JP2007102052A - Carrier for electrophotography and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for a two-component developer which allows output of images of stable image density over a prolonged period of time even in printing with low consumption; and also to provide an image forming method using the same. <P>SOLUTION: Magnetic carrier particles are obtained by coating the surfaces of magnetic carrier core particles comprising at least a binder resin, magnetic particles and a high dielectric compound with a coating material, wherein (1) the magnetic carrier particles have a volume resistivity at 5×10<SP>5</SP>V/m of 1×10<SP>9</SP>-1×10<SP>16</SP>Ωcm and (2) the high dielectric compound has a relative dielectric constant ε of ≥80. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic developer carrier used for electrophotography, electrostatic recording, and electrostatic printing, and an image forming method using the same.

  Conventionally, in an image forming apparatus using an electrophotographic method such as a printer or a copying machine, a two-component developer containing a toner and a magnetic carrier is suitably used from the viewpoint of image quality, durability, and high-speed compatibility. As a method of developing such a two-component developer, in order to secure a sufficient image density and improve fine line reproducibility, a magnetic brush of the developer is brought into contact with the photoconductor, and the peripheral speed of the photoconductor is determined. A developing method is used in which the peripheral speed of the developing sleeve is increased and the alternating electric field and the DC electric field are superimposed.

  By the way, in recent years, with the progress of full color, systemization, and digitalization, the demand for higher image quality, higher speed, and higher stability of output images has increased, and it is expected that copiers and various printers will enter the light printing market. Is done. In order to enter the printing market with the electrophotographic method generally used in copying machines and various printers, high image quality and high stability are the minimum issues.

  As the magnetic carrier used in such a two-component development method, a coated carrier in which an insulating resin is coated on the surface of ferrite, magnetite or the like is used. This is a carrier characteristic that requires a certain level of pressure resistance against an applied electric field. However, as the coating amount of the insulating resin is increased, the coat carrier is insulated and does not function as a developing electrode at the time of development, so that an edge effect appears between the halftone and the solid black, so-called white defects such as white spots are caused. May occur.

  These image defects are generally known to correlate with the resistance of the coat carrier. That is, when the resistance of the coat carrier is low, the latent image formed on the photosensitive member as the latent image holding member is easily filled with the charge of the toner, and image defects such as white spots are less likely to occur. As a result, the charge on the surface of the photoconductor is easily disturbed, resulting in poor dot reproducibility.

  On the other hand, when the resistance of the coat carrier is large, high-definition images can be reproduced for delicate images such as dots and fine lines, while white spots, uniformity of density, lack of density in solid images, etc. Image defects are likely to occur.

  Conventionally, selenium photoconductors, amorphous silicon photoconductors, organic photoconductors, etc. have been put to practical use as photoconductors used in the electrophotographic process. Among them, amorphous silicon photoconductors containing amorphous silicon are particularly good in image quality. In addition, it is known to have characteristics with excellent durability and is suitably used when high image quality, high speed, and high stability are required.

  However, when an amorphous silicon photoconductor is used to perform development by superimposing an AC electric field on a two-component developer containing a magnetic carrier, charge injection from the magnetic carrier for development to the photosensitive drum occurs in the developing unit. The white portion (the portion where the photosensitive drum is uniformly charged and then not exposed) and the black portion (the portion where the photosensitive drum is uniformly charged and then exposed) have a potential DC applied to the developing sleeve. It tends to converge on the component. For this reason, the potential difference between the white background portion and the developing sleeve is reduced, fogging occurs, and the potential difference between the black portion and the developing sleeve is also reduced, so that the image density is lowered. In order to solve these problems, a coat carrier having a relatively high resistance is used. However, since the amorphous silicon photoconductor has a large dielectric constant, the charge amount on the surface of the photoconductor is large. When using a high-resistance magnetic carrier and a high-charge-capacity photoconductor, both the driving force acting on the toner in the development area is small and the amount of toner necessary to fill the latent image is large. It is likely that the latent image charge generated on the photoreceptor is insufficient. Therefore, image defects such as white spots and image density unevenness are likely to occur.

  As a method for improving developability, a proposal has been made from the viewpoint of an image forming method. For example, in the case of realizing high speed, a developing device in which a plurality of developer carriers are arranged for the purpose of improving chargeability and transportability of toner is used in the development process (see, for example, Patent Document 1).

  On the other hand, as a developer, the particle size and magnetic force of the carrier are specified to aim for higher durability (see, for example, Patent Documents 2 and 3).

  Furthermore, it has been proposed to coat the surface of a magnetic material-dispersed carrier with a resin having an aminosilane coupling agent, a fluoroalkyl unit, a methylene unit, etc. to prevent toner spent and to further improve the releasability of the toner (for example, , See Patent Document 4).

  A method of increasing the dielectric constant of a coated carrier by putting a high dielectric substance in a coating agent of a ferrite carrier has been proposed (for example, see Document 5).

Japanese Patent Laid-Open No. 07-181800 JP-A-60-179766 JP 2002-13043 A JP 2000-39740 A Japanese Unexamined Patent Publication No. 60-19157

  However, as the demand for higher image quality, higher speed, and higher stability of output images is increasing, when a high-definition photoconductor is used, a photoconductor having a high charge capacity is required. In addition, as the resolution of images increases, it is necessary to further improve developability as a developer in order to reproduce characters with good texture and to satisfy the conditions of downsizing and speeding up the apparatus. come.

  Therefore, an object of the present invention is to provide a carrier for a two-component developer that has solved the above-described problems and an image forming method using the carrier.

  That is, an object of the present invention is to provide a carrier for a two-component developer having a high image density and excellent dot reproducibility and an image forming method using the same.

  A further object of the present invention is to provide a carrier for a two-component developer capable of outputting a stable image density image over a long period of time even in low consumption printing, and an image forming method using the same.

  The object of the present invention is to visualize an amorphous silicon photoconductor using a two-component developer and to use it in a full-color image forming method. In this case, the high durability and image clarity of the amorphous silicon photoconductor are utilized. It is an object to provide a carrier for component developer and an image forming method using the same.

The present invention provides a magnetic carrier particle obtained by coating the surface of a magnetic carrier core particle having at least a binder resin, magnetic particles, and a high dielectric compound with a coating material,
1) The magnetic carrier particles have a volume resistance of 1 × 10 ⁹ to 1 × 10 ¹⁶ Ωcm at 5 × 10 ⁵ V / m,
2) The carrier for electrophotography, wherein the high dielectric compound has a relative dielectric constant ε of 80 or more.

Further, the present invention provides an image forming method using magnetic carrier particles obtained by coating the surface of a magnetic carrier core particle having at least a binder resin, magnetic particles, and a high dielectric compound with a coating material.
1) The magnetic carrier particles have a volume resistance of 1 × 10 ⁹ to 1 × 10 ¹⁶ Ωcm at 5 × 10 ⁵ V / m,
2) The high dielectric compound has a relative dielectric constant ε of 80 or more,
3) An image forming method using an electrophotographic photosensitive member having a charge capacity of 1.0 to 8.0 μF / m ² .

  As a result of intensive studies, the present inventors have found that developability is remarkably improved by incorporating a high dielectric compound into magnetic carrier core particles composed of a binder resin and magnetic particles.

  This is considered to be due to the following effects.

The magnetic carrier particle of the present invention is a magnetic material-dispersed resin carrier in which a magnetic material is dispersed in a resin as described above. Magnetic particles (eg, magnetite) have a volume resistance of 10 ³ to 10 ⁸ Ωcm, which is a relatively low resistance. The inventors of the present invention have conventionally adjusted the resistance and the amount of magnetization by forming a carrier core with an arbitrary blending amount together with high-resistance nonmagnetic particles (for example, hematite). When the amount of magnetic particles added in the carrier is large, the resistance after coating is also low, and as a result, although the developability is excellent, the latent image is easily disturbed when outputting a high-quality image. In addition, when an amorphous silicon photoconductor is used, the phenomenon of unclear image due to charge injection and so-called carrier adhesion in which magnetic carrier particles adhere to a white background portion are likely to occur.

  Therefore, in order to increase the resistance of the magnetic carrier core, the amount of non-magnetic particles (haematite etc.) having high resistance is increased to increase the resistance of the carrier core. However, as the resistance increased, the developability decreased.

  Therefore, in the present invention, the above-mentioned problem is solved by using a high-dielectric compound having a relative dielectric constant ε of 80 or more as the high-resistance material.

  This is considered to be due to the following. In the developing step of the image forming method, positively or negatively charged toner particles are moved to the photosensitive member by electrostatic force in the gap between the developing unit and the photosensitive member, and are visualized to appear as a toner image. An electrostatic force called a developing bias becomes a driving force for toner particles by an electric field superimposed on a DC electric field and an AC electric field. In the present invention, in the case where AC is superimposed on the developing bias, the developability is improved even when the resistance of the magnetic carrier is high. That is, the high dielectric material inside the carrier core works with a low resistance against an AC electric field, but has a high resistance with a DC electric field, so that the latent image is hardly disturbed, and even when an amorphous silicon photoconductor is used. In addition, charge injection hardly occurs and adhesion of magnetic carrier particles can be prevented. Thus, the reason why a large amount of high dielectric material can be introduced into the carrier core is that the magnetic carrier core used in the present invention is a magnetic material-dispersed resin carrier.

