Electrostatic image developing carrier, electrostatic image developer, and image forming apparatus

Abstract

The present invention relates to a carrier for electrostatic image development, an electrostatic image developer, and an image forming apparatus. The carrier for electrostatic image development of the present invention has magnetic particles, and a resin layer that coats the magnetic particles and contains inorganic particles, the average particle diameter of the inorganic particles is 5 nm or more and 90 nm or less, the average thickness of the resin layer is 0.6 µm or more and 1.4 µm or less, and when a surface of the carrier for electrostatic image development is subjected to three-dimensional analysis, an area ratio B / A of an overhead area A of the carrier for electrostatic image development to a surface area B of the carrier for electrostatic image development is 1.020 or more and 1.100 or less.

Description

Technical Field

[0001] This invention relates to a carrier for electrostatic image development, an electrostatic image developer, and an image forming apparatus. Background Technology

[0002] Patent Document 1 discloses a carrier for an electrostatic latent image developer, which contains magnetic core particles and a coating layer covering the surface of the core particles. The coating layer contains two or more inorganic microparticles, at least one of which is an inorganic microparticle A that is conductive and has a peak particle size of 300 nm to 1000 nm. The ratio of the BET specific surface area of ​​the carrier to the BET specific surface area of ​​the core particles is 1.10 μm. 2 / g~1.90m 2 / g.

[0003] Patent Document 2 discloses a carrier for electrostatic latent image development, which is an electrostatic image developer carrier having a coating layer containing an adhesive resin and microparticles on a core material. The area ratio of the portion of the core material exposed on the surface of the carrier particles is 0.1% to 5.0%, the area of ​​the largest exposed portion of the core material is 0.03% or less of the surface area of ​​the core material, and the carrier contains 100 to 500 parts by weight of microparticles relative to 100 parts by weight of the adhesive resin.

[0004] Patent document 3 discloses a carrier for electrophotography, which is a carrier having a coated film containing an adhesive resin and particles, wherein the inherent resistance of the particles is 10 ohms. 12 Ω·cm or higher, particle size D and adhesive resin film thickness h are 1 <D / h<5。

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-066892

[0008] Patent Document 2: Japanese Patent Application Publication No. 2013-061511

[0009] Patent Document 3: Japanese Patent Application Publication No. 2001-188388 Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] The technical problem to be solved by the present invention is to provide a carrier for electrostatic image development that, compared with the following carriers for electrostatic image development, can suppress the blowing out of toners. The electrostatic image development carrier compared with the present invention has magnetic particles and a resin layer coated with the magnetic particles and containing inorganic particles, wherein the average particle size of the inorganic particles is less than 5 nm or greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A of the top view area A to the surface area B when performing three-dimensional analysis of the surface is less than 1.020 or greater than 1.100.

[0012] Methods for solving problems

[0013] The means used to solve the above-mentioned technical problems include the following methods.

[0014] <1> An electrostatic image developing carrier has magnetic particles and a resin layer coated with the magnetic particles and containing inorganic particles. The average particle size of the inorganic particles is 5 nm or more and 90 nm or less, and the average thickness of the resin layer is 0.6 μm or more and 1.4 μm or less. When performing three-dimensional analysis on the surface of the electrostatic image developing carrier, the area ratio B / A of the top view area A of the electrostatic image developing carrier to the surface area B of the electrostatic image developing carrier is 1.020 or more and 1.100 or less.

[0015] <2> like <1> The aforementioned carrier for electrostatic image development, wherein the area ratio B / A is 1.040 or more and 1.080 or less.

[0016] <3> like <1> The carrier for electrostatic image development, wherein the average particle size of the inorganic particles is 5 nm or more and 70 nm or less.

[0017] <4> like <1> The carrier for electrostatic image development, wherein the average thickness of the resin layer is 0.8 μm or more and 1.2 μm or less.

[0018] <5> like <1> The aforementioned carrier for electrostatic image development, wherein the inorganic particles are silicon dioxide particles, and the silicon concentration on the surface of the carrier for electrostatic image development, as determined by X-ray photoelectron spectroscopy, is greater than 2 atomic% and less than 20 atomic%.

[0019] <6> like <5> The carrier for electrostatic image development, wherein the silicon concentration is greater than 5 atomic% and less than 20 atomic%.

[0020] <7> An electrostatic image developer comprising <1> The carrier for electrostatic image development and the toner for electrostatic image development are described above.

[0021] <8> like <7> The electrostatic image developer, wherein the electrostatic image developing toner comprises: toner particles containing inorganic pigments containing metal atoms; and an additive adhering to the surface of the toner particles.

[0022] The area ratio B / A is above 1.020 and below 1.110.

[0023] <9> like <8> The electrostatic image developer wherein the average particle size of the inorganic pigment is 150 nm or more and 500 nm or less.

[0024] <10> like <8> The electrostatic image developer wherein the area ratio of the protrusions originating from the inorganic pigment on the surface of the toner particles is 0.30% to 5.00%.

[0025] <11> like <8> The electrostatic image developer wherein the average height of the protrusions originating from the inorganic pigment on the surface of the toner particles is 0.05 μm or more and 0.30 μm or less.

[0026] <12> like <7> The electrostatic image developer, wherein the electrostatic image developer has toner particles comprising crystalline resin, and an additive is attached to the surface of the toner particles.

[0027] <13> like <12> The electrostatic image developer wherein the melting point of the crystalline resin is above 65°C and below 90°C.

[0028] <14> like <12> The electrostatic image developer wherein the content of the crystalline resin is 5% by mass or more and 30% by mass or less relative to the total toner particles.

[0029] <15> like <12> The electrostatic image developer, wherein the toning agent has a half-fall temperature of 90°C to 140°C as determined by a flow tester.

[0030] <16> An image forming apparatus comprising:

[0031] Image holding volume;

[0032] A charging mechanism that charges the surface of the image holder;

[0033] An electrostatic image forming mechanism that forms an electrostatic image on the surface of the charged image holder;

[0034] The developing facility utilizes <7> The electrostatic image developer develops the electrostatic image into a toner image;

[0035] A transfer mechanism that transfers the aforementioned toner image onto the surface of a recording medium; and

[0036] A fixing unit fixes the toner image transferred to the surface of the recording medium.

[0037] Invention Effects

[0038] according to <1> The proposed solution provides a carrier for electrostatic image development that can suppress the blowing out of toner compared to cases where the average particle size of inorganic particles is less than 5 nm or greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A of the top view area A to the surface area B when performing three-dimensional analysis of the surface is less than 1.020 or greater than 1.100.

[0039] according to <2> The proposed solution provides a carrier for electrostatic image development that can suppress the blowing out of toner compared to cases where the area ratio B / A is less than 1.040 or greater than 1.080.

[0040] according to <3> The proposed solution provides a carrier for electrostatic image development that can suppress the blowing out of toners compared to cases where the average particle size of inorganic particles is less than 5 nm or greater than 70 nm.

[0041] according to <4> The proposed solution provides a carrier for electrostatic image development that can suppress the blowing out of toner compared to cases where the average thickness of the resin layer is less than 0.8 μm or greater than 1.2 μm.

[0042] according to <5> The proposed solution provides a carrier for electrostatic image development that, compared to cases where the inorganic particles are silica particles and the silicon element concentration on the surface of the carrier for electrostatic image development is less than 2 atomic% or more than 20 atomic%, can suppress the reduction of toner image transferability.

[0043] according to <6> The proposed solution provides a carrier for electrostatic image development that, compared to cases where the inorganic particles are silica particles and the silicon element concentration on the surface of the carrier for electrostatic image development is less than 5 atomic% or more than 20 atomic%, can suppress the reduction of toner image transferability.

[0044] according to <7> The proposed solution provides an electrostatic image developer that, compared to cases where the average particle size of inorganic particles in an electrostatic image developing carrier is less than 5 nm or greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A of the top view area A to the surface area B during three-dimensional analysis of the surface is less than 1.020 or greater than 1.100, can suppress the blowing out of toner.

[0045] according to <8> The proposed solution provides an electrostatic image developer that, compared to cases where the average particle size of the inorganic particles contained in the resin layer carrying the toner particles is greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A is less than 1.020 or greater than 1.110, can suppress the generation of color streaks in images formed after continuous output of low image density images or after long-term storage of the toner in a high temperature and high humidity environment.

[0046] according to <9> The proposed solution provides an electrostatic image developer that, compared to cases where the average particle size of the inorganic pigments containing metals is 150 nm to 500 nm, but the average particle size of the inorganic particles contained in the resin layer of the carrier is greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A is less than 1.020 or greater than 1.110, can suppress the generation of color stripes in images formed after continuous output of low image density images or after long-term storage of the toner in a high temperature and high humidity environment.

[0047] according to <10> The proposed solution provides an electrostatic image developer that, compared to cases where the area ratio of the protrusions on the surface of the toner particles is 0.30% to 5.00%, but the average particle size of the inorganic particles contained in the resin layer of the carrier is greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A is less than 1.020 or greater than 1.110, can suppress the generation of color stripes in images formed after continuous output of low image density images or after long-term storage of the toner in a high temperature and high humidity environment.

[0048] according to <11> The proposed solution provides an electrostatic image developer that, compared to cases where the average height of the protrusions on the surface of the toner particles is 0.05 μm to 0.30 μm, but the average particle size of the inorganic particles contained in the resin layer of the carrier is greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A is less than 1.020 or greater than 1.110, can suppress the generation of color stripes in images formed after continuous output of low image density images or after long-term storage of the toner in a high temperature and high humidity environment.

[0049] according to <12> The proposed solution provides an electrostatic image developer that, compared to cases where the toner particles contain crystalline resin and the resin layer of the carrier contains inorganic particles with an average particle size greater than 90 nm, or an average thickness of the resin layer less than 0.6 μm or greater than 1.4 μm, or an area ratio B / A less than 1.020 or greater than 1.100, can suppress uneven gloss in images.

[0050] according to <13> The proposed solution provides an electrostatic image developer that, compared to cases where the melting point of the crystalline resin is above 65°C and below 90°C, but the average particle size of the inorganic particles contained in the resin layer of the carrier is greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A is less than 1.020 or greater than 1.100, can suppress uneven gloss in images.

[0051] according to <14> The proposed solution provides an electrostatic image developer that, compared to cases where the content of crystalline resin is 5% to 30% by mass, but the average particle size of the inorganic particles contained in the resin layer of the carrier is greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A is less than 1.020 or greater than 1.100, can suppress uneven gloss in images.

[0052] according to <15> The proposed solution provides an electrostatic image developer that, compared to cases where the half-fall temperature of the toner measured using a flow tester is above 90°C and below 140°C, but the average particle size of the inorganic particles contained in the resin layer of the carrier is greater than 90 nm, or the average thickness of the resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A is less than 1.020 or greater than 1.100, can suppress uneven gloss in the image.

[0053] according to <16> The proposed solution provides an image forming apparatus that, compared to cases where the average particle size of inorganic particles in a carrier for electrostatic image development is less than 5 nm or greater than 90 nm, or the average thickness of a resin layer is less than 0.6 μm or greater than 1.4 μm, or the area ratio B / A of the top view area A to the surface area B during three-dimensional analysis of the surface is less than 1.020 or greater than 1.100, can suppress the blowing out of toner. Attached Figure Description

[0054] Figure 1 This is a schematic configuration diagram showing an example of the image forming apparatus of this embodiment.

[0055] Figure 2 This is a schematic configuration diagram showing an example of a processing box that is mounted and dismounted in an image forming apparatus according to this embodiment. Detailed Implementation

[0056] The embodiments of the present invention will now be described. These descriptions and examples are for illustrative purposes only and do not limit the scope of the embodiments.

[0057] In this invention, the numerical range represented by “~” indicates the range of values ​​recorded before and after “~” as the minimum and maximum values, respectively.

[0058] In this invention, the upper or lower limit of a numerical range recorded in stages can be replaced with the upper or lower limit of other numerical ranges recorded in different stages. Furthermore, the upper or lower limit of a numerical range recorded in this invention can be replaced with the values ​​shown in the embodiments.

[0059] The term "step" in this invention includes not only independent steps, but also steps that can be clearly distinguished from other steps, as long as the desired purpose of the step can be achieved.

[0060] In this invention, while embodiments are described with reference to the accompanying drawings, the configuration of these embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are schematic, and the relative sizes of the components are not limited thereto.

[0061] Each component in this invention may contain two or more corresponding substances. When referring to the amount of each component in the composition of this invention, if there are two or more substances corresponding to each component in the composition, it refers to the total amount of the two or more substances present in the composition unless otherwise stated.

[0062] The particles corresponding to each component in this invention may comprise two or more types. In the case where two or more particles corresponding to each component are present in the composition, unless otherwise stated, the particle size of each component refers to the value for a mixture of the two or more particles present in the composition.

[0063] In this invention, "(meth)acrylic acid" refers to at least one of acrylic acid and methacrylic acid, and "(meth)acrylate" refers to at least one of acrylate and methacrylate.

[0064] In this invention, "electrostatic image developing toner" is also referred to as "toner", "electrostatic image developing carrier" is also referred to as "carrier", and "electrostatic image developing agent" is also referred to as "developer".

[0065] <Carrier for Electrostatic Image Development>

[0066] The carrier in this embodiment is a resin-coated carrier, which has magnetic particles and a resin layer that coats the magnetic particles and contains inorganic particles.

[0067] Furthermore, in the carrier of this embodiment, the average particle size of the inorganic particles contained in the resin layer is 5 nm or more and 90 nm or less, the average thickness of the resin layer is 0.6 μm or more and 1.4 μm or less, and the area ratio B / A of the top view area A to the surface area B when performing three-dimensional analysis of the surface is 1.020 or more and 1.100 or less.

[0068] In this embodiment, carbon black is not considered as inorganic particles.

[0069] In this embodiment, the average particle size of the inorganic particles contained in the resin layer and the average thickness of the resin layer are determined by the following method.

[0070] The carrier was embedded in epoxy resin and cut using a microtome to create a cross-section. The cross-section was then photographed using a scanning electron microscope (SEM), and the resulting SEM images were imported into an image processing and analysis device for analysis. One hundred inorganic particles (primary particles) were randomly selected from the resin layers, and their equivalent circular diameters (nm) were calculated and averaged. This average value was taken as the average particle size (nm) of the inorganic particles. Furthermore, for each carrier particle, ten points were randomly selected to measure the resin layer thickness (μm). This measurement was performed on all 100 carriers, and the arithmetic mean of all measurements was taken as the average resin layer thickness (μm).

[0071] In this embodiment, the area ratio B / A is an indicator for evaluating surface roughness. As an example, the area ratio B / A is calculated using the following method.

[0072] As a device for three-dimensional analysis of the carrier surface, a scanning electron microscope (e.g., Elionix ERA-8900FE, Electron X-ray 3D Roughness Analysis System) with four secondary electron detectors was used for the following analysis. The surface of one carrier particle was magnified 5000 times. With a measurement point interval of 0.06 μm, 400 measurement points were taken longitudinally and 300 measurement points were taken transversely, measuring a 24 μm × 18 μm area to obtain 3D image data.

[0073] For 3D image data, the limiting wavelength of the spline filter (a frequency-selective filter using spline functions) is set to 12μm to remove wavelengths with a period greater than 12μm, thereby removing the undulation component of the carrier surface, extracting the roughness component, and obtaining the roughness curve.

[0074] The sampling length of the Gaussian high-pass filter (a frequency-selective filter using a Gaussian function) was further set to 2.0 μm to remove wavelengths with a period greater than 2.0 μm. This removed wavelengths equivalent to the protrusions of the magnetic particles exposed on the carrier surface from the roughness curve after processing by the spline filter, resulting in a roughness curve with wavelength components with a period greater than 2.0 μm removed.

[0075] Based on the 3D roughness curve data after filter processing, the central 12μm×12μm region (top-view area A=144μm) was determined.2 ) surface area B (μm) 2 ), calculate the area ratio B / A. For each of the 100 carriers, calculate the area ratio B / A and then take the arithmetic mean.

[0076] The carrier in this embodiment can suppress the extrusion of the colorant. The mechanism is presumably as follows.

[0077] When the toner is continuously stirred within the developing unit, toner aggregation occurs, resulting in an apparent increase in toner particle size. This causes electrical fluctuations, and toner may be blown out of the developing unit. This phenomenon is prone to occur when images with relatively low image density are continuously formed on a small area of ​​recording medium, followed by the formation of images with higher image density.

[0078] In contrast, for carriers with average particle size of inorganic particles in the resin layer, average thickness of the resin layer, and area ratio B / A within the above ranges, it is speculated that, based on the reasons stated in (a) to (c) below, toner aggregation is less likely to occur in the developing unit, thereby suppressing toner blowout.

[0079] (a) When the average particle size of the inorganic particles in the resin layer is less than 5 nm, it is difficult to obtain a filler effect that enhances the strength of the resin layer, and the resin layer is prone to peeling during repeated image formation. When the average particle size of the inorganic particles in the resin layer is greater than 90 nm, the inorganic particles are prone to detach from the protrusions of the resin layer, and the resin layer is prone to peeling during repeated image formation. It is speculated that in either of the above cases, the exposed area of ​​the magnetic particles on the carrier surface increases, the mechanical stress applied to the toner increases, the toner additives are embedded in the toner particles, and the toner agglomerates.

[0080] Based on the above, the average particle size of the inorganic particles in the resin layer is 5 nm to 90 nm, preferably 5 nm to 70 nm, more preferably 5 nm to 50 nm, and even more preferably 8 nm to 50 nm.

[0081] The average particle size of the inorganic particles contained in the resin layer can be controlled by the size of the inorganic particles used in the formation of the resin layer.

[0082] (b) It is speculated that when the average thickness of the resin layer is less than 0.6 μm, the resin layer is prone to peeling during repeated image formation, increasing the exposed area of ​​magnetic particles on the carrier surface, enhancing the mechanical stress applied to the toner, and causing the toner additives to become embedded in the toner particles, leading to toner aggregation. It is speculated that when the average thickness of the resin layer is greater than 1.4 μm, the toner additives are more likely to adhere to or become embedded in the resin layer after migrating to it, increasing the amount of additives migrating from the toner to the carrier, and causing toner aggregation.

