Magnetic Carrier

Abstract

To provide a magnetic carrier which maintains wear resistance for a long time, offers stable charging properties, and suppresses fogging, image defects, and scraping of a carrier coating layer even after prolonged use.SOLUTION: A magnetic carrier is provided, comprising a magnetic carrier particle having a magnetic core and a coating layer covering a surface of the magnetic core. The coating layer contains a coating resin and filler particles, and the filler particles are treated particles surface-treated with a coupling agent, where the coating resin and the filler particles are bonded together via the coupling agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a magnetic carrier used in an image forming method for visualizing an electrostatic image using an electrophotographic method. [Background technology]

[0002] Conventionally, electrophotographic image formation methods generally involve forming an electrostatic latent image on an electrostatic latent image carrier using various means, and then developing the electrostatic latent image by attaching toner to the electrostatic latent image. For this development, a two-component development method is widely used in which carrier particles called magnetic carriers are mixed with the toner, and the toner is frictionally charged to impart an appropriate amount of positive or negative charge to the toner, with the charge acting as a driving force for development. In two-component development, the magnetic carrier can be given functions such as developer agitation, transport, and charging, which clearly divides the functions between the carrier and the toner. This offers advantages such as good control of developer performance. Magnetic carriers often consist of a magnetic core that provides magnetism for transportability and a resin coating that provides charging capability to the toner. In this case, efforts have been made to improve the strength of the resin coating layer to prevent wear and peeling of the carrier coating resin, extend the life of the developer, and maintain charging characteristics. For example, Patent Document 1 discloses a method of improving the strength of the resin coating layer by incorporating specific additives into the resin coating layer. However, it is known that these additives may detach from the carrier surface as the number of printed sheets increases. Depending on the type of additive, this can cause image degradation, such as degrading the charging characteristics on the toner surface. Therefore, for example, Patent Document 2 discloses a configuration in which the surface of additive particles is chemically treated to prevent detachment from the coating resin layer. While this effect is significant, electrophotographic printers have become significantly faster in recent years, and the total number of printed pages is also on the rise, creating a demand for carriers that can realize developers with higher durability. While configurations such as those described in Patent Document 2 were able to produce good images in the initial stages of printing, they were unable to achieve the durability characteristics desired by the market in certain printer configurations, and further improvement is considered necessary. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-202381 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-78918 Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, materials that can be added to a resin coating layer to improve its strength are often low-resistance materials that affect charging characteristics when transferred to the toner. Furthermore, many of these materials have low affinity with commonly used coating resins, making them prone to detachment from the carrier surface. Furthermore, as detachment of these additives (hereinafter sometimes referred to as fillers or filler particles) progresses, the strength of the resin coating layer may decrease. Therefore, preventing detachment of filler particles is important from the perspective of improving the strength of the resin coating layer. That is, in order to realize a highly durable carrier, a technology is required to firmly fix filler particles, which have the ability to improve the strength of the coating resin layer, to the carrier. In view of the above, an object of the present invention is to provide a magnetic carrier that maintains excellent abrasion resistance over time, has stable charging characteristics, and is suppressed from causing fogging, image defects, and scraping of the carrier coating layer even after durability testing. [Means for solving the problem]

[0005] The present invention provides a magnetic carrier comprising magnetic carrier particles having a magnetic core and a coating layer that coats the surface of the magnetic core, The coating layer contains a coating resin and filler particles, and the filler particles are treated particles that have been surface-treated with a coupling agent, and the coating resin and filler particles are bonded via the coupling agent, making this a magnetic carrier. [Effects of the Invention]

[0006] According to the present invention, there is provided a magnetic carrier that maintains excellent abrasion resistance over time, has stable charging characteristics, and is suppressed from causing fogging, image defects, and scraping of the carrier coating layer even after durability testing. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a resistivity measuring device used in the present invention. [Figure 2] FIG. 2 is a schematic view of a surface treatment device for performing surface treatment on toner. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the present invention, the expressions "xx or more and xx or less" and "xx to xx" indicating a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified.

[0009] The object of the present invention is achieved by including hard filler particles inside the carrier coating resin layer, and by preventing the particles from being detached even during long-term use.

[0010] The surfaces of the filler particles used are modified with specific functional groups through chemical treatment, and part of the resin that forms the coating resin is chemically bonded to part of the treatment agent present on the particle surface, thereby preventing the filler particles from detaching and maintaining excellent durability.

[0011] The embodiments of the present invention will be described in more detail below.

[0012] [Magnetic Carrier Particles] <Magnetic core> The magnetic core of the magnetic carrier according to the present invention can be made of conventional magnetic particles such as ferrite or magnetite. Alternatively, a binder-type magnetic core in which magnetic powder is dispersed in a resin can also be used. Alternatively, a magnetic core in the form of porous ferrite or magnetite particles filled with a resin can also be used.

[0013] Among these, a binder-type magnetic core or a magnetic core in the form of magnetic particles having holes filled with a resin is preferred from the viewpoint of extending the life since it is possible to reduce the specific gravity of the magnetic carrier.

[0014] Lowering the specific gravity of the magnetic carrier reduces the load on the toner in the developer state in the developing device, prevents adhesion of toner constituents to the surface of the magnetic carrier particles, and reduces the load on the carrier particles themselves, leading to further suppression of detachment and destruction of the organosilicon polymer particles and peeling, chipping, and abrasion of the resin coating layer. It also improves dot reproducibility, making it possible to obtain high-resolution images.

[0015] The resin to be contained in the pores of the porous magnetic particles can be a copolymer resin used as a coating resin, but is not limited to this and any known resin can be used. As the thermoplastic resin, the copolymer used as the coating resin is preferred, but other examples include the following: polystyrene, polymethyl methacrylate, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinylpyrrolidone, petroleum resin, novolac resin, saturated alkyl polyester resin, aromatic polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyarylate, polyamide resin, polyacetal resin, polycarbonate resin, polyethersulfone resin, polysulfone resin, polyphenylene sulfide resin, and polyetherketone resin.

[0016] Examples of thermosetting resins include phenolic resins, modified phenolic resins, maleic resins, alkyd resins, epoxy resins, acrylic resins, unsaturated polyesters obtained by polycondensation of maleic anhydride, terephthalic acid, and polyhydric alcohols, urea resins, melamine resins, urea-melamine resins, xylene resins, toluene resins, guanamine resins, melamine-guanamine resins, acetoguanamine resins, glyptal resins, furan resins, silicone resins, polyimides, polyamide-imide resins, polyetherimide resins, and polyurethane resins.

[0017] One method for filling the voids of porous ferrite particles with a resin component is to dilute the resin component in a solvent and then add the diluted solution to the porous magnetic core particles. The solvent used here can be any solvent capable of dissolving each resin component. For organic solvent-soluble resins, organic solvents such as toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol can be used. For water-soluble or emulsion-type resins, water can be used. Methods for adding solvent-diluted resin components to the interior of the porous magnetic core particles include impregnating the resin component using a coating method such as dipping, spraying, brushing, fluidized bed coating, or kneading, followed by volatilizing the solvent. When filling with a thermosetting resin, the solvent is volatilized, followed by raising the temperature to the curing temperature of the resin used to initiate a curing reaction.

[0018] On the other hand, specific methods for producing magnetic material-dispersed resin particles include the following. For example, submicron magnetic materials such as iron powder, magnetite particles, and ferrite particles are kneaded in a thermoplastic resin so as to disperse them, and then pulverized to the desired magnetic carrier particle size, followed by thermal or mechanical spheronization as necessary. Alternatively, magnetic material-dispersed resin particles can be produced by dispersing the magnetic material in a monomer and polymerizing the monomer to form a resin.

[0019] Examples of resins in this case include vinyl resins, polyester resins, epoxy resins, phenolic resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, silicone resins, acrylic resins, and polyether resins. The resin may be a single type or a mixture of two or more types. Phenolic resins are particularly preferred because they increase the strength of the magnetic core. The true density and resistivity can be adjusted by adjusting the amount of magnetic material. Specifically, in the case of magnetic particles, they are preferably added in an amount of 70% by mass to 95% by mass relative to the magnetic carrier.

[0020] The magnetic core preferably has a volume average particle size (D50) of 20 μm or more and 80 μm or less so that it can be uniformly coated with the coating resin, and the density of the developer magnetic brush is appropriate to prevent magnetic carrier adhesion and obtain high-quality images.

[0021] The resistivity of the magnetic core is 1.0 x 10 at an electric field strength of 1000 (V / cm). 5 (Ω cm) or more 1.0×10 14 (Ω·cm) or less is preferable because good developability can be obtained.

[0022] <Coating resin> The coating resin constituting the magnetic carrier of the present invention contains a resin having a reactive functional group. The coating resin is not particularly limited as long as it is a resin having a reactive functional group, and known resins can be used, such as acrylic resin, methacrylic resin, silicone resin, urethane resin, polyethylene, polyethylene terephthalate, polystyrene, and phenolic resin, as well as copolymers and polymer mixtures containing these resins. In particular, it is preferable to use an acrylic resin or a silicone resin from the viewpoints of charging characteristics and prevention of adhesion of foreign matter to the carrier surface.