  By using the carrier of the present invention, the resolution of the image is increased and the texture is improved even when a high-definition photoconductor is used, which is used for high image quality, high speed and high stability. It is possible to reproduce good characters. Furthermore, it is possible to simplify the construction of the developing device of the electrophotographic apparatus, which has been necessary so far to obtain a high development name, and it is possible to reduce the size of the apparatus. Further, even under severe conditions for development such as high speed, it has become possible to further improve developability.

  According to the present invention, the amorphous silicon photoreceptor is visualized by using a two-component developer, and even in this case, which is used for a full-color image forming method, the high durability of the amorphous silicon photoreceptor and the sharpness of the image are utilized. A high-speed and long-term stable image forming method can be provided.

In the present invention, the volume resistance of the coated carrier at 5 × 10 ⁵ V / m is 1 × 10 ⁹ to 1 × 10 ¹⁶ Ωcm, and both excellent reproducibility of fine lines and developability can be achieved. More preferably, it is 1 × 10 ¹¹ to 1 × 10 ¹⁵ Ωcm. When the volume resistance is lower than 1 × 10 ⁹ Ωcm, the latent image is said to be distorted easily under the condition that the resolution of the image is increased. In addition, when an amorphous silicon photoconductor is used, an electric field generated from the developing bias makes it easier for current to flow through the carrier, and charge injection causes a reduction in contrast potential. Further, when the volume resistance is larger than 1 × 10 ¹⁶ Ωcm, the development tends to be insufficient even when the high dielectric substance of the present invention is introduced into the magnetic carrier core particles.

  The high dielectric material of the present invention means a material having a high volume resistance and a large dielectric constant of the material in an electrostatic field. When a magnetic carrier containing such a high dielectric substance was used, high developability could be obtained while increasing the resistance of the magnetic carrier.

  As the high dielectric material used in the present invention, a material having a relative dielectric constant ε of 80 or more, preferably 500 or more, more preferably 1000 or more is preferably used.

Furthermore, the high dielectric material used in the present invention preferably has a volume resistance of 10 ¹⁰ Ωcm or more. In this case, it is possible to increase the resistance of the magnetic carrier core particles and the magnetic carrier, and to provide a magnetic carrier with improved charge injection when using a rough and amorphous silicon photoconductor. More preferably, the volume resistance is 10 ¹¹ to 10 ¹⁵ Ωcm.

The high dielectric material, titanium _{oxide: TiO 2, BST: (Ba} , Sr) TiO 3, STO: SrTiO 3, BTO: BaTiO 3, SrTa 2 O 6, Sr 2 Ta 2 O 7, ZnO, HfO 2, Ta ₂ O ₅ etc. Among these, metal compounds CaTiO ₃ having a perovskite structure exhibiting a relatively high dielectric property, BST: (Ba, Sr) TiO ₃ , STO: SrTiO ₃ , BTO: BaTiO _{3 and the} like are preferable.

  These high dielectric substances are preferably contained in a mass ratio of 5 to 100% by mass with respect to the magnetic particles, and more preferably in a range of 10 to 70% by mass. When the amount of the high dielectric material is less than 5% by mass, the resistance of the magnetic carrier core particles becomes low, the resistance of the magnetic carrier after coating becomes difficult to control, and image defects such as charge injection and roughness are likely to occur. Even when the resistance is controlled, it is difficult to obtain sufficient developability in the development process in which AC charge superposition is performed. When the amount of the high dielectric substance is more than 100% by mass, the resistance of the magnetic carrier is increased, and the developability tends to be lowered. In addition, the amount of magnetization of the magnetic carrier becomes small, and image defects such as carrier adhesion tend to occur.

  In the production method, the magnetic carrier particle size distribution is uniform, and the influence of fine powder or the like is reduced. Therefore, it is preferable to produce magnetic carrier core particles by a polymerization method.

  Next, the magnetic carrier core particles used in the present invention will be described.

  The magnetic carrier core particles used for the magnetic carrier of the present invention are, for example, iron powder whose surface is oxidized or unoxidized iron powder, iron, lithium, calcium, magnesium, nickel, copper, zinc, cobalt, manganese, chromium In addition, a so-called resin carrier is a magnetic material-dispersed resin carrier containing metal particles such as rare earths, their alloy particles, oxide particles, magnetite, and a binder resin that holds a magnetic material such as ferrite in a dispersed state. The magnetic particles used in the present invention are preferably magnetite fine particles, or magnetic ferrite fine particles containing at least an iron element and a magnesium element.

  In the present invention, a high-resistance high-dielectric substance is used for the non-magnetic particles, but other non-magnetic materials may be used in combination as appropriate.

Inorganic fine particles can be used as the non-magnetic particles, but hematite (α-Fe ₂ O ₃ ) fine particles are more preferable for adjusting the magnetic properties and true specific gravity of the carrier.

  The magnetic particles contain 50 to 100% by mass of the magnetic material with respect to the total amount of the magnetic particles and the non-magnetic particles, thereby adjusting the strength of magnetization of the resin carrier to prevent carrier adhesion, It is preferable when adjusting the volume resistance value of the resin carrier.

  Examples of the binder resin include a vinyl resin having a methylene unit in a polymer chain, a polyester resin, an epoxy resin, a phenol resin, a urea resin, a polyurethane resin, a polyimide resin, a cellulose resin, and a polyether resin. These resins may be used as a mixture.

  Examples of vinyl monomers for forming the vinyl resin include styrene; o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p- n-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy Styrene derivatives such as styrene, p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene, p-nitrostyrene; ethylene and unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene; Unsaturated diolefins such as butadiene and isoprene; vinyl chloride, Vinyl halides such as vinylidene chloride, vinyl bromide, vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate; methacrylic acid; methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid α-methylene aliphatic monocarboxylic acid esters such as n-butyl, isobutyl methacrylate, methacrylate-n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate; acrylic acid; acrylic acid Methyl, ethyl acrylate, acrylic acid-n-butyl, acrylic acid isobutyl, propyl acrylate, acrylic acid-n-octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, acrylic acid-2- Acrylic acid esters such as chloroethyl and phenyl acrylate; maleic acid and maleic acid half esters; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone; vinylnaphthalene; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; acrolein, etc. . A polymer obtained by polymerizing one or more of these is used as the vinyl resin.

  As phenols for producing a phenol resin, in addition to phenol itself, alkylphenols such as m-cresol, p-tert-butylphenol, o-propylphenol, resorcinol, bisphenol A and a part of benzene nucleus or alkyl group or Examples thereof include compounds having a phenolic hydroxyl group such as halogenated phenols, all of which are substituted with chlorine atoms or bromine atoms. Of these, phenol (hydroxybenzene) is more preferable.

  Examples of aldehydes include formaldehyde and furfural in the form of either formalin or paraaldehyde. Of these, formaldehyde is particularly preferable.

  The molar ratio of aldehydes to phenols is preferably 1 to 4, particularly preferably 1.2 to 3. When the molar ratio of aldehydes to phenols is less than 1, particles are difficult to generate, and even if they are generated, the resin does not easily cure, so the strength of the generated particles tends to be weak. On the other hand, when the molar ratio of aldehydes to phenols is larger than 4, unreacted aldehydes remaining in the aqueous medium after the reaction tend to increase.

  Examples of the basic catalyst used in the condensation polymerization of phenols and aldehydes include those used in the production of ordinary resol type resins. Examples of such a basic catalyst include aqueous ammonia, hexamethylenetetramine and alkylamines such as dimethylamine, diethyltriamine, and polyethyleneimine. The molar ratio of these basic catalysts to phenols is preferably 0.02 to 0.3.

  As a method for producing magnetic carrier core particles, there is a method in which a binder resin monomer is mixed with other additives such as a magnetic substance and a high dielectric compound, and the monomer is polymerized to obtain magnetic carrier core particles. Alternatively, magnetic carrier core particles can be obtained by preparing fine particles in which a high dielectric compound is fixed around a magnetic material and mixing with fine particles. At this time, as monomers used for the polymerization, in addition to the vinyl monomers described above, bisphenols and epichlorohydrin for forming epoxy resins; phenols and aldehydes for forming phenol resins; urea resins are formed. For this purpose urea and aldehydes, melamine and aldehydes are used. For example, as a method for producing magnetic carrier core particles using a curable phenolic resin, a magnetic substance is placed in an aqueous medium, and phenols and aldehydes are polymerized in the presence of a basic catalyst in the aqueous medium. There are methods for obtaining core particles.

  Other methods for producing magnetic carrier core particles include vinyl or non-vinyl thermoplastic resins, magnetic materials, and other additives such as high dielectric compounds, which are thoroughly mixed with a mixer before heating rolls, kneaders, There is a method of obtaining magnetic carrier core particles by melting and kneading using a kneader such as an extruder, cooling this, and then pulverizing and classifying. At this time, it is preferable that the obtained magnetic carrier core particles are thermally or mechanically spheroidized and used as magnetic carrier core particles for the magnetic carrier. Among the above-mentioned binder resins, thermosetting resins such as phenol resins, melamine resins, and epoxy resins are preferable because they are excellent in durability, impact resistance, and heat resistance. The binder resin is more preferably a phenol resin in order to more suitably express the characteristics of the present invention.

  In the production of magnetic carrier core particles, the above is called a polymerization method, and the following is called a pulverization and kneading method.

  The coated carrier according to the present invention has a coating layer made of one or more kinds of resins on the surface of the magnetic carrier core particles.

  As a coating method, any conventionally known resin coating method of a carrier such as a method of dissolving or suspending a coating material such as a resin in a solvent and applying it to the carrier and simply mixing with a powder can be applied. .