[0083] Based on the above, the average thickness of the resin layer is preferably 0.6 μm or more and 1.4 μm or less, more preferably 0.8 μm or more and 1.2 μm or less, and even more preferably 0.8 μm or more and 1.1 μm or less.

[0084] The average thickness of the resin layer can be controlled by the amount of resin used in the formation of the resin layer. The more resin there is relative to the amount of magnetic particles, the thicker the average thickness of the resin layer.

[0085] (c) It is speculated that if the area ratio B / A is less than 1.020, the carrier surface is too flat, the contact between the carrier and the colorant is surface contact, the mechanical stress applied to the colorant is increased, the colorant additives are embedded in the colorant particles, and the colorant agglomerates. It is speculated that if the area ratio B / A is greater than 1.100, the number of uneven surfaces on the carrier is relatively large, or the height difference of the uneven surfaces on the carrier is relatively large. Therefore, more colorant additives enter the concave parts of the carrier surface, the migration of additives from the colorant to the carrier increases, and the colorant agglomerates.

[0086] Based on the above, the area ratio B / A is 1.020 to 1.100, preferably 1.040 to 1.080, and more preferably 1.040 to 1.070.

[0087] The area ratio B / A can be controlled by the manufacturing conditions that form the resin layer. Details are described below.

[0088] In this embodiment, the carrier has an area ratio (B / A) of 1.020 to 1.100, which helps to suppress the tendency for toner image transferability to decrease during repeated image formation over a long period. The carrier of this embodiment contains inorganic particles in the resin layer, and its surface has moderately fine irregularities. It is presumed that these irregularities are a structure where most of the resin covers the surface, but a portion of the inorganic particles are exposed. Unlike the resin, the exposed inorganic particles do not become charged when in contact with the toner, thus suppressing excessive charging of the carrier surface. Furthermore, when the resin layer of the carrier wears down during repeated image formation, these irregularities selectively wear down, and a portion of the inorganic particles in the resin layer are re-exposed. It is speculated that because a portion of the inorganic particles remains moderately and continuously exposed on the carrier surface, the surface charge of the carrier decreases, and the increase in toner charge is suppressed, resulting in good maintenance of toner image transferability. This phenomenon is significant when repeated image formation is performed on embossed paper under low temperature and low humidity conditions (e.g., temperature 10°C and relative humidity 15%).

[0089] In this embodiment, from the perspective of suppressing the decrease in toner image transferability during long-term repeated image formation, it is preferable that the resin layer contains silica particles and the silicon element concentration on the carrier surface, as determined by X-ray photoelectron spectroscopy, is greater than 2 atomic% and less than 20 atomic%.

[0090] A silicon concentration greater than 2 atomic% means that silicon dioxide particles are appropriately distributed on the surface of the resin layer, thus appropriately reducing the charge on the carrier surface.

[0091] A silicon concentration of less than 20 atomic% means that the amount of silica particles distributed on the surface of the resin layer will not be excessive, so the charge on the carrier surface will not be excessively reduced.

[0092] Based on the above, the silicon concentration is more preferably greater than 5 atomic% and less than 20 atomic%, and even more preferably greater than 6 atomic% and less than 19 atomic%.

[0093] The silicon concentration on the carrier surface can be controlled by the amount of silica particles used in the resin layer formation. The more silica particles there are relative to the amount of resin, the higher the silicon concentration on the carrier surface.

[0094] In the carrier of this embodiment, from the perspective of suppressing the decrease in image density during repeated image formation, the average thickness of the resin layer is preferably 0.6 μm or more and 1.4 μm or less. When the average thickness of the resin layer is 0.6 μm or more, the resin layer is less likely to peel off during repeated image formation, thus ensuring the exposed area ratio of magnetic particles. When the average thickness of the resin layer is 1.4 μm or less, fine irregularities are easily formed on the carrier surface due to inorganic particles in the resin layer, making it easier to control the area ratio B / A within the above-mentioned range.

[0095] Based on the above, the average thickness of the resin layer is more preferably 0.8 μm or more and 1.2 μm or less, and even more preferably 0.8 μm or more and 1.1 μm or less.

[0096] The average thickness of the resin layer can be controlled by the amount of resin used in the formation of the resin layer. The more resin there is relative to the amount of magnetic particles, the thicker the average thickness of the resin layer.

[0097] The carrier configuration of this embodiment will be described in detail below.

[0098] [Magnetic particles]

[0099] The magnetic particles are not particularly limited, and any known magnetic particles used as a core material for a carrier 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 formed by impregnating porous magnetic powder with resin; and magnetic powder-dispersed resin particles formed by dispersing and mixing magnetic powder in resin; etc. Ferrite particles are preferred as the magnetic particles in this embodiment.

[0100] The volume average particle size of the magnetic particles is preferably 15 μm to 100 μm, more preferably 20 μm to 80 μm, and even more preferably 30 μm to 60 μm.

[0101] The volume average particle size here refers to the particle size D accumulated at the 50% point from the smallest diameter side in the volume-based particle size distribution. 50v .

[0102] The arithmetic mean height Ra of the roughness curve of the magnetic particles, as measured according to JIS B0601:2001, is preferably 0.1 μm or more and 1 μm or less, more preferably 0.2 μm or more and 0.8 μm or less.

[0103] The arithmetic mean height Ra of the roughness curves of magnetic particles was obtained by observing the magnetic particles at an appropriate magnification (e.g., 1000x) using a surface shape measuring device (e.g., KEYENCE VK-9700 Ultra-Deep Color 3D Shape Measuring Microscope). A roughness curve was obtained with a sampling length of 0.08 mm. A reference length of 10 μm was extracted from the roughness curve along its mean line to calculate the height Ra. The Ra values ​​of 100 magnetic particles were then arithmetically averaged.

[0104] Regarding the magnetic force of the magnetic particles, the saturation magnetization in a magnetic field of 3000 Oersted is preferably 50 emu / g or more, more preferably 60 emu / g or more. The above-mentioned saturation magnetization is measured using a vibrating sample type magnetic force measuring apparatus VSMP10-15 (manufactured by Toei Kogyo Co., Ltd.). The test sample is placed in a cell with an inner diameter of 7 mm and a height of 5 mm and placed in the apparatus. During measurement, an external magnetic field is applied and scanned up to a maximum of 3000 Oersted. Then, the external magnetic field is reduced, and a hysteresis curve is plotted on recording paper. The saturation magnetization, residual magnetization, and holding force are determined based on the data from the curve.

[0105] The volume resistivity of the magnetic particles is preferably 1×10⁻⁶. 5 1×10 Ω·cm or above 9 Ω·cm or less, more preferably 1×10 7 1×10 Ω·cm or above 9 Below Ω·cm.

[0106] The volume resistivity (Ω·cm) of the magnetic particles was measured as follows. The object to be measured was placed flat on a surface with a thickness of 1 mm to 3 mm, within a 20 cm² support. 2 A layer is formed on the surface of the circular clamp for the electrode plate. The aforementioned 20cm [electrode plate] is then placed on it. 2 Electrode plates are used to sandwich the layers. To ensure there are no gaps between the objects being measured, a 4 kg load is applied to the electrode plates positioned on the layers, and then the layer thickness (cm) is measured. The upper and lower electrodes of the layer are connected to an electrometer and a high-voltage power supply. A high voltage of 103.8 V / cm is applied to the two electrodes, and the current flowing through them (A) is recorded. The measurement environment is assumed to be 20℃ and 50% relative humidity. The formula for calculating the volume resistivity (Ω·cm) of the object being measured is shown below.

[0107] R = E × 20 / (I - I0) / L

[0108] In the above formula, R represents the volume resistivity of the object being measured (Ω·cm), E represents the applied voltage (V), I represents the current value (A), I0 represents the current value when the applied voltage is 0V (A), and L represents the thickness of the layer (cm). The coefficient 20 represents the area of ​​the electrode plate (cm²). 2 ).

[0109] [Resin Layer]

[0110] Examples of resins constituting the resin layer include: styrene-acrylic acid copolymers; polyolefin resins such as polyethylene and polypropylene; polyvinyl or polyvinylene 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; pure organosilicon resins or their modifications containing organosiloxane bonds; fluoropolymers such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyesters; polyurethanes; polycarbonates; amino resins such as urea-formaldehyde resins; epoxy resins; and so on.

[0111] The resin layer preferably contains an acrylic resin with an alicyclic structure. As the polymerizing component of the acrylic resin with an alicyclic structure, lower alkyl esters of (meth)acrylic acid (e.g., alkyl esters of (meth)acrylic acid with 1 to 9 carbon atoms in the alkyl group) are preferred. Specifically, examples include methyl (meth)acrylic acid, ethyl (meth)acrylic acid, propyl (meth)acrylic acid, butyl (meth)acrylic acid, hexyl (meth)acrylic acid, cyclohexyl (meth)acrylic acid, and 2-ethylhexyl (meth)acrylic acid. One or more of these monomers may be used.

[0112] Acrylic resins with an alicyclic structure preferably contain cyclohexyl (meth)acrylate as a polymerization component. The content of monomer units derived from cyclohexyl (meth)acrylate in the alicyclic acrylic resin is preferably 75% by mass or more and 100% by mass or less, more preferably 85% by mass or more and 100% by mass or less, and even more preferably 95% by mass or more and 100% by mass or less, relative to the total mass of the alicyclic acrylic resin.

[0113] Examples of inorganic particles included in the resin layer include metal oxide particles such as silica, titanium dioxide, zinc oxide, and tin oxide; metal compound particles such as barium sulfate, aluminum borate, and potassium titanate; and metal particles such as gold, silver, and copper. Among these, silica particles are preferred from the perspectives of suppressing toner blowout and maintaining the toner image transferability.

[0114] The surface of inorganic particles can be hydrophobically treated. Examples of hydrophobic agents include known organosilicon compounds having alkyl groups (e.g., methyl, ethyl, propyl, butyl, etc.), specifically alkoxysilane compounds, siloxane compounds, and silazane compounds. Among these, silazane compounds are preferred, and hexamethyldisilazane is particularly preferred. A single hydrophobic agent can be used, or two or more can be used in combination.

[0115] Examples of methods for hydrophobizing inorganic particles using a hydrophobicating agent include: dissolving the hydrophobicating agent in supercritical carbon dioxide to attach it to the surface of the inorganic particles; applying (e.g., spraying or coating) a solution containing the hydrophobicating agent and a solvent dissolving the hydrophobicating agent to the surface of the inorganic particles in the atmosphere to attach the hydrophobicating agent to the surface of the inorganic particles; and adding a solution containing the hydrophobicating agent and a solvent dissolving the hydrophobicating agent to an inorganic particle dispersion in the atmosphere and maintaining the mixture thereafter, followed by drying the mixture of the inorganic particle dispersion and the solution.

[0116] The content of inorganic particles contained in the resin layer relative to the total mass of the resin layer is preferably 10% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less.

[0117] The content of silica particles contained in the resin layer relative to the total mass of the resin layer is preferably 10% by mass or more and 60% by mass or less, more preferably 15% by mass or more and 55% by mass or less, and even more preferably 20% by mass or more and 50% by mass or less.

[0118] The resin layer may contain conductive particles for the purpose of controlling charge or resistance. Examples of conductive particles include carbon black and conductive particles from the aforementioned inorganic particles.

[0119] Methods for forming a resin layer on the surface of magnetic particles include, for example, wet processing and dry processing. Wet processing uses a solvent to dissolve or disperse the resin constituting the resin layer. Dry processing, on the other hand, does not use the aforementioned solvent.

[0120] Examples of wet methods include: impregnation, in which magnetic particles are immersed in a resin solution for coating; spraying, in which a resin solution for coating is sprayed onto the surface of the magnetic particles; fluidized bed method, in which magnetic particles flow in a fluidized bed and a resin solution for coating is sprayed onto them; kneading coating method, in which magnetic particles are mixed with a resin solution for coating in a kneading coating machine and the solvent is removed; and so on. These methods can also be repeated or combined.

[0121] The resin liquid used in the wet process for forming the resin layer is prepared by dissolving or dispersing resin, inorganic particles, and other components in a solvent. There are no particular limitations on the solvent; for example, aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran and dioxane; and so on can be used.

[0122] As a dry preparation method, one example is to heat a mixture of magnetic particles and resin for forming a resin layer in a dry state to form a resin layer. Specifically, for example, magnetic particles and resin for forming a resin layer are mixed in the gas phase and heated to melt, thereby forming a resin layer.

[0123] The area ratio B / A can be controlled through manufacturing conditions.

[0124] For example, in a manufacturing method that forms a resin layer in stages by repeatedly performing a kneading coating process multiple times (e.g., twice), the area ratio B / A is controlled by adjusting the mixing time of the coated particles and the resin liquid for forming the resin layer in the final kneading coating step. The longer the mixing time in the final kneading coating step, the more likely the area ratio B / A will decrease.

[0125] Furthermore, for example, in a manufacturing method that applies a liquid composition containing inorganic particles (which may or may not contain resin) to the surface of a resin-coated carrier manufactured by a kneading coating machine using a spray method, the area ratio B / A is controlled by adjusting the particle size and content of the inorganic particles contained in the liquid composition or the amount of liquid composition applied to the resin-coated carrier.

[0126] The exposed area ratio of magnetic particles on the carrier surface is more preferably 5% to 30%, more preferably 7% to 25%, and even more preferably 10% to 25%. The exposed area ratio of magnetic particles in the carrier can be controlled by the amount of resin used in the formation of the resin layer; the more resin is used relative to the amount of magnetic particles, the smaller the exposed area ratio.

[0127] The exposed area ratio of magnetic particles on the carrier surface is a value obtained by the following method.

[0128] Prepare a carrier and magnetic particles from which the resin layer has been removed. Methods for removing the resin layer from the carrier include, for example, dissolving the resin components with an organic solvent or removing the resin layer by heating to approximately 800°C to eliminate the resin components. Prepare test samples for both the carrier and the magnetic particles. Quantify the Fe concentration (atomic%) on the sample surface using XPS. Calculate (Fe concentration of the carrier) ÷ (Fe concentration of the magnetic particles) × 100, and use this calculated value as the exposed area percentage (%) of the magnetic particles.

[0129] The volume average particle size of the carrier is preferably 10 μm or more and 120 μm or less, more preferably 20 μm or more and 100 μm or less, and even more preferably 30 μm or more and 80 μm or less.

[0130] The volume average particle size here refers to the particle size D accumulated at the 50% point from the smallest diameter side in the volume-based particle size distribution. 50v .

[0131] <Electrostatic Image Developer>

[0132] The developer in this embodiment is a two-component developer comprising the carrier and the toner of this embodiment. The toner comprises toner particles and, if necessary, additives.

[0133] The preferred mixing ratio (mass ratio) of the carrier and the toner in the developer is carrier:toner = 100:1 to 100:30, more preferably 100:3 to 100:20.

[0134] [Toning agent granules]

[0135] Colorant particles may consist of, for example, an adhesive resin and, if necessary, colorants, release agents and other additives.

[0136] -Adhesive resin-

[0137] Examples of adhesive resins include vinyl resins formed from homopolymers of the following monomers or copolymers of two or more of these monomers: styrene-based resins (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.), olefinic unsaturated nitrile resins (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 isopropyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.).

[0138] Examples of adhesive resins include epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, modified rosin, and other non-vinyl resins, mixtures thereof with the aforementioned vinyl resins, or graft polymers obtained by polymerizing vinyl monomers in their coexistence.

[0139] These adhesive resins can be used alone or in combination of two or more.

[0140] Polyester resin is suitable as an adhesive resin.

[0141] Examples of polyester resins include, for instance, well-known amorphous polyester resins. Among polyester resins, amorphous polyester resins and crystalline polyester resins can be used together. Specifically, the crystalline polyester resin content is preferably 2% to 40% by mass, and more preferably 2% to 20% by mass, relative to the total adhesive resin content.

[0142] The "crystallization" of a resin refers to the absence of a step-like change in endothermic heat during differential scanning calorimetry (DSC) and the presence of a distinct endothermic peak. Specifically, it refers to the half-width of the endothermic peak being less than 10°C when measured at a heating rate of 10°C / min.

[0143] On the other hand, the "amorphousness" of resin refers to a full width at half maximum (FWHM) greater than 10°C, exhibiting a step-like change in endothermic heat, or the absence of a clearly defined endothermic peak.

[0144] The adhesive resin is not limited to polyester resin, but preferably includes crystalline resin.

[0145] There are no particular limitations on crystalline resins; examples include crystalline polyester resins, crystalline vinyl resins (such as polyalkylene resins, long-chain (meth)acrylate alkyl ester resins, etc.), crystalline epoxy resins, crystalline polyurethane resins, crystalline cellulose resins, crystalline polyether resins, crystalline polyamide resins, modified rosin, and other known resins.

[0146] Among these, the adhesive resin preferably includes a crystalline polyester resin as the crystalline resin.

[0147] The melting point of the crystalline resin is preferably 65°C or higher and 90°C or lower, more preferably 70°C or higher and 85°C or lower, and even more preferably 70°C or higher and 80°C or lower.

[0148] By setting the melting point of the crystalline resin to below 90°C, low-temperature fixing properties of the toner are easily achieved. On the other hand, if the melting point of the crystalline resin is low, the surface of the toner particles tends to become soft. However, by including the aforementioned carrier, the embedding of additives is suppressed, and uneven gloss in the image is also suppressed. Furthermore, by setting the melting point of the crystalline resin to above 65°C, compared to the case where the melting point is below 65°C, the surface of the toner particles does not become excessively soft, the embedding of additives is easily suppressed, and uneven gloss in the image is also suppressed. In other words, by setting the melting point of the crystalline resin to between 65°C and 90°C, both low-temperature fixing and suppression of uneven gloss in the image can be achieved.

[0149] It should be noted that the melting point of the crystalline resin is determined by the DSC curve obtained by differential scanning calorimetry (DSC) based on the "melting peak temperature" recorded in the melting temperature determination method of JIS K7121-1987 "Method for determination of the transformation temperature of plastics".

[0150] From the perspective of balancing the low-temperature fixing of the toner and the suppression of uneven gloss in the image, the content of crystalline resin relative to the overall toner particles is preferably 5% to 30% by mass, more preferably 5% to 25% by mass, and even more preferably 5% to 20% by mass.