[0023] The reactive functional group can be selected from known functional groups such as a carboxy group, a hydroxy group, an epoxy group, an amino group, a vinyl group, an acryloyl group, a methacryloyl group, an isocyanate group, a mercapto group, an oxazoline group, etc. Specific examples of resins having a carboxy group include resins obtained by polymerizing acrylic acid, methacrylic acid, or itaconic acid as a monomer; resins having a hydroxy group include resins made of 3-hydroxymethylacrylic acid, 2-hydroxyethylacrylic acid, 2-hydroxypropylacrylic acid, 2-hydroxypropylmethacrylic acid, or 2-hydroxybutylacrylic acid; resins having a vinyl group include resins made of allyl acrylate, allyl methacrylate, etc.; resins having an epoxy group include resins made of glycidylic acrylic acid, hydroxybutyl glycidyl ether acrylate, or β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and resins having an amine include resins made of acrylamide or methacrylamide.

[0024] In addition, acrylic resins having an alicyclic hydrocarbon group such as a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclopentyl group, a cyclobutyl group, or a cyclopropyl group in the side chain and having the above-mentioned reactive functional group are also preferred because they smooth the surface (coating surface) of the resin coating layer that covers the surface of the magnetic core and can suppress adhesion of toner-derived components such as toner and external additives that impart fluidity to the toner.

[0025] Furthermore, the coating resin may be a copolymer with a monomer that does not have a reactive functional group, and may also have a structure such as a mixture or laminate with a polymer that does not have a reactive functional group, as long as the effects of the present invention are not impaired.

[0026] <Filler particles> The filler particles constituting the magnetic carrier of the present invention are treated particles whose surfaces are treated with a coupling agent and whose surfaces are modified with reactive functional groups.

[0027] As with the coating resin, known reactive functional groups such as a carboxy group, a hydroxy group, an epoxy group, an amino group, a vinyl group, an acryloyl group, a methacryloyl group, an isocyanate group, a mercapto group, and an oxazoline group can be selected as the reactive functional group.

[0028] Any known means can be used for the surface treatment of the filler particles. The surface treatment agent can also be selected from silane coupling agents, titanate coupling agents, aluminate coupling agents, etc. Among these, silane coupling agents are preferably used.

[0029] The material of the filler particles constituting the magnetic carrier of the present invention is not particularly limited as long as it can be surface-treated, and known materials can be selected and used.Specific examples include titanium oxide, zirconium oxide, zinc oxide, cerium oxide, magnesium oxide, barium sulfate, calcium sulfate, magnesium sulfate, calcium carbonate, magnesium carbonate, talc, mica, kaolin, sericite, aluminum silicate, magnesium silicate, calcium silicate, barium silicate, strontium silicate, metal tungstate, hydroxyapatite, vermiculite, zeolite, zirconia, alumina, aluminum hydroxide, boron nitride, boron nitride, silica, zinc stearate, aluminum stearate, calcium stearate, magnesium stearate, zinc myristate, magnesium myristate, zinc cetyl phosphate, calcium cetyl phosphate, sodium zinc cetyl phosphate, aluminum, copper, stainless steel, and iron.Among these, alumina, zirconia, titanium oxide, barium sulfate, silica, boron nitride, and calcium carbonate are preferred. The shape of the filler particles is not particularly limited, and they may be spherical, discoid, needle-like, or the like.

[0030] The filler particles preferably have a Young's modulus of 30 GPa or more, as this significantly improves the strength of the coating resin layer. A more significant effect can be achieved with a Young's modulus of 70 GPa or more, and a particularly preferred configuration is 200 GPa or more, as this provides the best effect. To improve the strength of the coating resin layer, a higher Young's modulus is preferable, but a modulus higher than 600 GPa raises concerns about wear on the toner and photosensitive drum, so a modulus of 600 GPa or less is preferred.

[0031] The number-average particle size of the primary particles of the filler particles is preferably 5 nm or more and 300 nm or less. That is, it is preferably 5 nm or more to more suitably exhibit the effect of improving the strength of the coating resin layer, and it is preferably 300 nm or less to further enhance the effect of preventing detachment. If it is 150 nm or less, the effect of preventing detachment is further enhanced, and therefore it is more preferable.

[0032] <Coating resin layer> The coating resin layer is composed of a coating resin and filler particles, and is characterized by the formation of a chemical bond between the reactive functional group of the coating resin and the reactive functional group derived from the coupling agent on the filler surface.

[0033] The average thickness of the coating resin layer is preferably 100 nm or more and 3000 nm or less. That is, if it is 100 nm or more, the carrier core is less likely to be exposed, resulting in a decrease in resistance, and the charging characteristics of the developer are more easily maintained, which is preferable. Furthermore, if it is thicker than 3000 nm, charge increase in a low-humidity environment is likely to occur, so it is preferably 3000 nm or less. If it is 1500 nm or less, charge increase in a low-humidity environment can be more effectively suppressed, which is preferable.

[0034] When the average thickness of the coating resin layer is d and the number-average particle size of the filler particles is r, it is preferable that the relationship r / d<0.8 is satisfied, since this suppresses exposure of the filler particles from the surface of the coating resin layer and enhances the effect of preventing detachment.

[0035] Furthermore, the filler particles preferably account for 35 vol% or more and 95 vol% or less of the composition of the coating resin layer. That is, when the filler particles account for 35 vol% or more, the strength of the coating resin layer is easily improved, which is preferable. Furthermore, when the filler particles account for 95 vol% or less, the effect of preventing detachment can be more effectively exhibited, which is preferable. A content of 40 vol% or more and 90 vol% or less is more preferable, and a content of 60 vol% or more and 80 vol% or less is particularly preferable.

[0036] If the reactive functional groups on the surface of the filler particles and the reactive functional groups on the coating resin are the same, this has the effect of stabilizing the charging characteristics during continuous printing, and is a preferred configuration. Although the reason for this is unclear, it is presumed that if the reactive functional groups on the surface of the filler particles and the reactive functional groups on the coating resin are different, microscopic unevenness in charging characteristics occurs depending on the distribution of functional groups in the coating resin layer.

[0037] The bond between the reactive functional groups of the coating resin and the reactive functional groups on the surface of the filler particles is formed by a reaction caused by heat, light irradiation, or the action of a polymerization initiator. Any known reaction can be selected and used for the reaction.

[0038] When a polymerization initiator is used, examples thereof include azo or diazo polymerization initiators such as 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, and azobisisobutyronitrile; and peroxide polymerization initiators such as benzoyl peroxide, t-butyl peroxy 2-ethylhexanoate, t-butyl peroxypivalate, t-butyl peroxyisobutyrate, t-butyl peroxyneodecanoate, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, and lauroyl peroxide.

[0039] When chemical bonds are formed between the reactive functional groups of the coating resin and the reactive functional groups derived from the coupling agent on the filler surface, it is preferable to use a third crosslinking agent component, as this more effectively prevents the filler particles from falling off. Although the reason for this is unclear, it is thought that the use of a crosslinking agent increases the bonding strength between the coating resin and the filler particles by forming a complex crosslinked structure that includes bonds not only between the filler surface and the coating resin, but also between filler surfaces and between coating resins.

[0040] The method for coating the carrier core surface with the coating resin is not particularly limited and can be performed by any known method. For example, there is the so-called immersion method, in which the magnetic core and coating resin solution are stirred while volatilizing the solvent, thereby coating the magnetic core surface with the coating resin. Specific examples include a universal mixer (manufactured by Fuji Paudal Co., Ltd.) and a Nauta Mixer (manufactured by Hosokawa Micron Corporation). Another method involves spraying the coating resin solution from a spray nozzle while forming a fluidized bed to coat the magnetic core surface with the coating resin. Specific examples include a Spiracoater (manufactured by Okada Seiko Co., Ltd.) and a Spiraflow (manufactured by Freund Corporation). Another method involves dry coating the magnetic core with the coating resin in particle form. Specific examples include treatment methods using devices such as a Hybridizer (manufactured by Nara Machinery Works, Ltd.), a Mechanofusion (manufactured by Hosokawa Micron Corporation), a Hiflex Gral (manufactured by Fukae Powtec), and a Theta Composer (manufactured by Tokuju Kogyosho Co., Ltd.).

[0041] <Magnetic carrier> The magnetic carrier consists of a magnetic core and a resin coating layer covering its surface. The magnetization strength is 40 (Am) under a magnetic field of 1000 / 4π (kA / m). 2 / kg) or more 80(Am 2 / kg) or less. When the magnetization strength of the magnetic carrier is within the above range, the magnetic binding force to the developing sleeve is appropriate, so that carrier adhesion can be more effectively suppressed. In addition, the stress applied to the toner in the magnetic brush can be reduced, so that toner deterioration and adhesion to other components can be effectively suppressed.

