JP2005099074A - Magnetic carrier and two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high sharpness image by stably imparting an electrostatic charge to toner for a period longer than the conventional resin coated carrier. <P>SOLUTION: The surface of a carrier core material is coated with a resin composed of colloidal silica and a resin composed of a siloxane resin. The carrier having such coating layer does not give rise to carrier contamination by the components of the toner and is the secure film which does not cause the peeling of the coating layer and therefore the high sharpness image with which the stable impartation of the electrostatic charge to the toner is possible for a long period of time can be provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic carrier used as a developer for developing an electrostatic charge image in an electrophotographic method, an electrostatic recording method, and the like, and a two-component developer containing the carrier and a toner.

  As electrophotographic methods, various methods are described in US Pat. No. 2,297,691, the specification of Japanese Patent Publication No. 42-23910, the Japanese Patent Publication No. 43-24748, and the like. An electrostatic latent image is formed by irradiating the photoconductive layer with a light image corresponding to the original, and then a colored fine powder called toner having a polarity opposite to the electrostatic latent image is adhered onto the electrostatic latent image. The electrostatic latent image is developed and, if necessary, the toner image is transferred onto a transfer material such as paper, and then fixed by heat, pressure, solvent vapor or the like to obtain a copy.

  The step of developing the electrostatic latent image is to attract toner particles charged to a polarity opposite to that of the latent image by electrostatic attraction and adhere to the electrostatic latent image (in the case of reversal development, A toner having a triboelectric charge of the same polarity as that of the latent image), a so-called two-component developer in which a small amount of toner is dispersed in a medium called a carrier as a method of developing such an electrostatic latent image using toner. A method of using is known.

  In developing such a two-component developer, it is desirable that the toner and the carrier are sufficiently agitated and mixed in the developing device so that the toner particles are uniformly charged.

  However, as a result of repeated copying, the toner particles and the carrier particles or the carrier particles are repeatedly brought into contact with each other under mechanical stress in the developing device. As a result, toner fusion called toner filming or the outside of the toner surface is gradually applied to the carrier surface. Changes in the carrier surface over time, such as removal of the additive and transfer to the carrier surface, will reduce the ability of the carrier to impart triboelectric charge. Such a deteriorated carrier makes toner charging unstable, for example, generates toner of reverse polarity and reduces the absolute value of the toner charge amount, causes ground fog and toner scattering, and deteriorates image quality.

  As means for suppressing such carrier deterioration, a method of coating the surface of the carrier core material with various resins has been proposed, but a sufficiently satisfactory one has not been obtained.

  For example, a carrier coated with a fluororesin such as a tetrafluoroethylene copolymer has a low critical surface tension, so toner filming is unlikely to occur. However, film formability is poor, adhesion to the carrier core material is weak, and Unsatisfactory in terms of wear. Further, due to the relationship with the charging series, the fluororesin-coated carrier cannot have a sufficient charging ability in the negative charging characteristics.

  On the other hand, a carrier coated with an acrylic resin such as a styrene / methacrylate copolymer has good film formability and good adhesion to the carrier core material. However, styrene-acrylic copolymers have a relatively high critical surface tension, and toner filming is relatively likely to occur during repeated use, and there are some problems with the life of the developer. Also, from the viewpoint of wear resistance, it cannot be said that the surface hardness is sufficient although it is relatively high.

  Silicone resin has a low surface energy and is known to reduce toner filming. However, the mechanical strength of the silicone resin itself is weak, and the coating layer is worn away while stirring in the developing device. It has been difficult to stabilize the charging characteristics.

  Furthermore, a method for coating the carrier surface with an inorganic substance has also been proposed. For example, JP-A-54-78136 discloses a carrier coated with inorganic glass, JP-A-61-188548 discloses a carrier on which a ferrite film is formed, and JP-A-2-116857. Proposes an electroless plated carrier.

  However, the method of coating the surface of the carrier with such an inorganic material has a problem that adhesion and coverage are insufficient.

  Accordingly, there is a demand for a carrier coating material that is excellent in toner filming resistance and durability stability, has high image quality, and is stable over a long period of time while satisfying the charging characteristics required for a carrier for a two-component developer. .

  An object of the present invention is to provide a magnetic carrier and a two-component developer that have a stable chargeability for a long period of time in development, and obtain a high-quality image without fogging and toner scattering.

  It is another object of the present invention to provide a magnetic carrier that is excellent in toner filming resistance and abrasion resistance and can stably obtain a high-quality image faithful to a latent image over a long period of time.

  The above object is achieved by the present invention described below. That is, the present invention is a magnetic carrier having a magnetic carrier core particle and a coating layer covering the surface of the magnetic carrier core particle, wherein the coating layer contains colloidal silica and a siloxane resin. It relates to a magnetic carrier.

  Furthermore, the present invention is a two-component developer comprising a toner and a carrier, and the toner has a weight average particle diameter of 1 to 10 μm, and a distribution cumulative value not more than ½ times the number average particle diameter (D1). 20% by number or less, a distribution cumulative value of 2 or more times the weight average particle diameter (D4) is 10% by volume or less, the magnetic carrier has a coating layer, and the coating layer is made of colloidal silica and siloxane resin. In particular, the present invention relates to a two-component developer.

  The siloxane resin described in the present invention means a silicone resin or a partially condensed oligomer obtained by condensation of a silicon compound having three hydrolyzable groups such as OH group and OR group per silicon atom.

  The magnetic carrier of the present invention has a coating layer containing colloidal silica and a siloxane resin on the surface, so that the coating layer does not peel off or toner filming occurs even in long-term use, so that the toner is stably charged. can do. Accordingly, there is no fogging or toner scattering, and a stable image can be obtained over a long period of time. In addition, the two-component developer using the magnetic carrier and toner of the present invention can be stably and satisfactorily developed over a long period of time, and can maintain a high-quality image.

  Hereinafter, the present invention will be described in detail.

  The reason why the present invention can provide various high-quality images stably over a long period of time is improved for the following reasons.

