A carrier for electrostatic latent image developer, a two-component developer, a replenishment developer, a process cartridge, an image forming apparatus, an image forming method, and a method for manufacturing a carrier for electrostatic latent image developer.

Abstract

To provide an electrostatic latent image developer carrier which features little charge fluctuations while printing for a long time, and is capable of suppressing toner scattering, carrier adhesion while printing solid images, and the like.SOLUTION: An electrostatic latent image developer carrier is provided, comprising a magnetic core particle and a coating layer containing a resin and at least partially covering a surface of the core particle. Defining t as an average thickness of the coating layer and s as a standard deviation of the thickness of the coating layer, a ratio s / t is 0.05-0.6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carrier for electrostatic latent image developer, a two-component developer, a replenishment developer, a process cartridge, an image forming apparatus, an image forming method, and a method for manufacturing a carrier for electrostatic latent image developer. [Background technology]

[0002] The electrophotographic method involves forming an electrostatic latent image on the surface of a photoreceptor using charging and exposure means, developing the electrostatic latent image with a developer containing a magnetic carrier and toner to obtain a toner image, and then transferring and fixing the obtained toner image onto a transfer member to obtain a visible image.

[0003] Electrophotography has come to be used not only in photocopiers, which have been widely used until now, but also in production printing, which can print images at higher speeds and with higher resolution. For this reason, there has been a demand for developers that can meet the requirements for higher image quality and faster image output.

[0004] As a carrier for use in such developers, a carrier has been proposed in which magnetic core material particles are coated with resin to stabilize their charging properties (for example, Patent Document 1). In addition, a carrier has been proposed in which the charging properties of the carrier are adjusted by controlling the amount of a charge control agent placed on the carrier surface (for example, Patent Document 2). [Overview of the project] [Problems that the invention aims to solve]

[0005] However, especially when printing continued over a long period, the stability of the carrier's charging characteristics and the adhesion of carriers to solid images were insufficient, which sometimes resulted in a decrease in image quality.

[0006] Therefore, one aspect of the present invention aims to provide a carrier for electrostatic latent image developer that exhibits minimal charge fluctuations during long-term printing and can suppress toner scattering and carrier adhesion in solid images. [Means for solving the problem]

[0007] A carrier for an electrostatic latent image developer according to one aspect of the present invention comprises magnetic core material particles and a coating layer containing a resin that covers at least a portion of the surface of the core material particles, The coating layer comprises a silicone resin and dodecamethylpentasiloxane. Let t be the average thickness of the coating layer and s be the standard deviation of the thickness of the coating layer. The average thickness t of the coating layer is 0.2 μm to 0.7 μm. The ratio s / t is between 0.05 and 0.6. [Effects of the Invention]

[0008] According to one aspect of the present invention, a carrier for electrostatic latent image developers can be provided that exhibits less charge fluctuation during long-term printing and suppresses carrier adhesion in solid images. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing an example of a process cartridge according to one embodiment. [Figure 2] Figure 2 is a schematic diagram showing an example of an image forming apparatus according to one embodiment. [Modes for carrying out the invention]

[0010] (Carrier for electrostatic latent image developer) An electrostatic latent image developer carrier (hereinafter also referred to as "carrier") according to one embodiment of the present invention comprises core material particles and a coating layer (hereinafter also referred to as "coating film," "coating layer," "coating film," or "carrier coating layer"), and further comprises other components as necessary. The coating layer covers at least a portion of the surface of the core material particles.

[0011] Carriers used in production printing are required to meet the demands for high image quality and high-speed image output. Therefore, it is preferable that both the magnetic force and electrical resistance of the carrier possess a certain level of strength or higher.

[0012] Generally, magnetic particles used as core materials (core particles) tend to have a decrease in electrical resistance as their saturation magnetization increases. In other words, there is a trade-off relationship between electrical resistance and saturation magnetization. Therefore, carriers in which the core material is covered with a coating layer such as resin have been proposed to achieve both. However, when carriers are used for a long time, the coating layer covering the core material may wear away, exposing the core material. When a material with high saturation magnetization is used for the core material, the exposure of the core material can reduce the overall electrical resistance of the carrier, which can lead to solid carrier adhesion (a phenomenon in which carriers tend to adhere to solid images). For this reason, carriers with improved coating layer durability have been proposed by increasing the thickness of the coating layer or by including inorganic fine particles in the specific convergence. However, in these proposals, areas with thin and thick coating layers tend to exist within a single carrier. Areas with a thin coating layer are at high risk of exposing the core material. These thin areas become leak points, reducing resistance (carrier resistance), making it difficult to achieve the desired improvement effect against solid carrier adhesion and potentially hindering the pursuit of even higher image quality.

[0013] Therefore, the inventors investigated carriers that can withstand high image quality. As a result of diligent investigation, they found that carriers that can withstand high image quality are carriers that can suppress the occurrence of solid carrier adhesion both initially and after a long period of time, and that such carriers are carriers with little unevenness in the coating layer (the unevenness of the coating layer is flattened). Furthermore, they found that by setting the relationship between the average thickness of the coating layer and the standard deviation of the thickness of the coating layer to a predetermined range, the occurrence of solid carrier adhesion can be sufficiently suppressed both initially and after a long period of time, and the quality of images obtained by printing using a developer containing such a carrier can be improved.

[0014] <Surface properties of carriers> In the carrier according to this embodiment, the average thickness (thickness of the coating layer) t of the coating layer is preferably 0.05 μm to 1 μm, and more preferably 0.2 μm to 0.7 μm. When the average thickness is 0.05 μm or more, it is possible to prevent the problem that the coating layer is easily broken by use and the film is worn away. When it is 1 μm or less, it is possible to suppress the excessive increase in the thickness of the coating layer that is not a magnetic material and the increase in the adhesion of the carrier to the image, and the effect of resistance adjustment is not hindered.

[0015] As described above, it is preferable that the unevenness of the coating layer is small. The unevenness of the coating layer can be represented by the ratio of the average thickness of the coating layer to the standard deviation of the thickness of the coating layer in the carrier. For example, when the average thickness of the coating layer is t and the standard deviation of the thickness of the coating layer is s, it can be represented by s / t. That is, it can be represented by the value of the ratio of the standard deviation of the thickness of the coating layer to the average thickness of the coating layer.