[0151] Furthermore, considering both the low-temperature fixing properties of the toner and the suppression of uneven gloss in the image, the content of crystalline resin is preferably 3% to 25% by mass, more preferably 3% to 20% by mass, and even more preferably 3% to 15% by mass, relative to the overall adhesive resin content.

[0152] In addition to crystalline resins, adhesive resins preferably further include amorphous resins.

[0153] Examples of amorphous resins include, for instance, vinyl resins formed from homopolymers of monomers or copolymers of two or more of these monomers: styrene-based resins (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.), olefinic unsaturated nitrile resins (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.).

[0154] Examples of amorphous resins include epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, modified rosin, and other non-vinyl resins, mixtures thereof with the aforementioned vinyl resins, or graft polymers obtained by polymerizing vinyl monomers in their coexistence.

[0155] Among these, the adhesive resin preferably includes amorphous polyester resin as the amorphous resin.

[0156] The glass transition temperature (Tg) of the amorphous resin is preferably 50°C or higher and 80°C or lower, more preferably 50°C or higher and 65°C or lower.

[0157] It should be noted that the glass transition temperature is determined by the DSC curve obtained by differential scanning calorimetry (DSC), or more specifically, by extrapolating the glass transition onset temperature as described in the method for determining the glass transition temperature in JIS K 7121-1987 "Method for determination of transition temperature of plastics".

[0158] It should be noted that the "crystallization" of the resin refers to the absence of a step-like change in endothermic heat in differential scanning calorimetry (DSC) and the presence of a distinct endothermic peak. Specifically, it means that the half-peak width of the endothermic peak is within 10°C when measured at a heating rate of 10°C / min.

[0159] On the other hand, the "amorphousness" of resin refers to a full width at half maximum (FWHM) greater than 10°C, exhibiting a step-like change in endothermic heat, or the absence of a clearly defined endothermic peak.

[0160] The adhesive resin preferably includes a crystalline polyester resin as a crystalline resin and an amorphous polyester resin as an amorphous resin.

[0161] The following sections will provide detailed descriptions of crystalline polyester resin and amorphous polyester resin, using crystalline and amorphous resins as examples respectively.

[0162] Amorphous polyester resin

[0163] Examples of amorphous polyester resins include condensation polymers of polycarboxylic acids and polyols. Commercially available or synthetic amorphous polyester resins can be used.

[0164] Examples of polycarboxylic acids include, for example, aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citracic acid, itaconic acid, pentenic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), their anhydrides, or their lower (e.g., alkyl esters with 1 to 5 carbon atoms). Among these, aromatic dicarboxylic acids are preferred as polycarboxylic acids.

[0165] In polycarboxylic acids, dicarboxylic acids can be used in combination with carboxylic acids of three or more members that have a cross-linked or branched structure. Examples of carboxylic acids of three or more members include trimellitic acid, benzopyrene, their anhydrides, or their lower (e.g., 1-5 carbon atoms) alkyl esters.

[0166] Polycarboxylic acids can be used alone or in combination of two or more.

[0167] Examples of polyols include aliphatic diols (such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (such as cyclohexanediol, cyclohexanediol, hydrogenated bisphenol A, etc.), and aromatic diols (such as ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, aromatic diols and alicyclic diols are preferred as polyols, and aromatic diols are more preferred.

[0168] As a polyol, a diol can be used in combination with a polyol of 3 or more members that has a cross-linked or branched structure. Examples of polyols of 3 or more members include glycerol, trimethylolpropane, and pentaerythritol.

[0169] Polyols can be used alone or in combination of two or more.

[0170] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50°C or higher and 80°C or lower, more preferably 50°C or higher and 65°C or lower.

[0171] The glass transition temperature is determined by the DSC curve obtained by differential scanning calorimetry (DSC), or more specifically, by extrapolating the glass transition onset temperature as described in the method for determining the glass transition temperature in JIS K7121:1987 "Method for determination of transition temperature of plastics".

[0172] The weight-average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 to 1,000,000, more preferably 7,000 to 500,000.

[0173] The number average molecular weight (Mn) of the amorphous polyester resin is preferably between 2,000 and 100,000.

[0174] The molecular weight distribution of the amorphous polyester resin, Mw / Mn, is preferably 1.5 to 100, more preferably 2 to 60.

[0175] Weight-average molecular weight and number-average molecular weight were determined by gel permeation chromatography (GPC). For the molecular weight determination using GPC, a Tosoh GPC HLC-8120 GPC was used, along with a Tosoh TSKgel SuperHM-M (15 cm) column, and THF solvent was employed. The weight-average molecular weight and number-average molecular weight were calculated from the determination results using a molecular weight calibration curve prepared from monodisperse polystyrene standard samples.

[0176] Amorphous polyester resins are obtained by known manufacturing methods. Specifically, for example, they are obtained by the following method: the polymerization temperature is set to 180°C or higher and 230°C or lower, and the reaction system is subjected to reduced pressure as needed, while removing water or alcohol generated during condensation.

[0177] If the raw monomers are insoluble or incompatible at the reaction temperature, a high-boiling-point solvent can be added as a dissolving agent to dissolve them. In this case, the polycondensation reaction is carried out while the dissolving agent is removed by distillation. If there are monomers with poor compatibility in the copolymerization reaction, the monomers with poor compatibility can be pre-condensed with the acid or alcohol to which they are to be polycondensed, and then polycondensed with the main component.

[0178] Crystalline polyester resin

[0179] Examples of crystalline polyester resins include condensation polymers of polycarboxylic acids and polyols. Commercially available products or synthetic compounds can be used as crystalline polyester resins.

[0180] Here, in order to facilitate the formation of a crystal structure by the crystalline polyester resin, a condensation polymer obtained by a linear aliphatic monomer is preferred over a condensation polymer obtained by using a polymeric monomer with an aromatic ring.

[0181] Examples of polycarboxylic acids include aliphatic dicarboxylic acids (such as oxalic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, etc.), their anhydrides, or their lower (e.g., alkyl esters with 1 to 5 carbon atoms).

[0182] In polycarboxylic acids, dicarboxylic acids can be used in combination with carboxylic acids of three or more members that have a cross-linked or branched structure. Examples of tricarboxylic acids include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), their anhydrides, or their lower (e.g., alkyl esters with 1 to 5 carbon atoms).

[0183] As polycarboxylic acids, these dicarboxylic acids can be used in combination with dicarboxylic acids having sulfonic acid groups or dicarboxylic acids having olefinic double bonds.

[0184] Polycarboxylic acids can be used alone or in combination of two or more.

[0185] Examples of polyols include aliphatic diols (e.g., straight-chain aliphatic diols with 7 to 20 carbon atoms in the main chain). Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanediol. Among these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred as aliphatic diols.

[0186] In polyols, diols can be combined with alcohols of three or more members that have a cross-linked or branched structure. Examples of alcohols of three or more members include glycerol, trimethylolethane, trimethylolpropane, and pentaerythritol.

[0187] Polyols can be used alone or in combination of two or more.

[0188] Here, the content of aliphatic diols in the polyol can be 80 mol% or more, preferably 90 mol% or more.

[0189] The melting temperature of the crystalline polyester resin is preferably 50°C to 100°C, more preferably 55°C to 90°C, and even more preferably 60°C to 85°C.

[0190] The melting temperature is determined by the "melting peak temperature" as described in the method for determining the melting temperature in JIS K7121:1987 "Method for determination of the transition temperature of plastics" based on the DSC curve obtained by differential scanning calorimetry (DSC).

[0191] The weight-average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0192] Crystalline polyester resins are obtained, for example, by known manufacturing methods, similar to amorphous polyesters.

[0193] The content of the adhesive resin relative to the overall colorant particles is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and even more preferably 60% by mass or more and 85% by mass or less.

[0194] -Coloring agents-

[0195] Examples of pigments that can be used as colorants include carbon black, chrome yellow, Hansa yellow, benzidine yellow, vat yellow, quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, sulfur-resistant orange, Voochug red, permanent red, bright carmine 3B, bright carmine 6B, DuPont oil red, pyrazolone red, litho red, rhodamine B lake, lake red C, pigment red, rose red, aniline blue, cyanine blue, oil-soluble blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, malachite green oxalate, etc.; acridine-based, xanthine-based, azo-based, benzoquinone-based, azazine-based, anthraquinone-based, thio-indigo-based, dioxazine-based, thiazine-based, azomethyl alkali-based, indigo-based, phthalocyanine-based, aniline black-based, polyacetylenic, triphenylmethane-based, diphenylmethane-based, thiazole-based, etc.

[0196] Colorants can be used alone or in combination of two or more.

[0197] Colorants can be surface-treated as needed, or they can be used in combination with dispersants. Additionally, two or more colorants can be used together.

[0198] The content of colorant relative to the overall colorant particles is preferably 1% to 30% by mass, more preferably 3% to 15% by mass.

[0199] As a coloring agent, it may also contain inorganic pigments containing metal atoms (hereinafter also referred to as "metal-containing inorganic pigments").

[0200] Toner particles containing inorganic metal pigments have a high specific gravity, thus increasing the collision energy during agitation in the developing unit. Furthermore, during continuous formation of low-density images, the toner particles are agitated together with the carrier for extended periods with infrequent toner replacement within the developing unit, causing additives to easily become embedded on the particle surface. Once additives are embedded on the particle surface, it becomes difficult to achieve the improved toner flowability provided by the additives; instead, the increased contact between toner particles may actually reduce toner flowability.

[0201] Furthermore, in high-temperature and high-humidity environments (e.g., 28.5°C and 85% humidity), moisture tends to adhere to the surface of the toner particles due to the polarization of the metallic inorganic pigments disposed near the particle surface. Therefore, the fluidity of the toner may decrease due to the adhered moisture.

[0202] Furthermore, if a developer containing a toner in a reduced-flow state is stored in the developing unit of an image forming apparatus, and the image forming apparatus is started after prolonged storage in a high-temperature and high-humidity environment (e.g., storage at 40°C and 90% humidity for 17 hours), toner clogging may occur within the developing unit due to toner aggregation. Specifically, toner clogging (so-called trimmer clogging) may occur, for example, between the developer holder and the layer regulating member in the developing unit. Once toner clogging occurs within the developing unit, an image with colored stripes due to the toner clogging will be obtained.

[0203] In contrast, in this embodiment, there are micro-uneven surfaces on the carrier surface.

[0204] Therefore, it can be considered that the micro-unevenness of the carrier surface makes the contact with the colorant point-to-point, reducing the contact area and thus mitigating the impact load caused by stirring, and suppressing the burial of the additives. Furthermore, it can be considered that the micro-unevenness of the carrier surface can scrape off and retain moisture adhering to the surface of the colorant particles, thereby removing bound moisture from the surface of the colorant particles.

[0205] Furthermore, it can be inferred that by suppressing the burial of the aforementioned additives and removing bound moisture, the decrease in the fluidity of the toner can be suppressed, and the blockage of the toner caused by toner aggregation in the developing mechanism when the image forming apparatus is started after long-term storage in a high temperature and high humidity environment can be suppressed, thereby suppressing the generation of color stripes in the image due to toner blockage.

[0206] Examples of metal-containing inorganic pigments include white pigments and glossy pigments.

[0207] Examples of white pigments include titanium dioxide, aluminum hydroxide, satin white, talc, zinc oxide, magnesium oxide, magnesium carbonate, kaolin, aluminosilicate, sericite, and bentonite.

[0208] Examples of luminescent pigments include metallic pigments such as aluminum, brass, bronze, nickel, stainless steel, and zinc; mica coated with titanium oxide, yellow iron oxide, etc.; thin-film or plate-like crystals such as alumina silicates, basic carbonates, barium sulfate, titanium oxide, and bismuth oxychloride; thin-film glass powder, and thin-film glass powder deposited with metal vapor; and so on.

[0209] Examples of metal-containing inorganic pigments include those with an average particle size of 150 nm or more, preferably 180 nm or more, and more preferably 200 nm or more. By making the average particle size of the metal-containing inorganic pigment 150 nm or more, protrusions originating from the metal-containing inorganic pigment are easily formed on the surface of the toner particles. The toner particles make point contact with other particles at the protrusions, thereby suppressing the reduction in toner flowability caused by the burial of additives.

[0210] The average particle size of the metal-containing inorganic pigment can be below 500 nm, below 450 nm, or below 400 nm. By making the average particle size of the metal-containing inorganic pigment below 500 nm, it has the advantage of excellent control over the structure within the colorant particles.

[0211] The average particle size of the metal-containing inorganic pigment is preferably 150 nm to 500 nm, more preferably 180 nm to 450 nm, and even more preferably 200 nm to 400 nm.

[0212] It should be noted that when the inorganic pigment containing metal is a luminescent pigment, the average particle size of the luminescent pigment can be 3μm or more and 20μm or less, 4.5μm or more and 18μm or less, or 6μm or more and 16μm or less.

[0213] The average particle size of the metal-containing inorganic pigment was determined using the same method as the average particle size of the inorganic particles contained in the resin layer of the aforementioned carrier.

[0214] Specifically, the toner is embedded in epoxy resin and cut using a microtome to create cross-sections of the toner particles. These cross-sections are then photographed using a scanning electron microscope (SEM), and the resulting SEM images are imported into an image processing and analysis device for analysis. Metal-containing inorganic pigments (primary particles) from 100 randomly selected toner particles are analyzed, and their equivalent circular diameters (nm) are calculated and averaged arithmetically. This average value is taken as the average particle size (nm) of the metal-containing inorganic pigment. In other words, the average particle size of the metal-containing inorganic pigment is the number-average particle size.

[0215] The content of the inorganic metal pigment relative to the total amount of the toner particles can be 1% by mass or more, or 5% by mass or more. Furthermore, the content of the inorganic metal pigment relative to the total amount of the toner particles is preferably 10% by mass or more, more preferably 25% by mass or more, and particularly preferably 32% by mass or more. In particular, by making the content of the inorganic metal pigment 10% by mass or more, protrusions originating from the inorganic metal pigment are easily formed on the surface of the toner particles, allowing point contact between the toner particles and other particles at these protrusions. This suppresses the reduction in toner flowability caused by the embedding of additives.

[0216] The content of the metal-containing inorganic pigment relative to the total toner particles can be 70% by mass or less, or even 50% by mass or less. In particular, by keeping the content of the metal-containing inorganic pigment at 50% by mass or less, image blurring caused by charge injection into the toner particles can be suppressed.

[0217] The content of the inorganic pigment containing metal is preferably 10% by mass or more and 50% by mass or less, more preferably 25% by mass or more and 50% by mass or less, and even more preferably 32% by mass or more and 50% by mass or less.

[0218] The electrostatic image developer of this embodiment may have the following toner and carrier: the toner comprises toner particles and an additive attached to the surface of the toner particles, the toner particles comprise an inorganic pigment containing metal atoms, the carrier comprises magnetic particles and a resin layer coated with the magnetic particles and comprising inorganic particles, wherein the average particle size of the inorganic particles is 5 nm or more and 90 nm or less, the average thickness of the resin layer is 0.6 μm or more and 1.4 μm or less, and when the surface of the carrier is analyzed in three dimensions, the area ratio B / A of the top view area A of the carrier to the surface area B of the carrier is 1.020 or more and 1.110 or less.

[0219] -Release agent-

[0220] Examples of release agents include: hydrocarbon waxes; natural waxes such as carnauba wax, rice bran wax, and candelilla wax; synthetic or mineral / petroleum-based waxes such as lignite wax; ester-based waxes such as fatty acid esters and lignite esters; and so on. Release agents are not limited to these.

[0221] The melting temperature of the release agent is preferably 50°C to 110°C, more preferably 60°C to 100°C.

[0222] The melting temperature is determined by the "melting peak temperature" as described in the method for determining the melting temperature in JIS K7121:1987 "Method for determination of the transition temperature of plastics" based on the DSC curve obtained by differential scanning calorimetry (DSC).

[0223] The release agent content is preferably 1% to 20% by mass and more preferably 5% to 15% by mass relative to the total colorant particles.

[0224] -Other Additives-

[0225] Other additives include, for example, known additives such as magnetic materials, charge control agents, and inorganic powders. These additives can be included as internal additives in colorant particles.

[0226] -Characteristics of colorant particles, etc.-

[0227] Toner particles can be monolayer toner particles or so-called core / shell toner particles consisting of a core (core particle) and a coating layer (shell) covering the core.

[0228] The core / shell structured colorant particles can, for example, consist of a core and a coating layer, wherein the core is formed by including an adhesive resin and, if necessary, other additives such as colorants and release agents, and the coating layer is formed by including an adhesive resin.

[0229] Volume average particle size (D) of colorant particles 50v Preferably, the micrometer is 2μm or more and 10μm or less, more preferably 4μm or more and 8μm or less.

[0230] Regarding the volume average particle size (D) of the colorant particles 50v The measurements were performed using a Coulter Multisizer II (manufactured by Beckman Coulter) and an ISOTON-II electrolyte (manufactured by Beckman Coulter).

[0231] During the determination, 0.5 mg to 50 mg of the test sample is added to 2 ml of a 5% aqueous solution of the surfactant (preferably sodium alkylbenzene sulfonate) as a dispersant. This is then added to 100 ml to 150 ml of electrolyte.

[0232] The electrolyte containing the suspended sample was dispersed using an ultrasonic disperser for 1 minute. The particle size distribution of particles ranging from 2 μm to 60 μm was measured using a Coulter Multisizer II with a 100 μm pore size. A total of 50,000 particles were sampled. The volumetric particle size distribution was plotted from the smallest diameter side, and the particle size at the cumulative 50% points was taken as the volume average particle size D. 50v .

[0233] The average roundness of the colorant particles is preferably 0.94 or more and 1.00 or less, more preferably 0.95 or more and 0.98 or less.

[0234] The average roundness of the toner particles is calculated using (equivalent circle circumference) / (circumference), i.e., (circumference of a circle with the same projected area as the particle image) / (circumference of the particle projection image). Specifically, it is the value obtained by measuring using the method described below.

[0235] First, toner particles, the object of measurement, are attracted and collected to form a flattened flow. A still image of the particles is obtained by momentarily flashing the particle image. The average roundness is then determined using a flow cytometry particle image analyzer (Sysmex FPIA-3000). Furthermore, the number of samples used to determine the average roundness is set to 3500.