  That is, the magnetic carrier of the present invention does not have toner filming or toner external additives attached to the carrier surface unlike conventional coated carriers, and can obtain a high-quality image over a long period of time. By providing a coating layer of a resin containing colloidal silica and a siloxane resin.

  That is, the coating layer made of colloidal silica and siloxane resin has extremely high film hardness and high adhesion to carrier core particles compared to conventional coating resins such as conventional acrylic resins and silicone resins. Furthermore, it has excellent surface releasability and charging stability to the toner. Therefore, there is no deterioration of the carrier due to long-term use, for example, toner filming on the carrier surface, adhesion or embedding of the toner external additive, and further, there is no peeling of the coating layer. Therefore, high-quality images can be maintained because stable and good development can be performed.

  The coating layer of the magnetic carrier of the present invention contains a siloxane resin containing colloidal silica, and is formed by coating, drying and curing on the surface of the magnetic carrier core particles.

  The composition of the coating layer of the magnetic carrier of the present invention comprises at least the following three components (a) to (c).

(A) Colloidal silica (b) Siloxane resin prepared by partial condensation of R—Si (OR ′) ₃ (R is an alkyl group having 1 to 4 carbon atoms, vinyl group, phenyl group, CnF _{2n + 1} C ₂ H ₄ -group (n = 1-18), γ-glycidoxypropyl group, or γ-methacryloxypropyl group may be selected from a single group or a plurality of groups, and R ′ is a single alkyl group having 1 to 3 carbon atoms or a hydrogen atom. (Multiple selections are made.)
(C) Lower aliphatic alcohol, solvent selected from water alone or a plurality thereof The magnetic carrier coating layer of the present invention is composed of colloidal silica in a range of 10 to 70% by weight and siloxane resin in a range of 30 to 90% by weight, As these solid contents, those dispersed in a 1 to 50% by weight lower alcohol-water mixed solution are used. If the solid content is 50% by weight or more, the stability of the composition is likely to deteriorate, and it becomes difficult to form a coating film well due to gelation and the like, and the period during which the coating can be applied is limited. Further, when the solid content is 1% by weight or less, there is a problem that the strength of the formed coating layer is not sufficient.

  Moreover, the ratio of colloidal silica in solid content is 10 to 70 weight%, and the ratio of siloxane resin is used at 30 to 90 weight%. When the proportion of the siloxane resin in the solid content is 30% by weight or less, the coating layer becomes brittle and it is difficult to form a good coating layer, and cracks are easily formed. When the proportion of colloidal silica is 10% by weight or less, the hardness of the formed coating layer is low. There is a tendency to become insufficient.

  The average particle size of the colloidal silica particles is preferably 5 to 150 nm, and particularly preferably 10 to 30 nm from the viewpoint of dispersion stability and optical properties.

The colloidal silica used for the coating layer of the magnetic carrier of the present invention is a commercially available aqueous dispersion (for example, “Ludox” manufactured by EI du Pont de Nemours & Co., “manufactured by Nalco Chemical” Nalcoag "etc.). As the colloidal silica particles, those having an alkali metal oxide content such as Na ₂ O of 2% by weight or less are used.

  The composition for the coating layer of the magnetic carrier of the present invention is adjusted to an acidic state of pH 3.0 to 6.0 by using an inorganic acid or an organic acid. If a strong acid is used, the stability of the composition is likely to be adversely affected, so a weak acid is preferably used, and the pH is adjusted to an acid state of 4.0 to 5.5.

  The composition for the coating layer applied to the surface of the magnetic carrier core particles is dried and then thermally cured to exhibit characteristics of hardness, strength, and low surface energy. Thermosetting proceeds completely as the temperature increases, but it becomes brittle as it is processed at a high temperature, and cracks and the like are easily generated, and it is easy to peel off from the carrier core particles. Therefore, the thermosetting is preferably performed at 80 to 180 ° C. However, it is more preferably performed at 100 ° C to 150 ° C.

  Curing progresses as the time for heat curing increases, but is adjusted so that appropriate hardness is developed at the processing temperature, and the processing time is generally about 10 minutes to 12 hours.

The coating layer obtained by thermosetting after drying contains at least a component represented by SiO ₂ as colloidal silica and a siloxane resin represented by RSiO _3/2 . Where R is an alkyl group having 1 to 4 carbon atoms, a vinyl group, a phenyl _{group, C n F 2n + 1 C} 2 H 4 - group (n = 1~18), γ- glycidoxypropyl group, .gamma. methacryl One or a plurality of loxypropyl groups are selected and used.

  The coating layer of the magnetic carrier of the present invention needs to have a low surface energy in order to satisfy the stain resistance against the toner component. The low surface energy measured by the water contact angle of the film formed on the glass plate is required to be 90 degrees or more. Below 90 degrees, the toner component's external additives and binder resin adhere to the carrier surface due to repeated use in the developer as the developer constituent material, and the ability to impart charge to the toner decreases, causing fog and toner scattering. Cause deterioration of the image.

  Furthermore, as a feature of the coating layer of the magnetic carrier of the present invention, extremely high surface hardness may be obtained in comparison with a normal organic compound because it contains colloidal silica and a siloxane resin. The surface hardness is appropriately selected from the balance with various physical properties depending on the content of colloidal silica and the structure of the siloxane resin, but the pencil hardness of the film formed on the glass plate is preferably 5H or more. If it is 5H or less, toner contamination and peeling of the coating layer are liable to occur due to contact with toner and various loads in the developing device.

  As a method for producing a resin composition containing colloidal silica and a siloxane resin used as essential components for the magnetic carrier coating layer of the present invention, the methods described in USP 4027073 and USP 3944702 can be used.

  The resin used for the coating layer of the magnetic carrier of the present invention is generally called a silicone-based hard coat resin, and consists of a hydrolysis condensate of a polyfunctional organosilicon compound having a hydrolyzable group in the molecule. Since the strength increases as the number of functional groups increases, the produced resin becomes harder. Among them, when colloidal silica is used in place of tetrafunctional organosilicon and trifunctional organosilicon is used, the particle size of colloidal silica, the amount added, and the hydrolysis condensation of trifunctional organosilicon are adjusted. As a result, a resin having high hardness and excellent film formability can be obtained.