[0016] The value of the ratio s / t is preferably 0.05 to 0.6, more preferably 0.10 to 0.6, and even more preferably 0.2 to 0.4. When the value of the ratio s / t is 0.05 or more, it is difficult for problems such as a decrease in charging performance due to toner adhesion to the carrier surface to occur, and a decrease in image quality can be suppressed. Also, when s / t is 0.6 or less, the unevenness between the thin and thick parts of the coating film thickness of the carrier is small, and the number of thin parts of the coating film thickness that become leakage parts decreases. As a result, the characteristics related to carrier adhesion, charging stability, and toner scattering, especially when printing for a long period of time, are improved.

[0017] As a method for adjusting the value of the ratio (s / t), for example, when forming the coating layer, adjusting the content of the additive compound (described in detail later) to be added, adjusting the heating temperature when forming the coating layer, and the like can be mentioned.

[0018] The above ratio value (s / t) is not particularly limited, but can be measured by the following method, for example. First, the carrier and embedding resin (e.g., Devcon, two-component mixture, 30-minute curing epoxy resin, manufactured by ITW Performance Polymers & Fluids Japan) are mixed and allowed to cure overnight, after which a rough cross-sectional sample is prepared by mechanical polishing. The cross section is finished using a cross-section polisher (SM-09010, manufactured by JEOL) under conditions such as an acceleration voltage of 5.0 kV and a beam current of 120 μA. Furthermore, images are taken using a scanning electron microscope (Merlin, manufactured by Carl Zeiss) under conditions such as an acceleration voltage of 0.8 kV and a magnification of 30,000x. The captured images can be analyzed using image analysis software (e.g., Image-Pro Plus, manufactured by Media Cybernetics). In this case, it is preferable to measure the average thickness of the coating layer at 50 points on the cross section of one carrier particle. By measuring the average thickness of the coating layer for 100 grains, the average thickness t and the standard deviation s of the coating layer thickness can be calculated, and the ratio (s / t) of the standard deviation s to the average thickness t can be determined.

[0019] <Core material particles> The core material particles used as carriers are not particularly limited as long as they are magnetic core material particles, and can be appropriately selected according to the purpose. As core material particles, they can be appropriately selected from those known as two-component carriers for electrophotography, for example, ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite, and ferrite; various alloys or compounds; and resin particles in which these magnetic materials are dispersed in a resin. These materials may be used individually or in combination of two or more. Among these, Mn-based ferrite, Mn-Mg-based ferrite, and Mn-Mg-Sr ferrite are preferred from an environmental perspective.

[0020] Core material particles may be synthesized as appropriate or commercially available. Core material particles can be manufactured by the following method, for example: Appropriate amounts of each raw material are blended to satisfy the composition formula: MFe2O4 (M: containing at least one selected from Mn, Mg, Li, Ca, Sr, Cu, and Zn), water, a binder, and a dispersant are added, the solid ratio is adjusted, and the mixture is crushed, mixed, and dried using a wet ball mill. Next, the slurry, which has been heated at 700°C to 1,100°C and then crushed in a wet ball mill, is granulated and dried. Next, using a firing furnace capable of controlling the oxygen concentration, the mixture is held at a firing temperature of 1,000°C to 1,300°C for 1 to 24 hours, after which it is crushed and the particle size is adjusted to obtain core material particles.

[0021] The average particle size of the core material particles is preferably 10 to 150 μm, and more preferably 40 to 100 μm. An average particle size of 10 μm or more of the core material particles further prevents carrier adhesion to the image and carrier scattering. Furthermore, an average particle size of 150 μm or less prevents the occurrence of abnormal images such as carrier streaks, thereby preventing a decrease in image quality. The volume-average particle size can be measured, for example, using a Microtrac particle size distribution analyzer model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

[0022] The BET specific surface area of ​​the core material particles is 0.27 m². 2 / g~0.31m 2 / g may be 0.28m 2 / g~0.30m 2 / g is preferred. The BET specific surface area is 0.27 m². 2 / g~0.31m 2 When the value is / g, the bonding between the resin of the coating layer and the core material particles is strong, and the coating layer is less likely to be worn away. Therefore, even with long-term use, a decrease in carrier resistance can be prevented, the toner is not damaged, and an increase in resistance due to toner spent (adhesion of toner to the carrier) can be prevented.

[0023] BET specific surface area is 0.27m 2By setting the BET specific surface area to 0.31 m² or higher, the bonding between the resin of the coating layer (carrier coating film) and the core material particles is enhanced, making the coating layer less susceptible to wear over time and maintaining carrier resistance. 2 By keeping the amount below / g, the increase in resistance due to toner spent caused by damaging the toner is suppressed. The BET specific surface area can be adjusted by the firing temperature during the manufacturing of the core material particles. The BET specific surface area can be measured by known methods.

[0024] <Coating layer> The coating layer only needs to cover at least a portion of the surface of the core material particles, but it is preferable that it covers the entire surface of the core material particles (i.e., there are no defects in the coating layer). The coating layer contains resin, and more preferably contains inorganic fine particles as needed, and further preferably contains other components as needed.

[0025] <<Resin>> The resin to be included in the coating layer is not particularly limited as long as it can impart the necessary electrostatic properties, and can be appropriately selected according to the purpose. Examples include silicone resin and acrylic resin. These can be used individually or in combination of two or more. Among these, a resin combining silicone resin and acrylic resin is preferred.

[0026] Acrylic resin has excellent abrasion resistance due to its strong adhesion and low brittleness. However, because acrylic resin has high surface energy, when used in combination with toners that are prone to splattering (adhering easily to carriers), problems such as a decrease in charge due to the accumulation of splattered toner components may occur. On the other hand, silicone resin has low surface energy, making it difficult for toner components to splatter, and thus reducing the accumulation of splattered components that can cause film abrasion (abrasion of the coating layer). However, silicone resin has weak adhesion and high brittleness, which can worsen abrasion resistance. Therefore, by using acrylic resin and silicone resin in combination, it is possible to obtain a coating layer that is resistant to splattering and also has abrasion resistance.

[0027] There are no particular restrictions on the silicone resin, and it can be appropriately selected from known silicone resins depending on the purpose. Examples of silicone resins include straight silicone resins consisting only of organosilosane bonds, and modified silicone resins modified with alkyds, polyesters, epoxys, acrylics, urethanes, etc. The silicone resin can be synthesized or a commercially available product can be used. Examples of commercially available straight silicone resins include KR271, KR255, KR152 (all manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406, SR2410 (all manufactured by Toray Dow Corning Silicone Co., Ltd.). These can be used as silicone resins alone, but it is also possible to use them simultaneously with other components that undergo crosslinking reactions, charge adjustment components, etc. Commercially available modified silicone resins include KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) (all manufactured by Shin-Etsu Chemical Co., Ltd.), SR2115 (epoxy modified), and SR2110 (alkyd modified) (all manufactured by Toray Dow Corning Silicone Co., Ltd.).