  The coating material on the surface of the magnetic carrier varies depending on the toner material, but both a thermosetting resin and a thermoplastic resin can be used. For example, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, Examples thereof include polyester resins, metal compounds of ditertiary butylsalicylic acid, styrene resins, acrylic resins, polyamides, polyvinyl butyral, nigrosine, and aminoacrylate resins. These may be used alone or in combination.

  The surface of the magnetic carrier core particle is (i) a combination of a fluorine-based resin and a styrene-based resin (for example, a combination of poly (vinylidene fluoride) and styrene-methyl methacrylate resin, polytetrafluoroethylene and styrene-methyl methacrylate resin Combination, combination of fluorine-based copolymer and styrene-based copolymer), preferably 90:10 to 20:80, more preferably 70:30 to 30:70, or (ii) ) Carrier coated with silicone resin.

  Examples of the fluorine-based copolymer include vinylidene fluoride-tetrafluoroethylene copolymers (10:90 to 90:10). As the styrene-based copolymer, styrene-acrylic acid 2-ethylhexyl copolymer (20: 80-80: 20), styrene-acrylic acid 2-ethylhexyl-methyl methacrylate copolymer (20-60: 5-30: 10-50).

  Further, other resin particles or inorganic compound particles may be included in the coating resin. Furthermore, it is more preferable to modify the surface with another material such as a reactive coupling agent before coating the resin. By performing the surface modification, the adhesion between the resin layer and the magnetic carrier core particles is improved, and more excellent durability can be obtained.

  Examples of the reactive coupling agent for the magnetic carrier core particles of the present invention include the following coupling agents.

  Silane coupling agents include those having a hydrophobic group, amino group, and epoxy group, and silane coupling agents having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, vinyl tris (β -Methoxy) silane and the like.

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

  Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, and the like.

  Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, and isopropyl tris (dioctyl pyrophosphate) titanate.

  Among these, the reactive coupling agent used is an aminosilane coupling agent in order to further improve the affinity on the surface of the magnetic carrier core particles and the negative chargeability when using a negatively charged toner. Those having a primary amino group are particularly preferred.

  The above coated carrier has a sharp particle size distribution, provides preferable triboelectric chargeability for the toner used in the present invention, and has an effect of improving electrophotographic characteristics.

  Next, the fine particles contained in the coating material will be described. When the coating material contains fine particles at a ratio of 1 to 40 parts by mass with respect to 100 parts by mass of the resin, it can be used as a method for controlling unevenness on the surface of the carrier and improving toner separation. As the fine particles, both organic and inorganic fine particles can be used. However, it is necessary to maintain the shape of the particles when coating the magnetic carrier, and preferably, crosslinked resin particles or inorganic fine particles are preferably used. be able to. Specifically, the crosslinked polymethyl methacrylate resin, the crosslinked polystyrene resin, the melamine resin, the phenol resin, the nylon resin, and the inorganic fine particles can be used alone or in combination from amorphous silica, titanium oxide, alumina, and the like.

  The particle diameter of the fine particles has a peak value of 0.1 to 0.5 μm (more preferably 0.2 to 0.3 μm) on the basis of the number. Therefore, it is necessary to improve the toner separation. Among the fine particles, amorphous silica produced by the sol-gel method is preferable in that the particle size distribution is very sharp, uniform irregularities can be formed, and toner separation and surface releasability are obtained.

  In addition, the magnetic carrier of the present invention may be added with 1 to 40 parts by mass of the fine particles to adjust the charge amount of the toner or 1 to 15 parts by mass of conductive particles with respect to the coating resin. The volume resistance of the carrier can be adjusted.

The conductive particles preferably have a volume resistance of 1 × 10 ⁸ Ωcm or less, and more preferably have a volume resistance of 1 × 10 ⁶ Ωcm or less. Specifically, the conductive particles are preferably particles containing at least one kind of particles selected from carbon black, magnetite, graphite, titanium oxide, alumina, zinc oxide, and tin oxide. In particular, as the conductive particles, carbon black can be preferably used without impairing irregularities caused by fine particles on the surface of the magnetic carrier having a small particle size. The particle size of the conductive particles has a peak value of 10 nm to 60 nm (more preferably 15 to 50 nm) on the basis of the number, so that residual charges on the surface of the magnetic carrier can be removed well and desorption from the magnetic carrier can be achieved. It is preferable for preventing it well.

  The coating amount of the resin forming the coating layer is preferably 0.3 to 4.0 parts by mass with respect to 100 parts by mass of the magnetic carrier core particles in order to obtain the effect of surface unevenness due to the fine particles. If the amount is less than 0.3 parts by mass, the fine particles cannot be retained, and there may be a problem that the fine particles fall off. If the amount exceeds 4.0 parts by mass, uniform coating may not be possible during coating, and charge up and the core surface may be exposed, resulting in toner spent at that portion.

  The magnetic carrier of the present invention has a number-based average particle size of 10 to 80 μm. Particles having an average particle size of less than 10 μm are likely to adhere to the carrier, and particles having an average particle size of more than 80 μm may not be able to be imparted with good charge due to a small specific surface area relative to the toner. In particular, in order to improve image quality and prevent carrier adhesion, the thickness is 15 to 60 μm, preferably 20 to 45 μm.

  The magnetic carrier and the toner of the present invention can be mixed and used in a form having a specific surface area. The toner concentration is preferably about 4 to 12% by mass with respect to 100% by mass of the two-component developer in consideration of charging amount provision, fogging, image density, prevention of white spots, and the like.

  The toner used in the present invention preferably contains a binder resin, a colorant and inorganic fine particles, and further contains a release agent as a toner used for oilless fixing.

  The toner of the present invention is a mixture of these raw materials, melted and kneaded, and then pulverized by mechanical impact to obtain a desired particle size by air classification, suspension polymerization, emulsion granulation, etc. A toner for obtaining toner particles can be used.

  The pulverized toner will be described in detail below.

  In the present invention, the binder resin preferably contains a “polyester unit”. “Polyester unit” refers to a portion derived from polyester, and as a polyester monomer constituting the polyester unit, a polyhydric alcohol, a polycarboxylic acid, a polycarboxylic anhydride, or two or more carboxyl groups are included. Carboxylic acid components such as polycarboxylic acid esters can be used as raw material monomers.

  Specifically, for example, as the dihydric alcohol component, polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (3.3) -2,2-bis ( 4-hydroxyphenyl) propane, polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (2.0) -polyoxyethylene (2.0) -2,2 -Bis (4-hydroxyphenyl) propane, polyoxypropylene (6) -2,2-bis (4-hydroxyphenyl) propane and other bisphenol A alkylene oxide adducts, ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol , Neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A, hydrogenated bisphenol A and the like.

  Examples of the trivalent or higher alcohol component 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, 1,3,5-trihydroxymethylbenzene, etc. Can be mentioned.

  Examples of the carboxylic acid component include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid or anhydrides thereof; alkyl dicarboxylic acids such as oxalic acid, adipic acid, sebacic acid and azelaic acid or anhydrides thereof; And succinic acid substituted with 12 to 12 alkyl groups or anhydrides thereof; unsaturated dicarboxylic acids such as fumaric acid, maleic acid and citraconic acid or anhydrides thereof;

  The polyester resin has a bisphenol derivative represented by the following general formula (1) as an alcohol component, and a carboxylic acid component (for example, fumaric acid) composed of a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof. A polyester resin obtained by polycondensation using acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) as an acid component is preferable because it has good charging characteristics as a color toner. .

  Examples of the trivalent or higher polyvalent carboxylic acid component for forming a polyester resin having a crosslinking site include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2 , 4-naphthalenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, and acid anhydrides and ester compounds thereof. The use amount of the trivalent or higher polyvalent carboxylic acid component is preferably 0.1 to 1.9 mol% based on the total monomers.

  In the present invention, (a) a polyester resin, (b) a hybrid resin having a polyester unit and a vinyl polymer unit, (c) a mixture of the hybrid resin and the vinyl polymer, (d) a polyester Use a resin selected from a mixture of a resin and a vinyl polymer, (e) a mixture of a hybrid resin and a polyester resin, and (f) a mixture of a polyester resin, a hybrid resin, and a vinyl polymer. Is preferred.

  Examples of the release agent used in the present invention include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight olefin copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; Oxides of aliphatic hydrocarbon waxes such as: waxes based on fatty acid esters such as aliphatic hydrocarbon ester waxes; and fatty acid esters such as deoxidized carnauba wax that have been partially or wholly deoxidized. It is done. Furthermore, a partially esterified product of a fatty acid such as behenic acid monoglyceride and a polyhydric alcohol; a methyl ester compound having a hydroxyl group obtained by hydrogenating vegetable oils and the like. Particularly preferred waxes are aliphatic hydrocarbon waxes such as paraffin wax, polyethylene wax, and Fischer-Tropsch wax that have a short molecular chain and little steric hindrance and excellent mobility.

  In the toner used in the present invention, a toner used for oilless fixing having a binder resin, a colorant, a release agent, and inorganic fine particles is preferable. The binder resin contains a polyester unit, and the release agent is a hydrocarbon. The endothermic curve in the differential thermal analysis measurement of the toner has one or more endothermic peaks in the temperature range of 30 to 200 ° C., and the maximum endothermic peak temperature is 65. A toner having a temperature of from 110 ° C. to 110 ° C. can be preferably used because it can appropriately increase the degree of aggregation of the toner to improve transferability and improve image defects such as white spots.

  The release agent used in the present invention preferably has a content of 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin. If the content is less than 1 part by mass, the releasability may not be exhibited well at the time of oilless fixing, or the low-temperature fixing property may not be satisfied. When the amount exceeds 10 parts by mass, the release agent tends to ooze out to the toner surface, and white spots may deteriorate.