  A suitable colloidal silica has an average particle diameter of 5 nm to 150 nm, and is dispersed in a lower alcohol containing water within the above-mentioned range, and a trifunctional organosilicon compound having a hydrolyzable group is converted to an acid or an alkali. Manufactured by hydrolysis in the presence. After completion of the reaction, a lower alcohol, a curing catalyst, a leveling agent and the like are further added as necessary. This is coated on the surface of the carrier core material by a method such as dip or spray. After removing the solvent, a film is generally formed by heat curing in the range of 80 to 150 degrees. The siloxane resin thus formed can exhibit a hardness of several H or more and 9H in pencil hardness. The hard coat resin is made of a silane compound called a silane coupling agent or a titanium compound called a titanium coupling agent for the purpose of improving the adhesion to the core material surface according to the carrier core material to be applied. Adhesion can also be improved by surface treatment or by modifying the surface by chemical or physical methods.

Further, the present inventors have conducted detailed studies. As a result, the magnetic carrier has a magnetic carrier magnetization strength of 40 to 350 emu / cm ³ at the developing pole (magnetic pole strength of about 1000 Oersted). It has been found that when a magnetic carrier having a diameter of 1 to 100 μm is used, the density of the developer magnetic brush at the developing pole becomes dense, and an image with good dot reproducibility can be obtained.

In addition, metal oxide particles exhibiting magnetism are preferred for use as the core particles of the above-described magnetic carrier of the present invention, and specific examples are represented by the general formula of MO · Fe ₂ O ₃ or MFe ₂ O ₄ exhibiting magnetism. Magnetite or ferrite.

  In the formula, M represents a trivalent, divalent or monovalent metal ion, and Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y , Zr, Nb, Mo, Cd, Sn, Ba, Pb, and Li. M can be used alone or in combination. For example, iron-based materials such as magnetite, Zn-based ferrite, Mn-Zn-based ferrite, Ni-Zn-based ferrite, Mn-Mg-based ferrite, Ca-Mn-based ferrite, Ca-Mg-based ferrite, Li-based ferrite, and Cu-Zn-based ferrite An oxide is mentioned.

  The coating amount of the coating layer composed of colloidal silica and siloxane resin on the carrier core particles of the magnetic carrier of the present invention is 0.01 to 10% by weight, preferably 0.1 to 2.0% by weight, based on the core particles. is there. When the coating amount is less than 0.1% by weight, it is difficult to obtain a uniform coating film, and when the coating amount exceeds 10% by weight, the effect of the coating is not substantially changed. Detrimental effects such as granulation are noticeable.

  The magnetic carrier of the present invention may be coated with a coupling agent contained in the coating layer for the purpose of adjusting the ability to impart triboelectric charge to the toner or controlling the fluidity of the carrier. As the coupling agent to be used, it is preferable to use one or a mixture of two or more selected from silane coupling agents, titanate coupling agents and the like.

  Specifically, a silane coupling agent having a hydrophobic group, an epoxy group or an amino group can be used. Examples of the silane coupling agent having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, and vinyltris (β-methoxy) silane. Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, and the like. .

  Examples of the silane coupling agent having an amino group include γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropylmethyldiethoxysilane, and N-β (aminoethyl) -γ-aminopropyl. Examples include trimethoxysilane, γ (2-aminoethyl) aminopropyltrimethoxysilane N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and the like.

  Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylvinsensulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, and the like. Examples of the titanate coupling agent having an amino group include isopropyl tri (N-aminoethyl-aminoethyl) titanate, isopropyl-4-aminobenzenesulfonyl-di (dodecylbenzenesulfonyl) titanate, and the like. .

  Moreover, the magnetic carrier of this invention can also use the 1 type, or 2 or more types of mixture chosen from organoalkoxysilane in a coating layer. Specific examples thereof include trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, Methyldimethoxysilane, methyldiethoxysilane, dimethylethoxysilane, cyclohexylmethyldimethoxysilane, hexyltrimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxy Silane etc. are mentioned.

  The amount of the coupling agent or organoalkoxysilane added is preferably 0.01 to 50% by weight based on the amount of the coating resin that coats the carrier core particles. Furthermore, the range of 0.1% by weight to 5% by weight is most preferable. If the addition amount is less than 0.01%, the effect of adding a coupling agent or an organoalkoxysilane is not exhibited, and if it is 50% by weight or more, the strength of the coating layer is insufficient or a uniform coating film is formed. There is not.

  As a method for preferably producing the magnetic carrier of the present invention, a method of spraying a solution of the resin composition for coating while suspending and flowing the carrier core particles to form a coat film on the surface of the core particles and a spray drying method can be mentioned. Further, as another coating method, the magnetic carrier of the present invention can also be produced by a coating method in which the solvent is gradually volatilized while applying a shear stress.

  The toner used in the present invention will be further described. The toner used in the present invention has a weight average particle diameter of 1 to 10 μm, preferably 3 to 8 μm. Further, the inversion component is that the cumulative distribution value of ½ times the number average particle diameter is 20% by number or less and the cumulative distribution value of the weight average particle diameter is 2 times or more is 10% by volume or less. This is essential for satisfying the satisfactory charging and latent image dot reproducibility. Further, in order to improve toner chargeability and improve dot reproducibility, the cumulative distribution value of ½ times the number average particle diameter is 15% by number or less, and the cumulative distribution is more than twice the weight average particle diameter. The value is more preferably 5% by volume or less. Further, it is more preferable that the cumulative distribution value of ½ times the number average particle diameter is 10% by number or less, and the cumulative distribution value of the double diameter of the weight average particle diameter is 2% by volume or less.