[0028] As for the acrylic resin, there are no particular restrictions as long as it contains an acrylic component, and it can be appropriately selected according to the purpose. The acrylic resin may be used alone, but it is also possible to use at least one other component that undergoes a crosslinking reaction simultaneously. There are no particular restrictions on the other component that undergoes a crosslinking reaction, and it can be appropriately selected according to the purpose, and examples include amino resins and acidic catalysts. As for the amino resin, there are no particular restrictions as long as it has catalytic activity, and it can be appropriately selected according to the purpose, and examples include those having reactive groups such as fully alkylated type, methylol group type, imino group type, and methylol / imino group type.

[0029] Furthermore, it is even more preferable that the coating layer contains a crosslinked product of acrylic resin and amino resin. This makes it possible to suppress fusion between the coating layers while maintaining appropriate elasticity. The amino resin is not particularly limited, but melamine resin and benzoguanamine resin are preferred because they can improve the carrier charge imparting ability. In addition, if it is necessary to appropriately control the carrier charge imparting ability, melamine resin and / or benzoguanamine resin may be used in combination with other amino resins.

[0030] The acrylic resin that can be crosslinked with the amino resin is preferably one having hydroxyl groups and / or carboxyl groups, and more preferably one having hydroxyl groups. This further improves adhesion with core material particles and conductive fine particles, and also improves the dispersion stability of the conductive fine particles. In this case, the acrylic resin is preferably one with a hydroxyl value of 10 mg KOH / g or more, and more preferably one with a hydroxyl value of 20 mg KOH / g or more.

[0031] <<Additional compounds>> In this embodiment, the coating layer preferably contains a predetermined additive compound. The additive compound contained in the coating layer plays a role in sufficiently wetting and spreading the coating material on the core material particle surface. The role of the additive compound in sufficiently wetting and spreading the coating material on the core material particle surface will be explained below. In general, the wetting spread of a liquid on a solid surface (the degree of wetting between a solid and a liquid) is quantified by the contact angle of the liquid on the solid, and this contact angle is influenced not only by the wettability of the liquid alone and the solid alone, but also by the compatibility between the liquid and the solid. This compatibility improves as the ratios of the dispersion component, polar component, and hydrogen bonding component of the surface free energy, which are unique to the liquid and the solid, become closer. In other words, to improve wettability, it is important to bring at least one of the ratios of the dispersion component, polar component, and hydrogen bonding component of the surface free energy close between the solid and the liquid. The core material (the material of the core material particles described above) has a higher ratio of polar components compared to the coating layer material.

[0032] In this embodiment, it is preferable to add a predetermined additive compound to the coating layer. By the additive compound, the ratio of the polar component of the surface free energy in the material of the coating layer can be increased, approaching the ratio of the polar component of the surface free energy in the core material. Therefore, when manufacturing the carrier, the liquid material of the coating layer can be sufficiently wetted and spread on the surface of the core material particles. By increasing the wettability of the liquid material of the coating layer, the unevenness on the surface of the coating layer can be reduced, and the function of the coating layer can be fully exerted.

[0033] The additive compound preferably improves the ratio of the polar component of the material of the coating layer, and an organosiloxane compound is preferred. The organosiloxane compound may be a polyorganosiloxane or silicone, and may be linear or branched. Also, the additive compound preferably has a liquid property at room temperature. As the polyorganosiloxane (silicone), the functional groups on the side chain and / or the terminal may have a methyl group, a phenyl group, or hydrogen. For example, dimethyl silicone, methylphenyl silicone, methylhydrogen silicone, etc. can be mentioned. Also, a modified siloxane in which a predetermined organic group is bonded to the side chain and / or the terminal may be used. In the case of a modified siloxane, polyester-modified siloxane, polyether-modified siloxane, methylstyryl-modified siloxane, alkyl-modified siloxane, etc. can be mentioned. Specific examples of the additive compound include polyester-modified polymethylalkylsiloxane, vinyl-based polymer silicone, dodecamethylpentasiloxane, polyether-modified organosiloxane.

[0034] The content of the additive compound in the obtained carrier is 5×10 -3 ~40×10 -3It is preferable that the amount be in mass percent. By having the content of the additive compound in the carrier within the above range, the ratio of the standard deviation of the thickness of the coating layer to the average thickness of the coating layer (s / t) can be set to an appropriate value. Therefore, it becomes less likely for the charging performance to deteriorate due to toner adhesion to the carrier surface, suppressing the deterioration of image quality, while reducing the unevenness between thin and thick areas of the carrier coating film and reducing the thin areas of coating film that become leakage points. As a result, the characteristics related to carrier adhesion, charging stability, and toner scattering are improved, especially when printing for long periods of time.

[0035] The content of the additive compound in the carrier can be measured, for example, by qualitatively identifying the additive compound using GCMS, and then determining the amount of endothermic peak due to evaporation using DSC, etc.

[0036] The ratio of the dispersion component, polar component, and hydrogen bonding component of the surface free energy of the coating layer material can be measured, for example, as follows: Measure the surface tension of the coating layer material and three types of liquids with known surface free energies. This surface tension can be measured using a Kyowa Measuring Science Co., Ltd. D-500. The surface tensions of the three liquids with known surface free energies can be substituted into the surface tension theoretical formula of the pendant drop method and solved by solving the simultaneous equations.

[0037] <<Inorganic fine particles>> There are no particular restrictions on the inorganic fine particles to be included in the coating layer, and they can be appropriately selected according to the purpose. For example, barium sulfate is preferred from the viewpoint of providing durability and electrostatic properties to the coating layer. Conductive fine particles are preferred from the viewpoint of providing durability and resistive properties to the coating layer. Examples of conductive fine particles include fillers in which tin dioxide or indium oxide is formed as a layer on a substrate, and carbon black. Examples of substrates include aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, and zirconium oxide, with aluminum oxide and titanium dioxide being preferred. In addition to the above, aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, zirconium oxide, etc. may also be used.

[0038] By incorporating inorganic fine particles into the coating layer, it is possible to prevent the carrier coating film from being lost during long-term runs, which would expose the core material, causing a sharp drop in resistance and worsening of solid carrier adhesion.