  The toner of the present invention can be used in combination with a known charge control agent. Examples of such charge control agents include organometallic complexes, metal salts, and chelate compounds such as monoazo metal complexes, acetylacetone metal complexes, hydroxycarboxylic acid metal complexes, polycarboxylic acid metal complexes, and polyol metal complexes. In addition, carboxylic acid derivatives such as metal salts of carboxylic acids, carboxylic acid anhydrides and esters, and condensates of aromatic compounds are also included. As the charge control agent, phenol derivatives such as bisphenols and calixarenes are also used. In the present invention, it is preferable to use a metal compound of an aromatic carboxylic acid in order to improve the rising of charging.

  In the present invention, the charge control agent preferably has a content of 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the binder resin. If the amount is less than 0.1 parts by mass, the change in the toner charge amount in an environment from high temperature and high humidity to low temperature and low humidity may become large. If the amount is more than 10 parts by mass, the toner may be inferior in low-temperature fixability.

  As the colorant used in the present invention, known pigments and dyes can be used alone or in combination. For example, as the dye, C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic green 6 etc. are mentioned.

  As pigments, mineral fast yellow, navel yellow, naphthol yellow S, hansa yellow G, permanent yellow NCG, tartrazine lake, molybdenum orange, permanent orange GTR, pyrazolone orange, benzidine orange G, permanent red 4R, watch red red calcium salt , Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue BC, Chrome Green, Pigment Green B, Malachite green lake, final yellow green G, etc. are mentioned.

  When used as a full-color image forming toner, the magenta color pigment includes C.I. I. 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, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, 238, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are mentioned.

  Although such a pigment may be used alone, it is more preferable from the viewpoint of the image quality of a full-color image to improve the sharpness by using a dye and a pigment together. Examples of the magenta dye include C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as Disperse Violet 1; I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, C.I. I. Basic dyes such as basic violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, and 28 may be mentioned.

  Examples of the color pigment for cyan include C.I. I. Pigment blue 2, 3, 15, 16, 17; I. Acid Blue 6; I. Examples thereof include Acid Blue 45 or a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on the phthalocyanine skeleton.

  Examples of the color pigment for yellow include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 93, 97, 155, 180, 185, C.I. I. Bat yellow 1, 3, 20 etc. are mentioned.

  The amount of the colorant used is preferably 1 to 15 parts by mass, more preferably 3 to 12 parts by mass, and still more preferably 4 to 10 parts by mass with respect to 100 parts by mass of the binder resin. . When the content of the colorant is more than 15 parts by mass, the transparency is lowered, and in addition, the reproducibility of intermediate colors as typified by human skin color is likely to be lowered, and further, the chargeability of the toner is stabilized. And the low-temperature fixability becomes difficult to obtain. When the content of the colorant is less than 1 part by mass, the coloring power is low, so that a large amount of toner must be used to obtain the density, the dot reproducibility is easily impaired, and a high-quality image with a high image density. Is difficult to obtain.

  The toner used in the present invention has a weight average particle diameter of 4.0 to 10.0 μm. The weight average particle diameter of the toner is preferably 4.0 μm to 10.0 μm from the viewpoint of sufficiently satisfying dot reproducibility and transfer efficiency. 5 to 9 μm is preferable. If the weight average particle diameter of the toner is less than 4.0 μm, the specific surface area of the toner becomes large, so that it becomes difficult to control the charge amount, the developability is lowered, and white spots may be deteriorated. When the weight average particle diameter of the toner exceeds 10.0 μm, the dot reproducibility is poor and there is a problem in improving the image quality. The weight average particle diameter of the toner can be adjusted by classification of the toner particles at the time of production, mixing of classified products, or the like.

  For the purpose of improving fluidity, transferability, particularly toner separation, and improving white spots, toner is added with fine particles. One of the external additives externally added to the toner surface is inorganic fine particles, and at least one of titanium oxide, alumina oxide and silica is used. The average particle size (number distribution) of the inorganic fine particles is used. Is preferably 80 nm or more and 200 nm or less in order to function as spacer particles for improving the toner separation from the carrier. The external additive is preferably used in combination with fine particles having an average particle diameter (peak value of the number distribution) of 50 nm or less in order to improve toner fluidity.

  Next, the photoreceptor used in the present invention will be described.

[Organic photoconductor: OPC]
Examples of the conductive substrate include metals such as aluminum and stainless steel, plastics having a coating layer made of aluminum alloy, indium oxide-tin oxide alloy, paper / plastic impregnated with conductive particles, plastics having a conductive polymer, etc. Cylindrical cylinders and films are used.

  On these conductive substrates, the purpose is to improve the adhesion of the photosensitive layer, improve coating properties, protect the substrate, cover defects on the substrate, improve charge injection from the substrate, and protect against electrical breakdown of the photosensitive layer. An undercoat layer may be provided. Undercoat layer is polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymer nylon, glue, gelatin, polyurethane -It is made of a material such as aluminum oxide. The film thickness is usually about 0.1 to 10 μm, preferably about 0.1 to 3 μm.

  The charge generation layer is made of azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes, selenium, amorphous silicon, etc. A charge generating material such as an inorganic material is dispersed in a suitable binder and applied, or vapor deposition is used. Of these, phthalocyanine pigments are preferred for adjusting the sensitivity of the photoreceptor to a sensitivity suitable for the present invention. The binder can be selected from a wide range of binder resins, such as polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin, phenol resin, silicone resin, epoxy resin, vinyl acetate resin, etc. Is mentioned. The amount of the binder contained in the charge generation layer is selected to be 80% by weight or less, preferably 0 to 40% by weight. The film thickness of the charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.

  The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a binder resin as required, and coating, and the film thickness is generally 5 to 40 μm. Examples of the charge transport material include polycyclic aromatic compounds having a structure such as biphenylene, anthracene, pyrene, phenanthrene in the main chain or side chain, nitrogen-containing cyclic compounds such as indole, carbazole, oxadiazole, pyrazoline, hydrazone compounds, Examples include styryl compounds, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.

  Examples of binder resins for dispersing these charge transport materials include polycarbonate resins, polyester resins, polymethacrylate esters, polystyrene resins, acrylic resins, polyamide resins, and other organic photoconductive materials such as poly-N-vinylcarbazole and polyvinylanthracene. Include a functional polymer.

  Moreover, you may provide a protective layer as a surface layer. As the resin for the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or a curing agent for these resins may be used alone or in combination of two or more.

  Moreover, you may disperse | distribute electroconductive fine particles in resin of a protective layer. Examples of the conductive fine particles include metals and metal oxides, preferably zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide coated titanium oxide, tin coated indium oxide, There are ultrafine particles such as antimony-coated tin oxide and zirconium oxide. These may be used alone or in combination of two or more. In general, when particles are dispersed in a protective layer, it is necessary that the particle diameter of the particles is smaller than the wavelength of the incident light in order to prevent scattering of incident light by the dispersed particles. The particle size of the conductive and insulating particles to be formed is preferably 0.5 μm or less. Moreover, 2 to 90 weight% is preferable with respect to the protective layer total weight, and, as for content in a protective layer, 5 to 80 mass% is more preferable. The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

  The surface layer can be applied by spray coating, beam coating or penetration (dipping) coating of the resin dispersion.

[Inorganic photoconductor: amorphous silicon photoconductor (a-Si)]
In general, a photoreceptor for an image forming apparatus using a-Si: H is obtained by heating a conductive support to 50 ° C. to 400 ° C., and vacuum deposition, sputtering, ion plating on the support. A photoconductive layer made of a-Si is formed by a film forming method such as a CVD method, a thermal CVD method, a photo CVD method, or a plasma CVD method (hereinafter referred to as “PCVD method”). Among these, the PCVD method, that is, the method of sequentially decomposing the source gas by direct current, high frequency or microwave glow discharge and sequentially forming the a-Si deposited film on the support is put into practical use.

[Support]
The support used in the present invention may be conductive or electrically insulating. Examples of the conductive support include well-known metals such as Al and Fe, and alloys thereof such as stainless steel. Also, a support obtained by conducting a conductive treatment on at least the surface on the side where the photosensitive layer is formed of an electrically insulating support such as a synthetic resin film or sheet, glass or ceramic can be used.

  In addition, as another method for more effectively eliminating the image defect due to the interference fringe pattern when using coherent light such as laser light, a plurality of charge carriers on the surface of the support in a range in which there is substantially no decrease in charge carriers. An uneven shape by a spherical trace depression may be provided, or an interference preventing layer or region such as a light absorption layer may be provided below the photosensitive layer.

[Photoconductive layer]
In the present invention, in order to effectively achieve the object, the photoconductive layer which is formed on the support and, if necessary, the undercoat layer and constitutes a part of the photosensitive layer is desired by the vacuum deposited film forming method. It is created by appropriately setting numerical conditions of film formation parameters so as to obtain characteristics.

  In order to form the photoconductive layer by the glow discharge method, basically, a source gas for supplying Si that can supply silicon atoms (Si) and a source gas for supplying H that can supply hydrogen atoms (H) or / And a source gas for X supply capable of supplying halogen atoms (X) is introduced in a desired gas state into a reaction vessel in which the inside can be depressurized to cause glow discharge in the reaction vessel. What is necessary is just to form the layer which consists of a-Si: H, X on the predetermined support body installed in the position.