  When the toner weight average particle diameter exceeds 10 μm, one particle for developing the latent image becomes large, so that development that is faithful to the latent image cannot be performed, and when electrostatic transfer is performed, scattering of toner becomes intense. . In addition, when the particle diameter is 1 μm or less, the handling property as a powder is inconvenient.

  Also, if the cumulative value of distribution of ½ times the number average particle diameter exceeds 20% by number, toner charge cannot be satisfactorily applied to the fine toner, the toner tribo distribution becomes wide, and charging failure (reversal component generation). In addition, the uneven distribution of the particle size of the developed toner causes problems such as a change in particle size due to durability. Further, if the cumulative distribution value of the double diameter or more of the weight average particle diameter exceeds 10% by volume, the frictional charge with the carrier cannot be performed satisfactorily, and the latent image cannot be faithfully reproduced.

  In the measurement of the particle size distribution used in the present invention, for example, a method using a laser scanning type CIS100 (GLAI) can be mentioned. A specific measurement method will be described later.

  The toner particle size of the present invention is closely related to the carrier particle size. When the carrier number average particle diameter is 15 to 50 μm, it is preferable that the toner has a weight average diameter of 3 to 8 μm or less in order to improve the chargeability and improve the image quality.

  Specific examples of the binder resin for the toner used in the present invention include a polymer compound obtained from styrene and its derivatives such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and styrene-p-. Chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, sterene-α-chloromethyl methacrylate copolymer Polymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, polyvinyl chloride, phenol resin, modified phenol Resin, maleic resin, acrylic Polyester having structural units of monomers selected from resins, methacrylic resins, polyvinyl acetate, silicone resins, aliphatic polyhydric alcohols, aliphatic dicarboxylic acids, aromatic dicarboxylic acids, aromatic dialcohols, and diphenols Examples include resins, polyurethane resins, polyamide resins, polyvinyl butyral, terpene resins, coumarone indene resins, petroleum resins, crosslinked styrene resins, and crosslinked polyester resins.

  Specific examples of the polymerizable monomer used in the styrene-acrylic copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, and acrylic acid. Acrylic esters having an ethylenic double bond such as 2-ethylhexyl, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, such as maleic acid and maleic acid Maleic acid half esters such as butyl acid, and diesters, vinyl acetate, vinyl chloride, vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl esters such as vinyl butyl ether, vinyl methyl Ketone, vinyl ethyl ketone, vinyl hexyl ketone, and said vinyl ketones.

  Examples of the crosslinking agent include compounds having two or more unsaturated bonds. Specifically, for example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene, ethylene glycol diacrylate, and ethylene glycol dimethacrylate. The use of carboxylic acid ester having two unsaturated bonds, divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone, and other divinyl compounds, and compounds having three or more unsaturated bonds, alone or in combination. Can do. The above-mentioned cross-linking agent is suitably used in an amount of 0.01 to 10% by weight, preferably 0.05 to 5% by weight, based on the binder resin.

  In the case of using the pressure fixing method, it is possible to use a binder resin for pressure fixing toner. Specifically, for example, polyethylene, polypropylene, polymethylene, polyurethane elastomer, ethylene-ethyl acrylate copolymer, ethylene Mention may be made of vinyl acetate copolymers, ionomer resins, styrene-butadiene copolymers, styrene-isoprene copolymers, linear saturated polyesters, paraffins and other waxes.

  In the toner used in the present invention, a charge control agent can be blended with the toner. By adding the charge control agent, the optimum charge amount according to the development system can be obtained. Such positive charge control agents include nigrosine, fatty acid metal salt derivatives, quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, dibutyltin oxide, dioctyltin oxide. Diorganotin oxide, dibutyltin oxide, dioctyltin borate and dicyclohexyltin borate can be used alone or in combination of two or more. Among the charge control agents described above, charge control agents such as nigrosine-based and quaternary ammonium salts are particularly suitable.

  In the present invention, a negative charge control agent can also be used. Specifically, for example, organometallic complexes and chelate compounds are effective, and aluminum acetylacetonate, iron (II) acetylacetonate, 3,5- Mention may be made of chromium dibutyl butylsalicylate. In particular, metal complexes of acetylacetone (including monoalkyl-substituted and dialkyl-substituted) salicylic acid-based metal complexes (including monoalkyl-substituted and dialkyl-substituted) or salts thereof are preferable, and salicylic acid-based metal salts are particularly preferable. It is. When the above-mentioned charge control agent is added to the toner, it is preferable to use 0.1 to 20 parts by weight, more preferably 0.2 to 10 parts by weight with respect to the binder resin. In particular, when used for color image formation, it is preferable to use a colorless or light-colored charge control agent.

It is preferable to add metal fine particles such as silica, alumina and titanium oxide, and organic fine particles such as polytetrafluoroethylene, polyvinylidene fluoride, polymethyl methacrylate, polystyrene and silicone resin to the toner used in the present invention. is there. By adding the above-mentioned fine particles to the toner, fine powder exists between the toner and the carrier, or between the toners, so that the fluidity of the developer is improved and the life of the developer is also improved. The surface area of the powder above fines, specific surface area by nitrogen adsorption by the BET method 30 m ² / g or more, is obtained in particular 50 to 400 m ² / g good results in the range of. The addition amount of such fine particles is preferably 0.1 to 20% by weight based on the toner.

  As the colorant that can be added to the toner used in the present invention, conventionally known dyes and pigments can be used. Specifically, for example, carbon black, magnetite, phthalocyanine blue, peacock blue, permanent Red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow and the like can be used. In this case, the additive is 0.1 to 20% by weight, preferably 0.5 to 20 parts by weight with respect to the binder resin, and further 12% by weight considering the transparency of a suitable OHP film for the toner image. It is preferably used in the following range, and most preferably 0.5 to 9% by weight.

  To the toner used in the present invention, a wax component such as polyethylene, polypropylene, microcrystalline wax, carnauba wax, sazol wax, paraffin wax may be added for the purpose of improving releasability at the time of heat roll fixing. it can.