[0039] There are no particular restrictions on the volume-average particle size of the inorganic fine particles, but 0.3 μm to 0.7 μm is preferred. There are also no particular restrictions on the content of inorganic fine particles, but it is preferred to be 20 to 80 parts by mass per 100 parts by mass of resin in the coating layer.

[0040] <<Other ingredients>> Other components are not particularly limited and can be appropriately selected depending on the purpose. Examples include silane coupling agents and polymerization condensation catalysts.

[0041] It is preferable to include a silane coupling agent in order to stably disperse inorganic fine particles. The silane coupling agent is not particularly limited, but may include r-(2-aminoethyl)aminopropyltrimethoxysilane, r-(2-aminoethyl)aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, and r-anilino Examples include propyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride, r-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3-divinyltetramethyldisilazane, methacrylateoxyethyldimethyl(3-trimethoxysilylpropyl)ammonium chloride, and two or more may be used in combination.

[0042] In addition, commercially available silane coupling agents include AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, sh6062, Z-6911, sz6300, sz6075, sz6079, sz6083, sz6070, sz6072, Z-6721, AY43-004, Z Examples include -6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z-6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-6920, Z-6940 (manufactured by Toray Silicone Co., Ltd.), etc.

[0043] The amount of silane coupling agent added is preferably 0.1 to 10% by mass relative to the silicone resin. If the amount of silane coupling agent added is less than 0.1% by mass, the adhesion between the core material particles or conductive fine particles and the silicone resin will decrease, and the coating layer may peel off during long-term use. If it exceeds 10% by mass, toner filming may occur during long-term use.

[0044] Examples of condensation catalysts include titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts. Among these, titanium-based catalysts are preferred because they have a strong effect in promoting the condensation reaction of silanol groups and are less prone to catalyst deactivation, with titanium diisopropoxybis(ethyl acetate) being even more preferred. There are no particular restrictions on the content of the condensation catalyst, and it can be appropriately selected depending on the purpose.

[0045] <Other ingredients> Other components in the coating layer are not particularly limited as long as they are those commonly used in carriers, and can be appropriately selected according to the purpose. The content of other components can also be appropriately selected according to the purpose.

[0046] (Method for manufacturing a carrier for electrostatic latent image developer) A method for manufacturing an electrostatic latent image developer carrier according to one embodiment of the present invention is a method for manufacturing the above-described electrostatic latent image developer carrier. The method for manufacturing an electrostatic latent image developer carrier may be a method of coating core material particles with a liquid containing a coating layer material (coating layer liquid).

[0047] The coating liquid preferably contains a resin and an additive compound, and may also contain other components as needed. The additive compound may be the same as the one described above, and the resin and other components may also be the same as those described above.

[0048] The content of the additive compound is preferably 0.01% to 1% by mass relative to the total amount of the coating layer liquid. Furthermore, the content of the additive compound is preferably 0.01 to 2.5 parts by mass per 100 parts by mass of resin. When the content is within the above range, the unevenness of the coating layer can be reduced, that is, the average thickness can be made more uniform. In addition, the above-mentioned s / t value can be set to an appropriate range. As a result, it becomes less likely for the charging performance to deteriorate due to toner adhesion to the carrier surface to occur, and the unevenness between thin and thick areas of the carrier coating film can be reduced, while suppressing the deterioration of image quality, and the areas with thin coating film that become leakage areas can be reduced. This improves the characteristics related to carrier adhesion, charging stability, and toner scattering, especially when printing for long periods of time.

[0049] There are no particular restrictions on the method of coating the core material particles with a coating liquid, as long as it is a commonly used coating method, and it can be appropriately selected according to the purpose. Examples include a rolling fluidized bed using a spray, and a method of immersing the core material in a dispersion liquid and drying the solvent.

[0050] (Two-component developer) The two-component developer according to this embodiment includes the carrier and toner described above.

[0051] <Toner> The toner contains at least a binder resin, and optionally other components such as colorants, antistatic agents, and release agents.

[0052] The toner may be clear toner, monochrome toner, or color toner. Clear toner is toner that does not contain colorants.

[0053] For application in oil-less systems where oil is not applied to the fuser roller to prevent toner adhesion, the toner may contain a release agent. Such toners are generally prone to filming, but the carrier according to this embodiment can suppress filming, so the developer according to this embodiment can maintain good quality over a long period of time.

[0054] Furthermore, color toners, especially yellow toners, generally have the problem of color staining due to the abrasion of the carrier coating layer, but the developer according to this embodiment can suppress the occurrence of color staining.

[0055] Toner can be manufactured using known methods such as grinding and polymerization. For example, when manufacturing toner using the grinding method, first, the molten mixture obtained by kneading the toner material is cooled, then ground and classified to produce matrix particles. Next, to further improve transferability and durability, an external additive is added to the matrix particles to produce toner.

[0056] In this case, the equipment used to knead the toner material is not particularly limited, but examples include batch-type two-roll extruders; Banbury mixers; continuous twin-screw extruders such as the KTK type twin-screw extruder (manufactured by Kobe Steel, Ltd.), TEM type twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), twin-screw extruder (manufactured by KCK Co., Ltd.), PCM type twin-screw extruder (manufactured by Ikegai Iron Works Co., Ltd.), and KEX type twin-screw extruder (manufactured by Kurimoto Iron Works Co., Ltd.); and continuous single-screw kneaders such as the Co-Kneader (manufactured by Buss Co., Ltd.).

[0057] Furthermore, when grinding the cooled molten mixture, it can be coarsely ground using a hammer mill, Rotoplex, etc., and then finely ground using a jet-stream pulverizer, mechanical pulverizer, etc. It is preferable to grind it so that the average particle size is 3 μm to 15 μm.

[0058] Furthermore, when classifying the crushed molten mixture, a wind-powered classifier or the like can be used. It is preferable to classify the material so that the average particle size of the parent particles is between 5 μm and 20 μm. Furthermore, when adding external additives to the parent particles, mixing and stirring with mixers causes the external additives to break down and adhere to the surface of the parent particles.

[0059] <<Binding resin>> The binder resin is not particularly limited, but examples include styrene and its substituted homopolymers such as polystyrene, poly-p-styrene, and polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, etc. Two or more may be used in combination.