  Examples of atoms that control conductivity include so-called impurities in the semiconductor field. As is well known, a periodic table group 13 element that provides p-type conduction characteristics or a periodic table group 15 element that provides n-type conduction characteristics is used. be able to.

  In the present invention, the layer thickness of the photoconductive layer is appropriately determined as desired from the viewpoint of obtaining desired electrophotographic characteristics and economic effects, etc., preferably 20-50 μm, more preferably 23-45 μm, optimally Is preferably 25 to 40 μm.

  In order to achieve the object of the present invention and form a photoconductive layer having desired film characteristics, the mixing ratio of Si supply gas and dilution gas, the gas pressure in the reaction vessel, the discharge power and the support temperature are set. It can be set appropriately.

[Surface layer]
In the present invention, it is preferable to further form a surface layer on the photoconductive layer formed on the support as described above. This surface layer has a free surface, and is provided to achieve the object of the present invention mainly in moisture resistance, continuous repeated use characteristics, electrical pressure resistance, use environment characteristics, and durability.

  The surface layer contains an amorphous silicon (a-Si) -based material, for example, an amorphous silicon containing hydrogen atoms (H) and / or halogen atoms (X) and further containing carbon atoms (hereinafter referred to as “a-SiC: H, X ”), amorphous silicon containing hydrogen atoms (H) and / or halogen atoms (X) and further containing oxygen atoms (hereinafter referred to as“ a-SiO: H, X ”), Amorphous silicon containing hydrogen atoms (H) and / or halogen atoms (X) and further containing nitrogen atoms (hereinafter referred to as “a-SiN: H, X”), hydrogen atoms (H) and / or halogens Amorphous silicon (hereinafter referred to as “a-SiCON: H, X”) containing an atom (X) and further containing at least one of a carbon atom, an oxygen atom and a nitrogen atom, or amo Amorphous carbon (a-C: H, X) material or the like is preferably used.

  The amount of carbon when the surface layer is composed mainly of a-SiC is preferably in the range of 30% to 90% with respect to the sum of silicon atoms and carbon atoms.

  The layer thickness of the surface layer in the present invention is usually 0.01 to 3 μm, preferably 0.05 to 2 μm, and most preferably 0.1 to 1 μm. If the layer thickness is less than 0.01 μm, the surface layer is lost due to wear or the like during use of the photoreceptor, and if it exceeds 3 μm, electrophotographic characteristics such as an increase in residual potential are observed.

  Furthermore, in the present invention, it is also possible to provide a blocking layer (lower surface layer) in which the content of carbon atoms, oxygen atoms and nitrogen atoms is reduced from the surface layer between the photoconductive layer and the surface layer. It is effective for further improvement.

[Charge injection blocking layer]
In the photoreceptor for an image forming apparatus of the present invention, it is more effective to provide a charge injection blocking layer that functions to block charge injection from the conductive support side between the conductive support and the photoconductive layer. Is.

  Examples of the atoms that control the conductivity contained in the charge injection blocking layer include so-called impurities in the semiconductor field. The periodic table group 13 element that provides p-type conduction characteristics or the periodic table 15 that provides n-type conduction characteristics. Group elements can be used.

  Further, the charge injection blocking layer contains at least one of carbon atom, nitrogen atom and oxygen atom, thereby improving the adhesion between the charge injection blocking layer and another layer provided in direct contact with the charge injection blocking layer. More can be achieved.

  In addition, hydrogen atoms and / or halogen atoms contained in the charge injection blocking layer in the present invention compensate for dangling bonds present in the layer, and are effective in improving the film quality.

  In the present invention, the layer thickness of the charge injection blocking layer is preferably from 0.1 to 5 μm, more preferably from 0.3 to 4 μm, optimally from the viewpoint of obtaining desired electrophotographic characteristics and economic effects. It is desirable to be 0.5 to 3 μm.

In the image forming apparatus photoconductor of the present invention, for the purpose of further improving the adhesion between the support and the photoconductive layer or the charge injection blocking layer, for example, Si ₃ N ₄ , SiO ₂ , An adhesion layer made of an amorphous material or the like containing SiO or silicon atoms as a base and containing hydrogen atoms and / or halogen atoms and carbon atoms and / or oxygen atoms and / or nitrogen atoms may be provided. Furthermore, as described above, a light absorption layer for preventing the generation of interference patterns due to the reflected light from the support may be provided.

In the image forming method of the present invention, it is preferable to use an electrophotographic photosensitive member having a charge capacity of 1.0 to 8.0 μF / m ² . More preferably, it is 1.5 to 6.0 μF / m ² . If the charge capacity is 1.0μF / m ² less than, although no problem with low resolution image, in accordance with the resolution increases, fidelity dot has resulted in lower. Also, when the charge capacity is greater than 8.0 μF / m ² , the dot charge is high, but the toner charge that fills the photoreceptor increases, and the charge cannot be fully filled. , Make it easier to pick up defects. In order to change the charge capacity, it is possible to produce a photoconductor having an arbitrary charge capacity by changing the material of the photoconductor, adjusting the dielectric constant of the photoconductor, and changing the film thickness of the charge holding region. As for the OPC photosensitive member, although it varies slightly depending on the material, it is desirable that the thickness of the charge holding region is in the range of 5 to 20 μm in order to make the charge capacity 1.5 to 6.0 μF / m ² . With respect to the amorphous silicon photoconductor, it is desirable to use the film thickness of the charge holding region in the range of 15 to 50 μm in order to make the charge capacity 1.5 to 6.0 μF / m ² .

  Next, the image forming method of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an electrophotographic full-color machine which is an image forming apparatus embodying the present invention.

  In FIG. 1, each ABCD station forms a full-color image of yellow, magenta, cyan, and black, but the color order of the stations does not matter at all. In the following description, for example, the primary charger 21 refers to the primary chargers 21A, 21B, 21C, and 21D in each ABCD station.

  In each station, image formation is performed as follows.

First, a photosensitive drum 4 serving as an image carrier is rotatably provided. The photosensitive drum 4 is uniformly charged by a primary charger 21, and then an information signal is exposed by a light emitting element 22 such as a laser to statically. An electrostatic latent image is formed and visualized by the developing device 9. Next, the visible image is transferred to the transfer paper 24 conveyed by the transfer paper conveyance sheet 27 by the transfer charger 23.
On the transfer paper 24, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred at each station. The transfer paper 24 on which the toner images of the four colors are laminated is mixed and fixed by heat and pressure in the fixing device 25, and is discharged out of the device as a full color image.

  A suitable method for measuring physical properties related to the present invention will be described below.

<Measurement of toner particle or toner particle size distribution>
As a measuring device, Coulter Counter TA-II or Coulter Multisizer II (manufactured by Coulter Inc.) is used. As the electrolytic solution, an about 1% NaCl aqueous solution is used. As the electrolytic solution, an electrolytic solution prepared using primary sodium chloride or, for example, ISOTON (registered trademark) -II (manufactured by Coulter Scientific Japan) can be used.

  As a measurement method, 0.1 to 5 ml of a surfactant (preferably alkylbenzenesulfone hydrochloride) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of the sample are measured for each channel by the measuring device using a 100 μm aperture as the aperture. The volume distribution and the number distribution are calculated. From these obtained distributions, the weight average particle diameter of the sample is determined. As channels, 2.00 to 2.52 μm; 2.52 to 3.17 μm; 3.17 to 4.00 μm; 4.00 to 5.04 μm; 5.04 to 6.35 μm; 6.35 to 8. 00 μm; 8.00 to 10.08 μm; 10.08 to 12.70 μm; 12.70 to 16.00 μm; 16.00 to 20.20 μm; 20.20 to 25.40 μm; 25.40 to 32.00 μm; 13 channels of 32-40.30 μm are used.

<Measurement of dielectric constant of fine particles>
Using a 4284A Precision LCR meter (manufactured by Hewlett-Packard Company), the dielectric constant ε at a frequency of 100000 Hz is measured after calibration at a frequency of 1000 Hz and 1 MHz.

  The fine particles are made into a disk-shaped measurement sample having a diameter of 25 mm and a thickness of 2 mm or less (preferably 0.5 mm to 1.5 mm). This measurement sample is mounted on ARES (manufactured by Rheometric Scientific F.E.) equipped with a dielectric constant measuring jig (electrode) having a diameter of 25 mm. It is obtained by measuring at a temperature of 25 ° C. with a frequency of 100000 Hz constant in a state where a load of 0.49 to 1.96 N (50 to 200 g) is applied. From the obtained dielectric constant, the porosity at the time of measurement is calculated from the sample amount and specific gravity, and the dielectric constant of the fine particles is calibrated.

<Measurement of particle size of magnetic carrier>
With respect to the particle size of the magnetic carrier particles, 300 or more magnetic carrier particles having a particle size of 0.1 μm or more are randomly extracted by a scanning electron microscope (5,000 times), and a digitizer has a number average horizontal ferret diameter. The number average particle diameter of the carrier is used.

<Measurement of particle size of magnetic material, inorganic fine particles and fine particles>
The particle size of the magnetic material was determined by extracting 300 or more particles having a particle size of 0.005 μm or more at random using a scanning electron microscope (20,000 to 50,000 times) in a cross section obtained by cutting the carrier with a microtome or the like. The axis and minor axis are measured with a digitizer, the average is taken as the particle size, and the number average particle size is calculated with the particle size that becomes the peak of the particle size distribution of 300 or more particles.