  The toner having such a composition is obtained by thoroughly mixing a vinyl-based or non-vinyl-based thermoplastic resin, a colorant, a charge control agent, and other additives with a mixer, and then heating rolls, kneaders, and extruders. The resin is sufficiently mixed by melting and kneading using the kneader mentioned above to mix the resins with each other, and the pigment or dye is dispersed therein. After cooling, the toner particles can be obtained by pulverization and classification.

  Furthermore, the toner used in the present invention can be used in whole or in part by a polymerization method. In such a toner, the residual monomer content needs to be 1000 ppm or less. It is also possible to use a toner having a core / shell structure and a shell portion formed by polymerization.

  Needless to say, the action of the core / shell structure can provide blocking resistance without deteriorating the excellent fixing property of the toner. When a wax component that easily causes carrier contamination is used as a core, a shell layer of a resin component is formed on the surface. By providing, it becomes possible to remarkably reduce carrier contamination. Further, in comparison with a bulk polymerized toner having no core, it is easier to remove the residual monomer in the post-treatment step after the polymerization step by polymerizing only the shell portion. When the wax component is used as a core, carrier contamination can be remarkably reduced by providing a shell layer of the resin component on the surface.

  Moreover, as a main component of a core part, a low softening point substance is preferable, and the compound whose main body maximum peak value measured based on ASTM D3418-8 shows 40-90 degreeC is preferable. When the maximum peak is less than 40 ° C., the self-aggregation force of the low softening point material becomes weak, and as a result, the high temperature offset property becomes weak, which is not preferable. On the other hand, if the maximum peak exceeds 90 ° C., the fixing temperature increases, which is not preferable. Furthermore, when toner is obtained by a direct polymerization method, granulation and polymerization are carried out in an aqueous system, so if the temperature of the maximum peak value is high, a low softening point substance mainly precipitates during granulation and inhibits the suspension system. It is not preferable. For the measurement of the temperature of the maximum peak value, for example, DSC-7 manufactured by Perkin Elmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. As the sample, an aluminum pan was used, an empty pan was set as a control, and the heating rate was 10 ° C./min. Measurements were made at

  Specifically, paraffin wax, polyolefin wax, Fischer tropical wax, amide wax, higher fatty acid, ester wax and derivatives thereof, or graft / block compounds thereof can be used.

  The low softening point material is preferably added to the toner in an amount of 5 to 30% by weight. If the addition is less than 5% by weight, the removal of the residual monomer described above is burdened. If it exceeds 30% by weight, the toner particles are likely to coalesce during granulation even in the production by the polymerization method. Those having a wide distribution are likely to be generated and are not suitable for the present invention.

  As described above, the toner particles produced by the pulverization method or the polymerization method can be used as they are, but the above-mentioned metal oxide fine particles and organic fine particles can be used by adding an appropriate amount of those necessary. It can also be used.

  Such external addition treatment of fine particles can be performed using a mixer such as a Henschel mixer. The toner thus obtained is mixed with the carrier particles of the present invention to form a two-component developer. When forming the above-described two-component developer, the ratio of the toner in the developer is typically in the range of 1 to 20% by weight, more preferably 1 to 10% by weight, depending on the development process. Is preferred. Further, the absolute value of the triboelectric charge amount of the toner of such a two-component developer is preferably in the range of 5 to 100 μC / g, and most preferably 5 to 60 μC / g.

  Various measurement methods used in the present invention are described below.

  Specific examples of toner particle size measurement used in the present invention will be shown. 0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added to 100 to 150 ml of pure water, and 2 to 20 mg of a measurement sample is added thereto. The electrolytic solution in which the sample is suspended is dispersed for 1 to 3 minutes with an ultrasonic disperser, and the particle size distribution and the like are measured using a laser scan particle size distribution analyzer CIS-100 (manufactured by GALAI). In the present invention, particles of 0.5 μm to 60 μm are measured, and the number average particle size and weight average particle size measured under these conditions are determined by computer processing.

  A method for measuring the triboelectric charge amount of the toner will be described. The toner and the carrier are mixed so that the toner weight becomes 5% by weight, and mixed for 2 minutes with a Yayoi-type shaker. This mixed powder (developer) is put in a metal container with a 635 mesh conductive screen on the bottom, and the toner is sucked with a suction machine and displayed on the electrometer connected to the container and the weight difference before and after suction. The triboelectric charge amount of the toner is obtained from the value of the charged amount Q ′. At this time, the suction pressure is 250 mmHg. By this method, the triboelectric charge amount Q of the toner is calculated using the following formula.

Q (μC / g) = Q ′ × (W ₁ −W ₂ ) −1
(W ₁ is the weight before suction, W ₂ is the weight after suction, and Q ′ is the value of the charge amount displayed on the electrometer connected to the metal container.)
The present invention will be described below with reference to examples, but the present invention is not limited to the examples.

[Preparation of resin composition (I) for carrier coating layer]
To the flask, 30.0 g of an aqueous dispersion of colloidal silica (40% solid) was taken, and 1/3 of a mixture of 21.5 g of methyltrimethoxysilane and 3.5 g of acetic acid was added with stirring. After the addition, the mixed solution was heated to 55 ° C., and when a rapid exotherm was observed, the mixture was iced immediately, and the remaining mixture was added while maintaining the temperature in the flask at 50-60 ° C. Cool the reaction solution to 20 ° C. and stir for 30 minutes when the temperature stabilizes. Thereafter, the reaction solution was diluted with 17.8 g of isopropyl alcohol, 2.8 g of dibutyltin di-2-ethylhexoate was gradually added, and 0.16 g of a 10% ethanol solution of polyether-modified dimethyl silicone was further added. . From the obtained reaction mixture, the precipitate was removed to prepare a resin composition (I) for the carrier coating layer.

  The resin composition (I) was applied to a glass plate using a bar coat and subjected to a drying heat treatment at 150 degrees for 2 hours. After drying, a transparent and uniform film of 5 μm was obtained. When the water contact angle of this film was measured, the surface energy was reduced to 90 deg. Moreover, when the pencil hardness was measured, it was as hard as 9H.