[0060] The binder resin for pressure fixing is not particularly limited, but examples include polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene; olefin copolymers such as ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, and ionomer resin; epoxy resin, polyester, styrene-butadiene copolymer, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, and phenol-modified terpene resin, and two or more may be used in combination.

[0061] <<Other ingredients>> Other ingredients include, for example, colorants, release agents, electrostatic control agents, and external additives.

[0062] -Coloring agent- The colorants (pigments or dyes) are not particularly limited, but include yellow pigments such as cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake; orange pigments such as molybdenum orange, permanent orange GTR, pyrazolone orange, balkan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK; red iron oxide, cadmium red, permanent red 4R, lysol red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, Examples of pigments include red pigments such as eosin lake, rhodamine lake B, alizarin lake, and brilliant carmine 3B; purple pigments such as fast violet B and methyl violet lake; blue pigments such as cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue, and indanthrene blue BC; green pigments such as chromium green, chromium oxide, pigment green B, and malachite green lake; and black pigments such as azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, as well as metal salt azo dyes, metal oxides, and complex metal oxides. Two or more of these may be used in combination.

[0063] -Release agent- While not particularly limited, examples of release agents include polyethylene, polypropylene and other polyolefins, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, ester wax, and more than one of these may be used in combination.

[0064] -Static control agent- The antistatic agent is not particularly limited, but may include nigrosine; azine dyes having alkyl groups with 2 to 16 carbon atoms; CIBasic Yello 2 (CI41000), CIBasic Yello 3, CIBasic Red 1 (CI45160), CIBasic Red 9 (CI42500), CIBasic Violet 1 (CI42535), CIBasic Violet 3 (CI42555), CIBasic Violet 10 (CI45170), CIBasic Violet 14 (CI42510), CIBasic Blue 1 (CI42025), CIBasic Blue 3 (CI51005), CIBasic Blue 5 (CI42140), CIBasic Blue 7 (CI42595), CIBasic Blue 9 (CI52015), CIBasic Blue 24 (CI52030), CIBasic Blue 25 (CI52025), CIBasic Blue Examples include basic dyes such as 26 (CI44045), CIBasic Green 1 (CI42040), and CIBasic Green 4 (CI42000); lake pigments of these basic dyes; quaternary ammonium salts such as CISolvent Black 8 (CI26150), benzoylmethylhexadecylammonium chloride, and decyltrimethyl chloride; dialkyltin compounds such as dibutyl and dioctyl; dialkyltin borate compounds; guanidine derivatives; polyamine resins such as vinyl polymers and condensation polymers having amino groups; metal complex salts of monoazo dyes; salicylic acid; metal complexes of dialkylsalicylic acid, naphthoic acid, and dicarboxylic acids such as Zn, Al, Co, Cr, and Fe; sulfonated copper phthalocyanine pigments; organoboro salts; fluorine-containing quaternary ammonium salts; and calixalene compounds, although two or more may be used in combination. For color toners other than black, metal salts of white salicylic acid derivatives are preferred.

[0065] -External additives- Examples of external additives are not particularly limited, but include inorganic particles such as silica, titanium dioxide, alumina, silicon carbide, silicon nitride, and boron nitride; and resin particles such as polymethyl methacrylate particles and polystyrene particles with an average particle size of 0.05 μm to 1 μm obtained by soap-free emulsion polymerization. Two or more types may be used in combination. Among these, metal oxide particles such as silica and titanium dioxide, whose surfaces are hydrophobically treated, are preferred. Furthermore, by using hydrophobically treated silica and hydrophobically treated titanium dioxide in combination, and by adding a larger amount of hydrophobically treated titanium dioxide than hydrophobically treated silica, a toner with excellent charge stability against humidity can be obtained.

[0066] (Refill developer) The replenishment developer consists of the carrier and toner according to the embodiment described above. By applying the replenishment developer to an image forming apparatus that performs image formation while discharging excess developer from the developing apparatus, extremely stable image quality can be obtained over a long period of time. In other words, the deteriorated carriers in the developing apparatus are replaced with the undegraded carriers in the replenishment developer, maintaining a stable charge level over a long period of time and obtaining a stable image. This method is particularly effective when printing high image area. When printing high image area, the main carrier degradation is carrier charge degradation due to toner consumption on the carrier, but by using this method, the amount of carrier replenishment is also large when printing high image area, so the frequency of replacement of deteriorated carriers increases. As a result, an extremely stable image can be obtained over a long period of time.

[0067] The mixing ratio of the replenishment developer is preferably 2 to 50 parts by mass of toner per 1 part by mass of carrier. If the toner is 2 parts by mass or more, the amount of replenishment carrier is too much, resulting in an oversupply of carriers and an excessively high carrier concentration in the developing device, which can prevent the problem of increased charge in the developer. Furthermore, it can prevent the problem of decreased developing ability and reduced image density due to increased charge in the developer. If the toner is 50 parts by mass or less, the proportion of carriers in the replenishment developer is small, which reduces the exchange of carriers in the image forming device and prevents the problem of reduced effectiveness against carrier degradation.

[0068] (Process cartridge) A process cartridge is a form of toner storage unit. A toner storage unit is a unit that has the function of storing toner and contains toner or developer. Here, examples of forms of toner storage units include a developer storage container, a developer unit, and a process cartridge. A developer storage container is a container that contains developer. A developing unit refers to a device that contains a developer and has the means to develop the film.

[0069] A process cartridge comprises an electrostatic latent image carrier, a charging means, a developing means, and a cleaning means, contains a developer, and is detachable from an image forming apparatus. The process cartridge may further include an exposure means.

[0070] An embodiment of the process cartridge will be described with reference to Figure 1. As shown in Figure 1, the process cartridge 10 includes an electrostatic latent image carrier 11, a charging device 12 for charging the electrostatic latent image carrier, a developing device 13 for developing the electrostatic latent image formed on the electrostatic latent image carrier using the developer set according to this embodiment to form a toner image, and a cleaning device 14 for removing the toner remaining on the electrostatic latent image carrier after transferring the toner image formed on the electrostatic latent image carrier to a recording medium. The process cartridge 10 is detachable from the main body of an image forming apparatus such as a copier or printer.