[0042] The magnetic carrier preferably has a volume average particle size (D50) of 20 μm or more and 80 μm or less from the viewpoints of the ability to charge the toner, suppressing carrier adhesion to the image area, and achieving high image quality, and more preferably 20 μm or more and 60 μm or less.

[0043] 〔toner〕 Next, the toner constitution that is preferable for achieving the object of the present invention will be described in detail below.

[0044] <Binder resin> The toner may use the following polymers as the binder resin: homopolymers of styrene and its substituted derivatives, such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene; styrene-based copolymers, such as styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, and styrene-methacrylic acid ester copolymer; styrene-based copolymer resins, polyester resins, mixtures of polyester resins and vinyl resins, or hybrid resins in which both are partially reacted; polyvinyl chloride, phenolic resins, naturally modified phenolic resins, naturally resin-modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyester resins, polyurethanes, polyamide resins, furan resins, epoxy resins, xylene resins, polyethylene resins, and polypropylene resins. Among these, those containing polyester resin as the main component are preferred from the viewpoint of low-temperature fixability.

[0045] Monomers used in the polyester unit of the polyester resin include polyhydric alcohols (divalent or trivalent or higher alcohols), polycarboxylic acids (divalent or trivalent or higher carboxylic acids), their acid anhydrides, or their lower alkyl esters. To create a branched polymer that exhibits "strain hardening," partial crosslinking within the molecule of the amorphous resin is effective, and for this purpose, it is preferable to use a polyfunctional compound with a valence of three or more. Therefore, it is preferable to include a trivalent or higher carboxylic acid, its acid anhydride, or its lower alkyl ester, and / or a trivalent or higher alcohol as the raw material monomer for the polyester unit.

[0046] As the polyhydric alcohol monomer used in the polyester unit of the polyester resin, the following polyhydric alcohol monomers can be used.

[0047] Dihydric alcohol components include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, and bisphenols represented by formula (A) and their derivatives;

[0048] [ka] (In the formula, R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x+y is 0 or more and 10 or less.) Diols represented by formula (B);

[0049] [ka]

[0050] Examples of trihydric or higher alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene. Among these, glycerol, trimethylolpropane, and pentaerythritol are preferred. These dihydric and trihydric or higher alcohols can be used alone or in combination.

[0051] As the polycarboxylic acid monomer used in the polyester unit of the polyester resin, the following polycarboxylic acid monomers can be used.

[0052] Examples of dicarboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, anhydrides of these acids, and lower alkyl esters thereof. Of these, maleic acid, fumaric acid, terephthalic acid, and n-dodecenylsuccinic acid are preferably used.

[0053] Examples of trivalent or higher carboxylic acids, their acid anhydrides, or their lower alkyl esters include 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, and their acid anhydrides or lower alkyl esters. Among these, 1,2,4-benzenetricarboxylic acid, i.e., trimellitic acid or its derivatives, is particularly preferred due to its low cost and easy reaction control. These divalent carboxylic acids and trivalent or higher carboxylic acids can be used alone or in combination.

[0054] The method for producing the polyester unit of the present invention is not particularly limited, and known methods can be used. For example, the aforementioned alcohol monomer and carboxylic acid monomer are simultaneously charged and polymerized via an esterification reaction or transesterification reaction and a condensation reaction to produce a polyester resin. The polymerization temperature is not particularly limited, but is preferably in the range of 180°C to 290°C. Polymerization of the polyester unit can be performed using a polymerization catalyst such as a titanium-based catalyst, a tin-based catalyst, zinc acetate, antimony trioxide, or germanium dioxide. In particular, the binder resin of the present invention preferably contains a polyester unit polymerized using a tin-based catalyst.

[0055] In addition, it is preferable from the viewpoint of fogging that the acid value of the polyester resin is 5 mgKOH / g or more and 20 mgKOH / g or less, and the hydroxyl value is 20 mgKOH / g or more and 70 mgKOH / g or less, since this reduces the amount of moisture adsorption in a high-temperature, high-humidity environment and keeps the non-electrostatic adhesion force low.

[0056] The binder resin may be a mixture of a low molecular weight resin and a high molecular weight resin. The ratio of the high molecular weight resin to the low molecular weight resin is preferably 40 / 60 or more and 85 / 15 or less by mass from the viewpoint of low temperature fixability and hot offset resistance.

[0057] <Release agent> Examples of waxes that can be used in toners include: hydrocarbon waxes such as low-molecular-weight polyethylene, low-molecular-weight polypropylene, alkylene copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; oxides of hydrocarbon waxes such as oxidized polyethylene wax or block copolymers thereof; waxes containing fatty acid esters as the main component such as carnauba wax; and partially or completely deoxidized fatty acid esters such as deoxidized carnauba wax. Further examples include the following. Saturated straight-chain fatty acids such as palmitic acid, stearic acid, and montanic acid; unsaturated fatty acids such as brassidic acid, eleostearic acid, and valinaric acid; saturated alcohols such as stearyl alcohol, aralkyl alcohols, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; polyhydric alcohols such as sorbitol; esters of fatty acids such as palmitic acid, stearic acid, behenic acid, and montanic acid with alcohols such as stearyl alcohol, aralkyl alcohols, behenyl alcohol, carnaubyl alcohol, ceryl alcohol, and melissyl alcohol; fatty acid amides such as linoleic acid amide, oleic acid amide, and lauric acid amide; methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, hexamethylene Saturated fatty acid bisamides such as bisstearamide; unsaturated fatty acid amides such as ethylene bisoleamide, hexamethylene bisoleamide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacamide; aromatic bisamides such as m-xylene bisstearamide and N,N'-distearyl isophthalamide; fatty metal salts (commonly known as metal soaps) such as calcium stearate, calcium laurate, zinc stearate, and magnesium stearate; waxes obtained by grafting aliphatic hydrocarbon waxes with vinyl monomers such as styrene and acrylic acid; partial esters of fatty acids and polyhydric alcohols such as behenic acid monoglyceride; and methyl ester compounds having hydroxyl groups obtained by hydrogenating vegetable oils and fats.

[0058] Among these waxes, hydrocarbon waxes such as paraffin wax and Fischer-Tropsch wax, or fatty acid ester waxes such as carnauba wax are preferred from the viewpoint of improving low-temperature fixability and fixation separation property, and in the present invention, hydrocarbon waxes are more preferred from the viewpoint of further improving hot offset resistance.

[0059] In the present invention, the wax is preferably used in an amount of 3 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the binder resin.

[0060] Furthermore, in an endothermic curve during temperature rise measured with a differential scanning calorimetry (DSC) device, the peak temperature of the maximum endothermic peak of the wax is preferably 45° C. or higher and 140° C. or lower. If the peak temperature of the maximum endothermic peak of the wax is within the above range, it is preferable because it is possible to achieve both storage stability and hot offset resistance of the toner.

[0061] (coloring agent) The toner may contain a colorant. Examples of the colorant include the following.

[0062] Examples of black colorants include carbon black, and those toned to black using a yellow colorant, a magenta colorant, and a cyan colorant. As the colorant, a pigment may be used alone, but it is more preferable to use a dye and a pigment in combination to improve the clarity from the viewpoint of the image quality of a full-color image.

[0063] Examples of pigments for magenta toner include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4, 49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81:1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, 282; CI Pigment Violet 19; CI Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

[0064] Dyes for magenta toner include solvent dyes such as CI Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, and 121; CI Disperse Red 9; CI Solvent Violet 8, 13, 14, 21, and 27; and CI Disperse Violet 1; and basic dyes such as CI Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, and 40; and CI Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, and 28.

[0065] Examples of pigments for cyan toner include CI Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, and 17; CI Vat Blue 6; and CI Acid Blue 45, and copper phthalocyanine pigments having 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.

[0066] An example of a dye for cyan toner is CI Solvent Blue 70.

[0067] Yellow toner pigments include the following: CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; CI Vat Yellow 1, 3, 20.

[0068] An example of a dye for yellow toner is CI Solvent Yellow 162.

[0069] These colorants may be used alone or in combination, or in the form of a solid solution. The colorant is selected in consideration of hue angle, chroma, brightness, lightfastness, transparency on an overhead projector, and dispersibility in toner.

[0070] The content of the colorant is preferably 0.1 parts by mass or more and 30.0 parts by mass or less relative to the total amount of the resin components.

[0071] <Inorganic fine particles> The toner preferably contains inorganic fine particles, mainly for the purpose of improving fluidity and chargeability, and the inorganic fine particles are preferably attached to the toner surface.

[0072] As inorganic fine particles serving as spacer particles for improving the releasability between the toner and the magnetic carrier, silica particles having a maximum peak particle size of 80 nm to 200 nm based on the number distribution are preferred, and in order to function as spacer particles while better suppressing separation from the toner, a particle size of 100 nm to 150 nm is more preferred.