[0236] When the colorant contains additives, the colorant (developer) to be measured is dispersed in water containing a surfactant, and then subjected to ultrasonic treatment to obtain colorant particles with additives removed.

[0237] When the colorant contains a metal-containing inorganic pigment, the area ratio of the protrusions on the surface of the colorant particles originating from the metal-containing inorganic pigment is preferably 0.30% to 5.00%, more preferably 0.35% to 3.00%, and even more preferably 0.40% to 1.50%.

[0238] By making the area ratio of the aforementioned protrusions 0.30% or more, toner particles can easily make point contact with other particles at the protrusions, thus suppressing the reduction in toner fluidity caused by the embedding of additives. Furthermore, by making the area ratio of the aforementioned protrusions 5.00% or less, image blurring caused by charge injection into the toner particles can be suppressed.

[0239] The area ratio of the aforementioned protrusions can be controlled, for example, by adjusting the amount of surfactant added during the manufacturing process of the colorant particles. Furthermore, when the colorant particles have a core / shell structure, the area ratio of the protrusions can be controlled by adjusting the thickness of the shell layer.

[0240] The area ratio of the aforementioned protrusions can be calculated, for example, as follows.

[0241] The test samples, obtained by evaporating platinum onto the toner particles for 10 seconds using a vapor deposition method, were observed using a high-resolution field emission scanning electron microscope (FE-SEM, Hitachi High Technology Co., Ltd., model: S-4700) at an accelerating voltage of 6kV. Image analysis was performed on the photographs of the toner particle surfaces. For 100 toner particles, the percentage (%) of the area of ​​the protrusions originating from the metallic inorganic pigment was determined, and the average value of the 100 toner particles was taken as the "protrusion area ratio".

[0242] The average height of the protrusions on the surface of the colorant particles, which originate from the inorganic pigment containing metal, is preferably 0.05 μm or more and 0.30 μm or less, more preferably 0.10 μm or more and 0.30 μm or less, and even more preferably 0.15 μm or more and 0.25 μm or less.

[0243] By making the average height of the aforementioned protrusions 0.05 μm or more, toner particles can easily make point contact with other particles at the protrusions, thus suppressing the reduction in toner flowability caused by the embedding of additives. Furthermore, by making the average height of the aforementioned protrusions 0.30 μm or less, image blurring caused by charge injection into the toner particles can be suppressed.

[0244] The average height of the aforementioned protrusions can be controlled, for example, by adjusting the amount of surfactant added during the manufacturing process of the colorant particles.

[0245] The average height of the aforementioned protrusion is calculated, for example, as follows.

[0246] The test sample, obtained by platinum vapor deposition of the toner (the test object) for 70 seconds using the vapor deposition method, was observed using SEM with an accelerating voltage of 2kV using an electron beam three-dimensional roughness analysis device (Elionix Co., Ltd., model: ERA-8900FE). Image analysis was performed on the obtained toner particle surface photographs. For 100 toner particles, the surface roughness, including the protrusions originating from the metallic inorganic pigment, was calculated according to JIS B 0601-2001. The maximum height Ry (μm) was determined, and the average value of the 100 toner particles was taken as the "average height of the protrusion".

[0247] The half-fall temperature of the colorant, as determined by a flow tester, is preferably 90°C to 140°C, more preferably 95°C to 120°C, and even more preferably 95°C to 115°C.

[0248] By setting the half-fall temperature of the toner, as measured using a flow tester, to be between 90°C and 140°C, low-temperature fixing properties of the toner are easily obtained. On the other hand, when the half-fall temperature of the toner, as measured using a flow tester, is between 90°C and 140°C, the surface of the toner particles tends to become soft. However, by including the aforementioned carrier, the embedding of the additives is suppressed, and uneven gloss in the image is also suppressed.

[0249] The half-fall temperature of the colorant was determined using a flow tester and a CFT-500C high-performance rheometer (manufactured by Shimadzu Corporation). The test was conducted with a die orifice diameter of 0.5 mm, an orifice length of 1 mm, and a pressure load of 0.98 MPa (10 kg / cm²). 2 Under the conditions of a preheating time of 5 minutes, a heating rate of 1℃ / minute, a measurement temperature interval of 1℃, and a starting temperature of 65℃, when a 1.1g sample melts and flows out, the temperature corresponding to half the height from the starting point to the ending point of the sample flow is defined as the 1 / 2 drop temperature.

[0250] -Manufacturing method of colorant particles-

[0251] Colorant particles can be manufactured using any of the following methods: dry manufacturing (e.g., mixing and pulverizing) or wet manufacturing (e.g., agglomeration, suspension polymerization, dissolution suspension). There are no particular limitations on these methods; well-known methods can be used. Among these, agglomeration is preferred for obtaining colorant particles.

[0252] Specifically, for example, in the case of manufacturing colorant particles by agglomeration and merging, the colorant particles are manufactured by the following steps: preparing a resin particle dispersion in which resin particles as binders are dispersed (resin particle dispersion preparation step); agglomerating the resin particles (and other particles if necessary) in the resin particle dispersion (or in the dispersion after mixing with other particle dispersions if necessary) to form agglomerated particles (agglomerated particle forming step); and heating the agglomerated particle dispersion in which the agglomerated particles are dispersed to fuse / merge the agglomerated particles to form colorant particles (fusion / merging step).

[0253] The following details each step.

[0254] The following description illustrates a method for obtaining colorant particles containing colorant and release agent; however, the colorant and release agent are additives used as needed. Of course, other additives besides colorant and release agent may also be used.

[0255] -Preparation steps for resin particle dispersion-

[0256] Prepare a resin particle dispersion containing resin particles as an adhesive resin, and simultaneously prepare, for example, a colorant particle dispersion containing colorant particles and a release agent particle dispersion containing release agent particles.

[0257] Resin particle dispersions are prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

[0258] Examples of dispersion media used in resin particle dispersions include aqueous media.

[0259] Examples of aqueous media include distilled water, ion-exchanged water, and alcohols. These media can be used individually or in combination.

[0260] Examples of surfactants include: anionic surfactants such as sulfate esters, sulfonates, phosphate esters, and soaps; cationic surfactants such as amine salts and quaternary ammonium salts; and nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyols. Among these, anionic and cationic surfactants are particularly noteworthy. Nonionic surfactants can also be used in combination with anionic or cationic surfactants.

[0261] Surfactants can be used alone or in combination of two or more.

[0262] In resin particle dispersions, common methods for dispersing resin particles in a dispersion medium include using a rotary shear homogenizer or a ball mill, sand mill, or bead mill with a media. Alternatively, depending on the type of resin particles, phase inversion emulsification can also be used. Phase inversion emulsification involves dissolving the resin to be dispersed in a hydrophobic organic solvent capable of dissolving the resin, adding an alkali to the organic continuous phase (O phase) for neutralization, and then introducing an aqueous medium (W phase). This results in a phase inversion from W / O to O / W, dispersing the resin in particulate form in the aqueous medium.

[0263] The volume average particle size of the resin particles dispersed in the resin particle dispersion is preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and even more preferably 0.1 μm or more and 0.6 μm or less.

[0264] Regarding the volume average particle size of the resin particles, the particle size distribution obtained by measurement using a laser diffraction particle size distribution measuring device (e.g., the LA-700 manufactured by Horiba Corporation) is used. For the divided particle size range (segment), the cumulative volume distribution is plotted from the smallest particle size side, and the particle size at the cumulative 50% point relative to all particles is measured and taken as the volume average particle size D. 50v The volume average particle size of particles in other dispersions was determined in the same manner.

[0265] The resin particle dispersion contains preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less.

[0266] Similar to resin particle dispersions, colorant particle dispersions and release agent particle dispersions are also prepared. That is, the volume average particle size, dispersion medium, dispersion method, and particle content of the particles in the resin particle dispersion are the same for the colorant particles dispersed in the colorant particle dispersion and the release agent particles dispersed in the release agent particle dispersion.

[0267] -Steps in the formation of aggregated particles-

[0268] Next, the resin particle dispersion, colorant particle dispersion, and release agent particle dispersion are mixed.

[0269] Subsequently, the resin particles, colorant particles, and release agent particles are heterogeneously aggregated in the mixed dispersion to form aggregated particles with a diameter similar to that of the target colorant particles and containing resin particles, colorant particles, and release agent particles.

[0270] Specifically, for example, a flocculant is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to acidic (e.g., pH 2 or higher than pH 5). A dispersion stabilizer is added as needed, and then the mixture is heated to a temperature close to the glass transition temperature of the resin particles (specifically, for example, above the glass transition temperature of the resin particles -30°C and below the glass transition temperature of -10°C) to cause the particles dispersed in the mixed dispersion to agglomerate and form aggregated particles.

[0271] In the aggregate particle formation step, for example, the aggregate can be added at room temperature (e.g., 25°C) while the mixed dispersion is stirred using a rotary shear homogenizer, the pH of the mixed dispersion is adjusted to acidic (e.g., pH 2 or higher than 5), and a dispersion stabilizer is added as needed before heating.

[0272] Examples of flocculants include surfactants with polarity opposite to that of the surfactant contained in the mixed dispersion, inorganic metal salts, and metal complexes with a polarity of two or higher. When metal complexes are used as flocculants, the amount of surfactant required is reduced, and the charging characteristics are improved.

[0273] Depending on the requirements, additives that form complexes or similar bonds with the metal ions of the flocculant can be used in conjunction with the flocculant. Chelating agents are suitable as such additives.

[0274] Examples of inorganic metal salts include calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide; and so on.

[0275] Water-soluble chelating agents can be used as chelating agents. Examples of chelating agents include hydroxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid; aminocarboxylic acids such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA); and so on.

[0276] The amount of chelating agent added relative to 100 parts by weight of resin particles is preferably 0.01 parts by weight or more and 5.0 parts by weight or less, more preferably 0.1 parts by weight or more and less than 3.0 parts by weight.

[0277] -Merge / merge steps-

[0278] Next, the dispersion of agglomerated particles containing the agglomerated particles is heated to, for example, above the glass transition temperature of the resin particles (e.g., a temperature 10°C to 30°C higher than the glass transition temperature of the resin particles) to cause the agglomerated particles to fuse / merge (fusion·unify) and form colorant particles.

[0279] After the above steps, colorant particles are obtained.

[0280] After obtaining the agglomerated particle dispersion containing agglomerated particles, the colorant particles can be manufactured by the following steps: further mixing the agglomerated particle dispersion with a resin particle dispersion containing resin particles, and agglomerating the resin particles in a manner that further adheres them to the surface of the agglomerated particles to form a second agglomerated particle; and heating the second agglomerated particle dispersion containing the second agglomerated particles to fuse / merge the second agglomerated particles to form a core / shell structured colorant particle.

[0281] After the fusion / merging step, the toner particles formed in the solution are subjected to known washing, solid-liquid separation, and drying steps to obtain dried toner particles. Regarding the washing step, from a power efficiency perspective, displacement washing using ion-exchanged water can be fully implemented. Regarding the solid-liquid separation step, from a productivity perspective, methods such as vacuum filtration and pressure filtration can be implemented. Regarding the drying step, from a productivity perspective, methods such as freeze drying, airflow drying, fluidized bed drying, and vibrating fluidized bed drying can be implemented.

[0282] Next, for example, an additive is added to the obtained dried colorant particles and mixed, thereby producing the colorant of this embodiment. Mixing can be performed using, for example, a V-type mixer, a Henschel mixer, a Loedige mixer, etc. Furthermore, coarse particles of the colorant can be removed as needed using a vibrating screen, a pneumatic screen, etc.

[0283] -Additives-

[0284] Examples of 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, and K2O·(TiO2). n Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, MgSO4, etc.

[0285] The surface of inorganic particles used as additives can be hydrophobically treated. Hydrophobic treatment can be performed, for example, by impregnating the inorganic particles with a hydrophobic agent. There are no particular limitations on the hydrophobic agent; examples include silane-based coupling agents, silicone oils, titanate-based coupling agents, and aluminum-based coupling agents. They can be used alone or in combination of two or more.

[0286] The amount of hydrophobic treatment agent is typically, for example, more than 1 part by mass and less than 10 parts by mass relative to 100 parts by mass of inorganic particles.

[0287] Other examples of additives include resin particles (such as polystyrene, polymethyl methacrylate, and melamine resin particles) and cleaning and activating agents (such as metal salts of higher fatty acids, such as zinc stearate, and particles of fluorine-based high molecular weight substances).

[0288] The amount of additive added is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.01% by mass or more and 2.0% by mass or less, relative to the colorant particles.

[0289] <Image forming apparatus, image forming method>

[0290] The image forming apparatus of this embodiment includes: an image holder; a charging mechanism for charging the surface of the image holder; an electrostatic image forming mechanism for forming an electrostatic image on the charged surface of the image holder; a developing mechanism 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 mechanism for transferring the toner image formed on the surface of the image holder to the surface of a recording medium; and a fixing mechanism for fixing the toner image transferred to the surface of the recording medium. Furthermore, the electrostatic image developer of this embodiment is used as the electrostatic image developer.

[0291] An image forming method (the image forming method of this embodiment) comprising the following steps is implemented using the image forming apparatus of this embodiment: a charging step, wherein the surface of an image holder is charged; an electrostatic image forming step, wherein an electrostatic image is formed on the charged surface of the image holder; a developing step, wherein the electrostatic image formed on the surface of the image holder is developed into a toner image using the electrostatic image developer of this embodiment; a transfer step, wherein the toner image formed on the surface of the image holder is transferred to the surface of a recording medium; and a fixing step, wherein the toner image transferred to the surface of the recording medium is fixed.

[0292] The image forming apparatus of this embodiment is applicable to the following known image forming apparatuses: a direct transfer method apparatus that directly transfers a toner image formed on the surface of an image holder to a recording medium; an intermediate transfer method apparatus that first transfers a toner image formed on the surface of an image holder to the surface of an intermediate transfer body, and then transfers the toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium a second time; an apparatus equipped with a cleaning mechanism for cleaning the surface of the image holder after the toner image transfer and before charging; an apparatus equipped with a de-energizing mechanism for irradiating the surface of the image holder with de-energizing light to de-energize it after the toner image transfer and before charging; and so on.

[0293] In the case where the image forming apparatus of this embodiment is an intermediate transfer method apparatus, the transfer mechanism is configured to have, for example, the following components: an intermediate transfer body that transfers a toner image to a surface; a primary transfer mechanism that transfers a toner image formed on the surface of an image holder to the surface of the intermediate transfer body in one step; and a secondary transfer mechanism that transfers the toner image transferred to the surface of the intermediate transfer body to the surface of a recording medium in a second step.

[0294] In the image forming apparatus of this embodiment, for example, the part including the developing mechanism can be a cassette structure (processing cassette) that is attached and detached from the image forming apparatus. As a processing cassette, for example, a processing cassette suitable for using the electrostatic image developer of this embodiment and having a developing mechanism is provided.

[0295] The following shows an example of the image forming apparatus of this embodiment, but it is not limited thereto. In the following description, the main parts shown in the figures will be described, and other descriptions will be omitted.

[0296] Figure 1 This is a schematic configuration diagram of the image forming apparatus according to this embodiment.

[0297] Figure 1 The image forming apparatus shown includes four image forming units 10Y, 10M, 10C, and 10K (image forming mechanisms) that output images of yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data in an electrophotographic manner. These image forming units (hereinafter sometimes simply referred to as "units") 10Y, 10M, 10C, and 10K are arranged side-by-side at predetermined distances in the horizontal direction. These units 10Y, 10M, 10C, and 10K can be processing boxes that are mounted and removed from the image forming apparatus.

[0298] Above each of the units 10Y, 10M, 10C, and 10K, an intermediate transfer belt (an example of an intermediate transfer body) 20 extends through each unit. The intermediate transfer belt 20 is wound around a drive roller 22 and a support roller 24, traveling in a direction from the first unit 10Y towards the fourth unit 10K. The support roller 24 applies force in a direction separate from the drive roller 22 via springs (not shown), applying tension to the intermediate transfer belt 20 wound around both rollers. An intermediate transfer body cleaning device 30, opposite to the drive roller 22, is provided on the image holding side of the intermediate transfer belt 20.

[0299] The developing apparatus (an example of a developing mechanism) 4Y, 4M, 4C, and 4K of each unit 10Y, 10M, 10C, and 10K respectively supplies yellow, magenta, cyan, and black toners stored in toner cartridges 8Y, 8M, 8C, and 8K.

[0300] Since units 1 to 4, 10Y, 10M, 10C, and 10K, have the same configuration and operation, the first unit 10Y, which forms the yellow image and is located on the upstream side of the intermediate transfer belt in the direction of travel, will be used as an example for explanation.

[0301] Unit 10Y has a photoreceptor 1Y that functions as an image holder. Around the photoreceptor 1Y are arranged in sequence: a charging roller (an example of a charging mechanism) 2Y, which charges the surface of the photoreceptor 1Y to a preset potential; an exposure device (an example of an electrostatic image forming mechanism) 3, which uses a laser line 3Y to expose the charged surface based on a color separation image signal to form an electrostatic image; a developing device (an example of a developing mechanism) 4Y, which supplies the charged toner to the electrostatic image to develop the electrostatic image; a primary transfer roller 5Y (an example of a primary transfer mechanism), which transfers the developed toner image onto an intermediate transfer belt 20; and a photoreceptor cleaning device (an example of a cleaning unit) 6Y, which removes the toner remaining on the surface of the photoreceptor 1Y after the primary transfer.

[0302] The primary transfer roller 5Y is positioned inside the intermediate transfer belt 20, opposite to the photosensitive element 1Y. Each unit's primary transfer rollers 5Y, 5M, 5C, and 5K are connected to a bias power supply (not shown) that applies a primary transfer bias voltage. The bias power supply changes the value of the transfer bias voltage applied to each primary transfer roller via a control unit (not shown).

[0303] The following explains the action of forming the yellow image in Unit 1, 10Y.

[0304] First, before the operation, the surface of the photosensitive element 1Y is charged to a potential of -600V to -800V using the charging roller 2Y.