<Measurement of particle size of inorganic fine particles and external additives>
Regarding the particle size of the inorganic fine particles and external additives on the toner surface, 500 or more particles having a particle size of 0.001 μm or more are randomly extracted by a scanning electron microscope (20,000 times), and the major axis and the minor axis are digitized. The average value is the particle size, and the peak value in the range of 0.001 to 0.06 μm is the number average particle size of the external additive, with the particle size becoming the peak of the particle size distribution of 500 or more particles. The diameter is calculated as the number average particle diameter of the inorganic fine particles with the peak value in the range of 0.06 or more.

<Measurement of magnetization intensity of magnetic carrier>
The strength of magnetization of the magnetic carrier is determined from the magnetic properties of the magnetic carrier and the true specific gravity of the magnetic carrier. The magnetic characteristics of the magnetic carrier can be measured by using an oscillating magnetic field type magnetic characteristic automatic recording apparatus BHV-30 manufactured by Riken Denshi Co., Ltd. As a measuring method, a cylindrical plastic container is filled with a magnetic carrier so as to be sufficiently dense, while an external magnetic field of 1 kilo-Oersted (79.6 kA / m) is formed, and in this state, the magnetic material filled in the container is filled. Measure the magnetization moment of the carrier. Further, the actual mass of the magnetic carrier filled in the container is measured to determine the magnetization strength (Am ² / kg) of the magnetic carrier.

<Measurement of true specific gravity of magnetic carrier>
The true specific gravity of the magnetic carrier particles can be determined by a dry automatic densimeter autopycnometer.

<Measurement of apparent specific gravity of magnetic carrier>
The apparent density of the carrier was measured according to JISZ-2504.

<Measurement of volume resistance of magnetic carrier, nonmagnetic inorganic compound and magnetic substance>
In addition, the volume resistance value of a nonmagnetic inorganic compound and a magnetic body is performed using the measuring apparatus shown in FIG. The cell E is filled with carrier particles, the lower electrode 11 and the upper electrode 12 are arranged so as to be in contact with the filled carrier particles, a voltage is applied between these electrodes, and the current flowing at that time is measured to measure the volume. A method for obtaining resistance is used. The measurement conditions of the volume resistance in the present invention are a contact area S between the filled carrier particles and the electrode of about 2.3 cm ² , a thickness d of about 0.5 mm, and a load of the upper electrode 12 of 180 g. Under these conditions, the volume resistance when an electric field of 5 × 10 ⁵ V / m was applied was measured.

<Measurement of white spots>
A chart in which halftone horizontal bands (30H width 10 mm) and solid black horizontal bands (FFH width 10 mm) are alternately arranged in the transfer paper conveyance direction is output. The image is read by a scanner and binarized. Taking the luminance distribution (256 gradations) of a certain line in the conveyance direction of the binarized image, drawing a tangent to the luminance of the halftone at that time, and deviating from the tangent at the rear end of the halftone part until it intersects with the solid part luminance The brightness area (area: sum of the brightness numbers) is used as the whiteness degree.
A: 50 or less Almost inconspicuous and very good.
B: 51 to 150 Good.
C: 151 to 300 There are white spots, but it is at a level where there is no practical problem.
D: 301 to 600 White spots are conspicuous, which is a problem.
E: 601 or more Very noticeable.

<Measurement of Graininess of Halftone (HT) Portion and Uniformity of Halftone (HT) Portion>
A 30H image was formed using the toner and the remodeling machine, this image was visually observed, and the dot reproducibility of the image was evaluated based on the following criteria. The 30H image is a value obtained by displaying 256 gradations in hexadecimal, and is a halftone image when 00H is solid white (non-image) and FFH is solid black (entire image).

The evaluation level of rustling is as follows.
A: Smooth and smooth.
B: I don't feel a lot of rustling.
C: Although there is a slight feeling of roughness, it is at a level where there is no practical problem.
D: There is a feeling of roughness and is a problem.
E: There is a very rough feeling.

The evaluation level of the uniformity of the halftone part is as follows. The image density was evaluated using a reflection densitometer 500 Series Spectrodensitometer manufactured by X-rite.
A: The concentration is uniform over the entire surface.
B: The density difference at the front end of the image is within 0.3, and there is no practical problem.
C: The density difference at the leading edge of the image is within 0.3 to 0.5, and the density difference is noticeable.
D: The density difference at the front end of the image is 0.5 or more, which is a problem.

<Measurement of change in surface potential>
A full-color copying machine CLC5000 made by Canon is used, and a photoconductor used in this embodiment is disposed.

Only the carrier was put in the developing device, and the amount of the carrier on the developing roller was adjusted with a regulating blade so as to be 30 mg / cm ² . Further, the distance between the developing roller and the photosensitive member was adjusted to be 400 μm.

  In addition, a 650 nm semiconductor laser was used as the laser, the spot diameter was reduced, and output was possible at 600 dpi.

  When an amorphous silicon photoconductor was used, when the carrier was not put into the developing device, the non-exposed portion potential: −450 V, the exposed portion potential: −100 V, the bias potential was set to DC: −300 V, and AC: main body setting.

  When using the OPC photoreceptor, the non-exposed portion potential: -700 V, the exposed portion potential: -200 V, the bias potential was set to DC: -500 V, and AC: main body setting.

  A potential sensor (Model 344 manufactured by Trek) was disposed immediately after the developing device, and the potential difference between when the carrier was present and when it was absent was determined.

  When the amount of potential change was less than 10 V, it was possible to output a gradation-contrast image with good reproducibility. In 10V-30V, although it was slight, the density | concentration fall of the high concentration part generate | occur | produced. Above 30 V, concentration reduction, carrier adhesion, fogging, discharge, etc. were likely to occur.

<Measurement of toner charge amount>
The developer was put in the evaluation machine used for measuring the amount of change in surface potential, and the toner charge amount was measured.

The toner charge amount on the photosensitive member is obtained by using a suction type Faraday cage method. The suction type Faraday cage method uses a developer recovery device to suck and collect all one-component developer in a fixed area on the developing sleeve of a copying machine or printer, and collects the charge amount of the collected developer and the suction unit In this method, the area is measured, and the charge amount per unit area of the developer, that is, the toner charge amount (μC / m ² ) is obtained from the measured charge amount and area of the developer.

  The developer recovery device used in this suction type Faraday cage method has a suction device portion for sucking air and a recovery device portion for recovering the developer connected to the suction device. The collecting device section includes an outer cylinder having a suction port having a tip corresponding to the outer peripheral curvature of the developing sleeve for sucking the developer on the developing sleeve, and a cylindrical filter paper for collecting the sucked developer. And an inner cylinder.

  In order to specifically perform the suction and recovery of the developer on the developing sleeve using this developer recovery device, the toner is developed from the developer holder onto the electrostatic holder, and the toner image is transferred onto the transfer paper. By using the developer collecting device described above, the developer on the electrostatic holding member is moved from the one end side to the other end side of the developing sleeve, and the suction port of the developer collecting device is moved along the longitudinal direction from the developing sleeve to the developing sleeve. Suction is applied while pressing against the surface, and the sucked developer is collected with a cylindrical filter paper.

In the case of the conditions used in this example, when the toner charge amount is larger than 500 μC / m ² , white spots and density unevenness can be improved. When the toner charge amount is smaller than 500 μC / m ² , white spots, unevenness, and the like are noticeable as the toner charge amount decreases.

  Embodiments included in the present invention are listed below.

  Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example of OPC photoconductor production)
First, the coating material for conductive layers was prepared by the following procedure. 50 parts by weight of conductive titanium oxide powder coated with tin oxide containing 10% antimony oxide, 25 parts by weight of phenol resin, 20 parts by weight of methyl cellosolve, 5 parts by weight of methanol and silicone oil (polydimethylsiloxane polyoxyalkylene copolymer) Polymer, average molecular weight 3000) 0.002 part by mass was prepared by dispersing for 2 hours in a sand mill using glass beads having a diameter of 1 mm. This paint was applied by dip coating on an aluminum cylinder having a mirror finish of 60 mm in diameter and dried at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 20 μm.

  Next, 5 parts by mass of N-methoxymethylated nylon was dissolved in 95 parts by mass of methanol to prepare an intermediate layer coating material. This paint was applied on the conductive layer by a dip coating method and dried at 100 ° C. for 20 minutes to form an intermediate layer having a thickness of 0.6 μm.

  Next, 3 masses of oxytitanium phthalocyanine having strong peaks at 9.0 °, 14.2 °, 23.9 ° and 27.1 ° of the Bragg angle (2θ ± 0.2 °) of CuKα characteristic X-ray diffraction Part, 2 parts by weight of polyvinyl butyral resin and 35 parts by weight of cyclohexanone were dispersed for 2 hours in a sand mill apparatus using glass beads having a diameter of 1 mm, and then 60 parts by weight of ethyl acetate was added to obtain a coating material for a charge generation layer. This paint was applied onto the intermediate layer by a dip coating method and dried at 90 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.2 μm.

  Next, a coating solution prepared by dissolving 10 parts by mass of a styryl compound represented by the following general formula (5) and 10 parts by mass of a polycarbonate resin in a mixed solvent of chlorobenzene and 30 parts by mass of dichloromethane is formed on the charge generation layer. It was applied by dip coating and dried at 120 ° C. for 60 minutes to form a charge transport layer having a thickness of 15 μm.