[0073] In order to improve the fluidity of the toner, it is preferable to incorporate inorganic fine particles having a maximum peak particle size of 20 nm or more and 50 nm or less based on the number distribution, and it is also preferable to use them in combination with the silica particles.

[0074] Furthermore, other external additives may be added to the toner particles in order to improve fluidity and transferability. The external additives added to the surface of the toner particles preferably contain inorganic fine particles such as titanium oxide, alumina oxide, and silica, and a plurality of types may be used in combination.

[0075] The total content of the external additives is preferably 0.3 to 5.0 parts by weight, more preferably 0.8 to 4.0 parts by weight, per 100 parts by weight of toner particles. Among these, the content of silica particles having a number distribution-based maximum peak particle size of 80 to 200 nm is 0.1 to 2.5 parts by weight, more preferably 0.5 to 2.0 parts by weight. Within this range, the effect as spacer particles becomes more pronounced.

[0076] The surfaces of silica particles or inorganic fine particles used as external additives are preferably subjected to a hydrophobic treatment, preferably using a coupling agent such as a titanium coupling agent or a silane coupling agent, a fatty acid or a metal salt thereof, a silicone oil, or a combination thereof.

[0077] Examples of titanium coupling agents include the following: tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, and bis(dioctyl pyrophosphate)oxyacetate titanate.

[0078] Examples of silane coupling agents include: γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyltrimethoxysilane, o-methylphenyltrimethoxysilane, and p-methylphenyltrimethoxysilane.

[0079] Examples of fatty acids include long-chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, and arachidonic acid. Examples of metals in these fatty acid metal salts include zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

[0080] Examples of silicone oils include dimethyl silicone oil, methylphenyl silicone oil, and amino-modified silicone oil.

[0081] The hydrophobic treatment is preferably carried out by adding a hydrophobic treatment agent to the particles to be treated in an amount of 1% by mass or more and 30% by mass or less (more preferably 3% by mass or more and 7% by mass or less) relative to the particles to be treated, thereby coating the particles to be treated.

[0082] The degree of hydrophobicity of the hydrophobized external additive is not particularly limited, but for example, the degree of hydrophobicity after the treatment is preferably 40 or more and 98 or less. The degree of hydrophobicity indicates the wettability of the sample with respect to methanol, and is an index of hydrophobicity.

[0083] [Two-component developer] When the magnetic carrier of the present invention is mixed with a toner to be used as a two-component developer, good results are usually obtained when the mixing ratio of the magnetic carrier is 2% by mass to 15% by mass, preferably 4% by mass to 13% by mass, in terms of the toner concentration in the developer. If the toner concentration is less than 2% by mass, the image density tends to decrease, and if it exceeds 15% by mass, fogging and scattering in the machine tend to occur.

[0084] In addition, in the case of a replenishment developer to be replenished to a developing device in response to a decrease in the toner concentration of the two-component developer in the developing device, the amount of toner is 2 parts by mass or more and 50 parts by mass or less per 1 part by mass of the replenishment magnetic carrier.

[0085] [Methods for measuring various physical properties] The methods for measuring various physical properties of toner, magnetic carrier, raw materials and intermediates are explained below.

[0086] <Method for measuring the volume average particle size (D50) of magnetic carriers and porous magnetic cores> The particle size distribution was measured using a laser diffraction / scattering particle size distribution measuring device "Microtrac MT3300EX" (manufactured by Nikkiso Co., Ltd.).

[0087] The volume average particle size (D50) of the magnetic carrier and porous magnetic core was measured using a sample supply device for dry measurement, the "One-Shot Dry Sample Conditioner Turbotrac" (manufactured by Nikkiso Co., Ltd.). The supply conditions for the Turbotrac were a dust collector used as the reduced pressure source, with an air volume of approximately 33 L / sec and a pressure of approximately 17 kPa. Control is performed automatically on the software. The particle size is calculated as the 50% particle size (D50), which is the cumulative value of the volume average. Control and analysis are performed using the accompanying software (version 10.3.3-202D). The measurement conditions are as follows:

[0088] SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 Particle refractive index: 1.81% Particle shape: non-spherical Measurement upper limit: 1408 μm Measurement lower limit: 0.243μm Measurement environment: Temperature 23°C, relative humidity 50%

[0089] <Method for measuring the number average particle size of primary particles of filler particles> A solution was prepared by adding 0.2 g of 5% Triton solution and 19.8 g of RO water to 0.01 g of dried filler particles. Next, the tip of the ultrasonic disperser probe was immersed in the solution and ultrasonically dispersed for 15 minutes at 20 W power to obtain a dispersion. The number-average particle size of this dispersion was then measured using a dynamic light scattering (DLS) particle size distribution analyzer (product name: Nanotrac 150, manufactured by Microtrac Bell). Mode: Transparent Particle condition: Spherical Particle refractive index: 1.45 Particle density: 1.30 Dispersion medium refractive index: 1.33 (water) Measurement time: 120 seconds

[0090] <Measurement of pore diameter and pore volume of porous magnetic core> The pore size distribution of the porous magnetic core is measured by mercury intrusion porosimetry.

[0091] The measurement principle is as follows.

[0092] In this measurement, the pressure applied to the mercury is varied, and the amount of mercury that penetrates into the pores is measured. The conditions under which mercury can penetrate into the pores can be expressed from the balance of forces as PD = -4σCOSθ, where P is the pressure, D is the pore diameter, θ is the contact angle of the mercury, and σ is the surface tension. If the contact angle and surface tension are constants, then the pressure P is inversely proportional to the pore diameter D into which mercury can penetrate at that time. For this reason, the pressure P and the amount of infiltrated liquid V at that time are measured by varying the pressure, and the horizontal axis P of the PV curve, obtained by this measurement, is then directly substituted for the pore diameter in this equation to determine the pore distribution.

[0093] Measurement can be performed using a measuring device such as a fully automatic multi-function mercury porosimeter PoreMaster series or PoreMaster-GT series manufactured by Yuasa Ionics Co., Ltd., or an automatic porosimeter Autopore IV9500 series manufactured by Shimadzu Corporation.

[0094] Specifically, measurements were carried out using an Autopore IV9520 manufactured by Shimadzu Corporation under the following conditions and procedures.

[0095] Measurement conditions Measurement environment: 20°C Measurement cell sample volume: 5 cm3, Indentation volume: 1.1 cm 3 , Application: For powder Measurement range: 2.0 psia (13.8 kPa) or more and 59989.6 psia (413.6 MPa) or less Measurement steps: 80 steps (When the pore diameter is calculated logarithmically, the steps are spaced at equal intervals.) Pressure parameters Exhaust pressure: 50 μmHg Exhaust time: 5.0 min Mercury injection pressure: 2.0 psia (13.8 kPa) Equilibrium time: 5secs High pressure parameter equilibration time: 5 seconds Mercury parameters: Advancing contact angle: 130.0 degrees Receding contact angle: 130.0degrees Surface tension: 485.0mN / m (485.0dynes / cm) Mercury density: 13.5335g / mL Measurement procedure (1) Approximately 1.0 g of the porous magnetic core is weighed and placed in the sample cell. Enter the weighing value. (2) In the low-pressure section, measure the range of 2.0 psia (13.8 kPa) to 45.8 psia (315.6 kPa). (3) In the high-pressure section, the range measured was between 45.9 psia (316.3 kPa) and 59,989.6 psia (413.6 MPa). (4) The pore size distribution is calculated from the mercury injection pressure and the amount of mercury injected. The above steps (2), (3), and (4) were performed automatically using the software provided with the device.

[0096] From the pore size distribution measured as described above, the pore size at which the differential pore volume is maximum in the pore size range of 0.1 μm to 3.0 μm is read, and this is taken as the pore size at which the differential pore volume is maximum.

[0097] In addition, the pore volume obtained by integrating the differential pore volume in the pore diameter range of 0.1 μm to 3.0 μm was calculated using the attached software.

[0098] <Method for measuring weight average particle size (D4)> The weight average particle diameter (D4) of the toner was measured using CDA-1000X (manufactured by Sysmex Corporation).

[0099] <Method for measuring the magnetization strength of a magnetic core> The magnetization strength of the magnetic core can be measured using a vibrating sample magnetometer or a direct current magnetization characteristic recorder (BH tracer). In the examples described below, the magnetization strength is measured using a vibrating sample magnetometer BHV-30 (manufactured by Riken Denshi Co., Ltd.) according to the following procedure.

[0100] The sample is a cylindrical plastic container packed with magnetic cores. The actual mass of the sample packed in the container is measured. The sample is then glued in place inside the plastic container with instant adhesive to prevent it from moving.

[0101] Using a standard sample, the external magnetic field axis and the magnetization moment axis are calibrated at 1000 / 4π (kA / m).