[0305] Photoreceptor 1Y has good electrical conductivity (e.g., a volume resistivity of 1×10⁻⁶ at 20°C). -6 A photosensitive layer is deposited on a substrate (within Ωcm or less). This photosensitive layer typically has high resistance (the resistance of common resins), but it has the property that the resistivity of the portion irradiated by the laser line changes when irradiated. Therefore, based on yellow image data sent from a control unit (not shown), a laser line 3Y is irradiated by the exposure apparatus 3 onto the surface of the charged photoreceptor 1Y. As a result, an electrostatic image of a yellow image pattern is formed on the surface of the photoreceptor 1Y.

[0306] An electrostatic image is an image formed on the surface of a photoreceptor 1Y by charging. It is a so-called negative latent image, which is formed as follows: the resistivity of the irradiated part of the photosensitive layer is reduced by using a laser line 3Y, causing the charged charge on the surface of the photoreceptor 1Y to flow; on the other hand, the charge remains in the part that is not irradiated by the laser line 3Y, thereby forming the negative latent image.

[0307] The electrostatic image formed on the photoreceptor 1Y rotates to a predetermined developing position as the photoreceptor 1Y rotates. At this developing position, the electrostatic image on the photoreceptor 1Y is developed into a toner image by the developing device 4Y and then visualized.

[0308] The developing apparatus 4Y stores an electrostatic image developer, for example, containing at least a yellow toner and a carrier. The yellow toner, inside the developing apparatus 4Y, becomes triboelectrically charged through agitation, acquiring a charge of the same polarity (negative polarity) as the charge on the photoreceptor 1Y, and is held on a developer roller (an example of a developer holder). The surface of the photoreceptor 1Y is then passed through the developing apparatus 4Y, thereby electrostatically attaching the yellow toner to the de-charged latent image portion on the surface of the photoreceptor 1Y, and developing the latent image using the yellow toner. The photoreceptor 1Y, with the yellow toner image formed, continues to rotate at a preset speed, conveying the developed toner image on the photoreceptor 1Y to a preset first transfer position.

[0309] When the yellow toner image on the photoreceptor 1Y is transferred to the primary transfer position, a primary transfer bias is applied to the primary transfer roller 5Y. The electrostatic force from the photoreceptor 1Y toward the primary transfer roller 5Y acts on the toner image, transferring the toner image on the photoreceptor 1Y onto the intermediate transfer belt 20. The applied transfer bias at this time has a (+) polarity opposite to the polarity (-) of the toner, and is controlled, for example, to +10 μA in the first unit 10Y by a control unit (not shown).

[0310] On the other hand, the toner residue on the photoreceptor 1Y is removed and recovered using the photoreceptor cleaning device 6Y.

[0311] The primary transfer bias applied to the primary transfer rollers 5M, 5C, and 5K after 10M in Unit 2 is also controlled according to Unit 1.

[0312] In this way, the intermediate transfer belt 20, which has transferred the yellow toner image using the first unit 10Y, is sequentially conveyed through the second to fourth units 10M, 10C, and 10K, and the toner images of each color are transferred multiple times in an overlay manner.

[0313] The intermediate transfer belt 20, which has undergone multiple transfer of four toner images via units 1 to 4, reaches the secondary transfer section. This secondary transfer section comprises the intermediate transfer belt 20, a support roller 24 in contact with the inner surface of the intermediate transfer belt, and a secondary transfer roller (an example of a secondary transfer mechanism) 26 disposed on the image holding side of the intermediate transfer belt 20. Meanwhile, recording paper (an example of a recording medium) P is fed to the gap between the secondary transfer roller 26 and the intermediate transfer belt 20 at a predetermined timing by a supply member, and a secondary transfer bias is applied to the support roller 24. The applied transfer bias has the same polarity (-) as the toner, and the electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, transferring the toner image from the intermediate transfer belt 20 onto the recording paper P. The secondary transfer bias is determined based on the resistance detected by a resistance detection mechanism (not shown) that detects the resistance of the secondary transfer section, and the voltage is controlled accordingly.

[0314] Then, the recording paper P is fed into the pressing part (engaging part) of a pair of fixing rollers in the fixing device (an example of a fixing mechanism) 28, and the toner image is fixed on the recording paper P to form a fixed image.

[0315] Recording paper P used for transferring toner images can include, for example, ordinary paper used in photocopiers and printers using electrophotographic methods. In addition to recording paper P, other examples of recording media include OHP transparent film.

[0316] To further improve the smoothness of the image surface after fixing, it is preferable that the surface of the recording paper P is also smooth, such as coated paper or art paper for printing, which are obtained by coating the surface of ordinary paper with resin or the like.

[0317] The recording paper P, which has been fixed with a color image, is sent to the discharge section, thus ending a series of color imaging actions.

[0318] <Processing Box>

[0319] The processing box of this embodiment is a processing box that is installed and removed from the image forming apparatus. It has a developing mechanism that stores the electrostatic image developer of this embodiment and uses the electrostatic image developer to develop the electrostatic image formed on the surface of the image holder into a toner image.

[0320] The processing box of this embodiment is not limited to the above configuration, and may also be configured to include a developing mechanism and, if necessary, at least one of other mechanisms selected from an image holder, a charging mechanism, an electrostatic image forming mechanism, and a transfer mechanism.

[0321] The following shows an example of the processing box of this embodiment, but it is not limited thereto. In the following description, the main parts shown in the figures will be described, and other descriptions will be omitted.

[0322] Figure 2 This is a schematic configuration diagram of the processing box in this embodiment. Figure 2 The processing cartridge 200 shown is constructed, for example, by integrating and holding the photosensitive element 107 (an example of an image holder) with the charging roller 108 (an example of a charging mechanism), the developing device 111 (an example of a developing mechanism), and the photosensitive element cleaning device 113 (an example of a cleaning mechanism) around the photosensitive element 107 in a housing 117 having a mounting rail 116 and an opening 118 for exposure, thus forming an ink cartridge.

[0323] Figure 2 In the diagram, 109 represents an exposure device (an example of an electrostatic image forming mechanism), 112 represents a transfer device (an example of a transfer mechanism), 115 represents a fixing device (an example of a fixing mechanism), and 300 represents recording paper (an example of a recording medium).

[0324] [Example]

[0325] The following detailed description of the embodiments of the invention is provided through examples, but the embodiments of the invention are not limited to these examples. In the following description, unless otherwise stated, "parts" and "%" are based on mass.

[0326] In the following description, the volume average particle size refers to the particle size D accumulated at the 50% point from the smallest diameter side in the particle size distribution on a volume basis. 50v .

[0327] <Making of Toning Agents>

[0328] [Preparation of Amorphous Polyester Resin Dispersion (A1)]

[0329] Ethylene glycol: 37 parts

[0330] Neopentyl glycol: 65 parts

[0331] ·1,9-Nonadiol: 32 parts

[0332] • Terephthalic acid: 96 parts

[0333] The above materials were added to a flask, and the temperature was raised to 200°C over 1 hour. After confirming that the reaction system was uniformly stirred, 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 stirring was continued at 240°C for 4 hours to obtain an amorphous polyester resin (acid value 9.4 mgKOH / g, weight-average molecular weight 13,000, glass transition temperature 62°C). The amorphous polyester resin was kept in a molten state and fed into an emulsifying disperser (Cavitron CD1010, Eurotec) at a rate of 100 g per minute. Separately, reagent ammonia was diluted with deionized water, and the resulting 0.37% concentration dilute ammonia solution was added to a tank and heated to 120°C using a heat exchanger. Simultaneously, it was fed into the emulsifying disperser along with the amorphous polyester resin at a rate of 0.1 liters per minute. The emulsifying disperser was operated at a rotor speed of 60 Hz and a pressure of 5 kg / cm². 2 Under the specified operating conditions, an amorphous polyester resin dispersion (A1) with a volume average particle size of 160 nm and a solid content of 20% was obtained.

[0334] [Preparation of Crystalline Polyester Resin Dispersion (C1)]

[0335] Sebacic acid: 81 parts

[0336] Hexanediol: 47 parts

[0337] The above materials were added to a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide were added. While distilling off the generated water, the temperature was raised to 200°C over 6 hours, and stirring was continued at 200°C for 4 hours. The reaction solution was then cooled, and solid-liquid separation was performed. The solid was dried at 40°C under reduced pressure to obtain crystalline polyester resin (C1) (melting point 64°C, weight average molecular weight 15,000).

[0338] • Crystalline polyester resin (C1): 50 parts

[0339] • Anionic surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., NEOGEN RK): 2 parts

[0340] • Ion-exchanged water: 200 parts

[0341] The above materials were heated to 120°C and thoroughly dispersed using a homogenizer (ULTRA-TURRAXT50, IKA). Further dispersion was then performed using a pressure-discharge homogenizer. The dispersion was recovered when the volume average particle size reached 180 nm, yielding a crystalline polyester resin dispersion (C1) with a solid content of 20%.

[0342] [Preparation of release agent particle dispersion (W1)]

[0343] • Solid paraffin wax (HNP-9, manufactured by Nippon Seika Co., Ltd.): 100 parts

[0344] • Anionic surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., NEOGEN RK): 1 part

[0345] • Ion-exchanged water: 350 parts

[0346] The above materials were mixed and heated to 100°C. After dispersion using a homogenizer (ULTRA-TURRAXT50 manufactured by IKA), the mixture was further dispersed using a pressure-discharge Gaulin homogenizer to obtain a release agent particle dispersion containing release agent particles with a volume average particle size of 200 nm. Ion-exchanged water was added to this release agent particle dispersion to reduce the solid content to 20%, thus preparing the release agent particle dispersion (W1).

[0347] [Preparation of colorant particle dispersion (K1)]

[0348] • Carbon black (manufactured by Cabot, Regal 330): 50 parts

[0349] • Anionic surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., NEOGEN RK): 5 parts

[0350] • Ion-exchanged water: 195 parts

[0351] The above materials were mixed and dispersed for 60 minutes using a high-pressure impact disperser (Ultimaizer HJP30006, SuginoMachine) to obtain a colorant particle dispersion (K1) with a solid content of 20%.

[0352] [Preparation of colorant particle dispersion (C1)]

[0353] • Cyan pigment (pigment blue 15:3, Daihisei Kagaku): 50 parts

[0354] • Anionic surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., NEOGEN RK): 5 parts

[0355] • Ion-exchanged water: 195 parts

[0356] The above materials were mixed and dispersed for 60 minutes using a high-pressure impact disperser (Ultimaizer HJP30006, SuginoMachine) to obtain a colorant particle dispersion (C1) with a solid content of 20%.

[0357] [Preparation of colorant particle dispersion (M1)]

[0358] • Magenta pigment (Pigment Red 122, DIC Company): 50 parts

[0359] • Anionic surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., NEOGEN RK): 5 parts

[0360] • Ion-exchanged water: 195 parts

[0361] The above materials were mixed and dispersed for 60 minutes using a high-pressure impact disperser (Ultimaizer HJP30006, SuginoMachine) to obtain a colorant particle dispersion (M1) with a solid content of 20%.

[0362] [Preparation of Black Toner Granules (K1)]

[0363] • Ion-exchanged water: 200 parts

[0364] • Amorphous polyester resin dispersion (A1): 150 parts

[0365] • Crystalline polyester resin dispersion (C1): 10 parts

[0366] • Release agent particle dispersion (W1): 10 parts

[0367] • Colorant particle dispersion (K1): 15 parts

[0368] • Anionic surfactant (TaycaPower): 2.8 parts

[0369] The above materials were added to a round stainless steel flask. After adjusting the pH to 3.5 with 0.1N nitric acid, an aqueous solution of polyaluminum chloride (30% powder, manufactured by Oji Paper Co., Ltd.) was added in 30 parts of deionized water. The mixture was dispersed at 30°C using a homogenizer (ULTRA-TURRAXT50, manufactured by IKA Co., Ltd.), and then heated to 45°C in an oil bath, maintaining the temperature until the volume average particle size reached 4.9 μm. Next, 60 parts of an amorphous polyester resin dispersion (A1) were added, and the mixture was maintained for 30 minutes. Then, when the volume average particle size reached 5.2 μm, another 60 parts of the amorphous polyester resin dispersion (A1) were added, and the mixture was maintained for 30 minutes. Finally, 20 parts of a 10% NTA (nitroglycerin) metal salt aqueous solution (Chelest 70, manufactured by Chelest Co., Ltd.) were added, along with a 1N sodium hydroxide aqueous solution, and the pH was adjusted to 9.0. Next, one part of anionic surfactant (Tayca Power) was added, and stirring continued while heating to 85°C and maintaining this temperature for 5 hours. Then, the mixture was cooled to 20°C at a rate of 20°C / min. The mixture was then filtered, thoroughly washed with deionized water, and dried to obtain black toner particles (K1) with a volume average particle size of 5.7 μm and an average roundness of 0.971.

[0370] [Preparation of Cyan Toner Particles (C1)]

[0371] The colorant particle dispersion (K1) was changed to a colorant particle dispersion (C1). Furthermore, cyan colorant particles (C1) were obtained in the same manner as the black colorant particles (K1).

[0372] [Preparation of magenta colorant granules (M1)]

[0373] The colorant particle dispersion (K1) was changed to a colorant particle dispersion (M1). Furthermore, magenta colorant particles (M1) were obtained in the same manner as the black colorant particles (K1).

[0374] [Making of Black Toning Agent (K1)]

[0375] 100 parts by weight of black colorant particles (K1) and 1.5 parts by weight of hydrophobic silica particles (NIPPON AEROSIL, RY50) were loaded into a sample mill and mixed at 10,000 rpm for 30 seconds. The mixture was then sieved using a vibrating sieve with a mesh size of 45 μm to obtain black colorant (K1) with a volume average particle size of 5.7 μm.

[0376] [Making of Cyan Toner (C1)]

[0377] The black toner particles (K1) are replaced with cyan toner particles (C1). Furthermore, the cyan toner (C1) is obtained in the same manner as the black toner (K1).

[0378] [Preparation of magenta colorant (M1)]

[0379] The black toner particles (K1) are replaced with magenta toner particles (M1), and the magenta toner (M1) is obtained in the same way as the black toner (K1).

[0380] <Preparation of Ferrite Particles>

[0381] 1318 parts of Fe2O3, 587 parts of Mn(OH)2, and 96 parts of Mg(OH)2 were mixed and pre-fired at 900℃ for 4 hours. The pre-fired product, 6.6 parts of polyvinyl alcohol, 0.5 parts of polycarboxylic acid as a dispersant, and 1 mm diameter zirconia beads were added to water. The mixture was then pulverized and mixed using a sand mill to obtain a dispersion. The volume average particle size of the particles in the dispersion was 1.5 μm.

[0382] The dispersion was used as raw material and granulated and dried using a spray dryer to obtain granules with a volume average particle size of 37 μm. Then, under an oxygen-nitrogen mixed atmosphere with an oxygen partial pressure of 1%, the granules were calcined in an electric furnace at 1450 °C for 4 hours, followed by heating in the atmosphere at 900 °C for 3 hours to obtain calcined particles. The calcined particles were then pulverized and classified to obtain ferrite particles (1) with a volume average particle size of 35 μm. The arithmetic mean height Ra of the roughness curve of the ferrite particles (1) based on JIS B0601:2001 was 0.6 μm.

[0383] <Preparation of silica particles added to the carrier resin layer>

[0384] [Silica particles (1)]

[0385] Prepare commercially available hydrophilic silica particles (fumed silica particles, untreated, with a volume average particle size of 40 nm) and use them as silica particles (1).

[0386] [Silica particles (2)]

[0387] In a 1.5L glass reaction vessel equipped with a stirrer, dropper, and thermometer, 890 parts of methanol and 210 parts of 9.8% ammonia were added and mixed to obtain an alkaline catalyst solution. After adjusting the alkaline catalyst solution to 45°C, 550 parts of tetramethoxysilane and 140 parts of 7.6% ammonia were simultaneously added dropwise over 450 minutes with stirring to obtain a silica particle dispersion (A). The volume average particle size of the silica particles in the silica particle dispersion (A) was 4 nm, and the volume particle size distribution index (D0, the particle size at the 16% cumulative point from the smallest diameter side in the volume-based particle size distribution) was [not specified]. 16v With a cumulative particle size D of 84% of the points 84v The square root of the ratio, i.e. (D) 84v / D 16v ) 1 / 2 The value is 1.2.

[0388] 300 parts of silica particle dispersion (A) were added to an autoclave equipped with a stirrer, which was then rotated at 100 rpm. While the stirrer continued to rotate, liquefied carbon dioxide was injected into the autoclave from a carbon dioxide storage tank via a pump. The autoclave was simultaneously heated by a heater and pressurized by the pump, achieving a supercritical state of 150°C and 15 MPa. The pressure valve was operated to maintain the pressure in the autoclave at 15 MPa while supercritical carbon dioxide was continuously flowing through it to remove methanol and water from the silica particle dispersion (A). The carbon dioxide supply was stopped when 900 parts of carbon dioxide were supplied to the autoclave, yielding silica particle powder.

[0389] The autoclave was maintained at 150°C and 15 MPa using a heater and pump to maintain a supercritical state of carbon dioxide. While the agitator in the autoclave was continuously rotating, hexamethyldisilazane (50 parts per 100 parts of silica particles) was injected into the autoclave using an azeotropic pump. The autoclave temperature was raised to 180°C, and the reaction was allowed to proceed for 20 minutes. Then, supercritical carbon dioxide was circulated through the autoclave again to remove any remaining hexamethyldisilazane. The agitation was then stopped, the pressure valve was opened, and the pressure inside the autoclave was increased to atmospheric pressure. The temperature was then lowered to room temperature (25°C). This yielded silica particles (2) that had undergone surface treatment with hexamethyldisilazane. The volume average particle size of the silica particles (2) was 4 nm, and the number average particle size was 5 nm.

[0390] [Silica particles (3)]

[0391] By increasing the amount of tetramethoxysilane and 7.6% ammonia added during the preparation of silica particle dispersion (A), the volume average particle size of the silica particles in the silica particle dispersion was changed to 6 nm. In addition, silica particles (3) that were surface-treated with hexamethyldisilazane were obtained in the same manner as silica particles (2). The volume average particle size of silica particles (3) was 7 nm.