[Preparation of resin composition (II) for coating magnetic carrier]
Into a flask, 8.7 g of an aqueous dispersion of colloidal silica (40% solids) is stirred, and 20.5 g of an isopropyl alcohol dispersion of colloidal silica (30% solids), 25.6 g of methyltriethoxysilane, 3, 3, 5.9 g of 4,4,5,5,6,6,6-nonafluorohexyltrimethoxysilane and 3.2 g of acetic acid were added. After the addition, the mixed solution was heated to 65 to 70 ° C. and reacted for 2 hours. Thereafter, the mixture is diluted with 21.7 g of isopropyl alcohol, 2.4 g of benzyltrimethylammonium acetate is added as a curing catalyst, and 0.16 g of a 10% ethanol solution of polyether-modified dimethylsilicone is further added to form a resin composition for coating a magnetic carrier. (II) was prepared.

  The resin composition (II) for coating the magnetic carrier was applied to a glass plate using a bar coat and subjected to a drying heat treatment at 150 ° C. for 2 hours. After drying, a transparent and uniform film of 5 μm was obtained. When the water contact angle of this film was measured, the surface energy was reduced to 99 deg. The pencil hardness was as hard as 9H.

[Preparation of resin composition (III) for coating magnetic carrier]
3.9 g of an aqueous dispersion of colloidal silica (40% solids) is taken in a flask and 26.8 g of an isopropyl alcohol dispersion of colloidal silica (30% solids), 1.5 g of methyltriethoxysilane, and γ-glycid are stirred. 1.9 g of xylpropyltrimethoxysilane, 2.4 g of 3,3,4,4,5,5,6,6,6-nonafluorohexyltrimethoxysilane and 3.1 g of acetic acid were added. After the addition, the mixed solution was heated to 65 to 70 ° C. and reacted for 2 hours. Thereafter, it is diluted with 23.3 g of isopropyl alcohol, 2.4 g of benzyltrimethylammonium acetate is added as a curing catalyst, and 0.16 g of a 10% ethanol solution of polyether-modified dimethylsilicone is further added to form a resin composition for coating a magnetic carrier. Product (III) was prepared.

  The resin composition (III) for coating the magnetic carrier was applied to a glass plate using a bar coat and subjected to a drying heat treatment at 150 ° C. for 2 hours. After drying, a transparent and uniform film of 5 μm was obtained. When the contact angle of water of the obtained film was measured, the surface energy was reduced to 100 deg. The pencil hardness was extremely hard at 7H.

[Toner Production Example 1]
To 710 g of ion-exchanged water, 450 g of a 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

on the other hand,
(Monomer) Styrene 165g
n-Butyl acrylate 35g
(Colorant) C.I. I. Pigment Blue 15: 3 15g
(Charge control agent) Salicylic acid metal compound 3g
(Polar resin) Saturated polyester 10g
(Acid value 14, peak molecular weight; 8000)
(Release agent) Ester wax (melting point 70 ° C.) 50 g
The above formulation was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition is charged into the aqueous medium and stirred at 10000 rpm for 10 minutes in a TK homomixer at 60 ° C. in an N ₂ atmosphere to granulate the polymerizable monomer composition. did. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve calcium phosphate, followed by filtration, washing with water, and drying to obtain cyan colored suspended particles.

  The obtained colored particles have a weight average diameter (D4) of about 6.4 μm, a number average particle diameter (D1) of 5.1 μm, and a distribution cumulative value less than ½ times the number average particle diameter is 5.1. The cumulative value of the distribution of the number average particle diameter of 2 times the weight average particle diameter was 0% by volume.

To 100 parts by weight of the obtained colored particles, 1.5 parts by weight of hydrophobic silica having a specific surface area by the BET method of 200 m ² / g was externally added to obtain polymerized toner A. The amount of residual monomer in the obtained toner was 470 ppm, and the particle size distribution after external addition of silica was substantially equivalent to that before external addition.

[Toner Production Example 2]
To 710 g of ion-exchanged water, 450 g of a 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

on the other hand,
(Monomer) Styrene 165g
n-Butyl acrylate 35g
(Colorant) C.I. I. Pigment Blue 15: 3 15g
(Charge control agent) Salicylic acid metal compound 3g
(Polar resin) Saturated polyester 10g
(Acid value 14, peak molecular weight; 8000)
(Release agent) Ester wax (melting point 70 ° C.) 50 g
The above formulation was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition is charged into the aqueous medium and stirred at 10000 rpm for 10 minutes in a TK homomixer at 57 ° C. in an N ₂ atmosphere to granulate the polymerizable monomer composition. did. Then, while stirring with a paddle stirring blade, the temperature was raised to 75 ° C. and reacted for 6 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve calcium phosphate, followed by filtration, washing with water, and drying to obtain cyan colored suspended particles.

  The obtained colored particles have a weight average diameter (D4) of about 6.4 μm, a number average particle diameter (D1) of 5.0 μm, and a distribution cumulative value less than ½ times the number average particle diameter is 5.3. The cumulative value of the distribution of the number average particle diameter of 2 times the weight average particle diameter was 0% by volume.

To 100 parts by weight of the obtained colored particles, 1.5 parts by weight of hydrophobic silica having a specific surface area by the BET method of 200 m ² / g was externally added to obtain polymerized toner B. The obtained toner had a residual monomer amount of 1280 ppm, and the particle size distribution after silica external addition was substantially the same as that before external addition.