  The surface protective layer was produced as follows. 100 parts by mass of antimony-containing tin oxide fine particles having an average particle size of 0.02 μm, 30 parts by mass of (3,3,3-trifluoropropyl) trimethoxysilane (trade name LS-1090, manufactured by Shin-Etsu Chemical Co., Ltd.), 95% After 300 parts by mass of ethanol-5% aqueous solution was milled, the solution was filtered, washed with ethanol, dried, and then subjected to surface treatment of tin oxide fine particles by drying at 120 ° C. for 1 hour. 100 parts by mass of a binder resin represented by the following structural formula on the surface-treated tin oxide fine particles

  30 parts by mass of a photopolymerization initiator represented by the following structural formula

及びエタノ−ル３００質量部を混合してサンドミルで９６時間分散し、保護層用の塗工液を調製した。

And 300 parts by mass of ethanol were mixed and dispersed in a sand mill for 96 hours to prepare a coating solution for the protective layer.

The coating liquid was applied by dip coating on the charge generation layer, 30 seconds to ultraviolet radiation at a light intensity of 500 mW / cm ² at a metal halide lamp, to form a protective layer having a thickness 3 [mu] m, the negatively charged OPC A photoconductor was prepared. This photoreceptor is referred to as an OPC photoreceptor 1. The charge capacity of this photoreceptor was 1.9 μF / m ² .

(Production Examples 1 and 2 of amorphous silicon photoconductor)
Using an apparatus for manufacturing a photoreceptor for an image forming apparatus by RF-PCVD method, a negatively charged photoreceptor was produced on an aluminum cylinder having a mirror finish with a diameter of 60 mm under the conditions shown in Table 1.

This photoreceptor is referred to as a-Si photoreceptor 1. The charge capacity of this photoreceptor was 2.8 μF / m ² .

  Next, only the photoconductive layer formation time was reduced, and a negatively charged photoconductor having a photoconductive layer thickness of 15 μm and other film thicknesses equal to those of the a-Si photoconductor 1 was produced.

This photoreceptor is referred to as a-Si photoreceptor 2. The charge capacity of this photoreceptor was 5.2 μF / m ² .

(Magnetic carrier production example 1)
4.0% by mass of a silane coupling agent (3- (2-aminoethylaminopropyl) with respect to a magnetite powder having a number average particle diameter of 0.25 μm and a strontium titanate powder having a number average particle diameter of 0.70 μm. ) Trimethoxysilane) was added and mixed and stirred at 100 ° C. or higher in a container to make each fine particle lipophilic.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 40%, methanol 10%, water 50%)
6 parts by mass / lipophilic magnetite 63 parts by mass / lipophilic strontium titanate powder 21 parts by mass The above materials, 5% by weight of 28% ammonia water, and 10 parts by mass of water are placed in a flask, and stirred and mixed. Then, the temperature was raised to 85 ° C. and maintained for 30 minutes, followed by polymerization reaction for 3 hours to cure. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain spherical magnetic carrier core particles in which a magnetic material was dispersed.

  Further, the surface of the magnetic resin particles obtained above was coated with a thermosetting silicone resin by the following method. At that time, a carrier coating solution of 10% by mass was prepared using toluene as a solvent so that the amount of the silicone coating resin on the surface of the resin particles was 1.0 part by mass. The coating solution was applied to the surface of the magnetic resin particles by volatilizing the solvent at 70 ° C. while continuously applying shear stress to the coating solution.

The resin-coated magnetic carrier particles were heat-treated for 3 hours while stirring at 200 ° C., after cooling, was crushed, 200 classified to number average particle size 35μm with a sieve of mesh, volume resistivity 2.1 × 10 ¹² , true specific gravity 3.6 g / cm ^3, an apparent specific gravity of 1.85 g / cm ^3, to obtain a carrier 1 of strength 45Am ² / kg magnetization. Table 2 shows the formulation of the magnetic carrier and Table 4 shows the characteristics.

(Magnetic carrier production examples 2 to 5)
The addition ratio shown in Table 2 was changed with respect to the magnetite powder having a number average particle diameter of 0.25 μm and the strontium titanate powder having a number average particle diameter of 0.10 μm in Magnetic Carrier Production Example 1. Magnetic carriers 2 to 5 were produced under the same conditions. Table 2 shows the magnetic carrier formulation and Table 4 shows the characteristics.

(Manufacture example 6 of a magnetic carrier)
4.0% by mass of a silane coupling agent (3- (2-aminoethylaminopropyl) trimethoxysilane) is added to magnetite powder having a number average particle size of 0.25 μm, and the temperature is 100 ° C. or higher in a container. The mixture was stirred at high speed to make each fine particle lipophilic.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 40%, methanol 10%, water 50%)
6 parts by mass, 84 parts by mass of lipophilic magnetite The above material, 5 parts by mass of 28% ammonia water, and 10 parts by mass of water are placed in a flask, and heated to 85 ° C. for 30 minutes while stirring and mixing. The mixture was polymerized for 3 hours to be cured. Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain spherical magnetic carrier core particles in which a magnetic material was dispersed.

  Thereafter, a silicone resin was coated under the same conditions as in Production Example 1 to produce a magnetic carrier 6.

(Magnetic carrier production examples 7 and 8)
Instead of the strontium titanate powder used in the magnetic carrier production example 1, hematite powder and silica powder having a number average particle size of 0.60 μm were used, and the magnetic carriers 7 and 8 were then used under the same conditions as in the production example 1. Produced. Table 2 shows the formulation of the magnetic carrier and Table 4 shows the characteristics.

(Magnetic carrier production examples 9, 10)
Using the coating material shown in Table 2 for the magnetic carrier core particles produced in Magnetic Carrier Production Example 1, magnetic carriers 9 and 10 were produced under the same conditions as in Magnetic Carrier 1. Table 4 shows the characteristics of the magnetic carrier. The carbon black used in the magnetic carrier 8 had a volume resistance of 1 × 10 ⁻² Ω · cm and a number average particle size of 30 nm.

(Manufacture example 11 of a magnetic carrier)
The magnetic carrier core particles prepared in Magnetic Carrier Production Example 1 were not coated and used as magnetic carrier 11 as they were. Table 4 shows the characteristics of the magnetic carrier.

(Magnetic Carrier Production Example 12) Crushing and kneading method 118 g of styrene and 82 g of butyl methacrylate were charged into a nitrogen-substituted flask, the internal temperature was raised to 130 ° C., and polymerization was performed at this temperature for 10 hours. Then, 100 g of xylene was added, and a solution of 0.5 g of azobisisobutyronitrile dissolved in 100 g of xylene was continuously added over 9 hours while maintaining the temperature at 135 ° C., followed by polymerization for 2 hours to obtain a styrene acrylic resin. Obtained. In addition, when the acid value of this styrene acrylic resin was measured by JIS K5400 method, it was 0 KOHmg / g and Tg was 60 degreeC. 20 parts by mass of this styrene acrylic resin (1), 60 parts by mass of lipophilic magnetite, and 20 parts by mass of lipophilic strontium titanate powder were sufficiently mixed with a Henschel mixer, and then bent biaxially kneaded. It is melt-kneaded at 180 ° C. with an apparatus, cooled, then coarsely pulverized with a feather mill, further finely pulverized with a jet pulverizer, and then air-classified. Manufactured by SFS-1 type) to obtain magnetic carrier core particles.

  Thereafter, a magnetic carrier 12 was produced under the same conditions as in Production Example 1. Table 4 shows the characteristics of the carrier.

(Manufacturing examples 13-15 of magnetic carrier)
Under the conditions shown in Table 2, each of the high dielectric compounds was added, and then the magnetic carriers 13 to 15 were produced under the same conditions as in Production Example 1. Table 4 shows the characteristics of the carrier.

(Manufacture example 16 of a magnetic carrier)
Instead of the strontium titanate powder used in Magnetic Carrier Production Example 1, calcium titanate powder having a number average particle size of 0.60 μm was used, and thereafter, magnetic carrier core particles were obtained under the same conditions as in Production Example 1. .

  As a coating material, 10% by mass of a copolymer of methyl methacrylate and methyl methacrylate having a perfluoroalkyl group (m = 7) (copolymerization ratio 8: 1 weight average molecular weight 45,000) in a mixed solvent of methyl ethyl ketone and toluene. Further, the carbon black is 5% by mass with respect to the methyl methacrylate copolymer. A coating solution was prepared. Furthermore, the amount of the coating solution was adjusted so that the methyl methacrylate copolymer was 2 masses with respect to the magnetic carrier core particles. The coating solution was applied to the surface of the magnetic resin particles by volatilizing the solvent at 70 ° C. while continuously applying shear stress to the coating solution. The resin-coated magnetic carrier particles were heat-treated with stirring at 100 ° C. for 2 hours, cooled, crushed, and classified with a 200-mesh sieve to produce a magnetic carrier 16. Table 4 shows the characteristics of the magnetic carrier.

(Magnetic carrier production example 17)
Under the conditions shown in Table 2, strontium titanate and hematite powder were added, and then the magnetic carrier 17 was produced under the same conditions as in Production Example 1. Table 4 shows the characteristics of the carrier.

(Manufacture example 18 of a magnetic carrier)
-Magnetite powder with a number average particle size of 0.25 µm 100 parts by mass · 4.5 parts by mass of alkoxysilane · 12 parts by mass of strontium titanate powder After coating the surface of magnetite powder with a number average particle size of 0.25 µm with alkoxysilane After adding strontium titanate powder with a number average particle size of 0.03 μm, followed by mixing and stirring to attach the strontium titanate fine particle powder to the alkoxysilane-coated particles, the mixture was stirred and mixed at a high speed at 100 ° C. or higher in a container. Each fine particle was oleophilicized.