[0392] [Silica particles (4)]

[0393] Commercially available hydrophobic silica particles (vaporized silica particles with surface treatment using hexamethyldisilazane, manufactured by Tokuyama Corporation, trade name: REOLOSIL HM20S, volume average particle size 12nm) were prepared and used as silica particles (4).

[0394] [Silica particles (5)]

[0395] Prepare commercially available hydrophilic silica particles (fumed silica particles, untreated, with a volume average particle size of 62 nm) and use them as silica particles (5).

[0396] [Silica particles (6)]

[0397] Prepare commercially available hydrophobic silica particles (gas-phase silica particles with a volume average particle size of 88 nm that have undergone surface treatment with hexamethyldisilazane) and use them as silica particles (6).

[0398] [Silica particles (7)]

[0399] Prepare commercially available hydrophobic silica particles (gas-phase silica particles with a volume average particle size of 93 nm that have undergone surface treatment with hexamethyldisilazane) and use them as silica particles (7).

[0400] <Preparation of coating agents for forming carrier resin layers>

[0401] [Coating agent (1)]

[0402] • Perfluoropropyl ethyl methacrylate-methyl methacrylate copolymer (polymerization ratio 30:70, weight average molecular weight 19000): 7.5 parts

[0403] • Cyclohexyl methacrylate resin (weight average molecular weight 50,000): 9 parts

[0404] • Carbon black (Cabot Corporation, VXC72): 0.5 parts

[0405] • Silica particles (1): 20 parts

[0406] Toluene: 250 parts

[0407] Isopropyl alcohol: 50 parts

[0408] The above materials and glass beads (1 mm in diameter, in the same amount as toluene) were put into a sand mill and stirred at 190 rpm for 30 minutes to obtain a coating agent with 11% solid content (1).

[0409] [Coating agents (2)~(7)]

[0410] The silica particles (1) are replaced with any one of silica particles (2) to (7), and the coating agents (2) to (7) are obtained in the same manner as the coating agent (1).

[0411] [Coating agent (8)~(11)]

[0412] The amount of silica particles (1) added was changed as described below. In addition, coating agents (8) to (11) were obtained in the same manner as the preparation of coating agent (1).

[0413] • Coating agent (8): 10 parts of silica particles (1)

[0414] • Coating agent (9): 12 parts of silica particles (1)

[0415] • Coating agent (10): 30 parts of silica particles (1)

[0416] • Coating agent (11): 40 parts of silica particles (1)

[0417] [Coating agent (12-1) and coating agent (12-2)]

[0418] -Coating agent (12-1)-

[0419] • Cyclohexyl methacrylate resin (weight average molecular weight 50,000): 20 parts

[0420] • Polyisocyanates (Tosoh Corporation, CORONETL): 4 parts

[0421] • Carbon black (Cabot Corporation, VXC72): 1 part

[0422] Toluene: 425 parts

[0423] Methanol: 50 parts

[0424] The above materials and glass beads (1 mm in diameter, in the same amount as toluene) were put into a sand mill and stirred at 1200 rpm for 30 minutes to obtain a coating agent (12-1) with a solid content of 5%.

[0425] -Coating agent (12-2)-

[0426] • Silica particles (4): 8 parts

[0427] Toluene: 92 parts

[0428] The above materials and glass beads (1 mm in diameter, in the same amount as toluene) were put into a sand mill and stirred at 1200 rpm for 30 minutes to obtain a coating agent (12-2) with 8% solid content.

[0429] <Fabrication of Resin-Coated Carriers>

[0430] [Carrier(1)]

[0431] 1000 parts of ferrite particles (1) and 125 parts of coating agent (1) were put into a kneader and mixed at room temperature (25°C) for 20 minutes. Then the mixture was heated to 70°C and dried under reduced pressure.

[0432] Cool the dried material to room temperature (25°C), add 125 parts of coating agent (1), and mix at room temperature (25°C) for 20 minutes. Then heat to 70°C and dry under reduced pressure.

[0433] Next, the dried material was removed from the kneader and sieved with a 75μm mesh to remove coarse powder, thus obtaining the carrier (1).

[0434] [Carriers (2)~(7)]

[0435] According to Table 1, the mixing time after adding the coating agent (1) was changed. In addition, carriers (2) to (7) were made in the same manner as carrier (1).

[0436] [Carriers (8)~(13)]

[0437] The coating agent (1) is changed to any one of the coating agents (2) to (7). In addition, the carriers (8) to (13) are made in the same manner as the carrier (1).

[0438] [Carriers (14)~(19)]

[0439] According to Table 1, the amount of coating agent (1) added was changed and added. In addition, carriers (14) to (19) were obtained in the same manner as the carrier (1).

[0440] [Carriers (20)~(23)]

[0441] The coating agent (1) is changed to any one of the coating agents (8) to (11), and the carriers (20) to (23) are obtained in the same manner as the carrier (1).

[0442] [Carrier (24)]

[0443] 100 parts of ferrite particles (1) and 40 parts of coating agent (12-1) were added to a vacuum degassing kneader. The mixture was heated and depressurized under stirring, and dried under an atmosphere of 90℃ / -720mHg for 30 minutes. The removed carrier was coated with 10 parts of coating agent (12-2) by spraying. After drying, it was placed in an electric furnace at 150℃ for 1 hour for firing. The coarse powder was removed by sieving through a 75μm mesh to obtain the carrier (24).

[0444] <Developing the Developer>

[0445] Any one of the carriers (1) to (24) is mixed with the black toner (K1) at a mass ratio of 100:10 and placed into a V-type mixer. The mixture is stirred for 20 minutes to obtain black developers (K1) to (K24).

[0446] The black tone agent (K1) was changed to the cyan tone agent (C1), and cyan developer agents (C1) to (C24) were obtained in the same manner as described above.

[0447] The black toning agent (K1) was changed to the magenta toning agent (M1), and magenta developers (M1) to (M24) were obtained in the same manner as described above.

[0448] Hereinafter, developer (K1), developer (C1) and developer (M1) will be collectively referred to as developer (1). The same applies to developers (2) to (24).

[0449] <Determination of the average particle size of silica particles in the resin layer>

[0450] The carrier was embedded in epoxy resin and cut using a microtome to create a cross-section. The cross-section was then imaged using a scanning transmission electron microscope (SEM, Hitachi, S-4100). The resulting SEM images were imported into an image processing and analysis system (NIRECO, Luzex AP) for analysis. One hundred silica particles (primary particles) were randomly selected from the resin layers, and their equivalent circular diameters (nm) were calculated. The arithmetic mean of these diameters was used as the average particle size (nm) of the silica particles.

[0451] <Determination of the average thickness of the resin layer>

[0452] The SEM images were imported into an image processing and analysis device (NIRECO Corporation, Luzex AP) for image analysis. Ten locations were randomly selected from each carrier particle to measure the resin layer thickness (μm). Further measurements were performed on 100 carriers, and the arithmetic mean of all values ​​was taken as the average resin layer thickness (μm).

[0453] <Carrier Surface Analysis>

[0454] As the apparatus for three-dimensional analysis of the carrier surface, the ERA-8900FE electron beam 3D roughness analysis apparatus manufactured by Elionix Co., Ltd. was used. The carrier surface analysis using the ERA-8900FE was performed as follows.

[0455] The surface of a carrier particle was magnified 5000 times, and 400 measurement points were taken longitudinally and 300 measurement points were taken laterally to perform 3D measurements. 3D image data was obtained for a 24μm × 18μm region. For the 3D image data, the limiting wavelength of the spline filter was set to 12μm to remove wavelengths with a period longer than 12μm. Furthermore, the sampling length of the Gaussian high-pass filter was set to 2.0μm to remove wavelengths with a period longer than 2.0μm, resulting in 3D roughness curve data. From the 3D roughness curve data, the central 12μm × 12μm region (top-view area A = 144μm) was determined. 2 ) surface area B (μm) 2 ), calculate the area ratio B / A. Calculate the area ratio B / A for each of the 100 carriers, and then take the arithmetic mean.

[0456] <Determination of Silicon Concentration>

[0457] Using a support as the sample, X-ray photoelectron spectroscopy (XPS) was used for analysis under the following conditions, and the silicon concentration (atomic%) was determined from the peak intensities of each element.

[0458] • XPS unit: Manufactured by ULVAC PHI, VersaProbe II

[0459] • Etching gun: Argon gun

[0460] Accelerating voltage: 5kV

[0461] • Radiation current: 20mA

[0462] Sputtering area: 2mm × 2mm

[0463] • Sputtering rate: 3 nm / min (SiO2 conversion)

[0464] <Evaluation of the colorant blown out>

[0465] Prepare a modified DocuPrintColor3540 image forming apparatus (manufactured by Fuji Xerox Co., Ltd.), and load any of the developer solutions (1) to (24) into the developing unit. Place the image forming apparatus in an environment with a temperature of 22.5°C and a relative humidity of 50% for 24 hours. At a temperature of 22.5°C and a relative humidity of 50%, continuously output 100,000 black test charts with an image density of 1% on A6-sized plain paper, and then continuously output 100,000 black test charts with an image density of 100% on A6-sized plain paper. After image formation, visually observe the interior of the image forming apparatus and classify it according to the following criteria.

[0466] A: No internal contamination caused by colorants has been confirmed.

[0467] B: Slight contamination of the machine caused by colorant was confirmed in a very small area.

[0468] C: Some internal contamination caused by colorants has been confirmed, but it is within the permissible range for actual use.

[0469] D: Significant internal contamination caused by colorants has been identified, posing a problem in actual use.

[0470] <Evaluation of Transferability>

[0471] Prepare an image forming apparatus, DocuPrintColor400 (manufactured by Fuji Xerox Co., Ltd.), and load any of the developer solutions (1) to (24) into the developing machine. Place the image forming apparatus in an environment with a temperature of 10°C and a relative humidity of 15% for 24 hours. In an environment with a temperature of 10°C and a relative humidity of 15%, continuously output 50,000 test charts with an image density of 1% (blue with a cyan concentration of 50% and a magenta concentration of 50%) on A4-sized embossed paper (Lesac 66, Tokusai Paper Co., Ltd.). During image forming, set the fixing temperature to 190°C and the fixing pressure to 4.0 kg / cm². 2 .

[0472] -Coloring agent scattering-

[0473] Use a 100x graduated magnifying glass to observe the background of the 10th and 50,000th images respectively, and classify them according to the following criteria.

[0474] G0: No colorant scattering occurred.

[0475] G1: Although colorant scattering occurs, there are no problems in actual use.

[0476] G2: Colorant may scatter, potentially causing problems in practical use.

[0477] G3: Colorant scattering occurs, causing problems in actual use.

[0478] -Color difference-

[0479] Using a spectrophotometer (X-Rite Ci62, manufactured by X-Rite), L values ​​were measured at three locations for the 10th and 50,000th images, respectively. * value, a * value and b * The color difference ΔE is calculated based on the following formula, and the color difference ΔE is graded according to the following criteria.

[0480]

[0481] In the formula, L1, a1, and b1 are the L values ​​of the 10th image. * value, a * value and b * Values ​​(averages at 3 points respectively), L2, a2, and b2 are the L values ​​of the 50,000th image. * value, a * value and b * Values ​​(average values ​​at 3 points).

[0482] G0: Color difference ΔE is less than 1.

[0483] G1: Color difference ΔE is greater than 1 and less than 3.

[0484] G2: Color difference ΔE is greater than 3 and less than 5.

[0485] G3: Color difference ΔE is greater than 5.

[0486] [Table 1]

[0487]

[0488] <Examples including inorganic pigments containing metals as colorants>

[0489] <Preparation of Colorant Particle Dispersion (W1)>

[0490] 0.15 mol of glycerol was added to 100 mL of a 1 mol / L titanium tetrachloride aqueous solution, and the mixture was heated at 90 °C for 4 hours to form white particles, which were then filtered. The resulting white particles were dispersed in 100 mL of ion-exchange water, and 0.4 mol of hydrochloric acid was added. The mixture was then heated again at 90 °C for 3 hours. After adjusting the pH to 7 with 0.1 N sodium hydroxide, the mixture was filtered, washed with water, and dried (105 °C for 12 hours) to obtain white pigment particles (1) as titanium dioxide particles. The particle size of the obtained white pigment particles (1) was 250 nm.

[0491] • White pigment particles (1): 100 parts

[0492] • Anionic surfactant (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., NEOGEN R): 15 parts

[0493] • Ion-exchanged water: 400 parts

[0494] The above materials are mixed and dispersed for about 3 hours using a high-pressure impact disperser Ultimaizer (manufactured by Sugino Machine Co., Ltd., HJP30006) to prepare a colorant particle dispersion (W1).

[0495] The solid content of the colorant particle dispersion (W1) is 23% by mass.

[0496] <Preparation of Colorant Particle Dispersion (W2)>

[0497] 0.15 mol of glycerol was added to 100 mL of a 1 mol / L titanium tetrachloride aqueous solution, and the mixture was heated at 25 °C for 1 hour to form white particles, which were then filtered. The resulting white particles were dispersed in 100 mL of ion-exchange water, and 0.4 mol of hydrochloric acid was added. The mixture was heated at 90 °C for 4 hours. After adjusting the pH to 7 with 0.1 N sodium hydroxide, the mixture was filtered, washed with water, and dried (105 °C for 12 hours) to obtain white pigment particles (2) as titanium dioxide particles. The particle size of the obtained white pigment particles (2) was 100 nm.

[0498] Except that white pigment particles (2) are used instead of white pigment particles (1), colorant particle dispersion (W2) is prepared in the same manner as colorant particle dispersion (W1). The solid content of colorant particle dispersion (W2) is 23% by mass.

[0499] <Preparation of Colorant Particle Dispersion (W3)>

[0500] 0.15 mol of glycerol was added to 100 mL of a 1 mol / L titanium tetrachloride aqueous solution, and the mixture was heated at 95 °C for 7 hours to form white particles, which were then filtered. The resulting white particles were dispersed in 100 mL of ion-exchange water, and 0.4 mol of hydrochloric acid was added. The mixture was then heated again at 95 °C for 4 hours. After adjusting the pH to 7 with 0.1 N sodium hydroxide, the mixture was filtered, washed with water, and dried (105 °C for 12 hours) to obtain white pigment particles (3) as titanium dioxide particles. The particle size of the obtained white pigment particles (3) was 750 nm.

[0501] Except that white pigment particles (3) are used instead of white pigment particles (1), colorant particle dispersion (W3) is prepared in the same way as colorant particle dispersion (W1).

[0502] The solid content of the colorant particle dispersion (W3) is 23% by mass.

[0503] <Preparation of Toning Agent Particles (W1)>

[0504] • Ion-exchanged water: 200 parts

[0505] • Amorphous polyester resin dispersion (A1): 150 parts

[0506] • Crystalline polyester resin dispersion (C1): 10 parts

[0507] • Release agent particle dispersion (W1): 10 parts

[0508] • Colorant particle dispersion (W1): 20 parts

[0509] • Anionic surfactant (TaycaPower): 2.8 parts

[0510] The above materials were added to a round stainless steel flask. After adjusting the pH to 3.5 with 0.1N nitric acid, an aqueous solution of polyaluminum chloride (30% powder, manufactured by Oji Paper Co., Ltd.) was added. The mixture was dispersed at 30°C using a homogenizer (ULTRA-TURRAX T50, manufactured by IKA Co., Ltd.), and then heated to 45°C in an oil bath until the volume average particle size reached 4.9 μm.

[0511] Next, add 60 parts of amorphous polyester resin dispersion (A1) and maintain for 30 minutes.

[0512] Next, when the volume average particle size reached 5.2 μm, 60 parts of amorphous polyester resin dispersion (A1) were added and maintained for 30 minutes.

[0513] Next, 20 parts of a 10% NTA (nitrotriacetic acid) metal salt aqueous solution (Chelest 70, manufactured by Chelest Co., Ltd.) were added, and the pH was adjusted to 9.0 by adding 1N sodium hydroxide aqueous solution. Then, 1 part of anionic surfactant (TaycaPower) was added, and the mixture was heated to 85°C while stirring, and maintained for 5 hours. Then, it was cooled to 20°C at a rate of 20°C / min. The mixture was then filtered, thoroughly washed with deionized water, and dried to obtain colorant particles (W1) with a volume average particle size of 5.7 μm and an average sphericity of 0.971.

[0514] In the following text, the amorphous polyester resin dispersion (A1) initially added to the round stainless steel flask is also referred to as the "initial amorphous polyester resin dispersion (A1)", the amorphous polyester resin dispersion (A1) added after maintaining the volume average particle size to 4.9 μm is also referred to as the "first added amorphous polyester resin dispersion (A1)", and the amorphous polyester resin dispersion (A1) added after the volume average particle size to 5.2 μm is also referred to as the "second added amorphous polyester resin dispersion (A1)".

[0515] <Making of Toning Agent (W1)>

[0516] 100 parts by weight of toner particles (W1) and 1.5 parts by weight of hydrophobic silica particles (manufactured by NIPPON AEROSIL, RY50) were loaded into a sample mill and mixed at a rotation speed of 10,000 rpm for 30 seconds. Then, the mixture was sieved using a vibrating sieve with a mesh size of 45 μm to obtain toner (W1) with a volume average particle size of 5.7 μm.

[0517] <Making of Toner Granules (W2) and Toner (W2)>

[0518] The amount of initial amorphous polyester resin dispersion (A1) added was changed to 100 parts, the amount of first additional amorphous polyester resin dispersion (A1) added was changed to 90 parts, and the amount of second additional amorphous polyester resin dispersion (A1) added was changed to 80 parts. Otherwise, toner particles (W2) and toner (W2) were obtained in the same manner as toner particles (W1) and toner (W1).

[0519] <Making of Toner Granules (W3) and Toner (W3)>

[0520] The amount of initial amorphous polyester resin dispersion (A1) added was changed to 180 parts, the amount of first additional amorphous polyester resin dispersion (A1) added was changed to 60 parts, and the amount of second additional amorphous polyester resin dispersion (A1) added was changed to 30 parts. Otherwise, toner particles (W3) and toner (W3) were obtained in the same manner as toner particles (W1) and toner (W1).