[Toner Production Example 3]
To 710 g of ion-exchanged water, 450 g of a 0.1M Na ₃ PO ₄ aqueous solution was added, heated to 60 ° C., and then stirred at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). To this, 68 g of 1.0 M CaCl ₂ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .

on the other hand,
(Monomer) Styrene 165g
n-Butyl acrylate 35g
(Colorant) C.I. I. Pigment Blue 15: 3 15g
(Charge control agent) Salicylic acid metal compound 3g
(Polar resin) Saturated polyester 10g
(Acid value 14, peak molecular weight; 8000)
The above formulation was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). Into this, 10 g of a polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

The polymerizable monomer composition is charged into the aqueous medium and stirred at 10000 rpm for 10 minutes in a TK homomixer at 60 ° C. in an N ₂ atmosphere to granulate the polymerizable monomer composition. did. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, the residual monomer was distilled off under reduced pressure under the same conditions as in toner production example 1, and after cooling, hydrochloric acid was added to dissolve calcium phosphate, followed by filtration, washing with water, and drying to obtain a cyan colored suspension. Particles were obtained. The obtained colored particles have a weight average diameter (D4) of about 6.3 μm, a number average particle diameter (D1) of 4.9 μm, and a distribution cumulative value less than ½ times the number average particle diameter is 7.1. The cumulative value of the distribution of the number average particle diameter of 2 times the weight average particle diameter was 0% by volume.

To 100 parts by weight of the obtained colored particles, 2.0 parts by weight of hydrophobized titanium oxide having a specific surface area by the BET method of 200 m ² / g was externally added to obtain polymerized toner C. The residual toner content of the obtained toner was 650 ppm, and the particle size distribution after the external addition of titanium oxide was substantially the same as that before the external addition.

[Toner Production Example 4]
Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts by weight Copper phthalocyanine pigment 5 parts by weight Chromium complex salt of di-tert-butylsalicylic acid 4 parts by weight are sufficiently premixed, and then melt-kneaded and cooled. It was coarsely pulverized to a particle size of about 1 to 2 mm using a post hammer mill. Subsequently, it was finely pulverized by an air jet type fine pulverizer. Furthermore, the obtained finely pulverized product was classified using an elbow jet classifier, and the cumulative distribution value was a weight average particle size of 6.5 μm, a number average particle size of 5.3 μm and a number average particle size equal to or less than ½ times the number average particle size. Was 8.9% by number, and a negatively chargeable cyan fine powder having a cumulative distribution value of at least twice the weight average particle diameter was 0.1% by volume. A pulverized toner D was prepared by mixing 100 parts by weight of the above cyan fine powder, 0.5 parts by weight of silica fine powder hydrophobized with hexamethyldisilazane, and 0.2 parts by weight of alumina fine powder with a Henschel mixer. . The obtained toner had a residual monomer amount of 250 ppm, and the particle size distribution after the external addition was substantially the same as that before the external addition.

[Toner Production Example 5]
Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts by weight Copper phthalocyanine pigment 5 parts by weight Chromium complex salt of di-tert-butylsalicylic acid 4 parts by weight are sufficiently premixed, and then melt-kneaded and cooled. It was coarsely pulverized to a particle size of about 1 to 2 mm using a post hammer mill. Subsequently, it was finely pulverized by an air jet type fine pulverizer. Furthermore, the obtained finely pulverized product was classified using an elbow jet classifier, and the cumulative distribution value was a weight average particle size of 6.5 μm, a number average particle size of 5.3 μm and a number average particle size equal to or less than ½ times the number average particle size. Was 24.9% by number, and a negatively chargeable cyan fine powder having a distribution cumulative value of 0.2% by volume or more of the double diameter of the weight average particle diameter was obtained. A pulverized toner E was prepared by mixing 100 parts by weight of the above cyan fine powder, 0.5 parts by weight of silica fine powder hydrophobized with hexamethyldisilazane, and 0.2 parts by weight of alumina fine powder with a Henschel mixer. . The amount of residual monomer in the obtained toner was 260 ppm, and the particle size distribution after the external addition was substantially the same as that before the external addition.

<Preparation of ferrite carrier core particles>
They were weighed so that the molar ratio was Fe ₂ O ₃ = 50 mol%, CuO = 27 mol%, and ZnO = 23 mol%, and mixed using a ball mill. After calcining this, it was pulverized by a ball mill and further granulated by a spray dryer. This was sintered to obtain carrier core particles having an average particle diameter of 45 μm.

  The surface of the carrier core particles was coated with the resin composition (I) for coating the magnetic carrier by the following method. The resin composition (I) for coating the magnetic carrier is diluted with isopropanol as a solvent so that the amount of the coating resin is 0.5% by weight of the carrier core particles, and a carrier coating resin solution having a resin solid content of 10% by weight is diluted. Prepared.

  The carrier core resin was coated on the carrier core particles by pouring the carrier coating resin solution while applying shear stress by stirring to the carrier core particles and heating to volatilize the solvent. The obtained carrier particles were heat-treated at 150 ° C. for 2 hours, then crushed and further classified with a 200 mesh sieve to obtain a magnetic carrier (a). The obtained magnetic carrier (a) had an average particle diameter of 46 μm. When the surface of the carrier was observed with a scanning electron microscope (FE-SEM), it was found that it was uniformly coated with a resin.

  A developer was prepared by mixing the magnetic carrier (a) produced as described above and the polymerized toner A described in Toner Production Example 1 so that the toner concentration was 5%. This developer was subjected to an image copy durability test on 10,000 sheets using a Canon full color laser copier CLC-500 remodeling machine. As a result, an excellent image having a fine solid line reproducibility and a high solid image density was obtained from the initial stage to 10,000 sheets. Further, no toner scattering or fogging was observed on the image. When the developer was taken out from the developing unit after the 10,000-sheet copying durability test and the state of the magnetic carrier was observed using a scanning electron microscope (FE-SEM), toner filming and peeling of the carrier coating resin were found at all. There wasn't.

(Comparative Example 1)
A magnetic carrier was prepared in the same manner as in Example 1 except that a thermosetting modified silicone resin (TSR187, manufactured by Toshiba Silicone Co., Ltd.) was used and the coating temperature was changed to 180 ° C. for 1 hour. The obtained magnetic carrier (b) had an average particle diameter of 46 μm. When the surface of the carrier was observed with a scanning electron microscope (FE-SEM), it was found that it was uniformly coated with a resin.

