing device fixes the toner image transferred onto the surface of the recording medium.

[0432] (15) An image forming method comprising:

[0433] a charging process for charging the surface of the image holding member;

[0434] an electrostatic image forming step of forming an electrostatic image on the charged surface of the image holding member;

[0435] a developing step of developing the electrostatic image formed on the surface of the image holding member into a toner image using the electrostatic image developer described in (12);

[0436] a transfer step of transferring the toner image formed on the surface of the image holding member to the surface of a recording medium; and

[0437] The fixing step fixes the toner image transferred onto the surface of the recording medium.

[0438] According to (1) or (2), there is provided a carrier for developing an electrostatic image, wherein the carrier has excellent image density stability in the obtained image compared to a case where the BA value is less than 0.5 atm % or exceeds 3.0 atm %.

[0439] According to (3), there is provided a carrier for electrostatic image development, wherein the obtained image has better image density stability than when the inorganic particles are titanium dioxide particles or aluminum oxide particles.

[0440] According to (4) or (5), there is provided a carrier for electrostatic image development, wherein the obtained image has better image density stability than when the inorganic particles are inorganic particles that have not been surface-treated.

[0441] According to (6), there is provided a carrier for electrostatic image development, which has a better image density stability in the obtained image than when the content of the inorganic particles in the resin coating layer is less than 15% by mass or more than 35% by mass relative to the total mass of the resin coating layer.

[0442] According to (7), there is provided a carrier for developing an electrostatic image, wherein the obtained image has a more excellent image density stability than when the value of B is less than 3.5 atm % or exceeds 12.0 atm %.

[0443] According to (8), there is provided a carrier for developing an electrostatic image, wherein the obtained image has a more excellent image density stability than when the value of A is less than 2.0 atm % or exceeds 10.0 atm %.

[0444] According to (9), there is provided a carrier for developing an electrostatic image, wherein the carrier has an image density stability that is more excellent in the obtained image than when the value of BA is less than 1.2 atm % or exceeds 2.3 atm %.

[0445] According to (10), a carrier for electrostatic image development is provided, which has better image density stability in the obtained image than when the ratio D1 / D2 of the average primary particle size D1 of the inorganic particles contained in the resin coating layer to the average primary particle size D2 of the resin particles is less than 0.01 or exceeds 0.15.

[0446] According to (11), there is provided a carrier for electrostatic image development, which has a more excellent image density stability in the obtained image than when the average primary particle size D2 of the resin particles contained in the resin coating layer is less than 100 nm or exceeds 400 nm.

[0447] According to (12), there is provided an electrostatic image developer having excellent image density stability in an obtained image compared to a case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %.

[0448] According to (13), there is provided a process cartridge in which the image density stability of an obtained image is excellent compared with the case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %.

[0449] According to (14), there is provided an image forming apparatus which obtains an image having excellent image density stability compared to a case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %.

[0450] According to (15), there is provided an image forming method in which the image density stability of the obtained image is excellent compared with the case where the BA value of the electrostatic image developing carrier is less than 0.5 atm % or exceeds 3.0 atm %.

[0451] The above-described embodiments of the present invention are provided for the purpose of illustration and explanation. In addition, the embodiments of the present invention do not fully and exhaustively include the present invention, and do not limit the present invention to the disclosed embodiments. It is obvious that various modifications and variations are self-evident to those skilled in the art to which the present invention belongs. The present embodiment is selected and described in order to most easily explain the principles of the present invention and its application. Thus, other technical personnel in this field can understand the present invention through various modifications optimized for specific uses of the assumed various embodiments. The scope of the present invention is defined by the above claims and their equivalents.

Claims

1. A carrier for electrostatic image development, comprising magnetic particles and a resin coating layer coating the magnetic particles, wherein: The resin coating layer contains inorganic particles, The element ratio of metals and semi-metals constituting the inorganic particles was analyzed along the depth direction by X-ray photoelectron spectroscopy. When the element ratio at 0 seconds of etching was set to A and the element ratio at 300 seconds of etching was set to B, the value of BA was greater than 0.5 atm% and less than 3.0 atm%.

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

3. The electrostatic image developing carrier according to claim 1 or 2, wherein The inorganic particles are silicon dioxide particles.

4. The electrostatic image developing carrier according to any one of claims 1 to 3, wherein The inorganic particles are surface-treated inorganic particles.

5. The electrostatic image developing carrier according to any one of claims 1 to 3, wherein The inorganic particles are inorganic particles whose surfaces have been hydrophobized.

6. The electrostatic image developing carrier according to any one of claims 1 to 5, wherein The content of the inorganic particles in the resin coating layer is 15% by mass or more and 35% by mass or less relative to the total mass of the resin coating layer.

7. The electrostatic image developing carrier according to any one of claims 1 to 6, wherein The value of B is 3.5 atm % or more and 12.0 atm % or less.

8. The electrostatic image developing carrier according to any one of claims 1 to 7, wherein The value of A is 2.0 atm % or more and 10.0 atm % or less.

9. The electrostatic image developing carrier according to any one of claims 1 to 8, wherein The BA value is 1.2 atm % or more and 2.3 atm % or less.

10. The electrostatic image developing carrier according to any one of claims 1 to 9, wherein The resin coating layer further contains resin particles, The value of 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 0.01 or more and 0.15 or less.

11. The electrostatic image developing carrier according to any one of claims 1 to 10, wherein The resin coating layer further includes resin particles, and the average primary particle size D2 of the resin particles included in the resin coating layer is 100 nm or more and 400 nm or less. 12 . An electrostatic image developer comprising the electrostatic image developing carrier according to claim 1 and a toner.

13. A process cartridge comprising a developing device, the developing device housing the electrostatic image developer according to claim 12 and developing an electrostatic image formed on a surface of an image holding member into a toner image using the electrostatic image developer, The process cartridge is attachable to and detachable from the image forming apparatus.

14. An image forming apparatus comprising: Image holding body; a charging device for charging the surface of the image holding member; an electrostatic image forming device for forming an electrostatic image on the charged surface of the image holding member; a developing device that accommodates the electrostatic image developer according to claim 12 and develops the electrostatic image formed on the surface of the image holding member into a toner image using the electrostatic image developer; a transfer device for transferring the toner image formed on the surface of the image holding member to the surface of a recording medium; and The fixing device fixes the toner image transferred onto the surface of the recording medium.

15. An image forming method comprising: a charging process for charging the surface of the image holding member; an electrostatic image forming step of forming an electrostatic image on the charged surface of the image holding member; a developing step of developing the electrostatic image formed on the surface of the image holding member into a toner image using the electrostatic image developer according to claim 12; a transfer step of transferring the toner image formed on the surface of the image holding member to the surface of a recording medium; and The fixing step fixes the toner image transferred onto the surface of the recording medium.

Images