[0521] <Making of Toner Granules (W4) and Toner (W4)>

[0522] Except for changing the amount of anionic surfactant (TaycaPower) added to 1.9 parts, toner particles (W4) and toner (W4) were obtained in the same manner as toner particles (W1) and toner (W1).

[0523] <Making of Toner Granules (W5) and Toner (W5)>

[0524] Except for changing the amount of anionic surfactant (TaycaPower) added to 3.5 parts, toner particles (W5) and toner (W5) are obtained in the same way as toner particles (W1) and toner (W1).

[0525] <Making of Toner Granules (W6) and Toner (W6)>

[0526] The amount of initial amorphous polyester resin dispersion (A1) added was changed to 80 parts, the amount of first additional amorphous polyester resin dispersion (A1) added was changed to 100 parts, and the amount of second additional amorphous polyester resin dispersion (A1) added was changed to 90 parts. Otherwise, toner particles (W6) and toner (W6) were obtained in the same manner as toner particles (W1) and toner (W1).

[0527] <Making of Toner Granules (W7) and Toner (W7)>

[0528] The amount of initial amorphous polyester resin dispersion (A1) added was changed to 170 parts, the amount of first additional amorphous polyester resin dispersion (A1) added was changed to 90 parts, and the amount of second additional amorphous polyester resin dispersion (A1) added was changed to 10 parts. Otherwise, toner particles (W7) and toner (W7) were obtained in the same manner as toner particles (W1) and toner (W1).

[0529] <Making of Toner Granules (W8) and Toner (W8)>

[0530] Add 20 parts of colorant particle dispersion (W2) instead of 20 parts of colorant particle dispersion (W1), and change the amount of anionic surfactant (TaycaPower) to 1.5 parts. Otherwise, colorant particles (W8) and colorant (W8) are obtained in the same way as colorant particles (W1) and colorant (W1).

[0531] <Making of Toner Granules (W9) and Toner (W9)>

[0532] Add 20 parts of colorant particle dispersion (W3) instead of 20 parts of colorant particle dispersion (W1), and change the amount of anionic surfactant (TaycaPower) to 4 parts. Otherwise, colorant particles (W9) and colorant (W9) are obtained in the same way as colorant particles (W1) and colorant (W1).

[0533] <Making of Toner Granules (W10) and Toner (W10)>

[0534] Add 5.7 parts of colorant particle dispersion (W1) to replace 20 parts of colorant particle dispersion (W1), and change the amount of anionic surfactant (TaycaPower) from 2.8 parts to 1.4 parts. Otherwise, colorant particles (W10) and colorant (W10) are obtained in the same way as colorant particles (W1) and colorant (W1).

[0535] <Making of Toner Granules (W11) and Toner (W11)>

[0536] Add 29 parts of colorant particle dispersion (W1) instead of 20 parts of colorant particle dispersion (W1) to obtain colorant particles (W11) and colorant (W11) in the same manner as colorant particles (W1) and colorant (W1).

[0537] <Making of Toner Granules (W12) and Toner (W12)>

[0538] Add 5 parts of colorant particle dispersion (W1) to replace 20 parts of colorant particle dispersion (W1), otherwise obtain colorant particles (W12) and colorant (W12) in the same way as colorant particles (W1) and colorant (W1).

[0539] <Making of Toner Granules (W13) and Toner (W13)>

[0540] Add 35 parts of colorant particle dispersion (W1) to replace 20 parts of colorant particle dispersion (W1), otherwise obtain colorant particles (W13) and colorant (W13) in the same manner as colorant particles (W1) and colorant (W1).

[0541] <Determination of Toning Agents>

[0542] For the obtained colorant, the area ratio of the protrusions originating from the white pigment on the surface of the colorant particles (“protrusion ratio” in Table 2), the average particle size of the white pigment (“pigment particle size” in Table 2), the content of white pigment relative to the total amount of colorant particles (“pigment amount” in Table 2), and the average height of the protrusions originating from the white pigment on the surface of the colorant particles (“protrusion height” in Table 2) were determined by the above method, and the results are shown in Table 2.

[0543] [Table 2]

[0544]

[0545] [Making the carrier]

[0546] <Silica particles (8)>

[0547] The alkaline catalyst solution used in preparing the silica particle dispersion (A) was adjusted to 70°C. The amounts of tetramethoxysilane and 7.6% ammonia added were then changed to 550 parts tetramethoxysilane and 100 parts 7.6% ammonia, and the dropping time was changed to 400 minutes. The average particle size of the silica particles in the dispersion was changed to 90 nm. Furthermore, silica particles (8) surface-treated with hexamethyldisilazane were obtained in the same manner as those prepared for silica particles (2). The average particle size of the silica particles (8) was 90 nm.

[0548] <Silica particles (9)>

[0549] In a 1.5L glass reaction vessel equipped with a stirrer, a dropper, and a thermometer, 890 parts of methanol and 210 parts of 9.8% ammonia were added and mixed to obtain an alkaline catalyst solution.

[0550] After adjusting the alkaline catalyst solution to 47°C, 550 parts of tetramethoxysilane and 140 parts of 7.6% ammonia were added dropwise over 450 minutes with stirring to obtain a hydrophilic silica particle dispersion (B) with a particle size of 1 nm and a particle size distribution of 1.25.

[0551] Surface treatment of silica particles using a silica particle dispersion (B) under a supercritical carbon dioxide atmosphere with siloxane compounds is performed as described below. It should be noted that the surface treatment uses an apparatus equipped with a carbon dioxide reservoir, a carbon dioxide pump, an azeotropic agent pump, a high-pressure reactor (500 ml capacity) with a stirrer, and a pressure valve.

[0552] First, 300 parts of silica particle dispersion (B) were added to a 500ml autoclave equipped with a stirrer, and the stirrer was rotated at 100 rpm. Then, liquefied carbon dioxide was injected into the autoclave, and the temperature was increased using a heater while the pressure was increased using a carbon dioxide pump, bringing the autoclave to a supercritical state of 150℃ and 15MPa. While maintaining the pressure at 15MPa using a pressure valve, supercritical carbon dioxide was circulated using the carbon dioxide pump to remove methanol and water from the silica particle dispersion (B) (solvent removal step), yielding silica particles (untreated silica particles).

[0553] Next, when the supercritical carbon dioxide flow rate (integral quantity: measured in the form of carbon dioxide flow rate under standard conditions) reaches 900 parts, the flow of supercritical carbon dioxide is stopped.

[0554] Subsequently, while maintaining a temperature of 150°C using a heater and a pressure of 15 MPa using a carbon dioxide pump, and maintaining a supercritical carbon dioxide state in the autoclave, hexamethyldisilazane (manufactured by HMDS: Organic Synthesis Chemicals Co., Ltd.) was pre-injected into the autoclave as a hydrophobic treatment agent at a ratio of 100 parts per 100 parts of the aforementioned silica particles (untreated silica particles) using an azeotropic agent pump. The reaction was then carried out at 180°C for 20 minutes with stirring. Afterwards, supercritical carbon dioxide was circulated again to remove the remaining treatment agent solution. Then, stirring was stopped, the pressure valve was opened, the pressure inside the autoclave was increased to atmospheric pressure, and the temperature was lowered to room temperature (25°C). This process of solvent removal and surface treatment with a siloxane compound was repeated sequentially to obtain silica particles (9) with a number-average particle size of 1 nm as surface-treated silica particles.

[0555] <Silica particles (10)>

[0556] As silica particles (10), commercially available hydrophobic silica particles (silica particles that have been surface-treated with hexamethyldisilazane, manufactured by CABOT Corporation, product number: TG-6020N, ​​average particle size 200nm) were prepared.

[0557] <Making of the carrier (25)>

[0558] Ferrite particles (1): 100 parts

[0559] • Cyclohexyl methacrylate / methyl methacrylate copolymer (copolymer ratio 95 mol: 5 mol): 3 parts

[0560] • Silica particles (4): 0.7 parts

[0561] 14 parts of toluene

[0562] The cyclohexyl methacrylate / methyl methacrylate copolymer, silica particles (1), toluene, and glass beads (1 mm in diameter, in the same amount as toluene) from the above materials were put into a sand mill (Kansai Paint Co., Ltd.) and stirred at 1200 rpm for 30 minutes to prepare a coating agent (13). Ferrite particles (1) were added to a vacuum degassed kneader, and the coating agent (13) was further added. While stirring at 40 rpm, the mixture was heated and depressurized for 30 minutes to remove toluene by distillation. The ferrite particles (1) were then coated with resin to form a resin layer. Then, the fine and coarse powders were removed by a sharp bend jet classification to obtain a carrier (25) as the resin coating carrier.

[0563] <Making of the carrier (26)>

[0564] Except for changing the heating and decompression time to 60 minutes, the same carrier (25) was obtained as carrier (26).

[0565] <Making of the carrier (27)>

[0566] Except for changing the heating and decompression time to 15 minutes, the same carrier (25) was obtained as carrier (27).

[0567] <Making of the carrier (28)>

[0568] 0.7 parts of silica particles (2) were used instead of 0.7 parts of silica particles (4), and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 3.4 parts. Otherwise, the carrier (28) was obtained in the same manner as the carrier (25).

[0569] <Making of the carrier (29)>

[0570] The carrier (29) was obtained in the same manner as the carrier (25) except that 0.7 parts of silica particles (8) were used instead of 0.7 parts of silica particles (4) and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 2 parts.

[0571] <Making of the carrier (30)>

[0572] Except for changing the heating and decompression time to 90 minutes, the same carrier (25) was used to obtain the carrier (30).

[0573] <Making of the carrier (31)>

[0574] Except for changing the heating and decompression time to 10 minutes, the same carrier (25) was used to obtain the carrier (31).

[0575] <Making of the carrier (32)>

[0576] The carrier (32) was obtained in the same manner as the carrier (25) except that 0.7 parts of silica particles (9) were used instead of 0.7 parts of silica particles (4), and the heating and depressurization time was changed to 45 minutes and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 3 parts.

[0577] <Making of the carrier (33)>

[0578] Except that 0.7 parts of silica particles (4) were used instead of 0.7 parts of silica particles (10), the carrier (33) was obtained in the same manner as the carrier (25).

[0579] <Making of the carrier (34)>

[0580] Except for changing the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added to 5 parts, the carrier (34) was obtained in the same manner as the carrier (25).

[0581] <Making of the carrier (35)>

[0582] Except for changing the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added to 1.3 parts, the carrier (35) was obtained in the same manner as the carrier (25).

[0583] <Making of the carrier (36)>

[0584] Except that silica particles (4) are not used, the carrier (36) is obtained in the same way as the carrier (25).

[0585] <Carrier Determination>

[0586] The area ratio B / A (“Area Ratio B / A” in Tables 3 and 4), the average particle size of the silica particles contained in the resin layer (“Inorganic Particle Size” in Tables 3 and 4), and the average thickness of the resin layer (“Film Thickness” in Tables 3 and 4) were determined using the above method for the obtained carrier, and the results are shown in Tables 3 and 4.

[0587] [Developing the developer]

[0588] The carriers shown in Tables 3 and 4 and the toners shown in Tables 3 and 4 were mixed in a V-type mixer at a ratio of carrier:to-toner = 100:10 (mass ratio) and stirred for 20 minutes to obtain white developer.

[0589] [Evaluation of Developers]

[0590] Under conditions of 28.5℃ and 85% humidity, a DocuCentreColor400 (manufactured by Fuji Xerox Co., Ltd.) modification machine was used, along with A4-sized colored paper (manufactured by Fuji Xerox Co., Ltd., light blue, basis weight 64g / m³). 2An experiment was conducted to output 100,000 images over 10 days, using image samples with rectangular patches written at an image density of 20%. After outputting 100,000 images, the printing press was shut down and left to stand for 24 hours (specifically, 17 hours at 40°C and 90% humidity). Subsequently, 7,000 images were printed in one day using the image samples with rectangular patches written at an image density of 20% in borderless printing mode, after which the printing press was again shut down and left to stand for 24 hours (specifically, 17 hours at 40°C and 90% humidity). The next day, image quality was evaluated using Test Chart No. 5 from the Imaging Society of Japan (ISS) (specifically, evaluations of color stripes and blurring were performed). The evaluation criteria for each evaluation are shown below, and the results are presented in Tables 3 and 4. It should be noted that in the evaluation, up to C represents the acceptable range.

[0591] Evaluation Criteria for Color Streaks

[0592] A: There's no problem with the image quality.

[0593] B: Upon visual inspection, slight unevenness was observed on the developing sleeve due to the developing brush, but the image quality was not affected.

[0594] C: Upon visual inspection, unevenness caused by the developing brush was observed on the developing sleeve, with slight colored stripes also observed.

[0595] D: Upon visual inspection, unevenness caused by the developing brush was observed on the developing sleeve, and colored stripes were clearly visible.

[0596] <Evaluation Criteria for Fogging>

[0597] A: The density E of the background area (i.e., the non-image area) of the image is less than 0.015. No blurring was observed visually, and no blurring was confirmed in the tape transfer test on the photoreceptor. There are no problems with the image quality.

[0598] B: The background density E of the image is above 0.015 and below 0.03. No blurring was observed visually. Slight blurring was confirmed in the transfer test on the photosensitive material, but the image quality was not a problem.

[0599] B-: The background density E of the image is above 0.03 and below 0.04. No blur is observed visually, but blur is confirmed in the transfer test on the photosensitive material, but the image quality is not a problem.

[0600] C: The background density E of the image is above 0.04 and below 0.05. No blur is observed visually. However, blur is clearly confirmed in the transfer test on the photosensitive material, but the image quality is within the acceptable range.

[0601] D: The background concentration E of the image is above 0.05, which is visually blurry, and uneven concentration is clearly visible on the image.

[0602] It should be noted that the above "concentration E" is the average concentration obtained by measuring the non-image part at 9 points using an image density meter (X-Rite 938: manufactured by X-Rite Corporation).

[0603] [Table 3]

[0604]

[0605] [Table 4]

[0606]

[0607] As shown in the table above, compared with the comparative example, the generation of color stripes in the image was suppressed in the embodiment.

[0608] <Examples of using crystalline resins as adhesive resins>

[0609] <Preparation of Crystalline Polyester Resin Dispersion (C2)>

[0610] Sebacic acid: 81 parts

[0611] Hexanediol: 47 parts

[0612] The above materials were added to a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide were added. While distilling off the generated water, the temperature was raised to 200°C over 6 hours, and stirring was continued at 200°C for 4 hours. The reaction solution was then cooled, and solid-liquid separation was performed. The solid was dried at 40°C under reduced pressure to obtain crystalline polyester resin (C2) (melting point 67°C, weight average molecular weight 15,000).

[0613] Except that a crystalline polyester resin (C2) is used instead of a crystalline polyester resin (C1), a crystalline polyester resin dispersion (C2) with a solid content of 20% by mass is obtained in the same manner as the crystalline polyester resin dispersion (C1).

[0614] <Preparation of Crystalline Polyester Resin Dispersion (C3)>

[0615] • Dodecanoic acid: 81 parts

[0616] Ethylene glycol: 47 parts

[0617] The above materials were added to a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide were added. While distilling off the generated water, the temperature was raised to 200°C over 6 hours, and stirring was continued at 200°C for 4 hours. The reaction solution was then cooled, and solid-liquid separation was performed. The solid was dried at 40°C under reduced pressure to obtain crystalline polyester resin (C3) (melting point 86°C, weight average molecular weight 15,000).

[0618] Except that a crystalline polyester resin (C3) is used instead of a crystalline polyester resin (C1), a crystalline polyester resin dispersion (C3) with a solid content of 20% by mass is obtained in the same manner as the crystalline polyester resin dispersion (C1).

[0619] <Preparation of Crystalline Polyester Resin Dispersion (C4)>

[0620] • Oleic acid: 81 servings

[0621] Ethylene glycol: 47 parts

[0622] The above materials were added to a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide were added. While distilling off the generated water, the temperature was raised to 200°C over 6 hours, and stirring was continued at 200°C for 4 hours. The reaction solution was then cooled, and solid-liquid separation was performed. The solid was dried at 40°C under reduced pressure to obtain crystalline polyester resin (C4) (melting point 63°C, weight average molecular weight 15,000).

[0623] Except that a crystalline polyester resin (C4) is used instead of a crystalline polyester resin (C1), a crystalline polyester resin dispersion (C4) with a solid content of 20% by mass is obtained in the same manner as the crystalline polyester resin dispersion (C1).

[0624] <Preparation of Crystalline Polyester Resin Dispersion (C5)>

[0625] Phthalic acid: 81 parts

[0626] Nonadiol: 47 parts

[0627] The above materials were added to a flask, and the temperature was raised to 160°C over 1 hour. After confirming that the reaction system was uniformly stirred, 0.03 parts of dibutyltin oxide were added. While distilling off the generated water, the temperature was raised to 200°C over 6 hours, and stirring was continued at 200°C for 4 hours. The reaction solution was then cooled, and solid-liquid separation was performed. The solid was dried at 40°C under reduced pressure to obtain crystalline polyester resin (C5) (melting point 91°C, weight average molecular weight 15,000).

[0628] Except that a crystalline polyester resin (C5) is used instead of a crystalline polyester resin (C1), a crystalline polyester resin dispersion (C5) with a solid content of 20% by mass is obtained in the same manner as the crystalline polyester resin dispersion (C1).