-Phenol 10 parts by mass-Formaldehyde solution (formaldehyde 40%, methanol 10%, water 50%)
6 parts by mass, magnetite coated with lipophilic strontium titanate powder
84 parts by weight The above materials, 5 parts by weight of 28% ammonia water, and 10 parts by weight of water were placed in a flask, heated and held at 85 ° C. for 30 minutes while stirring and mixing, and cured by polymerization reaction for 3 hours. . Then, after cooling to 30 degreeC and adding water, the supernatant liquid was removed, the precipitate was washed with water, and then air-dried. Subsequently, this was dried under reduced pressure (5 mmHg or less) at a temperature of 60 ° C. to obtain spherical magnetic carrier core particles in which a magnetic material was dispersed.

  Thereafter, a silicone resin was coated under the same conditions as in Production Example 1 to produce a magnetic carrier 18.

Production method of hybrid resin As vinyl copolymer, 1.9 mol of styrene, 0.21 mol of 2-ethylhexyl acrylate, 0.15 mol of fumaric acid, 0.03 mol of dimer of α-methylstyrene, dicumyl peroxide 0. Put 05 mol into the dropping funnel. In addition, 7.0 mol of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane; Put 0 mol, 3.0 mol of succinic acid, 2.0 mol of trimellitic anhydride, 5.0 mol of fumaric acid and 0.2 g of dibutyltin oxide in a 4-liter 4-neck flask made of glass, thermometer, stir bar, condenser and nitrogen The introduction tube was installed and placed in a mantle heater. Next, after the inside of the flask was replaced with nitrogen gas, the temperature was gradually increased while stirring, and while stirring at a temperature of 145 ° C., the monomer of the vinyl resin, the crosslinking agent and the polymerization initiator were added from the previous dropping funnel. It was dripped over 4 hours. Subsequently, the temperature was raised to 200 ° C. and reacted for 4 hours to obtain a hybrid resin (1).

<Example 1>
Cyan toner (Cyan 1) was prepared by the following method.

(First kneading step)
・ Hybrid resin resin (1) 60 mass parts ・ First paste form with a solid content of 40 mass% obtained by removing water from the pigment slurry to some extent from the filtration step of Cu phthalocyanine and without passing through the drying step. Pigment (the remaining 60% by mass is water) 100 parts by mass The above raw materials are first charged in a kneader mixer according to the above formulation, and the temperature is raised under no pressure while mixing. When the maximum temperature (necessarily determined by the boiling point of the solvent in the paste. In this case, about 90 to 100 ° C.) is reached, the pigment in the aqueous phase is distributed or transferred to the molten resin phase, and this is confirmed. After that, the mixture is further melted and kneaded for 30 minutes to sufficiently transfer the pigment in the paste. Then, once the mixer was stopped and hot water was discharged, the temperature was further raised to 130 ° C., heated and melted and kneaded for about 30 minutes, the pigment was dispersed and the water was distilled off, and the process was completed. The kneaded product was taken out and cooled to obtain a first kneaded product. The water content of the first kneaded product was about 0.5% by mass.

(Second kneading step)
Hybrid resin (1) 92.5 parts by mass The first kneaded product (pigment particle content 40% by mass) 12.5 parts by mass Wax A (paraffin Tg = 68 ° C) 5 parts by mass 0.2 parts by weight of aluminum compound of butyl salicylic acid (charge control agent) After thoroughly mixing the materials of the above formulation with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), the temperature is set to 130 ° C. Kneading with a biaxial kneader (PCM-30 type, manufactured by Ikegai Iron Works Co., Ltd.). The obtained kneaded material was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized material. The obtained coarsely pulverized toner was pulverized using a collision-type airflow pulverizer using high-pressure gas. The obtained finely pulverized product had a weight average diameter of 4.8 μm. Next, the finely pulverized product thus obtained was strictly and finely removed simultaneously with a multi-division classifier to obtain a cyan classified product.

  To the obtained cyan classified product, 1.0 part by mass of hydrophobized titanium oxide having an average particle size of 40 nm and 1.5 parts by mass of amorphous silica having an average particle size of 110 nm were externally added and mixed, and cyan toner (cyan 1 ) The resulting cyan toner had a weight average particle size of 5.5 μm and a number average particle size of 4.9 μm.

  A developer was prepared by mixing 92 parts by mass of magnetic carrier 1 with 8 parts by mass of the cyan toner using a tumbler mixer.

  Using this developer, it was evaluated with a Canon full color copier CLC5000. The amorphous silicon photoconductor (a-Si photoconductor 1) produced as described above was used.

The amount of developer loaded on the developing roller was adjusted with a regulating blade so as to be 30 mg / cm ² . Further, the distance between the developing roller and the amorphous silicon photosensitive member was adjusted to be 400 μm.

  In addition, a 650 nm semiconductor laser was used as the laser to reduce the spot diameter so that it could be output at 1200 dpi. Further, the surface layer of the fixing roller of the fixing unit was changed to a silicone tube, and the oil application mechanism was removed. Initial image evaluation was performed at normal temperature and normal humidity (NN environment: 23 ° C., 60% RH), and durability image output evaluation was performed under high temperature and high humidity (HH: 30 ° C., 80% RH). The test results are listed in Table 5.

<Examples 2 to 5>
Instead of the magnetic carrier 1 used in Example 1, magnetic carriers 2 to 5 were used to produce a developer. After that, the same test as in Example 1 was performed. The test results are listed in Table 5.

<Comparative Examples 1-6>
Instead of the magnetic carrier 1 used in Example 1, magnetic carriers 6 to 11 were used to produce a developer. After that, the same test as in Example 1 was performed. The test results are listed in Table 5.

<Examples 6 to 12>
Instead of the magnetic carrier 1 used in Example 1, magnetic carriers 12 to 18 were used to produce a developer. Further, the OPC photosensitive member 1 was used as the photosensitive member, and the same test as in Example 1 was performed thereafter. The test results are listed in Table 5.

<Example 13>
Example 1 Instead of the prepared Cu phthalocyanine pigment, C.I. I. A yellow toner (Yellow 1) was prepared using a paste pigment of Pigment Yellow-74 (hereinafter referred to as PY-74). The pigment content was 6 parts by mass with respect to 100 parts by mass of the binder resin. Furthermore, C.I. I. Pigment 57: 1 (hereinafter referred to as PR-57: 1) paste pigment was used, the pigment content was 6 parts by mass, magenta toner (magenta 1) was used, carbon black was used, and the pigment content was 5 A black toner (Black 1) was prepared so as to have a mass part.

  After that, when full-color image evaluation was performed with the evaluation machine used in Example 1, a clear image free of image defects could be obtained.

<Example 14>
An a-Si photosensitive member 2 was used instead of the photosensitive member used in Example 1, and the same test as in Example 1 was performed thereafter.

  In order to match the toner amount on the photoreceptor, the potential setting in the evaluation was changed as follows.

  Non-exposed portion potential: -350 V, exposed portion potential: -100 V, bias potential was set to DC: -200 V, and AC: body setting.

  The test results are listed in Table 5.

The figure showing the image forming apparatus using the developing device with a some developing agent holding body showing this invention. It is a schematic sectional drawing of the apparatus which measures the volume resistance of the magnetic carrier of this invention, a magnetic body, and a nonmagnetic inorganic compound.

Explanation of symbols

11 Lower electrode 12 Upper electrode 13 Insulator 14 Ammeter 15 Voltmeter 16 Constant voltage device 17 Carrier 18 Guide ring d Sample thickness E Resistance measurement cell

Claims (10)

In magnetic carrier particles formed by coating the surface of magnetic carrier core particles having at least a binder resin, magnetic particles, and a high dielectric compound with a coating material,
1) The magnetic carrier particles have a volume resistance of 1 × 10 ⁹ to 1 × 10 ¹⁶ Ωcm at 5 × 10 ⁵ V / m,
2) A carrier for electrophotography, wherein the relative dielectric constant ε of the high dielectric compound is 80 or more. The electrophotographic carrier according to claim 1, wherein the high dielectric compound has a resistance of 10 ¹⁰ Ωcm or more.   The electrophotographic carrier according to claim 1, wherein the high dielectric compound is a metal compound having a perovskite structure. 4. The electrophotographic apparatus according to claim 1, wherein the high dielectric compound is a metal oxide selected from CaTiO ₃ , SrTiO ₃ , BaTiO ₃ , and Ba _x Sr _1-x TiO ₃ . Career.   5. The electrophotographic carrier according to claim 1, wherein the high dielectric compound is contained in an amount of 5 to 100% by mass with respect to the magnetic particles.   The electrophotographic carrier according to claim 1, wherein the magnetic carrier particles are prepared by a polymerization method. In an image forming method using magnetic carrier particles formed by coating the surface of magnetic carrier core particles having at least a binder resin, magnetic particles, and a high dielectric compound with a coating material,
1) The magnetic carrier particles have a volume resistance of 1 × 10 ⁹ to 1 × 10 ¹⁶ Ωcm at 5 × 10 ⁵ V / m,
2) The high dielectric compound has a relative dielectric constant ε of 80 or more,
3) An image forming method using an electrophotographic photosensitive member having a charge capacity of 1.0 to 8.0 μF / m ² .   The image forming method according to claim 7, wherein the high dielectric compound is a metal compound having a perovskite structure.   9. The image forming method according to claim 7, wherein the electrophotographic photoreceptor is an amorphous silicon photoreceptor in which a light receiving layer is amorphous silicon. The image forming method according to claim 7, wherein the magnetic carrier particles have a volume resistance of 1 × 10 ¹¹ to 1 × 10 ¹⁵ Ωcm at 5 × 10 ⁵ V / m.

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