[0071] (Image forming apparatus and image forming method) The image forming apparatus according to this embodiment has a developer container containing at least one of the two-component developer according to this embodiment and the replenishment developer according to this embodiment. The image forming apparatus according to this embodiment preferably has a developer container, an electrostatic latent image carrier, a charging means for charging the electrostatic image carrier, an exposure means for forming an electrostatic latent image on the electrostatic latent image carrier, a developing means for forming a toner image by developing the electrostatic latent image formed on the electrostatic latent image carrier using the developer according to this embodiment contained in the above-mentioned developer container, a transfer means for transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a fixing means for fixing the toner image transferred to the recording medium. Furthermore, it is more preferable to have other means as appropriate, such as a cleaning means, as needed.

[0072] There are no particular restrictions on the means for forming the toner image, and they can be appropriately selected depending on the purpose, but a means of developing using a developer on which a magnetic brush is formed to form the toner image is preferred.

[0073] The image forming method according to this embodiment includes the steps of: forming an electrostatic latent image on an electrostatic latent image carrier; developing the electrostatic latent image formed on the electrostatic latent image carrier using a two-component developer obtained from the developer container according to the above embodiment to form a toner image; transferring the toner image formed on the electrostatic latent image carrier to a recording medium; and fixing the toner image transferred to the recording medium, and further including other appropriately selected means such as a cleaning step as needed.

[0074] There are no particular restrictions on the process for forming the toner image, and it can be appropriately selected depending on the purpose, but a process of developing using a developer with a magnetic brush formed on it to form the toner image is preferred.

[0075] An embodiment of the image forming apparatus will be described with reference to Figure 2. As shown in Figure 2, first, the electrostatic latent image carrier 20 is driven to rotate at a predetermined peripheral speed, and the circumferential surface of the electrostatic latent image carrier 20 is uniformly charged to a predetermined positive or negative potential by the charging device 32. Next, the circumferential surface of the electrostatic latent image carrier 20 is exposed by the exposure device 33, and electrostatic latent images are formed sequentially. Furthermore, the electrostatic latent images formed on the circumferential surface of the electrostatic latent image carrier 20 are developed by the developing device 40 using at least one of the developer set and the replenishment developer set of this embodiment, and a toner image is formed. Next, the toner image formed on the circumferential surface of the electrostatic latent image carrier 20 is sequentially transferred to the transfer paper fed between the electrostatic latent image carrier 20 and the transfer device 50 from the paper feeding section, in synchronization with the rotation of the electrostatic latent image carrier 20. Furthermore, the transfer paper onto which the toner image has been transferred is separated from the circumferential surface of the electrostatic latent image carrier 20, introduced into a fixing device, and fixed, and then printed out as a copy to the outside of the image forming apparatus 100. Meanwhile, the surface of the electrostatic latent image carrier 20 after the toner image has been transferred is cleaned by the cleaning device 60 to remove any remaining toner, then discharged by the static elimination device 70, and used repeatedly for image forming. [Examples]

[0076] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments. In the following, unless otherwise specified, "parts" means parts by mass, and "%" means mass percent.

[0077] (Example 1) A coating layer liquid was obtained by diluting the following resin solution with toluene: 78 parts of methyl silicone resin (manufactured by Toray Dow Corning Silicone Co., Ltd., 43% solids content) with a weight-average molecular weight of 15,000, made from bifunctional or trifunctional monomers; 8 parts of acrylic resin (24% solids content); 9 parts of titanium diisopropoxybis(ethyl acetoacetate) TC-750 (manufactured by Matsumoto Fine Chemical Co., Ltd.) as a catalyst; 3 parts of SH6020 (manufactured by Toray Silicone Co., Ltd.) as a silane coupling agent; and 0.5 parts of polyester-modified polymethylalkylsiloxane (manufactured by BYK Co., Ltd.) as an additive compound. This coating layer liquid was applied to 1,000 parts of ferrite core material using a fluidized bed coating apparatus, controlling the temperature in the fluidized bed to 60°C for 30 minutes (coating treatment), and then drying for 1 minute. The obtained carrier was calcined in an electric furnace at 180°C for 2 hours to obtain carrier A.

[0078] (Example 2) Carrier B was obtained in the same manner as in Example 1, except that the added compound was replaced with a vinyl polymer silicone (manufactured by Kusumoto Chemical Co., Ltd.).

[0079] (Example 3) Carrier C was obtained in the same manner as in Example 1, except that the added compound was replaced with dodecamethylpentasiloxane (manufactured by Toray Dow Corning Silicone Co., Ltd.).

[0080] (Example 4) Carrier D was obtained in the same manner as in Example 1, except that the added compound was replaced with a polyether-modified organosiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0081] (Example 5) Carrier E was obtained in the same manner as in Example 1, except that the added compounds were replaced with 0.25 parts of polyester-modified polymethylalkylsiloxane (manufactured by BYK) and 0.25 parts of polyether-modified organosiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0082] (Example 6) <Manufacturing of inorganic microparticles> 100 g of aluminum oxide (AKP-30, manufactured by Sumitomo Chemical Co., Ltd.) was dispersed in 1 liter of water to form a suspension, which was then heated to 70°C. To this suspension, a solution of 135 g of stannous chloride and 4.0 g of phosphorus pentoxide dissolved in 1.7 liters of 2N hydrochloric acid, along with 12% by weight aqueous ammonia, was added dropwise over 2 hours and 40 minutes until the pH of the suspension reached 7-8. After the addition, the suspension was filtered and washed, and the resulting cake was dried at 110°C. Next, this dried powder was treated in a nitrogen stream at 500°C for 1 hour to obtain inorganic fine particles P1.

[0083] A coating layer liquid was obtained by diluting the following resin solution with toluene: 78 parts of methyl silicone resin (Toray Dow Corning Silicone Co., Ltd., 43% solids content) with a weight-average molecular weight of 15,000, made from bifunctional or trifunctional monomers; 8 parts of acrylic resin (24% solids content); 9 parts of titanium diisopropoxybis(ethyl acetoacetate) TC-750 (Matsumoto Fine Chemical Co., Ltd.) as a catalyst; 3 parts of SH6020 (Toray Silicone Co., Ltd.) as a silane coupling agent; 0.5 parts of polyester-modified polymethylalkylsiloxane (BYK Co., Ltd.) as an additive compound; and 43 parts of inorganic fine particles (P1) as inorganic fine particles. This coating layer liquid was applied to 1,000 parts of a ferrite core material using a fluidized bed coating apparatus, controlling the temperature in the fluidized bed to 60°C for 30 minutes (coating treatment), and then drying for 5 minutes. The obtained carrier was calcined in an electric furnace at 180°C for 2 hours to obtain carrier F.