[0102] The magnetization strength was measured from the loop of the magnetization moment when an external magnetic field of 1000 / 4π (kA / m) was applied at a sweep speed of 5 (min / roop). From this, the magnetization strength (Am 2 / kg).

[0103] <Method for measuring Young's modulus of filler particles> The Young's modulus of the organosilicon polymer particles is determined by a microcompression test using a Hysitron PI 85L pico-indenter (manufactured by BRUKER).

[0104] The Young's modulus (MPa) is calculated from the slope of the profile (load-displacement curve) of the displacement (nm) and test force (μN) obtained in the measurement. Equipment and fixtures Base system: Hysitron PI-85L Measuring indenter: 1 μm flat-end indenter SEM used: Thermo Fisher Versa 3D SEM conditions: -10°tilt, 13pA at 10keV Measurement conditions Measurement mode: Displacement control Maximum displacement: 30nm Displacement speed: 1 nm / sec Hold time: 2 seconds Unloading speed: 5nm / sec ·Analysis method Hertz analysis is applied to the curve obtained when compressed from 0 nm to 10 nm in the load-displacement curve, and the Young's modulus of the filler particles is calculated. Sample preparation Filler particles are attached to a silicon wafer.

[0105] <Measurement of the average thickness of the resin coating layer> The average thickness of the resin coating layer was measured by observing the cross section of the magnetic carrier with a transmission electron microscope (TEM) (50,000x magnification).

[0106] Specifically, the magnetic carrier was subjected to ion milling using an argon ion milling device (Hitachi High-Technologies Corporation, product name E-3500), and the thickness of the resin coating layer on the cross section of the magnetic carrier was measured at any five points per particle using a transmission electron microscope (TEM) (50,000x magnification each).

[0107] The same measurement as above was carried out for 10 magnetic carrier particles, and the average value of 50 measured values ​​of the thickness of the resin coating layer obtained was taken as the average layer thickness. The ion milling measurement conditions were as follows: Beam diameter: 400 μm (half width) Ion gun acceleration voltage: 5 kV Ion gun discharge voltage: 4kV Ion gun discharge current: 463 μA Ion gun irradiation current: 90μA / cm3 / 1min

[0108] <Measurement of the volume ratio of filler particles in the resin coating layer> The average thickness of the resin coating layer was determined by observing the cross section of the magnetic carrier with a transmission electron microscope (TEM) (50,000x magnification) and measuring the volume ratio of the filler particles in the resin coating layer.

[0109] Specifically, the magnetic carrier was subjected to ion milling using an argon ion milling device (Hitachi High-Technologies Corporation, product name E-3500), and the coating resin layer of the cross section of the magnetic carrier was observed under a transmission electron microscope (TEM) (50,000x magnification). The cross-sectional area ratio of the filler particles in the cross section of the coating resin layer was calculated by image binarization processing.

[0110] The same measurement as above was carried out for 30 magnetic carrier particles, and the average value of the cross-sectional area ratios obtained was taken as the volume ratio of the filler particles in the resin coating layer. The ion milling measurement conditions were as follows: Beam diameter: 400 μm (half width) Ion gun acceleration voltage: 5 kV Ion gun discharge voltage: 4kV Ion gun discharge current: 463 μA Ion gun irradiation current: 90 μA / cm 3 / 1min

[0111] <Measurement of magnetic carrier resistivity> The resistivity value of the magnetic carrier is measured using the measuring device shown in FIG.

[0112] The resistivity is measured by filling cell E with magnetic carrier particles, arranging a lower electrode and an upper electrode so that they are in contact with the magnetic carrier particles, applying a voltage between these electrodes, and measuring the current that flows at that time to determine the resistivity. The resistivity measurement conditions are: contact area S between the filled magnetic carrier and the electrodes = approximately 2.4 cm 2 The sample thickness d was approximately 0.2 cm, and the load on the upper electrode was 240 g. The voltage was applied under conditions (I), (II), and (III) in that order, and the current was measured under the applied voltage under condition (III). The sample thickness d was then accurately measured, and the resistivity (Ω·cm) at each electric field strength (V / cm) was calculated. The resistivity at an electric field strength of 3000 V / cm was taken as the resistivity of the sample's magnetic carrier.

[0113] Application conditions (I): (Change from 0V to 1000V: Increase in steps of 200V every 30 seconds) (II): (1000V, 30 seconds hold) (III): (Change from 1000V to 0V: Decrease in steps of 200V every 30 seconds) Magnetic carrier resistivity (Ω·cm) = (applied voltage (V) / measured current (A)) × S (cm 2 ) / d(cm) Electric field strength (V / cm) = applied voltage (V) / d (cm) [Example]

[0114] The effects of the present invention will be explained below with reference to examples. The materials, additives, amounts and concentrations used, and processing methods and procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the content of the examples. Furthermore, "parts" means "parts by mass."

[0115] [Toner Production] <Production Example of Low Molecular Weight Polyester Resin A> Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 76.3 parts Terephthalic acid: 16.1 parts Succinic acid: 7.6 parts Titanium tetrabutoxide (esterification catalyst): 0.5 parts The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. After the atmosphere in the flask was replaced with nitrogen gas, the temperature was gradually raised with stirring, and the mixture was allowed to react at 200°C for 4 hours with stirring.

[0116] Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained at that level for 1 hour, after which the vessel was cooled to 160°C and returned to atmospheric pressure (first reaction step). tert-butylcatechol (polymerization inhibitor): 0.1 parts The above materials were then added, the pressure in the reactor was reduced to 8.3 kPa, and the reaction was carried out for 1 hour while maintaining the temperature at 180°C. Once it was confirmed that the softening point measured according to ASTM D36-86 had reached 90°C, the temperature was reduced to stop the reaction (second reaction step), yielding Resin A. The resulting Resin A had a peak molecular weight Mp of 4500, a softening point Tm of 90°C, and a glass transition temperature Tg of 54°C.

[0117] <Production Example of High Molecular Weight Polyester Resin B> Polyoxypropylene (2.2)-2,2-bis(4-hydroxyphenyl)propane: 74.8 parts Terephthalic acid: 12.9 parts Adipic acid: 7.9 parts Titanium tetrabutoxide (esterification catalyst): 0.5 parts The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. After the atmosphere in the flask was replaced with nitrogen gas, the temperature was gradually raised with stirring, and the mixture was allowed to react at 200°C for 2 hours with stirring.

[0118] Furthermore, the pressure inside the reaction vessel was reduced to 8.3 kPa and maintained at that level for 1 hour, after which the vessel was cooled to 160°C and returned to atmospheric pressure (first reaction step). Trimellitic acid: 5.9 parts tert-butylcatechol (polymerization inhibitor): 0.1 parts The above materials were then added, the pressure in the reactor was reduced to 8.3 kPa, and the reaction was carried out for 15 hours while maintaining the temperature at 200°C. Once it was confirmed that the softening point measured according to ASTM D36-86 had reached 140°C, the temperature was reduced to stop the reaction (second reaction step), yielding Resin B. The resulting Resin B had a peak molecular weight Mp of 10,000, a softening point Tm of 140°C, and a glass transition temperature Tg of 60°C.

[0119] <Production Example of Crystalline Resin C> Hexanediol: 33.9 parts Dodecanedioic acid: 66.1 parts The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. After the atmosphere in the flask was replaced with nitrogen gas, the temperature was gradually raised with stirring, and the mixture was allowed to react for 3 hours at 140°C with stirring. Tin 2-ethylhexanoate: 0.5 parts The above materials were then added, the pressure in the reaction vessel was reduced to 8.3 kPa, and the reaction was carried out for 4 hours while maintaining the temperature at 200°C, thereby obtaining crystalline resin C (first reaction step). The obtained crystalline resin C had a weight average molecular weight Mw of 11,000 and a melting peak temperature Tp of 72°C.

[0120] <Production example of wax dispersant D> Low molecular weight polypropylene (Viscol 660P manufactured by Sanyo Chemical Industries, Ltd.): 10.0 parts Xylene: 25.0 parts The above materials were weighed and placed in a reaction vessel equipped with a condenser, a stirrer, a nitrogen inlet tube, and a thermocouple. The atmosphere in the flask was then replaced with nitrogen gas, and the temperature was gradually raised to 175°C while stirring. Styrene: 65.0 parts Cyclohexyl acrylate: 5.5 parts Butyl acrylate: 12.5 parts Methacrylic acid: 5.5 parts Xylene: 10.0 parts Di-t-butylperoxyhexahydroterephthalate: 0.5 parts The above material was then added dropwise over 3 hours and stirred for an additional 30 minutes. The solvent was then distilled off to obtain Wax Dispersant D, in which a styrene-acrylic polymer was graft-polymerized onto a polyolefin. Wax Dispersant D had a peak molecular weight Mp of 6000 and a softening point of 125°C.