  A developer was prepared by mixing the magnetic carrier (b) and the polymerized toner B described in Toner Production Example 1 so that the toner concentration was 5%. Using this developer, an image copy durability test was conducted on 10,000 sheets in the same manner as in Example 1. As a result, it was recognized that the toner charge amount gradually decreased from the initial stage to 10,000 sheets of toner, and the density of the image increased. In addition, fog was observed on the image, and the toner was scattered around the developing device inside the machine. Further, after the 10,000 sheet copying durability test, the developer was taken out from the developing device, and when the surface state of the magnetic carrier was observed using a scanning electron microscope (FE-SEM), toner filming was observed. The evaluation results are shown in Table 1.

  A magnetic carrier (c) was produced in the same manner as in Example 1 except that the resin composition (II) for coating the magnetic carrier was used. The obtained magnetic carrier (c) had an average particle diameter of 46 μm. When the surface of the carrier was observed with a scanning electron microscope (FE-SEM), it was found that it was uniformly coated with a resin.

  A developer was prepared by mixing the magnetic carrier (c) produced as described above and the above polymerized toner C so that the toner concentration was 5%. This developer was subjected to an image copy durability test on 10,000 sheets using a Canon full color laser copier CLC-500 remodeling machine. As a result, an excellent image having a fine solid line reproducibility and a high solid image density was obtained from the initial stage to 10,000 sheets. Further, no toner scattering or fogging was observed on the image. When the developer was taken out from the developing unit after the 10,000-sheet copying durability test and the state of the magnetic carrier was observed using a scanning electron microscope (FE-SEM), toner filming and peeling of the carrier coating resin were found at all. There wasn't. The evaluation results are shown in Table 1.

  A magnetic carrier (c) was produced in the same manner as in Example 1 except that the resin composition (II) for coating the magnetic carrier was used. The obtained magnetic carrier (c) had an average particle diameter of 46 μm. When the surface of the carrier was observed with a scanning electron microscope (FE-SEM), it was found that it was uniformly coated with a resin. Using this magnetic carrier (c) and the pulverized toner (D), an image copy durability test was conducted in the same manner as in Example 1. As a result, the same good results as in Example 1 were obtained. The evaluation results are shown in Table 1.

(Comparative Example 2)
An image copy durability test was conducted in the same manner as in Example 3 except that the pulverized toner (E) was used as the toner. As a result, the fog was conspicuous at the beginning of the durability, the image density was as low as 1.34, the fog was further deteriorated after the endurance of 10,000 sheets, and the image density was also as high as 1.59. When the carrier surface was observed with a scanning electron microscope (FE-SEM) after the endurance of 10,000 sheets, toner filming and peeling of the coating layer were not observed. The evaluation results are shown in Table 1.

  A magnetic carrier (d) was produced in the same manner as in Example 1 except that the resin composition (III) for coating the magnetic carrier was used. The obtained magnetic carrier (d) had an average particle diameter of 47 μm. When the surface of the carrier was observed with a scanning electron microscope (FE-SEM), it was found that it was uniformly coated with a resin. Using this magnetic carrier (d) and the polymerized toner (A), an image copy durability test was conducted in the same manner as in Example 1. As a result, the same good results as in Example 1 were obtained. The evaluation results are shown in Table 1.

  The surface of the carrier core particles used in Example 1 was coated with a resin composition for coating a magnetic carrier by the following method. After the resin composition (I) for coating the magnetic carrier was diluted with isopropanol as a solvent so that the amount of the coating resin was 0.5% by weight of the carrier core particles, and the resin solid content concentration was 10% by weight, Further, 3-aminopropyltrimethoxylane was added at 5% by weight of the resin solid content to prepare a carrier-coated resin solution.

  Next, the carrier core resin was coated on the carrier core particles by pouring the above-mentioned carrier coating resin solution while applying shear stress by stirring to the carrier core particles and heating to volatilize the solvent. The obtained carrier particles were heat-treated at 150 ° C. for 2 hours, then crushed and further classified with a 200-mesh sieve to obtain a magnetic carrier (e). The obtained magnetic carrier (e) had an average particle diameter of 46 μm. When the surface of the carrier was observed with a scanning electron microscope (FE-SEM), it was found that it was uniformly coated with a resin.

  A developer was prepared by mixing the magnetic carrier (e) produced as described above and the polymerized toner A described in Toner Production Example 1 so that the toner concentration was 5%. This developer was subjected to an image copy durability test on 10,000 sheets using a Canon full color laser copier CLC-500 remodeling machine. As a result, an excellent image having a fine solid line reproducibility and a high solid image density was obtained from the initial stage to 10,000 sheets. Further, no toner scattering or fogging was observed on the image. When the developer was taken out from the developing unit after the 10,000-sheet copying durability test and the state of the magnetic carrier was observed using a scanning electron microscope (FE-SEM), toner filming and peeling of the carrier coating resin were found at all. There wasn't.

Claims (4)

  A magnetic carrier having a magnetic carrier core particle and a coating layer on the surface of the magnetic carrier core particle, wherein the coating layer contains colloidal silica and a siloxane resin. The coating layer contains a siloxane resin, and the siloxane resin is obtained by condensing a siloxane monomer in the presence of colloidal silica, and the structure of the siloxane resin is represented by the following general formula (I)
RSiO _3/2 (I)
(R is an alkyl group having 1 to 4 carbon atoms, vinyl group, phenyl group, CnF _{2n + 1} C ₂ H ₄ — group (n = 1-18), γ-glycidoxypropyl group, γ-methacryloxypropyl group. , Single or multiple selections from.
The magnetic carrier according to claim 1, represented by:   A magnetic carrier comprising the coating layer containing at least one selected from the group of silane coupling agents or titanate coupling agents. In a two-component developer composed of a toner and a magnetic carrier, the toner has a weight average particle diameter of 1 to 10 μm, and a cumulative distribution value of ½ times the number average particle diameter (D1) or less is 20 number% or less. And a cumulative distribution value of at least twice the weight average particle diameter (D4) is 10% by volume or less, and the magnetic carrier is the magnetic carrier according to any one of claims 1 to 3. Developer.