[0084] (Comparative Example 1) Carrier a was obtained in the same manner as in Example 1, except that the added compound was replaced with 0.1 parts of polyester-modified polymethylalkylsiloxane (manufactured by BYK).

[0085] (Comparative Example 2) Carrier b was obtained in the same manner as in Example 1, except that the added compound was replaced with 2.0 parts of polyester-modified polymethylalkylsiloxane (manufactured by BYK).

[0086] <Measurement of unevenness (s / t) of the coating layer> 1.0 g of the obtained carrier was mixed with 0.01 g of embedding resin (Devcon, two-component mixture, 30-minute curing epoxy resin, manufactured by ITW Performance Polymers & Fluids Japan), and allowed to cure overnight. The cured resin was mechanically polished to prepare a rough cross-sectional sample. The obtained cross-sectional sample was then finished using a cross-section polisher (SM-09010, manufactured by JEOL) under the conditions of an acceleration voltage of 5.0 kV and a beam current of 120 μA.

[0087] Next, the cross-section was imaged using a scanning electron microscope (Merlin, Carl Zeiss) under conditions of an acceleration voltage of 0.8 kV and a magnification of 30,000x.

[0088] The captured images were imported into TIFF format, and the thickness of the selected coating layer was automatically obtained by selecting the desired coating layer using image analysis software (Image-Pro Plus, Media Cybernetics). The thickness of the coating layer was measured at 50 cross-sectional points per carrier particle. Furthermore, the thickness of the coating layer was measured for 100 carrier particles, and the average thickness (m) was calculated by averaging the thicknesses of 5,000 coating layers (100 × 50 = 5,000 points) from each of the 100 particles. The standard deviation (s) of these 5,000 coating layer thicknesses was also calculated, and the ratio of the average thickness to the standard deviation (s / m) was determined to represent the measurement result of the coating layer's surface irregularities. The obtained measurement results of the coating layer's surface irregularities are shown in Table 1.

[0089] <Measurement of the content of additive compounds in the carrier> The obtained carrier (50 mg) was placed in a dedicated cup and inserted into a GCMS (QP-2010, Shimadzu Corporation). The temperature was increased from an initial temperature of 40°C to 320°C at a rate of 20°C / min to obtain a chromatograph. The obtained chromatograph was analyzed to qualitatively identify the additive compounds contained in the carrier.

[0090] The additive compounds, whose properties were qualitatively determined, were collected as samples in a sample container with a pinhole. These samples were then heated at a constant rate using a DSC (DSC7000, manufactured by Hitachi High-Tech Science Corporation) up to a temperature higher than the evaporation termination temperature, and the content was determined from the amount of endothermic peak due to evaporation. The obtained measurement results are shown in Table 1.

[0091] [Table 1]

[0092] <Toner Manufacturing> [Synthesis of polyester resin A] In a reaction vessel equipped with a thermometer, stirrer, condenser, and nitrogen inlet tube, 443 parts of bisphenol A PO adduct (hydroxyl value: 320 mg KOH / g), 135 parts of diethylene glycol, 422 parts of terephthalic acid, and 2.5 parts of dibutyltin oxide were added and reacted at 200°C until the acid value reached 10 mg KOH / g to obtain [Polyester Resin A]. The obtained [Polyester Resin A] had a Tg of 63°C and a peak number-average molecular weight of 6,000.

[0093] The peak number-average molecular weight was measured by GPC (gel permeation chromatography) using an HLC-8320GPC column (manufactured by Tosoh Corporation). More specifically, the column was stabilized in a heat chamber at 40°C, and THF was flowed through the column at this temperature at a flow rate of 1 mL / min as the solvent. 50 μL to 200 μL of a THF sample solution of the resin, prepared to a sample concentration of 0.05% to 0.6% by mass, was injected and measured. For molecular weight measurement, the molecular weight distribution of the sample was calculated from the relationship between the logarithm of a calibration curve prepared using several monodisperse polystyrene standard samples and the count. Standard polystyrene samples used for calibration curve preparation included, for example, those manufactured by Pressure Chemical Co. or Toyo Soda Industries Co., Ltd., with a molecular weight of 6 × 10⁶. 2 , 2.1 × 10 3 , 4×10 3 , 1.75 × 10 4 , 5.1×10 4 , 1.1 × 105 , 3.9×10 5 , 8.6×10 5 , 2×10 6 , or 4.48 × 10 6 The following materials were used. At least 10 standard polystyrene samples were used. An RI (refractive index) detector was used.

[0094] [Synthesis of polyester resin B] In a reaction vessel equipped with a thermometer, stirrer, condenser, and nitrogen inlet tube, 443 parts of bisphenol A PO adduct (hydroxyl value: 320 mg KOH / g), 135 parts of diethylene glycol, 422 parts of terephthalic acid, and 2.5 parts of dibutyltin oxide were added and reacted at 230°C until the acid value became 7 mg KOH / g to obtain [Polyester Resin B]. The Tg of this resin was 65°C, and the peak number-average molecular weight was 16,000.

[0095] <Manufacturing of Toner Base Particle 1> Polyester resin A... 40 parts • Polyester resin B... 60 parts • Carnauba wax (Product name: Carnauba Wax No. 2, manufactured by Kato Yoko Co., Ltd.) ... 1 piece • Carbon black (#44, manufactured by Mitsubishi Chemical Corporation) ... 15 units The above toner components were mixed at 1,500 rpm for 3 minutes using a Henschel mixer (Henschel 20B, manufactured by Mitsui Mining Co., Ltd.), and then kneaded in a single-shaft kneader (small Bussco kneader, manufactured by Buss) under the following conditions (set temperature: inlet 100°C, outlet 50°C, feed rate: 2 kg / Hr) to obtain [toner matrix particles A1].

[0096] The obtained [toner matrix particles A1] were kneaded, rolled, and cooled, then pulverized in a pulperizer. After that, they were milled in an I-type mill (IDS-2 model, manufactured by Nippon Pneumatic Co., Ltd.) using a flat impact plate and an air pressure of 6.8 atm / cm². 2 The material was then finely ground under a feed rate of 0.5 kg / hr. Further classification (using Alpine 132MP) was performed to obtain [toner matrix particles 1].

[0097] To 100 parts of [Toner matrix particles 1], 1.0 part of hydrophobic silica microparticles (R972, manufactured by Nippon Aerosil Co., Ltd.) was added as an external additive and mixed in a Henschel mixer to obtain toner particles (hereinafter referred to as [Toner 1]).