[0121] <Toner 1 manufacturing example> Resin A 62 parts ·Resin B 28 parts ·Crystalline resin C 10 parts Wax Dispersant D 4 parts Fischer-Tropsch wax (maximum endothermic peak temperature 90°C) 4 parts CI Pigment Blue 15:3 7 parts The above materials were mixed in a Henschel mixer (FM-75 model, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 20 s. -1 After mixing for 5 minutes, the mixture was kneaded in a twin-screw kneader (PCM-30, manufactured by Ikegai Corporation) set at a temperature of 130°C. The kneaded mixture was cooled and coarsely pulverized to 1 mm or less using a hammer mill to obtain a coarsely pulverized product. The coarsely pulverized product was then finely pulverized using a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.). It was then classified using a Faculty F-300 (manufactured by Hosokawa Micron Corporation) to obtain toner particles. The operating conditions were a classifying rotor rotation speed of 130 s -1 , distributed rotor rotation speed 120s -1 It was decided.

[0122] The obtained toner particles were subjected to heat treatment using the surface treatment device shown in Figure 2 (for details of each part of the device, see JP 2020-41533 A and JP 2021-189367 A), to obtain heat-treated toner particles. The operating conditions were a feed rate of 5 kg / hr, a hot air temperature of 160 °C, and a hot air flow rate of 6 m 3 / min., cold air temperature = -5℃, cold air flow rate = 4m 3 / min., Blower air volume = 20m 3 / min., injection air flow rate = 1m 3 / min.

[0123] 100 parts of the obtained heat-treated toner particles were mixed with hydrophobic silica (BET: 200 m 2 / g) 1.0 part, titanium oxide fine particles surface-treated with isobutyltrimethoxysilane (BET: 80m 2 1.0 parts of 1 / g of ethanol was mixed in a Henschel mixer (FM-75, manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) at a rotation speed of 30 s. -1 The mixture was mixed for 10 minutes, and a toner 1 was obtained.

[0124] The weight average particle size (D4) of Toner 1 was measured using a CDA-1000X (aperture diameter: 100 μm, manufactured by Sysmex Corporation) and was found to be 6.3 μm. The average circularity of Toner 1 was measured using a flow particle image analyzer FPIA-3000 (manufactured by Sysmex Corporation) and was found to be 0.967.

[0125] [Production of Magnetic Carrier] <Magnetic core 1 manufacturing example> Process 1 (weighing and mixing process) ·Fe2O361.7% by mass ·MnCO334.2% by mass ·Mg(OH)23.0% by mass ·SrCO31.1% by mass The ferrite raw material was weighed so that

[0126] Thereafter, the mixture was ground and mixed for 2 hours in a dry ball mill using zirconia balls (φ10 mm).

[0127] Process 2 (pre-firing process) After crushing and mixing, the mixture was fired in air at 950°C for 2 hours in a burner-type firing furnace to produce calcined ferrite. The composition of the ferrite was as follows: (MnO) a (MgO) b (SrO) c (Fe2O3) d In the above formula, a=0.40, b=0.07, c=0.01, d=0.52

[0128] Process 3 (crushing process) After crushing to about 0.5 mm using a crusher, 30 parts of water was added to 100 parts of the calcined ferrite and crushed in a wet ball mill using zirconia balls (φ1.0 mm) for 2 hours. After separating the balls, the mixture was crushed in a wet bead mill using zirconia beads (φ1.0 mm) for 3 hours to obtain a ferrite slurry.

[0129] Process 4 (granulation process) To the ferrite slurry, 2.0 parts of polyvinyl alcohol was added as a binder per 100 parts of calcined ferrite, and the mixture was granulated into 40 μm spherical particles using a spray dryer (manufacturer: Okawahara Kakoki).

[0130] Step 5 (baking process) In order to control the firing atmosphere, firing was carried out in an electric furnace under a nitrogen atmosphere (oxygen concentration 1.0% by volume) at 1150°C for 4 hours.

[0131] Process 6 (sorting process) The aggregated particles were broken down and then sieved through a sieve with 250 μm openings to remove coarse particles, thereby obtaining porous magnetic core particles.

[0132] Process 7 (resin filling process) 100.0 parts of porous magnetic core particles were placed in a mixing vessel (Dalton Corporation, universal mixer, NDMV model). While maintaining the temperature at 60°C, nitrogen was introduced while reducing the pressure to 2.3 kPa. A silicone resin solution was added dropwise under reduced pressure to a resin content of 7.5 parts relative to the porous magnetic core particles. Stirring was continued for 2 hours after the dropwise addition. The temperature was then raised to 70°C, the solvent was removed under reduced pressure, and the porous magnetic core particles were filled with the silicone resin composition obtained from the silicone resin solution. After cooling, the resulting filled core particles were transferred to a mixer (Sugiyama Heavy Industries, Ltd., UD-AT model drum mixer) equipped with a spiral blade in a rotatable mixing vessel. The mixture was heated to 220°C at a heating rate of 2°C / min under a nitrogen atmosphere and atmospheric pressure. The mixture was heated and stirred at this temperature for 60 minutes to harden the resin. After heat treatment, low-magnetic-force products were separated by magnetic separation and classified using a 150 μm sieve to obtain magnetic core 1.

[0133] The physical properties of the magnetic core 1 obtained are shown in Table 1.

[0134] <Magnetic core 2 manufacturing example> Magnetite microparticles (spherical, number-average particle size 250 nm) and a silane coupling agent (3-(2-aminoethylaminopropyl)trimethoxysilane; 3.0% by mass relative to the mass of the magnetite microparticles) were introduced into a container. Then, the mixture was mixed and stirred at high speed at a temperature of 100°C or higher in the container to surface-treat the magnetite microparticles. 10 parts phenol Formaldehyde solution (37% formaldehyde aqueous solution) 16 parts 84 parts of the above surface-treated magnetite particles The above materials were introduced into a reactor and mixed thoroughly at a temperature of 40°C.

[0135] The mixture was then heated to 85°C at an average heating rate of 3°C / min while stirring, and 4 parts by mass of 28% ammonia water and 25 parts by mass of water were added to the reactor. The temperature was maintained at 85°C, and the mixture was polymerized and cured for 3 hours. The peripheral speed of the stirring blade was 1.8 m / sec.

[0136] After the polymerization reaction, the mixture was cooled to 30°C and water was added. The supernatant was removed, and the resulting precipitate was washed with water and air-dried. The air-dried product was dried under reduced pressure (5 hPa or less) at 60°C to obtain magnetic material-dispersed resin core particles. These were designated magnetic core 2.

[0137] The physical properties of the magnetic core 2 thus obtained are shown in Table 1.

[0138] <Magnetic core 3 manufacturing example> Process 1 (weighing and mixing process) ·Fe2O361.7% by mass ·MnCO334.2% by mass ·Mg(OH)23.0% by mass ·SrCO31.1% by mass The ferrite raw material was weighed so that

[0139] Thereafter, the mixture was ground and mixed for 2 hours in a dry ball mill using zirconia balls (φ10 mm).

[0140] Process 2 (pre-firing process) After crushing and mixing, the mixture was fired in air at 1000°C for 2 hours in a burner-type firing furnace to produce calcined ferrite. The composition of the ferrite was as follows: (MnO) a (MgO) b (SrO) c (Fe2O3) d In the above formula, a=0.40, b=0.07, c=0.01, d=0.52

[0141] Process 3 (crushing process) After crushing to about 0.5 mm using a crusher, 30 parts of water was added to 100 parts of the calcined ferrite and crushed in a wet ball mill using stainless steel balls (φ1.0 mm) for 2 hours. After separating the balls, the mixture was crushed in a wet bead mill using stainless steel balls (φ1.0 mm) for 3 hours to obtain a ferrite slurry.

[0142] Process 4 (granulation process) To the ferrite slurry, 2.0 parts of polyvinyl alcohol was added as a binder to 100 parts of the calcined ferrite, and the mixture was granulated into 45 μm spherical particles using a spray dryer (manufacturer: Okawahara Kakoki).

[0143] Step 5 (baking process) In order to control the firing atmosphere, firing was carried out in an electric furnace under a nitrogen atmosphere (oxygen concentration 0.6% by volume) at 1200°C for 6 hours.

[0144] Process 6 (sorting process) After the aggregated particles were crushed, the particles were sieved through a sieve with 250 μm openings to remove coarse particles, thereby obtaining ferrite core particles, which are designated as magnetic core 3. The physical properties of the obtained magnetic core 3 are shown in Table 1.

[0145] [Table 1]

[0146] <Resin 1 manufacturing example> 60 parts of cyclohexyl methacrylate and 40 parts of acrylic acid were added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a rotary stirrer.

[0147] Further, 100 parts of toluene, 100 parts of methyl ethyl ketone, and 2.0 parts of azobisisovaleronitrile were added. The resulting mixture was maintained at 70°C for 10 hours under a nitrogen stream, and after the polymerization reaction was completed, washing was repeated to obtain a resin 1 solution (solid content 35% by mass).