[0629] <Making of Black Toner Granules (K2)>

[0630] • Ion-exchanged water: 200 parts

[0631] • Amorphous polyester resin dispersion (A1): 375 parts

[0632] • Crystalline polyester resin dispersion (C1): 50 parts

[0633] • Release agent particle dispersion (W1): 50 parts

[0634] • Colorant particle dispersion (K1): 25 parts

[0635] • Anionic surfactant (TaycaPower): 2.8 parts

[0636] The above materials were added to a round stainless steel flask. After adjusting the pH to 3.5 with 0.1N nitric acid, an aqueous solution of polyaluminum chloride (30% powder, manufactured by Oji Paper Co., Ltd.) was added in 30 parts of deionized water. The mixture was dispersed at 30°C using a homogenizer (ULTRA-TURRAX T50, manufactured by IKA Co., Ltd.), and then heated to 45°C in an oil bath, maintaining the temperature until the volume average particle size reached 4.9 μm. Next, 60 parts of an amorphous polyester resin dispersion (A1) were added, and the mixture was maintained for 30 minutes. Then, when the volume average particle size reached 5.2 μm, another 60 parts of the amorphous polyester resin dispersion (A1) were added, and the mixture was maintained for 30 minutes. Finally, 20 parts of a 10% NTA (nitroglycerin) metal salt aqueous solution (Chelest 70, manufactured by Chelest Co., Ltd.) were added, along with a 1N sodium hydroxide aqueous solution, and the pH was adjusted to 9.0. Next, 1 part of anionic surfactant (TaycaPower) was added, and stirring continued while heating to 85°C and maintaining this temperature for 5 hours. Then, the mixture was cooled to 20°C at a rate of 20°C / min. The mixture was then filtered, thoroughly washed with deionized water, and dried to obtain black toner particles (K2) with a volume average particle size of 5.7 μm and an average roundness of 0.971.

[0637] It should be noted that the content of crystalline polyester resin (C1) relative to the total content of black colorant particles (K2) is 10% by mass.

[0638] <Making of Black Toner (K2)>

[0639] 100 parts by weight of black colorant particles (K2) and 1.5 parts by weight of hydrophobic silica particles (additive, manufactured by NIPPONAEROSIL, RY50, average particle size: 40 nm) were added to a sample mill and mixed at 10,000 rpm for 30 seconds. The mixture was then sieved using a vibrating sieve with a 45 μm mesh size to obtain a black colorant (K2) with a volume average particle size of 5.7 μm. The half-fall temperature based on the flow tester was 105 °C.

[0640] <Making of Black Toner Granules (K3) and Black Toner (K3)>

[0641] Except for adding 75 parts of crystalline polyester resin dispersion (C2) to replace 10 parts of crystalline polyester resin dispersion (C1), black toner particles (K3) and black toner (K2) are obtained in the same manner as black toner particles (K2) and black toner (K2).

[0642] It should be noted that the content of crystalline polyester resin (C2) relative to the total content of black colorant particles (K3) is 14.3% by mass. The half-drop temperature of the flow tester is 95°C.

[0643] <Making Black Toner Granules (K4) and Black Toner (K4)>

[0644] Except for adding 35 parts of crystalline polyester resin dispersion (C3) to replace 10 parts of crystalline polyester resin dispersion (C1), black toner particles (K4) and black toner (K2) are obtained in the same manner as black toner particles (K2) and black toner (K2).

[0645] In addition, the content of crystalline polyester resin (C3) relative to the total content of black colorant particles (K4) is 7.2% by mass. The half-drop temperature based on the flow tester is 135°C.

[0646] <Making Black Toner Granules (K5) and Black Toner (K5)>

[0647] Except for adding 125 parts of crystalline polyester resin dispersion (C4) to replace 10 parts of crystalline polyester resin dispersion (C1), black tone agent particles (K5) and black tone agent (K2) are obtained in the same manner as black tone agent particles (K2) and black tone agent (K2).

[0648] It should be noted that the content of crystalline polyester resin (C4) relative to the total content of black colorant particles (K5) is 21.7% by mass. The half-fall temperature of the flow tester is 85°C.

[0649] <Making of Black Toner Granules (K6) and Black Toner (K6)>

[0650] Except for adding 25 parts of crystalline polyester resin dispersion (C5) to replace 10 parts of crystalline polyester resin dispersion (C1), black tone agent particles (K6) and black tone agent (K2) are obtained in the same way as black tone agent particles (K2) and black tone agent (K2).

[0651] In addition, the content of crystalline polyester resin (C5) relative to the total content of black colorant particles (K6) is 5.2% by mass. The half-fall temperature based on the flow tester is 145°C.

[0652] <Silica particles (11)>

[0653] As silica particles (11), commercially available hydrophobic silica particles (vaporized silica particles that have been surface-treated with dimethyl silicone oil, manufactured by Tokuyama Corporation, product name: PM09, average primary particle size: 60nm) are prepared.

[0654] <Silica particles (12)>

[0655] The temperature of the alkaline catalyst solution was changed to 35°C. In addition, silica particles (12) that were surface-treated with hexamethyldisilazane were obtained in the same manner as silica particles (2). The average primary particle size of silica particles (12) was 75 nm.

[0656] <Silica particles (13)>

[0657] As silica particles (13), commercially available hydrophobic silica particles (gas phase silica particles with surface treatment using hexamethyldisilazane, manufactured by NIPPON AEROSIL, product name: RX50, average primary particle size: 85nm) were prepared.

[0658] <Silica particles (14)>

[0659] The temperature of the alkaline catalyst solution was changed to 45°C. In addition, silica particles (14) that had been surface-treated with hexamethyldisilazane were obtained in the same manner as silica particles (2). The average primary particle size of silica particles (14) was 2 nm.

[0660] <Making of the carrier (37)>

[0661] Ferrite particles (1): 100 parts

[0662] Toluene: 10 parts

[0663] • Styrene / methyl methacrylate copolymer (copolymer ratio 15 mol: 85 mol): 0.8 parts

[0664] • Cyclohexyl methacrylate / methyl methacrylate copolymer (copolymer ratio 95 mol: 5 mol): 0.8 parts

[0665] • Carbon black: 0.08 parts

[0666] • Silica particles (4): 0.9 parts

[0667] The styrene / methyl methacrylate copolymer, cyclohexyl methacrylate / methyl methacrylate copolymer, silica particles (4), toluene, and glass beads (1 mm in diameter, in the same amount as toluene) from the above materials were added to a sand mill (Kansai Paint Co., Ltd.) and stirred at 1200 rpm for 30 minutes to prepare a coating agent (14). Ferrite particles (1) were added to a vacuum degassed kneader, followed by half the amount of coating agent (14). The mixture was stirred at 40 rpm while being heated to 70°C and held for 15 minutes. Then, the mixture was subjected to reduced pressure for 30 minutes to remove toluene by distillation. After cooling to room temperature (25°C), the remaining half of the coating agent (14) was added, and the mixture was stirred at 40 rpm while being heated to 70°C and mixed for 20 minutes. Then, the mixture was subjected to reduced pressure for 30 minutes to remove toluene by distillation. Finally, the fine and coarse powders were removed by a sharp-curve jet classification to obtain a carrier (37) as a resin coating carrier.

[0668] <Making of the carrier (38)>

[0669] 0.6 parts of silica particles (13) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.9 parts, the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.9 parts, and the second mixing time (i.e., the time for mixing while stirring at 40 rpm and heating to 70°C with half of the remaining amount of coating agent (14) added) was changed from 20 minutes to 40 minutes. Otherwise, the carrier (38) was obtained in the same manner as the carrier (37).

[0670] <Making of the carrier (39)>

[0671] 1.1 parts of silica particles (2) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.8 parts, the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.8 parts, and the second mixing time (i.e., the time for mixing while stirring at 40 rpm and heating to 70°C with half of the remaining amount of coating agent (14) added) was changed from 20 minutes to 15 minutes. Otherwise, the carrier (39) was obtained in the same manner as the carrier (37).

[0672] <Making of the carrier (40)>

[0673] 0.8 parts of silica particles (11) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.9 parts, the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.9 parts, and the second mixing time (i.e., the time for mixing while stirring at 40 rpm and heating to 70°C with half of the remaining amount of coating agent (14) added) was changed from 20 minutes to 30 minutes. Otherwise, the carrier (40) was obtained in the same manner as the carrier (37).

[0674] <Making of the carrier (41)>

[0675] 1.0 part of silica particles (12) was used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.8 parts, the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.8 parts, and the second mixing time (i.e., the time for mixing while stirring at 40 rpm and heating to 70°C with half of the remaining amount of coating agent (14) added) was changed from 20 minutes to 35 minutes. Otherwise, the carrier (41) was obtained in the same manner as the carrier (37).

[0676] <Making of the carrier (42)>

[0677] The carrier (42) was obtained in the same manner as the carrier (37) except that 0.4 parts of silica particles (4) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.6 parts and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.6 parts.

[0678] <Making of the carrier (43)>

[0679] The carrier (43) was obtained in the same manner as the carrier (37) by replacing 0.9 parts of silica particles (4) with 1.4 parts of silica particles (4) and changing the amount of styrene / methyl methacrylate copolymer added to 1.0 parts and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added to 1.0 parts.

[0680] <Making of the carrier (44)>

[0681] The carrier (44) was obtained in the same manner as the carrier (37) except that 0.8 parts of silica particles (4) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.7 parts and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.7 parts.

[0682] <Making of the carrier (45)>

[0683] The carrier (45) was obtained in the same manner as the carrier (37) except that 1.1 parts of silica particles (4) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.9 parts and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.9 parts.

[0684] <Making of the carrier (46)>

[0685] Without adding silica particles (4), and changing the amount of styrene / methyl methacrylate copolymer added to 1.1 parts and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added to 1.1 parts, the carrier (46) was obtained in the same manner as the carrier (37).

[0686] <Making of the carrier (47)>

[0687] 0.8 parts of silica particles (14) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.8 parts, the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.8 parts, and the second mixing time (i.e., the time for mixing while stirring at 40 rpm and heating to 70°C with half of the remaining amount of coating agent (14) added) was changed from 20 minutes to 10 minutes. Otherwise, the carrier (47) was obtained in the same manner as the carrier (37).

[0688] <Making of the carrier (48)>

[0689] The carrier (48) was obtained in the same manner as the carrier (37) except that 0.2 parts of silica particles (4) were used instead of 0.9 parts of silica particles (4), and the amount of styrene / methyl methacrylate copolymer added was changed to 0.3 parts and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added was changed to 0.3 parts.

[0690] <Making of the carrier (49)>

[0691] The carrier (49) was obtained in the same manner as the carrier (37) by replacing 0.9 parts of silica particles (4) with 1.6 parts of silica particles (4) and changing the amount of styrene / methyl methacrylate copolymer added to 1.1 parts and the amount of cyclohexyl methacrylate / methyl methacrylate copolymer added to 1.1 parts.

[0692] <Carrier Determination>

[0693] For the obtained carrier, the area ratio B / A (“Area Ratio B / A” in Table 5), the average particle size of the silica particles contained in the resin layer (“Inorganic Particle Size” in Table 5), and the average thickness of the resin layer (“Film Thickness” in Table 5) were determined by the above method, and the results are shown in Table 5.

[0694] [Evaluation of Developers]

[0695] Under conditions of 28.5℃ and 85% humidity, a modified DocuCentreColor400 (manufactured by Fuji Xerox Co., Ltd.) recording machine was used, along with A4-sized recording paper (manufactured by Fuji Xerox Co., Ltd., basis weight 64g / m³). 2 This process creates 10,000 midtone images with a 10% image density, which are then printed on A4-sized thin recording paper (manufactured by Fuji Xerox Co., Ltd., ST paper, 78μm thick, 54g / m²). 2 An image with 100% image density was generated on the image. The gloss at 60 degrees was measured at 10 points using a gloss meter (BYK Micro-Tri-Gloss meter (20+60+85°), manufactured by Gardner). Gloss unevenness was evaluated based on the difference in gloss at these 10 points (maximum value - minimum value) and the standard deviation. The evaluation criteria are as follows.

[0696] <Evaluation Criteria>

[0697] A: The difference in gloss is less than 5% and the standard deviation of the 10 gloss measurement points is less than 2.

[0698] B: The difference in gloss is less than 5% and the standard deviation of the 10 gloss measurement points is greater than 2.

[0699] C: The difference in gloss is greater than 5% but less than 7.5%.

[0700] D: The difference in gloss is 7.5% or more but less than 10%.

[0701] E: The difference in gloss is 10% or more.

[0702] [Table 5]

[0703]

[0704] As shown in the table above, compared with the comparative example, the embodiment suppressed uneven gloss in the image.

[0705] Symbol Explanation

[0706] 1Y, 1M, 1C, 1K photoreceptors (an example of image retainers)

[0707] 2Y, 2M, 2C, 2K electrified rollers (an example of an electrified mechanism)

[0708] 3. Exposure apparatus (an example of an electrostatic image forming mechanism)

[0709] 3Y, 3M, 3C, 3K laser lines

[0710] 4Y, 4M, 4C, 4K developing apparatus (an example of a developing mechanism)

[0711] 5Y, 5M, 5C, 5K - Primary transfer rollers (an example of a primary transfer mechanism)

[0712] 6Y, 6M, 6C, 6K photoreceptor cleaning device (an example of a cleaning mechanism)

[0713] 8Y, 8M, 8C, 8K Tone Kits

[0714] 10Y, 10M, 10C, 10K image forming units

[0715] 20. Intermediate transfer belt (an example of an intermediate transfer body)

[0716] 22 drive rollers

[0717] 24 support rollers

[0718] 26. Secondary transfer roller (an example of a secondary transfer mechanism)

[0719] 28. Fixing device (an example of a fixing mechanism)

[0720] 30 Intermediate Transfer Body Cleaning Device

[0721] P Recording paper (an example of a recording medium)

[0722] 107 Photoreceptor (an example of an image preserver)

[0723] 108 Charging roller (an example of a charging mechanism)

[0724] 109 Exposure apparatus (an example of an electrostatic image forming mechanism)

[0725] 111 Developing apparatus (an example of a developing mechanism)

[0726] 112 Transfer device (an example of a transfer mechanism)

[0727] 113 Photoreceptor cleaning device (an example of a cleaning mechanism)

[0728] 115 Fixing device (an example of a fixing mechanism)

[0729] 116 Mounting rails

[0730] 117 Housing

[0731] 118 Opening for exposure

[0732] 200 processing boxes

[0733] 300 Recording paper (an example of a recording medium)

Claims

1. An electrostatic image developer comprising an electrostatic image developing carrier and an electrostatic image developing toner, the electrostatic image developing carrier has: magnetic particles; and a resin layer covering the magnetic particles and containing inorganic particles and carbon black, the average particle diameter of the inorganic particles is 5 nm or more and 90 nm or less, the average thickness of the resin layer is 0.6 μm or more and 1.4 μm or less, wherein the area ratio B / A of the planar area A of the electrostatic image developing carrier to the surface area B of the electrostatic image developing carrier is 1.020 or more and 1.100 or less when the surface of the electrostatic image developing carrier is subjected to three-dimensional analysis, the electrostatic image developing toner contains toner particles containing a crystalline polyester resin, the inorganic particles are selected from the group consisting of silica particles, metal oxide particles, and metal particles.

2. An electrostatic image developer comprising an electrostatic image developing carrier and an electrostatic image developing toner, the electrostatic image developing carrier has: magnetic particles; and a resin layer covering the magnetic particles and containing inorganic particles and carbon black, the average particle diameter of the inorganic particles is 5 nm or more and 90 nm or less, the average thickness of the resin layer is 0.6 μm or more and 1.4 μm or less, wherein the area ratio B / A of the planar area A of the electrostatic image developing carrier to the surface area B of the electrostatic image developing carrier is 1.020 or more and 1.100 or less when the surface of the electrostatic image developing carrier is subjected to three-dimensional analysis, the electrostatic image developing toner contains toner particles containing a crystalline polyester resin, the inorganic particles are metal compound particles.

3. The electrostatic image developer according to claim 1 or 2, wherein the content of the crystalline polyester resin is 2 mass% or more and 20 mass% or less with respect to the total binder resin of the toner particles.

4. The electrostatic image developer according to claim 1 or 2, wherein the toner particles further contain an amorphous polyester resin, the content of the crystalline polyester resin is 2 mass% or more and 20 mass% or less with respect to the total binder resin of the toner particles.

5. The electrostatic image developer as claimed in claim 1 or 2, wherein, the area ratio B / A is 1.040 or more and 1.080 or less.

6. The electrostatic image developer as claimed in claim 1 or 2, wherein, the average particle diameter of the inorganic particles is 5 nm or more and 70 nm or less.

7. The electrostatic image developer as claimed in claim 1 or 2, wherein, the average thickness of the resin layer is 0.8 μm or more and 1.2 μm or less.

8. The electrostatic image developer as claimed in claim 1, wherein, the inorganic particles are silica particles, and the silicon element concentration at the surface of the electrostatic image developing carrier, which is obtained by X-ray photoelectron spectroscopy, is greater than 2 atomic% and less than 20 atomic%.

9. The electrostatic image developer as claimed in claim 8, wherein, the silicon element concentration is greater than 5 atomic% and less than 20 atomic%.

10. The electrostatic image developer as claimed in claim 1 or 2, wherein, the electrostatic image developing toner has toner particles containing an inorganic pigment containing a metal atom and an external additive attached to the surface of the toner particles, the area ratio B / A is 1.020 or more and 1.110 or less.

11. The electrostatic image developer as claimed in claim 10, wherein, the average particle diameter of the inorganic pigment is 150 nm or more and 500 nm or less.

12. The electrostatic image developer as claimed in claim 10, wherein, The area ratio of the protrusions derived from the inorganic pigment on the surface of the toner particles is 0.30% or more and 5.00% or less.

13. The electrostatic image developer as claimed in claim 10, wherein, The average height of the protrusions derived from the inorganic pigment on the surface of the toner particles is 0.05 μm or more and 0.30 μm or less.

14. The electrostatic image developer as claimed in claim 1 or 2, wherein, The electrostatic image developing toner has toner particles containing a crystalline resin and an external additive adhering to the surface of the toner particles.

15. The electrostatic image developer as claimed in claim 14, wherein, The melting point of the crystalline resin is 65°C or more and 90°C or less.

16. The electrostatic image developer as claimed in claim 14, wherein, The content of the crystalline resin is 5 mass% or more and 30 mass% or less relative to the entire toner particles.

17. The electrostatic image developer as claimed in claim 14, wherein, The 1 / 2 drop temperature of the toner, measured by a flow tester, is 90°C or more and 140°C or less.

18. An image forming apparatus comprising: an image holding body; a charging mechanism that charges a surface of the image holding body; an electrostatic image forming mechanism that forms an electrostatic image on the surface of the charged image holding body; a developing mechanism that develops the electrostatic image into a toner image using the electrostatic image developing agent according to claim 1 or 2; a transferring mechanism that transfers the toner image to a surface of a recording medium; and a fixing mechanism that fixes the toner image transferred to the surface of the recording medium. ​

Images