[0098] <Preparation of developers A-F and a-c> To the obtained carriers A-F and a-b (93 parts), 7.0 parts of [toner 1] (7.2 μm) were added and stirred in a ball mill for 20 minutes to prepare developers A-F and a-b.

[0099] (Developer characteristics evaluation) To evaluate the adhesion of the current material to solid carriers, we assessed initial solid carrier adhesion and solid carrier adhesion over time. Furthermore, to evaluate the electrostatic stability during long-term printing, we assessed the electrostatic stability over time and also evaluated the toner scattering over time.

[0100] <Adhering to Betacarrier> Running evaluations were conducted using the obtained developers. More specifically, using a digital color copier / printer (RICOH Pro C9100, manufactured by Ricoh Co., Ltd.), the adhesion of solid carriers after 10,000 runs (initial solid carrier adhesion) and after 1,000,000 runs (solid carrier adhesion over time) were evaluated using the obtained developers A-F and a-b, with an image area ratio of 40%.

[0101] A solid image was processed under specified development conditions (charging potential (Vd): -600V, potential after exposure of the image area (solid original): -100V, development bias: DC, -500V). Imaging was interrupted by methods such as turning off the power during the process, and the number of carrier deposits on the photoreceptor after transfer was counted. Based on the following evaluation criteria, the amount of solid carrier deposits after 10,000 runs and after 1,000,000 runs were evaluated. The evaluation results are shown in Table 2. The evaluation area was a 10mm x 100mm area on the photoreceptor. In addition, in the following criteria, △ or higher indicates usable (acceptable). -Evaluation Criteria- ◎:0 pieces ○:1~3 pieces △:4~8 pieces ×:9 or more

[0102] <Static Stability> The charge level was measured after 1 million runs. First, the initial charge level (Q1) of the carriers was measured using developers A-F and a-b with a TB-200 blow-off device (manufactured by Toshiba Chemical Co., Ltd.). Then, the charge level (Q2) of the carriers after 1 million runs was measured using the blow-off device, except that the carriers used were those from which the toners of each color had been removed from the developer after running, in the same manner as the measurement of the initial charge level (Q1). The rate of change in charge level was defined as the absolute value of (Q1-Q2) / (Q1)×100. The evaluation results are shown in Table 2. Furthermore, under the following criteria, a value of △ or higher is considered usable (acceptable). -Evaluation Criteria- 0 or more but less than 5: ◎ (Excellent) 5 or higher but less than 10: ○ (Good) 10 or more but less than 20: △ (Usable) 20 or more: × (defective)

[0103] <Toner scattering> After 1 million prints, the amount of toner accumulated at the bottom of the developer carrier was suctioned and collected, and the toner weight was measured. The evaluation criteria are shown below. The evaluation results are shown in Table 2. In addition, under the following criteria, a score of △ or higher indicates usable (acceptable). -Evaluation Criteria- 0mg to less than 50mg: ◎ (Excellent) 50mg or more but less than 100mg: ○ (Good) 100mg or more but less than 250mg: △ (Usable) 250mg or more: × (Poor)

[0104] [Table 2]

[0105] Tables 1 and 2 show that in Examples 1 to 6, where the s / t value was in the range of 0.05 to 0.6, good results were observed in initial and over time solid carrier adhesion, over time static charge stability, and toner scattering. In contrast, in Comparative Example 1, where the s / t value was greater than 0.6, the over time static charge stability and toner scattering were equivalent to those of Examples 1 to 4, but the evaluation of initial and over time solid carrier adhesion was inferior to that of Examples 1 to 6. Furthermore, in Comparative Example 2, where the s / t value was less than 0.05, the evaluation of initial and over time solid carrier adhesion was equivalent to that of Examples 1 to 5, but the over time static charge stability and toner scattering were inferior to those of Examples 1 to 6. [Explanation of Symbols]

[0106] 10 Process Cartridges 11 Photoreceptor 12 Charging device 13. Developing device 14 Cleaning device 20 Electrostatic latent image carrier 32 Charging device 33 Exposure equipment 40 Developing equipment 50 Transfer device 60 Cleaning device 70 Static eliminator 100 Image forming apparatus [Prior art documents] [Patent Documents]

[0107] [Patent Document 1] Japanese Patent Application Publication No. 6-250443 [Patent Document 2] Patent No. 4972537

Claims

1. A carrier for an electrostatic latent image developer, comprising magnetic core material particles and a coating layer containing a resin that covers at least a portion of the surface of the core material particles, The coating layer comprises a silicone resin and dodecamethylpentasiloxane. A carrier for electrostatic latent image developer, wherein the average thickness of the coating layer is t, the standard deviation of the thickness of the coating layer is s, the average thickness t of the coating layer is 0.2 μm to 0.7 μm, and s / t is 0.05 to 0.

6.

2. The carrier for electrostatic latent image developer according to claim 1, wherein the coating layer further contains inorganic fine particles.

3. A two-component developer comprising a carrier for electrostatic latent image developer according to claim 1 or 2, and a toner.

4. A carrier for electrostatic latent image developer according to any one of claims 1 to 3, A replenishment developer comprising 1 part by mass of the electrostatic latent image developer carrier and 2 to 50 parts by mass of toner.

5. An electrostatic latent image carrier, and a charging means for charging the surface of the electrostatic latent image carrier, A developing means for developing an electrostatic latent image formed on the electrostatic latent image carrier using the two-component developer described in claim 3, A process cartridge comprising a cleaning means for cleaning toner remaining on the surface of the electrostatic latent image carrier.

6. An image forming apparatus having a developer container containing at least one of the two-component developer described in claim 3 and the replenishment developer described in claim 4.

7. A step of forming an electrostatic latent image on an electrostatic latent image carrier, A step of developing the electrostatic latent image formed on the electrostatic latent image carrier using the two-component developer described in claim 3 to form a toner image, A step of transferring a toner image formed on the electrostatic latent image carrier to a recording medium, An image forming method comprising the step of fixing a toner image transferred to the recording medium.

8. This includes forming a coating layer by coating the surface of magnetic core material particles with a coating liquid containing resin, The coating layer comprises a silicone resin and dodecamethylpentasiloxane. A method for manufacturing a carrier for an electrostatic latent image developer, wherein the average thickness of the coating layer is t, the standard deviation of the thickness of the coating layer is s, the average thickness t of the coating layer is 0.2 μm to 0.7 μm, and s / t is 0.05 to 0.6.

Images