[0148] <Resin 2 manufacturing example> Resin 2 solution was obtained in the same manner as Resin 1, except that 50 parts of cyclohexyl methacrylate and 50 parts of glycidyl methacrylate were used instead of 60 parts of cyclohexyl methacrylate and 40 parts of acrylic acid.

[0149] <Resin 3 manufacturing example> Resin 3 solution was obtained in the same manner as Resin 1, except that 50 parts of cyclohexyl methacrylate and 50 parts of 2-hydroxyethyl methacrylate were used instead of 60 parts of cyclohexyl methacrylate and 40 parts of acrylic acid.

[0150] <Resin 4 manufacturing example> 100 parts of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane was added to a four-neck flask equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a rotary stirrer.

[0151] Further, 0.12 parts of magnesium chloride, 11 parts of water, and 11 parts of propylene glycol monomethyl ether were added. The resulting mixture was stirred at 130°C for 3 hours under a nitrogen stream, and then devolatilized under reduced pressure at 60°C. 200 parts of propylene glycol monomethyl ether was then added to obtain a resin 4 solution (solid content 35% by mass).

[0152] <Resin 5 manufacturing example> Resin 5 solution was obtained in the same manner as Resin 1, except that 45 parts of methyl methacrylate and 55 parts of acrylic acid were used instead of 60 parts of cyclohexyl methacrylate and 40 parts of acrylic acid.

[0153] <Manufacturing example of filler particle 1> 20 parts of ethanol, 80 parts of water, and hydrochloric acid equivalent to 0.02 parts of HCl were added to a three-necked flask equipped with a thermometer, a nitrogen inlet tube, and a grinding stirrer. 1 part of a carboxylic acid-based silane coupling agent (manufactured by Shin-Etsu Silicones Co., Ltd.) was also added.

[0154] To the resulting solution, 10 parts of alumina particles having a number average particle size of 15 nm were added, and the resulting mixture was stirred at 50°C for 2 hours under a nitrogen stream, and then the solution was allowed to stand for 24 hours. The solid content was filtered and washed to obtain filler particles 1.

[0155] <Manufacturing example of filler particles 2> Filler particles 2 were obtained in the same manner as filler particles 1, except that 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane was used instead of the carboxylic acid-based silane coupling agent.

[0156] <Manufacturing example of filler particle 3> Filler particles 3 were obtained in the same manner as filler particles 1, except that zirconia particles having a number average particle size of 15 nm were used instead of alumina particles having a volume average particle size of 15 nm.

[0157] <Production example of filler particle 4> Filler particles 4 were obtained in the same manner as filler particles 1, except that silica particles having a number average particle size of 15 nm were used instead of alumina particles having a volume average particle size of 15 nm.

[0158] <Production Example of Filler Particle 5> Filler particles 5 were obtained in the same manner as filler particles 1, except that calcium carbonate particles having a number-average particle size of 15 nm were used instead of alumina particles having a volume-average particle size of 15 nm, and acetic acid was used instead of hydrochloric acid.

[0159] <Production example of filler particle 6> Filler particles 6 were obtained in the same manner as filler particles 1, except that zirconia particles having a number average particle size of 3 nm were used instead of alumina particles having a volume average particle size of 15 nm.

[0160] <Production example of filler particle 7> Filler particles 7 were obtained in the same manner as filler particles 1, except that zirconia particles having a number average particle size of 400 nm were used instead of alumina particles having a volume average particle size of 15 nm.

[0161] <Production example of filler particle 8> Filler particles 8 were obtained in the same manner as filler particles 1, except that zirconia particles having a number average particle size of 180 nm were used instead of alumina particles having a volume average particle size of 15 nm.

[0162] <Production example of filler particle 9> Filler particles 9 were obtained in the same manner as filler particles 1, except that phenyltrimethoxysilane was used instead of the carboxylic acid-based silane coupling agent.

[0163] <Production example of resin coating liquid 1> To 100 parts by mass of Filler 1, 13.2 parts by mass of Resin 1 solution (resin solids) was added, and toluene and methyl ethyl ketone were added in a 1:1 ratio to achieve a solids ratio of 5% by mass. The resulting mixture was shaken and stirred for 15 minutes using a paint shaker (manufactured by RADIA), and then a 20% by mass toluene solution of a copolymer of 2-vinyloxazoline and styrene, an oxazoline crosslinker, was added at 50% by mass of the resin component solids. The resulting mixture was shaken and stirred for 1 minute using a paint shaker (manufactured by RADIA) to obtain Resin Coating Solution 1.

[0164] <Production examples of resin coating solutions 2 to 20> Resin coating solutions 2 to 20 were obtained in the same manner as for Resin coating solution 1, except that the filler particles, resin solution, and crosslinking agent were changed as shown in Table 2.

[0165] The crosslinking agents in Table 2 are the following substances. Crosslinker 1: 20% by weight toluene solution of copolymer of 2-vinyloxazoline and styrene Crosslinker 2: 20% by weight toluene solution of polyacrylic acid Crosslinker 3: 20% by weight solution of dimethylol urea in methanol Crosslinker 4: 20% by mass ethanol solution of 2,4-diamino-6-phenyl-1,3,5-triazine (benzoguanamine) Crosslinking agent 5: Isocyanate-based curing agent (manufactured by Asahi Kasei Corporation, product name MF-K60B)

[0166] <Production example of resin coating liquid 21> Toluene and methyl ethyl ketone were added to Resin 1 solution in a 1:1 ratio to achieve a solids ratio of 5% by mass. The resulting mixture was shaken and stirred for 15 minutes using a paint shaker (manufactured by RADIA), and then a 20% by mass toluene solution of a copolymer of 2-vinyloxazoline and styrene (an oxazoline crosslinking agent) was added in an amount of 50% by mass of the resin component solids. The resulting mixture was shaken and stirred for 1 minute using a paint shaker (manufactured by RADIA), to obtain Resin Coating Solution 21.

[0167] <Production examples of resin coating solutions 22 and 23> Resin coating solutions 22 and 23 were obtained in the same manner as for Resin Coating Solution 1, except that the filler particles, resin solution, and crosslinking agent were changed as shown in Table 2.

[0168] <Manufacturing example of resin coating liquid 24> To 100 parts of 15 nm diameter alumina particles, 13.2 parts of Resin 1 solution (resin solids) were added, and toluene and methyl ethyl ketone were added in a 1:1 ratio to achieve a solids ratio of 5% by mass. The resulting mixture was shaken and stirred for 15 minutes using a paint shaker (manufactured by RADIA), and then a 20% by mass toluene solution of a copolymer of 2-vinyloxazoline and styrene, an oxazoline crosslinker, was added at 50% by mass of the resin component solids. The resulting mixture was shaken and stirred for 1 minute using a paint shaker (manufactured by RADIA) to obtain Resin Coating Solution 24.

[0169] [Table 2]

[0170] <Magnetic Carrier 1 Manufacturing Example> Using magnetic core 1, resin coating liquid 1 was added to a planetary mixer (Nauta Mixer VN, manufactured by Hosokawa Micron Corporation) maintained at a reduced pressure (1.5 kPa) and a temperature of 60°C, so that the solid content was 6.0 parts per 100 parts of magnetic core. The resin coating liquid was added in an amount of 1 / 3, and the solvent was removed and applied for 20 minutes. Next, another 1 / 3 of the resin coating liquid was added, and the solvent was removed and applied for 20 minutes. Another 1 / 3 of the resin coating liquid was then added, and the solvent was removed and applied for 20 minutes. The temperature was then raised to 120°C, and the crosslinking reaction was allowed to proceed for 30 minutes.

[0171] The magnetic carrier coated with the coating resin composition was then transferred to a mixer (a UD-AT drum mixer manufactured by Sugiyama Heavy Industries Co., Ltd.) equipped with a spiral blade in a rotatable mixing container. The mixture was heat-treated for 2 hours at 120°C in a nitrogen atmosphere while stirring at 10 revolutions per minute. The obtained magnetic carrier 1 was separated by magnetic separation to separate out low magnetic particles, which were passed through a sieve with 150 μm openings and then classified with an air classifier to obtain magnetic carrier 1. The physical properties of the obtained magnetic carrier 1 are shown in Table 3.

[0172] <Manufacturing Examples of Magnetic Carriers 2 to 28> Magnetic Carriers 2 to 28 were obtained in the same manner as Magnetic Carrier 1, except that the magnetic core and resin coating liquid were changed as shown in Table 3. The physical properties of Magnetic Carriers 2 to 28 obtained are shown in Table 3.

[0173] [Table 3]

[0174] [Production of Developer] <Manufacturing example of two-component developer 1> 10 parts by mass of toner 1 was added to 90 parts by mass of magnetic carrier 1, and the mixture was shaken in a shaker (product name: YS-8D model, manufactured by Yayoi Co., Ltd.) to prepare 300 g of a two-component developer. The shaking conditions using the shaker were 200 rpm and 5 minutes.

[0175] <Production examples of two-component developers 2 to 28> In the production example of two-component developer 1, the same operation was carried out except that the combinations were changed to those shown in Table 4, thereby obtaining two-component developers 2 to 28.

[0176] <Production example of replenishment developer 1> 95 parts by mass of toner 1 was added to 5 parts by mass of magnetic carrier 1, and mixed for 5 minutes in a V-type mixer in a temperature 23°C / humidity 50% RH (normal temperature and humidity) environment (hereinafter referred to as "N / N environment") to obtain replenishment developer 1.

[0177] <Production Examples of Replenishment Developers 2 to 28> Replenishment developers 2 to 28 were obtained in the same manner as in the production example of replenishing developer 1, except that the combinations were changed to those shown in Table 4.

[0178] [Table 4]

[0179] Example 1 The following evaluations were carried out using two-component developer 1 and replenishment developer 1.

[0180] As the image forming apparatus, a modified full-color copying machine (product name: imageRUNNER ADVANCE C9075 PRO) manufactured by Canon Inc. was used.

[0181] A two-component developer was placed in the developing device, a replenishment developer container containing a replenishment developer was set, an image was formed, and various evaluations were carried out while a durability test was carried out.

[0182] The durability test was conducted in Step 1 and Step 2, outputting a total of 300,000 images, while changing the environment and image ratio as follows:

[0183] Step 1 (1st to 200,000th) Temperature 30℃ / Humidity 80%RH (hereinafter referred to as "H / H environment") FFH output chart with 60% image ratio Step 2 (200001st to 300000th sheets) Temperature 23℃ / Humidity 5%RH (hereinafter referred to as "N / L environment") FFH output chart with 3% image ratio Here, FFH is a value that represents 256 gradations in hexadecimal, with 00H being the first gradation of the 256 gradations (white background) and FFH being the 256th gradation of the 256 gradations (solid area).

[0184] Other conditions are as follows: Paper: GFC-081 (81.0g / m 2 )(Canon Marketing Japan Inc.) Image formation speed: Modified to output 80 sheets per minute in full color, A4 size. Development conditions: The development contrast can be adjusted to any value, and the automatic correction by the main unit has been modified to prevent it from operating.

[0185] The alternating electric field was modified so that its peak-to-peak voltage (Vpp) could be varied in 0.1 kV increments from 0.7 kV to 1.8 kV at a frequency of 2.0 kHz.

[0186] Each color was modified so that images could be output in a single color.

[0187] Using this main body, the following evaluations (1) to (5) were carried out, and the results are shown in Table 5.

[0188] For measurements with measurement errors, the measurements were repeated until the measurement errors were sufficiently small, and the arithmetic mean value was used as the measurement value.

[0189] (1) Coverage After 100,000 sheets were output in Step 1, 10 sheets of 00H output chart (A4 full-scale white image) with an image ratio of 100% were output, and the whiteness of the white background was measured using a reflectometer (Tokyo Denshoku Co., Ltd.). The fog density (%) was calculated from the difference between this whiteness and the whiteness of the transfer paper, and the sheet with the highest fog density among the 10 sheets was evaluated. The evaluation criteria were as follows: A: Less than 0.5% B: 0.5% or more and less than 1.0% C: 1.0% or more and less than 1.5% D: 1.5% or more

[0190] (2) Image density difference before and after durability testing for each step At the beginning and end of Step 1, one FFH output chart (A4 full-page solid image) with an image ratio of 100% was output. The image density was measured and judged using a spectrodensitometer 500 series (manufactured by X-Rite).

[0191] The measurement site is At a position 0.5 cm from the tip of the image (the side where the image was formed first), and at three points 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image (the side where the image was formed first is considered the top), At a position 7.0 cm from the tip of the image, three points are located at 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image. At a position 14.0 cm from the tip of the image, three points are located at 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image. At a position 20.0 cm from the tip of the image, three points are located at 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image. The total score was 12 points, and the average of the 12 points was calculated.

[0192] The evaluation was based on the difference between the first and last 12-point average values ​​and judged according to the following criteria. A: 0.00 or more and less than 0.05 B: 0.05 or more and less than 0.10 C: 0.10 or more and less than 0.15 D: 0.15 or more

[0193] (3) Whiteout In Step 2, immediately after 200 sheets of paper have been fed continuously, a chart is output in which halftone horizontal bands (30H width 10mm) and solid black horizontal bands (FFH width 10mm) are arranged alternately in the direction of transfer paper transport. The image is read by a scanner and binarized. The luminance distribution (256 gradations) of a line in the transport direction of the binarized image is taken. A tangent line is drawn to the halftone luminance at that time, and the luminance area (area: sum of luminance values) that deviates from the tangent line at the rear end of the halftone area until it intersects with the luminance of the solid area is taken as the degree of whiteout, and is evaluated based on the following criteria. A: Less than 20 B: 20 ​​or more and less than 30 C: 30 or more and less than 40 D: 40 or more

[0194] (4) Dispersion In Step 1, after 100,000 sheets were output, the developing unit was removed from the main body, and the state of toner scattering inside and outside the developing unit and the main body was visually inspected and evaluated according to the following criteria. A: No toner scattering B: Slight toner scattering C: Toner scattering D: Serious toner scattering

[0195] (5) Coated resin abrasion resistance After performing Step 1, the developer was removed from the main body, and 1 g of the developer or the developer before durability testing, 30 mL of distilled water, and 0.1 mL of Contaminon N (a 10% by weight aqueous solution of a pH 7 neutral detergent for cleaning precision measuring instruments, consisting of a nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a 100 mL flat-bottom glass beaker, and the process of ultrasonically cleaning for 1 minute and then removing the supernatant was repeated three times, and the resulting residue was dried in a dryer at 50°C for 24 hours to obtain a magnetic carrier sample. The resistivity of the obtained magnetic carrier sample was measured, and the rate of change in the measured value before and after durability testing was judged according to the following criteria. A: The decrease in resistivity due to durability is less than 10% compared to before durability B: The decrease in resistivity due to durability is 10% or more but less than 25% compared to before durability C: The decrease in resistivity due to durability is 25% or more but less than 50% compared to before durability D: The resistivity after durability testing is reduced by 50% or more compared to before durability testing.

[0196] When the product was rated A to C, which is equivalent to or better than existing technical products, for all of the above evaluation items (1) to (5), it was determined that the effects of the present invention were achieved.

[0197] [Examples 2 to 24, Comparative Examples 1 to 4] The evaluation was carried out in the same manner as in Example 1, except that the two-component developer and the replenishment developer were changed as shown in Table 5. The results are shown in Table 5.

[0198] [Table 5] [Explanation of symbols]

[0199] 1. Raw material constant volume supply means, 2. Compressed gas flow rate adjustment means, 3. Inlet pipe, 4. Projecting member, 5. Supply pipe, 6. Treatment chamber, 7. Hot air supply means, 8 (8-1, 8-2, 8-3). Cold air supply means, 9. Regulating means, 10. Recovery means, 11. Hot air supply means outlet, 12. Distribution member, 13. Swirling member, 14. Powder particle supply port

Claims

1. A magnetic carrier comprising magnetic carrier particles having a magnetic core and a coating layer that coats the surface of the magnetic core, The magnetic carrier is characterized in that the coating layer contains a coating resin and filler particles, the filler particles are treated particles that have been surface-treated with a coupling agent, and the coating resin and filler particles are bonded via the coupling agent.

2. 2. The magnetic carrier according to claim 1, wherein the filler particles have a Young's modulus of 30 GPa or more.

3. 3. The magnetic carrier according to claim 1, wherein the coating layer has an average thickness d of 100 nm or more and 3,000 nm or less, the filler particles have a number-average primary particle diameter r of 5 nm or more and 300 nm or less, and d and r satisfy r / d<0.

8.

4. 4. The magnetic carrier according to claim 1, wherein the filler particles account for 35 vol % or more and 95 vol % or less of the composition of the resin coating layer.

5. 5. The magnetic carrier according to claim 1, wherein the coupling agent is a silane coupling agent.

6. 6. The magnetic carrier according to claim 1, wherein the coating resin and the filler particles are bonded together by a reaction mediated by a crosslinking agent.

7. 7. The magnetic carrier according to claim 1, wherein the coating resin contains a silicone resin.

8. 8. The magnetic carrier according to claim 1, wherein the coating resin contains an acrylic resin or a methacrylic resin.

9. 9. The magnetic carrier according to claim 8, wherein the coating resin has an alicyclic hydrocarbon group.

10. The magnetic carrier according to any one of claims 1 to 9, wherein the coating resin and the filler particles surface-treated with a coupling agent are bonded via a crosslinking agent in addition to the coupling agent, and the bond formed between the coupling agent and the crosslinking agent and the bond formed between the crosslinking agent and the coating resin are formed using the same reactive functional group.

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